Science.gov

Sample records for nh3 temperature-programmed desorption

  1. Temperature programmed desorption and infrared spectroscopic studies of thin water films on MgO(100)

    E-print Network

    Reisler, Hanna

    Temperature programmed desorption and infrared spectroscopic studies of thin water films on MgO(100 Abstract Thin water (D2O) films on MgO(100) surfaces have been studied. Water was deposited at 115 K solid to cubic ice is known to take place, and then re-cooling. Temperature programmed desorption traces

  2. Reduction Kinetics of Graphene Oxide Determined by Electrical Transport Measurements and Temperature Programmed Desorption

    E-print Network

    and Temperature Programmed Desorption Inhwa Jung, Daniel A. Field, Nicholas J. Clark, Yanwu Zhu, Dongxing Yang, Richard D. Piner, Sasha Stankovich,§ Dmitriy A. Dikin,§ Heike Geisler,| Carl A. Ventrice, Jr

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  4. 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.

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

    SciTech Connect

    Stowe, A; Ragaiy Zidan, R

    2006-11-07

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

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

    NASA Astrophysics Data System (ADS)

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

    2000-01-01

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

  7. 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.

  8. CO adsorption on Ce-Pt(111) studied with LEED, XPS, and temperature programmed desorption

    SciTech Connect

    Vermang, B.; Juel, M.; Raaen, S.

    2006-01-15

    CO adsorption on Ce-Pt(111) has been studied by temperature programmed desorption (TPD), low energy electron diffraction (LEED) and x-ray photoelectron spectroscopy (XPS). Thin layers (1 to 3 ML) of Ce on Pt(111) form upon annealing to 1000 K a surface alloy which most likely is Pt terminated. The CO overlayer structure on Ce-Pt(111) at saturation coverage is argued to be an intermediate between (2x2) and c(4x2) superstructures. This intermediate structure exhibits a c(4x2) LEED pattern in which some of the spots appear together as ordered triangles. The thermal desorption spectra for the Ce-Pt(111) surface alloy are shifted down by a temperature of about 120 K compared to the CO desorption of pure Pt(111), most likely due to a change in the d-band due to hybridization between Ce and Pt states, which results in a weakening of the resonant interaction between CO 5{sigma} and Pt 5d states.

  9. Analysis of molecular hydrogen formation on low-temperature surfaces in temperature programmed desorption experiments.

    PubMed

    Vidali, G; Pirronello, V; Li, L; Roser, J; Manicó, G; Congiu, E; Mehl, H; Lederhendler, A; Perets, H B; Brucato, J R; Biham, O

    2007-12-13

    The study of the formation of molecular hydrogen on low-temperature surfaces is of interest both because it enables the exploration of elementary steps in the heterogeneous catalysis of a simple molecule and because of its applications in astrochemistry. Here, we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments, beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations, and the energy barriers of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results are used in order to evaluate the formation rate of H2 on dust grains under the actual conditions present in interstellar clouds. It is found that, under typical conditions in diffuse interstellar clouds, amorphous silicate grains are efficient catalysts of H2 formation when the grain temperatures are between 9 and 14 K. This temperature window is within the typical range of grain temperatures in diffuse clouds. It is thus concluded that amorphous silicates are good candidates to be efficient catalysts of H2 formation in diffuse clouds. PMID:17988107

  10. CF3I on a silicon surface: Adsorption, temperature-programmed desorption, and electron-stimulated desorption

    NASA Astrophysics Data System (ADS)

    Sanabia, Jason E.; Moore, John H.; Tossell, John A.

    2002-06-01

    CF3I adsorption on a silicon surface and the effect of low-energy electron bombardment of a CF3I-covered silicon surface are relevant to plasma etching. Dissociative chemisorption of CF3I on Si(100) surface is observed at 370 K. Uptake measurements corroborated by work-function change measurements and temperature-programmed desorption (TPD) gives a sticking probability of at least 0.34plus-or-minus0.05. Molecular orbital calculations yield an adsorption energy greater than 3 eV for dissociative chemisorption of CF3X (X=F, Cl, Br, and I) on Si(100) (modeled by Si9H12) with X transferred to a silicon atom. We conclude that the variation in the sticking probability across the CF3X family is a consequence of the activation energy barrier for C-X bond cleavage. In TPD, SiF4 desorbs at 370 and 840 K, SiF3 radical at 770 K, and atomic iodine at 790 K. The parent CF3I does not desorb. Electron-stimulated desorption (ESD) yields F+, F- and a trace of I+. The threshold for the appearance of F+ is 20 eV and for F- is 29 eV. Dissociative ionization and dipolar dissociation are possible mechanisms for ESD of F+. Dipolar dissociation and harpooning are possible mechanisms for ESD of F-. There is evidence that iodine on the surface quenches the electronically excited states that lead to desorption of F-.

  11. Characterization of early-stage coal oxidation by temperature-programmed desorption

    SciTech Connect

    Wei-Yin Chen; Guang Shi; Shaolong Wan

    2008-11-15

    To obtain representative temperature-programmed desorption (TPD) profiles of young oxidized chars up to 1650{degree}C with minimal reactor wall interferences, the chemistry and physics of four ceramic materials has been critically reviewed. A two-staged experimental apparatus is then uniquely designed to produce chars in an Al{sub 2}O{sub 3} flow reactor with 1-21% O{sub 2} followed by in situ TPD with a SiC tube. Comparison of TPD profiles of oxidized chars with those from pyrolyzed chars and ashes suggests early-stage char oxidation is profoundly influenced by oxygen from three sources: organic oxygen, mineral matters, and gas phase O{sub 2}. Young chars oxidized at 1000{degree}C with less than 0.3 s residence time shows CO desorption peaks during TPD at three distinct temperatures: 730, 1280, and 1560{degree}C. The peaks at 730{degree}C are mainly caused by incomplete devolatilization. The peaks at 1280{degree}C mainly represent desorption of stable surface oxides and incomplete devolatilization. Increasing the gas phase oxidants notably increases the amount of stable surface oxides. The broad peaks between 1400 and 1650{degree}C are attributed to the reactions of oxidants decomposed from minerals and carbon in the char or SiC tube. Gas-phase oxygen shifts these reactions to lower temperatures. Detailed oxygen balance based on the CO and CO{sub 2} yields and elemental compositions of both pyrolysis and oxidized chars reveals that oxygen uptakes are very high, +0.056 mg O per mg of carbon, in chars derived from bituminous coal, whereas lignite chars show negative oxygen uptake, -0.020 mg O per mg of carbon, in char. Indeed, lignite char seems to possess little amount of stable surface oxides other than those contributed by the minerals. The extensive emissions of CO from lignite chars during TPD seem to suggest that either O{sub 2} or minerals promotes the oxygen transfer on char surface and subsequent carbon oxidation. 85 refs., 5 figs., 4 tabs.

  12. Interactions of N-alcohols with self-assembled monolayer surfaces on nickel(111) studied by temperature-programmed desorption

    NASA Astrophysics Data System (ADS)

    Vogt, Andrew Dale

    1999-12-01

    The interactions of molecules with self-assembled monolayer (SAM) surfaces formed on nickel (111) as studied by temperature-programmed desorption (TPD) are discussed. First, the adsorption of 11-mercaptoundecanoic acid (HS(CH 2)10COOH), 11-mercaptoundecanol (HS(CH2) 11OH) and octadecyl mercaptan (HS(CH2)17CH 3) was characterized by X-ray photoelectron spectroscopy (XPS) and angle-dependent XPS (ADXPS). These long-chain functionalized n-alkanethiols adsorbed onto a clean nickel (111) single crystal via their sulfur atom and the alkyl chain and the carboxyl-, hydroxyl- and methyl-terminal groups were disposed away from the nickel surface. The basic concepts of XPS, AMPS and TPD are discussed. Second, TPD showed that the interactions of low-molecular-weight straight-chain alcohols (n- CxH2x+1 OH for x = 1 through 6) with the carboxyl-, hydroxyl- and methyl-terminated SAM surfaces exhibited an alcohol-coverage-dependent effect on the alcohol's desorption energy based on their respective sets of TPD spectra at different alcohol coverages and based on the desorption spectra's subsequent analysis for desorption energy. The threshold TPD method (TTPD) was used to determine the desorption energy as a function of coverage for all alcohol-substrate pairs. For these adsorbate-substrate systems the desorption energies (TTPD) were the lowest (10--25 kJ mol-1) for the lowest relative alcohol coverages and increased to a desorption energy of 40--60 kJ mol-1 that was invariant with relative coverage after reaching a monolayer. The constant desorption energy (TTPD) at high relative coverages suggests there might be a completely formed hydrogen bonding network between adsorbates on the surfaces at alcohol coverages near a monolayer. The Redhead method, the "complete analysis" and the TTPD method are discussed and compared.

  13. Temperature programed desorption of C{sub 2}H{sub 4} from pure and graphite-covered Pt(111)

    SciTech Connect

    Vermang, B.; Juel, M.; Raaen, S.

    2007-11-15

    Ethylene adsorption on Pt(111) at 95 K was studied by temperature programed desorption (TPD), low energy electron diffraction (LEED), and x-ray photoelectron spectroscopy. Ethylene desorbs reversibly at 112 K and irreversibly at 255 and 280 K. It is generally accepted that annealing of ethylene adsorbed on Pt(111) to 300 K results in a dehydrogenation to ethylidyne through an ethylidene intermediate. This was observed by a hydrogen desorption peak at 300 K. Also, hydrogenation of the adsorbed ethylene was observed by a small ethane desorption peak at 300 K. Upon heating to 700 K, the ethylidyne species will further dehydrogenate to carbidic carbon species with hydrogen desorption peaks at 460 and 640 K. If the carbidic species is heated to higher temperatures (up to 1000 K), it will further dehydrogenate and form graphitic islands which will accumulate by Ostwald ripening in larger islands at the step edges of the surface. After annealing the sample to 1000 K, a statistically distributed 8x8 superstructure of these graphite islands is achieved, as interpreted from A pattern in the LEED data. The TPD results indicate that ethylene adsorption on Pt(111) results in the formation of graphitic islands upon heating to 1000 K, contrary to previous conjectures of formation of a full graphite monolayer.

  14. Interaction of D2 with H2O amorphous ice studied by temperature-programed desorption experiments

    NASA Astrophysics Data System (ADS)

    Amiaud, L.; Fillion, J. H.; Baouche, S.; Dulieu, F.; Momeni, A.; Lemaire, J. L.

    2006-03-01

    The gas-surface interaction of molecular hydrogen D2 with a thin film of porous amorphous solid water (ASW) grown at 10K by slow vapor deposition has been studied by temperature-programed-desorption (TPD) experiments. Molecular hydrogen diffuses rapidly into the porous network of the ice. The D2 desorption occurring between 10 and 30K is considered here as a good probe of the effective surface of ASW interacting with the gas. The desorption kinetics have been systematically measured at various coverages. A careful analysis based on the Arrhenius plot method has provided the D2 binding energies as a function of the coverage. Asymmetric and broad distributions of binding energies were found, with a maximum population peaking at low energy. We propose a model for the desorption kinetics that assumes a complete thermal equilibrium of the molecules with the ice film. The sample is characterized by a distribution of adsorption sites that are filled according to a Fermi-Dirac statistic law. The TPD curves can be simulated and fitted to provide the parameters describing the distribution of the molecules as a function of their binding energy. This approach contributes to a correct description of the interaction of molecular hydrogen with the surface of possibly porous grain mantles in the interstellar medium.

  15. Processes for desorption from LiAlO sub 2 treated with H sub 2 as studied by temperature programmed desorption

    SciTech Connect

    Fischer, A.K.

    1990-01-01

    The energetics and kinetics of the evolution of H{sub 2}O and H{sub 2} from LiAlO{sub 2} are being studied by the temperature programmed desorption technique. The concentrations of H{sub 2}, H{sub 2}O, N{sub 2}, and O{sub 2} in a helium stream during a temperature ramp are measured simultaneously with a mass spectrometer. Blank experiments with an empty sample tube showed that square wave spikes of H{sub 2} introduced into the helium gas stream were severely distorted by reaction with the tube walls. The tube could be stabilized, however, by sufficiently prolonged heat treatment with H{sub 2} so that H{sub 2} peaks would not be distorted up to approximately 923 K(650{degree}C). The amount of H{sub 2}adsorption/desorption is small compared to the amount of H{sub 2}O adsorption/desorption. After prolonged treatment with helium containing 990 ppm H{sub 2} at 400{degree}C, H{sub 2}O evolution into the He-H{sub 2} stream was observed during 473 to 1023 K (200 to 750{degree}C) ramps at rates of 2 or 5.6 K/min. The different peak shapes reflecting this process were deconvoluted to show that they are composites of only 2 or 3 reproducible processes. The activation energies and pre-exponential terms was evaluated. The different behavior originates in the differences among different surface sites for adsorption. The interpretation of higher temperature peaks (above 873 K (650{degree}C)) must still consider the possibility of contributions from interactions with steel walls. It was found that H{sub 2} enhances evolution of N{sub 2} from the steel. 1 tab., 6 figs., 11 refs.

  16. Interaction between Water Molecules and Zinc Sulfide Nanoparticles Studied by Temperature-Programmed Desorption and Molecular Dynamics Simulations.

    SciTech Connect

    Zhang, Hengzon; Rustad, James R.; Banfield, Jillian F.

    2007-05-23

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We have investigated the bonding of water molecules to the surfaces of ZnS nanoparticles (2-3 nm sphalerite) using temperature-programmed desorption (TPD). The activation energy for water desorption was derived as a function of the surface coverage through kinetic modeling of the experimental TPD curves. The binding energy of water equals the activation energy of desorption if it is assumed that the activation energy for adsorption is nearly zero. Molecular dynamics (MD) simulations of water adsorption on 3 and 5 nm sphalerite nanoparticles provided insights into the adsorption process and water binding at the atomic level. Water binds with the ZnS nanoparticle surface mainly via formation of Zn-O bonds. As compared with bulk ZnS crystals, ZnS nanoparticles can adsorb more water molecules per unit surface area due to the greatly increased curvature, which increases the distance between adjacent adsorbed molecules. Results from both TPD and MD show that the water binding energy increases with decreasing the water surface coverage. We attribute the increase in binding energy with decreasing surface water coverage to the increasing degree of surface under-coordination as removal of water molecules proceeds. MD also suggests that the water binding energy increases with decreasing particle size due to the further distance and hence lower interaction between adsorbed water molecules on highly curved smaller particle surfaces. Results also show that the binding energy, and thus the strength of interaction of water, is highest in isolated nanoparticles, lower in nanoparticle aggregates, and lowest in bulk crystals. Given that water binding is driven by surface energy reduction, we attribute the decreased binding energy for aggregated as compared to isolated particles to the decrease in surface energy that occurs as the result of inter-particle interactions.

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

    SciTech Connect

    Tewell, Craig R.

    2002-08-19

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

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

    PubMed Central

    Gro?, 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

  19. Thermal desorption of ammonia from crystalline forsterite surfaces

    NASA Astrophysics Data System (ADS)

    Suhasaria, T.; Thrower, J. D.; Zacharias, H.

    2015-12-01

    The thermal desorption of ammonia (NH3) from single crystal forsterite (010) has been investigated using temperature-programmed desorption. The effect of defects on the desorption process has been probed by the use of a rough cut forsterite surface prepared from the cleaved forsterite sample. Several approaches have been used to extract the desorption energy and pre-exponential factor describing the desorption kinetics. In the sub-monolayer coverage regime, the NH3 desorption shows a broad distribution of desorption energies, indicating the presence of different adsorption sites, which results in an apparent coverage-dependent desorption energy. This distribution is sensitive to the surface roughness with the cut forsterite surface displaying a significantly broader distribution of desorption energies compared to the cleaved forsterite surface. The cut forsterite surface exhibits sites with desorption energies up to 62.5 kJ mol-1 in comparison to a desorption energy of up to 58.0 kJ mol-1 for the cleaved surface. Multilayer desorption is independent of the nature of the forsterite surface used, with a desorption energy of (25.8 ± 0.9) kJ mol-1. On astrophysically relevant heating time-scales, the presence of a coverage-dependent desorption energy distribution results in a lengthening of the NH3 desorption time-scale by 5.9 × 104 yr compared to that expected for a single desorption energy. In addition, the presence of a larger number of high-energy adsorption sites on the rougher cut forsterite surface leads to a further lengthening of ca. 7000 yr.

  20. Thermal desorption of ammonia from crystalline forsterite surfaces

    E-print Network

    Suhasaria, T; Zacharias, H

    2015-01-01

    The thermal desorption of ammonia (NH$_3$) from single crystal forsterite (010) has been investigated using temperature-programmed desorption. The effect of defects on the desorption process has been probed by the use of a rough cut forsterite surface prepared from the cleaved forsterite sample. Several approaches have been used to extract the desorption energy and pre-exponential factor describing the desorption kinetics. In the sub-monolayer coverage regime, the NH$_3$ desorption shows a broad distribution of desorption energies, indicating the presence of different adsorption sites, which results in an apparent coverage-dependent desorption energy. This distribution is sensitive to the surface roughness with the cut forsterite surface displaying a significantly broader distribution of desorption energies compared to the cleaved forsterite surface. The cut forsterite surface exhibits sites with desorption energies up to 62.5 kJ mol$^{-1} $ in comparison to a desorption energy of up to 58.0 kJ mol$^{-1} $ fo...

  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. Thermomagnetic Torque in Nh3 

    E-print Network

    Adair, Thomas W.; McClurg, G. R.

    1970-01-01

    , i.e. , where v& fx: (E)? PHYSICAL REVIEW A VOLUME 2, NUMBER 5 NOVEMBER 1970 Thermomagnetie Torque in NH ~3 T. W. Adair, III, and G. R. McClurg Department of Physics, Texas ASM University, College Station, Texas 77843 (Received 15 June 1970) A... field Hp for each pressure P is given by Hp ?-b(P+a), where a=-4. 4&&10 3 Torr and b=3. 18&&103 Oe/Torr. INTRODUCTION In 1967 Scott, Sturner, and Williamson' opened an exciting new field with the discovery of a thermo- magnetic torque on a torsion...

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

    SciTech Connect

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

    2009-09-15

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

  5. 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.

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

    SciTech Connect

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

    2015-09-03

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

  7. Temperature-programmed desorption of hydrogen from platinum particles on {gamma}-Al{sub 2}O{sub 3}: Evidence of platinum-catalyzed dehydroxylation of {gamma}-Al{sub 2}O{sub 3}

    SciTech Connect

    Alexeev, O.; Kim, D.W.; Gates, B.C.; Graham, G.W.; Shelef, M.

    1999-07-01

    Samples of Pt on {gamma}-Al{sub 2}O{sub 3} were prepared by reduction in H{sub 2} at 400 C of [PtCl{sub 2}(PhCN){sub 2}], adsorbed intact from n-pentane solution onto {gamma}-Al{sub 2}O{sub 3} powder that had been partially dehydroxylated under vacuum at 400 C. The Pt dispersion was determined to be about 0.58 by standard methods, namely, chemisorption of hydrogen, of oxygen, and of CO, titration of chemisorbed oxygen with hydrogen, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The supported Pt particles were resistant to sintering in the presence of O{sub 2} at temperatures up to 400 C, as shown by chemisorption and EXAFS data, but the latter indicated that a combination of O{sub 2} and H{sub 2} treatments at 200--400 C led to changes in particle morphology. The samples were investigated by temperature-programmed desorption (TPD) of preadsorbed hydrogen; a TPD peak centered at 120 C represents hydrogen adsorbed on Pt and confirms the value of 0.58 for the dispersion. TPD of preadsorbed H{sub 2} gave evidence of a second desorption peak, at 580 C, which was always accompanied by desorption of water at the same temperature; its presence was found to depend chiefly on the sample reduction temperature and evacuation time (it was absent when there was no Pt on the {gamma}-Al{sub 2}O{sub 3}). The desorption of H{sub 2} or D{sub 2} that had been adsorbed on Pt/{gamma}-Al{sub 2}O{sub 3} reduced with D{sub 2} or H{sub 2}, respectively, shows that hydrogen species desorbed at about 580 C originate from water (hydroxyl) species as a result of Pt-catalyzed decomposition.

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

    Atmospheric Science Data Center

    2015-01-30

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

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

    Atmospheric Science Data Center

    2015-08-26

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

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

    Atmospheric Science Data Center

    2015-08-28

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

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

    Atmospheric Science Data Center

    2015-01-30

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

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

    SciTech Connect

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

    1999-09-10

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

  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

    2011-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  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

    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 +}.

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

    SciTech Connect

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

    2004-02-02

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

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

    PubMed

    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 NH(3) sample, the main species ejected are NH(3), H(2), and N(2), where the hydrogen and nitrogen increase with laser fluence. This increase in N(2) 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 H(2) and N(2) in the mass spectrometer, consistent with the very small mass loss during the experiment and with a <5% decrease in the NH(3) infrared absorption bands spectroscopy after a fluence of ~3 × 10(19) photons/cm(2). The results imply that ammonia-ice mixtures in the outer solar system are relatively stable under solar irradiation. PMID:21142307

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

    NASA Astrophysics Data System (ADS)

    Sandford, Scott A.; Allamandola, Louis J.

    1993-11-01

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

  19. 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.

  20. 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.

  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. 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.

  3. NH3 Production In Comet C/2002 T7 LINEAR

    NASA Astrophysics Data System (ADS)

    Magee-Sauer, Karen P.; Feuss, J. W.; Dello Russo, N.; DiSanti, M. A.; Bonev, B. P.; Gibb, E. L.; Villanueva, G. L.; Anderson, W. M.; Mumma, M. J.

    2006-09-01

    We observed Comet C/2002 T7 LINEAR (C/T7) from 3-9 May 2004 using CSHELL at the NASA/IRTF. High-resolution spectra of parent volatiles were acquired, emphasizing the oxygen, hydrocarbon, and nitrile chemistry. A major goal was to detect and measure the relative abundance of NH3. At infrared wavelengths, NH3 is difficult to detect since it requires a significant geocentric velocity to shift the strongest NH3 emissions out of the terrestrial atmospheric water absorption. The high Doppler shift (- 65 km/s) of C/T7 during early May made it an excellent target for searching NH3. Several lines of the Q-branch and R-branch of the ?1 band were detected. NH3 is the dominant (observable) nitrogen-containing volatile in comets, present at 1% relative to water. Previously at infrared wavelengths, a single line of the ?1 band near 3-?m was detected in comet C/1995 O1 Hale-Bopp, and a more secure infrared detection was achieved in 153P/Ikeya-Zhang. Our 153P NH3 spectra showed that the NH3 molecule was not rotationally relaxed as previously thought and that a different model was needed to predict line g-factors. Our goal for observing NH3 in C/T7 was to observe a range of rotational levels and transitions to test a newer rotationally equilibrated model for NH3. This paper presents results of that test based on spectra obtained for C/T7. We present production rates and relative abundances to water for C/T7 and we apply this model to our other NH3 detections from past comets. We also compare our results with NH3 production rates reported from radio observations by other groups. We gratefully acknowledge support from the NSF RUI Program to KM-S and the NASA PAST to MJM, MAD, and NDR.

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

    PubMed

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

    2005-01-15

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

  5. 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).

  6. 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...

  7. Probing NH3 Formation in Oxygen-rich Circumstellar Envelopes

    NASA Astrophysics Data System (ADS)

    Wong, K. T.; Menten, K. M.; Kami?ski, T.; Wyrowski, F.

    2015-08-01

    The chemistry of ammonia (NH3) in the circumstellar envelopes (CSEs) of AGB stars and red supergiants is poorly understood. Thermodynamic equilibrium (TE) chemistry predicts an abundance of ?10-8, orders of magnitudes below values reported from observations (˜10-7-10-6). To date, there is no consistent model explaining the origin of such high abundances. To better understand the physical conditions necessary for the formation of NH3, we analysed the NH3 rotational and inversion lines observed in the spectrum of IK Tauri. The strength of the rotational lines clearly confirms the high abundances as compared to the TE predictions. From 1D radiative transfer modelling including infrared pumping via vibrational bands, we infer a total NH3 abundance of 7.5× 10-7, along with an ortho-to-para ratio (OPR) of ? 1.5 : 1, slightly above the statistical equilibrium value of 1. We discuss these preliminary results and the possible origin of NH3 in oxygen-rich CSEs.

  8. 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.

  9. High density tracers in outflow regions: NH3 vs. CS

    NASA Astrophysics Data System (ADS)

    Lopez, R.; Morata, O.; Sepulveda, I.; Estalella, R.; Anglada, G.; Pastor, J.; Planesas, P.

    1994-06-01

    We present CS(J = 1 approaches 0) observations of the high density gas in a sample of eleven star forming regions with molecular or optical outflows. The sources of this sample cover a wide range of physical sizes. All these sources had been previously mapped in NH3 (1,1) with similar angular resolution. In all the sources of this sample CS emission was detected, indicating a global correlation between the emissions traced by the CS and the NH3 molecules. However, the detailed characteristics of these two emissions (e.g., the extent and the location of the emission peak) show, in general, significant differences in the sources which are well resolved by the beam. As a general trend, the emission traced by the NH3 molecule appears as compact clumps which engulf an outflow activity center. In contrast, the emission traced by the CS molecule, usually more extended, appears as a background which connects different outflow activity centers associated with each NH3 clump.

  10. Dissociative adsorption of NH3 on cleaved Si(111)

    NASA Astrophysics Data System (ADS)

    Chérif, S. M.; Lacharme, J.-P.; Sébenne, C. A.

    1992-08-01

    Clean cleaved Si(111) surfaces were exposed to NH3 up to a few langmuirs and studied by low energy electron diffraction, Auger electron spectroscopy, electron energy loss spectroscopy and photoemission yield spectroscopy. The sticking coefficient is unity almost up to saturation which occurs at a N coverage of {1}/{4} monolayer. There, the surface structure is 1 × 1 with some disorder, the ionization energy and the work function are decreased by 0.425 and 0.6 eV, respectively, and the clean surface state band is replaced by a narrow band, 0.1 eV below the valence band edge. The results are explained by a high degree of dissociation of the adsorbed NH3 molecules, mainly into N, or NH and H atoms without large loss of hydrogen.

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

    PubMed

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

    2013-05-14

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

  12. 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.

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

    PubMed

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

    2015-05-01

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

  14. Catalysis Letters Vol. 76, No. 12, 2001 35 Second order isothermal desorption kinetics

    E-print Network

    Asscher, Micha

    Catalysis Letters Vol. 76, No. 1­2, 2001 35 Second order isothermal desorption kinetics Y. Lilach desorption; second order kinetics; recombinative desorption 1. Introduction Temperature-programmed desorption species, and for obtaining their desorption kinetics. Comprehensive reviews on the subject exist

  15. Rapid Ammonia Gas Transport Accounts for Futile Transmembrane Cycling under NH3/NH4

    E-print Network

    Kronzucker, Herbert J.

    Rapid Ammonia Gas Transport Accounts for Futile Transmembrane Cycling under NH3/NH4 + Toxicity toxicity conditions. Ammonia/ammonium (NH3/NH4 + ) toxicity in higher plants has resulted in crop reduction

  16. cis-{Pt(NH3)2(L)}2+/+ (L ) Cl, H2O, NH3) Binding to Purines and CO: Does -Back-Donation Play a Role?

    E-print Network

    Baik, Mu-Hyun

    cis-{Pt(NH3)2(L)}2+/+ (L ) Cl, H2O, NH3) Binding to Purines and CO: Does -Back-Donation Play a Role ) Cl, H2O, NH3) is a poor -donor and that -back-donation does not play an important role for Pt metal d-orbital to the ligand-based *- orbital does not play an important role.11 We concluded

  17. Effect of proton motion on molecular properties in the BrH NH3 complex

    NASA Astrophysics Data System (ADS)

    Aicken, A. M.; Buckingham, A. D.; Tantirungrotechai, Y.

    1999-07-01

    The nuclear magnetic shielding, electric dipole moment and electric field gradient at the nuclei were studied by ab initio computations as a function of the one-dimensional proton transfer coordinate in BrH NH3. The properties are vibrationally averaged along this reaction coordinate for BrH NH3 and BrD NH3. The effect of a matrix has been approximated, as in previous calculations, by surrounding BrH NH3 with three argon atoms.

  18. Enhanced Performance of Perovskite CH3NH3PbI3 Solar Cell by Using CH3NH3I as Additive in Sequential Deposition.

    PubMed

    Xie, Yian; Shao, Feng; Wang, Yaoming; Xu, Tao; Wang, Deliang; Huang, Fuqiang

    2015-06-17

    Sequential deposition is a widely adopted method to prepare CH3NH3PbI3 on mesostructured TiO2 electrode for organic lead halide perovskite solar cells. However, this method often suffers from the uncontrollable crystal size, surface morphology, and residual PbI2 in the resulting CH3NH3PbI3, which are all detrimental to the device performance. We herein present an optimized sequential solution deposition method by introducing different amount of CH3NH3I in PbI2 precursor solution in the first step to prepare CH3NH3PbI3 absorber on mesoporous TiO2 substrates. The addition of CH3NH3I in PbI2 precursor solution can affect the crystallization and composition of PbI2 raw films, resulting in the variation of UV-vis absorption and surface morphology. Proper addition of CH3NH3I not only enhances the absorption but also improves the efficiency of CH3NH3PbI3 solar cells from 11.13% to 13.37%. Photoluminescence spectra suggest that the improvement of device performance is attributed to the decrease of recombination rate of carriers in CH3NH3PbI3 absorber. This current method provides a highly repeatable route for enhancing the efficiency of CH3NH3PbI3 solar cell in the sequential solution deposition method. PMID:26009927

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

    NASA Astrophysics Data System (ADS)

    Pijnenburg, B.; Ritmann, J.

    2015-08-01

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

  20. 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.

  1. [UO2(NH3)5]Br2·NH3: synthesis, crystal structure, and speciation in liquid ammonia solution by first-principles molecular dynamics simulations.

    PubMed

    Woidy, Patrick; Bühl, Michael; Kraus, Florian

    2015-04-28

    Pentaammine dioxido uranium(VI) dibromide ammonia (1/1), [UO2(NH3)5]Br2·NH3, was synthesized in the form of yellow crystals by the reaction of uranyl bromide, UO2Br2, with dry liquid ammonia. The compound crystallizes orthorhombic in space group Cmcm and is isotypic to [UO2(NH3)5]Cl2·NH3 with a = 13.2499(2), b = 10.5536(1), c = 8.9126(1) Å, V = 1246.29(3) Å(3) and Z = 4 at 123 K. The UO2(2+) cation is coordinated by five ammine ligands and the coordination polyhedron can be best described as pentagonal bipyramid. Car-Parrinello molecular dynamics simulations are reported for [UO2(NH3)5](2+) in the gas phase and in liquid NH3 solution (using the BLYP density functional). According to free-energy simulations, solvation by ammonia has only a small effect on the uranyl-NH3 bond strength. PMID:25797497

  2. 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).

  3. Hydrogen atom transfer in indole(NH_3)n clusters: formation dynamics of (NH_{3)_{n-1}NH4}, n = 1 6, fragments

    NASA Astrophysics Data System (ADS)

    Lippert, H.; Stert, V.; Hesse, L.; Schulz, C. P.; Radloff, W.; Hertel, I. V.

    2002-09-01

    The H atom transfer reaction in electronically excited indole(NH3)n clusters is studied in pump-probe experiments with femtosecond laser pulses. By applying different probe photon energies we are able to detect the dissociation products (NH3)_{n-1}NH4 for n = 1 6. Furthermore we show that the analysis of the corresponding ion signals is not distorted by contributions from larger cluster ions due to evaporation of NH3 molecules. The formation times of the products are ca. 140 ps for n=2 4 and about 80 ps for n=5,6.

  4. 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.

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

    DOEpatents

    Linker, Kevin L. (Albuquerque, NM); Bouchier, Frank A. (Albuquerque, NM); Theisen, Lisa (Albuquerque, NM); Arakaki, Lester H. (Edgewood, NM)

    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.

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

    NASA Astrophysics Data System (ADS)

    Hetma?czyk, Joanna; Hetma?czyk, ?ukasz; Migda?-Mikuli, Anna; Mikuli, Edward

    2015-02-01

    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 3385 cm-1, associated with: ?r(NH3) and ?as(N-H) modes, respectively, indicate that there exist fast (correlation times ?R ? 10-12-10-13 s) reorientational motions of NH3 ligands, with a mean values of activation energies: 7.8 and 4.5 kJ mol-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 TCc = 137.6 K (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.

  7. Effects of NH3 flow rate on the thermal plasma synthesis of AlN nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Tae-Hee; Choi, Sooseok; Park, Dong-Wha

    2013-11-01

    Aluminium nitride (AlN) nanoparticles were synthesized by using a non-transferred arc plasma. A pellet of micro-sized aluminium (Al) powders was evaporated by using an argon-nitrogen thermal plasma flame, and ammonia (NH3) was introduced into the reactor as a reactive gas. The flow rate of NH3 was controlled from 5 to 25 L/min at a fixed input power of 10.2 kW. In experiments, unreacted Al powder was found at low NH3 flow rates at 5 and 10 L/min. The size and the crystallinity of the synthesized AlN particles increased with increasing flow rate of NH3 until 20 L/min. The maximum particle size of AlN nanoparticle was about 100 nm at a 20 L/min NH3 flow rate. At an excessive flow rate of NH3 of 25 L/min, however, the size and the crystallinity of AlN were decreased. In order to analyze the experimental results for the thermal plasma synthesis of AlN nanoparticles, we carried out numerical simulations on the thermal plasma. The vortex flow of the thermal plasma near the Al pellet was gradually enhanced with increasing NH3 flow rate from 10 to 20 L/min. The strength of the vortex flow, however, was decreased at the highest NH3 flow rate of 25 L/min.

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

    PubMed

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

    2015-01-01

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

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

    PubMed

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

    2015-12-01

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

  10. Study on adsorption and desorption of ammonia on graphene

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  12. Tetra-amminelithium triamminelithium tris-ulfide, [Li(NH(3))(4)][Li(NH(3))(3)S(3)].

    PubMed

    Guentner, Christian; Korber, Nikolaus

    2012-11-01

    The title compound, [Li(NH(3))(4)](+)[Li(NH(3))(3)S(3)](-), an ammo-niate of the previously unknown lithium tris-ulfide, was obtained from the reaction of lithium and sulfur in liquid ammonia. The asymmetric unit consists of two crystallographically independent formula units. The [Li(NH(3))(4)](+) cations are close to regular LiN(4) tetra-hedra. The anions contain LiSN(3) tetra-hedra; the S-S-S bond angles are 110.43?(5) and 109.53?(5)°. In the crystal, the components are linked by multiple N-H?S hydrogen bonds. A weak N-H?N hydrogen bond is also present. PMID:23284314

  13. Tetra­amminelithium triamminelithium tris­ulfide, [Li(NH3)4][Li(NH3)3S3

    PubMed Central

    Guentner, Christian; Korber, Nikolaus

    2012-01-01

    The title compound, [Li(NH3)4]+[Li(NH3)3S3]?, an ammo­niate of the previously unknown lithium tris­ulfide, was obtained from the reaction of lithium and sulfur in liquid ammonia. The asymmetric unit consists of two crystallographically independent formula units. The [Li(NH3)4]+ cations are close to regular LiN4 tetra­hedra. The anions contain LiSN3 tetra­hedra; the S—S—S bond angles are 110.43?(5) and 109.53?(5)°. In the crystal, the components are linked by multiple N—H?S hydrogen bonds. A weak N—H?N hydrogen bond is also present. PMID:23284314

  14. Crystal structure of (NH 3- R-NH 3)(NH 3- R-NH 2)PbI 5 ( R=5,5'-bis(ethylsulfanyl)-2,2'-bithiophene): NH 3+⋯NH 2 interaction as a tool to reach densely packed organic layers in organic-inorganic perovskites

    NASA Astrophysics Data System (ADS)

    Zhu, Xu-Hui; Mercier, Nicolas; Allain, Magali; Frère, Pierre; Blanchard, Philippe; Roncali, Jean; Riou, Amédée

    2004-04-01

    In the layered (NH 3- R-NH 3)(NH 3- R-NH 2)PbI 5 ( R=5,5'-bis(ethylsulfanyl)-2,2'-bithiophene) organic-inorganic hybrid compound, a PbI 53- 1D network of corner sharing octahedra defines ordered deficient perovskite layers separated by the organic sheets. The NH 3+⋯NH 2 interactions together with NH 3+⋯I contacts, which take place at the inorganic-organic interface, favor rather strong S⋯S intermolecular interactions between bithiophene units, compared to those found in purely organic compounds or in (NH 3- R-NH 3)PbI 4. Crystal data: (C 24H 35S 8N 4)PbI 5, Mr=1477.73, monoclinic, P2 1/ c, a=17.553(2) Å, b=8.710(1) Å, c=27.122(5) Å, ?=97.57(2)°, V=4110(1) Å 3, Z=4, R=0.053, Rw=0.119.

  15. Concentration-dependent NH 3 deposition processes for moorland plant species with and without stomata

    NASA Astrophysics Data System (ADS)

    Jones, M. R.; Leith, I. D.; Raven, J. A.; Fowler, D.; Sutton, M. A.; Nemitz, E.; Cape, J. N.; Sheppard, L. J.; Smith, R. I.

    Currently, in operational modelling of NH 3 deposition a fixed value of canopy resistance ( Rc) is generally applied, irrespective of the plant species and NH 3 concentration. This study determined the effect of NH 3 concentration on deposition processes to individual moorland species. An innovative flux chamber system was used to provide accurate continuous measurements of NH 3 deposition to Deschampsia cespitosa (L.) Beauv., Calluna vulgaris (L.) Hull, Eriophorum vaginatum L., Cladonia spp., Sphagnum spp., and Pleurozium schreberi (Brid.) Mitt. Measurements were conducted across a wide range of NH 3 concentrations (1-140 ?g m -3). NH 3 concentration directly affects the deposition processes to the vegetation canopy, with Rc, and cuticular resistance ( Rw) increasing with increasing NH 3 concentration, for all the species and vegetation communities tested. For example, the Rc for C. vulgaris increased from 14 s m -1 at 2 ?g m -3 to 112 s m -1 at 80 ?g m -3. Diurnal variations in NH 3 uptake were observed for higher plants, due to stomatal uptake; however, no diurnal variations were shown for non-stomatal plants. Rc for C. vulgaris at 80 ?g m -3 was 66 and 112 s m -1 during day and night, respectively. Differences were found in NH 3 deposition between plant species and vegetation communities: Sphagnum had the lowest Rc (3 s m -1 at 2 ?g m -3 to 23 at 80 ?g m -3), and D. cespitosa had the highest nighttime value (18 s m -1 at 2 ?g m -3 to 197 s m -1 at 80 ?g m -3).

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  19. 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.

  20. Worldwide spatiotemporal atmospheric ammonia (NH3) columns variability revealed by satellite

    NASA Astrophysics Data System (ADS)

    Van Damme, M.; Erisman, J. W.; Clarisse, L.; Dammers, E.; Whitburn, S.; Clerbaux, C.; Dolman, A. J.; Coheur, P.-F.

    2015-10-01

    We exploit 6 years of measurements from the Infrared Atmospheric Sounding Interferometer (IASI)/MetOp-A instrument to identify seasonal patterns and interannual variability of atmospheric NH3. This is achieved by analyzing the time evolution of the monthly mean NH3 columns in 12 subcontinental areas around the world, simultaneously considering measurements from IASI morning and evening overpasses. For most regions, IASI has a sufficient sensitivity throughout the years to capture the seasonal patterns of NH3 columns, and we show that each region is characterized by a well-marked and distinctive cycle, with maxima mainly related to underlying emission processes. The largest column abundances and seasonal amplitudes throughout the years are found in southwestern Asia, with maxima twice as large as what is observed in southeastern China. The relation between emission sources and retrieved NH3 columns is emphasized at a smaller regional scale by inferring a climatology of the month of maximum columns.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  3. Synthesis, structure and spectroscopic investigations of two new organic-inorganic hybrids NH3(C6H4)2NH3CuCl4 and NH3(C6H4)2NH3HgCl4

    NASA Astrophysics Data System (ADS)

    Belhouchet, M.; Wamani, W.; Mhiri, T.

    2010-11-01

    Two metal organic-inorganic hybrid compounds, NH3(C6H4)2NH3CuCl4, 1, and NH3(C6H4)2NH3HgCl4, 2, have been synthesized and structurally characterized by single-crystal X-ray diffraction. The two compounds crystallize in the monoclinic space groups P21/c and C2/c, respectively, with a = 14.3774 (7), b = 7.3472 (4), c = 7.1669 (3), ? = 96.589 (3)°, Z = 2 and R1 = 0.037 for 1, and a = 6.2986 (4), b = 18.2911 (12), c = 28.5854 (17), ? = 91.836 (2)°, Z = 8 and R1 = 0.049 for 2. The organic-inorganic layered perovskite structure of compound 1 features well-ordered sheets of corner-sharing distorted CuCl6 octahedra, due to the presence of Jahn-Teller effect in the d9 electronic system of Cu(II), separated by layers of benzidinium cations. The structure of compound 2 consists of anionic parallel layers built up from discrete tetrahedral HgCl42- species, alternating with layers of organic molecules [NH3(C6H4)2NH3]2+. The structures of the two compounds are stabilized by an extensive network of N-H...C1 hydrogen bonds. These compounds are also investigated by IR spectroscopy.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  5. Unipolar self-doping behavior in perovskite CH3NH3PbBr3

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  6. 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 ?/?, 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.

  7. 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 ...

  8. A resistance change effect in perovskite CH3NH3PbI3 films induced by ammonia.

    PubMed

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

    2015-10-01

    The resistance of the perovskite CH3NH3PbI3 film was found to decrease significantly in seconds when the film was exposed to an NH3 atmosphere at room-temperature, and recover to its original value in seconds when out of the NH3 environment. PMID:26344914

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

    PubMed

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

    2015-11-18

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  11. 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.

  12. 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.

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

    PubMed

    Krupa, S V

    2003-01-01

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

  14. Accurate Potential Energy Surface, Rovibrational Energy Levels, and Transitions of Ammonia C_{3v} Isotopologues: ^{14}NH_3, ^{15}NH_3, ^{14}ND_3 and ^{14}NT_3

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

    A further refined, global potential energy surface (PES) is computed for the C_{3v} symmetry isotopologues of ammonia, including ^{14}NH_3, ^{15}NH_3, ^{14}ND_3 and ^{14}NT_3. The refinement procedure was similar to that used in our previously reported PES, but now extends to higher J energy levels and other isotopologues. Both the diagonal Born-Oppenheimer correction and the non-adiabatic correction were included. J=0-6 rovibrational energy levels and transition frequencies of ^{14}NH_3 computed on this PES are in excellent agreement with HITRAN data. Statistics on nearly 4100 transitions and more than 1000 energy levels demonstrate the accuracy achieved by the state-of-the-art "Best Theory + Experiment" strategy. Most transition frequencies are of ±0.01-0.02 cm^{-1} accuracy. Similar accuracy has been found on ^{15}NH_3 J=0-3 rovibrational energy levels. Several transitions and energy levels in HITRAN have been identified as unreliable or suspicious, and some have been re-assigned. For ^{14}ND_3 and ^{14}NT_3, J=0-3 calculations have been performed. Agreement for pure rotation-inversion transitions is nearly perfect, with more reliable energy levels presented. On the other hand, our J=0 results suggest a re-analysis on the ^{14}ND_3 ?_1 band origin is needed. Finally, we will discuss possible future refinements leading to an even better final PES for Ammonia. X. Huang, D.W. Schwenke, and T.J. Lee, J. Chem. Phys. 129, 214304 (2008).

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

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

  16. Nitrogen conversion in relation to NH3 and HCN during microwave pyrolysis of sewage sludge.

    PubMed

    Tian, Yu; Zhang, Jun; Zuo, Wei; Chen, Lin; Cui, Yanni; Tan, Tao

    2013-04-01

    The nitrogen conversions in relation to NH3 and HCN were investigated during microwave pyrolysis of sewage sludge. The nitrogen distributions and evolution of nitrogen functionalities in the char, tar, and gas fractions were conducted. The results suggested that the thermal cracking of protein in sludge produced three important intermediate compounds, including the amine-N, heterocyclic-N, and nitrile-N compounds. The deamination of amine-N compounds resulted from labile proteins cracking led to the formation of NH3 (about 7.5% of SS-N) between 300 and 500 °C. The cracking of nitrile-N and heterocyclic-N compounds in the tars from the dehydrogenation and polymerization of amine-N generated HCN (6.6%) from 500 to 800 °C, respectively. Moreover, the ring-opening of heterocyclic-N in the char and tar contributed to the release of NH3 accounting for about 18.3% of SS-N with the temperature increasing from 500 to 800 °C. Specifically, the thermal cracking of amine-N, heterocyclic-N and nitrile-N compounds contributed to above 80% of the total (HCN+NH3) productions. Consequently, it might be able to reduce the HCN and NH3 emissions through controlling the three intermediates production at the temperature of 500-800 °C. PMID:23477529

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

    SciTech Connect

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

    2012-04-30

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

  18. 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. PMID:26233134

  19. Internal Dynamics in SF6\\cdot\\cdot\\cdotNH3 Observed by Broadband Rotational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Bittner, Dror M.; Zaleski, Daniel P.; Stephens, Susanna L.; Walker, Nick; Legon, Anthony

    2015-06-01

    The rotational spectra of SF6\\cdot\\cdot\\cdotNH3 isotopologues have been observed in a pulsed nozzle chirped pulse Fourier-transform microwave spectrometer in the frequency range 6.5-18.5 GHz. The spectrum of SF6\\cdot\\cdot\\cdot14NH3 has been fitted to a Hamiltonian describing a symmetric top complex in which two symmetric top subunits undergo free internal rotation about a common symmetry axis. The distance between the centers of mass of the two monomers was found to be 4.15776(7) Å. Challenges associated with fitting m =1 transitions (correlating with K of free NH3) for SF6\\cdot\\cdot\\cdot14ND3 imply complicated internal dynamics occurs within the complex.

  20. Facile route to freestanding CH3NH3PbI3 crystals using inverse solubility

    PubMed Central

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

    2015-01-01

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

  1. Do Cu 2+NH 3 and Cu 2+OH 2 exist?: theory confirms `yes!'

    NASA Astrophysics Data System (ADS)

    El-Nahas, Ahmed M.; Tajima, Nobuo; Hirao, Kimihiko

    2000-02-01

    CCSD(T) and MRMP calculations with TZP+ quality basis sets are used to study the interaction of Cu 2+ with up to two ligand molecules L (L=H 2O, H 2S, NH 3, and PH 3). The dissociation to Cu + and L + is much more stable than the formation of Cu 2+L adducts (by 76-100 kcal/mol). Nevertheless, it might be possible to obtain a one-ligand complex for H 2O and NH 3; barrier heights of 7 and 9 kcal/mol, respectively, are assigned for the dissociation process. Two ligands from H 2O and NH 3 can give more stable complexes with Cu 2+ as the barrier heights reach 40 kcal/mol. In order to obtain stable complexes of PH 3 or H 2S with Cu 2+, at least two ligands are required.

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

    PubMed

    Loreau, J; van der Avoird, A

    2015-11-14

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

  3. 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

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

    NASA Astrophysics Data System (ADS)

    Loreau, J.; van der Avoird, A.

    2015-11-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Joiner, Joanna; Steffes, Paul G.

    1991-01-01

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

  7. An A-site mixed-ammonium solid solution perovskite series of [(NH2 NH3 )x (CH3 NH3 )1-x ][Mn(HCOO)3 ] (x=1.00-0.67).

    PubMed

    Chen, Sa; Shang, Ran; Wang, Bing-Wu; Wang, Zhe-Ming; Gao, Song

    2015-09-14

    The A-site mixed-ammonium solid solutions of metal-organic perovskites [(NH2 NH3 )x (CH3 NH3 )1-x ][Mn(HCOO)3 ] (x=1.00-0.67) exhibit para- to ferroelectric diffuse phase transitions with lowered transition temperatures from x=1.00 to 0.67. These properties are due to the decreased framework distortion and polarization in their low temperature ferroelectric phases caused by the increased CH3 NH3 (+) concentration. PMID:26245518

  8. Vibrationally state-selected reactions of ammonia ions. III. NHt(v)+ND3 and NDt(v)+ NH3

    E-print Network

    that the hydrogen atom abstraction reaction does occur in addition to the pro- ton transfer reactionVibrationally state-selected reactions of ammonia ions. III. NHt(v)+ND3 and NDt(v)+ NH3 William E umbrella-bending mode of ND/ (.X,v = 0 to 10) and NH3+ (X,v = 0 to 9) on the reaction with NH3 and ND3

  9. Na, NH3, MeOH Chem 115Birch ReductionMyers

    E-print Network

    . In Encyclopedia of Reagents for Organic Synthesis, Paquette, L. A., Ed.; John Wiley and Sons: New York, 1995, Vol reduction potential at ­50 °C in NH3 (V) Additivity of Substituent Effects: · Reduction in low molecular weight amines (Benkeser reduction): · Reduction in low molecular weight amines (in the absence of alcohol

  10. 10 Years of NH3 Variability over the US Measured by AIRS

    NASA Astrophysics Data System (ADS)

    Warner, J. X.; Wei, Z.; Strow, L. L.

    2013-12-01

    Atmospheric InfraRed Sensor provides twice daily and nearly global coverage of tropospheric compositions due to AIRS wide swaths. With longer than 10 years of data records, these measurements have been used not only for daily monitoring purposes but also for inter-annual variability and short-term trend studies. We have developed a new daily and global tropospheric ammonia product from AIRS measurements. AIRS NH3 is retrieved from an add-on module to the AIRS operational codes; and this module uses the Optimal Estimation (OE) technique. Using OE method, the retrieved products provide sensitivity properties, in addition to NH3 concentrations, e.g., the Averaging Kernels (AKs), error covariance matrices, and the Degrees Of Freedom for Signal (DOFS). Globally, AIRS captures NH3 emissions from biogenic and anthropogenic activities over many emission regions. We will focus in this presentation the ammonia distribution over the US, and will particularly emphasize its variability in the last 10 years. Validation examples using in situ measurements for AIRS NH3 will also be presented.

  11. 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.

  12. 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 ?-basicity, charge state, and geometric flexibility. PMID:26001022

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

    NASA Technical Reports Server (NTRS)

    Jennings, D. E.

    1978-01-01

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

  14. Heteronuclear NMR Spectroscopy for Lysine NH3 Groups in Proteins: Unique Effect of Water Exchange on

    E-print Network

    Clore, G. Marius

    design principles as the HISQC, all the NH3 cross-peaks observed in the HISQC spectrum could be assigned is feasible because of hydrogen bonding or salt bridges that protect them from rapid water exchange. Finally recognition, through the formation of salt bridges with carboxylates of glutamate and aspartate

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

    PubMed

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

    2014-04-01

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

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

    SciTech Connect

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

    2015-01-01

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

  17. Reaction Dynamics of H2O+ (D2O+) + NH3 Studied with Crossed Molecular Beams and Density Functional Theory Calculations

    E-print Network

    Farrar, James M.

    Reaction Dynamics of H2O+ (D2O+) + NH3 Studied with Crossed Molecular Beams and Density Functional and proton transfer reactions between H2O+ (D2O+ ) and NH3 were studied at collision energies below 1 e. The reaction products include NH3D+ formed by deuterium ion transfer, NH3 + produced by charge transfer, and NH

  18. 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.

  19. Nucleobases and prebiotic molecules in organic residues produced from the ultraviolet photo-irradiation of pyrimidine in NH(3) and H(2)O+NH(3) ices.

    PubMed

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

    2012-04-01

    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 H(2)O ices leads to the formation of a suite of oxidized pyrimidine derivatives, including the nucleobase uracil. In the present work, NH(3):pyrimidine and H(2)O:NH(3):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. PMID:22519971

  20. Laboratory study of sticking and desorption of H2 and its significance in the chemical evolution of dense interstellar medium

    NASA Astrophysics Data System (ADS)

    Acharyya, K.

    2014-09-01

    The temperature-programmed desorption spectra of H2 is recorded under ultrahigh vacuum conditions on an olivine substrate with more than 90 per cent forsterite content for different coverage and temperatures. Then, using an empirical kinetic model, binding energy of H2 on the substrate is found to be 480 ± 10 K (41.36 ± 0.86 meV). Lower limit of sticking coefficient is estimated by comparing gas load at room temperature and at low temperature, which varies between 0.82 and 0.25 for temperatures between 7 and 14 K. Using a gas-grain chemical network, it is found out that a steady state is reached around after 50 yr at 10 K and both the steady-state abundance and time required to attend steady state is a strong function of temperature. Then, this model is used to check the effect of sticking of H2 on the grain surface chemistry. It is found that for H2O, CH4, NH3 and HCN, abundance due to reaction pathways involving H2 is within 1 per cent, when compared with the abundance achieved considering most dominant pathways. Thus, neglecting sticking of H2 will not change overall abundance of these molecules. For carbon chain molecules, it was found that the reaction pathways with H2 may be important and could contribute significantly to account for the observed abundances. Since, sticking of H2 is temperature sensitive, increase in temperature will reduce the effect of these reactions.

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

    EPA Science Inventory

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

  2. Study of Reaction NH3 + H NH2 + H2 by a Simple Program to Determine the Reaction Rate

    E-print Network

    Study of Reaction NH3 + H NH2 + H2 by a Simple Program to Determine the Reaction Rate Patr´icia R developed a simple program to determine the reaction rate by using conventional transition state theory abstraction in the reaction NH3 + H NH2 + H2 is used as a model to demonstrate usage of the program. The rate

  3. 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.

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

    PubMed

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

    2014-12-14

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

  5. 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.

  6. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  9. KFPA Mapping of NH3 in the G111 Infrared Dark Cloud Filament

    NASA Astrophysics Data System (ADS)

    Schlingman, Wayne M.; Shirley, Y. L.; Langston, G.; Ginsburg, A.

    2012-01-01

    We present new K-band Focal Plane Array (KFPA) maps of ammonia in the G111 Infrared Dark Cloud near NGC 7538. We observe NH3 (1,1) and (2,2) inversion transitions simultaneously on each of the KFPA's seven pixels. We also present a temperature map of the filament from the ratio of these two lines. We also present H20 masers mapped with the KFPA. We directly compare the kinetic gas temperature with the dust temperature estimated from continuum observations. We also estimate the contribution from turbulence along the filament. We compare the properties of NH3 and H2O emission with evolutionary indicators for the G111 cores.

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

    PubMed

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

    2001-01-01

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

  11. Probing hydrogen bonding orbitals: resonant inelastic soft X-ray scattering of aqueous NH3.

    PubMed

    Weinhardt, L; Ertan, E; Iannuzzi, M; Weigand, M; Fuchs, O; Bär, M; Blum, M; Denlinger, J D; Yang, W; Umbach, E; Odelius, M; Heske, C

    2015-10-28

    To probe the influence of hydrogen bonding on the electronic structure of ammonia, gas phase and aqueous NH3 have been investigated using soft X-ray absorption (XAS), resonant inelastic soft X-ray scattering (RIXS), and electronic structure calculations including dynamical effects. Strong spectral differences in the XAS scans as well as in the RIXS spectra between gas phase and aqueous NH3 are attributed to orbital mixing with the water orbitals, dipole-dipole interactions, differences in vibronic coupling, and nuclear dynamics on the time-scale of the RIXS process. All of these effects are consequences of hydrogen bonding and the impact of the associated orbitals, demonstrating the power of XAS and RIXS as unique tools to study hydrogen bonding in liquids. PMID:26417728

  12. 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

  13. Semiclassical line broadening calculations using an ab initio potential. Application to NH3 perturbed by argon

    NASA Astrophysics Data System (ADS)

    Ayari, C.; Loreau, J.; Dhib, M.; Daussy, C.; Aroui, H.

    2015-12-01

    The semiclassical formalism of Robert and Bonamy is used to calculate the linewidths of rovibrational transitions of ammonia in collision with argon. Two accurate ab initio potential energy surfaces (PES) have been applied to model the NH3-Ar interactions. In this work and contrary to our previous calculations, the transitions with ?K = ±3n (n integer) have been introduced into the expressions of the differential collision cross section S(b). Comparisons with previous theoretical and experimental studies are reported. A detailed analysis of the contribution of the various anisotropic components of the PES shows that the induced ?K = ±3 transitions play a crucial role. Calculations performed in the ?4 and ?1 vibrational bands of NH3 are in good agreement with the experimental data and correct dependences of the broadening coefficients with the rotational quantum numbers J and K are obtained.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    High-resolution absorption spectra of NH3 in the region 500-2100 cm-1 at temperatures up to 1027 °C and approximately atmospheric pressure (1013±20 mbar) are measured. NH3 concentrations of 1000 ppm, 0.5% and 1% in volume fraction were used in the measurements. Spectra are recorded in high temperature gas flow cells using a Fourier Transform Infrared (FTIR) spectrometer at a nominal resolution of 0.09 cm-1. Measurements at 22.7 °C are compared to high-resolution cross sections available from the Pacific Northwest National Laboratory (PNNL). The higher temperature spectra are analysed by comparison to a variational line list, BYTe, and experimental energy levels determined using the MARVEL procedure. Approximately 2000 lines have been assigned, of which 851 are newly assigned to mainly hot bands involving vibrational states as high as v2=5.

  15. Room-Temperature NH3 Gas Sensor Based on Hydrothermally Grown ZnO Nanorods

    NASA Astrophysics Data System (ADS)

    Wei, Ang; Wang, Zhao; Pan, Liu-Hua; Li, Wei-Wei; Xiong, Li; Dong, Xiao-Chen; Huang, Wei

    2011-08-01

    A NH3 gas sensor based on a ZnO nanorod array is fabricated by hydrothermal decomposition on a Au electrode. The as-grown ZnO nanorods have uniform diameter distribution and good crystal structure, shown by scanning electron microscopy, x-ray diffraction, high resolution transmission electron microscopy and photoluminescence emission characterizations. The gas sensing results show that the ZnO nanorod-based device responds well to ammonia gas at room temperature (sensitivity S is about 8).

  16. 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 ? or ? 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. PMID:26269196

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

    NASA Astrophysics Data System (ADS)

    Vorderwisch, Peter; Sobolev, Oleg; Desmedt, Arnaud

    2004-07-01

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

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

    PubMed

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

    2015-11-11

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

  19. Dynamics of CH3NH3PbI3 from first principles simulations

    NASA Astrophysics Data System (ADS)

    Kachmar, Ali; Carignano, Marcelo

    2015-03-01

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

  20. 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.

  1. Experimental Study of Coaxial Cylinder Dielectric Barrier Discharge in Ar/NH3 Mixtures under the Atmosphere-Pressure.

    PubMed

    Li, Yan-qin; Bu, De-cai; Di, Lan-bo; Zhang, Xiu-ling; Liu, Zhi-sheng; Li, Xue-hui

    2015-03-01

    An atmosphere-pressure Dielectric Barrier Discharge in Ar/NH3 mixtures between cylinder electrodes is studied by Optical Emission Spectroscopy and the main particles of atmosphere-pressure Ar/NH3 DBD plasma are NH, N, N+, N2, Ar, H(?) and OH. NH is decomposition products of NH3, and NH(c 1?) and NH(A 3?) are two kinds of excited-state neutral particles and produced by penning ionization of Ar* and NH3. The nitrogen active atom is detected at 674.5 nm which may provide the experimental foundation for the synthesis of ?-Fe3N ferroparticles by the atmosphere-pressure Ar/NH3 DBD plasma. The intensities of main particles are analyzed at different NH3 flow rate and applied voltage peak-peak value. The results show that the spectral line intensities of various particles increase with the rise of the applied voltage peak-peak value at the same NH3 flow rate, and first increase and then decrease with the increase of the NH3 flow rate at the same applied voltage peak-peak value. The applied voltage peak-peak value being kept constant, the spectral line intensity of nitrogen active atom first increases and then decreases with the increase of the NH3 flow rate. When NH3 flow rate is 20 mL x min(-1), the spectral line intensity of nitrogen active atom reaches a maximum at the same applied voltage peak-peak value. The spectral line intensity of nitrogen active atom decreases gradually with increasing the applied voltage peak-peak value at the same NH3 flow rate and it is mainly because of the translation of discharge mode from multi-pulse APGD to filamentary discharge in the atmosphere-pressure Ar/NH3 DBD. The microdischarge channels overlap and the microdischarges affect each other in multi-pulse APGD; hence the increasing rate of the spectral line intensity is quicker in multi-pulse APGD than in filamentary discharge with increasing the applied voltage peak-peak value. When the applied voltage peak-peak value is up from 4 600 to 6 400 V, the single-pulse and two-pulse APGD mode which are two kinds of homogeneous DBD mode are found in the atmosphere-pressure Ar/NH3 DBD and the increasing rate of the spectral line intensity is quicker in multi-pulse APGD than in filamentary discharge which is beneficial to synthesize ?-Fe3N ferroparticles. PMID:26117894

  2. 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. PMID:25216367

  3. Characterizing the influence of highways on springtime NO2 and NH3 concentrations in regional forest monitoring plots.

    PubMed

    Watmough, Shaun A; McDonough, Andrew M; Raney, Shanel M

    2014-07-01

    Highways are major sources of nitrogen dioxide (NO2) and ammonia (NH3). In this study, springtime NO2 and NH3 concentrations were measured at 17 Ontario Forest Biomonitoring Network (OFBN) plots using passive samplers. Average springtime NO2 concentrations were between 1.3 ?g m(-3) and 27 ?g m(-3), and NH3 concentrations were between 0.2 ?g m(-3) and 1.7 ?g m(-3), although concentrations measured in May (before leaf out) were typically twice as high as values recorded in June. Average NO2 concentrations, and to a lesser extent NH3, could be predicted by road density at all radii (around the plot) tested (500 m, 1000 m, 1500 m). Springtime NO2 concentrations were predicted for a further 50 OFBN sites. Normalized plant/lichen N concentrations were positively correlated with estimated springtime NO2 and NH3 concentrations. Epiphytic foliose lichen richness decreased with increasing NO2 and NH3, but vascular plant richness was positively related to estimated springtime NO2 and NH3. PMID:24747347

  4. Desorption kinetics from a surface derived from direct imaging of the adsorbate layer

    NASA Astrophysics Data System (ADS)

    Günther, S.; Mente?, T. O.; Niño, M. A.; Locatelli, A.; Böcklein, S.; Wintterlin, J.

    2014-05-01

    There are numerous indications that adsorbed particles on a surface do not desorb statistically, but that their spatial distribution is important. Evidence almost exclusively comes from temperature-programmed desorption, the standard method for measuring desorption rates. However, this method, as a kinetics experiment, cannot uniquely prove an atomic mechanism. Here we report a low-energy electron microscopy investigation in which a surface is microscopically imaged while simultaneously temperature-programmed desorption is recorded. The data show that during desorption of oxygen molecules from a silver single crystal surface, islands of oxygen atoms are present. By correlating the microscopy and the kinetics data, a model is derived that includes the shapes of the islands and assumes that the oxygen molecules desorb from the island edges. The model quantitatively reproduces the complex desorption kinetics, confirming that desorption is affected by islands and that the often used mean-field treatment is inappropriate.

  5. Experimental and theoretical studies of reactions of neutral vanadium and tantalum oxide clusters with NO and NH3.

    PubMed

    Heinbuch, S; Dong, F; Rocca, J J; Bernstein, E R

    2010-11-01

    Reactions of neutral vanadium and tantalum oxide clusters with NO, NH(3), and an NO/NH(3) mixture in a fast flow reactor are investigated by time of flight mass spectrometry and density functional theory (DFT) calculations. Single photon ionization through a 46.9 nm (26.5 eV) extreme ultraviolet (EUV) laser is employed to detect both neutral cluster distributions and reaction products. Association products VO(3)NO and V(2)O(5)NO are detected for V(m)O(n) clusters reacting with pure NO, and reaction products, TaO(3,4)(NO)(1,2), Ta(2)O(5)NO, Ta(2)O(6)(NO)(1-3), and Ta(3)O(8)(NO)(1,2) are generated for Ta(m)O(n) clusters reacting with NO. In both instances, oxygen-rich clusters are the active metal oxide species for the reaction M(m)O(n)+NO?M(m)O(n)(NO)(x). Both V(m)O(n) and Ta(m)O(n) cluster systems are very active with NH(3). The main products of the reactions with NH(3) result from the adsorption of one or two NH(3) molecules on the respective clusters. A gas mixture of NO:NH(3) (9:1) is also added into the fast flow reactor: the V(m)O(n) cluster system forms stable, observable clusters with only NH(3) and no V(m)O(n)(NO)(x)(NH(3))(y) species are detected; the Ta(m)O(n) cluster system forms stable, observable mixed clusters, Ta(m)O(n)(NO)(x)(NH(3))(y), as well as Ta(m)O(n)(NO)(x) and Ta(m)O(n)(NH(3))(y) individual clusters, under similar conditions. The mechanisms for the reactions of neutral V(m)O(n) and Ta(m)O(n) clusters with NO/NH(3) are explored via DFT calculations. Ta(m)O(n) clusters form stable complexes based on the coadsorption of NO and NH(3). V(m)O(n) clusters form weakly bound complexes following the reaction pathway toward end products N(2)+H(2)O without barrier. The calculations give an interpretation of the experimental data that is consistent with the condensed phase reactivity of V(m)O(n) catalyst and suggest the formation of intermediates in the catalytic chemistry. PMID:21054039

  6. Overtone, 2NH (?1 + ?3) spectroscopy of 15NH3-Ar

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  8. 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

    2015-12-01

    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. PMID:26551036

  9. Control of charge transport in the perovskite CH3 NH3 PbI3 thin film.

    PubMed

    Shi, Jiangjian; Wei, Huiyun; Lv, Songtao; Xu, Xin; Wu, Huijue; Luo, Yanhong; Li, Dongmei; Meng, Qingbo

    2015-03-16

    Carrier density and transport properties in the CH3 NH3 PbI3 thin film have been investigated. It is found that the carrier density, the depletion field, and the charge collection and transport properties in the CH3 NH3 PbI3 absorber film can be controlled effectively by different concentrations of reactants. That is, the carrier properties and the self-doping characteristics in CH3 NH3 PbI3 films are strongly influenced by the reaction thermodynamic and kinetic processes. Furthermore, by employing mixed solvents with ethanol and isopropanol to deposit the CH3 NH3 PbI3 film, the charge collection and transport efficiencies are improved significantly, thereby yielding an overall enhanced cell performance. PMID:25581504

  10. Improvement of CH3NH3PbI3 Formation for Efficient and Better Reproducible Mesoscopic Perovskite Solar Cells.

    PubMed

    Jiang, Changyun; Lim, Siew Lay; Goh, Wei Peng; Wei, Feng Xia; Zhang, Jie

    2015-11-11

    High-performance perovskite solar cells (PSCs) are obtained through optimization of the formation of CH3NH3PbI3 nanocrystals on mesoporous TiO2 film, using a two-step sequential deposition process by first spin-coating a PbI2 film and then submerging it into CH3NH3I solution for perovskite conversion (PbI2 + CH3NH3I ? CH3NH3PbI3). It is found that the PbI2 morphology from different film formation process (thermal drying, solvent extraction, and as-deposited) has a profound effect on the CH3NH3PbI3 active layer formation and its nanocrystalline composition. The residual PbI2 in the active layer contributes to substantial photocurrent losses, thus resulting in low and inconsistent PSC performances. The PbI2 film dried by solvent extraction shows enhanced CH3NH3PbI3 conversion as the loosely packed disk-like PbI2 crystals allow better CH3NH3I penetration and reaction in comparison to the multicrystal aggregates that are commonly obtained in the thermally dried PbI2 film. The as-deposited PbI2 wet film, without any further drying, exhibits complete conversion to CH3NH3PbI3 in MAI solution. The resulting PSCs reveal high power conversion efficiency of 15.60% with a batch-to-batch consistency of 14.60 ± 0.55%, whereas a lower efficiency of 13.80% with a poorer consistency of 11.20 ± 3.10% are obtained from the PSCs using thermally dried PbI2 films. PMID:26492516

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

    PubMed Central

    2012-01-01

    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. PMID:22401350

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

    PubMed

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

    2016-01-14

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

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

    PubMed

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

    2015-01-01

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

  14. The G305 star forming complex: Wide-Area molecular mapping of NH3 and H2O masers

    E-print Network

    Hindson, L; Urquhart, J S; Clark, J S; Davies, B

    2010-01-01

    We present wide area radio (12 mm) Mopra Telescope observations of the complex and rich massive star forming region G305. Our goals are to determine the reservoir for star formation within G305 using NH3 to trace the dense molecular content, and thus, the gas available to form stars; estimate physical parameters of detected NH3 clumps (temperature, column density, mass etc); locate current areas of active star formation via the presence of H2O and methanol masers and the distribution of YSOs and ultra compact HII regions associated with this region. This paper details the NH3 (J,K), (1,1), (2,2) and (3,3) inversion transition and 22 GHz H2O maser observations. We observed a \\sim 1.5\\circ x 1\\circ region with \\sim 2' angular resolution and a sensitivity of \\sim 60 mK per 0.4 km s^-1 channel. We identify 15 NH3 (1,1), 12 NH3 (2,2) and 6 NH3 (3,3) clumps surrounding the central HII region. The sizes of the clumps vary between 10^4 M\\odot and find the total molecular mass of the complex to be \\sim 6x10^5 M\\odot....

  15. Enhanced NH3-Sensitivity of Reduced Graphene Oxide Modified by Tetra-?-Iso-Pentyloxymetallophthalocyanine Derivatives

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  16. Enhanced NH3-Sensitivity of Reduced Graphene Oxide Modified by Tetra-?-Iso-Pentyloxymetallophthalocyanine Derivatives.

    PubMed

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

    2015-12-01

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

  17. Plasma nitridation of silicon by N2 and NH3 in PECVD reactor

    NASA Astrophysics Data System (ADS)

    Bakardjieva, V. S.; Alexieva, Z. I.; Beshkov, G. D.; Mateev, E. S.

    2010-04-01

    The effect was investigated of nitrogen and ammonia plasma treatment of monocrystalline Si wafers. The experiments were carried out in a plasma-enhanced chemical vapor deposition reactor. The wafers were subjected to N2 and NH3 plasma treatment for varying times at temperature of 380 °C. The plasma treated surfaces were studied by transmission electron microscopy with C-Pt replicas, reflection high-energy electron diffraction and Auger electron spectroscopy. The results point to the growth of an amorphous layer on the surface. The Auger electron spectroscopy depth profiles obtained by sputtering show the presence of an oxynitride layer with varying composition depending on the time of plasma treatment. The Auger electron spectroscopy analysis shows that after 60 s of treatment in N2 plasma, the nitrogen content is 8 at.%, while after 300 s it is 22 at.%, the thickness of the oxynitride nanolayer being 2.5-7.2 nm. In the case of NH3 plasma the thickness calculated from the sputtering time (from 50 s to 15 min) varies between 2 and 12 nm, and the nitrogen content, between 5 and 35 at.%.

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

    PubMed

    Paoli, Luca; Masla?áková, Ivana; Grassi, Alice; Ba?kor, 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?g/m(3)), an area of intermediate impact (2-35?g/m(3)) and an area of high impact (10-315?g/m(3)), with a peak of pollution reached between the fourth and fifth week. Ammonia affected both the photobiont and the mycobiont in F. caperata, while in X. parietina only the photosynthetic performance of the photobiont was altered after exposure to the highest concentration. In the photobiont of F. caperata we recorded chlorophyll degradation as indicated by OD435/415 ratio, decrease of the photosynthetic performance (as reflected by the maximum quantum yield of primary photochemistry FV/FM and the performance index PIABS); in the mycobiont, ergosterol reduction, membrane lipid peroxidation (as reflected by the increase of thiobarbituric acid reactive substances), alteration (decrease) of the secondary metabolite usnic acid. No effects were detected on caperatic acid and dehydrogenase activity. In X. parietina, the only signal determined by NH3 was the alteration of FV/FM and the performance index PIABS. The results suggest that physiological parameters in N-sensitive lichens well reflect the effects of NH3 exposure and can be applied as early indicators in monitoring studies. PMID:26342688

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

    PubMed Central

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

    2009-01-01

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

  20. 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.

  1. RELAP5/MOD2 assessment simulation of semiscale MOD-2C test S-NH-3

    SciTech Connect

    Megahed, M M

    1987-10-01

    This report documents an evaluation of the RELAP5/MOD2/Cycle 36.05 thermal hydraulic computer code for a simulation of a small-break loss-of-coolant accident transient (SBLOCA). The experimental data base for the evaluation is the results of Test S-NH-3 performed in the Semiscale MOD-2C test facility. The test modeled a 0.5% SBLOCA with an accompanying failure of the high-pressure injection emergency core cooling system. The test facility and RELAP5/MOD2 model used in the calculations are described. Evaluations of the accuracy of the calculations are presented in the form of comparisons of measured and calculated histories of selected parameters associated with the primary and secondary systems. A conclusion was reached that the code is capable of making SBLOCA calculations efficiently. However, some of the SBLOCA-related phenomena were not properly predicted by the code, suggesting a need for code improvement.

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

    PubMed

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

    2012-11-01

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

  3. Electronic structure evolution of fullerene on CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Wang, Chenggong; Wang, Congcong; Liu, Xiaoliang; Kauppi, John; Shao, Yuchuan; Xiao, Zhengguo; Bi, Cheng; Huang, Jinsong; Gao, Yongli

    2015-03-01

    The thickness dependence of fullerene on CH3NH3PbI3 perovskite film 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 perovskite film to fullerene molecules. Further deposition of fullerene forms C60 solid, accompanied by the reduction of the electron transfer. The strongest electron transfer happened at 1/4 monolayer of fullerene.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

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

    PubMed

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

    2013-08-15

    The analytical, full-dimensional, and global representation of the potential energy surface of NH(3) in the lowest adiabatic electronic state developed previously (Marquardt, R.; et al. J. Phys. Chem. B 2005, 109, 8439–8451) is improved by adjustment of parameters to an enlarged set of electronic energies from ab initio calculations using the coupled cluster method with single and double substitutions and a perturbative treatment of connected triple excitations (CCSD(T)) and the method of multireference configuration interaction (MRCI). CCSD(T) data were obtained from an extrapolation of aug-cc-pVXZ results to the basis set limit (CBS), as described in a previous work (Yurchenko, S.N.; et al. J. Chem. Phys 2005, 123, 134308); they cover the region around the NH3 equilibrium structures up to 20,000 hc cm(–1). MRCI energies were computed using the aug-cc-pVQZ basis to describe both low lying singlet dissociation channels. Adjustment was performed simultaneously to energies obtained from the different ab initio methods using a merging strategy that includes 10,000 geometries at the CCSD(T) level and 500 geometries at the MRCI level. Characteristic features of this improved representation are NH3 equilibrium geometry r(eq)(NH(3)) ? 101.28 pm, ?(eq)(NH(3)) ? 107.03°, the inversion barrier at r(inv)(NH(3)) ? 99.88 pm and 1774 hc cm(–1) above the NH(3) minimum, and dissociation channel energies 41,051 hc cm(–1) (for NH(3) ? ((2)B(2))NH(2) + ((2)S(1/2))H) and 38,450 hc cm(–1) (for NH(3) ? ((3)?(–))NH +((1)?(g)(+))H(2)); the average agreement between calculated and experimental vibrational line positions is 11 cm(–1) for (14)N(1)H(3) in the spectral region up to 5000 cm(–1). A survey of our current knowledge on the vibrational spectroscopy of ammonia and its isotopomers is also given. PMID:23688044

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    PubMed

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

    1992-01-01

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

  8. Ultrasensitive Photodetectors Based on Island-Structured CH3NH3PbI3 Thin Films.

    PubMed

    Zhang, Yin; Du, Juan; Wu, Xiaohan; Zhang, Guoqian; Chu, Yingli; Liu, Dapeng; Zhao, Yixin; Liang, Ziqi; Huang, Jia

    2015-10-01

    CH3NH3PbI3 perovskite-based optoelectronics have attracted intense research interests recently because of their easy fabrication process and high power conversion efficiency. Herein, we report a novel photodetector based on unique CH3NH3PbI3 perovskite films with island-structured morphology. The light-induced electronic properties of the photodetectors were investigated and compared to those devices based on conventional compact CH3NH3PbI3 films. The island-structured CH3NH3PbI3 photodetectors exhibited a rapid response speed (<50 ms), good stability at a temperature of up to 100 °C, a large photocurrent to dark current ratio (Ilight/Idark > 1 × 10(4) under an incident light of ?6.59 mW/cm(2), and Ilight/Idark > 1 × 10(2) under low incident light ?0.018 mW/cm(2)), and excellent reproducibility. Especially, the performance of the island-structured devices markedly exceed that of the conventional compact CH3NH3PbI3 thin-film devices. These excellent performances render the island-structured device to be potentially applicable for a wide range of optoelectronics. PMID:26387552

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

    NASA Astrophysics Data System (ADS)

    Liu, Xunchen; Xu, Yunjie

    2011-06-01

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

  10. CO and N$_2$ desorption energies from water ice

    E-print Network

    Fayolle, Edith C; Loomis, Ryan; Bergner, Jennifer; Graninger, Dawn M; Rajappan, Mahesh; Öberg, Karin I

    2015-01-01

    The relative desorption energies of CO and N$_2$ are key to interpretations of observed interstellar CO and N$_2$ abundance patterns, including the well-documented CO and N$_2$H$^+$ anti-correlations in disks, protostars and molecular cloud cores. Based on laboratory experiments on pure CO and N$_2$ ice desorption, the difference between CO and N$_2$ desorption energies is small; the N$_2$-to-CO desorption energy ratio is 0.93$\\pm$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 $^{13}$CO and $^{15}$N$_2$ on porous and compact amorphous water ices and, for reference, of pure ices. In all experiments, $^{15}$N$_2$ desorption begins a few degrees before the onset of $^{13}$CO desorption. The $^{15}$N$_2$ and $^{13}$CO energy barriers are 770 and 866 K for the pure ices, 1034-1143 K and 1155-1298 K for different sub-monolayer co...

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

    PubMed

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

    2015-10-28

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

  12. Characterization of Biochar using Temperature Programmed Oxidation

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  13. 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.

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

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    2004-01-01

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

  15. Microstructures and properties of CH3NH3PbI3-xClx hybrid solar cells

    NASA Astrophysics Data System (ADS)

    Suzuki, Kohei; Suzuki, Atsushi; Zushi, Masahito; Oku, Takeo

    2015-02-01

    Halide-perovskite CH3NH3PbI3 was produced on mesoporous TiO2 layer by spin-coating a precursor solution of PbCl2 and CH3NH3I in dimethylformamide. The role of the annealing process and chlorine (Cl) doping for the perovskite-phase formation was investigated. It was found that crystallization of the perovskite materials was stimulated by the annealing process, and that longer annealing time is necessary for the Cl-doped perovskite compared with that of non-doped perovskite phase.

  16. Ultra-Low Thermal Conductivity in Organic-Inorganic Hybrid Perovskite CH3NH3PbI3.

    PubMed

    Pisoni, Andrea; Ja?imovi?, Ja?im; Bariši?, Osor S; Spina, Massimo; Gaál, Richard; Forró, László; Horváth, Endre

    2014-07-17

    We report on the temperature dependence of thermal conductivity of single crystalline and polycrystalline organometallic perovskite CH3NH3PbI3. The comparable absolute values and temperature dependence of the two samples' morphologies indicate the minor role of the grain boundaries on the heat transport. Theoretical modeling demonstrates the importance of the resonant scattering in both specimens. The interaction between phonon waves and rotational degrees of freedom of CH3NH3(+) sublattice emerges as the dominant mechanism for attenuation of heat transport and for ultralow thermal conductivity of 0.5 W/(Km) at room temperature. PMID:26277821

  17. Water desorption from nanostructured graphite surfaces.

    PubMed

    Clemens, Anna; Hellberg, Lars; Grönbeck, Henrik; Chakarov, Dinko

    2013-12-21

    Water interaction with nanostructured graphite surfaces is strongly dependent on the surface morphology. In this work, temperature programmed desorption (TPD) in combination with quadrupole mass spectrometry (QMS) has been used to study water ice desorption from a nanostructured graphite surface. This model surface was fabricated by hole-mask colloidal lithography (HCL) along with oxygen plasma etching and consists of a rough carbon surface covered by well defined structures of highly oriented pyrolytic graphite (HOPG). The results are compared with those from pristine HOPG and a rough (oxygen plasma etched) carbon surface without graphite nanostructures. The samples were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The TPD experiments were conducted for H2O coverages obtained after exposures between 0.2 and 55 langmuir (L) and reveal a complex desorption behaviour. The spectra from the nanostructured surface show additional, coverage dependent desorption peaks. They are assigned to water bound in two-dimensional (2D) and three-dimensional (3D) hydrogen-bonded networks, defect-bound water, and to water intercalated into the graphite structures. The intercalation is more pronounced for the nanostructured graphite surface in comparison to HOPG surfaces because of a higher concentration of intersheet openings. From the TPD spectra, the desorption energies for water bound in 2D and 3D (multilayer) networks were determined to be 0.32 ± 0.06 and 0.41 ± 0.03 eV per molecule, respectively. An upper limit for the desorption energy for defect-bound water was estimated to be 1 eV per molecule. PMID:24018989

  18. 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 ?-OH- and ?-(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. PMID:26493181

  19. The NH3 Hyperfine Intensity Anomaly in High-Mass Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Camarata, Matthew A.; Jackson, James M.; Chambers, Edward

    2015-06-01

    Anomalous ammonia (NH3) spectra, exhibiting asymmetric hyperfine satellite intensity profiles in the (J,K) = (1, 1) inversion transition, have been observed in star-forming regions for over 35 years. We present a systematic study of this “hyperfine intensity anomaly” (HIA) toward a sample of 334 high-mass star forming regions: 310 high-mass (?100 {{M}? }) clumps and 24 infrared dark clouds. The HIA is ubiquitous in high-mass star forming regions. Although LTE excitation predicts that the intensity ratios of the outer satellites and inner satellites are exactly unity, for this sample the ensemble average ratios are 0.812 ± 0.004 and 1.125 ± 0.005, respectively. We have quantified the HIA and find no significant relationships between the HIA and temperature, line width, optical depth, and the stage of stellar evolution. The fact that HIAs are common in high-mass star-forming regions suggests that the conditions that lead to HIAs are ubiquitous in these regions. A possible link between HIAs and the predictions of the competitive accretion model of high-mass star formation is suggested; however, the expected trends of HIA strength with clump evolutionary stage, rotational temperature, and line width for evolving cores in competitive accretion models are not found. Thus, the exact gas structures that produce HIAs remain unknown. Turbulent gas structures are a possible explanation, but the details need to be explored.

  20. 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.

  1. 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.

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

    PubMed

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

    2013-05-28

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

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

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

    PubMed

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

    2015-04-01

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

  5. Electronic Structure Evolution of Fullerene on CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Wang, Chenggong; Wang, Congcong; Liu, Xiaoliang; Bi, Cheng; Shao, Yuchuan; Xiao, Zhengguo; Huang, Jinsong; Gao, Yongli

    2015-03-01

    The thickness dependence of fullerene on CH3NH3PbI3 perovskite film 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 (LUMO) 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 an initial shift of core levels to lower binding energy in the perovskite, which indicates that electrons transfer from the perovskite film to fullerene molecules. We observed that the WF of the perovskite is 5.0 eV and the VBM is 0.6 eV. The band gap of the perovskite is 1.66 eV, which is in accordance with previous reports. We also observed the HOMO level of C60 shifts to lower binding energy, indicating a band bending in the C60 region. The perovskite core levels show a strong initial shift to lower binding energy, indicating electron transfer from the perovskite film to fullerene molecules. The strongest electron transfer happened at 1/4 monolayer of fullerene, and further deposition reduced the transfer as forms fullerene forms C60 solid film. NSF CBET-1437656.

  6. 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.

  7. Novel nanoporous MnOx (x=?1.75) sorbent for the removal of SO2 and NH3 made from MnC2O4·2H2O.

    PubMed

    Ma, Xiaowei; Campbell, Nicholas; Madec, Lénaïc; Rankin, Matthew A; Croll, Lisa M; Dahn, J R

    2016-03-01

    In this work, nanoporous manganese oxides (MnOx) were prepared by thermal decomposition of MnC2O4·2H2O at 225°C for 6h in air. The manganese oxalate dihydrate precipitate was made from manganese sulfate and ammonium oxalate during ultrasonication and stirring. The physical properties of the oxalate precursors and the resulting MnOx samples were characterized with SEM, TGA-DSC, FTIR and powder XRD. The specific surface areas and porosity of MnOx were studied by single-point BET and multi-point N2 adsorption-desorption measurements. The amorphous MnOx from oxalate prepared by sonication showed a specific surface area as large as 499.7m(2)/g. Dynamic SO2 and NH3 flow tests indicated that the adsorption capacity of MnOx, especially for SO2, can be increased by increased surface area. Compared to the best Mn3O4-impregnated activated carbon adsorbent, nanoporous MnOx could remove approximately three times as much SO2 and a comparable amount of NH3 per gram of adsorbent. This could lead to respirators of lower weight and smaller size which will be attractive to users. PMID:26692496

  8. Mechanisms for sealing of porous low-k SiOCH by combined He and NH3 plasma treatment

    E-print Network

    Kushner, Mark

    Mechanisms for sealing of porous low-k SiOCH by combined He and NH3 plasma treatment Juline Shoeba the dielectric constant and so decrease the RC time delay. Sealing of the pores (up to a few nm in diameter is potentially a means of sealing pores while maintaining the low-k of the dielectric. The He plasma activates

  9. Effects of NH3 and N2 additions to hot filament activated CH4 H2 gas mixtures

    E-print Network

    Bristol, University of

    densities, and NH column densities, in a hot filament HF reactor designed for diamond chemical vapor in the formation of N atoms with calculated steady state number densities 1013 cm 3 in the case of 1% NH3 additions to participate in diamond growth. The deduced reduction in CH3 number density due to competing gas phase

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

    PubMed

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

    2015-04-14

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  12. Ultralow Absorption Coefficient and Temperature Dependence of Radiative Recombination of CH3NH3PbI3 Perovskite from

    E-print Network

    Perovskite from Photoluminescence Chog Barugkin, Jinjin Cong, The Duong, Shakir Rahman, Hieu T. Nguyen perovskite methylammonium lead iodide (CH3NH3PbI3) films from 675 to 1400 nm. Unlike other methods used of organic-inorganic halide perovskite- based solar cells has attracted enormous interest from the entire PV

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

    PubMed

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

    2015-02-01

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

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

    PubMed

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

    2015-12-01

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

  15. Proton transfer dynamics of the reaction H3O ,,NH3 ,H2O...NH4

    E-print Network

    Farrar, James M.

    Proton transfer dynamics of the reaction H3O¿ ,,NH3 ,H2O...NH4 ¿ studied using the crossed, Rochester, New York 14627 Received 29 September 2003; accepted 8 October 2003 The proton transfer reaction combination. These results indicate that the proton transfer proceeds through a direct reaction mechanism

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

    PubMed

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

    2015-12-01

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

  17. Crystal structure of the ionic liquid EtNH3NO3-insights into the thermal phase behavior of protic ionic liquids.

    PubMed

    Henderson, Wesley A; Fylstra, Paul; De Long, Hugh C; Trulove, Paul C; Parsons, Simon

    2012-12-14

    The crystal structure of the salt ethylammonium nitrate (EtNH(3)NO(3)) has been determined. EtNH(3)NO(3) is one of the most widely studied protic ionic liquids (PILs)-ILs formed by proton transfer from a Brønsted acid to a Brønsted base. The structural features from the crystal structure, in concert with a Raman spectroscopic analysis of the ions, provide direct insight as to why EtNH(3)NO(3) melts below ambient temperature, while other related salts (such as EtNH(3)Cl) do not. PMID:23099473

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

    SciTech Connect

    Partridge Jr, William P; Choi, Jae-Soon

    2009-01-01

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

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

    PubMed

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

    2015-01-01

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

  20. 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. PMID:23437676

  1. 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. PMID:25302396

  2. 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.

  3. Synthesis, structure and magnetic characterization of a one-dimensional iron phosphate, [NH3CH2CH2CH(NH3)CH2CH3]2+ ?1[FeF(HPO4) 2]2-

    NASA Astrophysics Data System (ADS)

    Mandal, Sukhendu; Natarajan, Srinivasan; Klein, Wilhelm; Panthöfer, Martin; Jansen, Martin

    2003-07-01

    The hydrothermal synthesis, structure and magnetic studies of a one-dimensional iron fluro-phosphate, [NH3CH2CH2CH(NH3)CH2CH3]2+ ?1[FeF(HPO4) 2]2- , I, is presented. The structure, solved by single-crystal X-ray diffraction, consists of isolated 1?[FeF(HPO 4) 2] 2- chains of the tancoite type with diprotonated amine molecules situated in between. Magnetic studies indicate anti-ferromagnetic interactions. Crystal data: space group= P2 1/ m (no. 12), a=8.846(2) Å, b=7.211(1) Å, c=9.893(2) Å, ?=97.10(3)°, V=626.2(2) Å 3, Z=4, ?calc=1.968 g cm -3, ?(Mo K?)=1.511 mm -1, R1=0.044, w R2=0.099, S=1.016 for 134 parameters.

  4. Optical band gap transition from direct to indirect induced by organic content of CH3NH3PbI3 perovskite films

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    Most of the systematic studies on tuning the band gap in the family of organolead halide perovskites have focused on changing the compositions of halogens. Here, the effects of varying the organic content on the band gap of CH3NH3PbI3 were studied. The methylammonium lead iodide (CH3NH3PbI3) films were fabricated with different molar ratios of CH3NH3I to PbI2. We found that the films become compact and the crystalline size decreased from 6.0 to 0.2 ?m and the optical band gap of CH3NH3PbI3 could be transferred from direct to indirect with increasing CH3NH3I content in the precursor. The experimental results demonstrated that the existence of the indirect band gap in CH3NH3PbI3 film and the CH3NH3I content plays a key role in adjusting the film morphology and optical band. The investigation of the optical band transition induced by changing organic content could provide a different view on studying CH3NH3PbI3 materials.

  5. Kinetic compensation effect in thermal desorption

    NASA Astrophysics Data System (ADS)

    Zuniga-Hansen, Nayeli; Silbert, Leonardo E.; Calbi, Mercedes

    The parameters which characterize the rates of many thermally activated processes are often extracted using the Arrhenius equation. A series of closely related thermally activated processes exhibit systematic variations in the energies of activation, Ea, and preexponential factor, ?, in response to a perturbation, which leads to the concept of `kinetic compensation', such that the different parameters in the Arrhenius equation balance each other out thereby leading to an implicitly assumed constant rate. However, the compensation effect has not been generally demonstrated and its origins are not completely understood. Using kinetic Monte Carlo simulations on a model interface, we explore how site-adsorbate and adsorbate-adsorbate interactions, and surface structural changes influence surface coverage and the kinetic parameters during a typical temperature programmed desorption process. We find that the concept of the compensation effect for interacting species breaks down and the time characterizing desorption increases with increasing interaction strength due to an increase in the effective activation energy. At the `molecular' level the changes are the result of enhanced site correlations with increasing adsorbate interaction strength suppressing the onset of desorption.

  6. Effect of NH3 plasma passivation on the electrical characteristics of a nanolaminated ALD HfAlO on InGaAs MOS capacitor

    NASA Astrophysics Data System (ADS)

    Choi, Jae-Sung; Park, Jea-Gun

    2015-06-01

    The electrical characteristics of a nanolaminated atomic layer deposition (ALD) HfAlO/InGaAs metal-oixde-semiconductor (MOS) capacitor with NH3 plasma passivation are investigated. Results show that the samples with NH3 plasma passivation exhibit better capacitance behavior with relatively small frequency dispersion in the inversion region than the unpassivated sample. The leakage current level of the NH3 plasma-passivated samples shows a much lower value compared to the unpassivated sample. The mid-gap value for the density of interface traps, D it , also shows that NH3 plasma-passivated samples have relatively low values compared to the unpassivated sample. Superior electrical performance, compared to the unpassivated sample, was demonstrated with NH3 plasma passivation through those electrical characterizations.

  7. A facile solvothermal growth of single crystal mixed halide perovskite CH3NH3Pb(Br(1-x)Cl(x))3.

    PubMed

    Zhang, Taiyang; Yang, Mengjin; Benson, Eric E; Li, Zijian; van de Lagemaat, Jao; Luther, Joseph M; Yan, Yanfa; Zhu, Kai; Zhao, Yixin

    2015-05-01

    We demonstrate a facile synthetic approach for preparing mixed halide perovskite (CH3NH3)Pb(Br1-xClx)3 single crystals by the solvothermal growth of stoichiometric PbBr2 and [(1 - y)CH3NH3Br + yCH3NH3Cl] DMF precursor solutions. The band gap of (CH3NH3)Pb(Br1-xClx)3 single crystals increased and the unit cell dimensions decreased with an increase in Cl content x, consistent with previous theoretical predictions. Interestingly, the Cl/Br ratio in the (CH3NH3)Pb(Br1-xClx)3 single crystals is larger than that of the precursor solution, suggesting an unusual crystal growth mechanism. PMID:25853846

  8. Electronic and magnetic properties of an organic multiferroic: (C2H5NH3)2CuCl4

    NASA Astrophysics Data System (ADS)

    Ding, Jun; Li, HaiSheng; Wen, LiWei; Kang, XiuBao; Li, HaiDong; Zhang, JianMin

    2013-11-01

    (C2H5NH3)2CuCl4 was proposed to be a ferroelectric material with dominant ferromagnetic interactions. Using first-principles calculations we find that the insulating state and in-plane ferromagnetism induced by dz2-x2-dz2-y2 orbital order can be expressed well by generalized gradient approximation (GGA) at ambient pressure. While the Jahn Teller distortion (JTD) is suppressed under critical pressure of 4 GPa, as a result the new dz2 orbital order leads to in-plane antiferromagnetism. Meanwhile the conventional GGA gives a wrong metal state. Our results suggest that (C2H5NH3)2CuCl4 is a strong correlated charge transfer insulator, while the depress of JTD by pressure changes it to a Mott Hubbard insulator.

  9. Exploring the PX3:NCH and PX3:NH3 potential surfaces, with X = F, Cl, and Br

    NASA Astrophysics Data System (ADS)

    Alkorta, Ibon; Elguero, José; Del Bene, Janet E.

    2015-11-01

    Ab initio MP2/aug?-cc-pVTZ calculations have been carried out to explore the PX3:NCH and PX3:NH3 potential surfaces, with X = F, Cl and Br. Four unique minima exist on the PX3:NCH surfaces, and three on the PX3:NH3 surfaces. Complexes stabilized by pnicogen bonds, hydrogen bonds, halogen bonds, and electrostatic interactions have been found at these minima. The global minimum on each surface is a complex with a P···N pnicogen bond. Binding energies at corresponding minima are ordered with respect to the PX3 molecules as PF3 < PCl3 < PBr3. Charge-transfer stabilizes all complexes with intermolecular bonds.

  10. Synthesis, structure, and properties of SrC(NH)3 , a nitrogen-based carbonate analogue with the trinacria motif.

    PubMed

    Missong, Ronja; George, Janine; Houben, Andreas; Hoelzel, Markus; Dronskowski, Richard

    2015-10-01

    Strontium guanidinate, SrC(NH)3 , the first compound with a doubly deprotonated guanidine unit, was synthesized from strontium and guanidine in liquid ammonia and characterized by X-ray and neutron diffraction, IR spectroscopy, and density-functional theory including harmonic phonon calculations. The compound crystallizes in the hexagonal space group P63 /m, constitutes the nitrogen analogue of strontium carbonate, SrCO3 , and its structure follows a layered motif between Sr(2+) ions and complex anions of the type C(NH)3 (2-) ; the anions adopt the peculiar trinacria shape. A comparison of theoretical phonons with experimental IR bands as well as quantum-chemical bonding analyses yield a first insight into bonding and packing of the formerly unknown anion in the crystal. PMID:26308739

  11. The role of NH3 and hydrocarbon mixtures in GaN pseudo-halide CVD: a quantum chemical study.

    PubMed

    Gadzhiev, Oleg B; Sennikov, Peter G; Petrov, Alexander I; Kachel, Krzysztof; Golka, Sebastian; Gogova, Daniela; Siche, Dietmar

    2014-11-01

    The prospects of a control for a novel gallium nitride pseudo-halide vapor phase epitaxy (PHVPE) with HCN were thoroughly analyzed for hydrocarbons-NH3-Ga gas phase on the basis of quantum chemical investigation with DFT (B3LYP, B3LYP with D3 empirical correction on dispersion interaction) and ab-initio (CASSCF, coupled clusters, and multireference configuration interaction including MRCI+Q) methods. The computational screening of reactions for different hydrocarbons (CH4, C2H6, C3H8, C2H4, and C2H2) as readily available carbon precursors for HCN formation, potential chemical transport agents, and for controlled carbon doping of deposited GaN was carried out with the B3LYP method in conjunction with basis sets up to aug-cc-pVTZ. The gas phase intermediates for the reactions in the Ga-hydrocarbon systems were predicted at different theory levels. The located ?-complexes Ga…C2H2 and Ga…C2H4 were studied to determine a probable catalytic activity in reactions with NH3. A limited influence of the carbon-containing atmosphere was exhibited for the carbon doping of GaN crystal in the conventional GaN chemical vapor deposition (CVD) process with hydrocarbons injected in the gas phase. Our results provide a basis for experimental studies of GaN crystal growth with C2H4 and C2H2 as auxiliary carbon reagents for the Ga-NH3 and Ga-C-NH3 CVD systems and prerequisites for reactor design to enhance and control the PHVPE process through the HCN synthesis. PMID:25316343

  12. 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.

  13. Estimating NH3 emissions from agricultural fertilizer application in China using the bi-directional CMAQ model coupled to an agro-ecosystem model

    NASA Astrophysics Data System (ADS)

    Fu, X.; Wang, S. X.; Ran, L. M.; Pleim, J. E.; Cooter, E.; Bash, J. O.; Benson, V.; Hao, J. M.

    2015-01-01

    Atmospheric ammonia (NH3) plays an important role in atmospheric chemistry. China is one of the largest NH3 emitting countries with the majority of NH3 emissions coming from the agricultural practices, such as fertilizer application and livestock. The current NH3 emission estimates in China are mainly based on pre-defined emission factors that lack the temporal or spatial details, which are needed to accurately predict NH3 emissions. In this study, we estimate, for the first time, the NH3 emission from the agricultural fertilizer application in China online using an agricultural fertilizer modeling system coupling a regional air quality model (the Community Multi-Scale Air Quality model, CMAQ) and an agro-ecosystem model (the Environmental Policy Integrated Climate model, EPIC), which improves the spatial and temporal resolution of NH3 emission from this sector. Cropland area data of 14 crops from 2710 counties and the Moderate Resolution Imaging Spectroradiometer (MODIS) land use data are combined to determine the crop distribution. The fertilizer application rate and method for different crop are collected at provincial or agriculture-regional level. The EPIC outputs of daily fertilizer application and soil characteristics are inputed into the CMAQ model and the hourly NH3 emission are calculated online with CMAQ running. The estimated agricultural fertilizer NH3 emission in this study is about 3 Tg in 2011. The regions with the highest modeled emission rates are located in the North China Plain. Seasonally, the peak ammonia emissions occur from April to July.Compared with previous researches, this method considers more influencing factors, such as meteorological fields, soil and the fertilizer application, and provides improved NH3 emission with higher spatial and temporal resolution.

  14. Effect of phosphogypsum and dicyandiamide as additives on NH3, N20 and CH4 emissions during composting.

    PubMed

    Luo, Yiming; Li, Guoxue; Luo, Wenhai; Schuchardt, Frank; Jiang, Tao; Xu, Degang

    2013-07-01

    A laboratory scale experiment of composting in a forced aeration system using pig manure with cornstalks was carried out to investigate the effects of both phosphogypsum and dicyandiamide (DCD, C2H4N4) as additives on gaseous emissions and compost quality. Besides a control, there were three amended treatments with different amounts of additives. The results indicated that the phosphogypsum addition at the rate of 10% of mixture dry weight decreased NH3 and CH4 emissions significantly during composting. The addition of DCD at the rate of 0.2% of mixture dry weight together with 10% of phosphogypsum further reduced the N2O emission by affecting the nitrification process. Reducing the phosphogypsum addition to 5% in the presence of 0.2% DCD moderately increased the NH3 emissions but not N2O emission. The additives increased the ammonium content and electrical conductivity significantly in the final compost. No adverse effect on organic matter degradation or the germination index of the compost was found in the amended treatments. It was recommended that phosphogypsum and DCD could be used in composting for the purpose of reducing NH3, CH4 and N2O emissions. Optimal conditions and dose of DCD additive during composting should be determined with different materials and composting systems in further study. PMID:24218845

  15. NH3 in Oph A: Studying the small-scale temperature structure in a cluster-forming core

    NASA Astrophysics Data System (ADS)

    Friesen, Rachel; Bourke, Tyler; di Francesco, James; Myers, Phil; Caselli, Paola; Rushton, Christopher

    2010-04-01

    We propose to observe a small mosaic over the nearby, small stellar group-forming Ophiuchus A Core in NH3 (1,1) and (2,2) inversion emission at 23.7 GHz. Ophiuchus is our nearest source of ongoing, clustered star formation, allowing sensitive, high resolution observations of the physical conditions of dense gas associated with the formation of stellar groups. Through these observations, we will determine the kinetic temperature of the dense gas associated with this active star forming region, and study the distribution, kinematics and chemical differentiation of the Core at densities n ~ 10^4 cm^-3 where the NH3 lines are excited. We will use the derived temperatures to model the physical and chemical structure of embedded small-scale clumps within Oph A using radiative transfer codes, and compare the NH3 distribution with the thermal dust continuum and previously published N2H+ observations. These data are key to understanding the initial conditions of clustered star formation in Ophiuchus, and will help constrain models of dense core fragmentation and evolution in the Oph A Core.

  16. 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

  17. Multifaceted Excited State of CH3NH3PbI3. Charge Separation, Recombination, and Trapping.

    PubMed

    Christians, Jeffrey A; Manser, Joseph S; Kamat, Prashant V

    2015-06-01

    A need to understand the excited-state behavior of organic-inorganic hybrid perovskites, such as CH3NH3PbI3, has arisen due to the rapid development of perovskite solar cells. The photoinduced processes leading to the efficient charge separation observed in these materials remain somewhat elusive. This Perspective presents an overview of the initial attempts to characterize the excited-state and charge recombination dynamics in the prototypical material CH3NH3PbI3. While much has been accomplished in designing high-efficiency solar cells, the multifaceted nature of the CH3NH3PbI3 excited state offers ample challenges for the photovoltaic community to better comprehend. Building on this foundation may enable us to tackle the stability concerns that have shadowed the rise of perovskite solar cells. Furthermore, a better understanding of the excited-state properties can provide insight into the specific properties that have thrust this material to the forefront of photovoltaic research. PMID:26266507

  18. 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

    2015-09-01

    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. PMID:26313318

  19. Fiber-Amplifier-Enhanced QEPAS Sensor for Simultaneous Trace Gas Detection of NH3 and H2S

    PubMed Central

    Wu, Hongpeng; Dong, Lei; Liu, Xiaoli; Zheng, Huadan; Yin, Xukun; Ma, Weiguang; Zhang, Lei; Yin, Wangbao; Jia, Suotang

    2015-01-01

    A selective and sensitive quartz enhanced photoacoustic spectroscopy (QEPAS) sensor, employing an erbium-doped fiber amplifier (EDFA), and a distributed feedback (DFB) laser operating at 1582 nm was demonstrated for simultaneous detection of ammonia (NH3) and hydrogen sulfide (H2S). Two interference-free absorption lines located at 6322.45 cm?1 and 6328.88 cm?1 for NH3 and H2S detection, respectively, were identified. The sensor was optimized in terms of current modulation depth for both of the two target gases. An electrical modulation cancellation unit was equipped to suppress the background noise caused by the stray light. An Allan-Werle variance analysis was performed to investigate the long-term performance of the fiber-amplifier-enhanced QEPAS sensor. Benefitting from the high power boosted by the EDFA, a detection sensitivity (1?) of 52 parts per billion by volume (ppbv) and 17 ppbv for NH3 and H2S, respectively, were achieved with a 132 s data acquisition time at atmospheric pressure and room temperature. PMID:26506351

  20. N2O and NH3 emissions from a bioreactor landfill operated under limited aerobic degradation conditions.

    PubMed

    He, Pinjing; Yang, Na; Gu, Huili; Zhang, Hua; Shao, Liming

    2011-01-01

    The combination of leachate recirculation and aeration to landfill may be an efficient way for in-situ nitrogen removal. However, nitrogenous substances contained in the landfill layer are concomitantly transformed into N2O and NH3, leading to increased emissions into the atmosphere. In the present study, the emissions of N2O and NH3 were measured under conditions of fresh or partially stabilized refuse with or without leachate recirculation or intermittent aeration. The results showed that the largest N2O emission (12.4 mg-N/L of the column) was observed in the aerated column loaded with partially stabilized refuse and recycled with the leachate of low C/N ratio; while less than 0.33 mg-N/L of the column was produced in the other columns. N2O production was positively correlated with the prolonged aerobic time and negatively related with the C/N ratio in the recycled leachate. NH3 volatilization increased with enhanced gas flow and concentration of free ammonia in the leachate, and the highest cumulative volatilization quantity was 1.7 mg-N/L of the column. PMID:22066225

  1. 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 ?_2 in an unprecedented accuracy, which revealed significant deficiencies in the NH_3 intensities, for instance, some weak ?K = 3 lines were predicted to be ~100 times stronger. Measurement of line intensity for these lines in a consistent manner is demanded because the ?K = 3 forbidden lines are only way other than collisions and l-doubled states to excite NH_3 to K > 0 levels. Recalling that NH_3 transition lines in the high J and K up to 18 were detected toward the galactic center in the star forming region of Sgr B_2, their accurate intensity measurements are critical in explaining the observed high K excitation, which will provide insights into radiative-transfer vs.levels. The interaction between a large amplitude torsional motion and the hyperfine coupling may also lead to a less known hyperfine effect, the so-called magnetic spin-torsion coupling, which was first studied by Heuvel and Dymanus and which has not yet been conclusively evidenced. In this talk, the magnetic hyperfine structure of the non-rigid methanol molecule will be investigated experimentally and theoretically. 13 hyperfine patterns were recorded using two molecular beam microwave spectrometers. These patterns, along with previously recorded ones,^c were analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling. The theoretical approach setup to analyze the observed data accounts for the spin-torsion coupling, in addition to the familiar magnetic spin-rotation and spin-spin couplings, and relies on symmetry considerations to build a hyperfine coupling Hamiltonian and a spin-rotation-torsion wavefunction compatible with the Pauli exclusion principle. In the talk, the results of the analysis will be presented. The hyperfine coupling parameters retrieved will be discussed and we hope to be able to conclusively evidence the effects of the magnetic spin-torsion. S. Yu, et al. J. Chem. Phys. (2010) 174317/1-174317/14. Coudert and Lopez, J. Mol. Spectrosc.~239 (2006) 135; and Tudorie, Coudert, Huet, Jegouso, and Sedes, J. Chem. Phys.~134 (2011) 074314

  2. 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 ?cUmo(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 ?cHmo(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 ?fHmo(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.

  3. 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 ?m), 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.

  4. Synthesis, crystal structures and properties of the bis-(trimetaphosphimato)-metallates Na 4{Co[(PO 2NH) 3] 2}·12H 2O and Na 4{Ni[(PO 2NH) 3] 2}·12H 2O

    NASA Astrophysics Data System (ADS)

    Correll, Sascha; Stock, Norbert; Schnick, Wolfgang

    2004-09-01

    Tetrasodium- bis-(trimetaphosphimato)-cobaltate(II) dodecahydrate, Na 4{Co[(PO 2NH) 3] 2}·12H 2O ( 1), and tetrasodium- bis-(trimetaphosphimato)-nickelate(II) dodecahydrate, Na 4{Ni[(PO 2NH) 3] 2}·12H 2O ( 2), were obtained by the stoichiometric reaction of an aqueous solution of Na 3(PO 2NH) 3·4H 2O with the respective metal nitrate or halide. The structures of 1 and 2 were found to be isomorphous and were solved by single-crystal X-ray methods ( 1a: C2/ c, a=888.9(1) pm, b=1901.8(2) pm, c=1711.2(2) pm, ?=104.59(1)°, Z=4; 2a: C2/ c, a=894.4(1) pm, b=1890.6(1) pm, c=1723.6(1) pm, ?=104.49(1)°, Z=4). At low temperature a reversible phase transition occurs and the symmetry of the structure changes from C2/ c to P2 1/ n ( 1b: P2 1/ n, a=887.1(2) pm, b=1900.1(4) pm, c=1707.2(3) pm, ?=104.59(2)°, Z=4; 2b: P2 1/ n, a=890.3(1) pm, b=1890.2(2) pm, c=1713.3(2) pm, ?=104.62(1)°, Z=4). The phase transition is caused by a structural ordering of Na + and H 2O at low temperature. The P 3N 3 rings of the trimetaphosphimate ions exhibit a chair conformation. The trimetaphosphimate ions act as tridentate ligands. Thus, anionic complexes {M[(PO 2NH) 3] 2} 4- (M=Co, Ni) are formed. These structural elements are interconnected in the crystal by N?H⋯O and O?H⋯O hydrogen bonds and by coordination to Na + forming a three-dimensional network. Upon heating, 1 and 2 loose their crystal water around 100 °C and above 400 °C new crystalline phases are formed, which have not been identified so far.

  5. 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 ?NH3/?CH4 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.

  6. On-board Measurement of HCN and NH3 Emissions from Vehicles During Real-World Driving

    NASA Astrophysics Data System (ADS)

    Moss, J. A.; Baum, M. M.

    2013-12-01

    Emission control systems in light-duty motor vehicles have played an important role in improving regional air quality by dramatically reducing the concentration of criteria pollutants (carbon monoxide, hydrocarbons, and nitrogen oxides) in exhaust emissions. Unintended side-reactions occurring on the surface of three-way catalysts can, however, lead to emission of non-criteria pollutants such as ammonia (NH3) and hydrogen cyanide (HCN). A pair of spectrometers based on tunable diode lasers (TDL) emitting in the near-infrared (1529 nm) and mid-infrared (2975 nm) have been developed for determination of HCN and acetylene (C2H2) emission rates from light-duty motor vehicles in real-time, while driving. Both spectrometers have been evaluated extensively using standard gas mixtures in the laboratory and exhaust from idling and moving vehicles. The TDL spectrometers were incorporated into an on-board instrument suite containing instrumentation for measurement of CO2, HCN, C2H2, NH3 and amines, and exhaust flow rate. On-board measurements were carried out on a fleet of ten vehicles driving a 30 minute circuit representative of real-world urban driving conditions. These measurements afforded emission factors for NH3 (194 × 147 mg km-1) and HCN (3.33 × 3.61 mg km-1), as well as the first report of methylamine emission factors, 0.70 × 0.61 mg km-1. Emissions of both amines were highly correlated (R2 = 0.95). The temporally-resolved TDL spectrometer measurements indicate that the highest HCN and C2H2 emissions occur during specific emission modes that are a function of driving conditions.

  7. The H2O Southern Galactic Plane Survey: NH3 (1,1) and (2,2) catalogues

    NASA Astrophysics Data System (ADS)

    Purcell, C. R.; Longmore, S. N.; Walsh, A. J.; Whiting, M. T.; Breen, S. L.; Britton, T.; Brooks, K. J.; Burton, M. G.; Cunningham, M. R.; Green, J. A.; Harvey-Smith, L.; Hindson, L.; Hoare, M. G.; Indermuehle, B.; Jones, P. A.; Lo, N.; Lowe, V.; Phillips, C. J.; Thompson, M. A.; Urquhart, J. S.; Voronkov, M. A.; White, G. L.

    2012-11-01

    The H2O Southern Galactic Plane Survey (HOPS) has mapped a 100° strip of the Galactic plane (-70° > l > 30°, |b| < 0°.5) using the 22 m Mopra antenna at 12 mm wavelengths. Observations were conducted in on-the-fly mode using the Mopra spectrometer (MOPS), targeting water masers, thermal molecular emission and radio-recombination lines. Foremost among the thermal lines are the 23 GHz transitions of NH3 J,K = (1,1) and (2,2), which trace the densest parts of molecular clouds (n > 104 cm-3). In this paper, we present the NH3 (1,1) and (2,2) data, which have a resolution of 2 arcmin and cover a velocity range of ±200 km s-1. The median sensitivity of the NH3 data cubes is ?T mb =0.20±0.06 K. For the (1,1) transition, this sensitivity equates to a 3.2 kpc distance limit for detecting a 20 K, 400 M? cloud at the 5? level. Similar clouds of mass 5000 M? would be detected as far as the Galactic Centre, while 30 000 M? clouds would be seen across the Galaxy. We have developed an automatic emission finding procedure based on the Australian Telescope National Facility (ATNF) DUCHAMP software and have used it to create a new catalogue of 669 dense molecular clouds. The catalogue is 100 per cent complete at the 5? detection limit (Tmb = 1.0 K). A preliminary analysis of the ensemble cloud properties suggests that the near-kinematic distances are favoured. The cloud positions are consistent with current models of the Galaxy containing a long bar. Combined with other Galactic plane surveys this new molecular-line data set constitutes a key tool for examining Galactic structure and evolution. Data cubes, spectra and catalogues are available to the community via the HOPS website.

  8. Oxygen sorption and desorption properties of selected lanthanum manganites and lanthanum ferrite manganites.

    PubMed

    Nielsen, Jimmi; Skou, Eivind M; Jacobsen, Torben

    2015-06-01

    Temperature-programmed desorption (TPD) with a carrier gas was used to study the oxygen sorption and desorption properties of oxidation catalysts and solid-oxide fuel cell (SOFC) cathode materials (La(0.85) Sr(0.15)0.95 MnO(3+?) (LSM) and La(0.60) Sr(0.40) Fe(0.80) Mn(0.20) O(3-?) (LSFM). The powders were characterized by X-ray diffractometry, atomic force microscopy (AFM), and BET surface adsorption. Sorbed oxygen could be distinguished from oxygen originating from stoichiometry changes. The results indicated that there is one main site for oxygen sorption/desorption. The amount of sorbed oxygen was monitored over time at different temperatures. Furthermore, through data analysis it was shown that the desorption peak associated with oxygen sorption is described well by second-order desorption kinetics. This indicates that oxygen molecules dissociate upon adsorption and that the rate-determining step for the desorption reaction is a recombination of monatomic oxygen. Typical problems with re-adsorption in this kind of TPD setup were revealed to be insignificant by using simulations. Finally, different key parameters of sorption and desorption were determined, such as desorption activation energies, density of sorption sites, and adsorption and desorption reaction order. PMID:25784205

  9. Infrared photodissociation spectroscopy of Mg +(NH 3) n ( n=3-6): direct coordination or solvation through hydrogen bonding

    NASA Astrophysics Data System (ADS)

    Ohashi, Kazuhiko; Terabaru, Kazutaka; Inokuchi, Yoshiya; Mune, Yutaka; Machinaga, Hironobu; Nishi, Nobuyuki; Sekiya, Hiroshi

    2004-07-01

    The infrared photodissociation spectra of mass-selected Mg +(NH 3) n ( n=3-6) are measured and analyzed with the aid of density functional theory calculations. No large frequency reduction is observed for the NH stretches of ammonia, suggesting that either all the ammonia molecules coordinate directly to the Mg + ion or an additional ammonia in the second shell bridges two ammonias in the first shell through hydrogen bonds. Four or possibly five ammonia molecules are allowed to occupy the first shell, in striking contrast to the closure of the first shell in Mg +(H 2O) 3.

  10. Highly Sensitive NH3 Detection Based on Organic Field Effect Transistors with Tris(pentafluorophenyl)Borane as Receptor

    PubMed Central

    Huang, Weiguo; Besar, Kalpana; LeCover, Rachel; Rule, Ana María; Breysse, Patrick N.; Katz, Howard E.

    2012-01-01

    We have increased organic field-effect transistor (OFET) NH3 response using tris-(pentafluorophenyl)borane (TPFB) as receptor. OFETs with this additive detect concentrations of 450 ppb v/v, with a limit of detection of 350 ppb, the highest sensitivity yet from semiconductor films; in comparison, when triphenylmethane (TPM) and triphenylborane (TFB) were used as an additive, no obvious improvement of sensitivity was observed. These OFETs also show considerable selectivity with respect to common organic vapors, and stability to storage. Furthermore, excellent memory of exposure was achieved by keeping the exposed devices in a sealed container stored at ?30°C, the first such capability demonstrated with OFETs. PMID:22934620

  11. Synthesis, structural and optical properties of perovskite type CH3NH3PbI3 nanorods

    NASA Astrophysics Data System (ADS)

    Rajamanickam, N.; Rajashabala, S.; Ramachandran, K.

    2015-06-01

    Perovskite type methyl ammonium lead triiodide (CH3NH3PbI3) thin films were prepared by coprecipitation method. The structural and optical properties were investigated by XRD, SEM, Raman and UV-Vis spectroscopy. Perovskite structured tetragonal phase was observed by XRD. The UV spectrum exhibits a band gap of 1.63 eV. The nanorods are arranged in flower like structure distinguished by SEM. Raman spectrum of this organo-halide perovskite was studied for the full exploitation in solar cells.

  12. Laboratory measurements of the 7.5-9.38-mm absorption of gaseous ammonia (NH3) under simulated Jovian conditions

    NASA Technical Reports Server (NTRS)

    Joiner, Joanna; Steffes, Paul G.; Jenkins, Jon M.

    1989-01-01

    An attempt is made to infer the abundance and distribution of ammonia from RF emission measurements more accurately than heretofore, on the basis of the results of laboratory measurements for the mm-wave opacity of gaseous ammonia under simulated Jovian atmosphere conditions. The measurements were conducted at various frequencies in the 32-40 GHz range at 2 atm and 203 K; the atmospheric mixture was 88.34 percent H2, 9.81 percent He, and 1.85 percent NH3. Experimental results are found to be readily modeled by the Gross (1955) line-shape factor, rather than that of Van Vleck and Weisskopf (1945).

  13. The C(3P) + NH3 Reaction in Interstellar Chemistry. II. Low Temperature Rate Constants and Modeling of NH, NH2, and NH3 Abundances in Dense Interstellar Clouds

    NASA Astrophysics Data System (ADS)

    Hickson, Kevin M.; Loison, Jean-Christophe; Bourgalais, Jérémy; Capron, Michael; Le Picard, Sébastien D.; Goulay, Fabien; Wakelam, Valentine

    2015-10-01

    A continuous supersonic flow reactor has been used to measure rate constants for the C(3P) + NH3 reaction over the temperature range 50-296 K. C(3P) atoms were created by the pulsed laser photolysis of CBr4. The kinetics of the title reaction were followed directly by vacuum ultra-violet laser induced fluorescence of C(3P) loss and through H(2S) formation. The experiments show unambiguously that the reaction is rapid at 296 K, becoming faster at lower temperatures, reaching a value of (1.8 ± 0.2) × 10-10 cm3 molecule-1 s-1 at 50 K. As this reaction is not currently included in astrochemical networks, its influence on interstellar nitrogen hydride abundances is tested through a dense cloud model including gas-grain interactions. In particular, the effect of the ortho-to-para ratio of H2, which plays a crucial role in interstellar NH3 synthesis, is examined.

  14. Electron irradiation and thermal driven chemistry on H2S-CH3OH-NH3-H2O and CH3OH-NH3-H2O ices: application to Jupiter Trojans

    NASA Astrophysics Data System (ADS)

    Mahjoub, A.; Poston, M.; Hand, K.; Brown, M.; Blacksberg, J.; Eiler, J.; Hodyss, R.; Carlson, R.; Ehlmann, B.; Choukroun, M.

    2015-10-01

    In this work we investigate chemical reactions driven by irradiation and thermal processing of outer solar system simulants and the resultant products. The main goal of this laboratory simulation work is testing migration hypotheses predicted by solar system formation models [1]. The ice samples are chosen to simulate the differences between chemistry in objects initially located inside and outside the stability line of H2S. CH3OH-NH3-H2O (3-ice) and H2S-CH3OH-NH3-H2O (4-ice) ice films was irradiated under ultrahigh vacuum conditions. Mid- IR analysis of the ice composition and mass spectrometry monitoring of the released volatiles during the heating of the irradiated mixtures show a rich chemistry for both mixtures. Our experimental work suggests that S-bearing molecules like OCS and SO2 could be formed under conditions expected for objects that initially contained near-surface frozen H2S and were then exposed to space weathering, particularly heating and irradiation while migrating to a position close to Jupiter's orbit.

  15. Atomic oxygen diffusion on and desorption from amorphous silicate surfaces.

    PubMed

    He, Jiao; Jing, Dapeng; Vidali, Gianfranco

    2014-02-28

    Surface reactions involving atomic oxygen have attracted much attention in astrophysics and astrochemistry, but two of the most fundamental surface processes, desorption and diffusion, are not well understood. We studied diffusion and desorption of atomic oxygen on or from amorphous silicate surfaces under simulated interstellar conditions using a radio-frequency dissociated oxygen beam. Temperature programmed desorption (TPD) experiments were performed to study the formation of ozone from reaction of atomic and molecular oxygen deposited on the surface of a silicate. It is found that atomic oxygen begins to diffuse significantly between 40 K and 50 K. A rate equation model was used to study the surface kinetics involved in ozone formation experiments. The value of atomic oxygen desorption energy has been determined to be 152 ± 20 meV (1764 ± 232 K). The newly found atomic oxygen desorption energy, which is much higher than the well-accepted value, might explain the discrepancy in abundance of molecular oxygen in space between observations and chemical models. PMID:24434834

  16. Application of Cavity-ring Down Spectroscopy to Quantify NH3 Fluxes from Fertilizer Application in the Midwestern U.S.

    NASA Astrophysics Data System (ADS)

    Caldwell, J. A.; Sibble, D.; Heuer, M.; Johnson, E.; Rood, M. J.; Koloutsou-Vakakis, S.; Myles, L.

    2014-12-01

    Ammonia (NH3) emissions from managed agriculture in the Midwestern region of the U.S. contribute to increased levels of particulate matter in the atmosphere and detrimental ecological changes. To better understand the exchange of ammonia between the atmosphere and biosphere and identify the drivers of these processes, measurements of NH3 flux were conducted over a 200 m2 fertilized maize field in Illinois. A flux-gradient system paired with a cavity-ring down spectrometer measured fluxes from pre-cultivation through senescence of the crop. The use of a custom automated exchange mechanism allowed for continuous sampling, both above-canopy and in-canopy. Results indicated diurnal cycling of NH3 with higher concentrations in the early afternoon, although the pattern was not consistent. As expected, fertilization of the field at planting produced a marked increase in NH3 emission from the field.

  17. The Nature of the Dense Core Population in the Pipe Nebula: A Survey of NH3, CCS, and HC5N Molecular Line Emission

    NASA Astrophysics Data System (ADS)

    Rathborne, J. M.; Lada, C. J.; Muench, A. A.; Alves, J. F.; Lombardi, M.

    2008-02-01

    Recent extinction studies of the Pipe Nebula (d=130 pc) reveal many cores spanning a range in mass from 0.2 to 20.4 Msolar. These dense cores were identified via their high extinction and comprise a starless population in a very early stage of development. Here we present a survey of NH3 (1,1), NH3 (2,2), CCS (21-10), and HC5N (9,8) emission toward 46 of these cores. An atlas of the 2MASS extinction maps is also presented. In total, we detect 63% of the cores in NH3 (1,1), 22% in NH 3 (2,2), 28% in CCS, and 9% in HC5N emission. We find the cores are associated with dense gas (~104 cm-3) with 9.5 K<=TK<=17 K. Compared to C18O, we find the NH3 line widths are systematically narrower, implying that the NH3 is tracing the dense component of the gas and that these cores are relatively quiescent. We find no correlation between core line width and size. The derived properties of the Pipe cores are similar to cores within other low-mass star-forming regions: the only differences are that the Pipe cores have weaker NH 3 emission and most show no current star formation as evidenced by the lack of embedded infrared sources. Such weak NH3 emission could arise due to low column densities and abundances or reduced excitation due to relatively low core volume densities. Either alternative implies that the cores are relatively young. Thus, the Pipe cores represent an excellent sample of dense cores in which to study the initial conditions for star formation and the earliest stages of core formation and evolution.

  18. Resistive Switching Behavior in Organic-Inorganic Hybrid CH3 NH3 PbI3-x Clx Perovskite for Resistive Random Access Memory Devices.

    PubMed

    Yoo, Eun Ji; Lyu, Miaoqiang; Yun, Jung-Ho; Kang, Chi Jung; Choi, Young Jin; Wang, Lianzhou

    2015-10-01

    The CH3 NH3 PbI3- x Clx organic-inorganic hybrid perovskite material demonstrates remarkable resistive switching behavior, which can be applicable in resistive random access memory devices. The simply designed Au/CH3 NH3 PbI3- x Clx /FTO structure is fabricated by a low-temperature, solution-processable method, which exhibits remarkable bipolar resistive switching and nonvolatile properties. PMID:26331363

  19. Growth of CH3NH3PbI3 cuboids with controlled size for high-efficiency perovskite solar cells.

    PubMed

    Im, Jeong-Hyeok; Jang, In-Hyuk; Pellet, Norman; Grätzel, Michael; Park, Nam-Gyu

    2014-11-01

    Perovskite solar cells with submicrometre-thick CH(3)NH(3)PbI(3) or CH(3)NH(3)PbI(3-x)Cl(x) active layers show a power conversion efficiency as high as 15%. However, compared to the best-performing device, the average efficiency was as low as 12%, with a large standard deviation (s.d.). Here, we report perovskite solar cells with an average efficiency exceeding 16% and best efficiency of 17%. This was enabled by the growth of CH(3)NH(3)PbI(3) cuboids with a controlled size via a two-step spin-coating procedure. Spin-coating of a solution of CH(3)NH(3)I with different concentrations follows the spin-coating of PbI(2), and the cuboid size of CH(3)NH(3)PbI(3) is found to strongly depend on the concentration of CH(3)NH(3)I. Light-harvesting efficiency and charge-carrier extraction are significantly affected by the cuboid size. Under simulated one-sun illumination, average efficiencies of 16.4% (s.d. ± 0.35), 16.3% (s.d. ± 0.44) and 13.5% (s.d. ± 0.34) are obtained from solutions of CH(3)NH(3)I with concentrations of 0.038 M, 0.050 M and 0.063 M, respectively. By controlling the size of the cuboids of CH(3)NH(3)PbI(3) during their growth, we achieved the best efficiency of 17.01% with a photocurrent density of 21.64 mA cm(-2), open-circuit photovoltage of 1.056 V and fill factor of 0.741. PMID:25173829

  20. 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.

  1. 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. PMID:23452149

  2. 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. PMID:25733191

  3. Efficient hybrid mesoscopic solar cells with morphology-controlled CH3NH3PbI3-xClx derived from two-step spin coating method.

    PubMed

    Xu, Yuzhuan; Zhu, Lifeng; Shi, Jiangjian; Lv, Songtao; Xu, Xin; Xiao, Junyan; Dong, Juan; Wu, Huijue; Luo, Yanhong; Li, Dongmei; Meng, Qingbo

    2015-02-01

    A morphology-controlled CH3NH3PbI3-xClx film is synthesized via two-step solution deposition by spin-coating a mixture solution of CH3NH3Cl and CH3NH3I onto the TiO2/PbI2 film for the first time. It is revealed that the existence of CH3NH3Cl is supposed to result in a preferential growth along the [110] direction of perovskite, which can improve both the crystallinity and surface coverage of perovskite and reduce the pinholes. Furthermore, the formation process of CH3NH3PbI3-xClx perovskite is explored, in which intermediates containing chlorine are suggested to exist. 13.12% of power conversion efficiency has been achieved for the mesoscopic cell, higher than 12.08% of power conversion efficiency of the devices fabricated without CH3NH3Cl via the same process. The improvement mainly lies in the increasing open-circuit photovoltage which is ascribed to the reduction of reverse saturation current density. PMID:25587643

  4. Infrared spectroscopy of metal-solvent clusters: Li(NH3)n and Li(MeNH2)n

    NASA Astrophysics Data System (ADS)

    Ellis, Andrew; Salter, Tom; Evans, Corey; Mikhailov, Victor

    2006-03-01

    Mass-selected infrared spectra of the uncharged metal-solvent clusters Li(NH3)n and Li(MeNH2)n in the N-H stretching region have been recorded using two techniques, photodepletion spectroscopy and two-colour (IR+UV) REMPI. Infrared REMPI is the most suitable for the smaller clusters, since the energy input into the cluster by the IR photon is insufficient to cause dissociation. Our latest findings for this technique will be presented alongside computational predictions of the cluster spectra. For the larger clusters, injection of an IR photon in the N-H stretching region causes rapid dissociation and offers the opportunity to record mass-selected IR spectra by photodepletion spectroscopy. IR photodepletion spectra of Li(NH3)n near 3 ?m recorded for n = 4-7 show vibrational structure that points to completion of the first solvation shell at n = 4, with additional ammonia molecules entering a second shell in which the solvent molecules are more weakly bound to the cluster. Photodepletion spectra have also been recorded for other clusters, including Li(MeNH2)n, and the latest findings for these species will be described.

  5. 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.

  6. Anharmonic calculation of the structure, vibrational frequencies and intensities of the NH3···trans-HONO complex.

    PubMed

    Bulychev, Valentin P; Buturlimova, Marina V; Tokhadze, Konstantin G

    2013-09-19

    The equilibrium geometry of the NH3···trans-HONO complex and the harmonic vibrational frequencies and intensities are calculated in the MP2/aug-cc-pVTZ approximation with the basis set superposition error taken into account. Effects of anharmonic interactions on spectroscopic parameters are studied by solving vibrational Schrödinger equations in 1-4 dimensions using the variational method. Anharmonic vibrational equations are formulated in the space of normal coordinates of the complex. Detailed analysis is performed for the H-bond stretching vibration and internal vibrations of the trans-HONO isomer in the complex. The intermode anharmonicity and anharmonic coupling between two, three, and four vibrational modes are studied on the basis of correct ab initio potential energy surfaces calculated in the above approximation. The combinations of normal modes of the complex most strongly coupled to one another are examined. The calculated frequencies and intensities of vibrational bands are compared with the experimental data on the NH3···trans-HONO complex in an argon matrix and results of earlier calculations of monomeric HONO. In this calculation the strong resonance between the first excited state of the OH stretching vibration and the doubly excited state of the NOH bending vibration of trans-HONO isomer in the complex is thoroughly studied by solving vibrational equations in two and four dimensions. PMID:23944642

  7. Characterization of an Fe?N-NH2 Intermediate Relevant to Catalytic N2 Reduction to NH3

    PubMed Central

    Connor, Bridget A.; Gunderson, William A.; Zhang, Limei; Hoffman, Brian M.; Peters, Jonas C.

    2015-01-01

    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. Herein 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. 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. 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. PMID:26000443

  8. Depletion region effect of highly efficient hole conductor free CH3NH3PbI3 perovskite solar cells.

    PubMed

    Aharon, Sigalit; Gamliel, Shany; El Cohen, Bat; Etgar, Lioz

    2014-06-14

    The inorganic-organic perovskite is currently attracting a lot of attention due to its use as a light harvester in solar cells. The large absorption coefficients, high carrier mobility and good stability of organo-lead halide perovskites present good potential for their use as light harvesters in mesoscopic heterojunction solar cells. This work concentrated on a unique property of the lead halide perovskite, its function simultaneously as a light harvester and a hole conductor in the solar cell. A two-step deposition technique was used to optimize the perovskite deposition and to enhance the solar cell efficiency. It was revealed that the photovoltaic performance of the hole conductor free perovskite solar cell is strongly dependent on the depletion layer width which was created at the TiO2-CH3NH3PbI3 junction. X-ray diffraction measurements indicate that there were no changes in the crystallographic structure of the CH3NH3PbI3 perovskite over time, which supports the high stability of these hole conductor free perovskite solar cells. Furthermore, the power conversion efficiency of the best cells reached 10.85% with a fill factor of 68%, a Voc of 0.84 V, and a Jsc of 19 mA cm(-2), the highest efficiency to date of a hole conductor free perovskite solar cell. PMID:24736900

  9. Growth of freshly nucleated particles in the troposphere: Roles of NH3, H2SO4, HNO3, and HCl

    NASA Astrophysics Data System (ADS)

    Kerminen, Veli-Matti; Wexler, Anthony S.; Potukuchi, Sudhakar

    1997-02-01

    Growth of airborn, nanometer-size nuclei was examined in a H2SO4-HNO3-HCl-NH3-H2O system using a single-particle condensation model. Under conditions typical of the lower troposphere, growth is driven initially by the flux of sulfuric acid, followed by thermodynamic equilibration by the more abundant water and ammonia vapors. Pure sulfuric acid-water-ammonia condensation was shown to be rather slow and unable to produce cloud condensation nuclei (CCN) in the atmosphere. Under favorable conditions and after reaching a certain size, nuclei may start to absorb large quantities of nitric or hydrochloric acid together with ammonia, which produces CCN-size particles over a timescale of a few minutes. The resulting CCN are susceptible to evaporation as the ambient conditions change but may become stable via cloud processing. The fast, HNO3-HCl-NH3-driven condensation was estimated to occur frequently in continental aerosol systems. Marine CCN production cannot be explained by this process; it requires either the participation of other condensable vapors, such as organics, or a different growth mechanism.

  10. Mechanical Origin of the Structural Phase Transition in Methylammonium Lead Iodide CH3NH3PbI3.

    PubMed

    Ong, Khuong P; Goh, Teck Wee; Xu, Qiang; Huan, Alfred

    2015-02-19

    The methylammonium lead iodide perovskite (MAPbI3) is presently a desirable material for photovoltaic application. Its structure is orthorhombic at low temperature and tetragonal at room temperature. Most theoretical works have focused on either tetragonal or orthorhombic phase alone leaving a gap in the understanding of the structural phase transition in between. In this work, by ab initio calculations, we elucidate the origin of structural phase transition between these two phases. We show that there exists a critical ratio of out-of-plane to in-plane lattice constants, c/a ? 1.45, where at low c/a the orthorhombic Pnma phase is stable while the tetragonal I4/mcm phase is stable at high c/a. Varying the c/a ratio leads to a change of PbI6 octahedral tilting with the rotation of CH3NH3(+) cations about the NH3 component in and out of the Oxy plane. The origin of this rotation is identified. We propose that under epitaxial conditions a gradual change in structural phase of the MAPbI3 perovskite may exist and understanding its electronic properties will be beneficial toward the solar cell community. PMID:26262485

  11. 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.

  12. Extremely Slow Photoconductivity Response of CH3NH3PbI3 Perovskites Suggesting Structural Changes under Working Conditions.

    PubMed

    Gottesman, Ronen; Haltzi, Eynav; Gouda, Laxman; Tirosh, Shay; Bouhadana, Yaniv; Zaban, Arie; Mosconi, Edoardo; De Angelis, Filippo

    2014-08-01

    Photoconductivity measurements of CH3NH3PbI3 deposited between two dielectric-protected Au electrodes show extremely slow response. The CH3NH3PbI3, bridging a gap of ?2000 nm, was subjected to a DC bias and cycles of 5 min illumination and varying dark duration. The approach to steady -state photocurrent lasted tens of seconds with a strong dependence on the dark duration preceding the illumination. On the basis of DFT calculations, we propose that under light + bias the methylammonium ions are freed to rotate and align along the electric field, thus modifying the structure of the inorganic scaffold. While ions alignment is expected to be fast, the adjustment of the inorganic scaffold seems to last seconds as reflected in the extremely slow photoconductivity response. We propose that under working conditions a modified, photostable, perovskite structure is formed, depending on the bias and illumination parameters. Our findings seem to clarify the origin of the well-known hysteresis in perovskite solar cells. PMID:26277960

  13. NH3 assisted photoreduction and N-doping of graphene oxide for high performance electrode materials in supercapacitors

    NASA Astrophysics Data System (ADS)

    Huang, Haifu; Luo, Guangsheng; Xu, Lianqiang; Lei, Chenglong; Tang, Yanmei; Tang, Shaolong; Du, Youwei

    2015-01-01

    Nitrogen-doped graphene was synthesized by simple photoreduction of graphene oxide (GO) deposited on nickel foam under NH3 atmosphere. The combination of photoreduction and NH3 not only reduces the GO in a shorter time but also induces nitrogen doping easily. The nitrogen doped content of N-rGO@NF reaches a high of 5.99 at% with 15 min of irradiation. The nitrogen-doped graphene deposited on Ni foam (N-rGO@NF) can be directly used as an electrode for supercapacitors, without any conductive agents and polymer binders. In the electrochemical measurement, N-rGO@NF displays remarkable electrochemical performance. In particular, the N-rGO@NF irradiated for 45 min at a high current density of 92.3 A g-1 retained about 77% (190.4 F g-1) of its initial specific capacitance (247.1 F g-1 at 0.31 A g-1). Furthermore, the stable voltage window could be extended to 2.0 and 1.5 V by using Li2SO4 and a mixed Li2SO4/KOH electrolyte, and the maximum energy density was high up to 32.6 and 21.2 Wh kg-1, respectively. The results show that compared to Li2SO4, a mixed electrolyte (Li2SO4/KOH) more efficiently balances the relationship between the high energy densities and high power densities.Nitrogen-doped graphene was synthesized by simple photoreduction of graphene oxide (GO) deposited on nickel foam under NH3 atmosphere. The combination of photoreduction and NH3 not only reduces the GO in a shorter time but also induces nitrogen doping easily. The nitrogen doped content of N-rGO@NF reaches a high of 5.99 at% with 15 min of irradiation. The nitrogen-doped graphene deposited on Ni foam (N-rGO@NF) can be directly used as an electrode for supercapacitors, without any conductive agents and polymer binders. In the electrochemical measurement, N-rGO@NF displays remarkable electrochemical performance. In particular, the N-rGO@NF irradiated for 45 min at a high current density of 92.3 A g-1 retained about 77% (190.4 F g-1) of its initial specific capacitance (247.1 F g-1 at 0.31 A g-1). Furthermore, the stable voltage window could be extended to 2.0 and 1.5 V by using Li2SO4 and a mixed Li2SO4/KOH electrolyte, and the maximum energy density was high up to 32.6 and 21.2 Wh kg-1, respectively. The results show that compared to Li2SO4, a mixed electrolyte (Li2SO4/KOH) more efficiently balances the relationship between the high energy densities and high power densities. Electronic supplementary information (ESI) available: Digital images of nickel foam, GO deposited in nickel foam, N-rGO@NF, and N-rGO@NF electrodes (1.0 × 1.0 cm); Digital images: (1) N-rGO@NF sheet was put into 1 M FeCl3 at room temperature dissolve the Ni metal and (2) a whole N-rGO sheet without Ni foam support after nickel etching; image of film with fragile features after being irradiated by a high-pressure Hg lamp (500 W) in Ar and NH3 atmosphere. See DOI: 10.1039/c4nr05776g

  14. Estimates of N2O, NO and NH3 Emissions From Croplands in East, Southeast and South Asia

    NASA Astrophysics Data System (ADS)

    Yan, X.; Ohara, T.; Akimoto, H.

    2002-12-01

    Agricultural activities have greatly altered the global nitrogen cycle and produced nitrogenous gases of environmentally significance. More than half of the global chemical nitrogen fertilizer is used for crop production in East, Southeast and South Asia where rice the center of nutrition. Emissions of nitrous oxide (N2O), nitric oxide (NO) and ammonia (NH3) from croplands in this region were estimated by considering both background emission and emissions resulted from nitrogen added to croplands, including chemical nitrogen, animal manure used as fertilizer, biological fixed nitrogen and nitrogen in crop residue returned to field. Background emission fluxes of N2O and NO from croplands were estimated at 1.16 and 0.52 kg N ha-1yr-1, respectively. A fertilizer-induced N2O emission factor of 1.25% for upland was adopted from IPCC guidelines, and a factor of 0.25% was derived for paddy field from measurements. Total N2O emission from croplands in the region was estimated at 1.16 Tg N yr-1, with 41% contributed by background emission which was not considered in previous global estimates. However, the average fertilizer-induced N2O emission is only 0.93%, lower than the default IPCC value of 1.25% due to the low emission factor from paddy field. A fertilizer-induced NO emission factor of 0.66% for upland was derived from field measurements, and a factor of 0.13% was assumed for paddy field. Total NO emission was 572 Gg N yr-1 in the region, with 38% due to background emission. Average fertilizer-induce NO emission factor was 0.48%. Extrapolating this estimate to global scale will result in a global NO emission from cropland of 1.6 Tg N yr-1, smaller than other global estimates. Total NH3 emission was estimated at 11.8 Tg N yr-1. The use of urea and ammonium bicarbonate and the cultivation of rice lead to a high average NH3 loss rate of chemical fertilizer in the region. Emissions were distributed at 0.5° grid by using a global landuse database.

  15. Emissions of NO and NH3 from a Typical Vegetable-Land Soil after the Application of Chemical N Fertilizers in the Pearl River Delta

    PubMed Central

    Li, Dejun

    2013-01-01

    Cropland soil is an important source of atmospheric nitric oxide (NO) and ammonia (NH3). Chinese croplands are characterized by intensive management, but limited information is available with regard to NO emissions from croplands in China and NH3 emissions in south China. In this study, a mesocosm experiment was conducted to measure NO and NH3 emissions from a typical vegetable-land soil in the Pearl River Delta following the applications of 150 kg N ha?1 as urea, ammonium nitrate (AN) and ammonium bicarbonate (ABC), respectively. Over the sampling period after fertilization (72 days for NO and 39 days for NH3), mean NO fluxes (± standard error of three replicates) in the control and urea, AN and ABC fertilized mesocosms were 10.9±0.9, 73.1±2.9, 63.9±1.8 and 66.0±4.0 ng N m?2 s?1, respectively; mean NH3 fluxes were 8.9±0.2, 493.6±4.4, 144.8±0.1 and 684.7±8.4 ng N m?2 s?1, respectively. The fertilizer-induced NO emission factors for urea, AN and ABC were 2.6±0.1%, 2.2±0.1% and 2.3±0.2%, respectively. The fertilizer-induced NH3 emission factors for the three fertilizers were 10.9±0.2%, 3.1±0.1% and 15.2±0.4%, respectively. From the perspective of air quality protection, it would be better to increase the proportion of AN application due to its lower emission factors for both NO and NH3. PMID:23527173

  16. The optoelectronic role of chlorine in CH3NH3PbI3(Cl)-based perovskite solar cells

    PubMed Central

    Chen, Qi; Zhou, Huanping; Fang, Yihao; Stieg, Adam Z.; Song, Tze-Bin; Wang, Hsin-Hua; Xu, Xiaobao; Liu, Yongsheng; Lu, Shirong; You, Jingbi; Sun, Pengyu; McKay, Jeff; Goorsky, Mark S.; Yang, Yang

    2015-01-01

    Perovskite photovoltaics offer a compelling combination of extremely low-cost, ease of processing and high device performance. The optoelectronic properties of the prototypical CH3NH3PbI3 can be further adjusted by introducing other extrinsic ions. Specifically, chlorine incorporation has been shown to affect the morphological development of perovksite films, which results in improved optoelectronic characteristics for high efficiency. However, it requires a deep understanding to the role of extrinsic halide, especially in the absence of unpredictable morphological influence during film growth. Here we report an effective strategy to investigate the role of the extrinsic ion in the context of optoelectronic properties, in which the morphological factors that closely correlate to device performance are mostly decoupled. The chlorine incorporation is found to mainly improve the carrier transport across the heterojunction interfaces, rather than within the perovskite crystals. Further optimization according this protocol leads to solar cells achieving power conversion efficiency of 17.91%. PMID:26068804

  17. Growth of bulk AlN crystals by vapor-phase epitaxy from atomic Al and NH3

    NASA Astrophysics Data System (ADS)

    Pogorel'skii, M. Yu.; Alekseev, A. N.; Pogorel'skii, Yu. V.; Shkurko, A. P.

    2015-09-01

    A new approach to obtaining bulk AlN single crystals by vapor-phase epitaxy has been tested. NH3 and Al vapor were used as growth reagents. The following ranges of growth parameters were admissible for the laboratory equipment (experimental growth installation): temperatures of 1050-1500°C at ammonia flow rates of up to 50 sccm and pressures on the order of 10-5-10-4 bar, growth rates of up to 200 ?m h-1. At a temperature of 1450°C, samples of strained bulk block AlN crystals with thicknesses of up to 200 ?m were obtained in the wurtzite phase in the [0001] direction on MBE templates based on sapphire substrates with a diameter of 2?.

  18. Atomistic origins of CH3NH3PbI3 degradation to PbI2 in vacuum

    NASA Astrophysics Data System (ADS)

    Deretzis, I.; Alberti, A.; Pellegrino, G.; Smecca, E.; Giannazzo, F.; Sakai, N.; Miyasaka, T.; La Magna, A.

    2015-03-01

    We study the mechanisms of CH3NH3PbI3 degradation and its transformation to PbI2 by means of X-ray diffraction and the density functional theory. The experimental analysis shows that the material can degrade in both air and vacuum conditions, with humidity and temperature-annealing strongly accelerating such process. Based on ab initio calculations, we argue that even in the absence of humidity, a decomposition of the perovskite structure can take place through the statistical formation of molecular defects with a non-ionic character, whose volatility at surfaces should break the thermodynamic defect equilibria. We finally discuss the strategies that can limit such phenomenon and subsequently prolong the lifetime of the material.

  19. Vibrational signatures of hydrogen bonding in the protonated ammonia clusters NH4+(NH3)1-4

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Kühn, O.; Santambrogio, G.; Goebbert, D. J.; Asmis, K. R.

    2008-12-01

    The gas phase vibrational spectroscopy of the protonated ammonia dimer N2H7+, a prototypical system for strong hydrogen bonding, is studied in the spectral region from 330 to 1650 cm-1 by combining infrared multiple photon dissociation and multidimensional quantum mechanical simulations. The fundamental transition of the antisymmetric proton stretching vibration is observed at 374 cm-1 and assigned on the basis of a six-dimensional model Hamiltonian, which predicts this transition at 471 cm-1. Photodissociation spectra of the larger protonated ammonia clusters NH4+(NH3)n with n =2-4 are also reported for the range from 1050 to 1575 cm-1. The main absorption features can be assigned within the harmonic approximation, supporting earlier evidence that hydrogen bonding in these clusters is considerably weaker than for n =1.

  20. Exploring Deep Icy World Oceans through New Experimental Equations of State for Aqueous MgSO4 and NH3

    NASA Astrophysics Data System (ADS)

    Vance, S.; Brown, J.

    2011-12-01

    Observational evidence supports the presence of very deep oceans in Europa, Ganymede, Callisto, Titan, and Enceladus. Thermal models for other bodies to be more thoroughly explored also suggest internal liquid layers in the present or past. Hydrostatic pressure at the bottom oceans in the three largest of the solar system's icy world oceans exceeds the formation pressures of high-pressure ice phases. Temperature- and pressure-dependent thermodynamic effects on fluid transport and phase stability may have profound geophysical and astrobiological implications, but experimental constraints on these properties are only now becoming available. In this context, we present equations of state for aqueous NH3 and MgSO4 derived from speeds of sound obtained by the method of impulsive stimulated scattering. Using these, we provide new constraints on the presence of liquids within ice layers at the tops and bottoms of icy world oceans.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

    Yang, Ye; Yan, Yong; Yang, Mengjin; Choi, Sukgeun; Zhu, Kai; Luther, Joseph M.; Beard, Matthew C.

    2015-08-01

    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 ?m to avoid the influence of surface recombination on the effective carrier lifetime.

  3. The optoelectronic role of chlorine in CH3NH3PbI3(Cl)-based perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Chen, Qi; Zhou, Huanping; Fang, Yihao; Stieg, Adam Z.; Song, Tze-Bin; Wang, Hsin-Hua; Xu, Xiaobao; Liu, Yongsheng; Lu, Shirong; You, Jingbi; Sun, Pengyu; McKay, Jeff; Goorsky, Mark S.; Yang, Yang

    2015-06-01

    Perovskite photovoltaics offer a compelling combination of extremely low-cost, ease of processing and high device performance. The optoelectronic properties of the prototypical CH3NH3PbI3 can be further adjusted by introducing other extrinsic ions. Specifically, chlorine incorporation has been shown to affect the morphological development of perovksite films, which results in improved optoelectronic characteristics for high efficiency. However, it requires a deep understanding to the role of extrinsic halide, especially in the absence of unpredictable morphological influence during film growth. Here we report an effective strategy to investigate the role of the extrinsic ion in the context of optoelectronic properties, in which the morphological factors that closely correlate to device performance are mostly decoupled. The chlorine incorporation is found to mainly improve the carrier transport across the heterojunction interfaces, rather than within the perovskite crystals. Further optimization according this protocol leads to solar cells achieving power conversion efficiency of 17.91%.

  4. 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.

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

    PubMed

    Yang, Ye; Yan, Yong; Yang, Mengjin; Choi, Sukgeun; Zhu, Kai; Luther, Joseph M; Beard, Matthew C

    2015-01-01

    Organic-inorganic hybrid perovskites are attracting intense research effort due to their impressive performance in solar cells. While the carrier transport parameters such as mobility and bulk carrier lifetime shows sufficient characteristics, the surface recombination, which can have major impact on the solar cell performance, has not been studied. Here we measure surface recombination dynamics in CH3NH3PbBr3 perovskite single crystals using broadband transient reflectance spectroscopy. The surface recombination velocity is found to be 3.4±0.1 × 10(3)?cm?s(-1), ?2-3 orders of magnitude lower than that in many important unpassivated semiconductors employed in solar cells. Our result suggests that the planar grain size for the perovskite thin films should be larger than ?30??m to avoid the influence of surface recombination on the effective carrier lifetime. PMID:26245855

  6. 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.

  7. 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.

  8. 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. PMID:17714863

  9. 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%.

  10. Efficient planar heterojunction solar cell employing CH3NH3PbI2+xCl1-x mixed halide perovskite utilizing modified sequential deposition

    NASA Astrophysics Data System (ADS)

    Zhang, Chunfu; Tang, Shi; Yan, Jing; Wang, Zhizhe; Xi, He; Chen, Dazheng; Yang, Haifeng; Zhang, Jincheng; Han, Genquan; Liu, Yan; Hao, Yue

    2015-09-01

    In this work, a modified method of sequential deposition of a CH3NH3PbI2+xCl1-x organometal halide perovskite material with a low chlorine fraction and easy morphology control is developed. The as-prepared mixed halide perovskite CH3NH3PbI2+xCl1-x thin film shows an intense adsorption from 400-800 nm. Scanning electron microscopy images show that almost the entire compact TiO2 surface is covered with CH3NH3PbI2+xCl1-x mixed halide perovskite with grain sizes of 250-350 nm. The planar heterojunction solar cell employing CH3NH3PbI2+xCl1-x mixed halide perovskite shows a twofold enhancement of photovoltaic performance, compared with a planar CH3NH3PbI3 heterojunction solar cell, achieving a 9.53% power conversion efficiency (PCE) with a VOC of 0.96 V, a JSC of 18.86 mA/cm2, and a fill factor (FF) of 0.53.

  11. Study on the correlations between the structure and photoelectric properties of CH3NH3PbI3 perovskite light-harvesting material

    NASA Astrophysics Data System (ADS)

    Xie, Junjie; Liu, Yan; Liu, Jianjun; Lei, Lei; Gao, Qianqian; Li, Jiaqing; Yang, Songwang

    2015-07-01

    The [PbI6] inorganic framework in the CH3NH3PbI3 could be affected by the oxidization effect of I- ions in atmosphere. The [PbI6] octahedral torsion angle increased ?4.94° after the newly prepared CH3NH3PbI3 powders were stored in dry atmosphere for 30 days at 20 °C according to the results of XRD Rietveld refinement and X-ray Absorption Fine Structure. Analyses based on density of states indicated that UV-vis adsorption edge at ?850 cm-1 corresponded to electron transition from I-5p orbitals to empty Pb-6p orbitals. The increased [PbI6] octahedral torsion angle made the band gap energy of CH3NH3PbI3 increased according to First-principle calculation and UV-vis absorption spectra. As a result, the band gap energy of CH3NH3PbI3 were strongly related to the structure of [PbI6] inorganic framework because the electrons diffused along the [PbI6] octahedral chains in CH3NH3PbI3 perovskite.

  12. Effect of water vapor on NH3-NO/NO2 SCR performance of fresh and aged MnOx-NbOx-CeO2 catalysts.

    PubMed

    Chen, Lei; Si, Zhichun; Wu, Xiaodong; Weng, Duan; Wu, Zhenwei

    2015-05-01

    A MnOx-NbOx-CeO2 catalyst for low temperature selective catalytic reduction (SCR) of NOx with NH3 was prepared by a sol-gel method, and characterized by NH3-NO/NO2 SCR catalytic activity, NO/NH3 oxidation activity, NOx/NH3 TPD, XRD, BET, H2-TPR and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The results indicate that the MnOx-NbOx-CeO2 catalyst shows excellent low temperature NH3-SCR activity in the temperature range of 150-300°C. Water vapor inhibits the low temperature activity of the catalyst in standard SCR due to the inhibition of NOx adsorption. As the NO2 content increases in the feed, water vapor does not affect the activity in NO2 SCR. Meanwhile, water vapor significantly enhances the N2 selectivity of the fresh and the aged catalysts due to its inhibition of the decomposition of NH4NO3 into N2O. PMID:25968280

  13. 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

  14. A photoelectrochemical biosensor for fibroblast-like synoviocyte cell using visible light-activated NCQDs sensitized-ZnO/CH3NH3PbI3 heterojunction.

    PubMed

    Pang, Xuehui; Zhang, Yong; Pan, Jihong; Zhao, Yanxia; Chen, Yao; Ren, Xiang; Ma, Hongmin; Wei, Qin; Du, Bin

    2016-03-15

    Based on ZnO nanorods (NRs)/CH3NH3PbI3/nitrogen-doped carbon quantum dots (NCQDs) nanocomposites, the highly sensitive detection of fibroblast-like synoviocyte (FLS) cell was realized by a photoelectrochemical (PEC) biosensor. ZnO/CH3NH3PbI3/NCQDs nanocomposites were exploited as the photo-to-electron generator to produce the signal. CH3NH3PbI3 was spin-coated on ZnO surface after ZnO NRs grew on ITO electrode then by dropping on the modified electrode, NCQDs were diffused and adhered to the surface of ZnO and CH3NH3PbI3. In the presence of EDC/NHS, the combination of CH3NH3PbI3 and NCQDs was achieved by the carboxyl groups (-COOH) and amino groups (-NH2) in the preparation process. Furthermore, the capture probe of FLS cell, CD95 antibody, can be anchored by -COOH and -NH2 groups through EDC/NHS. The specific recognition between the antibody capture probes and cell targets gained high-sensitive detection for FLS cell for the first time. The developed biosensor showed a wide linear range from 1.0×10(4)cell/mL to 10cell/mL and a low detection limit of 2cell/mL. This kind of biosensor would provide a novel detection strategy for FLS cell. PMID:26433065

  15. 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. ...

  16. Significant Promotion Effect of Mo Additive on a Novel Ce-Zr Mixed Oxide Catalyst for the Selective Catalytic Reduction of NO(x) with NH3.

    PubMed

    Ding, Shipeng; Liu, Fudong; Shi, Xiaoyan; Liu, Kuo; Lian, Zhihua; Xie, Lijuan; He, Hong

    2015-05-13

    A novel Mo-promoted Ce-Zr mixed oxide catalyst prepared by a homogeneous precipitation method was used for the selective catalytic reduction (SCR) of NO(x) with NH3. The optimal catalyst showed high NH3-SCR activity, SO2/H2O durability, and thermal stability under test conditions. The addition of Mo inhibited growth of the CeO2 particle size, improved the redox ability, and increased the amount of surface acidity, especially the Lewis acidity, all of which were favorable for the excellent NH3-SCR performance. It is believed that the catalyst is promising for the removal of NO(x) from diesel engine exhaust. PMID:25894854

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    A high-quality CH3NH3PbI3 film is crucial in the manufacture of a high-performance perovskite solar cell. Here, a recrystallization process via facile fumigation with DMF vapor has been successfully introduced to self-repair of CH3NH3PbI3 films with poor coverage and low crystallinity prepared by the commonly used one-step spin-coating method. We found that the CH3NH3PbI3 films with dendritic structures can spontaneously transform to the uniform ones with full coverage and high crystallinity by adjusting the cycles of the recrystallization process. The mesostructured perovskite solar cells based on these repaired CH3NH3PbI3 films showed reproducible optimal power conversion efficiency (PCE) of 11.15% and average PCE of 10.25 +/- 0.90%, which are much better than that of devices based on the non-repaired CH3NH3PbI3 films. In addition, the hysteresis phenomenon in the current-voltage test can also be effectively alleviated due to the quality of the films being improved in the optimized devices. Our work proved that the fumigation of solvent vapor can modify metal organic perovskite films such as CH3NH3PbI3. It offers a novel and attractive way to fabricate high-performance perovskite solar cells.A high-quality CH3NH3PbI3 film is crucial in the manufacture of a high-performance perovskite solar cell. Here, a recrystallization process via facile fumigation with DMF vapor has been successfully introduced to self-repair of CH3NH3PbI3 films with poor coverage and low crystallinity prepared by the commonly used one-step spin-coating method. We found that the CH3NH3PbI3 films with dendritic structures can spontaneously transform to the uniform ones with full coverage and high crystallinity by adjusting the cycles of the recrystallization process. The mesostructured perovskite solar cells based on these repaired CH3NH3PbI3 films showed reproducible optimal power conversion efficiency (PCE) of 11.15% and average PCE of 10.25 +/- 0.90%, which are much better than that of devices based on the non-repaired CH3NH3PbI3 films. In addition, the hysteresis phenomenon in the current-voltage test can also be effectively alleviated due to the quality of the films being improved in the optimized devices. Our work proved that the fumigation of solvent vapor can modify metal organic perovskite films such as CH3NH3PbI3. It offers a novel and attractive way to fabricate high-performance perovskite solar cells. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00225g

  19. Partial pressures and nature of products. Application to the photolysis of PH 3 and NH 3 in the atmosphere of jupiter and saturn

    NASA Astrophysics Data System (ADS)

    Guillemin, J.-C.; El Chaouch, S.; Bouayad, A.; Janati, T.

    The photolysis of mixtures of gases containing NH 3 or PH 3 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 NH 3, PH 3 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.

  20. Bulk intermixing-type perovskite CH3NH3PbI3/TiO2 nanorod hybrid solar cells

    NASA Astrophysics Data System (ADS)

    Li, Shao-Sian; Wang, Ying-Chiao; Tsai, Chin-Ming; Wen, Cheng-Yen; Yu, Chia-Hao; Yang, Yu-Pei; Lin, Jou-Chun; Wang, Di-Yan; Chen, Chia-Chun; Yeh, Yun-Chieh; Chen, Chun-Wei

    2015-08-01

    To replace high-temperature sintered scaffold materials in conventional CH3NH3PbI3-based solar cells, this study demonstrates a new device structure of a bulk intermixing (BI)-type CH3NH3PbI3/TiO2 nanorod (NR) hybrid solar cell, where dispersed TiO2 NRs from chemical synthesis are intermixed with the perovskite absorbing layer to form a BI-type perovskite/TiO2 NR hybrid for device fabrication. Through interface engineering between the TiO2 NR surface and the photoactive perovskite material of CH3NH3PbI3 by ligand exchange treatment, a remarkable power conversion efficiency (PCE) of over 12% was achieved based on the simple BI-type CH3NH3PbI3/TiO2 NR hybrid device structure. The proposed hybrids not only provide great flexibility for deposition on various substrates through spin coating at low temperatures but also enable layer-by-layer deposition for the future development of perovskite-based multi-junction solar cells.To replace high-temperature sintered scaffold materials in conventional CH3NH3PbI3-based solar cells, this study demonstrates a new device structure of a bulk intermixing (BI)-type CH3NH3PbI3/TiO2 nanorod (NR) hybrid solar cell, where dispersed TiO2 NRs from chemical synthesis are intermixed with the perovskite absorbing layer to form a BI-type perovskite/TiO2 NR hybrid for device fabrication. Through interface engineering between the TiO2 NR surface and the photoactive perovskite material of CH3NH3PbI3 by ligand exchange treatment, a remarkable power conversion efficiency (PCE) of over 12% was achieved based on the simple BI-type CH3NH3PbI3/TiO2 NR hybrid device structure. The proposed hybrids not only provide great flexibility for deposition on various substrates through spin coating at low temperatures but also enable layer-by-layer deposition for the future development of perovskite-based multi-junction solar cells. Electronic supplementary information (ESI) available: TiO2 synthesis and ligand exchange process, device fabrication and characterization. See DOI: 10.1039/c5nr04076k

  1. Bias-dependent effects in planar perovskite solar cells based on CH3NH3PbI(3-x)Clx films.

    PubMed

    Lyu, Miaoqiang; Yun, Jung-Ho; Ahmed, Rasin; Elkington, Daniel; Wang, Qiong; Zhang, Meng; Wang, Hongxia; Dastoor, Paul; Wang, Lianzhou

    2015-09-01

    A unique bias-dependent phenomenon in CH3NH3PbI(3-x)Cl(x) based planar perovskite solar cells has been demonstrated, in which the photovoltaic parameters derived from the current-voltage (I-V) curves are highly dependent on the initial positive bias of the I-V measurement. In FTO/CH3NH3PbI(3-x)Cl(x)/Au devices, the open-circuit voltage and short-circuit current increased by ca. 337.5% and 281.9% respectively, by simply increasing the initial bias from 0.5 V to 2.5 V. PMID:25956128

  2. Synthesis and molecular structure of [Cu(NH3)4][Ni(CN)4]: A missing piece in the [Cu(NH3)n][Ni(CN)4] story

    NASA Astrophysics Data System (ADS)

    Solanki, Dina; Hogarth, Graeme

    2015-11-01

    Reaction of CuCl2·2H2O and K2[Ni(CN)4]·2H2O in aqueous ammonia gave blue rod-like crystals of [Cu(NH3)4][Ni(CN)4]. An X-ray crystallographic reveals that square-planar anions and cations are weakly associated through coordination of a cis pair of cyanide ligands to copper, with one short and one long contact and thus the copper centre is best described as a square-based pyramid. Crystals lose ammonia readily upon removal from the solvent and this has been probed by TGA and DSC measurements. For comparison we have also re-determined the structure of the related ethylenediamine (en) complex [Cu(en)2][Ni(CN)4] at 150 K. This consists of a 1D chain in which a trans pair of cyanide ligands bind to copper such that the latter has an overall tetragonally distorted octahedral coordination geometry.

  3. 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.

  4. Impedance Spectroscopic Indication for Solid State Electrochemical Reaction in (CH3NH3)PbI3 Films.

    PubMed

    Zohar, Arava; Kedem, Nir; Levine, Igal; Zohar, Dorin; Vilan, Ayelet; Ehre, David; Hodes, Gary; Cahen, David

    2016-01-01

    Halide perovskite-based solar cells still have limited reproducibility, stability, and incomplete understanding of how they work. We track electronic processes in [CH3NH3]PbI3(Cl) ("perovskite") films in vacuo, and in N2, air, and O2, using impedance spectroscopy (IS), contact potential difference, and surface photovoltage measurements, providing direct evidence for perovskite sensitivity to the ambient environment. Two major characteristics of the perovskite IS response change with ambient environment, viz. -1- appearance of negative capacitance in vacuo or post-vacuo N2 exposure, indicating for the first time an electrochemical process in the perovskite, and -2- orders of magnitude decrease in the film resistance upon transferring the film from O2-rich ambient atmosphere to vacuum. The same change in ambient conditions also results in a 0.5 V decrease in the material work function. We suggest that facile adsorption of oxygen onto the film dedopes it from n-type toward intrinsic. These effects influence any material characterization, i.e., results may be ambient-dependent due to changes in the material's electrical properties and electrochemical reactivity, which can also affect material stability. PMID:26687721

  5. GaN materials growth by MOVPE in a new-design reactor using DMHy and NH 3

    NASA Astrophysics Data System (ADS)

    Gautier, S.; Sartel, C.; Ould-Saad, S.; Martin, J.; Sirenko, A.; Ougazzaden, A.

    2007-01-01

    Thin films of GaN were grown on template substrates of 4-?m-thick GaN layers on sapphire substrates by low-pressure metal organic vapour-phase epitaxy (LP-MOVPE) in a new-design reactor with the shape T. Wide range of growth temperature from 520 to 1100 °C was explored. At low temperature growth between 550 and 690 °C, dimethylhydrazine (DMHy) was used as source of atomic nitrogen while ammonia (NH 3) was used at high temperature growth (1000-1100 °C). At low temperature micro-Raman spectroscopy revealed a significant relaxation of the selection rules for the scattering by the optical phonons in the films grown at lower temperatures. Variation of the intensity ratio for E 2H and E 1 phonon modes has been attributed to changes in the structural quality of the films grown at different temperatures. At high temperature, the quality of GaN layers were comparable to that of the substrate before growth.

  6. 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; Djuriši?, 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

  7. Preparation and transport properties of hybrid organic-inorganic CH3NH3SnBr3 films

    NASA Astrophysics Data System (ADS)

    Chiarella, F.; Ferro, P.; Licci, F.; Barra, M.; Biasiucci, M.; Cassinese, A.; Vaglio, R.

    2007-01-01

    We describe the preparation, structural and transport properties of CH3NH3SnBr3 organic-inorganic hybrid films (500 nm thick), which crystallize as cubic perovskites. They were deposited by single source thermal ablation technique, in a 10-6 mbar vacuum chamber on glass, polymeric and crystalline substrates. X-ray diffraction proved that they were well crystallized and c-axis oriented. Resistivity measurements as a function of temperature showed a semiconductor behaviour. The activation energy, ?E, was estimated by fitting the linear portions of the resistivity vs. temperature plots and was found to be (0.30±0.01) eV in the 260-230 K temperature interval. A significant change in resistivity was observed at a low temperature T=225 K in coincidence with the structural distortion in the Sn-Br-Sn chains. A field effect device was used to determine the charge carrier type and mobility as a function of temperature and field. The charge carriers were hole type. Their mobility at room temperature was about 10-5 cm2V- 1s- 1. It increased by two orders of magnitude at 320 K and exhibited an almost exponential dependence on the applied gate voltage.

  8. Density Functional Studies of Stoichiometric Surfaces of Orthorhombic Hybrid Perovskite CH3NH3PbI3

    SciTech Connect

    Wang, Yun; Huang, Jingsong; Sumpter, Bobby G; Zhang, Haimin; Liu, Porun; Yang, Huagui; Zhao, Huijun

    2015-01-01

    Organic/inorganic hybrid perovskite materials are highly attractive for dye-sensitized solar cells as demonstrated by their rapid advances in energy conversion efficiency. In this work, the structures, energetics, and electronic properties for a range of stoichiometric surfaces of the orthorhombic perovskite CH3NH3PbI3 are theoretically studied using density functional theory. Various possible spatially and constitutionally isomeric surfaces are considered by diversifying the spatial orientations and connectivities of surface Pb-I bonds. The comparison of the surface energies for the most stable configurations identified for various surfaces shows that the stabilities of stoichiometric surfaces are mainly dictated by the coordination numbers of surface atoms, which are directly correlated with the numbers of broken bonds. Additionally, Coulombic interactions between I anions and organic countercations on the surface also contribute to the stabilization. Electronic properties are compared between the most stable (100) surface and the bulk phase, showing generally similar features except for the lifted band degeneracy and the enhanced bandgap energy for the surface. These studies on the stoichiometric surfaces serve as the first step toward gaining a fundamental understanding of the interfacial properties in the current structural design of perovskite based solar cells, in order to achieve further breakthroughs in solar conversion efficiencies.

  9. Feasible boundaries of aqueous two-phase systems with NH(3) and CO(2) as recyclable volatile salts.

    PubMed

    van Berlo, M; Ottens, M; Luyben, K C; van Der Wielen, L A

    2000-10-01

    Aqueous two-phase systems (ATPSs) have great potential for use in the downstream processing of fermentation products. A major drawback of these systems, limiting application in industrial practice up till now, is the consumption of large amounts of auxiliary materials such as polymers and salts. Making use of alternative auxiliaries can diminish this relatively large discharge. A possible approach is to make use of volatile salts induced by combinations of ammonia and carbon dioxide that can be recycled to the extraction system. As part of an ongoing research effort on ATPSs with volatile salts, this work aims at getting more information on the system boundaries or operating conditions of these systems in terms of phase behavior. The results show that the NH(3)/CO(2) ratio is an important parameter that has a large influence on the system boundaries. Both for systems with PEG 2000 and PEG 4000, this ratio has to be larger than about 1.75 to make a liquid-liquid phase separation possible. The most optimal ratio seems to be 2.0 for reasons of solution composition and absence of solid salt. PMID:10940864

  10. Effect of hyperfine interactions on ultracold molecular collisions: NH(3?-) with Mg(1S) in magnetic fields

    NASA Astrophysics Data System (ADS)

    González-Martínez, Maykel L.; Hutson, Jeremy M.

    2011-11-01

    We investigate the effect of hyperfine interactions on ultracold molecular collisions in magnetic fields, using 24Mg(1S)+14NH(3?-) as a prototype system. We explore the energy and magnetic-field dependence of the cross sections, comparing the results with previous calculations that neglected hyperfine interactions [A.O.G. Wallis and J. M. Hutson, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.103.183201 103, 183201 (2009)]. The main effect of hyperfine interactions for spin relaxation cross sections is that the kinetic energy release of the dominant outgoing channels does not reduce to zero at low fields. This results in reduced centrifugal suppression of the cross sections and increased inelastic cross sections at low energy and low field. We also analyze state-to-state cross sections, for various initial states, and show that hyperfine interactions introduce additional mechanisms for spin relaxation. In particular, there are hyperfine-mediated collisions to outgoing channels that are not centrifugally suppressed. However, for Mg+NH these unsuppressed channels make only small contributions to the total cross sections. We consider the implications of our results for sympathetic cooling of NH by Mg and conclude that the ratio of elastic to inelastic cross sections remains high enough for sympathetic cooling to proceed.

  11. Thermal Assisted Oxygen Annealing for High Efficiency Planar CH3NH3PbI3 Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Ren, Zhiwei; Ng, Annie; Shen, Qian; Gokkaya, Huseyin Cem; Wang, Jingchuan; Yang, Lijun; Yiu, Wai-Kin; Bai, Gongxun; Djuriši?, Aleksandra B.; Leung, Wallace Woon-Fong; Hao, Jianhua; Chan, Wai Kin; Surya, Charles

    2014-10-01

    We report investigations on the influences of post-deposition treatments on the performance of solution-processed methylammonium lead triiodide (CH3NH3PbI3)-based planar solar cells. The prepared films were stored in pure N2 at room temperature or annealed in pure O2 at room temperature, 45°C, 65°C and 85°C for 12 hours prior to the deposition of the metal electrodes. It is found that annealing in O2 leads to substantial increase in the power conversion efficiencies (PCEs) of the devices. Furthermore, strong dependence on the annealing temperature for the PCEs of the devices suggests that a thermally activated process may underlie the observed phenomenon. It is believed that the annealing process may facilitate the diffusion of O2 into the spiro-MeOTAD for inducing p-doping of the hole transport material. Furthermore, the process can result in lowering the localized state density at the grain boundaries as well as the bulk of perovskite. Utilizing thermal assisted O2 annealing, high efficiency devices with good reproducibility were attained. A PCE of 15.4% with an open circuit voltage (VOC) 1.04 V, short circuit current density (JSC) 23 mA/cm2, and fill factor 0.64 had been achieved for our champion device.

  12. Rashba Spin-Orbit Coupling Enhanced Carrier Lifetime in CH3NH3PbI3.

    PubMed

    Zheng, Fan; Tan, Liang Z; Liu, Shi; Rappe, Andrew M

    2015-12-01

    Organometal halide perovskites are promising solar-cell materials for next-generation photovoltaic applications. The long carrier lifetime and diffusion length of these materials make them very attractive for use in light absorbers and carrier transporters. While these aspects of organometal halide perovskites have attracted the most attention, the consequences of the Rashba effect, driven by strong spin-orbit coupling, on the photovoltaic properties of these materials are largely unexplored. In this work, taking the electronic structure of CH3NH3PbI3 (methylammonium lead iodide) as an example, we propose an intrinsic mechanism for enhanced carrier lifetime in three-dimensional (3D) Rashba materials. On the basis of first-principles calculations and a Rashba spin-orbit model, we demonstrate that the recombination rate is reduced due to the spin-forbidden transition. These results are important for understanding the fundamental physics of organometal halide perovskites and for optimizing and designing the materials with better performance. The proposed mechanism including spin degrees of freedom offers a new paradigm of using 3D Rashba materials for photovoltaic applications. PMID:26461166

  13. 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

  14. Reinterpretation of the Vibrational Spectroscopy of the Medicinal Bioinorganic Synthon c,c,t-[Pt(NH3)2Cl2(OH)2]†

    PubMed Central

    Johnstone, Timothy C.

    2014-01-01

    The Pt(IV) complex c,c,t-[Pt(NH3)2Cl2(OH)2] is an important intermediate in the synthesis of Pt(IV) anticancer prodrugs and has been investigated as an anticancer agent in its own right. An analysis of the vibrational spectroscopy of this molecule was previously reported [Faggiani et al., 1982, Can. J. Chem. 60, 529] in which crystallographic determination of the structure of the complex permitted a site group approach. The space group, however, was incorrectly assigned. In the present study we have redetermined at high resolution crystal structures of c,c,t-[Pt(NH3)2Cl2(OH)2] and c,c,t-[Pt(NH3)2Cl2(OH)2]·H2O2, which enable discussion of the effect of hydrogen bonding on the N–H and O–H vibrational bands. The correct crystallographic site symmetry of the platinum complex in the c,c,t-[Pt(NH3)2Cl2(OH)2] structure is employed to conduct a new vibrational analysis using both group theoretical and modern DFT methods. This analysis reveals the nature and symmetry of the “missing band” described in the original publication and suggests a possible explanation for its disappearance. PMID:24515615

  15. Difference in chemical reactions in bulk plasma and sheath regions during surface modification of graphene oxide film using capacitively coupled NH3 plasma

    NASA Astrophysics Data System (ADS)

    Lee, Sung-Youp; Kim, Chan; Kim, Hong Tak

    2015-09-01

    Reduced graphene oxide (r-GO) films were obtained from capacitively coupled NH3 plasma treatment of spin-coated graphene oxide (GO) films at room temperature. Variations were evaluated according to the two plasma treatment regions: the bulk plasma region (Rbulk) and the sheath region (Rsheath). Reduction and nitridation of the GO films began as soon as the NH3 plasma was exposed to both regions. However, with the increase in treatment time, the reduction and nitridation reactions differed in each region. In the Rbulk, NH3 plasma ions reacted chemically with oxygen functional groups on the GO films, which was highly effective for reduction and nitridation. While in the Rsheath, physical reactions by ion bombardment were dominant because plasma ions were accelerated by the strong electrical field. The accelerated plasma ions reacted not only with the oxygen functional groups but also with the broken carbon chains, which caused the removal of the GO films by the formation of hydrocarbon gas species. These results showed that reduction and nitridation in the Rbulk using capacitively coupled NH3 plasma were very effective for modifying the properties of r-GO films for application as transparent conductive films.

  16. Modified two-step deposition method for high-efficiency TiO2/CH3NH3PbI3 heterojunction solar cells.

    PubMed

    Shi, Jiangjian; Luo, Yanhong; Wei, Huiyun; Luo, Jianheng; Dong, Juan; Lv, Songtao; Xiao, Junyan; Xu, Yuzhuan; Zhu, Lifeng; Xu, Xin; Wu, Huijue; Li, Dongmei; Meng, Qingbo

    2014-06-25

    Hybrid organic-inorganic perovskites (e.g., CH3NH3PbI3) are promising light absorbers for the third-generation photovoltaics. Herein we demonstrate a modified two-step deposition method to fabricate a uniform CH3NH3PbI3 capping layer with high-coverage and thickness of 300 nm on top of the mesoporous TiO2. The CH3NH3PbI3 layer shows high light-harvesting efficiency and long carrier lifetime over 50 ns. On the basis of the as-prepared film, TiO2/CH3NH3PbI3 heterojunction solar cells achieve a power conversion efficiency of 10.47% with a high open-circuit voltage of 948 mV, the highest recorded to date for hole-transport-material-free (HTM-free) perovskite-based heterojunction cells. The efficiency exceeding 10% shows promising prospects for the HTM-free solar cells based on organic lead halides. PMID:24830329

  17. Comparison of the Cardiac MicroPET Images Obtained Using [18F]FPTP and [13N]NH3 in Rat Myocardial Infarction Models

    PubMed Central

    2014-01-01

    The short half-life of current positron emission tomography (PET) cardiac tracers limits their widespread clinical use. We previously developed a 18F-labeled phosphonium cation, [18F]FPTP, that demonstrated sharply defined myocardial defects in a corresponding infarcted myocardium. The aim of this study was to compare the image properties of PET scans obtained using [18F]FPTP with those obtained using [13N]NH3 in rat myocardial infarction models. Perfusion abnormality was analyzed in 17 segments of polar map images. The myocardium-to-liver and myocardium-to-lung ratios of [18F]FPTP were 10.48 and 2.65 times higher, respectively, than those of [13N]NH3 in images acquired 30 min after tracer injection. The myocardial defect size measured by [18F]FPTP correlated more closely with the hypoperfused area measured by quantitative 2,3,5-triphenyltetrazolium chloride staining (r = 0.89, P < 0.01) than did [13N]NH3 (r = 0.84, P < 0.01). [18F]FPTP might be useful as a replacement for the myocardial agent [13N]NH3 in cardiac PET/CT applications. PMID:25313324

  18. The Impact of Fertilizer Type and Application Method on the Loss of Greenhouse (CO2, N2O, CH4), and Air Quality (NH3) Gases

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An experiment initiated in the Spring of 2007 at the Sand Mountain Agricultural Experiment Station in Crossville, AL will be discussed. The objective of this experiment is to evaluate the loss of NH3 from different land management (conventional tillage vs. conservation tillage), fertilizers (urea-a...

  19. Microengineered CH3 NH3 PbI3 Nanowire/Graphene Phototransistor for Low-Intensity Light Detection at Room Temperature.

    PubMed

    Spina, Massimo; Lehmann, Mario; Náfrádi, Bálint; Bernard, Laurent; Bonvin, Eric; Gaál, Richard; Magrez, Arnaud; Forró, László; Horváth, Endre

    2015-10-01

    The first hybrid phototransistors are reported where the performance of a network of photoactive CH3 NH3 PbI3 nanowires is enhanced by CVD-grown monolayer graphene. These devices show responsivities as high as ?2.6 × 10(6) A W(-1) in the visible range, showing potential as room-temperature single-electron detectors. PMID:26172855

  20. quantum mechanics finite dimensional systems Ammonia (NH3) is a highly polar molecule, with dipole moment p = 4.7 10-30 C m. Ammonia

    E-print Network

    quantum mechanics finite dimensional systems Ammonia Ammonia (NH3) is a highly polar molecule, with dipole moment p = 4.7 × 10-30 C · m. Ammonia undergoes quantum oscillations between the two phases of up of the rotating molecule is preserved. Let us consider the ammonia molecule in the presence of an electric field

  1. Effect of ammonia on new particle formation: A kinetic H2SO4-H2O-NH3 nucleation model constrained by laboratory measurements

    E-print Network

    Yu, Fangqun

    Effect of ammonia on new particle formation: A kinetic H2SO4-H2O- NH3 nucleation model constrained investigations are discussed. Citation: Yu, F. (2006), Effect of ammonia on new particle formation: A kinetic H2 of this paper is on the possible role of ammonia in stabilizing the critical embryo and thus enhancing

  2. Low-temperature surface formation of NH3 and HNCO: hydrogenation of nitrogen atoms in CO-rich interstellar ice analogues

    NASA Astrophysics Data System (ADS)

    Fedoseev, G.; Ioppolo, S.; Zhao, D.; Lamberts, T.; Linnartz, H.

    2015-01-01

    Solid-state astrochemical reaction pathways have the potential to link the formation of small nitrogen-bearing species, like NH3 and HNCO, and prebiotic molecules, specifically amino acids. To date, the chemical origin of such small nitrogen-containing species is still not well understood, despite the fact that ammonia is an abundant constituent of interstellar ices towards young stellar objects and quiescent molecular clouds. This is mainly because of the lack of dedicated laboratory studies. The aim of this work is to experimentally investigate the formation routes of NH3 and HNCO through non-energetic surface reactions in interstellar ice analogues under fully controlled laboratory conditions and at astrochemically relevant temperatures. This study focuses on the formation of NH3 and HNCO in CO-rich (non-polar) interstellar ices that simulate the CO freeze-out stage in dark interstellar cloud regions, well before thermal and energetic processing start to become relevant. We demonstrate and discuss the surface formation of solid HNCO through the interaction of CO molecules with NH radicals - one of the intermediates in the formation of solid NH3 upon sequential hydrogenation of N atoms. The importance of HNCO for astrobiology is discussed.

  3. On the Surface Formation of NH3 and HNCO in Dark Molecular Clouds - Searching for Wöhler Synthesis in the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Fedoseev, Gleb; Lamberts, Thanja; Linnartz, Harold; Ioppolo, Sergio; Zhao, Dongfeng

    Despite its potential to reveal the link between the formation of simple species and more complex molecules (e.g., amino acids), the nitrogen chemistry of the interstellar medium (ISM) is still poorly understood. Ammonia (NH _{3}) is one of the few nitrogen-bearing species that have been observed in interstellar ices toward young stellar objects (YSOs) and quiescent molecular clouds. The aim of the present work is to experimentally investigate surface formation routes of NH _{3} and HNCO through non-energetic surface reactions in interstellar ice analogues under fully controlled laboratory conditions and at astrochemically relevant cryogenic temperatures. This study focuses on the formation of NH _{3} and HNCO in CO-rich (non-polar) interstellar ices that simulate the CO freeze-out stage in interstellar dark cloud regions, well before thermal and energetic processing start to become predominant. Our work confirms the surface formation of ammonia through the sequential addition of three hydrogen/deuterium atoms to a single nitrogen atom at low temperature. The H/D fractionation of the formed ammonia is also shown. Furthermore, we show the surface formation of solid HNCO through the interaction of CO molecules with NH radicals - one of the intermediates in the formation of solid NH _{3}. Finally, we discuss the implications of HNCO in astrobiology, as a possible starting point for the formation of more complex prebiotic species.

  4. Air Pollution Grant Ideas Possible air pollutants to study: SO2, H2S, NO2, NH3, CO, CO2, O3.

    E-print Network

    Short, Daniel

    Air Pollution Grant Ideas Possible air pollutants to study: SO2, H2S, NO2, NH3, CO, CO2, O3 ­ increase awareness of air pollution. Would include tubes and chemicals. Can request advanced monitoring EPA's National Ambient Air Quality Standard covers this entire group of NOx, NO2 is the component

  5. The challenge of deciphering linkage isomers in mixtures of oligomeric complexes derived from 9-methyladenine and trans-(NH3)2Pt(II) units.

    PubMed

    Ibáñez, Susana; Mihály, Béla; Sanz Miguel, Pablo J; Steinborn, Dirk; Pretzer, Irene; Hiller, Wolf; Lippert, Bernhard

    2015-04-01

    Metal coordination to N9-substituted adenines, such as the model nucleobase 9-methyladenine (9MeA), under neutral or weakly acidic pH conditions in water preferably occurs at N1 and/or N7. This leads, not only to mononuclear linkage isomers with N1 or N7 binding, but also to species that involve both N1 and N7 metal binding in the form of dinuclear or oligomeric species. Application of a trans-(NH3)2Pt(II) unit and restriction of metal coordination to the N1 and N7 sites and the size of the oligomer to four metal entities generates over 50 possible isomers, which display different feasible connectivities. Slowly interconverting rotamers are not included in this number. Based on (1)H?NMR spectroscopic analysis, a qualitative assessment of the spectroscopic features of N1,N7-bridged species was attempted. By studying the solution behavior of selected isolated and structurally characterized compounds, such as trans-[PtCl(9MeA-N7)(NH3)2]ClO4?2H2O or trans,trans-[{PtCl(NH3)2}2(9MeA-N1,N7)][ClO4]2?H2O, and also by application of a 9MeA complex with an (NH3)3Pt(II) entity at N7, [Pt(9MeA-N7)(NH3)3][NO3]2, which blocks further cross-link formation at the N7 site, basic NMR spectroscopic signatures of N1,N7-bridged Pt(II) complexes were identified. Among others, the trinuclear complex trans-[Pt(NH3)2{?-(N1-9MeA-N7)Pt(NH3)3}2][ClO4]6?2H2O was crystallized and its rotational isomerism in aqueous solution was studied by NMR spectroscopy and DFT calculations. Interestingly, simultaneous Pt(II) coordination to N1 and N7 acidifies the exocyclic amino group of the two 9MeA ligands sufficiently to permit replacement of one proton each by a bridging heterometal ion, Hg(II) or Cu(II), under mild conditions in water. PMID:25737270

  6. Planar CH3NH3PbBr3 hybrid solar cells with 10.4% power conversion efficiency, fabricated by controlled crystallization in the spin-coating process.

    PubMed

    Heo, Jin Hyuck; Song, Dae Ho; Im, Sang Hyuk

    2014-12-23

    A power conversion efficiency of 10.4% is demonstrated in planar CH3 NH3 PbBr3 hybrid solar cells without hysteresis of the J-V curve, by way of controlled crystallization in the spin-coating process. The high efficiency is attributed to the formation of a dense CH3 NH3 PbBr3 thin film by the introduction of HBr solution because the HBr increases the solubility of the CH3 NH3 PbBr3 and forms a thinner CH3 NH3 PbBr3 layer with full surface coverage. PMID:25348285

  7. Using stable isotopes of reactive N in dry and wet deposition to investigate the source, transport, and fate of NOx and NH3

    NASA Astrophysics Data System (ADS)

    Felix, J.; Elliott, E. M.

    2011-12-01

    Reactive N emissions (NH3 and NOx) can reach the land surfaces via both wet (NH4+, NO3) and dry (NOx, HNO3, NH3, NH4+) depositional processes. Together, these reactive N compounds are important global contributors to air and water quality degradation. Although nitrate concentrations in wet deposition have decreased in the U.S. during the last two decades due to NOx emission regulations set forth by the Clean Air Act, ammonium concentrations in wet deposition have recently increased. In order to further decrease NOx emissions and decrease NH3 emissions, additional tools for reactive N source apportionment are essential. The stable isotopic composition of reactive N may be one such tool for characterizing source, transport, and fate of reactive N emissions. Here, we present results from a comprehensive inventory of the isotopic composition of reactive N emission sources, focusing mainly on agricultural and fossil fuel sources. We build on these inventory results by tracing reactive N emissions across multiple landscapes including: a dairy operation, a conventionally managed cornfield, a tallgrass prairie, and a concentrated animal feeding operation. We then use two examples to illustrate how reactive N isotopes can be used in a regional context. First, we illustrate how passive NH3 samplers deployed at nine U.S. monitoring sites reflect spatial variations in predominant NH3 sources. Secondly, we reconstruct the regional influence of agricultural NOx emissions to nitrate deposition recorded in an ice core from Summit, Greenland. These results reveal significant evidence that the trend in the N isotopic composition of 20th century nitrate deposition in Greenland was driven by increasing biogenic soil NOx emissions induced by fertilizer application in the US over the last century. Together, these studies demonstrate the isotopic composition of reactive N emissions can be an additional tool for investigators to source and trace reactive N emissions in both historical and modern contexts and across spatial scales.

  8. VizieR Online Data Catalog: A variationally computed hot NH3 line list - BYTe (Yurchenko+, 2011)

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

    We present 'BYTe' a comprehensive 'hot' line list of ro-vibrational transitions of ammonia, 14NH3, in its ground electronic state. It comprises 1,138,323,351 transitions with frequencies up to 12,000cm-1^, constructed from 1,373,897 energy levels below 18,000cm-1^ having J values less than 37. The line list is sufficiently accurate and complete for high resolution spectroscopy and atmospheric modelling of astrophysical objects, including brown dwarfs and exoplanets at temperatures up to 1,500K. The data are in two parts. The first, nh3_0-41.dat contains a list of 4,167,360 rovibrational states, ordered by J (max= 41), symmetry block and energy (in cm-1^). Only one third of the states (1,373,897) are within the parameters used for generating transitions (see above), but all the states are required for computing temperature-dependent partition functions. Each state is labelled with: seven normal mode vibrational quantum numbers; three rotational quantum numbers and the total symmetry quantum number, Gamma. In addition there are six local mode vibrational numbers and a local mode vibrational symmetry quantum numbers, which we include because the basis set used in our calculations is expressed in terms of these local mode quantum numbers. Each rovibrational state has a unique number, which is the number of the row in which it appears in the file. This number is the means by which the state is related to the second part of the data system, the transitions files. Because of their size, the transitions are listed in 120 separate files, each containing all the transitions in a 100cm-1^ frequency range. These and their contents are ordered by increasing frequency. The name of the file includes the lowest frequency in the range; thus the a-00500.dat file contains all the transitions in the frequency range 500-600cm-1^. The transition files contain three columns: the reference number in the energy file of the upper state; that of the lower state; and the Einstein A coefficient of the transition. The energy file and the transitions files are zipped, and need to be extracted before use. There is a Fortran 90 programme, sp_byte.f90 which may be used to generate synthetic spectra (see sp_byte.txt for details). Using this, it is possible to generate absorption or emission spectra in either 'stick' form or else convoluted with a gaussian with the half-width at half maximum being specified by the user, or with a the temperature-dependent doppler half-width. Three sample input files for use with sp_byte.f90 are supplied: "stick300.in", "gauss300.in", and "sp08900.in" (generates a spectrum for 8900-9000cm-1^). (126 data files).

  9. Hydrogen-release mechanisms in LiNH2BH3·NH3BH3: A theoretical study

    NASA Astrophysics Data System (ADS)

    Tao, Jingcong; Lv, Naixia; Wen, Li; Qi, Yong; Lv, Xiaobo

    2015-02-01

    The molecular mechanism of the dehydrogenation of LiNH2BH3·NH3BH3 to form [LiN2B2H] by the loss of five molar equiv of H2 at two consecutive temperatures of 373 K and 501 K has been investigated using computational quantum chemistry methods (B3LYP, MP2 and CCSD(T) methods). The intermediate LiNHBH2·NH2BH2 can be obtained through the pathway A at 373 K, in which LiH structures are formed by the transfer of hydridic H- from NH2BH3- to Li+ followed by the redox reactions of H?+ and H?- to form two molar equiv of H2. The intermediate LiNH2BHdbnd NHBH3 can also be generated via the pathway B at 373 K, in which a new Nsbnd B bond forms and two equiv of H2 are released by the redox reactions. At 501 K, the predominant final product P1 (LiNBNBH) is given most likely through the formation of LiH and a series of redox reactions with the loss of three molar equiv of H2 in the pathway A. Meanwhile, the products P2 (LiNBBNH) and P3 [Li(sbnd NBBNsbnd)H] may be also obtained by the dehydrogenation via a sequence of redox reactions of H?+ and H?- to release three equiv of H2 at the temperature of 501 K. The present study would be helpful for experimental chemists to design better hydrogen-storage media.

  10. Efficient hysteresis-less bilayer type CH3NH3PbI3 perovskite hybrid solar cells.

    PubMed

    Park, Jin Kyoung; Heo, Jin Hyuck; Han, Hye Ji; Lee, Min Ho; Song, Dae Ho; You, Myoung Sang; Sung, Shi-Joon; Kim, Dae-Hwan; Im, Sang Hyuk

    2016-01-15

    Bilayer type CH3NH3PbI3 (MAPbI3) perovskite hybrid solar cells were fabricated via a one-step spin-coating process by using solubility controlled MAPbI3 solutions of MAPbI3-DMSO (dimethyl sulfoxide) and MAPbI3-DMF (N, N-dimethylformamide)-HI. The best DMSO-bilayer device showed 1.07 ± 0.02 V V oc (open-circuit voltage), 20.2 ± 0.1 mA cm(-2) J sc (short-circuit current density), 68 ± 2% FF (fill factor), and 15.2 ± 0.3% ? (overall power conversion efficiency) under the forward scan direction and 1.07 ± 0.02 V V oc, 20.4 ± 0.1 mA cm(-2) J sc, 70 ± 3% FF, and 15.9 ± 0.4% ? under the reverse scan direction. The best HI-bilayer device had 1.08 ± 0.02 V V oc, 20.6 ± 0.1 mA cm(-2) J sc, 75 ± 1% FF, and 17.2 ± 0.2% ? under the forward scan direction and 1.08 ± 0.02 V V oc, 20.6 ± 0.1 mA cm(-2) J sc, 76 ± 2% FF, and 17.4 ± 0.3% ? under the reverse scan direction. The deviation of average device efficiency ([Formula: see text] of 20 DMSO samples and 20 HI samples was 14.2 ± 0.95% and 16.2 ± 0.85%, respectively. Therefore, the HI-bilayer devices exhibited better device efficiency and smaller J-V (current density-voltage) hysteresis with respect to the scan direction than the DMSO-bilayer devices due to the reduced recombination and traps by the formation of a purer and larger MAPbI3 perovskite crystalline film. PMID:26618542

  11. Influence of ceria modification on the properties of TiO2-ZrO2 supported V2O5 catalysts for selective catalytic reduction of NO by NH3.

    PubMed

    Zhang, Yaping; Zhu, Xiaoqiang; Shen, Kai; Xu, Haitao; Sun, Keqin; Zhou, Changcheng

    2012-06-15

    TiO(2)-ZrO(2) (hereafter denoted as Ti-Zr) supported V(2)O(5) catalysts with different loadings of CeO(2) were synthesized, and their physicochemical properties were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), in situ Fourier transform infrared spectroscopy (in situ FT-IR) and temperature-programmed reduction (TPR). Their catalytic activities toward the NO(x) reduction reaction with NH(3) were tested. We found that with the addition of CeO(2), more NO was removed in a wide temperature range of 220-500 °C. As the CeO(2) content was increased from 10% to 20% (i.e., the molar ratio of Ce to Ti-Zr), NO conversion increased significantly; after that, increasing CeO(2) content, however, decreased NO conversion. In particular, the addition of CeO(2) to V(2)O(5)/Ti-Zr suppressed the coke deposition and rendered a stable and high catalytic activity. The characterization results indicated that: (1) the deposited vanadium and cerium oxides were highly dispersed over the Ti-Zr support, and in addition to ZrV(2)O(7), a common binary compound observed in V(2)O(5)/Ti-Zr, CeVO(4) and Ce(3)ZrO(8) was formed upon increasing CeO(2) content; (2) the introduction of CeO(2) to V(2)O(5)/Ti-Zr sample promoted the redox ability of the resulting catalysts; and (3) the Ce-containing catalysts possessed the greater amount of surface acidic and active intermediate. PMID:22464542

  12. Rapid screening of pharmaceutical drugs using thermal desorption - SALDI mass spectrometry

    NASA Astrophysics Data System (ADS)

    Grechnikov, A. A.; Kubasov, A. E.; Georgieva, V. B.; Borodkov, A. S.; Nikiforov, S. M.; Simanovsky, Ya O.; Alimpiev, S. S.

    2012-12-01

    A novel approach to the rapid screening of pharmaceutical drugs by surface assisted laser desorption-ionization (SALDI) mass spectrometry with the rotating ball interface coupled with temperature programmed thermal desorption has been developed. Analytes were thermally desorbed and deposited onto the surface of amorphous silicon substrate attached to the rotating ball. The ball was rotated and the deposited analytes were analyzed using SALDI. The effectiveness of coupling SALDI mass spectrometry with thermal desorption was evaluated by the direct and rapid analysis of tablets containing lidocaine, diphenhydramine and propranolol without any sample pretreatment. The overall duration of the screening procedure was 30÷40 sec. Real urine samples were studied for drug analysis. It is shown that with simple preparation steps, urine samples can be quantitatively analyzed using the proposed technique with the detection limits in the range of 0.2÷0.5 ng/ml.

  13. Estimating the agricultural fertilizer NH3 emission in China based on the bi-directional CMAQ model and an agro-ecosystem model

    NASA Astrophysics Data System (ADS)

    Wang, S.

    2014-12-01

    Atmospheric ammonia (NH3) plays an important role in fine particle formation. Accurate estimates of ammonia can reduce uncertainties in air quality modeling. China is one of the largest countries emitting ammonia with the majority of NH3 emissions coming from the agricultural practices, such as fertilizer applications and animal operations. The current ammonia emission estimates in China are mainly based on pre-defined emission factors. Thus, there are considerable uncertainties in estimating NH3 emissions, especially in time and space distribution. For example, fertilizer applications vary in the date of application and amount by geographical regions and crop types. In this study, the NH3 emission from the agricultural fertilizer use in China of 2011 was estimated online by an agricultural fertilizer modeling system coupling a regional air-quality model and an agro-ecosystem model, which contains three main components 1) the Environmental Policy Integrated Climate (EPIC) model, 2) the meso-scale meteorology Weather Research and Forecasting (WRF) model and 3) the CMAQ air quality model with bi-directional ammonia fluxes. The EPIC output information about daily fertilizer application and soil characteristics would be the input of the CMAQ model. In order to run EPIC model, much Chinese local information is collected and processed. For example, Crop land data are computed from the MODIS land use data at 500-m resolution and crop categories at Chinese county level; the fertilizer use rate for different fertilizer types, crops and provinces are obtained from Chinese statistic materials. The system takes into consideration many influencing factors on agriculture ammonia emission, including weather, the fertilizer application method, timing, amount, and rate for specific pastures and crops. The simulated fertilizer data is compared with the NH3 emissions and fertilizer application data from other sources. The results of CMAQ modeling are also discussed and analyzed with field measurements. The estimated agricultural fertilizer NH3 emission in this study is about 3Tg in 2011. The regions with the highest emission rates are located in the North China Plain. Monthly, the peak ammonia emissions occur in April to July.

  14. Desorption of a two-state system: Laser probing of gallium atom spin-orbit states from silicon (100)

    NASA Astrophysics Data System (ADS)

    Carleton, Karen L.; Bourguignon, Bernard; Leone, Stephen R.

    The interactions of gallium atom spin-orbit states with silicon (100) surfaces are studied by temperature programmed desorption (TPD) using laser-induced fluorescence detection. State-resolved sticking coefficients are measured and are found to be unity for both spin-orbit states ( 2P{1}/{2}, 2P{3}/{2}, ?E = 2.5 kcal mol-1, 10.5 kJ mol-1) up to surface temperatures of 1000 K. A Redhead analysis of the state-specific TPD spectra yields essentially identical energies and pre-exponential factors for both spin-orbit states. A statistical branching ratio is observed between the 2P {1}/{2} and 2P {3}/{2} Ga states at the peak of the TPD curves. These results may be accounted for by a rapid interconversion between the two states during the desorption. Since the spin-orbit splitting in this case is small, a rapid interconversion may be anticipated; however, modeling the desorption kinetics yields important features for the desorption of a two-state system. The model shows that the Redhead analysis is not adequate to measure the desorption kinetic parameters of the individual states. The TPD spectra of the two states differ only very slightly because their shape is mainly controlled by the overall rate of desorption for the sum of the two channels. The population ratio between the states allows a direct comparison of the desorption energetics of the two channels. Errors of 5-10 kcal mol -1 can occur in a determination of the desorption energy of a hypothetical, slowly desorbing state if the presence of a rapid desorption channel is ignored. The model can be generalized to describe any multiple channel surface process, including multi-state desorption of the competition between desorption and diffusion into the bulk. These results are of interest in the epitaxial growth of GaAs on Si(100).

  15. Enhanced NH3 gas sensing properties of a QCM sensor by increasing the length of vertically orientated ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Minh, Vu Anh; Tuan, Le Anh; Huy, Tran Quang; Hung, Vu Ngoc; Quy, Nguyen Van

    2013-01-01

    Vertically aligned ZnO nanorods were directly synthesised on a gold electrode of quartz crystal microbalance (QCM) by a simple low-temperature hydrothermal method for a NH3 gas sensing application. The length of vertically aligned ZnO nanorods was increased to purpose enhancement in the gas sensing response of the sensor. The length of ZnO nanorods increased with an increase in growth time. The growth time of ZnO nanorods was systematically varied in the range of 1-4 h to examine the effect of the length of the ZnO nanorods on the gas sensing properties of the fabricated sensors. The gas sensing properties of sensors with different ZnO nanorods lengths was examined at room temperature for various concentrations of NH3 (50-800 ppm) in synthetic air. Enhancement in gas sensing response by increasing the length of ZnO nanorods was observed.

  16. Synthesis, optical properties and photostability of novel fluorinated organic-inorganic hybrid (R-NH3)2PbX4 semiconductors

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Audebert, P.; Galmiche, L.; Lauret, J.-S.; Deleporte, E.

    2013-04-01

    We report on the synthesis and the optical properties of several novel semiconductors (R-NH3)2PbX4(X = Br-, I- or Cl-). These semiconductors are two-dimensional organic-inorganic perovskite (2DOIP) materials and have multiple quantum-well energy level structures. We vary the organic components (R{--}NH_{3}^{+}) , introducing fluorine atoms into the organic part, on the phenyl ring of the amine. We discuss its influence on the self-organization ability and long-term photostability of the 2DOIPs. The trends of introducing fluorine atoms on the self-organization and long-term photostability of 2DOIPs are obtained by analysing the optical experimental results, and show that the influence of the fluorine position on the benzene ring is quite important. The most promising compounds seem to be the ones with the fluorine atom sitting on the para position of the phenyl group.

  17. The naked-eye detection of NH(3) -HCl by polyaniline-infiltrated TiO(2) inverse opal photonic crystals.

    PubMed

    Liu, Cihui; Gao, Guizhi; Zhang, Yuqi; Wang, Libin; Wang, Jingxia; Song, Yanlin

    2012-03-16

    A reversible color change of a polyaniline-infiltrated TiO(2) inverse opal photonic crystal (PC) film can be obtained when the PC is switched from an acidic to alkali vapor environment. In a saturated NH(3) environment, the stopband of the as-prepared PCs changes from 556 to 688 nm; such large shift of 132 nm could be observed, corresponding to a clear color change from green to red. After placing in HCl vapor, the stopband undergoes a blue-shift and the color turns back to green. The result is ascribed to PANI being doped or dedoped by acid or base and the effective refractive index of the PC film varying accordingly. The naked-eye detection of NH(3) and HCl vapors can be realized by the reversible color change of the PC film, which is of importance for chemical and biological sensors. PMID:22287386

  18. Direct Observation of Long Electron-Hole Diffusion Distance beyond 1 Micrometer in CH3NH3PbI3 Perovskite Thin Film

    E-print Network

    Li, Yu; Li, Yunlong; Wang, Wei; Bian, Zuqiang; Xiao, Lixin; Wang, Shufeng; Gong, Qihuang

    2015-01-01

    In high performance perovskite based on CH3NH3PbI3, the formerly reported short charge diffusion distance is a confliction to thick working layer in solar cell devices. We carried out a study on charge diffusion in spin-coated CH3NH3PbI3 perovskite thin film by transient fluorescent spectroscopy. A thickness-dependent fluorescent lifetime was found. This effect correlates to the defects at crystal grain boundaries. By coating the film with electron or hole transfer layer, PCBM or Spiro-OMeTAD respectively, we observed the charge transfer directly through the fluorescent decay. One-dimensional diffusion model was applied to obtain long charge diffusion distances, which is ~1.3 micron for electrons and ~5.2 micron for holes. This study gives direct support to the high performance of perovskite solar cells.

  19. The recombination mechanisms leading to amplified spontaneous emission at the true-green wavelength in CH3NH3PbBr3 perovskites

    NASA Astrophysics Data System (ADS)

    Priante, D.; Dursun, I.; Alias, M. S.; Shi, D.; Melnikov, V. A.; Ng, T. K.; Mohammed, O. F.; Bakr, O. M.; Ooi, B. S.

    2015-02-01

    We investigated the mechanisms of radiative recombination in a CH3NH3PbBr3 hybrid perovskite material using low-temperature, power-dependent (77 K), and temperature-dependent photoluminescence (PL) measurements. Two bound-excitonic radiative transitions related to grain size inhomogeneity were identified. Both transitions led to PL spectra broadening as a result of concurrent blue and red shifts of these excitonic peaks. The red-shifted bound-excitonic peak dominated at high PL excitation led to a true-green wavelength of 553 nm for CH3NH3PbBr3 powders that are encapsulated in polydimethylsiloxane. Amplified spontaneous emission was eventually achieved for an excitation threshold energy of approximately 350 ?J/cm2. Our results provide a platform for potential extension towards a true-green light-emitting device for solid-state lighting and display applications.

  20. (CH3NH3)2Pb(SCN)2I2: A More Stable Structural Motif for Hybrid Halide Photovoltaics?

    PubMed

    Ganose, Alex M; Savory, Christopher N; Scanlon, David O

    2015-11-19

    Hybrid halide perovskites have recently emerged as a highly efficient class of light absorbers; however, there are increasing concerns over their long-term stability. Recently, incorporation of SCN(-) has been suggested as a novel route to improving stability without negatively impacting performance. Intriguingly, despite crystallizing in a 2D layered structure, (CH3NH3)2Pb(SCN)2I2 (MAPSI) possesses an ideal band gap of 1.53 eV, close to that of the 3D connected champion hybrid perovskite absorber, CH3NH3PbI3 (MAPI). Here, we identify, using hybrid density functional theory, the origin of the smaller than expected band gap of MAPSI through a detailed comparison with the electronic structure of MAPI. Furthermore, assessment of the MAPSI structure reveals that it is thermodynamically stable with respect to phase separation, a likely source of the increased stability reported in experiment. PMID:26525942

  1. Direct Conversion of CH3NH3PbI3 from Electrodeposited PbO for Highly Efficient Planar Perovskite Solar Cells

    PubMed Central

    Huang, Jin-hua; Jiang, Ke-jian; Cui, Xue-ping; Zhang, Qian-qian; Gao, Meng; Su, Mei-ju; Yang, Lian-ming; Song, Yanlin

    2015-01-01

    Organic-inorganic hybrid perovskite materials have recently been identified as a promising light absorber for solar cells. In the efficient solar cells, the perovskite active layer has generally been fabricated by either vapor deposition or two-step sequential deposition process. Herein, electrochemically deposited PbO film is in situ converted into CH3NH3PbI3 through solid-state reaction with adjacent CH3NH3I layer, exhibiting a large-scale flat and uniform thin film with fully substrate coverage. The resultant planar heterojunction photovoltaic device yields a best power conversion efficiency of 14.59% and an average power conversion efficiency of 13.12?±?1.08% under standard AM 1.5 conditions. This technique affords a facile and environment-friendly method for the fabrication of the perovskite based solar cells with high reproducibility, paving the way for the practical application. PMID:26510520

  2. Direct Conversion of CH3NH3PbI3 from Electrodeposited PbO for Highly Efficient Planar Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Huang, Jin-Hua; Jiang, Ke-Jian; Cui, Xue-Ping; Zhang, Qian-Qian; Gao, Meng; Su, Mei-Ju; Yang, Lian-Ming; Song, Yanlin

    2015-10-01

    Organic-inorganic hybrid perovskite materials have recently been identified as a promising light absorber for solar cells. In the efficient solar cells, the perovskite active layer has generally been fabricated by either vapor deposition or two-step sequential deposition process. Herein, electrochemically deposited PbO film is in situ converted into CH3NH3PbI3 through solid-state reaction with adjacent CH3NH3I layer, exhibiting a large-scale flat and uniform thin film with fully substrate coverage. The resultant planar heterojunction photovoltaic device yields a best power conversion efficiency of 14.59% and an average power conversion efficiency of 13.12?±?1.08% under standard AM 1.5 conditions. This technique affords a facile and environment-friendly method for the fabrication of the perovskite based solar cells with high reproducibility, paving the way for the practical application.

  3. Direct Conversion of CH3NH3PbI3 from Electrodeposited PbO for Highly Efficient Planar Perovskite Solar Cells.

    PubMed

    Huang, Jin-Hua; Jiang, Ke-Jian; Cui, Xue-Ping; Zhang, Qian-Qian; Gao, Meng; Su, Mei-Ju; Yang, Lian-Ming; Song, Yanlin

    2015-01-01

    Organic-inorganic hybrid perovskite materials have recently been identified as a promising light absorber for solar cells. In the efficient solar cells, the perovskite active layer has generally been fabricated by either vapor deposition or two-step sequential deposition process. Herein, electrochemically deposited PbO film is in situ converted into CH3NH3PbI3 through solid-state reaction with adjacent CH3NH3I layer, exhibiting a large-scale flat and uniform thin film with fully substrate coverage. The resultant planar heterojunction photovoltaic device yields a best power conversion efficiency of 14.59% and an average power conversion efficiency of 13.12?±?1.08% under standard AM 1.5 conditions. This technique affords a facile and environment-friendly method for the fabrication of the perovskite based solar cells with high reproducibility, paving the way for the practical application. PMID:26510520

  4. A laboratory Atlas of the 5 nu-1 NH3 absorption band at 6475 A with applications to Jupiter and Saturn

    NASA Technical Reports Server (NTRS)

    Giver, L. P.; Miller, J. H.; Boese, R. W.

    1975-01-01

    A complete atlas of the 5 nu-1 absorption band of NH3 is presented together with measurements of the total band intensity, line intensities, and self-broadening coefficients. The spectrum, which is displayed in the interval from 6418 to 6550 A, was obtained photoelectrically at a pressure of 0.061 atm, and many more lines were seen in this spectrum than in a previous one obtained at a pressure of 0.39 atm. The band intensity is used to derive the NH3 abundance in the atmospheres of Jupiter and Saturn, and the abundances in a single vertical path are found to be about 10 m amagat for Jupiter and 2 m amagat for Saturn. These results are shown to be in agreement with previous results obtained from higher resolution photographic spectra.

  5. Ion—polar-molecule reactions: A CRESU study of He +, C +, N + + H 2O, NH 3 at 27, 68 and 163 K

    NASA Astrophysics Data System (ADS)

    Marquette, J. B.; Rowe, B. R.; Dupeyrat, G.; Poissant, G.; Rebrion, C.

    1985-12-01

    The first measurements of ion—polar-molecule reaction rate constants at very low temperatures are presented. They have been obtained using the CRESU (cine_.tique de reactions en ecoulement supersonique uniforme) technique for H +.C + and N + ions reacting with H 2O and NH 3 at 27 and 68 K in helium buffer. Additional data have been obtained for N + reactions at 163 K in nitrogen buffer. In the 27-300 K (27-163 K for N + + NH 3) temperature range, all the results yield a power law, k = k0T- n (0 < n < 1), for the rate coefficient of each reaction, which should be applied in interstellar cloud model in place of the room-temperature values. The results are compared with various theoretical calculations. Rather good agreement is found although no general behavior can be simply drawn from these experiments.

  6. Full Printable Processed Mesoscopic CH3NH3PbI3/TiO2 Heterojunction Solar Cells with Carbon Counter Electrode

    PubMed Central

    Ku, Zhiliang; Rong, Yaoguang; Xu, Mi; Liu, Tongfa; Han, Hongwei

    2013-01-01

    A mesoscopic methylammonium lead iodide (CH3NH3PbI3) perovskite/TiO2 heterojunction solar cell is developed with low-cost carbon counter electrode (CE) and full printable process. With carbon black/spheroidal graphite CE, this mesoscopic heterojunction solar cell presents high stability and power conversion efficiency of 6.64%, which is higher than that of the flaky graphite based device and comparable to the conventional Au version. PMID:24185501

  7. Site preference of NH3-adsorption on Co, Pt and CoPt surfaces: the role of charge transfer, magnetism and strain.

    PubMed

    Bhattacharjee, S; Gupta, K; Jung, N; Yoo, S J; Waghmare, U V; Lee, S C

    2015-04-14

    Oxidation of Co at the surface poses a major problem in the cyclable use of CoPt, a cost-effective catalyst for proton exchange membrane fuel cells. This can be alleviated by attaching a ligand selectively to Co-sites to stop its oxidation without compromising the catalytic activity. Here, we present a comparative analysis of adsorption of NH3 on the (0001) surface of Co in the HCP structure and (111) surfaces of Pt and CoPt alloy in the FCC structure, using first-principles density functional theoretical calculations. While NH3 binds more strongly with the Pt surface than with the Co surface, we find that its binding with the Co atom is stronger than that with the Pt atom on the surface of the CoPt alloy. Our analysis of the charge density and electronic structure shows how this originates from (a) the electron transfer from the minority spin d-band of Co to Pt, and (b) shift in the energy of d-bands and the magnetic moments of Co atoms on the surface of the CoPt alloy relative to those on the (0001) surface of Co. Hybridization of the d-states of Co in CoPt with pz states of N in NH3 used to stop Co oxidation also results in improving the charge transfer from Co to Pt that is relevant to the catalytic activity of CoPt. We finally present the analysis of how the interaction of NH3 with the CoPt surface can be tuned with strain. PMID:25760894

  8. Efficient CH3 NH3 PbI3 Perovskite Solar Cells Employing Nanostructured p-Type NiO Electrode Formed by a Pulsed Laser Deposition.

    PubMed

    Park, Jong Hoon; Seo, Jangwon; Park, Sangman; Shin, Seong Sik; Kim, Young Chan; Jeon, Nam Joong; Shin, Hee-Won; Ahn, Tae Kyu; Noh, Jun Hong; Yoon, Sung Cheol; Hwang, Cheol Seong; Seok, Sang Il

    2015-07-15

    Highly transparent and nanostructured nickel oxide (NiO) films through pulsed laser deposition are introduced for efficient CH3 NH3 PbI3 perovskite solar cells. The (111)-oriented nanostructured NiO film plays a key role in extracting holes and preventing electron leakage as hole transporting material. The champion device exhibits a power conversion efficiency of 17.3% with a very high fill factor of 0.813. PMID:26038099

  9. Enhanced photovoltaic performance of CH3NH3PbI3 perovskite solar cells through interfacial engineering using self-assembling monolayer.

    PubMed

    Zuo, Lijian; Gu, Zhuowei; Ye, Tao; Fu, Weifei; Wu, Gang; Li, Hanying; Chen, Hongzheng

    2015-02-25

    Morphology control is critical to achieve high efficiency CH3NH3PbI3 perovskite solar cells (PSC). The surface properties of the substrates on which crystalline perovskite thin films form are expected to affect greatly the crystallization and, thus, the resulting morphology. However, this topic is seldom examined in PSC. Here we developed a facile but efficient method of modifying the ZnO-coated substrates with 3-aminopropanioc acid (C3-SAM) to direct the crystalline evolution and achieve the optimal morphology of CH3NH3PbI3 perovskite film. With incorporation of the C3-SAM, highly crystalline CH3NH3PbI3 films were formed with reduced pin-holes and trap states density. In addition, the work function of the cathode was better aligned with the conduction band minimum of perovskite for efficient charge extraction and electronic coupling. As a result, the PSC performance remarkably increased from 9.81(±0.99)% (best 11.96%) to 14.25(±0.61)% (best 15.67%). We stress the importance of morphology control through substrate surface modification to obtain the optimal morphology and device performance of PSC, which should generate an impact on developing highly efficient PSC and future commercialization. PMID:25650811

  10. DRIFT studies on promotion mechanism of H3PW12O40 in selective catalytic reduction of NO with NH3.

    PubMed

    Weng, Xiaole; Dai, Xiaoxia; Zeng, Qingshan; Liu, Yue; Wu, Zhongbiao

    2016-01-01

    Heteropoly acids (HPAs) have been effectively utilized in selective catalytic reduction (SCR) of NO to improve the NH3 absorption capacity and alkaline/alkali metal resistance for SCR catalysts. However, despite the promise on super-acidities, their other properties that would work on SCR process are still lack of exploration. In this study, a 12-tungstaphosphoric acid (H3PW12O40, HPW) was selected to modify a well-reported CeO2 catalyst. The resulted CeO2/HPW catalyst was subsequently utilized for SCR of NO with excess NH3, which revealed a significantly promoted performance in SCR reaction. DRIFT analyses showed that the unique NO2 absorption capacity of HPW could prevent the NO2 being further oxidized into nitrate species and the abundant Brønsted acid sites could effectively retain the NH3, avoiding them being over-oxidized at evaluated temperatures. The presence of NO2 was demonstrated able to induce a so called "fast SCR" reaction over the CeO2/HPW catalyst, which effectively facilitated the SCR reaction. Furthermore, we have also constructed a CeO2@HPW catalyst, which showed an enhanced SO2 poisoning resistance in SCR reaction. PMID:26397902

  11. Efficient perovskite solar cells based on low-temperature solution-processed (CH3NH3)PbI3 perovskite/CuInS2 planar heterojunctions

    PubMed Central

    2014-01-01

    In this work, the solution-processed CH3NH3PbI3 perovskite/copper indium disulfide (CuInS2) planar heterojunction solar cells with Al2O3 as a scaffold were fabricated at a temperature as low as 250°C for the first time, in which the indium tin oxide (ITO)-coated glass instead of the fluorine-doped tin oxide (FTO)-coated glass was used as the light-incidence electrode and the solution-processed CuInS2 layer was prepared to replace the commonly used TiO2 layer in previously reported perovskite-based solar cells. The influence of the thickness of the as-prepared CuInS2 film on the performance of the ITO/CuInS2(n)/Al2O3/(CH3NH3)PbI3/Ag cells was investigated. The ITO/CuInS2(2)/Al2O3/(CH3NH3)PbI3/Ag cell showed the best performance and achieved power conversion efficiency up to 5.30%. PMID:25278818

  12. Ultrasensitive solution-processed broad-band photodetectors using CH3NH3PbI3 perovskite hybrids and PbS quantum dots as light harvesters

    NASA Astrophysics Data System (ADS)

    Liu, Chang; Wang, Kai; Du, Pengcheng; Wang, Enmin; Gong, Xiong; Heeger, Alan J.

    2015-10-01

    Sensing from ultraviolet-visible to infrared is critical for both scientific and industrial applications. In this work, we demonstrate solution-processed ultrasensitive broad-band photodetectors (PDs) utilizing organolead halide perovskite materials (CH3NH3PbI3) and PbS quantum dots (QDs) as light harvesters. Through passivating the structural defects on the surface of PbS QDs with diminutive molecular-scaled CH3NH3PbI3, both trap states in the bandgap of PbS QDs for charge carrier recombination and the leakage currents occurring at the defect sites are significantly reduced. In addition, CH3NH3PbI3 itself is an excellent light harvester in photovoltaics, which contributes a great photoresponse in the ultraviolet-visible region. Consequently, operated at room temperature, the resultant PDs show a spectral response from 375 nm to 1100 nm, with high responsivities over 300 mA W-1 and 130 mA W-1, high detectivities exceeding 1013 Jones (1 Jones = 1 cm Hz1/2 W-1) and 5 × 1012 Jones in the visible and near infrared regions, respectively. These device performance parameters are comparable to those from pristine inorganic counterparts. Thus, our results offer a facile and promising route for advancing the performance of broad-band PDs.

  13. Homogeneous Emission Line Broadening in the Organo Lead Halide Perovskite CH3NH3PbI3-xClx.

    PubMed

    Wehrenfennig, Christian; Liu, Mingzhen; Snaith, Henry J; Johnston, Michael B; Herz, Laura M

    2014-04-17

    The organic-inorganic hybrid perovskites methylammonium lead iodide (CH3NH3PbI3) and the partially chlorine-substituted mixed halide CH3NH3PbI3-xClx emit strong and broad photoluminescence (PL) around their band gap energy of ?1.6 eV. However, the nature of the radiative decay channels behind the observed emission and, in particular, the spectral broadening mechanisms are still unclear. Here we investigate these processes for high-quality vapor-deposited films of CH3NH3PbI3-xClx using time- and excitation-energy dependent photoluminescence spectroscopy. We show that the PL spectrum is homogenously broadened with a line width of 103 meV most likely as a consequence of phonon coupling effects. Further analysis reveals that defects or trap states play a minor role in radiative decay channels. In terms of possible lasing applications, the emission spectrum of the perovskite is sufficiently broad to have potential for amplification of light pulses below 100 fs pulse duration. PMID:26269971

  14. Ammonia as an in situ sanitizer: inactivation kinetics and mechanisms of the ssRNA virus MS2 by NH3.

    PubMed

    Decrey, Loïc; Kazama, Shinobu; Udert, Kai M; Kohn, Tamar

    2015-01-20

    Sanitizing human and animal waste (e.g., urine, fecal sludge, or grey water) is a critical step in reducing the spread of disease and ensuring microbially safe reuse of waste materials. Viruses are particularly persistent pathogens and can be transmitted through inadequately sanitized waste. However, adequate storage or digestion of waste can strongly reduce the number of viruses due to increases in pH and uncharged aqueous ammonia (NH3), a known biocide. In this study we investigated the kinetics and mechanisms of inactivation of the single-stranded RNA virus MS2 under temperature, pH and NH3 conditions representative of waste storage. MS2 inactivation was mainly controlled by the activity of NH3 over a pH range of 7.0–9.5 and temperatures lower than 40 °C. Other bases (e.g., hydroxide, carbonate) additionally contributed to the observed reduction of infective MS2. The loss in MS2 infectivity could be rationalized by a loss in genome integrity, which was attributed to genome cleavage via alkaline transesterification. The contribution of each base to genome transesterification, and hence inactivation, could be related to the base pKa by means of a Bronsted relationship. The Bronsted relationship in conjunction with the activity of bases in solution enabled an accurate prediction of MS2 inactivation rates. PMID:25496714

  15. Dual functions of Lewis acid and base of Se in F2C=Se and their interplay in F 2CSe•••NH 3•••HX.

    PubMed

    Guo, Xin; Li, Qingzhong

    2015-06-01

    High-level quantum chemical calculations of the ternary systems F2CSe???NH3???HX (X=BeH, BH2, OH, CN, OCH3, Cl, and F) and the corresponding binary systems have been carried out in view of geometries, vibrational frequencies, interaction energies, orbital interactions, and electron densities. The molecular electrostatic potentials of F2CSe demonstrate that the Se atom could play a dual role of Lewis acid and base to form a chalcogen bond with NH3 and a hydrogen bond or a covalent interaction with HX, respectively. The chalcogen bond can compete with the hydrogen bond for the complexes involving F2CSe, but the covalent interaction is far stronger than the chalcogen bond. In the ternary complexes, both types of interactions are strengthened by each other, characterized by a shorter binding distance, a larger electron density, and a stronger orbital interaction. The covalent interaction has a greater enhancing effect on the chalcogen bond than the hydrogen bond does, resulting in a prominent shortening of ~0.23 Å distance for the Se???N distance in F2CSe???NH3???BH3. The enhancement of both interactions in the ternary complexes has been understood with the electrostatic potentials and orbital interactions. Graphical Abstract The dual functions of Lewis acid and base of Se in F2CSe are enhanced each other in the ternary complexes. PMID:26016943

  16. Room-temperature NH3 gas sensors based on Ag-doped ?-Fe2O3/SiO2 composite films with sub-ppm detection ability.

    PubMed

    Tang, Yongliang; Li, Zhijie; Zu, Xiaotao; Ma, Jinyi; Wang, Lu; Yang, Jing; Du, Bo; Yu, Qingkai

    2015-11-15

    In this report, NH3 gas sensors based on Ag-doped ?-Fe2O3/SiO2 composite films are investigated. The composite films were prepared with a sol-gel process, and the films' electrical resistance responded to the change of NH3 concentration in the environment. The SEM and AFM investigations showed that the films had a porous structure, and the XRD investigation indicated that the size of Ag particles changed with the modification of Ag loading content. Through a comparative gas sensing study among the Ag-doped composite films, undoped composite film, ?-Fe2O3 film, and SiO2 film, the Ag-doped composite films were found to be much more sensitive than the sensors based on the undoped composite film and ?-Fe2O3 film at room temperature, indicating the significant influences of the SiO2 and Ag on the sensing property. Moreover, the sensor based on Ag-doped (4%) ?-Fe2O3/SiO2 composite film was able to detect the NH3 gas at ppb level. Conversely, the responses of the sensor to other test gases (C2H5OH, CO, H2, CH4 and H2S) were all markedly low, suggesting excellent selectivity. PMID:26057440

  17. Complex Refractive Index Spectra of CH3NH3PbI3 Perovskite Thin Films Determined by Spectroscopic Ellipsometry and Spectrophotometry.

    PubMed

    Löper, Philipp; Stuckelberger, Michael; Niesen, Bjoern; Werner, Jérémie; Filipi?, Miha; Moon, Soo-Jin; Yum, Jun-Ho; Topi?, Marko; De Wolf, Stefaan; Ballif, Christophe

    2015-01-01

    The complex refractive index (dielectric function) of planar CH3NH3PbI3 thin films at room temperature is investigated by variable angle spectroscopic ellipsometry and spectrophotometry. Knowledge of the complex refractive index is essential for designing photonic devices based on CH3NH3PbI3 thin films such as solar cells, light-emitting diodes, or lasers. Because the directly measured quantities (reflectance, transmittance, and ellipsometric spectra) are inherently affected by multiple reflections, the complex refractive index has to be determined indirectly by fitting a model dielectric function to the experimental spectra. We model the dielectric function according to the Forouhi-Bloomer formulation with oscillators positioned at 1.597, 2.418, and 3.392 eV and achieve excellent agreement with the experimental spectra. Our results agree well with previously reported data of the absorption coefficient and are consistent with Kramers-Kronig transformations. The real part of the refractive index assumes a value of 2.611 at 633 nm, implying that CH3NH3PbI3-based solar cells are ideally suited for the top cell in monolithic silicon-based tandem solar cells. PMID:26263093

  18. In situ DRIFTS-MS studies on the oxidation of adsorbed NH3 by NOx over a Cu-SSZ-13 zeolite

    SciTech Connect

    Zhu, Haiyang; Kwak, Ja Hun; Peden, Charles HF; Szanyi, Janos

    2013-04-30

    DRIFT spectroscopy combined with mass spectrometry was used to investigate the oxidation of adsorbed ammonia by NO2, NO+O2 and NO2+O2 on a copper ion exchanged SSZ 13 (Cu-SSZ-13) zeolite. Compared with both NO2 and NO, the adsorption of ammonia is much stronger on the Cu-SSZ-13 zeolite. Two adsorbed ammonia species were found over the Cu-SSZ-13 zeolite studied here; notably ammonia on Brönsted acid sites (proton) and ammonia on Lewis acid sites (copper ions). These adsorbed ammonia species present different activity profiles and selectivity to N2 during NH3 oxidation. The results obtained suggest that ammonia adsorbed onto copper ions in Cu-SSZ-13 are more active at low temperatures than proton-adsorbed NH3, and give rise to a higher selectivity to N2. The formation of N2O is associated primarily with the reaction of NOx with proton-adsorbed NH3 via the formation and subsequent thermal decomposition of NH4NO3. Financial support was provided by the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program. Portions of this work were performed in the Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory (PNNL). The EMSL is a national scientific user facility supported by the US DOE, Office of Biological and Environmental Research. PNNL is a multi-program national laboratory operated for the US DOE by Battelle.

  19. Ultrasensitive solution-processed broad-band photodetectors using CH3NH3PbI3 perovskite hybrids and PbS quantum dots as light harvesters.

    PubMed

    Liu, Chang; Wang, Kai; Du, Pengcheng; Wang, Enmin; Gong, Xiong; Heeger, Alan J

    2015-10-01

    Sensing from ultraviolet-visible to infrared is critical for both scientific and industrial applications. In this work, we demonstrate solution-processed ultrasensitive broad-band photodetectors (PDs) utilizing organolead halide perovskite materials (CH3NH3PbI3) and PbS quantum dots (QDs) as light harvesters. Through passivating the structural defects on the surface of PbS QDs with diminutive molecular-scaled CH3NH3PbI3, both trap states in the bandgap of PbS QDs for charge carrier recombination and the leakage currents occurring at the defect sites are significantly reduced. In addition, CH3NH3PbI3 itself is an excellent light harvester in photovoltaics, which contributes a great photoresponse in the ultraviolet-visible region. Consequently, operated at room temperature, the resultant PDs show a spectral response from 375 nm to 1100 nm, with high responsivities over 300 mA W(-1) and 130 mA W(-1), high detectivities exceeding 10(13) Jones (1 Jones = 1 cm Hz(1/2) W(-1)) and 5 × 10(12) Jones in the visible and near infrared regions, respectively. These device performance parameters are comparable to those from pristine inorganic counterparts. Thus, our results offer a facile and promising route for advancing the performance of broad-band PDs. PMID:26395642

  20. Hydrogen desorption from hydrogen fluoride and remote hydrogen plasma cleaned silicon carbide (0001) surfaces

    SciTech Connect

    King, Sean W. Tanaka, Satoru; Davis, Robert F.; Nemanich, Robert J.

    2015-09-15

    Due to the extreme chemical inertness of silicon carbide (SiC), in-situ thermal desorption is commonly utilized as a means to remove surface contamination prior to initiating critical semiconductor processing steps such as epitaxy, gate dielectric formation, and contact metallization. In-situ thermal desorption and silicon sublimation has also recently become a popular method for epitaxial growth of mono and few layer graphene. Accordingly, numerous thermal desorption experiments of various processed silicon carbide surfaces have been performed, but have ignored the presence of hydrogen, which is ubiquitous throughout semiconductor processing. In this regard, the authors have performed a combined temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS) investigation of the desorption of molecular hydrogen (H{sub 2}) and various other oxygen, carbon, and fluorine related species from ex-situ aqueous hydrogen fluoride (HF) and in-situ remote hydrogen plasma cleaned 6H-SiC (0001) surfaces. Using XPS, the authors observed that temperatures on the order of 700–1000?°C are needed to fully desorb C-H, C-O and Si-O species from these surfaces. However, using TPD, the authors observed H{sub 2} desorption at both lower temperatures (200–550?°C) as well as higher temperatures (>700?°C). The low temperature H{sub 2} desorption was deconvoluted into multiple desorption states that, based on similarities to H{sub 2} desorption from Si (111), were attributed to silicon mono, di, and trihydride surface species as well as hydrogen trapped by subsurface defects, steps, or dopants. The higher temperature H{sub 2} desorption was similarly attributed to H{sub 2} evolved from surface O-H groups at ?750?°C as well as the liberation of H{sub 2} during Si-O desorption at temperatures >800?°C. These results indicate that while ex-situ aqueous HF processed 6H-SiC (0001) surfaces annealed at <700?°C remain terminated by some surface C–O and Si–O bonding, they may still exhibit significant chemical reactivity due to the creation of surface dangling bonds resulting from H{sub 2} desorption from previously undetected silicon hydride and surface hydroxide species.

  1. Desorption and sublimation kinetics for fluorinated aluminum nitride surfaces

    SciTech Connect

    King, Sean W. Davis, Robert F.; Nemanich, Robert J.

    2014-09-01

    The adsorption and desorption of halogen and other gaseous species from surfaces is a key fundamental process for both wet chemical and dry plasma etch and clean processes utilized in nanoelectronic fabrication processes. Therefore, to increase the fundamental understanding of these processes with regard to aluminum nitride (AlN) surfaces, temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS) have been utilized to investigate the desorption kinetics of water (H{sub 2}O), fluorine (F{sub 2}), hydrogen (H{sub 2}), hydrogen fluoride (HF), and other related species from aluminum nitride thin film surfaces treated with an aqueous solution of buffered hydrogen fluoride (BHF) diluted in methanol (CH{sub 3}OH). Pre-TPD XPS measurements of the CH{sub 3}OH:BHF treated AlN surfaces showed the presence of a variety of Al-F, N-F, Al-O, Al-OH, C-H, and C-O surfaces species in addition to Al-N bonding from the AlN thin film. The primary species observed desorbing from these same surfaces during TPD measurements included H{sub 2}, H{sub 2}O, HF, F{sub 2}, and CH{sub 3}OH with some evidence for nitrogen (N{sub 2}) and ammonia (NH{sub 3}) desorption as well. For H{sub 2}O, two desorption peaks with second order kinetics were observed at 195 and 460?°C with activation energies (E{sub d}) of 51?±?3 and 87?±?5?kJ/mol, respectively. Desorption of HF similarly exhibited second order kinetics with a peak temperature of 475?°C and E{sub d} of 110?±?5?kJ/mol. The TPD spectra for F{sub 2} exhibited two peaks at 485 and 585?°C with second order kinetics and E{sub d} of 62?±?3 and 270?±?10?kJ/mol, respectively. These values are in excellent agreement with previous E{sub d} measurements for desorption of H{sub 2}O from SiO{sub 2} and AlF{sub x} from AlN surfaces, respectively. The F{sub 2} desorption is therefore attributed to fragmentation of AlF{sub x} species in the mass spectrometer ionizer. H{sub 2} desorption exhibited an additional high temperature peak at 910?°C with E{sub d}?=?370?±?10?kJ/mol that is consistent with both the dehydrogenation of surface AlOH species and H{sub 2} assisted sublimation of AlN. Similarly, N{sub 2} exhibited a similar higher temperature desorption peak with E{sub d}?=?535?±?40?kJ/mol that is consistent with the activation energy for direct sublimation of AlN.

  2. Ultraviolet laser desorption of indole

    NASA Astrophysics Data System (ADS)

    Elam, Jeffrey W.; Levy, Donald H.

    1997-06-01

    Ultraviolet laser desorption from a thick, 120 K indole film was studied. Using a 2660 Å, 10 ns desorption laser at 75 mJ/cm2, 2.0 monolayers of indole are removed per shot. Indole0 is the only neutral species desorbed and it has an internal temperature Ti=210 K and a translational temperature Tt=3400 K. The velocity distribution is non-Boltzmann and the angular distribution is bimodal and forward peaked with major component proportional to cos7(?). No evidence of "jetlike" structure in the desorbed plume is found: Different regions of the plume are at the same internal temperature and both internally hot and cold molecules have identical angle velocity distributions. While existing collisional models cannot account for the details of these distributions, they suggest that 2-7 collisions per molecule occur following desorption producing minor vibrational cooling (<10%). Laser desorbed indole+ is observed at a concentration of ˜10-5 that of indole0 with an angle velocity distribution similar to that of indole0. We show that indole+ results from resonant two photon ionization of indole0 by the desorption laser and that desorption laser heating of the plume occurs at 2660 Å.

  3. The release of trapped gases from amorphous solid water films. II. ``Bottom-up'' induced desorption pathways

    NASA Astrophysics Data System (ADS)

    Alan May, R.; Scott Smith, R.; Kay, Bruce D.

    2013-03-01

    In this (Paper II) and the preceding companion paper (Paper I; R. May, R. Smith, and B. Kay, J. Chem. Phys. 138, 104501 (2013), 10.1063/1.4793311), we investigate the mechanisms for the release of trapped gases from underneath amorphous solid water (ASW) films. In Paper I, we focused on the low coverage regime where the release mechanism is controlled by crystallization-induced cracks formed in the ASW overlayer. In that regime, the results were largely independent of the particular gas underlayer. Here in Paper II, we focus on the high coverage regime where new desorption pathways become accessible prior to ASW crystallization. In contrast to the results for the low coverage regime (Paper I), the release mechanism is a function of the multilayer thickness and composition, displaying dramatically different behavior between Ar, Kr, Xe, CH4, N2, O2, and CO. Two primary desorption pathways are observed. The first occurs between 100 and 150 K and manifests itself as sharp, extremely narrow desorption peaks. Temperature programmed desorption is utilized to show that these abrupt desorption bursts are due to pressure induced structural failure of the ASW overlayer. The second pathway occurs at low temperature (typically <100 K) where broad desorption peaks are observed. Desorption through this pathway is attributed to diffusion through pores formed during ASW deposition. The extent of desorption and the line shape of the low temperature desorption peak are dependent on the substrate on which the gas underlayer is deposited. Angle dependent ballistic deposition of ASW is used to vary the porosity of the overlayer and strongly supports the hypothesis that the low temperature desorption pathway is due to porosity that is templated into the ASW overlayer by the underlayer during deposition.

  4. The Release of Trapped Gases from Amorphous Solid Water Films: II. “Bottom-Up” Induced Desorption Pathways

    SciTech Connect

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

    2013-03-14

    In this (Paper II) and the preceding companion paper (Paper I) we investigate the mechanisms for the release of trapped gases from underneath of amorphous solid water (ASW) films. In Paper I, we focused on the low coverage (pressure) regime where the release mechanism is controlled by crystallization-induced cracks formed in the ASW overlayer. In that regime the results were largely independent of the particular gas underlayer. Here in Paper II, we focus on the high coverage (pressure) regime where new desorption pathways become accessible prior to ASW crystallization. In contrast to the results for the low coverage regime (Paper I), the release mechanism is a function of the multilayer thickness and composition, displaying dramatically different behavior between Ar, Kr, Xe, CH4, N2, O2, and CO. Two primary desorption pathways are observed. The first occurs between 100 and 150 K and manifests itself as sharp, extremely narrow desorption peaks. Temperature programmed desorption is utilized to show that abrupt desorption bursts are due to pressure induced structural failure of the ASW overlyaer. The second pathway occurs at low temperature (typically <100 K) where broad desorption peaks are observed. Desorption through this pathway is attributed to diffusion through pores and connected pathways formed during ASW deposition. The extent of desorption and the lineshape of the low temperature desorption peak are dependent on the substrate on which the gas underlayer is deposited. Angle dependent ballistic deposition of the ASW is used vary the porosity of overlayer and confirm that the low temperature desorption pathway is due to porosity that is inherent in the ASW overlayer during deposition.

  5. Transition from the Tetragonal to Cubic Phase of Organohalide Perovskite: The Role of Chlorine in Crystal Formation of CH3NH3PbI3 on TiO2 Substrates.

    PubMed

    Wang, Qiong; Lyu, Miaoqiang; Zhang, Meng; Yun, Jung-Ho; Chen, Hongjun; Wang, Lianzhou

    2015-11-01

    The role of chlorine in the superior electronic property and photovoltaic performance of CH3NH3PbI(3-x)Clx perovskite has attracted recent research attention. Here, we study the impact of chlorine in the perspective of the crystal structure of the perovskite layer, which can provide important understanding of its excellent charge mobility and extended lifetimes. In particular, we find that in the presence of chlorine (PbCl2 or CH3NH3Cl), when CH3NH3PbI3 films are deposited on a TiO2 mesoporous layer instead of a planar TiO2 substrate, a stable cubic phase rather than the commonly observed tetragonal phase is formed in CH3NH3PbI3 perovskite at room temperature. The relative peak intensity of two major facets of cubic CH3NH3PbI3 crystals, (100)C and (200)C facets, can also be easily tuned, depending on the film thickness. Furthermore, compared with pristine CH3NH3PbI3 perovskite films, in the presence of chlorine, CH3NH3PbI3 crystals grown on planar substrates exhibit strong preferred orientations on (110)T and (220)T facets. PMID:26538049

  6. Effect of Rh particle size on CO desorption from Rh/alumina model catalysts

    NASA Astrophysics Data System (ADS)

    Belton, David N.; Schmieg, Steven J.

    1988-08-01

    The adsorption of CO on small Rh particles on oxidized Al(100) was studied using temperature programmed desorption (TPD) and Auger electron spectroscopy (AES). The desorption data for CO were obtained for two {Rh}/{Al 2O 3} samples as well as for Rh(111). The supported Rh model catalysts were prepared from thermal decomposition of [Rh(CO 2Cl] 2 on an oxidized Al(100) substrate. By varying the substrate temperature and the amount of deposited Rh, samples were prepared with average Rh particles sizes of 20 and 70 Å. TPD data from the 70 Å Rh particles were similar to that from Rh(111), with a major peak at 500 K and a shoulder at 400 K for a saturation CO exposure. TPD from the small particles was very different from Rh(111) and the larger particles, showing a single broad peak centered at 415 K. The data show a particle size effect for the desorption on CO from supported Rh. Redhead analysis of the data for first-order desorption gave an activation energy of 30 kcal/mol for all of the samples at low CO coverages. A more detailed analysis using peak widths and peak temperatures was also performed. These calculations gave a very low activation energy, 19.8 kcal/mol, and preexponential, 1×10 8{cm2}/{s} for the small particles. These very low values were interpreted to mean that multiple desorption states, mobile precursors, or coverage dependent activation energies were affecting the data from the small particles. Calculations of first-order desorption rates showed that desorption states different than those on Rh(111) are the dominant species on the small particles at high CO coverages.

  7. FT-IR measurements of mid-IR propene (C3H6) cross sections and far-IR ammonia (NH3) line intensities

    NASA Astrophysics Data System (ADS)

    Sung, Keeyoon; Toon, Geoffrey C.; Crawford, Timothy J.; Yu, Shanshan; Pearson, John C.; Kwabia Tchana, Fridolin; Manceron, Laurent; Pirali, Olivier

    2015-11-01

    We present spectroscopy measurements of propene (C3H6) in the mid-infrared and ammonia (NH3) in the far-infrared from two different laboratory studies. [1] For propene (CH2-CH-CH3, alias. propylene), which was detected in the stratosphere of Titan [Nixon et al. 2013], temperature dependent cross sections in the 650 – 1530 cm-1 (6.5 – 15.3 ?m) have been measured from a series of high-resolution (0.0022 cm-1) spectra of pure and N2-mixture samples of C3H6 recorded at 150 – 296 K at Jet Propulsion Laboratory. The observed spectral features cover the strongest v19 band with its outstanding Q-branch peak at 912 cm-1 and three other strong bands of v18, v16 and v7 at 990, 1442, and 1459 cm-1, respectively. In addition, we have generated a HITRAN-format empirical ‘pseudoline list' containing line positions, intensities, and effective lower state energies by fitting all the observed spectra simultaneously. The results are compared with early work from relatively warm temperatures (278 – 323 K). [2] For ammonia (NH3), we obtained multiple sets of high-resolution spectra in the THz and far-infrared region (50 – 650 cm-1) at room temperature using AILES beamline at Synchrotron SOLEIL, France (NH3). In this work, we have measured line intensities for more than 4500 transitions, and made quantum assignments for ~2900 lines including ~960 very weak ?K = 3 forbidden lines. Final results will be compared with the current databases (e.g., HITRAN, GEISA) and ab initio calculations. [Research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Sung and Yu acknowledge the Synchrotron Soleil for the AILES beam line time.

  8. Growth and optical, magnetic and transport properties of (C4H9NH3)2MCl4 organic-inorganic hybrid films (M = Cu, Sn)

    NASA Astrophysics Data System (ADS)

    Aruta, C.; Licci, F.; Zappettini, A.; Bolzoni, F.; Rastelli, F.; Ferro, P.; Besagni, T.

    2005-10-01

    Films of (C4H9NH3)2MCl4 (M=Cu and Sn) organic-inorganic hybrid perovskites have been deposited in-situ by a single-source thermal ablation technique on glassy, crystalline and polymeric substrates. Independently of the substrate, the films were well crystallized, c-axis oriented and with a narrow rocking curve of the (0010) reflection (full width at half maximum <1°). The (0 0 ?) reflections were consistent with those of the bulk orthorhombic phases and the “c” lattice parameters were 30.85±0.05 and 32.35±0.05 Å, for the Cu- and the Sn-compound, respectively. (C4H9NH3)2CuCl4 films had an optical absorption peak at 375 nm at room temperature. From the magnetic point of view they act as layered nanocomposites with a dominant ferromagnetic component localized in planes (2D magnetism). Tc was 7.3±0.1 K and a moderate easy-plane anisotropy was observed. The photoluminescence spectra of typical (C4H9NH3)2SnCl4 films at 12 K had a broad yellow band, which did not correspond to any significant peak in the absorption spectrum. The films were semiconducting down to 250 K or, in the case of the best samples, down to 200 K and became insulating at lower temperature. The resistivity of the best films was (5±1) 104 ? cm at 300 K, and the energy gap was 1.11 eV.

  9. Elucidating the band structure and free charge carrier dynamics of pure and impurities doped CH3NH3PbI3-xClx perovskite thin films.

    PubMed

    Zhang, Zhen-Yu; Chen, Xin; Wang, Hai-Yu; Xu, Ming; Gao, Bing-Rong; Chen, Qi-Dai; Sun, Hong-Bo

    2015-11-28

    CH3NH3PbI3-xClx perovskite material has been commonly used as the free charge generator and reservoir in highly efficient perovskite-based solid-state solar photovoltaic devices. However, many of the underlying fundamental photophysical mechanisms in this material such as the perovskite transition band structure as well as the dependent relationship between the carrier properties and lattice properties still lack sufficient understanding. Here, we elucidated the fundamental band structure of the pure CH3NH3PbI3-xClx pervoskite lattice, and then reported about the dependent relationship between the free charge carrier characteristic and the different CH3NH3PbI3-xClx pervoskite lattice thin films utilizing femtosecond time-resolved pump-probe technologies. The data demonstrated that the pure perovskite crystal band structure should only have one conduction and one valence band rather than dual valences, and the pure perovskite lattice could trigger more free charge carriers with a slower recombination rate under an identical pump intensity compared with the impurities doped perovskite crystal. We also investigated the perovskite film performance when exposed to moisture and water, the corresponding results gave us a dip in the optimization of the performance of perovskite based devices, and so as a priority this material should be isolated from moisture (water). This work may propose a deeper perspective on the comprehension for this material and it is useful for future optimization of applications in photovoltaic and light emission devices. PMID:26497219

  10. Solvent effects on the metal-to-ligand charge transfer transition of the complex [Ru(NH3)5(Pyrazine)]2+

    NASA Astrophysics Data System (ADS)

    Chagas, Marcelo A.; Rocha, Willian R.

    2014-09-01

    In this work the solvent effects on the structure and metal-to-ligand charge transfer (MLCT) transition of the complex [Ru(NH3)5(Pyrazine)]2+ was investigated in aqueous solution, using the hybrid Density Functional Theory/Effective Fragment Potential Hamiltonian (DFT/EFP/MD) approach. The MLCT transition causes a large charge separation in the complex and produces a dipole moment variation of 8.3 ± 1.1 Debye upon excitation in solution and causes a large red-shift of 0.55 ± 0.15 eV. The solvatochromic shift can be attributed to the large charge separation accompanying the MLCT transition in solution.

  11. The L1495-B218 filaments in Taurus seen in NH3 & CCS and Dynamical Stability of Filaments and Dense Cores

    NASA Astrophysics Data System (ADS)

    Seo, Youngmin

    2016-01-01

    We present deep NH3 map of L1495-B218 filaments and the dense cores embedded within the filaments in Taurus. The L1495-B218 filaments form an interconnected, nearby, large complex extending 8 pc. We observed the filaments in NH3 (1,1) & (2,2) and CCS 21-10 with spectral resolution of 0.038 km/s and spatial resolution of 31". The CSAR algorithm, which is a hybrid of seeded-watershed and binary dendrogram algorithm, identifies 39 leaves and 16 branches in NH3 (1,1). Applying a virial analysis for the 39 NH3 leaves, we find only 9 out of 39 leaves are gravitationally bound, and 12 out of 30 gravitationally unbound leaves are pressure-confined. Our analysis suggests that a dense core may form as a pressure-confined structure, evolve to a gravitationally bound core, and then undergo collapse to form a protostar (Seo et al. 2015).We also present more realistic dynamic stability conditions for dense cores with converging motions and under the influence of radiation pressure. The critical Bonnor-Ebert sphere and the isothermal cylinder have been widely used to test stability of dense cores and filaments; however, these assume a quiescent environment while actual star forming regions are turbulent and illuminated by radiation. In a new analysis of stability conditions we account for converging motions which have been modeled toward starless cores (Seo et al. 2011) and the effect of radiation fields into account. We find that the critical size of a dense core having a homologous converging motion with its peak speed being the sound speed is roughly half of the critical size of the Bonnor-Ebert sphere (Seo et al. 2013). We also find that the critical mass/line density of a dense core/filament irradiated by radiation are considerably smaller than that of the Bonnor-Ebert sphere/isothermal cylinder when the radiation pressure is stronger than the central gas pressure of dense core/isothermal cylinder. For inner Galactic regions and regions near OB associations, the critical mass/line density of dense structure may be less than 20% of the critical mass/line density of Bonnor-Ebert sphere/isothermal cylinder (Seo et al., in prep.).

  12. Degradation mechanism of perovskite CH3NH3PbI3 diode devices studied by electroluminescence and photoluminescence imaging spectroscopy

    NASA Astrophysics Data System (ADS)

    Okano, Makoto; Endo, Masaru; Wakamiya, Atsushi; Yoshita, Masahiro; Akiyama, Hidefumi; Kanemitsu, Yoshihiko

    2015-10-01

    We investigate the degradation behavior of non-sealed perovskite CH3NH3PbI3 diode devices in air at room temperature by means of electroluminescence (EL) and photoluminescence (PL) imaging techniques. From the comparison of these images, we determine that the spatial fluctuation of the EL intensity is mainly due to fluctuations in the luminescence efficiency of the perovskite layer itself. By applying a constant voltage for tens of minutes, the EL intensity decreases gradually. It is observed that the temporal evolution of the EL intensity is governed by the degradation of the perovskite layer and the carrier injection at the interface.

  13. VUV dissociative excitation cross sections of H2O, NH3, and CH4 by electron impact. [Vacuum Ultra-Violet

    NASA Technical Reports Server (NTRS)

    Morgan, H. D.; Mentall, J. E.

    1974-01-01

    Absolute excitation functions for excited fragments resulting from electron bombardment of H2O, NH3, and CH4 by low-energy electrons (0 to 300 eV) have been measured in the vacuum ultraviolet (1100 to 1950 A). The predominant emission for each molecule was the H Lyman-alpha line, while the O I, N I, C I, and C II emissions were at least an order of magnitude weaker. Absolute cross sections at 100 eV are given along with the appearance potential of the various processes and the possible dissociative-excitation channels through which such processes proceed.

  14. Cooperative effects between halogen bonds and pnicogen bonds in XBr???OFH2P???NH3 (X = F, Cl, CN, NC, OH, and NO2) complexes.

    PubMed

    Zhao, Qiang

    2016-01-01

    Quantum chemical calculations were carried out to investigate interplay between halogen bonds and pnicogen bonds in XBr???OFH2P???NH3 (X = F, Cl, CN, NC, OH, and NO2) complexes at the M06-2X/aug-cc-pVDZ level. Cooperative effects are observed when halogen bonds and pnicogen bonds coexist in the same complex. These effects are analyzed in terms of geometric and energetic properties of the complexes. The mechanism of cooperative effects is analyzed in view with molecular electrostatic potential, natural bond orbital, and density difference of molecule formation analyses. PMID:26645809

  15. Nanowires of methylammonium lead iodide (CH3NH3PbI3) prepared by low temperature solution-mediated crystallization.

    PubMed

    Horváth, Endre; Spina, Massimo; Szekrényes, Zsolt; Kamarás, Katalin; Gaal, Richard; Gachet, David; Forró, László

    2014-12-10

    We report the synthesis of Methylammonium Lead Iodide (CH(3)NH(3)PbI(3)) nanowires by a low temperature solution processed crystallization using a simple slip-coating method. The anisotropic particle shape exhibits advantages over nanoparticles in terms of charge transport under illumination. These results provide a basis for solvent-mediated tailoring of structural properties like the crystallite size and orientation in trihalide perovskite thin films, which, once implemented into a device, may ultimately result in an enhanced charge carrier extraction. PMID:25354371

  16. New insights from comprehensive on-road measurements of NOx, NO2 and NH3 from vehicle emission remote sensing in London, UK

    NASA Astrophysics Data System (ADS)

    Carslaw, David C.; Rhys-Tyler, Glyn

    2013-12-01

    In this paper we report the first direct measurements of nitrogen dioxide (NO2) in the UK using a vehicle emission remote sensing technique. Measurements of NO, NO2 and ammonia (NH3) from almost 70,000 vehicles were made spanning vehicle model years from 1985 to 2012. These measurements were carefully matched with detailed vehicle information data to understand the emission characteristics of a wide range of vehicles in a detailed way. Overall it is found that only petrol fuelled vehicles have shown an appreciable reduction in total NOx emissions over the past 15-20 years. Emissions of NOx from diesel vehicles, including those with after-treatment systems designed to reduce emissions of NOx, have not reduced over the same period of time. It is also evident that the vehicle manufacturer has a strong influence on emissions of NO2 for Euro 4/5 diesel cars and urban buses. Smaller-engined Euro 4/5 diesel cars are also shown to emit less NO2 than larger-engined vehicles. It is shown that NOx emissions from urban buses fitted with Selective Catalytic Reduction (SCR) are comparable to those using Exhaust Gas Recirculation for Euro V vehicles, while reductions in NOx of about 30% are observed for Euro IV and EEV vehicles. However, the emissions of NO2 vary widely dependent on the bus technology used. Almost all the NOx emission from Euro IV buses with SCR is in the form of NO, whereas EEV vehicles (Enhanced Environmentally friendly Vehicle) emit about 30% of the NOx as NO2. We find similarly low amounts of NO2 from trucks (3.5-12t and >12t). Finally, we show that NH3 emissions are most important for older generation catalyst-equipped petrol vehicles and SCR-equipped buses. The NH3 emissions from petrol cars have decreased by over a factor of three from the vehicles manufactured in the late 1990s compared with those manufactured in 2012. Tables of emission factors are presented for NOx, NO2 and NH3 together with uncertainties to assist the development of new emission inventories.

  17. ENGINEERING BULLETIN: THERMAL DESORPTION TREATMENT

    EPA Science Inventory

    Thermal desorption is an EX SITU means to physically separate volatile and some semivolatile contaminants from soil, sediments, sludge, and filter cakes by heating them at temperatures high enough to volatilize the organic contaminants. or wastes containing up to 10 percent organ...

  18. ENGINEERING BULLETIN: THERMAL DESORPTION TREATMENT.

    EPA Science Inventory

    Thermal desorption is an EX SITU means to physically separate volatile and some semivolatile contaminants from soil, sediments, sludge, and filter cakes by heating them at temperatures high enough to volatilize the organic contaminants. For wastes containing up to 10 percent orga...

  19. Selective Catalytic Reduction (SCR) of nitric oxide with ammonia using Cu-ZSM-5 and Va-based honeycomb monolith catalysts: effect of H2 pretreatment, NH3-to-NO ratio, O2, and space velocity 

    E-print Network

    Gupta, Saurabh

    2004-09-30

    In this work, the steady-state performance of zeolite-based (Cu-ZSM-5) and vanadium-based honeycomb monolith catalysts was investigated in the selective catalytic reduction process (SCR) for NO removal using NH3. The aim ...

  20. Erbium hydride thermal desorption : controlling kinetics.

    SciTech Connect

    Ferrizz, Robert Matthew

    2007-08-01

    Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report show that hydride film processing parameters directly impact thermal stability. Issues to be addressed include desorption kinetics for dihydrides and trihydrides, and the effect of film growth parameters, loading parameters, and substrate selection on desorption kinetics.

  1. Search for potential minimum positions in metal-organic hybrids, (C2H5NH3)2CuCl4 and (C6H5CH2CH2NH3)2CuCl4, by using density functional theory

    NASA Astrophysics Data System (ADS)

    Suprayoga, E.; Nugroho, A. A.; Polyakov, A. O.; Palstra, T. T. M.; Watanabe, I.

    2014-12-01

    The ab-initio density functional theory analysis was applied to metal-organic hybrids, (C2H5NH3)2CuCl4 (EA) and (C6H5CH2CH2NH3)2CuCl4 (PEA), in order to estimate possible muons stopping positions. Six potential minimum positions and eight ones were revealed in PA and PEA, respectively. Those potential minimum positions can be regarded as initial stopping positions of injected muons. All of expected potential minimum points in EA were near and around the apical Cl and the CuCl2 plane of the CuCl6 octahedra. Instead, in the case of PEA, two of eight positions were close to the phenyl ring giving a possibility that there would be muon states which couple surrounding electrons via a radical formation.

  2. Direct Observation of Long Electron-Hole Diffusion Distance in CH3NH3PbI3 Perovskite Thin Film

    PubMed Central

    Li, Yu; Yan, Weibo; Li, Yunlong; Wang, Shufeng; Wang, Wei; Bian, Zuqiang; Xiao, Lixin; Gong, Qihuang

    2015-01-01

    In high performance perovskite based solar cells, CH3NH3PbI3 is the key material. We carried out a study on charge diffusion in spin-coated CH3NH3PbI3 perovskite thin film by transient fluorescent spectroscopy. A thickness-dependent fluorescent lifetime was found. By coating the film with an electron or hole transfer layer, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) or 2,2?,7,7?-tetrakis(N,N-di-p-methoxyphenylamine)-9,9?-spirobifluorene (Spiro-OMeTAD) respectively, we observed the charge transfer directly through the fluorescence quenching. One-dimensional diffusion model was applied to obtain long charge diffusion distances in thick films, which is ~1.7??m for electrons and up to ~6.3??m for holes. Short diffusion distance of few hundreds of nanosecond was also observed in thin films. This thickness dependent charge diffusion explained the formerly reported short charge diffusion distance (~100?nm) in films and resolved its confliction to thick working layer (300–500?nm) in real devices. This study presents direct support to the high performance perovskite solar cells and will benefit the devices’ design. PMID:26416186

  3. Tunable Optical Properties and Charge Separation in CH3NH3Sn(x)Pb(1-x)I3/TiO2-Based Planar Perovskites Cells.

    PubMed

    Feng, Hong-Jian; Paudel, Tula R; Tsymbal, Evgeny Y; Zeng, Xiao Cheng

    2015-07-01

    A sharp potential drop across the interface of the Pb-rich halide perovskites/TiO2 heterostructure is predicted from first-principles calculations, suggesting enhanced separation of photoinduced charge carriers in the perovskite-based photovoltaic solar cells. The potential drop appears to be associated with the charge accumulation at the polar interface. More importantly, on account of both the ? phase structure of CH3NH3Sn(x)Pb(1-x)I3 for x < 0.5 and the ? phase structure of CH3NH3Sn(x)Pb(1-x)I3 for x ? 0.5, the computed optical absorption spectra from time-dependent density functional theory (TD-DFT) are in very good agreement with the measured spectra from previous experiments. Our TD-DFT computation also confirms the experimental structures of the mixed Pb-Sn organometal halide perovskites. These computation results provide a highly sought answer to the question why the lead-based halide perovskites possess much higher power conversion efficiencies than the tin-based counterparts for solar-cell applications. PMID:26011597

  4. Hole-Conductor-Free Mesoscopic TiO2/CH3NH3PbI3 Heterojunction Solar Cells Based on Anatase Nanosheets and Carbon Counter Electrodes.

    PubMed

    Rong, Yaoguang; Ku, Zhiliang; Mei, Anyi; Liu, Tongfa; Xu, Mi; Ko, Songguk; Li, Xiong; Han, Hongwei

    2014-06-19

    A hole-conductor-free fully printable mesoscopic TiO2/CH3NH3PbI3 heterojunction solar cell was developed with TiO2 nanosheets containing high levels of exposed (001) facets. The solar cell embodiment employed a double layer of mesoporous TiO2 and ZrO2 as a scaffold infiltrated by perovskite as a light harvester. No hole conductor or Au reflector was employed. Instead, the back contact was simply a printable carbon layer. The perovskite was infiltrated from solution through the porous carbon layer. The high reactivity of (001) facets in TiO2 nanosheets improved the interfacial properties between the perovskite and the electron collector. As a result, photoelectric conversion efficiency of up to 10.64% was obtained with the hole-conductor-free fully printable mesoscopic TiO2/CH3NH3PbI3 heterojunction solar cell. The advantages of fully printable technology and the use of low-cost carbon-materials-based counter electrode and hole-conductor-free structure provide this design a promising prospect to approach low-cost photovoltaic devices. PMID:26270509

  5. Large-Size CH3NH3PbBr3 Single Crystal: Growth and In Situ Characterization of the Photophysics Properties.

    PubMed

    Zhao, Pengjun; Xu, Jinbao; Dong, Xiaoyu; Wang, Lei; Ren, Wei; Bian, Liang; Chang, Aimin

    2015-07-01

    We reported a facile single-solution fabrication method to grow large-scale CH3NH3PbBr3 hybrid perovskite single crystal at room temperature. The obtained single crystal in this experiment was 14 × 14 mm. The sample's in situ photophysics properties under dark and illumination, including the surface morphology, work function, surface current distribution, microcosmic I-V curves, as well as the polarization behavior, were in situ characterized by integrated utilization of a scanning probe microscopy, respectively. Piezoresponse force microscopy (PFM) phase angles indicated the existence of "polarization" in CH3NH3PbBr3 lattice. Interestingly, the "polarization effect" was enhanced by the plus light source. Moreover, a surface potential shift as large as 200 mV was observed under the condition of the illumination on and off. This research is proposed to provide an opportunity to take a fresh look at the architectural design and photovoltaic performance origin of the hybrid perovskite solar cells. PMID:26266744

  6. Direct Observation of Long Electron-Hole Diffusion Distance in CH3NH3PbI3 Perovskite Thin Film.

    PubMed

    Li, Yu; Yan, Weibo; Li, Yunlong; Wang, Shufeng; Wang, Wei; Bian, Zuqiang; Xiao, Lixin; Gong, Qihuang

    2015-01-01

    In high performance perovskite based solar cells, CH3NH3PbI3 is the key material. We carried out a study on charge diffusion in spin-coated CH3NH3PbI3 perovskite thin film by transient fluorescent spectroscopy. A thickness-dependent fluorescent lifetime was found. By coating the film with an electron or hole transfer layer, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) or 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) respectively, we observed the charge transfer directly through the fluorescence quenching. One-dimensional diffusion model was applied to obtain long charge diffusion distances in thick films, which is ~1.7??m for electrons and up to ~6.3??m for holes. Short diffusion distance of few hundreds of nanosecond was also observed in thin films. This thickness dependent charge diffusion explained the formerly reported short charge diffusion distance (~100?nm) in films and resolved its confliction to thick working layer (300-500?nm) in real devices. This study presents direct support to the high performance perovskite solar cells and will benefit the devices' design. PMID:26416186

  7. Catalytic reduction of N2 to NH3 by an Fe-N2 complex featuring a C-atom anchor

    PubMed Central

    Creutz, Sidney E.; Peters, Jonas C.

    2014-01-01

    While recent spectroscopic studies have established the presence of an interstitial carbon atom at the center of the iron-molybdenum cofactor (FeMoco) of MoFe-nitrogenase, its role is unknown. We have pursued Fe-N2 model chemistry to explore a hypothesis whereby this C-atom (previously denoted as a light X-atom) may provide a flexible trans interaction with an Fe center to expose an Fe-N2 binding site. In this context, we now report on Fe complexes of a new tris(phosphino)alkyl (CPiPr3) ligand featuring an axial carbon donor. It is established that the iron center in this scaffold binds dinitrogen trans to the Calkyl-atom anchor in three distinct and structurally characterized oxidation states. Fe-Calkyl lengthening is observed upon reduction, reflective of significant ionic character in the Fe-Calkyl interaction. The anionic (CPiPr3)FeN2- species can be functionalized by a silyl electrophile to generate (CPiPr3)Fe-N2SiR3. (CPiPr3)FeN2- also functions as a modest catalyst for the reduction of N2 to NH3 when supplied with electrons and protons at -78 °C under 1 atm N2 (4.6 equiv NH3/Fe). PMID:24350667

  8. [CH(3)(CH(2))(11)NH(3)]SnI(3): a hybrid semiconductor with MoO(3)-type tin(II) iodide layers.

    PubMed

    Xu, Zhengtao; Mitzi, David B

    2003-10-20

    The organic-inorganic hybrid [CH(3)(CH(2))(11)NH(3)]SnI(3) presents a lamellar structure with a Sn-I framework isotypic to that of MoO(3). The SnI(3)(-) layer consists of edge and corner-sharing SnI(6) octahedra in which one of the six Sn-I bonds is distinctly elongated (e.g., 3.62 A), indicating lone-pair stereoactivity for the Sn(II) atom. The overall electronic character remains comparable with that of the well-studied SnI(4)(2)(-)-based perovskite semiconductors, such as [CH(3)(CH(2))(11)NH(3)](2)SnI(4), with a red-shifted and broadened exciton peak associated with the band gap, apparently due to the increased dimensionality of the Sn-I framework. The title compound offers, aside from the hybrid perovskites, a new type of solution-processable Sn-I network for potential applications in semiconductive devices. PMID:14552605

  9. SiO 2 nanospheres with tailorable interiors by directly controlling Zn 2+ and NH 3·H 2O species in an emulsion process

    NASA Astrophysics Data System (ADS)

    Liao, Yuchao; Wu, Xiaofeng; Wang, Zhen; Chen, Yun-Fa

    2011-07-01

    SiO 2 nanospheres with tailorable interiors were synthesized by a facile one-spot microemulsion process using TEOS as silica source, wherein cyclohexane including triton X-100 and n-octanol as oil phase and Zn 2+ or NH 3·H 2O aqueous solution as dispersive phase, respectively. The products were characterized by Scanning Electron Microscopy, Transmission Electron Microscopy and X-ray Powder Diffraction. It was suggested that the as-synthesized silica nanospheres possessed grape-stone-like porous or single hollow interior, and also found that the ammonia dosage and aging time played key roles in controlling the size and structure of silica nanospheres. Furthermore, the comparative results confirmed that in-situ zinc species [ZnO/Zn(OH) 2] acted as the temporary templates to construct grape-stone-like interior, and a simultaneously competing etching process occurred owing to the soluble Zn(NH 3) 42+ complex formation while the additional excessive ammonia was introduced. With the aging time being extended, the in-situ nanocrystals tended to grow into bigger ones by Ostwald Ripening, producing single hollow interior.

  10. Photoelectrochemical behaviour of CdS/NaI.3.3NH3 /liquid sodium iodide ammoniate/ junctions - Utilization in solar energy conversion

    NASA Astrophysics Data System (ADS)

    Guyomard, D.; Herlem, M.; Heindl, R.; Sculfort, J.-L.

    1981-09-01

    A liquid NaI.3.3NH3 solution was used as the medium in a photoelectrochemical cell to stabilize the working of CdS photoanodes and results are reported. The reference voltage of in situ Ag-Ag(plus) electrodes in the NaI.3.3NH3 solution is 0.27 V. The CdS samples were polished with diamond paste, rinsed in distilled water, and etched with HCl; ohmic contacts were formed on the backs with an evaporated gold and indium coating. Cyclic voltammetry was used to measure the electroactivity range, and a depletion layer was determined to exist in the space charge layer when an anodic current was found with reverse bias. High sensitivity to daylight was found, and this is attributed to the etching treatment and reactions to bulk energy levels. The addition of iodine to the solution was found to stabilize the photocurrent with a simultaneous rise in acidity; the iodine eventually vanishes unless the NH4(plus) is above 0.5 M or when the pH is near zero. An overall efficiency of 2 percent is noted, and the stabilization due to iodine presence resulted in cell operation for over a month.

  11. Emulsion Synthesis of Size-Tunable CH3NH3PbBr3 Quantum Dots: An Alternative Route toward Efficient Light-Emitting Diodes.

    PubMed

    Huang, Hailong; Zhao, Fangchao; Liu, Lige; Zhang, Feng; Wu, Xian-Gang; Shi, Lijie; Zou, Bingsuo; Pei, Qibing; Zhong, Haizheng

    2015-12-30

    We report a facile nonaqueous emulsion synthesis of colloidal halide perovskite quantum dots by controlled addition of a demulsifier into an emulsion of precursors. The size of resulting CH3NH3PbBr3 quantum dots can be tuned from 2 to 8 nm by varying the amount of demulsifier. Moreover, this emulsion synthesis also allows the purification of these quantum dots by precipitation from the colloidal solution and obtains solid-state powder which can be redissolved for thin film coating and device fabrication. The photoluminescence quantum yields of the quantum dots is generally in the range of 80-92%, and can be well-preserved after purification (?80%). Green light-emitting diodes fabricated comprising a spin-cast layer of the colloidal CH3NH3PbBr3 quantum dots exhibited maximum current efficiency of 4.5 cd/A, power efficiency of 3.5 lm/W, and external quantum efficiency of 1.1%. This provides an alternative route toward high efficient solution-processed perovskite-based light-emitting diodes. In addition, the emulsion synthesis is versatile and can be extended for the fabrication of inorganic halide perovskite colloidal CsPbBr3 nanocrystals. PMID:26652661

  12. Elementary steps of the catalytic NO(x) reduction with NH3: cluster studies on reaction paths and energetics at vanadium oxide substrate.

    PubMed

    Gruber, M; Hermann, K

    2013-12-28

    We consider different reaction scenarios of the selective catalytic reduction (SCR) of NO in the presence of ammonia at perfect as well as reduced vanadium oxide surfaces modeled by V2O5(010) without and with oxygen vacancies. Geometric and energetic details as well as reaction paths are evaluated using extended cluster models together with density-functional theory. Based on earlier work of adsorption, diffusion, and reaction of the different surface species participating in the SCR we confirm that at Brønsted acid sites (i.e., OH groups) of the perfect oxide surface nitrosamide, NH2NO, forms a stable intermediate. Here adsorption of NH3 results in NH4 surface species which reacts with gas phase NO to produce the intermediate. Nitrosamide is also found as intermediate of the SCR near Lewis acid sites of the reduced oxide surface (i.e., near oxygen vacancies). However, here the adsorbed NH3 species is dehydrogenated to surface NH2 before it reacts with gas phase NO to produce the intermediate. The calculations suggest that reaction barriers for the SCR are overall higher near Brønsted acid sites of the perfect surface compared with Lewis acid sites of the reduced surface, examined for the first time in this work. The theoretical results are consistent with experimental findings and confirm the importance of surface reduction for the SCR process. PMID:24387382

  13. Thermal and plasma-enhanced atomic layer deposition of TiN using TDMAT and NH3 on particles agitated in a rotary reactor.

    PubMed

    Longrie, Delphine; Deduytsche, Davy; Haemers, Jo; Smet, Philippe F; Driesen, Kris; Detavernier, Christophe

    2014-05-28

    Titanium nitride (TiN) shows metallic-type electrical behavior and is therefore an interesting material to improve the conductivity of a wide variety of powders. Atomic layer deposition (ALD) is an excellent technique for achieving the desired ultrathin but conformal coatings. To conformally coat large amounts of particles using ALD, agitation of the particles and efficient reactant usage are necessary. Thermal and plasma-enhanced ALD growth of TiN using tetrakis(dimethylamino)titanium (TDMAT) and NH3 as precursors on agitated particles was performed using a rotary reactor to deposit TiN on ZnO submicrometer powder. The NH3 plasma pulse was monitored using in situ mass spectrometry (MS) and optical emission spectroscopy (OES) measurements to gain insight into the reaction mechanism of the plasma-enhanced process. X-ray photoelectron spectroscopy (XPS) and powder resistivity measurements were performed to determine the influence of the deposition process on the composition and conductivity of the deposited TiN layers. PMID:24801740

  14. TDLAS-based NH3 mole fraction measurement for exhaust diagnostics during selective catalytic reduction using a fiber-coupled 2.2-µm DFB diode laser

    NASA Astrophysics Data System (ADS)

    Stritzke, Felix; Diemel, Oliver; Wagner, Steven

    2015-04-01

    A new developed tunable diode laser spectrometer for the measurement of ammonia (NH3) mole fractions in exhaust gas matrices with strong CO2 and H2O background at temperatures up to 800 K is presented. In situ diagnostics in harsh exhaust environments during SCR after treatment are enabled by the use of ammonia transitions in the ?2 + ?3 near-infrared band around 2300 nm. Therefore, three lines have been selected, coinciding near 2200.5 nm (4544.5 cm-1) with rather weak temperature dependency and minimal interference with CO2 and H2O. A fiber-coupled 2.2-?m distributed feedback laser diode was used and attached to the hot gas flow utilizing adjustable gas tight high-temperature fiber ports. The spectrometer spans four coplanar optical channels across the measurement plane and simultaneously detects the direct absorption signal via a fiber-coupled detector unit. An exhaust simulation test rig was used to characterize the spectrometer's performance in ammonia-doped hot gas environments. We achieved a temporal resolution of 13 Hz and temperature-dependent precisions of NH3 mole fraction ranging from 50 to 70 ppmV. There the spectrometer achieved normalized ammonia detection limits of 7-10 and 2-3.

  15. Elementary steps of the catalytic NOx reduction with NH3: Cluster studies on reaction paths and energetics at vanadium oxide substrate

    NASA Astrophysics Data System (ADS)

    Gruber, M.; Hermann, K.

    2013-12-01

    We consider different reaction scenarios of the selective catalytic reduction (SCR) of NO in the presence of ammonia at perfect as well as reduced vanadium oxide surfaces modeled by V2O5(010) without and with oxygen vacancies. Geometric and energetic details as well as reaction paths are evaluated using extended cluster models together with density-functional theory. Based on earlier work of adsorption, diffusion, and reaction of the different surface species participating in the SCR we confirm that at Brønsted acid sites (i.e., OH groups) of the perfect oxide surface nitrosamide, NH2NO, forms a stable intermediate. Here adsorption of NH3 results in NH4 surface species which reacts with gas phase NO to produce the intermediate. Nitrosamide is also found as intermediate of the SCR near Lewis acid sites of the reduced oxide surface (i.e., near oxygen vacancies). However, here the adsorbed NH3 species is dehydrogenated to surface NH2 before it reacts with gas phase NO to produce the intermediate. The calculations suggest that reaction barriers for the SCR are overall higher near Brønsted acid sites of the perfect surface compared with Lewis acid sites of the reduced surface, examined for the first time in this work. The theoretical results are consistent with experimental findings and confirm the importance of surface reduction for the SCR process.

  16. OTEC gas-desorption studies

    SciTech Connect

    Chen, F.C.; Golshani, A.

    1981-01-01

    OTEC gas desorption studies were initiated with the goal of mitigating these effects and were carried out in four areas: (1) vacuum deaeration in a packed column, (2) deaeration in a barometric water intake system, (3) noncondensibles disposal through hydraulic air compression, and (4) OTEC deaeration subsystems' analysis. Laboratory experiments to date have completed the vacuum deaeration test of three different kinds of packings, barometric intake deaeration experiments, and a series of hydraulic air compression tests. Preliminary analyses based on the experimental data have shown that, as compared to the previous baseline study, reduction both in deaerator cost and pumping power can be realized with a combination of barometric intake and packed column deaeration. The design and operation of the gas desorption test loop, experimental and computer simulation results obtained, and an analysis of OTEC deaeration subsystem design based on the test results and their implication on OTEC open-cycle power systems are presented.

  17. Desorption of water from distinct step types on a curved silver crystal.

    PubMed

    Janlamool, Jakrapan; Bashlakov, Dima; Berg, Otto; Praserthdam, Piyasan; Jongsomjit, Bunjerd; Juurlink, Ludo B F

    2014-01-01

    We have investigated the adsorption of H2O onto the A and B type steps on an Ag single crystal by temperature programmed desorption. For this study, we have used a curved crystal exposing a continuous range of surface structures ranging from [5(111) × (100)] via (111) to [5(111) × (110)]. LEED and STM studies verify that the curvature of our sample results predominantly from monoatomic steps. The sample thus provides a continuous array of step densities for both step types. Desorption probed by spatially-resolved TPD of multilayers of H2O shows no dependence on the exact substrate structure and thus confirms the absence of thermal gradients during temperature ramps. In the submonolayer regime, we observe a small and linear dependence of the desorption temperature on the A and B step density. We argue that such small differences are only observable by means of a single curved crystal, which thus establishes new experimental benchmarks for theoretical calculation of chemically accurate binding energies. We propose an origin of the observed behavior based on a "two state" desorption model. PMID:25068782

  18. The first layer of water on Rh(111): Microscopic structure and desorption kinetics

    SciTech Connect

    Beniya, Atsushi; Yamamoto, Susumu; Mukai, Kozo; Yamashita, Yoshiyuki; Yoshinobu, Jun

    2006-08-07

    The adsorption states and growth process of the first water (D{sub 2}O) layer on Rh(111) were investigated using infrared reflection absorption spectroscopy, temperature programed desorption, and spot-profile-analysis low energy electron diffraction. Water molecules wet the Rh(111) surface intact. At the early stage of first layer growth, a ({radical}3x{radical}3)R30 deg. commensurate water layer grows where 'up' and 'down' species coexist; the up and down species represent water molecules which have free OD, pointing to a vacuum and the substrate, respectively. The up domain was a flatter structure than an icelike bilayer. Water desorption from Rh(111) was a half-order process. The activation energy and the preexponential factor of desorption are estimated to be 60 kJ/mol and 4.8x10{sup 16} ML{sup 1/}2/s at submonolayer coverage, respectively. With an increase in water coverage, the flat up domain becomes a zigzag layer, like an ice bilayer. At the saturation coverage, the amount of down species is 1.3 times larger than that of the up species. In addition, the activation energy and the preexponential factor of desorption decrease to 51 kJ/mol and 1.3x10{sup 14} ML{sup 1/2}/s, respectively.

  19. Herschel/PACS spectroscopy of NGC 4418 and Arp 220: H2O, H218O, OH, 18OH, O I, HCN, and NH3

    NASA Astrophysics Data System (ADS)

    González-Alfonso, E.; Fischer, J.; Graciá-Carpio, J.; Sturm, E.; Hailey-Dunsheath, S.; Lutz, D.; Poglitsch, A.; Contursi, A.; Feuchtgruber, H.; Veilleux, S.; Spoon, H. W. W.; Verma, A.; Christopher, N.; Davies, R.; Sternberg, A.; Genzel, R.; Tacconi, L.

    2012-05-01

    Full range Herschel/PACS spectroscopy of the (ultra)luminous infrared galaxies NGC 4418 and Arp 220, observed as part of the SHINING key programme, reveals high excitation in H2O, OH, HCN, and NH3. In NGC 4418, absorption lines were detected with Elower > 800 K (H2O), 600 K (OH), 1075 K (HCN), and 600 K (NH3), while in Arp 220 the excitation is somewhat lower. While outflow signatures in moderate excitation lines are seen in Arp 220 as have been seen in previous studies, in NGC 4418 the lines tracing its outer regions are redshifted relative to the nucleus, suggesting an inflow with ? ? 12 M? yr-1. Both galaxies have compact and warm (Tdust ? 100 K) nuclear continuum components, together with a more extended and colder component that is much more prominent and massive in Arp 220. A chemical dichotomy is found in both sources: on the one hand, the nuclear regions have high H2O abundances, ~10-5, and high HCN/H2O and HCN/NH3 column density ratios of 0.1-0.4 and 2-5, respectively, indicating a chemistry typical of evolved hot cores where grain mantle evaporation has occurred. On the other hand, the high OH abundance, with OH/H2O ratios of ~0.5, indicates the effects of X-rays and/or cosmic rays. The nuclear media have high surface brightnesses (?1013 L?/kpc2) and are estimated to be very thick (NH ? 1025 cm-2). While NGC 4418 shows weak absorption in H218O and 18OH, with a 16O-to-18O ratio of ?250-500, the relatively strong absorption of the rare isotopologues in Arp 220 indicates 18O enhancement, with 16O-to-18O of 70-130. Further away from the nuclear regions, the H2O abundance decreases to ?10-7 and the OH/H2O ratio is reversed relative to the nuclear region to 2.5-10. Despite the different scales and morphologies of NGC 4418, Arp 220, and Mrk 231, preliminary evidence is found for an evolutionary sequence from infall, hot-core like chemistry, and solar oxygen isotope ratio to high velocity outflow, disruption of the hot core chemistry and cumulative high mass stellar processing of 18O. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  20. Observations of the Partitioning of Trace Acids During CalNex, Bakersfield: HONO, HCl and Oxalic Acid in an NH3-rich Environment

    NASA Astrophysics Data System (ADS)

    Vandenboer, T. C.; Markovic, M. Z.; Sanders, J.; Ren, X.; Murphy, J. G.

    2010-12-01

    The 2010 California Research at the Nexus of Air Quality and Climate Change (CalNex) field campaign supersite in Bakersfield, CA, presented an opportunity to investigate the gas-particle partitioning of trace atmospheric species in a low-sulphur high-NH3 environment. With the demand for cleaner energy, atmospheric S levels are expected to continue to decrease across North America, while restrictions on NH3 emissions are still in preliminary stages. Despite the absence of significant sulphur emissions contributing to particulate matter (PM) formation, California’s San Joaquin Valley still experiences some of the worst air quality in the continental US. Partitioning of other trace gases may become more important in low sulphur regions; here we report our observations of HONO, HCl and oxalic acid partitioning. Observations of the water-soluble composition of atmospheric gases and fine particulate matter (PM2.5) were made with an Ambient Ion Monitor - Ion Chromatography (AIM-IC) system from University Research Glassware (Chapel Hill, NC). The AIM-IC was fitted with a newly designed impactor inlet that minimizes gas and particle losses prior to collection by a wet wall parallel plate denuder and super saturated steam condensation chamber, respectively, situated at a height of 4.5 m for this study. Observations of NH3 indicated ambient levels typically in excess of 10 ppb, up to 60 ppb, and all observed inorganic aerosol was found to be completely neutralized throughout the campaign by NH4+. Mixing ratios of HONO showed excellent agreement with concurrent measurements made by a LOPAP instrument from University of Miami, maximizing during the night at values in the range of 1 - 1.5 ppb. On several nights, particulate NO2- mass loadings in the range of 0.2 ?g m-3 (equivalent to 0.1 ppb HONO) were observed by the AIM-IC. The diurnal pattern of HCl showed maximum mixing ratios of 0.2 - 0.3 ppb occurring near 13:00 PST, and near zero values at night. Intermittent bursts of Cl- were also detected, however the Cl- present in PM2.5 was significantly less than that present as HCl. These online observations are some of the few to date describing simultaneous measurements of both gas and particle phase reservoirs of chlorine as HCl/Cl-. The diurnal pattern of oxalic acid showed maximum mixing ratios less than 0.1 ppb near 16:00 PST and near zero values at night. The presence of oxalate in PM2.5 was observed throughout the campaign with mass loadings in the range of 0 - 0.2 ?g m-3 also maximizing during the day.

  1. Probing the formation and evolution of comets via nuclear spin temperatures of C_2H_6, CH_3OH, CH_4, NH_3, and H_2O

    NASA Astrophysics Data System (ADS)

    Villanueva, G.; Mumma, M.; Bonev, B.; DiSanti, M.; Paganini, L.; Magee-Sauer, K.; Gibb, E.

    2014-07-01

    Comets are true remnants of our primordial Solar System, and provide unique clues to its formation and evolution, including the delivery of organics and water to our planet. A key indicator stored in the molecular structure of the nuclear ices is the spin temperature (T_{spin}), derived from spin-isomeric ratios (R_{spin}, e.g., ortho/para). At the time when cometary ices formed, the prevailing temperature defined the relative abundance of the different spin-isomeric species, and herewith R_{spin} and T_{spin} are normally treated as ''remnant thermometers'' probing the formation environments of cometary molecules. Radiative and collisional transitions between the ortho and para states are strongly forbidden and herewith this indicator is preserved over time. Most of our knowledge of this indicator comes from the measurements of the ortho-para ratios in water and NH_2 (a proxy for ammonia), suggesting a common T_{spin} near 30 K. This information is based on a restricted sample of comets, and the measurements are particularly sensitive to the molecular modeling technique and adopted spectral database. Here, we present new methodologies for extracting spin temperatures from ethane (C_2H_6), methane (CH_4), and methanol (CH_3OH), and advanced new models for ortho/para water (H_2O) and ammonia (NH_3). Our H_2O analysis is based on the most complete fluorescence radiative-transfer model to date, which incorporates 1,200 million transitions including those originating from high-energy levels that are activated in comets via a non-resonant cascade. In a similar fashion, we developed non-resonant fluorescence models for NH_3 and HCN, and quantum-band models for the ?_7 band of C_2H_6 and ?_3 band of CH_3OH. All models respect spin-symmetry non-conversion radiative rules, and make use of a realistic solar spectrum for the computation of fluorescence pumps. We applied these new methods to derive spin-isomeric ratios for H_2O, CH_4, C_2H_6, CH_3OH, and NH_3 from three high- quality cometary datasets: 1) C/2007 W1 (Boattini), 2) C/2001 A2 (LINEAR), and 3) 8P/Tuttle. We compare our results to the measured organic compositions for these comets, and present possible formation and evolution scenarios.

  2. Porous and shape-anisotropic single crystals of the semiconductor perovskite CH3NH3PbI3 from a single-source precursor.

    PubMed

    Kollek, Tom; Gruber, Dominik; Gehring, Julia; Zimmermann, Eugen; Schmidt-Mende, Lukas; Polarz, Sebastian

    2015-01-19

    Significant progress in solar-cell research is currently made by the development of metal-organic perovskites (MOPs) owing to their superior properties, such as high absorption coefficients and effective transport of photogenerated charges. As for other semiconductors, it is expected that the properties of MOPs may be significantly improved by a defined nanostructure. However, their chemical sensitivity (e.g., towards hydrolysis) prohibits the application of methods already known for the synthesis of other nanomaterials. A new and general method for the synthesis of various (CH3NH3)PbI3 nanostructures from a novel single-source precursor is presented. Nanoporous MOP single crystals are obtained by a crystal-to-crystal transformation that is accompanied by spinodal demixing of the triethylene glycol containing precursor structure. Selective binding of a capping agent can be used to tune the particle shape of the MOP nanocrystals. PMID:25470357

  3. Effective hole extraction using MoOx-Al contact in perovskite CH3NH3PbI3 solar cells

    NASA Astrophysics Data System (ADS)

    Zhao, Yixin; Nardes, Alexandre M.; Zhu, Kai

    2014-05-01

    We report an 11.4%-efficient perovskite CH3NH3PbI3 solar cell using low-cost molybdenum oxide/aluminum (i.e., MoOx/Al) as an alternative top contact to replace noble/precious metals (e.g., Au or Ag) for extracting photogenerated holes. The device performance of perovskite solar cells using a MoOx/Al top contact is comparable to that of cells using the standard Ag top contact. Analysis of impedance spectroscopy measurements suggests that using 10-nm-thick MoOx and Al does not affect charge-recombination properties of perovskite solar cells. Using a thicker (20-nm) MoOx layer leads to a lower cell performance caused mainly by a reduced fill factor. Our results suggest that MoOx/Al is promising as a low-cost and effective hole-extraction contact for perovskite solar cells.

  4. Improving the efficiency of perovskite solar cells through optimization of the CH3NH3PbI3 film growth in solution process method

    NASA Astrophysics Data System (ADS)

    Zhao, Ying; Liu, Jian; Lu, Xinrong; Gao, Yandong; You, Xiaozeng; Xu, Xiangxing

    2015-12-01

    Perovskite-structured organic-inorganic materials such as CH3NH3PbI3 are attracting much interest in the scientific community because of their abilities to function as revolutionary light harvesters and charge transfer materials for solar cells. To achieve high power conversion efficiency (PCE), it is critical to optimize the perovskite film layer. This paper reports the temperature and concentration controls on the two-step solution process. A diffusion-controlled growth mechanism is proposed for this process in tuning the morphology and purity of the perovskite film, which are proven to be important factors contributing to the photovoltaic performance. The highest PCE of 11.92% is achieved with an optimized perovskite crystal size of ?150 nm and an appropriate amount of residual PbI2. This study sheds light on the design and fabrication of highly efficient, low-cost, solution-processed perovskite solar cells.

  5. Dynamic Optical Properties of CH3NH3PbI3 Single Crystals As Revealed by One- and Two-Photon Excited Photoluminescence Measurements.

    PubMed

    Yamada, Yasuhiro; Yamada, Takumi; Phuong, Le Quang; Maruyama, Naoki; Nishimura, Hidetaka; Wakamiya, Atsushi; Murata, Yasujiro; Kanemitsu, Yoshihiko

    2015-08-26

    The dynamic optical properties of perovskite CH3NH3PbI3 single crystals were studied by means of time-resolved photoluminescence (PL) spectroscopy at room temperature. The PL peak under one-photon excitation exhibits a red-shift with elapsing time, while two-photon PL is time-independent and appears at lower energy levels. The low-energy two-photon PL can be attributed to emissions from the localized states because of strong band-to-band absorption and photon re-absorption of the emitted light in the interior region. We revealed that the PL behaviors can be explained by the diffusion of photocarriers generated in the near-surface region to the interior region. The excitation fluence dependence of the one-photon PL dynamics is also discussed in terms of the electron-hole radiative recombination and carrier diffusion effects. PMID:26263192

  6. The binding energies of Cu(+)-(H2O)n and Cu(+)-(NH3)n (n = 1-4)

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Partridge, Harry

    1991-01-01

    The successive binding energies of up to four H2O and NH3 ligands to Cu(+) are computed at the self-consistent-field and modified coupled-pair functional levels. The most stable structures are those where all ligands are equivalent. Replacing Cu(+) by a point charge gives binding energies that are in good agreement with ab initio and experimental results, and is consistent with bonding that is largely charge dipole in nature. About two-thirds of the large reduction in ligand binding energy between the second and third ligand is due to ligand-ligand repulsion, while one-third is due to increased metal-ligand repulsion resulting from a loss of sd-sigma hybridization. The first and second ligand binding energies increase substantially at the correlated level due to an improved description of sd-sigma hybridization.

  7. Ferroelectric Polarization of CH3NH3PbI3: A Detailed Study Based on Density Functional Theory and Symmetry Mode Analysis.

    PubMed

    Stroppa, Alessandro; Quarti, Claudio; De Angelis, Filippo; Picozzi, Silvia

    2015-06-18

    Ferroelectricity in halide perovskites currently represents a crucial issue, as it may have an important role for the enhancement of solar cells efficiency. Simulations of ferroelectric properties based on density functional theory are conceptually more demanding compared with "conventional" inorganic ferroelectrics due to the presence of both organic and inorganic components in the same compound. Here we present a detailed study focused on the prototypical CH3NH3PbI3 perovskite. By using density functional theory combined with symmetry mode analysis, we disentangle the contributions of the methylammonium cations and the role of the inorganic framework, therefore suggesting possible routes to enhance the polarization in this compound. Our estimate of the polarization for the tetragonal phase at low temperature is ?4.42 ?C/cm(2), which is substantially lower than that of traditional perovskite oxides. PMID:26266595

  8. Phase transition in organic-inorganic perovskite (C9H19NH3)2 PbI2Br2 of long-chain alkylammonium

    NASA Astrophysics Data System (ADS)

    Abid, H.; Trigui, A.; Mlayah, A.; Hlil, E. K.; Abid, Y.

    2012-01-01

    Single perovskite slab alkylammonium lead iodides bromides (C9H19NH3)2PbI2Br2 is a new member of the family of hybrid organic-inorganic perovskite compounds. It exhibits a single structural phase transition with changes in the conformation of alkylammonium chains below room temperature. Differential scanning calorimetry (DSC), powder X-ray diffraction and FT-Raman spectroscopy were used to investigate this phase transition. These changes were characterized by a decreased conformational disorder of the methylene units of the alkyl chains. Phase transition was examined in light of the interesting optical properties of this material, as well as the relevance of this system as models for phase transitions in lipid bilayers.

  9. Chaotic regimes of antiferromagnetic resonance in a quasi-two-dimensional easy-axis antiferromagnet (NH_3)_2 (CH_2)_4 MnCl_4

    E-print Network

    Mikhail M. Bogdan; Mikhail I. Kobets; Eugene N. Khats'ko

    2001-04-11

    Chaotic regimes of the microwave energy absorption are experimentally observed and analyzed for two-dimensional metallorganic antiferromagnet (NH_3)_2(CH_2)_4MnCl_4 at low temperatures under the conditions of nonlinear antiferromagnetic resonance. Relaxation oscillations of energy absorption are investigated in detail. Their frequency spectra, frequency-amplitude characteristics, and dependences of absorbed power on driving power and static magnetic field are studied. It is shown that the dynamics of relaxation oscillations undergoes a transition to chaos by "irregular periods". Peculiarities of the transition are described consistently. Among other things, the conditions for the emergence of energy absorption regimes with a spike-like and a saw-tooth signal structure are determined, and the characteristics of chaotic oscillations such as the dimensions of strange attractors are calculated. The chaotic dynamics is found to be high-dimensional with a large contribution from noise which is of deterministic origin in the antiferromagnet under investigation.

  10. Solvent effects on the oxidation (electron transfer) reaction of [Fe(CN) 6] 4- by [Co(NH 3) 5pz] 3+

    NASA Astrophysics Data System (ADS)

    Muriel, F.; Jiménez, R.; López, M.; Prado-Gotor, R.; Sánchez, F.

    2004-03-01

    Solvent effects on the title reaction were studied in different reaction media constituted by water and organic cosolvents (methanol, tert-butyl alcohol, ethyleneglycol and glucose) at 298.2 K. The results are considered in light of the Marcus-Hush approach for electron transfer reactions. Variations of the electron transfer rate constant are shown to be mainly due to changes in the reaction free energy. On the other hand the energies of the MMCT band, corresponding to the optical electron transfer within the ion pair [Fe(CN) 6] 4-/[Co(NH 3) 5pz] 3+, in the different reaction media, have been obtained. The activation free energies of the thermal electron transfer process have been calculated from the band ( Eop) data, and compared with those obtained from the kinetic study. Quantitative agreement is found between the two series of data. This shows the possibility of estimating activation free energies for electron transfer reactions from static (optical) measurements.

  11. Density functional theory study on the full ALD process of silicon nitride thin film deposition via BDEAS or BTBAS and NH3.

    PubMed

    Huang, Liang; Han, Bo; Han, Bing; Derecskei-Kovacs, Agnes; Xiao, Manchao; Lei, Xinjian; O'Neill, Mark L; Pearlstein, Ronald M; Chandra, Haripin; Cheng, Hansong

    2014-09-14

    A detailed reaction mechanism has been proposed for the full ALD cycle of Si3N4 deposition on the ?-Si3N4(0001) surface using bis(diethylamino)silane (BDEAS) or bis(tertiarybutylamino)silane (BTBAS) as a Si precursor with NH3 acting as the nitrogen source. Potential energy landscapes were derived for all elementary steps in the proposed reaction network using a periodic slab surface model in the density functional approximation. Although the dissociative reactivity of BTBAS was slightly better than that of BDEAS, the thermal deposition process was still found to be an inherently high temperature process due to the high activation energies during the dissociative chemisorption of both precursors and the surface re-amination steps. These results underline the need to develop new precursors and alternative nitrogen sources when low temperature thermal silicon nitride films are targeted. PMID:25072273

  12. Nature of the band gap of halide perovskites ABX3 (A = CH3NH3, Cs; B = Sn, Pb; X = Cl, Br, I): First-principles calculations

    NASA Astrophysics Data System (ADS)

    Yuan, Ye; Xu, Run; Xu, Hai-Tao; Hong, Feng; Xu, Fei; Wang, Lin-Jun

    2015-11-01

    The electronic structures of cubic structure of ABX3(A=CH3NH3, Cs; B=Sn, Pb; X=Cl, Br, I) are analyzed by density functional theory using the Perdew–Burke–Ernzerhof exchange–correlation functional and using the Heyd–Scuseria–Ernzerhof hybrid functional. The valence band maximum (VBM) is found to be made up by an antibonding hybridization of B s and X p states, whereas bands made up by the ? antibonding of B p and X p states dominates the conduction band minimum (CBM). The changes of VBM, CBM, and band gap with ion B and X are then systematically summarized. The natural band offsets of ABX3 are partly given. We also found for all the ABX3 perovskite materials in this study, the bandgap increases with an increasing lattice parameter. This phenomenon has good consistency with the experimental results. Project supported by the National Natural Science Foundation of China (Grant No. 11375112).

  13. N- and O-heterocycles Produced from the Irradiation of Benzene and Naphthalene in H2O/NH3-containing Ices

    NASA Astrophysics Data System (ADS)

    Materese, Christopher K.; Nuevo, Michel; Sandford, Scott A.

    2015-02-01

    Aromatic heterocyclic molecules are an important class of molecules of astrophysical and biological significance that include pyridine, pyrimidine, and their derivatives. Such compounds are believed to exist in interstellar and circumstellar environments, though they have never been observed in the gas phase. Regardless of their presence in the gas phase in space, numerous heterocycles have been reported in carbonaceous meteorites, which indicates that they are formed under astrophysical conditions. The experimental work described here shows that N- and O-heterocyclic molecules can form from the ultraviolet (UV) irradiation of the homocyclic aromatic molecules benzene (C6H6) or naphthalene (C10H8) mixed in ices containing H2O and NH3. This represents an alternative way to generate aromatic heterocycles to those considered before and may have important implications for astrochemistry and astrobiology.

  14. One-pot synthesis of hierarchical FeZSM-5 zeolites from natural aluminosilicates for selective catalytic reduction of NO by NH3.

    PubMed

    Yue, Yuanyuan; Liu, Haiyan; Yuan, Pei; Yu, Chengzhong; Bao, Xiaojun

    2015-01-01

    Iron-modified ZSM-5 zeolites (FeZSM-5s) have been considered to be a promising catalyst system to reduce nitrogen oxide emissions, one of the most important global environmental issues, but their synthesis faces enormous economic and environmental challenges. Herein we report a cheap and green strategy to fabricate hierarchical FeZSM-5 zeolites from natural aluminosilicate minerals via a nanoscale depolymerization-reorganization method. Our strategy is featured by neither using any aluminum-, silicon-, or iron-containing inorganic chemical nor involving any mesoscale template and any post-synthetic modification. Compared with the conventional FeZSM-5 synthesized from inorganic chemicals with the similar Fe content, the resulting hierarchical FeZSM-5 with highly-dispersed iron species showed superior catalytic activity in the selective catalytic reduction of NO by NH3. PMID:25791958

  15. One-pot synthesis of hierarchical FeZSM-5 zeolites from natural aluminosilicates for selective catalytic reduction of NO by NH3

    PubMed Central

    Yue, Yuanyuan; Liu, Haiyan; Yuan, Pei; Yu, Chengzhong; Bao, Xiaojun

    2015-01-01

    Iron-modified ZSM-5 zeolites (FeZSM-5s) have been considered to be a promising catalyst system to reduce nitrogen oxide emissions, one of the most important global environmental issues, but their synthesis faces enormous economic and environmental challenges. Herein we report a cheap and green strategy to fabricate hierarchical FeZSM-5 zeolites from natural aluminosilicate minerals via a nanoscale depolymerization-reorganization method. Our strategy is featured by neither using any aluminum-, silicon-, or iron-containing inorganic chemical nor involving any mesoscale template and any post-synthetic modification. Compared with the conventional FeZSM-5 synthesized from inorganic chemicals with the similar Fe content, the resulting hierarchical FeZSM-5 with highly-dispersed iron species showed superior catalytic activity in the selective catalytic reduction of NO by NH3. PMID:25791958

  16. High-performance CH3NH3PbI3 perovskite solar cells fabricated under ambient conditions with high relative humidity

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    Hygroscopic perovskite solar cells are commonly fabricated under conditions of inert atmosphere or low relative humidity (RH). To generate high-performance perovskite light-absorbing layers for super power conversion efficiency (PCE), we fabricated CH3NH3PbI3 solar cells under ambient conditions (RH = 42-48%) by a flowing gas directly from high-RH air. The primary advantage of this technique, together with the casting of a hot solution and quick conduction, enabled us to achieve the highest and average PCEs of 16.32 and 14.27% respectively, with an extremely small deviation of 0.49%. Our research will be of significance for fabricating highly efficient and reproducible perovskite photovoltaics.

  17. One-pot synthesis of hierarchical FeZSM-5 zeolites from natural aluminosilicates for selective catalytic reduction of NO by NH3

    NASA Astrophysics Data System (ADS)

    Yue, Yuanyuan; Liu, Haiyan; Yuan, Pei; Yu, Chengzhong; Bao, Xiaojun

    2015-03-01

    Iron-modified ZSM-5 zeolites (FeZSM-5s) have been considered to be a promising catalyst system to reduce nitrogen oxide emissions, one of the most important global environmental issues, but their synthesis faces enormous economic and environmental challenges. Herein we report a cheap and green strategy to fabricate hierarchical FeZSM-5 zeolites from natural aluminosilicate minerals via a nanoscale depolymerization-reorganization method. Our strategy is featured by neither using any aluminum-, silicon-, or iron-containing inorganic chemical nor involving any mesoscale template and any post-synthetic modification. Compared with the conventional FeZSM-5 synthesized from inorganic chemicals with the similar Fe content, the resulting hierarchical FeZSM-5 with highly-dispersed iron species showed superior catalytic activity in the selective catalytic reduction of NO by NH3.

  18. Multiferroicity and hydrogen-bond ordering in (C2H5NH3)2CuCl4 featuring dominant ferromagnetic interactions

    NASA Astrophysics Data System (ADS)

    Kundys, B.; Lappas, A.; Viret, M.; Kapustianyk, V.; Rudyk, V.; Semak, S.; Simon, Ch.; Bakaimi, I.

    2010-06-01

    We demonstrate that ethylammonium copper chloride, (C2H5NH3)2CuCl4 , a member of the hybrid perovskite family is an electrically polar and magnetic compound with dielectric anomaly around the Curie point (247 K). We have found large spontaneous electric polarization below this point accompanied with a color change in the sample. The system is also ferroelectric, with large remnant polarization (37?C/cm2) that is comparable to classical ferroelectric compounds. The results are ascribed to hydrogen-bond ordering of the organic chains. The coexistence of ferroelectricity and dominant ferromagnetic interactions allows to relate the sample to a rare group of magnetic multiferroic compounds. In such hybrid perovskites the underlying hydrogen bonding of easily tunable organic building blocks in combination with the 3d transition-metal layers offers an emerging pathway to engineer multifuctional multiferroics.

  19. Intercalation of HF, H2O, and NH3 Clusters within the Bilayers of Graphene and Graphene Oxide: Predictions from Coronene-Based Model Systems.

    PubMed

    Rohini, K; Sylvinson, Daniel M R; Swathi, R S

    2015-11-01

    Understanding molecular interactions with monolayers and bilayers of graphene and its derivatized forms is very important because of their fundamental role in gas sensing and separation, gas storage, catalysis, etc. Herein, motivated by the recent realization of graphene-based sensors for the detection of single gas molecules, we use density functional theory to study the noncovalent interactions of molecules and molecular clusters with graphene, graphene oxide, and graphane, which are represented by coronene-based molecular model systems, C24H12 (coronene), C24OH12 (coroepoxide), and C24H36 (perhydrocoronene), respectively. The objective is to understand the structural and energetic changes that occur as a result of adsorption on monolayers and intercalation within bilayers. To begin with, the interactions of coronene, coroepoxide, and perhydrocoronene with a variety of small molecules like HF, HCl, HBr, H2O, H2S, NH3, and CH4 are studied. Subsequently, the binding of coronene and coroepoxide substrates with molecular clusters of HF, H2O, and NH3 is studied to understand the strength of adsorption on the substrates and the effect of substrates on hydrogen-bonding interactions within the molecular clusters. Further, bilayers of the model systems, namely, coronene-coronene, coronene-coroepoxide, and two configurations of coroepoxide-coroepoxide (one in which the oxygen atoms are facing each other and the other in which they do not face each other) are generated. The energetics for the nanoscale confinement or intercalation of the clusters within the bilayers along with the impact of the intercalation on the intermolecular hydrogen-bonding interactions are investigated. Our coronene-based model systems can provide a simple way of describing the rather complex events that occur in representative regions of graphene-based heterogeneous substrates. PMID:26469770

  20. Ion-orbital coupling in Car-Parrinello calculations of hydrogen-bond vibrational dynamics: Case study with the NH3-HCl dimer

    NASA Astrophysics Data System (ADS)

    Ong, S. W.; Lee, B. X. B.; Kang, H. C.

    2011-09-01

    We have performed Car-Parrinello molecular dynamics (CPMD) calculations of the hydrogen-bonded NH3-HCl dimer. Our main aim is to establish how ionic-orbital coupling in CPMD affects the vibrational dynamics in hydrogen-bonded systems by characterizing the dependence of the calculated vibrational frequencies upon the orbital mass in the adiabatic limit of Car-Parrinello calculations. We use the example of the NH3-HCl dimer because of interest in its vibrational spectrum, in particular the magnitude of the frequency shift of the H-Cl stretch due to the anharmonic interactions when the hydrogen bond is formed. We find that an orbital mass of about 100 a.u. or smaller is required in order for the ion-orbital coupling to be linear in orbital mass, and the results for which can be accurately extrapolated to the adiabatic limit of zero orbital mass. We argue that this is general for hydrogen-bonded systems, suggesting that typical orbital mass values used in CPMD are too high to accurately describe vibrational dynamics in hydrogen-bonded systems. Our results also show that the usual application of a scaling factor to the CPMD frequencies to correct for the effects of orbital mass is not valid. For the dynamics of the dimer, we find that the H-Cl stretch and the N-H-Cl bend are significantly coupled, suggesting that it is important to include the latter degree of freedom in quantum dynamical calculations. Results from our calculations with deuterium-substitution show that both these degrees of freedom have significant anharmonic interactions. Our calculated frequency for the H-Cl stretch using the Becke-exchange Lee-Yang-Parr correlation functional compares reasonably well with a previous second-order Møller-Plesset calculation with anharmonic corrections, although it is low compared to the experimental value for the dimer trapped in a neon-matrix.

  1. Controlling CH3NH3PbI(3-x)Cl(x) Film Morphology with Two-Step Annealing Method for Efficient Hybrid Perovskite Solar Cells.

    PubMed

    Liu, Dong; Wu, Lili; Li, Chunxiu; Ren, Shengqiang; Zhang, Jingquan; Li, Wei; Feng, Lianghuan

    2015-08-01

    The methylammonium lead halide perovskite solar cells have become very attractive because they can be prepared with low-cost solution-processable technology and their power conversion efficiency have been increasing from 3.9% to 20% in recent years. However, the high performance of perovskite photovoltaic devices are dependent on the complicated process to prepare compact perovskite films with large grain size. Herein, a new method is developed to achieve excellent CH3NH3PbI3-xClx film with fine morphology and crystallization based on one step deposition and two-step annealing process. This method include the spin coating deposition of the perovskite films with the precursor solution of PbI2, PbCl2, and CH3NH3I at the molar ratio 1:1:4 in dimethylformamide (DMF) and the post two-step annealing (TSA). The first annealing is achieved by solvent-induced process in DMF to promote migration and interdiffusion of the solvent-assisted precursor ions and molecules and realize large size grain growth. The second annealing is conducted by thermal-induced process to further improve morphology and crystallization of films. The compact perovskite films are successfully prepared with grain size up to 1.1 ?m according to SEM observation. The PL decay lifetime, and the optic energy gap for the film with two-step annealing are 460 ns and 1.575 eV, respectively, while they are 307 and 327 ns and 1.577 and 1.582 eV for the films annealed in one-step thermal and one-step solvent process. On the basis of the TSA process, the photovoltaic devices exhibit the best efficiency of 14% under AM 1.5G irradiation (100 mW·cm(-2)). PMID:26154760

  2. Infrared laser induced population transfer and parity selection in (14)NH3: A proof of principle experiment towards detecting parity violation in chiral molecules.

    PubMed

    Dietiker, P; Miloglyadov, E; Quack, M; Schneider, A; Seyfang, G

    2015-12-28

    We have set up an experiment for the efficient population transfer by a sequential two photon-absorption and stimulated emission-process in a molecular beam to prepare quantum states of well defined parity and their subsequent sensitive detection. This provides a proof of principle for an experiment which would allow for parity selection and measurement of the time evolution of parity in chiral molecules, resulting in a measurement of the parity violating energy difference ?pvE between enantiomers of chiral molecules. Here, we present first results on a simple achiral molecule demonstrating efficient population transfer (about 80% on the average for each step) and unperturbed persistence of a selected excited parity level over flight times of about 1.3 ms in the beam. In agreement with model calculations with and without including nuclear hyperfine structure, efficient population transfer can be achieved by a rather simple implementation of the rapid adiabatic passage method of Reuss and coworkers and considering also the stimulated Raman adiabatic passage technique of Bergmann and coworkers as an alternative. The preparation step uses two powerful single mode continuous wave optical parametric oscillators of high frequency stability and accuracy. The detection uses a sensitive resonantly enhanced multiphoton ionization method after free flight lengths of up to 0.8 m in the molecular beam. Using this technique, we were able to also resolve the nuclear hyperfine structure in the rovibrational levels of the ?1 and ?3 fundamentals as well as the 2?4 overtone of (14)NH3, for which no previous data with hyperfine resolution were available. We present our new results on the quadrupole coupling constants for the ?1, ?3, and 2?4 levels in the context of previously known data for ?2 and its overtone, as well as ?4, and the ground state. Thus, now, (14)N quadrupole coupling constants for all fundamentals and some overtones of (14)NH3 are known and can be used for further theoretical analysis. PMID:26723669

  3. Organic solvent desorption from two tegafur polymorphs.

    PubMed

    Bobrovs, Raitis; Acti?š, Andris

    2013-11-30

    Desorption behavior of 8 different solvents from ? and ? tegafur (5-fluoro-1-(tetrahydro-2-furyl)uracil) has been studied in this work. Solvent desorption from samples stored at 95% and 50% relative solvent vapor pressure was studied in isothermal conditions at 30 °C. The results of this study demonstrated that: solvent desorption rate did not differ significantly for both phases; solvent desorption in all cases occurred faster from samples with the largest particle size; and solvent desorption in most cases occurred in two steps. Structure differences and their surface properties were not of great importance on the solvent desorption rates because the main factor affecting desorption rate was sample particle size and sample morphology. Inspection of the structure packing showed that solvent desorption rate and amount of solvent adsorbed were mainly affected by surface molecule arrangement and ability to form short contacts between solvent molecule electron donor groups and freely accessible tegafur tetrahydrofuran group hydrogens, as well as between solvents molecule proton donor groups and fluorouracil ring carbonyl and fluoro groups. Solvent desorption rates of acetone, acetonitrile, ethyl acetate and tetrahydrofuran multilayers from ? and ? tegafur were approximately 30 times higher than those of solvent monolayers. Scanning electron micrographs showed that sample storage in solvent vapor atmosphere promotes small tegafur particles recrystallization to larger particles. PMID:24060368

  4. Stable and low-cost mesoscopic CH3NH3PbI2 Br perovskite solar cells by using a thin poly(3-hexylthiophene) layer as a hole transporter.

    PubMed

    Zhang, Meng; Lyu, Miaoqiang; Yu, Hua; Yun, Jung-Ho; Wang, Qiong; Wang, Lianzhou

    2015-01-01

    Mesoscopic perovskite solar cells using stable CH3 NH3 PbI2 Br as a light absorber and low-cost poly(3-hexylthiophene) (P3HT) as hole-transporting layer were fabricated, and a power conversion efficiency of 6.64?% was achieved. The partial substitution of iodine with bromine in the perovskite led to remarkably prolonged charge carrier lifetime. Meanwhile, the replacement of conventional thick spiro-MeOTAD layer with a thin P3HT layer has significantly reduced the fabrication cost. The solar cells retained their photovoltaic performance well when they were exposed to air without any encapsulation, presenting a favorable stability. The combination of CH3 NH3 PbI2 Br and P3HT may render a practical and cost-effective solid-state photovoltaic system. The superior stability of CH3 NH3 PbI2 Br is also promising for other photoconversion applications. PMID:25358456

  5. Double functions of porous TiO2 electrodes on CH3NH3PbI3 perovskite solar cells: Enhancement of perovskite crystal transformation and prohibition of short circuiting

    NASA Astrophysics Data System (ADS)

    Murugadoss, Govindhasamy; Mizuta, Gai; Tanaka, Soichiro; Nishino, Hitoshi; Umeyama, Tomokazu; Imahori, Hiroshi; Ito, Seigo

    2014-08-01

    In order to analyze the crystal transformation from hexagonal PbI2 to CH3NH3PbI3 by the sequential (two-step) deposition process, perovskite CH3NH3PbI3 layers were deposited on flat and/or porous TiO2 layers. Although the narrower pores using small nanoparticles prohibited the effective transformation, the porous-TiO2 matrix was able to help the crystal transformation of PbI2 to CH3NH3PbI3 by sequential two-step deposition. The resulting PbI2 crystals in porous TiO2 electrodes did not deteriorate the photovoltaic effects. Moreover, it is confirmed that the porous TiO2 electrode had served the function of prohibiting short circuits between working and counter electrodes in perovskite solar cells.

  6. Correlation between the processes of water desorption and tritium release from Li4SiO4 ceramic pebbles

    NASA Astrophysics Data System (ADS)

    Ran, Guangming; Xiao, Chengjian; Chen, Xiaojun; Gong, Yu; Kang, Chunmei; Wang, Xiaolin

    2015-11-01

    The correlation between water desorption and tritium release from Li4SiO4 pebbles was studied by temperature programmed desorption. The released water and tritium from irradiated samples were monitored simultaneously. The main peak for tritium release from the irradiated samples that were exposed to air for more than a month, was shifted from 500 to about 250 °C, as compared to that from the unexposed samples. The peak temperatures for water desorption and tritium release overlapped very well, suggesting a strong correlation between the two processes. Accordingly, a two-step mechanism, involving isotope exchange between the tritium trapped on the grain surface and the surface hydroxyls (-OH), and subsequent desorption of tritiated water through recombination of the -OH/-OT groups, was proposed to explain the tritium release behavior for the air-exposed samples. It is believed that the formation and desorption of surface hydroxyl groups at 200-300 °C can affect the behavior of tritium release from Li4SiO4 significantly.

  7. Ab initio potential energy surfaces for NH,,3 -...NH,,3 -

    E-print Network

    .1063/1.3268920 I. INTRODUCTION The field of cold T 1 K and ultracold 1 mK molecules has attracted great interest in the last few years. The production of such ultra cold species may find impor- tant applications,11 There are, in principle, two different strate- gies for producing molecular samples at ultra low tempera

  8. Memory Devices: Resistive Switching Behavior in Organic-Inorganic Hybrid CH3 NH3 PbI3-x Clx Perovskite for Resistive Random Access Memory Devices (Adv. Mater. 40/2015).

    PubMed

    Yoo, Eun Ji; Lyu, Miaoqiang; Yun, Jung-Ho; Kang, Chi Jung; Choi, Young Jin; Wang, Lianzhou

    2015-10-01

    Y. J. Choi, L. Wang, and co-workers report on page 6170 a new application of an organic-inorganic hybrid perovskite (CH3 NH3 PbI3-x Clx ) in a resistive random-access-memory device. The memory device has a very simple structure consisting of Au/CH3 NH3 PbI3-x Clx on conductive substrates, which exhibits a typical resistive-switching behavior and non-volatile properties with a low operating voltage, as well as good stability and reproducibility. This finding adds another important potential application of hybrid perovskites to their functionality library. PMID:26487021

  9. Probing the interaction of hydrogen chloride with low-temperature water ice surfaces using thermal and electron-stimulated desorption.

    PubMed

    Olanrewaju, Babajide O; Herring-Captain, Janine; Grieves, Gregory A; Aleksandrov, Alex; Orlando, Thomas M

    2011-06-16

    The interaction and autoionization of HCl on low-temperature (80-140 K) water ice surfaces has been studied using low-energy (5-250 eV) electron-stimulated desorption (ESD) and temperature programmed desorption (TPD). There is a reduction of H(+) and H(2)(+) and a concomitant increase in H(+)(H(2)O)(n=1-7) ESD yields due to the presence of submonolayer quantities of HCl. These changes are consistent with HCl induced reduction of dangling bonds required for H(+) and H(2)(+) ESD and increased hole localization necessary for H(+)(H(2)O)(n=1-7) ESD. For low coverages, this can involve nonactivated autoionization of HCl, even at temperatures as low as 80 K; well below those typical of polar stratospheric cloud particles. The uptake and autoionization of HCl is supported by TPD studies which show that for HCl doses ?0.5 ± 0.2 ML (ML = monolayer) at 110 K, desorption of HCl begins at 115 K and peaks at 180 K. The former is associated with adsorption of a small amount of molecular HCl and is strongly dependent on the annealing history of the ice. The latter peak at 180 K is commensurate with desorption of HCl via recombinative desorption of solvated separated ion pairs. The activation energy for second-order desorption of HCl initially in the ionized state is 43 ± 2 kJ/mol. This is close to the zero-order activation energy for ice desorption. PMID:21548613

  10. Synthesis and Characterization of an Organically Templated Lamellar Vanadium-Gallium Phosphate, [NH 3(CH 2) 2NH 3] 4[Ga 4- xV x(HPO 4) 5(PO 4) 3H(OH) 2]( x=1.65)

    NASA Astrophysics Data System (ADS)

    Chippindale, Ann M.; Cowley, Andrew R.

    2001-06-01

    A new two-dimensional vanadium-gallium phosphate (VGaPO), [NH3(CH2)2NH3]4[Ga4-xVx(HPO4)5(PO4)3H(OH)2](x=1.65), has been synthesized under solvothermal conditions at 433 K in the presence of ethylenediamine and the structure determined using room-temperature single-crystal X-ray diffraction data (Mr=1296.22, triclinic, space group P-1; a=9.991(1), b=12.367(1), and c=15.082(1) Å; ?=90.751(6), ?=91.720(7), and ?=91.449(8)°; V=1861.8.4 Å3; Z=2; R=3.93% and Rw=4.77% for 5985 observed data (I>3(?(I))). The inorganic layers consist of PO4 tetrahedra and M4O20 (M=V, Ga) tetramers assembled from edge- and corner-sharing MO6 octahedra. The structure contains various types of hydrogen bonding interactions: short symmetrical and asymmetrical hydrogen bonds within the layers, strong interlamellar hydrogen bonds holding the layers together, and amine-framework interactions holding the ethylenediammonium cations in place in the interlayer voids.

  11. High-pressure experiments on the stability of methane hydrates in the H2O-NH3-CH4 system with applications to Titan's cryovolcanism.

    NASA Astrophysics Data System (ADS)

    Choukroun, M.; Le Menn, E.; Grasset, O.

    2007-08-01

    The current methane abundance in Titan's thick atmosphere cannot be explained without the existence of replenishment processes. Indeed, the intense photochemistry taking place in the atmosphere would destroy the 2-5% CH4 amounts measured by the GCMS onboard the Huygens probe [1] within 10-100 Myr [e.g. 2]. Among the several hypotheses that could explain this replenishment, release of methane during cryovolcanic events seems highly likely. The VIMS [3] and Radar instruments [4] onboard the Cassini spacecraft have brought substantial evidence for cryovolcanic features on Titan's surface. A numerical model has shown the possibility to release CH4 by dissociating methane clathrate hydrates at depth, due to interaction of a clathrate layer with warm ice intrusions [5]. However, the effect of volatile compounds, dissolved (e.g. N2) or in solution (e.g. NH3), would most certainly play a major role in cryovolcanic processes. High-pressure low-temperature experimental investigations on the effect of ammonia on methane hydrates' dissociation are conducted within an optical sapphire-anvil cell. Preliminary results have been previously presented, which lead to contradictory interpretations so far [6,7]. As further experiments are being performed, the reliability of the experimental measurements and the reasons for observing discrepancies in the results can be adressed with more and more confidence. This poster will discuss the experimental issues encountered in the H2O-NH3-CH4 system, up-todate experimental results, as well as their implications for Titan's cryovolcanism. References: [1] Niemann HB et al., Nature 438, 779-784 (2005). [2] Yung YL et al., Astrophys. J. Suppl., 55, 465-506 (1984). [3] Sotin C et al., Nature 435, 786-789 (2005). [4] Lopes RMC et al., Icarus 186, 395-412 (2007). [5] Tobie G et al., Nature 440 (2), 61-64 (2006). [6] Choukroun M et al., 37th Lunar and Planet. Sci. Conf. Abstract #1640 (2006). [7] Choukroun M et al., 38th Lunar and Planet. Sci. Conf. Abstract #1606 (2007).

  12. 140 H/D isotopomers identified by long-range NMR hyperfine shifts in ruthenium(III) ammine complexes. Hyperconjugation in Ru-NH3 bonding.

    PubMed

    Laidlaw, W Michael; Denning, Robert G; Green, Jennifer C; Boyd, Jonathan; Harmer, Jeffrey; Thompson, Amber L

    2013-06-17

    (1)H NMR spectra of the paramagnetic cyanide-bridged mixed-valence compound [(?(5)-C5H5)Fe(CO)2(?-CN)Ru(NH3)5](CF3SO3)3 (I) have been obtained in several solvents. When traces of partially deuterated water are present, instead of a single cyclopentadienyl (Cp) resonance shifted by the hyperfine interaction, numerous well-resolved resonances are observed. The spectra were simulated satisfactorily by giving the appropriate statistical weight to 140 possible H/D isotopomers formed by deuteration in the five ruthenium(III) ammine ligands. The proliferation of distinct resonances occurs because (a) the hyperfine shifts (HSs) due to each sequential deuteration in a single ammine are different and (b) while deuteration in an ammine cis to the cyanide bridge causes a downfield shift, in the trans ammine it causes an upfield shift that is nearly twice as large. All of these shifts exhibit a 1/T dependence, but temperature-independent components, due to large second-order Zeeman effects at the Ru(III) center, are also present. Combining the results of density functional theory calculations with data from metal-metal charge-transfer optical transitions and with the effect of solvent-induced NMR HSs, it is argued that Fermi contact shifts at the Cp protons are insignificant compared to those due to the dipolar (pseudocontact) mechanism. Analytical expressions are presented for the dependence of the HS on the tetragonal component of the ligand field at the Ru(III) ion. The tetragonal field parameter, defined as the energy by which the 4d(xy) orbital exceeds the mean t(2g) orbital energy, was found to be 147, 52, and 76 cm(-1), in dimethylformamide, acetone, and nitromethane, respectively. The effects of deuteration show that there is a significant component of hyperconjugation in the Ru-ammine interaction and that ND3 is a weaker ? donor than NH3. A single deuteration in an axial ammine increases the tetragonal field parameter (?) by +2.8 cm(-1), resulting in a HS of -37 ppb in the Cp proton resonance, whereas a single deuteration in an equatorial ammine decreases the field by -1.5 cm(-1) with a HS of +20 ppb, despite a nominal separation of seven chemical bonds. We analyze the origin of this remarkable sensitivity, which relies on the favorable characteristics of the Ru(III) low-spin t(2g)(5) configuration, having a spin-orbit coupling constant ? ? 950 cm(-1). PMID:23697337

  13. Far-UV, visible, and near-IR reflectance spectra of frosts of H2O, CO2, NH3 and SO2

    NASA Technical Reports Server (NTRS)

    Hapke, B.; Wells, E.; Wagner, J.; Partlow, W.

    1981-01-01

    Measurements in the 0.1-2.5 micron range are presented for the reflectance spectra of the frosts of several volatiles pertinent to the study of comet nuclei. The frost spectra have distinctive features permitting their identification by spectroscopic reflectance remote sensing, notably in the far UV. It is found that: (1) H2O has a minimum at 0.16 microns and a maximum at 0.13 microns; (2) CO2 has minima near 0.21, 0.18 and 0.125 microns, with maxima at 0.19, 0.135 and 0.120 microns; (3) NH3 is bright at wavelengths longer than 0.21 microns, where reflectance drops to a value of only a few per cent at shorter wavelengths; (4) SO2 has a sharp drop at 0.32 microns, with a minimum at 0.18 microns and a maximum at 0.13 microns. The features in the frost spectra largely correspond to absorption line bands in the gas phase.

  14. Amino acids produced from the ultraviolet/extreme-ultraviolet irradiation of naphthalene in a H2O+NH3 ice mixture

    NASA Astrophysics Data System (ADS)

    Chen, Y.-J.; Nuevo, M.; Yih, T.-S.; Ip, W.-H.; Fung, H.-S.; Cheng, C.-Y.; Tsai, H.-R.; Wu, C.-Y. R.

    2008-02-01

    In this work, we show that the irradiation of naphthalene (C10H8), the smallest polycyclic aromatic hydrocarbon (PAH), mixed in a H2O+NH3 ice mixture with 4-20 eV (62-310 nm, i.e. in the ultraviolet/extreme-ultraviolet ranges) photons at 15 K leads to the formation of an organic residue where many amino acids were identified. However, the distribution of these amino acids is different from what was reported in previous laboratory experiments where ice mixtures containing other sources of carbon (CO, CO2, CH4 and CH3OH) were irradiated with ultraviolet photons, indicating that amino acids can be formed via several mechanisms. This result also implies that naphthalene, and probably other PAHs, constitute a non-negligible source of interstellar carbon likely to form organic molecules after photolysis, supporting a scenario where molecules of biological interest could be formed in many different astrophysical environments before being delivered to the early Earth by meteorites.

  15. Infrared spectrum and normal-mode assignment in methyl-ammonium lead halide perovskite CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Perez Osorio, Miguel Angel; Filip, Marina; Docherty, Callum; Herz, Laura; Johnston, Michael; Giustino, Feliciano

    2015-03-01

    Solar cells based on MAPbI3 (MA=CH3NH3) have attracted enormous attention during the past two years owing to their high energy-conversion efficiency, reaching up to 19.3 % in record devices. A detailed understanding of the structure/property relations of this compound may help us explain its extraordinary performance. Here, we investigate the vibrational modes and infrared (IR) absorption spectrum of MAPbI3 by combining first-principles calculations and experiment. Our calculations indicate that the normal modes at high frequency, 400-3100 cm-1, correspond to internal vibrations of the MA cations, whereas those at low frequency, up to 180 cm-1, can be assigned either to vibrations of the PbI nework or to the libration and spinning of the cations. Using a factor group analysis we establish the symmetry of the normal modes and predict which mode will be IR or Raman active. In order to confirm these assignments we explicitly calculate the IR spectrum of the MAPbI3. The calculated spectrum is in good agreement with experiment, therefore we now have a complete characterization of the vibrational properties of MAPbI3. This work will serve as a solid reference for future structural and characterization studies of hybrid organic-inorganic perovskites.

  16. Mechanical properties of hybrid organic-inorganic CH3NH3BX3 (B = Sn, Pb; X = Br, I) perovskites for solar cell absorbers

    NASA Astrophysics Data System (ADS)

    Feng, Jing

    2014-08-01

    The crystal structures, elastic and anisotropic properties of CH3NH3BX3 (B = Sn, Pb; X = Br, I) compounds as solar cell absorber layers are investigated by the first-principles calculations. The type and strength of chemical bond B-X are found to determine the elastic properties. B-X bonds and the organic cations are therefore crucial to the functionalities of such absorbers. The bulk, shear, Young's modulus ranges from 12 to 30 GPa, 3 to 12 GPa, and 15 to 37 GPa, respectively. Moreover, the interaction among organic and inorganic ions would have negligible effect for elastic properties. The B/G and Poisson's ratio show it would have a good ductile ability for extensive deformation as a flexible/stretchable layer on the polymer substrate. The main reason is attributed to the low shear modulus of such perovskites. The anisotropic indices AU, AB AG, A1, A2, and A3 show ABX3 perovskite have very strong anisotropy derived from the elastic constants, chemical bonds, and symmetry.

  17. Atomic Layer Deposition of Ru Thin Films Using a New Beta-Diketonate Ru Precursor and NH3 Plasma as a Reactant.

    PubMed

    Jung, Jae-Hun; Lee, Seung-Joon; Lee, Hyun-Jung; Lee, Min Young; Cheon, Taehoon; Bae, So Ik; Saito, Masayuki; Suzuki, Kazuharu; Nabeya, Shunichi; Lee, Jeongyeop; Kim, Sangdeok; Yeom, Seungjin; Seo, Jong Hyun; Kim, Soo-Hyun

    2015-11-01

    Ruthenium (Ru) thin films were grown on thermally-grown SiO2 substrates by plasma enhanced atomic layer deposition (PEALD) using a sequential supply of a new betadiketonate Ru metallorganic precursor, dicarbonyl-bis(5-methyl-2,4-hexanediketonato) Ru(II) (C16H22O6Ru) with a high vapor pressure and NH3 plasma as a reactant at the substrate temperature ranging from 175 and 310 degrees C. A self-limited film growth was confirmed at the deposition temperature of 225 degrees C and the growth rate was 0.063 nm/cycle on the SiO2 substrate with very short number of incubation cycles (approximately 10 cycles). The resistivity of PEALD-Ru films was dependent on the microstructural features characterized by grain size and crystallinity, which could be controlled by varying the deposition temperature. Ru film with the resistivity of -20 ??-cm and high density of 11.5 g/cm3 was obtained at the deposition temperature as low as 225 degrees C. It formed polycrystalline structure with hexagonal-close-packed phase that was confirmed by X-ray diffractometry and transmission electronic microscopy analysis. Step coverage of PEALD-Ru film deposited with the optimum condition was good (-75%) at the very small-sized trench (aspect ratio: -4.5 and the top opening size of 25 nm). PMID:26726537

  18. Band alignment and charge transfer in rutile-TiO2/CH3NH3PbI3-xClx interfaces.

    PubMed

    Nemnes, G A; Goehry, C; Mitran, T L; Nicolaev, Adela; Ion, L; Antohe, S; Plugaru, N; Manolescu, A

    2015-11-11

    Rutile-TiO2/hybrid halide perovskite CH3NH3PbI3-xClx interfaces are investigated by ab initio density functional theory calculations. The role of chlorine in achieving enhanced solar cell power conversion efficiencies is in the focus of recent studies, which point to increased carrier mobilities, reduced recombination rates, a driven morphology evolution of the perovskite layer and improved carrier transport across the interface. As it was recently established that chlorine is preferentially localized in the vicinity of the interface and not in the bulk of the perovskite layer, we analyze the changes introduced in the electronic properties by varying the chlorine concentration near the interface. In particular, we discuss the effects introduced in the electronic band structure and show the role of chlorine in the enhanced electron injection into the rutile-TiO2 layer. Taking into account these implications, we discuss the conditions for optimizing the solar cell efficiency in terms of interfacial chlorine concentration. PMID:26509658

  19. Modeling of nitrogen compounds in cometary atmospheres: Fluorescence models of ammonia (NH3), hydrogen cyanide (HCN), hydrogen isocyanide (HNC) and cyanoacetylene (HC3N)

    NASA Astrophysics Data System (ADS)

    Villanueva, G. L.; Magee-Sauer, K.; Mumma, M. J.

    2013-11-01

    We developed full cascade fluorescence models for NH3, HCN and HNC, and a new band model for the ?1 ro-vibrational band of HC3N. The models are based on ab-initio spectral databases containing millions of spectral lines and also include extremely precise spectral information contained in several high-resolution spectral databases. Using these new models we derive detailed cascade maps for these species, and obtain realistic fluorescence efficiencies applicable to high-resolution infrared spectra. The new models permit accurate synthesis of line-by-line spectra for a wide range of rotational temperatures. We validated the models by comparing simulated emissions of these nitrogen species with measured spectra of comet C/2007 W1 (Boattini) acquired with high-resolution infrared spectrometers at high altitude sites. The new models accurately describe the complex emission spectrum, providing distinct rotational temperatures and production rates at greatly improved accuracy compared with results derived from earlier fluorescence models. In addition, we made use of the completeness and scope of the new databases to investigate possible HCN?HNC radiative isomerization mechanisms, obtaining estimates of conversion efficiencies under typical cometary conditions.

  20. Domain Walls Conductivity in Hybrid Organometallic Perovskites and Their Essential Role in CH3NH3PbI3 Solar Cell High Performance

    PubMed Central

    Rashkeev, Sergey N.; El-Mellouhi, Fedwa; Kais, Sabre; Alharbi, Fahhad H.

    2015-01-01

    The past several years has witnessed a surge of interest in organometallic trihalide perovskites, which are at the heart of the new generation of solid-state solar cells. Here, we calculated the static conductivity of charged domain walls in n- and p- doped organometallic uniaxial ferroelectric semiconductor perovskite CH3NH3PbI3 using the Landau-Ginzburg-Devonshire (LGD) theory. We find that due to the charge carrier accumulation, the static conductivity may drastically increase at the domain wall by 3 – 4 orders of magnitude in comparison with conductivity through the bulk of the material. Also, a two-dimensional degenerated gas of highly mobile charge carriers could be formed at the wall. The high values of conductivity at domain walls and interfaces explain high efficiency in organometallic solution-processed perovskite films which contains lots of different point and extended defects. These results could suggest new routes to enhance the performance of this promising class of novel photovoltaic materials. PMID:26088321

  1. Light Harvesting and Charge Recombination in CH3NH3PbI3 Perovskite Solar Cells Studied by Hole Transport Layer Thickness Variation.

    PubMed

    Marinova, Nevena; Tress, Wolfgang; Humphry-Baker, Robin; Dar, M Ibrahim; Bojinov, Vladimir; Zakeeruddin, Shaik Mohammed; Nazeeruddin, Mohammad Khaja; Grätzel, Michael

    2015-04-28

    A tailored optimization of perovskite solar cells requires a detailed understanding of the processes limiting the device efficiency. Here, we study the role of the hole transport layer (HTL) spiro-MeOTAD and its thickness in a mesoscopic TiO2-based solar cell architecture. We find that a sufficiently thick (200 nm) HTL not only increases the charge carrier collection efficiency but also the light harvesting efficiency. This is due to an enhanced reflection of a smooth HTL/Au-electrode interface. The rough CH3NH3PbI3 perovskite surface requires an HTL thickness of >400 nm to avoid surface recombination and guarantee a high open-circuit voltage. Analyses of the electroluminescence efficiency and the diode ideality factor show that the open-circuit voltage becomes completely limited by trap-assisted recombination in the perovskite for a thick HTL. Thus, spiro-MeOTAD is a very good HTL choice from the device physics' point of view. The fill factor analyzed by the Suns-Voc method is not transport limited, but trap-recombination limited as well. Consequently, a further optimization of the device has to focus on defects in the polycrystalline perovskite film. PMID:25769194

  2. Kinetic modeling of the adsorption and desorption of CO2 on ?-Fe2O3.

    PubMed

    Breyer, Christine; Reichert, Dirk; Seidel, Juergen; Hüttl, Regina; Mertens, Florian; Kureti, Sven

    2015-10-28

    The present paper addresses the interaction of CO2 with polycrystalline ?-Fe2O3 revealing considerable catalytic activity in CO oxidation to yield CO2. The mechanism of adsorption and desorption of CO2 was investigated by diffuse reflectance infrared fourier transform spectroscopy (DRIFTS), while the kinetics was examined by temperature-programmed desorption (CO2-TPD). For numeric modeling as well as simulation of the surface coverage, an elementary kinetic mean field model was constructed using Arrhenius-based rate expressions. The kinetic parameters of desorption were taken from fitting calculations (A2 = 3.01 × 10(5) mol (m(2) s)(-1), E2(0) = 112.8 kJ mol(-1), ?2 = 70.2 kJ mol(-1)), whereas the adsorption was considered to be non-activated and the pre-exponential factor was estimated from kinetic gas theory (A1 = 0.0192 m s(-1), E1 = 0 kJ mol(-1)). For model validation, predicted and experimental CO2-TPD profiles were compared and thermodynamic consistency was evaluated by using differential scanning calorimetry (?adsH(250 °C) = -129 kJ mol(-1)) as well as literature data. PMID:26411579

  3. ?- to ?-[C 6H 4(NH 3) 2] 2Bi 2I 10 reversible solid-state transition, thermochromic and optical studies in the p-phenylenediamine-based iodobismuthate(III) material

    NASA Astrophysics Data System (ADS)

    Hrizi, Chakib; Trigui, Ameni; Abid, Younes; Chniba-Boudjada, Nassira; Bordet, Pierre; Chaabouni, Slaheddine

    2011-12-01

    ?-[C 6H 4(NH 3) 2] 2Bi 2I 10, which is a new material containing low-dimensional iodobismuthate anions, was synthesized and through its single crystal X-ray diffraction measurements, was proven to crystallize at room temperature in the centrosymmetric space group P2 1/c. It consists of a p-phenylenediammonium dication and a discrete (0-D) anion built up of edge-sharing bioctahedron. Due to the hydrogen bonds and the interatomic distances (Bi-I, I⋯I and ?-?) changes, ?-phase was transformed into the corresponding centrosymmetric ?-phase, ?-[C 6H 4(NH 3) 2] 2Bi 2I 10, through a single-crystal to single-crystal transformation occurring upon cooling to -28/-26 °C. Below the transition temperature, ?-[C 6H 4(NH 3) 2] 2Bi 2I 10 crystallizes in the monoclinic system, centrosymmetric space group P2 1/n. Besides, the optical transmission measurements on ?-[C 6H 4(NH 3) 2] 2Bi 2I 10 thin films have revealed two absorption bands at 2.47 and 3.01 eV. Finally, two room temperature photoluminescence emissions attributed to excitons radiative recombinations confined within the bioctahedra Bi 2I 104-, were observed in the red spectral range at 1.9 and 2.05 eV energy.

  4. Hole-Conductor-Free, Metal-Electrode-Free TiO2/CH3NH3PbI3 Heterojunction Solar Cells Based on a Low-Temperature Carbon Electrode.

    PubMed

    Zhou, Huawei; Shi, Yantao; Dong, Qingshun; Zhang, Hong; Xing, Yujin; Wang, Kai; Du, Yi; Ma, Tingli

    2014-09-18

    Low cost, high efficiency, and stability are straightforward research challenges in the development of organic-inorganic perovskite solar cells. Organolead halide is unstable at high temperatures or in some solvents. The direct preparation of a carbon layer on top becomes difficult. In this study, we successfully prepared full solution-processed low-cost TiO2/CH3NH3PbI3 heterojunction (HJ) solar cells based on a low-temperature carbon electrode. Power conversion efficiency of mesoporous (M-)TiO2/CH3NH3PbI3/C HJ solar cells based on a low-temperature-processed carbon electrode achieved 9%. The devices of M-TiO2/CH3NH3PbI3/C HJ solar cells without encapsulation exhibited advantageous stability (over 2000 h) in air in the dark. The ability to process low-cost carbon electrodes at low temperature on top of the CH3NH3PbI3 layer without destroying its structure reduces the cost and simplifies the fabrication process of perovskite HJ solar cells. This ability also provides higher flexibility to choose and optimize the device, as well as investigate the underlying active layers. PMID:26276339

  5. The composition of Saturn's atmosphere at northern temperate latitudes from Voyager IRIS spectra - NH3, PH3, C2H2, C2H6, CH3D, CH4, and the Saturnian D/H isotopic ratio

    NASA Technical Reports Server (NTRS)

    Courtin, R.; Gautier, D.; Marten, A.; Bezard, B.; Hanel, R.

    1984-01-01

    The vertical distributions and mixing ratios of minor constituents in the northern hemisphere of Saturn are investigated. Results are obtained for NH3, PH3, C2H2, C2H6, CH3D, and CH4; the D/H ratio is obtained from the CH4 and CH3D abundances. The NH3 mixing ratio in the upper atmosphere is found to be compatible with the saturated partial pressure. The inferred PH3/H2 ratio of 1.4 + or - 0.8 x 10 to the -6th is higher than the value derived from the solar P/H ratio. The stratospheric C2H2/H2 and C2H6/H2 ratios are, respectively, 2.1 + or - 1.4 x 10 to the -7th and 3.0 + or - 1.1 x 10 to the -6th; the latter decreases sharply below the 20-50 mbar level. The results for CH3D/H2 and CH4/H2 imply an enrichment of Saturn's upper atmosphere in carbon by a factor of at least three over the solar abundance. The interpretation of two NH3 lines in the five-micron window suggests a NH3/H2 ratio at the two bar level below the solar value.

  6. Trends in Syntheses, Structures, and Properties for Three Series of Ammine Rare-Earth Metal Borohydrides, M(BH4)3·nNH3 (M = Y, Gd, and Dy).

    PubMed

    Jepsen, Lars H; Ley, Morten B; ?erný, Radovan; Lee, Young-Su; Cho, Young Whan; Ravnsbæk, Dorthe; Besenbacher, Flemming; Skibsted, Jørgen; Jensen, Torben R

    2015-08-01

    Fourteen solvent- and halide-free ammine rare-earth metal borohydrides M(BH4)3·nNH3, M = Y, Gd, Dy, n = 7, 6, 5, 4, 2, and 1, have been synthesized by a new approach, and their structures as well as chemical and physical properties are characterized. Extensive series of coordination complexes with systematic variation in the number of ligands are presented, as prepared by combined mechanochemistry, solvent-based methods, solid-gas reactions, and thermal treatment. This new synthesis approach may have a significant impact within inorganic coordination chemistry. Halide-free metal borohydrides have been synthesized by solvent-based metathesis reactions of LiBH4 and MCl3 (3:1), followed by reactions of M(BH4)3 with an excess of NH3 gas, yielding M(BH4)3·7NH3 (M = Y, Gd, and Dy). Crystal structure models for M(BH4)3·nNH3 are derived from a combination of powder X-ray diffraction (PXD), (11)B magic-angle spinning NMR, and density functional theory (DFT) calculations. The structures vary from two-dimensional layers (n = 1), one-dimensional chains (n = 2), molecular compounds (n = 4 and 5), to contain complex ions (n = 6 and 7). NH3 coordinates to the metal in all compounds, while BH4(-) has a flexible coordination, i.e., either as a terminal or bridging ligand or as a counterion. M(BH4)3·7NH3 releases ammonia stepwise by thermal treatment producing M(BH4)3·nNH3 (6, 5, and 4), whereas hydrogen is released for n ? 4. Detailed analysis of the dihydrogen bonds reveals new insight about the hydrogen elimination mechanism, which contradicts current hypotheses. Overall, the present work provides new general knowledge toward rational materials design and preparation along with limitations of PXD and DFT for analysis of structures with a significant degree of dynamics in the structures. PMID:26196159

  7. Desorption induced by multiple electronic transitions

    NASA Astrophysics Data System (ADS)

    Misewich, J. A.; Heinz, T. F.; Newns, D. M.

    1992-06-01

    A new mechanism is introduced to describe desorption from surfaces under conditions of strong electronic excitation. When repetitive excitations occur within the relaxation time for the adsorbate-surface vibration, the process of desorption induced by multiple electronic transitions may provide an enhancement of orders of magnitude over a single-excitation mechanism. This generalization of the classic Menzel-Gomer-Redhead picture encompasses within one formalism both single-excitation processes and a thermal limit. The mechanism may be operative in desorption by femtosecond laser pulses.

  8. Monte Carlo evaluation of thermal desorption rates

    SciTech Connect

    Adams, J.E.; Doll, J.D.

    1981-05-01

    The recently reported method for computing thermal desorption rates via a Monte Carlo evaluation of the appropriate transition state theory expression (J. E. Adams and J. D. Doll, J. Chem. Phys. 74, 1467 (1980)) is extended, by the use of importance sampling, so as to generate the complete temperature dependence in a single calculation. We also describe a straightforward means of calculating the activation energy for the desorption process within the same Monte Carlo framework. The result obtained in this way represents, for the case of a simple desorptive event, an upper bound to the true value.

  9. Plasma Desorption Mass Spectrometry: Coming of Age.

    ERIC Educational Resources Information Center

    Cotter, Robert J.

    1988-01-01

    Discusses the history and development of Plasma Desorption Mass Spectrometry to determine molecular weights and structures of proteins and polymers. Outlines theory, instrumentation, and sample preparation commonly used. Gives several examples of resulting spectra. (ML)

  10. Experimental investigation of aminoacetonitrile formation through the Strecker synthesis in astrophysical-like conditions: reactivity of methanimine (CH2NH), ammonia (NH3), and hydrogen cyanide (HCN)

    NASA Astrophysics Data System (ADS)

    Danger, G.; Borget, F.; Chomat, M.; Duvernay, F.; Theulé, P.; Guillemin, J.-C.; Le Sergeant D'Hendecourt, L.; Chiavassa, T.

    2011-11-01

    Context. Studing chemical reactivity in astrophysical environments is an important means for improving our understanding of the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. Laboratory simulations of the reactivity of ice analogs provide important insight into the reactivity in these environments. Here, we use these experimental simulations to investigate the Strecker synthesis leading to the formation of aminoacetonitrile in astrophysical-like conditions. The aminoacetonitrile is an interesting compound because it was detected in SgrB2, hence could be a precursor of the smallest amino acid molecule, glycine, in astrophysical environments. Aims: We present the first experimental investigation of the formation of aminoacetonitrile NH2CH2CN from the thermal processing of ices including methanimine (CH2NH), ammonia (NH3), and hydrogen cyanide (HCN) in interstellar-like conditions without VUV photons or particules. Methods: We use Fourier Transform InfraRed (FTIR) spectroscopy to monitor the ice evolution during its warming. Infrared spectroscopy and mass spectroscopy are then used to identify the aminoacetonitrile formation. Results: We demonstrate that methanimine can react with -CN during the warming of ice analogs containing at 20 K methanimine, ammonia, and [NH4+ -CN] salt. During the ice warming, this reaction leads to the formation of poly(methylene-imine) polymers. The polymer length depend on the initial ratio of mass contained in methanimine to that in the [NH4+ -CN] salt. In a methanimine excess, long polymers are formed. As the methanimine is progressively diluted in the [NH4+ -CN] salt, the polymer length decreases until the aminoacetonitrile formation at 135 K. Therefore, these results demonstrate that aminoacetonitrile can be formed through the second step of the Strecker synthesis in astrophysical-like conditions.

  11. Effect of HCl/SO2/NH3/O2 and mineral sorbents on the partitioning behaviour of heavy metals during the thermal treatment of solid wastes.

    PubMed

    Huang, Qunxing; Cai, Xu; Alhadj Mallah, Moussa Mallaye; Chi, Yong; Yan, Jianhua

    2015-12-01

    The high concentration of heavy metals in solid wastes may cause serious pollution during thermal treatment. We have investigated, theoretically and experimentally, the effects of several important flue gas species and mineral sorbents on the partitioning behaviour of four major heavy metals (cadmium, lead, zinc and copper) which are often present in municipal solid waste (MSW). Their concentrations in bottom ash, fly ash and flue gas were quantified when model MSW samples were treated thermally under different conditions. The evaporation ratio of the four metals, excluding Cu, increased with decreasing oxygen concentration. The presence of HCl promotes heavy metal evaporation by preventing the formation of stable metallic species, especially for Zn (evaporation of more than 20%). An increase in oxygen concentration has a negative influence on the effect of HCl. In the presence of SO2, Cd and Pb exhibited a higher evaporation ratio, while Zn and Cu were insensitive to the change. SO2 also inhibits Cd vaporization in an oxidative atmosphere. The effect of NH3 on reducing the metal volatilization rate was established indirectly. Calcium oxide addition enhances metal evaporation except for that of Zn (which shows a decrease of 38%). Although desulphurization by calcium injection decreases the volume of acid gas, calcium affects heavy metal pollution control adversely. The presence or addition of SiO2- or Al2O3-containing minerals can lead to the formation of stable metallic salts. This may favour the control of Cd, Pb, Zn and Cu volatilization up to 13%, 50%, 17.5% and 19%, respectively. PMID:25204800

  12. Microwave Plasma-Activated Chemical Vapor Deposition of Nitrogen-Doped Diamond. I. N2/H2 and NH3/H2 Plasmas.

    PubMed

    Truscott, Benjamin S; Kelly, Mark W; Potter, Katie J; Johnson, Mack; Ashfold, Michael N R; Mankelevich, Yuri A

    2015-12-31

    We report a combined experimental/modeling study of microwave activated dilute N2/H2 and NH3/H2 plasmas as a precursor to diagnosis of the CH4/N2/H2 plasmas used for the chemical vapor deposition (CVD) of N-doped diamond. Absolute column densities of H(n = 2) atoms and NH(X(3)?(-), v = 0) radicals have been determined by cavity ring down spectroscopy, as a function of height (z) above a molybdenum substrate and of the plasma process conditions, i.e., total gas pressure p, input power P, and the nitrogen/hydrogen atom ratio in the source gas. Optical emission spectroscopy has been used to investigate variations in the relative number densities of H(n = 3) atoms, NH(A(3)?) radicals, and N2(C(3)?u) molecules as functions of the same process conditions. These experimental data are complemented by 2-D (r, z) coupled kinetic and transport modeling for the same process conditions, which consider variations in both the overall chemistry and plasma parameters, including the electron (Te) and gas (T) temperatures, the electron density (ne), and the plasma power density (Q). Comparisons between experiment and theory allow refinement of prior understanding of N/H plasma-chemical reactivity, and its variation with process conditions and with location within the CVD reactor, and serve to highlight the essential role of metastable N2(A(3)?(+)u) molecules (formed by electron impact excitation) and their hitherto underappreciated reactivity with H atoms, in converting N2 process gas into reactive NHx (x = 0-3) radical species. PMID:26593853

  13. Structural phase transition causing anomalous photoluminescence behavior in perovskite (C6H11NH3)2[PbI4].

    PubMed

    Yangui, A; Pillet, S; Mlayah, A; Lusson, A; Bouchez, G; Triki, S; Abid, Y; Boukheddaden, K

    2015-12-14

    Optical and structural properties of the organic-inorganic hybrid perovskite-type (C6H11NH3)2[PbI4] (abbreviated as C6PbI4) were investigated using optical absorption, photoluminescence (PL), and x-ray diffraction measurements. Room temperature, optical absorption measurements, performed on spin-coated films of C6PbI4, revealed two absorption bands at 2.44 and 3.21 eV. Upon 325 nm (3.815 eV) laser irradiation, strong green PL emission peaks were observed at 2.41 eV (P1) and 2.24 eV (P2) and assigned to free and localized excitons, respectively. The exciton binding energy was estimated at 356 meV. At low temperature, two additional emission bands were detected at 2.366 eV (P3) and a large band (LB) at 1.97 eV. The former appeared only below 40 K and the latter emerged below 130 K. The thermal dependence of the PL spectra revealed an abnormal behavior accompanied by singularities in the peak positions and intensities at 40 and 130 K. X-ray diffraction studies performed on powder and single crystals as a function of temperature evidenced significant changes of the interlayer spacing at 50 K and ?138 K. Around 138 K, a commensurate to incommensurate structural phase transition occurred on cooling. It involves a symmetry breaking leading to a distortion of the PbI6 octahedron. The resulting incommensurate spatial modulation of the Pb-I distances (and Pb-I-Pb angles) causes a spatial modulation of the band gap, which is at the origin of the emergence of the LB below ?130 K and the anomalous behavior of the position of P1 below 130 K. The change of the interlayer spacing in the 40-50 K range may in turn be related to the significant decrease of the intensity of P2 and the maximum emission of the LB. These results underline the intricate character of the structural and the PL properties of the hybrid perovskites; understanding such properties should benefit to the design of optoelectronic devices with targeted properties. PMID:26671368

  14. No activation barrier synthetic route of glycine from simple molecules (NH 3, CH 2, and CO 2) via carboxylation of ammonium ylide: a theoretical study by the scaled hypersphere search method

    NASA Astrophysics Data System (ADS)

    Maeda, Satoshi; Ohno, Koichi

    2004-11-01

    A new synthetic route of glycine with no activation barriers, NH 3 + CH 2 + CO 2 ? H 2NCH 2COOH, has been discovered by the scaled hypersurface search method for ab initio potential energy surfaces. The route is composed of two steps with no activation barriers, an addition reaction of ammonia with singlet methylene yielding ammonium ylide (NH 3 + 1:CH 2 ? H 2CNH 3) followed by carboxylation of the ylide with carbon dioxide (H 2CNH 3 + CO 2 ? H 2NCH 2COOH). A sideway reaction of the ylide decomposing into methyleneimine and hydrogen (H 2CNH 3 ? H 2CNH + H 2) via new transition state was found in addition to an isomerization route to methylamine (H 2CNH 3 ? CH 3NH 2).

  15. Thermally-induced first-order phase transition in the (FC6H4C2H4NH3)2[PbI4] photoluminescent organic-inorganic material

    NASA Astrophysics Data System (ADS)

    Koubaa, M.; Dammak, T.; Garrot, D.; Castro, M.; Codjovi, E.; Mlayah, A.; Abid, Y.; Boukheddaden, K.

    2012-03-01

    The thermal properties of the perovskite slab alkylammonium lead iodide (FC6H4C2H4NH3)2[PbI4] are investigated using spectroscopic ellipsometry, differential scanning calorimetry, photoluminescence, and Raman spectroscopy. The spectroscopic ellipsometry, performed in the heating mode, clearly evidenced the presence of a singularity at 375 K. This is corroborated by the temperature dependence of the photoluminescence, which pointed out a first-order order-disorder phase transition at ˜375 K, with a hysteresis loop of 40 K width. Raman spectroscopy data suggest that this transition arises from a dynamic rotational disordering of the ammonium headgroups of the alkylammonium chain. In contrast, differential scanning calorimetry measurements on a pellet sample led to an entropy change value ?S ?0.39 J/K/mol at the transition, suggesting the existence of a residual short-range order of the NH3+ on cooling from the high temperature phase.

  16. An efficient planar-heterojunction solar cell based on wide-bandgap CH3NH3PbI2.1Br0.9 perovskite film for tandem cell application.

    PubMed

    Zhu, Weidong; Bao, Chunxiong; Li, Faming; Zhou, Xiaoxin; Yang, Jie; Yu, Tao; Zou, Zhigang

    2016-01-01

    A dense and homogenous flat wide-bandgap (1.75 eV) CH3NH3PbI2.1Br0.9 perovskite film was prepared via a facile halide exchange route. The planar-heterojunction solar cell shows an optimal power conversion efficiency of 12.67% with negligible current hysteresis due to the film's large grains and vertically oriented grain boundaries. PMID:26513761

  17. A Liquid Junction Photoelectrochemical Solar Cell Based on p-Type MeNH3PbI3 Perovskite with 1.05 V Open-Circuit Photovoltage.

    PubMed

    Hsu, Hsien-Yi; Ji, Li; Ahn, Hyun S; Zhao, Ji; Yu, Edward T; Bard, Allen J

    2015-11-25

    A liquid junction photoelectrochemical (PEC) solar cell based on p-type methylammonium lead iodide (p-MeNH3PbI3) perovskite with a large open-circuit voltage is developed. MeNH3PbI3 perovskite is readily soluble or decomposed in many common solvents. However, the solvent dichloromethane (CH2Cl2) can be employed to form stable liquid junctions. These were characterized with photoelectrochemical cells with several redox couples, including I3(-)/I(-), Fc/Fc(+), DMFc/DMFc(+), and BQ/BQ(•-) (where Fc is ferrocene, DMFc is decamethylferrocene, BQ is benzoquinone) in CH2Cl2. The solution-processed MeNH3PbI3 shows cathodic photocurrents and hence p-type behavior. The difference between the photocurrent onset potential and the standard potential for BQ/BQ(•-) is 1.25 V, which is especially large for a semiconductor with a band gap of 1.55 eV. A PEC photovoltaic cell, with a configuration of p-MeNH3PbI3/CH2Cl2, BQ (2 mM), BQ(•-) (2 mM)/carbon, shows an open-circuit photovoltage of 1.05 V and a short-circuit current density of 7.8 mA/cm(2) under 100 mW/cm(2) irradiation. The overall optical-to-electrical energy conversion efficiency is 6.1%. The PEC solar cell shows good stability for 5 h under irradiation. PMID:26523921

  18. Dynamics and fragmentation of van der Waals clusters: ,,H2O...n, ,,CH3OH...n, and ,,NH3...n upon ionization by a 26.5 eV soft x-ray laser

    E-print Network

    Rocca, Jorge J.

    Dynamics and fragmentation of van der Waals clusters: ,,H2O...n, ,,CH3OH...n, and ,,NH3...n upon that are typically dominated by the protonated cluster ions H2O nH+ : these species are produced by a fast proton ions H2O 21H+ and H2O 28H+ are identified as "magic number" clusters in this mass spectrum since

  19. Conformational analysis of the adduct cis-[Pt(NH3)2 d(GpG)]+ in aqueous solution. A high field (500-300 MHz) nuclear magnetic resonance investigation.

    PubMed Central

    den Hartog, J H; Altona, C; Chottard, J C; Girault, J P; Lallemand, J Y; de Leeuw, F A; Marcelis, A T; Reedijk, J

    1982-01-01

    A 500, 400 and 300 MHz proton NMR study of the reaction product of cis-Pt(NH3)2Cl2 or cis-[Pt(NH3)2 (H2O)2] (NO3)2 with the deoxydinucleotide d(GpG): cis-[Pt(NH3)2 d(GpG)] was carried out. Complete assignment of the proton resonances by decoupling experiments and computer simulation of the high field part of the spectrum yield proton-proton and proton-phosphorus coupling constants of high precision. Analysis of these coupling constants reveal a 100% N (C3'-endo) conformation for the deoxyribose ring at the 5'-terminal part of the chelated d(GpG) moiety. In contrast, the 3'-terminal -pG part of the molecule displays the normal behaviour for deoxyriboses: the sugar ring prefers to adopt an S (C2'-endo) conformation (about 70%). Extrapolating from this model compound, it is suggested that Pt chelation by a -dGpdG- sequence of DNA would require a S to N conformational change of one deoxyribose moiety as the main conformational alteration and lead to a kink in one strand of the double-helical structure of DNA. PMID:6890203

  20. Ab initio Quantum Chemical Studies of Reactions in Astrophysical Ices. Reactions Involving CH3OH, CO2, CO, HNCO in H2CO/NH3/H2O Ices

    NASA Technical Reports Server (NTRS)

    Woon, David E.

    2006-01-01

    While reactions between closed shell molecules generally involve prohibitive barriers in the gas phase, prior experimental and theoretical studies have demonstrated that some of these reactions are significantly enhanced when confined within an icy grain mantle and can occur efficiently at temperatures below 100 K with no additional energy processing. The archetypal case is the reaction of formaldehyde (H2CO) and ammonia (NH3) to yield hydroxymethylamine (NH2CH2OH). In the present work we have characterized reactions involving methanol (CH3OH), carbon dioxide (CO2), carbon monoxide (CO), and isocyanic acid (HNCO) in search of other favorable cases. Most of the emphasis is on CH3OH, which was investigated in the two-body reaction with one H2CO and the three-body reaction with two H2CO molecules. The addition of a second H2CO to the product of the reaction between CH3OH and H2CO was also considered as an alternative route to longer polyoxymethylene polymers of the -CH2O- form. The reaction between HNCO and NH3 was studied to determine if it can compete against the barrierless charge transfer process that yields OCN(-) and NH4(+). Finally, the H2CO + NH3 reaction was revisited with additional benchmark calculations that confirm that little or no barrier is present when it occurs in ice.

  1. Adsorption, Desorption, and Displacement Kinetics of H2O and CO2 on Forsterite, Mg2SiO4(011)

    SciTech Connect

    Smith, R. Scott; Li, Zhenjun; Dohnalek, Zdenek; Kay, Bruce D.

    2014-12-18

    We have examined the adsorbate-substrate interaction kinetics of CO2 and H2O on a natural forsterite crystal surface, Mg2SiO4(011), with 10-15% of substitutional Fe2+. We use temperature programmed desorption (TPD) and molecular beam techniques to determine the adsorption, desorption, and displacement kinetics for H2O and CO2. Neither CO2 nor H2O has distinct sub-monolayer desorption peaks but instead both have a broad continuous desorption feature that evolve smoothly into multilayer desorption. Inversion of the monolayer coverage spectra for both molecules reveals that the corresponding binding energies for H2O are greater than that for CO2 on all sites. The relative strength of these interactions is the dominant factor in the competitive adsorption/displacement kinetics. In experiments where the two adsorbates are co-dosed, H2O always binds to the highest energy binding sites available and displaces CO2. The onset of CO2 displacement by H2O occurs between 65 and 75 K.

  2. Adsorption-Desorption Kinetics of Soft Particles

    NASA Astrophysics Data System (ADS)

    Osberg, Brendan; Nuebler, Johannes; Gerland, Ulrich

    2015-08-01

    Adsorption-desorption processes are ubiquitous in physics, chemistry, and biology. Models usually assume hard particles, but within the realm of soft matter physics the adsorbing particles are compressible. A minimal 1D model reveals that softness fundamentally changes the kinetics: Below the desorption time scale, a logarithmic increase of the particle density replaces the usual Rényi jamming plateau, and the subsequent relaxation to equilibrium can be nonmonotonic and much faster than for hard particles. These effects will impact the kinetics of self-assembly and reaction-diffusion processes.

  3. Phosphorus adsorption and desorption properties of lunar simulants 

    E-print Network

    Sutter, Brad

    1995-01-01

    efficient phosphorus (P) fertilizer rate that would provide optimal crop growth in Minnesota Basalt Lunar Simulant (MBLS) and Lunar Glass Simulant (LGS). To achieve this objective, simulant P adsorption, desorption and kinetic desorption Q/I relationships...

  4. APPLICATION OF THERMAL DESORPTION TECHNOLOGIES TO HAZARDOUS WASTE SITES

    EPA Science Inventory

    Thermal desorption is a separation process frequently used to remediate many Superfund sites. Thermal desorption technologies are recommended and used because of (1) the wide range of organic contaminants effectively treated, (2) availability and mobility of commercial systems, ...

  5. Dosimeter-Type NO[subscript x] Sensing Properties of KMnO[subscript 4] and Its Electrical Conductivity during Temperature Programmed Desorption

    E-print Network

    Groß, Andrea

    An impedimetric NO[subscript x] dosimeter based on the NO[subscript x] sorption material KMnO[subscript 4] is proposed. In addition to its application as a low level NO[subscript x] dosimeter, KMnO[subscript 4] shows ...

  6. Thermal Desorption of Sodium Atoms from Thin SiO2 Films

    NASA Astrophysics Data System (ADS)

    Yakshinskiy, B. V.; Madey, T. E.; Ageev, V. N.

    The adsorption and thermal desorption of Na from thin SiO2 films have been studied. X-ray photoelectron spectroscopy (XPS), angle-resolved XPS (ARXPS), low energy ion scattering (LEIS), temperature-programmed desorption (TPD), low energy electron diffraction (LEED) and work function measurements have been used to characterize the growth mechanism and properties of stoichiometric SiO2 films deposited onto a Re (0001) substrate. Upon deposition of Na onto SiO2 at 250 K, the first monolayer of Na exhibits ionic character, and evidence of metallic Na (plasmon features in XPS) is observed for higher coverages. TPD spectra for Na from SiO2 include a monolayer peak at ~700 K, and the multilayer peak due to sublimation of bulk Na at ~330 K. Penetration of Na into SiO2 can be induced by heating, or by He ion bombardment of a Na/SiO2 layer. The sticking probability for Na on SiO2 is ~0.5 at 250 K, and it decreases at higher substrate temperatures.

  7. Adsorption and desorption kinetics of alkanethiols on gold(100) and silver(111)

    NASA Astrophysics Data System (ADS)

    Yu, Yan

    The work reported here is concerned with the adsorption and desorption kinetics of short chain-length alkanethiols and hydrogen sulfide on the Au(100) and Ag(111) substrates. A combination of temperature programmed desorption/reaction (TPD/R), low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and molecular beam (MB) methods were used in a UHV system. This study has given insight in to the kinetic mechanism of thiol self-assembled monolayers (SAMs) formation. Similar adsorption and desorption kinetics were observed for methanethiol, ethanethiol, propanethiol, butanethiol, and pentanethiol on Au(100). The TPD/R results clearly show that these short chain-length alkanethiols adsorbs into both a chemisorbed and a physisorbed state. A detail study was performed for butanethiol on the Au(100) substrate. Desorption of physisorbed butanethiol occurs molecularly at ˜38 K. By contrast, desorption of the chemisorbed butanethiolate species occurs with decomposition at ˜500 K to yield primarily 1-butene; the thiol sulfur remained adsorbed on the surface and either desorbed or possibly dissolved into the bulk of the gold sample at above 700 K. The substrate temperature dependence of the chemisorption process suggests a precursor mechanism for the chemisorption kinetics. The TPD results also show that chemisorption does not occur on a very clean and ordered Au(100)-(5x20) surface at 100 K, and that low coverages of pre-adsorbed sulfur atoms facilitate the chemisorption process, suggesting a defect-mediated precursor mechanism. Precursor-mediated adsorption kinetics were observed for the adsorption of H2S on the Au(100)-(5x20) and Ag(111) between 80 and 100 K, while Langmuir adsorption kinetics were observed for the adsorption of H 2S on the sulfide covered Au(100)-(1x1)-SH and Ag(111). The TPD/R of H2S from Au(100)-(1x1)-SH showed additional features at higher temperatures which were associated with the disproportionation of chemisorbed HS(ad). Those features were not observed for H2S from sulfide Ag(111).

  8. A microsystems enabled field desorption source.

    SciTech Connect

    Hertz, Kristin L.; Resnick, Paul James; Schwoebel, Paul R.; Holland, Christopher E.; Chichester, David L.

    2010-07-01

    Technologies that have been developed for microelectromechanical systems (MEMS) have been applied to the fabrication of field desorption arrays. These techniques include the use of thick films for enhanced dielectric stand-off, as well as an integrated gate electrode. The increased complexity of MEMS fabrication provides enhanced design flexibility over traditional methods.

  9. Mercury compounds characterization by thermal desorption.

    PubMed

    Rumayor, M; Diaz-Somoano, M; Lopez-Anton, M A; Martinez-Tarazona, M R

    2013-09-30

    The ability to accurately determine metal mercury content and identify different mercury species in solid samples is essential for developing remediation and control strategies. The aim of the present study is to characterize mercury compounds based on thermal desorption. For this purpose a series of samples was prepared and the operational parameters-heating velocity, carrier gas-were optimized. Fifteen commercial mercury compounds were analyzed for use as fingerprints. The results of the study show that the identification of mercury species by the method of thermal desorption is possible. The temperature of desorption increased according to the following order HgI2desorption curve shows that recoveries of 79-104% for HgS can be estimated. The proposed method represents a significant step forward in direct mercury analysis in solid samples. PMID:23953477

  10. Indaziflam sorption-desorption in diverse soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Indaziflam is a new preemergence-herbicide active ingredient, classified as a member of the new chemical class “alkylazine”. There is no published information on its fate and behavior in soil. This study is aimed at characterizing the adsorption and desorption of indaziflam in soils with different p...

  11. Quantum theory of laser-stimulated desorption

    NASA Technical Reports Server (NTRS)

    Slutsky, M. S.; George, T. F.

    1978-01-01

    A quantum theory of laser-stimulated desorption (LSDE) is presented and critically analyzed. It is shown how LSDE depends on laser-pulse characteristics and surface-lattice dynamics. Predictions of the theory for a Debye model of the lattice dynamics are compared to recent experimental results.

  12. Method of enhancing selective isotope desorption from metals

    DOEpatents

    Knize, R.J.; Cecchi, J.L.

    1983-07-26

    This invention relates generally to the field of gas desorption from metals; and, more particularly, to a method of enhancing the selective desorption of a particular isotope of a gas from metals. Enhanced selective desorption is especially useful in the operation of fusion devices.

  13. Desorption of intrinsic cesium from smectite: inhibitive effects of clay particle organization on cesium desorption.

    PubMed

    Fukushi, Keisuke; Sakai, Haruka; Itono, Taeko; Tamura, Akihiro; Arai, Shoji

    2014-09-16

    Fine clay particles have functioned as transport media for radiocesium in terrestrial environments after nuclear accidents. Because radiocesium is expected to be retained in clay minerals by a cation-exchange reaction, ascertaining trace cesium desorption behavior in response to changing solution conditions is crucially important. This study systematically investigated the desorption behavior of intrinsic Cs (13 nmol/g) in well-characterized Na-montmorillonite in electrolyte solutions (NaCl, KCl, CaCl2, and MgCl2) under widely differing cation concentrations (0.2 mM to 0.2 M). Batch desorption experiments demonstrated that Cs(+) desorption was inhibited significantly in the presence of the environmental relevant concentrations of Ca(2+) and Mg(2+) (>0.5 mM) and high concentrations of K(+). The order of ability for Cs desorption was Na(+) = K(+) > Ca(2+) = Mg(2+) at the highest cation concentration (0.2 M), which is opposite to the theoretical prediction based on the cation-exchange selectivity. Laser diffraction grain-size analyses revealed that the inhibition of Cs(+) desorption coincided with the increase of the clay tactoid size. Results suggest that radiocesium in the dispersed fine clay particles adheres on the solid phase when the organization of swelling clay particles occurs because of changes in solution conditions caused by both natural processes and artificial treatments. PMID:25144123

  14. Reversibility, Dopant Desorption, and Tunneling in the Temperature-Dependent Conductivity of Type-Separated, Conductive Carbon Nanotube Networks

    SciTech Connect

    Barnes, T. M.; Blackburn, J. L.; van de Lagemaat, J.; Coutts, T. J.; Heben, M. J.

    2008-09-01

    We present a comprehensive study of the effects of doping and temperature on the conductivity of single-walled carbon nanotube (SWNT) networks. We investigated nearly type-pure networks as well as networks comprising precisely tuned mixtures of metallic and semiconducting tubes. Networks were studied in their as-produced state and after treatments with nitric acid, thionyl chloride, and hydrazine to explore the effects of both intentional and adventitious doping. For intentionally and adventitiously doped networks, the sheet resistance (R{sub s}) exhibits an irreversible increase with temperature above {approx}350 K. Dopant desorption is shown to be the main cause of this increase and the observed hysteresis in the temperature-dependent resistivity. Both thermal and chemical dedoping produced networks free of hysteresis. Temperature-programmed desorption data showed that dopants are most strongly bound to the metallic tubes and that networks consisting of metallic tubes exhibit the best thermal stability. At temperatures below the dopant desorption threshold, conductivity in the networks is primarily controlled by thermally assisted tunneling through barriers at the intertube or interbundle junctions.

  15. Adsorption, Desorption, and Displacement Kinetics of H2O and CO2 on TiO2(110)

    SciTech Connect

    Smith, R. Scott; Li, Zhenjun; Chen, Long; Dohnalek, Zdenek; Kay, Bruce D.

    2014-07-17

    The adsorption, desorption, and displacement kinetics of H2O and CO2 on TiO2(110) are investigated using temperature programmed desorption (TPD) and molecular beam techniques. The TPD spectra for both H2O and CO2 have well-resolved peaks corresponding to desorption from bridge-bonded oxygen (BBO), Ti, and oxygen vacancies (VO) sites in order of increasing peak temperature. Analysis of the saturated monolayer peak for both species reveals that the corresponding adsorption energies on all sites are greater for H2O and for CO2. Sequential dosing of H2O and CO2 reveals that, independent of the dose order, H2O molecules will displace CO2 in order to occupy the highest energy binding sites available. Isothermal experiments show that the displacement of CO2 by H2O occurs between 75 and 80 K. Further analysis shows that a ratio of 4 H2O to 3 CO2 molecules is needed to displace CO2 from the TiO2(110) surface.

  16. Determination of the Arrhenius Activation Energy Using a Temperature-Programmed Flow Reactor.

    ERIC Educational Resources Information Center

    Chan, Kit-ha C.; Tse, R. S.

    1984-01-01

    Describes a novel method for the determination of the Arrhenius activation energy, without prejudging the validity of the Arrhenius equation or the concept of activation energy. The method involves use of a temperature-programed flow reactor connected to a concentration detector. (JN)

  17. Thermodynamics of the formation of sulfuric acid dimers in the binary (H2SO4-H2O) and ternary (H2SO4-H2O-NH3) system

    NASA Astrophysics Data System (ADS)

    Kürten, A.; Münch, S.; Rondo, L.; Bianchi, F.; Duplissy, J.; Jokinen, T.; Junninen, H.; Sarnela, N.; Schobesberger, S.; Simon, M.; Sipilä, M.; Almeida, J.; Amorim, A.; Dommen, J.; Donahue, N. M.; Dunne, E. M.; Flagan, R. C.; Franchin, A.; Kirkby, J.; Kupc, A.; Makhmutov, V.; Petäjä, T.; Praplan, A. P.; Riccobono, F.; Steiner, G.; Tomé, A.; Tsagkogeorgas, G.; Wagner, P. E.; Wimmer, D.; Baltensperger, U.; Kulmala, M.; Worsnop, D. R.; Curtius, J.

    2015-09-01

    Sulfuric acid is an important gas influencing atmospheric new particle formation (NPF). Both the binary (H2SO4-H2O) system and the ternary system involving ammonia (H2SO4-H2O-NH3) may be important in the free troposphere. An essential step in the nucleation of aerosol particles from gas-phase precursors is the formation of a dimer, so an understanding of the thermodynamics of dimer formation over a wide range of atmospheric conditions is essential to describe NPF. We have used the CLOUD chamber to conduct nucleation experiments for these systems at temperatures from 208 to 248 K. Neutral monomer and dimer concentrations of sulfuric acid were measured using a chemical ionization mass spectrometer (CIMS). From these measurements, dimer evaporation rates in the binary system were derived for temperatures of 208 and 223 K. We compare these results to literature data from a previous study that was conducted at higher temperatures but is in good agreement with the present study. For the ternary system the formation of H2SO4·NH3 is very likely an essential step in the formation of sulfuric acid dimers, which were measured at 210, 223, and 248 K. We estimate the thermodynamic properties (dH and dS) of the H2SO4·NH3 cluster using a simple heuristic model and the measured data. Furthermore, we report the first measurements of large neutral sulfuric acid clusters containing as many as 10 sulfuric acid molecules for the binary system using chemical ionization-atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometry.

  18. Kinetic study of the oxidation of [Fe(CN) 6] 4- by [Co(NH 3) 4pzCO 2] 2+ and SO82- in the presence of the tripodal ligand Tren Aminopropil

    NASA Astrophysics Data System (ADS)

    García-España, E.; Sornosa-Ten, A.; Albelda, M. T.; Sánchez, F.; Marchena, M.

    2011-03-01

    Oxidations (electron transfers) of [Fe(CN) 6] 4- by [Co(NH 3) 4pzCO 2] 2+ and SO82- have been studied in solutions containing the receptor N,N',N?-(aminopropil)-tris (2-aminoetil) amina [Tren Aminopropil, TAL], which can incorporate [Fe(CN) 6] 4- and SO82- but not the cobalt complex. The results can be explained using the Brönsted equation that allows to obtain the binding constant of the transition state, a parameter that the Pseudophase Model cannot provide.

  19. NH3 Binding to the S2 State of the O2-Evolving Complex of Photosystem II: Analogue to H2O Binding during the S2 ? S3 Transition.

    PubMed

    Askerka, Mikhail; Vinyard, David J; Brudvig, Gary W; Batista, Victor S

    2015-09-29

    Ammonia binds directly to the oxygen-evolving complex of photosystem II (PSII) upon formation of the S2 intermediate, as evidenced by electron paramagnetic resonance spectroscopy. We explore the binding mode by using quantum mechanics/molecular mechanics methods and simulations of extended X-ray absorption fine structure spectra. We find that NH3 binds as an additional terminal ligand to the dangling Mn4, instead of exchanging with terminal water. Because water and ammonia are electronic and structural analogues, these findings suggest that water binds analogously during the S2 ? S3 transition, leading to rearrangement of ligands in a carrousel around Mn4. PMID:26378340

  20. Thermal desorption study of physical forces at the PTFE surface

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.; Pepper, S. V.

    1985-01-01

    Thermal desorption spectroscopy (TDS) of the polytetrafluoroethylene (PTFE) surface was successfully employed to study the possibile role of physical forces in the enhancement of metal-PTFE adhesion by radiation. The thermal desorption spectra were analyzed without assumptions to yield the activation energy for desorption over a range of xenon coverage from less than 0.1 monolayer to more than 100 monolayers. For multilayer coverage, the desorption is zero-order with an activation energy equal to the sublimation energy of xenon. For submonolayer coverages, the order for desorption from the unirradiated PTFE surface is 0.73 and the activation energy for desorption is between 3.32 and 3.36 kcal/mol; less than the xenon sublimation energy. The effect of irradiation is to increase the activation energy for desorption to as high as 4 kcal/mol at low coverage.

  1. Sample Desorption/Onization From Mesoporous Silica

    DOEpatents

    Iyer, Srinivas (Los Alamos, NM); Dattelbaum, Andrew M. (Los Alamos, NM)

    2005-10-25

    Mesoporous silica is shown to be a sample holder for laser desorption/ionization of mass spectrometry. Supported mesoporous silica was prepared by coating an ethanolic silicate solution having a removable surfactant onto a substrate to produce a self-assembled, ordered, nanocomposite silica thin film. The surfactant was chosen to provide a desired pore size between about 1 nanometer diameter and 50 nanometers diameter. Removal of the surfactant resulted in a mesoporous silica thin film on the substrate. Samples having a molecular weight below 1000, such as C.sub.60 and tryptophan, were adsorbed onto and into the mesoporous silica thin film sample holder and analyzed using laser desorption/ionization mass spectrometry.

  2. Plutonium sorption and desorption behavior on bentonite.

    PubMed

    Begg, James D; Zavarin, Mavrik; Tumey, Scott J; Kersting, Annie B

    2015-03-01

    Understanding plutonium (Pu) sorption to, and desorption from, mineral phases is key to understanding its subsurface transport. In this work we study Pu(IV) sorption to industrial grade FEBEX bentonite over the concentration range 10(-7)-10(-16) M to determine if sorption at typical environmental concentrations (?10(-12) M) is the same as sorption at Pu concentrations used in most laboratory experiments (10(-7)-10(-11) M). Pu(IV) sorption was broadly linear over the 10(-7)-10(-16) M concentration range during the 120 d experimental period; however, it took up to 100 d to reach sorption equilibrium. At concentrations ?10(-8) M, sorption was likely affected by additional Pu(IV) precipitation/polymerization reactions. The extent of sorption was similar to that previously reported for Pu(IV) sorption to SWy-1 Na-montmorillonite over a narrower range of Pu concentrations (10(-11)-10(-7) M). Sorption experiments with FEBEX bentonite and Pu(V) were also performed across a concentration range of 10(-11)-10(-7) M and over a 10 month period which allowed us to estimate the slow apparent rates of Pu(V) reduction on a smectite-rich clay. Finally, a flow cell experiment with Pu(IV) loaded on FEBEX bentonite demonstrated continued desorption of Pu over a 12 day flow period. Comparison with a desorption experiment performed with SWy-1 montmorillonite showed a strong similarity and suggested the importance of montorillonite phases in controlling Pu sorption/desorption reactions on FEBEX bentonite. PMID:25574607

  3. History of desorption induced by electronic transitions

    NASA Astrophysics Data System (ADS)

    Madey, Theodore E.

    1994-01-01

    Desorption induced by electronic transitions (DIET) encompasses electron- and photon-stimulated desorption (ESD and PSD) of atoms, molecules and ions from surfaces. In this paper, we focus on the key experimental and theoretical developments that have led to a fundamental understanding of DIET processes. We emphasize the effects of ionizing radiation, i.e., electrons and photons with energies ? 10 eV. The first DIET studies were occasioned mainly by the observation of anomalous peaks in mass spectrometers and spurious signals in ionization gauges. These observations were followed in the early 1960's by systematic studies of Redhead, and Menzel and Gomer, who independently proposed a Franck-Condon excitation model for electron-stimulated desorption of ions and neutrals from surfaces. In the years after this seminal work, ESD and PSD developed as fields of active interest to surface scientists. In addition to providing insights into the fundamental mechanisms linking atomic motion and electronic energy dissipation at surfaces, DIET investigations are continuing to impact upon radiation damage processes in areas as diverse as X-ray optics, semiconductor electronics, surface analysis and synthesis of molecules in interplanetary space.

  4. Ambient pressure laser desorption and laser-induced acoustic desorption ion mobility spectrometry detection of explosives.

    PubMed

    Ehlert, Sven; Walte, Andreas; Zimmermann, Ralf

    2013-11-19

    The development of fast, mobile, and sensitive detection systems for security-relevant substances is of enormous importance. Because of the low vapor pressures of explosives and improvised explosive devices, adequate sampling procedures are crucial. Ion mobility spectrometers (IMSs) are fast and sensitive instruments that are used as detection systems for explosives. Ambient pressure laser desorption (APLD) and ambient pressure laser-induced acoustic desorption (AP-LIAD) are new tools suitable to evaporate explosives in order to detect them in the vapor phase. Indeed, the most important advantage of APLD or AP-LIAD is the capability to sample directly from the surface of interest without any transfer of the analyte to other surfaces such as wipe pads. A much more gentle desorption, compared to classical thermal-based desorption, is possible with laser-based desorption using very short laser pulses. With this approach the analyte molecules are evaporated in a very fast process, comparable to a shock wave. The thermal intake is reduced considerably. The functionality of APLD and AP-LIAD techniques combined with a hand-held IMS system is shown for a wide range of common explosives such as EGDN (ethylene glycol dinitrate), urea nitrate, PETN (pentaerythritol tetranitrate), HMTD (hexamethylene triperoxide diamine), RDX (hexogen), tetryl (2,4,6-trinitrophenylmethylnitramine), and TNT (trinitrotoluene). Detection limits down to the low nanogram range are obtained. The successful combination of IMS detection and APLD/AP-LIAD sampling is shown. PMID:24116702

  5. Parametrization of the Stillinger-Weber potential for Si/N/H system and its application to simulations of silicon nitride film deposition with SiH4/NH3

    NASA Astrophysics Data System (ADS)

    Deng, Xiaodi; Song, Yixu; Li, JinChun; Pu, Yikang

    2014-02-01

    We determined the Stillinger-Weber interatomic potential parameters for Si/N/H system based on first principles density functional calculations. This new potential can be used to perform classical molecular dynamics simulation for silicon nitride deposition on Si substrate. During the first principles calculations, cluster models have been carefully and systematically chosen to make sampling of the interatomic potential supersurface more thoroughly. Global optimization method was used to fit the ab initio data into Stillinger-Weber form. We used a recursive method to perform the classical molecular dynamics simulations for silicon nitride (SiN) film growth on Si substrate with SiH4/NH3 gas mixtures. During the simulation, we could clearly observe the silicon nitride film growth progress. In this paper, we present the details of potential derivation and simulation results with different SiH4:NH3 ratios. It is demonstrated that this new potential is suitable to describe the surface reactions of the Si/N/H system and allows us to explore more complex SiN growing process such as plasma-enhanced chemical vapor deposition.

  6. Bibliographic review and new measurements of the infrared band strengths of pure molecules at 25 K: H2O, CO2, CO, CH4, NH3, CH3OH, HCOOH and H2CO

    NASA Astrophysics Data System (ADS)

    Bouilloud, M.; Fray, N.; Bénilan, Y.; Cottin, H.; Gazeau, M.-C.; Jolly, A.

    2015-08-01

    Infrared observations of the interstellar medium revealed the presence of several molecules in the solid phase such as H2O, CO2, CO, CH4, NH3, CH3OH, H2CO and HCOOH. Measurements of column densities and molecular abundances relative to water require the knowledge of infrared band strengths. We present a review of refractive indices at visible wavelengths, densities and infrared band strengths for all eight molecules. We also present new band strengths measured on icy films whose thicknesses have been determined using laser interference techniques. For CO2, CO, CH4 and NH3, our measurements are in agreement with previous determinations taking into account an uncertainty of about 20 per cent. For H2O ice films, the porosity and the density remain unreliable, leading to large uncertainties on the measured band strengths. Concerning amorphous CH3OH, H2CO and HCOOH, the densities and refractive indices are unknown leading to large uncertainties on the band strengths. However, we propose new values that are slightly different from previous determination. Our review and experimental work point out the most reliable band strengths for the eight studied molecules. For CH4, CH3OH, HCOOH and H2CO, the band strengths used to calculate abundances in the ices of interstellar medium seem to be inaccurate, leading to some doubts on the determined values.

  7. Revealing the role of Pb(2+) in the stability of organic-inorganic hybrid perovskite CH3NH3Pb1-xCdxI3: an experimental and theoretical study.

    PubMed

    Navas, Javier; Sánchez-Coronilla, Antonio; Gallardo, Juan Jesús; Martín, Elisa I; Hernández, Norge C; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; Martín-Calleja, Joaquín

    2015-10-01

    This paper presents the synthesis of organic-inorganic hybrid perovskite CH3NH3Pb1-xCdxI3. The effect of incorporating Cd(2+) or Pb(2+) on the stability of the perovskite structure was analysed from a theoretical and experimental viewpoint. The XRD results showed that the tetragonal perovskite structure was formed for x values of up to 0.5, which seems to indicate that the presence of a considerable amount of Pb(2+) is necessary to stabilise the structure. In turn, UV-Vis spectroscopy showed how the presence of Cd(2+) led to a reduction in the optical band gap of the perovskite structure of up to 9% for CH3NH3Pb0.5Cd0.5I3 with regard to the MAPbI3 structure. Moreover, periodic-DFT calculations were performed to understand the effect of the increased concentration of Cd on the structural and electronic properties of MAPbI3 perovskites. The analysis of both the ELF and the non-covalent interaction (NCI) index show the important role played by the Pb(2+) ions in stabilizing this kind of hybrid perovskite structures. Finally, the DOS analysis confirmed the experimental results obtained using UV-Vis spectroscopy. The theoretical band gap values decreased as the concentration of Cd increased. PMID:26308377

  8. G W quasiparticle band gap of the hybrid organic-inorganic perovskite CH3NH3PbI3 : Effect of spin-orbit interaction, semicore electrons, and self-consistency

    NASA Astrophysics Data System (ADS)

    Filip, Marina R.; Giustino, Feliciano

    2014-12-01

    We study the quasiparticle band gap of the hybrid organic-inorganic lead halide perovskite CH3NH3PbI3 , using many-body perturbation theory based on the G W approximation. We perform a systematic analysis of the band gap sensitivity to relativistic spin-orbit effects, to the description of semicore Pb-5 d and I-4 d electrons, and to the starting Kohn-Sham eigenvalues. We find that the inclusion of semicore states increases the calculated band gap by 0.2 eV, and self-consistency on the quasiparticle eigenvalues using a scissor correction increases the band gap by 0.5 eV with respect to the G0W0 result. These findings allow us to resolve an inconsistency between previously reported G W calculations for CH3NH3PbI3 . Our most accurate band gap is 1.72 eV, and is in good agreement with the measured optical gap after considering a small excitonic shift as determined in experiments.

  9. Rapid and robust spatiotemporal dynamics of the first-order phase transition in crystals of the organic-inorganic perovskite (C12H25NH3)2PbI4

    NASA Astrophysics Data System (ADS)

    Yangui, Aymen; Sy, Mouhamadou; Li, Liang; Abid, Younes; Naumov, Pan?e; Boukheddaden, Kamel

    2015-11-01

    The dynamics of the thermally induced first-order structural phase transition in a high-quality single crystal of the organic-inorganic perovskite (C12H25NH3)2PbI4 was investigated by optical microscopy. The propagation of the straight phase front (habit plane) during the phase transition along the cooling and heating pathways of the thermal hysteresis was observed. The thermochromic character of the transition allowed monitoring of the thermal dependence of average optical density and aided the visualization of the interface propagation. The thermal hysteresis loop is 10?K wide, and the interface velocity is constant at V???1.6?mm s–1. The transition is accompanied with sizeable change in crystal size, with elongation of ~6% along the b axis and compression of ~ –2% along the a axis, in excellent agreement with previously reported X-ray diffraction data. The progression of the habit plane is at least 160 times faster than in spin-crossover materials, and opens new prospects for organic-inorganic perovskites as solid switching materials. Moreover, the crystals of (C12H25NH3)2PbI4 are unusually mechanically robust and present excellent resilience to thermal cycling. These hitherto unrecognized properties turn this and possibly similar hybrid perovskites into perspective candidates as active medium for microscopic actuation.

  10. Rapid and robust spatiotemporal dynamics of the first-order phase transition in crystals of the organic-inorganic perovskite (C12H25NH3)2PbI4.

    PubMed

    Yangui, Aymen; Sy, Mouhamadou; Li, Liang; Abid, Younes; Naumov, Pan?e; Boukheddaden, Kamel

    2015-01-01

    The dynamics of the thermally induced first-order structural phase transition in a high-quality single crystal of the organic-inorganic perovskite (C12H25NH3)2PbI4 was investigated by optical microscopy. The propagation of the straight phase front (habit plane) during the phase transition along the cooling and heating pathways of the thermal hysteresis was observed. The thermochromic character of the transition allowed monitoring of the thermal dependence of average optical density and aided the visualization of the interface propagation. The thermal hysteresis loop is 10?K wide, and the interface velocity is constant at V???1.6?mm s(-1). The transition is accompanied with sizeable change in crystal size, with elongation of ~6% along the b axis and compression of ~ -2% along the a axis, in excellent agreement with previously reported X-ray diffraction data. The progression of the habit plane is at least 160 times faster than in spin-crossover materials, and opens new prospects for organic-inorganic perovskites as solid switching materials. Moreover, the crystals of (C12H25NH3)2PbI4 are unusually mechanically robust and present excellent resilience to thermal cycling. These hitherto unrecognized properties turn this and possibly similar hybrid perovskites into perspective candidates as active medium for microscopic actuation. PMID:26568147

  11. New insights into organic-inorganic hybrid perovskite CH3NH3PbI3 nanoparticles. An experimental and theoretical study of doping in Pb2+ sites with Sn2+, Sr2+, Cd2+ and Ca2+

    NASA Astrophysics Data System (ADS)

    Navas, Javier; Sánchez-Coronilla, Antonio; Gallardo, Juan Jesús; Cruz Hernández, Norge; Piñero, Jose Carlos; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; de Los Santos, Desireé M.; Aguilar, Teresa; Martín-Calleja, Joaquín

    2015-03-01

    This paper presents the synthesis of the organic-inorganic hybrid perovskite, CH3NH3PbI3, doped in the Pb2+ position with Sn2+, Sr2+, Cd2+ and Ca2+. The incorporation of the dopants into the crystalline structure was analysed, observing how the characteristics of the dopant affected properties such as the crystalline phase, emission and optical properties. XRD showed how doping with Sn2+, Sr2+ and Cd2+ did not modify the normal tetragonal phase. When doping with Ca2+, the cubic phase was obtained. Moreover, DR-UV-Vis spectroscopy showed how the band gap decreased with the dopants, the values following the trend Sr2+ < Cd2+ < Ca2+ < CH3NH3PbI3 ~ Sn2+. The biggest decrease was generated by Sr2+, which reduced the CH3NH3PbI3 value by 4.5%. In turn, cathodoluminescence (CL) measurements confirmed the band gap obtained. Periodic-DFT calculations were performed to understand the experimental structures. The DOS analysis confirmed the experimental results obtained using UV-Vis spectroscopy, with the values calculated following the trend Sn2+ ~ Pb2+ > Cd2+ > Sr2+ for the tetragonal structure and Pb2+ > Ca2+ for the cubic phase. The electron localization function (ELF) analysis showed similar electron localizations for undoped and Sn2+-doped tetragonal structures, which were different from those doped with Sr2+ and Cd2+. Furthermore, when Cd2+ was incorporated, the Cd-I interaction was strengthened. For Ca2+ doping, the Ca-I interaction had a greater ionic nature than Cd-I. Finally, an analysis based on the non-covalent interaction (NCI) index is presented to determine the weak-type interactions of the CH3NH3 groups with the dopant and I atoms. To our knowledge, this kind of analysis with these hybrid systems has not been performed previously.This paper presents the synthesis of the organic-inorganic hybrid perovskite, CH3NH3PbI3, doped in the Pb2+ position with Sn2+, Sr2+, Cd2+ and Ca2+. The incorporation of the dopants into the crystalline structure was analysed, observing how the characteristics of the dopant affected properties such as the crystalline phase, emission and optical properties. XRD showed how doping with Sn2+, Sr2+ and Cd2+ did not modify the normal tetragonal phase. When doping with Ca2+, the cubic phase was obtained. Moreover, DR-UV-Vis spectroscopy showed how the band gap decreased with the dopants, the values following the trend Sr2+ < Cd2+ < Ca2+ < CH3NH3PbI3 ~ Sn2+. The biggest decrease was generated by Sr2+, which reduced the CH3NH3PbI3 value by 4.5%. In turn, cathodoluminescence (CL) measurements confirmed the band gap obtained. Periodic-DFT calculations were performed to understand the experimental structures. The DOS analysis confirmed the experimental results obtained using UV-Vis spectroscopy, with the values calculated following the trend Sn2+ ~ Pb2+ > Cd2+ > Sr2+ for the tetragonal structure and Pb2+ > Ca2+ for the cubic phase. The electron localization function (ELF) analysis showed similar electron localizations for undoped and Sn2+-doped tetragonal structures, which were different from those doped with Sr2+ and Cd2+. Furthermore, when Cd2+ was incorporated, the Cd-I interaction was strengthened. For Ca2+ doping, the Ca-I interaction had a greater ionic nature than Cd-I. Finally, an analysis based on the non-covalent interaction (NCI) index is presented to determine the weak-type interactions of the CH3NH3 groups with the dopant and I atoms. To our knowledge, this kind of analysis with these hybrid systems has not been performed previously. Electronic supplementary information (ESI) available: Elemental analysis obtained by ICP-AES, and XRF (Table S1). XRD patterns of the samples synthesized (Fig. S1). XRD patterns of commercials PbI2 and CdI2 used as reagents (Fig. S2). XRD patterns of MAPb0.5Sn0.5I3 (Fig. S3). UV-Vis spectra, in mode reflectance diffuse, of the samples synthesized (Fig. S4). UV-Vis spectra, in mode reflectance diffuse, of MAPbI3 and MAPb0.5Sn0.5I3 samples (Fig. S5). XPS spectra for MAPbI3 and MAPb1-xBxI3 (B: Sn, Sr, Cd, Ca) with x

  12. Spatiotemporal distribution of NOx storage and impact on NH3 and N2O selectivities during lean/rich cycling of a Ba-based lean NOx trap catalyst

    SciTech Connect

    Choi, Jae-Soon; Partridge Jr, William P; Pihl, Josh A; Kim, Miyoung; Koci, Petr; Daw, C Stuart

    2012-01-01

    We summarize results from an investigation of the spatiotemporal distribution of NO{sub x} storage and intermediate gas species in determining the performance of a fully formulated, Ba-based, lean NO{sub x} trap catalyst under lean/rich cycling conditions. By experimentally resolving spatiotemporal profiles of gas composition, we found that stored NO{sub x} was significantly redistributed along the monolith axis during the rich phase of the cycle by release and subsequent downstream re-adsorption. Sulfur poisoning of upstream NO{sub x} storage sites caused the active NO{sub x}-storage zone to be displaced downstream. This axial displacement in turn influenced rich-phase NO{sub x} release and re-adsorption. As sulfur poisoning increased, NH3 slip at the catalyst exit also increased due to its formation closer to the catalyst outlet and decreased exposure to downstream oxidation by surface oxygen. N{sub 2}O formation was found to be associated with nitrate reduction rather than oxidation of NH3 by stored oxygen. We propose that the observed evolution of N{sub 2}O selectivity with sulfation can be explained by changes in the spatiotemporal distribution of NO{sub x} storage resulting in either increased or decreased number of precious-metal sites surrounded by nitrates.

  13. Rapid and robust spatiotemporal dynamics of the first-order phase transition in crystals of the organic-inorganic perovskite (C12H25NH3)2PbI4

    PubMed Central

    Yangui, Aymen; Sy, Mouhamadou; Li, Liang; Abid, Younes; Naumov, Pan?e; Boukheddaden, Kamel

    2015-01-01

    The dynamics of the thermally induced first-order structural phase transition in a high-quality single crystal of the organic-inorganic perovskite (C12H25NH3)2PbI4 was investigated by optical microscopy. The propagation of the straight phase front (habit plane) during the phase transition along the cooling and heating pathways of the thermal hysteresis was observed. The thermochromic character of the transition allowed monitoring of the thermal dependence of average optical density and aided the visualization of the interface propagation. The thermal hysteresis loop is 10?K wide, and the interface velocity is constant at V???1.6?mm s–1. The transition is accompanied with sizeable change in crystal size, with elongation of ~6% along the b axis and compression of ~ –2% along the a axis, in excellent agreement with previously reported X-ray diffraction data. The progression of the habit plane is at least 160 times faster than in spin-crossover materials, and opens new prospects for organic-inorganic perovskites as solid switching materials. Moreover, the crystals of (C12H25NH3)2PbI4 are unusually mechanically robust and present excellent resilience to thermal cycling. These hitherto unrecognized properties turn this and possibly similar hybrid perovskites into perspective candidates as active medium for microscopic actuation. PMID:26568147

  14. Ultralow temperature kinetics of neutral-neutral reactions. The technique and results for the reactions CN+O2 down to 13 K and CN+NH3 down to 25 K

    NASA Astrophysics Data System (ADS)

    Sims, I. R.; Queffelec, J.-L.; Defrance, A.; Rebrion-Rowe, C.; Travers, D.; Bocherel, P.; Rowe, B. R.; Smith, I. W. M.

    1994-03-01

    An entirely new experimental method is described which enables the rate constants of neutral-neutral gas-phase reactions to be measured at ultralow temperatures. The measurements are made by applying the pulsed laser photolysis (PLP), laser-induced fluorescence (LIF) technique of studying the kinetics of free radical reactions in the ultracold environment provided by the gas flow in a Cinétique de Réaction en Ecoulement Supersonique Uniforme (CRESU) apparatus. The experimental method is described in some detail and its application and limitations are discussed. Results are reported for the reactions of CN radicals with O2 and NH3. For reaction (1) between CN and O2 data are reported for the temperature range T=13-295 K and the rate constants are well-matched by the expression k1(T)=(2.49±0.17)×10-11 (T/298)(-0.63±0.04) cm3 molecule-1 s-1. For reaction (2) between CN and NH3, rate constants in the temperature range T=25-295 K fit the expression k2(T)=(2.77±0.67)×10-11 (T/298)(-1.14±0.15) cm3 molecule-1 s-1. The kinetic data are discussed in terms of the latest quantum chemical and reaction rate theories for these systems.

  15. The effect of selective desorption mechanisms during interstellar ice formation

    E-print Network

    Kalvans, Juris

    2015-01-01

    Major components of ices on interstellar grains in molecular clouds - water and carbon oxides - occur at various optical depths. This implies that selective desorption mechanisms are at work. An astrochemical model of a contracting low-mass molecular cloud core is presented. Ice was treated as consisting of the surface and three subsurface layers (sublayers). Photodesorption, reactive desorption, and indirect reactive desorption were investigated. The latter manifests itself through desorption from H+H reaction on grains. Desorption of shallow subsurface species was included. Modeling results suggest the existence of a "photon-dominated ice" during the early phases of core contraction. Subsurface ice is chemically processed by interstellar photons, which produces complex organic molecules. Desorption from the subsurface layer results in high COM gas-phase abundances at Av = 2.4...10mag. This may contribute towards an explanation for COM observations in dark cores. It was found that photodesorption mostly gove...

  16. Adsorption and desorption of HCl on ice

    SciTech Connect

    Isakson, M.J.; Sitz, G.O.

    1999-04-01

    It is now generally accepted that chemical reactions occurring on the surface of ice particles in polar stratospheric clouds (PSC`s) play a crucial role in the catalytic cycle of chlorine responsible for the ozone destruction. Pulsed molecular beam and mass spectrometric techniques are used to study the adsorption of hydrogen chloride on thin ice films at temperatures from 100 to 170 K. The adsorption and desorption of HCl from an ice surface is relevant to the polar stratosphere where it is thought that chlorine atoms are liberated from reservoir species such as HCl by heterogeneous reactions occurring on the surface of polar stratospheric clouds. The authors have measured the sticking coefficient for HCl at an incident translational energy of 0.09 eV on thin film ice surfaces using a modified version of the reflectivity technique of King and Wells. By modeling the HCl partial pressure versus time waveforms for surface temperatures of 100--125 K, they obtain a sticking coefficient of 0.91 {+-} 0.06. The model incorporates first-order HCl desorption and a loss term also first order in HCl. Fitted kinetic parameters are E{sub des} = 28 kJ/mol, {nu}{sub des} = 2 {times} 10{sup 14} s{sup {minus}1} for desorption and E{sub loss} = 21 kJ/mol, {nu}{sub loss} = 4 {times} 10{sup 11} s{sup {minus}1} for the loss. The loss may be associated with the onset of water diffusion on the ice surface and subsequent ionization or hydration of the HCl. The measured waveforms are inconsistent with diffusion of HCl into the bulk. The apparent reflectivity decreases substantially in the temperature range of 126 to 140 K. This decrease cannot be attributed to an increase in sticking coefficient, a phase change in the ice, or the formation of the hexahydrate state of HCl.

  17. Field desorption of Na and Cs from graphene on iridium

    NASA Astrophysics Data System (ADS)

    Bernatskii, D. P.; Pavlov, V. G.

    2015-08-01

    Field electron and desorption microscopy has been used to study specific features of the field desorption of sodium and cesium ions adsorbed on the surface of iridium with graphene. It was found that adsorbed sodium atoms most strongly reduce the work function on graphene islands situated over densely packed faces of iridium. A strong electric field qualitatively similarly affects the sodium and cesium desorption processes from a field emitter to give two desorption phases and has no noticeable effect on the disintegration of the graphene layer.

  18. HYDROGEN AND ITS DESORPTION IN RHIC.

    SciTech Connect

    HSEUH,H.C.

    2002-11-11

    Hydrogen is the dominating gas specie in room temperature, ultrahigh vacuum systems of particle accelerators and storage rings, such as the Relativistic Heavy Ion Collider (RHIC) at Brookhaven. Rapid pressure increase of a few decades in hydrogen and other residual gases was observed during RHIC's recent high intensity gold and proton runs. The type and magnitude of the pressure increase were analyzed and compared with vacuum conditioning, beam intensity, number of bunches and bunch spacing. Most of these pressure increases were found to be consistent with those induced by beam loss and/or electron stimulated desorption from electron multipacting.

  19. Modelling of field desorption of monocrystal nanotip

    NASA Astrophysics Data System (ADS)

    Nikiforov, K. A.; Krasnova, A. A.

    2015-11-01

    Mathematical and computer model of field desorption process from metal nanocrystal tip is proposed. The radius of curvature on the top of the emitter is about 50 lattice parameters. The model includes initial calculation of intersection between the crystal lattice and emitter shape for bcc and fcc crystal structures. Arbitrary axisymmetric shapes (figures of rotation) can be used for the emitter model. The algorithm for allocation of atoms being desorbed at given time step is based on an analysis of geometric environment with specified local electric field. Polyhedron nanostructured shape of emitter is obtained as result of evaporation. Computer program realization (Matlab stand alone application) is presented.

  20. Elucidating the degradation of methylammonium lead iodide perovskite (CH3NH3PbI3) at high temperatures and humid conditions via molecular dynamics simulations with ab initio force fields

    NASA Astrophysics Data System (ADS)

    Akin-Ojo, Omololu

    2015-03-01

    In recent times, the efficiencies of lead halide perovskite solar cells have soared to more than 15% and there is a potential for further increase. However, these solar cells degrade quickly when exposed to heat and moisture. This degradation limits the large scale production of the device. In this work we use molecular dynamics simulations to study CH3NH3PbI3 when exposed to high temperatures (30 -80° C) and water. The force fields used in the simulations were determined from ab initio calculations on the system. The structural changes that occur in methylammonium lead halide perovskite under conditions of high temperature and humidity will be inferred from the simulations.

  1. Theoretical study of the cooperative effects between the triel bond and the pnicogen bond in BF3···NCXH2···Y (X = P, As, Sb; Y = H2O, NH3) complexes.

    PubMed

    Liu, Ming-Xiu; Zhuo, Hong-Ying; Li, Qing-Zhong; Li, Wen-Zuo; Cheng, Jian-Bo

    2016-01-01

    The interplay between the triel bond and the pnicogen bond in BF3···NCXH2···Y (X = P, As, Sb; Y = H2O, NH3) complexes was studied theoretically. Both bonds exhibited cooperative effects, with shorter binding distances, larger interaction energies, and greater electron densities found for the ternary complexes than for the corresponding binary ones. The cooperative effects between the triel bond and the pnicogen bond were probed by analyzing molecular electrostatic potentials, charge transfer, and orbital interactions. The results showed that the enhancement of the triel bond can mainly be attributed to the electrostatic interaction, while the strengthening of the pnicogen bond can be ascribed chiefly to the electrostatic and orbital interactions. In addition, the origins of both the triel bond and the pnicogen bond were deduced via energy decomposition. PMID:26669879

  2. Phonon Mode Transformation Across the Orthohombic-Tetragonal Phase Transition in a Lead Iodide Perovskite CH3NH3PbI3: A Terahertz Time-Domain Spectroscopy Approach.

    PubMed

    La-O-Vorakiat, Chan; Xia, Huanxin; Kadro, Jeannette; Salim, Teddy; Zhao, Daming; Ahmed, Towfiq; Lam, Yeng Ming; Zhu, Jian-Xin; Marcus, Rudolph A; Michel-Beyerle, Maria-Elisabeth; Chia, Elbert E M

    2016-01-01

    We study the temperature-dependent phonon modes of the organometallic lead iodide perovskite CH3NH3PbI3 thin film across the terahertz (0.5-3 THz) and temperature (20-300 K) ranges. These modes are related to the vibration of the Pb-I bonds. We found that two phonon modes in the tetragonal phase at room temperature split into four modes in the low-temperature orthorhombic phase. By use of the Lorentz model fitting, we analyze the critical behavior of this phase transition. The carrier mobility values calculated from the low-temperature phonon mode frequencies, via two theoretical approaches, are found to agree reasonably with the experimental value (?2000 cm(2) V(-1) s(-1)) from a previous time-resolved THz spectroscopy work. Thus, we have established a possible link between terahertz phonon modes and the transport properties of perovskite-based solar cells. PMID:26633131

  3. Near-band-edge optical responses of solution-processed organic-inorganic hybrid perovskite CH3NH3PbI3 on mesoporous TiO2 electrodes

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    We studied the near-band-edge optical responses of solution-processed CH3NH3PbI3 on mesoporous TiO2 electrodes, which is utilized in mesoscopic heterojunction solar cells. Photoluminescence (PL) and PL excitation spectra peaks appear at 1.60 and 1.64 eV, respectively. The transient absorption spectrum shows a negative peak at 1.61 eV owing to photobleaching at the band-gap energy, indicating a direct band-gap semiconductor. On the basis of the temperature-dependent PL and diffuse reflectance spectra, we clarified that the absorption tail at room temperature is explained in terms of an Urbach tail and consistently determined the band-gap energy to be ˜1.61 eV at room temperature.

  4. Resonance effects of Wannier-Frenkel excitons in luminescence properties of layered perovskite compounds (C6H5CH2NH3)2PbClxBr4-x

    NASA Astrophysics Data System (ADS)

    Nagao, Katsuhiko; Kawano, Naoki; Koshimizu, Masanori; Asai, Keisuke

    2014-02-01

    To analyze the luminescence properties under resonance between inorganic-organic layers, (C6H5CH2NH3)2PbClxBr4-x thin films was fabricated. The Wannier exciton level in inorganic layer has been tuned to triplet excited levels in benzylamine in layered perovskite-type compounds by changing the halogen composition in the inorganic layer. When the Wannier exciton level was higher than the triplet state of benzylamine, energy transfer from the former to the latter occurred. The phosphorescence peak at 3.59 eV was sharpened and enhanced in the films with x = 3.75 and 3.80, and this effect can be ascribed to the enhancement of an electronic transition due to the resonance between the organic and inorganic layers.

  5. H2, He, and CO2 line-broadening coefficients, pressure shifts and temperature-dependence exponents for the HITRAN database. Part 1: SO2, NH3, HF, HCl, OCS and C2H2

    NASA Astrophysics Data System (ADS)

    Wilzewski, Jonas S.; Gordon, Iouli E.; Kochanov, Roman V.; Hill, Christian; Rothman, Laurence S.

    2016-01-01

    To increase the potential for use of the HITRAN database in astronomy, experimental and theoretical line-broadening coefficients, line shifts and temperature-dependence exponents of molecules of planetary interest broadened by H2, He, and CO2 have been assembled from available peer-reviewed sources. The collected data were used to create semi-empirical models so that every HITRAN line of the studied molecules has corresponding parameters. Since H2 and He are major constituents in the atmospheres of gas giants, and CO2 predominates in atmospheres of some rocky planets with volcanic activity, these spectroscopic data are important for remote sensing studies of planetary atmospheres. In this paper we make the first step in assembling complete sets of these parameters, thereby creating datasets for SO2, NH3, HF, HCl, OCS and C2H2.

  6. Syntheses of [F5TeNH3][AsF6], [F5TeN(H)Xe][AsF6], and F5TeNF2 and characterization by multi-NMR and Raman spectroscopy and by electronic structure calculations: the X-ray crystal structures of alpha- and beta-F5TeNH2, [F5TeNH3][AsF6], and [F5TeN(H)Xe][AsF6].

    PubMed

    Fir, Barbara; Whalen, J Marc; Mercier, Hélène P A; Dixon, David A; Schrobilgen, Gary J

    2006-03-01

    The salt, [F5TeN(H)Xe][AsF6], has been synthesized in the natural abundance and 99.5% 15N-enriched forms. The F5TeN(H)Xe+ cation has been obtained as the product of the reactions of [F5TeNH3][AsF6] with XeF2 (HF and BrF5 solvents) and F5TeNH2 with [XeF][AsF6] (HF solvent) and characterized in solution by 129Xe, 19F, 125Te, 1H, and 15N NMR spectroscopy at -60 to -30 degrees C. The orange [F5TeN(H)Xe][AsF6] and colorless [F5TeNH3][AsF6] salts were crystallized as a mixture from HF solvent at -35 degrees C and were characterized by Raman spectroscopy at -165 degrees C and by X-ray crystallography. The crystal structure of the low-temperature phase, alpha-F5TeNH2, was obtained by crystallization from liquid SO2 between -50 and -70 degrees C and is fully ordered. The high-temperature phase, beta-F5TeNH2, was obtained by sublimation at room temperature and exhibits a 6-fold disorder. Decomposition of [F5TeN(H)Xe][AsF6] in the solid state was rapid above -30 degrees C. The decomposition of F5TeN(H)Xe+ in HF and BrF5 solution at -33 degrees C proceeded by fluorination at nitrogen to give F5TeNF2 and Xe gas. Electronic structure calculations at the Hartree-Fock and local density-functional theory levels were used to calculate the gas-phase geometries, charges, Mayer bond orders, and Mayer valencies of F5TeNH2, F5TeNH3+, F5TeN(H)Xe+, [F5TeN(H)Xe][AsF6], F5TeNF2, and F5TeN2- and to assign their experimental vibrational frequencies. The F5TeN(H)Xe+ and the ion pair, [F5TeN(H)Xe][AsF6], systems were also calculated at the MP2 and gradient-corrected (B3LYP) levels. PMID:16499359

  7. The Transition from Hydrogen Bonding to Ionization in (HCI)n(NH3)n and (HCI)n(H2O)n Clusters: Consequences for Anharmonic Vibrational Spectroscopy

    NASA Technical Reports Server (NTRS)

    Chaban, Galina M.; Gerber, R. Benny; Janda, Kenneth C.; Kwak, Dochan (Technical Monitor)

    2001-01-01

    Anharmonic vibrational frequencies and intensities are calculated for 1:1 and 2:2 (HCl)(sub n)(NH3)(sub n) and (HCl)(sub n)(H2O)(sub n) complexes, employing the correlation-corrected vibrational self-consistent field method with ab initio potential surfaces at the MP2/TZP computational level. In this method, the anharmonic coupling between all vibrational modes is included, which is found to be important for the systems studied. For the 4:4 (HCl)(sub n)(H2O)(sub n) complex, the vibrational spectra are calculated at the harmonic level, and anharmonic effects are estimated. Just as the (HCl)(sub n)(NH3)(sub n) structure switches from hydrogen-bonded to ionic for n=2, the (HCl)(sub n)(H2O)(sub n) switches to ionic structure for n=4. For (HCl)2(H2O)2, the lowest energy structure corresponds to the hydrogen-bonded form. However, configurations of the ionic form are separated from this minimum by a barrier of less than an O-H stretching quantum. This suggests the possibility of experiments on ionization dynamics using infrared excitation of the hydrogen-bonded form. The strong cooperative effects on the hydrogen bonding, and concomitant transition to ionic bonding, makes an accurate estimate of the large anharmonicity crucial for understanding the infrared spectra of these systems. The anharmonicity is typically of the order of several hundred wave numbers for the proton stretching motions involved in hydrogen or ionic bonding, and can also be quite large for the intramolecular modes. In addition, the large cooperative effects in the 2:2 and higher order (HCl(sub n)(H2O)(sub n) complexes may have interesting implications for solvation of hydrogen halides at ice surfaces.

  8. Dynamic and Steady-State Responses of Inorganic Nitrogen Pools and NH3 Exchange in Leaves of Lolium perenne and Bromus erectus to Changes in Root Nitrogen Supply1

    PubMed Central

    Mattsson, Marie; Schjoerring, Jan K.

    2002-01-01

    Short- and long-term responses of inorganic N pools and plant-atmosphere NH3 exchange to changes in external N supply were investigated in 11-week-old plants of two grass species, Lolium perenne and Bromus erectus, characteristic of N-rich and N-poor grassland ecosystems, respectively. A switch of root N source from NO3? to NH4+ caused within 3 h a 3- to 6-fold increase in leaf apoplastic NH4+ concentration and a simultaneous decrease in apoplastic pH of about 0.4 pH units in both species. The concentration of total extractable leaf tissue NH4+ also increased two to three times within 3 h after the switch. Removal of exogenous NH4+ caused the apoplastic NH4+ concentration to decline back to the original level within 24 h, whereas the leaf tissue NH4+concentration decreased more slowly and did not reach the original level in 48 h. After growing for 5 weeks with a steady-state supply of NO3? or NH4+, L. perenne were in all cases larger, contained more N, and utilized the absorbed N more efficiently for growth than B. erectus, whereas the two species behaved oppositely with respect to tissue concentrations of NO3?, NH4+, and total N. Ammonia compensation points were higher for B. erectus than for L. perenne and were in both species higher for NH4+- than for NO3?-grown plants. Steady-state levels of apoplastic NH4+, tissue NH4+, and NH3 emission were significantly correlated. It is concluded that leaf apoplastic NH4+ is a highly dynamic pool, closely reflecting changes in the external N supply. This rapid response may constitute a signaling system coordinating leaf N metabolism with the actual N uptake by the roots and the external N availability. PMID:11842177

  9. Analysing the effect of crystal size and structure in highly efficient CH3NH3PbI3 perovskite solar cells by spatially resolved photo- and electroluminescence imaging.

    PubMed

    Mastroianni, S; Heinz, F D; Im, J-H; Veurman, W; Padilla, M; Schubert, M C; Würfel, U; Grätzel, M; Park, N-G; Hinsch, A

    2015-11-19

    CH3NH3PbI3 perovskite solar cells with a mesoporous TiO2 layer and spiro-MeOTAD as a hole transport layer (HTL) with three different CH3NH3I concentrations (0.032 M, 0.044 M and 0.063 M) were investigated. Strong variations in crystal size and morphology resulting in diversified cell efficiencies (9.2%, 16.9% and 12.3%, respectively) were observed. The physical origin of this behaviour was analysed by detailed characterization combining current-voltage curves with photo- and electroluminescence (PL and EL) imaging as well as light beam induced current measurements (LBIC). It was found that the most efficient cell shows the highest luminescence and the least efficient cell is most strongly limited by non-radiative recombination. Crystal size, morphology and distribution in the capping layer and in the porous scaffold strongly affect the non-radiative recombination. Moreover, the very non-uniform crystal structure with multiple facets, as evidenced by SEM images of the 0.032 M device, suggests the creation of a large number of grain boundaries and crystal dislocations. These defects give rise to increased trap-assisted non-radiative recombination as is confirmed by high-resolution ?-PL images. The different imaging techniques used in this study prove to be well-suited to spatially investigate and thus correlate the crystal morphology of the perovskite layer with the electrical and radiative properties of the solar cells and thus with their performance. PMID:26548804

  10. The tropospheric gas composition of Jupiter's north equatorial belt (NH3, PH3, CH3D, GeH4, H2O) and the Jovian D/H isotropic ratio

    NASA Technical Reports Server (NTRS)

    Kunde, V.; Hanel, R.; Maguire, W.; Gautier, D.; Baluteau, J. P.; Marten, A.; Chedin, A.; Husson, N.; Scott, N.

    1982-01-01

    The gas composition of the troposphere of Jupiter in the clearest regions of the North Equatorial Belt (NEB) was derived from the Voyager 1 IRIS data. The infrared spectrum for this homogeneous cloud free region was modeled to infer altitude profiles for NH3, PH3, GeH4 and H2O. The Profiles for NH3 and PH3 were found to be depleted in the upper troposphere but otherwise in agreement with their solar values at the 1 bar level. The mole fraction for CH3D was determined to be 3.5(+1.0 or -1.3) x 10 to the minus 7th power. The GeH4 mole fraction of 7+ or -2 x 10 to the minus 10th power at the 2 to 3 bar level is a factor of 10 lower than the solar value. The H2O mole fraction is approximately 1 x 0.00001 at the 2.5 bar level and is increasing to approximately 3 x 0.00001 at 4 bars where it is a factor of 30 lower than solar. Using IRIS infrared values for the mole fractions of CH3D and CH4 a value of D/H = 3.6(+1.0 or -1.4)x 0.00001 is derived. Assuming this Jovian D/H ratio is representative of the protosolar nebula, and correcting for chemical galactic evolution, yields a value of 5.5 - 9.0 x 0.00001 for the primordial D/H ratio and an upper limit of 1.8 to 2.4 x 10 to the minus 31st power cu cm for the present day baryon density.

  11. Novel devices for solvent delivery and temperature programming designed for capillary liquid chromatography.

    PubMed

    Coutinho, Lincoln Figueira Marins; Nazario, Carlos Eduardo Domingues; Monteiro, Alessandra Maffei; Lanças, Fernando Mauro

    2014-08-01

    Analyses in chromatographic systems able to save mobile and stationary phases without reducing efficiency and resolution are of current interest. These advantages regarding savings have challenged us to develop a system dedicated to miniaturized liquid chromatography. This paper reports on the development of a high-pressure syringe-type pump, an oven able to perform isothermal and temperature programming and a software program to control these chromatographic devices. The experimental results show that the miniaturized system can generate reproducible and accurate temperature and flow rate. The system was applied to the separation of statins and tetracylines and showed excellent performance. PMID:24838528

  12. Laser desorption lamp ionization source for ion trap mass spectrometry

    E-print Network

    Zare, Richard N.

    Laser desorption lamp ionization source for ion trap mass spectrometry Qinghao Wu and Richard N. Zare* A two-step laser desorption lamp ionization source coupled to an ion trap mass spectrometer (LDLI-ITMS) has been constructed and characterized. The pulsed infrared (IR) output of an Nd:YAG laser (1064 nm

  13. THERMAL DESORPTION...NOW YOU'RE COOKIN'

    EPA Science Inventory

    Thermal desorption includes a number of ex situ processes that use either direct or indirect heat exchange to heat a waste material to volatilize organic materials. hermal desorption systems typically operate at soil treatment temperatures in the range of 400 to 600 degrees F to ...

  14. Modeling Organic Contaminant Desorption from Municipal Solid Waste Components

    NASA Astrophysics Data System (ADS)

    Knappe, D. R.; Wu, B.; Barlaz, M. A.

    2002-12-01

    Approximately 25% of the sites on the National Priority List (NPL) of Superfund are municipal landfills that accepted hazardous waste. Unlined landfills typically result in groundwater contamination, and priority pollutants such as alkylbenzenes are often present. To select cost-effective risk management alternatives, better information on factors controlling the fate of hydrophobic organic contaminants (HOCs) in landfills is required. The objectives of this study were (1) to investigate the effects of HOC aging time, anaerobic sorbent decomposition, and leachate composition on HOC desorption rates, and (2) to simulate HOC desorption rates from polymers and biopolymer composites with suitable diffusion models. Experiments were conducted with individual components of municipal solid waste (MSW) including polyvinyl chloride (PVC), high-density polyethylene (HDPE), newsprint, office paper, and model food and yard waste (rabbit food). Each of the biopolymer composites (office paper, newsprint, rabbit food) was tested in both fresh and anaerobically decomposed form. To determine the effects of aging on alkylbenzene desorption rates, batch desorption tests were performed after sorbents were exposed to toluene for 30 and 250 days in flame-sealed ampules. Desorption tests showed that alkylbenzene desorption rates varied greatly among MSW components (PVC slowest, fresh rabbit food and newsprint fastest). Furthermore, desorption rates decreased as aging time increased. A single-parameter polymer diffusion model successfully described PVC and HDPE desorption data, but it failed to simulate desorption rate data for biopolymer composites. For biopolymer composites, a three-parameter biphasic polymer diffusion model was employed, which successfully simulated both the initial rapid and the subsequent slow desorption of toluene. Toluene desorption rates from MSW mixtures were predicted for typical MSW compositions in the years 1960 and 1997. For the older MSW mixture, which had a low plastics content, the model predicted that 50% of the initially sorbed toluene desorbed over a period of 5.8 days. In contrast, the model predicted that 50% of the initially sorbed toluene desorbed over a period of 4 years for the newer MSW mixture. These results suggest that toluene desorption rates from old MSW mixtures exceed methanogenic toluene degradation rates (toluene half-lives of about 30 to 100 days have been reported for methanogenic systems) and thus imply that biodegradation kinetics control the rate at which sorbed toluene is mineralized in old landfills. For newer MSW mixtures with a larger plastics content, toluene desorption rates are substantially slower; therefore, toluene desorption kinetics likely control the rate at which sorbed toluene can be mineralized in new landfills.

  15. Mercury Sorption and Desorption on Gold: A Comparative Analysis of Surface Acoustic Wave and Quartz Crystal Microbalance-Based Sensors.

    PubMed

    Kabir, K M Mohibul; Sabri, Ylias M; Esmaielzadeh Kandjani, Ahmad; Matthews, Glenn I; Field, Matthew; Jones, Lathe A; Nafady, Ayman; Ippolito, Samuel J; Bhargava, Suresh K

    2015-08-01

    Microelectromechanical sensors based on surface acoustic wave (SAW) and quartz crystal microbalance (QCM) transducers possess substantial potential as online elemental mercury (Hg(0)) vapor detectors in industrial stack effluents. In this study, a comparison of SAW- and QCM-based sensors is performed for the detection of low concentrations of Hg(0) vapor (ranging from 24 to 365 ppbv). Experimental measurements and finite element method (FEM) simulations allow the comparison of these sensors with regard to their sensitivity, sorption and desorption characteristics, and response time following Hg(0) vapor exposure at various operating temperatures ranging from 35 to 75 °C. Both of the sensors were fabricated on quartz substrates (ST and AT cut quartz for SAW and QCM devices, respectively) and employed thin gold (Au) layers as the electrodes. The SAW-based sensor exhibited up to ?111 and ?39 times higher response magnitudes than did the QCM-based sensor at 35 and 55 °C, respectively, when exposed to Hg(0) vapor concentrations ranging from 24 to 365 ppbv. The Hg(0) sorption and desorption calibration curves of both sensors were found to fit well with the Langmuir extension isotherm at different operating temperatures. Furthermore, the Hg(0) sorption and desorption rate demonstrated by the SAW-based sensor was found to decrease as the operating temperature increased, while the opposite trend was observed for the QCM-based sensor. However, the SAW-based sensor reached the maximum Hg(0) sorption rate faster than the QCM-based sensor regardless of operating temperature, whereas both sensors showed similar response times (t90) at various temperatures. Additionally, the sorption rate data was utilized in this study in order to obtain a faster response time from the sensor upon exposure to Hg(0) vapor. Furthermore, comparative analysis of the developed sensors' selectivity showed that the SAW-based sensor had a higher overall selectivity (90%) than did the QCM counterpart (84%) while Hg(0) vapor was measured in the presence of ammonia (NH3), humidity, and a number of volatile organic compounds at the chosen operating temperature of 55 °C. PMID:26169072

  16. Chemical desorption and diffusive dust chemistry

    NASA Astrophysics Data System (ADS)

    Dulieu, Francois; Pirronello, Valerio; Minissale, Marco; Congiu, Emanuele; Baouche, Saoud; Chaabouni, Henda; Moudens, Audrey; Accolla, Mario; Cazaux, Stephanie; Manicò, Giulio

    In molecular clouds, gaseous species can accrete efficiently on the cold surfaces of dust grains. As for radical-radical reactions, the surface of the grains acts as a third body, and changes dramatically the efficiency of the reactions (i.e., H2 formation), or lowers considerably the barrier to formation (i.e., H2O synthesis) in comparison with gas phase reaction processes. These properties make dust grains efficient catalytic templates. However, the chemical role of dust grains depends on the diffusive properties of the reactive partners. Over the last years, we have developed experimental tools and methods to explore the chemistry occurring on cold (6-50K) surfaces. We have obtained some hints about the diffusivity of H on amorphous ice, and studied in detail the diffusion of O atoms. The latter species appears to have a hopping rate in the range 0.01-100 hops/sec. The diffusion rate of O atoms is dependent on the surface morphology and on the surface temperature. The diffusion law is compatible with a diffusion dominated by quantum tunnelling rather than classical thermal hopping. Using H, O, N atoms and, indirectly, OH and HCO radicals, we have begun to explore many chemical reactive networks. In this presentation, I will focus on the formation of H2O and CO2, and will propose many possible formation routes to obtain these chemical traps. The molecules formed on surfaces have a certain probability of desorbing upon their formation. This non-thermal desorption mechanism, or chemical desorption, has been proposed to explain why some molecules can be detected in the gas phase of those region where they were believed to be part of the icy mantles covering dust grains. We have shown that this process can be very efficient, but is very sensitive to the substrate and the surroundings of the reaction site, is dependent on the kind of molecule formed and its chemical pathway. In my presentation I will present how the surface coverage and the type of reaction can play a major role in the chemical desorption process. I will discuss of possible key parameters that rule this process.

  17. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Final report

    SciTech Connect

    Chunshan Song; Schobert, H.H.; Parfitt, D.P.

    1997-11-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that dispersed catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on exploring novel bimetallic dispersed catalysts for coal liquefaction and the effectiveness of temperature-programmed liquefaction using dispersed catalysts. The primary objective of this research was to explore novel bimetallic dispersed catalysts from organometallic molecular precursors, that could be used in low concentrations but exhibit relatively high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. We have synthesized and tested various catalyst precursors in liquefaction of subbituminous and bituminous coals and in model compound studies to examine how do the composition and structure of the catalytic precursors affect their effectiveness for coal liquefaction under different reaction conditions, and how do these factors affect their catalytic functions for hydrogenation of polyaromatic hydrocarbons, for cleavage of C-C bonds in polycyclic systems such as 4-(1-naphthylmethyl)bibenzyl, for hydrogenolysis of C-O bond such as that in dinaphthylether, for hydrodeoxygenation of phenolic compounds and other oxygen-containing compounds such as xanthene, and for hydrodesulfurization of polycyclic sulfur compounds such as dibenzothiophene. The novel bimetallic and monometallic precursors synthesized and tested in this project include various Mo- and Fe-based compounds.

  18. Ammonia formation from NO reaction with surface hydroxyls on rutile TiO2 (110) - 1×1

    SciTech Connect

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

    2015-01-15

    The reaction of NO with hydroxylated rutile TiO2(110)-1×1 surface (h-TiO2) was investigated as a function of NO coverage using temperature-programmed desorption. Our results show that NO reaction with h-TiO2 leads to formation of NH3 which is observed to desorb at ~ 400 K. Interestingly, the amount of NH3 produced depends nonlinearly on the coverage of NO. The yield increases up to a saturation value of ~1.3×1013 NH3/cm2 at a NO dose of 5×1013 NO/cm2, but subsequently decreases at higher NO doses. Preadsorbed H2O is found to have a negligible effect on the NH3 desorption yield. Additionally, no NH3 is formed in the absence of surface hydroxyls (HOb’s) upon coadsorption of NO and H2O on a stoichiometric TiO2(110) (s-TiO2(110)). Based on these observations, we conclude that nitrogen from NO has a strong preference to react with HOb’s on the bridge-bonded oxygen rows (but not with H2O) to form NH3. The absolute NH3 yield is limited by competing reactions of HOb species with titanium-bound oxygen adatoms to form H2O. Our results provide new mechanistic insight about the interactions of NO with hydroxyl groups on TiO2(110) .

  19. Integrated field emission array for ion desorption

    DOEpatents

    Resnick, Paul J; Hertz, Kristin L; Holland, Christopher; Chichester, David; Schwoebel, Paul

    2013-09-17

    An integrated field emission array for ion desorption includes an electrically conductive substrate; a dielectric layer lying over the electrically conductive substrate comprising a plurality of laterally separated cavities extending through the dielectric layer; a like plurality of conically-shaped emitter tips on posts, each emitter tip/post disposed concentrically within a laterally separated cavity and electrically contacting the substrate; and a gate electrode structure lying over the dielectric layer, including a like plurality of circular gate apertures, each gate aperture disposed concentrically above an emitter tip/post to provide a like plurality of annular gate electrodes and wherein the lower edge of each annular gate electrode proximate the like emitter tip/post is rounded. Also disclosed herein are methods for fabricating an integrated field emission array.

  20. Slow desorption of volatile organic compounds from soil: evidence of desorption step limitations.

    PubMed

    Raihala, T S; Wang, Y; Jackman, A P

    1999-03-19

    Transient adsorption and desorption of 1,2 dichloroethane and toluene on dry Yolo silt loam soil were studied by continuously measuring the composition of the effluent from a soil-packed chromatography column with a mass spectrometer. After obtaining complete breakthrough at approximately 30% relative saturation of one chemical in nitrogen, pure nitrogen feed was initiated and maintained for several hours. Of the material adsorbed at breakthrough, 9.7% of the 1,2 dichloroethane and 14.2% of the toluene were highly resistant to desorption and remained sorbed on the soil even after 5 h of nitrogen flow. When a second chemical with a higher adsorption affinity was introduced into the soil column (water following toluene or toluene following 1,2 dichloroethane), the majority of the first chemical was quickly desorbed and began leaving the soil column before breakthrough of the second chemical. Conversely, when a second chemical with a smaller adsorption affinity was introduced into the soil column, only a small amount of the first chemical was displaced and began leaving the soil column after breakthrough of the second chemical. The results of this study indicate that the desorption step itself may be the rate-limiting step for sorbate which remains after prolonged exposure to sorbate-free gas. PMID:10337401