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Sample records for measured nh3 concentrations

  1. 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...

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

    NASA Astrophysics Data System (ADS)

    Fischer, M. L.; Littlejohn, D.

    2005-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    DOE PAGES

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

    2014-11-27

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    PubMed

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

    2015-03-21

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

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

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

    PubMed

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

    2005-11-01

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

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

    EPA Science Inventory

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

  16. Measurements of NO2, SO2, NH3, HNO3 and O3 in West African urban environments

    NASA Astrophysics Data System (ADS)

    Adon, Marcellin; Yoboué, Véronique; Galy-Lacaux, Corinne; Liousse, Catherine; Diop, Babakar; Doumbia, El Hadji Thierno; Gardrat, Eric; Ndiaye, Seydi Ababacar; Jarnot, Christian

    2016-06-01

    In this paper, we present the measurements of atmospheric gas concentrations of NO2, SO2, NH3, HNO3, and O3 performed at two traffic sites in the context of the POLCA (Pollution of African Capitals) program. These gases were measured using a passive sampling technique from Jan. 2008 to Dec. 2009 at Dakar and from Jun. 2008 to Dec. 2009 at Bamako. In addition, during these periods there were two intensive measurement campaigns (from 19 Jan. to 2 Feb. 2009 at Bamako and from 30 Nov. to 13 Dec. 2009 at Dakar) where real-time active analysers were used to measure NO2 and SO2. Results show that Dakar has a pollution level for NO2 and SO2 higher than that of Bamako, whereas it is lower for NH3 concentrations. Monthly values of NO2 range between 21.1 and 43.5 ppb in Dakar with an annual mean concentration of 31.7 ppb (59.6 μg/m3). NO2 values in Bamako are 9.4-22.6 ppb with a mean of 16.2 ppb. At Dakar, the mean annual NO2 limit value (21.3 ppb or 40 μg/m3) recommended by the World Health Organization (WHO) is widely exceeded. The mean annual concentration of SO2 is 15.9 ppb in Dakar and 3.6 ppb in Bamako. These differences may be explained by different sources of traffic between Bamako (with mainly gasoline vehicles) and Dakar (with mainly diesel vehicles). The annual mean NH3 concentration is about two times higher in Bamako (46.7 ppb) than in Dakar (21.1 ppb). In addition to other possible sources, we assume that the ammonia from domestic fires and uncontrolled garbage incineration may have more influence at Bamako than at Dakar. The mean annual concentrations of HNO3 and O3 are 1.3 ppb and 7.7 ppb in Dakar and 0.6 ppb and 5.1 ppb in Bamako, respectively. Seasonal variation in measured gas concentrations are low in Bamako and more pronounced in Dakar, except for HNO3 and NH3. At Dakar, NO2 and SO2 daily mean concentrations are higher during the weekdays than on weekends, when urban activities are reduced, whereas at Bamako, no significant difference was observed

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

    EPA Science Inventory

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

  18. 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 ...

  19. Evaluating ammonia (NH3) predictions in the NOAA National Air Quality Forecast Capability (NAQFC) using in situ aircraft, ground-level, and satellite measurements from the DISCOVER-AQ Colorado campaign

    NASA Astrophysics Data System (ADS)

    Battye, William H.; Bray, Casey D.; Aneja, Viney P.; Tong, Daniel; Lee, Pius; Tang, Youhua

    2016-09-01

    The U.S. National Oceanic and Atmospheric Administration (NOAA) is responsible for forecasting elevated levels of air pollution within the National Air Quality Forecast Capability (NAQFC). The current research uses measurements gathered in the DISCOVER-AQ Colorado field campaign and the concurrent Front Range Air Pollution and Photochemistry Experiment (FRAPPE) to test performance of the NAQFC CMAQ modeling framework for predicting NH3. The DISCOVER-AQ and FRAPPE field campaigns were carried out in July and August 2014 in Northeast Colorado. Model predictions are compared with measurements of NH3 gas concentrations and the NH4+ component of fine particulate matter concentrations measured directly by the aircraft in flight. We also compare CMAQ predictions with NH3 measurements from ground-based monitors within the DISCOVER-AQ Colorado geographic domain, and from the Tropospheric Emission Spectrometer (TES) on the Aura satellite. In situ aircraft measurements carried out in July and August of 2014 suggest that the NAQFC CMAQ model underestimated the NH3 concentration in Northeastern Colorado by a factor of ∼2.7 (NMB = -63%). Ground-level monitors also produced a similar result. Average satellite-retrieved NH3 levels also exceeded model predictions by a factor of 1.5-4.2 (NMB = -33 to -76%). The underestimation of NH3 was not accompanied by an underestimation of particulate NH4+, which is further controlled by factors including acid availability, removal rate, and gas-particle partition. The average measured concentration of NH4+ was close to the average predication (NMB = +18%). Seasonal patterns measured at an AMoN site in the region suggest that the underestimation of NH3 is not due to the seasonal allocation of emissions, but to the overall annual emissions estimate. The underestimation of NH3 varied across the study domain, with the largest differences occurring in a region of intensive agriculture near Greeley, Colorado, and in the vicinity of Denver. The

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    Luminescence spectra are recorded for the reactions of Xe+ + NH3 and Xe2+ + NH3 at energies ranging from 11.5 to 206 eV in the center-of-mass (Ecm) frame. Intense features of the luminescence spectra are attributed to the NH (A 3Πi-X 3Σ-), hydrogen Balmer series, and Xe I emission observable for both primary ions. Evidence for charge transfer products is only found through Xe I emission for both primary ions and NH+ emission for Xe2+ primary ions. For both primary ions, the absolute NH (A-X) cross section increases with collision energy before leveling off at a constant value, approximately 9 × 10-18 cm2, at about 50 eV while H-α emission increases linearly with collision energy. The nascent NH (A) populations derived from the spectral analysis are found to be independent of collision energy and have a constant rotational temperature of 4200 K.

  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 ν_2 in an unprecedented accuracy, which revealed significant deficiencies in the NH_3 intensities, for instance, some weak ΔK = 3 lines were predicted to be ~100 times stronger. Measurement of line intensity for these lines in a consistent manner is demanded because the ΔK = 3 forbidden lines are only way other than collisions and l-doubled states to excite NH_3 to K > 0 levels. Recalling that NH_3 transition lines in the high J and K up to 18 were detected toward the galactic center in the star forming region of Sgr B_2, their accurate intensity measurements are critical in explaining the observed high K excitation, which will provide insights into radiative-transfer vs.levels. The interaction between a large amplitude torsional motion and the hyperfine coupling may also lead to a less known hyperfine effect, the so-called magnetic spin-torsion coupling, which was first studied by Heuvel and Dymanus and which has not yet been conclusively evidenced. In this talk, the magnetic hyperfine structure of the non-rigid methanol molecule will be investigated experimentally and theoretically. 13 hyperfine patterns were recorded using two molecular beam microwave spectrometers. These patterns, along with previously recorded ones,^c were analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling. The theoretical approach setup to analyze the observed data accounts for the spin-torsion coupling, in addition to the familiar magnetic spin-rotation and spin-spin couplings, and relies on symmetry

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

    PubMed

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

    2008-04-01

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

  3. The reaction NH2 + PH3 yields NH3 + PH2 - Absolute rate constant measurement and implication for NH3 and PH3 photochemistry in the atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Bosco, S. R.; Brobst, W. D.; Nava, D. F.; Stief, L. J.

    1983-01-01

    The rate constant is measured over the temperature interval 218-456 K using the technique of flash photolysis-laser-induced fluorescence. NH2 radicals are produced by the flash photolysis of ammonia highly diluted in argon, and the decay of fluorescent NH2 photons is measured by multiscaling techniques. For each of the five temperatures employed in the study, the results are shown to be indepenent of variations in PH3 concentration, total pressure (argon), and flash intensity. It is found that the rate constant results are best represented for T between 218 and 456 K by the expression k = (1.52 + or - 0.16) x 10 to the -12th exp(-928 + or - 56/T) cu cm per molecule per sec; the error quoted is 1 standard deviation. This is the first determination of the rate constant for the reaction NH2 + PH3. The data are compared with an estimate made in order to explain results of the radiolysis of NH3-PH3 mixtures. The Arrhenius parameters determined here for NH2 + PH3 are then contrasted with those for the corresponding reactions of H and OH with PH3.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  6. Mobile mapping and eddy covariance flux measurements of NH3 emissions from cattle feedlots with a portable laser-based open-path sensor

    NASA Astrophysics Data System (ADS)

    Tao, L.; Sun, K.; Pan, D.; Golston, L.; Stanton, L. G.; Ham, J. M.; Shonkwiler, K. B.; Nash, C.; Zondlo, M. A.

    2014-12-01

    Ammonia (NH3) is the dominant alkaline species in the atmosphere and an important compound in the global nitrogen cycle. There is a large uncertainty in NH3 emission inventory from agriculture, which is the largest source of NH3, including livestock farming and fertilizer applications. In recent years, a quantum cascade laser (QCL)-based open-path sensor has been developed to provide high-resolution, fast-response and high-sensitivity NH3 measurements. It has a detection limit of 150 pptv with a sample rate up to 20 Hz. This sensor has been integrated into a mobile platform mounted on the roof of a car to perform measurement of multiple trace gases. We have also used the sensor for eddy covariance (EC) flux measurements. The mobile sensing method provides high spatial resolution and fast mapping of measured gases. Meanwhile, the EC flux method offers accurate flux measurements and resolves the diurnal variability of NH3emissions. During the DISCOVER-AQ and FRAPPÉ field campaigns in 2014, this mobile platform was used to study NH3 emissions from cattle feedlot near Fort Morgan, Colorado. This specific feedlot was mapped multiple times in different days to study the variability of its plume characteristics. At the same time, we set up another open-path NH3 sensor with LICOR open-path sensors to perform EC flux measurements of NH3, CH4 and CO2 simultaneously in the same cattle feedlot as shown in Fig. 1. NH3/CH4 emission flux ratio show a strong temperature dependence from EC flux measurements. The median value of measured NH3 and CH4 emission flux ratio is 0.60 ppmv/ppmv. In contrast, the median value of ΔNH3/ΔCH4 ratios measured from mobile platform is 0.53 ppmv/ppmv for the same farm. The combination of mobile mapping and EC flux measurements with the same open-path sensors greatly improves understanding of NH3 emissions both spatially and temporally.

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

    NASA Astrophysics Data System (ADS)

    Steadman, Jhobe; Syage, Jack A.

    1990-04-01

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

  8. Shock temperature measurements of planetary ices - NH3, CH4, and 'synthetic Uranus'

    NASA Astrophysics Data System (ADS)

    Radousky, H. B.; Mitchell, A. C.; Nellis, W. J.

    1990-12-01

    Shock temperature measurements have been performed on several materials which have relevance to the modeling of the outer planets. These materials are methane, ammonia and a mixture of water, ammonia, and isopropanol known as synthetic Uranus. Temperatures have been measured in these materials over the pressure range 33-76 GPa for which there also exists measurements of equation of state and electrical conductivity. The temperatures are found to agree well with available calculations, with small discrepancies between data and theory ascribed to energy absorbing processes such as dissociation and molecular ionization.

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

    PubMed

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

    2017-01-03

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

  10. Calibrated Passive Sampling--Multi-plot Field Measurements of NH3 Emissions with a Combination of Dynamic Tube Method and Passive Samplers.

    PubMed

    Pacholski, Andreas

    2016-03-21

    Agricultural ammonia (NH3) emissions (90% of total EU emissions) are responsible for about 45% airborne eutrophication, 31% soil acidification and 12% fine dust formation within the EU15. But NH3 emissions also mean a considerable loss of nutrients. Many studies on NH3 emission from organic and mineral fertilizer application have been performed in recent decades. Nevertheless, research related to NH3 emissions after application fertilizers is still limited in particular with respect to relationships to emissions, fertilizer type, site conditions and crop growth. Due to the variable response of crops to treatments, effects can only be validated in experimental designs including field replication for statistical testing. The dominating ammonia loss methods yielding quantitative emissions require large field areas, expensive equipment or current supply, which restricts their application in replicated field trials. This protocol describes a new methodology for the measurement of NH3 emissions on many plots linking a simple semi-quantitative measuring method used in all plots, with a quantitative method by simultaneous measurements using both methods on selected plots. As a semi-quantitative measurement method passive samplers are used. The second method is a dynamic chamber method (Dynamic Tube Method) to obtain a transfer quotient, which converts the semi-quantitative losses of the passive sampler to quantitative losses (kg nitrogen ha(-1)). The principle underlying this approach is that passive samplers placed in a homogeneous experimental field have the same NH3 absorption behavior under identical environmental conditions. Therefore, a transfer co-efficient obtained from single passive samplers can be used to scale the values of all passive samplers used in the same field trial. The method proved valid under a wide range of experimental conditions and is recommended to be used under conditions with bare soil or small canopies (<0.3 m). Results obtained from

  11. Rapid Ammonia Deposition Measured Near Concentrated Animal Feeding Operations

    NASA Astrophysics Data System (ADS)

    Stanton, L. G.; Pan, D.; Sun, K.; Golston, L.; Tao, L.; Zondlo, M. A.

    2014-12-01

    Concentrated animal feeding operations (CAFOs) emit massive amounts of ammonia (NH3) to the atmosphere. Current measurements of NH3 are generally conducted far away from the sources (satellites, airplanes, etc.). There is insufficient knowledge about the dry deposition rate of NH3 near the sources, which might contribute to the large discrepancies between measured concentrations at CAFOs and those from models. During the 2014 NASA DISCOVER-AQ campaign, we designed a series of tests to measure the deposition rate of NH3 by utilizing a suite of sensors, including a LICOR LI-7700 methane sensor and Princeton University's custom open path NH3 sensor, which was mounted on top of a small SUV. Our mobile sampling technique enables us to follow feedlot emission plumes to see how ambient NH3 concentration decays as gases moves away from the CAFO. The mobile platform is used to perform upwind and downwind sampling to characterize the NH3 emission source. We tracked the change of the enhancement of NH3 concentration relative to the enhancement of CH4 concentrationNH3:ΔCH4), while transecting the plume of individual cattle feedlots. Measured data shows that the high concentration of NH3 seen at the source decreases quickly as one moves further downwind from it. A time constant of approximately ten minutes has been calculated from the decay of the ΔNH3:ΔCH4 ratios while moving away from the sources. We also will compare our measurements with those of NASA's P-3B aerosol measurements to show that the majority must be lost to dry deposition. This rapid deposition suggests that large amounts of NH3 are being deposited in very close proximity to these CAFOs, which is consistent with previous findings of locally high soil pH near NH3 sources. Our results will be used to better characterize nitrogen deposition from cattle feedlots and estimate NH3 lifetime.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  13. EMRP JRP MetNH3: Towards a Consistent Metrological Infrastructure for Ammonia Measurements in Ambient Air

    NASA Astrophysics Data System (ADS)

    Leuenberger, Daiana; Balslev-Harder, David; Braban, Christine F.; Ebert, Volker; Ferracci, Valerio; Gieseking, Bjoern; Hieta, Tuomas; Martin, Nicholas A.; Pascale, Céline; Pogány, Andrea; Tiebe, Carlo; Twigg, Marsailidh M.; Vaittinen, Olavi; van Wijk, Janneke; Wirtz, Klaus; Niederhauser, Bernhard

    2016-04-01

    Measuring ammonia in ambient air is a sensitive and priority issue due to its harmful effects on human health and ecosystems. In addition to its acidifying effect on natural waters and soils and to the additional nitrogen input to ecosystems, ammonia is an important precursor for secondary aerosol formation in the atmosphere. 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 regarding certified reference material (CRM), applicable analytical methods, measurement uncertainty, quality assurance and quality control (QC/QA) procedures as well as in the infrastructure to attain metrological traceability. As shown in a key comparison in 2007, there are even discrepancies between reference materials provided by European National Metrology Institutes (NMIs) at amount fraction levels up to three orders of magnitude higher than ambient air levels. MetNH3 (Metrology for ammonia in ambient air), a three-year project that started in June 2014 in the framework of the European Metrology Research Programme (EMRP), aims to reduce the gap between requirements set by the European emission regulations and state-of-the-art of analytical methods and reference materials. The overarching objective of the JRP is to achieve metrological traceability for ammonia measurements in ambient air from primary certified reference material CRM and instrumental standards to the field level. This requires the successful completion of the three main goals, which have been assigned to three technical work packages: To develop improved reference gas mixtures by static and dynamic gravimetric generation methods Realisation and characterisation of traceable preparative calibration standards (in pressurised cylinders as well as mobile generators) of ammonia amount fractions similar to those in ambient air based on existing methods for other reactive analytes. The

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

    PubMed

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

    2014-09-01

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

  15. 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.

  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

  17. Atmospheric ammonia measurements at low concentration ...

    EPA Pesticide Factsheets

    We evaluated the relative importance of dry deposition of ammonia (NH3) gas at several headwater areas of the Susquehanna River, the largest single source of nitrogen pollution to Chesapeake Bay, including three that are remote from major sources of NH3 emissions (CTH, ARN, and KEF) and one (HFD) that is near a major agricultural source. We also examined the importance of nitrogen dioxide (NO2) deposition at one of these sites. Over the past decade, increasing evidence has suggested that NH3 deposition, in particular, may be an important contributor to total nitrogen deposition and to downstream nitrogen pollution. We used Ogawa passive samplers to measure NH3 concentrations over several years (2006–2011) for CTH, and primarily in 2008 and 2009 for the other sites. NO2 was measured at CTH mainly in 2007. Chamber calibration studies for NH3 and NO2, and field comparisons with annular denuders for NH3, validated the use of these passive samplers over a range of temperatures and humidity observed in the field, if attention is given to field and laboratory blank issues. The annual mean NH3 concentrations for the forested sites were 0.41 ± 0.03, 0.41 ± 0.06 and 0.25 ± 0.08 µg NH3/m3 for CTH, ARN and KEF, respectively. NO2 passive sampler mean annual concentration was 3.19 ± 0.42 µg NO2/m3 at CTH. Direct comparison of our measured values with the widely used Community Multiscale Air Quality (CMAQ) model (v4.7.1) show reasonably good agreement. However, the mod

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  19. 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.

  20. Measurement of OH, H2SO4, MSA, NH3 and DMSO Aboard the NASA P-3B Aircraft

    NASA Technical Reports Server (NTRS)

    Eisele, Fred

    2001-01-01

    This project involved the installation of a downsized multichannel mass spectrometer instrument on the NASA P-3B aircraft and its subsequent use on the PEM-Tropics B mission. The new instrument performed well, measuring a number of difficult-to-measure compounds and providing much new photochemical and sulfur data as well as possibly uncovering a new nighttime DMSO source. The details of this effort are discussed.

  1. The effect of Si and Al concentrations on the removal of U(VI) in the alkaline conditions created by NH3 gas

    SciTech Connect

    Katsenovich, Yelena P.; Cardona, Claudia; Lapierre, Robert; Szecsody, Jim; Lagos, Leonel E.

    2016-10-01

    Remediation of uranium in the deep unsaturated zone is a challenging task, especially in the presence of oxygenated, high-carbonate alkalinity soil and pore water composition typical for arid and semi-arid environments of the western regions of the U.S. This study evaluates the effect of various pore water constituencies on changes of uranium concentrations in alkaline conditions, created in the presence of reactive gases such as NH3 to effectively mitigate uranium contamination in the vadose zone sediments. This contaminant is a potential source for groundwater pollution through slow infiltration of soluble and highly mobile uranium species towards the water table. The objective of this research was to evaluate uranium sequestration efficiencies in the alkaline synthetic pore water solutions prepared in a broad range of Si, Al, and bicarbonate concentrations typically present in field systems of the western U.S. regions and identify solid uranium-bearing phases that result from ammonia gas treatment. In previous studies (Szecsody et al. 2012; Zhong et al. 2015), although uranium mobility was greatly decreased, solid phases could not be identified at the low uranium concentrations in field-contaminated sediments. The chemical composition of the synthetic pore water used in the experiments varied for silica (5–250 mM), Al3+ (2.8 or 5 mM), HCO3- (0–100 mM) and U(VI) (0.0021–0.0084 mM) in the solution mixture. Experiment results suggested that solutions with Si concentrations higher than 50 mM exhibited greater removal efficiencies of U(VI). Solutions with higher concentrations of bicarbonate also exhibited greater removal efficiencies for Si, Al, and U(VI). Overall, the silica polymerization reaction leading to the formation of Si gel correlated with the removal of U(VI), Si, and Al from the solution. If no Si polymerization was observed, there was no U removal from the supernatant solution. Speciation modeling indicated that the dominant uranium species in the

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    PubMed

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

    2013-12-01

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

  4. The NH3Cl+ Cation

    DTIC Science & Technology

    2007-11-02

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

  5. Multi-walled carbon nanotubes plastic NH3 gas sensor

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

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

    NASA Astrophysics Data System (ADS)

    McKarns, T.; Kutter, M. F.

    2015-12-01

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

  7. Coexistence of Two Electronic Nano-Phases on a CH3NH3PbI3-xClx Surface Observed in STM Measurements.

    PubMed

    Yost, Andrew J; Pimachev, Artem; Ho, Chun-Chih; Darling, Seth B; Wang, Leeyih; Su, Wei-Fang; Dahnovsky, Yuri; Chien, TeYu

    2016-10-10

    Scanning tunneling microscopy is utilized to investigate the local density of states of a CH3NH3PbI3-xClx perovskite in cross-sectional geometry. Two electronic phases, 10-20 nm in size, with different electronic properties inside the CH3NH3PbI3-xClx perovskite layer are observed by the dI/dV mapping and point spectra. A power law dependence of the dI/dV point spectra is revealed. In addition, the distinct electronic phases are found to have preferential orientations close to the normal direction of the film surface. Density functional theory calculations indicate that the observed electronic phases are associated with local deviation of I/Cl ratio, rather than different orientations of the electric dipole moments in the ferroelectric phases. By comparing the calculated results with experimental data we conclude that phase A (lower contrast in dI/dV mapping at -2.0 V bias) contains a lower I/Cl ratio than that in phase B (higher contrast in dI/dV).

  8. Coexistence of two electronic nano-phases on a CH3NH3PbI3–xClx surface observed in STM measurements

    DOE PAGES

    Yost, Andrew J.; Pimachev, Artem; Ho, Chun -Chih; ...

    2016-10-10

    Scanning tunneling microscopy is utilized to investigate the local density of states of a CH3NH3PbI3-xClx perovskite in cross-sectional geometry. Two electronic phases, 10-20 nm in size, with different electronic properties inside the CH3NH3PbI3-xClx perovskite layer are observed by the dI/ dV mapping and point spectra. A power law dependence of the dI/dV point spectra is revealed. In addition, the distinct electronic phases are found to have preferential orientations close to the normal direction of the film surface. Density functional theory calculations indicate that the observed electronic phases are associated with local deviation of I/Cl ratio, rather than different orientations ofmore » the electric dipole moments in the ferroelectric phases. Furthermore, by comparing the calculated results with experimental data we conclude that phase A (lower contrast in dI/dV mapping at -2.0 V bias) contains a lower I/Cl ratio than that in phase B (higher contrast in dI/dV).« less

  9. Degradation of CH3NH3PbI3 perovskite due to soft x-ray irradiation as analyzed by an x-ray photoelectron spectroscopy time-dependent measurement method

    NASA Astrophysics Data System (ADS)

    Motoki, Keisuke; Miyazawa, Yu; Kobayashi, Daisuke; Ikegami, Masashi; Miyasaka, Tsutomu; Yamamoto, Tomoyuki; Hirose, Kazuyuki

    2017-02-01

    The effects of soft X-ray exposure on structures of CH3NH3PbI3 perovskite were investigated using an X-ray photoelectron spectroscopy (XPS) time-dependent measurement method. A crystalline sample was fabricated with the inverse-temperature crystallization method. The time evolutions of the core-level and valence-band spectra were recorded to determine the compositional ratios and valence band electronic structure of the sample, respectively. In addition, first-principles calculations were conducted to evaluate the valence band XPS spectra. The in situ XPS analysis combined with theoretical calculations demonstrated a degradation of the surface of CH3NH3PbI3 perovskite into PbI2 owing to the evaporation of methylammonium iodide.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  12. 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.

  13. 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.

  14. MetNH3: Metrology for ammonia in ambient air

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    PubMed

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

    2016-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  18. Bibliographic review and new measurements of the integrated cross sections of 8 molecules (H2O, CO, CO2, CH3OH, NH3, CH4, HCOOH and H2CO) in the solid form at 25K

    NASA Astrophysics Data System (ADS)

    Michaelle, B.; Nicolas, F.; Yves, B.; Hervé, C.; Antoine, J.; Claire, G. Marie

    2014-04-01

    Infrared spectra from ISO and Spitzer telescopes revealed the presence of several molecules in the solid phase such as H2O, CO, CO2, CH3OH, NH3, CH4, HCOOH and H2CO in the environment of some Young Stellar Objects (YSOs) ([1], [2], [3], [4]. To quantify the column density of those molecules, the knowledge of some spectroscopic parameters, especially the integrated cross section A (cm.molecule-1) is required. For some molecules, inconsistencies on the values of spectroscopic parameters can be found in the literature. The purpose of this study is to compare all the values found in the literature with the ones that we have measured recently in order to propose more convincing values.

  19. Measurements of Atmospheric NH3, NOy/NOx, and NO2 and Deposition of Total Nitrogen at the Beaufort, NC CASTNET Site (BFT142)

    EPA Science Inventory

    The Clean Air Status and Trends Network (CASTNET) is a long-term environmental monitoring program that measures trends in ambient air quality and atmospheric dry pollutant deposition across the United States. CASTNET has been operating since 1987 and currently consists of 89 moni...

  20. Photodissociation of Mg +(NH 3) ion

    NASA Astrophysics Data System (ADS)

    Yoshida, Shinji; Okai, Nobuhiro; Fuke, Kiyokazu

    2001-10-01

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

  1. 14NH_3 Line Positions and Intensities in the Far-Infrared Comparison of Ft-Ir Measurements to Empirical Hamiltonian Model Predictions

    NASA Astrophysics Data System (ADS)

    Sung, Keeyoon; Yu, Shanshan; Pearson, John; Pirali, Olivier; Kwabia Tchana, F.; Manceron, Laurent

    2016-06-01

    We have analyzed multiple spectra of high purity (99.5%) normal ammonia sample recorded at room temperatures using the FT-IR and AILES beamline at Synchrotron SOLEIL, France. More than 2830 line positions and intensities are measured for the inversion-rotation and rovibrational transitions in the 50 - 660 wn region. Quantum assignments were made for 2047 transitions from eight bands including four inversion-rotation bands (gs(a-s), νb{2}(a-s), 2νb{2}(a-s), and νb{4}(a-s)) and four ro-vibrational bands (νb{2} - gs, 2νb{2} - gs, νb{4} - νb{2}, and 2νb{2} -νb{4}), as well as covering more than 300 lines of ΔK = 3 forbidden transitions. Out of the eight bands, we note that 2νb{2} - νb{4} has not been listed in the HITRAN 2012 database. The measured line positions for the assigned transitions are in an excellent agreement (typically better than 0.001 wn) with the predictions from the empirical Hamiltonian model [S. Yu, J.C. Pearson, B.J. Drouin, et al.(2010)] in a wide range of J and K for all the eight bands. The comparison with the HITRAN 2012 database is also satisfactory, although systematic offsets are seen for transitions with high J and K and those from weak bands. However, differences of 20% or so are seen in line intensities for allowed transitions between the measurements and the model predictions, depending on the bands. We have also noticed that most of the intensity outliers in the Hamiltonian model predictions belong to transitions from gs(a-s) band. We present the final results of the FT-IR measurements of line positions and intensities, and their comparisons to the model predictions and the HITRAN 2012 database. Research described in this paper was performed at the Jet Propulsion Laboratory and California Institute of Technology, under contracts and cooperative agreements with the National Aeronautics and Space Administration.

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

    Atmospheric Science Data Center

    2017-02-27

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

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

    Atmospheric Science Data Center

    2016-10-31

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

  4. 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.

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

    PubMed

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

    2016-03-01

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

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

    DTIC Science & Technology

    1981-04-10

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

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

    NASA Astrophysics Data System (ADS)

    Spector, Oded; Jacobson, Esther

    1999-12-01

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

  8. 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.

  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:  Search and Order:   Order Data ...

  10. Birefringence Imaging Measurements on Various Structural Phase Transitions in (CnH2n+1NH3)2MnCl4 with n = 1, 2, and 3 Using Multiple Wavelengths

    NASA Astrophysics Data System (ADS)

    Manaka, Hirotaka; Fukuda, Takumi; Miura, Yoko

    2016-12-01

    Birefringence imaging microscopy is well suited for comprehensively investigating various structural phase transitions but its weak point is that it imposes an inherent limit on the maximum retardance that can be detected. To detect retardance above this limit, we performed simultaneous birefringence measurements at multiple wavelengths on (CnH2n+1NH3)2MnCl4 with n = 1,2,3. For n = 1, we successfully detected large jumps in retardance (over six times greater than the limit) in the first-order phase transitions at Tc1 ≃ 88 K and Tc2 ≃ 251 K. For n = 2, a gradual change in retardance appears in the second-order phase transition at Tc = 214 K. High-definition images of optical fast-axis azimuths provided information on the misorientation of the alkylammonium chains. For n = 3, a retardance kink appears at Tc4 ≃ 152-155 K, and a retardance jump appears in the commensurate-incommensurate phase transition at Tc5 ≃ 96-99 K.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

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

    PubMed

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

    2014-01-17

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

  13. 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.

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

    PubMed Central

    Woidy, Patrick; Kraus, Florian

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

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

    PubMed

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

    2015-02-07

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

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

    PubMed

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

    2013-12-01

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

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

    PubMed

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

    2014-02-28

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

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

    NASA Astrophysics Data System (ADS)

    Hetmańczyk, Łukasz; Hetmańczyk, Joanna

    2016-07-01

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

  3. 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

  4. Effect of alum additions to poultry litter on in-house ammonia and greenhouse gas concentrations and emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Alum (Al2(SO4)3 •14H2O) additions to poultry litter have been shown to reduce ammonia (NH3) concentrations in poultry houses and NH3 fluxes from litter; however, continuous, accurate measurements of in-house NH3 concentrations and emissions from alum-treated and untreated commercial poultry houses i...

  5. 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

  6. The CU mobile Solar Occultation Flux instrument: structure functions and emission rates of NH3, NO2 and C2H6

    NASA Astrophysics Data System (ADS)

    Kille, Natalie; Baidar, Sunil; Handley, Philip; Ortega, Ivan; Sinreich, Roman; Cooper, Owen R.; Hase, Frank; Hannigan, James W.; Pfister, Gabriele; Volkamer, Rainer

    2017-02-01

    We describe the University of Colorado mobile Solar Occultation Flux instrument (CU mobile SOF). The instrument consists of a digital mobile solar tracker that is coupled to a Fourier transform spectrometer (FTS) of 0.5 cm-1 resolution and a UV-visible spectrometer (UV-vis) of 0.55 nm resolution. The instrument is used to simultaneously measure the absorption of ammonia (NH3), ethane (C2H6) and nitrogen dioxide (NO2) along the direct solar beam from a moving laboratory. These direct-sun observations provide high photon flux and enable measurements of vertical column densities (VCDs) with geometric air mass factors, high temporal resolution of 2 s and spatial resolution of 5-19 m. It is shown that the instrument line shape (ILS) of the FTS is independent of the azimuth and elevation angle pointing of the solar tracker. Further, collocated measurements next to a high-resolution FTS at the National Center for Atmospheric Research (HR-NCAR-FTS) show that the CU mobile SOF measurements of NH3 and C2H6 are precise and accurate; the VCD error at high signal to noise ratio is 2-7 %. During the Front Range Air Pollution and Photochemistry Experiment (FRAPPE) from 21 July to 3 September 2014 in Colorado, the CU mobile SOF instrument measured median (minimum, maximum) VCDs of 4.3 (0.5, 45) × 1016 molecules cm-2 NH3, 0.30 (0.06, 2.23) × 1016 molecules cm-2 NO2 and 3.5 (1.5, 7.7) × 1016 molecules cm-2 C2H6. All gases were detected in larger 95 % of the spectra recorded in urban, semi-polluted rural and remote rural areas of the Colorado Front Range. We calculate structure functions based on VCDs, which describe the variability of a gas column over distance, and find the largest variability for NH3. The structure functions suggest that currently available satellites resolve about 10 % of the observed NH3 and NO2 VCD variability in the study area. We further quantify the trace gas emission fluxes of NH3 and C2H6 and production rates of NO2 from concentrated animal feeding

  7. Addition of NH3 to Al3O3-

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    1998-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Häni, Christoph; Neftel, Albrecht; Sintermann, Jörg

    2016-04-01

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

  11. Validation of Ogawa passive samplers for the determination of gaseous ammonia concentrations in agricultural settings

    NASA Astrophysics Data System (ADS)

    Roadman, M. J.; Scudlark, J. R.; Meisinger, J. J.; Ullman, W. J.

    The Ogawa passive sampler (Ogawa USA, Pompano Beach, Florida) is a useful tool for monitoring atmospheric ammonia (NH 3(g)) concentrations and assessing the effects of agricultural waste management practices on NH 3(g) emissions. The Ogawa sampler, with filter-discs impregnated with citric acid, was used to trap and determine NH 3(g) concentrations in a variety of agricultural settings. A wide range of NH 3(g) concentrations can be monitored by varying the sampler exposure time, provided that no more than ˜10 μg of NH 3-N are adsorbed on the acid-coated filters. Concentrations less than 1 μg NH 3-N m -3 can be detected using long deployments (⩽14 days), while concentrations as great as 10 mg NH 3-N m -3 may be determined in very short (e.g. 5 min) deployments. Reproducibility ranged from 5% to 10% over the range of concentrations studied and passive determinations of NH 3(g) were similar to those determined using dilute-acid gas scrubbers. Background levels of NH 3(g) at a non-agricultural site in southern Delaware were typically <1 μg NH 3-N m -3. The air entering a chicken house was 10 μg NH 3-N m -3, reflecting the background levels in agricultural settings in this region. Within the house, concentrations ⩽8.5 mg NH 3-N m -3 were observed, reflecting the high rates of NH 3(g) emission from chicken excreta. Using measured NH 3(g) concentrations and poultry house ventilation rates, we estimate that each broiler grown to production size over 6 weeks contributes approximately 19±3 g of NH 3-N to the atmosphere, a value consistent with other published results.

  12. 3-D agricultural air quality modeling: Impacts of NH3/H2S gas-phase reactions and bi-directional exchange of NH3

    NASA Astrophysics Data System (ADS)

    Wang, Kai; Zhang, Yang

    2014-12-01

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

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

    PubMed

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

    2015-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  16. 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

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

    PubMed

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

    2007-11-01

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

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  2. Rotational Spectroscopy of the NH3-H2 Molecular Complex

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  5. Gaseous NH3 Confers Porous Pt Nanodendrites Assisted by Halides

    PubMed Central

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

    2016-01-01

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

  6. [Protein and amino acid metabolism in the gastrointestinal tract of young bulls. 3. Flow of NH3-free raw protein into the duodenum].

    PubMed

    Gabel, M; Poppe, S

    1985-10-01

    The amount of NH3-free crude protein getting into the duodenum corrected by the endogenous crude protein quota was determined on the basis of 28 differently composed rations for growing bulls in the live weight range of 140-460 kg provided with duodenal re-entrant cannulae. The experimental results were generalized by means of regression analysis and can be summarized as follows: The amount of NH3-free crude protein getting into the duodenum can partially be calculated with the regression equation (Formula: see text) resp. NH3-free crude protein D = 155 app. dig. org. matter + 0.262 pure protein +/- 42. The remaining dispersion amounts to +/- 6% of the mean value. The coincidence between the values calculated with these equations and those measured experimentally is very good. There is an interaction between the pure protein of feed getting into the duodenum in % of pure protein intake (y) and the bacteria crude protein D/kg app. dig. org. matter (x) characterized by the equation y = 116.8-0.52 x +/- 12.9. The amount of NH3-free crude protein duod. is not influenced by the flow rate (kg digesta/kg intake of org. matter) and not by the "dilution rate' (g bacteria free org. matter duod./kg live weight 0.75/h) either at a DM intake adequate to the production level. Apart from the partial estimation of the NH3-free crude protein duod. a evaluation based on the crude protein and pure protein concentration in app. dig. org. matter of the ration is possible.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1993-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  10. Non-Controlled Emission of Inorganic Toxic gas Components (CO, H2S, NH3 and Hg0) to the atmosphere from Arico's landfill, Tenerife, Canary Islands, Spain

    NASA Astrophysics Data System (ADS)

    Echeita, A.; Perez, C.; Hernandez, C.; Fariña, L.; Lima, R.; Salazar, J.; Hernandez, P.; Perez, N.

    2001-12-01

    Landfill gas is mainly constituted by CO2 and CH4. However, other inorganic toxic gas components such as CO, NH3, H2S and Hg0, are also present. Reduced gas species are produced and released during the anaerobic decomposition of urban waste, while Hg0 is originally present in the waste and it is released as a volatile. Significant amounts of non-controlled emission of these components could be released to the atmosphere in the form of diffuse degassing, The goal of this study is to evaluate the "non-controlled" emissions of these inorganic toxic gas components from Arico's landfill, Tenerife. Arico's landfill (0.35 Km2) holds about 1,200 t/d of urban solid waste with an average organic matter content of 48%. Diffuse CO2 emission has been measured at the surface of Arico's landfill by means of a NDIR according with the accumulation chamber method. Landfill gases were also collected at 40 cm depth using a metallic probe and analyzed within 24 hours for CO2 and CO composition by means of a VARIAN micro-GC QUAD. H2S and Hg0 were analyzed by means of a Polytron-II electrochemical sensor and a JEROME 431-X mercury analyzer, respectively. NH3 was fixed in a boric acid solution and determined by means of a selective electrode. CO concentration ranged from non-detectable to 2,531 ppmv, with a median of 24.3 ppmv. The highest observed Hg0 concentration in the surface landfill gas is 0.004 ppbv, while H2S concentration reached levels up to 12 ppmv. NH3 contents were lower than 1 ppmv. CO, Hg0, H2S and NH3 fluxes have been estimated by multiplying CO2 efflux times (Tox.I.C.)i/CO2 where (Tox.I.C.)i is the concentration of CO, Hg0, H2S and NH3. The highest efflux values for CO, Hg0, H2S and NH3 were 6.8 gm-2d-1, 0.04 µ gm-2d-1, 1.7 mgm-2d-1 and 0.23 gm-2d-1, respectively.

  11. Temporal variation in atmospheric ammonia concentrations above seabird colonies

    NASA Astrophysics Data System (ADS)

    Blackall, T. D.; Wilson, L. J.; Bull, J.; Theobald, M. R.; Bacon, P. J.; Hamer, K. C.; Wanless, S.; Sutton, M. A.

    Recent studies have shown that seabirds are an important source of ammonia (NH 3) emissions in remote coastal ecosystems. Nesting behaviour, which varies between seabird species, is likely to be a major factor in determining the proportion of excreted nitrogen (N) volatilised to the atmosphere as NH 3. A long-term NH 3 monitoring programme was implemented at a Scottish seabird colony with a range of species and associated nesting behaviours. The average monthly NH 3 concentration was measured at 12 locations over a 14-month period, to infer spatial (i.e. species-specific) and temporal (seasonal) changes in NH 3 emissions from different seabird species. An emissions model of seabird NH 3, based on species-specific bioenergetics and behaviour, was applied to produce spatial estimates for input to a dispersion model. Atmospheric NH 3 concentrations demonstrated spatial variability as a result of differing local populations of breeding seabirds, with the highest concentrations measured above cliff nesting species such as Common guillemot Uria aalge, Razorbill Alca torda and Black-legged kittiwake Rissa tridactyla. NH 3 concentrations above a colony of burrow nesting Atlantic puffin Fratercula arctica were low, considering the high number of birds. Emission of NH 3 from excreted N exhibits a time lag of approximately a month. It is likely that all excreted N is lost from the colony by volatilisation as NH 3 or surface run-off between breeding seasons. Modelled NH 3 emissions and concentrations correlated with measured concentrations, but were much higher, reflecting uncertainties in the local turbulent characteristics. The results allow multi-species seabird population data to be used for the calculation of regional and global NH 3 emission inventories, whilst improving understanding of N budgets of remote coastal ecosystems.

  12. Applications of Kalman filtering to real-time trace gas concentration measurements

    NASA Technical Reports Server (NTRS)

    Leleux, D. P.; Claps, R.; Chen, W.; Tittel, F. K.; Harman, T. L.

    2002-01-01

    A Kalman filtering technique is applied to the simultaneous detection of NH3 and CO2 with a diode-laser-based sensor operating at 1.53 micrometers. This technique is developed for improving the sensitivity and precision of trace gas concentration levels based on direct overtone laser absorption spectroscopy in the presence of various sensor noise sources. Filter performance is demonstrated to be adaptive to real-time noise and data statistics. Additionally, filter operation is successfully performed with dynamic ranges differing by three orders of magnitude. Details of Kalman filter theory applied to the acquired spectroscopic data are discussed. The effectiveness of this technique is evaluated by performing NH3 and CO2 concentration measurements and utilizing it to monitor varying ammonia and carbon dioxide levels in a bioreactor for water reprocessing, located at the NASA-Johnson Space Center. Results indicate a sensitivity enhancement of six times, in terms of improved minimum detectable absorption by the gas sensor.

  13. 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.

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

    PubMed

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

    2016-12-01

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

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

    PubMed

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

    2015-12-03

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

  16. Comparison of Techniques to Estimate Ammonia Emissions at Cattle Feedlots Using Time-Averaged and Instantaneous Concentration Measurements

    NASA Astrophysics Data System (ADS)

    Shonkwiler, K. B.; Ham, J. M.; Williams, C. M.

    2013-12-01

    Ammonia (NH3) that volatilizes from confined animal feeding operations (CAFOs) can form aerosols that travel long distances where such aerosols can deposit in sensitive regions, potentially causing harm to local ecosystems. However, quantifying the emissions of ammonia from CAFOs through direct measurement is very difficult and costly to perform. A system was therefore developed at Colorado State University for conditionally sampling NH3 concentrations based on weather parameters measured using inexpensive equipment. These systems use passive diffusive cartridges (Radiello, Sigma-Aldrich, St. Louis, MO, USA) that provide time-averaged concentrations representative of a two-week deployment period. The samplers are exposed by a robotic mechanism so they are only deployed when wind is from the direction of the CAFO at 1.4 m/s or greater. These concentration data, along with other weather variables measured during each sampler deployment period, can then be used in a simple inverse model (FIDES, UMR Environnement et Grandes Cultures, Thiverval-Grignon, France) to estimate emissions. There are not yet any direct comparisons of the modeled emissions derived from time-averaged concentration data to modeled emissions from more sophisticated backward Lagrangian stochastic (bLs) techniques that utilize instantaneous measurements of NH3 concentration. In the summer and autumn of 2013, a suite of robotic passive sampler systems were deployed at a 25,000-head cattle feedlot at the same time as an open-path infrared (IR) diode laser (GasFinder2, Boreal Laser Inc., Edmonton, Alberta, Canada) which continuously measured ammonia concentrations instantaneously over a 225-m path. This particular laser is utilized in agricultural settings, and in combination with a bLs model (WindTrax, Thunder Beach Scientific, Inc., Halifax, Nova Scotia, Canada), has become a common method for estimating NH3 emissions from a variety of agricultural and industrial operations. This study will first

  17. 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.

  18. Tunable high-efficient pulsed NH3 terahertz lasers

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  19. Tunable high-efficient pulsed NH3 terahertz lasers

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  20. Investigation of the Poisoning Mechanism of Lead on the CeO2-WO3 Catalyst for the NH3-SCR Reaction via in Situ IR and Raman Spectroscopy Measurement.

    PubMed

    Peng, Yue; Si, Wenzhe; Li, Xiang; Chen, Jianjun; Li, Junhua; Crittenden, John; Hao, Jiming

    2016-09-06

    The in situ IR and Raman spectroscopy measurements were conducted to investigate lead poisoning on the CeO2-WO3 catalysts. The deactivation mechanisms were studied with respect to the changes of surface acidity, redox property, nitrate/nitrite adsorption behaviors, and key active sites (note that the results of structure-activity relationship of CeO2-WO3 were based on our previous research). (1) Lewis acid sites originated from CeO2 and crystalline WO3, whereas Brønsted acid sites originated from Ce2(WO4)3. The poisoned catalysts exhibited a lower surface acidity than the fresh catalysts: the number of acid sites decreased, and their thermal stability weakened. (2) The reducibility of catalysts and the amount of active oxygen exhibited a smaller influence after poisoning because lead preferred to bond with surface WOx species rather than CeO2. (3) The quantity of active nitrate species decreased due to the lead coverage on the catalyst and the partial bridged-nitrate species induced by lead exhibited a low degree of activity at 200 °C. (4) Crystalline WO3 and Ce2(WO4)3 originated from the transformation of polytungstate sites. These sites were the key active sites during the SCR process. The formation temperatures of polytungstate on the poisoned catalysts were higher than those on the fresh catalysts.

  1. 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.

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

    PubMed

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

    2015-12-01

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

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

    PubMed

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

    2016-06-29

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

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

    PubMed

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

    1999-06-14

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

  5. General working principles of CH3NH3PbX3 perovskite solar cells.

    PubMed

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

    2014-02-12

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  8. Measuring Hydrogen Concentrations in Metals

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1985-01-01

    Commercial corrosion-measurement system adapted to electrochemical determination of hydrogen concentrations in metals. New technique based on diffusion of hydrogen through foil specimen of metal. In sample holder, hydrogen produced on one side of foil, either by corrosion reaction or by cathodic current. Hydrogen diffused through foil removed on other side by constant anode potential, which leads to oxidation of hydrogen to water. Anode current is measure of concentration of hydrogen diffusing through foil. System used to study hydrogen uptake, hydrogen elimination by baking, effect of heat treatment, and effect of electroplating on high-strength steels.

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

    NASA Astrophysics Data System (ADS)

    Sahiner, Nurettin; Demirci, Sahin; Sel, Kivanc

    2016-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

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

  11. Sensing Mechanisms for Carbon Nanotube Based NH3 Gas Detection

    SciTech Connect

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

    2009-03-31

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

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

    PubMed

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

    2009-04-01

    There has been an argument on carbon nanotube (CNT) based gas detectors with a field-effect transistor (FET) geometry: do the response signals result from charge transfer between adsorbed gas molecules and the CNT channel and/or from the gas species induced Schottky barrier modulation at the CNT/metal contacts? To differentiate the sensing mechanisms, we employed three CNTFET structures, i.e., (1) the entire CNT channel and CNT/electrode contacts are accessible to NH(3) gas; (2) the CNT/electrode contacts are passivated with a Si(3)N(4) thin film, leaving the CNT channel open to the gas and, in contrast, (3) the CNT channel is covered with the film, while the contacts are open to the gas. We suggest that the Schottky barrier modulation at the contacts is the dominant mechanism from room temperature to 150 degrees C. At higher temperatures, the charge transfer process contributes to the response signals. There is a clear evidence that the adsorption of NH(3) on the CNT channel is facilitated by environmental oxygen.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  15. Global Ammonia Concentrations Seen by the 13-years AIRS Measurements

    NASA Astrophysics Data System (ADS)

    Warner, Juying; Wei, Zigang; Larrabee Strow, L.; Dickerson, Russell; Nowak, John; Wang, Yuxuan

    2016-04-01

    Ammonia is an integral part of the nitrogen cycle and is projected to be the largest single contributor to each of acidification, eutrophication and secondary particulate matter in Europe by 2020 (Sutton et al., 2008). The impacts of NH3 also include: aerosol production affecting global radiative forcing, increases in emissions of the greenhouse gases nitrous oxide (N2O) and methane (CH4), and modification of the transport and deposition patterns of SO2 and NOx. Therefore, monitoring NH3 global distribution of sources is vitally important to human health with respect to both air and water quality and climate change. We have developed new daily and global ammonia (NH3) products from AIRS hyperspectral measurements. These products add value to AIRS's existing products that have made significant contributions to weather forecasts, climate studies, and air quality monitoring. With longer than 13 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 will discuss the global NH3 emission sources from biogenic and anthropogenic activities over many emission regions captured by AIRS. We will focus their variability in the last 13 years.

  16. 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.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    Okai, Nobuhiro; Takahata, Akihiro; Fuke, Kiyokazu

    2004-03-01

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

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

    PubMed

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

    2016-12-15

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

  20. A variationally computed line list for hot NH3

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  2. Simulating the phase partitioning of NH3, HNO3, and HCl with size-resolved particles over northern Colorado in winter

    NASA Astrophysics Data System (ADS)

    Kelly, James T.; Baker, Kirk R.; Nolte, Christopher G.; Napelenok, Sergey L.; Keene, William C.; Pszenny, Alexander A. P.

    2016-04-01

    Numerical modeling of inorganic aerosol processes is useful in air quality management, but comprehensive evaluation of modeled aerosol processes is rarely possible due to the lack of comprehensive datasets. During the Nitrogen, Aerosol Composition, and Halogens on a Tall Tower (NACHTT) campaign in February and March 2011, the phase partitioning of soluble trace gases with size-resolved particles and related meteorological conditions were measured continuously at a site in Colorado about 33 km north of Denver. These size-resolved measurements of particulate SO42-, NH4+, NO3-, Cl-, Na+, Ca2+, Mg2+, and K+ and inorganic gases are used here to assess the ability of a continental U.S. modeling platform to simulate the gas-particle partitioning of NH3, HNO3, and HCl at this location. Modeling is based on the Community Multiscale Air Quality (CMAQ) model with 12 km horizontal resolution. Baseline, sensitivity, and source apportionment simulations are conducted to fully characterize the model predictions. Considering the limitations in representing regional terrain features in the national 12 km modeling, predictions agree reasonably well with measured concentrations and gas-particle partitioning at this location. However, the median sum of NH4+ and NH3 is underpredicted in the baseline simulation by a factor of four suggesting a need for improved bottom-up NH3 emissions inventories in this area. The median sum of Cl- and HCl is underpredicted by a factor of 2.8, while levels of Ca2+, Mg2+, and K+ are overpredicted. Improvements in windblown and fugitive dust emissions may improve and/or better constrain these predictions. Mass size distributions for inorganic particle constituents are generally simulated well, although the modeled fine particle mode is shifted to slightly larger diameters relative to measurements. Source apportionment modeling estimates of source sector and boundary contributions to air quality at the site are provided.

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

    SciTech Connect

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

    2012-11-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  5. Lattice potential energy and standard molar enthalpy in the formation of 1—dodecylamine hydrobromide (1-C12H25NH3·Br)(s)

    NASA Astrophysics Data System (ADS)

    Liu, Yu-Pu; Di, You-Ying; Dan, Wen-Yan; He, Dong-Hua; Kong, Yu-Xia; Yang, Wei-Wei

    2011-02-01

    This paper reports that 1-dodecylamine hydrobromide (1-C12H25NH3·Br)(s) has been synthesized using the liquid phase reaction method. The lattice potential energy of the compound 1-C12H25NH3·Br and the ionic volume and radius of the 1-C12H25NH3+ cation are obtained from the crystallographic data and other auxiliary thermodynamic data. The constant-volume energy of combustion of 1-C12H25NH3·Br(s) is measured to be ΔcUmo(1-C12H25NH3·Br, s) = -(7369.03±3.28) kJ·mol-1 by means of an RBC-II precision rotating-bomb combustion calorimeter at T = (298.15±0.001) K. The standard molar enthalpy of combustion of the compound is derived to be ΔcHmo(1-C12H25NH3·Br, s) = -(7384.52±3.28) kJ·mol-1 from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound is calculated to be ΔfHmo(1-C12H25NH3·Br, s)=-(1317.86±3.67) kJ·mol-1 from the standard molar enthalpy of combustion of the title compound and other auxiliary thermodynamic quantities through a thermochemical cycle.

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

    PubMed

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

    2016-10-01

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

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

    PubMed

    Wang, Xiaobo; Gui, Keting

    2013-12-01

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

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

    USGS Publications Warehouse

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

    1995-01-01

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

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

    PubMed

    Eichhöfer, Andreas; Buth, Gernot

    2016-11-01

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

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

    PubMed

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

    2015-05-15

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

  11. Modifying CH3NH3PbBr3 nanocrystals with arylamines

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  12. 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).

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

    PubMed

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

    2016-10-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

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

    PubMed

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

    2014-11-21

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

  16. The ν 1 and ν 3 band system of 15NH3

    NASA Astrophysics Data System (ADS)

    Fusina, Luciano; Nivellini, Giandomenico; Spezzano, Silvia

    2011-09-01

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

  17. Ammonia concentrations and modeling of inorganic particulate matter in the vicinity of an egg production facility in Southeastern USA.

    PubMed

    Li, Qian-Feng; Wang-Li, Lingjuan; Shah, Sanjay B; Jayanty, R K M; Bloomfield, Peter

    2014-03-01

    Ammonia (NH3) is an important base gas and can react with acidic species to form atmospheric aerosols. Due to the rapid growth of poultry and swine production in the North Carolina Coastal Plain, atmospheric NH3 concentrations across the region have subsequently increased. Ammonia concentrations and inorganic particulate matter (PM) at four ambient stations in the vicinity of an egg production facility were measured for 1 year using PM2.5 speciation samplers with honeycomb denuders and ion chromatography (IC). Meanwhile, concentrations of NH3 and inorganic PM in one of the egg production houses were also simultaneously measured using a gas analyzer for NH3 and the filter pack plus IC method for inorganic PM. An equilibrium model-ISORROPIA II was applied to predict the behavior of inorganic aerosols in response to precursor gas concentrations and environmental parameters. Average ambient NH3 concentrations varied from 10.0 to 27.0 μg/m(3), and they were negatively correlated with the distances from the ambient location to the nearest egg production house exhausts. Ambient NH3 concentrations were higher in warm seasons than in cold seasons. Measured NH3 concentrations agreed well with ISORROPIA II model predictions at all sampling stations. For the ambient stations, there was a good agreement in particle phase NH4 (+) between the model simulation and observations. For the in-house station, the model simulation was applied to correct the overestimation of particle phase NH4 (+) due to gas phase NH3 breaking through the denuders. Changes in SO4 (2-), NO3 (-), and Cl(-) yield proportional changes in inorganic PM mass. Due to the abundance of NH3 gas in the vicinity area of the monitored farm, changes in NH3 concentrations had a small effect on inorganic PM mass. Aerosol equilibrium modeling may be used to assess the influence of precursor gas concentrations on inorganic PM formation when the measurements for some species are unavailable.

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

    PubMed

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

    2015-02-05

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

  19. 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.

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

    DTIC Science & Technology

    2015-09-01

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

  1. Non-Controlled Biogenic Emission of CO, H2S, NH3 and Hg0 from Lazareto's Landfill, Tenerife, Canary Islands

    NASA Astrophysics Data System (ADS)

    Nolasco, D.; Lima, R.; Salazar, J.; Hernández, P. A.; Pérez, N. M.

    2002-12-01

    Landfills are important sources of contaminant gases to the surrounding environment and a significant amount of them could be released to the atmosphere through the surface environment in a diffuse form, also known as non-controlled emission of landfill gases. CH4 and CO2 are major components in landfill gases and other gas species are only present in minor amounts. Trace compounds include both inorganic and a large number of volatile organic components. The goal of this study is to evaluate the non-controlled biogenic emission of inorganic toxic gases from Lazareto's landfill. Which is located in the city of Santa Cruz de Tenerife, with a population of about 150,000, and is used as a Palm tree park. Lazareto's landfill has an extension of 0.22 Km2 and it is not operative since 1980. A non-controlled biogenic gas emission survey of 281 sampling sites was carried out from February tod March, 2002. Surface CO2 efflux measurements were performed by means of a portable NDIR sensor according with the accumulation chamber method. Surface CO2 efflux ranged from negligible values up to 30,600 gm-2d-1. At each sampling site, surface landfill gas samples were collected at 40 cm depth using a metallic soil probe. These gas samples were analyzed within 24 hours for major and inorganic toxic gas species by means of microGC and specific electrochemical sensors. The highest concentrations of CO, H2S, NH3 and Hg0 were 3, 20, 2,227, 0.010 ppmV, respectively. Non-controlled biogenic emission rate of CO, H2S, NH3, and Hg0 were estimated by multiplying the observed surface CO2 efflux times (Inorganic Toxic Gas)i/CO2 weight ratio at each sampling site, respectively. The highest surface inorganic toxic gas efllux rates were 699 gm-2d-1 for NH3, 81, 431 and 4 mgm-2d-1 for CO, H2S and Hg0, respectively. Taking into consideration the spatial distribution of the inorganic toxic gas efflux values as well as the extension of the landfill, the non-controlled biogenic emission of CO, H2S, NH3

  2. Kinetic modelling of NH3 production in N2–H2 non-equilibrium atmospheric-pressure plasma catalysis

    NASA Astrophysics Data System (ADS)

    Hong, Jungmi; Pancheshnyi, Sergey; Tam, Eugene; Lowke, John J.; Prawer, Steven; Murphy, Anthony B.

    2017-04-01

    Detailed plasma kinetics modelling is presented of a low electron energy N2–H2 atmospheric-pressure discharge for ammonia synthesis. The model considers both electron and vibrational kinetics, including excited N2(X, ν) and H2(X, ν) species, and surface reactions such as those occurring by the Eley–Rideal and Langmuir–Hinshelwood mechanisms and dissociative adsorption of molecules. The predictions of the model are compared to the measured NH3 concentration produced in a packed-bed dielectric barrier discharge reactor as a function of process parameters such as input gas composition and applied voltage. Unlike typical low-pressure plasma processes, under the plasma conditions considered here (reduced electric field E/N in the range 30–50 Td, electron density of the order 108 cm‑3), the influence of ions is not significant. Instead, the reactions between radicals and vibrationally-excited molecules are more important. The active species in surface reactions, such as surface-adsorbed atomic nitrogen N(s) or hydrogen H(s), are found to be predominantly generated through the dissociative adsorption of molecules, in contrast to previously proposed mechanisms for plasma catalysis under low-pressure, high-E/N conditions. It is found that NH radicals play an important role at the early stages of the NH3-generation process, NH in turn is produced from N and H2(ν). Electron kinetics is shown to play a critical role in the molecular dissociation and vibrational excitation reactions that produce these precursors. It is further found that surface-adsorbed atomic hydrogen H(s) takes a leading role in the formation of NH3, which is another significant difference from the mechanisms in conventional thermo-chemical processes and low-pressure plasmas. The applied voltage, the gas temperature, the N2:H2 ratio in the input gas mixture and the reactivity of the surface material are all found to influence the ammonia production. The calculated results reproduce the observed

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

    PubMed

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

    2015-10-01

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

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

    PubMed

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

    2017-03-16

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

  5. Measurement of Bi-Directional Ammonia Exchange Above a Maize Canopy in the Midwestern United States

    NASA Astrophysics Data System (ADS)

    Nelson, A. J.; Vieira-Filho, M. S.; Heuer, M.; Lehmann, C.; Myles, L.; Koloutsou-Vakakis, S.; Rood, M. J.

    2014-12-01

    Crop fertilization contributes to more than 40% of total anthropogenic emissions of ammonia (NH3) in Illinois. NH3 released into the atmospheric environment reacts readily with acidic compounds to form small diameter (<2.5μm) particulate matter (PM2.5) resulting in human health effects and deposition to surfaces causing eutrophication. Such emissions are not well characterized, and improved measurements are needed to further validate air quality models. This study seeks to provide improved understanding of the emission pathway of agricultural NH3 by measuring bi-directional flux of gaseous NH3 in an intensively managed agroecosystem. A relaxed eddy accumulation (REA) system was deployed above a maize canopy at the University of Illinois at Urbana-Champaign (UIUC) Energy Biosciences Institute (EBI) Energy Farm. Average NH3 flux was measured throughout the growing season in four-hour periods during the morning and afternoon. The REA coefficient (β) was monitored for the duration of the season. The highest atmospheric NH3 concentration (8.11 μg/m3) was observed during the period nearest fertilization, with a mean concentration of 4.02 μg/m3 ± 2.15 μg/m3. Generally, larger upward fluxes of gaseous NH3 coincided with higher atmospheric NH3 concentration, but large variations were observed during the season. Observed NH3 flux ranged from -0.20 µg /m2s to 0.97 µg/m2s, where negative flux indicates deposition.

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

    NASA Astrophysics Data System (ADS)

    Surin, L.; Schnell, M.

    2016-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

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

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

    DTIC Science & Technology

    2008-07-14

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Song, Hongwei; Yang, Minghui; Guo, Hua

    2016-10-01

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

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

    PubMed

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

    2014-08-20

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

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

    PubMed

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

    2016-09-01

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

  13. Perovskite CH3NH3PbI3 crystals and films. Synthesis and characterization

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

  14. Electrets to measure ion concentration in air.

    PubMed

    Kotrappa, P

    2005-08-01

    Positive and negative ions are produced in air, mainly due to radon and terrestrial/cosmic radiation sources. Measuring ion concentration in air indirectly provides a measure of these sources. Electrets (electrically charged pieces of Teflon), when exposed in the environment, collect ions of opposite sign leading to a measurable decrease in charge, depending upon the exposure time and ion concentration. This work describes a method of correlating electret discharge rate to the ion concentration as measured by a calibrated ion density meter. Once calibrated, electrets can then be used to measure ion concentration of either sign. The ion concentration in ambient air was measured to be about 200 ions mL(-1), measured over several hours. Both positive and negative ion concentrations were similar. In a typical room, negative ion concentration was about 3,500 ions mL(-1), and, surprisingly, there were no positive ions at all in that room. Being an integrating passive device, the method provides the unique possibility of measuring low or high concentrations of positive or negative ions over extended periods, which is difficult to do with other ion concentration measuring instruments.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

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

    NASA Technical Reports Server (NTRS)

    Kraemer, Kathleen E.; Jackson, James M.

    1995-01-01

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

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

    PubMed Central

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

    2013-01-01

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

  18. 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%.

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

    PubMed

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

    2015-09-09

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  1. Diffusion length of photo-generated charge carriers in layers and powders of CH3NH3PbI3 perovskite

    NASA Astrophysics Data System (ADS)

    Dittrich, Th.; Lang, F.; Shargaieva, O.; Rappich, J.; Nickel, N. H.; Unger, E.; Rech, B.

    2016-08-01

    The diffusion or transport lengths of photo-generated charge carriers in CH3NH3PbI3 layers (thickness up to 1 μm) and powders have been directly measured with high accuracy by modulated surface photovoltage after Goodman. The values of the diffusion lengths of photo-generated charge carriers ranged from 200 nm to tenths of μm. In thin CH3NH3PbI3 layers, the transport lengths corresponded to the layer thickness whereas in thicker layers and in crystallites of CH3NH3PbI3 powders the grain size limited the diffusion length. For grains, the diffusion length of photo-generated charge carriers depended on the measurement conditions.

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

    Li, Zhi; Zhao, Zhen; Li, Xuehui

    2012-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

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

    PubMed

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

    2005-07-07

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

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

    DOE PAGES

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

    2016-10-13

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

  9. Computed tomographic measurement of canine urine concentration.

    PubMed

    Zwingenberger, Allison L; Carrade Holt, Danielle D

    2017-02-01

    Computed tomography (CT) is able to measure the attenuation of urine in Hounsfield units (HU) on abdominal imaging studies. This study was designed to measure the correlation of urine attenuation with urine specific gravity in urine samples of 40 dogs, providing a noninvasive measure of urine concentration. The HU of urine explained 72% of the variance in measured urine specific gravity [R(2) = 0.72, F(1,38) = 95.55, P < 0.001]. This noninvasive measurement can be used to estimate urine concentration in dogs undergoing abdominal CT imaging.

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

    NASA Astrophysics Data System (ADS)

    Tsujimori, Atsushi; Ozaki, Eiichi; Nakao, Kazushige

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

  11. Measuring surfactant concentration in plating solutions

    DOEpatents

    Bonivert, William D.; Farmer, Joseph C.; Hachman, John T.

    1989-01-01

    An arrangement for measuring the concentration of surfactants in a electrolyte containing metal ions includes applying a DC bias voltage and a modulated voltage to a counter electrode. The phase angle between the modulated voltage and the current response to the modulated voltage at a working electrode is correlated to the surfactant concentration.

  12. Giant Rashba Splitting in CH3NH3PbBr3 Organic-Inorganic Perovskite

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    PubMed

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

    2015-04-07

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

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

    NASA Astrophysics Data System (ADS)

    Wang, Na; Zhang, Yunhong

    2016-04-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1991-09-01

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

  18. Cyclic Concentration Measurements for Characterizing Pulsating Flow

    SciTech Connect

    Bamberger, Judith A.

    2013-07-07

    Slurry mixed in vessels via pulse jet mixers has a periodic, rather than steady, concentration profile. Measurements of local concentration taken at the center of the tank at a range of elevations within the mixed region were analyzed to obtain a greater understanding of how the periodic pulse jet mixing cycle affects the local concentration. Data were obtained at the critical suspension velocity, when all solids are suspended at the end of the pulse. The data at a range of solids loadings are analyzed to observe the effect of solids concentration during the suspension and settling portions of the mixing cycle.

  19. Photoelectric characteristics of CH3NH3PbI3/p-Si heterojunction

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    PubMed

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

    2003-12-01

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

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

    PubMed

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

    2017-03-01

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

  4. Electric polarization of CH3NH3PbI3 and enhancement by Cl substitution

    NASA Astrophysics Data System (ADS)

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

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

  5. 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.

  6. 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.

  7. Ferroelectricity of CH3NH3PbI3 Perovskite.

    PubMed

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

    2015-04-02

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

  8. Active sites, deactivation and stabilization of Fe-ZSM-5 for the selective catalytic reduction (SCR) of NO with NH(3).

    PubMed

    Kröcher, Oliver; Brandenberger, Sandro

    2012-01-01

    Fe-ZSM-5 has been systematically investigated as catalyst for the selective catalytic reduction (SCR) of NO with NH(3), concentrating on the active sites, the deactivation mechanism during hydrothermal aging and the chemical possibilities to stabilize this type of SCR catalyst. Regarding the active SCR sites, it could be shown that monomeric species start to become active at the lowest temperatures (E(a,app) ≈ 36.3 ± 0.2 kJ/mol), followed by dimeric species at intermediate temperatures (E(a,app) ≈ 77 ± 16 kJ/mol) and oligomeric species at high temperatures. Experiments with Fe-ZSM-5 samples, in which the Brønsted acidity was specifically removed, proved that Brønsted acidity is not required for high SCR activity and that NH(3) can also be adsorbed on other acidic sites on the zeolite surface. The hydrothermal deactivation of Fe-ZSM-5 could be explained by the migration of active iron ions from the exchange sites. Parallel to the iron migration dealumination of the zeolite framework occurs, which has to be regarded as an independent process. The migration of iron can be reduced by the targeted reaction of the aluminum hydroxide groups in the lattice with trimethylaluminium followed by calcination. With respect to the application of iron zeolites in the SCR process in diesel vehicles, the most efficient stabilization method would be to switch from the ZSM-5 to the BEA structure type. The addition of NO(2) to the feed gas is another effective measure to increase the activity of even strongly deactivated iron zeolites tremendously.

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

  10. Ammonia and carbon dioxide concentrations in a layer house.

    PubMed

    Kilic, Ilker; Yaslioglu, Erkan

    2014-08-01

    Higher concentrations of ammonia (NH3) and carbon dioxide (CO2) in animal barns can negatively affect production and health of animals and workers. This paper focuses on measurements of summer concentrations of ammonia (NH3) and carbon dioxide (CO2) in a naturally ventilated laying henhouse located at an egg production facility in Bursa region, western Turkey. Also, indoor and ambient environmental conditions such as temperature and relative humidity were measured simultaneously with pollutant gas concentrations. The average NH3 concentrations during summer of 2013 was 8.05 ppm for exhaust and 5.42 ppm for inlet while average CO2 concentration was 732 ppm for exhaust and 625 ppm for inlet throughout summer. The overall minimum, average and maximum values and humidity were obtained as 16.8°C, 24.72°C, and 34.71°C for indoor temperature and 33.64%, 63.71%, and 86.18% for relative humidity. The lowest exhaust concentrations for NH3 and CO2 were 6.98 ppm and 609 ppm, respectively. They were measured in early morning at the maximum diurnal ventilation rate in July 2013 and August 2013. The highest concentrations were 10.58 ppm for NH3 and 904 ppm for CO2 recorded in the afternoon when the ventilation rate was the lowest in June 2013.

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

    PubMed

    Zhang, Minhua; Huang, Xuewei; Chen, Yifei

    2016-10-19

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

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

    PubMed

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

    2014-01-28

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

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

    PubMed

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

    2014-10-15

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

  14. 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.

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

    PubMed Central

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  19. NH3 sensing properties polyaniline: TiO2 nanorods heterostructure

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  1. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  4. 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.

  5. A theoretical investigation of gaseous absorption by water droplets from SO2-HNO3-NH3-CO2-HCl mixtures

    NASA Technical Reports Server (NTRS)

    Adewuyi, Y. G.; Carmichael, G. R.

    1982-01-01

    A physical-chemical model is developed and used to investigate gaseous absorption by water droplets from trace gas mixtures. The model is an extension of that of Carmichael and Peters (1979) and includes the simultaneous absorption of SO2, NH3, HNO3, CO2, and HCl. Gas phase depletion is also considered. Presented results demonstrate that the absorption behavior of raindrops is strongly dependent on drop size, fall distance, trace gas concentrations, and the chemical and physical properties of the constituents of the mixture. In addition, when gas phase depletion is considered, the absorption rates and equilibrium values are also dependent on the precipitation rate itself. Also, the trace constituents liquid phase concentrations may be a factor of six or more lower when gas depletion is considered then when the depletion is ignored. However, the hydrogen ion concentration may be insensitive to the gas phase depletion.

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

    PubMed

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

    2017-02-28

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

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

    PubMed

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

    2013-02-07

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

  8. Biochar applied with appropriate rates can reduce N leaching, keep N retention and not increase NH3 volatilization in a coastal saline soil.

    PubMed

    Sun, Haijun; Lu, Haiying; Chu, Lei; Shao, Hongbo; Shi, Weiming

    2017-01-01

    The impacts of biochar addition on nitrogen (N) leaching, (ammonia) NH3 volatilization from coastal saline soils are not well understood. In this soil column study, the effects of wheat straw biochar application at rates of 0.5%, 1%, 2% and 4% by weight to a coastal saline soil on N leaching, NH3 volatilization, soil pH and N retention were investigated. Results showed that 0.5% and 1% biochar amendments reduce the NH4(+)-N, NO3(-)-N and total N concentrations of leachate and thereby significantly decrease their cumulative lost loads by 11.6-24.0%, 13.2-29.7%, and 14.6-26.0%, respectively, in compared with the control. The biochar-induced soil N leaching mitigation efficiency was weakened when the biochar application rates increased to 2% and 4%. However, the impact of biochar addition on cumulative NH3 volatilizations were negative and significantly 25.6-53.6% higher NH3 volatilizations in soils with 2% and 4% biochar amended than control were detected, which was mainly attributed to the averaged 0.53-0.88units higher soil pH as results of biochar addition. On average, the total N concentrations of soil were kept same with 1.01-1.06gkg(-1) under control and biochar treatments. Therefore, biochar application to the coastal saline soils with appropriate rates (i.e., 0.5% and 1% in current study) can reduce N leaching, keep soil N retention, and not increase NH3 volatilization, which was beneficial for sustainable use of saline soils.

  9. Measuring protein concentration with entangled photons

    NASA Astrophysics Data System (ADS)

    Crespi, Andrea; Lobino, Mirko; Matthews, Jonathan C. F.; Politi, Alberto; Neal, Chris R.; Ramponi, Roberta; Osellame, Roberto; O'Brien, Jeremy L.

    2012-06-01

    Optical interferometry is amongst the most sensitive techniques for precision measurement. By increasing the light intensity, a more precise measurement can usually be made. However, if the sample is light sensitive entangled states can achieve the same precision with less exposure. This concept has been demonstrated in measurements of known optical components. Here, we use two-photon entangled states to measure the concentration of a blood protein in an aqueous buffer solution. We use an opto-fluidic device that couples a waveguide interferometer with a microfluidic channel. These results point the way to practical applications of quantum metrology to light-sensitive samples.

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

    NASA Astrophysics Data System (ADS)

    Twagirayezu, Sylvestre; Sears, Trevor; Hall, Gregory

    2016-06-01

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

  11. SURFATM-NH3: a model combining the surface energy balance and bi-directional exchanges of ammonia applied at the field scale

    NASA Astrophysics Data System (ADS)

    Personne, E.; Loubet, B.; Herrmann, B.; Mattsson, M.; Schjoerring, J. K.; Nemitz, E.; Sutton, M. A.; Cellier, P.

    2009-08-01

    A new biophysical model SURFATM-NH3, simulating the ammonia (NH3) exchange between terrestrial ecosystems and the atmosphere is presented. SURFATM-NH3 consists of two coupled models: (i) an energy budget model and (ii) a pollutant exchange model, which distinguish the soil and plant exchange processes. The model describes the exchanges in terms of adsorption to leaf cuticles and bi-directional transport through leaf stomata and soil. The results of the model are compared with the flux measurements over grassland during the GRAMINAE Integrated Experiment at Braunschweig, Germany. The dataset of GRAMINAE allows the model to be tested in various meteorological and agronomic conditions: prior to cutting, after cutting and then after the application of mineral fertilizer. The whole comparison shows close agreement between model and measurements for energy budget and ammonia fluxes. The major controls on the ground and plant emission potential are the physicochemical parameters for liquid-gas exchanges which are integrated in the compensation points for live leaves, litter and the soil surface. Modelled fluxes are highly sensitive to soil and plant surface temperatures, highlighting the importance of accurate estimates of these terms. The model suggests that the net flux depends not only on the foliar (stomatal) compensation point but also that of leaf litter. SURFATM-NH3 represents a comprehensive approach to studying pollutant exchanges and its link with plant and soil functioning. It also provides a simplified generalised approach (SVAT model) applicable for atmospheric transport models.

  12. SURFATM-NH3: a model combining the surface energy balance and bi-directional exchanges of ammonia applied at the field scale

    NASA Astrophysics Data System (ADS)

    Personne, E.; Loubet, B.; Herrmann, B.; Mattsson, M.; Schjoerring, J. K.; Nemitz, E.; Sutton, M. A.; Cellier, P.

    2009-01-01

    A new biophysical model SURFATM-NH3, simulating the ammonia (NH3) exchange between terrestrial ecosystems and the atmosphere is presented. SURFATM-NH3 consists of two coupled models: (i) an energy budget model and (ii) a pollutant exchange model, which distinguish the soil and plant exchange processes. The model describes the exchanges in terms of adsorption to leaf cuticles and bi-directional transport through leaf stomata and soil. The results of the model are compared with the flux measurements over grassland during the GRAMINAE Integrated Experiment at Braunschweig, Germany. The dataset of GRAMINAE allows the model to be tested in various climatic and agronomic conditions: prior to cutting, after cutting and then after the application of mineral fertilizer. The whole comparison shows close agreement between model and measurements for energy budget and ammonia fluxes. The major controls on the soil and plant emission potential are the physicochemical parameters for liquid-gas exchanges which are integrated in the compensation points for live leaves, litter and the soil surface. Modelled fluxes are highly sensitive to soil and plant surface temperatures, highlighting the importance of accurate estimates of these terms. The model suggests that the net flux depends not only on the foliar (stomatal) compensation point but also that of leaf litter. SURFATM-NH3 represents a comprehensive approach to studying pollutant exchanges and its link with plant and soil functioning. It also provides a simplified generalised approach (SVAT model) applicable for atmospheric transport models.

  13. Neutral thermospheric temperature from ion concentration measurements

    NASA Technical Reports Server (NTRS)

    Breig, E. L.; Donaldson, J. S.; Hanson, W. B.; Hoffman, J. H.; Power, R. A.; Kayser, D. C.; Spencer, N. W.; Wharton, L. E.

    1981-01-01

    A technique for extracting information on neutral temperature from in situ F region measurements of O(+) and H(+) ion concentrations is analyzed and evaluated. Advantage is taken of the condition of charge-exchange equilibrium of these species in the neighborhood of 320 km to infer the associated relative abundances of neutral oxygen and hydrogen. Results are shown to be generally consistent with other concurrent in situ measurements.

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

    PubMed

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

    2014-09-01

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

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

    PubMed

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

    2009-01-15

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

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

    PubMed

    Tachikawa, Hiroto

    2006-01-12

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

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

    PubMed

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

    2014-05-01

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

  18. LOW-CONCENTRATION NOX EMISSIONS MEASUREMENT

    EPA Science Inventory

    The paper gives results of a recent series of low-concentration nitrogen oxides (NOx) emission measurements, made by Midwest Research Institute (MRI) during U.S. EPA-sponsored Environmental Technology Verification (ETV) test of a NOx control system called Xonon (TM) Cool Combust...

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

    PubMed

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

    2016-12-14

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  2. Direct observation of intrinsic twin domains in tetragonal CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2013-08-07

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

  6. Direct observation of intrinsic twin domains in tetragonal CH3NH3PbI3

    PubMed Central

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

    2017-01-01

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

  7. Perovskite CH3NH3PbI3(Cl) Single Crystals: Rapid Solution Growth, Unparalleled Crystalline Quality, and Low Trap Density toward 10(8) cm(-3).

    PubMed

    Lian, Zhipeng; Yan, Qingfeng; Gao, Taotao; Ding, Jie; Lv, Qianrui; Ning, Chuangang; Li, Qiang; Sun, Jia-Lin

    2016-08-03

    Single crystal reflects the intrinsic physical properties of a material, and single crystals with high-crystalline quality are highly desired for the acquisition of high-performance devices. We found that large single crystals of perovskite CH3NH3PbI3(Cl) could be grown rapidly from chlorine-containing solutions. Within 5 days, CH3NH3PbI3(Cl) single crystal as large as 20 mm × 18 mm × 6 mm was harvested. As a most important index to evaluate the crystalline quality, the full width at half-maximum (fwhm) in the high-resolution X-ray rocking curve (HR-XRC) of as-grown CH3NH3PbI3(Cl) single crystal was measured as 20 arcsec, which is far superior to so far reported CH3NH3PbI3 single crystals (∼1338 arcsec). The unparalleled crystalline quality delivered a low trap-state density of down to 7.6 × 10(8) cm(-3), high carrier mobility of 167 ± 35 cm(2) V(-1) s(-1), and long transient photovoltaic carrier lifetime of 449 ± 76 μs. The improvement in the crystalline quality, together with the rapid growth rate and excellent carrier transport property, provides state-of-the-art single crystalline hybrid perovskite materials for high-performance optoelectronic devices.

  8. Ternary H2SO4-H2O-NH3 neutral and charged nucleation rates for a wide range of atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Kürten, Andreas; Bianchi, Federico; Almeida, Joao; Duplissy, Jonathan; Dunne, Eimear M.; Breitenlechner, Martin; Praplan, Arnaud P.; Ortega, Ismael K.; Kupiainen, Oona; Rondo, Linda; Ehrhart, Sebastian; Kirkby, Jasper; Curtius, Joachim; Cloud Collaboration

    2013-05-01

    The formation of new particles for the ternary system involving sulfuric acid, water vapor and ammonia has been studied in detail. The nucleation rates were obtained from experiments at the CERN CLOUD chamber which allows the measurement of new particle formation under very well defined conditions. Some of its key features are the suppression of contaminants at the technological limit and a very precise control of a wide range of temperatures, trace gas concentrations and nucleation rates. The effect of ionizing radiation on the ternary nucleation rates was investigated by using the CERN proton synchrotron beam (beam conditions), natural galactic cosmic rays (gcr conditions) as well as the high voltage clearing field inside the chamber to suppress the effect of charges (neutral conditions). The dependence of the nucleation rate on ion concentration, sulfuric acid and ammonia concentration as well as temperature was studied extensively. This way, an unprecedented set of data was collected giving insight into the role of neutral and charged ternary NH3 nucleation and the relative importance of the different parameters.

  9. Apparent deposition velocity and compensation point of ammonia inferred from gradient measurements above and through alfalfa

    NASA Astrophysics Data System (ADS)

    Dabney, Seth M.; Bouldin, David R.

    Understanding the cycling of ammonia between croplands and the atmosphere is of importance to agriculturalists and atmospheric scientists. Flux densities of gaseous ammonia (NH 3), particulate ammonium (NH 4+), and total ammoniacal nitrogen (AN) were measured using an aerodynamic method above an alfalfa ( Medicago sativa, L.) canopy between April and July 1981 at a rural location in central New York State. In air not influenced by local sources, NH 3 and NH 4+ averaged 1.5 and 3.0 ppb, respectively, at 1 m above the crop. Ambient NH 4+ varied consistently with synoptic air masses, being lowest (2.3 ppb) for NW and highest (6.4 ppb) for SW flows. Concentrations and gradients of both species were higher during periods of hay harvest. Gradients of NH 3 were much steeper than those of NH 4+ within the alfalfa canopy, but NH 4+ contributed appreciably (36% on average) to above-canopy AN gradients. Alfalfa's NH 3 compensation point was estimated by combining concentration and gradient data with transport resistances. Gaseous gradients indicated a compensation point of 2 ppb, lower than previously published estimates. Conversion of NH 3 to NH 4+ within the canopy air could have reduced NH 3 gradients and caused a low estimate of the compensation point. Acidic aerosols, by keeping NH 3 levels low, may compete with plants for NH 3. Future studies of ammonia exchange should distinguish between NH 3 and NH 4+ if flux densities are to be related to ambient conditions. Total AN level is a poor predictor of soil-plant-atmosphere ammonia exchange since high AN was frequently associated with low NH 3, and NH 3 is more surface reactive than NH 4+.

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

    PubMed

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

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

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

    PubMed

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

    2014-04-07

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

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  16. 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.

  17. ZnO nanoplates surfaced-decorated by WO3 nanorods for NH3 gas sensing application

    NASA Astrophysics Data System (ADS)

    Dien Nguyen, Dac; Do, Duc Tho; Hien Vu, Xuan; Vuong Dang, Duc; Chien Nguyen, Duc

    2016-03-01

    Zinc oxide (ZnO) nanoplates and tungsten trioxide (WO3) nanorods were synthesized by hydrothermal treatment from zinc nitrate/potassium hydroxide and sodium tungstate/hydrochloric acid, respectively. The structure, morphology and compositions of the as-prepared WO3/ZnO nano-composites were characterized by x-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy. The obtained ZnO nanoplates have regular shape, single-crystal wurtzite structure with the thickness of 40 nm and 200 versus 400 nm in lateral dimensions. The WO3 nanorods possess the average diameter of 20 nm and the length of approximately 120 nm which were distributed on the surfaces of ZnO nanoplates. The WO3/ZnO nano-composites were prepared by grinding WO3 nanorods powder with ZnO nanoplates powder in various weight ratios (1:2, 1:1 and 2:1). The NH3 gas sensing properties of WO3/ZnO nano-composites were examined through the electrical resistance measurement. The gas sensing performance of the WO3/ZnO composite with weight ratio of 1:1 was better compared with that of other samples. For this sample, the maximum response to 300 ppm NH3 was 24 at the operating temperature of 250 °C. In addition, the gas sensing mechanism of the WO3/ZnO composites was discussed.

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

    DOE PAGES

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

    2015-10-13

    The product formation channels of ground state carbon atoms, C(3P), reacting with ammonia, NH3, have been investigated using two complementary experiments and electronic structure calculations. Reaction products are detected in a gas flow tube experiment (330 K, 4 Torr) using tunable vacuum-ultraviolet (VUV) photoionization coupled with time of flight mass spectrometry. Temporal profiles of the species formed and photoionization spectra are used to identify primary products of the C + NH3 reaction. In addition, H-atom formation is monitored by VUV laser induced fluorescence (LIF) from room temperature to 50 K in a supersonic gas flow generated by the Laval nozzlemore » technique. Electronic structure calculations are performed to derive intermediates, transition states, and complexes formed along the reaction coordinate. The combination of photoionization and LIF experiments supported by theoretical calculations indicate that in the temperature and pressure range investigated, the H + H2CN production channel represents 100% of the product yield for this reaction. As a result, kinetics measurements of the title reaction down to 50 K and the effect of the new rate constants on interstellar nitrogen hydride abundances using a model of dense interstellar clouds are reported in Paper II.« less

  19. Continuous gaseous and total ammonia measurements from the southeastern aerosol research and characterization (SEARCH) study

    NASA Astrophysics Data System (ADS)

    Saylor, Rick D.; Edgerton, Eric S.; Hartsell, Benjamin E.; Baumann, Karsten; Hansen, D. Alan

    2010-12-01

    Continuous ammonia (NH 3) measurements with a temporal resolution of 5 min were implemented at selected SEARCH sites in the southeastern U. S. during 2007. The SEARCH continuous NH 3 instrument uses a citric acid denuder difference technique employing a dual-channel nitric oxide-ozone chemiluminescence analyzer. Data from two SEARCH sites are presented, Jefferson Street, Atlanta (JST) (urban), and Yorkville, Georgia (YRK) (rural), for the period July-December, 2007. Highest NH x (total ammonia = gaseous NH 3 + PM 2.5 NH 4+) values were observed in August and September at both JST and YRK. Highest NH 3 values occurred in August and September at JST, but in August through October at YRK. Lowest NH 3 and NH x values occurred in December at both sites. YRK is significantly impacted by nearby poultry sources, routinely experiencing hourly average NH 3 mixing ratios above 20 ppbv. Wind sector analysis clearly implicates the nearby poultry operations as the source of the high NH 3 values. Weekday versus weekend differences in composite hourly mean diurnal profiles of NH 3 at JST indicate that mobile sources have a measurable but relatively small impact on NH 3 observed at that site, and little or no impact on NH 3 observed at YRK. A distinctive composite mean hourly diurnal variation was observed at both JST and YRK, exhibiting maxima in the morning and evening with a broad minimum during midday. Analysis of observed NH 3 diurnal variations from the literature suggests a hypothesized mechanism for the observed behavior based on interaction of local emissions and dry deposition with the formation and collapse of the dynamically mixed atmospheric boundary layer during the day and shallow nocturnal layer at night. Simple mixed layer concentration box model simulations confirm the plausibility of the suggested mechanism.

  20. Measures of net oxidant concentration in seawater

    NASA Astrophysics Data System (ADS)

    Jackson, George A.; Williams, Peter M.

    1988-02-01

    Dissolved oxygen deficits in the ocean have been used as a measure of the organic matter oxidized in a volume of water. Such organic matter is usually assumed to be predominantly settled particles. Using dissolved oxygen concentration in this way has two problems: first, it does not differentiate between oxidant consumed by the pool of dissolved organic matter present near the ocean surface and oxidant consumed by organic matter contained by falling particles; second, it does not account for other oxidant sources, such as nitrate, which can be as important to organic matter decay as oxygen in low-oxygen water, such as off Peru or in the Southern California submarine basins. New parameters provide better measures of the net oxidant concentration in a water parcel. One such, NetOx, is changed only by gaseous exchange with the atmosphere, exchange with the benthos, or the production or consumption of sinking particles. A simplified version of NetOx, NetOx = [O2] + 1.25[NO3-] - [TOC], where TOC (total organic carbon), the dissolved organic carbon (DOC) plus the suspended particulate organic carbon (POC), provides an index based on the usually dominant variables. Calculation of NetOx and a second property, NetOC ([O2] - [TOC]), for data from GEOSECS and ourselves in the Atlantic and Pacific oceans using property-property graphs show differences from those from oxygen deficits alone. Comparison of NetOx and NetOC concentrations at high and low latitudes of the Pacific Ocean shows the difference in surface water oxidant concentrations is even larger than the difference in oxygen concentration. Vertical particle fluxes off Peru calculated from NetOx gradients are much greater than those calculated from oxygen gradients. The potential value of NetOx and NetOC as parameters to understand particle fluxes implies that determination of TOC should be a routine part of hydrographic measurements.

  1. Measurement of total organic concentration in water

    NASA Technical Reports Server (NTRS)

    Winkler, E.

    1978-01-01

    Instrument for determining total organic concentration in water uses no corrosive reagents or gases. Instead continuous ultraviolet photolysis process converts organic compounds to carbon dioxide (CO2). CO2 electrode is used to measure CO2 content. Only reagent necessary is oxygen, generated in situ by electrolyzing some water. In addition to application in aerospace industry, system has potential uses in pollution monitoring and in laboratory analyses.

  2. Optical measurement of drug concentrations in tissue

    SciTech Connect

    Mourant, J.R.; Bigio, I.J.; Jack, D.A.; Johnson, T.M.; Miller, H.D.

    1997-10-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The aim of this project was to develop noninvasive fiber-optic methods for measuring drug concentrations in tissue. Such a system would make possible the study of chemotherapy drug kinetics at specific, targeted locations in the body after the drug is administered. The major result of this project is the development of techniques for measuring changes in absorption of a medium with unknown scattering properties. The developed method was verified by testing on several media with scattering properties in the range typically found for tissue.

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

    NASA Astrophysics Data System (ADS)

    Shirahata, Yasuhiro; Oku, Takeo

    2017-01-01

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

  4. 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

  5. Enhanced Structural Stability and Photo Responsiveness of CH3 NH3 SnI3 Perovskite via Pressure-Induced Amorphization and Recrystallization.

    PubMed

    Lü, Xujie; Wang, Yonggang; Stoumpos, Constantinos C; Hu, Qingyang; Guo, Xiaofeng; Chen, Haijie; Yang, Liuxiang; Smith, Jesse S; Yang, Wenge; Zhao, Yusheng; Xu, Hongwu; Kanatzidis, Mercouri G; Jia, Quanxi

    2016-10-01

    An organic-inorganic halide CH3 NH3 SnI3 perovskite with significantly improved structural stability is obtained via pressure-induced amorphization and recrystallization. In situ high-pressure resistance measurements reveal an increased electrical conductivity by 300% in the pressure-treated perovskite. Photocurrent measurements also reveal a substantial enhancement in visible-light responsiveness. The mechanism underlying the enhanced properties is shown to be associated with the pressure-induced structural modification.

  6. Enhanced structural stability and photo responsiveness of CH3NH3SnI3 perovskite via pressure-induced amorphization and recrystallization

    DOE PAGES

    Lu, Xujie; Wang, Yonggang; Stoumpos, Constantinos C.; ...

    2016-10-01

    An organic–inorganic halide CH3NH3SnI3 perovskite with significantly improved structural stability is obtained via pressure-induced amorphization and recrystallization. In situ high-pressure resistance measurements reveal an increased electrical conductivity by 300% in the pressure-treated perovskite. Photocurrent measurements also reveal a substantial enhancement in visible-light responsiveness. In conclusion, the mechanism underlying the enhanced properties is shown to be associated with the pressure-induced structural modification.

  7. Mechanism of N2O formation during the low-temperature selective catalytic reduction of NO with NH3 over Mn-Fe spinel.

    PubMed

    Yang, Shijian; Xiong, Shangchao; Liao, Yong; Xiao, Xin; Qi, Feihong; Peng, Yue; Fu, Yuwu; Shan, Wenpo; Li, Junhua

    2014-09-02

    The mechanism of N2O formation during the low-temperature selective catalytic reduction reaction (SCR) over Mn-Fe spinel was studied. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and transient reaction studies demonstrated that the Eley-Rideal mechanism (i.e., the reaction of adsorbed NH3 species with gaseous NO) and the Langmuir-Hinshelwood mechanism (i.e., the reaction of adsorbed NH3 species with adsorbed NOx species) both contributed to N2O formation. However, N2O selectivity of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism was much less than that through the Eley-Rideal mechanism. The ratio of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism remarkably increased; therefore, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the decrease of the gas hourly space velocity (GHSV). As the gaseous NH3 concentration increased, N2O selectivity of NO reduction over Mn-Fe spinel increased because of the promotion of NO reduction through the Eley-Rideal mechanism. Meanwhile, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the increase of the gaseous NO concentration because the formation of NH on Mn-Fe spinel was restrained. Therefore, N2O selectivity of NO reduction over Mn-Fe spinel was related to the GHSV and concentrations of reactants.

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

    PubMed

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

    2017-03-28

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    PubMed

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

    2014-12-14

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

  12. 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.

  13. 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.

  14. Method for measuring lead concentrations in blood

    DOEpatents

    Nogar, Nicholas S.

    2001-01-01

    Method for measuring lead concentrations in blood. The present invention includes the use of resonant laser ablation to analyze .ltoreq.1 .mu.L (or equivalent mass) samples of blood for lead content. A typical finger prick, for example, yields about 10 .mu.L. Solid samples may also readily be analyzed by resonant laser ablation. The sample is placed on a lead-free, electrically conducting substrate and irradiated with a single, focused laser beam which simultaneously vaporizes, atomizes, and resonantly ionizes an analyte of interest in a sample. The ions are then sorted, collected and detected using a mass spectrometer.

  15. Diagnosing shock temperature with NH3 and H2O profiles

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  17. Photovoltaic performance and the energy landscape of CH3NH3PbI3.

    PubMed

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

    2015-09-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

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

    PubMed

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

    1975-08-05

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

  2. Effect of fluorine additive on CeO2(ZrO2)/TiO2 for selective catalytic reduction of NO by NH3.

    PubMed

    Jin, Qijie; Shen, Yuesong; Zhu, Shemin

    2017-02-01

    A series of CeO2(ZrO2)/TiO2 catalysts with fluorine additive were prepared by impregnation method and tested for selective catalytic reduction (SCR) of NO by NH3. These samples were characterized by XRD, N2-BET, Raman spectra, SEM, TEM, NH3-TPD, H2-TPR and XPS, respectively. Results showed that the optimal catalyst with the appropriate HF exhibited excellent performance for NH3-SCR and more than 96% NO conversion at 360°C under GHSV of 71,400h(-1). It was found that the grain size of TiO2 increased and the specific surface area reduced with the modulation of HF, which was not good for the adsorption of gas molecule. However, the modulation of HF exposed the high energy (001) facets of TiO2 and increased the surface chemisorbed oxygen concentration, oxygen storage capacity and Ce(3+) concentration of catalyst. In addition, the synergy of (101) and (001) facets was beneficial to the improvement of catalytic activity.

  3. Applications of tunable diode laser spectroscopy for the detection of exhaled endogenous gases: CO, NH3, CH4, N20, and CO2

    NASA Astrophysics Data System (ADS)

    Kouznetsov, Andrian I.; Stepanov, Eugene V.

    1996-04-01

    Tunable diode laser spectroscopy (TDLS) is proposed for content measurements of trace gases like CO, carbon-dioxide, NH3, CH4, NO, NO2 in human and animal's exhalation. High sensitivity and wide dynamic range of the method ensure fast detection of these gases at ppb level and within the accuracy better than 10%. One-expiration sample is enough to reach these parameters. There is no need for any preliminary preparations of tested samples. Some pairs of the gases, for instance, CO and carbon-dioxide, NH3 and carbon- dioxide, or CO and nitrous oxide, can be measured simultaneously by one laser providing complex studies. The high sensitive gas analysis could provide necessary background to the noninvasive diagnostics in a wide variety of medical problems. Perspectives of the TDLS methods in application to medicine diagnostics are demonstrated by the first results of exhalation tests.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  5. 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.

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

    DOE PAGES

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

    2015-08-06

    Organic-inorganic hybrid perovskites are attracting intense research effort due to their impressive performance in solar cells. While the carrier transport parameters such as mobility and bulk carrier lifetime shows sufficient characteristics, the surface recombination, which can have major impact on the solar cell performance, has not been studied. Here we measure surface recombination dynamics in CH3NH3PbBr3 perovskite single crystals using broadband transient reflectance spectroscopy. The surface recombination velocity is found to be 3.4±0.1 103 cm s-1, B2–3 orders of magnitude lower than that in many important unpassivated semiconductors employed in solar cells. Our result suggests that the planar grain sizemore » for the perovskite thin films should be larger thanB30 mm to avoid the influence of surface recombination on the effective carrier lifetime.« less

  7. 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.

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

    PubMed Central

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

    2015-01-01

    Organic-inorganic hybrid perovskites are attracting intense research effort due to their impressive performance in solar cells. While the carrier transport parameters such as mobility and bulk carrier lifetime shows sufficient characteristics, the surface recombination, which can have major impact on the solar cell performance, has not been studied. Here we measure surface recombination dynamics in CH3NH3PbBr3 perovskite single crystals using broadband transient reflectance spectroscopy. The surface recombination velocity is found to be 3.4±0.1 × 103 cm s−1, ∼2–3 orders of magnitude lower than that in many important unpassivated semiconductors employed in solar cells. Our result suggests that the planar grain size for the perovskite thin films should be larger than ∼30 μm to avoid the influence of surface recombination on the effective carrier lifetime. PMID:26245855

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

    PubMed

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

    2011-01-28

    Several aspects of ammonia rovibrational spectra have been investigated using the new HSL-2 potential energy surface that includes an approximate correction for nonadiabatic effects. The unprecedented accuracy of rovibrational energy levels and transition energies computed using HSL-2 was demonstrated in Part I of this study. For (14)NH(3), new assignments for a few ν(3) + ν(4) band transitions and energy levels are suggested, and discrepancies between computed and HITRAN energy levels in the 2ν(4) band are analyzed (2ν(4) is the most difficult band below 5000 cm(-1)). New assignments are suggested for existing or missing 2ν(4) levels. Several new vibrational bands are identified from existing, unassigned HITRAN data, including 2ν(2) + ν(4), (ν(3) + ν(4)) -A(')∕A("), ν(1) + 2ν(2), and 2ν(2) + 2ν(4). The strong mixing between the 2ν(4) and 2ν(2) + ν(4) bands is carefully examined and found to be the source of the difficulties in the experimental modeling of 2ν(4). Discussion is presented for preliminary J = 10 results, where the overall root-mean-square error is estimated to be less than 0.039 cm(-1). The analysis of the 4ν(2) band demonstrates both the reliability and the accuracy of predictions from HSL-2. The full list of computed J = 0 band origins (with assignments) and the inversion splittings up to 7000-8000 cm(-1) above the zero-point energy are presented. J = 0-2 levels are reported for those bands below 5100 cm(-1) that are missing from the HITRAN database. For (15)NH(3), excellent agreement is found for the available ν(2) and ν(3) + ν(4)(E) transition energies, but significant deficiencies are shown for HITRAN levels and several corrections are suggested. The (15)N isotopic effects are presented for the J = 0-6 levels of 13 HITRAN bands. For (14)ND(3), we reproduce the pure rotational inversion spectra line frequencies with an accuracy similar to that for (14)NH(3). However, it is not possible to reproduce simultaneously all four

  10. Farm-scale evaluation of ozonation for mitigating ammonia concentrations in broiler houses.

    PubMed

    Wang, Lingjuan; Oviedo-Rondón, Edgar O; Small, John; Liu, Zifei; Sheldon, Brian W; Havenstein, Gerald B; Williams, C Mike

    2010-07-01

    This study evaluated the effectiveness of in-house ozonation within the public health standard limit (0.1 parts per million [ppm]) for mitigating ammonia (NH3) concentrations inside commercial broiler houses. The project was conducted in four identical tunnel-ventilated houses. Two houses served as treatment and the other two served as control units. The experiment was replicated in five consecutive flocks. Except for ozonation treatment, all other operational parameters including feed, broiler strain, age and number of broilers, and ventilation system were the same among four houses. NH3 and carbon dioxide (CO2) concentrations in the treatment and control houses were measured for a minimum of 48 hr/week throughout the five flocks of 8 or 9 weeks each. The gas measurements were conducted using portable multigas units (PMUs). House temperatures were recorded with data loggers in each flock. Comparison of temperatures and CO2 concentrations among houses indicated no significant differences in ventilation rates among treatment and control houses in any of the five flocks. As a result, comparisons of NH3 concentrations inside houses were used to evaluate the effectiveness of house ozonation for NH3 emission mitigation. Statistical test of mean NH3 concentrations for each flock separated by house indicated that the house-to-house variation was significantly smaller than the flock-to-flock variation. There was a substantial variation in NH3 concentrations across different flocks, but no house had consistently higher or lower mean NH3 concentrations than any other. Evaluations for differences in mean NH3 from week to week, between treatment groups, and differences in week-to-week variations between treatment groups suggested that ozone effect was not uniform for each week and the effect was not statistically significant for any week. Tests of overall ozone treatment effect and treatment-week interaction indicated there was no difference in mean NH3 between the control and

  11. Vapor concentration measurement with photothermal deflectometry

    NASA Technical Reports Server (NTRS)

    Banish, R. Michael; Xiao, Rong-Fu; Rosenberger, Franz

    1988-01-01

    Theoretical and experimental results for using the photothermal deflection technique to measure vapor species concentration, while minimizing the disturbance of the transport (material) parameters due to vapor heating, are developed and described. In contrast to common practice, the above constraints require using a pump-beam duty cycle of less than 50 percent. The theoretical description of the shortened heating time is based on a step-function formulation of the pumping cycle. The results are obtained as closed-form solutions of the energy equation for many chopping cycles until steady state is reached, by use of a Green's-function method. The Euler formulation of the Fermat principle is used to calculate the deflection angle. The equations are expanded to include the effects of vapor velocity on both the temperature and temperature gradient profiles. The effects of finite (unfocused) pump and probe beams and thermal (Soret) diffusion are also accounted for. Excellent agreement between theory and experiment is obtained.

  12. Dynamics of NH3 ligands and ClO4- anions in the phase transition in [Cd(NH3)6](ClO4)2 studied by x-ray powder diffraction, neutron scattering methods and infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Hetmańczyk, Łukasz; Hetmańczyk, Joanna

    2017-02-01

    Phase transition, reorientational dynamics of NH3 ligands and ClO4- anions and crystal structure changes were investigated using x-ray powder diffraction (XRPD), neutron powder diffraction (NPD), quasi-elastic neutron scattering (QENS) and Fourier transform infrared spectroscopy (FT-IR). Most measurements were carried out in the temperature range 9-300 K. The diffraction techniques revealed that NH3 ligands and ClO4- anions are orientationally disordered at room temperature. During the cooling process, the high temperature cubic phase transforms into a lower symmetry phase (most probably of monoclinic structure). The QENS results confirm that NH3 ligands perform picoseconds reorientational motions both in the high and low temperature phases. This motion is almost unaffected by the observed phase transition (Tc=138.9 K on heating) and can be well described assuming the three fold jump model. On the other hand, the band shape analysis performed for the IR band connected with ClO4- internal vibration mode δd(OClO)E at 461 cm-1 clearly shows that ClO4- anions reorientate quickly in the high temperature phase, but that motion begins slowing down in the vicinity of the phase transition. Below 150 K the exponential reorientation relaxation term vanishes and only the vibrational relaxation term is present; small discontinuity is also visible. Moreover, below the phase transition temperature Tc splitting of the infrared absorption bands connected with some NH3 internal vibrations is observed.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  14. Investigation of the Performance of HEMT-Based NO, NO2 and NH3 Exhaust Gas Sensors for Automotive Antipollution Systems

    PubMed Central

    Halfaya, Yacine; Bishop, Chris; Soltani, Ali; Sundaram, Suresh; Aubry, Vincent; Voss, Paul L.; Salvestrini, Jean-Paul; Ougazzaden, Abdallah

    2016-01-01

    We report improved sensitivity to NO, NO2 and NH3 gas with specially-designed AlGaN/GaN high electron mobility transistors (HEMT) that are suitable for operation in the harsh environment of diesel exhaust systems. The gate of the HEMT device is functionalized using a Pt catalyst for gas detection. We found that the performance of the sensors is enhanced at a temperature of 600 °C, and the measured sensitivity to 900 ppm-NO, 900 ppm-NO2 and 15 ppm-NH3 is 24%, 38.5% and 33%, respectively, at 600 °C. We also report dynamic response times as fast as 1 s for these three gases. Together, these results indicate that HEMT sensors could be used in a harsh environment with the ability to control an anti-pollution system in real time. PMID:26907298

  15. Effect of Electron Transporting Layer on Bismuth-Based Lead-Free Perovskite (CH3NH3)3 Bi2I9 for Photovoltaic Applications.

    PubMed

    Singh, Trilok; Kulkarni, Ashish; Ikegami, Masashi; Miyasaka, Tsutomu

    2016-06-15

    Methylammonium iodo bismuthate ((CH3NH3)3Bi2I9) (MBI) perovskite is a promising alternative to rapidly progressing hybrid organic-inorganic lead perovskites because of its better stability and low toxicity compared to lead-based perovskites. Solution-processed perovskite fabricated by single-step spin-coating and subsequent heating produced polycrystalline films of hybrid perovskite (CH3NH3)3Bi2I9), whose morphology was influenced drastically by the nature of substrates. The optical measurements showed a strong absorption band around 500 nm. The devices made on anatase TiO2 mesoporous layer showed good performance with current density over 0.8 mA cm(-2) while the devices on brookite TiO2 layer and planar (free of porous layer) was inefficient. However, all the MBI devices were stable to ambient conditions for more than 10 weeks.

  16. 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 μJ/cm2. Our results provide a platform for potential extension towards a true-green light-emitting device for solid-state lighting and display applications.

  17. Photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 in the VUV region

    NASA Technical Reports Server (NTRS)

    Xia, T. J.; Chien, T. S.; Wu, C. Y. Robert; Judge, D. L.

    1991-01-01

    Using synchrotron radiation as a continuum light source, the photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 have been measured from their respective ionization thresholds to 1060 A. The vibrational constants associated with the nu(2) totally symmetric, out-of-plane bending vibration of the ground electronic state of PH3(+) have been obtained. The cross sections and quantum yields for producing neutral products through photoexcitation of these molecules in the given spectral regions have also been determined. In the present work, autoionization processes were found to be less important than dissociation and predissociation processes in NH3, PH3, and C2H4. Several experimental techniques have been employed in order to examine the various possible systematic errors critically.

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

    DOE PAGES

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

    2016-02-02

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

  19. 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.

  20. VizieR Online Data Catalog: W51 Main NH3 and CH3OH data cubes

    NASA Astrophysics Data System (ADS)

    Goddi, C.; Ginsburg, A.; Zhang, Q.

    2016-04-01

    Observations of NH3 toward the W51 complex were conducted usi Karl G. Jansky Very Large Array (JVLA) of the National Radio Astronomy Observatory (NRAO)1 in the B configuration. By using the broadband JVLA K- and Ka-band receivers, we observed a total of five metastable inversion transitions of NH3: (J,K) = (6, 6), (7, 7), (9, 9), (10, 10), and (13, 13) at the 1cm band with frequencies ranging from ~25GHz for the (6, 6) line to ~33GHz for the (13, 13) line. Transitions were observed in pairs of independently tunable basebands during 6h tracks (two targets per track: W51 - this paper; NGC 7538 IRS1 - Paper I, Goddi et al., 2015A&A...573A.108G) on three different dates in 2012: the (6, 6) and (7, 7) lines on May 31 at K-band, the (9, 9) and (13, 13) lines on June 21, and the (10, 10) transition on August 7, both at Ka-band. Each baseband had eight sub-bands with a 4MHz bandwidth (~40km/s at 30GHz), providing a total coverage of 32MHz (~320km/s at 30GHz). Each sub-band consisted of 128 channels with a separation of 31.25kHz (~0.3km/s at 30GHz). The typical on-source integration time was about 80min. Each transition was observed with fast switching, where 80s scans on target were alternated with 40s scans on the nearby (1.2° on the sky) QSO J1924+1540 (measured flux density 0.6-0.7Jy, depending on frequency). We derived absolute flux calibration from observations of 3C 48 (Sν=0.5-0.7Jy, depending on frequency), and bandpass calibration from observations of 3C 84 (Sν=27-29Jy, depending on frequency). (2 data files).

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    PubMed Central

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

    2016-01-01

    Organometallic halide perovskite solar cells (PSCs) have shown great promise as a low-cost, high-efficiency photovoltaic technology. Structural and electro-optical properties of the perovskite absorber layer are most critical to device operation characteristics. Here we present a facile fabrication of high-efficiency PSCs based on compact, large-grain, pinhole-free CH3NH3PbI3−xBrx (MAPbI3−xBrx) thin films with high reproducibility. A simple methylammonium bromide (MABr) treatment via spin-coating with a proper MABr concentration converts MAPbI3 thin films with different initial film qualities (for example, grain size and pinholes) to high-quality MAPbI3−xBrx thin films following an Ostwald ripening process, which is strongly affected by MABr concentration and is ineffective when replacing MABr with methylammonium iodide. A higher MABr concentration enhances I–Br anion exchange reaction, yielding poorer device performance. This MABr-selective Ostwald ripening process improves cell efficiency but also enhances device stability and thus represents a simple, promising strategy for further improving PSC performance with higher reproducibility and reliability. PMID:27477212

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

    DOE PAGES

    Yang, Mengjin; Zhang, Taiyang; Schulz, Philip; ...

    2016-08-01

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

  4. Electron–acoustic phonon coupling in single crystal CH3NH3PbI3 perovskites revealed by coherent acoustic phonons

    PubMed Central

    Mante, Pierre-Adrien; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.; Yartsev, Arkady

    2017-01-01

    Despite the great amount of attention CH3NH3PbI3 has received for its solar cell application, intrinsic properties of this material are still largely unknown. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. We apply this method to characterize a CH3NH3PbI3 single crystal. We measure the acoustic phonon properties and characterize electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. Our results reveal high electron and hole mobilities of 2,800 and 9,400 cm2 V−1 s−1, respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH3NH3PbI3. PMID:28176755

  5. Electron-acoustic phonon coupling in single crystal CH3NH3PbI3 perovskites revealed by coherent acoustic phonons.

    PubMed

    Mante, Pierre-Adrien; Stoumpos, Constantinos C; Kanatzidis, Mercouri G; Yartsev, Arkady

    2017-02-08

    Despite the great amount of attention CH3NH3PbI3 has received for its solar cell application, intrinsic properties of this material are still largely unknown. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. We apply this method to characterize a CH3NH3PbI3 single crystal. We measure the acoustic phonon properties and characterize electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. Our results reveal high electron and hole mobilities of 2,800 and 9,400 cm(2) V(-1) s(-1), respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH3NH3PbI3.

  6. Electron–acoustic phonon coupling in single crystal CH3NH3PbI3 perovskites revealed by coherent acoustic phonons

    DOE PAGES

    Mante, Pierre-Adrien; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.; ...

    2017-02-08

    The intrinsic properties of CH3NH3PbI3 are still largely unknown in spite of the great amount of attention it has received for its solar cell application. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. Furthermore, we apply this method to characterize a CH3NH3PbI3 single crystal.We measure the acoustic phonon properties and characterize electron-acoustic phonon scattering. Then, using themore » deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. These results reveal high electron and hole mobilities of 2,800 and 9,400 cm2V-1 s -1 , respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH3NH3PbI3.« less

  7. Electron-acoustic phonon coupling in single crystal CH3NH3PbI3 perovskites revealed by coherent acoustic phonons

    NASA Astrophysics Data System (ADS)

    Mante, Pierre-Adrien; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.; Yartsev, Arkady

    2017-02-01

    Despite the great amount of attention CH3NH3PbI3 has received for its solar cell application, intrinsic properties of this material are still largely unknown. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. We apply this method to characterize a CH3NH3PbI3 single crystal. We measure the acoustic phonon properties and characterize electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. Our results reveal high electron and hole mobilities of 2,800 and 9,400 cm2 V-1 s-1, respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH3NH3PbI3.

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

    PubMed

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

    2012-12-17

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  10. Retrieval of ammonia from ground-based FTIR measurements and its use for validation of satellite observations by IASI

    NASA Astrophysics Data System (ADS)

    Dammers, Enrico; Palm, Mathias; Warneke, Thorsten; Van Damme, Martin; Smale, Daniel; Vigouroux, Corinne; Mahieu, Emmanuel; Notholt, Justus; Willem Erisman, Jan

    2015-04-01

    Atmospheric Ammonia (NH3) has a major impact on human health and ecosystem services and plays a major role in the formation of aerosols [Erisman et al.,2013; Paulot and Jacob 2014]. NH3 concentrations are highly variable in space and time with overall short lifetime due to deposition and aerosol formation. The global atmospheric budget of nitrogen and in turn NH3 is still uncertain which asks for more ground-based and satellite observations around the world. Recent papers have described the possibility to measure NH3 with satellite infrared sounders which open up the way for calculations of global and regional nitrogen budgets [Clarisse et al 2009,Van Damme et al 2014a]. Validation of the satellite observations is essential to determine the uncertainty in the signal and its potential use. So far available surface layer observations of atmospheric NH3 concentrations have been used for comparisons with total columns retrieved from satellite observations [Van Damme 2014b]. We developed a retrieval for NH3 column density concentrations (molecules NH3/cm2) by fitting a set of spectral windows to ground-based solar absorption Fourier transform infrared (FTIR) measurements with the spectral fitting program SFIT4 [Hase et al., 2004]. The retrieval is then applied to FTIR measurements from a set of spectrometer sites from the Network for detection of Atmospheric Composition Change (NDACC) to retrieve NH3 columns for the sites located in Bremen, Germany; Lauder, New Zealand; Jungfraujoch, Switzerland; and the island of Reunion, France. Using eight years (2005-2013) of retrieved NH3 columns clear seasonal cycles are observed for each of the stations. Maximum concentrations can be related to NH3 emission sources, specific for the regions. A comparison between the retrieved NH3 columns and observations from the recent IASI- NH3 product [Van Damme et al, 2014a] using strict spatial and temporal criteria for the selection of observations showed a good correlation (R=0.82; slope=0

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

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

    PubMed

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

    2016-11-24

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-04-28

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

  17. Surface Properties of CH3NH3PbI3 for Perovskite Solar Cells.

    PubMed

    Haruyama, Jun; Sodeyama, Keitaro; Han, Liyuan; Tateyama, Yoshitaka

    2016-03-15

    Perovskite solar cells (PSCs) have attracted considerable interest because of their high potential for solar energy conversion. Power conversion efficiencies of the PSCs have rapidly increased from 3.8 to over 20% only in the past few years. PSCs have several similarities to dye-sensitized solar cells in their device compositions; mesoporous TiO2 (mp-TiO2) is sensitized by light-absorbing components and placed into a medium containing hole transporting materials (HTMs). On the other hand, the perovskite materials for the light-harvesting, for example, CH3NH3PbI3 (MAPbI3), have a greater advantage for the photovoltaic applications; extremely long photocarrier diffusion lengths (over 1 μm) enable carrier transports without singnificant loss. In this respect, the surface states, that can be possible recombination centers, are also of great importance. Availability of solution processes is another important aspect in terms of low cost fabrication of PSCs. Two-step methods, where PbI2 is first introduced from solution onto a mp-TiO2 film and subsequently transformed into the MAPbI3 by the exposition of a solution containing MAI, suggest that use of such a high PbI2 concentration is crucial to obtain higher performance. The experiments also indicate that the PbI2-rich growth condition modifies TiO2/ or HTM/MAPbI3 interfaces in such a way that the photocarrier transport is improved. Thus, the characteristics of surfaces and interfaces play key roles in the high efficiencies of the PSCs. In this Account, we focus on the structural stability and electronic states of the representative (110), (001), (100), and (101) surfaces of tetragonal MAPbI3, which can be regarded as reasonable model HTM/MAPbI3 interfaces, by use of first-principles calculations. By examining various types of PbIx polyhedron terminations, we found that there are two major phases on all of the four surface facets. They can be classified as vacant- and flat-type terminations, and the former is more stable

  18. Ammonia concentration and modeled emission rates from a beef cattle feedyard

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ambient NH3 concentrations were measured at a beef cattle feedyard during the spring and summer months of 2007. Concentrations were measured every five minutes, 24-hours per day at a sample intake height of 3.3 m using a chemiluminescence analyzer. On site weather data was collected concurrently....

  19. Monitoring a Silent Phase Transition in CH3NH3PbI3 Solar Cells via Operando X-ray Diffraction

    DOE PAGES

    Schelhas, Laura T.; Christians, Jeffrey A.; Berry, Joseph J.; ...

    2016-10-13

    The relatively modest temperature of the tetragonal-to-cubic phase transition in CH3NH3PbI3 perovskite is likely to occur during real world operation of CH3NH3PbI3 solar cells. In this work, we simultaneously monitor the structural phase transition of the active layer along with solar cell performance as a function of the device operating temperature. The tetragonal to cubic phase transition is observed in the working device to occur reversibly at temperatures between 60.5 and 65.4 degrees C. In these operando measurements, no discontinuity in the device performance is observed, indicating electronic behavior that is insensitive to the structural phase transition. Here, this decouplingmore » of device performance from the change in long-range order across the phase transition suggests that the optoelectronic properties are primarily determined by the local structure in CH3NH3PbI3. That is, while the average crystal structure as probed by X-ray diffraction shows a transition from tetragonal to cubic, the local structure generally remains well characterized by uncorrelated, dynamic octahedral rotations that order at elevated temperatures but are unchanged locally.« less

  20. Electron-hole diffusion lengths >175 μm in solution-grown CH3NH3PbI3 single crystals

    DOE PAGES

    Dong, Qingfeng; Fang, Yanjun; Shao, Yuchuan; ...

    2015-02-27

    Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm–2) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smaller trap densities in the single crystals thanmore » in polycrystalline thin films. As a result, the long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source.« less

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

    PubMed

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

    2015-01-02

    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.

  2. 12 CFR Appendix C to Subpart A to... - Concentration Measures

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 12 Banks and Banking 5 2012-01-01 2012-01-01 false Concentration Measures C Appendix C to Subpart...—Concentration Measures The concentration score is the higher of the higher-risk assets to Tier 1 capital and reserves score or the growth-adjusted portfolio concentrations score. The concentration score for...

  3. Kinetics of absorption and transformation of CO2 to Nesquehonite in the Mg-NH3 system

    NASA Astrophysics Data System (ADS)

    Zhu, C.; Zhao, L.; Ji, J.; Jun, C.; Teng, H.

    2012-12-01

    Mineral sequestration of CO2 is one of the safer options in the portfolio of available Carbon Storage and Sequestration (CCS) stratagems. To date, numerous efforts were made to optimize the absorption of CO2 using various media. For example, Satoshi K et al. proposed a pH-swing CO2 mineralization process recycling ammonium chloride to lower the costs of the operation. However, few studies have concerned CO2 absorption kinetics under low CO2 partial pressure. Such lacks of knowledge of absorption rate makes it difficult to estimate the scale and cost of absorption devices and to determine the quantity of stock material supply in industrial settings. The purpose of this research is to investigate the rate and kinetic controlling factors for CO2 absorption and mineralization in MgCl2-NH3 solutions. CO2 absorption experiments were carried out at 298 K in solutions of different compositions (0.05~0.2molL-1 MgCl2) to measure the reaction kinetics using a wetted wall column setup similar to those reported in Pacheco (1998) and Victor (2011). The solution chemistry was maintained at conditions where brucite precipitation was not allowed. The absorption solution was then cycled between the column and a jacked glass reactor with its pH maintained constant, and the transmittance at 546 nm was monitored in real-time. Magnesium concentration was analyzed by ICP-AES with interval sampling. Preliminary results indicate that initial concentration of Mg in solution has little effect on CO2 absorption. Although CO2 absorption rate increased slightly over time with increasing ammonia addition, pH appeared to be the dominant controlling factor. The higher the solution pH was, the faster the absorption rate increased. Upon reaching saturation, nesquehonite precipitated to lower the transmittance, leading to rapid addition of aqueous ammonia. However, precipitation of nesquehonite unexpectedly showed little influence on CO2 absorption, suggesting that the interaction between aqueous CO2

  4. Etude calorimétrique et structure cristalline du putrescinium monohydrogénomonophosphate dihydrate NH 3(CH 2) 4NH 3HPO 42H 2O

    NASA Astrophysics Data System (ADS)

    Kamoun, Slaheddine; Jouini, Amor

    1990-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    PubMed

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

    2009-12-15

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2005-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  11. 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

  12. Room temperature three-photon pumped CH3NH3PbBr3 perovskite microlasers

    PubMed Central

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

    2017-01-01

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

  13. Summer ammonia measurements in a densely populated Mediterranean city

    NASA Astrophysics Data System (ADS)

    Pandolfi, M.; Amato, F.; Reche, C.; Alastuey, A.; Otjes, R. P.; Blom, M. J.; Querol, X.

    2012-08-01

    Real-time measurements of ambient concentrations of gas-phase ammonia (NH3) were performed in Barcelona (NE Spain) in summer between May and September 2011. Two measurement sites were selected: one in an urban background traffic-influenced area (UB) and the other in the historical city centre (CC). Levels of NH3 were higher at CC (5.6 ± 2.1 μg m-3 or 7.5 ± 2.8 ppbv) compared with UB (2.2 ± 1.0 μg m-3 or 2.9 ± 1.3 ppbv). This difference is attributed to the contribution from non-traffic sources such as waste containers, sewage systems, humans and open markets more dense in the densely populated historical city centre. Under high temperatures in summer these sources had the potential to increase the ambient levels of NH3 well above the urban-background-traffic-influenced UB measurement station. Measurements were used to assess major local emissions, sinks and diurnal evolution of NH3. The measured levels of NH3, especially high in the old city, may contribute to the high mean annual concentrations of secondary sulfate and nitrate measured in Barcelona compared with other cities in Spain affected by high traffic intensity. Ancillary measurements, including PM10, PM2.5, PM1 levels (Particulate Matter with aerodynamic diameter smaller than 10 μm, 2.5 μm, and 1 μm), gases and black carbon concentrations and meteorological data, were performed during the measurement campaign. The analysis of specific periods (3 special cases) during the campaign revealed that road traffic was a significant source of NH3. However, its effect was more evident at UB compared with CC where it was masked given the high levels of NH3 from non-traffic sources measured in the old city. The relationship between SO42- daily concentrations and gas-fraction ammonia (NH3/(NH3 + NH4+)) revealed that the gas-to-particle phase partitioning (volatilization or ammonium salts formation) also played an important role in the evolution of NH3 concentration in summer in Barcelona.

  14. Five-year measurements of ambient ammonia and its relationships with other trace gases at an urban site of Delhi, India

    NASA Astrophysics Data System (ADS)

    Saraswati; Sharma, S. K.; Mandal, T. K.

    2017-02-01

    In this study, we present the 5-year measurements of ambient ammonia (NH3), oxides of nitrogen (NO and NO2) and carbon monoxide (CO) along with the meteorological parameters at an urban site of Delhi, India from January 2011 to December 2015. The average mixing ratios of ambient NH3, NO, NO2 and CO over the entire period of observations were recorded as 19.3 ± 4.4 (ppb), 20.1 ± 5.9 (ppb), 18.6 ± 4.6 (ppb) and 1.8 ± 0.5 (ppm), respectively. The mixing ratios of NH3, NO, NO2 and CO were recorded highest during winter season, followed by summer and monsoon season. In the present case, a substantial seasonal variation of NH3 was observed during all the seasons except NO, NO2 and CO. The results emphasized that the traffic could be one of the significant sources of ambient NH3 at the urban site of Delhi as illustrated by positive correlations of NH3 with traffic related pollutants (NO x and CO). Surface wind as well as back trajectory analysis also supports the road side traffic and agricultural activities at the nearby area indicating possible major sources of ambient NH3 at observational site. Trajectory analysis, potential source contribution function and concentration weighted trajectory analysis indicated the surrounding nearby areas (NCR, Haryana, Punjab, Rajasthan and Uttar Pradesh) as a significant source region of ambient NH3 at the observational site of Delhi.

  15. Field methods for measuring concentrated flow erosion

    NASA Astrophysics Data System (ADS)

    Castillo, C.; Pérez, R.; James, M. R.; Quinton, J. N.; Taguas, E. V.; Gómez, J. A.

    2012-04-01

    techniques (3D) for measuring erosion from concentrated flow (pole, laser profilemeter, photo-reconstruction and terrestrial LiDAR) The comparison between two- and three-dimensional methods has showed the superiority of the 3D techniques for obtaining accurate cross sectional data. The results from commonly-used 2D methods can be subject to systematic errors in areal cross section that exceed magnitudes of 10 % on average. In particular, the pole simplified method has showed a clear tendency to understimate areas. Laser profilemeter results show that further research on calibrating optical devices for a variety of soil conditions must be carried out to improve its performance. For volume estimations, photo-reconstruction results provided an excellent approximation to terrestrial laser data and demonstrate that this new remote sensing technique has a promising application field in soil erosion studies. 2D approaches involved important errors even over short measurement distances. However, as well as accuracy, the cost and time requirements of a technique must be considered.

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Spilker, Thomas R.

    1995-01-01

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

  19. COMPARISON OF METHODS FOR MEASURING CONCENTRATIONS OF SEMIVOLATILE PARTICULATE MATTER

    EPA Science Inventory

    The paper gives results of a comparison of methods for measuring concentrations of semivolatile particulate matter (PM) from indoor-environment, small, combustion sources. Particle concentration measurements were compared for methods using filters and a small electrostatic precip...

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    1995-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Tsujimori, Atsushi; Ozaki, Eiichi; Nakao, Kazushige

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

  3. Intense Pulsed Light Sintering of CH3NH3PbI3 Solar Cells.

    PubMed

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

    2016-04-06

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

  4. Electronic structure evolution of fullerene on CH3NH3PbI3

    DOE PAGES

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

    2015-03-19

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  6. 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.

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

    PubMed

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

    2015-03-01

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

  8. 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.

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

    PubMed

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

    2008-12-07

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

  10. Crystal structure, stability, and optoelectronic properties of the organic-inorganic wide-band-gap perovskite CH3NH3BaI3 : Candidate for transparent conductor applications

    NASA Astrophysics Data System (ADS)

    Kumar, Akash; Balasubramaniam, K. R.; Kangsabanik, Jiban; Vikram, Alam, Aftab

    2016-11-01

    Structural stability, electronic structure, and optical properties of CH3NH3BaI3 hybrid perovskite are examined from theory as well as experiment. Solution-processed thin films of CH3NH3BaI3 exhibited a high transparency in the wavelength range of 400-825 nm (1.5-3.1 eV for which the photon current density is highest in the solar spectrum) which essentially justifies a high band gap of 4 eV obtained by theoretical estimation. Also, the x-ray diffraction patterns of the thin films match well with the {00 l } peaks of the simulated pattern obtained from the relaxed unit cell of CH3NH3BaI3 , crystallizing in the I 4 /m c m space group, with lattice parameters, a =9.30 Å, c =13.94 Å. Atom projected density of state and band structure calculations reveal the conduction and valence band edges to be comprised primarily of barium d orbitals and iodine p orbitals, respectively. The larger band gap of CH3NH3BaI3 compared to CH3NH3PbI3 can be attributed to the lower electronegativity coupled with the lack of d orbitals in the valence band of Ba2 +. A more detailed analysis reveals the excellent chemical and mechanical stability of CH3NH3BaI3 against humidity, unlike its lead halide counterpart, which degrades under such conditions. We propose La to be a suitable dopant to make this compound a promising candidate for transparent conductor applications, especially for all perovskite solar cells. This claim is supported by our calculated results on charge concentration, effective mass, and vacancy formation energies.

  11. A comparative study of metal oxide and sulfate catalysts for selective catalytic reduction of NO with NH3.

    PubMed

    Zhu, Lin; Zhong, Zhaoping; Yang, Han; Wang, Chunhua

    2017-05-01

    The properties and characteristics of metal oxide and sulfate catalysts with different active elements for selective catalytic reduction of NO with NH3 were investigated. Cerium-based oxide catalyst showed the widest temperature window for NO x removal and manganese-based oxide catalyst exhibited the best catalytic performance at low temperature. For all the catalysts, the SCR activities at low temperature were directly related with the redox abilities of catalysts. The existence of sulfate groups inhibited the redox abilities of active species for sulfate catalysts compared with the metal oxide catalysts. The catalytic activities of CeWTi-S and MnWTi-S were seriously decreased in contrast to CeWTi-N and MnWTi-N. The temperature window of CuWTi-S was shifted toward higher temperature comparing with CuWTi-N. The FeWTi-N and FeWTi-S catalysts both showed high NO x conversion in the temperature range between 300°C and 400°C and N2O concentrations for iron-based samples were least among the same kind of catalysts. The abundance of acid sites and weak stability of surface sulfate groups for iron- and copper-based sulfate catalysts might be the main reasons accounting for the better NO x conversion in the medium-temperature range.

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

    SciTech Connect

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

    1987-11-01

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

  13. Magnetic properties and critical behavior of the pure and diluted two-dimensional weak ferromagnet (CH3NH3)2Mn1-xCdxCl4

    NASA Astrophysics Data System (ADS)

    Paduan-Filho, A.; Becerra, C. C.

    2002-05-01

    The compound (CH3NH3)2MnCl4 had for a long time been considered a good example of a quasi-two-dimensional Heisenberg antiferromagnet, however, it is a weak ferromagnet with a nearly quadratic layer structure. In this work we measure the magnetization of (CH3NH3)2MnCl4 and the diluted with cadmium compound (CH3NH3)2Mn0.95Cd0.05Cl4. The Néel temperature for the pure sample was determined as TN=44.75 K and a weak-ferromagnetic moment was observed within the nearly quadratic layer (perpendicular to the easy axis). From the measured weak magnetic moment, we estimate a canting angle for the sublattices magnetizations θ˜0.07° from the easy axis. The overall temperature dependence of the weak magnetic moment is the same as that previously measured for the sublattice magnetization in neutron diffraction experiments (as expected). However, close to TN the critical exponent β of the magnetization changes from β1=0.17±0.02 [0.01<(1-T/TN)<0.1] to β2=0.23±0.02 [0.001<(1-T/TN)<0.01] in the immediate neighborhood of TN. In the diluted compound (TN=41.0±0.5 K) and below 0.9TN the magnetization due to the weak component follows the same behavior found for the pure system but closer to TN an almost linear dependence of the magnetization with temperature is observed.

  14. Effect of glow DBD modulation on gas and thin film chemical composition: case of Ar/SiH4/NH3 mixture

    NASA Astrophysics Data System (ADS)

    Vallade, Julien; Bazinette, Remy; Gaudy, Laura; Massines, Françoise

    2014-06-01

    In recent years, atmospheric pressure plasma-enhanced chemical vapour deposition has been identified as a convenient way to deposit good quality thin films. With this type of process, where the gas mixture is injected on one side of the electrodes, the chemical composition of the gas evolves with the gas residence time in the plasma. The consequence is a possible gradient in the chemical composition over the thickness of in-line coatings. The present work shows that the modulation of the plasma with a square signal significantly reduces this gradient while the drawback of low growth rate is avoided by increasing the discharge power. This study deals with plane/plane glow dielectric barrier discharges (DBDs) in an Ar/NH3/SiH4 gas mixture to make thin films. The 50 kHz discharge power of the glow DBD was varied by increasing voltage and modulating excitation. The impact on (i) the plasma development was observed through emission spectroscopy and (ii) the thin film coating through Fourier transform infrared measurements. It is shown that the modulation significantly decreases the time and the energy needed to achieve stable chemistry, enhances secondary chemistry and limits disturbance induced by impurities because of a slower decrease of SiH4 concentration and thus a higher ratio of SiH4/impurities, all very important points for in-line AP-PECVD development. When the growth rate is limited by diffusion, coating growth continues when the discharge is off, so long as there is a precursor gradient between the surface and the gas bulk. A higher discharge power steepens this gradient, which enhances diffusion from the bulk and thus growth rate.

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

    PubMed

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

    2017-03-17

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

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

    PubMed

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

    2015-11-05

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  18. Mapping the Photoresponse of CH3NH3PbI3 Hybrid Perovskite Thin Films at the Nanoscale.

    PubMed

    Kutes, Yasemin; Zhou, Yuanyuan; Bosse, James L; Steffes, James; Padture, Nitin P; Huey, Bryan D

    2016-06-08

    Perovskite solar cells (PSCs) based on thin films of organolead trihalide perovskites (OTPs) hold unprecedented promise for low-cost, high-efficiency photovoltaics (PVs) of the future. While PV performance parameters of PSCs, such as short circuit current, open circuit voltage, and maximum power, are always measured at the macroscopic scale, it is necessary to probe such photoresponses at the nanoscale to gain key insights into the fundamental PV mechanisms and their localized dependence on the OTP thin-film microstructure. Here we use photoconductive atomic force microscopy spectroscopy to map for the first time variations of PV performance at the nanoscale for planar PSCs based on hole-transport-layer free methylammonium lead triiodide (CH3NH3PbI3 or MAPbI3) thin films. These results reveal substantial variations in the photoresponse that correlate with thin-film microstructural features such as intragrain planar defects, grains, grain boundaries, and notably also grain-aggregates. The insights gained into such microstructure-localized PV mechanisms are essential for guiding microstructural tailoring of OTP films for improved PV performance in future PSCs.

  19. Effects of SO2 on selective catalytic reduction of NO with NH3 over a TiO2 photocatalyst

    NASA Astrophysics Data System (ADS)

    Yamamoto, Akira; Teramura, Kentaro; Hosokawa, Saburo; Tanaka, Tsunehiro

    2015-04-01

    The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst.

  20. Effects of SO2 on selective catalytic reduction of NO with NH3 over a TiO2 photocatalyst

    PubMed Central

    Yamamoto, Akira; Hosokawa, Saburo; Tanaka, Tsunehiro

    2015-01-01

    The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst. PMID:27877768

  1. Photoluminescence characterisations of a dynamic aging process of organic-inorganic CH3NH3PbBr3 perovskite

    NASA Astrophysics Data System (ADS)

    Sheng, R.; Wen, X.; Huang, S.; Hao, X.; Chen, S.; Jiang, Y.; Deng, X.; Green, M. A.; Ho-Baillie, A. W. Y.

    2016-01-01

    After unprecedented development of organic-inorganic lead halide perovskite solar cells over the past few years, one of the biggest barriers towards their commercialization is the stability of the perovskite material. It is thus important to understand the interaction between the perovskite material and oxygen and/or humidity and the associated degradation process in order to improve device and encapsulation design for better durability. Here we characterize the dynamic aging process in vapour-assisted deposited (VASP) CH3NH3PbBr3 perovskite thin films using advanced optical techniques, such as time-resolved photoluminescence and fluorescence lifetime imaging microscopy (FLIM). Our investigation reveals that the perovskite grains grow spontaneously and the larger grains are formed at room temperature in the presence of moisture and oxygen. This crystallization process leads to a higher density of defects and a shorter carrier lifetime, specifically in the larger grains. Excitation-intensity-dependent steady-state photoluminescence shows both N2 stored and aged perovskite exhibit a super-linear increase of photoluminescence intensity with increasing excitation intensity; and the larger slope in aged sample suggests a larger density of defects is generated, consistent with time-resolved PL measurements.

  2. High intrinsic carrier mobility and photon absorption in the perovskite CH3NH3PbI3.

    PubMed

    Wang, Youwei; Zhang, Yubo; Zhang, Peihong; Zhang, Wenqing

    2015-05-07

    The carrier transport and optical properties of the hybrid organic-inorganic perovskite CH3NH3PbI3 are investigated using first-principles approaches. We found that the electron and hole mobilities could reach surprisingly high values of 7-30 × 10(3) and 1.5-5.5 × 10(3) cm(2) V(-1) s(-1), respectively, and both are estimated to be much higher than the current experimental measurements. The high carrier mobility is ascribed to the intrinsically small effective masses of anti-bonding band-edge states. The above results imply that there is still space to improve the performance of related solar cells. This material also has a sharp photon absorption edge and an absorption coefficient as high as 10(5) cm(-1), both of which contribute to effective utilization of solar radiation. Although band-edge states are mainly derived from the inorganic ions of Pb and I, thermal movement of the organic base has indirect influences on the bandgap and carrier effective masses, resulting in the temperature-dependent solar cell efficiencies.

  3. Effects of SO2 on selective catalytic reduction of NO with NH3 over a TiO2 photocatalyst.

    PubMed

    Yamamoto, Akira; Teramura, Kentaro; Hosokawa, Saburo; Tanaka, Tsunehiro

    2015-04-01

    The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst.

  4. 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

    2015-12-14

    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 μ-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.

  5. 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.

  6. Experimental (FT-IR and FT-RS) and theoretical (QC-DFT) studies of vibrational modes and molecular structure of new low-temperature phases of [Ru(NH3)6](BF4)3 and [Ru(NH3)6](ClO4)3.

    PubMed

    Dołęga, Diana; Mikuli, Edward; Chruszcz-Lipska, Katarzyna

    2012-12-01

    Vibrational spectra of [Ru(NH(3))(6)](BF(4))(3) and [Ru(NH(3))(6)](ClO(4))(3) in their novel low-temperature solid phases were recorded using FT-IR and FT-RS. Quantum chemical calculations of molecular structure and vibrational modes were made separately for BF(4)(-),ClO(4)(-)and[Ru(NH(3))(6)](3+) ions. The harmonic vibrational frequencies and the related IR and RS bands intensities and activities, respectively, were simulated at the B3LYP/6-311+G(d) and B3LYP/LANL2TZ(f)/6-311+G(d,p) levels of the DFT. Full interpretation of the vibrational spectra has been carried out with the aid of the normal coordinate analysis. The assignments of the vibrational modes were based on the potential energy distribution data, using the MOLVIB program. The calculated Ru-N stretching frequencies are too low, in comparison to experiment, which indicates that B3LYP method underestimates the Ru-N bond strength. Some values of calculated and measured (obtained from X-ray) bond lengths and angles were also compared. Conclusions about possible interactions inside and between the complex ions were drawn.

  7. 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

  8. Measurements of ambient ammonia using a tunable diode laser absorption spectrometer: Characteristics of ambient ammonia emissions in an urban area of New York City

    NASA Astrophysics Data System (ADS)

    Li, Yongquan; Schwab, James J.; Demerjian, Kenneth L.

    2006-05-01

    A tunable diode laser absorption spectrometer (TDLAS) was deployed during the PMTACS-NY Supersite winter 2004 intensive field campaign at Queens College in New York City to measure the ambient gaseous ammonia. For the characterization of ammonia emissions from the mobile sources, a LI-7000 CO2/H2O analyzer was also collocated with the TDLAS to measure ambient CO2 and H2O vapor. The field measurements and laboratory calibration with certified ammonia standard have been used to evaluate the performance of the TDLAS system. High time resolved TDLAS ambient ammonia measurements performed at Queens College from 10 January to 6 February showed high variability, with NH3 concentrations ranging from below the detection limit (0.1 ppb) to maxima of 197.4 ppb and a mean value of 0.8 ppb over the entire campaign. Many high-frequency NH3 spikes spanning over a less than 1-min duration were observed during the high traffic periods. The occurrence of the NH3 spikes was closely correlated with observed CO2 spikes, a good marker of traffic exhaust. This correlation yielded an NH3 emission ratio of 0.12 ppbv/ppmv, which can be used to estimate an NH3 emission factor of 35.5 mg/km. The [NH3]/[CO2] ratios over the entire field study was also obtained and added into the best NH3 emission estimates. On a snowy day, no obvious drop of NH3 and CO2 concentrations was measured as the ambient H2O vapor increased. The observed dramatic decrease in the ambient NH3 and CO2 concentrations on a rainy day resulted from a quick air mass switch. Two similar bimodal diurnal patterns associated with the rush hour traffic were observed during school holidays and school days of Queens College, New York. More NH3 emissions from cold start vehicles might contribute to a higher peak in the late afternoon hours. Such observations suggest that the NH3 emissions from the traffic exhaust could be a major source of the ambient NH3 in urban areas.

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

    SciTech Connect

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

    1995-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2000-11-01

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

  14. Isolation of Polypeptide Sample and Measurement of Its Concentration.

    ERIC Educational Resources Information Center

    Beanan, Maureen J.

    2000-01-01

    Introduces a laboratory experiment that isolates a bacterial polypeptide sample and measures the concentration of polypeptides in the sample. Uses Escherichia coli strain MM294 and performs a bio-rad assay to determine the concentration of polypeptides. (YDS)

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

    PubMed

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

    2007-08-15

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

  16. Effects of SbBr3 addition to CH3NH3PbI3 solar cells

    NASA Astrophysics Data System (ADS)

    Oku, Takeo; Ohishi, Yuya; Suzuki, Atsushi

    2017-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Esmaili, Sasan

    2015-08-01

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

  18. 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.

  19. Ozone concentration in the cabin of a Gates Learjet measured simultaneously with atmospheric ozone concentrations

    NASA Technical Reports Server (NTRS)

    Briehl, D.; Perkins, P. J.

    1978-01-01

    A Gates Learjet Model 23 was instrumented with monitors to measure simultaneously the atmospheric and the cabin concentrations of ozone at altitudes up to 13 kilometers. Six data flights were made in February 1978. Results indicated that only a small amount of the atmospheric ozone is destroyed in the cabin pressurization system. Ozone concentrations measured in the cabin near the conditioned-air outlets were only slightly lower than the atmospheric ozone concentration. For the two cabin configurations tested, the ozone retention in the cabin was 63 and 41 percent of the atmospheric ozone concentration. Maximum cabin ozone concentration measured during these flights was 410 parts per billion by volume.

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

    PubMed

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

    2011-03-16

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

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

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

    PubMed

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

    2014-09-04

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

  3. Promotional effect of fluorine on the selective catalytic reduction of NO with NH3 over CeO2-TiO2 catalyst at low temperature

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Zhong, Qin; Zhao, Wei; Yu, Lemeng; Qu, Hongxia

    2014-01-01

    In order to investigate the effect of F on CeO2-TiO2 catalyst for the selective catalytic reduction (SCR) of NO with NH3, a series of F-doped CeO2-TiO2 catalysts were prepared by co-precipitation method. Compared with Ce0.3TiF0 catalyst, Ce0.3TiF1.5 catalyst exhibited the best catalytic activity, yielding 92.19% NO conversion at 180 °C. The catalysts were characterized by Brunauer-Emmett-Teller (BET) surface area, X-ray powder diffraction (XRD), photoluminescence (PL) spectra, Raman spectra, X-ray photoelectron spectroscopy (XPS) and Diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques. It was found that the enhanced catalytic activity was ascribed to several beneficial effects produced by the introduction of F: inhibition of the crystallization, decrease of the particle size, increase of the oxygen vacancies (F+ centers) and lattice defects. Raman measurements disclosed the formation of superoxide (O2-) ions in chemisorbed oxygen which was crucial for the formation of reaction intermediates (NO2-, NO3-). The study of DRIFTS proved that the addition of F could bring more ad-NOx and reaction intermediates. The NH3-TPD studies confirmed that the right amount of F could improve the number of acid sites over CeO2-TiO2 catalyst, especially the Lewis acid sites. These factors simultaneously enhanced the catalytic activity for NH3-SCR of NO. The effect of H2O and SO2 on the NO conversion was also investigated in our work.

  4. Quasi-two-dimensional S =1/2 magnetism of Cu[ C6H2 (COO)4][ C2H5NH3 ] 2

    NASA Astrophysics Data System (ADS)

    Nath, R.; Padmanabhan, M.; Baby, S.; Thirumurugan, A.; Ehlers, D.; Hemmida, M.; Krug von Nidda, H.-A.; Tsirlin, A. A.

    2015-02-01

    We report structural and magnetic properties of the spin-1/2 quantum antiferromagnet Cu[ C6H2(COO) 4 ][ C2H5NH3 ] 2 by means of single-crystal x-ray diffraction, magnetization, heat capacity, and electron-spin-resonance (ESR) measurements on polycrystalline samples, as well as band-structure calculations. The triclinic crystal structure of this compound features CuO4 plaquette units connected into a two-dimensional framework through anions of the pyromellitic acid [ C6H2(COO) 4 ]4 -. The ethylamine cations [ C2H5NH3]+ are located between the layers and act as spacers. Magnetic susceptibility and heat capacity measurements establish a quasi-two-dimensional, weakly anisotropic, and nonfrustrated spin-1/2 square lattice with the ratio of the couplings Ja/Jc≃0.7 along the a and c directions, respectively. No clear signatures of the long-range magnetic order are seen in thermodynamic measurements down to 1.8 K. However, the gradual broadening of the ESR line suggests that magnetic ordering occurs at lower temperatures. Leading magnetic couplings are mediated by the organic anion of the pyromellitic acid and exhibit a nontrivial dependence on the Cu-Cu distance, with the stronger coupling between those Cu atoms that are farther apart.

  5. α- to β-[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

    α-[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 π-π) changes, α-phase was transformed into the corresponding centrosymmetric β-phase, β-[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, β-[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 α-[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.

  6. Operational characteristics of efficient co-removal of H2S and NH3 in a horizontal biotrickling filter using exhausted carbon.

    PubMed

    Jiang, Xia; Tay, Joo Hwa

    2010-04-15

    Odorous H(2)S and NH(3) gases were effectively biodegraded in a horizontal biotrickling filter (HBTF) packed with H(2)S-exhausted carbon. During the process, the operational characteristics including the distribution of degradation products, biomass accumulation and biological activity, carbon surface characteristics and pressure drop were investigated. The results show that the content of biodegradation products on carbon was low, i.e. 0.9-2.8 wt% S and 0.3-1.0 wt% N. The low content benefited the stable operation of the HBTF, due to preventing a toxic concentration of degradation products on packing bed over a long-term operation. The biomass was distributed evenly along the HBTF . This avoided the problems of bed clogging and activity loss. On the other hand, the deteriorated performance was observed due to the biomass accumulation over a long-term operation. Carbon surface characteristics in the HBTF remained almost unchanged. pH values of carbon were neutral and micropore structure of carbon remained relatively stable. In addition, the pressure drop in the HBTF was very low. These operational characteristics of the HBTF system significantly contributed to efficient co-removal of H(2)S and NH(3) in the HBTF over a long-term operation.

  7. Instability and efficiency of mixed halide perovskites CH3NH3AI3-xClx (A = Pb and Sn): A first-principles, computational study

    DOE PAGES

    He, Yuping; Galli, Giulia

    2016-12-14

    Here, we carried out calculations based on density functional theory to investigate the electronic, vibrational, and dielectric properties of mixed halide perovskites CH3NH3AI3–xClx with A = Pb and Sn. Computed free energies indicated that Cl mixed systems may be formed only for Cl concentrations not exceeding 1019 cm–3, and phonon calculations showed that the disorder induced in the host lattice by the presence of a smaller halogen is responsible for mechanical instabilities. However, we found that the presence of chloride may be beneficial to the electronic properties of the perovskites. Chloride anions cause the organic cations to be displaced frommore » the center of the cage; such a displacement induces preferential orientations of the cation dipole, which in turn are responsible for notable changes in the dielectric properties of the material and possibly for the formation of local ferroelectric domains. The latter are instrumental in separating electron hole pairs and hence in contributing to long charge-carrier diffusion lengths, in spite of polarons being more likely formed in mixed perovksites than in CH3NH3AI3.« less

  8. CH 4/NH 3/H 2O spark tholin: Chemical analysis and interaction with Jovian aqueous clouds

    NASA Astrophysics Data System (ADS)

    McDonald, Gene D.; Khare, Bishun N.; Reid Thompson, W.; Sagan, Carl

    1991-12-01

    The organic solid (tholin) produced by spark discharge in a CH 4 + NH 3 + H 2O atmosphere is investigated, along with the separable components of its water-soluble fraction. The chemistry of this material serves as a provisional model for the interaction of Jovian organic heteropolymers with the deep aqueous clouds of Jupiter. Intact (unhydrolyzed) tholin is resolved into four chemically distinct fractions by high-pressure liquid chromatography (HPLC). Gel filtration chromatography reveals abundant components at molecular weights ⋍600-700 and 200-300 Da. Gas chromatography/mass spectrometry of derivatized hydrolysis products of unfractionated tholin shows about 10% by mass protein and nonprotein amino acids, chiefly glycine, alanine, aspartic acid, β-alanine, and β-aminobutyric acid, and 12% by mass other organic acids and hydroxy acids. The stereospecificity of alanine is investigated and shown to be racemic. The four principal HPLC fractions yield distinctly different proportions of amino acids. Chemical tests show that small peptides or organic molecules containing multiple amino acid precursors are a possibility in the intact tholins, but substantial quantities of large peptides are not indicated. Candidate 700-Da molecules have a central unsaturated, hydrocarbon- and nitrile-rich core, linked by acid-labile (ester or amide) bonds to amino acid and carboxylic acid side groups. The core is probably not HCN "polymer." The concentration of amino acids from tholin hydrolysis in the lower aqueous clouds of Jupiter, about 0.1 μ M, is enough to maintain small populations of terrestrial microorganisms even if the amino acids must serve as the sole carbon source.

  9. Hot ammonia around young O-type stars. I. JVLA imaging of NH3 (6, 6) to (14, 14) in NGC 7538 IRS1

    NASA Astrophysics Data System (ADS)

    Goddi, C.; Zhang, Q.; Moscadelli, L.

    2015-01-01

    Context. The formation of massive (O-type) stars through the same accretion processes as low-mass stars is problematic, mainly because of the feedback massive stars provide to the environment, which halts the accretion. In order to constrain theoretical models of high-mass star formation, observational signatures of mass accretion in O-type forming stars are desirable. The high-mass star forming region NGC 7538 IRS1 (distance = 2.7 kpc) is an ideal target, because VLBI measurements of CH3OH masers recently identified a triple system of high-mass young stellar object (YSOs) in the region: IRS1a, IRS1b, and IRS1c. The first two YSOs seem to be surrounded by rotating disks. Aims: We want to characterize physical conditions and kinematics of circumstellar molecular gas around O-type young stars. Sub-arcsecond resolution observations of highly-excited lines from high-density tracers are useful, since these probe the hottest and densest gas, which presumably is close to O-type forming stars, i.e., in disks and the innermost portions of envelopes. Methods: Using the Karl Jansky Very Large Array (JVLA), we have mapped the hot and dense molecular gas in the hot core associated with NGC 7538 IRS1, with ~0.''2 angular resolution, in seven metastable (J = K) inversion transitions of ammonia (NH3): (J,K) = (6, 6), (7, 7), (9, 9), (10, 10), (12, 12), (13, 13), and (14, 14). These lines arise from energy levels between ~400 K and ~1950 K above the ground state, and are observed in absorption against the HC-HII region associated with NGC 7538 IRS1. The CH3OH JK = 132 - 131 and CH3CN (2-1) lines were also included in our spectral setup, but only the former was detected. We also obtained sensitive continuum maps at frequencies between 25 and 35 GHz. Results: For each transition, we produced resolved images of total intensity and velocity field, as well as position-velocity diagrams. The intensity maps show that the NH3 absorption follows the continuum emission closely. With a 500 AU

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

    PubMed

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

    2015-12-01

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

  11. Laser-initiated channels for ion transport: CO2-laser absorption and heating of NH3 and C2H4 gases

    NASA Astrophysics Data System (ADS)

    Olsen, J. N.

    1981-05-01

    Initiation and guiding of an electrical discharge by CO2-laser heating of a molecular gas can provide a channel suitable for the transport of a light ion beam for inertial-confinement fusion. We report absorption measurements for a CO2 laser tuned to the molecular vibrations of NH3 and C2H4 as a function of gas pressure, laser frequency, and laser energy density. The SATUR laser-gas-interaction code models the details of the absorption saturation process for NH3, calculating gas temperature in the process. The calculation is normalized to absorption data at 0.04 J/cm2 and tested with transmission measurements up to 15 J/cm2 into a 50-cm cell. These calculations are the basis for understanding the electrical breakdown and discharge evolution as observed and simulated in the following report. Of particular importance is the calculation of gas temperature of 1900-2100 °K for 15-35-J/cm2 incident laser energy density.

  12. Morphological and luminescent characteristics of GaN dots deposited on AlN by alternate supply of TMG and NH 3

    NASA Astrophysics Data System (ADS)

    Tsai, Yu-Li; Gong, Jyh-Rong; Lin, Tai-Yuan; Lin, Hsia-Yu; Chen, Yang-Fang; Lin, Kun-Ming

    2006-03-01

    GaN dots were deposited on AlN underlayers by alternate supply of trimethylgallium (TMG) and ammonia (NH 3) in an inductively heated quartz reactor operated at atmospheric pressure. Various growth parameters including deposition temperature, TMG admittance and pulse time between TMG and NH 3 exposures were proposed to investigate the influence of growth parameters on the size distribution of GaN dots. It appears that GaN dots with uniform size distribution can be achieved under certain growth conditions. Based on the study of atomic force microscopy (AFM), high deposition temperature was found to be in favor of forming large GaN dots with small dot density. Decrement of TMG flow rate or reduction in the number of growth cycle tends to enable the formation of GaN dots with small dot sizes. The results of room temperature (RT) cathodoluminescence (CL) measurements of the GaN dots exhibit an emission peak at 3.735 eV. A remarkable blue shift of GaN dot emission was observed by reduced temperature photoluminescence (PL) measurements.

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

    PubMed

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

    2002-03-07

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

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

    PubMed

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Jung, Sung-Hoon; Kang, Sang-Won

    2001-05-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-04-01

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

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Hiraoka, Kenzo; Mochizuki, Noritaka; Wada, Akira

    2006-09-01

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

  20. Charge transport in bulk CH3NH3PbI3 perovskite

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

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

    PubMed

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

    2013-02-21

    The adsorption of CO and NO over Cu-SSZ-13 zeolite catalysts, highly active in the selective catalytic reduction of NO(x) with NH(3), was investigated by FTIR spectroscopy, and the results obtained were compared to those collected from other Cu-ion exchanged zeolites (Y,FAU and ZSM-5). Under low CO pressures and at room temperature (295 K), CO forms monocarbonyls exclusively on the Cu(+) ions, while in the presence of gas phase CO dicarbonyls on Cu(+) and adsorbed CO on Cu(2+) centers form, as well. At low (cryogenic) sample temperatures, tricarbonyl formation on Cu(+) sites was also observed. The adsorption of NO produces IR bands that can be assigned to nitrosyls bound to both Cu(+) and Cu(2+) centers, and NO(+) species located in charge compensating cationic positions of the chabasite framework. On the reduced Cu-SSZ-13 samples the formation of N(2)O was also detected. The assignment of the adsorbed NO(x) species was aided by adsorption experiments with isotopically labeled (15)NO. The movement of Cu ions from the sterically hindered six member ring position to the more accessible cavity positions as a result of their interaction with adsorbates (NO and H(2)O) was clearly evidenced. Comparisons of the spectroscopy data obtained in the static transmission IR system to those collected in the flow-through diffuse reflectance cell points out that care must be taken when general conclusions are drawn about the adsorptive and reactive properties of metal cation centers based on a set of data collected under well defined, specific experimental conditions.

  2. Spatial variability of ammonia and methane dairy emissions in the Central Valley, California with open-path mobile measurements during NASA DISCOVER-AQ 2013

    NASA Astrophysics Data System (ADS)

    Miller, D. J.; Sun, K.; Tao, L.; Zondlo, M. A.

    2013-12-01

    Atmospheric ammonia (NH3) is an important fine aerosol gas-phase precursor, with implications for regional air quality and climate change. Atmospheric methane (CH4) is an important greenhouse gas, with high uncertainties in the partitioning of various emission sources. Ammonia and methane agricultural emissions are highly variable in space and time and are highly uncertain, with a lack of widespread, in-situ measurements. We characterize the spatial variability of dairy livestock emissions by performing high resolution (5 Hz), in-situ, on-road mobile measurements of NH3, CH4, CO2, N2O, CO and H2O simultaneously with open-path sensors mounted on a passenger vehicle. This suite of multiple trace gas measurements allows for emission ratio calculations and separation of agricultural, petrochemical and combustion emission signatures. Mobile measurements were performed in the Tulare County dairy farm region (~120 dairy farms sampled downwind) in the Central Valley, California during NASA DISCOVER-AQ in winter 2013. We calculate the ΔNH3/ΔCH4 and ΔNH3/ΔCO2 emission ratios for each dairy farm sampled downwind. Emission plumes from individual farms are isolated based on known dairy farm locations and high resolution (1 km) surface wind field simulations. Background concentrations are subtracted to calculate the emission ratios. We find high spatial variability of ammonia and methane concentrations, with localized maximums of >1 ppmv NH3 downwind of individual dairy farms. The spatial extent of individual farm emission plumes are evaluated for NH3, CH4 and CO2, which all show well-defined enhancements localized to the dairy farms near the roadside (typical sampling proximity of ≤ 50 m). The NH3 concentrations are correlated with the distance from each dairy farm. The observed median concentration within 100 m downwind of the dairy farms is 63 ppbv NH3, with the 95th percentile at 417 ppbv NH3 and decreases to background conditions at ~500 m distance downwind. The

  3. Absolute concentration measurements inside a jet plume using video digitization

    NASA Astrophysics Data System (ADS)

    Vauquelin, O.

    An experimental system based on digitized video image analysis is used to measure the local value of the concentration inside a plume. Experiments are carried out in a wind-tunnel for a smoke-seeded turbulent jet plume illuminated with a laser beam. Each test is filmed, subsequently video images are digitized and analysed in order to determine the smoke absolute concentration corresponding to each pixel gray level. This non-intrusive measurement technique is first calibrated and different laws connecting gray level to concentration are established. As a first application, concentration measurements are made inside a turbulent jet plume and compared with measurements conducted using a classic gas analysis method. We finally present and discuss the possibilities offered for the measurements of absolute concentration fluctuations.

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

    PubMed

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

    2016-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

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

    PubMed

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

    2007-06-15

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

  7. Ab initio based potential energy surface and kinetics study of the OH + NH3 hydrogen abstraction reaction.

    PubMed

    Monge-Palacios, M; Rangel, C; Espinosa-Garcia, J

    2013-02-28

    A full-dimensional analytical potential energy surface (PES) for the OH + NH3 → H2O + NH2 gas-phase reaction was developed based exclusively on high-level ab initio calculations. This reaction presents a very complicated shape with wells along the reaction path. Using a wide spectrum of properties of the reactive system (equilibrium geometries, vibrational frequencies, and relative energies of the stationary points, topology of the reaction path, and points on the reaction swath) as reference, the resulting analytical PES reproduces reasonably well the input ab initio information obtained at the coupled-cluster single double triple (CCSD(T)) = FULL/aug-cc-pVTZ//CCSD(T) = FC/cc-pVTZ single point level, which represents a severe test of the new surface. As a first application, on this analytical PES we perform an extensive kinetics study using variational transition-state theory with semiclassical transmission coefficients over a wide temperature range, 200-2000 K. The forward rate constants reproduce the experimental measurements, while the reverse ones are slightly underestimated. However, the detailed analysis of the experimental equilibrium constants (from which the reverse rate constants are obtained) permits us to conclude that the experimental reverse rate constants must be re-evaluated. Another severe test of the new surface is the analysis of the kinetic isotope effects (KIEs), which were not included in the fitting procedure. The KIEs reproduce the values obtained from ab initio calculations in the common temperature range, although unfortunately no experimental information is available for comparison.

  8. (CH3 NH3 )2 PdCl4 : A Compound with Two-Dimensional Organic-Inorganic Layered Perovskite Structure.

    PubMed

    Huang, Tang Jiao; Thiang, Zhang Xian; Yin, Xuesong; Tang, Chunhua; Qi, Guojun; Gong, Hao

    2016-02-01

    The synthesis of previously unknown perovskite (CH3 NH3 )2 PdCl4 is reported. Despite using an organic cation with the smallest possible alkyl group, a 2D organic-inorganic layered Pd-based perovskites was still formed. This demonstrates that Pd-based 2D perovskites can be obtained even if the size of the organic cation is below the size limit predicted by the Goldschmidt tolerance-factor formula. The (CH3 NH3 )2 PdCl4 phase has a bulk resistivity of 1.4 Ω cm, a direct optical gap of 2.22 eV, and an absorption coefficient on the order of 10(4)  cm(-1) . XRD measurements suggest that the compound is moderately stable in air, an important advantage over several existing organic-inorganic perovskites that are prone to phase degradation problems when exposed to the atmosphere. Given the recent interest in organic-inorganic perovskites, the synthesis of this new Pd-based organic-inorganic perovskite may be helpful in the preparation and understanding of other organic-inorganic perovskites.

  9. Antiferroelectric Nature of CH3NH3PbI3‑xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Sewvandi, Galhenage A.; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

    2016-07-01

    Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3‑xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3‑xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation.

  10. Antiferroelectric Nature of CH3NH3PbI3−xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells

    PubMed Central

    Sewvandi, Galhenage A.; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

    2016-01-01

    Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3−xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3−xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation. PMID:27468802

  11. A new analysis of charge transfer and polarization for ligand-metal bonding - Model studies of Al4CO and Al4NH3

    NASA Technical Reports Server (NTRS)

    Bagus, P. S.; Hermann, K.; Bauschlicher, C. W., Jr.

    1984-01-01

    The nature of the bonding of CO and NH3 ligands to Al is analyzed, and the intra-unit charge polarization and inter-unit donation for the interaction of ligands with metals are studied. The consequences of metal-to-ligand and ligand-to-metal charge transfer are separately considered by performing a constrained space orbital variation (CSOV) with the electrons of the metal member of the complex in the field of frozen ligand. The electrons of the metal atoms are then frozen in the relaxed distribution given by the CSOV SCF wave function and the ligand electrons are allowed to relax. Quantitative measures of the importance of inter-unit charge transfers and intra-unit polarization are obtained using results of SCF studies of Al4CO and Al4NH3 clusters chosen to simulate the adsorption of the ligands at an on-top side of the Al(111) surface. The electrostatic attraction of the effective dipole moments of the metal and ligand units makes an important contribution to the bond.

  12. The role of isolated Cu2+ location in structural stability of Cu-modified SAPO-34 in NH3-SCR of NO.

    PubMed

    Yan, Chundi; Cheng, Hao; Yuan, Zhongshan; Wang, Shudong

    2015-01-01

    In this study, three different methods (ion exchange, wet mixing and impregnation) were employed to prepare Cu-modified SAPO-34 molecular sieves. All these freshly prepared catalysts showed excellent activities towards the selective catalytic reduction (SCR) of NO with NH3 (NH3-SCR) no matter which preparation method was used. However, hydrothermal ageing significantly reduced the catalytic activities of those catalysts prepared by the wet-mixing and impregnation methods, respectively. The results of X-ray powder diffraction, H2-TPR and electron paramagnetic resonance measurements for these catalysts suggested that the decrease in catalytic activity may be attributed to the migration of Cu2+ ion to the centre of the hexagonal prism (site III), the formation of CuxOy and the collapse of the molecular framework during hydrothermal ageing. The degrees of structural collapse of each Cu-modified molecular sieve were different, probably due to Cu2+ species in different sites (in the ellipsoidal cavity (site I) for ion-exchange sample, near the eight-ring window (site IV) for the wet-mixing and impregnation samples). Cu2+ located at site I was more stable than that located at site IV.

  13. Optical analysis of CH3NH3Sn x Pb1-x I3 absorbers: a roadmap for perovskite-on-perovskite tandem solar cells.

    PubMed

    Anaya, Miguel; Correa-Baena, Juan P; Lozano, Gabriel; Saliba, Michael; Anguita, Pablo; Roose, Bart; Abate, Antonio; Steiner, Ullrich; Grätzel, Michael; Calvo, Mauricio E; Hagfeldt, Anders; Míguez, Hernán

    2016-08-07

    Organic-inorganic perovskite structures in which lead is substituted by tin are exceptional candidates for broadband light absorption. Herein we present a thorough analysis of the optical properties of CH3NH3Sn x Pb1-x I3 films, providing the field with definitive insights about the possibilities of these materials for perovskite solar cells of superior efficiency. We report a user's guide based on the first set of optical constants obtained for a series of tin/lead perovskite films, which was only possible to measure due to the preparation of optical quality thin layers. According to the Shockley-Queisser theory, CH3NH3Sn x Pb1-x I3 compounds promise a substantial enhancement of both short circuit photocurrent and power conversion efficiency in single junction solar cells. Moreover, we propose a novel tandem architecture design in which both top and bottom cells are made of perovskite absorbers. Our calculations indicate that such perovskite-on-perovskite tandem devices could reach efficiencies over 35%. Our analysis serves to establish the first roadmap for this type of cells based on actual optical characterization data. We foresee that this study will encourage the research on novel near-infrared perovskite materials for photovoltaic applications, which may have implications in the rapidly emerging field of tandem devices.

  14. 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 β phase structure of CH3NH3Sn(x)Pb(1-x)I3 for x < 0.5 and the α 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.

  15. Emissions of NH3, CO2 and H2S during swine wastewater management: Characterization of transient emissions after air-liquid interface disturbances

    NASA Astrophysics Data System (ADS)

    Blanes-Vidal, V.; Guàrdia, M.; Dai, X. R.; Nadimi, E. S.

    2012-07-01

    Air contaminants emitted from stored animal wastewater affect human health and the environment. Measurements of gaseous emissions from undisturbed animal wastewater are abundant in the literature. However, in-barn wastewater management is characterized by the frequent occurrence of surface liquid disturbances. Information about emissions during and after wastewater disturbances is scarce. This study evaluates emissions of NH3, CO2 and H2S under transient conditions after wastewater disturbances (caused by slurry addition, water addition and mixing), and describes the mechanisms involved until reaching steady-state conditions. All three disturbances modified the gas emission patterns. Emissions of NH3 immediately decreased after the disturbances (-61% after slurry and water addition and by -91% after mixing), and then gradually increased during 90-200 min. Emissions of CO2 increased during the disturbances (40% during slurry and water addition and 1515% during mixing), and then decreased during up to 30 min after the disturbance. H2S emissions sharply increased during all three disturbances and then decreased for 2 min to 20 min. Emissions under transient conditions were related to the formation of a pH profile. Transient emissions should be considered in gas emission studies as they may represent an important part of the cumulative gas emissions during slurry storage.

  16. Characterization of organic-inorganic hybrid layered perovskite and intercalated compound (n-C12H25NH3)2ZnCl4

    NASA Astrophysics Data System (ADS)

    Abdel-Kader, M. M.; Aboud, A. I.; Gamal, W. M.

    2016-05-01

    We report on some electrical properties and solid-solid phase transitions of organic-inorganic hybrid layered halide perovskite and intercalated compound (n-C12H25NH3)2ZnCl4 which is one member of the long-chain compounds of the series (n-CnH2n+1NH3)2,(n = 8-18). The complex dielectric permittivity ɛ*(ω,T) and the ac conductivity σ (ω,T) were measured as functions of temperature 100 K < T < 390 K and frequency 5 kHz < f < 100 kHz. Moreover, the differential scanning calorimetery and the differential thermal analysis thermograms were performed. The analysis of our data confirms the existence of a structural phase transition at T ≈ (362 ± 2) K, where the compound changes its state from intercalation to non-intercalation with a drastic increase in the c-axis by about 16.4%. The behavior of the frequency-dependent conductivity follows the Jonscher universal power law: σ (ω, T) αῳs(ῳ,T). The mechanism of electrical conduction in the low-temperature phase (phase II) can be described as quantum mechanical tunneling model.

  17. Time delay for aerial ammonia concentration measurements in livestock buildings.

    PubMed

    Rom, Hans Benny; Zhang, Guo-Qiang

    2010-01-01

    Correct measurements of ammonia concentration in air still present considerable challenges. The high water solubility and polarity can cause it to adsorb on surfaces in the entire sampling system, including sampling lines, filters, valves, pumps and instruments, causing substantial measuring errors and time delays. To estimate time delay characteristics of a Photo Acoustic Multi Gas Monitor 1312 and a Multi Point Sampler continuous measurement of aerial ammonia concentrations at different levels was performed. In order to obtain reproducible data, a wind tunnel was used to generate selected concentrations inside and a background concentration representing the air inlet of the tunnel. Four different concentration levels (0.8 ppm, 6.2 ppm, 9.7 ppm and 13.7 ppm) were used in the experiments, with an additional outdoor concentration level as background. The results indicated a substantial time delay when switching between the measuring positions with high and low concentration and vice versa. These properties may course serious errors for estimation of e.g. gas emissions whenever more than one measuring channel is applied. To reduce the measurement errors, some suggestions regarding design of the measurement setup and measuring strategies were presented.

  18. 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.

  19. Defining the smallest analyte concentration an immunoassay can measure.

    PubMed

    Brown, E N; McDermott, T J; Bloch, K J; McCollom, A D

    1996-06-01

    An immunoassay's minimal detectable concentration (MDC), the smallest analyte concentration the assay can reliably measure, is one of its most important properties. Bayes' theorem is used to unify the five current mathematical MDC definitions. The unified definition has significant implications for defining positive results for screening and diagnostic tests, setting criteria for immunoassay quality control and optimal design, reliably measuring biological substances at low concentrations, and, in general, measuring small analyte concentrations with calibrated analytic methods. As an illustration, we apply the unified definition to the microparticle capture enzyme immunoassay for prostate-specific antigen (PSA) developed for the Abbott IMx automated immunoassay system. The MDC of this assay as estimated by our unifying approach is shown to be 4.1-7.1 times greater than currently reported. As a consequence, the ability of the assay to measure reliably small concentrations of PSA to detect early recurrences of prostate cancer is probably overstated.

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

    PubMed

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

    2009-11-28

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

  1. Continuous ammonia emission measurements from a commercial beef feedyard in Texas

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ambient NH3 concentrations were measured continuously at a beef cattle feedyard for 12 months beginning in March 2007. Concentrations were measured every five minutes, 24 hours per day, at a sample intake height of 3.3 m using a chemiluminescence analyzer. On-site weather data was collected concur...

  2. ATMOSPHERIC CONCENTRATIONS OF AMMONIA AND AMMONIUM AT AN AGRICULTURAL SITE IN THE SOUTHEAST UNITED STATES

    EPA Science Inventory

    In this study, we present approximately 1 year (October 1998 - September 1999) of 12-hour mean ammonia [NH3], ammonium [NH4(+)], hydrochloric acid [HCl], nitrate [NO3(-)], nitric acid [HNO3], nitrous acid [HNO2], sulfate [SO4(- -)], and sulfur dioxide [SO2] concentrations measure...

  3. High-sensitivity in situ QCLAS-based ammonia concentration sensor for high-temperature applications

    NASA Astrophysics Data System (ADS)

    Peng, W. Y.; Sur, R.; Strand, C. L.; Spearrin, R. M.; Jeffries, J. B.; Hanson, R. K.

    2016-07-01

    A novel quantum cascade laser (QCL) absorption sensor is presented for high-sensitivity in situ measurements of ammonia (hbox {NH}_3) in high-temperature environments, using scanned wavelength modulation spectroscopy (WMS) with first-harmonic-normalized second-harmonic detection (scanned WMS-2 f/1 f) to neutralize the effect of non-absorption losses in the harsh environment. The sensor utilized the sQ(9,9) transition of the fundamental symmetric stretch band of hbox {NH}_3 at 10.39 {\\upmu }hbox {m} and was sinusoidally modulated at 10 kHz and scanned across the peak of the absorption feature at 50 Hz, leading to a detection bandwidth of 100 Hz. A novel technique was used to select an optimal WMS modulation depth parameter that reduced the sensor's sensitivity to spectral interference from hbox {H}_2hbox {O} and hbox {CO}_2 without significantly sacrificing signal-to-noise ratio. The sensor performance was validated by measuring known concentrations of hbox {NH}_3 in a flowing gas cell. The sensor was then demonstrated in a laboratory-scale methane-air burner seeded with hbox {NH}_3, achieving a demonstrated detection limit of 2.8 ± 0.26 ppm hbox {NH}_3 by mole at a path length of 179 cm, equivalence ratio of 0.6, pressure of 1 atm, and temperatures of up to 600 K.

  4. Using broadband absorption spectroscopy to measure concentration of sulfur dioxide

    NASA Astrophysics Data System (ADS)

    Wang, H. S.; Zhang, Y. G.; Wu, S. H.; Lou, X. T.; Zhang, Z. G.; Qin, Y. K.

    2010-09-01

    A linear relationship between concentration of sulfur dioxide (SO2) and optical parameter (OP) is established using the Beer-Lambert law. The SO2 measuring system is set up to measure the concentration of sulfur dioxide in the wavelength range 275-315 nm. Experimental results indicate that the detection limit of the sulfur dioxide measuring system is below 0.2 ppm per meter of path length, and the measurement precision is better than ±1%. The proposed SO2 measuring method features limited interference from other gases and dust, and high stability and short response time.

  5. A statistical comparison of active and passive ammonia measurements collected at Clean Air Status and Trends Network (CASTNET) sites.

    PubMed

    Puchalski, Melissa A; Rogers, Christopher M; Baumgardner, Ralph; Mishoe, Kevin P; Price, Garry; Smith, Michael J; Watkins, Nealson; Lehmann, Christopher M

    2015-02-01

    Atmospheric concentrations of ammonia (NH3) are not well characterized in the United States due to the sparse number of monitors, the relatively short lifetime of NH3 in the atmosphere, and the difficulty in measuring non-point source emissions such as fertilized agricultural land. In this study, we compare measured weekly concentrations of NH3 collected by two denuder systems with a bi-weekly passive NH3 sampler used by the National Atmospheric Deposition Program's (NADP) Ammonia Monitoring Network (AMoN). The purpose of the study was to verify the passive samplers used by AMoN and characterize any uncertainties introduced when using a bi-weekly versus weekly sampling time period. The study was conducted for 1 year at five remote Clean Air Status and Trends Network (CASTNET) sites. Measured ambient NH3 concentrations ranged from 0.03 μg NH3 m(-3) to 4.64 μg NH3 m(-3) in upstate New York and northwest Texas, respectively, while dry deposition estimates ranged from 0.003 kg N ha(-1) wk(-1) to 0.47 kg N ha(-1) wk(-1). Results showed that the bi-weekly passive samplers performed well compared to annular denuder systems (ADS) deployed at each of the five CASTNET sites, while the MetOne Super SASS Mini-Parallel Plate Denuder System (MPPD) was biased low when compared to the ADS. The mean relative percent difference (MRPD) between the ADS and MPPD and the ADS and AMoN sampler was -38% and -9%, respectively. Precision of the ADS and MPPD was 5% and 13%, respectively, while the precision of the passive samplers was 5%. The results of this study demonstrate that the NH3 concentrations measured by AMoN are comparable to the ADS and may be used to supplement the high-time resolution measurements to gain information on spatial gradients of NH3, long-term trends and seasonal variations in NH3 concentrations.

  6. 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.

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

    PubMed Central

    Kraus, Florian; Fichtl, Matthias; Baer, Sebastian

    2016-01-01

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

  8. Measurement and Characterization of Concentrator Solar Cells II

    NASA Technical Reports Server (NTRS)

    Scheiman, Dave; Sater, Bernard L.; Chubb, Donald; Jenkins, Phillip; Snyder, Dave

    2005-01-01

    Concentrator solar cells are continuing to get more consideration for use in power systems. This interest is because concentrator systems can have a net lower cost per watt in solar cell materials plus ongoing improvements in sun-tracking technology. Quantitatively measuring the efficiency of solar cells under concentration is difficult. Traditionally, the light concentration on solar cells has been determined by using a ratio of the measured solar cell s short circuit current to that at one sun, this assumes that current changes proportionally with light intensity. This works well with low to moderate (<20 suns) concentration levels on "well-behaved" linear cells but does not apply when cells respond superlinearly, current increases faster than intensity, or sublinearly, current increases more slowly than intensity. This paper continues work on using view factors to determine the concentration level and linearity of the solar cell with mathematical view factor analysis and experimental results [1].

  9. Estimation of background gas concentration from differential absorption lidar measurements

    NASA Astrophysics Data System (ADS)

    Harris, Peter; Smith, Nadia; Livina, Valerie; Gardiner, Tom; Robinson, Rod; Innocenti, Fabrizio

    2016-10-01

    Approaches are considered to estimate the background concentration level of a target species in the atmosphere from an analysis of the measured data provided by the National Physical Laboratory's differential absorption lidar (DIAL) system. The estimation of the background concentration level is necessary for an accurate quantification of the concentration level of the target species within a plume, which is the quantity of interest. The focus of the paper is on methodologies for estimating the background concentration level and, in particular, contrasting the assumptions about the functional and statistical models that underpin those methodologies. An approach is described to characterise the noise in the recorded signals, which is necessary for a reliable estimate of the background concentration level. Results for measured data provided by a field measurement are presented, and ideas for future work are discussed.

  10. Atmospheric radionuclide concentrations measured by Pacific Northwest Laboratory since 1961

    SciTech Connect

    Young, J.A.; Thomas, C.W.

    1981-03-01

    The atmospheric concentrations of a wide spectrum of radionuclides produced by nuclear weapons, nuclear reactors, cosmic rays, radon and thoron decay and the SNAP-9A burn-up ({sup 238}Pu) have been measured at Richland, Washington, since 1961; at Barrow, Alaska, since 1964; and at other stations for shorter periods of time. There has been considerable concern over the health hazard presented by these radionuclides, but it has also been recognized that atmospheric mixing and deposition rates can be determined from their measurement. Therefore, Pacific Northwest Laboratory began the continuous measurement of the atmospheric concentrations of a wide spectrum of radionuclides produced by nuclear weapons, nuclear reactors, cosmic rays, and radon and thoron decay. This report will discuss the concentrations of the longer-lived radionuclides (T 1/2 > 12 days). The concentrations of shorter-lived radionuclides measured following Chinese nuclear tests since 1972 are discussed in another report.

  11. Atmospheric radionuclide concentrations measured by Pacific Northwest Laboratory since 1961

    SciTech Connect

    Young, J.A.; Thomas, C.W.

    1981-03-01

    The atmospheric concentrations of a wide spectrum of radionuclides produced by nuclear weapons, nuclear reactors, cosmic rays, radon and thoron decay and the SNAP-9A burn-up ([sup 238]Pu) have been measured at Richland, Washington, since 1961; at Barrow, Alaska, since 1964; and at other stations for shorter periods of time. There has been considerable concern over the health hazard presented by these radionuclides, but it has also been recognized that atmospheric mixing and deposition rates can be determined from their measurement. Therefore, Pacific Northwest Laboratory began the continuous measurement of the atmospheric concentrations of a wide spectrum of radionuclides produced by nuclear weapons, nuclear reactors, cosmic rays, and radon and thoron decay. This report will discuss the concentrations of the longer-lived radionuclides (T 1/2 > 12 days). The concentrations of shorter-lived radionuclides measured following Chinese nuclear tests since 1972 are discussed in another report.

  12. Laser Adaptive System for Measurement of Molecule Mass and Concentration

    NASA Astrophysics Data System (ADS)

    Romashko, R. V.; Kulchin, Y. N.; Efimov, T. A.; Sergeev, A. A.; Nepomnyashiy, A. V.

    A Laser adaptive microweighting system for measurement of molecules mass based on the principles of adaptive holog aphic interferometry is proposed and experimentally tested in task of gas concentration measurement. A sensitive element of the system is a microcantilever coated by a layer of chitosan, which can adsorb different molecules. Changes in gas concentration re ult in change in mass of molecules adsorbed in chitosan, and, as sequence, result in change in natural frequency of cantilever oscillations, which are measured by an adaptive holographic interferometer. The operation of the system has been experimentally demonstrated in measurement of water vapor concentration. The detected change in concentration of H2O molecules amounted to 125 ppm.

  13. Direct measurement of surface carbon concentrations. [in lunar soil

    NASA Technical Reports Server (NTRS)

    Filleux, C.; Tombrello, T. A.; Burnett, D. S.

    1977-01-01

    Measurements of surface concentrations of carbon in lunar soils and soil breccias provide information on the origin of carbon in the regolith. The reaction C-12 (d, p sub zero) is used to measure 'surface' and 'volume' concentrations in lunar samples. This method has a depth resolution of 1 micron, which permits only a 'surface' and a 'volume' component to be measured. Three of four Apollo 16 double drive tube samples show a surface carbon concentration of about 8 by 10 to the 14th power/sq cm, whereas the fourth sample gave 4 by 10 to the 14th power/sq cm. It can be convincingly shown that the measured concentration does not originate from fluorocarbon or hydrocarbon contaminants. Surface adsorbed layers of CO or CO2 are removed by a sputter cleaning procedure using a 2-MeV F beam. It is shown that the residual C concentration of 8 by 10 to the 14th power/sq cm cannot be further reduced by increased F fluence, and it is therefore concluded that it is truly lunar. If one assumes that the measured surface C concentration is a steady-state concentration determined only by a balance between solar-wind implantation and sputtering, a sputter erosion rate of 0.1 A/yr is obtained. However, it would be more profitable to use an independently derived sputter erosion rate to test the hypothesis of a solar-wind origin of the surface carbon.

  14. 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 ν_7 band of C_2H_6 and ν_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

  15. Varying forage type, metabolizable protein concentration, and carbohydrate source affects manure excretion, manure ammonia, and nitrogen metabolism of dairy cows.

    PubMed

    Weiss, W P; Willett, L B; St-Pierre, N R; Borger, D C; McKelvey, T R; Wyatt, D J

    2009-11-01

    Effects of forage source, concentration of metabolizable protein (MP), and type of carbohydrate on manure excretion by dairy cows and production of ammonia from that manure were evaluated using a central composite experimental design. All diets (dry basis) contained 50% forage that ranged from 25:75 to 75:25 alfalfa silage:corn silage. Diets contained 10.7% rumen-degradable protein with variable concentrations of undegradable protein so that dietary MP ranged from 8.8 to 12%. Starch concentration ranged from 22 to 30% with a concomitant decrease in neutral detergent fiber. A total of 15 diets were fed to 36 Holstein cows grouped in 6 blocks. Each block was a replicated 3 x 3 Latin square resulting in 108 observations. Manure output (urine and feces) was measured using total collection, and fresh feces and urine were combined into slurries and incubated for 48 h to measure NH3-N production. Feces, urine, and manure output averaged 50.5, 29.5, and 80.1 kg/d, respectively. Manure output increased with increasing dry matter intake (approximately 3.5 kg of manure/kg of dry matter intake), increased concentrations of alfalfa (mostly via changes in urine output), and decreased concentrations of starch (mostly via changes in fecal output). The amount of NH3-N produced per gram of manure decreased with increasing alfalfa because excreted N shifted from urine to feces. Increasing MP increased NH3-N produced per gram of manure mainly because of increased urinary N, but increased fecal N also contributed to the manure NH3. Manure NH3-N production per cow (accounts for effects on manure production and NH3-N produced per unit of manure) was least and milk protein yields were maximal for diets with high alfalfa (75% of the forage), moderate MP (11% of diet dry matter), and high starch (30% of diet dry matter).

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

    PubMed

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

    2017-03-29

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

  17. Workplace aerosol mass concentration measurement using optical particle counters.

    PubMed

    Görner, Peter; Simon, Xavier; Bémer, Denis; Lidén, Göran

    2012-02-01

    Direct-reading aerosol measurement usually uses the optical properties of airborne particles to detect and measure particle concentration. In the case of occupational hygiene, mass concentration measurement is often required. Two aerosol monitoring methods are based on the principle of light scattering: optical particle counting (OPC) and photometry. The former analyses the light scattered by a single particle, the latter by a cloud of particles. Both methods need calibration to transform the quantity of scattered light detected into particle concentration. Photometers are simpler to use and can be directly calibrated to measure mass concentration. However, their response varies not only with aerosol concentration but also with particle size distribution, which frequently contributes to biased measurement. Optical particle counters directly measure the particle number concentration and particle size that allows assessment of the particle mass provided the particles are spherical and of known density. An integrating algorithm is used to calculate the mass concentration of any conventional health-related aerosol fraction. The concentrations calculated thus have been compared with simultaneous measurements by conventional gravimetric sampling to check the possibility of field OPC calibration with real workplace aerosols with a view to further monitoring particle mass concentration. Aerosol concentrations were measured in the food industry using the OPC GRIMM® 1.108 and the CIP 10-Inhalable and CIP 10-Respirable (ARELCO®) aerosol samplers while meat sausages were being brushed and coated with calcium carbonate. Previously, the original OPC inlet had been adapted to sample inhalable aerosol. A mixed aerosol of calcium carbonate and fungi spores was present in the workplace. The OPC particle-size distribution and an estimated average particle density of both aerosol components were used to calculate the mass concentration. The inhalable and respirable aerosol fractions

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

    NASA Astrophysics Data System (ADS)

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

    2002-11-01

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

  19. 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.

  20. 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

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

    PubMed

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

    2016-12-01

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

  2. Origin of High Electronic Quality in Solar Cell Absorber CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Yin, Wanjian; Shi, Tingting; Wei, Suhua; Yan, Yanfa

    Thin-film solar cells based on CH3NH3PbI3 halide perovskites have recently shown remarkable performance. First-principle calculations and molecular dynamic simulations show that the structure of pristine CH3NH3PbI3 is much more disordered than the inorganic archetypal thin-film semiconductor CdTe. However, the structural disorders from thermal fluctuation, point defects and grain boundaries introduce rare deep defect states within the bandgaps; therefore, the material has high electronic quality. We have further shown that this unusually high electronic quality is attributed to the unique electronic structures of halide perovskite: the strong coupling between cation lone-pair Pb s orbitals and anion p orbitals and the large atomic size of constitute cation atoms. We further found that although CH3NH3PbI3 GBs do not introduce a deep gap state, the defect level close to the VBM can still act as a shallow hole trap state. Cl and O can spontaneously segregate into GBs and passivate those defect levels and deactivate the trap state.

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

    NASA Astrophysics Data System (ADS)

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

    1993-04-01

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

  4. Ultrasound-assistant preparation of Cu-SAPO-34 nanocatalyst for selective catalytic reduction of NO by NH3.

    PubMed

    Panahi, Parvaneh Nakhostin; Niaei, Ali; Salari, Darush; Mousavi, Seyed Mahdi; Delahay, Gérard

    2015-09-01

    The influence of the various preparation methods of Cu-SAPO-34 nanocatalysts on the selective catalytic reduction of NO with NH3 under excess oxygen was studied. Cu-SAPO-34 nanocatalysts were prepared by using four techniques: conventional impregnation (IM), ultrasound-enhanced impregnation (UIM), conventional deposition precipitation (DP) using NaOH and homogeneous deposition precipitation (HDP) using urea. These catalysts were characterized in detail by various techniques such as N2-sorption, XRD, TEM, H2-TPR, NH3-TPD and XPS to understand the catalyst structure, the nature and the dispersed state of the copper species, and the acid sites for NH3 adsorption. All of the nanocatalysts showed high activities for NO removal. However, the activities were different and followed the sequence of Cu-SAPO-34 (UIM)>Cu-SAPO-34 (HDP)>Cu-SAPO-34 (IM)>Cu-SAPO-34 (DP). Based on the obtained results, it was concluded that the NO conversion on Cu-SAPO-34 nanocatalysts was mainly related to the high reducibility of the isolated Cu(2+) ions and CuO species, the number of the acid sites and the dispersion of CuO species on SAPO-34.

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

    PubMed

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

    2017-04-05

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

  6. 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.

  7. Comparative analysis of radon, thoron and thoron progeny concentration measurements.

    PubMed

    Janik, Miroslaw; Tokonami, Shinji; Kranrod, Chutima; Sorimachi, Atsuyuki; Ishikawa, Tetsuo; Hosoda, Masahiro; McLaughlin, James; Chang, Byung-Uck; Kim, Yong Jae

    2013-07-01

    This study examined correlations between radon, thoron and thoron progeny concentrations based on surveys conducted in several different countries. For this purpose, passive detectors developed or modified by the National Institute of Radiological Sciences (NIRS) were used. Radon and thoron concentrations were measured using passive discriminative radon-thoron detectors. Thoron progeny measurements were conducted using the NIRS-modified detector, originally developed by Zhuo and Iida. Weak correlations were found between radon and thoron as well as between thoron and thoron progeny. The statistical evaluation showed that attention should be paid to the thoron equilibrium factor for calculation of thoron progeny concentrations based on thoron measurements. In addition, this evaluation indicated that radon, thoron and thoron progeny were independent parameters, so it would be difficult to estimate the concentration of one from those of the others.

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

    PubMed Central

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  10. Device for measuring the total concentration of oxygen in gases

    DOEpatents

    Isaacs, Hugh S.; Romano, Anthony J.

    1977-01-01

    This invention provides a CO equilibrium in a device for measuring the total concentration of oxygen impurities in a fluid stream. To this end, the CO equilibrium is produced in an electrochemical measuring cell by the interaction of a carbon element in the cell with the chemically combined and uncombined oxygen in the fluid stream at an elevated temperature.

  11. Reflective measurement of water concentration using millimeter wave illumination

    NASA Astrophysics Data System (ADS)

    Sung, Shijun; Bennett, David; Taylor, Zachary; Bajwa, Neha; Tewari, Priyamvada; Maccabi, Ashkan; Culjat, Martin; Singh, Rahul; Grundfest, Warren

    2011-04-01

    THz and millimeter wave technology have shown the potential to become a valuable medical imaging tool because of its sensitivity to water and safe, non-ionizing photon energy. Using the high dielectric constant of water in these frequency bands, reflectionmode THz sensing systems can be employed to measure water content in a target with high sensitivity. This phenomenology may lead to the development of clinical systems to measure the hydration state of biological targets. Such measurements may be useful in fast and convenient diagnosis of conditions whose symptoms can be characterized by changes in water concentration such as skin burns, dehydration, or chemical exposure. To explore millimeter wave sensitivity to hydration, a reflectometry system is constructed to make water concentration measurements at 100 GHz, and the minimum detectable water concentration difference is measured. This system employs a 100 GHz Gunn diode source and Golay cell detector to perform point reflectivity measurements of a wetted polypropylene towel as it dries on a mass balance. A noise limited, minimum detectable concentration difference of less than 0.5% by mass can be detected in water concentrations ranging from 70% to 80%. This sensitivity is sufficient to detect hydration changes caused by many diseases and pathologies and may be useful in the future as a diagnostic tool for the assessment of burns and other surface pathologies.

  12. Optical fiber system for saline concentration measurement in drilling fluids

    NASA Astrophysics Data System (ADS)

    Caetano, L. A. C.; Fontoura, S. A. B.; Torres, P. I.; Valente, L. C. G.

    2001-08-01

    Laboratory setups are used to simulate real conditions in which drilling fluid and shales interact during an oil well drilling process. The present work describes the development of fiber optic systems capable of measuring the ionic diffusion in water-based fluids under high pressure. Two alternatives have been tested and calibrations are presented for both. The most successful one was tested in a real experiment in which the concentration of CaCl2 has been continuously measured during five days. Starting from pure water, the final ionic concentration measured by this method was compared with the result from chemical analysis of the fluid with very good agreement.

  13. Radiocarbon tracer measurements of atmospheric hydroxyl radical concentrations

    NASA Technical Reports Server (NTRS)

    Campbell, M. J.; Farmer, J. C.; Fitzner, C. A.; Henry, M. N.; Sheppard, J. C.

    1986-01-01

    The usefulness of the C-14 tracer in measurements of atmospheric hydroxyl radical concentration is discussed. The apparatus and the experimental conditions of three variations of a radiochemical method of atmosphere analysis are described and analyzed: the Teflon bag static reactor, the flow reactor (used in the Wallops Island tests), and the aircraft OH titration reactor. The procedure for reduction of the aircraft reactor instrument data is outlined. The problems connected with the measurement of hydroxyl radicals are discussed. It is suggested that the gas-phase radioisotope methods have considerable potential in measuring tropospheric impurities present in very low concentrations.

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

  19. The active titration method for measuring local hydroxyl radical concentration

    NASA Technical Reports Server (NTRS)

    Sprengnether, Michele; Prinn, Ronald G.

    1994-01-01

    We are developing a method for measuring ambient OH by monitoring its rate of reaction with a chemical species. Our technique involves the local, instantaneous release of a mixture of saturated cyclic hydrocarbons (titrants) and perfluorocarbons (dispersants). These species must not normally be present in ambient air above the part per trillion concentration. We then track the mixture downwind using a real-time portable ECD tracer instrument. We collect air samples in canisters every few minutes for roughly one hour. We then return to the laboratory and analyze our air samples to determine the ratios of the titrant to dispersant concentrations. The trends in these ratios give us the ambient OH concentration from the relation: dlnR/dt = -k(OH). A successful measurement of OH requires that the trends in these ratios be measureable. We must not perturb ambient OH concentrations. The titrant to dispersant ratio must be spatially invariant. Finally, heterogeneous reactions of our titrant and dispersant species must be negligible relative to the titrant reaction with OH. We have conducted laboratory studies of our ability to measure the titrant to dispersant ratios as a function of concentration down to the few part per trillion concentration. We have subsequently used these results in a gaussian puff model to estimate our expected uncertainty in a field measurement of OH. Our results indicate that under a range of atmospheric conditions we expect to be able to measure OH with a sensitivity of 3x10(exp 5) cm(exp -3). In our most optimistic scenarios, we obtain a sensitivity of 1x10(exp 5) cm(exp -3). These sensitivity values reflect our anticipated ability to measure the ratio trends. However, because we are also using a rate constant to obtain our (OH) from this ratio trend, our accuracy cannot be better than that of the rate constant, which we expect to be about 20 percent.

  20. Online measurement of urea concentration in spent dialysate during hemodialysis

    NASA Astrophysics Data System (ADS)

    Olesberg, Jonathon T.; Armitage, Ben; Arnold, Mark A.; Flanigan, Michael

    2002-05-01

    We describe on-line optical measurements of urea concentration during the regular hemodialysis treatment of several patients. The spectral measurements were performed in the effluent dialysate stream after the dialysis membrane using an FTIR spectrometer equipped with a flow-through cell. Spectra were recorded across the 5000-4000 cm-1 (2.0-2.5 micrometers at 1-minute intervals. Optically determined concentrations matched concentrations obtained from standard chemical assays with a root-mean-square error of 0.29 mM for urea (0.8 mg/dl urea nitrogen), 0.03 mM for creatinine, 0.11 mM for lactate, and 0.22 mM for glucose. The observed concentration ranges were 0-11 mM for urea, 0-0.35 mM for creatinine, 0-0.75 mM for lactate, and 9-12.5 mM for glucose.

  1. Normalized vitamin D metabolite concentrations are better correlated to pharmacological effects than measured concentrations

    PubMed Central

    Mason, Darius; Donabella, Paul J; Nnani, Daryl; Musteata, Florin Marcel

    2015-01-01

    Background: Vitamin D deficiency has been associated with a multitude of diseases, ranging from fractures to cancer. Nearly 99% of vitamin D metabolites are bound to proteins, altering the relationship between concentration and activity. Methods & results: Normalized concentrations were calculated and validated using published data regarding the correlation of 25-hydroxyvitamin D with bone mineral density. In addition, healthy and kidney disease subjects were recruited for preliminary investigations. Use of the normalizing equations resulted in statistically significant improvements in the relationship between vitamin D metabolites and several markers of health status. Conclusion: Normalized concentrations are similar to clinically reported values and are easier to interpret than free or bioavailable concentrations, since their values match the range of measured total concentrations. PMID:28031931

  2. Effect of analytical techniques on measured ambient NO2 concentrations.

    PubMed

    Goyal, S K; Gavane, A G

    2005-06-01

    A study was carried out with specific reference to NO2 measurements in three countries (designated as A, B and C), which use three different manual methods; viz. Sodium Arsenite, Greiss Saltzman and TGS-ANSA for the determination of NO2 in ambient air. Significant deviation (up to 36 + %) was observed in measured NO, ion concentration when spiked samples were analyzed using these methods. Further, to make the data inter-comparable, exhaustive laboratory studies were carried out on these manual methods. Different concentration levels of NO2 were generated in the laboratory and analyzed by these methods simultaneously. The results were evaluated statistically. An interrelationship among the methods was established as method conversion factors (MCF). This would be useful in relating atmospheric concentration of NO2 among various countries, where different measurement techniques are adopted.

  3. A measure of the concentration of rare events

    PubMed Central

    Prieto Curiel, Rafael; Bishop, Steven

    2016-01-01

    We introduce here an index, which we call the Rare Event Concentration Coefficient (RECC), that is a measure of the dispersion/concentration of events which have a low frequency but tend to have a high level of concentration, such as the number of crimes suffered by a person. The Rare Event Concentration Coefficient is a metric based on a statistical mixture model, with a value closer to zero meaning that events are homogeneously distributed, and a value closer to one meaning that the events have a higher degree of concentration. This measure may be used to compare the concentration of events over different time periods and over different regions. Other traditional approaches for the dispersion/concentration of a variable tend to be blind to structural changes in the pattern of occurrence of rare events. The RECC overcomes this issue and we show here two simple applications, first by using the number of burglaries suffered in Netherlands and then by using the number of volcanic eruptions in the world. PMID:27577532

  4. Measuring concentrations of volatile organic compounds in vinyl flooring.

    PubMed

    Cox, S S; Little, J C; Hodgson, A T

    2001-08-01

    The initial solid-phase concentration of volatile organic compounds (VOCs) is a key parameter influencing the emission characteristics of many indoor materials. Solid-phase measurements are typically made using solvent extraction or thermal headspace analysis. The high temperatures and chemical solvents associated with these methods can modify the physical structure of polymeric materials and, consequently, affect mass transfer characteristics. To measure solid-phase concentrations under conditions resembling those in which the material would be installed in an indoor environment, a new technique was developed for measuring VOC concentrations in vinyl flooring (VF) and similar materials. A 0.09-m2 section of new VF was punched randomly to produce -200 0.78-cm2 disks. The disks were milled to a powder at -140 degrees C to simultaneously homogenize the material and reduce the diffusion path length without loss of VOCs. VOCs were extracted from the VF particles at room temperature by fluidized-bed desorption (FBD) and by direct thermal desorption (DTD) at elevated temperatures. The VOCs in the extraction gas from FBD and DTD were collected on sorbent tubes and analyzed by gas chromatography/mass spectrometry (GC/MS). Seven VOCs emitted by VF were quantified. Concentration measurements by FBD ranged from 5.1 microg/g VF for n-hexadecane to 130 microg/g VF for phenol. Concentrations measured by DTD were higher than concentrations measured by FBD. Differences between FBD and DTD results may be explained using free-volume and dual-mobility sorption theory, but further research is necessary to more completely characterize the complex nature of a diffusant in a polymer matrix.

  5. In situ refractometry for concentration measurements in refrigeration systems

    SciTech Connect

    Newell, T.A.

    1997-12-31

    An in situ refractometer was developed that is capable of measuring both the concentrations of oil in refrigerants, and the concentrations of aqueous coolant brines. A description of the technique, and example data are presented for R-134a/PAG oil, aqueous ethylene glycol, and aqueous propylene glycol solutions. The R-134a/PAG oil sensor data show a measurement sensitivity of less than 0.1% oil in the refrigerant, although error between data sets shows an uncertainty of approximately {+-}0.8%. Ethylene glycol and propylene glycol data show high signal level variations due to the large variation of the index of refraction between water and the glycols.

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

    PubMed

    Mani, Fabrizio; Peruzzini, Maurizio; Barzagli, Francesco

    2008-01-01

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

  7. Effect of Ce doping of TiO2 support on NH3-SCR activity over V2O5-WO3/CeO2-TiO2 catalyst.

    PubMed

    Cheng, Kai; Liu, Jian; Zhang, Tao; Li, Jianmei; Zhao, Zhen; Wei, Yuechang; Jiang, Guiyuan; Duan, Aijun

    2014-10-01

    CeO2-TiO2 composite supports with different Ce/Ti molar ratios were prepared by a homogeneous precipitation method, and V2O5-WO3/CeO2-TiO2 catalysts for the selective catalytic reduction (SCR) of NOx with NH3 were prepared by an incipient-wetness impregnation method. These catalysts were characterized by means of BET, XRD, UV-Vis, Raman and XPS techniques. The results showed that the catalytic activity of V2O5-WO3/TiO2 was greatly enhanced by Ce doping (molar ratio of Ce/Ti=1/10) in the TiO2 support. The catalysts that were predominantly anatase TiO2 showed better catalytic performance than the catalysts that were predominantly fluorite CeO2. The Ce additive could enhance the surface adsorbed oxygen and accelerate the SCR reaction. The effects of O2 concentration, ratio of NH3/NO, space velocity and SO2 on the catalytic activity were also investigated. The presence of oxygen played an important role in NO reduction. The optimal ratio of NH3/NO was 1/1 and the catalyst had good resistance to SO2 poisoning.

  8. Room-temperature NH3 gas sensors based on Ag-doped γ-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 γ-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, γ-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 γ-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%) γ-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.

  9. Application of response surface methodology (RSM) for optimisation of COD, NH3-N and 2,4-DCP removal from recycled paper wastewater in a pilot-scale granular activated carbon sequencing batch biofilm reactor (GAC-SBBR).

    PubMed

    Muhamad, Mohd Hafizuddin; Sheikh Abdullah, Siti Rozaimah; Mohamad, Abu Bakar; Abdul Rahman, Rakmi; Hasan Kadhum, Abdul Amir

    2013-05-30

    In this study, the potential of a pilot-scale granular activated carbon sequencing batch biofilm reactor (GAC-SBBR) for removing chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N) and 2,4-dichlorophenol (2,4-DCP) from recycled paper wastewater was assessed. For this purpose, the response surface methodology (RSM) was employed, using a central composite face-centred design (CCFD), to optimise three of the most important operating variables, i.e., hydraulic retention time (HRT), aeration rate (AR) and influent feed concentration (IFC), in the pilot-scale GAC-SBBR process for recycled paper wastewater treatment. Quadratic models were developed for the response variables, i.e., COD, NH3-N and 2,4-DCP removal, based on the high value (>0.9) of the coefficient of determination (R(2)) obtained from the analysis of variance (ANOVA). The optimal conditions were established at 750 mg COD/L IFC, 3.2 m(3)/min AR and 1 day HRT, corresponding to predicted COD, NH3-N and 2,4-DCP removal percentages of 94.8, 100 and 80.9%, respectively.

  10. Electrochemical concentration measurements for multianalyte mixtures in simulated electrorefiner salt

    NASA Astrophysics Data System (ADS)

    Rappleye, Devin Spencer

    The development of electroanalytical techniques in multianalyte molten salt mixtures, such as those found in used nuclear fuel electrorefiners, would enable in situ, real-time concentration measurements. Such measurements are beneficial for process monitoring, optimization and control, as well as for international safeguards and nuclear material accountancy. Electroanalytical work in molten salts has been limited to single-analyte mixtures with a few exceptions. This work builds upon the knowledge of molten salt electrochemistry by performing electrochemical measurements on molten eutectic LiCl-KCl salt mixture containing two analytes, developing techniques for quantitatively analyzing the measured signals even with an additional signal from another analyte, correlating signals to concentration and identifying improvements in experimental and analytical methodologies. (Abstract shortened by ProQuest.).

  11. The influence of thoron on instruments measuring radon activity concentration.

    PubMed

    Michielsen, N; Bondiguel, S

    2015-11-01

    Thoron, the isotope 220 of radon, is a radionuclide whose concentration may influence the measurement of the activity concentration of (222)Rn in the air. If in the case of continuous and active sampling measuring instruments, using a pump for example, the influence of thoron on radon measurement is obvious and is taken into account in the apparatus, it is often assumed that in the case of a passive sampling, by diffusion through a filter for example, this thoron influence is negligible. This is due to the very short radioactive half-life of thoron, 55.6 s (3.82 d for (222)Rn), and the assumption that the diffusion time of thoron in the detection chamber is long enough beside that of the thoron half-life. The objective of this study is to check whether this assumption is true or not for different kinds of commercial electronic apparatus used to measure radon activity concentration from soil to dwellings. First of all, the devices were calibrated in activity concentration of radon, and then they were exposed to a controlled thoron atmosphere. The experiments concerning the thoron aimed to investigate the sensitivity to thoron in the radon measuring mode of the apparatus. Results of these experiments show that all devices have a very quick answer to thoron atmosphere, even though the sensitivities vary from one instrument to another. Results clearly show that this influence on radon measurement due to the thoron is observed also after the exposition because of the decay of (212)Pb and its progenies. In conclusion, the sensitivity to thoron in the radon measuring mode depends strongly on the type of instruments. The results of the present investigation show that for some apparatus, the influence of thoron cannot be disregarded especially when measuring radon in soil.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  13. Three wavelength optical oxymetry including the measurement of carboxyhemoglobin concentration

    NASA Astrophysics Data System (ADS)

    Pieralli, Christian; Devillers, Robert; Tribillon, Gilbert M.; Barthelemy, Jean-Claude; Geyssant, Andre

    1995-02-01

    The measurement of blood component concentrations is of great interest for medical applications such as anaesthetizing monitoring, heart disease evolution, respiratory insufficiency, etc. The common system is the spectroscopic analysis of blood samples. Analyzing the absorption versus wavelengths permits the determination of blood component concentrations by comparison to the theoretical extinction coefficients of the investigated components. The functional saturation rate of oxyhemoglobin HbO2 called SfO2 is therefore accessible. A new system is presented in this paper utilizing three laser diodes at wavelengths 660, 830, and 1060 nm. We have, therefore, access to a supplementary parameter which is the concentration of carboxyhemoglobin HbCO. The set-up can be portable because it utilizes small light sources, optical fibers, and integrated electrical supply and signal processing device. The performances reach a SfO2 resolution of 2% and 1% on HbCO measurement.

  14. Monensin concentrations measured in feeder cattle using enzyme immunoassay.

    PubMed

    Mount, M E; Cullor, J S; Kass, P H; Garret, W

    1996-06-01

    Thirty heifers were fed a ration containing 30 g monensin/ton. Fecal, urinary and seral samples were collected at varying intervals prior to and after initiating administration of the monensin-containing feed, and monensin concentrations were determined using a modified indirect enzyme immunoassay. Fecal samples contained measurable (micrograms/g; ppm) concentrations of monensin in most samples. The majority of sera and urine samples contained monensin at ng/ml (ppb) concentrations, which were above background levels prior to monensin feeding. Twelve head were fed monensin at 60 g/ton and 90 g/ton for 5 d with collection of similar samples. Higher concentrations of monensin were detected with increasing ration amounts in all 3 sample types. Enzyme immunoassay for monensin in these biological samples identified presence of the feed additive.

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    SciTech Connect

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

    2016-05-05

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

  18. Electrophotolysis oxidation system for measurement of organic concentration in water

    NASA Technical Reports Server (NTRS)

    Winkler, H. E. (Inventor)

    1981-01-01

    Methods and apparatus for determining organic carbon in aqueous solution are described. The method comprises subjecting the aqueous solution to electrolysis, for generating oxygen from water, and simultaneously to ultraviolet radiation, for oxidation of substantially all organic carbon to carbon dioxide. The carbon dioxide is measured and the value is related to the concentration of organic carbon in the aqueous solution.

  19. Two instruments based on differential optical absorption spectroscopy (DOAS) to measure accurate ammonia concentrations in the atmosphere

    NASA Astrophysics Data System (ADS)

    Volten, H.; Bergwerff, J. B.; Haaima, M.; Lolkema, D. E.; Berkhout, A. J. C.; van der Hoff, G. R.; Potma, C. J. M.; Wichink Kruit, R. J.; van Pul, W. A. J.; Swart, D. P. J.

    2012-02-01

    We present two Differential Optical Absorption Spectroscopy (DOAS) instruments built at RIVM: the RIVM DOAS and the miniDOAS. Both instruments provide virtually interference-free measurements of NH3 concentrations in the atmosphere, since they measure over an open path, without suffering from inlet problems or interference problems by ammonium aerosols dissociating on tubes or filters. They measure concentrations up to at least 200 μg m-3, have a fast response, low maintenance demands, and a high up-time. The RIVM DOAS has a high accuracy of typically 0.15 μg m-3 for ammonia for 5-min averages and over a total light path of 100 m. The miniDOAS has been developed for application in measurement networks such as the Dutch National Air Quality Monitoring Network (LML). Compared to the RIVM DOAS it has a similar accuracy, but is significantly reduced in size, costs, and handling complexity. The RIVM DOAS and miniDOAS results showed excellent agreement (R2 = 0.996) during a field measurement campaign in Vredepeel, the Netherlands. This measurement site is located in an agricultural area and is characterized by highly variable, but on average high ammonia concentrations in the air. The RIVM-DOAS and miniDOAS results were compared to the results of the AMOR instrument, a continuous-flow wet denuder system, which is currently used in the LML. Averaged over longer time spans of typically a day, the (mini)DOAS and AMOR results agree reasonably well, although an offset of the AMOR values compared to the (mini)DOAS results exists. On short time scales, the (mini)DOAS shows a faster response and does not show the memory effects due to inlet tubing and transport of absorption fluids encountered by the AMOR. Due to its high accuracy, high uptime, low maintenance and its open path, the (mini)DOAS shows a good potential for flux measurements by using two (or more) systems in a gradient set-up and applying the aerodynamic gradient technique.

  20. Two instruments based on differential optical absorption spectroscopy (DOAS) to measure accurate ammonia concentrations in the atmosphere

    NASA Astrophysics Data System (ADS)

    Volten, H.; Bergwerff, J. B.; Haaima, M.; Lolkema, D. E.; Berkhout, A. J. C.; van der Hoff, G. R.; Potma, C. J. M.; Wichink Kruit, R. J.; van Pul, W. A. J.; Swart, D. P. J.

    2011-08-01

    We present two Differential Optical Absorption Spectroscopy (DOAS) instruments built at RIVM, the RIVM DOAS and the miniDOAS. Both instruments provide virtually interference free measurements of NH3 concentrations in the atmosphere, since they measure over an open path, without suffering from inlet problems or interference problems by ammonium aerosols dissociating on tubes or filters. They measure concentrations up to at least 200 μg m-3, have a fast response, low maintenance demands, and a high up-time. The RIVM DOAS has a high accuracy of typically 0.15 μg m-3 for ammonia over 5-min averages and over a total light path of 100 m. The miniDOAS has been developed for application in measurement networks such as the Dutch National Air Quality Monitoring Network (LML). Compared to the RIVM DOAS it has a similar accuracy, but is significantly reduced in size, costs, and handling complexity. The RIVM DOAS and miniDOAS results showed excellent agreement (R2 = 0.996) during a field measurement campaign in Vredepeel, the Netherlands. This measurement site is located in an agricultural area and is characterized by highly variable, but on average high ammonia concentrations in the air. The RIVM-DOAS and miniDOAS results were compared to the results of the AMOR instrument, a continuous-flow wet denuder system, which is currently used in the LML. Averaged over longer time spans of typically a day the (mini)DOAS and AMOR results agree reasonably well, although an offset of the AMOR values compared to the (mini)DOAS results exists. On short time scales the (mini)DOAS shows a faster response and does not show the memory effects due to inlet tubing and transport of absorption fluids encountered by the AMOR. Due to its high accuracy, high uptime, low maintenance and its open path, the (mini)DOAS shows a good potential for flux measurements by using two (or more) systems in a gradient set-up and applying the aerodynamic gradient technique.

  1. Measurement of particle concentrations in a dental office.

    PubMed

    Sotiriou, Maria; Ferguson, Stephen F; Davey, Mark; Wolfson, Jack M; Demokritou, Philip; Lawrence, Joy; Sax, Sonja N; Koutrakis, Petros

    2008-02-01

    Particles in a dental office can be generated by a number of instruments, such as air-turbine handpieces, low-speed handpieces, ultrasonic scalers, bicarbonate polishers, polishing cups, as well as drilling and air sprays inside the oral cavity. This study examined the generation of particles during dental drilling and measured particle size, mass, and trace elements. The air sampling techniques included both continuous and integrated methods. The following particle continuous measurements were taken every minute: (1) size-selective particle number concentration (Climet); (2) total particle number concentration (PTRAK), and; (3) particle mass concentration (DustTrak). Integrated particle samples were collected for about 5 h on each of five sampling days, using a PM(2.5) sampler (ChemComb) for elemental/organic carbon analysis, and a PM(10) sampler (Harvard Impactor) for mass and elemental analyses. There was strong evidence that these procedures result in particle concentrations above background. The dental procedures produced number concentrations of relatively small particles (<0.5 microm) that were much higher than concentrations produced for the relatively larger particles (>0.5 microm). Also, these dental procedures caused significant elevation above background of certain trace elements (measured by X-ray fluorescence) but did not cause any elevation of elemental carbon (measured by thermal optical reflectance). Dental drilling procedures aerosolize saliva and products of drilling, producing particles small enough to penetrate deep into the lungs. The potential health impacts of the exposure of dental personnel to such particles need to be evaluated. Increased ventilation and personal breathing protection could be used to minimize harmful effects.

  2. Practical considerations for measuring hydrogen concentrations in groundwater

    USGS Publications Warehouse

    Chapelle, F.H.; Vroblesky, D.A.; Woodward, J.C.; Lovley, D.R.

    1997-01-01

    Several practical considerations for measuring concentrations of dissolved molecular hydrogen (H2) in groundwater including 1 sampling methods 2 pumping methods and (3) effects of well casing materials were evaluated. Three different sampling methodologies (a downhole sampler, a gas- stripping method, and a diffusion sampler) were compared. The downhole sampler and gas-stripping methods gave similar results when applied to the same wells, the other hand, appeared to The diffusion sampler, on overes