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Sample records for situ reaction study

  1. In situ ambient pressure X-ray photoelectron spectroscopy studies of lithium-oxygen redox reactions.

    PubMed

    Lu, Yi-Chun; Crumlin, Ethan J; Veith, Gabriel M; Harding, Jonathon R; Mutoro, Eva; Baggetto, Loïc; Dudney, Nancy J; Liu, Zhi; Shao-Horn, Yang

    2012-01-01

    The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li(4+x)Ti(5)O(12)/LiPON/Li(x)V(2)O(5) cell and examine in situ the chemistry of Li-O(2) reaction products on Li(x)V(2)O(5) as a function of applied voltage under ultra high vacuum (UHV) and at 500 mtorr of oxygen pressure using ambient pressure X-ray photoelectron spectroscopy (APXPS). Under UHV, lithium intercalated into Li(x)V(2)O(5) while molecular oxygen was reduced to form lithium peroxide on Li(x)V(2)O(5) in the presence of oxygen upon discharge. Interestingly, the oxidation of Li(2)O(2) began at much lower overpotentials (~240 mV) than the charge overpotentials of conventional Li-O(2) cells with aprotic electrolytes (~1000 mV). Our study provides the first evidence of reversible lithium peroxide formation and decomposition in situ on an oxide surface using a solid-state cell, and new insights into the reaction mechanism of Li-O(2) chemistry. PMID:23056907

  2. In Situ Ambient Pressure X-ray Photoelectron Spectroscopy Studies of Lithium-Oxygen Redox Reactions

    PubMed Central

    Lu, Yi-Chun; Crumlin, Ethan J.; Veith, Gabriel M.; Harding, Jonathon R.; Mutoro, Eva; Baggetto, Loïc; Dudney, Nancy J.; Liu, Zhi; Shao-Horn, Yang

    2012-01-01

    The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li4+xTi5O12/LiPON/LixV2O5 cell and examine in situ the chemistry of Li-O2 reaction products on LixV2O5 as a function of applied voltage under ultra high vacuum (UHV) and at 500 mtorr of oxygen pressure using ambient pressure X-ray photoelectron spectroscopy (APXPS). Under UHV, lithium intercalated into LixV2O5 while molecular oxygen was reduced to form lithium peroxide on LixV2O5 in the presence of oxygen upon discharge. Interestingly, the oxidation of Li2O2 began at much lower overpotentials (~240 mV) than the charge overpotentials of conventional Li-O2 cells with aprotic electrolytes (~1000 mV). Our study provides the first evidence of reversible lithium peroxide formation and decomposition in situ on an oxide surface using a solid-state cell, and new insights into the reaction mechanism of Li-O2 chemistry. PMID:23056907

  3. In Situ Ambient Pressure X-ray Photoelectron Spectroscopy Studies of Lithium-Oxygen Redox Reactions

    NASA Astrophysics Data System (ADS)

    Lu, Yi-Chun; Crumlin, Ethan J.; Veith, Gabriel M.; Harding, Jonathon R.; Mutoro, Eva; Baggetto, Loïc; Dudney, Nancy J.; Liu, Zhi; Shao-Horn, Yang

    2012-10-01

    The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li4+xTi5O12/LiPON/LixV2O5 cell and examine in situ the chemistry of Li-O2 reaction products on LixV2O5 as a function of applied voltage under ultra high vacuum (UHV) and at 500 mtorr of oxygen pressure using ambient pressure X-ray photoelectron spectroscopy (APXPS). Under UHV, lithium intercalated into LixV2O5 while molecular oxygen was reduced to form lithium peroxide on LixV2O5 in the presence of oxygen upon discharge. Interestingly, the oxidation of Li2O2 began at much lower overpotentials (~240 mV) than the charge overpotentials of conventional Li-O2 cells with aprotic electrolytes (~1000 mV). Our study provides the first evidence of reversible lithium peroxide formation and decomposition in situ on an oxide surface using a solid-state cell, and new insights into the reaction mechanism of Li-O2 chemistry.

  4. In Situ Ambient Pressure X-ray Photoelectron Spectroscopy Studies of Lithium-Oxygen Redox Reactions

    SciTech Connect

    Lu, Yi-Chun; Crumlin, Ethan J.; Veith, Gabriel M.; Harding, Jonathon R.; Mutoro, Eva; Baggetto, Loïc; Dudney, Nancy J.; Liu, Zhi; Shao-Horn, Yang

    2012-10-08

    The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li4+xTi5O12/LiPON/LixV2O5 cell and examine in situ the chemistry of Li-O2 reaction products on LixV2O5 as a function of applied voltage under ultra high vacuum (UHV) and near ambient-pressure of oxygen using X-ray photoelectron spectroscopy (APXPS). Oxygen reduction and evolution reactions take place on the surface of the mixed electronic and Li+ ionic conductor, LixV2O5, which eliminate parasitic reactions between oxygen reduction/evolution reaction intermediates and aprotic electrolytes used in Li-O2 batteries reported to date. Under UHV, reversible lithium intercalation and de-intercalation from LixV2O5 was noted, where the changes in the vanadium valence state revealed from XPS in this study were comparable to that reported previously from Li/LixV2O5 thin film batteries. In presence of oxygen near ambient pressure, the LixV2O5 surface was covered gradually by the reaction product of oxygen reduction, namely lithium peroxide (Li2O2) (approximately 1-2 unit cells) upon discharge. Interestingly, the LixV2O5 surface became re-exposed upon charging, and the oxidation of Li2O2 began at much lower overpotentials (~240 mV) than the charge overpotentials of Li-O2 cells (~1000 mV) with aprotic electrolytes, which can be attributed to subnanometer-thick Li2O2 with surfaces free of contaminants such as carbonate species. Our study provides first evidence of reversible lithium peroxide formation and decomposition in situ on an oxide surface using a solid-state cell, and new insights into the reaction mechanism of Li-O2 chemistry.

  5. Development of wet environment TEM (wet-ETEM) for in situ studies of liquid-catalyst reactions on the nanoscale.

    PubMed

    Gai, Pratibha L

    2002-02-01

    We present the development of in situ wet environmental transmission electron microscopy (wet-ETEM) for direct probing of controlled liquid-catalyst reactions at operating temperatures on the nanoscale. The first nanoscale imaging and electron diffraction of dynamic liquid hydrogenation and polymerization reactions in the manufacture of polyamides reported here opens up new opportunities for high resolution studies of a wide range of solution-solid and solution-gas-solid reactions in the chemical and biological sciences. PMID:14710723

  6. An in situ photoemission study of the dehydrogenation reaction of methanol on Ni( 1 0 0 )

    NASA Astrophysics Data System (ADS)

    Neubauer, R.; Whelan, C. M.; Denecke, R.; Steinrück, H.-P.

    2002-06-01

    Making use of the high intensity and resolution of synchrotron radiation at MAX-II (Sweden) we studied the dehydrogenation reaction of methanol on Ni(1 0 0) as a function of temperature by core level photoelectron spectroscopy. The temperature was increased linearly from 105 to 425 K with a heating rate of 0.06 K s -1. Measurement times of 60 s per C 1s spectrum allowed the dehydrogenation reaction to be monitored in situ. The different binding energies of the core level characteristic of different adsorbed species are reported. After exposure at 105 K, the C 1s spectra exhibit two peaks, representing methanol in multilayer and monolayer states. Above 160 K the multilayer is completely desorbed and methanol from the monolayer starts to dehydrogenate to form a methoxy species which decomposes above 240 K to carbon monoxide adsorbed in the bridge site. The onset of the on-top site occupation is observed at 270 K. The data suggests conversion from bridge to on-top site CO around 290 K. Our results show good agreement with literature values from temperature programmed desorption and Fourier transform infra-red experiments and provide new information in the form of quantitative data on the decomposition pathway of methanol adsorbed on Ni(1 0 0).

  7. In situ high pressure and temperature carbon-13 nmr for the study of carbonation reactions of carbon dioxide

    NASA Astrophysics Data System (ADS)

    Surface, James Andrew

    The aqueous reactions of carbon dioxide with various Mg-containing minerals [MgO, Mg(OH)2, and Mg2SiO4] at several different pressures (1-200 bar) and temperatures (25-150C) have been studied using a novel, elevated pressure and temperature 13C NMR probe. Critical observations about reaction rates, chemical exchange, and pH measurements throughout these reactions and the implications of the in situ measurements made during these reactions are discussed. A new method is used to elucidate pH under high pressure and temperature conditions which utilizes a calculation scheme wherein experimental data and a computational model are combined. Additionally, a 1D pH imaging method is employed to observe pH gradient effects across mineral samples during their reaction with CO2. Finally, other experimental details are discussed including ex situ analysis on carbonate products using pXRD, Raman, and MAS NMR. Detailed discussion outlines how to use 13C NMR to study CO2 mineralization reactions.

  8. Development of a reaction cell for in-situ/operando studies of surface of a catalyst under a reaction condition and during catalysis.

    PubMed

    Nguyen, Luan; Tao, Franklin Feng

    2016-06-01

    Tracking surface chemistry of a catalyst during catalysis is significant for fundamental understanding of catalytic performance of the catalyst since it allows for establishing an intrinsic correlation between surface chemistry of a catalyst at its working status and its corresponding catalytic performance. Ambient pressure X-ray photoelectron spectroscopy can be used for in-situ studies of surfaces of different materials or devices in a gas. To simulate the gaseous environment of a catalyst in a fixed-bed a flowing gaseous environment of reactants around the catalyst is necessary. Here, we report the development of a new flowing reaction cell for simulating in-situ study of a catalyst surface under a reaction condition in gas of one reactant or during catalysis in a mixture of reactants of a catalytic reaction. The homemade reaction cell is installed in a high vacuum (HV) or ultrahigh vacuum (UHV) environment of a chamber. The flowing gas in the reaction cell is separated from the HV or UHV environment through well sealings at three interfaces between the reaction cell and X-ray window, sample door and aperture of front cone of an energy analyzer. Catalyst in the cell is heated through infrared laser beam introduced through a fiber optics interfaced with the reaction cell through a homemade feedthrough. The highly localized heating on the sample holder and Au-passivated internal surface of the reaction cell effectively minimizes any unwanted reactions potentially catalyzed by the reaction cell. The incorporated laser heating allows a fast heating and a high thermal stability of the sample at a high temperature. With this cell, a catalyst at 800 °C in a flowing gas can be tracked readily. PMID:27370473

  9. Development of a reaction cell for in-situ/operando studies of surface of a catalyst under a reaction condition and during catalysis

    NASA Astrophysics Data System (ADS)

    Nguyen, Luan; Tao, Franklin Feng

    2016-06-01

    Tracking surface chemistry of a catalyst during catalysis is significant for fundamental understanding of catalytic performance of the catalyst since it allows for establishing an intrinsic correlation between surface chemistry of a catalyst at its working status and its corresponding catalytic performance. Ambient pressure X-ray photoelectron spectroscopy can be used for in-situ studies of surfaces of different materials or devices in a gas. To simulate the gaseous environment of a catalyst in a fixed-bed a flowing gaseous environment of reactants around the catalyst is necessary. Here, we report the development of a new flowing reaction cell for simulating in-situ study of a catalyst surface under a reaction condition in gas of one reactant or during catalysis in a mixture of reactants of a catalytic reaction. The homemade reaction cell is installed in a high vacuum (HV) or ultrahigh vacuum (UHV) environment of a chamber. The flowing gas in the reaction cell is separated from the HV or UHV environment through well sealings at three interfaces between the reaction cell and X-ray window, sample door and aperture of front cone of an energy analyzer. Catalyst in the cell is heated through infrared laser beam introduced through a fiber optics interfaced with the reaction cell through a homemade feedthrough. The highly localized heating on the sample holder and Au-passivated internal surface of the reaction cell effectively minimizes any unwanted reactions potentially catalyzed by the reaction cell. The incorporated laser heating allows a fast heating and a high thermal stability of the sample at a high temperature. With this cell, a catalyst at 800 °C in a flowing gas can be tracked readily.

  10. An in situ electron microscopy technique for the study of thermally activated reactions in multilayered materials

    SciTech Connect

    Wall, M.A.; Barbee, T.W. Jr.; Weihs, T.P.

    1995-04-14

    A novel in situ transmission electron microscopy technique for the observation of reaction processes in multilayered materials is reported. The technique involves constant heating rate experiments of multilayered materials in image and diffraction modes. Because the fine scale microstructure of multilayered materials is typically a small fraction of the TEM specimen thickness, realistic comparison of the microstructural evolution with that of similarly processed thick foil samples is possible. Such experiments, when well designed, can provide rapid characterization of phase transformations and stability of nano-structured materials. The results of these experiments can be recorded in both video and micrograph format. The results and limitations of this technique will be shown for the Al/Zr and Al/Monel multilayered systems.

  11. Reaction of Formic Acid over Amorphous Manganese Oxide Catalytic Systems: An In Situ Study

    SciTech Connect

    Durand, Jason; Senanayake, Sanjaya D; Mullins, David R; Suib, Steven

    2010-01-01

    The interaction of formic acid with amorphous manganese oxide (AMO) is investigated using in situ photoelectron and infrared spectroscopy techniques. Soft X-ray photoelectron spectroscopy (sXPS) and in situ FTIR illustrate two possible modes of formate bound species at the AMO surface. Two peaks in the IR region from 1340-1390 cm{sup -1} are indicative of formate species bound to the surface in a bidentate configuration. However, a 224 cm{sup -1} band gap between v{sub s}OCO and v{sub as}OCO suggests formate is bound in a bridging configuration. Temperature-programmed desorption studies confirm the formate bound species desorbs as carbon dioxide from the surface at multiple binding sites. At temperatures above 700 K, the presence of K{sup +} {hor_ellipsis} OC complex suggests the bound species interacts at vacant sites related to framework oxygen and cation mobility.

  12. Reaction of Formic Acid over Amorphous Manganese Oxide Catalytic Systems: An In Situ Study

    SciTech Connect

    J Durand; S Senanayake; S Suib; D Mullins

    2011-12-31

    The interaction of formic acid with amorphous manganese oxide (AMO) is investigated using in situ photoelectron and infrared spectroscopy techniques. Soft X-ray photoelectron spectroscopy (sXPS) and in situ FTIR illustrate two possible modes of formate bound species at the AMO surface. Two peaks in the IR region from 1340-1390 cm{sup -1} are indicative of formate species bound to the surface in a bidentate configuration. However, a 224 cm{sup -1} band gap between v{sub s}OCO and v{sub as}OCO suggests formate is bound in a bridging configuration. Temperature-programmed desorption studies confirm the formate bound species desorbs as carbon dioxide from the surface at multiple binding sites. At temperatures above 700 K, the presence of K{sup +} {hor_ellipsis} OC complex suggests the bound species interacts at vacant sites related to framework oxygen and cation mobility.

  13. Utilizing in Situ Electrochemical SHINERS for Oxygen Reduction Reaction Studies in Aprotic Electrolytes.

    PubMed

    Galloway, Thomas A; Hardwick, Laurence J

    2016-06-01

    Spectroscopic detection of reaction intermediates upon a variety of electrode surfaces is of major interest within physical chemistry. A notable technique in the study of the electrochemical interface has been surface-enhanced Raman spectroscopy (SERS). The drawback of SERS is that it is limited to roughened gold and silver substrates. Herein we report that shell-isolated nanoparticles for enhanced Raman spectroscopy (SHINERS) can overcome the limitations of SERS and has followed the oxygen reduction reaction (ORR), within a nonaqueous electrolyte, on glassy carbon, gold, palladium, and platinum disk electrodes. The work presented demonstrates SHINERS for spectroelectrochemical studies for applied and fundamental electrochemistry in aprotic electrolytes, especially for the understanding and development of future metal-oxygen battery applications. In particular, we highlight that with the addition of Li(+), both the electrode surface and solvent influence the ORR mechanism, which opens up the possibility of tailoring surfaces to produce desired reaction pathways. PMID:27195529

  14. Development of an FTIR in situ reactor for real time study of surface reactions in photocatalysis

    NASA Astrophysics Data System (ADS)

    Hauchecorne, Birger

    For many years, photocatalysis has been proposed as one of the promising techniques to abate environmental pollutants. To improve the catalytic efficiency, it is vital to know the reaction mechanisms of the photocatalytic degradation. Different methods are therefore described in literature to study these mechanisms at the gaseous phase/photocatalyst interface with Fourier transform infrared (FTIR) spectroscopy as a commonly used method. The reactors described in literature and/or available on the market experience some technical and scientific difficulties. Generally, the catalyst can only be investigated after the reactions have occurred, or it is only possible to look at the changes in the gas phase concentrations while the reactions are taking place. It is thus a major challenge to develop a reactor which makes it possible to detect changes on the catalyst surface at the moment the reactions are happening. In this work, a new reactor is developed that makes it possible to study the catalytic surface at the moment the reactions occur, by means of transmission-absorption FTIR spectroscopy. Moreover, by using UV LEDs, it was possible to install the UV light inside the reactor area, so that no harmful UV light can leave the reactor, inherently making it a safer method. It was also opted to construct the reactor in a modular way, so that every part was interchangeable and could easily be replaced according to the needs of the researcher. A special screw cap is designed to hold the UV LEDs on a printed circuit board and to fit in every standard FTIR spectrometer. This study provides exciting new insights in the photocatalytic degradation mechanism of ethylene and acetaldehyde. It is for instance found that OH radicals are used as the oxidising agents to abate these pollutants. For ethylene it was proven that the molecular orbitals play an important role, resulting in the formation of both formaldehyde and formic acid as intermediates before complete mineralisation

  15. Reactions of graphene supported Co3O4 nanocubes with lithium and magnesium studied by in situ transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Luo, Langli; Wu, Jinsong; Li, Qianqian; Dravid, Vinayak P.; Poeppelmeier, Kenneth R.; Rao, Qunli; Xu, Junming

    2016-02-01

    Reaction beyond intercalation and the utilization of metal ions beyond lithium-ions are two promising approaches for developing the next generation of high capacity and low cost energy storage materials. Here, we use graphene supported Co3O4 nanocubes and study their reaction with lithium, magnesium and aluminum using in situ transmission electron microscopy. On lithiation, the Co3O4 nanocubes decompose to Co metal nanoparticles (2 to 3 nm) and embed in as-formed Li2O matrix; conversely, the CoO nanoparticles form on the Co site accompanying the decomposition of Li2O in the delithiation process. The lithiation process is dominated by surface diffusion of Li+, and graphene sheets enhance the Li+ diffusion. However, upon charge with magnesium, the Mg2+ diffusion is sluggish, and there is no sign of conversion reaction between Mg and Co3O4 at room temperature. Instead, a thin film consisting of metal Mg nanoparticles is formed on the surface of graphene due to a process similar to metal plating. The Al3+ diffusion is even more sluggish and no reaction between Al and Co3O4 is observed. These findings provide insights to tackle the reaction mechanism of multivalent ions with electrode materials.

  16. Reactions of graphene supported Co3O4 nanocubes with lithium and magnesium studied by in situ transmission electron microscopy.

    PubMed

    Luo, Langli; Wu, Jinsong; Li, Qianqian; Dravid, Vinayak P; Poeppelmeier, Kenneth R; Rao, Qunli; Xu, Junming

    2016-02-26

    Reaction beyond intercalation and the utilization of metal ions beyond lithium-ions are two promising approaches for developing the next generation of high capacity and low cost energy storage materials. Here, we use graphene supported Co3O4 nanocubes and study their reaction with lithium, magnesium and aluminum using in situ transmission electron microscopy. On lithiation, the Co3O4 nanocubes decompose to Co metal nanoparticles (2 to 3 nm) and embed in as-formed Li2O matrix; conversely, the CoO nanoparticles form on the Co site accompanying the decomposition of Li2O in the delithiation process. The lithiation process is dominated by surface diffusion of Li(+), and graphene sheets enhance the Li(+) diffusion. However, upon charge with magnesium, the Mg(2+) diffusion is sluggish, and there is no sign of conversion reaction between Mg and Co3O4 at room temperature. Instead, a thin film consisting of metal Mg nanoparticles is formed on the surface of graphene due to a process similar to metal plating. The Al(3+) diffusion is even more sluggish and no reaction between Al and Co3O4 is observed. These findings provide insights to tackle the reaction mechanism of multivalent ions with electrode materials. PMID:26808457

  17. In Situ Potentiodynamic Analysis of the Electrolyte/Silicon Electrodes Interface Reactions--A Sum Frequency Generation Vibrational Spectroscopy Study.

    PubMed

    Horowitz, Yonatan; Han, Hui-Ling; Ross, Philip N; Somorjai, Gabor A

    2016-01-27

    The key factor in long-term use of batteries is the formation of an electrically insulating solid layer that allows lithium ion transport but stops further electrolyte redox reactions on the electrode surface, hence solid electrolyte interphase (SEI). We have studied a common electrolyte, 1.0 M LiPF6/ethylene carbonate (EC)/diethyl carbonate (DEC), reduction products on crystalline silicon (Si) electrodes in a lithium (Li) half-cell system under reaction conditions. We employed in situ sum frequency generation vibrational spectroscopy (SFG-VS) with interface sensitivity in order to probe the molecular composition of the SEI surface species under various applied potentials where electrolyte reduction is expected. We found that, with a Si(100)-hydrogen terminated wafer, a Si-ethoxy (Si-OC2H5) surface intermediate forms due to DEC decomposition. Our results suggest that the SEI surface composition varies depending on the termination of Si surface, i.e., the acidity of the Si surface. We provide the evidence of specific chemical composition of the SEI on the anode surface under reaction conditions. This supports an electrochemical electrolyte reduction mechanism in which the reduction of the DEC molecule to an ethoxy moiety plays a key role. These findings shed new light on the formation mechanism of SEI on Si anodes in particular and on SEI formation in general. PMID:26651259

  18. A study on the orientation inheritance in laminated NiAl produced by in situ reaction annealing.

    PubMed

    Du, Yan; Fan, Guohua; Geng, Lin

    2016-04-01

    In order to promote the performance of B2 NiAl by texture control of orientation during in situ processing, phase transformation in laminated NiAl with bimodal grain size distribution manufactured by reaction annealing of Ni and Al foils has been studied. It turned out that there existed a Kurdjumov-Sachs orientation relationship (K-S OR) between parent Ni and product NiAl by crystallography analysis according to the electron backscatter diffraction (EBSD) results. The parent Ni did not transform to the product NiAl directly but via the formation of Ni3Al firstly according to the transmission electron microscope (TEM) observation of the interface. This led to a new K-S OR between Ni3Al and NiAl with a small atomic misfit, which made less residual stress generated through the formation of Ni3Al than directly from the parent Ni. PMID:26867210

  19. In Situ Study on Current Density Distribution and Its Effect on Interfacial Reaction in a Soldering Process

    NASA Astrophysics Data System (ADS)

    Qu, Lin; Zhao, Ning; Ma, Haitao; Zhao, Huijing; Huang, Mingliang

    2015-01-01

    The interfacial reaction in Cu/Sn/Cu solder joint during liquid-solid eletromigration (EM) was in situ studied using synchrotron radiation real-time imaging technology. The current density distribution in the solder joint was analyzed with the finite element method (FEM). The relationships among solder shape, current density distribution, Cu dissolution, and the formation and dissolution of interfacial intermetallic compound (IMC) were revealed. The current promoted dissolution of the cathode IMC and growth of the anode IMC and suppressed the dissolution of anode Cu. The change of interfacial IMC had little effect on the current density distribution; however, the dissolution of cathode Cu, which changed the solder shape, had a significant effect on the current density distribution. The dissolution of cathode Cu under forward current and cathode IMC under reverse current and the growth of anode IMC under forward current was faster where the current density was higher. The synchrotron radiation real-time imaging technology can not only in situ observe the change of solder shape, the dissolution and growth behavior of interfacial IMC and the dissolution behavior of substrate in a soldering process but also provide data needed for numerical simulation of current density distribution in a solder joint.

  20. A straightforward implementation of in situ solution electrochemical ¹³C NMR spectroscopy for studying reactions on commercial electrocatalysts: ethanol oxidation.

    PubMed

    Huang, L; Sorte, E G; Sun, S-G; Tong, Y Y J

    2015-05-11

    Identifying and quantifying electrocatalytic-reaction-generated solution species, be they reaction intermediates or products, are highly desirable in terms of understanding the associated reaction mechanisms. We report herein a straightforward implementation of in situ solution electrochemical (13)C NMR spectroscopy for the first time that enables in situ studies of reactions on commercial fuel-cell electrocatalysts (Pt and PtRu blacks). Using ethanol oxidation reaction (EOR) as a working example, we discovered that (1) the complete oxidation of ethanol to CO2 only took place dominantly at the very beginning of a potentiostatic chronoamperometric (CA) measurement and (2) the PtRu had a much higher activity in catalysing oxygen insertion reaction that leads to acetic acid. PMID:25868425

  1. In-situ time resolved synchrotron powder diffraction studies of synthesis and chemical reactions

    SciTech Connect

    Norby, P.

    1995-09-01

    Equipment for time and temperature dependent powder diffraction has been developed, especially in order to be able to study hydrothermal syntheses of zeolites. The system is very versatile and has so far been used to study e.g. hydrothermal syntheses of zeolites and aluminophosphates, syntheses of layered phosphates, formation of Sorel cements, dehydration and phase transformations of zeolites, solid state synthesis of lanthanum manganites, ion exchange of zeolites using molten salt, and oxidation/reduction of lanthanum manganites at high temperatures. The sample is contained in quartz capillaries and is heated using a stream of hot air. External pressure can be applied allowing hydrothermal syntheses at temperatures up to 200 C to be performed. Controlled atmosphere is obtained by flowing gas or a mixture of gases through the capillary.

  2. Study on the Electrochemical Reaction Mechanism of ZnFe2O4 by In Situ Transmission Electron Microscopy

    PubMed Central

    Su, Qingmei; Wang, Shixin; Yao, Libing; Li, Haojie; Du, Gaohui; Ye, Huiqun; Fang, Yunzhang

    2016-01-01

    A family of mixed transition–metal oxides (MTMOs) has great potential for applications as anodes for lithium ion batteries (LIBs). However, the reaction mechanism of MTMOs anodes during lithiation/delithiation is remain unclear. Here, the lithiation/delithiation processes of ZnFe2O4 nanoparticles are observed dynamically using in situ transmission electron microscopy (TEM). Our results suggest that during the first lithiation process the ZnFe2O4 nanoparticles undergo a conversion process and generate a composite structure of 1–3 nm Fe and Zn nanograins within Li2O matrix. During the delithiation process, volume contraction and the conversion of Zn and Fe take place with the disappearance of Li2O, followed by the complete conversion to Fe2O3 and ZnO not the original phase ZnFe2O4. The following cycles are dominated by the full reversible phase conversion between Zn, Fe and ZnO, Fe2O3. The Fe valence evolution during cycles evidenced by electron energy–loss spectroscopy (EELS) techniques also exhibit the reversible conversion between Fe and Fe2O3 after the first lithiation, agreeing well with the in situ TEM results. Such in situ TEM observations provide valuable phenomenological insights into electrochemical reaction of MTMOs, which may help to optimize the composition of anode materials for further improved electrochemical performance. PMID:27306189

  3. Study on the Electrochemical Reaction Mechanism of ZnFe2O4 by In Situ Transmission Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Su, Qingmei; Wang, Shixin; Yao, Libing; Li, Haojie; Du, Gaohui; Ye, Huiqun; Fang, Yunzhang

    2016-06-01

    A family of mixed transition–metal oxides (MTMOs) has great potential for applications as anodes for lithium ion batteries (LIBs). However, the reaction mechanism of MTMOs anodes during lithiation/delithiation is remain unclear. Here, the lithiation/delithiation processes of ZnFe2O4 nanoparticles are observed dynamically using in situ transmission electron microscopy (TEM). Our results suggest that during the first lithiation process the ZnFe2O4 nanoparticles undergo a conversion process and generate a composite structure of 1–3 nm Fe and Zn nanograins within Li2O matrix. During the delithiation process, volume contraction and the conversion of Zn and Fe take place with the disappearance of Li2O, followed by the complete conversion to Fe2O3 and ZnO not the original phase ZnFe2O4. The following cycles are dominated by the full reversible phase conversion between Zn, Fe and ZnO, Fe2O3. The Fe valence evolution during cycles evidenced by electron energy–loss spectroscopy (EELS) techniques also exhibit the reversible conversion between Fe and Fe2O3 after the first lithiation, agreeing well with the in situ TEM results. Such in situ TEM observations provide valuable phenomenological insights into electrochemical reaction of MTMOs, which may help to optimize the composition of anode materials for further improved electrochemical performance.

  4. Study on the Electrochemical Reaction Mechanism of ZnFe2O4 by In Situ Transmission Electron Microscopy.

    PubMed

    Su, Qingmei; Wang, Shixin; Yao, Libing; Li, Haojie; Du, Gaohui; Ye, Huiqun; Fang, Yunzhang

    2016-01-01

    A family of mixed transition-metal oxides (MTMOs) has great potential for applications as anodes for lithium ion batteries (LIBs). However, the reaction mechanism of MTMOs anodes during lithiation/delithiation is remain unclear. Here, the lithiation/delithiation processes of ZnFe2O4 nanoparticles are observed dynamically using in situ transmission electron microscopy (TEM). Our results suggest that during the first lithiation process the ZnFe2O4 nanoparticles undergo a conversion process and generate a composite structure of 1-3 nm Fe and Zn nanograins within Li2O matrix. During the delithiation process, volume contraction and the conversion of Zn and Fe take place with the disappearance of Li2O, followed by the complete conversion to Fe2O3 and ZnO not the original phase ZnFe2O4. The following cycles are dominated by the full reversible phase conversion between Zn, Fe and ZnO, Fe2O3. The Fe valence evolution during cycles evidenced by electron energy-loss spectroscopy (EELS) techniques also exhibit the reversible conversion between Fe and Fe2O3 after the first lithiation, agreeing well with the in situ TEM results. Such in situ TEM observations provide valuable phenomenological insights into electrochemical reaction of MTMOs, which may help to optimize the composition of anode materials for further improved electrochemical performance. PMID:27306189

  5. A flow-through reaction cell for in situ X-ray diffraction and absorption studies of heterogeneous powder-liquid reactions and phase transformations.

    PubMed

    Ferrer, Pilar; da Silva, Iván; Rubio-Zuazo, Juan; Alfonso, Belén F; Trobajo, Camino; Khainakov, Sergei; Garcia, Jose R; Garcia-Granda, Santiago; Castro, Germán R

    2012-01-01

    A portable powder-liquid high-corrosion-resistant reaction cell has been designed to follow in situ reactions by X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques. The cell has been conceived to be mounted on the experimental stations for diffraction and absorption of the Spanish CRG SpLine-BM25 beamline at the European Synchrotron Radiation Facility. Powder reactants and/or products are kept at a fixed position in a vertical geometry in the X-ray pathway by a porous membrane, under forced liquid reflux circulation. Owing to the short pathway of the X-ray beam through the cell, XRD and XAS measurements can be carried out in transmission configuration/mode. In the case of the diffraction technique, data can be collected with either a point detector or a two-dimensional CCD detector, depending on specific experimental requirements in terms of space or time resolution. Crystallization processes, heterogeneous catalytic processes and several varieties of experiments can be followed by these techniques with this cell. Two experiments were carried out to demonstrate the cell feasibility: the phase transformations of layered titanium phosphates in boiling aqueous solutions of phosphoric acid, and the reaction of copper carbonate and L-isoleucine amino acid powders in boiling aqueous solution. In this last case the shrinking of the solid reactants and the formation of Cu(isoleucine)(2) is observed. The crystallization processes and several phase transitions have been observed during the experiments, as well as an unexpected reaction pathway. PMID:22186649

  6. Oxygen storage properties of La1-xSrxFeO3- for chemical-looping reactions an in-situ neutron and synchrotron X-ray study

    DOE PAGESBeta

    Taylor, Daniel; Schreiber, Nathaniel; Levitas, Benjamin; Xu, Wenqian; Rodriguez, Efrain E

    2016-01-01

    Oxygen storage materials (OSMs) provide lattice oxygen for a number of chemical-looping reactions including natural gas combustion and methane reforming. La1 xSrxFeO3 has shown promise for use as an OSM in methane reforming reactions due to its high product selectivity, fast oxide diffusion, and cycle stability. Here, we investigate the structural evolution of the series La1 xSrxFeO3 for x = 0, 1/3, 1/2, 2/3, and 1, using in situ synchrotron X-ray and neutron diffraction, as it is cycled under the conditions of a chemical-looping reactor (methane and oxygen atmospheres). In the compositions x = 1/3, 1/2, 2/3, and 1, wemore » discover an envelope , or temperature range, of oxygen storage capacity (OSC), where oxygen can easily and reversibly be inserted and removed from the OSM. Our in situ X-ray and neutron diffraction results reveal that while samples with higher Sr contents had a higher OSC, those same samples suffered from slower reaction kinetics and some, such as the x = 1/2 and x = 2/3 compositions, had local variations in Sr content, which led to inhomogeneous regions with varying reaction rates. Therefore, we highlight the importance of in situ diffraction studies, and we propose that these measurements are required for the thorough evaluation of future candidate OSMs. We recommend La2/3Sr1/3FeO3 as the optimal OSM in the series because its structure remains homogeneous throughout the reaction, and its OSC envelope is similar to that of the higher doped materials.« less

  7. Oxygen storage properties of La1-xSrxFeO3- for chemical-looping reactions an in-situ neutron and synchrotron X-ray study

    SciTech Connect

    Taylor, Daniel; Schreiber, Nathaniel; Levitas, Benjamin; Xu, Wenqian; Rodriguez, Efrain E

    2016-01-01

    Oxygen storage materials (OSMs) provide lattice oxygen for a number of chemical-looping reactions including natural gas combustion and methane reforming. La1 xSrxFeO3 has shown promise for use as an OSM in methane reforming reactions due to its high product selectivity, fast oxide diffusion, and cycle stability. Here, we investigate the structural evolution of the series La1 xSrxFeO3 for x = 0, 1/3, 1/2, 2/3, and 1, using in situ synchrotron X-ray and neutron diffraction, as it is cycled under the conditions of a chemical-looping reactor (methane and oxygen atmospheres). In the compositions x = 1/3, 1/2, 2/3, and 1, we discover an envelope , or temperature range, of oxygen storage capacity (OSC), where oxygen can easily and reversibly be inserted and removed from the OSM. Our in situ X-ray and neutron diffraction results reveal that while samples with higher Sr contents had a higher OSC, those same samples suffered from slower reaction kinetics and some, such as the x = 1/2 and x = 2/3 compositions, had local variations in Sr content, which led to inhomogeneous regions with varying reaction rates. Therefore, we highlight the importance of in situ diffraction studies, and we propose that these measurements are required for the thorough evaluation of future candidate OSMs. We recommend La2/3Sr1/3FeO3 as the optimal OSM in the series because its structure remains homogeneous throughout the reaction, and its OSC envelope is similar to that of the higher doped materials.

  8. A reaction cell with sample laser heating for in situ soft X-ray absorption spectroscopy studies under environmental conditions.

    PubMed

    Escudero, Carlos; Jiang, Peng; Pach, Elzbieta; Borondics, Ferenc; West, Mark W; Tuxen, Anders; Chintapalli, Mahati; Carenco, Sophie; Guo, Jinghua; Salmeron, Miquel

    2013-05-01

    A miniature (1 ml volume) reaction cell with transparent X-ray windows and laser heating of the sample has been designed to conduct X-ray absorption spectroscopy studies of materials in the presence of gases at atmospheric pressures. Heating by laser solves the problems associated with the presence of reactive gases interacting with hot filaments used in resistive heating methods. It also facilitates collection of a small total electron yield signal by eliminating interference with heating current leakage and ground loops. The excellent operation of the cell is demonstrated with examples of CO and H2 Fischer-Tropsch reactions on Co nanoparticles. PMID:23592631

  9. A portable powder-liquid high corrosion-resistant reaction cell for in situ X-ray diffraction and absorption studies of heterogeneous powder-liquid reactions and phase transformations

    NASA Astrophysics Data System (ADS)

    Ferrer, P.; da Silva, I.; Heyman, C.; Rubio-Zuazo, J.; Castro, G. R.

    2013-03-01

    A portable powder-liquid high corrosion-resistant reaction cell has been designed to follow in situ reactions by X-ray powder diffraction and X-ray absorption spectroscopy techniques in transmission mode. The cell has been conceived to be mounted on the experimental stations for diffraction and absorption of the Spanish CRG SpLine-BM25 beamline at the ESRF. In the case of the diffraction technique, data can be collected with either a point detector or a two-dimensional CCD detector. Using the 2D-CCD camera, the cell can be used for time-resolved in situ studies of phase transitions and reactions. Powder reactants and/or products are kept at a fixed position in a vertical geometry in the X-ray pathway, which is minimized in order to reduce the X-ray absorption by the reaction bath. Sample is fixed by a porous membrane under forced liquid reflux circulation, assuring total powder-liquid contact, with an accurate temperature control in the range from 20 to 220°C.

  10. An in situ sample environment reaction cell for spatially resolved x-ray absorption spectroscopy studies of powders and small structured reactors

    NASA Astrophysics Data System (ADS)

    Zhang, Chu; Gustafson, Johan; Merte, Lindsay R.; Evertsson, Jonas; Norén, Katarina; Carlson, Stefan; Svensson, Hâkan; Carlsson, Per-Anders

    2015-03-01

    An easy-to-use sample environment reaction cell for X-ray based in situ studies of powders and small structured samples, e.g., powder, pellet, and monolith catalysts, is described. The design of the cell allows for flexible use of appropriate X-ray transparent windows, shielding the sample from ambient conditions, such that incident X-ray energies as low as 3 keV can be used. Thus, in situ X-ray absorption spectroscopy (XAS) measurements in either transmission or fluorescence mode are facilitated. Total gas flows up to about 500 mln/min can be fed while the sample temperature is accurately controlled (at least) in the range of 25-500 °C. The gas feed is composed by a versatile gas-mixing system and the effluent gas flow composition is monitored with mass spectrometry (MS). These systems are described briefly. Results from simultaneous XAS/MS measurements during oxidation of carbon monoxide over a 4% Pt/Al2O3 powder catalyst are used to illustrate the system performance in terms of transmission XAS. Also, 2.2% Pd/Al2O3 and 2% Ag - Al2O3 powder catalysts have been used to demonstrate X-ray absorption near-edge structure (XANES) spectroscopy in fluorescence mode. Further, a 2% Pt/Al2O3 monolith catalyst was used ex situ for transmission XANES. The reaction cell opens for facile studies of structure-function relationships for model as well as realistic catalysts both in the form of powders, small pellets, and coated or extruded monoliths at near realistic conditions. The applicability of the cell for X-ray diffraction measurements is discussed.

  11. An in situ sample environment reaction cell for spatially resolved x-ray absorption spectroscopy studies of powders and small structured reactors

    SciTech Connect

    Zhang, Chu; Gustafson, Johan; Merte, Lindsay R.; Evertsson, Jonas; Norén, Katarina; Carlson, Stefan; Svensson, Håkan; Carlsson, Per-Anders

    2015-03-15

    An easy-to-use sample environment reaction cell for X-ray based in situ studies of powders and small structured samples, e.g., powder, pellet, and monolith catalysts, is described. The design of the cell allows for flexible use of appropriate X-ray transparent windows, shielding the sample from ambient conditions, such that incident X-ray energies as low as 3 keV can be used. Thus, in situ X-ray absorption spectroscopy (XAS) measurements in either transmission or fluorescence mode are facilitated. Total gas flows up to about 500 ml{sub n}/min can be fed while the sample temperature is accurately controlled (at least) in the range of 25–500 °C. The gas feed is composed by a versatile gas-mixing system and the effluent gas flow composition is monitored with mass spectrometry (MS). These systems are described briefly. Results from simultaneous XAS/MS measurements during oxidation of carbon monoxide over a 4% Pt/Al{sub 2}O{sub 3} powder catalyst are used to illustrate the system performance in terms of transmission XAS. Also, 2.2% Pd/Al{sub 2}O{sub 3} and 2% Ag − Al{sub 2}O{sub 3} powder catalysts have been used to demonstrate X-ray absorption near-edge structure (XANES) spectroscopy in fluorescence mode. Further, a 2% Pt/Al{sub 2}O{sub 3} monolith catalyst was used ex situ for transmission XANES. The reaction cell opens for facile studies of structure-function relationships for model as well as realistic catalysts both in the form of powders, small pellets, and coated or extruded monoliths at near realistic conditions. The applicability of the cell for X-ray diffraction measurements is discussed.

  12. Study of Epstein-Barr virus expression in Burkitt's lymphoma by polymerase chain reaction and in situ hybridization: A study in Iran

    PubMed Central

    Deyhimi, Parviz; Kalantari, Mahsa

    2014-01-01

    Background: The association of Epstein-Barr virus (EBV) with Burkitt's lymphoma (BL) is variable in different geographic regions. In developing countries, the association of EBV with BL is regarded to be of an endemic-type in equatorial Africa (> 95%) and sporadic-type in the developed countries (15-30%). The purpose of this study is to assess the frequency of EBV infection in BL, in Iran. The study also aims to compare Ribonucleic acid (RNA) in situ hybridization (RISH), the standard diagnostic method, with the polymerase chain reaction (PCR)-based method for diagnosing BL. Materials and Methods: In this epidemiological study, the paraffinized specimens of 18 cases of BL were selected. Next, the ISH of EBV-encoded RNA (EBER-RISH) and PCR assays that were based on Epstein Barr Nuclear Antigen 2 (EBNA2) amplification were used. The EBV strain was determined by PCR. The data were analyzed using the SPSS10 software and by performing Pearson correlation coefficient formula at a significant level of 0.05. Results: EBV RNA was detected in 50% of the BL specimens. Type 1 and 2 accounted for 70 and 30% of the cases, respectively. Regarding RISH as the standard method for EBV diagnosis, the PCR assays showed a sensitivity and specificity of 100 and 88.9%, respectively. Conclusion: According to the obtained findings, the frequency of EBV in BL was 50% and PCR and RISH showed high concordance and sensitivity in EBV detection. Therefore, PCR can be used as a faster method for EBV detection in high-risk geographical regions. PMID:25097650

  13. Aberration corrected environmental STEM (AC ESTEM) for dynamic in-situ gas reaction studies of nanoparticle catalysts

    NASA Astrophysics Data System (ADS)

    Boyes, E. D.; Gai, P. L.

    2014-06-01

    Environmental scanning transmission electron microscopy (ESTEM) with aberration correction (AC) has recently been added to the capabilities of the more established ETEM for analysis of heterogeneous nanoparticle based catalysts. It has helped to reveal the importance and potentially unique properties of individual atoms as active sites in their own right as well as pathways between established nanoparticles. A new capability is introduced for dynamic in-situ experiments under controlled conditions of specimen temperature and gas environment related to real world conditions pertinent to a range of industrial and societal priorities for new and improved chemical processes, materials, fuels, pharmaceutical products and processes, and in control or remediation of environmental emissions.

  14. A study of plasma reaction mechanisms and kinetics in glow discharges of methyl methacrylate and related precursors using in situ FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Pan, Yu-Chi Vickie

    In order to understand plasma deposition processes, it is important to have a knowledge of the plasma gas-phase reactions. In this project, in situ Fourier Transform Infrared Spectroscopy (FTIR) was utilized to study the plasma gas-phase chemistry in a capacitively coupled glow discharge. Gas-phase measurements of a number of organic plasmas were performed. The precursors include methyl methacrylate (MMA), methyl crotonate, methyl isobutyrate, ethyl methacrylate, vinyl acetate, isopropanol, methanol, tetramethyl cyclobutanedione and formaldehyde. However, MMA was studied most extensively. In addition to the gas-phase study, plasma polymerized films were also characterized. A number of dissociation products were detected by FTIR in the plasmas. Calibration curves of these products and some monomers were prepared to determine the species concentrations and gas-phase composition. Plasma reaction kinetics were studied in closed systems to determine parameters such as dissociation pathway efficiencies, monomer decomposition rate coefficients, and intermediate species decomposition rate coefficients. The study shows that there are two major electron-impact induced dissociation pathways in MMA plasmas: the C-O bond cleavage reaction and decarboxylations. The C-O bond cleavage reaction accounts for approximately half of the MMA dissociation, and neutral formaldehyde and dimethyl ketene (DMK) molecules are produced via intramolecular rearrangement. Decarboxylation reactions produce CO, COsb2 and a number of radicals that subsequently stabilize to form neutral molecules, such as propylene, allene and methanol. These intermediate species then further dissociate in the plasma to small hydrocarbons (methane, acetylene and ethylene), CO, COsb2 and Hsb2. The reaction mechanisms in the plasmas of other alpha ,beta-unsaturated esters and vinyl acetate were found to be similar to the MMA mechanisms. However, the saturated ester (methyl isobutyrate) and isopropanol plasmas were found

  15. In situ study on the effect of thermomigration on intermetallic compounds growth in liquid-solid interfacial reaction

    SciTech Connect

    Qu, Lin; Zhao, Ning; Ma, Haitao Zhao, Huijing; Huang, Mingliang

    2014-05-28

    Synchrotron radiation real-time imaging technology was carried out in situ to observe and characterize the effect of thermomigration on the growth behavior of interfacial intermetallic compounds (IMCs) in Cu/Sn/Cu solder joint during soldering. The thermomigration resulted in asymmetrical formation and growth of the interfacial IMCs. Cu{sub 6}Sn{sub 5} and Cu{sub 3}Sn IMCs formed at the cold end and grew rapidly during the whole soldering process. However, only Cu{sub 6}Sn{sub 5} IMC formed at the hot end and remained relatively thin until solidification. The IMCs at the cold end were nearly seven times thicker than that at the hot end after solidification. The Cu dissolution at the cold end was significantly restrained, while that at the hot end was promoted, which supplied Cu atoms to diffuse toward the cold end under thermomigration to feed the rapid IMC growth. Moreover, the thermomigration also caused asymmetrical morphology of the interfacial IMCs at the cooling stage, i.e., the Cu{sub 6}Sn{sub 5} IMC at the cold end transformed into facet structure, while that at the hot end remained scallop-type. The asymmetrical growth behavior of the interfacial IMCs was analyzed from the view point of kinetics.

  16. The reaction of ceria coatings on mica with H{sub 2}S An in-situ X-ray diffraction study

    SciTech Connect

    Bertaux, S.; Reynders, P.; Schweda, E

    2004-05-05

    Thin layers of ceria were deposited on the surface of mica platelets in solution. The reaction of such particles with hydrogen sulfide yields a red colored special effect pigment. The ceria layer reacts with H{sub 2}S to produce a variety of sulfide and oxysulfide phases. The reaction path discovered in situ by time and temperature resolved X-ray diffraction is CeO{sub 2}{yields}CeS{sub 2}{yields}C-Ce{sub 2}S{sub 3}{yields}Ce{sub 10}S{sub 14}O. The reaction itself is extremely variable depending on gas flow, heating rates and decomposition atmospheres. Effects on the thin film are recorded by scanning electron microscopy (SEM) and revealed a destruction of the layer once red Ce{sub 10}S{sub 14}O was formed. The product layer then reveals the typical nonwetting behaviour of a liquid on a surface.

  17. Monitoring enzymatic reactions with in situ sensors

    NASA Astrophysics Data System (ADS)

    Young, Ian T.; Iordanov, V.; Kroon, Arthur; Dietrich, Heidi R. C.; Moerman, R.; van den Doel, L. R.; van Dedem, G. W. K.; Bossche, Andre; Gray, Bonnie L.; Sarro, Lina; Verbeek, Piet W.; van Vliet, Lucas J.

    2003-07-01

    In previous publications and presentations we have described our construction of a laboratory-on-a-chip based on nanoliter capacity wells etched in silicon. We have described methods for dispensing reagents as well as samples, for preventing evaporation, for embedding electronics in each well to measure fluid volume per well in real-time, and for monitoring the production or consumption of NADH in enzyme-catalyzed reactions such as those found in the glycolytic pathway of yeast. In this paper we describe the use of light sensors (photodiodes) in each well to measure both fluorescence (such as that evidenced in NADH) as well as bioluminescence (such as evidenced in ATP assays). We show that our detection limit for NADH fluorescence in 100 μM and for ATP/luciferase bioluminescence is 2.4 μM.

  18. In situ analysis of copper electrodeposition reaction using unilateral NMR sensor

    NASA Astrophysics Data System (ADS)

    Gomes, B. F.; Nunes, L. M. S.; Lobo, C. M. S.; Carvalho, A. S.; Cabeça, L. F.; Colnago, L. A.

    2015-12-01

    The uses of high-resolution NMR spectroscopy and imaging (MRI) to study electrochemical reactions in situ have greatly increased in the last decade. However, most of these applications are limited to specialized NMR laboratories and not feasible for routine analysis. Recently we have shown that a bench top, time domain NMR spectrometer can be used to monitor in situ copper electrodeposition reaction and the effect of Lorentz force in the reaction rate. However these spectrometers limit the cell size to the magnet gap and cannot be used with standard electrochemical cells. In this paper we are demonstrating that unilateral NMR sensor (UNMR), which does not limit sample size/volume, can be used to monitor electrodeposition of paramagnetic ions in situ. The copper electrodeposition reaction was monitored remotely and in situ, placing the electrochemical cell on top of the UNMR sensor. The Cu2+ concentration was measured during three hours of the electrodeposition reactions, by using the transverse relaxation rate (R2) determined with the Carr-Purcell-Meiboom-Gill pulse sequence. The reaction rate increased fourfold when the reaction was performed in the presence of a magnetic field (in situ), in comparison to the reactions in the absence of the magnetic field (ex situ). The increase of reaction rate, in the presence of the UNMR magnet, was related to the magneto hydrodynamic force (FB) and magnetic field gradient force (F∇B). F∇B was calculated to be one order of magnitude stronger than FB. The UNMR sensor has several advantages for in situ measurements when compared to standard NMR spectrometers. It is a low cost, portable, open system, which does not limit sample size/volume and can be easily be adapted to standard electrochemical cells or large industrial reactors.

  19. In situ analysis of copper electrodeposition reaction using unilateral NMR sensor.

    PubMed

    Gomes, B F; Nunes, L M S; Lobo, C M S; Carvalho, A S; Cabeça, L F; Colnago, L A

    2015-12-01

    The uses of high-resolution NMR spectroscopy and imaging (MRI) to study electrochemical reactions in situ have greatly increased in the last decade. However, most of these applications are limited to specialized NMR laboratories and not feasible for routine analysis. Recently we have shown that a bench top, time domain NMR spectrometer can be used to monitor in situ copper electrodeposition reaction and the effect of Lorentz force in the reaction rate. However these spectrometers limit the cell size to the magnet gap and cannot be used with standard electrochemical cells. In this paper we are demonstrating that unilateral NMR sensor (UNMR), which does not limit sample size/volume, can be used to monitor electrodeposition of paramagnetic ions in situ. The copper electrodeposition reaction was monitored remotely and in situ, placing the electrochemical cell on top of the UNMR sensor. The Cu(2+) concentration was measured during three hours of the electrodeposition reactions, by using the transverse relaxation rate (R2) determined with the Carr-Purcell-Meiboom-Gill pulse sequence. The reaction rate increased fourfold when the reaction was performed in the presence of a magnetic field (in situ), in comparison to the reactions in the absence of the magnetic field (ex situ). The increase of reaction rate, in the presence of the UNMR magnet, was related to the magneto hydrodynamic force (FB) and magnetic field gradient force (F∇B). F∇B was calculated to be one order of magnitude stronger than FB. The UNMR sensor has several advantages for in situ measurements when compared to standard NMR spectrometers. It is a low cost, portable, open system, which does not limit sample size/volume and can be easily be adapted to standard electrochemical cells or large industrial reactors. PMID:26540649

  20. In Situ Studies of the Active Sites for the Water Gas Shift Reaction over Cu-CeO2 Catalysts: Complex Interaction Between Metallic Copper and Oxygen Vacancies of Ceria

    SciTech Connect

    Wang,X.; Rodriguez, J.; Hanson, J.; Gamarra, D.; Martinez-Arias, A.; Fernandez-Garcia, M.

    2006-01-01

    New information about the active sites for the water gas shift (WGS) reaction over Cu-CeO{sub 2} systems was obtained using in-situ, time-resolved X-ray diffraction (TR-XRD), X-ray absorption spectroscopy (TR-XAS, Cu K and Ce L3 edges), and infrared spectroscopy (DRIFTS). Cu-CeO{sub 2} nanoparticles prepared by a novel reversed microemulsion method (doped Ce1-xCuxO2 sample) and an impregnation method (impregnated CuO{sub x}/CeO{sub 2} sample) were studied. The results from all of the samples indicate that both metallic copper and oxygen vacancies in ceria were involved in the generation of active sites for the WGS reaction. Evidence was found for a synergistic Cu-O vacancy interaction. This interaction enhances the chemical activity of Cu, and the presence of Cu facilitates the formation of O vacancies in ceria under reaction conditions. Water dissociation occurred on the O vacancy sites or the Cu-O vacancy interface. No significant amounts of formate were formed on the catalysts during the WGS reaction. The presence of strongly bound carbonates is an important factor for the deactivation of the catalysts at high temperatures. This work identifies for the first time the active sites for the WGS reaction on Cu-CeO{sub 2} catalysts and illustrates the importance of in situ structural studies for heterogeneous catalytic reactions.

  1. In-situ Studies of the Reactions of Bifunctional and Heterocyclic Molecules over Noble Metal Single Crystal and Nanoparticle Catalysts Studied with Kinetics and Sum-Frequency Generation Vibrational Spectroscopy

    SciTech Connect

    Kliewer, Christopher J.

    2009-06-30

    Sum frequency generation surface vibrational spectroscopy (SFG-VS) in combination with gas chromatography (GC) was used in-situ to monitor surface bound reaction intermediates and reaction selectivities for the hydrogenation reactions of pyrrole, furan, pyridine, acrolein, crotonaldehyde, and prenal over Pt(111), Pt(100), Rh(111), and platinum nanoparticles under Torr reactant pressures and temperatures of 300K to 450K. The focus of this work is the correlation between the SFG-VS observed surface bound reaction intermediates and adsorption modes with the reaction selectivity, and how this is affected by catalyst structure and temperature. Pyrrole hydrogenation was investigated over Pt(111) and Rh(111) single crystals at Torr pressures. It was found that pyrrole adsorbs to Pt(111) perpendicularly by cleaving the N-H bond and binding through the nitrogen. However, over Rh(111) pyrrole adsorbs in a tilted geometry binding through the {pi}-aromatic orbitals. A surface-bound pyrroline reaction intermediate was detected over both surfaces with SFG-VS. It was found that the ring-cracking product butylamine is a reaction poison over both surfaces studied. Furan hydrogenation was studied over Pt(111), Pt(100), 10 nm cubic platinum nanoparticles and 1 nm platinum nanoparticles. The product distribution was observed to be highly structure sensitive and the acquired SFG-VS spectra reflected this sensitivity. Pt(100) exhibited more ring-cracking to form butanol than Pt(111), while the nanoparticles yielded higher selectivities for the partially saturated ring dihydrofuran. Pyridine hydrogenation was investigated over Pt(111) and Pt(100). The α-pyridyl surface adsorption mode was observed with SFG-VS over both surfaces. 1,4-dihydropyridine was seen as a surface intermediate over Pt(100) but not Pt(111). Upon heating the surfaces to 350K, the adsorbed pyridine changes to a flat-lying adsorption mode. No evidence was found for the pyridinium cation. The hydrogenation of the

  2. In–situ Spatiotemporal Chemical Reactions at Water-Solid Interfacial Processes using Microelectrode Techniques: from Biofilm to Metal Corrosion

    EPA Science Inventory

    Recent developments in microscale sensors allows the non-destructive and in–situ measurement of both the absolute and changes in chemical concentrations in engineered and natural aquatic systems. Microelectrodes represent a unique tool for studying in–situ chemical reactions in b...

  3. In situ XANES & XRD Study of interphasial reaction between uncharged Li2FeSiO4 cathode and LiPF6-based electrolyte

    NASA Astrophysics Data System (ADS)

    Arthur, Z.; Chiu, H. C.; Lu, X.; Chen, N.; Emond, V.; Demopoulos, G. P.; Jiang, D. T.

    2016-05-01

    In situ synchrotron radiation XANES and XRD have been carried out on Li2FeSiO4 cathode material in a lithium-ion-battery (LIB) cell. The evolution of the long range lattice structure and the local iron oxidation state has been observed at a charging rate of C/20 for the formation cycle for one Lithium extraction; additional ex situ measurements of the pristine cathode material were taken for comparison. The observed spontaneous interaction between the cathode and the fluorinated electrolyte and the impact of subsequent cycling are discussed.

  4. In situ alkali-silica reaction observed by x-ray microscopy

    SciTech Connect

    Kurtis, K.E.; Monteiro, P.J.M.; Brown, J.T.; Meyer-Ilse, W.

    1997-04-01

    In concrete, alkali metal ions and hydroxyl ions contributed by the cement and reactive silicates present in aggregate can participate in a destructive alkali-silica reaction (ASR). This reaction of the alkalis with the silicates produces a gel that tends to imbibe water found in the concrete pores, leading to swelling of the gel and eventual cracking of the affected concrete member. Over 104 cases of alkali-aggregate reaction in dams and spillways have been reported around the world. At present, no method exists to arrest the expansive chemical reaction which generates significant distress in the affected structures. Most existing techniques available for the examination of concrete microstructure, including ASR products, demand that samples be dried and exposed to high pressure during the observation period. These sample preparation requirements present a major disadvantage for the study of alkali-silica reaction. Given the nature of the reaction and the affect of water on its products, it is likely that the removal of water will affect the morphology, creating artifacts in the sample. The purpose of this research is to observe and characterize the alkali-silica reaction, including each of the specific reactions identified previously, in situ without introducing sample artifacts. For observation of unconditioned samples, x-ray microscopy offers an opportunity for such an examination of the alkali-silica reaction. Currently, this investigation is focusing on the effect of calcium ions on the alkali-silica reaction.

  5. Cu(II)-Gd(III) cryogenic magnetic refrigerants and Cu8Dy9 single-molecule magnet generated by in situ reactions of picolinaldehyde and acetylpyridine: experimental and theoretical study.

    PubMed

    Liu, Jun-Liang; Lin, Wei-Quan; Chen, Yan-Cong; Gómez-Coca, Silvia; Aravena, Daniel; Ruiz, Eliseo; Leng, Ji-Dong; Tong, Ming-Liang

    2013-12-16

    A series of heterometallic [Ln(III)(x)Cu(II)(y)] complexes, [Gd2Cu2]n (1), [Gd4Cu8] (2), [Ln9Cu8] (Ln=Gd, 3·Gd; Ln=Dy, 3·Dy), were successfully synthesized by a one-pot route at room temperature with three kinds of in situ carbonyl-related reactions: Cannizzaro reaction, aldol reaction, and oxidation. This strategy led to dysprosium analogues that behaved as single-molecule magnets (SMMs) and gadolinium analogues that showed significant magnetocaloric effect (MCE). In this study a numerical DFT approach is proposed by using pseudopotentials to calculate the exchange coupling constants in three polynuclear [Gd(x)Cu(y)] complexes; with these values exact diagonalization or quantum Monte Carlo simulations have been performed to calculate the variation of the magnetic entropy involved in the MCE. For the [Dy9Cu8] complexes, local magnetic properties of the Dy(III) centers have been determined by using the CASSCF+RASSI method. PMID:24265054

  6. Laboratory support for in situ gasification: reaction kinetics. Annual report October 1977-September 1978

    SciTech Connect

    Young, J.E.; Wong, S.H.; Johnson, J.E.; Sikand, N.; Jonke, A.A.

    1980-02-01

    This work is directed toward support studies for the national program for the development and demonstration of in situ coal gasification processes. The objective of this work is to determine the reaction-controlling variables and reaction kinetics for the gasification of chars obtained by pyrolyzing coal in simulated underground gasification conditions. The reactions being studied and to be studied include steam-char, CO/sub 2/-char, H/sub 2/-char, the water-gas shift reaction, and the methanation reaction. In this report are presented data regarding the kinetics of the reaction of steam with chars prepared from Pittsburgh seam high-volatile bituminous coal. In addition, a reaction model is described correlating the steam-char reaction rates measured earlier for Hanna subbituminous coal with operating conditions including temperature, partial pressures of steam and hydrogen, and extent of carbon gasification. Partial results are presented and discussed for an investigation of structural parameters of Hanna char as a function of pyrolysis conditions and extent of carbon gasified.

  7. Studying Reaction Intermediates Formed at Graphenic Surfaces

    NASA Astrophysics Data System (ADS)

    Sarkar, Depanjan; Sen Gupta, Soujit; Narayanan, Rahul; Pradeep, Thalappil

    2014-03-01

    We report in-situ production and detection of intermediates at graphenic surfaces, especially during alcohol oxidation. Alcohol oxidation to acid occurs on graphene oxide-coated paper surface, driven by an electrical potential, in a paper spray mass spectrometry experiment. As paper spray ionization is a fast process and the time scale matches with the reaction time scale, we were able to detect the intermediate, acetal. This is the first observation of acetal formed in surface oxidation. The process is not limited to alcohols and the reaction has been extended to aldehydes, amines, phosphenes, sugars, etc., where reaction products were detected instantaneously. By combining surface reactions with ambient ionization and mass spectrometry, we show that new insights into chemical reactions become feasible. We suggest that several other chemical transformations may be studied this way. This work opens up a new pathway for different industrially and energetically important reactions using different metal catalysts and modified substrate.

  8. In Situ Raman Monitoring of Silver(I)-Aided Laser-Driven Cleavage Reaction of Cyclobutane.

    PubMed

    Chen, Dengtai; Han, Xijiang; Du, Yunchen; Wang, Hsing-Lin; Xu, Ping

    2016-01-01

    The cyclobutane cleavage reaction is an important process and has received continuous interest. Herein, we demonstrate the visible laser-driven cleavage reaction of cyclobutane in crystal form by using in situ Raman spectroscopy. Silver(I) coordination-induced strain and thermal effects from the laser irradiation are the two main driving forces for the cleavage of cyclobutane crystals. This work may open up a new avenue for studying cyclobutane cleavage reactions, as compared to the conventional routes using ex situ techniques. PMID:26510491

  9. In-situ investigation of Cu-In-Se reactions by thin film calorimetry

    SciTech Connect

    Wolf, D.; Mueller, G.

    1998-12-31

    Studies of the reaction path during annealing of Cu-In-Se thin films for solar cell absorbers have been limited up to now to ex-situ analyses of the phase composition by X-Ray Diffraction (XRD) after processing by a specific temperature-time program. As an indirect method, the application of ex-situ XRD /is not sufficient for the determination of reaction temperatures and reaction times for setting up a general model of CIS-formation. The authors show in this paper that the use of a calorimetric method (Thin film Calorimetry, TFC) offers the advantage of a direct (in-situ) observation of thin film reactions. Special care is taken to use film thicknesses of practical interest for industrial application (1.5--3 {micro}m). In a first step the authors show results of binary reactions in the Cu-In, In-Se and Cu-Se systems. Their knowledge is necessary for understanding the processes involved in the ternary CIS-layers. It turned out that thin Cu-In and Cu-Se films react already at room temperature and behave as predicted by the bulk equilibrium phase diagrams during heating. In-Se thin films show prominent exothermic reactions starting with the melting of In. The first phase to be formed is generally In{sub 2}Se which is then converted to more Se-rich compounds. In ternary Cu-In-Se films (Cu/In = 1.00) the authors observe transitions of the Cu-Se-system which can be attributed to the decomposition of CuSe{sub 2} and CuSe. Consequences for the model of improved CIS-growth by a Cu-Se flux agent are discussed.

  10. In situ reaction kinetic analysis of dental restorative materials

    NASA Astrophysics Data System (ADS)

    Younas, Basma; Samad Khan, Abdul; Muzaffar, Danish; Hussain, Ijaz; Chaudhry, Aqif Anwar; Rehman, Ihtesham Ur

    2013-12-01

    The objective of this study was to evaluate in situ structural and thermal changes of dental restorative materials at periodical time intervals. The commercial materials included zinc oxide eugenol (ZOE), zinc phosphate type I (ZnPO4), glass ionomer cement type II (GIC) and resin-based nano-omposite (Filtek Z350 XT). These materials were processed according to manufacturer's instructions. For the structural analysis Fourier transform infrared spectroscopy (FTIR) was used at high resolution. TGA was used to evaluate thermal weight-loss. The FTIR spectra were collected at periodic time intervals. FTIR spectra showed that with time passing all materials exhibited an increase in peak intensities and a new appearance of shoulders and shifting of peaks for example, ZnPO4 (P-O), ZOE (C═O, C═N, C-O-C), GIC (COO-, C-H, Si-OH), composites (C═O, C═C, C═N, C-N-H). The peaks were replaced by bands and these bands became broader with time interval. Composites showed a degree of conversion and new peaks corresponded to the cross-linking of polymer composites. TGA analysis showed that significant changes in weight loss of set materials were observed after 24 h, where ZOE showed continuous changes in thermal degradation. The spectral changes and thermal degradation with time interval elucidated in situ setting behaviour and understanding of their bonding compatibility with tooth structure and change in relation to time.

  11. An in situ heating TEM analysis method for an interface reaction.

    PubMed

    Tanigaki, Toshiaki; Ito, Katsuji; Nagakubo, Yasuhira; Asakawa, Takayuki; Kanemura, Takashi

    2009-10-01

    In order to analyze the thermal property of nano-sized materials, an in situ observation technique that allows highly sensitive energy dispersive x-ray spectroscopic (EDX) analyses and high-resolution in situ heating observation of precision specimens is required. A method for the in situ observation of the interface reaction using an analytical transmission electron microscopy (TEM) and a specimen-heating holder was developed. The specimen holder used in this study was a direct-heating type having a fine tungsten wire heater. For sensitive analyses including an EDX map of composition changes during the interface reaction, a space toward the EDX detector with a take-off angle of 20 degrees was made in the specimen holder. Samples were prepared by attaching a micro-sample directly to the heater using the focused ion beam (FIB) micro-sampling technique. It was confirmed that the sensitive EDX map and electron diffraction analyses were possible during the reaction, and that the resolution of this technique was of the order of 0.223 nm at 550 degrees C. PMID:19376815

  12. Following the Transient Reactions in Lithium-Sulfur Batteries Using In an In Situ Nuclear Magnetic Resonance Technique

    SciTech Connect

    Xiao, Jie; Hu, Jian Z.; Chen, Honghao; Vijayakumar, M.; Zheng, Jianming; Pan, Huilin; Walter, Eric D.; Hu, Mary Y.; Deng, Xuchu; Feng, Ju; Liaw, Bor Yann; Gu, Meng; Deng, Zhiqun; Lu, Dongping; Xu, Suochang; Wang, Chong M.; Liu, Jun

    2015-05-13

    Li-S batteries hold great potential for next-generation, large-format power source applications; yet, the fundamental understanding of the electrochemical reaction pathways remains lacking to enable their functionality as promised. Here, in situ NMR technique employing a specially designed cylindrical micro battery was used to monitor the chemical environments around Li+ ions during repetitive charge-discharge process and track the transient electrochemical and chemical reactions occurring in the whole Li-S system. The in situ NMR provides real time, quantitative information related to the temporal concentration variations of the polysulfides with various chain lengths, providing important clues for the reaction pathways during both discharge and charge processes. The in-situ technique also reveals that redox reactions may involve transient species that are difficult to detect in ex-situ NMR study. Intermediate species such as charged free radicals may play an important role in the formation of the polysulfide products. Additionally, in situ NMR measurement simultaneously reveals vital information on the 7Li chemical environments in the electrochemical and parasitic reactions on the lithium anode that promotes the understanding of the failure mechanism in the Li-S system. These new insights could help design effective strategies to accelerate the development of Li-S battery technology.

  13. In situ liquid-cell electron microscopy of silver-palladium galvanic replacement reactions on silver nanoparticles.

    PubMed

    Sutter, E; Jungjohann, K; Bliznakov, S; Courty, A; Maisonhaute, E; Tenney, S; Sutter, P

    2014-01-01

    Galvanic replacement reactions provide an elegant way of transforming solid nanoparticles into complex hollow morphologies. Conventionally, galvanic replacement is studied by stopping the reaction at different stages and characterizing the products ex situ. In situ observations by liquid-cell electron microscopy can provide insight into mechanisms, rates and possible modifications of galvanic replacement reactions in the native solution environment. Here we use liquid-cell electron microscopy to investigate galvanic replacement reactions between silver nanoparticle templates and aqueous palladium salt solutions. Our in situ observations follow the transformation of the silver nanoparticles into hollow silver-palladium nanostructures. While the silver-palladium nanocages have morphologies similar to those obtained in ex situ control experiments the reaction rates are much higher, indicating that the electron beam strongly affects the galvanic-type process in the liquid-cell. By using scavengers added to the aqueous solution we identify the role of radicals generated via radiolysis by high-energy electrons in modifying galvanic reactions. PMID:25208691

  14. In situ liquid-cell electron microscopy of silver-palladium galvanic replacement reactions on silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Sutter, E.; Jungjohann, K.; Bliznakov, S.; Courty, A.; Maisonhaute, E.; Tenney, S.; Sutter, P.

    2014-09-01

    Galvanic replacement reactions provide an elegant way of transforming solid nanoparticles into complex hollow morphologies. Conventionally, galvanic replacement is studied by stopping the reaction at different stages and characterizing the products ex situ. In situ observations by liquid-cell electron microscopy can provide insight into mechanisms, rates and possible modifications of galvanic replacement reactions in the native solution environment. Here we use liquid-cell electron microscopy to investigate galvanic replacement reactions between silver nanoparticle templates and aqueous palladium salt solutions. Our in situ observations follow the transformation of the silver nanoparticles into hollow silver-palladium nanostructures. While the silver-palladium nanocages have morphologies similar to those obtained in ex situ control experiments the reaction rates are much higher, indicating that the electron beam strongly affects the galvanic-type process in the liquid-cell. By using scavengers added to the aqueous solution we identify the role of radicals generated via radiolysis by high-energy electrons in modifying galvanic reactions.

  15. Electrochemical in-situ reaction cell for X-ray scattering, diffraction and spectroscopy

    SciTech Connect

    Braun, Artur; Granlund, Eric; Cairns, Elton J.

    2003-01-27

    An electrochemical in-situ reaction cell for hard X-ray experiments with battery electrodes is described. Applications include the small angle scattering, diffraction, and near-edge spectroscopy of lithium manganese oxide electrodes.

  16. In-situ X-ray characterization of the reaction of lithium with InSe

    SciTech Connect

    Levy-Clement, C.; Dahn, J.R.; McKinnon, W.R.; Rioux, J.

    1984-12-01

    The reaction at room temperature of Li with InSe in Li/InSe electrochemical cells was studied using in-situ X-ray diffraction. Li reacts with InSe first to form Li/sub 2/Se and In, then reacts with the In to form InLi. An intermediate phase appears in each of these two steps. The first intermediate phase may be an intercalation compound Li /SUB x/ InSe, the second some In-Li alloy.

  17. Engineered injection and extraction to enhance reaction for improved in situ remediation

    NASA Astrophysics Data System (ADS)

    Piscopo, Amy N.; Neupauer, Roseanna M.; Mays, David C.

    2013-06-01

    During in situ remediation, a treatment solution is often injected into a contaminated aquifer to degrade the groundwater contaminant. Since contaminant degradation reactions occur only at locations where the treatment solution and groundwater contaminant overlap, mixing of the treatment solution and the contaminated groundwater is necessary for reaction to occur. Mixing results from molecular diffusion and pore-scale dispersion, which operate over small length scales; thus, mixing during in situ remediation can only occur where the separation distance between the treatment solution and contaminated groundwater is small. To promote mixing, advection can be used to spread the treatment solution into the contaminated groundwater to increase the extent of the region where the two solutions coexist. A certain degree of passive spreading is the natural consequence of aquifer heterogeneity, which is manifested as macrodispersion. An alternative mechanism is active spreading, in which unsteady flows lead to stretching and folding of plumes. Active spreading can be accomplished by engineered injection and extraction (EIE), in which clean water is injected and extracted at wells surrounding a contaminant plume to create unsteady flow fields that stretch and fold the treatment solution and contaminant plumes. For a model system in which nested plumes of two reactants undergo scalar transport and instantaneous reaction, the simulation results reported here indicate that EIE enhances degradation of groundwater contamination in homogeneous and heterogeneous aquifers compared to baseline models without EIE. Furthermore, this study shows that the amount of reaction provided by the spreading due to EIE is greater than the amount of reaction due to spreading from heterogeneity alone.

  18. In situ high-resolution X-ray photoelectron spectroscopy - Fundamental insights in surface reactions

    NASA Astrophysics Data System (ADS)

    Papp, Christian; Steinrück, Hans-Peter

    2013-11-01

    Since the advent of third generation synchrotron light sources optimized for providing soft X-rays up to 2 keV, X-ray photoelectron spectroscopy (XPS) has been developed to be an outstanding tool to study surface properties and surface reactions at an unprecedented level. The high resolution allows identifying various surface species, and for small molecules even the vibrational fine structure can be resolved in the XP spectra. The high photon flux reduces the required measuring time per spectrum to the domain of a few seconds or even less, which enables to follow surface processes in situ. Moreover, it also provides access to very small coverages down to below 0.1% of a monolayer, enabling the investigation of minority species or processes at defect sites. The photon energy can be adjusted according to the requirement of a particular experiment, i.e., to maximize or minimize the surface sensitivity or the photoionization cross-section of the substrate or the adsorbate. For a few instruments worldwide, a next step forward was taken by combining in situ high-resolution spectrometers with supersonic molecular beams. These beams allow to control and vary the kinetic and internal energies of the incident molecules and provide a local pressure of up to ~10-5 mbar, which can be switched on and off in a controllable way, thus offering a well-defined time structure to study adsorption or reaction processes.

  19. Next-Generation in Situ Hybridization Chain Reaction: Higher Gain, Lower Cost, Greater Durability

    PubMed Central

    2014-01-01

    Hybridization chain reaction (HCR) provides multiplexed, isothermal, enzyme-free, molecular signal amplification in diverse settings. Within intact vertebrate embryos, where signal-to-background is at a premium, HCR in situ amplification enables simultaneous mapping of multiple target mRNAs, addressing a longstanding challenge in the biological sciences. With this approach, RNA probes complementary to mRNA targets trigger chain reactions in which metastable fluorophore-labeled RNA hairpins self-assemble into tethered fluorescent amplification polymers. The properties of HCR lead to straightforward multiplexing, deep sample penetration, high signal-to-background, and sharp subcellular signal localization within fixed whole-mount zebrafish embryos, a standard model system for the study of vertebrate development. However, RNA reagents are expensive and vulnerable to enzymatic degradation. Moreover, the stringent hybridization conditions used to destabilize nonspecific hairpin binding also reduce the energetic driving force for HCR polymerization, creating a trade-off between minimization of background and maximization of signal. Here, we eliminate this trade-off by demonstrating that low background levels can be achieved using permissive in situ amplification conditions (0% formamide, room temperature) and engineer next-generation DNA HCR amplifiers that maximize the free energy benefit per polymerization step while preserving the kinetic trapping property that underlies conditional polymerization, dramatically increasing signal gain, reducing reagent cost, and improving reagent durability. PMID:24712299

  20. In-situ observations of catalytic surface reactions with soft x-rays under working conditions

    NASA Astrophysics Data System (ADS)

    Toyoshima, Ryo; Kondoh, Hiroshi

    2015-03-01

    Catalytic chemical reactions proceeding on solid surfaces are an important topic in fundamental science and industrial technologies such as energy conversion, pollution control and chemical synthesis. Complete understanding of the heterogeneous catalysis and improving its efficiency to an ultimate level are the eventual goals for many surface scientists. Soft x-ray is one of the prime probes to observe electronic and structural information of the target materials. Most studies in surface science using soft x-rays have been performed under ultra-high vacuum conditions due to the technical limitation, though the practical catalytic reactions proceed under ambient pressure conditions. However, recent developments of soft x-ray based techniques operating under ambient pressure conditions have opened a door to the in-situ observation of materials under realistic environments. The near-ambient-pressure x-ray photoelectron spectroscopy (NAP-XPS) using synchrotron radiation enables us to observe the chemical states of surfaces of condensed matters under the presence of gas(es) at elevated pressures, which has been hardly conducted with the conventional XPS technique. Furthermore, not only the NAP-XPS but also ambient-pressure compatible soft x-ray core-level spectroscopies, such as near-edge absorption fine structure (NEXAFS) and x-ray emission spectroscopy (XES), have been significantly contributing to the in-situ observations. In this review, first we introduce recent developments of in-situ observations using soft x-ray techniques and current status. Then we present recent new findings on catalytically active surfaces using soft x-ray techniques, particularly focusing on the NAP-XPS technique. Finally we give a perspective on the future direction of this emerging technique.

  1. In situ measurement of reaction volume and calculation of pH of weak acid buffer solutions under high pressure.

    PubMed

    Min, Stephen K; Samaranayake, Chaminda P; Sastry, Sudhir K

    2011-05-26

    Direct measurements of reaction volume, so far, have been limited to atmospheric pressure. This study describes a method for in situ reaction volume measurements under pressure using a variable volume piezometer. Reaction volumes for protonic ionization of weak acid buffering agents (MES, citric acid, sulfanilic acid, and phosphoric acid) were measured in situ under pressure up to 400 MPa at 25 °C. The methodology involved initial separation of buffering agents within the piezometer using gelatin capsules. Under pressure, the volume of the reactants was measured at 25 °C, and the contents were heated to 40 °C to dissolve the gelatin and allow the reaction to occur, and cooled to 25 °C, where the volume of products was measured. Reaction volumes were used to calculate pH of the buffer solutions as a function of pressure. The results show that the measured reaction volumes as well as the calculated pH values generally quite agree with their respective theoretically predicted values up to 100 MPa. The results of this study highlight the need for a comprehensive theory to describe the pressure behavior of ionization reactions in realistic systems especially at higher pressures. PMID:21542618

  2. In Situ Vitrification Treatability Study Work Plan

    SciTech Connect

    Charboneau, B.L.; Landon, J.L.

    1989-03-01

    The Buried Waste Program was established in October, 1987 to accelerate the studies needed to develop a recommended long-term management plan for the buried mixed waste at the Radioactive Waste Management Complex at the Idaho National Engineering Laboratory. The In Situ Vitrification Project is being conducted in a Comprehensive Environmental Response, Compensation, and Liability Act Feasibility Study format to identify methods for the long-term management of the mixed waste buried. This In Situ Vitrification Treatability Study Work Plan gives a brief description of the site, work breakdown structure, and project organization: the in situ vitrification technology; the purpose of the tests and demonstrations; and the equipment and materials required for the tests and demonstration. 5 refs., 6 figs., 3 tabs.

  3. Photocatalytic removal of soot: unravelling of the reaction mechanism by EPR and in situ FTIR spectroscopy.

    PubMed

    Smits, Marianne; Ling, Yun; Lenaerts, Silvia; Van Doorslaer, Sabine

    2012-12-21

    Photocatalytic soot oxidation is studied on P25 TiO(2) as an important model reaction for self-cleaning processes by means of electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) spectroscopy. Contacting of carbon black with P25 leads on the one hand to a reduction of the local dioxygen concentration in the powder. On the other hand, the weakly adsorbed radicals on the carbon particles are likely to act as alternative traps for the photogenerated conduction-band electrons. We find furthermore that the presence of dioxygen and oxygen-related radicals is vital for the photocatalytic soot degradation. The complete oxidation of soot to CO(2) is evidenced by in situ FTIR spectroscopy, no intermediate CO is detected during the photocatalytic process. PMID:23150192

  4. In Situ Catalyst Modification in Atom Transfer Radical Reactions with Ruthenium Benzylidene Complexes.

    PubMed

    Lee, Juneyoung; Grandner, Jessica M; Engle, Keary M; Houk, K N; Grubbs, Robert H

    2016-06-01

    Ruthenium benzylidene complexes are well-known as olefin metathesis catalysts. Several reports have demonstrated the ability of these catalysts to also facilitate atom transfer radical (ATR) reactions, such as atom transfer radical addition (ATRA) and atom transfer radical polymerization (ATRP). However, while the mechanism of olefin metathesis with ruthenium benzylidenes has been well-studied, the mechanism by which ruthenium benzylidenes promote ATR reactions remains unknown. To probe this question, we have analyzed seven different ruthenium benzylidene complexes for ATR reactivity. Kinetic studies by (1)H NMR revealed that ruthenium benzylidene complexes are rapidly converted into new ATRA-active, metathesis-inactive species under typical ATRA conditions. When ruthenium benzylidene complexes were activated prior to substrate addition, the resulting activated species exhibited enhanced kinetic reactivity in ATRA with no significant difference in overall product yield compared to the original complexes. Even at low temperature, where the original intact complexes did not catalyze the reaction, preactivated catalysts successfully reacted. Only the ruthenium benzylidene complexes that could be rapidly transformed into ATRA-active species could successfully catalyze ATRP, whereas other complexes preferred redox-initiated free radical polymerization. Kinetic measurements along with additional mechanistic and computational studies show that a metathesis-inactive ruthenium species, generated in situ from the ruthenium benzylidene complexes, is the active catalyst in ATR reactions. Based on data from (1) H, (13)C, and (31)P NMR spectroscopy and X-ray crystallography, we suspect that this ATRA-active species is a RuxCly(PCy3)z complex. PMID:27186790

  5. Spectroscopic detection of aqueous contaminants using in situ corona reactions.

    PubMed

    Johnson, M

    1997-04-01

    An apparently novel technique to aid the detection of a variety of inorganic and organic compounds in environmental and drinking water samples is described. Background absorbance due to optical scattering, cell fouling, and a variety of contaminants is suppressed by combining UV spectroscopy with chemical reactions initiated by reactive species generated in a high-voltage corona discharge. Injection of the reactive species takes place through a free water surface from the "corona wind". Initial measurements on aqueous chlorine in drinking water and BTEX (benzene, toluene, ethylbenzene, and xylene) in unfiltered river water down to parts-per-million concentration are given which show, by comparison with a conventional UV absorption measurement, good background suppression. The experimental arrangement is simpler than that in typical fluorescence detection systems, and the geometrical flexibility means that corona "dosing" can be applied also to Raman and other spectroscopies, to electrochemical detection schemes, and to planar and windowless geometries. PMID:9105172

  6. The reaction product of hydrogen and electro-refined plutonium observed by in situ electron microscopy

    NASA Astrophysics Data System (ADS)

    Brierley, M.; Knowles, J. P.; Preuss, M.

    2016-02-01

    Electro-refined plutonium was reacted with hydrogen within the preparation chamber of a Field Emission Gun Scanning Electron Microscope and in situ images were obtained. The plutonium hydride reaction product was observed to have precipitated at the oxide metal interface as angular particulates (ca 2 μm in length) and was also present within micro cracks intersecting the surface.

  7. In situ characterization of catalysts and membranes in a microchannel under high-temperature water gas shift reaction conditions

    NASA Astrophysics Data System (ADS)

    Cavusoglu, G.; Dallmann, F.; Lichtenberg, H.; Goldbach, A.; Dittmeyer, R.; Grunwaldt, J.-D.

    2016-05-01

    Microreactor technology with high heat transfer in combination with stable catalysts is a very attractive approach for reactions involving major heat effects such as methane steam reforming and to some extent, also the high temperature water gas shift (WGS) reaction. For this study Rh/ceria catalysts and an ultrathin hydrogen selective membrane were characterized in situ in a microreactor specially designed for x-ray absorption spectroscopic measurements under WGS conditions. The results of these experiments can serve as a basis for further development of the catalysts and membranes.

  8. Intermolecular enantioselective dearomatization reaction of β-naphthol using meso-aziridine: a bifunctional in situ generated magnesium catalyst.

    PubMed

    Yang, Dongxu; Wang, Linqing; Han, Fengxia; Li, Dan; Zhao, Depeng; Wang, Rui

    2015-02-01

    A direct, facile, and highly diastereo- and enantioselective dearomatization reaction of β-naphthol derivatives with aziridines has been developed for the first time. A newly designed Box-OH ligand was employed for an in situ generated magnesium catalyst and proved to be efficient. The corresponding dearomatization product was transformed into a polycyclic scaffold and polyhydroxylated compound. (1) H NMR studies revealed the activation mode of the dearomatization process of β-naphthols, and a clear positive nonlinear effect was observed in the reaction, and provides insight into the coordination environment around the Mg(II) center and the possible active species. PMID:25589219

  9. A novel system for in-situ observations of early hydration reactions in wet conditions in conventional SEM

    SciTech Connect

    Katz, A.; Bentur, A. . E-mail: bentur@tx.technion.ac.il; Kovler, K.

    2007-01-15

    A novel system enabling wet microscopy in conventional SEM is described and its performance for in-situ study of hydration reactions is demonstrated. The technology is based on a sealed specimen capsule, which is protected from the microscope vacuum by an electron-transparent partition membrane. Thus, the wet sample can be placed and observed in a 'conventional' SEM without the need for drying or employing environmental SEM. Early hydration reactions of gypsum and cement systems were followed during the first 24 h.

  10. Design and operation of an in situ high pressure reaction cell for x-ray absorption spectroscopy.

    SciTech Connect

    Bare, S. R.; Yang, N.; Kelly, S. D.; Mickelson, G. E.; Modica, F. S.; UOP LLC; EXAFS Analysis

    2007-01-01

    The design and initial operation of an in situ catalysis reaction cell for x-ray absorption spectroscopy measurements at high pressure is described. The design is based on an x-ray transparent tube fabricated from beryllium. This forms a true plug flow reactor for catalysis studies. The reactor is coupled to a portable microprocessor-controlled versatile feed system, and incorporates on-line analysis of reaction products. XAFS data recorded during the reduction of a NiRe/carbon catalyst at 4 bar are used to illustrate the performance of the reactor.

  11. Observing Metal-Catalyzed Chemical Reactions in Situ Using Surface-Enhanced Raman Spectroscopy on Pd–Au Nanoshells

    PubMed Central

    Heck, Kimberly N.; Janesko, Benjamin G.; Scuseria, Gustavo E.

    2016-01-01

    Insight into the nature of transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions is obtainable from a number of surface spectroscopic techniques. Carrying out these investigations under actual reaction conditions is preferred but remains challenging, especially for catalytic reactions that occur in water. Here, we report the direct spectroscopic study of the catalytic hydrodechlorination of 1,1-dichloroethene in H2O using surface-enhanced Raman spectroscopy (SERS). With Pd islands grown on Au nanoshell films, this reaction can be followed in situ using SERS, exploiting the high enhancements and large active area of Au nanoshell SERS substrates, the transparency of Raman spectroscopy to aqueous solvents, and the catalytic activity enhancement of Pd by the underlying Au metal. The formation and subsequent transformation of several adsorbate species was observed. These results provide the first direct evidence of the room-temperature catalytic hydrodechlorination of a chlorinated solvent, a potentially important pathway for groundwater cleanup, as a sequence of dechlorination and hydrogenation steps. More broadly, the results highlight the exciting prospects of studying catalytic processes in water in situ, like those involved in biomass conversion and proton-exchange membrane fuel cells. PMID:19554693

  12. Reversible lability by in situ reaction of self-assembled monolayers.

    PubMed

    Saavedra, Héctor M; Thompson, Christopher M; Hohman, J Nathan; Crespi, Vincent H; Weiss, Paul S

    2009-02-18

    We describe a new methodology for the fabrication of controllably displaceable monolayers using a carboxyl-functionalized self-assembled monolayer and in situ Fischer esterification, a simple and reversible chemical reaction. Using an 11-mercaptoundecanoic acid monolayer as a model system, we show that in situ esterification results in the creation of subtle chemical and structural defects. These defects promote molecular exchange reactions with n-dodecanethiol molecules, leading to the complete and rapid displacement of the exposed areas. Displacement results in well-ordered crystalline n-dodecanethiolate monolayer films. We also show that the complementary hydrolysis reaction can be employed to quench the reacted monolayer, significantly hindering further displacement. The generality of reversible lability was tested by applying the in situ esterification reaction to the structurally distinct carboxyl-functionalized molecule 3-mercapto-1-adamantanecarboxylic acid. Beyond its applicability to create mixed-composition monolayers, this methodology could be combined with chemical patterning techniques, such as microdisplacement printing, to fabricate complex functional surfaces. PMID:19170497

  13. Study of char gasification reactions

    SciTech Connect

    Ballal, G.D.

    1986-01-01

    A Texas lignite, an anthracite and two bituminous coals, Pittsburgh number8 and Illinois number6, were pyrolyzed in a nitrogen atmosphere to prepare chars. Optical microscopy, mercury porosimetry and gas adsorption techniques using nitrogen, CO/sub 2/ and CO, were employed for pore structure characterization. The lignite char exhibited the fastest rates of gaseous diffusion, followed in order of decreasing diffusivities by the Illinois number6, Pittsburgh number8 and anthracite chars. The changes in reactivities and pore structures of chars were measured experimentally during their reaction with oxygen (400-550C) and CO/sub 2/ (800-1000C). For a particular char-gas system, the normalized rate-conversion pattern was invariant with respect to temperature and gaseous concentration. In the case of lignite and Pittsburgh number8 chars, the rate-conversion pattern was similar during reaction with oxygen and CO/sub 2/. Adsorption experiments on partially reacted chars indicated that the micropores in the lignite char were accessible to both reactants. The micropores in the Illinois number6 char were, however, not accessible during its reaction with oxygen. The evolution of pore structure during reaction was modeled by using a probabilistic approach which accounts for overlapping pores with different shapes and sizes. The kinetics of gasification of the lignite and the Pittsburgh number8 chars was studied using a Langmuir-Hinshelwood type kinetic expression to correlate the experimental data. CO was found to inhibit the reaction substantially. The effect of a potassium carbonate catalyst on the reaction of these two chars was also investigated. Substantial increases in reaction rates were observed, and the enhancement was approximately proportional to the catalyst loading.

  14. Mechanistic studies of malonic acid-mediated in situ acylation.

    PubMed

    Chandra, Koushik; Naoum, Johnny N; Roy, Tapta Kanchan; Gilon, Chaim; Gerber, R Benny; Friedler, Assaf

    2015-09-01

    We have previously introduced an easy to perform, cost-effective and highly efficient acetylation technique for solid phase synthesis (SPPS). Malonic acid is used as a precursor and the reaction proceeds via a reactive ketene that acetylates the target amine. Here we present a detailed mechanistic study of the malonic acid-mediated acylation. The influence of reaction conditions, peptide sequence and reagents was systematically studied. Our results show that the methodology can be successfully applied to different types of peptides and nonpeptidic molecules irrespective of their structure, sequence, or conformation. Using alkyl, phenyl, and benzyl malonic acid, we synthesized various acyl peptides with almost quantitative yields. The ketenes obtained from the different malonic acid derived precursors were characterized by in situ (1) H-NMR. The reaction proceeded in short reaction times and resulted in excellent yields when using uronium-based coupling agents, DIPEA as a base, DMF/DMSO/NMP as solvents, Rink amide/Wang/Merrifield resins, temperature of 20°C, pH 8-12 and 5 min preactivation at inert atmosphere. The reaction was unaffected by Lewis acids, transition metal ions, surfactants, or salt. DFT studies support the kinetically favorable concerted mechanism for CO2 and ketene formation that leads to the thermodynamically stable acylated products. We conclude that the malonic acid-mediated acylation is a general method applicable to various target molecules. PMID:25846609

  15. Quasi in situ scanning force microscope with an automatic operated reaction chamber.

    PubMed

    Hund, Markus; Olszowka, Violetta; Fischer, Franz; Krejtschi, Heinz

    2011-11-01

    We describe the design and performance of a quasi in situ scanning force microscope with an automatic operated reaction chamber. The design provides a repetitive hermetically sealed sample environment for successive processing. The reaction chamber is based on a combination of a flexure-guided cover, a piezo-positioning system and a force applicator system. An axial force seals the cover against the reactor enabling flow-through applications at low pressure, ambient pressure, or elevated pressure. The position stability of the sample relative to the probe is characterized and a full automated operation of the instrument is explored by the alignment of an ABC terblock copolymer thin film undergoing solvent vapor annealing in the presence of a high electric field. Due to the high electric field strength and the sharp scanning force microscope tip it is impossible to perform in situ scanning in the presence of the electric field. PMID:22128986

  16. Orientation relationship in WC-Co composite nanoparticles synthesized by in situ reactions.

    PubMed

    Wang, Xilong; Song, Xiaoyan; Liu, Xuemei; Liu, Xingwei; Wang, Haibin; Zhou, Cheng

    2015-04-10

    Using the nanoscale violet tungsten oxide as the tungsten source, the WC-Co composite powder was synthesized by the in situ reactions. The particle size of the WC-Co composite powder has a narrow distribution with the mean particle size below 100 nm, and the single composite particle has a nanocrystalline structure with a mean grain size smaller than 10 nm. The detailed characterizations of the nanoparticle microstructure reveal that the orientation relationship and coherence at the interfaces can form during the in situ reactions and further inherit in the consolidated cemented carbide bulk material. The favorable crystallographic characteristics of the WC-Co composite nanoparticles play a significant role in the enhancement of the mechanical properties of the prepared cemented carbide bulk material. PMID:25785577

  17. Orientation relationship in WC-Co composite nanoparticles synthesized by in situ reactions

    NASA Astrophysics Data System (ADS)

    Wang, Xilong; Song, Xiaoyan; Liu, Xuemei; Liu, Xingwei; Wang, Haibin; Zhou, Cheng

    2015-04-01

    Using the nanoscale violet tungsten oxide as the tungsten source, the WC-Co composite powder was synthesized by the in situ reactions. The particle size of the WC-Co composite powder has a narrow distribution with the mean particle size below 100 nm, and the single composite particle has a nanocrystalline structure with a mean grain size smaller than 10 nm. The detailed characterizations of the nanoparticle microstructure reveal that the orientation relationship and coherence at the interfaces can form during the in situ reactions and further inherit in the consolidated cemented carbide bulk material. The favorable crystallographic characteristics of the WC-Co composite nanoparticles play a significant role in the enhancement of the mechanical properties of the prepared cemented carbide bulk material.

  18. Addition of CFCl3 to Aromatic Aldehydes via in Situ Grignard Reaction.

    PubMed

    Barkakaty, Balaka; Talukdar, Bandana; Lokitz, Bradley S

    2015-01-01

    Synthetic modification of trichlorofluoromethane (CFCl3) to non-volatile and useful fluorinated precursors is a cost-effective and an environmentally benign strategy for the safe consumption/destruction of the ozone depleting potential of the reagent. In this report, we present a novel method for in situ Grignard reaction using magnesium powder and CFCl3 for synthesis of dichlorofluoromethyl aromatic alcohols. PMID:26295221

  19. Addition of CFCl3 to Aromatic Aldehydes via in Situ Grignard Reaction

    DOE PAGESBeta

    Barkakaty, Balaka; Talukdar, Bandana; Lokitz, Bradley

    2015-08-18

    In the case of synthetic modification of trichlorofluoromethane (CFCl3) to non-volatile and useful fluorinated precursors, we realized that it is a cost-effective and an environmentally benign strategy for the safe consumption/destruction of the ozone depleting potential of the reagent. In our report, we present a novel method for in situ Grignard reaction using magnesium powder and CFCl3 for synthesis of dichlorofluoromethyl aromatic alcohols.

  20. Addition of CFCl3 to Aromatic Aldehydes via in Situ Grignard Reaction

    SciTech Connect

    Barkakaty, Balaka; Talukdar, Bandana; Lokitz, Bradley

    2015-08-18

    In the case of synthetic modification of trichlorofluoromethane (CFCl3) to non-volatile and useful fluorinated precursors, we realized that it is a cost-effective and an environmentally benign strategy for the safe consumption/destruction of the ozone depleting potential of the reagent. In our report, we present a novel method for in situ Grignard reaction using magnesium powder and CFCl3 for synthesis of dichlorofluoromethyl aromatic alcohols.

  1. In situ observation of surface species on iridium oxide nanoparticles during the oxygen evolution reaction.

    PubMed

    Sanchez Casalongue, Hernan G; Ng, May Ling; Kaya, Sarp; Friebel, Daniel; Ogasawara, Hirohito; Nilsson, Anders

    2014-07-01

    An iridium oxide nanoparticle electrocatalyst under oxygen evolution reaction conditions was probed in situ by ambient-pressure X-ray photoelectron spectroscopy. Under OER conditions, iridium undergoes a change in oxidation state from Ir(IV) to Ir(V) that takes place predominantly at the surface of the catalyst. The chemical change in iridium is coupled to a decrease in surface hydroxide, providing experimental evidence which strongly suggests that the oxygen evolution reaction on iridium oxide occurs through an OOH-mediated deprotonation mechanism. PMID:24889896

  2. Four unexpected lanthanide coordination polymers involving in situ reaction of solvent N, N-Dimethylformamide

    SciTech Connect

    Jin, Jun-Cheng; Tong, Wen-Quan; Fu, Ai-Yun; Xie, Cheng-Gen; Chang, Wen-Gui; Wu, Ju; Xu, Guang-Nian; Zhang, Ya-Nan; Li, Jun; Li, Yong; Yang, Peng-Qi

    2015-05-15

    Four unexpected 2D lanthanide coordination polymers have been synthesized through in situ reactions of DMF solvent under solvothermal conditions. The isostructural complexes 1–3 contain four types of 2{sub 1} helical chains. While the Nd(III) ions are bridged through μ{sub 2}-HIDC{sup 2−} and oxalate to form a 2D sheet along the bc plane without helical character in 4. Therefore, complex 1 exhibits bright red solid-state phosphorescence upon exposure to UV radiation at room temperature. - Graphical abstract: Four unexpected 2D lanthanide coordination polymers have been synthesized through in situ reactions of solvent DMF to formate acid or oxalic acid under solvothermal conditions. The isostructural complexes 1–3 contain four types of different 2{sub 1} helical chains in the 2D layer and 1 exhibits bright red solid-state phosphorescence upon UV radiation. - Highlights: • Four unexpected 2D lanthanide coordination compounds have been synthesized through in situ reactions under solvothermal conditions. • The complexes 1–3 contain four types of 2{sub 1} helical chains in the layer. • Complex 1 exhibits bright red solid-state phosphorescence upon exposure to UV radiation at room temperature.

  3. Interfacial Reaction Studies Using ONIOM

    NASA Technical Reports Server (NTRS)

    Cardelino, Beatriz H.

    2003-01-01

    In this report, we focus on the calculations of the energetics and chemical kinetics of heterogeneous reactions for Organometallic vapor phase epitaxy (OMVPE). The work described in this report builds upon our own previous thermochemical and chemical kinetics studies. The first of these articles refers to the prediction of thermochemical properties, and the latter one deals with the prediction of rate constants for gaseous homolytic dissociation reactions. The calculations of this investigation are at the microscopic level. The systems chosen consisted of a gallium nitride (GaN) substrate, and molecular nitrogen (N2) and ammonia (NH3) as adsorbants. The energetics for the adsorption and the adsorbant dissociation processes were estimated, and reaction rate constants for the dissociation reactions of free and adsorbed molecules were predicted. The energetics for substrate decomposition was also computed. The ONIOM method, implemented in the Gaussian98 program, was used to perform the calculations. This approach has been selected since it allows dividing the system into two layers that can be treated at different levels of accuracy. The atoms of the substrate were modeled using molecular mechanics6 with universal force fields, whereas the adsorbed molecules were approximated using quantum mechanics, based on density functional theory methods with B3LYP functionals and 6-311G(d,p) basis sets. Calculations for the substrate were performed in slabs of several unit cells in each direction. The N2 and NH3 adsorbates were attached to a central location at the Ga-lined surface.

  4. Mechanisms and reaction pathways for simultaneous oxidation of NOx and SO₂ by ozone determined by in situ IR measurements.

    PubMed

    Sun, Chenglang; Zhao, Nan; Zhuang, Zhuokai; Wang, Haiqiang; Liu, Yue; Weng, Xiaole; Wu, Zhongbiao

    2014-06-15

    Ozone (O3) oxidation combined with wet scrubbing is a promising method for the simultaneous removal of SO2 and NOx in flue gas. In this study, the O3 oxidation processes of NO and SO2, as well as their coexistence, were investigated using an in situ IR spectrometer. Experimental results showed that the O3 concentration and the reaction temperature played critical roles in the O3 oxidation process of NO. Around 80°C, when inlet molar ratio of O3/NO was less than 1, NO was mainly oxidized to NO2, while when the ratio was greater than 1, NO would be further oxidized to NO3, N2O5, and HNO3. NO3 was the key intermediate product for the formation of N2O5 and HNO3. However, the subsequent reactions of NO3 were temperature dependence. With the increase of reaction temperature above 100°C, the concentration of NO2 increased whereas the concentrations of N2O5 and HNO3 decreased. The oxidation of SO2 by O3 was negligible and SO2 had little influence on the oxidation of NO in the simultaneous oxidation of NO and SO2. Finally, based on the in situ IR results, the oxidation mechanism is discussed and the reaction pathways are proposed. PMID:24801895

  5. Resonance Raman spectroscopy as an in situ probe for monitoring catalytic events in a Ru-porphyrin mediated amination reaction.

    PubMed

    Zardi, Paolo; Gallo, Emma; Solan, Gregory A; Hudson, Andrew J

    2016-05-10

    Resonance Raman microspectroscopy has been widely used to study the structure and dynamics of porphyrins and metal complexes containing the porphyrin ligand. Here, we have demonstrated that the same technique can be adapted to examine the mechanism of a homogeneously-catalysed reaction mediated by a transition-metal-porphyrin complex. Previously it has been challenging to study this type of reaction using in situ spectroscopic monitoring due to the low stability of the reaction intermediates and elevated-temperature conditions. We have made a straightforward modification to the sample stage on a microscope for time-lapsed Raman microspectroscopy from reaction mixtures in these media. The allylic amination of unsaturated hydrocarbons by aryl azides, which can be catalysed by a ruthenium-porphyrin complex, has been used as an illustrative example of the methodology. The mechanism of this particular reaction has been studied previously using density-functional theory and kinetic approaches. The Raman measurements support the mechanism proposed in the earlier publications by providing the first experimental verification of a precursor reaction complex between the aryl azide and the ruthenium metal ion, and evidence for the formation of a mono-imido intermediate complex under conditions of high concentration of the reactant olefin. PMID:27070335

  6. (Laser enhanced chemical reaction studies)

    SciTech Connect

    Not Available

    1992-01-01

    Experimental studies of dynamic molecular processes are described with particular emphasis on the use of a powerful infrared diode laser probe technique developed in our laboratory. This technique allows us to determine the final states of CO{sub 2} (and other molecules) produced by collisions, photofragmentation, or chemical reactions with a spectral resolution of 0.0003 cm{sup {minus}1} and a time resolution of 10{sup {minus}7} sec. Such high spectral resolution provides a detailed picture of the vibrational and rotational states of molecules produced by these dynamic events. We have used this experimental method to probe collisions between hot hydrogen/deuterium atoms and CO{sub 2}, between O({sup 1}D) atoms and CO{sub 2}, to study the final states of DC1 molecules produced as a result of the reactions of hot Cl atoms, and to investigate the dynamics of the reaction between OH and CO molecules. Advances in our techniques over the past two years have allowed us to identify and study more than 200 final rotational states in ten different vibrational levels of CO{sub 2} encompassing all 3 normal modes, many overtones, and combination states of the molecule. We have extended the technique to probe a variety of new molecules such as OCS, N{sub 2}O, DCl, and CS{sub 2}. All of this work is aimed at providing experimental tests for polyatomic molecule potential energy surfaces, chemical transition states in complex systems, and theories of reaction dynamic in molecules with more than 3 atoms.

  7. Fundamental studies of high-temperature corrosion reactions. Fifth annual progress report

    SciTech Connect

    Rapp, R.A.

    1980-02-01

    The in-situ study of metal oxidation reactions and the mechanism of the sulfidation of molybdenum by sulfur gases were studied. Equipment including a SEM microscope, heater and power supply which were used is described. (FS)

  8. In Situ Imidazole Activation of Ribonucleotides for Abiotic RNA Oligomerization Reactions

    NASA Astrophysics Data System (ADS)

    Burcar, Bradley T.; Jawed, Mohsin; Shah, Hari; McGown, Linda B.

    2015-06-01

    The hypothesis that RNA played a significant role in the origin of life requires effective and efficient abiotic pathways to produce RNA oligomers. The most successful abiotic oligomerization reactions to date have utilized high-energy, modified, or pre-activated ribonucleotides to generate strands of RNA up to 50-mers in length. In spite of their success, these modifications and pre-activation reactions significantly alter the ribonucleotides in ways that are highly unlikely to have occurred on a prebiotic Earth. This research seeks to address this problem by exploring an aqueous based method for activating the canonical ribonucleotides in situ using 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and imidazole. The reactions were run with and without a montmorillonite clay catalyst and compared to reactions that used ribonucleotides that were pre-activated with imidazole. The effects of pH and ribonucleotide concentration were also investigated. The results demonstrate the ability of in situ activation of ribonucleotides to generate linear RNA oligomers in solution, providing an alternative route to produce RNA for use in prebiotic Earth scenarios.

  9. Hybrid Photopatterned Enzymatic Reaction (HyPER) for In situ Cell Manipulation

    PubMed Central

    Griffin, Donald R; Borrajo, Jacob; Soon, Allyson; Acosta-Vélez, Giovanny F.; Oshita, Victor; Darling, Nicole; Mack, Julia; Barker, Thomas; Iruela-Arispe, M. Luisa; Segura, Tatiana

    2014-01-01

    The ability to design artificial extracellular matrices as cell instructive scaffolds has opened the door to technologies capable of studying cell fate in vitro and to guide tissue repair in vivo. One main component of the design of artificial extracellular matrices is the incorporation of biochemical cues to guide cell phenotype and multicellular organization. The extracellular matrix is composed of a heterogeneous mixture of proteins that present a variety of spatially discrete signals to residing cell populations. In contrast, most engineered ECMs do not mimic this heterogeneity. In recent years the use of photodeprotection has been used to achieve spatial immobilization of signals. However, these approaches have been limited mostly to small peptides. Here we combine photodeprotection with enzymatic reaction to achieve spatially controlled immobilization of active bioactive signals that range from small molecules to large proteins. A peptide substrate for transglutaminase factor XIII (FXIIIa) is caged with a photodeprotectable group, which is then immobilized to the bulk of a cell compatible hydrogel. With the use of focused light the substrate can be deprotected and used to immobilize patterned bioactive signals. This approach offers an innovative strategy to immobilize delicate bioactive signals, such as growth factors, without loss of activity and enables In situ cell manipulation of encapsulated cells. PMID:24399784

  10. Monitoring of galvanic replacement reaction between silver nanowires and HAuCl4 by in situ transmission X-ray microscopy.

    PubMed

    Sun, Yugang; Wang, Yuxin

    2011-10-12

    Galvanic replacement reaction between silver nanowires and an aqueous solution of HAuCl(4) has been successfully monitored in real time by using in situ transmission X-ray microscopy (TXM) in combination with a flow cell reactor. The in situ observations clearly show the morphological evolution of the solid silver nanowires to hollow gold nanotubes in the course of the reaction. Careful analysis of the images reveals that the galvanic replacement reaction on the silver nanowires involves multiple steps: (i) local initiation of pitting process; (ii) anisotropic etching of the silver nanowires and uniform deposition of the resulting gold atoms on the surfaces of the nanowires; and (iii) reconstruction of the nanotube walls via an Ostwald ripening process. The in situ TXM represents a promising approach for studying dynamic processes involved in the growth and chemical transformation of nanomaterials in solutions, in particular for nanostructures with dimensions larger than 50 nm. PMID:21894944

  11. Uranyl triazolate formation via an in situ Huisgen 1,3-dipolar cycloaddition reaction

    SciTech Connect

    Knope, Karah E.; Cahill, Christopher L.

    2010-08-27

    A two dimensional UO22+ coordination polymer, (UO2)3(C10H5N3O4)2(OH)2(H2O)2, has been synthesized under solvothermal conditions. The triazolate ligand, 1-(4-carboxyphenyl)-1H-1,2,3-triazole-4-carboxylic acid (CPTAZ) has been generated via a 1,3-dipolar cycloaddition of 4-azidobenzoic acid and propiolic acid. Reactions of the UO22+ cation with both the in situ generated triazolate ligand and the presynthesized ligand have been explored. The structure, fluorescent and thermal behaviour of this material are presented, as is a discussion of the utility of in situ ligand formation versus direct assembly.

  12. In situ Regeneration of NADH via Lipoamide Dehydrogenase-catalyzed Electron Transfer Reaction Evidenced by Spectroelectrochemistry

    SciTech Connect

    Tam, Tsz Kin; Chen, Baowei; Lei, Chenghong; Liu, Jun

    2012-08-01

    NAD/NADH is a coenzyme found in all living cells, carrying electrons from one reaction to another. We report on characterizations of in situ regeneration of NADH via lipoamide dehydrogenase (LD)-catalyzed electron transfer reaction to regenerate NADH using UV-vis spectroelectrochemistry. The Michaelis-Menten constant (Km) and maximum velocity (Vmax) of NADH regeneration were measured as 0.80 {+-} 0.15 mM and 1.91 {+-} 0.09 {micro}M s-1 in a 1-mm thin-layer spectroelectrochemical cell using gold gauze as the working electrode at the applied potential -0.75 V (vs. Ag/AgCl). The electrocatalytic reduction of the NAD system was further coupled with the enzymatic conversion of pyruvate to lactate by lactate dehydrogenase to examine the coenzymatic activity of the regenerated NADH. Although the reproducible electrocatalytic reduction of NAD into NADH is known to be difficult compared to the electrocatalytic oxidation of NADH, our spectroelectrochemical results indicate that the in situ regeneration of NADH via LD-catalyzed electron transfer reaction is fast and sustainable and can be potentially applied to many NAD/NADH-dependent enzyme systems.

  13. Vaginal micropapillary lesions are not related to human papillomavirus infection: in situ hybridization and polymerase chain reaction detection techniques.

    PubMed

    Garzetti, G G; Ciavattini, A; Goteri, G; Menzo, S; De Nictolis, M; Clementi, M; Brugia, M; Romanini, C

    1994-01-01

    The objective of this study was to assess the human papillomavirus DNA presence in vaginal papillary lesions, with particular regard to micropapillomatosis to better define their clinical significance. Prospective study: the study population was composed of 62 women who were recruited consecutively from the Colposcopy Centre of the Ancona University, Department of Obstetrics and Gynecology, on the grounds of vaginal papillomatosis or/and typical acuminata warts. Biopsies for routine histology, and for human papillomavirus (HPV) DNA detection by means of in situ hybridization and polymerase chain reaction (PCR) were taken from the papillary lesions and from 24 healthy women, who were selected as controls. Macroscopically, vaginal micropapillomatosis was ascertained in 51 cases (82.3%), while in 11 cases (17.7%) the colposcopic diagnosis was condyloma acuminatum. During in situ hybridization, HPV DNA positivity was observed in 8 (9.4%) out of 85 samples of squamous papillae and in 11 (64.7%) out of 17 samples of condylomata; in control specimens, HPV DNA was detected in 2 (8.3%) out of 24 bioptic samples. The correspondence between in situ hybridization and PCR was 96.1%, with 17.4% more diagnosis obtained by PCR. Vaginal micropapillomatosis may be regarded as a variation in the normal anatomy of the lower genital tract without any significant relationship with HPV infection, and as a lesion easily distinguishable from condylomata acuminata by clinical examination alone. PMID:7959342

  14. Adsorption, Coadsorption and Reaction of Acetaldehyde and NO₂ on Na-Y,FAU: an in situ FTIR Investigation

    SciTech Connect

    Szanyi, Janos; Kwak, Ja Hun; Moline, Ryan A.; Peden, Charles HF

    2004-11-04

    The adsorption of acetaldehyde and its co-adsorption and reaction with NO₂ were investigated on a Na-Y, FAU zeolite using in situ FTIR spectroscopy. Acetaldehyde adsorbs strongly over Na-Y and desorbs molecularly at around 400K with very limited extent of condensation or polymerization. Reaction between CH₃CHO and NO₂ takes place in co-adsorption experiments even at 300K. In the initial step, acetaldehyde is oxidized to acetic acid accompanied by the formation of NO, which can be observed as N2O₃ formed via a further reaction between NO and NO₂. The key intermediates in the overall NOx reduction in this process are nitro- and nitrosomethane, which form in the next step. Their decomposition and further reaction with adsorbed NOx species lead to the formation of HCN, HNCO, N₂O, CO₂ and organic nitrile species identified by their characteristic IR vibrational signatures. At 473K, the reaction between adsorbed CH₃CHO and NO₂ is very fast. The results seem to suggest a mechanism in which N-N bond formation takes place among ionic nitrogen containing species (NO⁺ and CN⁻ or NCO⁻). No evidence has been found to suggest the participation of NHx⁺NOy⁻ type species in the N⁻N bond formation under the experimental conditions of this study.

  15. New platform for cytochrome p450 reaction combining in situ immobilization on biopolymer.

    PubMed

    Lee, Jae Hyung; Nam, Dong Heon; Lee, Sahng Ha; Park, Jong Hyun; Park, Si Jae; Lee, Seung Hwan; Park, Chan Beum; Jeong, Ki Jun

    2014-12-17

    We describe an efficienct chemical conversion platform with in situ immobilization of P450-BM3 on poly(3-hydroxybutyrate) granules. Through fusion with phasin, P450-BM3 is easily immobilized on poly(3-hydroxybutyrate) granules in Escherichia coli. In our work, the immobilized P450 exhibited higher stability and catalytic activity compared to free P450 against changes of pH, temperature, and concentrations of urea and ions. Through quick recovery of immobilized enzyme, the P450-P(3HB) complex successfully catalyzed an O-dealkylation reaction several times with maintained activity. Using the robust P450-P(3HB) complex, we performed a P450-catalyzed reaction on a preparative reactor scale (100 mL) and high-level production (12.3 μM) of 7-hydroxycoumarine from 7-ethoxycoumarin could be achieved. PMID:25322062

  16. Transfer Reaction Studies with JENSA

    NASA Astrophysics Data System (ADS)

    Thompson, P.; Bardayan, D. W.; Blackmon, J. C.; Chipps, K. A.; Greife, U.; Linhardt, L. E.; Kontos, A.; Kozub, R. L.; Matos, M.; Montes, F.; Pain, S. D.; Pittman, S. T.; Sachs, A.; Schatz, H.; Schmitt, K. T.; Smith, M. S.; Jensa Collaboration

    2015-10-01

    The Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas jet target system was designed to provide a gas target that was pure, localized, and dense. Several commissioning experiments with the JENSA target, performed at Oak Ridge National Laboratory (ORNL), were undertaken to demonstrate the unique capability of JENSA for transfer reaction studies. JENSA has since completed its move from ORNL to the ReA3 reaccelerated beam hall at the National Superconducting Cyclotron Laboratory (NSCL). An overview of the JENSA design and operation will be presented, as well as a brief discussion of the experiments performed at ORNL with JENSA, with a focus on preliminary results from the 20Ne(p,t)18Ne commissioning experiment.

  17. The in-situ characterization of a transesterification reaction using electrical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Cho, Sungjin

    Impedance Spectroscopy has been used in the in-situ monitoring of a transesterfication reaction of soybean biodiesel. This paper describes the application of Electrical Impedance Spectroscopy (EIS) to observe and characterize the transesterfication reaction and its interfacial behavior phenomena electrically. In particular, the dielectric properties of soybean biodiesel were measured at broad range frequencies from 10-2 to 106 Hz at different temperatures, methanol molar ratio to biodiesel, concentration of catalyst and reaction time. Measurement of dielectric property have provided an important approach to understanding the structure of matter. Measurements of the dielectric properties are a reliable and efficient method for evaluating the biodiesel production to determine their quality and yield for reducing the production cost. The dielectric constant (epsilon') and loss (epsilon") are the most convenient indicators for quality control in commercial biodiesel manufacturing. Dielectric properties were correlated with chemically measured changes in soybean oil such as free fatty acids, amount of catalyst and alcohols at different temperatures as well as reaction times. It was observed that there is a good correlation between the dielectric constant (epsilon') and loss (epsilon") in soybean biodiesel. The result indicated that the dielectric properties increased with the (1) increasing temperature (2) increasing methanol; (3) increasing catalyst; (4) increasing reaction time. Dielectric properties was a useful index for the rapid quality evaluation of soybean biodiesel. Dielectric properties were compared to conventional methods of analysis (Infrared Spectroscopy) for evaluating the quality of soybean biodiesel. The results indicated that dielectric constant and dielectric loss are essential measurement for predicting the best biodiesel yield. Moreover, the electrical impedance parameters such as bulk resistance (Rb), bulk capacitance (Cb) and time constant(tau b

  18. In situ visualization of metallurgical reactions in nanoscale Cu/Sn diffusion couples

    SciTech Connect

    Yin, Qiyue; Stach, Eric A.; Gao, Fan; Zhou, Guangwen; Gu, Zhiyong

    2015-02-10

    The Cu–Sn metallurgical soldering reaction in two-segmented Cu–Sn nanowires is visualized by in-situ transmission electron microscopy. By varying the relative lengths of Cu and Sn segments, we show that the metallurgical reaction starts at ~ 200 ° with the formation of a Cu–Sn solid solution for the Sn/Cu length ratio smaller than 1:5 while the formation of Cu–Sn intermetallic compounds (IMCs) for larger Sn/Cu length ratios. Upon heating the nanowires up to ~ 500 °C, two phase transformation pathways occur, η-Cu₆Sn₅ → ε-Cu₃Sn → δ-Cu₄₁Sn₁₁ for nanowires with a long Cu segment and η-Cu₆Sn₅ → ε-Cu₃Sn → γ-Cu₃Sn with a short Cu segment. The dynamic in situ TEM visualization of the evolution of Kirkendall voids demonstrates that Cu diffuses faster both in Sn and IMCs than that of Sn in Cu₃ and IMCs, which is the underlying cause of the dependence of the IMC formation and associated phase evolution on the relative lengths of the Cu and Sn segments.

  19. In situ visualization of metallurgical reactions in nanoscale Cu/Sn diffusion couples

    DOE PAGESBeta

    Yin, Qiyue; Stach, Eric A.; Gao, Fan; Zhou, Guangwen; Gu, Zhiyong

    2015-02-10

    The Cu–Sn metallurgical soldering reaction in two-segmented Cu–Sn nanowires is visualized by in-situ transmission electron microscopy. By varying the relative lengths of Cu and Sn segments, we show that the metallurgical reaction starts at ~ 200 ° with the formation of a Cu–Sn solid solution for the Sn/Cu length ratio smaller than 1:5 while the formation of Cu–Sn intermetallic compounds (IMCs) for larger Sn/Cu length ratios. Upon heating the nanowires up to ~ 500 °C, two phase transformation pathways occur, η-Cu₆Sn₅ → ε-Cu₃Sn → δ-Cu₄₁Sn₁₁ for nanowires with a long Cu segment and η-Cu₆Sn₅ → ε-Cu₃Sn → γ-Cu₃Sn with amore » short Cu segment. The dynamic in situ TEM visualization of the evolution of Kirkendall voids demonstrates that Cu diffuses faster both in Sn and IMCs than that of Sn in Cu₃ and IMCs, which is the underlying cause of the dependence of the IMC formation and associated phase evolution on the relative lengths of the Cu and Sn segments.« less

  20. Structure and properties of composites synthesized in situ using solid state displacement reactions

    SciTech Connect

    Henager, C.H. Jr.; Brimhall, J.L.

    1993-10-01

    Solid state displacement reactions can produce in situ intermetallic and ceramic matrix composites in a process where an intermetallic or ceramic phase(s) and a potential reinforcing phase(s) are grown together during a solid state reaction. Interpenetrating and dispersed microstructures, important for desirable composite properties, have been produced by means of displacement reaction processing techniques. Two such composites have been synthesized which exhibit two distinct microstructures: MoSi{sub 2} reinforced with SiC particles, which exhibits a dispersed-phase structure, and NiAl/Ni{sub 3}Al reinforced with Al{sub 2}O{sub 3}, which exhibits an interpenetrating-phase structure. Strength in bending and chevron-notch fracture toughness have been determined as a function of temperature, and measured properties compare favorably with composites produced by other means. The measured properties are discussed with regard to the observed microstructures. The potential for displacement reaction processing is assessed, and it appears to be a cost-effective synthesis method compared to others.

  1. Nuclear Structure and Reaction Mechanism Studies with Multinucleon Reactions

    SciTech Connect

    Regan, P. H.; Jones, G. A.; Podolyak, Zs.; Abdullah, M.; Gelletly, W.; Langdown, S. D.; Wollel, G.; De Angelis, G.; Gadea, A.; Kroell, Th.; Marginean, N.; Martinez, T.; Napoli, D. R.; Rusu, C.; Tonev, D.; Zhang, Y. H.; Ur, C. A.; Axiotis, M.; Bazzacco, D.; Farnea, E.

    2006-08-14

    This contribution reports on the results of an experiment to study the near-yrast states in selenium- and osmium-like nuclei, following their population in thick-target, multinucleon transfer reactions between an 82Se beam and a 192Os target. The experimental results for the level scheme for 84Se are presented together with investigations into the use of multi-dimensional gamma-ray energy gating to investigate angular momentum population in such heavy-ion binary reactions.

  2. Experimental Study of Serpentinization Reactions

    NASA Technical Reports Server (NTRS)

    Cohen, B. A.; Brearley, A. J.; Ganguly, J.; Liermann, H.-P.; Keil, K.

    2004-01-01

    Current carbonaceous chondrite parent-body thermal models [1-3] produce scenarios that are inconsistent with constraints on aqueous alteration conditions based on meteorite mineralogical evidence, such as phase stability relationships within the meteorite matrix minerals [4] and isotope equilibration arguments [5, 6]. This discrepancy arises principally because of the thermal runaway effect produced by silicate hydration reactions (here loosely called serpentinization, as the principal products are serpentine minerals), which are so exothermic as to produce more than enough heat to melt more ice and provide a self-sustaining chain reaction. One possible way to dissipate the heat of reaction is to use a very small parent body [e.g., 2] or possibly a rubble pile model. Another possibility is to release this heat more slowly, which depends on the alteration reaction path and kinetics.

  3. LONG TERM IN SITU DISPOSAL ENGINEERING STUDY

    SciTech Connect

    ADAMS; CARLSON; BROCKMAN

    2003-07-23

    Patent application pulled per Ken Norris (FH General Counsel). The objective of this study is to devise methods, produce conceptual designs, examine and select alternatives, and estimate costs for the demonstration of long-term (300-year) in situ disposal of an existing waste disposal site. The demonstration site selected is the 216-A-24 Crib near the 200 East Area. The site contains a fission product inventory and has experienced plant, animal, and inadvertent than intrusion. Of the potential intrusive events and transport pathways at the site, potential human intrusion has been given primary consideration in barrier design. Intrusion by wind, plants, and animals has been given secondary consideration. Groundwater modeling for a number of barrier configurations has been carried out to help select a barrier that will minimize water infiltration and waste/water contact time. The estimated effective lifetime and cost of 20 barrier schemes, using a variety of materials, have been evaluated. The schemes studied include single component surface barriers, multicomponent barriers, and massively injected grout barriers. Five barriers with high estimated effective lifetimes and relatively low costs have been selected for detailed evaluation. They are basalt riprap barriers, massive soil barriers, salt basin barriers, multi-component fine/coarse barriers, and cemented basalt barriers. A variety of materials and configurations for marking the site have also been considered. A decision analysis was completed to select a barrier scheme for demonstration. The analysis indicated that the basalt riprap alternative would be the preferred choice for a full-scale demonstration. The recommended approach is to demonstrate the basalt riprap barrier at the 216-A-24 Crib as soon as possible. Methods and costs of assessing effectiveness of the demonstration are also described. Preliminary design modifications and costs for applying the five selected barrier schemes to other site types are

  4. Kinetic studies of elementary chemical reactions

    SciTech Connect

    Durant, J.L. Jr.

    1993-12-01

    This program concerning kinetic studies of elementary chemical reactions is presently focussed on understanding reactions of NH{sub x} species. To reach this goal, the author is pursuing experimental studies of reaction rate coefficients and product branching fractions as well as using electronic structure calculations to calculate transition state properties and reaction rate calculations to relate these properties to predicted kinetic behavior. The synergy existing between the experimental and theoretical studies allow one to gain a deeper insight into more complex elementary reactions.

  5. In situ surface characterization and oxygen reduction reaction on shape-controlled gold nanoparticles.

    PubMed

    Hernández, J; Solla-Gullón, J; Herrero, E; Feliu, J M; Aldaz, A

    2009-04-01

    Gold nanoparticles of different shapes/surface structures were synthesized and electrochemically characterized. An in-situ surface characterization of the Au nanoparticles, which was able to obtain qualitative information about the type and relative sizes of the different facets present in the surface of the Au nanoparticles, was carried out by using Pb Under Potential Deposition (UPD) in alkaline solutions as a surface sensitive tool. The results obtained show that the final atomic arrangement on the surface can be different from that expected from the bulk structure of the well-defined shape Au nanoparticles. In this way, the development of precise in-situ methods to measure the distribution of the different sites on the nanoparticle surface, as lead UPD on gold surfaces, is highlighted. Oxygen Reduction Reaction (ORR) was performed on the different Au nanoparticles. In agreement with the particular sensitivity of the oxygen reduction to the presence of Au(100) surface domains, cubic Au nanoparticles show much better electrocatalytic activity for ORR than small spherical particles and long nanorods, in agreement with the presence of a great fraction of (100) terrace sites on the surface of cubic gold nanoparticles. PMID:19437963

  6. In situ generation of electron acceptor for photoelectrochemical biosensing via hemin-mediated catalytic reaction.

    PubMed

    Zang, Yang; Lei, Jianping; Zhang, Lei; Ju, Huangxian

    2014-12-16

    A novel photoelectrochemical sensing strategy is designed for DNA detection on the basis of in situ generation of an electron acceptor via the catalytic reaction of hemin toward H2O2. The photoelectrochemical platform was established by sequential assembly of near-infrared CdTe quantum dots, capture DNA, and a hemin-labeled DNA probe to form a triple-helix molecular beacon (THMB) structure on an indium tin oxide electrode. According to the highly catalytic capacity of hemin toward H2O2, a photoelectrochemical mechanism was then proposed, in which the electron acceptor of O2 was in situ-generated on the electrode surface, leading to the enhancement of the photocurrent response. The utilization of CdTe QDs can extend the absorption edge to the near-infrared band, resulting in an increase in the light-to-electricity efficiency. After introducing target DNA, the THMB structure is disassembled and releases hemin and, thus, quenches the photocurrent. Under optimized conditions, this biosensor shows high sensitivity with a linear range from 1 to 1000 pM and detection limit of 0.8 pM. Moreover, it exhibits good performance of excellent selectivity, high stability, and acceptable fabrication reproducibility. This present strategy opens an alternative avenue for photoelectrochemical signal transduction and expands the applications of hemin-based materials in photoelectrochemical biosensing and clinical diagnosis. PMID:25393151

  7. Investigation of CaO-CO₂ reaction kinetics by in-situ XRD using synchrotron radiation

    SciTech Connect

    Biasin, A.; Segre, C. U.; Salviulo, G.; Zorzi, F.; Strumendo, M.

    2015-02-05

    In this work, in-situ synchrotron radiation x-ray powder diffraction (SR-XRPD), performed at the Advanced Photon Source (APS) facilities of the Argonne National Laboratory, was applied to investigate the CaO–CO2 reaction. A set of CO2 absorption experiments were conducted in a high temperature reaction capillary with a controlled atmosphere (CO2 partial pressure of 1 bar), in the temperature range between 450 °C and 750 °C using CaO based sorbents obtained by calcination of commercial calcium carbonate. The evolution of the crystalline phases during CO2 uptake by the CaO solid sorbents was monitored for a carbonation time of 20 min as a function of the carbonation temperature and of the calcination conditions. The Rietveld refinement method was applied to estimate the calcium oxide conversion during the reaction progress and the average size of the initial (at the beginning of carbonation) calcium oxide crystallites. The measured average initial carbonation rate (in terms of conversion time derivative) of 0.280 s-1 (±13.2% standard deviation) is significantly higher than the values obtained by thermo-gravimetric analysis and reported thus far in the literature. Additionally, a dependence of the conversion versus time curves on the initial calcium oxide crystallite size was observed and a linear relationship between the initial CaO crystallite size and the calcium oxide final conversion was identified.

  8. Detection of HTLV-1 by polymerase chain reaction in situ hybridization in adult T-cell leukemia/lymphoma.

    PubMed

    Setoyama, M; Kerdel, F A; Elgart, G; Kanzaki, T; Byrnes, J J

    1998-03-01

    A method for nonradioactive polymerase chain reaction in situ hybridization was developed and used to determine the distribution of human T-lymphotropic virus type I (HTLV-I) proviral DNA in paraffin-embedded surgical specimens of adult T-cell leukemia/lymphoma (ATLL). As controls, we used biopsy samples of five cases of mycosis fungoides, cells of an HTLV-I-infected cell line (MT2), as well as HTLV-1-negative cells (YAS). We successfully detected the amplicon of the HTLV-1 tax sequence in the nuclei of the cutaneous infiltrating lymphoid cells in 90% (9/10) of ATLL cases. Studies also revealed the existence of HTLV-1 provirus DNA in nuclei of sweat gland epithelial cells and vascular endothelial cells as well as lymphoid cells in ATLL patients. Mycosis fungoides and YAS cells were negative for the HTLV-I tax sequence, but MT2 cells were strongly positive. The results indicated that this technique was more sensitive in detecting intracellular amplicons than was the previous in situ hybridization method. Through its use, we were able to easily determine the distribution of HTLV-I-positive cells among the various cells and tissues of paraffin-embedded archival materials. PMID:9502410

  9. In-situ synchrotron x-ray spectroscopy of ruthenium nanoparticles modified with selenium for oxygen reduction reaction.

    SciTech Connect

    Inukai, J.; Cao, D.; Wieckowski, A.; Chang, K.-C.; Menzel, A.; Komanicky, V.; You, H.; Materials Science Division; Univ. of Illinois; Univ. of Yamanashi

    2007-11-15

    We used in situ Se K-edge X-ray spectroscopy to characterize Ru nanoparticles chemically modified with submonolayers of selenium (Se/Ru) [Cao et al. J. Electrochem. Soc. 2006, 153, A869]. X-ray powder diffraction verified that the Se/Ru catalyst had metallic Ru cores. The in situ X-ray absorption near edge structure taken at the open circuit potential showed that there were both elemental and oxidized selenium on the as-prepared Se/Ru samples. All selenium oxide was reduced to the elemental form of selenium by applying negative potentials. By applying positive potentials, selenium was subsequently reoxidized. The analysis of the extended X-ray absorption fine structure shows the appearance of selenium hydration (Se-OH{sub 2}) in a deaerated solution, which was not observed during the oxygen reduction reaction. We present evidence that Se-free Ru atoms play an important role in the ORR activity of the Se/Ru catalyst studied in this paper.

  10. In situ synchrotron x-ray spectroscopy of ruthenium nanoparticles modified with selenium for an oxygen reduction reaction.

    SciTech Connect

    Inukai, J.; Cao, D.; Wieckowski, A.; Chang, K.-C.; Menzel, A.; Komanicky, V.; You, H.; Univ. Illinois; Univ. Yamanashi

    2007-11-15

    We used in situ Se K-edge X-ray spectroscopy to characterize Ru nanoparticles chemically modified with submonolayers of selenium (Se/Ru) [Cao et al. J. Electrochem. Soc. 2006, 153, A869]. X-ray powder diffraction verified that the Se/Ru catalyst had metallic Ru cores. The in situ X-ray absorption near edge structure taken at the open circuit potential showed that there were both elemental and oxidized selenium on the as-prepared Se/Ru samples. All selenium oxide was reduced to the elemental form of selenium by applying negative potentials. By applying positive potentials, selenium was subsequently reoxidized. The analysis of the extended X-ray absorption fine structure shows the appearance of selenium hydration (Se-OH{sub 2}) in a deaerated solution, which was not observed during the oxygen reduction reaction. We present evidence that Se-free Ru atoms play an important role in the ORR activity of the Se/Ru catalyst studied in this paper.

  11. Electrophilic activation of alkynes for enyne cycloisomerization reactions with in situ generated early/late heterobimetallic Pt-Ti catalysts.

    PubMed

    Talley, Michael R; Stokes, Ryjul W; Walker, Whitney K; Michaelis, David J

    2016-06-14

    In situ formation of heterobimetallic Pt-Ti catalysts enables rapid room temperature catalysis in enyne cycloisomerization reactions. The Lewis acidic titanium atom in the ligand framework is shown to be essential for fast catalysis. A range of enyne substrates are efficiently cyclized to carbocycles and heterocycles in high yield. PMID:27240482

  12. Uncovering the Role of Metal Catalysis in Tetrazole Formation by an In Situ Cycloaddition Reaction: An Experimental Approach.

    PubMed

    Zhong, Di-Chang; Wen, Ya-Qiong; Deng, Ji-Hua; Luo, Xu-Zhong; Gong, Yun-Nan; Lu, Tong-Bu

    2015-09-28

    Using an experimental approach, the role of metal catalysis has been investigated in the in situ cycloaddition reaction of nitrile with azide to form tetrazoles. It has been shown that metal catalysis serves to activate the cyano group in the nitrile reagent by a coordinative interaction. PMID:26293313

  13. In situ monitoring of the Li-O2 electrochemical reaction on nanoporous gold using electrochemical AFM.

    PubMed

    Wen, Rui; Byon, Hye Ryung

    2014-03-11

    The lithium-oxygen (Li-O2) electrochemical reaction on nanoporous gold (NPG) is observed using in situ atomic force microscopy (AFM) imaging coupled with potentiostatic measurement. Dense Li2O2 nanoparticles form a film at 2.5 V, which is decomposed at 3.8-4.0 V in an ether-based electrolyte. PMID:24469227

  14. Optimizing Metalloporphyrin-Catalyzed Reduction Reactions for In Situ Remediation of DOE Contaminants

    SciTech Connect

    Schlautman, Mark A.

    2013-07-14

    Past activities have resulted in a legacy of contaminated soil and groundwater at Department of Energy facilities nationwide. Uranium and chromium are among the most frequently encountered and highest-priority metal and radionuclide contaminants at DOE installations. Abiotic chemical reduction of uranium and chromium at contaminated DOE sites can be beneficial because the reduced metal species are less soluble in water, less mobile in the environment, and less toxic to humans and ecosystems. Although direct biological reduction has been reported for U(VI) and Cr(VI) in laboratory studies and at some field sites, the reactions can sometimes be slow or even inhibited due to unfavorable environmental conditions. One promising approach for the in-situ remediation of DOE contaminants is to develop electron shuttle catalysts that can be delivered precisely to the specific subsurface locations where contaminants reside. Previous research has shown that reduction of oxidized organic and inorganic contaminants often can be catalyzed by electron shuttle systems. Metalloporphyrins and their derivatives are well known electron shuttles for many biogeochemical systems, and thus were selected to study their catalytic capabilities for the reduction of chromium and uranium in the presence of reducing agents. Zero valent iron (ZVI) was chosen as the primary electron donor in most experimental systems. Research proceeded in three phases and the key findings of each phase are reported here. Phase I examined Cr(VI) reduction and utilized micro- and nano-sized ZVI as the electron donors. Electron shuttle catalysts tested were cobalt- and iron-containing metalloporphyrins and Vitamin B12. To aid in the recycle and reuse of the nano-sized ZVI and soluble catalysts, sol-gels and calcium-alginate gel beads were tested as immobilization/support matrices. Although the nano-sized ZVI could be incorporated within the alginate gel beads, preliminary attempts to trap it in sol-gels were not

  15. Microbial Studies Supporting Implementation of In Situ Bioremediation at TAN

    SciTech Connect

    Barnes, Joan Marie; Matthern, Gretchen Elise; Rae, Catherine; Ely, R. L.

    2000-11-01

    The Idaho National Engineering and Environmental Laboratory is evaluating in situ bioremediation of contaminated groundwater at its Test Area North Facility. To determine feasibility, microcosm and bioreactor studies were conducted to ascertain the ability of indigenous microbes to convert trichloroethene and dichloroethene to non-hazardous byproducts under aerobic and anaerobic conditions, and to measure the kinetics of microbial reactions associated with the degradation process. Microcosms were established from core samples and groundwater obtained from within the contaminant plume. These microcosms were amended with nutrients, under aerobic and anaerobic conditions, to identify electron donors capable of stimulating the degradation process. Results of the anaerobic microcosm studies showed that lactate, acetate and propionate amendments stimulated indigenous cell growth and functioned as effective substrates for reductive degradation of chloroethenes. Bioreactors inoculated with cultures from these anaerobic microcosms were operated under a batch mode for 42 days then converted to a fed-batch mode and operated at a 53-day hydraulic residence time. It was demonstrated that indigenous microbes capable of complete anaerobic reductive dechlorination are present in the subject well. It was also demonstrated that aerobic microbes capable of oxidizing chlorinated compounds produced by anaerobic reductive dechlorination are present. Kinetic data suggest that controlling the type and concentration of electron donors can increase trichlorethene conversion rates. In the event that complete mineralization of trichlorethene does not occur following stimulation, and anaerobic/aerobic treatment scheme is feasible.

  16. In Situ Real-time Environmental High Resolution Electron Microscopy of Nanometer Size Novel Xerogel Catalysts for Hydrogenation Reactions in Nylon 6,6.

    PubMed

    Gai; Kourtakis; Ziemecki

    2000-07-01

    In situ real-time environmental high resolution electron microscopy (EHREM) under controlled reaction environments permits direct atomic resolution imaging of dynamic surface and sub-surface microstructures of reacting catalysts. Using the EHREM and complementary microscopy methods, we have investigated selective hydrogenation reaction mechanisms over novel xerogel catalysts of ruthenium and Ru with Co and Au promoters on titania supports, and report an alternative heterogeneous catalytic process for the hydrogenation of adiponitrile (ADN) in the manufacture of Nylon 6,6. The direct EHREM observations are supported by ultra-high resolution low voltage scanning electron microscope (SEM) of spatial distributions of the highly dispersed nanometer-size catalyst particles and parallel chemical studies. The results demonstrate the important role of in situ EHREM in the design of heterogeneous catalytic hydrogenation processes on the nanoscale. PMID:10898817

  17. N-Heterocyclic Carbene Catalyzed [4 + 2] Annulation Reactions with in Situ Generated Heterocyclic ortho-Quinodimethanes.

    PubMed

    Xu, Jianfeng; Yuan, Shiru; Miao, Maozhong

    2016-08-01

    An efficient strategy for the in situ generation of heterocyclic ortho-quinodimethanes (oQDMs) from 2-methyl-heteroarene-3-carboxylic esters by N-heterocyclic carbene (NHC) catalysis is disclosed. These heterocyclic oQDMs undergo highly enantioselective [4 + 2] annulation reactions with isatin-derived ketimines to afford optically pure heteroarene-fused δ-lactams bearing a quaternary stereogenic center. The main features of this reaction include challenging direct C(sp(3))-H bond functionalizations, excellent enantioselectivities, readily available starting materials, mild reaction conditions, high efficiency, and operational simplicity. PMID:27391039

  18. Aryl formate as bifunctional reagent: applications in palladium-catalyzed carbonylative coupling reactions using in situ generated CO.

    PubMed

    Li, Haoquan; Neumann, Helfried; Beller, Matthias; Wu, Xiao-Feng

    2014-03-17

    After decades of development, carbonylation reactions have become one of the most powerful tools in modern organic synthesis. However, the requirement of CO gas limits the applications of such reactions. Reported herein is a versatile and practical protocol for carbonylative reactions which rely on the cooperation of phenyl formate and nonaflate, and the generation of CO in situ. This protocol has a high functionalgroup tolerance and could be applied in carbonylations with C, N, and, O nucleophiles. The corresponding amides, alkynones, furanones, and aryl benzoates were synthesized in good yields. PMID:24677435

  19. MEMS Lubrication by In-Situ Tribochemical Reactions From the Vapor Phase.

    SciTech Connect

    Dugger, Michael T.; Asay, David B.; Kim, Seong H.

    2008-01-01

    Vapor Phase Lubrication (VPL) of silicon surfaces with pentanol has been demonstrated. Two potential show stoppers with respect to application of this approach to real MEMS devices have been investigated. Water vapor was found to reduce the effectiveness of VPL with alcohol for a given alcohol concentration, but the basic reaction mechanism observed in water-free environments is still active, and devices operated much longer in mixed alcohol and water vapor environments than with chemisorbed monolayer lubricants alone. Complex MEMS gear trains were successfully lubricated with alcohol vapors, resulting in a factor of 104 improvement in operating life without failure. Complex devices could be made to fail if operated at much higher frequencies than previously used, and there is some evidence that the observed failure is due to accumulation of reaction products at deeply buried interfaces. However, if hypothetical reaction mechanisms involving heated surfaces are valid, then the failures observed at high frequency may not be relevant to operation at normal frequencies. Therefore, this work demonstrates that VPL is a viable approach for complex MEMS devices in conventional packages. Further study of the VPL reaction mechanisms are recommended so that the vapor composition may be optimized for low friction and for different substrate materials with potential application to conventionally fabricated, metal alloy parts in weapons systems. Reaction kinetics should be studied to define effective lubrication regimes as a function of the partial pressure of the vapor phase constituent, interfacial shear rate, substrate composition, and temperature.

  20. 2D NMR studies of aminoglycoside antibiotics. Use of relayed coherence transfer for /sub 1/H resonance assignment and in situ structure elucidation of amikacin derivatives in reaction mixtures

    SciTech Connect

    Andersen, N.H.; Eaton, H.L.; Nguyen, K.T.; Hartzell, C.; Nelson, R.J.; Priest, J.H.

    1988-04-19

    Phase-sensitive 2D /sup 1/H//sup 1/H COSY spectra can be used to identify the structures of individual pure specimens of the aminoglycoside antibiotic amikacin and its N-hemisuccinyl derivatives. However, even at 500 MHz the 2D chemical shift dispersion does not allow for unambiguous assignment of all cross-peaks. By use of 2D relayed coherence transfer experiments (RELAY) optimized to detect two-step /sup 1/H//sup 1/H scalar interactions in which one of the J-values is small, sufficient additional correlations can be obtained from the frequency-isolated resonances to allow facile tracing of all scalar connectivities. Complete assignments of the /sup 1/H NMR spectra of amikacin, its 6'-N-hemisuccinamide, and a novel bis(acylate) (..gamma..-N-(p-vinylbenzoyl)amikacin 6'-N-hemisuccinamide) were obtained for aqueous media. The NMR spectrum of amikacin free base was also assigned in dimethyl sulfoxide solution. The RELAY experiment can be extended to the analysis of reaction mixtures, which allows for the identification and resonance assignment of regioisomeric amikacin haptens in the mixture state. All of the N-monohemisuccinyl isomers of amikacin have been identified in reaction mixtures through the RELAY experiment. The relative reactivities of the amino functions of amikacin toward acylating agents were found to be 6'-N > 3-N greater than or equal to 3''-N greater than or equal to ..gamma..-N. However, this reactivity order is altered after the initial acylation event.

  1. Controlling the Formation of Nanocavities in Kirkendall Nanoobjects through Sequential Thermal Ex Situ Oxidation and In Situ Reduction Reactions.

    PubMed

    Mel, Abdel-Aziz El; Tessier, Pierre-Yves; Buffiere, Marie; Gautron, Eric; Ding, JunJun; Du, Ke; Choi, Chang-Hwan; Konstantinidis, Stephanos; Snyders, Rony; Bittencourt, Carla; Molina-Luna, Leopoldo

    2016-06-01

    Controlling the porosity, the shape, and the morphology of Kirkendall hollow nanostructures is the key factor to tune the properties of these tailor-made nanomaterials which allow in turn broadening their applications. It is shown that by applying a continuous oxidation to copper nanowires following a temperature ramp protocol, one can synthesize cuprous oxide nanotubes containing periodic copper nanoparticles. A further oxidation of such nanoobjects allows obtaining cupric oxide nanotubes with a bamboo-like structure. On the other hand, by applying a sequential oxidation and reduction reactions to copper nanowires, one can synthesize hollow nanoobjects with complex shapes and morphologies that cannot be obtained using the Kirkendall effect alone, such as necklace-like cuprous oxide nanotubes, periodic solid copper nanoparticles or hollow cuprous oxide nanospheres interconnected with single crystal cuprous oxide nanorods, and aligned and periodic hollow nanospheres embedded in a cuprous oxide nanotube. The strategy demonstrated in this study opens new avenues for the engineering of hollow nanostructures with potential applications in gas sensing, catalysis, and energy storage. PMID:27061060

  2. In situ observation of reaction between metal and Si surface by low energy RBS/channeling

    NASA Astrophysics Data System (ADS)

    Hasegawa, Masataka; Kobayashi, Naoto

    1997-02-01

    We have developed a low energy Rutherford backscattering spectrometry (RBS)/ion channeling measurement system for the analysis of thin films and solid surfaces with the use of several tens keV hydrogen ions, and of a time-of-flight spectrometer which was originally developed by Mendenhall and Weller. The depth resolution of our system is better than that of conventional RBS system with MeV helium ions and silicon surface barrier detectors. This RBS/ion channeling system is small in size compared to the conventional RBS/ion channeling measurement system with the use of MeV He ions, because of the small ion accelerator for several tens keV ions. The analysis of crystalline thin films which utilizes ion channeling effect can be performed with this low energy RBS/ion channeling measurement system. The in situ observation of the thermal reaction between iron and silicon substrate with the use of this measurement system is demonstrated. The deposited Fe (3.3 ML) on Si(001) clean surface diffused into the substrate by 380 °C annealing, while on the hydrogen-terminated (dihydride) Si(001) the 480 °C annealing did not lead to the diffusion. Present results indicates that the hydrogen termination of Si(001) surface prevents the deposited Fe from diffusing into the substrate up to relatively high temperature compared to the clean surface.

  3. In situ measurement of molecular diffusion during catalytic reaction by pulsed-field gradient NMR spectroscopy

    SciTech Connect

    Hong, Y.; Kaerger, J.; Hunger, B. ); Feoktistova, N.N.; Zhdanov, S.P. )

    1992-09-01

    Pulsed-field gradient (PFG) NMR spectroscopy is applied to study the intracrystalline diffusivity of the reactant and product molecules during the conversion of cyclopropane to propene in Zeolite X. The diffusivities are found to be large enough that any influence of intracrystalline diffusion on the overall reaction in flow reactors may be excluded.

  4. In Situ and Ex Situ TEM Study of Lithiation Behaviours of Porous Silicon Nanostructures.

    PubMed

    Shen, Chenfei; Ge, Mingyuan; Luo, Langli; Fang, Xin; Liu, Yihang; Zhang, Anyi; Rong, Jiepeng; Wang, Chongmin; Zhou, Chongwu

    2016-01-01

    In this work, we study the lithiation behaviours of both porous silicon (Si) nanoparticles and porous Si nanowires by in situ and ex situ transmission electron microscopy (TEM) and compare them with solid Si nanoparticles and nanowires. The in situ TEM observation reveals that the critical fracture diameter of porous Si particles reaches up to 1.52 μm, which is much larger than the previously reported 150 nm for crystalline Si nanoparticles and 870 nm for amorphous Si nanoparticles. After full lithiation, solid Si nanoparticles and nanowires transform to crystalline Li15Si4 phase while porous Si nanoparticles and nanowires transform to amorphous LixSi phase, which is due to the effect of domain size on the stability of Li15Si4 as revealed by the first-principle molecular dynamic simulation. Ex situ TEM characterization is conducted to further investigate the structural evolution of porous and solid Si nanoparticles during the cycling process, which confirms that the porous Si nanoparticles exhibit better capability to suppress pore evolution than solid Si nanoparticles. The investigation of structural evolution and phase transition of porous Si nanoparticles and nanowires during the lithiation process reveal that they are more desirable as lithium-ion battery anode materials than solid Si nanoparticles and nanowires. PMID:27571919

  5. In Situ and Ex Situ TEM Study of Lithiation Behaviours of Porous Silicon Nanostructures

    PubMed Central

    Shen, Chenfei; Ge, Mingyuan; Luo, Langli; Fang, Xin; Liu, Yihang; Zhang, Anyi; Rong, Jiepeng; Wang, Chongmin; Zhou, Chongwu

    2016-01-01

    In this work, we study the lithiation behaviours of both porous silicon (Si) nanoparticles and porous Si nanowires by in situ and ex situ transmission electron microscopy (TEM) and compare them with solid Si nanoparticles and nanowires. The in situ TEM observation reveals that the critical fracture diameter of porous Si particles reaches up to 1.52 μm, which is much larger than the previously reported 150 nm for crystalline Si nanoparticles and 870 nm for amorphous Si nanoparticles. After full lithiation, solid Si nanoparticles and nanowires transform to crystalline Li15Si4 phase while porous Si nanoparticles and nanowires transform to amorphous LixSi phase, which is due to the effect of domain size on the stability of Li15Si4 as revealed by the first-principle molecular dynamic simulation. Ex situ TEM characterization is conducted to further investigate the structural evolution of porous and solid Si nanoparticles during the cycling process, which confirms that the porous Si nanoparticles exhibit better capability to suppress pore evolution than solid Si nanoparticles. The investigation of structural evolution and phase transition of porous Si nanoparticles and nanowires during the lithiation process reveal that they are more desirable as lithium-ion battery anode materials than solid Si nanoparticles and nanowires. PMID:27571919

  6. Externally controlled pressure and temperature microreactor for in situ x-ray diffraction, visual and spectroscopic reaction investigations under supercritical and subcritial conditions

    SciTech Connect

    Diefenbacher, J.; McKelvy, M.; Chizemeshya, A.V.; Wolf, G.H.

    2010-07-13

    A microreactor has been developed for in situ, spectroscopic investigations of materials and reaction processes with full external pressure and temperature control from ambient conditions to 400 C and 310 bar. The sample chamber is in direct contact with an external manifold, whereby gases, liquids or fluids can be injected and their activities controlled prior to and under investigation conditions. The microreactor employs high strength, single crystal moissanite windows which allow direct probe beam interaction with a sample to investigate in situ reaction processes and other materials properties. The relatively large volume of the cell, along with full optical accessibility and external temperature and pressure control, make this reaction cell well suited for experimental investigations involving any combination of gas, fluid, and solid interactions. The microreactor's capabilities are demonstrated through an in situ x-ray diffraction study of the conversion of a meta-serpentine sample to magnesite under high pressure and temperature. Serpentine is one of the mineral candidates for the implementation of mineral carbonation, an intriguing carbon sequestration candidate technology.

  7. Externally controlled pressure and temperature microreactor for in situ x-ray diffraction, visual and spectroscopic reaction investigations under supercritical and subcritical conditions

    SciTech Connect

    Diefenbacher, Jason; McKelvy, Michael; Chizmeshya, Andrew V.G.; Wolf, George H.

    2005-01-01

    A microreactor has been developed for in situ, spectroscopic investigations of materials and reaction processes with full external pressure and temperature control from ambient conditions to 400 deg. C and 310 bar. The sample chamber is in direct contact with an external manifold, whereby gases, liquids or fluids can be injected and their activities controlled prior to and under investigation conditions. The microreactor employs high strength, single crystal moissanite windows which allow direct probe beam interaction with a sample to investigate in situ reaction processes and other materials properties. The relatively large volume of the cell, along with full optical accessibility and external temperature and pressure control, make this reaction cell well suited for experimental investigations involving any combination of gas, fluid, and solid interactions. The microreactor's capabilities are demonstrated through an in situ x-ray diffraction study of the conversion of a meta-serpentine sample to magnesite under high pressure and temperature. Serpentine is one of the mineral candidates for the implementation of mineral carbonation, an intriguing carbon sequestration candidate technology.

  8. Fluorescent metal-organic polymers of zinc and cadmium from hydrothermal in situ acylation reaction.

    PubMed

    Yu, Xiao-Yang; Ye, Ling; Zhang, Xiao; Cui, Xiao-Bing; Zhang, Jian-Po; Xu, Ji-Qing; Hou, Qin; Wang, Tie-Gang

    2010-11-28

    A series of metal-organic complexes based on d(10) metals and the ligand H(4)bbh (H(4)bbh = benzene-1, 2, 4, 5-biformhydrazide), formed through hydrothermal in situ acylate reaction of H(4)bta (H(4)bta = benzene-1, 2, 4, 5-tetracarboxylic acid) with hydrazine hydrate (N(2)H(4)·H(2)O), have been prepared and structurally characterized by single-crystal X-ray diffraction. Compounds [Zn(μ(2)-H(2)bbh)(phen)(H(2)O)](2) (1) (phen = 1, 10-phenanthroline) and [Zn(μ(2)-H(2)bbh)(2, 2'-bpy)](2) (2) (2, 2'-bpy = 2, 2'-bipyridine) are both dinuclear complexes in which bridging ligands H(2)bbh(2-) display different μ(2)- coordination modes. [Zn(μ(2)-H(2)bbh)(1/2)(μ(2)-H(2)bbh)(1/2)(H(2)O)](n) (3) exhibits a two-dimensional (2-D) layer structure containing simultaneously two kinds of different coordination modes of H(2)bbh(2-): μ(2)-bidentate and μ(4)-tetradentate. [Cd(μ(3)-H(2)bbh)(phen)](n) (4) consists of one-dimensional (1-D) double-metal chains. The crystal structures of these compounds are stabilized by hydrogen bonds and π···π interactions, forming three-dimensional supramolecular networks. All of the compounds were characterized by IR, UV-vis spectra and elemental analysis and they show good fluorescence properties in the solid state at room temperature. In order to understand the emission mechanism, we carried out TDDFT calculations on the excited electronic states of compound 2. PMID:20886135

  9. Controlling stereoselectivity in the aminocatalytic enantioselective Mannich reaction of aldehydes with in situ generated N-carbamoyl imines.

    PubMed

    Galzerano, Patrizia; Agostino, Dario; Bencivenni, Giorgio; Sambri, Letizia; Bartoli, Giuseppe; Melchiorre, Paolo

    2010-05-25

    A simple and convenient method for the direct, aminocatalytic, and highly enantioselective Mannich reactions of aldehydes with in situ generated N-carbamoyl imines has been developed. Both alpha-imino esters and aromatic imines serve as suitable electrophilic components. Moreover, the judicious selection of commercially available secondary amine catalysts allows selective access to the desired stereoisomer of the N-tert-butoxycarbonyl (Boc) or N-carbobenzyloxy (Cbz) Mannich adducts, with high control over the syn or anti relative configuration and almost perfect enantioselectivity. Besides the possibility to fully control the stereochemistry of the Mannich reaction, the main advantage of this method lies in the operational simplicity; the highly reactive N-carbamate-protected imines are generated in situ from stable and easily handled alpha-amido sulfones. PMID:20397160

  10. Intermediates in the cation reactions in solution probed by an in situ surface enhanced Raman scattering method

    PubMed Central

    Tan, Chih-Shan; Chen, Hung-Ying; Chen, Hsueh-Szu; Gwo, Shangjr; Chen, Lih-Juann

    2015-01-01

    For chemical reactions in liquid state, such as catalysis, understanding of dynamical changes is conducive to practical applications. Solvation of copper salts in aqueous solution has implications for life, the environment, and industry. In an ongoing research, the question arises that why the color of aqueous CuCl2 solution changes with solution concentration? In this work, we have developed a convenient and efficient in situ surface enhanced Raman scattering technique to probe the presence of many intermediates, some of them are responsible for color change, in crystallization of aqueous copper chloride solution. The versatility of the novel technique was confirmed in the identification of five intermediates states in the transition from CdS to MoS2 nanowires in solution. The facile in situ method is expected to be widely applicable in probing intermediate states in a variety of chemical reactions in solution. PMID:26333518

  11. Intermediates in the cation reactions in solution probed by an in situ surface enhanced Raman scattering method

    NASA Astrophysics Data System (ADS)

    Tan, Chih-Shan; Chen, Hung-Ying; Chen, Hsueh-Szu; Gwo, Shangjr; Chen, Lih-Juann

    2015-09-01

    For chemical reactions in liquid state, such as catalysis, understanding of dynamical changes is conducive to practical applications. Solvation of copper salts in aqueous solution has implications for life, the environment, and industry. In an ongoing research, the question arises that why the color of aqueous CuCl2 solution changes with solution concentration? In this work, we have developed a convenient and efficient in situ surface enhanced Raman scattering technique to probe the presence of many intermediates, some of them are responsible for color change, in crystallization of aqueous copper chloride solution. The versatility of the novel technique was confirmed in the identification of five intermediates states in the transition from CdS to MoS2 nanowires in solution. The facile in situ method is expected to be widely applicable in probing intermediate states in a variety of chemical reactions in solution.

  12. In Situ Transmission Electron Microscopy And Spectroscopy Studies Of Rechargeable Batteries Under Dynamic Operating Conditions: A Retrospective And Perspective View

    SciTech Connect

    Wang, Chong M.

    2015-02-14

    Since the advent of the transmission electron microscope (TEM), continuing efforts have been made to image material under native and reaction environments that typically involve liquids, gases, and external stimuli. With the advances of aberration-corrected TEM for improving the imaging resolution, steady progress has been made on developing methodologies that allow imaging under dynamic operating conditions, or in situ TEM imaging. The success of in situ TEM imaging is closely associated with advances in microfabrication techniques that enable manipulation of nanoscale objects around the objective lens of the TEM. This paper summarizes and highlights recent progress involving in situ TEM studies of energy storage materials, especially rechargeable batteries. The paper is organized to cover both the in situ TEM techniques and the scientific discoveries made possible by in situ TEM imaging.

  13. Grain rotation and lattice deformation during photoinduced chemical reactions revealed by in situ X-ray nanodiffraction.

    PubMed

    Huang, Zhifeng; Bartels, Matthias; Xu, Rui; Osterhoff, Markus; Kalbfleisch, Sebastian; Sprung, Michael; Suzuki, Akihiro; Takahashi, Yukio; Blanton, Thomas N; Salditt, Tim; Miao, Jianwei

    2015-07-01

    In situ X-ray diffraction (XRD) and transmission electron microscopy (TEM) have been used to investigate many physical science phenomena, ranging from phase transitions, chemical reactions and crystal growth to grain boundary dynamics. A major limitation of in situ XRD and TEM is a compromise that has to be made between spatial and temporal resolution. Here, we report the development of in situ X-ray nanodiffraction to measure high-resolution diffraction patterns from single grains with up to 5 ms temporal resolution. We observed, for the first time, grain rotation and lattice deformation in chemical reactions induced by X-ray photons: Br(-) + hv → Br + e(-) and e(-) + Ag(+) → Ag(0). The grain rotation and lattice deformation associated with the chemical reactions were quantified to be as fast as 3.25 rad s(-1) and as large as 0.5 Å, respectively. The ability to measure high-resolution diffraction patterns from individual grains with a temporal resolution of several milliseconds is expected to find broad applications in materials science, physics, chemistry and nanoscience. PMID:26053760

  14. Alpha resonant scattering for astrophysical reaction studies

    SciTech Connect

    Yamaguchi, H.; Kahl, D.; Nakao, T.; Wakabayashi, Y.; Kubano, S.; Hashimoto, T.; Hayakawa, S.; Kawabata, T.; Iwasa, N.; Teranishi, T.; Kwon, Y. K.; Binh, D. N.; Khiem, L. H.; Duy, N. G.

    2014-05-02

    Several alpha-induced astrophysical reactions have been studied at CRIB (CNS Radioactive Ion Beam separator), which is a low-energy RI beam separator at Center for Nuclear Study (CNS) of the University of Tokyo. One of the methods to study them is the α resonant scattering using the thick-target method in inverse kinematics. Among the recent studies at CRIB, the measurement of {sup 7}Be+α resonant scattering is discussed. Based on the result of the experiment, we evaluated the contributions of high-lying resonances for the {sup 7}Be(α,γ) reaction, and proposed a new cluster band in {sup 11}C.

  15. Alpha resonant scattering for astrophysical reaction studies

    NASA Astrophysics Data System (ADS)

    Yamaguchi, H.; Kahl, D.; Nakao, T.; Wakabayashi, Y.; Kubano, S.; Hashimoto, T.; Hayakawa, S.; Kawabata, T.; Iwasa, N.; Teranishi, T.; Kwon, Y. K.; Binh, D. N.; Khiem, L. H.; Duy, N. G.

    2014-05-01

    Several alpha-induced astrophysical reactions have been studied at CRIB (CNS Radioactive Ion Beam separator), which is a low-energy RI beam separator at Center for Nuclear Study (CNS) of the University of Tokyo. One of the methods to study them is the α resonant scattering using the thick-target method in inverse kinematics. Among the recent studies at CRIB, the measurement of 7Be+α resonant scattering is discussed. Based on the result of the experiment, we evaluated the contributions of high-lying resonances for the 7Be(α,γ) reaction, and proposed a new cluster band in 11C.

  16. (Reaction mechanism studies of heavy ion induced nuclear reactions)

    SciTech Connect

    Mignerey, A.C.

    1991-01-01

    This report discusses the following research projects; decay of excited nuclei formed in La-induced reactions at E/A = 45 MeV; mass and charge distributions in Cl-induced heavy ion reactions; and mass and charge distributions in {sup 56}Fe + {sup 165}Ho at E/A = 12 MeV.

  17. Theoretical studies of chemical reaction dynamics

    SciTech Connect

    Schatz, G.C.

    1993-12-01

    This collaborative program with the Theoretical Chemistry Group at Argonne involves theoretical studies of gas phase chemical reactions and related energy transfer and photodissociation processes. Many of the reactions studied are of direct relevance to combustion; others are selected they provide important examples of special dynamical processes, or are of relevance to experimental measurements. Both classical trajectory and quantum reactive scattering methods are used for these studies, and the types of information determined range from thermal rate constants to state to state differential cross sections.

  18. In situ and real-time monitoring of mechanochemical milling reactions using synchrotron X-ray diffraction.

    PubMed

    Halasz, Ivan; Kimber, Simon A J; Beldon, Patrick J; Belenguer, Ana M; Adams, Frank; Honkimäki, Veijo; Nightingale, Richard C; Dinnebier, Robert E; Friščić, Tomislav

    2013-09-01

    We describe the only currently available protocol for in situ, real-time monitoring of mechanochemical reactions and intermediates by X-ray powder diffraction. Although mechanochemical reactions (inducing transformations by mechanical forces such as grinding and milling) are normally performed in commercially available milling assemblies, such equipment does not permit direct reaction monitoring. We now describe the design and in-house modification of milling equipment that allows the reaction jars of the operating mill to be placed in the path of a high-energy (∼90 keV) synchrotron X-ray beam while the reaction is taking place. Resulting data are analyzed using conventional software, such as TOPAS. Reaction intermediates and products are identified using the Cambridge Structural Database or Inorganic Crystal Structure Database. Reactions are analyzed by fitting the time-resolved diffractograms using structureless Pawley refinement for crystalline phases that are not fully structurally characterized (such as porous frameworks with disordered guests), or the Rietveld method for solids with fully determined crystal structures (metal oxides, coordination polymers). PMID:23949378

  19. In situ electrochemical-electron spin resonance investigations of multi-electron redox reaction for organic radical cathodes

    NASA Astrophysics Data System (ADS)

    Huang, Qian; Walter, Eric D.; Cosimbescu, Lelia; Choi, Daiwon; Lemmon, John P.

    2016-02-01

    The multi-electron redox reaction of an organic radical based composite cathode comprised of poly(2,2,6,6- tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA)-Ketjenblack is investigated using an in situ electrochemical-electron spin resonance (ESR) methodology. The experiments allow each electrochemical state to be associated with the chemical state (or environment) of the radical species upon the cell cycling. In situ ESR spectra of the composite cathode demonstrate a two-electron redox reaction of PTMA that is from an aminoxy anion (n-type, at 2.5-2.6 V vs. Li/Li+) via a radical (at 3.2-3.5 V vs. Li/Li+) to an oxoammonium cation (p-type, at 3.7-4.0 V vs. Li/Li+). In particular, an adjustable n-type doping process of PTMA is first observed during the discharging process. Moreover, two different local environments of radical species are found in the PTMA-Ketjenblack composite electrode that includes both concentrated and isolated radicals. These two types of radical species, showing similarities during the redox reaction process while behaving quite different in the non-faradic reaction of ion sorption/desorption on the electrode surface, govern the electrochemical behavior of PTMA based composite electrode.

  20. Studying photonuclear reactions using the activation technique

    NASA Astrophysics Data System (ADS)

    Belyshev, S. S.; Ermakov, A. N.; Ishkhanov, B. S.; Khankin, V. V.; Kurilik, A. S.; Kuznetsov, A. A.; Shvedunov, V. I.; Stopani, K. A.

    2014-05-01

    The experimental setup that is used at the Skobeltsyn Institute of Nuclear Physics of the Moscow State University to study photonuclear reactions using the activation technique is described. The system is based on two modern compact race track microtrons with maximum energy of electrons of up to 55 and 67.7 MeV. A low-background HPGe detector is used to measure the induced gamma activity. The data acquisition and analysis system, used to process the measured spectra, is described. The described system is used to study multiparticle photonuclear reactions and production of nuclei far from the beta stability region.

  1. Time-resolved in situ Studies of Apatite Formation in Aqueous Solutions

    SciTech Connect

    Borkiewicz, O.; Rakovan, J; Cahill, C

    2010-01-01

    Formation of hydroxylapatite through the precipitation and evolution of calcium phosphate precursor phases under varying conditions of temperature (25-90 C), pH (6.5-9.0), and calcium to phosphorus ratio (1.0, 1.33, 1.5, and 1.67) comparable to those found in many sediments and soils were studied. The products of low-temperature precipitation were analyzed by ex situ X-ray diffraction and SEM, as well as time-resolved in situ synchrotron X-ray diffraction. Rietveld refinement was used for quantitative evaluation of relative abundances during phase evolution. The results of ex situ investigations conducted at ambient temperature and near-neutral pH indicate formation of amorphous calcium phosphate, which over the course of experiments transforms to brushite and ultimately hydroxylapatite. The results of in situ X-ray diffraction experiments suggest a more complex pathway of phase development under the same conditions. Some of the initially formed amorphous calcium phosphate and/or crystalline brushite transformed to octacalcium phosphate. In the later stage of the reactions, octacalcium phosphate transforms quite rapidly to hydroxylapatite. This is accompanied or followed by the transformation of the remaining brushite to monetite. Hydroxylapatite and monetite coexist in the sample throughout the remainder of the experiments. In contrast to the near-neutral pH experiments, the results from ex situ and in situ diffraction investigations performed at higher pH yield similar results. The precipitate formed in the initial stages in both types of experiments was identified as amorphous calcium phosphate, which over the course of the reaction quite rapidly transformed to hydroxylapatite without any apparent intermediate phases. This is the first application of time-resolved in situ synchrotron X-ray diffraction to precipitation reactions in the Ca(OH){sub 2}-H{sub 3}PO{sub 4}-H{sub 2}O system. The results indicate that precursors are likely to occur during the natural or

  2. Hyaluronic Acid Hydrogels Formed in Situ by Transglutaminase-Catalyzed Reaction.

    PubMed

    Ranga, Adrian; Lutolf, Matthias P; Hilborn, Jöns; Ossipov, Dmitri A

    2016-05-01

    Enzymatically cross-linked hydrogels can be formed in situ and permit highly versatile and selective tethering of bioactive molecules, thereby allowing for a wealth of applications in cell biology and tissue engineering. While a number of studies have reported the bioconjugation of extracellular matrix (ECM) proteins and peptides into such matrices, the site-specific incorporation of biologically highly relevant polysaccharides such as hyaluronic acid (HA) has thus far not been reported, limiting our ability to reconstruct this key feature of the in vivo ECM. Here we demonstrate a novel strategy for transglutaminase-mediated covalent linking of HA moieties to a synthetic poly(ethylene glycol) (PEG) macromer resulting in the formation of hybrid HA-PEG hydrogels. We characterize the ensuing matrix properties and demonstrate how these cytocompatible gels can serve to modulate the cellular phenotype of human mammary cancer epithelial cells as well as mouse myoblasts. The use of HA as a novel building block in the increasingly varied library of synthetic PEG-based artificial ECMs should have applications as a structural as well as a signaling component and offers significant potential as an injectable matrix for regenerative medicine. PMID:27014785

  3. In situ and ex situ XANES study of nanodispersed Mo species in zeolites used in fine chemistry catalysis.

    PubMed

    Rentería, M; Traverse, A; Anunziata, O A; Lede, E J; Pierella, L; Requejo, F G

    2001-03-01

    Mo K-edge XANES experiments on Mo-containing zeolites at low Mo loading (1 and 2 wt% of Mo on H-ZSM-11, H-BETA and H-ZSM-5 catalysts), active in fine chemistry reactions, were performed ex situ as function of sample calcination temperature in air (in the range 773-973 K) or in situ at 873 and 973K under N2 flow. The results showed a 4-fold oxygen coordination for the incorporated Mo species in the activated (dehydrated) state. Combining these results with additional data evidences an almost total Mo exchange inside the zeolite channels. PMID:11512876

  4. Redox Reaction in Silicate Melts Monitored by ''Static'' In-Situ Fe K-Edge XANES up to 1180 deg. C

    SciTech Connect

    Wilke, Max; Partzsch, Georg M.; Welter, Edmund; Farges, Francois

    2007-02-02

    A new experimental setup to measure in-situ kinetics of redox reactions in silicate melts is presented. To study the progress of the Fe-redox reaction, the variation of the signal is recorded at an energy, where the difference between the spectra of the oxidized and reduced Fe in the melt is largest (''static XANES''). To control the redox conditions, the gas atmosphere could be changed between to types of gases using computer-controlled valves (N2:H2 and air, respectively). In this way, a number of reduction/oxidation cycles can be monitored in-situ and continuously. Applied at the Fe K-edge in molten silicates, we obtained a set of high quality data, which includes the very first steps of the redox reaction. An Avrami-type equation is used to investigate rate-controlling parameters for the iron oxidation/reduction kinetics for two melts (basaltic and Na trisilicate) for temperatures up to 1180 deg. C.

  5. Single-Tube Reaction Using Perfluorocarbons: A Prerequisite Step Leading to the Whole-Slide In Situ Technique on Histopathological Slides.

    PubMed

    Chen, Yi-Chang; Teng, Tsung-Han; Tsai, Jane S-C; Huang, Hsien-Da; Chang, Yih-Leong; Liang, Cher-Wei

    2016-01-01

    Developing a robust, novel method for performing multiple reactions in a single tube is not only time- and cost-saving but also critical for future high-throughput whole-slide in situ techniques on diseased tissues. In this study, we introduce the use of perfluorocarbons and compound-coated magnetic particles to create pseudochambers in a single tube, allowing different reactions to be performed in different phases. Perfluorocarbons also serve as cell lysis buffer and polymerase chain reaction (PCR) buffer owing to their highly penetrating, repellent and emulsifiable properties. Using this method, nucleic acids can be isolated and purified from various sample types and sizes, followed by PCR, real-time PCR, or multiplex PCR in the same tube. No incubation or enzyme digesting time is needed and the risk of cross-contamination is reduced. Tests can be performed in microemulsions (water-in-oil droplets) containing sequence-specific captures and probes for further high-throughput detection. We present a simple, quick, and robust procedure as a prerequisite step to future high-throughput in situ techniques. PMID:27336363

  6. Single-Tube Reaction Using Perfluorocarbons: A Prerequisite Step Leading to the Whole-Slide In Situ Technique on Histopathological Slides

    PubMed Central

    Chen, Yi-Chang; Teng, Tsung-Han; Tsai, Jane S.-C.; Huang, Hsien-Da; Chang, Yih-Leong

    2016-01-01

    Developing a robust, novel method for performing multiple reactions in a single tube is not only time- and cost-saving but also critical for future high-throughput whole-slide in situ techniques on diseased tissues. In this study, we introduce the use of perfluorocarbons and compound-coated magnetic particles to create pseudochambers in a single tube, allowing different reactions to be performed in different phases. Perfluorocarbons also serve as cell lysis buffer and polymerase chain reaction (PCR) buffer owing to their highly penetrating, repellent and emulsifiable properties. Using this method, nucleic acids can be isolated and purified from various sample types and sizes, followed by PCR, real-time PCR, or multiplex PCR in the same tube. No incubation or enzyme digesting time is needed and the risk of cross-contamination is reduced. Tests can be performed in microemulsions (water-in-oil droplets) containing sequence-specific captures and probes for further high-throughput detection. We present a simple, quick, and robust procedure as a prerequisite step to future high-throughput in situ techniques. PMID:27336363

  7. In situ probing of the active site geometry of ultrathin nanowires for the oxygen reduction reaction

    SciTech Connect

    Liu, Haiqing; Wong, Stanislaus S.; An, Wei; Li, Yuanyuan; Frenkel, Anatoly I.; Sasaki, Kotaro; Koenigsmann, Christopher; Su, Dong; Anderson, Rachel M.; Crooks, Richard M.; Adzic, Radoslav R.; Liu, Ping

    2015-09-24

    To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (~2 nm) core–shell Pt~Pd9Au nanowires, which have been previously shown to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu~Pd configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Thus, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general.

  8. In situ probing of the active site geometry of ultrathin nanowires for the oxygen reduction reaction

    DOE PAGESBeta

    Liu, Haiqing; Wong, Stanislaus S.; An, Wei; Li, Yuanyuan; Frenkel, Anatoly I.; Sasaki, Kotaro; Koenigsmann, Christopher; Su, Dong; Anderson, Rachel M.; Crooks, Richard M.; et al

    2015-09-24

    To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (~2 nm) core–shell Pt~Pd9Au nanowires, which have been previously shownmore » to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu~Pd configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Thus, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general.« less

  9. In Situ Probing of the Active Site Geometry of Ultrathin Nanowires for the Oxygen Reduction Reaction.

    PubMed

    Liu, Haiqing; An, Wei; Li, Yuanyuan; Frenkel, Anatoly I; Sasaki, Kotaro; Koenigsmann, Christopher; Su, Dong; Anderson, Rachel M; Crooks, Richard M; Adzic, Radoslav R; Liu, Ping; Wong, Stanislaus S

    2015-10-01

    To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (∼2 nm) core-shell Pt∼Pd9Au nanowires, which have been previously shown to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu∼Pd configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Hence, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general. PMID:26402364

  10. Metal cocatalyzed tandem alkynylative cyclization reaction of in situ formed N-iminoisoquinolinium ylides with bromoalkynes via C-H bond activation.

    PubMed

    Huang, Ping; Yang, Qin; Chen, Zhiyuan; Ding, Qiuping; Xu, Jingshi; Peng, Yiyuan

    2012-09-21

    Silver triflate and copper(I) iodide cocatalyzed direct alkynylation and cyclization reaction of in situ formed N-iminoisoquinolinium ylides with bromoalkynes is described. The reaction proceeds efficiently through a combination of C-H activation and subsequent tandem reaction in one pot, leading to diverse H-pyrazolo[5,1-a]isoquinolines in good yields under mild reaction conditions. PMID:22946742

  11. Design and Operation of a High Pressure Reaction Cell for in situ X-ray Absorption Spectroscopy

    SciTech Connect

    Bare,S.; Yang, N.; Kelly, S.; Mickelson, G.; Modica, F.

    2007-01-01

    X-ray absorption spectroscopy measurements of catalytic reactions have been instrumental in advancing the understanding of catalytic processes. These measurements require an in situ catalysis reaction cell with unique properties. Here we describe the design and initial operation of an in situ/operando catalysis reaction cell for transmission X-ray absorption spectroscopy measurements. The cell is designed: to be an ideal catalytic reactor with no mass transfer effects; to give the same conversion and selectivity under similar space velocities as standard laboratory micro-reactors; to be operational temperatures up to 600 {sup o}C and pressures up to 14 bar; to be X-ray transparent allowing XAS measurement to be collected in transmission for all elements with Z {>=} 23 (vanadium K-edge at 5.5 keV); to measure the actual catalyst bed temperature; to not use o-ring seals, or water cooling; to be robust, compact, easy to assemble, and use, and relatively low cost to produce. The heart of the cell is fabricated from an X-ray transparent beryllium tube that forms a plug flow reactor. XAFS data recorded during the reduction of a Re/{gamma}-A{sub 2}O{sub 3} catalyst as a function of hydrogen pressure from 0.05 to 8 bar, and from a Pt-Sn/{gamma}-A{sub 2}O{sub 3} catalyst during n-heptane reforming are given as initial examples of the versatility of the reactor.

  12. Determination of redox reaction rates and orders by in situ liquid cell electron microscopy of Pd and Au solution growth

    SciTech Connect

    Sutter, Eli A.; Sutter, Peter W.

    2014-11-19

    In-situ liquid cell transmission and scanning transmission electron microscopy (TEM/STEM) experiments are important as they provide direct insight into processes in liquids, such as solution growth of nanoparticles among others. In liquid cell TEM/STEM redox reaction experiments the hydrated electrons e⁻aq created by the electron beam are responsible for the reduction of metal-ion complexes. Here we investigate the rate equation of redox reactions involving reduction by e⁻aq generated by the electron beam during in-situ liquid TEM/STEM. Specifically we consider the growth of Pd on Au seeds in aqueous solutions containing Pd-chloro complexes. From the quantification of the rate of Pd deposition at different electron beam currents and as a function of distance from a stationary, nanometer-sized exciting beam, we determine that the reaction is first order with respect to the concentration of hydrated electrons, [e⁻aq]. In addition, by comparing Pd- and Au-deposition, we further demonstrate that measurements of the local deposition rate on nanoparticles in the solution via real-time imaging can be used to measure not only [e⁻aq] but also the rate of reduction of a metal-ion complex to zero-valent metal atoms in solution.

  13. Determination of redox reaction rates and orders by in situ liquid cell electron microscopy of Pd and Au solution growth

    DOE PAGESBeta

    Sutter, Eli A.; Sutter, Peter W.

    2014-11-19

    In-situ liquid cell transmission and scanning transmission electron microscopy (TEM/STEM) experiments are important as they provide direct insight into processes in liquids, such as solution growth of nanoparticles among others. In liquid cell TEM/STEM redox reaction experiments the hydrated electrons e⁻aq created by the electron beam are responsible for the reduction of metal-ion complexes. Here we investigate the rate equation of redox reactions involving reduction by e⁻aq generated by the electron beam during in-situ liquid TEM/STEM. Specifically we consider the growth of Pd on Au seeds in aqueous solutions containing Pd-chloro complexes. From the quantification of the rate of Pdmore » deposition at different electron beam currents and as a function of distance from a stationary, nanometer-sized exciting beam, we determine that the reaction is first order with respect to the concentration of hydrated electrons, [e⁻aq]. In addition, by comparing Pd- and Au-deposition, we further demonstrate that measurements of the local deposition rate on nanoparticles in the solution via real-time imaging can be used to measure not only [e⁻aq] but also the rate of reduction of a metal-ion complex to zero-valent metal atoms in solution.« less

  14. In-Situ Cure Monitoring of the Immidization Reaction of PMR-15

    NASA Technical Reports Server (NTRS)

    Cossins, Sheryl; Kellar, Jon J.; Winter, Robb M.

    1997-01-01

    Glass fiber reinforced polymer composites are becoming widely used in industry. With this increase in production, an in-situ method of quality control for the curing of the polymer is desirable. This would allow for the production of high-quality parts having more uniform properties.' Recently, in-situ fiber optic monitoring of polymer curing has primarily focused on epoxy resins and has been performed by Raman or fluorescence methods. In addition, some infrared (IR) investigations have been performed using transmission or ATR cells. An alternate IR approach involves using optical fibers as a sensor by utilizing evanescent wave spectroscopy.

  15. Combining direct residence time measurements and biogeochemistry to calculate in-situ reaction rates in the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Pittroff, Marco; Gilfedder, Benjamin

    2015-04-01

    The hyporheic zone is an active interface between groundwater, riparian and surface water systems. Exchange and reaction of water, nutrients, and organic matter occur due to variations in surface and groundwater flow regimes, bed topography and active biogeochemistry fuelled by bioavailable carbon. There has been an increasing focus on coupling the residence time of surface water in the hyporheic zone with biogeochemical reactions. However, there are very few tracers that can be used to measure residence times in-situ, especially in complex groundwater-surface water settings. In this work we have used the natural radioisotope Radon (222Rn) as an in-situ tracer for river water residence time in a riffle-pool sequence (Rote Main River), and combined this information with biogeochemical parameters (DOC and C quality, O3, NO3, CO2). We can clearly observe a dependence of reaction progress on the water residence times, with oxygen and nitrate reduction following inverse logarithmic trends as a function of time. By comparing with initial concentrations (the river end member) with riverbed levels we have estimated first-order in-situ reduction rates for nitrate and oxygen. Nitrate reduction rates are at the higher end of published values, which is likely due to the continual supply of bioavailable carbon from the river system. This work helps to better understand the function and efficiency of the hyporheic zone as a natural filter for redox sensitive species such as nitrate at the groundwater - steam interface. It also provides a useful method for estimating residence times in complex, higher order river systems.

  16. Reactions Between Silicon and Graphite Substrates at High Temperature: In Situ Observations

    NASA Astrophysics Data System (ADS)

    White, Jesse F.; Ma, Luyao; Forwald, Karl; Sichen, Du

    2013-09-01

    Graphite as a refractory material has found wide application in many process steps to produce photovoltaic silicon. In the current study, the melting behavior of silicon in contact with different grades of graphite was investigated. The infiltration of silicon into graphite was found to be highly dependent on the internal structure of the graphite substrate. It was confirmed that the heating history of silicon in contact with a graphite substrate strongly influences the melting behavior, which is likely attributed to a gas-solid reaction that forms SiC at less than the liquidus temperature of silicon and alters the surface properties of the graphite. It was also observed that a concentration of CO greater than 5 pct in the inlet gas leads to SiC formation on the surface of the silicon and severely hinders melting.

  17. GEOCHEMICAL AND MICROBIAL REACTIONS AFFECTING THE LONG-TERM PERFORMANCE OF IN SITU 'IRON BARRIERS'

    EPA Science Inventory

    The in situ application of granular iron (Fe0) has become popular for the destruction of halogenated organic compounds for the immobilization of specific metals in groundwater. However, a knowledge gap exists concerning the long-term performance of the Fe0-barriers. The corrosi...

  18. In-situ x-ray absorption study of copper films in ground watersolutions

    SciTech Connect

    Kvashnina, K.O.; Butorin, S.M.; Modin, A.; Soroka, I.; Marcellini, M.; Nordgren, J.; Guo, J.-H.; Werme, L.

    2007-10-29

    This study illustrates how the damage from copper corrosion can be reduced by modifying the chemistry of the copper surface environment. The surface modification of oxidized copper films induced by chemical reaction with Cl{sup -} and HCO{sub 3}{sup -} in aqueous solutions was monitored by in situ X-ray absorption spectroscopy. The results show that corrosion of copper can be significantly reduced by adding even a small amount of sodium bicarbonate. The studied copper films corroded quickly in chloride solutions, whereas the same solution containing 1.1 mM HCO{sub 3}{sup -} prevented or slowed down the corrosion processes.

  19. In situ X-ray absorption study of copper films in ground water solutions

    NASA Astrophysics Data System (ADS)

    Kvashnina, K. O.; Butorin, S. M.; Modin, A.; Soroka, I.; Marcellini, M.; Nordgren, J.; Guo, J.-H.; Werme, L.

    2007-10-01

    This study illustrates how the damage from copper corrosion can be reduced by modifying the chemistry of the copper surface environment. The surface modification of oxidized copper films induced by chemical reaction with Cl - and HCO3- in aqueous solutions was monitored by in situ X-ray absorption spectroscopy. The results show that corrosion of copper can be significantly reduced by adding even a small amount of sodium bicarbonate. The studied copper films corroded quickly in chloride solutions, whereas the same solution containing 1.1 mM HCO3- prevented or slowed down the corrosion processes.

  20. Temperature-dependent size exclusion chromatography for the in situ investigation of dynamic bonding/debonding reactions.

    PubMed

    Brandt, Josef; Guimard, Nathalie K; Barner-Kowollik, Christopher; Schmidt, Friedrich G; Lederer, Albena

    2013-11-01

    Polymers capable of dynamic bonding/debonding reactions are of great interest in modern day research. Potential applications can be found in the fields of self-healing materials or printable networks. Since temperature is often used as a stimulus for triggering reversible bonding reactions, an analysis operating at elevated temperatures is very useful for the in situ investigation of the reaction mechanism, as unwanted side effects can be minimized when performing the analyses at the same temperature at which the reactions occur. A temperature-dependent size exclusion chromatographic system (TD SEC) has been optimized for investigating the kinetics of retro Diels-Alder-based depolymerization of Diels-Alder polymers. The changing molecular weight distribution of the analyzed polymers during depolymerization gives valuable quantitative information on the kinetics of the reactions. Adequate data interpretation methods were developed for the correct evaluation of the chromatograms. The results are confirmed by high-temperature dynamic light scattering, thermogravimetric analysis, and time-resolved nuclear magnetic resonance spectroscopy at high temperatures. In addition, the SEC system and column material stability under application conditions were assessed using thermoanalysis methods, infrared spectroscopy, nitrogen physisorption, and scanning electron microscopy. The findings demonstrate that the system is stable and, thus, we can reliably characterize such dynamically bonding/debonding systems with TD SEC. PMID:23877179

  1. Underwater microscopy for in situ studies of benthic ecosystems

    PubMed Central

    Mullen, Andrew D.; Treibitz, Tali; Roberts, Paul L. D.; Kelly, Emily L. A.; Horwitz, Rael; Smith, Jennifer E.; Jaffe, Jules S.

    2016-01-01

    Microscopic-scale processes significantly influence benthic marine ecosystems such as coral reefs and kelp forests. Due to the ocean's complex and dynamic nature, it is most informative to study these processes in the natural environment yet it is inherently difficult. Here we present a system capable of non-invasively imaging seafloor environments and organisms in situ at nearly micrometre resolution. We overcome the challenges of underwater microscopy through the use of a long working distance microscopic objective, an electrically tunable lens and focused reflectance illumination. The diver-deployed instrument permits studies of both spatial and temporal processes such as the algal colonization and overgrowth of bleaching corals, as well as coral polyp behaviour and interspecific competition. By enabling in situ observations at previously unattainable scales, this instrument can provide important new insights into micro-scale processes in benthic ecosystems that shape observed patterns at much larger scales. PMID:27403715

  2. Underwater microscopy for in situ studies of benthic ecosystems

    NASA Astrophysics Data System (ADS)

    Mullen, Andrew D.; Treibitz, Tali; Roberts, Paul L. D.; Kelly, Emily L. A.; Horwitz, Rael; Smith, Jennifer E.; Jaffe, Jules S.

    2016-07-01

    Microscopic-scale processes significantly influence benthic marine ecosystems such as coral reefs and kelp forests. Due to the ocean's complex and dynamic nature, it is most informative to study these processes in the natural environment yet it is inherently difficult. Here we present a system capable of non-invasively imaging seafloor environments and organisms in situ at nearly micrometre resolution. We overcome the challenges of underwater microscopy through the use of a long working distance microscopic objective, an electrically tunable lens and focused reflectance illumination. The diver-deployed instrument permits studies of both spatial and temporal processes such as the algal colonization and overgrowth of bleaching corals, as well as coral polyp behaviour and interspecific competition. By enabling in situ observations at previously unattainable scales, this instrument can provide important new insights into micro-scale processes in benthic ecosystems that shape observed patterns at much larger scales.

  3. Underwater microscopy for in situ studies of benthic ecosystems.

    PubMed

    Mullen, Andrew D; Treibitz, Tali; Roberts, Paul L D; Kelly, Emily L A; Horwitz, Rael; Smith, Jennifer E; Jaffe, Jules S

    2016-01-01

    Microscopic-scale processes significantly influence benthic marine ecosystems such as coral reefs and kelp forests. Due to the ocean's complex and dynamic nature, it is most informative to study these processes in the natural environment yet it is inherently difficult. Here we present a system capable of non-invasively imaging seafloor environments and organisms in situ at nearly micrometre resolution. We overcome the challenges of underwater microscopy through the use of a long working distance microscopic objective, an electrically tunable lens and focused reflectance illumination. The diver-deployed instrument permits studies of both spatial and temporal processes such as the algal colonization and overgrowth of bleaching corals, as well as coral polyp behaviour and interspecific competition. By enabling in situ observations at previously unattainable scales, this instrument can provide important new insights into micro-scale processes in benthic ecosystems that shape observed patterns at much larger scales. PMID:27403715

  4. Molecular beam studies of reaction dynamics

    SciTech Connect

    Lee, Yuan T.

    1991-03-01

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

  5. Molecular beam studies of reaction dynamics

    SciTech Connect

    Lee, Y.T.

    1993-12-01

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

  6. Indentation device for in situ Raman spectroscopic and optical studies

    NASA Astrophysics Data System (ADS)

    Gerbig, Y. B.; Michaels, C. A.; Forster, A. M.; Hettenhouser, J. W.; Byrd, W. E.; Morris, D. J.; Cook, R. F.

    2012-12-01

    Instrumented indentation is a widely used technique to study the mechanical behavior of materials at small length scales. Mechanical tests of bulk materials, microscopic, and spectroscopic studies may be conducted to complement indentation and enable the determination of the kinetics and physics involved in the mechanical deformation of materials at the crystallographic and molecular level, e.g., strain build-up in crystal lattices, phase transformations, and changes in crystallinity or orientation. However, many of these phenomena occurring during indentation can only be observed in their entirety and analyzed in depth under in situ conditions. This paper describes the design, calibration, and operation of an indentation device that is coupled with a Raman microscope to conduct in situ spectroscopic and optical analysis of mechanically deformed regions of Raman-active, transparent bulk material, thin films or fibers under contact loading. The capabilities of the presented device are demonstrated by in situ studies of the indentation-induced phase transformations of Si thin films and modifications of molecular conformations in high density polyethylene films.

  7. [Laser enhanced chemical reaction studies]. [Progress report

    SciTech Connect

    Not Available

    1992-04-01

    Experimental studies of dynamic molecular processes are described with particular emphasis on the use of a powerful infrared diode laser probe technique developed in our laboratory. This technique allows us to determine the final states of CO{sub 2} (and other molecules) produced by collisions, photofragmentation, or chemical reactions with a spectral resolution of 0.0003 cm{sup {minus}1} and a time resolution of 10{sup {minus}7} sec. Such high spectral resolution provides a detailed picture of the vibrational and rotational states of molecules produced by these dynamic events. We have used this experimental method to probe collisions between hot hydrogen/deuterium atoms and CO{sub 2}, between O({sup 1}D) atoms and CO{sub 2}, to study the final states of DC1 molecules produced as a result of the reactions of hot Cl atoms, and to investigate the dynamics of the reaction between OH and CO molecules. Advances in our techniques over the past two years have allowed us to identify and study more than 200 final rotational states in ten different vibrational levels of CO{sub 2} encompassing all 3 normal modes, many overtones, and combination states of the molecule. We have extended the technique to probe a variety of new molecules such as OCS, N{sub 2}O, DCl, and CS{sub 2}. All of this work is aimed at providing experimental tests for polyatomic molecule potential energy surfaces, chemical transition states in complex systems, and theories of reaction dynamic in molecules with more than 3 atoms.

  8. Structure and growth of stearate monolayers on calcite: First results of an in situ X-ray reflectivity study

    SciTech Connect

    Fenter, P.; Sturchio, N.C.

    1999-10-01

    The adsorption of organic molecules at mineral-fluid interfaces has a profound influence upon geochemical reaction and transport processes, yet little is known about the in situ structures or properties of organic layers at mineral-fluid interfaces. The authors describe an X-ray reflectivity study of stearate monolayers adsorbed at the calcite surface from methanolic solutions. Using these measurements the authors are able to determine important aspects of the in situ structure, bonding, adsorption, and growth mechanisms of stearate monolayers. The experimental approach demonstrated here can be applied widely in studying the interaction of organic molecules with mineral surfaces in aqueous systems.

  9. XAFS characterization of industrial catalysts: in situ study of phase transformation of nickel sulfide

    NASA Astrophysics Data System (ADS)

    Wang, J.; Jia, Z.; Wang, Q.; Zhao, S.; Xu, Z.; Yang, W.; Frenkel, A. I.

    2016-05-01

    The online sulfiding process for nickel-contained catalyst often ends up with a nickel sulfide mixture in refinery plant. To elucidate the local environment of nickel and its corresponding sulfur species, a model catalyst (nickel sulfide) and model thermal process were employed to explore the possibilities for characterization of real catalysts in industrial conditions. The present investigation shows effectiveness of in situ XANES and EXAFS measurements for studying the phase stability and phase composition in these systems, which could be used to simulate real sulfiding process in industrial reactions, such as hydrodesulfurizations of oil.

  10. Studies of in-situ calcium-based sorbents in advanced pressurized coal conversion systems

    SciTech Connect

    Katta, S.; Shires, P.J.; O'Donnell, J.J.

    1992-01-01

    The overall objective of the project is to obtain experimental data on the reactions of calcium-based sorbents in gasification systems and to evaluate or develop kinetic models applicable to the commercial design of such systems. Both air-blown coal gasification systems and second generation fluid bed combustion systems (partial gasification) will be investigated, as well as subsequent stabilization of the solid wastes (calcium sulfide/ash) produced. More specifically, the objectives are to: Develop data on kinetics of in-situ desulfurization reactions; study the effect of calcium on the kinetics of carbon conversion rate; study kinetics of oxidation of CaS to CaSO[sup 4]; Develop and identify viable techniques to stabilize CaS; and, carry out further development work on most promising method and determine its commercial economics.

  11. Studies of in-situ calcium-based sorbents in advanced pressurized coal conversion systems

    SciTech Connect

    Katta, S.; Shires, P.J.; O`Donnell, J.J.

    1992-11-01

    The overall objective of the project is to obtain experimental data on the reactions of calcium-based sorbents in gasification systems and to evaluate or develop kinetic models applicable to the commercial design of such systems. Both air-blown coal gasification systems and second generation fluid bed combustion systems (partial gasification) will be investigated, as well as subsequent stabilization of the solid wastes (calcium sulfide/ash) produced. More specifically, the objectives are to: Develop data on kinetics of in-situ desulfurization reactions; study the effect of calcium on the kinetics of carbon conversion rate; study kinetics of oxidation of CaS to CaSO{sup 4}; Develop and identify viable techniques to stabilize CaS; and, carry out further development work on most promising method and determine its commercial economics.

  12. Analysis and modeling of PEM fuel cell stack performance: Effect of in situ reverse water gas shift reaction and oxygen bleeding

    NASA Astrophysics Data System (ADS)

    Karimi, G.; Li, Xianguo

    In this study the performance of a polymer electrolyte membrane (PEM) fuel cell stack is analyzed with a mathematical model when the stack operates on hydrocarbon reformate gas as the anode feed stream. It is shown that the effect of carbon dioxide dilution of the hydrogen dominated reformate gas has a minimal impact on the stack performance. However, the CO-poisoning effect due to the in situ reverse water gas shift reaction in the anode feed stream could have a very serious adverse impact on the stack performance, especially at high current densities. Thermodynamic calculations indicate that the equilibrium concentrations of CO could be as high as 100 ppm, generated by the in situ reverse water gas shift reaction, under the typical conditions of PEM fuel cell operation; and are influenced by the stack operating temperature and water content of the reformate anode feed. This CO-poisoning of the stack performance is shown mitigated effectively by introducing about 0.5-1% oxygen to the anode feed.

  13. Small-volume, ultrahigh-vacuum-compatible high-pressure reaction cell for combined kinetic and in situ IR spectroscopic measurements on planar model catalysts

    NASA Astrophysics Data System (ADS)

    Zhao, Z.; Diemant, T.; Häring, T.; Rauscher, H.; Behm, R. J.

    2005-12-01

    We describe the design and performance of a high-pressure reaction cell for simultaneous kinetic and in situ infrared reflection (IR) spectroscopic measurements on model catalysts at elevated pressures, between 10-3 and 103mbars, which can be operated both as batch reactor and as flow reactor with defined gas flow. The cell is attached to an ultrahigh-vacuum (UHV) system, which is used for sample preparation and also contains facilities for sample characterization. Specific for this design is the combination of a small cell volume, which allows kinetic measurements with high sensitivity under batch or continuous flow conditions, the complete isolation of the cell from the UHV part during UHV measurements, continuous temperature control during both UHV and high-pressure operation, and rapid transfer between UHV and high-pressure stage. Gas dosing is performed by a designed gas-handling system, which allows operation as flow reactor with calibrated gas flows at adjustable pressures. To study the kinetics of reactions on the model catalysts, a quadrupole mass spectrometer is connected to the high-pressure cell. IR measurements are possible in situ by polarization-modulation infrared reflection-absorption spectroscopy, which also allows measurements at elevated pressures. The performance of the setup is demonstrated by test measurements on the kinetics for CO oxidation and the CO adsorption on a Au /TiO2/Ru(0001) model catalyst film at 1-50 mbar total pressure.

  14. Early age hydration and pozzolanic reaction in natural zeolite blended cements: Reaction kinetics and products by in situ synchrotron X-ray powder diffraction

    SciTech Connect

    Snellings, R.; Mertens, G.; Cizer, O.; Elsen, J.

    2010-12-15

    The in situ early-age hydration and pozzolanic reaction in cements blended with natural zeolites were investigated by time-resolved synchrotron X-ray powder diffraction with Rietveld quantitative phase analysis. Chabazite and Na-, K-, and Ca-exchanged clinoptilolite materials were mixed with Portland cement in a 3:7 weight ratio and hydrated in situ at 40 {sup o}C. The evolution of phase contents showed that the addition of natural zeolites accelerates the onset of C{sub 3}S hydration and precipitation of CH and AFt. Kinetic analysis of the consumption of C{sub 3}S indicates that the enveloping C-S-H layer is thinner and/or less dense in the presence of alkali-exchanged clinoptilolite pozzolans. The zeolite pozzolanic activity is interpreted to depend on the zeolite exchangeable cation content and on the crystallinity. The addition of natural zeolites alters the structural evolution of the C-S-H product. Longer silicate chains and a lower C/S ratio are deduced from the evolution of the C-S-H b-cell parameter.

  15. Adsorption and oxidation of formaldehyde on a polycrystalline Pt film electrode: An in situ IR spectroscopy search for adsorbed reaction intermediates

    PubMed Central

    Behm, R Jürgen

    2014-01-01

    Summary As part of a mechanistic study of the electrooxidation of C1 molecules we have systematically investigated the dissociative adsorption/oxidation of formaldehyde on a polycrystalline Pt film electrode under experimental conditions optimizing the chance for detecting weakly adsorbed reaction intermediates. Employing in situ IR spectroscopy in an attenuated total reflection configuration (ATR-FTIRS) with p-polarized IR radiation to further improve the signal-to-noise ratio, and using low reaction temperatures (3 °C) and deuterium substitution to slow down the reaction kinetics and to stabilize weakly adsorbed reaction intermediates, we could detect an IR absorption band at 1660 cm−1 characteristic for adsorbed formyl intermediates. This assignment is supported by an isotope shift in wave number. Effects of temperature, potential and deuterium substitution on the formation and disappearance of different adsorbed species (COad, adsorbed formate, adsorbed formyl), are monitored and quantified. Consequences on the mechanism for dissociative adsorption and oxidation of formaldehyde are discussed. PMID:24991512

  16. Combined in situ XRD and in situ XANES studies on the reduction behavior of a rhenium promoted cobalt catalyst.

    PubMed

    Kumar, Nitin; Payzant, E A; Jothimurugesan, K; Spivey, J J

    2011-08-28

    A 10% Co-4% Re/(2% Zr/SiO(2)) catalyst was prepared by co-impregnation using a silica support modified by 2% Zr. The catalyst was characterized by temperature programmed reduction (TPR), in situ XRD and in situ XANES analysis where it was simultaneously exposed to H(2) using a temperature programmed ramp. The results showed the two step reduction of large crystalline Co(3)O(4) with CoO as an intermediate. TPR results showed that the reduction of highly dispersed Co(3)O(4) was facilitated by reduced rhenium by a H(2)-spillover mechanism. In situ XRD results showed the presence of both, Co-hcp and Co-fcc phases in the reduced catalyst at 400 °C. However, the Co-hcp phase was more abundant, which is thought to be the more active phase as compared to the Co-fcc phase for CO hydrogenation. CO hydrogenation at 270 °C and 5 bar pressure produces no detectable change in the phases during the time of experiment. In situ XANES results showed a decrease in the metallic cobalt in the presence of H(2)/CO, which can be attributed due to oxidation of the catalyst by reaction under these conditions. PMID:21743918

  17. ALDOL- AND MANNICH-TYPE REACTIONS VIA IN SITU OLEFIN MIGRATION IN IONIC LIQUID

    EPA Science Inventory


    An aldol-type and a Mannich-type reaction via the cross-coupling of aldehydes and imines with allylic alcohols catalyzed by RuCl2(PPh3)3 was developed with ionic liquid as the solvent. The solvent/catalyst system could be reused for at least five times with no loss of reactiv...

  18. Viscous fingering with chemical reaction: effect of in-situ production of surfactants

    NASA Astrophysics Data System (ADS)

    Fernandez, Juan; Homsy, G. M.

    2003-04-01

    Viscous fingering experiments are performed in a radial Hele-Shaw cell for a liquid liquid system in the presence of a well-characterized interfacial reaction capable of changing the surface tension on the time scale of the experiments. The reaction is a neutralization of a fatty acid by an alkaline material to form a surfactant, which exhibits first-order kinetics for the surface tension as a function of time. The experiments are carried out for capillary numbers, Ca, high enough for the fingering to always be in the fractal regime, and for a wide range of Damköhler numbers, Da. The fingers are typically wider in the presence of the chemical reaction than the non-reactive case. We observe two different-behaviours of the reactive fingering patterns. For intermediate values of Da, 0.5 < Da < 4, the fractal dimension d_{f} is higher than the classical value measured for the non-reactive fingering patterns and reaches a maximum of about 1.9. For both small (Da < 0.5) and high Da (Da > 4), the reactive fingering patterns are similar to the fingers with no reaction: the fractal dimension is found to be the same for both systems. These effects are consistent with the hypothesis that Marangoni stresses are present and produce wider fingers.

  19. Liquid chromatography with amperometric reaction detection involving electrogenerated reagents: applications with in-situ generated bromine.

    PubMed

    King, W P; Kissinger, P T

    1980-09-01

    We describe the use of electrogenerated reactants for continuous on-line reaction detection with thin-layer hydrodynamic amperometry. The reagent is introduced into the liquid-chromatographic column effluent at a constant rate by using controlled-current electrochemistry. After the effluent passes through a short reaction coil, the reagent concentration is monitored at the detector. Reaction of eluted compounds with bromine is signalled by changes in the current detected. The direct electrochemical control of the reagent concentration allows changes to be made, even during the course of obtaining a chromatogram. Depending on the specific reagent or reaction, the reagent is supplied either by addition of a second stream or by direct generation in the mobile phase. The latter configuration provides sufficient baseline stability to permit detection of the uptake of as little as 10 pmol of reagent bromine. The technique has been used to detect nanograms of underivatized fatty acids, prostaglandins, and phenols after separation by reversed-phase liquid chromatography. PMID:7408178

  20. Calcite dissolution: an in situ study in the Panama Basin

    SciTech Connect

    Thunell, R.C.; Keir, R.S.; Honjo, S.

    1981-05-08

    The results of an in situ study of calcite dissolution in the Panama Basin indicate that the rate of dissolution in the water column increases suddenly below a water depth of about 2800 meters. This coincides with the depth at which the calcium carbonate content of surface sediments begins to decrease rapidly or the sedimentary lysocline. Since this level of increased dissolution both in the water column and on the sea floor does not appear to be related to the transition from supersaturation to undersaturation with respect to carbonate, there may be a kinetic origin for the lysocline in this region.

  1. In situ studies of grain growth in thin metal films

    SciTech Connect

    Nichols, C.S.; Mansuri, C.M. . Dept. of Materials Science and Engineering); Townsend, S.J. . Dept. of Physics); Smith, D.A. . T.J. Watson Research Center)

    1993-06-01

    Grain growth in thin films of aluminum has been studied using in situ transmission electron microscopy and a heating stage. Videotapes taken during grain growth were analyzed with the intent of searching for the predominant local rearrangement processes responsible for growth. Evolution of a soap froth can be decomposed into only two elementary local topology rearranging events. The authors have found numerous exceptions to prevailing theories that compare grain growth in thin films to the evolution of such froths. These observations suggest that a more complete picture of grain growth is necessary and that such a theory must include more complex local rearrangement processes.

  2. In situ x-ray photoelectron spectroscopy for electrochemical reactions in ordinary solvents

    SciTech Connect

    Masuda, Takuya; Yoshikawa, Hideki; Kobata, Masaaki; Kobayashi, Keisuke; Noguchi, Hidenori; Kawasaki, Tadahiro; Uosaki, Kohei

    2013-09-09

    In situ electrochemical X-ray photoelectron spectroscopy (XPS) apparatus, which allows XPS at solid/liquid interfaces under potential control, was constructed utilizing a microcell with an ultra-thin Si membrane, which separates vacuum and a solution. Hard X-rays from a synchrotron source penetrate into the Si membrane surface exposed to the solution. Electrons emitted at the Si/solution interface can pass through the membrane and be analyzed by an analyzer placed in vacuum. Its operation was demonstrated for potential-induced Si oxide growth in water. Effect of potential and time on the thickness of Si and Si oxide layers was quantitatively determined at sub-nanometer resolution.

  3. Experimental studies of gas-aerosol reactions

    NASA Astrophysics Data System (ADS)

    Gupta, Anand

    1991-05-01

    The aqueous phase oxidation of SO2 by H2O2 is believed to the principle mechanism for atmospheric sulfate formation in cloud droplets. However, no studies in noncloud aerosol systems have been reported. The objective is to quantify the importance of the noncloud liquid phase reactions of SO2 by H2O2 in the atmosphere. Growth rates of submicron droplets exposed to SO2 and H2O2 were measured using the tandem differential mobility analyzer (TDMA) technique (Rader and McMurry, 1986). The technique uses differential mobility analyzers (DMA's) to generate monodisperse particles and to measure particle size after the reaction. To facilitate submicron monodisperse droplet production with the DMA, a low-ion-concentration charter capable of generating singly charged particles up to 1.0 microns was developed and experimentally evaluated. The experiments were performed using dry and deliquesced (NH4)2SO4 particles with SO2 and H2O2 concentrations from 0-860 ppb and 0-150 ppb, respectively. No growth was observed for dry particles. For droplets greater than or equal to 0.3 microns, the fractional diameter growth was independent of particle size and for droplets less than or equal to 0.2 microns, it decreased as particle size decreased. The observed decrease is due to NH3 evaporation. As ammonia evaporates, droplet pH decreases causing the oxidation rate to decrease, leading to a lower growth rate. To predict the size-dependent growth rates, a theoretical model was developed using solution thermodynamics, gas/particle equilibrium, and chemical kinetics. The experimental and theoretical results are in reasonable agreement. For dry (NH4)2SO4 particles exposed to SO2, H2O2, NH3, and H2O vapor, surface reaction-controlled growth was observed. Particle growth was very sensitive to particle composition. No growth was observed for Polystyrene latex particles, whereas (NH4)2SO4 particles doped with catalysts (Fe(2+), Fe(3+), Mn(2+) and Cu(2+)) in a molar ratio of 1:500 grew slower than

  4. Fluorescent labelling of in situ hybridisation probes through the copper-catalysed azide-alkyne cycloaddition reaction.

    PubMed

    Hesse, Susann; Manetto, Antonio; Cassinelli, Valentina; Fuchs, Jörg; Ma, Lu; Raddaoui, Nada; Houben, Andreas

    2016-09-01

    In situ hybridisation is a powerful tool to investigate the genome and chromosome architecture. Nick translation (NT) is widely used to label DNA probes for fluorescence in situ hybridisation (FISH). However, NT is limited to the use of long double-stranded DNA and does not allow the labelling of single-stranded and short DNA, e.g. oligonucleotides. An alternative technique is the copper(I)-catalysed azide-alkyne cycloaddition (CuAAC), at which azide and alkyne functional groups react in a multistep process catalysed by copper(I) ions to give 1,4-distributed 1,2,3-triazoles at a high yield (also called 'click reaction'). We successfully applied this technique to label short single-stranded DNA probes as well as long PCR-derived double-stranded probes and tested them by FISH on plant chromosomes and nuclei. The hybridisation efficiency of differently labelled probes was compared to those obtained by conventional labelling techniques. We show that copper(I)-catalysed azide-alkyne cycloaddition-labelled probes are reliable tools to detect different types of repetitive sequences on chromosomes opening new promising routes for the detection of single copy gene. Moreover, a combination of FISH using such probes with other techniques, e.g. immunohistochemistry (IHC) and cell proliferation assays using 5-ethynyl-deoxyuridine, is herein shown to be easily feasible. PMID:27095480

  5. Quasi-in-situ single-grain photoelectron microspectroscopy of Co/PPy nanocomposites under oxygen reduction reaction.

    PubMed

    Bocchetta, Patrizia; Amati, Matteo; Bozzini, Benedetto; Catalano, Massimo; Gianoncelli, Alessandra; Gregoratti, Luca; Taurino, Antonietta; Kiskinova, Maya

    2014-11-26

    This paper reports an investigation into the aging of pyrolyzed cobalt/polypyrrole (Co/PPy) oxygen reduction reaction (ORR) electrocatalysts, based on quasi-in-situ photoelectron microspectroscopy. The catalyst precursor was prepared by potentiostatic reverse-pulse coelectrodeposition from an acetonitrile solution on graphite. Accelerated aging was obtained by quasi-in-situ voltammetric cycling in an acidic electrolyte. Using photoelectron imaging and microspectroscopy of single Co/PPy grains at a resolution of 100 nm, we tracked the ORR-induced changes in the morphology and chemical state of the pristine material, consisting of uniformly distributed ∼20 nm nanoparticles, initially consisting of a mixture of Co(II) and Co(III) oxidation states in almost equal amounts. The evolution of the Co 2p, O 1s, and N 1s spectra revealed that the main effects of aging are a gradual loss of the Co present at the surface and the reduction of Co(III) to Co(II), accompanied by the emergence and growth of a N 1s signal, corresponding to electrocatalytically active C-N sites. PMID:25369153

  6. In situ generated highly active copper oxide catalysts for the oxygen evolution reaction at low overpotential in alkaline solutions.

    PubMed

    Liu, Xiang; Cui, Shengsheng; Qian, Manman; Sun, Zijun; Du, Pingwu

    2016-04-25

    Developing efficient water oxidation catalysts made up of earth-abundant elements has attracted much attention as a step toward for future clean energy production. Herein we report a simple one-step method to generate a low cost copper oxide catalyst film in situ from a copper(ii) ethylenediamine complex. The resulting catalyst has excellent activity toward the oxygen evolution reaction in alkaline solutions. A catalytic current density of 1.0 mA cm(-2) and 10 mA cm(-2) for the catalyst film requires the overpotentials of only ∼370 mV and ∼475 mV in 1.0 M KOH, respectively. This catalytic performance shows that the new catalyst is one of the best Cu-based heterogeneous OER catalysts to date. PMID:27020763

  7. Synthesis of iron aluminide-Al{sub 2}O{sub 3} composites by in-situ displacement reactions

    SciTech Connect

    Subramanian, R.; McKamey, C.G.; Buck, L.R.; Schneibel, J.H.

    1997-09-01

    Composites consisting of an iron aluminide matrix with ceramic particle reinforcements, such as alumina, could improve the high temperature strength without compromising the oxidation resistance. In this paper, the feasibility of processing Fe-Al alloy/Al{sub 2}O{sub 3} composites by an in-situ displacement reaction between Fe-40 at.% Al and iron oxide, Fe{sub 2}O{sub 3}, is investigated. Simple powder metallurgical processing was performed without resorting to an externally applied pressures or deformations during the high temperature processing step. The microstructural features of the composites are rationalized based on results from diffusion couples. Preliminary mechanical properties such as fracture toughness, yield strength and hardness are determined and compared with the values obtained for monolithic iron aluminide - Fe-28 at.% Al. Results suggest that a significant improvement in the properties is needed and further avenues for modifications, such as changes in the interface strength and externally applied forces during processing, are suggested.

  8. Reaction rate kinetics for in situ combustion retorting of Michigan Antrim oil shale

    USGS Publications Warehouse

    Rostam-Abadi, M.; Mickelson, R.W.

    1984-01-01

    The intrinsic reaction rate kinetics for the pyrolysis of Michigan Antrim oil shale and the oxidation of the carbonaceous residue of this shale have been determined using a thermogravimetric analysis method. The kinetics of the pyrolysis reaction were evaluated from both isothermal and nonisothermal rate data. The reaction was found to be second-order with an activation energy of 252.2 kJ/mole, and with a frequency factor of 9.25 ?? 1015 sec-1. Pyrolysis kinetics were not affected by heating rates between 0.01 to 0.67??K/s. No evidence of any reactions among the oil shale mineral constituents was observed at temperatures below 1173??K. However, it was found that the presence of pyrite in oil shale reduces the primary devolatilization rate of kerogen and increases the amount of residual char in the spent shale. Carbonaceous residues which were prepared by heating the oil shale at a rate of 0.166??K/s to temperatures between 923??K and 1073??K, had the highest reactivities when oxidized at 0.166??K/s in a gas having 21 volume percent oxygen. Oxygen chemisorption was found to be the initial precursor to the oxidation process. The kinetics governing oxygen chemisorption is (Equation Presented) where X is the fractional coverage. The oxidation of the carbonaceous residue was found also to be second-order. The activation energy and the frequency factor determined from isothermal experiments were 147 kJ/mole and 9.18??107 sec-1 respectively, while the values of these parameters obtained from a nonisothermal experiment were 212 kJ/mole and 1.5??1013 sec-1. The variation in the rate constants is attributed to the fact that isothermal and nonisothermal analyses represent two different aspects of the combustion process.

  9. In situ TEM studies of carbon and gold nanostructures

    NASA Astrophysics Data System (ADS)

    Casillas Garcia, Gilberto

    Properties of matter change as structures go down in size to the nanoscale, creating new possibilities for creating new functional materials with better properties than the bulk. In situ TEM techniques were used to probe the properties of two different materials: atomic carbon chains and gold nanoparticles. Carbon chains were synthesized by in situ TEM electron beam irradiation from few-layers-graphene (FLG) flakes. Several chains up to 5 nm long were observed. Aberration corrected TEM confirmed the dimerization of the linear chain as predicted by Peierls. Moreover, it was observed that two linear carbon chains can cross-bond every 9 atoms, and it was confirmed by DFT calculations. Five-fold nanoparticles are not supposed to be stable beyond 5 nm size. Here, decahedra with high index facets in the order of 300 nm were studied by TEM. It was found that the high index facets were only stable by adding a capping agent, otherwise, smooth edges were observed. In this case, a (5x1) hexagonal surface reconstruction was observed on the {001} surfaces, with the hexagonal strings along a [110] and a [410] direction. Additionally, mechanical properties of gold nanoparticles, with and without twin boundaries, under 100 nm were measured by in situ TEM compression experiments. All of the nanoparticles presented yield strengths in the order of GPa. Multi twinned nanoparticles were found to be more malleable, reaching real compressing strains of 100 %, while the single crystal nanoparticle presented less plastic flow. Molecular dynamics simulations revealed that the twin boundaries contribute to the malleability of the nanoparticles, at the same time it provides a mechanism to stop dislocations, hence, strain hardening the nanoparticle at later stages of compression. Finally, the behavior of a single grain boundary was studied by in situ TEM manipulation of nanoparticles. A liquid-like behavior of a grain boundary is observed after two 40 nm gold nanoparticles are brought to

  10. In situ measurements of heterogeneous reactions on ambient aerosol particles: Impacts on atmospheric chemistry and climate

    SciTech Connect

    Bertram, Timothy

    2015-02-11

    Aerosol particles play a critical role in the Earth’s energy budget through the absorption and scattering of radiation, and/or through their ability to form clouds and alter cloud lifetime. Heterogeneous and multi-phase reactions alter the climate-relevant properties of aerosol particles and catalyze reaction pathways that are energetically unfavorable in the gas phase. The chemical composition of aerosol particles dictates the kinetics of heterogeneous and multi-phase reactions. At present, the vast majority of the molecular level information on these processes has been determined in laboratory investigations on model aerosol systems. The work described here provides a comprehensive investigation into the reactivity of complex, ambient aerosol particles is proposed to determine: 1) how representative laboratory investigations of heterogeneous and multi-phase processes conducted on model, simple systems are of the real atmosphere, and 2) the impact of heterogeneous and multi-phase processes on ambient particle optical properties and their ability to nucleate clouds. This work has focused on the uptake kinetics for ammonia (NH3) and dinitrogen pentoxide (N2O5). The results of these investigations will be used to directly improve the representation of heterogeneous and multi-phase processes in global climate models, by identifying the key mechanistic drivers that control the variability in the observed kinetics.

  11. In situ loading of well-dispersed silver nanoparticles on nanocrystalline magnesium oxide for real-time monitoring of catalytic reactions by surface enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Kaige; Li, Gongke; Hu, Yuling

    2015-10-01

    The surface-enhanced Raman spectroscopy (SERS) technique is of great importance for insight into the transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions under actual reaction conditions, especially in water. Herein, we demonstrate a facile method for in situ synthesis of nanocrystalline magnesium oxide-Ag(0) (nano MgO-Ag(0)) hybrid nanomaterials with dispersed Ag nanoparticles (Ag NPs) on the surface of nanocrystalline magnesium oxide (nano MgO) via Sn2+ linkage and reduction. As a benefit from the synergy effect of nano MgO and Ag NPs, the nano MgO-Ag(0) exhibited both excellent SERS and catalytic activities for the reduction of 4-nitrothiophenol in the presence of NaBH4. The nano MgO-Ag(0) was used for real-time monitoring of the catalytic reaction process of 4-nitrothiophenol to 4-aminothiophenol in an aqueous medium by observing the SERS signals of the reactant, intermediate and final products. The intrinsic reaction kinetics and reaction mechanism of this reaction were also investigated. This SERS-based synergy technique provides a novel approach for quantitative in situ monitoring of catalytic chemical reaction processes.The surface-enhanced Raman spectroscopy (SERS) technique is of great importance for insight into the transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions under actual reaction conditions, especially in water. Herein, we demonstrate a facile method for in situ synthesis of nanocrystalline magnesium oxide-Ag(0) (nano MgO-Ag(0)) hybrid nanomaterials with dispersed Ag nanoparticles (Ag NPs) on the surface of nanocrystalline magnesium oxide (nano MgO) via Sn2+ linkage and reduction. As a benefit from the synergy effect of nano MgO and Ag NPs, the nano MgO-Ag(0) exhibited both excellent SERS and catalytic activities for the reduction of 4-nitrothiophenol in the presence of NaBH4. The nano MgO-Ag(0) was used for real

  12. Adsorption, Coadsorption, and Reaction of Acetaldehyde and NO2 on Na-Y,FAU: An In Situ FTIR Investigation

    SciTech Connect

    János, Szanyi; Ja Hun, Kwak; Ryan A.,Moline; Charles H. F.,Peden

    2004-11-01

    The adsorption of acetaldehyde and its coadsorption and reaction with NO2 were investigated on a Na-Y,FAU zeolite using in situ FTIR spectroscopy. Acetaldehyde adsorbs strongly over Na-Y and desorbs molecularly at around 400 K with very limited extent of condensation or polymerization. Reaction between CH3CHO and NO2 takes place in coadsorption experiments even at 300 K. In the initial step, acetaldehyde is oxidized to acetic acid accompanied by the formation of NO, which can be observed as N2O3 formed via a further reaction between NO and NO2. The key intermediates in the overall NOx reduction in this process are nitromethane and, possibly, nitrosomethane, which form in the next step. Their decomposition and further reaction with adsorbed NOx species lead to the formation of HCN, HNCO, N2O, CO2, and organic nitrile species identified by their characteristic IR vibrational signatures. At 473 K, the reaction between adsorbed CH3CHO and NO2 is very fast. The results seem to suggest a mechanism in which N-N bond formation takes place among ionic nitrogen containing species (NO+ and CN- or NCO-). Finally, no evidence has been found to suggest the participation of NHx+NOy- type species in the N-N bond formation under the experimental conditions of this study, although their role in the overall N2 formation process cannot be ruled out under realistic catalytic conditions.

  13. Aniline-Promoted Cyclization-Replacement Cascade Reactions of 2-Hydroxycinnamaldehydes with Various Carbonic Nucleophiles through In Situ Formed N,O-Acetals.

    PubMed

    Yu, Chenguang; Huang, He; Li, Xiangmin; Zhang, Yueteng; Li, Hao; Wang, Wei

    2016-06-27

    In this study, we report the harnessing of new reactivity of N,O-acetals in an aminocatalytic fashion for organic synthesis. Unlike widely used strategies requiring the use of acids and/or elevated temperatures, direct replacement of the amine component of the N,O-acetals by carbon-centered nucleophiles for C-C bond formation is realized under mild reaction conditions. Furthermore, without necessary preformation of the N,O-acetals, an amine-catalyzed in situ formation of N,O-acetals is developed. Coupling both reactions into a one-pot operation enables the achievement of a catalytic process. We demonstrate the employment of simple anilines as promoters for the cyclization-substitution cascade reactions of trans-2-hydroxycinnamaldehydes with various carbonic nucleophiles including indoles, pyrroles, naphthols, phenols, and silyl enol ethers. The process offers an alternative approach to structurally diverse, "privileged" 2-substituted 2H-chromenes. The synthetic power of the new process is furthermore shown by its application in a 2-step synthesis of the natural product candenatenin E and for the facile installation of 2-substituted 2H-chromene moieties into biologically active indoles. PMID:27230417

  14. In situ temperature measurements of reaction spaces under microwave irradiation using photoluminescent probes.

    PubMed

    Ano, Taishi; Kishimoto, Fuminao; Sasaki, Ryo; Tsubaki, Shuntaro; Maitani, Masato M; Suzuki, Eiichi; Wada, Yuji

    2016-05-11

    We demonstrate two novel methods for the measurement of the temperatures of reaction spaces locally heated by microwaves, which have been applied here to two example systems, i.e., BaTiO3 particles covered with a SiO2 shell (BaTiO3-SiO2) and layered tungstate particles. Photoluminescent (PL) probes showing the temperature-sensitivity in their PL lifetimes are located in the nanospaces of the above systems. In the case of BaTiO3-SiO2 core-shell particles, rhodamine B is loaded into the mesopores of the SiO2 shell covering the BaTiO3 core, which generates the heat through the dielectric loss of microwaves. The inner nanospace temperature of the SiO2 shell is determined to be 28 °C higher than the bulk temperature under microwave irradiation at 24 W. On the other hand, Eu(3+) is immobilized in the interlayer space of layered tungstate as the PL probe, showing that the nanospace temperature of the interlayer is only 4 °C higher than the bulk temperature. This method for temperature-measurement is powerful for controlling microwave heating and elucidates the ambiguous mechanisms of microwave special effects often observed in chemical reactions, contributing greatly to the practical application of microwaves in chemistry and materials sciences. PMID:27136754

  15. Comparative Reactivity Study of Forsterite and Antigorite in Wet Supercritical CO2 by In Situ Infrared Spectroscopy

    SciTech Connect

    Thompson, Christopher J.; Loring, John S.; Rosso, Kevin M.; Wang, Zheming

    2013-10-01

    The carbonation reactions of forsterite (Mg2SiO4) and antigorite [Mg3Si2O5(OH)4], representatives of olivine and serpentine minerals, in dry and wet supercritical carbon dioxide (scCO2) at conditions relevant to geologic carbon sequestration (35 °C and 100 bar) were studied by in-situ Fourier transform infrared (FT-IR) spectroscopy. Our results confirm that water plays a critical role in the reactions between metal silicate minerals and scCO2. For neat scCO2, no reaction was observed in 24 hr for either mineral. When water was added to the scCO2, a thin water film formed on the minerals’ surfaces, and the reaction rates and extents increased as the water saturation level was raised from 54% to 116% (excess water). For the first time, the presence of bicarbonate, a key reaction intermediate for metal silicate reactions with scCO2, was observed in a heterogeneous system where mineral solids, an adsorbed water film, and bulk scCO2 co-exist. In excess-water experiments, approximately 4% of forsterite and less than 2% of antigorite transformed into hydrated Mg-carbonates. A precipitate similar to nesquehonite (MgCO3•3H2O) was observed for forsterite within 6 hr of reaction time, but no such precipitate was formed from antigorite until after water was removed from the scCO2 following a 24-hr reaction period. The reduced reactivity and carbonate-precipitation behavior of antigorite was attributed to slower, incongruent dissolution of the mineral and lower concentrations of Mg2+ and HCO3- in the water film. The in situ measurements employed in this work make it possible to quantify metal carbonate precipitates and key reaction intermediates such as bicarbonate for the investigation of carbonation reaction mechanisms relevant to geologic carbon sequestration.

  16. In situ AFM imaging of Li-O2 electrochemical reaction on highly oriented pyrolytic graphite with ether-based electrolyte.

    PubMed

    Wen, Rui; Hong, Misun; Byon, Hye Ryung

    2013-07-24

    Understanding the lithium-oxygen (Li-O2) electrochemical reaction is of importance to improve reaction kinetics, efficiency, and mitigate parasitic reactions, which links to the strategy of enhanced Li-O2 battery performance. Many in situ and ex situ analyses have been reported to address chemical species of reduction intermediate and products, whereas details of the dynamic Li-O2 reaction have not as yet been fully unraveled. For this purpose, visual imaging can provide straightforward evidence, formation and decomposition of products, during the Li-O2 electrochemical reaction. Here, we present real-time and in situ views of the Li-O2 reaction using electrochemical atomic force microscopy (EC-AFM). Details of the reaction process can be observed at nano-/micrometer scale on a highly oriented pyrolytic graphite (HOPG) electrode with lithium ion-containing tetraglyme, representative of the carbon cathode and ether-based electrolyte extensively employed in the Li-O2 battery. Upon oxygen reduction reaction (ORR), rapid growth of nanoplates, having axial diameter of hundreds of nanometers, length of micrometers, and ~5 nm thickness, at a step edge of HOPG can be observed, which eventually forms a lithium peroxide (Li2O2) film. This Li2O2 film is decomposed during the oxygen evolution reaction (OER), for which the decomposition potential is related to a thickness. There is no evidence of byproduct analyzed by X-ray photoelectron spectroscopy (XPS) after first reduction and oxidation reaction. However, further cycles provide unintended products such as lithium carbonate (Li2CO3), lithium acetate, and fluorine-related species with irregular morphology due to the degradation of HOPG electrode, tetraglyme, and lithium salt. These observations provide the first visualization of Li-O2 reaction process and morphological information of Li2O2, which can allow one to build strategies to prepare the optimum conditions for the Li-O2 battery. PMID:23808397

  17. Reversible Luminescence Modulation upon Photochromic Reactions in Rare-Earth Doped Ferroelectric Oxides by in Situ Photoluminescence Spectroscopy.

    PubMed

    Zhang, Qiwei; Sun, Haiqin; Wang, Xusheng; Hao, Xihong; An, Shengli

    2015-11-18

    Reversible luminescence photoswitching upon photochromic reactions with excellent reproducibility is achieved in a new inorganic luminescence material: Na(0.5)Bi(2.5)Nb2O9: Pr(3+) (NBN:Pr) ferroelectric oxides. Upon blue light (452 nm) or sunlight irradiation, the material exhibits a reversible photochromism (PC) performance between dark gray and green color by alternating visible light and thermal stimulus without inducing any structure changes and is accompanied by a red emission at 613 nm. The coloration and decoloration process can be quantitatively evaluated by in situ photoluminescence spectroscopy. Meanwhile, the luminescence emission intensity based on PC reactions is effectively tuned by changing irradiation time and excitation wavelength, and the degree of luminescence modulation has no significant degradation after several periods, showing very excellent reproducibility. On the basis of the luminescence modulation behavior, a double-exponential relaxation model is proposed, and a combined equation is adopted to well describe the luminescence response to light irradiation, being in agreement with the experimental data. PMID:26496504

  18. Interphase fluorescence in situ hybridization and reverse transcription polymerase chain reaction as a diagnostic aid for synovial sarcoma.

    PubMed Central

    Shipley, J.; Crew, J.; Birdsall, S.; Gill, S.; Clark, J.; Fisher, C.; Kelsey, A.; Nojima, T.; Sonobe, H.; Cooper, C.; Gusterson, B.

    1996-01-01

    Identification of the t(X;18)(p11.2;q11.2) that is associated with a high proportion of synovial sarcoma can be a useful diagnostic aid. The translocation results in fusion of the SYT gene on chromosome 18 to either the SSX1 or the SSX2 gene, two homologous genes within Xp11.2. Two-color interphase fluorescence in situ hybridization and reverse transcription polymerase chain reaction were assessed as approaches to identify the rearrangement in well characterized cases. The presence of the translocation, and the specific chromosome X gene disrupted, were inferred from the configuration of signals from chromosome-specific centromere probes, paints, and markers flanking each gene in preparations of interphase nuclei. Rearrangement was found in two cell lines and eight of nine tumor samples, including analysis of five touch imprints. This was consistent with cytogenetic data in four cases and reverse transcription polymerase chain reaction analysis using primers known to amplify both SYT-SSX1 and SYT-SSX2 transcripts. The transcripts were distinguished by restriction with LspI and SmaI. Contrary to previous suggestions, there was no obvious correlation between histological subtype and involvement of the SSX1 or SSX2 gene. These approaches could also be applied to the identification of tumor-free margins and metastatic disease. Images Figure 1 Figure 3 PMID:8579118

  19. Nickel-alumina composites: In situ synthesis by a displacement reaction, and mechanical properties

    SciTech Connect

    Jones, S.A.; Burlitch, J.M.; Uestuendag, E.; Yoo, J.; Zehnder, A.T.

    1995-10-01

    Nickel-alumina composites have the potential to be high performance materials. Alumina, with its excellent oxidation resistance, combined with a ductile phase such as nickel may provide a tough material with a lower density and higher Young`s modulus, overall, a higher specific modulus than typical Superalloys. Dense, interpenetrating Ni-Al{sub 2}O{sub 3} composites were synthesized using a displacement reaction between NiO and aluminum. The resulting composites were characterized in terms of their mechanical properties such as hardness, flexure strength, fracture toughness and elastic constants. The synthesis, characterization, and mechanical properties, as well as the effect of the interpenetrating microstructure on the toughening mechanisms and other properties will be discussed.

  20. Density functional studies of representative pericyclic reactions

    NASA Astrophysics Data System (ADS)

    Carpenter, John E.; Sosa, Carlos P.

    1994-07-01

    Density functional theory (DFT) has traditionally been shunned by computational chemists, but has long seen widespread use in the physics community. Recently, however, DFT has been adopted by the ab initio quantum chemistry community and much activity has been devoted to refining the methodology and exploring the range of its applicability. We investigate the use of DFT (both local (LDF) and non-local (NLDF) spin density approximations) to calculate transition and equilibrium structures for three representative pericyclic reactions: the electrocyclic ring opening reaction of cyclobutene, the [1,5] sigmatropic hydrogen shift reaction in (Z)-1,3-pentadiene, and the Diels-Alder cycloaddition reaction between ethylene and butadiene. LDF theory tends to overemphasize the stability of the ringed structures in each of these reactions. For example, LDF predicts a very low (6 kcal mol -1) barrier to reaction for the Deils-Alder reaction. NLDF theory substantially improves the calculated reaction barrier (20 kcal mol -1), but it is still low with respect to experiment.

  1. Active phase of a Pd-Cu/ZSM-5 catalyst for benzene hydroxylation: In-situ XAFS studies

    NASA Astrophysics Data System (ADS)

    Cho, Kye-Sung; Lee, Yong-Kul

    2012-07-01

    The gas-phase hydroxylation of benzene by using a mixture of oxygen and hydrogen has been carried out over Cu/ZSM-5 catalysts modified with palladium. In-situ X-ray absorption studies employed in the course of H2-tempereature programmed reduction (H2-TPR) followed by benzene hydroxylation confirmed that the oxidic phase of Cu2+ was transformed to Cu+ during the reaction. The addition of Pd to Cu/ZSM-5 noticeably improved the reducibility of the oxidic Cu phase, which resulted in an increase in the activity of the reaction.

  2. Intraductal Therapy of Ductal Carcinoma In Situ: A Presurgery Study

    PubMed Central

    Mahoney, M. Ellen; Gordon, Eva J.; Rao, Jian Yu; Jin, Yusheng; Hylton, Nola; Love, Susan M.

    2014-01-01

    Many women with ductal carcinoma in situ (DCIS) are treated with extensive surgery, radiation, and hormone therapy due to the inability to monitor the disease and to determine which cases will progress to invasive cancer. We assessed the safety and feasibility of administering chemotherapy directly into DCIS-containing ducts in 13 women before definitive surgery. The treatment was safe, feasible, and well tolerated, supporting further development of this strategy for management of DCIS. Introduction Ductal carcinoma in situ (DCIS) is a noninvasive breast cancer wherein malignant cells are confined within a ductal lobular unit. Although less than half the cases of DCIS will progress to invasive disease, most women are treated aggressively with surgery, radiation, and/or hormone therapy due to the inability to clinically evaluate the extent and location of the disease. Intraductal therapy, in which a drug is administered directly into the mammary duct through the nipple, is a promising approach for treating DCIS, but the feasibility of instilling drug into a diseased duct has not been established. Patients and Methods Four to 6 weeks before their scheduled surgery, 13 women diagnosed with DCIS were subjected to cannulation of the affected duct. After both the absence of perforation and presence of dye in the duct were confirmed by ductogram, pegylated liposomal doxorubicin was instilled. Histopathologic assessment was performed after surgery to assess the treatment effects. Results Of the 13 women enrolled in the study, 6 had their DCIS duct successfully cannulated without perforation and instilled with the drug. The treatment was well tolerated, and no serious adverse events have been reported. Biomarker studies indicated a general decrease in Ki-67 levels but an increase in annexin-1 and 8-hydroxydeoxyguanosine in the lumen of DCIS-containing ducts, which suggests a local response to pegylated liposomal doxorubicin treatment. Conclusions Intraductal therapy offers

  3. Detection of Newcastle disease virus RNA by reverse transcription polymerase chain reaction using formalin-fixed, paraffin-embedded tissue and comparison with immunohistochemistry and in situ hybridization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The usefulness of reverse transcription polymerase chain reaction (RT-PCR) from formalin-fixed, paraffin-embedded (FFPE) tissues was examined and compared to the immunohistochemistry (IHC) and in situ hybridization (ISH) assays for detection of Newcastle disease virus (NDV). Spleen and lung tissues...

  4. Electrophilic Reaction of 2,2,2-Trifluorodiazoethane with the in Situ Generated N-Heterocyclic Carbenes: Access to N-Aminoguanidines.

    PubMed

    Guo, Ran; Zheng, Yan; Ma, Jun-An

    2016-09-01

    A facile and efficient electrophilic reaction of 2,2,2-trifluorodiazoethane (CF3CHN2) with the in situ generated N-heterocyclic carbenes is reported. Under basic conditions, a series of trifluoromethylated N-aminoguanidines were obtained in good to high yields. Furthermore, this protocol was applied in the synthesis of the agrochemical Imidacloprid analogue. PMID:27540867

  5. Study of char gasification in a reaction/adsorption apparatus

    SciTech Connect

    Sotirchos, S.V.; Crowley, J.A.

    1987-09-01

    The reaction of an activated carbon (coconut char) with CO/sub 2/ was studied in a reaction/adsorption apparatus which allows successive reactivity and physical adsorption measurements to be made on the same solid sample. Reaction and surface area evolution data were obtained in the temperature range from 800 to 900/sup 0/C. All reaction rate trajectories obtained in this study showed a maximum in the reaction rate, 2-3 times higher than the initial rate, at about 85% conversion. There was no correlation between these results and the evolution of the internal surface area although the reaction appeared to take place initially in the kinetically controlled regime.

  6. Remote and in situ sensing products in chemical reaction using a flexible terahertz pipe waveguide.

    PubMed

    You, Borwen; Lu, Ja-Yu

    2016-08-01

    The feasibility of remote chemical detection is experimentally demonstrated by using a Teflon pipe as a scanning arm in a continuous-terahertz wave sensing and imaging system. Different tablets with distinct mixed ratios of aluminum and polyethylene powders are well distinguished by measuring the power reflectivities of 0.4 THz wave associated with their distinct terahertz refractive indices. Given its refractive index sensitivity and fast response, the reflective terahertz sensing system can be used to real-time trace and quantitatively analyze the ammonium-chloride aerosols produced by the chemical reaction between hydrochloric acid and ammonia vapors. With a tightly focusing terahertz beam spot, the spatial and concentration distributions of the generated chemical product are successfully mapped out by the 1D scan of the flexible pipe probe. In consideration of the responsitivity, power stability, and focused spot size of the system, its detection limit for the ammonium-chloride aerosol is estimated to be approximately 165 nmol/mm2. The reliable and compact terahertz pipe scan system is potentially suitable for practical applications, such as biomedical or industrial fiber endoscopy. PMID:27505768

  7. A theoretical guide for fabricating a conductive molecular wire on a silicon surface via an in situ surface polymerization reaction

    NASA Astrophysics Data System (ADS)

    Yao, Xiaojing; Wang, Jinlan; Yuan, Shijun; Zhang, Xiuyun; Wu, Gang; Wang, Xiaobai; Yang, Shuo-Wang

    2015-09-01

    It has been a long-standing goal to make conductive molecular wires or linear polymer chains on traditional semiconductors or insulator substrates to satisfy the ongoing miniaturization in electronic devices. Here, we have proposed a surface in situ polymerization reaction for a pre-absorbed molecule, 4-hydrazinyl-3-(pyridin-4-ylmethyl)-benzaldehyde (HPyMB), to produce a conductive molecular wire on a silicon surface. Our first-principles calculations show that HPyMB molecules can absorb alternatively on the exposed Si atoms created via ultrahigh vacuum scanning tunneling microscopy on a hydrogen passivated H-Si(001)2 × 1 surface along the [110] direction. The adsorption is exothermic and its generated energy is sufficient for the following intermolecular dehydration polymerization reaction to overcome the activation energy barriers and thereafter form a molecular wire on the surface. This polymerized molecular wire is mechanically stable since it is chemically bonded onto the surface. After polymerization, the system becomes conductive due to the charge transfer from the molecule-surface bonds to their pyridine rings. More importantly, by removing 1.1 electrons from the system, the surface polymer chain is the sole conductive channel. Furthermore, its conducting nature remains robust even under a large external electric field. Our findings open a new window for the fabrication of conductive molecular wires or polymer chains on semiconductor surfaces, and provide insights into the mechanism behind the molecular wire conductivity.It has been a long-standing goal to make conductive molecular wires or linear polymer chains on traditional semiconductors or insulator substrates to satisfy the ongoing miniaturization in electronic devices. Here, we have proposed a surface in situ polymerization reaction for a pre-absorbed molecule, 4-hydrazinyl-3-(pyridin-4-ylmethyl)-benzaldehyde (HPyMB), to produce a conductive molecular wire on a silicon surface. Our first

  8. Reaction studies of hot silicon, germanium and carbon atoms

    SciTech Connect

    Gaspar, P.P.

    1986-11-15

    Research has been continued on hot silicon, germanium and carbon atoms. Progress in the period November 16, 1985 to November 15, 1986 is reviewed in the following areas: (1) Recoil atom reaction studies. (2) Reactions of thermally generated free atoms.

  9. Studies of photoredox reactions on nanosize semiconductors

    SciTech Connect

    Wilcoxon, J.P.; Parsapour, F.; Kelley, D.F.

    1997-08-01

    Light induced electron transfer (ET) from nanosize semiconductors of MoS{sub 2} to organic electron acceptors such as 2,2{prime}-bipyridine (bpy) and methyl substituted 4,4{prime},5,5{prime}-tetramethyl-2,2{prime}-bipyridine (tmb) was studied by static and time resolved photoluminescence spectroscopy. The kinetics of ET were varied by changing the nanocluster size (the band gap), the electron acceptor, and the polarity of the solvent. MoS{sub 2} is an especially interesting semiconductor material as it is an indirect semiconductor in bulk form, and has a layered covalent bonding arrangement which is highly resistant to photocorrosion. Et occurs following photoexcitation of the direct band gap. Quantum confinement results in the smaller nanoclusters having higher conduction band energies, and therefore larger ET driving forces. The ET reaction energies may be varied by changing the electron acceptor, by varying the size of the MoS{sub 2} nanocluster or by varying the polarity of the solvent. In addition, varying the polarity of the solvent affects the reorganization energy and the barrier to electron transfer. TMB is harder to reduce, and thus has a smaller ET driving force than bpy. The solvent polarity is varied by varying the composition of acetonitrile/benzene mixed solvents.

  10. In-situ early-age hydration study of sulfobelite cements by synchrotron powder diffraction

    SciTech Connect

    Álvarez-Pinazo, G.; Cuesta, A.; García-Maté, M.; Santacruz, I.; Losilla, E.R.; Fauth, F.; Aranda, M.A.G.; De la Torre, A.G.

    2014-02-15

    Eco-friendly belite calcium sulfoaluminate (BCSA) cement hydration behavior is not yet well understood. Here, we report an in-situ synchrotron X-ray powder diffraction study for the first hours of hydration of BCSA cements. Rietveld quantitative phase analysis has been used to establish the degree of reaction (α). The hydration of a mixture of ye'elimite and gypsum revealed that ettringite formation (α ∼ 70% at 50 h) is limited by ye'elimite dissolution. Two laboratory-prepared BCSA cements were also studied: non-active-BCSA and active-BCSA cements, with β- and α′{sub H}-belite as main phases, respectively. Ye'elimite, in the non-active-BCSA system, dissolves at higher pace (α ∼ 25% at 1 h) than in the active-BCSA one (α ∼ 10% at 1 h), with differences in the crystallization of ettringite (α ∼ 30% and α ∼ 5%, respectively). This behavior has strongly affected subsequent belite and ferrite reactivities, yielding stratlingite and other layered phases in non-active-BCSA. The dissolution and crystallization processes are reported and discussed in detail. -- Highlights: •Belite calcium sulfoaluminate cements early hydration mechanism has been determined. •Belite hydration strongly depends on availability of aluminum hydroxide. •Orthorhombic ye’elimite dissolved at a higher pace than cubic one. •Ye’elimite larger reaction degree yields stratlingite formation by belite reaction. •Rietveld method quantified gypsum, anhydrite and bassanite dissolution rates.

  11. A large volume cell for in situ neutron diffraction studies of hydrothermal crystallizations

    NASA Astrophysics Data System (ADS)

    Xia, Fang; Qian, Gujie; Brugger, Joël; Studer, Andrew; Olsen, Scott; Pring, Allan

    2010-10-01

    A hydrothermal cell with 320 ml internal volume has been designed and constructed for in situ neutron diffraction studies of hydrothermal crystallizations. The cell design adopts a dumbbell configuration assembled with standard commercial stainless steel components and a zero-scattering Ti-Zr alloy sample compartment. The fluid movement and heat transfer are simply driven by natural convection due to the natural temperature gradient along the fluid path, so that the temperature at the sample compartment can be stably sustained by heating the fluid in the bottom fluid reservoir. The cell can operate at temperatures up to 300 °C and pressures up to 90 bars and is suitable for studying reactions requiring a large volume of hydrothermal fluid to damp out the negative effect from the change of fluid composition during the course of the reactions. The capability of the cell was demonstrated by a hydrothermal phase transformation investigation from leucite (KAlSi2O6) to analcime (NaAlSi2O6ṡH2O) at 210 °C on the high intensity powder diffractometer Wombat in ANSTO. The kinetics of the transformation has been resolved by collecting diffraction patterns every 10 min followed by Rietveld quantitative phase analysis. The classical Avrami/Arrhenius analysis gives an activation energy of 82.3±1.1 kJ mol-1. Estimations of the reaction rate under natural environments by extrapolations agree well with petrological observations.

  12. Characteristics of vestibulosensory reactions studied by experimental caloric test

    NASA Technical Reports Server (NTRS)

    Kapranov, V. Z.

    1980-01-01

    Vestibulo-sensory reactions were studied in 135 workers who were in contact with nitroethers, by the method of an experimental caloric test. The response vestibulo-sensory reactions were recorded by means of an electroencephalograph. The changes in the sensory reaction depended on the duration of the workers' contact with toxic agents. A study of illusion reactions by the labyrinth calorization widens diagnostic possibilities in the examination of functional condition of the vestibular analyser considerably.

  13. Oxidation Induced Doping of Nanoparticles Revealed by in Situ X-ray Absorption Studies.

    PubMed

    Kwon, Soon Gu; Chattopadhyay, Soma; Koo, Bonil; Dos Santos Claro, Paula Cecilia; Shibata, Tomohiro; Requejo, Félix G; Giovanetti, Lisandro J; Liu, Yuzi; Johnson, Christopher; Prakapenka, Vitali; Lee, Byeongdu; Shevchenko, Elena V

    2016-06-01

    Doping is a well-known approach to modulate the electronic and optical properties of nanoparticles (NPs). However, doping at nanoscale is still very challenging, and the reasons for that are not well understood. We studied the formation and doping process of iron and iron oxide NPs in real time by in situ synchrotron X-ray absorption spectroscopy. Our study revealed that the mass flow of the iron triggered by oxidation is responsible for the internalization of the dopant (molybdenum) adsorbed at the surface of the host iron NPs. The oxidation induced doping allows controlling the doping levels by varying the amount of dopant precursor. Our in situ studies also revealed that the dopant precursor substantially changes the reaction kinetics of formation of iron and iron oxide NPs. Thus, in the presence of dopant precursor we observed significantly faster decomposition rate of iron precursors and substantially higher stability of iron NPs against oxidation. The same doping mechanism and higher stability of host metal NPs against oxidation was observed for cobalt-based systems. Since the internalization of the adsorbed dopant at the surface of the host NPs is driven by the mass transport of the host, this mechanism can be potentially applied to introduce dopants into different oxidized forms of metal and metal alloy NPs providing the extra degree of compositional control in material design. PMID:27152970

  14. SISGR - In situ characterization and modeling of formation reactions under extreme heating rates in nanostructured multilayer foils

    SciTech Connect

    Hufnagel, Todd C.

    2014-06-09

    Materials subjected to extreme conditions, such as very rapid heating, behave differently than materials under more ordinary conditions. In this program we examined the effect of rapid heating on solid-state chemical reactions in metallic materials. One primary goal was to develop experimental techniques capable of observing these reactions, which can occur at heating rates in excess of one million degrees Celsius per second. One approach that we used is x-ray diffraction performed using microfocused x-ray beams and very fast x-ray detectors. A second approach is the use of a pulsed electron source for dynamic transmission electron microscopy. With these techniques we were able to observe how the heating rate affects the chemical reaction, from which we were able to discern general principles about how these reactions proceed. A second thrust of this program was to develop computational tools to help us understand and predict the reactions. From atomic-scale simulations were learned about the interdiffusion between different metals at high heating rates, and about how new crystalline phases form. A second class of computational models allow us to predict the shape of the reaction front that occurs in these materials, and to connect our understanding of interdiffusion from the atomistic simulations to measurements made in the laboratory. Both the experimental and computational techniques developed in this program are expected to be broadly applicable to a wider range of scientific problems than the intermetallic solid-state reactions studied here. For example, we have already begun using the x-ray techniques to study how materials respond to mechanical deformation at very high rates.

  15. Cascade Reaction of Donor-Acceptor Cyclopropanes: Mechanistic Studies on Cycloadditions with Nitrosoarenes and cis-Diazenes.

    PubMed

    Chidley, Tristan; Vemula, Naresh; Carson, Cheryl A; Kerr, Michael A; Pagenkopf, Brian L

    2016-06-17

    Tandem ring opening, elimination, and cycloaddition of donor-acceptor cyclopropanes were observed in Yb(OTf)3-catalyzed cycloaddition with nitrosoarenes. The reaction results in formation of tetrahydro-1,2-oxazine instead of the normal cycloadduct isoxazolidine via in situ nitrone formation. A similar cascade sequence was observed with cis-diazines. Mechanistic studies on this unique transformation offer an entirely new approach for reaction design with donor-acceptor cyclopropanes. PMID:27267360

  16. Studying The Kinetics Of Crystalline Silicon Nanoparticle Lithiation With In-Situ Transmission Electron Microscopy

    SciTech Connect

    Mcdowell, Matthew T.; Ryu, Ill; Lee, Seokwoo; Wang, Chong M.; Nix, William D.; Cui, Yi

    2012-11-27

    Silicon is an attractive high-capacity anode material for Li-ion batteries, but a comprehensive understanding of the massive ~300% volume change and fracture during lithiation/delithiation is necessary to reliably employ Si anodes. Here, in-situ transmission electron microscopy (TEM) of the lithiation of crystalline Si nanoparticles reveals that the reaction slows down as it progresses into the particle interior. Analysis suggests that this behavior is due to the influence of mechanical stress at the reaction front on the driving force for the reaction. These experiments give insight into the factors controlling the kinetics of this unique reaction.

  17. Kinetic Study of the Heck Reaction: An Interdisciplinary Experiment

    ERIC Educational Resources Information Center

    Gozzi, Christel; Bouzidi, Naoual

    2008-01-01

    The aim of this experiment is to study and calculate the kinetic constant of a Heck reaction: the arylation of but-3-en-2-ol by iodobenzene catalyzed by palladium acetate in presence of triethylamine in DMF. The reaction leads to a mixture of two ketones. Students use GC analysis to quantify reagents and products of reaction. They control the…

  18. Staff Reactions to Challenging Behaviour: An Observation Study

    ERIC Educational Resources Information Center

    Lambrechts, Greet; Van Den Noortgate, Wim; Eeman, Lieve; Maes, Bea

    2010-01-01

    Staff reactions play an important role in the development and maintaining of clients' challenging behaviour. Because there is a paucity of research on staff reactions in naturalistic settings, this study examined sequential associations between challenging behaviour and staff reactions by means of a descriptive analysis. We analysed video…

  19. Soot Reaction Properties (Ground-Based Study)

    NASA Technical Reports Server (NTRS)

    Dai, Z.; El-Leathy, A. M.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2000-01-01

    Three major soot reaction processes are needed to predict soot properties in flame environments: soot growth, or the formation of soot on soot nuclei and soot particles; soot oxidation, or the reaction of soot with oxidizing species to yield the combustion products of soot oxidation; and soot nucleation, or the formation of soot nuclei from soot precursors having large molecular weights (generally thought to be large and particularly stable PAH molecules in flame environments, called stabilomers). These processes are addressed in the following, considering soot growth, oxidation and nucleation, in turn, by exploiting the soot and flame structure results for premixed and diffusion flames already discussed in Section 2.

  20. Molecular beam studies of reaction dynamics

    SciTech Connect

    Lee, Y.T.

    1987-03-01

    Purpose of this research project is two-fold: (1) to elucidate detailed dynamics of simple elementary reactions which are theoretically important and to unravel the mechanism of complex chemical reactions or photo chemical processes which play an important role in many macroscopic processes and (2) to determine the energetics of polyatomic free radicals using microscopic experimental methods. Most of the information is derived from measurement of the product fragment translational energy and angular distributions using unique molecular beam apparati designed for these purposes.

  1. In situ identification of crystal facet-mediated chemical reactions on tetrahexahedral gold nanocrystals using surface-enhanced Raman spectroscopy.

    PubMed

    Lang, Xiufeng; You, Tingting; Yin, Penggang; Tan, Enzhong; Zhang, Yan; Huang, Yifan; Zhu, Hongping; Ren, Bin; Guo, Lin

    2013-11-28

    Direct monitoring of a metal-catalyzed reaction by surface-enhanced Raman scattering (SERS) is always a challenging issue as it needs bifunctional metal structures that have plasmonic properties and also act as catalysts. Here we demonstrate that the tetrahexahedral (THH) gold nanocrystals (Au NCs) with exposed {520} facets give highly enhanced Raman signals from molecules at the interface, permitting in situ observation of chemical transformation from para-aminothiophenol (PATP) to 4,4'-dimercaptoazobenzene (DMAB). The origin of the intense SERS signals of DMAB is carefully investigated based on the comparison of the SERS spectra of PATP obtained with both the THH Au NCs and the Au nanospheres with the exposed {111} facets. It is elucidated that the high-index {520} facet rather than the localized surface plasmons of the THH Au NCs plays a key role in producing a high yield of the product DMAB which is accompanied by the selective enhancement of the characteristic Raman signals. PMID:24121935

  2. In situ Raman spectroscopy study of metal-enhanced hydrogenation and dehydrogenation of VO2.

    PubMed

    Wu, Hao; Fu, Qiang; Bao, Xinhe

    2016-11-01

    Vanadium dioxide (VO2) has a phase transition from insulator to metal at 340 K, and this transition can be strongly modified by hydrogenation. In this work, two dimensional (2D) VO2 sheets have been grown on Si(1 1 1) surfaces through chemical vapor deposition, and metal (Au, Pt) thin films were deposited on VO2 surfaces by sputtering. The hydrogenation and dehydrogenation of VO2 and metal-decorated VO2 structures in H2 and in air were in situ studied by Raman. We found that hydrogenation and dehydrogenation temperatures have been significantly decreased with the VO2 surface decorated by Au and Pt. The enhanced hydrogenation and dehydrogenation reactions can be attributed to catalytic dissociation of H2 and O2 molecules on metal surfaces and subsequent spillover of dissociated H and O atoms to the oxide surfaces. PMID:27603090

  3. Single-Molecule Nanocatalysis Shows In Situ Deactivation of Pt/C Electrocatalysts during the Hydrogen-Oxidation Reaction.

    PubMed

    Zhang, Yuwei; Chen, Tao; Alia, Shaun; Pivovar, Bryan S; Xu, Weilin

    2016-02-24

    By coupling a Pt-catalyzed fluorogenic reaction with the Pt-electrocatalyzed hydrogen-oxidation reaction (HOR), we combine single-molecule fluorescence microscopy with traditional electrochemical methods to study the real-time deactivation kinetics of a Pt/C electrocatalyst at single-particle level during electrocatalytic hydrogen-oxidation reaction. The decay of the catalytic performance of Pt/C could be mainly attributed to the electrocatalysis-induced etching or dissolution of Pt nanoparticles. Spontaneous regeneration of activity and incubation period of the Pt electrocatalyst were also observed at single-particle level. All these new insights are practically useful for the understanding and rational design of highly efficient electrocatalysts for application in fuel cells. PMID:26821777

  4. Versatile and Amplified Biosensing through Enzymatic Cascade Reaction by Coupling Alkaline Phosphatase in Situ Generation of Photoresponsive Nanozyme.

    PubMed

    Jin, Lu-Yi; Dong, Yu-Ming; Wu, Xiu-Ming; Cao, Gen-Xia; Wang, Guang-Li

    2015-10-20

    The alkaline phosphatase (ALP) biocatalysis followed by the in situ enzymatic generation of a visible light responsive nanozyme is coupled to elucidate a novel amplification strategy by enzymatic cascade reaction for versatile biosensing. The enzymatic hydrolysis of o-phosphonoxyphenol (OPP) to catechol (CA) by ALP is allowed to coordinate on the surface of TiO2 nanoparticles (NPs) due to the specificity and high affinity of enediol ligands to Ti(IV). Upon the stimuli by CA generated from ALP, the inert TiO2 NPs is activated, which demonstrates highly efficient oxidase mimicking activity for catalyzing the oxidation of the typical substrate of 3,3',5,5'-tetramethylbenzidine (TMB) under visible light (λ ≥ 400 nm) irradiation utilizing dissolved oxygen as an electron acceptor. On the basis of the cascade reaction of ALP and the nanozyme of CA coordinated TiO2 (TiO2-CA) NPs, we design exquisitely colorimetric biosensors for probing ALP activity and its inhibitor of 2, 4-dichlorophenoxyacetic acid (2,4-DA). Quantitative probing of ALP activity in a wide linear range from 0.01 to 150 U/L with the detection limit of 0.002 U/L is realized, which endows the methodology with sufficiently high sensitivity for potentially practical applications in real samples of human serum (ALP level of 40-190 U/L for adults). In addition, a novel immunoassay protocol by taking mouse IgG as an example is validated using the ALP/nanozyme cascade amplification reaction as the signal transducer. A low detection limit of 2.0 pg/mL is attained for mouse IgG, which is 4500-fold lower than that of the standard enzyme-linked immuno-sorbent assay (ELISA) kit. Although only mouse IgG is used as a proof-of-concept in our experiment, we believe that this approach is generalizable to be readily extended to other ELISA systems. This methodology opens a new horizon for amplified and versatile biosensing including probing ALP activity and following ALP-based ELISA immunoassays. PMID:26419907

  5. In Situ Single-Nanoparticle Spectroscopy Study of Bimetallic Nanostructure Formation.

    PubMed

    Smith, Jeremy G; Chakraborty, Indranath; Jain, Prashant K

    2016-08-16

    Bimetallic nanostructures (NSs), with utility in catalysis, are typically prepared using galvanic exchange (GE), but the final catalyst morphology is dictated by the dynamics of the process. In situ single nanoparticle (NP) optical scattering spectroscopy, coupled with ex situ electron microscopy, is used to capture the dynamic structural evolution of a bimetallic NS formed in a GE reaction between Ag and [PtCl6 ](2-) . We identify an early stage involving anisotropic oxidation of Ag to AgCl concomitant with reductive deposition of small Pt clusters on the NS surface. At later stages of GE, unreacted Ag inclusions phase segregate from the overcoated AgCl as a result of lattice strain between Ag and AgCl. The nature of the structural evolution elucidates why multi-domain Ag/AgCl/Pt NSs result from the GE process. The complex structural dynamics, determined from single-NP trajectories, would be masked in ensemble studies due to heterogeneity in the response of different NPs. PMID:27381891

  6. In situ studies of a platform for metastable inorganic crystal growth and materials discovery

    PubMed Central

    Shoemaker, Daniel P.; Hu, Yung-Jin; Chung, Duck Young; Halder, Gregory J.; Chupas, Peter J.; Soderholm, L.; Mitchell, J. F.; Kanatzidis, Mercouri G.

    2014-01-01

    Rapid shifts in the energy, technological, and environmental demands of materials science call for focused and efficient expansion of the library of functional inorganic compounds. To achieve the requisite efficiency, we need a materials discovery and optimization paradigm that can rapidly reveal all possible compounds for a given reaction and composition space. Here we provide such a paradigm via in situ X-ray diffraction measurements spanning solid, liquid flux, and recrystallization processes. We identify four new ternary sulfides from reactive salt fluxes in a matter of hours, simultaneously revealing routes for ex situ synthesis and crystal growth. Changing the flux chemistry, here accomplished by increasing sulfur content, permits comparison of the allowable crystalline building blocks in each reaction space. The speed and structural information inherent to this method of in situ synthesis provide an experimental complement to computational efforts to predict new compounds and uncover routes to targeted materials by design. PMID:25024201

  7. Circovirus-infected geese studied by in situ hybridization.

    PubMed

    Smyth, Joan; Soike, D; Moffett, Deborah; Weston, J H; Todd, D

    2005-06-01

    It has now been established that circovirus infection is common in farmed geese, but little is known about the clinicopathological significance of such infections. Ten clinically diseased geese suspected of being infected by circovirus were studied by in situ hybridization using a goose circovirus DNA probe. Circovirus DNA was demonstrated in the bursa of Fabricius (BF), spleen, thymus, bone marrow, liver, kidney, lung and heart, indicating that infection can be multisystemic. In some birds, virus DNA was present in very large quantities, most notably in the BF, liver and small intestine. With the exception of BF and thymus, there were no histological findings that would have suggested the presence of such quantities of circovirus DNA. In view of the very large quantities of virus DNA labelling present in some tissues, and by analogy to porcine circovirus type 2 infection and psittacine beak and feather virus infections, which are known to cause severe disease, and which have similar virus distribution to that found in our geese, it seems probable that the circovirus was important in the disease manifestations shown by the infected geese. PMID:16191706

  8. A laser flash photolysis kinetics study of the reaction OH + H2O2 yields HO2 + H2O

    NASA Technical Reports Server (NTRS)

    Wine, P. H.; Semmes, D. H.; Ravishankara, A. R.

    1981-01-01

    Absolute rate constants for the reaction are reported as a function of temperature over the range 273-410 K. OH radicals are produced by 266 nm laser photolysis of H2O2 and detected by resonance fluorescence. H2O2 concentrations are determined in situ in the slow flow system by UV photometry. The results confirm the findings of two recent discharge flow-resonance fluorescence studies that the title reaction is considerably faster, particularly at temperatures below 300 K, than all earlier studies had indicated. A table giving kinetic data from the reaction is included.

  9. Experimental Study of Stellar Reactions at CNS

    SciTech Connect

    Kubono, S.; Yamaguchi, H.; Wakabayashi, Y.; Amadio, G.; Hayakawa, S.; He, J. J.; Saito, A.; Teranishi, T.; Nishimura, S.; Fukunishi, N.; Iwasa, N.; Inafuku, K.; Kato, S.; Tanaka, M. H.; Fuchi, Y.; Moon, J. Y.; Kwon, K.; Lee, C. S.; Khiem, Le Hong; Chen, A.

    2006-11-02

    After a brief review on low-energy RI beam production technology, nuclear astrophysics programs at CNS are presented including a scope of the field in the Wako campus. The CRIB project involves a total development of the whole facility to maximize the low-energy RI beam intensities, including the ion source, the AVF cyclotron and the low-energy RI beam separator CRIB, Some recent nuclear astrophysics experiments performed with the RI beams were discussed, including the measurement of the 14O({alpha},p)17F reaction, the key stellar reaction for the onset of the high-temperature rp-process. The first experiment performed with a newly installed high-resolution magnetic spectrograph PA of CNS was also presented. Collaboration possibilities for nuclear astrophysics in the RIKEN campus are also touched.

  10. Experimental Study of Stellar Reactions at CNS

    NASA Astrophysics Data System (ADS)

    Kubono, S.; Yamaguchi, H.; Wakabayashi, Y.; Amadio, G.; Hayakawa, S.; He, J. J.; Saito, A.; Teranishi, T.; Nishimura, S.; Fukunishi, N.; Iwasa, N.; Inafuku, K.; Kato, S.; Tanaka, M. H.; Fuchi, Y.; Moon, J. Y.; Kwon, K.; Lee, C. S.; Khiem, Le Hong; Chen, A.; Pearson, J.

    2006-11-01

    After a brief review on low-energy RI beam production technology, nuclear astrophysics programs at CNS are presented including a scope of the field in the Wako campus. The CRIB project involves a total development of the whole facility to maximize the low-energy RI beam intensities, including the ion source, the AVF cyclotron and the low-energy RI beam separator CRIB, Some recent nuclear astrophysics experiments performed with the RI beams were discussed, including the measurement of the 14O(α,p)17F reaction, the key stellar reaction for the onset of the high-temperature rp-process. The first experiment performed with a newly installed high-resolution magnetic spectrograph PA of CNS was also presented. Collaboration possibilities for nuclear astrophysics in the RIKEN campus are also touched.

  11. Theoretical study of chemical reactions in solution

    SciTech Connect

    Yokogawa, D.

    2015-12-31

    Quantum chemical calculations in solution are becoming more and more important in chemistry. Reference interaction site model self-consistent field (RISM-SCF) is one of the powerful approaches to perform quantum chemical calculations in solution. In this work, we developed a new generation of RISM-SCF, where a robust fitting method was newly introduced. We applied the new method to tautomerization reaction of cytosine in aqueous phase. Our calculation reproduced experimentally obtained relative stabilities and relative free energies correctly.

  12. In Situ Fabrication of PtCo Alloy Embedded in Nitrogen-Doped Graphene Nanopores as Synergistic Catalyst for Oxygen Reduction Reaction

    SciTech Connect

    Zhong, Xing; Wang, Lei; Zhou, Hu; Qin, Yingying; Xu, Wenlei; Jiang, Yu; Sun, Youyi; Shi, Zheqi; Zhuang, Guilin; Li, Xiaonian; Mei, Donghai; Wang, Jian-guo

    2015-11-23

    A novel PtCo alloy in situ etched and embedded in graphene nanopores (PtCo/NPG) as a high-performance catalyst for ORR was reported. Graphene nanopores were fabricated in situ while forming PtCo nanoparticles that were uniformly embedded in the graphene nanopores. Given the synergistic effect between PtCo alloy and nanopores, PtCo/NPG exhibited 11.5 times higher mass activity than that of the commercial Pt/C cathode electrocatalyst. DFT calculations indicated that the nanopores in NPG cannot only stabilize PtCo nanoparticles but can also definitely change the electronic structures, thereby change its adsorption abilities. This enhancement can lead to a favorable reaction pathway on PtCo/NPG for ORR. This study showed that PtCo/NPG is a potential candidate for the next generation of Pt-based catalysts in fuel cells. This study also offered a promising alternative strategy and enabled the fabrication of various kinds of metal/graphene nanopore nanohybrids with potential applications in catalysts and potential use for other technological devices. The authors acknowledge the financial support from the National Basic Research Program (973 program, No. 2013CB733501), Zhejiang Provincial Education Department Research Program (Y201326554) and the National Natural Science Foundation of China (No. 21306169, 21101137, 21136001, 21176221 and 91334013). D. Mei acknowledges the support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. Computing time was granted by the grand challenge of computational catalysis of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) and by the National Energy Research Scientific Computing Center (NERSC).

  13. Model studies on the first enzyme-catalyzed Ugi reaction.

    PubMed

    Kłossowski, Szymon; Wiraszka, Barbara; Berłożecki, Stanisław; Ostaszewski, Ryszard

    2013-02-01

    Multicomponent reactions are powerful tools for organic chemistry, and among them, the Ugi reaction provides remarkable improvement in many fields of organic chemistry such us combinatorial chemistry, medicinal chemistry, and peptide chemistry. A new, enzyme-catalyzed example of the Ugi three-component reaction is presented. The studies include the selection of an enzyme as well as determination of the scope and limitations of the newly described reaction. The presented method combines the enzyme promiscuity and multicomponent reaction advantages in the first one-pot formation of dipeptide 1. PMID:23343100

  14. Neutron-induced reaction studies using stored ions

    NASA Astrophysics Data System (ADS)

    Glorius, Jan; Litvinov, Yuri A.; Reifarth, René

    2015-11-01

    Storage rings provide unique possibilities for investigations of nuclear reactions. Radioactive ions can be stored if the ring is connected to an appropriate facility and reaction studies are feasible at low beam intensities because of the recycling of beam particles. Using gas jet or droplet targets, charged particle-induced reactions on short-lived isotopes can be studied in inverse kinematics. In such a system a high-flux reactor could serve as a neutron target extending the experimental spectrum to neutron-induced reactions. Those could be studied over a wide energy range covering the research fields of nuclear astrophysics and reactor safety, transmutation of nuclear waste and fusion.

  15. Study of reaction of sulfur halides with unsaturated compounds. reaction of sulfur monochloride with adamantylideneadamantane

    SciTech Connect

    Tolstikov, G.A.; Belogaeva, T.A.; Lerman, B.M.

    1986-09-20

    In a continuation of the study of the reaction of olefin (I) with sulfur halides, the authors investigate its reaction with sulfur monochloride. It is shown that the reaction of (I) with S/sub 2/C1/sub 2/ proceeds readily in CH/sub 2/C1/sub 2/, CHC1/sub 3/, CC1/sub 4/, leading to compounds of the same structure as in the reaction of (I) with SC1/sub 2/. The preferential formation of the epithio compound (II) and chloroepithio compound (III) takes place at near-to-equimolar ratio of the reagents and 100-fold excess of the solvent, while the reaction of chlorine-substituted adamantylideneadamantanes proceeds at an excess of the reagent. In contrast to SC1/sub 2/, sulfur monochloride does not react with (I) in hexane.

  16. Room temperature reaction of oxygen with gold: an in situ ambient-pressure X-ray photoelectron spectroscopy investigation

    SciTech Connect

    Jiang, Peng; Porsgaard, Soeren; Borondics, Ferenc; Kober, Mariana; Caballero, Alfonso; Bluhm, Hendrik; Besenbacher, Flemming; Salmeron, Miquel

    2010-02-01

    Gold is commonly regarded as the most inert element.1 However, the discovery of the exceptional catalytic properties of gold nanoparticles (NPs) for low temperature CO oxidation2 initiated great interest due to its promising applications and spawned a large number of studies devoted to the understanding of the reaction mechanism.3-6 Nevertheless, no consistent and conclusive picture has arisen.7-13

  17. Study of an anaphylactoid reaction to acetaminophen.

    PubMed

    Liao, Chien-Ming; Chen, Wu-Charng; Lin, Ching-Yuang

    2002-01-01

    Generalized itching, urticaria and anaphylactic shock developed in a 9-year-old girl on two separate occasions after she ingested acetaminophen. She was admitted to our hospital for observation during oral challenge. Total eosinophil counts, total serum IgE, IgA, IgG, IgM, C3, and C4, specific IgE antibodies to six common allergens, and skin prick tests to purified acetaminophen and acetylsalicylic acid (aspirin) were unremarkable. No reaction occurred on open challenge with acetylsalicylic acid and mefenamic acid. However, urticaria and itching sensation occurred 45 min after ingesting 50 mg of purified acetaminophen. Dizziness, shivering, tachycardia and fainting also developed later. These symptoms resolved after treatment with a diphenhydramine injection and intravenous infusion of normal saline. There was a marked increase in the blood histamine level after challenge. In vitro histamine release before oral challenge was also abnormally as high as 50%. In summary, she had an immediate allergic reaction to acetaminophen but was tolerant to acetylsalicylic acid. PMID:12148965

  18. Behavior of Supported Palladium Oxide Nanoparticles under Reaction Conditions, Studied with near Ambient Pressure XPS.

    PubMed

    Jürgensen, Astrid; Heutz, Niels; Raschke, Hannes; Merz, Klaus; Hergenröder, Roland

    2015-08-01

    Near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) is a promising method to close the "pressure gap", and thus, study the surface composition during heterogeneous reactions in situ. The specialized spectrometers necessary for this analytical technique have recently been adapted to operate with a conventional X-ray source, making it available for routine quantitative analysis in the laboratory. This is shown in the present in situ study of the partial oxidation of 2-propanol catalyzed with PdO nanoparticles supported on TiO2, which was investigated under reaction conditions as a function of gas composition (alcohol-to-oxygen ratio) and temperature. Exposure of the nanoparticles to 2-propanol at 30 °C leads to immediate partial reduction of the PdO, followed by a continuous reduction of the remaining PdO during heating. However, gaseous oxygen inhibits the reduction of PdO below 90 °C, and the oxidation of 2-propanol to carboxylates only occurs in the presence of oxygen above 90 °C. These results support the theory that metallic palladium is the active catalyst material, and they show that environmental conditions affect the nanoparticles and the reaction process significantly. The study also revealed challenges and limitations of this analytical method. Specifically, the intensity and fixed photon energy of a conventional X-ray source limit the spectral resolution and surface sensitivity of lab-based NAP-XPS, which affect precision and accuracy of the quantitative analysis. PMID:26144222

  19. Low temperature hydrogen plasma-assisted atomic layer deposition of copper studied using in situ infrared reflection absorption spectroscopy

    SciTech Connect

    Chaukulkar, Rohan P.; Rai, Vikrant R.; Agarwal, Sumit; Thissen, Nick F. W.

    2014-01-15

    Atomic layer deposition (ALD) is an ideal technique to deposit ultrathin, conformal, and continuous metal thin films. However, compared to the ALD of binary materials such as metal oxides and metal nitrides, the surface reaction mechanisms during metal ALD are not well understood. In this study, the authors have designed and implemented an in situ reflection-absorption infrared spectroscopy (IRAS) setup to study the surface reactions during the ALD of Cu on Al{sub 2}O{sub 3} using Cu hexafluoroacetylacetonate [Cu(hfac){sub 2}] and a remote H{sub 2} plasma. Our infrared data show that complete ligand-exchange reactions occur at a substrate temperature of 80 °C in the absence of surface hydroxyl groups. Based on infrared data and previous studies, the authors propose that Cu(hfac){sub 2} dissociatively chemisorbs on the Al{sub 2}O{sub 3} surface, where the Al-O-Al bridge acts as the surface reactive site, leading to surface O-Cu-hfac and O-Al-hfac species. Surface saturation during the Cu(hfac){sub 2} half-cycle occurs through blocking of the available chemisorption sites. In the next half-reaction cycle, H radicals from an H{sub 2} plasma completely remove these surface hfac ligands. Through this study, the authors have demonstrated the capability of in situ IRAS as a tool to study surface reactions during ALD of metals. While transmission and internal reflection infrared spectroscopy are limited to the first few ALD cycles, IRAS can be used to probe all stages of metal ALD starting from initial nucleation to the formation of a continuous film.

  20. Degradation of Bimetallic Model Electrocatalysts ___ an in situ XAS Study

    SciTech Connect

    Friebel, Daniel

    2011-06-22

    One of the major challenges in the development of clean energy fuel cells is the performance degradation of the electrocatalyst, which, apart from poisoning effects, can suffer from corrosion due to its exposure to a harsh environment under high potentials. In this communication, we demonstrate how interactions of Pt with a transition metal support affect not only, as commonly intended, the catalytic activity, but also the reactivity of Pt towards oxide formation or dissolution. We use two well-defined single-crystal model systems, Pt/Rh(111) and Pt/Au(111) and a unique x-ray spectroscopy technique with enhanced energy resolution to monitor the potential-dependent oxidation state of Pt, and find two markedly different oxidation mechanisms on the two different substrates. This information can be of great significance for future design of more active and more stable catalysts. We have studied the potential-induced degradation of Pt monolayer model electrocatalysts on Rh(111) and Au(111) single-crystal substrates. The anodic formation of Pt oxides was monitored using in situ high energy resolution fluorescence detection x-ray absorption spectroscopy (HERFD XAS). Although Pt was deposited on both substrates in a three-dimensional island growth mode, we observed remarkable differences during oxide formation that can only be understood in terms of strong Pt-substrate interactions throughout the Pt islands. Anodic polarization of Pt/Rh(111) up to +1.6 V vs. RHE (reversible hydrogen electrode) leads to formation an incompletely oxidized passive layer, whereas formation of PtO2 and partial Pt dissolution is observed for Pt/Au(111).

  1. Localization of Herpes Simplex Virus Type 1 DNA in Latently Infected BALB/c Mice Neurons Using in situ Polymerase Chain Reaction

    PubMed Central

    Khansarinejad, Behzad; Soleimanjahi, Hoorieh; Ghaemi, Amir; Tiraihi, Taki; Pour Beiranvand, Shahram

    2010-01-01

    Background: Herpes simplex virus type-1 (HSV-1) establishes a lifelong latent infection in neurons following primary infection. The existence of latent HSV-1 DNA in the trigeminal ganglia of infected BALB/c mice was examined using a direct in situ PCR technique, based on Digoxigenin-11-dUTP detection system with anti-digoxigenin-peroxidase and 3,3'-diaminobenzidine (DAB) substrate. Methods: Eight-week-old male BALB/c mice were inoculated via the eye by 104 plaque forming unit of wild type Iranian isolates of HSV-1. After establishment of latency, trigeminal ganglia were removed and examined using in situ PCR to detect HSV-1 genome. Finally, the results of in situ PCR were verified by a two-round PCR method, using amplification cocktail of in situ reaction, as a template for a conventional gel base PCR. Results and Conclusion: The results suggest that a direct in situ PCR method using a peroxidase and DAB detection system is a useful means for detection of latent HSV-1 DNA in the latently infected ganglia. PMID:21079658

  2. Remedition case studies: Thermal desorption, soil washing, and in situ vitrification

    SciTech Connect

    1995-03-01

    The purpose of this report is to provide case studies of site cleanup projects utilizing thermal desorption, soil washing, and in situ vitrification. This volume contains reports on projects using thermal desorption, including six completed applications at sites contaminated with PCBs, pesticides, or chlorinated aliphatics. Two projects in this volume used soil washing and in situ vitrification technologies.

  3. [Reaction mechanism studies of heavy ion induced nuclear reactions]. Annual progress report, [January 1992--February 1993

    SciTech Connect

    Mignerey, A.C.

    1993-02-01

    Completed work is summarized on the topics of excitation energy division in deep-inelastic reactions and the onset of multifragmentation in La-induced reactions at E/A = 45 MeV. Magnetic fields are being calculated for the PHOBOS detector system, a two-arm multiparticle spectrometer for studying low-transverse-momentum particles produced at the Relativistic Heavy Ion Collider. The Maryland Forward Array is being developed for detection of the reaction products from very peripheral collisions; it consists of two individual units of detectors: the annular silicon detector in front and the plastic phoswich detector at back.

  4. In situ infrared study of adsorbed species during catalytic oxidation and carbon dioxide adsorption

    NASA Astrophysics Data System (ADS)

    Khatri, Rajesh A.

    2005-11-01

    Hydrogen is considered to be the fuel of the next century. Hydrogen can be produced by either water splitting using the solar or nuclear energy or by catalytic cracking and reforming of the fossil fuels. The water splitting process using solar energy and photovoltaics is a clean way to produce hydrogen, but it suffers from very low efficiency. A promising scheme to produce H 2 from natural gas involves following steps: (i) partial oxidation and reforming of natural gas to syngas, (ii) water-gas shift reaction to convert CO in the syngas to additional H2, (iii) separation of the H2 from CO2, and (iv) CO2 sequestration. The requirements for the above scheme are (i) a highly active coke resistant catalyst for generation of syngas by direct partial oxidation, (ii) a highly active sulfur tolerant catalyst for the water-gas shift reaction, and (iii) a low cost sorbent with high CO2 adsorption capacity for CO2 sequestration. This dissertation will address the mechanisms of partial oxidation, CO2 adsorption, and water-gas shift catalysis using in situ IR spectroscopy coupled with mass spectrometry (MS). The results from these studies will lead to a better understanding of the reaction mechanism and design of both the catalyst and sorbent for production of hydrogen with zero emissions. Partial oxidation of methane is studied over Rh/Al2O 3 catalyst to elucidate the reaction mechanism for synthesis gas formation. The product lead-lag relationship observed with in situ IR and MS results revealed that syngas is produced via a two-step reforming mechanism: the first step involving total oxidation of CH4 to CO2 and H 2O and the second step involving the reforming of unconverted methane with CO2 and H2O to form syngas. Furthermore, the Rh on the catalyst surface remains predominantly in the partially oxidized state (Rhdelta+ and Rh0). For the water-gas shift reaction, addition of Re to the Ni/CeO2 catalyst enhanced the water gas shift activity by a factor of three. The activity

  5. In situ Raman study of Electrochemically Intercalted Bisulfate Ions in Carbon Nanotube Bundles

    NASA Astrophysics Data System (ADS)

    Sumanasekera, G. U.; Allen, J. L.; Rao, A. M.; Fang, S. L.; Eklund, P. C.

    1998-03-01

    We have investigated the electrochemical intercalation of bisulfate ions in single-walled carbon nanotubes (SWNT) using in situ Raman spectroscopy. SWNTs pressed onto a Pt plate was used as the working electrode, a Pt wire and Ag/AgCl were used, respectively, as the counter electrode and reference electrode. Sulfuric acid (95%) was used as the electrolyte. Using Raman scattering we have observed an apparent rapid spontaneous reaction involving charge transfer between ionically bonded HSO_4^- anions and the nanotubes. This is evidenced by an instantaneous shift of the Raman-active tangential mode frequency from 1593 cm -1 to 1604 cm-1 (It was not possible to reverse this shift electrochemically to 1593 cm-1, even at the expense of large reverse bias). In forward bias, after this initial instantaneous reaction, the tangential mode frequency again upshifted from 1604 cm-1 to 1614 cm-1 linearly with external electrochemical charge Q. From the slope of ω(Q) we found in this regime, δω/δ f= 1220 cm-1 (f = holes/carbon). Upon further charging, a second regime with slope δω/δ f = 118 cm-1 was observed where the frequency upshifted from 1614 cm-1 to 1620 cm-1. The results are compared to similar studies in C_p^+HSO_4^-.xH_2SO4 graphite intercalation compounds.

  6. Matrix isolation as a tool for studying interstellar chemical reactions

    NASA Technical Reports Server (NTRS)

    Ball, David W.; Ortman, Bryan J.; Hauge, Robert H.; Margrave, John L.

    1989-01-01

    Since the identification of the OH radical as an interstellar species, over 50 molecular species were identified as interstellar denizens. While identification of new species appears straightforward, an explanation for their mechanisms of formation is not. Most astronomers concede that large bodies like interstellar dust grains are necessary for adsorption of molecules and their energies of reactions, but many of the mechanistic steps are unknown and speculative. It is proposed that data from matrix isolation experiments involving the reactions of refractory materials (especially C, Si, and Fe atoms and clusters) with small molecules (mainly H2, H2O, CO, CO2) are particularly applicable to explaining mechanistic details of likely interstellar chemical reactions. In many cases, matrix isolation techniques are the sole method of studying such reactions; also in many cases, complexations and bond rearrangements yield molecules never before observed. The study of these reactions thus provides a logical basis for the mechanisms of interstellar reactions. A list of reactions is presented that would simulate interstellar chemical reactions. These reactions were studied using FTIR-matrix isolation techniques.

  7. Fundamental studies of retrograde reactions in direct liquefaction

    SciTech Connect

    Serio, M.A.; Solomon, P.R.; Bassilakis, R.; Kroo, E.

    1989-01-01

    Most of the proposed processing schemes for improving liquefaction yields involve favoring bond-breaking and radical stabilization reactions over the retrograde reactions. The retrograde reactions are often encountered before liquefaction temperatures are reached. The objective of this program is to elucidate and model the retrograde reaction chemistry in direct coal liquefaction through the application of experimental techniques and theoretical models which have been successfully employed at Advanced Fuel Research (AFR) and SRI International (a subcontractor) to understand and predict coal reaction behavior. The study of retrograde reactions is being done using an integrated approach using extensive characterization of the liquefaction chemistry of three kinds of systems: (1) model polymers; (2) coal; and (3) modified coals.

  8. Transverse flow reactor studies of the dynamics of radical reactions

    SciTech Connect

    Macdonald, R.G.

    1993-12-01

    Radical reactions are in important in combustion chemistry; however, little state-specific information is available for these reactions. A new apparatus has been constructed to measure the dynamics of radical reactions. The unique feature of this apparatus is a transverse flow reactor in which an atom or radical of known concentration will be produced by pulsed laser photolysis of an appropriate precursor molecule. The time dependence of individual quantum states or products and/or reactants will be followed by rapid infrared laser absorption spectroscopy. The reaction H + O{sub 2} {yields} OH + O will be studied.

  9. In-situ spectroscopic studies of electrochromic tungsten oxide films

    NASA Astrophysics Data System (ADS)

    Ozer, Nilgun; Demirbas, Muharrem; Ozyurt, Secuk

    2001-11-01

    Tungsten oxide thin films were prepared using an ethanolic solution of tungsten hexachloride (WCl6) by sol-gel spin coating. The films were spin coated on indium tin oxide (ITO) coated glass substrate at temperatures in the range of 100 to 450 degree(s)C. The films were characterized by x-ray diffractometry (XRD), scanning electron microscopy (SEM) UV- visible spectroscopy and cyclic voltammetry (CV). XRD showed that they had a polycrystalline WO3 structure for heat treatment temperatures at above 350 degree(s)C. The SEM examinations showed that the surface texture was very uniform and homogeneous. In situ electrochemical reduction of WO3/ITO (2M HCl) produced a blue color in less than a second. Coloration efficiency (CE) was found to be 21 cm2/mC. In situ spectroscopic investigations showed that these films could be used as a working electrode in electrochromic devices.

  10. Towards microfluidic reactors for in situ synchrotron infrared studies

    NASA Astrophysics Data System (ADS)

    Silverwood, I. P.; Al-Rifai, N.; Cao, E.; Nelson, D. J.; Chutia, A.; Wells, P. P.; Nolan, S. P.; Frogley, M. D.; Cinque, G.; Gavriilidis, A.; Catlow, C. R. A.

    2016-02-01

    Anodically bonded etched silicon microfluidic devices that allow infrared spectroscopic measurement of solutions are reported. These extend spatially well-resolved in situ infrared measurement to higher temperatures and pressures than previously reported, making them useful for effectively time-resolved measurement of realistic catalytic processes. A data processing technique necessary for the mitigation of interference fringes caused by multiple reflections of the probe beam is also described.