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Sample records for halide substrates heterogeneous

  1. An heterogeneous nucleation model for the irradiation coloring of alkali halides

    International Nuclear Information System (INIS)

    Aguilar, M.; Jaque, F.; Agullo-Lopez, F.

    1980-01-01

    An heterogeneous nucleation model for the radiation-induced coloring of alkali halides is presented. The model assumes a primary mechanism producing F and H pairs, followed by secondary thermally activated reactions including F-H recombination as well interstitial capture. The existence of a very unstable interstitial aggregate is explicitely considered. The model is able to account for the three-stages structure of the F-coloring curve and the inhibition in the occurrence of the late-stage by lowering dose-rate or by impurity doping

  2. Chemoselective Radical Dehalogenation and C-C Bond Formation on Aryl Halide Substrates Using Organic Photoredox Catalysts.

    Science.gov (United States)

    Poelma, Saemi O; Burnett, G Leslie; Discekici, Emre H; Mattson, Kaila M; Treat, Nicolas J; Luo, Yingdong; Hudson, Zachary M; Shankel, Shelby L; Clark, Paul G; Kramer, John W; Hawker, Craig J; Read de Alaniz, Javier

    2016-08-19

    Despite the number of methods available for dehalogenation and carbon-carbon bond formation using aryl halides, strategies that provide chemoselectivity for systems bearing multiple carbon-halogen bonds are still needed. Herein, we report the ability to tune the reduction potential of metal-free phenothiazine-based photoredox catalysts and demonstrate the application of these catalysts for chemoselective carbon-halogen bond activation to achieve C-C cross-coupling reactions as well as reductive dehalogenations. This procedure works both for conjugated polyhalides as well as unconjugated substrates. We further illustrate the usefulness of this protocol by intramolecular cyclization of a pyrrole substrate, an advanced building block for a family of natural products known to exhibit biological activity.

  3. Thermokinetics of heterogeneous droplet nucleation on conically textured substrates.

    Science.gov (United States)

    Singha, Sanat K; Das, Prasanta K; Maiti, Biswajit

    2015-11-28

    Within the framework of the classical theory of heterogeneous nucleation, a thermokinetic model is developed for line-tension-associated droplet nucleation on conical textures considering growth or shrinkage of the formed cluster due to both interfacial and peripheral monomer exchange and by considering different geometric configurations. Along with the principle of free energy extremization, Katz kinetic approach has been employed to study the effect of substrate conicity and wettability on the thermokinetics of heterogeneous water droplet nucleation. Not only the peripheral tension is found to have a considerable effect on the free energy barrier but also the substrate hydrophobicity and hydrophilicity are observed to switch over their roles between conical crest and trough for different growth rates of the droplet. Besides, the rate of nucleation increases and further promotes nucleation for negative peripheral tension as it diminishes the free energy barrier appreciably. Moreover, nucleation inhibition can be achievable for positive peripheral tension due to the enhancement of the free energy barrier. Analyzing all possible geometric configurations, the hydrophilic narrower conical cavity is found to be the most preferred nucleation site. These findings suggest a physical insight into the context of surface engineering for the promotion or the suppression of nucleation on real or engineered substrates.

  4. Palladium clusters deposited on the heterogeneous substrates

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Kun, E-mail: cqdxwk@126.com [College of Power Engineering, Chongqing University, Chongqing 400044 (China); Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education of PRC, Chongqing 400044 (China); Liu, Juanfang, E-mail: juanfang@cqu.edu.cn [College of Power Engineering, Chongqing University, Chongqing 400044 (China); Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education of PRC, Chongqing 400044 (China); Chen, Qinghua, E-mail: qhchen@cqu.edu.cn [College of Power Engineering, Chongqing University, Chongqing 400044 (China); Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education of PRC, Chongqing 400044 (China)

    2016-07-15

    Graphical abstract: The site-exchange between the substrate and cluster atoms can result in the formation of the surface alloys and the reconstruction of the cluster structure before the collision system approaching the thermal equilibrium. The deposited cluster adjusted the atom arrangement as possibly as to match the substrate lattice arrangement from bottom to up. The structural reconstruction is accompanied by the system potential energy minimization. - Highlights: • The deposition process can divide explicitly into three stages: adsorption, collision, relaxation. • The local melt does not emerge inside the substrate during the deposition process. • Surface alloys are formed by the site-exchange between the cluster and substrate atoms. • The cluster reconstructs the atom arrangement following as the substrate lattice arrangement from bottom to up. • The structural reconstruction ability and scope depend on the cluster size and incident energy. - Abstract: To improve the performance of the Pd composite membrane prepared by the cold spraying technology, it is extremely essential to give insights into the deposition process of the cluster and the heterogeneous deposition of the big Pd cluster at the different incident velocities on the atomic level. The deposition behavior, morphologies, energetic and interfacial configuration were examined by the molecular dynamic simulation and characterized by the cluster flattening ratio, the substrate maximum local temperature, the atom-embedded layer number and the surface-alloy formation. According to the morphology evolution, three deposition stages and the corresponding structural and energy evolution were clearly identified. The cluster deformation and penetrating depth increased with the enhancement of the incident velocity, but the increase degree also depended on the substrate hardness. The interfacial interaction between the cluster and the substrate can be improved by the higher substrate local temperature

  5. Improved catalytic properties of halohydrin dehalogenase by modification of the halide-binding site.

    Science.gov (United States)

    Tang, Lixia; Torres Pazmiño, Daniel E; Fraaije, Marco W; de Jong, René M; Dijkstra, Bauke W; Janssen, Dick B

    2005-05-03

    Halohydrin dehalogenase (HheC) from Agrobacterium radiobacter AD1 catalyzes the dehalogenation of vicinal haloalcohols by an intramolecular substitution reaction, resulting in the formation of the corresponding epoxide, a halide ion, and a proton. Halide release is rate-limiting during the catalytic cycle of the conversion of (R)-p-nitro-2-bromo-1-phenylethanol by the enzyme. The recent elucidation of the X-ray structure of HheC showed that hydrogen bonds between the OH group of Tyr187 and between the Odelta1 atom of Asn176 and Nepsilon1 atom of Trp249 could play a role in stabilizing the conformation of the halide-binding site. The possibility that these hydrogen bonds are important for halide binding and release was studied using site-directed mutagenesis. Steady-state kinetic studies revealed that mutant Y187F, which has lost both hydrogen bonds, has a higher catalytic activity (k(cat)) with two of the three tested substrates compared to the wild-type enzyme. Mutant W249F also shows an enhanced k(cat) value with these two substrates, as well as a remarkable increase in enantiopreference for (R)-p-nitro-2-bromo-1-phenylethanol. In case of a mutation at position 176 (N176A and N176D), a 1000-fold lower catalytic efficiency (k(cat)/K(m)) was obtained, which is mainly due to an increase of the K(m) value of the enzyme. Pre-steady-state kinetic studies showed that a burst of product formation precedes the steady state, indicating that halide release is still rate-limiting for mutants Y187F and W249F. Stopped-flow fluorescence experiments revealed that the rate of halide release is 5.6-fold higher for the Y187F mutant than for the wild-type enzyme and even higher for the W249F enzyme. Taken together, these results show that the disruption of two hydrogen bonds around the halide-binding site increases the rate of halide release and can enhance the overall catalytic activity of HheC.

  6. Thallous and cesium halide materials for use in cryogenic applications

    International Nuclear Information System (INIS)

    Lawless, W.N.

    1983-01-01

    Certain thallous and cesium halides, either used alone or in combination with other ceramic materials, are provided in cryogenic applications such as heat exchange material for the regenerator section of a closed-cycle cryogenic refrigeration section, as stabilizing coatings for superconducting wires, and as dielectric insulating materials. The thallous and cesium halides possess unusually large specific heats at low temperatures, have large thermal conductivities, are nonmagnetic, and are nonconductors of electricity. They can be formed into a variety of shapes such as spheres, bars, rods, or the like and can be coated or extruded onto substrates or wires. (author)

  7. Cuprous halides semiconductors as a new means for highly efficient light-emitting diodes

    Science.gov (United States)

    Ahn, Doyeol; Park, Seoung-Hwan

    2016-01-01

    In group-III nitrides in use for white light-emitting diodes (LEDs), optical gain, measure of luminous efficiency, is very low owing to the built-in electrostatic fields, low exciton binding energy, and high-density misfit dislocations due to lattice-mismatched substrates. Cuprous halides I-VII semiconductors, on the other hand, have negligible built-in field, large exciton binding energies and close lattice matched to silicon substrates. Recent experimental studies have shown that the luminescence of I-VII CuCl grown on Si is three orders larger than that of GaN at room temperature. Here we report yet unexplored potential of cuprous halides systems by investigating the optical gain of CuCl/CuI quantum wells. It is found that the optical gain and the luminescence are much larger than that of group III-nitrides due to large exciton binding energy and vanishing electrostatic fields. We expect that these findings will open up the way toward highly efficient cuprous halides based LEDs compatible to Si technology. PMID:26880097

  8. Wetting at the nanometer scale: effects of long-range forces and substrate heterogeneities

    International Nuclear Information System (INIS)

    Checco, Antonio

    2003-01-01

    Wetting phenomena on the nano-scale remain poorly understood in spite of their growing theoretical and practical interest. In this context, the present work aimed at studying partial wetting of nanometer-sized alkane droplets on 'model' surfaces build by self-assembly of organic monolayers. For this purpose a novel technique, based on 'noncontact' Atomic Force Microscopy (AFM), has been developed to image, with minimal artefacts, drops of adjustable size directly condensed on so- lid surfaces. We have thus shown that contact angle of alkanes, wetting a weakly heterogeneous, silanized substrate, noticeably decreases from its macroscopic value for droplets sizes in the submicron range. The line tension, arising in this case from purely dispersive long-range interactions between the liquid and the substrate, is theoretically too weak to be responsible for the observed effect. Therefore we have supposed that contact angle is affected by mesoscopic chemical heterogeneities of the substrate whenever the droplets size becomes sufficiently small. This scenario has been supported by numerical simulations based on a simplified model of the spatial distribution of surface defects. Similar experiments, performed on different substrates (monolayers made of alkane-thiols self-assembled on gold and of alkyl chains covalently bound onto a silicon surface), have also shown that wetting on small scales is strongly affected by minimal physical and chemical surface heterogeneities. Finally, to provide further examples of the potential of the above mentioned AFM technique, we have studied the wettability of nano-structured surfaces and the local wetting properties of hair. (author) [fr

  9. Dehalogenation of aromatic halides by polyaniline/zero-valent iron composite nanofiber: Kinetics and mechanisms

    CSIR Research Space (South Africa)

    Giri, S

    2016-03-01

    Full Text Available Dehalogenation of aryl halides was demonstrated using polyaniline/zero valent iron composite nanofiber (termed as PANI/Fe0) as a cheap, efficient and environmentally friendly heterogeneous catalyst. The catalyst was prepared via rapid mixing...

  10. Inverse kinetic solvent isotope effect in TiO2 photocatalytic dehalogenation of non-adsorbable aromatic halides: a proton-induced pathway.

    Science.gov (United States)

    Chang, Wei; Sun, Chunyan; Pang, Xibin; Sheng, Hua; Li, Yue; Ji, Hongwei; Song, Wenjing; Chen, Chuncheng; Ma, Wanhong; Zhao, Jincai

    2015-02-09

    An efficient redox reaction between organic substrates in solution and photoinduced h(+) vb /e(-) cb on the surface of photocatalysts requires the substrates or solvent to be adsorbed onto the surface, and is consequentially marked by a normal kinetic solvent isotope effect (KSIE ≥ 1). Reported herein is a universal inverse KSIE (0.6-0.8 at 298 K) for the reductive dehalogenation of aromatic halides which cannot adsorb onto TiO2 in a [D0 ]methanol/[D4 ]methanol solution. Combined with in situ ATR-FTIR spectroscopy investigations, a previously unknown pathway for the transformation of these aromatic halides in TiO2 photocatalysis was identified: a proton adduct intermediate, induced by released H(+) /D(+) from solvent oxidation, accompanies a change in hybridization from sp(2) to sp(3) at a carbon atom of the aromatic halides. The protonation event leads these aromatic halides to adsorb onto the TiO2 surface and an ET reaction to form dehalogenated products follows. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Manganese-Catalyzed Cross-Coupling of Aryl Halides and Grignard Reagents by a Radical Mechanism

    DEFF Research Database (Denmark)

    Antonacci, Giuseppe; Ahlburg, Andreas; Fristrup, Peter

    2017-01-01

    The substrate scope and the mechanism have been investigated for the MnCl2-catalyzed cross-coupling reaction between aryl halides and Grignard reagents. The transformation proceeds rapidly and in good yield when the aryl halide component is an aryl chloride containing a cyano or an ester group....... Two radical-clock experiments were carried out, and in both cases an intermediate aryl radical was successfully trapped. The cross-coupling reaction is therefore believed to proceed by an SRN1 mechanism, with a triorganomanganate complex serving as the most likely nucleophile and single-electron donor...

  12. Refined global methyl halide budgets with respect to rapeseed (Brassica napus) by life-cycle measurements

    Science.gov (United States)

    Jiao, Y.; Acdan, J.; Xu, R.; Deventer, M. J.; Rhew, R. C.

    2017-12-01

    A precise quantification of global methyl halide budgets is needed to evaluate the ozone depletion potential of these compounds and to predict future changes of stratospheric ozone. However, the global budgets of methyl halides are not balanced between currently identified and quantified sources and sinks. Our study re-evaluated the methyl bromide budget from global cultivated rapeseed (Brassica napus) through life-cycle flux measurements both in the greenhouse and in the field, yielding a methyl bromide emission rate that scales globally to 1.0 - 1.2 Gg yr-1. While this indicates a globally significant source, it is much smaller than the previously widely cited value of 5 - 6 Gg yr-1(Mead et al., 2008), even taking into account the near tripling of annual global yield of rapeseed since the previous evaluation was conducted. Our study also evaluated the methyl chloride and methyl iodide emission levels from rapeseed, yielding emission rates that scale to 5.4 Gg yr-1 for methyl chloride and 1.8 Gg yr-1 of methyl iodide. The concentrations of the methyl donor SAM (S-adenosyl methionine) and the resultant product SAH (S-Adenosyl-L-homocysteine) were also analyzed to explore their role in biogenic methyl halide formation. Halide gradient incubations showed that the magnitude of methyl halide emissions from rapeseed is highly correlated to soil halide levels, thus raising the concern that the heterogeneity of soil halide contents geographically should be considered when extrapolating to global budget.

  13. Heterogeneous nucleation on convex spherical substrate surfaces: A rigorous thermodynamic formulation of Fletcher's classical model and the new perspectives derived.

    Science.gov (United States)

    Qian, Ma; Ma, Jie

    2009-06-07

    Fletcher's spherical substrate model [J. Chem. Phys. 29, 572 (1958)] is a basic model for understanding the heterogeneous nucleation phenomena in nature. However, a rigorous thermodynamic formulation of the model has been missing due to the significant complexities involved. This has not only left the classical model deficient but also likely obscured its other important features, which would otherwise have helped to better understand and control heterogeneous nucleation on spherical substrates. This work presents a rigorous thermodynamic formulation of Fletcher's model using a novel analytical approach and discusses the new perspectives derived. In particular, it is shown that the use of an intermediate variable, a selected geometrical angle or pseudocontact angle between the embryo and spherical substrate, revealed extraordinary similarities between the first derivatives of the free energy change with respect to embryo radius for nucleation on spherical and flat substrates. Enlightened by the discovery, it was found that there exists a local maximum in the difference between the equivalent contact angles for nucleation on spherical and flat substrates due to the existence of a local maximum in the difference between the shape factors for nucleation on spherical and flat substrate surfaces. This helps to understand the complexity of the heterogeneous nucleation phenomena in a practical system. Also, it was found that the unfavorable size effect occurs primarily when R<5r( *) (R: radius of substrate and r( *): critical embryo radius) and diminishes rapidly with increasing value of R/r( *) beyond R/r( *)=5. This finding provides a baseline for controlling the size effects in heterogeneous nucleation.

  14. Adsorption of molecular additive onto lead halide perovskite surfaces: A computational study on Lewis base thiophene additive passivation

    Science.gov (United States)

    Zhang, Lei; Yu, Fengxi; Chen, Lihong; Li, Jingfa

    2018-06-01

    Organic additives, such as the Lewis base thiophene, have been successfully applied to passivate halide perovskite surfaces, improving the stability and properties of perovskite devices based on CH3NH3PbI3. Yet, the detailed nanostructure of the perovskite surface passivated by additives and the mechanisms of such passivation are not well understood. This study presents a nanoscopic view on the interfacial structure of an additive/perovskite interface, consisting of a Lewis base thiophene molecular additive and a lead halide perovskite surface substrate, providing insights on the mechanisms that molecular additives can passivate the halide perovskite surfaces and enhance the perovskite-based device performance. Molecular dynamics study on the interactions between water molecules and the perovskite surfaces passivated by the investigated additive reveal the effectiveness of employing the molecular additives to improve the stability of the halide perovskite materials. The additive/perovskite surface system is further probed via molecular engineering the perovskite surfaces. This study reveals the nanoscopic structure-property relationships of the halide perovskite surface passivated by molecular additives, which helps the fundamental understanding of the surface/interface engineering strategies for the development of halide perovskite based devices.

  15. Electrochemically reduced titanocene dichloride as a catalyst of reductive dehalogenation of organic halides

    International Nuclear Information System (INIS)

    Magdesieva, Tatiana V.; Graczyk, Magdalena; Vallat, Alain; Nikitin, Oleg M.; Demyanov, Petr I.; Butin, Kim P.; Vorotyntsev, Mikhail A.

    2006-01-01

    We have studied a reaction between the reduced form of titanocene dichloride (Cp 2 TiCl 2 ) and a group of organic halides: benzyl derivatives (4-X-C 6 H 4 CH 2 Cl, X = H, NO 2 , CH 3 ; 4-X-C 6 H 4 CH 2 Br, X = H, NO 2 , PhC(O); 4-X-C 6 H 4 CH 2 SCN, X = H, NO 2 ) as well as three aryl halides (4-NO 2 C 6 H 4 Hal, Hal = Cl, Br; 4-CH 3 O-C 6 H 4 Cl). It has been shown that the electrochemical reduction of Cp 2 TiCl 2 in the presence of these benzyl halides leads to a catalytic cycle resulting in the reductive dehalogenation of these organic substrates to yield mostly corresponding toluene derivatives as the main product. No dehalogenation has been observed for aryl derivatives. Based on electrochemical data and digital simulation, possible schemes of the catalytic process have been outlined. For non-substituted benzyl halides halogen atom abstraction is a key step. For the reaction of nitrobenzyl halides the complexation of Ti(III) species with the nitro group takes place, with the electron transfer from Ti(III) to this group (owing to its highest coefficient in LUMO of the nitro benzyl halide) followed by an intramolecular dissociative electron redistribution in the course of the heterolytic C-Hal bond cleavage. The results for reduced titanocene dichloride centers immobilized inside a polymer film showed that the catalytic reductive dehalogenation of the p-nitrobenzyl chloride does occur but with a low efficiency because of the partial deactivation of the film due to the blocking of the electron charge transport between the electrode and catalytic centers

  16. Electrochemically reduced titanocene dichloride as a catalyst of reductive dehalogenation of organic halides

    Energy Technology Data Exchange (ETDEWEB)

    Magdesieva, Tatiana V. [Department Chemistry, M.V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation)]. E-mail: tvm@org.chem.msu.ru; Graczyk, Magdalena [LSEO-UMR 5188 CNRS, Universite de Bourgogne, Dijon (France); Vallat, Alain [LSEO-UMR 5188 CNRS, Universite de Bourgogne, Dijon (France); Nikitin, Oleg M. [Department Chemistry, M.V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation); Demyanov, Petr I. [Department Chemistry, M.V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation); Butin, Kim P. [Department Chemistry, M.V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation); Vorotyntsev, Mikhail A. [LSEO-UMR 5188 CNRS, Universite de Bourgogne, Dijon (France)]. E-mail: MV@u-bourgogne.fr

    2006-11-12

    We have studied a reaction between the reduced form of titanocene dichloride (Cp{sub 2}TiCl{sub 2}) and a group of organic halides: benzyl derivatives (4-X-C{sub 6}H{sub 4}CH{sub 2}Cl, X = H, NO{sub 2}, CH{sub 3}; 4-X-C{sub 6}H{sub 4}CH{sub 2}Br, X = H, NO{sub 2}, PhC(O); 4-X-C{sub 6}H{sub 4}CH{sub 2}SCN, X = H, NO{sub 2}) as well as three aryl halides (4-NO{sub 2}C{sub 6}H{sub 4}Hal, Hal = Cl, Br; 4-CH{sub 3}O-C{sub 6}H{sub 4}Cl). It has been shown that the electrochemical reduction of Cp{sub 2}TiCl{sub 2} in the presence of these benzyl halides leads to a catalytic cycle resulting in the reductive dehalogenation of these organic substrates to yield mostly corresponding toluene derivatives as the main product. No dehalogenation has been observed for aryl derivatives. Based on electrochemical data and digital simulation, possible schemes of the catalytic process have been outlined. For non-substituted benzyl halides halogen atom abstraction is a key step. For the reaction of nitrobenzyl halides the complexation of Ti(III) species with the nitro group takes place, with the electron transfer from Ti(III) to this group (owing to its highest coefficient in LUMO of the nitro benzyl halide) followed by an intramolecular dissociative electron redistribution in the course of the heterolytic C-Hal bond cleavage. The results for reduced titanocene dichloride centers immobilized inside a polymer film showed that the catalytic reductive dehalogenation of the p-nitrobenzyl chloride does occur but with a low efficiency because of the partial deactivation of the film due to the blocking of the electron charge transport between the electrode and catalytic centers.

  17. Methods for producing single crystal mixed halide perovskites

    Science.gov (United States)

    Zhu, Kai; Zhao, Yixin

    2017-07-11

    An aspect of the present invention is a method that includes contacting a metal halide and a first alkylammonium halide in a solvent to form a solution and maintaining the solution at a first temperature, resulting in the formation of at least one alkylammonium halide perovskite crystal, where the metal halide includes a first halogen and a metal, the first alkylammonium halide includes the first halogen, the at least one alkylammonium halide perovskite crystal includes the metal and the first halogen, and the first temperature is above about 21.degree. C.

  18. Photofragmentation of metal halides

    International Nuclear Information System (INIS)

    Veen, N.J.A. van.

    1980-01-01

    The author deals with photodissociation of molecules of alkali halides. It is shown that the total absorption cross section consists of two contributions arising from transitions to excited states of total electronic angular momentum Ω=0 + and Ω=1. From the inversion of the absorption continua potential energy curves of the excited states can be constructed in the Franck-Condon region. It is found that for all alkali halides the 0 + state is higher in energy than the Ω=1 state. Extensive studies are reported on three thallium halides, TlI, TlBr and TlCl at various wavelengths covering the near ultraviolet region. (Auth.)

  19. Preparation of textured high Tc superconducting films by CVD using halides on technical substrates with appropriate buffer layers. Final report

    International Nuclear Information System (INIS)

    Selbmann, D.; Balarin, M.; Klosowski, J.

    1993-01-01

    On the basis of a thermodynamical calculation of the system Y-Ba-Cu-O-Hal-C-H, Hal = I, Br, Cl the deposition conditions of the 123-phase and the other phases in this system was investigated. For the practical applications a reaction temperature higher 850 C and an oxidizer excesse higher 5 . 10 3 is necessary in order to deposit halid- and carbon free layers. A new Aerosol-CVD-process has been developed, which allows the reproducible preparation of superconducting YBa 2 Cu 3 O 7 thin films. The process uses a solution source of Y-, Ba-, Cu-bromide dissolved in suitable organic solvents. With the process the films consisting of the 123-phase, however the content of other phases is too high. With this composition it is not possible to deposit textured layers. This behaviour is due to flow technical problems. In order to avoid the formation of oxides in the evaporator it is necessary to mix the oxidizer directly near the substrate. Therefore the development of a new reactor and a process optimization is necessary. (orig.) [de

  20. Relation between the electroforming voltage in alkali halide-polymer diodes and the bandgap of the alkali halide

    International Nuclear Information System (INIS)

    Bory, Benjamin F.; Wang, Jingxin; Janssen, René A. J.; Meskers, Stefan C. J.; Gomes, Henrique L.; De Leeuw, Dago M.

    2014-01-01

    Electroforming of indium-tin-oxide/alkali halide/poly(spirofluorene)/Ba/Al diodes has been investigated by bias dependent reflectivity measurements. The threshold voltages for electrocoloration and electroforming are independent of layer thickness and correlate with the bandgap of the alkali halide. We argue that the origin is voltage induced defect formation. Frenkel defect pairs are formed by electron–hole recombination in the alkali halide. This self-accelerating process mitigates injection barriers. The dynamic junction formation is compared to that of a light emitting electrochemical cell. A critical defect density for electroforming is 10 25 /m 3 . The electroformed alkali halide layer can be considered as a highly doped semiconductor with metallic transport characteristics

  1. Metal-Mediated Halogen Exchange in Aryl and Vinyl Halides: a Review

    Science.gov (United States)

    Evano, Gwilherm; Nitelet, Antoine; Thilmany, Pierre; Dewez, Damien F.

    2018-04-01

    Halogenated arenes and alkenes are of prime importance in many areas of science, especially in the pharmaceutical, agrochemical and chemical industries. While the simplest ones are commercially available, some of them are still hardly accessible depending on their substitution patterns and the nature of the halogen atom. Reactions enabling the selective and efficient replacement of the halogen atom of an aryl or alkenyl halide by another one, lighter or heavier, are therefore of major importance since they can be used for example to turn a less reactive aryl/alkenyl chloride into the more reactive iodinated derivatives or, in a reversed sense, to block an undesired reactivity, for late-stage modifications or for the introduction of a radionuclide. If some halogen exchange reactions are possible with activated substrates, they usually require catalysis with metal complexes. Remarkably efficient processes have been developed for metal-mediated halogen exchange in aryl and vinyl halides: they are overviewed, in a comprehensive manner, in this review article.

  2. Structure of polyvalent metal halide melts

    International Nuclear Information System (INIS)

    Tosi, M.P.

    1990-12-01

    A short review is given of recent progress in determining and understanding the structure of molten halide salts involving polyvalent metal ions. It covers the following three main topics: (i) melting mechanisms and types of liquid structure for pure polyvalent-metal chlorides; (ii) geometry and stability of local coordination for polyvalent metal ions in molten mixtures of their halides with alkali halides; and (iii) structure breaking and electron localization on addition of metal to the melt. (author). 28 refs, 3 figs, 1 tab

  3. Halide-Dependent Electronic Structure of Organolead Perovskite Materials

    KAUST Repository

    Buin, Andrei; Comin, Riccardo; Xu, Jixian; Ip, Alexander H.; Sargent, Edward H.

    2015-01-01

    -based perovskites, in line with recent experimental data. As a result, the optimal growth conditions are also different for the distinct halide perovskites: growth should be halide-rich for Br and Cl, and halide-poor for I-based perovskites. We discuss stability

  4. Development of Halide and Oxy-Halides for Isotopic Separations

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Leigh R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Johnson, Aaron T. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Pfeiffer, Jana [Idaho National Lab. (INL), Idaho Falls, ID (United States); Finck, Martha R. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-10-01

    The goal of this project was to synthesize a volatile form of Np for introduction into mass spectrometers at INL. Volatile solids of the 5f elements are typically those of the halides (e.g. UF6), however fluorine is highly corrosive to the sensitive internal components of the mass separator, and the other volatile halides exist as several different stable isotopes in nature. However, iodide is both mono-isotopic and volatile, and as such presents an avenue for creation of a form of Np suitable for introduction into the mass separator. To accomplish this goal, the technical work in the project sought to establish a novel synthetic route for the conversion NpO2+ (dissolved in nitric acid) to NpI3 and NpI4.

  5. Effect of halide-mixing on the switching behaviors of organic-inorganic hybrid perovskite memory

    Science.gov (United States)

    Hwang, Bohee; Gu, Chungwan; Lee, Donghwa; Lee, Jang-Sik

    2017-03-01

    Mixed halide perovskite materials are actively researched for solar cells with high efficiency. Their hysteresis which originates from the movement of defects make perovskite a candidate for resistive switching memory devices. We demonstrate the resistive switching device based on mixed-halide organic-inorganic hybrid perovskite CH3NH3PbI3-xBrx (x = 0, 1, 2, 3). Solvent engineering is used to deposit the homogeneous CH3NH3PbI3-xBrx layer on the indium-tin oxide-coated glass substrates. The memory device based on CH3NH3PbI3-xBrx exhibits write endurance and long retention, which indicate reproducible and reliable memory properties. According to the increase in Br contents in CH3NH3PbI3-xBrx the set electric field required to make the device from low resistance state to high resistance state decreases. This result is in accord with the theoretical calculation of migration barriers, that is the barrier to ionic migration in perovskites is found to be lower for Br- (0.23 eV) than for I- (0.29-0.30 eV). The resistive switching may be the result of halide vacancy defects and formation of conductive filaments under electric field in the mixed perovskite layer. It is observed that enhancement in operating voltage can be achieved by controlling the halide contents in the film.

  6. Effective dielectric functions of samples obtained by evaporation of alkali halides

    International Nuclear Information System (INIS)

    Sturm, J.; Grosse, P.; Theiss, W.

    1991-01-01

    This paper investigates the dielectric properties of inhomogeneous samples consisting of small alkali halide particles (NaCl, KBr) on gold-coated substrates. Our reflection measurements in the far infrared can be simulated as a thin layer of the power with an effective dielectric function on a perfectly reflecting substrate. Scanning electron micrographs provide useful information about sample topology. Several mixing formulas (e.g. the Maxwell-Garnett, the Bruggeman- and the Looyenga-formula) lead to effective dielectric functions neglecting the individual arrangement of the particles. The essence of our work is that, in contrast, the general ansatz of the Bergman spectral representation has to be employed in order to take into account topology effects on the dielectric function based on the so-called spectral density g adjustable to the specific situation. (orig.)

  7. Morphology-Controlled Synthesis of Organometal Halide Perovskite Inverse Opals.

    Science.gov (United States)

    Chen, Kun; Tüysüz, Harun

    2015-11-09

    The booming development of organometal halide perovskites in recent years has prompted the exploration of morphology-control strategies to improve their performance in photovoltaic, photonic, and optoelectronic applications. However, the preparation of organometal halide perovskites with high hierarchical architecture is still highly challenging and a general morphology-control method for various organometal halide perovskites has not been achieved. A mild and scalable method to prepare organometal halide perovskites in inverse opal morphology is presented that uses a polystyrene-based artificial opal as hard template. Our method is flexible and compatible with different halides and organic ammonium compositions. Thus, the perovskite inverse opal maintains the advantage of straightforward structure and band gap engineering. Furthermore, optoelectronic investigations reveal that morphology exerted influence on the conducting nature of organometal halide perovskites. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Environmental Friendly Azide-Alkyne Cycloaddition Reaction of Azides, Alkynes, and Organic Halides or Epoxides in Water: Efficient "Click" Synthesis of 1,2,3-Triazole Derivatives by Cu Catalyst

    Institute of Scientific and Technical Information of China (English)

    刘建明; 刘慕文; 岳园园; 姚美焕; 卓克垒

    2012-01-01

    An efficient click synthesis of 1,2,3-triazole derivatives from benzyl halides or alkyl halides, epoxides, terminal alkynes, and sodium azides in the presence of copper salts and relative benzimidazole salts have been developed. This procedure eliminates the need to handle potentially organic azides, which are generated in situ. A broad spec- trum of substrates can participate in the process effectively to produce the desired products in good yields.

  9. Making and Breaking of Lead Halide Perovskites

    KAUST Repository

    Manser, Joseph S.; Saidaminov, Makhsud I.; Christians, Jeffrey A.; Bakr, Osman; Kamat, Prashant V.

    2016-01-01

    To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice

  10. TRANSURANIC METAL HALIDES AND A PROCESS FOR THE PRODUCTION THEREOF

    Science.gov (United States)

    Fried, S.

    1951-03-20

    Halides of transuranic elements are prepared by contacting with aluminum and a halogen, or with an aluminum halide, a transuranic metal oxide, oxyhalide, halide, or mixture thereof at an elevated temperature.

  11. Effects of Annealing Conditions on Mixed Lead Halide Perovskite Solar Cells and Their Thermal Stability Investigation.

    Science.gov (United States)

    Yang, Haifeng; Zhang, Jincheng; Zhang, Chunfu; Chang, Jingjing; Lin, Zhenhua; Chen, Dazheng; Xi, He; Hao, Yue

    2017-07-21

    In this work, efficient mixed organic cation and mixed halide (MA 0.7 FA 0.3 Pb(I 0.9 Br 0.1 )₃) perovskite solar cells are demonstrated by optimizing annealing conditions. AFM, XRD and PL measurements show that there is a better perovskite film quality for the annealing condition at 100 °C for 30 min. The corresponding device exhibits an optimized PCE of 16.76% with V OC of 1.02 V, J SC of 21.55 mA/cm² and FF of 76.27%. More importantly, the mixed lead halide perovskite MA 0.7 FA 0.3 Pb(I 0.9 Br 0.1 )₃ can significantly increase the thermal stability of perovskite film. After being heated at 80 °C for 24 h, the PCE of the MA 0.7 FA 0.3 Pb(I 0.9 Br 0.1 )₃ device still remains at 70.00% of its initial value, which is much better than the control MAPbI₃ device, where only 46.50% of its initial value could be preserved. We also successfully fabricated high-performance flexible mixed lead halide perovskite solar cells based on PEN substrates.

  12. The creation of defects in ammonium halides by excitons

    International Nuclear Information System (INIS)

    Kim, L.M.

    2002-01-01

    The ammonium halides crystals and alkali halides crystals are analogous by kind chemical bonds and crystalline lattices. The anionic sublattice is identical in this crystals. It is known the main mechanism of defect creation by irradiation is radiationless decay of excitons in alkali halides crystals. The F-, H-centers are formation in this processes. However, F, H-centres are not detected in ammonium halides. The goal of this work is investigation the creation of defects in ammonium halides by excitons. We established that excitons in ammonium chlorides and bromides are similar to excitons in alkali halides. It is known excitons are self-trapped and have identical parameters of the exciton-phonon interaction in both kind crystals. It is supposed, that processes of radiationless disintegration of excitons are identical in ammonium and alkali halides. It is necessary to understand why F-, H-centers are absent in ammonium halides. V k -centres are created by the excitation of the ammonium halides crystals in the absorption band of excitons. It was established by thermoluminescence and spectrums of absorption. The V k -centers begin to migrate at 110-120 K in ammonium chlorides and bromides. The curve of thermoluminescence have peak with maximum at this temperatures. It is known V k -centers in ammonium chlorides have the absorption band at 380 nm. We discovered this absorption band after irradiation of crystals by ultra-violet. In alkali halides F-center is anionic vacancy with electron. The wave function of electron are spread ed at the cations around anionic vacancy. We established the cation NH 4 + in ammonium halides can to capture electron. The ion NH 4 2+ is unsteady. It is disintegrated to NH 3 + and H + . We suppose that excitons in ammonium and alkali halides are disintegrated identically. When cation NH 4 + capture electron, in the anionic sublattice the configuration are created in a direction (100) The indicated configuration is unsteady in relation to a

  13. M-center growth in alkali halides: computer simulation

    International Nuclear Information System (INIS)

    Aguilar, M.; Jaque, F.; Agullo-Lopez, F.

    1983-01-01

    The heterogeneous interstitial nucleation model previously proposed to explain F-center growth curves in irradiated alkali halides has been extended to account for M-center kinetics. The interstitials produced during the primary irradiation event are assumed to be trapped at impurities and interstitial clusters or recombine with F and M centers. For M-center formation two cases have been considered: (a) diffusion and aggregation of F centers, and (b) statistical generation and pairing of F centers. Process (b) is the only one consistent with the quadratic relationship between M and F center concentrations. However, to account for the F/M ratios experimentally observed as well as for the role of dose-rate, a modified statistical model involving random creation and association of F + -F pairs has been shown to be adequate. (author)

  14. Muonium centers in the alkali halides

    International Nuclear Information System (INIS)

    Baumeler, H.; Kiefl, R.F.; Keller, H.; Kuendig, W.; Odermatt, W.; Patterson, B.D.; Schneider, J.W.; Savic, I.M.

    1986-01-01

    Muonium centers (Mu) in single crystals and powdered alkali halides have been studied using the high-timing-resolution transverse field μSR technique. Mu has been observed and its hyperfine parameter (HF) determined in every alkali halide. For the rocksalt alkali halides, the HF parameter A μ shows a systematic dependence on the host lattice constant. A comparison of the Mu HF parameter with hydrogen ESR data suggests that the Mu center is the muonic analogue of the interstitial hydrogen H i 0 -center. The rate of Mu diffusion can be deduced from the motional narrowing of the nuclear hyperfine interaction. KBr shows two different Mu states, a low-temperature Mu I -state and a high-temperature Mu II -state. (orig.)

  15. Cross-Coupling of Sodium Sulfinates with Aryl, Heteroaryl and Vinyl Halides by Nickel/photoredox dual catalysis

    KAUST Repository

    Yue, Huifeng

    2017-12-06

    An efficient photoredox/nickel dual catalyzed sulfonylation reaction of aryl, heteroaryl, and vinyl halides has been achieved for the first time. This newly developed sulfonylation protocol provides a versatile method for the synthesis of diverse aromatic sulfones at room temperature and shows excellent functional group tolerance. The electrophilic coupling partners are not limited to aryl, heteroaryl and vinyl bromides but also less reactive aryl chlorides are suitable substrates for this transformation.

  16. Cross-Coupling of Sodium Sulfinates with Aryl, Heteroaryl and Vinyl Halides by Nickel/photoredox dual catalysis

    KAUST Repository

    Yue, Huifeng; Zhu, Chen; Rueping, Magnus

    2017-01-01

    An efficient photoredox/nickel dual catalyzed sulfonylation reaction of aryl, heteroaryl, and vinyl halides has been achieved for the first time. This newly developed sulfonylation protocol provides a versatile method for the synthesis of diverse aromatic sulfones at room temperature and shows excellent functional group tolerance. The electrophilic coupling partners are not limited to aryl, heteroaryl and vinyl bromides but also less reactive aryl chlorides are suitable substrates for this transformation.

  17. Investigation of surface halide modification of nitrile butadiene rubber

    Science.gov (United States)

    Sukhareva, K. V.; Mikhailov, I. A.; Andriasyan, Yu O.; Mastalygina, E. E.; Popov, A. A.

    2017-12-01

    The investigation is devoted to the novel technology of surface halide modification of rubber samples based on nitrile butadiene rubber (NBR). 1,1,2-trifluoro-1,2,2-trichlorethane was used as halide modifier. The developed technology is characterized by production stages reduction to one by means of treating the rubber compound with a halide modifier. The surface halide modification of compounds based on nitrile butadiene rubber (NBR) was determined to result in increase of resistance to thermal oxidation and aggressive media. The conducted research revealed the influence of modification time on chemical resistance and physical-mechanical properties of rubbers under investigation.

  18. The alkali halide disk technique in infra-red spectrometry : Anomalous behaviour of some samples dispersed in alkali halide disks

    NARCIS (Netherlands)

    Tolk, A.

    1961-01-01

    Some difficulties encountered in the application of the alkali halide disk technique in infra-red spectrometry are discussed. Complications due to interaction of the sample with the alkali halide have been studied experimentally. It was found that the anomalous behaviour of benzoic acid, succinic

  19. Atrial Heterogeneity Generates Re-entrant Substrate during Atrial Fibrillation and Anti-arrhythmic Drug Action: Mechanistic Insights from Canine Atrial Models

    Science.gov (United States)

    Varela, Marta; Hancox, Jules C.; Aslanidi, Oleg V.

    2016-01-01

    Anti-arrhythmic drug therapy is a frontline treatment for atrial fibrillation (AF), but its success rates are highly variable. This is due to incomplete understanding of the mechanisms of action of specific drugs on the atrial substrate at different stages of AF progression. We aimed to elucidate the role of cellular, tissue and organ level atrial heterogeneities in the generation of a re-entrant substrate during AF progression, and their modulation by the acute action of selected anti-arrhythmic drugs. To explore the complex cell-to-organ mechanisms, a detailed biophysical models of the entire 3D canine atria was developed. The model incorporated atrial geometry and fibre orientation from high-resolution micro-computed tomography, region-specific atrial cell electrophysiology and the effects of progressive AF-induced remodelling. The actions of multi-channel class III anti-arrhythmic agents vernakalant and amiodarone were introduced in the model by inhibiting appropriate ionic channel currents according to experimentally reported concentration-response relationships. AF was initiated by applied ectopic pacing in the pulmonary veins, which led to the generation of localized sustained re-entrant waves (rotors), followed by progressive wave breakdown and rotor multiplication in both atria. The simulated AF scenarios were in agreement with observations in canine models and patients. The 3D atrial simulations revealed that a re-entrant substrate was typically provided by tissue regions of high heterogeneity of action potential duration (APD). Amiodarone increased atrial APD and reduced APD heterogeneity and was more effective in terminating AF than vernakalant, which increased both APD and APD dispersion. In summary, the initiation and sustenance of rotors in AF is linked to atrial APD heterogeneity and APD reduction due to progressive remodelling. Our results suggest that anti-arrhythmic strategies that increase atrial APD without increasing its dispersion are

  20. Treatment of alcaline metals halides for developing crystals

    International Nuclear Information System (INIS)

    Spurney, R.W.

    1974-01-01

    A process is described whereby crystals of an alkaline metal halide may be dried and placed in a crucible for development by the Bridgeman-Stockbarger method. Purified alkaline halides from a suspension are dried and formed into dense cakes of transverse section slightly smaller than that of the crucible, where they are packed, melted and grown into crystals according to the Bridgeman-Stockbarger technique. This method applies to the preparation of alkaline halide crystals, particularly sodium iodide for optical elements or scintillation counters [fr

  1. Cation-Dependent Light-Induced Halide Demixing in Hybrid Organic-Inorganic Perovskites.

    Science.gov (United States)

    Sutter-Fella, Carolin M; Ngo, Quynh P; Cefarin, Nicola; Gardner, Kira L; Tamura, Nobumichi; Stan, Camelia V; Drisdell, Walter S; Javey, Ali; Toma, Francesca M; Sharp, Ian D

    2018-06-13

    Mixed cation metal halide perovskites with increased power conversion efficiency, negligible hysteresis, and improved long-term stability under illumination, moisture, and thermal stressing have emerged as promising compounds for photovoltaic and optoelectronic applications. Here, we shed light on photoinduced halide demixing using in situ photoluminescence spectroscopy and in situ synchrotron X-ray diffraction (XRD) to directly compare the evolution of composition and phase changes in CH(NH 2 ) 2 CsPb-halide (FACsPb-) and CH 3 NH 3 Pb-halide (MAPb-) perovskites upon illumination, thereby providing insights into why FACs-perovskites are less prone to halide demixing than MA-perovskites. We find that halide demixing occurs in both materials. However, the I-rich domains formed during demixing accumulate strain in FACsPb-perovskites but readily relax in MA-perovskites. The accumulated strain energy is expected to act as a stabilizing force against halide demixing and may explain the higher Br composition threshold for demixing to occur in FACsPb-halides. In addition, we find that while halide demixing leads to a quenching of the high-energy photoluminescence emission from MA-perovskites, the emission is enhanced from FACs-perovskites. This behavior points to a reduction of nonradiative recombination centers in FACs-perovskites arising from the demixing process and buildup of strain. FACsPb-halide perovskites exhibit excellent intrinsic material properties with photoluminescence quantum yields that are comparable to MA-perovskites. Because improved stability is achieved without sacrificing electronic properties, these compositions are better candidates for photovoltaic applications, especially as wide bandgap absorbers in tandem cells.

  2. Heterogenous integration of a thin-film GaAs photodetector and a microfluidic device on a silicon substrate

    International Nuclear Information System (INIS)

    Song, Fuchuan; Xiao, Jing; Udawala, Fidaali; Seo, Sang-Woo

    2011-01-01

    In this paper, heterogeneous integration of a III–V semiconductor thin-film photodetector (PD) with a microfluidic device is demonstrated on a SiO 2 –Si substrate. Thin-film format of optical devices provides an intimate integration of optical functions with microfluidic devices. As a demonstration of a multi-material and functional system, the biphasic flow structure in the polymeric microfluidic channels was co-integrated with a III–V semiconductor thin-film PD. The fluorescent drops formed in the microfluidic device are successfully detected with an integrated thin-film PD on a silicon substrate. The proposed three-dimensional integration structure is an alternative approach to combine optical functions with microfluidic functions on silicon-based electronic functions.

  3. Formability of ABX3 (X=F,Cl,Br,I) halide perovskites

    International Nuclear Information System (INIS)

    Li Chonghea; Lu Xionggang; Ding Weizhong; Feng Liming; Gao Yonghui; Guo Ziming

    2008-01-01

    In this study a total of 186 complex halide systems were collected; the formabilities of ABX 3 (X = F, Cl, Br and I) halide perovskites were investigated using the empirical structure map, which was constructed by Goldschmidt's tolerance factor and the octahedral factor. A model for halide perovskite formability was built up. In this model obtained, for all 186 complex halides systems, only one system (CsF-MnF 2 ) without perovskite structure and six systems (RbF-PbF 2 , CsF- BeF 2 , KCl-FeCl 2 , TlI-MnI 2 , RbI-SnI 2 , TlI-PbI 2 ) with perovskite structure were wrongly classified, so its predicting accuracy reaches 96%. It is also indicated that both the tolerance factor and the octahedral factor are a necessary but not sufficient condition for ABX 3 halide perovskite formability, and a lowest limit of the octahedral factor exists for halide perovskite formation. This result is consistent with our previous report for ABO 3 oxide perovskite, and may be helpful to design novel halide materials with the perovskite structure. (orig.)

  4. Synthesis, Reactivity and Stability of Aryl Halide Protecting Groups towards Di-Substituted Pyridines

    Directory of Open Access Journals (Sweden)

    Ptoton Mnangat Brian

    2016-03-01

    Full Text Available This paper reports the synthesis and reactivity of different Benzyl derivative protecting groups. The synthesis and stability of Benzyl halides, 4-methoxybenzyl halides, 3,5-dimethoxybenzyl halides, 3,4-dimethoxybenzyl halides, 3,4,5-trimethoxybenzyl halide protecting groups and their reactivity towards nitrogen atom of a di-substituted pyridine ring in formation of pyridinium salts is also reported.

  5. Influence of airflow rate and substrate nature on heterogeneous struvite precipitation.

    Science.gov (United States)

    Saidou, H; Ben Moussa, S; Ben Amor, M

    2009-01-01

    In wastewater treatment plants a hard scale consisting of struvite crystals can be formed, in pipes and recirculation pumps, during anaerobic digestion of wastewater. This study was conducted to evaluate the effect of airflow rate and substrate nature on nucleation type, induction period and supersaturation coefficient during struvite precipitation. A crystallization reactor similar to that designed for calcium carbonate precipitation was used. The pH of synthetic wastewater solution was increased by air bubbling. Experimental results indicated that the airflow increased heterogeneous precipitation of struvite. The susceptibility to scale formation was more important on polyamide and polyvinyl chloride than on stainless steel. In all cases, X-ray diffraction and infrared spectroscopy showed that the precipitated solid phase was solely struvite. No difference in crystal morphology was observed. However, at similar experimental conditions, the particle size of struvite was higher for stainless-steel material than that for plastic materials.

  6. High temperature reactions between molybdenum and metal halides

    International Nuclear Information System (INIS)

    Boeroeczki, A.; Dobos, G.; Josepovits, V.K.; Hars, Gy.

    2006-01-01

    Good colour rendering properties, high intensity and efficacy are of vital importance for high-end lighting applications. These requirements can be achieved by high intensity discharge lamps doped with different metal halide additives (metal halide lamps). To improve their reliability, it is very important to understand the different failure processes of the lamps. In this paper, the corrosion reactions between different metal halides and the molybdenum electrical feed-through electrode are discussed. The reactions were studied in the feed-through of real lamps and on model samples too. X-ray photoelectron spectroscopy (XPS) was used to establish the chemical states. In case of the model samples we have also used atomic absorption spectroscopy (AAS) to measure the reaction product amounts. Based on the measurement results we were able to determine the most corrosive metal halide components and to understand the mechanism of the reactions

  7. Halide-Dependent Electronic Structure of Organolead Perovskite Materials

    KAUST Repository

    Buin, Andrei

    2015-06-23

    © 2015 American Chemical Society. Organometal halide perovskites have recently attracted tremendous attention both at the experimental and theoretical levels. These materials, in particular methylammonium triiodide, are still limited by poor chemical and structural stability under ambient conditions. Today this represents one of the major challenges for polycrystalline perovskite-based photovoltaic technology. In addition to this, the performance of perovskite-based devices is degraded by deep localized states, or traps. To achieve better-performing devices, it is necessary to understand the nature of these states and the mechanisms that lead to their formation. Here we show that the major sources of deep traps in the different halide systems have different origin and character. Halide vacancies are shallow donors in I-based perovskites, whereas they evolve into a major source of traps in Cl-based perovskites. Lead interstitials, which can form lead dimers, are the dominant source of defects in Br-based perovskites, in line with recent experimental data. As a result, the optimal growth conditions are also different for the distinct halide perovskites: growth should be halide-rich for Br and Cl, and halide-poor for I-based perovskites. We discuss stability in relation to the reaction enthalpies of mixtures of bulk precursors with respect to final perovskite product. Methylammonium lead triiodide is characterized by the lowest reaction enthalpy, explaining its low stability. At the opposite end, the highest stability was found for the methylammonium lead trichloride, also consistent with our experimental findings which show no observable structural variations over an extended period of time.

  8. Population dynamics on heterogeneous bacterial substrates

    Science.gov (United States)

    Mobius, Wolfram; Murray, Andrew W.; Nelson, David R.

    2012-02-01

    How species invade new territories and how these range expansions influence the population's genotypes are important questions in the field of population genetics. The majority of work addressing these questions focuses on homogeneous environments. Much less is known about the population dynamics and population genetics when the environmental conditions are heterogeneous in space. To better understand range expansions in two-dimensional heterogeneous environments, we employ a system of bacteria and bacteriophage, the viruses of bacteria. Thereby, the bacteria constitute the environment in which a population of bacteriophages expands. The spread of phage constitutes itself in lysis of bacteria and thus formation of clear regions on bacterial lawns, called plaques. We study the population dynamics and genetics of the expanding page for various patterns of environments.

  9. Solvated Positron Chemistry. Competitive Positron Reactions with Halide Ions in Water

    DEFF Research Database (Denmark)

    Christensen, Palle; Pedersen, Niels Jørgen; Andersen, J. R.

    1979-01-01

    It is shown by means of the angular correlation technique that the binding of positrons to halides is strongly influenced by solvation effects. For aqueous solutions we find increasing values for the binding energies between the halide and the positron with increasing mass of the halide...

  10. Entropy in halide perovskites

    Science.gov (United States)

    Katan, Claudine; Mohite, Aditya D.; Even, Jacky

    2018-05-01

    Claudine Katan, Aditya D. Mohite and Jacky Even discuss the possible impact of various entropy contributions (stochastic structural fluctuations, anharmonicity and lattice softness) on the optoelectronic properties of halide perovskite materials and devices.

  11. The coacervation of aqueous solutions of tetraalkylammonium halides

    International Nuclear Information System (INIS)

    Mugnier de Trobriand, Anne.

    1979-09-01

    The coacervation of aqueous solutions of tatraalkylammonium halides in the presence of not of inorganic halides and acids has been studied, considering thermodynamic and spectroscopic aspects. The importance of dispersion forces as well as forces resulting from hydrophobic hydration has been assessed. The analogy between these systems and anionic ion exchange resins has been shown especially for Uranium VI extraction [fr

  12. Computational screening of mixed metal halide ammines

    DEFF Research Database (Denmark)

    Jensen, Peter Bjerre; Lysgaard, Steen; Quaade, Ulrich

    2013-01-01

    Metal halide ammines, e.g. Mg(NH3)6Cl2 and Sr(NH3)8Cl2, can reversibly store ammonia, with high volumetric hydrogen storage capacities. The storage in the halide ammines is very safe, and the salts are therefore highly relevant as a carbon-free energy carrier in future transportation infrastructure...... selection. The GA is evolving from an initial (random) population and selecting those with highest fitness, a function based on e.g. stability, release temperature and storage capacity. The search space includes all alkaline, alkaline earth, 3d and 4d metals and the four lightest halides. In total...... the search spaces consists of millions combinations, which makes a GA ideal, to reduce the number of necessary calculations. We are screening for a one step release from either a hexa or octa ammine, and we have found promising candidates, which will be further investigated ? both computationally...

  13. Catalytic effect of halide additives ball milled with magnesium hydride

    Energy Technology Data Exchange (ETDEWEB)

    Malka, I.E.; Bystrzycki, J. [Department of Advanced Materials and Technologies, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland); Czujko, T. [Department of Advanced Materials and Technologies, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland); CanmetENERGY, Hydrogen Fuel Cells and Transportation Energy, Natural Resources (Canada)

    2010-02-15

    The influence of various halide additives milled with magnesium hydride (MgH{sub 2}) on its decomposition temperature was studied. The optimum amount of halide additive and milling conditions were evaluated. The MgH{sub 2} decomposition temperature and energy of activation reduction were measured by temperature programmed desorption (TPD) and differential scanning calorimetry (DSC). The difference in catalytic efficiency between chlorides and fluorides of the various metals studied is presented. The effects of oxidation state, valence and position in the periodic table for selected halides on MgH{sub 2} decomposition temperature were also studied. The best catalysts, from the halides studied, for magnesium hydride decomposition were ZrF{sub 4}, TaF{sub 5}, NbF{sub 5}, VCl{sub 3} and TiCl{sub 3}. (author)

  14. Alkali metal and alkali earth metal gadolinium halide scintillators

    Science.gov (United States)

    Bourret-Courchesne, Edith; Derenzo, Stephen E.; Parms, Shameka; Porter-Chapman, Yetta D.; Wiggins, Latoria K.

    2016-08-02

    The present invention provides for a composition comprising an inorganic scintillator comprising a gadolinium halide, optionally cerium-doped, having the formula A.sub.nGdX.sub.m:Ce; wherein A is nothing, an alkali metal, such as Li or Na, or an alkali earth metal, such as Ba; X is F, Br, Cl, or I; n is an integer from 1 to 2; m is an integer from 4 to 7; and the molar percent of cerium is 0% to 100%. The gadolinium halides or alkali earth metal gadolinium halides are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

  15. Methyl halide emissions from greenhouse-grown mangroves

    Science.gov (United States)

    Manley, Steven L.; Wang, Nun-Yii; Walser, Maggie L.; Cicerone, Ralph J.

    2007-01-01

    Two mangrove species, Avicennia germinans and Rhizophora mangle, were greenhouse grown for nearly 1.5 years from saplings. A single individual of each species was monitored for the emission of methyl halides from aerial tissue. During the first 240 days, salinity was incrementally increased with the addition of seawater, and was maintained between 18 and 28‰ for the duration of the study. Exponential growth occurred after 180 days. Methyl halide emissions normalized to leaf area were measured throughout the study and varied dramatically. Emission rates normalized to land area (mg m-2 y-1), assuming a LAI = 5, yielded 82 and 29 for CH3Cl, 10 and 1.6 for CH3Br, and 26 and 11 for CH3I, for A. germinans and R. mangle, respectively. From these preliminary determinations, only CH3I emissions emerge as being of possible global atmospheric significance. This study emphasizes the need for field studies of methyl halide emissions from mangrove forests.

  16. Complexes in polyvalent metal - Alkali halide melts

    International Nuclear Information System (INIS)

    Akdeniz, Z.; Tosi, M.P.

    1991-03-01

    Experimental evidence is available in the literature on the local coordination of divalent and trivalent metal ions by halogens in some 140 liquid mixtures of their halides with alkali halides. After brief reference to classification criteria for main types of local coordination, we focus on statistical mechanical models that we are developing for Al-alkali halide mixtures. Specifically, we discuss theoretically the equilibrium between (AlF 6 ) 3- and (AlF 4 ) - complexes in mixtures of AlF 3 and NaF as a function of composition in the NaF-rich region, the effect of the alkali counterion on this equilibrium, the possible role of (AlF 5 ) 2- as an intermediate species in molten cryolite, and the origin of the different complexing behaviours of Al-alkali fluorides and chlorides. We also present a theoretical scenario for processes of structure breaking and electron localization in molten cryolite under addition of sodium metal. (author). 26 refs, 2 tabs

  17. Lamp-Ballast Compatibility Index for Efficient Ceramic Metal Halide Lamp Operation

    OpenAIRE

    Sourish Chatterjee

    2013-01-01

    Development of energy efficient products and exploration of energy saving potential are major challenges for present day’s technology. Ceramic Metal Halide lamp is the latest improved version of metal halide lamp that finds its wide applications in indoor commercial lighting especially in retail shop lighting. This lamp shows better performance in terms of higher lumen per watt and colour constancy in comparison to conventional metal halide lamp. The inherent negative incremental impedance of...

  18. Making and Breaking of Lead Halide Perovskites

    KAUST Repository

    Manser, Joseph S.

    2016-02-16

    A new front-runner has emerged in the field of next-generation photovoltaics. A unique class of materials, known as organic metal halide perovskites, bridges the gap between low-cost fabrication and exceptional device performance. These compounds can be processed at low temperature (typically in the range 80–150 °C) and readily self-assemble from the solution phase into high-quality semiconductor thin films. The low energetic barrier for crystal formation has mixed consequences. On one hand, it enables inexpensive processing and both optical and electronic tunability. The caveat, however, is that many as-formed lead halide perovskite thin films lack chemical and structural stability, undergoing rapid degradation in the presence of moisture or heat. To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice of solvent treatment. Proper characterization and tuning of processing parameters can aid in rational optimization of perovskite devices. Likewise, gaining a comprehensive understanding of the degradation mechanism and identifying components of the perovskite structure that may be particularly susceptible to attack by moisture are vital to mitigate device degradation under operating conditions. This Account provides insight into the lifecycle of organic–inorganic lead halide perovskites, including (i) the nature of the precursor solution, (ii) formation of solid-state perovskite thin films and single crystals, and (iii) transformation of perovskites into hydrated phases upon exposure to moisture. In particular, spectroscopic and structural characterization techniques shed light on the thermally driven evolution of the perovskite structure. By tuning precursor stoichiometry and chemistry, and thus the lead halide charge-transfer complexes present in solution, crystallization

  19. Miscellaneous Lasing Actions in Organo-Lead Halide Perovskite Films.

    Science.gov (United States)

    Duan, Zonghui; Wang, Shuai; Yi, Ningbo; Gu, Zhiyuan; Gao, Yisheng; Song, Qinghai; Xiao, Shumin

    2017-06-21

    Lasing actions in organo-lead halide perovskite films have been heavily studied in the past few years. However, due to the disordered nature of synthesized perovskite films, the lasing actions are usually understood as random lasers that are formed by multiple scattering. Herein, we demonstrate the miscellaneous lasing actions in organo-lead halide perovskite films. In addition to the random lasers, we show that a single or a few perovskite microparticles can generate laser emissions with their internal resonances instead of multiple scattering among them. We experimentally observed and numerically confirmed whispering gallery (WG)-like microlasers in polygon shaped and other deformed microparticles. Meanwhile, owing to the nature of total internal reflection and the novel shape of the nanoparticle, the size of the perovskite WG laser can be significantly decreased to a few hundred nanometers. Thus, wavelength-scale lead halide perovskite lasers were realized for the first time. All of these laser behaviors are complementary to typical random lasers in perovskite film and will help the understanding of lasing actions in complex lead halide perovskite systems.

  20. Single Crystals of Organolead Halide Perovskites: Growth, Characterization, and Applications

    KAUST Repository

    Peng, Wei

    2017-04-01

    With the soaring advancement of organolead halide perovskite solar cells rising from a power conversion efficiency of merely 3% to more than 22% shortly in five years, researchers’ interests on this big material family have been greatly spurred. So far, both in-depth studies on the fundamental properties of organolead halide perovskites and their extended applications such as photodetectors, light emitting diodes, and lasing have been intensively reported. The great successes have been ascribed to various superior properties of organolead halide hybrid perovskites such as long carrier lifetimes, high carrier mobility, and solution-processable high quality thin films, as will be discussed in Chapter 1. Notably, most of these studies have been limited to their polycrystalline thin films. Single crystals, as a counter form of polycrystals, have no grain boundaries and higher crystallinity, and thus less defects. These characteristics gift single crystals with superior optical, electrical, and mechanical properties, which will be discussed in Chapter 2. For example, organolead halide perovskite single crystals have been reported with much longer carrier lifetimes and higher carrier mobilities, which are especially intriguing for optoelectronic applications. Besides their superior optoelectronic properties, organolead halide perovskites have shown large composition versatility, especially their organic components, which can be controlled to effectively adjust their crystal structures and further fundamental properties. Single crystals are an ideal platform for such composition-structure-property study since a uniform structure with homogeneous compositions and without distraction from grain boundaries as well as excess defects can provide unambiguously information of material properties. As a major part of work of this dissertation, explorative work on the composition-structure-property study of organic-cation-alloyed organolead halide perovskites using their single

  1. Local Polar Fluctuations in Lead Halide Perovskite Crystals

    Science.gov (United States)

    Yaffe, Omer; Guo, Yinsheng; Tan, Liang Z.; Egger, David A.; Hull, Trevor; Stoumpos, Constantinos C.; Zheng, Fan; Heinz, Tony F.; Kronik, Leeor; Kanatzidis, Mercouri G.; Owen, Jonathan S.; Rappe, Andrew M.; Pimenta, Marcos A.; Brus, Louis E.

    2017-03-01

    Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH3 NH3 PbBr3 ) and all-inorganic (CsPbBr3 ) lead-halide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. MD simulations indicate that head-to-head Cs motion coupled to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr3 .

  2. Femtosecond time-resolved photodissociation dynamics of methyl halide molecules on ultrathin gold films

    Directory of Open Access Journals (Sweden)

    Mihai E. Vaida

    2011-09-01

    Full Text Available The photodissociation of small organic molecules, namely methyl iodide, methyl bromide, and methyl chloride, adsorbed on a metal surface was investigated in real time by means of femtosecond-laser pump–probe mass spectrometry. A weakly interacting gold surface was employed as substrate because the intact adsorption of the methyl halide molecules was desired prior to photoexcitation. The gold surface was prepared as an ultrathin film on Mo(100. The molecular adsorption behavior was characterized by coverage dependent temperature programmed desorption spectroscopy. Submonolayer preparations were irradiated with UV light of 266 nm wavelength and the subsequently emerging methyl fragments were probed by photoionization and mass spectrometric detection. A strong dependence of the excitation mechanism and the light-induced dynamics on the type of molecule was observed. Possible photoexcitation mechanisms included direct photoexcitation to the dissociative A-band of the methyl halide molecules as well as the attachment of surface-emitted electrons with transient negative ion formation and subsequent molecular fragmentation. Both reaction pathways were energetically possible in the case of methyl iodide, yet, no methyl fragments were observed. As a likely explanation, the rapid quenching of the excited states prior to fragmentation is proposed. This quenching mechanism could be prevented by modification of the gold surface through pre-adsorption of iodine atoms. In contrast, the A-band of methyl bromide was not energetically directly accessible through 266 nm excitation. Nevertheless, the one-photon-induced dissociation was observed in the case of methyl bromide. This was interpreted as being due to a considerable energetic down-shift of the electronic A-band states of methyl bromide by about 1.5 eV through interaction with the gold substrate. Finally, for methyl chloride no photofragmentation could be detected at all.

  3. Non-hydrolytic metal oxide films for perovskite halide overcoating and stabilization

    Science.gov (United States)

    Martinson, Alex B.; Kim, In Soo

    2017-09-26

    A method of protecting a perovskite halide film from moisture and temperature includes positioning the perovskite halide film in a chamber. The chamber is maintained at a temperature of less than 200 degrees Celsius. An organo-metal compound is inserted into the chamber. A non-hydrolytic oxygen source is subsequently inserted into the chamber. The inserting of the organo-metal compound and subsequent inserting of the non-hydrolytic oxygen source into the chamber is repeated for a predetermined number of cycles. The non-hydrolytic oxygen source and the organo-metal compound interact in the chamber to deposit a non-hydrolytic metal oxide film on perovskite halide film. The non-hydrolytic metal oxide film protects the perovskite halide film from relative humidity of greater than 35% and a temperature of greater than 150 degrees Celsius, respectively.

  4. The coalescence of heterogeneous liquid metal on nano substrate

    Science.gov (United States)

    Wang, Long; Li, Yifan; Zhou, Xuyan; Li, Tao; Li, Hui

    2017-06-01

    Molecular dynamics simulation has been performed to study the asymmetric coalescence of heterogeneous liquid metal on graphene. Simulation results show that the anomalies in the drop coalescence is mainly caused by the wettability of heterogeneous liquid metal. The silver atoms incline to distribute on the outer layer of the gold and copper droplets, revealing that the structure is determined by the interaction between different metal atoms. The coalescence and fusion of heterogeneous liquid metal drop can be predicted by comparing the wettability and the atomic mass of metallic liquid drops, which has important implications in the industrial application such as ink-jet printing and metallurgy.

  5. Methyl halide emission estimates from domestic biomass burning in Africa

    Science.gov (United States)

    Mead, M. I.; Khan, M. A. H.; White, I. R.; Nickless, G.; Shallcross, D. E.

    Inventories of methyl halide emissions from domestic burning of biomass in Africa, from 1950 to the present day and projected to 2030, have been constructed. By combining emission factors from Andreae and Merlet [2001. Emission of trace gases and aerosols from biomass burning. Global Biogeochemical Cycles 15, 955-966], the biomass burning estimates from Yevich and Logan [2003. An assessment of biofuel use and burning of agricultural waste in the developing world. Global Biogeochemical Cycles 17(4), 1095, doi:10.1029/2002GB001952] and the population data from the UN population division, the emission of methyl halides from domestic biomass usage in Africa has been estimated. Data from this study suggest that methyl halide emissions from domestic biomass burning have increased by a factor of 4-5 from 1950 to 2005 and based on the expected population growth could double over the next 25 years. This estimated change has a non-negligible impact on the atmospheric budgets of methyl halides.

  6. Solar cells, structures including organometallic halide perovskite monocrystalline films, and methods of preparation thereof

    KAUST Repository

    Bakr, Osman M.

    2017-03-02

    Embodiments of the present disclosure provide for solar cells including an organometallic halide perovskite monocrystalline film (see fig. 1.1B), other devices including the organometallic halide perovskite monocrystalline film, methods of making organometallic halide perovskite monocrystalline film, and the like.

  7. Definition of a high intensity metal halide discharge reference lamp

    NARCIS (Netherlands)

    Stoffels, W.W.; Baede, A.H.F.M.; Mullen, van der J.J.A.M.; Haverlag, M.; Zissis, G.

    2006-01-01

    The design of a ref. metal halide discharge lamp is presented. This lamp is meant as a common study object for researchers working on metal halide discharge lamps, who by using the same design will be able to compare results between research groups, diagnostic techniques and numerical models. The

  8. Unraveling halide hydration: A high dilution approach.

    Science.gov (United States)

    Migliorati, Valentina; Sessa, Francesco; Aquilanti, Giuliana; D'Angelo, Paola

    2014-07-28

    The hydration properties of halide aqua ions have been investigated combining classical Molecular Dynamics (MD) with Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Three halide-water interaction potentials recently developed [M. M. Reif and P. H. Hünenberger, J. Chem. Phys. 134, 144104 (2011)], along with three plausible choices for the value of the absolute hydration free energy of the proton (ΔG [minus sign in circle symbol]hyd[H+]), have been checked for their capability to properly describe the structural properties of halide aqueous solutions, by comparing the MD structural results with EXAFS experimental data. A very good agreement between theory and experiment has been obtained with one parameter set, namely LE, thus strengthening preliminary evidences for a ΔG [minus sign in circle symbol]hyd[H] value of -1100 kJ mol(-1) [M. M. Reif and P. H. Hünenberger, J. Chem. Phys. 134, 144104 (2011)]. The Cl(-), Br(-), and I(-) ions have been found to form an unstructured and disordered first hydration shell in aqueous solution, with a broad distribution of instantaneous coordination numbers. Conversely, the F(-) ion shows more ordered and defined first solvation shell, with only two statistically relevant coordination geometries (six and sevenfold complexes). Our thorough investigation on the effect of halide ions on the microscopic structure of water highlights that the perturbation induced by the Cl(-), Br(-), and I(-) ions does not extend beyond the ion first hydration shell, and the structure of water in the F(-) second shell is also substantially unaffected by the ion.

  9. 78 FR 51463 - Energy Conservation Program: Energy Conservation Standards for Metal Halide Lamp Fixtures

    Science.gov (United States)

    2013-08-20

    ... merging the metal halide lamp fixture and the high-intensity discharge (HID) lamp rulemakings. This NOPR... Conservation Program: Energy Conservation Standards for Metal Halide Lamp Fixtures; Proposed Rule #0;#0;Federal...: Energy Conservation Standards for Metal Halide Lamp Fixtures AGENCY: Office of Energy Efficiency and...

  10. Energetics of the ruthenium-halide bond in olefin metathesis (pre)catalysts

    KAUST Repository

    Falivene, Laura; Poater, Albert; Cazin, Catherine S J; Slugovc, Christian; Cavallo, Luigi

    2013-01-01

    A DFT analysis of the strength of the Ru-halide bond in a series of typical olefin metathesis (pre)catalysts is presented. The calculated Ru-halide bond energies span the rather broad window of 25-43 kcal mol-1. This indicates that in many systems dissociation of the Ru-halide bond is possible and is actually competitive with dissociation of the labile ligand generating the 14e active species. Consequently, formation of cationic Ru species in solution should be considered as a possible event. © 2013 The Royal Society of Chemistry.

  11. Development of halide copper vapor laser (the characteristics of using Cul)

    International Nuclear Information System (INIS)

    Oouti, Kazumi; Wada, Yukio; Sasao, Nobuyuki

    1990-01-01

    We are developing halide copper vapor laser that is high efficiency and high reputation rate visible laser. Halide copper vapor laser uses halide copper of copper vapor source. It melts low temperature in comporison with metal copper, because laser tube structure is very simple and it can operate easy. This time, we experiment to use Cul for copper vapor source. We resulted maximum output energy 17.8 (W) and maximum efficiency 0.78 (%) when operate condition was reputation rate 30 (kHz), gas pressure 90 (Torr), charging voltage 13 (kV). (author)

  12. Broadly tunable metal halide perovskites for solid-state light-emission applications

    NARCIS (Netherlands)

    Adjokatse, Sampson; Fang, Hong-Hua; Loi, Maria Antonietta

    2017-01-01

    The past two years have witnessed heightened interest in metal-halide perovskites as promising optoelectronic materials for solid-state light emitting applications beyond photovoltaics. Metal-halide perovskites are low-cost solution-processable materials with excellent intrinsic properties such as

  13. Systemic analysis of thermodynamic properties of lanthanide halides

    International Nuclear Information System (INIS)

    Mirsaidov, U.; Badalov, A.; Marufi, V.K.

    1992-01-01

    System analysis of thermodynamic characteristics of lanthanide halides was carried out. A method making allowances for the influence of spin and orbital moments of momentum of the main states of lanthanide trivalent ions in their natural series was employed. Unknown in literature thermodynamic values were calculated and corrected for certain compounds. The character of lanthanide halide thermodynamic parameter change depending on ordinal number of the metals was ascertained. Pronouncement of tetrad-effect in series of compounds considered was pointed out

  14. Two-Dimensional Halide Perovskites for Emerging New- Generation Photodetectors

    DEFF Research Database (Denmark)

    Tang, Yingying; Cao, Xianyi; Chi, Qijin

    2018-01-01

    Compared to their conventional three-dimensional (3D) counterparts, two-dimensional (2D) halide perovskites have attracted more interests recently in a variety of areas related to optoelectronics because of their unique structural characteristics and enhanced performances. In general, there are two...... distinct types of 2D halide perovskites. One represents those perovskites with an intrinsic layered crystal structure (i.e. MX6 layers, M = metal and X = Cl, Br, I), the other defines the perovskites with a 2D nanostructured morphology such as nanoplatelets and nanosheets. Recent studies have shown that 2D...... halide perovskites hold promising potential for the development of new-generation photodetectors, mainly arising from their highly efficient photoluminescence and absorbance, color tunability in the visible-light range and relatively high stability. In this chapter, we present the summary and highlights...

  15. Heterogeneous Nucleation of Colloidal Crystals on a Glass Substrate with Depletion Attraction.

    Science.gov (United States)

    Guo, Suxia; Nozawa, Jun; Hu, Sumeng; Koizumi, Haruhiko; Okada, Junpei; Uda, Satoshi

    2017-10-10

    The heterogeneous nucleation of colloidal crystals with attractive interactions has been investigated via in situ observations. We have found two types of nucleation processes: a cluster that overcomes the critical size for nucleation with a monolayer, and a method that occurs with two layers. The Gibbs free energy changes (ΔG) for these two types of nucleation processes are evaluated by taking into account the effect of various interfacial energies. In contrast to homogeneous nucleation, the change in interfacial free energy, Δσ, is generated for colloidal nucleation on a foreign substrate such as a cover glass in the present study. The Δσ and step free energy of the first layer, γ 1 , are obtained experimentally based on the equation deduced from classical nucleation theory (CNT). It is concluded that the ΔG of q-2D nuclei is smaller than of monolayer nuclei, provided that the same number of particles are used, which explains the experimental result that the critical size in q-2D nuclei is smaller than that in monolayer nuclei.

  16. Spatial environmental heterogeneity affects plant growth and thermal performance on a green roof

    Energy Technology Data Exchange (ETDEWEB)

    Buckland-Nicks, Michael; Heim, Amy; Lundholm, Jeremy, E-mail: jlundholm@smu.ca

    2016-05-15

    Green roofs provide ecosystem services, including stormwater retention and reductions in heat transfer through the roof. Microclimates, as well as designed features of green roofs, such as substrate and vegetation, affect the magnitude of these services. Many green roofs are partially shaded by surrounding buildings, but the effects of this within-roof spatial environmental heterogeneity on thermal performance and other ecosystem services have not been examined. We quantified the effects of spatial heterogeneity in solar radiation, substrate depth and other variables affected by these drivers on vegetation and ecosystem services in an extensive green roof. Spatial heterogeneity in substrate depth and insolation were correlated with differential growth, survival and flowering in two focal plant species. These effects were likely driven by the resulting spatial heterogeneity in substrate temperature and moisture content. Thermal performance (indicated by heat flux and substrate temperature) was influenced by spatial heterogeneity in vegetation cover and substrate depth. Areas with less insolation were cooler in summer and had greater substrate moisture, leading to more favorable conditions for plant growth and survival. Spatial variation in substrate moisture (7%–26% volumetric moisture content) and temperature (21 °C–36 °C) during hot sunny conditions in summer could cause large differences in stormwater retention and heat flux within a single green roof. Shaded areas promote smaller heat fluxes through the roof, leading to energy savings, but lower evapotranspiration in these areas should reduce stormwater retention capacity. Spatial heterogeneity can thus result in trade-offs between different ecosystem services. The effects of these spatial heterogeneities are likely widespread in green roofs. Structures that provide shelter from sun and wind may be productively utilized to design higher functioning green roofs and increase biodiversity by providing habitat

  17. Spatial environmental heterogeneity affects plant growth and thermal performance on a green roof

    International Nuclear Information System (INIS)

    Buckland-Nicks, Michael; Heim, Amy; Lundholm, Jeremy

    2016-01-01

    Green roofs provide ecosystem services, including stormwater retention and reductions in heat transfer through the roof. Microclimates, as well as designed features of green roofs, such as substrate and vegetation, affect the magnitude of these services. Many green roofs are partially shaded by surrounding buildings, but the effects of this within-roof spatial environmental heterogeneity on thermal performance and other ecosystem services have not been examined. We quantified the effects of spatial heterogeneity in solar radiation, substrate depth and other variables affected by these drivers on vegetation and ecosystem services in an extensive green roof. Spatial heterogeneity in substrate depth and insolation were correlated with differential growth, survival and flowering in two focal plant species. These effects were likely driven by the resulting spatial heterogeneity in substrate temperature and moisture content. Thermal performance (indicated by heat flux and substrate temperature) was influenced by spatial heterogeneity in vegetation cover and substrate depth. Areas with less insolation were cooler in summer and had greater substrate moisture, leading to more favorable conditions for plant growth and survival. Spatial variation in substrate moisture (7%–26% volumetric moisture content) and temperature (21 °C–36 °C) during hot sunny conditions in summer could cause large differences in stormwater retention and heat flux within a single green roof. Shaded areas promote smaller heat fluxes through the roof, leading to energy savings, but lower evapotranspiration in these areas should reduce stormwater retention capacity. Spatial heterogeneity can thus result in trade-offs between different ecosystem services. The effects of these spatial heterogeneities are likely widespread in green roofs. Structures that provide shelter from sun and wind may be productively utilized to design higher functioning green roofs and increase biodiversity by providing habitat

  18. A Combined Theoretical and Experimental View on Valence and Conduction Band Densities of States of Lead Halide Perovskites

    Science.gov (United States)

    Kronik, Leeor; Endres, James; Egger, David A.; Kulbak, Michael; Kerner, Ross A.; Zhao, Lianfeng; Silver, Scott H.; Hodes, Gary; Rand, Barry P.; Cahen, David; Kahn, Antoine

    We present results for the valence and conduction band density of states (DOS), measured via ultraviolet and inverse photoemission spectroscopies for three lead halide perovskites. Specifically, the DOS of MAPbI3, MAPbBr3, and CsPbBr3, grown on different substrates, are compared. Theoretical DOS, calculated via hybrid density functional theory and including spin-orbit coupling, are compared to experimental data. The agreement between experiment and theory, obtained after correcting the latter for quantitative discrepancies, leads to the identification of valence and conduction band spectral features. In particular, this comparison allows for precise determination of the energy position of the band edges, namely ionization energies and electron affinities of these materials. We find an unusually low DOS at the valence band maximum (VBM) of these systems, which confirms and generalizes previous findings of strong band dispersion and low DOS at the VBM of MAPbI3. This calls for special attention when using electron spectroscopy to determine the frontier electronic states of lead halide perovskites.

  19. Sonogashira Reaction of Aryl and Heteroaryl Halides with Terminal Alkynes Catalyzed by a Highly Efficient and Recyclable Nanosized MCM-41 Anchored Palladium Bipyridyl Complex

    Directory of Open Access Journals (Sweden)

    Chung-Yuan Mou

    2010-12-01

    Full Text Available A heterogeneous catalyst, nanosized MCM-41-Pd, was used to catalyze the Sonogashira coupling of aryl and heteroaryl halides with terminal alkynes in the presence of CuI and triphenylphosphine. The coupling products were obtained in high yields using low Pd loadings to 0.01 mol%, and the nanosized MCM-41-Pd catalyst was recovered by centrifugation of the reaction solution and re-used in further runs without significant loss of reactivity.

  20. Spatial environmental heterogeneity affects plant growth and thermal performance on a green roof.

    Science.gov (United States)

    Buckland-Nicks, Michael; Heim, Amy; Lundholm, Jeremy

    2016-05-15

    Green roofs provide ecosystem services, including stormwater retention and reductions in heat transfer through the roof. Microclimates, as well as designed features of green roofs, such as substrate and vegetation, affect the magnitude of these services. Many green roofs are partially shaded by surrounding buildings, but the effects of this within-roof spatial environmental heterogeneity on thermal performance and other ecosystem services have not been examined. We quantified the effects of spatial heterogeneity in solar radiation, substrate depth and other variables affected by these drivers on vegetation and ecosystem services in an extensive green roof. Spatial heterogeneity in substrate depth and insolation were correlated with differential growth, survival and flowering in two focal plant species. These effects were likely driven by the resulting spatial heterogeneity in substrate temperature and moisture content. Thermal performance (indicated by heat flux and substrate temperature) was influenced by spatial heterogeneity in vegetation cover and substrate depth. Areas with less insolation were cooler in summer and had greater substrate moisture, leading to more favorable conditions for plant growth and survival. Spatial variation in substrate moisture (7%-26% volumetric moisture content) and temperature (21°C-36°C) during hot sunny conditions in summer could cause large differences in stormwater retention and heat flux within a single green roof. Shaded areas promote smaller heat fluxes through the roof, leading to energy savings, but lower evapotranspiration in these areas should reduce stormwater retention capacity. Spatial heterogeneity can thus result in trade-offs between different ecosystem services. The effects of these spatial heterogeneities are likely widespread in green roofs. Structures that provide shelter from sun and wind may be productively utilized to design higher functioning green roofs and increase biodiversity by providing habitat

  1. An effective approach to synthesize monolayer tungsten disulphide crystals using tungsten halide precursor

    International Nuclear Information System (INIS)

    Thangaraja, Amutha; Shinde, Sachin M.; Kalita, Golap; Tanemura, Masaki

    2016-01-01

    The synthesis of large-area monolayer tungsten disulphide (WS 2 ) single crystal is critical for realistic application in electronic and optical devices. Here, we demonstrate an effective approach to synthesize monolayer WS 2 crystals using tungsten hexachloride (WCl 6 ) as a solid precursor in atmospheric chemical vapor deposition process. In this technique, 0.05M solution of WCl 6 in ethanol was drop-casted on SiO 2 /Si substrate to create an even distribution of the precursor, which was reduced and sulfurized at 750 °C in Ar atmosphere. We observed growth of triangular, star-shaped, as well as dendritic WS 2 crystals on the substrate. The crystal geometry evolves with the shape and size of the nuclei as observed from the dendritic structures. These results show that controlling the initial nucleation and growth process, large WS 2 single crystalline monolayer can be grown using the WCl 6 precursor. Our finding shows an easier and effective approach to grow WS 2 monolayer using tungsten halide solution-casting, rather than evaporating the precursor for gas phase reaction

  2. Electrochemistry of plutonium in molten halides

    International Nuclear Information System (INIS)

    McCurry, L.E.; Moy, G.M.M.; Bowersox, D.F.

    1987-01-01

    The electrochemistry of plutonium in molten halides is of technological importance as a method of purification of plutonium. Previous authors have reported that plutonium can be purified by electrorefining impure plutonium in various molten haldies. Work to eluciate the mechanism of the plutonium reduction in molten halides has been limited to a chronopotentiometric study in LiCl-KCl. Potentiometric studies have been carried out to determine the standard reduction potential for the plutonium (III) couple in various molten alkali metal halides. Initial cyclic voltammetric experiments were performed in molten KCL at 1100 K. A silver/silver chloride (10 mole %) in equimolar NaCl-KCl was used as a reference electrode. Working and counter electrodes were tungsten. The cell components and melt were contained in a quartz crucible. Background cyclic voltammograms of the KCl melt at the tungsten electrode showed no evidence of electroactive impurities in the melt. Plutonium was added to the melt as PuCl/sub 3/, which was prepared by chlorination of the oxide. At low concentrations of PuCl/sub 3/ in the melt (0.01-0.03 molar), no reduction wave due to the reduction of Pu(III) was observed in the voltammograms up to the potassium reduction limit of the melt. However on scan reversal after scanning into the potassium reduction limit a new oxidation wave was observed

  3. Palladium(II-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

    Directory of Open Access Journals (Sweden)

    Tanveer Mahamadali Shaikh

    2013-08-01

    Full Text Available A series of general and selective Pd(II-catalyzed Heck reactions were investigated under mild reaction conditions. The first protocol has been developed employing an imidazole-based secondary phosphine oxide (SPO ligated palladium complex (6 as a precatalyst. The catalytic coupling of aryl halides and olefins led to the formation of the corresponding coupled products in excellent yields. A variety of substrates, both electron-rich and electron-poor olefins, were converted smoothly to the targeted products in high yields. Compared with the existing approaches employing SPO–Pd complexes in a Heck reaction, the current strategy features mild reaction conditions and broad substrate scope. Furthermore, we described the coupling of arylboronic acids with olefins, which were catalyzed by Pd(OAc2 and employed N-bromosuccinimide as an additive under ambient conditions. The resulted biaryls have been obtained in moderate to good yields.

  4. Impact of the organic halide salt on final perovskite composition for photovoltaic applications

    KAUST Repository

    Moore, David T.

    2014-08-01

    The methylammonium lead halide perovskites have shown significant promise as a low-cost, second generation, photovoltaic material.Despite recent advances, however, there are still a number of fundamental aspects of their formation as well as their physical and electronic behavior that are not well understood. In this letter we explore the mechanism by which these materials crystallize by testing the outcome of each of the reagent halide salts. We find that components of both salts, lead halide and methylammonium halide, are relatively mobile and can be readily exchanged during the crystallization process when the reaction is carried out in solution or in the solid state. We exploit this fact by showing that the perovskite structure is formed even when the lead salt\\'s anion is a non-halide, leading to lower annealing temperature and time requirements for film formation. Studies into these behaviors may ultimately lead to improved processing conditions for photovoltaic films. © 2014 Author(s).

  5. Impact of the organic halide salt on final perovskite composition for photovoltaic applications

    Directory of Open Access Journals (Sweden)

    David T. Moore

    2014-08-01

    Full Text Available The methylammonium lead halide perovskites have shown significant promise as a low-cost, second generation, photovoltaic material. Despite recent advances, however, there are still a number of fundamental aspects of their formation as well as their physical and electronic behavior that are not well understood. In this letter we explore the mechanism by which these materials crystallize by testing the outcome of each of the reagent halide salts. We find that components of both salts, lead halide and methylammonium halide, are relatively mobile and can be readily exchanged during the crystallization process when the reaction is carried out in solution or in the solid state. We exploit this fact by showing that the perovskite structure is formed even when the lead salt's anion is a non-halide, leading to lower annealing temperature and time requirements for film formation. Studies into these behaviors may ultimately lead to improved processing conditions for photovoltaic films.

  6. Observation of vapor pressure enhancement of rare-earth metal-halide salts in the temperature range relevant to metal-halide lamps

    Energy Technology Data Exchange (ETDEWEB)

    Curry, J. J.; Henins, A.; Hardis, J. E. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Estupinan, E. G. [Osram Sylvania Inc., Beverly, Massachusetts 01915 (United States); Lapatovich, W. P. [Independent Consultant, 51 Pye Brook Lane, Boxford, Massachusetts 01921 (United States); Shastri, S. D. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2012-02-20

    Total vapor-phase densities of Dy in equilibrium with a DyI{sub 3}/InI condensate and Tm in equilibrium with a TmI{sub 3}/TlI condensate have been measured for temperatures between 900 K and 1400 K. The measurements show strong enhancements in rare-earth vapor densities compared to vapors in equilibrium with the pure rare-earth metal-halides. The measurements were made with x-ray induced fluorescence on the sector 1-ID beam line at the Advanced Photon Source. The temperature range and salt mixtures are relevant to the operation of metal-halide high-intensity discharge lamps.

  7. Application of spatial time domain reflectometry measurements in heterogeneous, rocky substrates

    Science.gov (United States)

    Gonzales, C.; Scheuermann, A.; Arnold, S.; Baumgartl, T.

    2016-10-01

    Measurement of soil moisture across depths using sensors is currently limited to point measurements or remote sensing technologies. Point measurements have limitations on spatial resolution, while the latter, although covering large areas may not represent real-time hydrologic processes, especially near the surface. The objective of the study was to determine the efficacy of elongated soil moisture probes—spatial time domain reflectometry (STDR)—and to describe transient soil moisture dynamics of unconsolidated mine waste rock materials. The probes were calibrated under controlled conditions in the glasshouse. Transient soil moisture content was measured using the gravimetric method and STDR. Volumetric soil moisture content derived from weighing was compared with values generated from a numerical model simulating the drying process. A calibration function was generated and applied to STDR field data sets. The use of elongated probes effectively assists in the real-time determination of the spatial distribution of soil moisture. It also allows hydrologic processes to be uncovered in the unsaturated zone, especially for water balance calculations that are commonly based on point measurements. The elongated soil moisture probes can potentially describe transient substrate processes and delineate heterogeneity in terms of the pore size distribution in a seasonally wet but otherwise arid environment.

  8. Solution growth of single crystal methylammonium lead halide perovskite nanostructures for optoelectronic and photovoltaic applications.

    Science.gov (United States)

    Fu, Yongping; Meng, Fei; Rowley, Matthew B; Thompson, Blaise J; Shearer, Melinda J; Ma, Dewei; Hamers, Robert J; Wright, John C; Jin, Song

    2015-05-06

    Understanding crystal growth and improving material quality is important for improving semiconductors for electronic, optoelectronic, and photovoltaic applications. Amidst the surging interest in solar cells based on hybrid organic-inorganic lead halide perovskites and the exciting progress in device performance, improved understanding and better control of the crystal growth of these perovskites could further boost their optoelectronic and photovoltaic performance. Here, we report new insights on the crystal growth of the perovskite materials, especially crystalline nanostructures. Specifically, single crystal nanowires, nanorods, and nanoplates of methylammonium lead halide perovskites (CH3NH3PbI3 and CH3NH3PbBr3) are successfully grown via a dissolution-recrystallization pathway in a solution synthesis from lead iodide (or lead acetate) films coated on substrates. These single crystal nanostructures display strong room-temperature photoluminescence and long carrier lifetime. We also report that a solid-liquid interfacial conversion reaction can create a highly crystalline, nanostructured MAPbI3 film with micrometer grain size and high surface coverage that enables photovoltaic devices with a power conversion efficiency of 10.6%. These results suggest that single-crystal perovskite nanostructures provide improved photophysical properties that are important for fundamental studies and future applications in nanoscale optoelectronic and photonic devices.

  9. Electrochemical depositing rGO-Ti-rGO heterogeneous substrates with higher thermal conductivity and heat transfer performance compared to pure Ti.

    Science.gov (United States)

    Wang, Jing; Wang, Huatao; Zhang, Wenying; Yang, Xinyi; Wen, Guangwu; Wang, Yijie; Zhou, Weiwei

    2017-02-17

    Titanium (Ti) and its alloys are widely applied in many high strength, light weight applications, but their thermal conductivity is lower compared to that of other metals, which limits their further applications. In this paper, we demonstrated experimentally that rGO-Ti-rGO heterogeneous substrates with higher thermal conductivity, up to ∼38.8% higher than Ti, could be fabricated by electrochemical depositing rGO on their surface. The rGO layers are grown on the surface of Ti substrates, with appearance of bedclothes on the beds. The thickness of rGO layers is around 300-500 nm and around 600-1000 nm when deposited for 5 cycles and 10 cycles, respectively. According to the cooling experiment results, as-prepared Ti + rGO substrates can present excellent thermal conduction performance, and reduce the chip temperature close to 3.2 °C-13.1 °C lower than Ti alloy substrates with the heat flow density of 0.4-3.6 W cm -2 . Finally, the approach to electro-chemically deposit hundreds of nanometer rGO layers on the surface of Ti substrates can improve their thermal conductivity and heat transfer performance, which may have further application in the increasing thermal conduction of other metal-alloys, ceramics and polymers.

  10. Ultrafast time-resolved spectroscopy of lead halide perovskite films

    Science.gov (United States)

    Idowu, Mopelola A.; Yau, Sung H.; Varnavski, Oleg; Goodson, Theodore

    2015-09-01

    Recently, lead halide perovskites which are organic-inorganic hybrid structures, have been discovered to be highly efficient as light absorbers. Herein, we show the investigation of the excited state dynamics and emission properties of non-stoichiometric precursor formed lead halide perovskites grown by interdiffusion method using steady-state and time-resolved spectroscopic measurements. The influence of the different ratios of the non-stoichiometric precursor solution was examined. The observed photoluminescence properties were correlated with the femtosecond transient absorption measurements.

  11. Lanthanide doped strontium-barium cesium halide scintillators

    Science.gov (United States)

    Bizarri, Gregory; Bourret-Courchesne, Edith; Derenzo, Stephen E.; Borade, Ramesh B.; Gundiah, Gautam; Yan, Zewu; Hanrahan, Stephen M.; Chaudhry, Anurag; Canning, Andrew

    2015-06-09

    The present invention provides for a composition comprising an inorganic scintillator comprising an optionally lanthanide-doped strontium-barium, optionally cesium, halide, useful for detecting nuclear material.

  12. Origin of vertical orientation in two-dimensional metal halide perovskites and its effect on photovoltaic performance.

    Science.gov (United States)

    Chen, Alexander Z; Shiu, Michelle; Ma, Jennifer H; Alpert, Matthew R; Zhang, Depei; Foley, Benjamin J; Smilgies, Detlef-M; Lee, Seung-Hun; Choi, Joshua J

    2018-04-06

    Thin films based on two-dimensional metal halide perovskites have achieved exceptional performance and stability in numerous optoelectronic device applications. Simple solution processing of the 2D perovskite provides opportunities for manufacturing devices at drastically lower cost compared to current commercial technologies. A key to high device performance is to align the 2D perovskite layers, during the solution processing, vertical to the electrodes to achieve efficient charge transport. However, it is yet to be understood how the counter-intuitive vertical orientations of 2D perovskite layers on substrates can be obtained. Here we report a formation mechanism of such vertically orientated 2D perovskite in which the nucleation and growth arise from the liquid-air interface. As a consequence, choice of substrates can be liberal from polymers to metal oxides depending on targeted application. We also demonstrate control over the degree of preferential orientation of the 2D perovskite layers and its drastic impact on device performance.

  13. luminescence in coloured alkali halide crystals

    Indian Academy of Sciences (India)

    have studied the effect of annealing in chlorine gas on the ML of X-rayed KCl crystals. ..... high temperature because of the thermal bleaching of the coloration in alkali halide ..... [31] J Hawkins, Ph.D. Thesis (University of Reading, 1976).

  14. Purcell effect in an organic-inorganic halide perovskite semiconductor microcavity system

    International Nuclear Information System (INIS)

    Wang, Jun; Wang, Yafeng; Hu, Tao; Wu, Lin; Shen, Xuechu; Chen, Zhanghai; Cao, Runan; Xu, Fei; Da, Peimei; Zheng, Gengfeng; Lu, Jian

    2016-01-01

    Organic-inorganic halide perovskite semiconductors with the attractive physics properties, including strong photoluminescence (PL), huge oscillator strengths, and low nonradiative recombination losses, are ideal candidates for studying the light-matter interaction in nanostructures. Here, we demonstrate the coupling of the exciton state and the cavity mode in the lead halide perovskite microcavity system at room temperature. The Purcell effect in the coupling system is clearly observed by using angle-resolved photoluminescence spectra. Kinetic analysis based on time-resolved PL reveals that the spontaneous emission rate of the halide perovskite semiconductor is significantly enhanced at resonance of the exciton energy and the cavity mode. Our results provide the way for developing electrically driven organic polariton lasers, optical devices, and on-chip coherent quantum light sources

  15. 10 CFR 431.322 - Definitions concerning metal halide lamp ballasts and fixtures.

    Science.gov (United States)

    2010-01-01

    ... high intensity discharge fixture, the efficiency of a lamp and ballast combination, expressed as a... lamps. Metal halide lamp means a high intensity discharge lamp in which the major portion of the light... 10 Energy 3 2010-01-01 2010-01-01 false Definitions concerning metal halide lamp ballasts and...

  16. An effective approach to synthesize monolayer tungsten disulphide crystals using tungsten halide precursor

    Energy Technology Data Exchange (ETDEWEB)

    Thangaraja, Amutha; Shinde, Sachin M.; Kalita, Golap, E-mail: kalita.golap@nitech.ac.jp; Tanemura, Masaki [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2016-02-01

    The synthesis of large-area monolayer tungsten disulphide (WS{sub 2}) single crystal is critical for realistic application in electronic and optical devices. Here, we demonstrate an effective approach to synthesize monolayer WS{sub 2} crystals using tungsten hexachloride (WCl{sub 6}) as a solid precursor in atmospheric chemical vapor deposition process. In this technique, 0.05M solution of WCl{sub 6} in ethanol was drop-casted on SiO{sub 2}/Si substrate to create an even distribution of the precursor, which was reduced and sulfurized at 750 °C in Ar atmosphere. We observed growth of triangular, star-shaped, as well as dendritic WS{sub 2} crystals on the substrate. The crystal geometry evolves with the shape and size of the nuclei as observed from the dendritic structures. These results show that controlling the initial nucleation and growth process, large WS{sub 2} single crystalline monolayer can be grown using the WCl{sub 6} precursor. Our finding shows an easier and effective approach to grow WS{sub 2} monolayer using tungsten halide solution-casting, rather than evaporating the precursor for gas phase reaction.

  17. NMRON on a mixed halide antiferromagnet, (54Mn)Mn(Cl0.6Br0.4)2.4H2O

    International Nuclear Information System (INIS)

    Chaplin, D.H.; Harker, S.J.; Hutchison, W.D.; Bowden, G.J.

    2000-01-01

    Full text: Recently we reported on the significant gains that can be made in Low Temperature Nuclear Orientation (LTNO) of the magnetically dominant species in an antiferromagnetic single crystal by heterogeneous mixing of the halide ligands. This new approach relies on enhanced nuclear spin lattice relaxation (NSLR) at the magnetic ion, in this case Mn, through broadbanded electronic magnons, in the cooled, single crystal host. Whereas the isomorphous terminal compounds ( 54 Mn)MnCI 2 .4H 2 O and ( 54 Mn)MnBr 2 .4H 2 O, have yielded zero field directional anisotropies of only 5% and 14%, respectively, from the daughter gamma from the long-lived parent 54 Mn, the mixed halides have yielded up to 40% zero field gamma anisotropy at the same base temperature of about 7-8 millikelvin. This improved zero field LTNO provides sufficient sensitivity to enable meaningful NMRON studies of the details of the hyperfine parameters at the Mn site in these mixed halide systems. In this paper we provide the NMRON results for single crystal ( 54 Mn)Mn(CI 0.6 Br 0.4 ) 2 .4H 2 O and compare them with the two terminal compounds which possess surprisingly different NMR responses due to different ratios of magnetic exchange to magnetic anisotropy fields. It is shown that whereas the static magnetic hyperfine field at the Mn nucleus is largely unchanged, and the spin flop field nicely interpolates when compared with the terminal compounds, there are significant differences in the pseudoquadrupolar splittings and sub-resonance linewidths

  18. Complexes of alkylphenols with aluminium halides

    International Nuclear Information System (INIS)

    Golounin, A.V.

    1997-01-01

    Interaction of aluminium halides with alkylphenols is studied through the NMR method. The peculiarity of complex formation of pentamethylphenol with AlI 3 is revealed. By AlI 3 action on the pentamethylphenol the complexes are formed both of keto- and oxy form [ru

  19. Tolerance of GaAs as an original substrate for HVPE growth of free standing GaN

    Science.gov (United States)

    Suzuki, Mio; Sato, T.; Suemasu, T.; Hasegawa, F.

    2004-09-01

    In order to investigate possibility of thick GaN growth on a GaAs substrate by halide vapar phase epitaxy (HVPE), GaN was grown on GaAs(111)/Ti wafer with Ti deposited by E-gun. It was found that surface treatment of the GaAs substrate by HF solution deteriorated greatly the tolerence of GaAs and that Ti can protected GaAs from erosion by NH3. By depositing Ti on GaAs(111)A surface, a millor-like GaN layer could be grown at 1000 °C for 1 hour without serious deterioration of the original GaAs substrate. By increasing the growth rate, a thick free standing GaN will be obtained with GaAs as an original substrate in near future.

  20. Maximizing and stabilizing luminescence from halide perovskites with potassium passivation

    Science.gov (United States)

    Abdi-Jalebi, Mojtaba; Andaji-Garmaroudi, Zahra; Cacovich, Stefania; Stavrakas, Camille; Philippe, Bertrand; Richter, Johannes M.; Alsari, Mejd; Booker, Edward P.; Hutter, Eline M.; Pearson, Andrew J.; Lilliu, Samuele; Savenije, Tom J.; Rensmo, Håkan; Divitini, Giorgio; Ducati, Caterina; Friend, Richard H.; Stranks, Samuel D.

    2018-03-01

    Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield—a quantity that must be maximized to obtain high efficiency—remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can

  1. Broadly tunable metal halide perovskites for solid-state light-emission applications

    OpenAIRE

    Adjokatse, Sampson; Fang, Hong-Hua; Loi, Maria Antonietta

    2017-01-01

    The past two years have witnessed heightened interest in metal-halide perovskites as promising optoelectronic materials for solid-state light emitting applications beyond photovoltaics. Metal-halide perovskites are low-cost solution-processable materials with excellent intrinsic properties such as broad tunability of bandgap, defect tolerance, high photoluminescence quantum efficiency and high emission color purity (narrow full-width at half maximum). In this review, the photophysical propert...

  2. Cation-Dependent Light-Induced Halide Demixing in Hybrid Organic-Inorganic Perovskites

    OpenAIRE

    Sutter-Fella, CM; Ngo, QP; Cefarin, N; Gardener, K; Tamura, N; Stan, CV; Drisdell, WS; Javey, A; Toma, FM; Sharp, ID

    2018-01-01

    © 2018 American Chemical Society. Mixed cation metal halide perovskites with increased power conversion efficiency, negligible hysteresis, and improved long term stability under illumination, moisture, and thermal stressing have emerged as promising compounds for photovoltaic and optoelectronic applications. Here, we shed light on photo-induced halide demixing using in-situ photoluminescence spectroscopy and in-situ synchrotron X-ray diffraction (XRD) to directly compare the evolution of comp...

  3. Comparative biodegradation of alkyl halide insecticides by the white rot fungus, Phanerochaete chrysosporium (BKM-F-1767)

    International Nuclear Information System (INIS)

    Kennedy, D.W.; Aust, S.D.; Bumpus, J.A.

    1990-01-01

    The ability of Phanerochaete chrysosporium to degrade six alkyl halide insecticides (aldrin, dieldrin, heptachlor, chlordane, lindane, and mirex) in liquid and soil-corncob matrices was compared by using 14 C-labeled compounds. Of these, only [ 14 C]lindane and [ 14 C]chlordane underwent extensive biodegradation, as evidenced by the fact that 9.4 to 23.4% of these compounds were degraded to 14 CO 2 in 30 days in liquid cultures and 60 days in soil-corncob cultures inoculated with P. chrysosporium. Although [ 14 C]aldrin, [ 14 C]dieldrin, [ 14 C]heptachlor, and [14D]mirex were poorly mineralized, substantial bioconversion occurred, as determined by substrate disappearance and metabolite formation. Nonbiological disappearance was observed only with chlordane and heptachlor

  4. Solar cells, structures including organometallic halide perovskite monocrystalline films, and methods of preparation thereof

    KAUST Repository

    Bakr, Osman; Peng, Wei; Wang, Lingfei

    2017-01-01

    Embodiments of the present disclosure provide for solar cells including an organometallic halide perovskite monocrystalline film (see fig. 1.1B), other devices including the organometallic halide perovskite monocrystalline film, methods of making

  5. Heterofacial alkylation of alkylenediamines by higher alkyl halides

    International Nuclear Information System (INIS)

    Semenov, V.A.; Kryshko, G.M.; Sokal'skaya, L.I.; Zhukova, N.G.

    1985-01-01

    A study of the physiochemical properties of alkylenediamines substituted by lower alkyls, showed that they possess increased complex-forming ability with respect to salts of different metals as titanium, niobium, zirconium, molybdenum, and zinc. To create a simpler method of synthesis of higher tetraaklyalkylalklyenediamines, based on the use of the accessible domestic raw material, the authors investigated the reaction of alkylenediamines with various alkyl halides. It was established that the best reagents can be obtained using alkyl bromides. It is concluded that the procedure of alkylation of alkylenediamines by higher alkyl halides in the presence of water developed permits the production of terraalkylalkylenediamines in one step with good yield and with purity acceptable for use as extraction reagents

  6. Epitaxial growth of a methoxy-functionalized quaterphenylene on alkali halide surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Balzer, F., E-mail: fbalzer@mci.sdu.dk [University of Southern Denmark, Mads Clausen Institute, Alsion 2, DK-6400 Sønderborg (Denmark); Sun, R. [University of Southern Denmark, Mads Clausen Institute, Alsion 2, DK-6400 Sønderborg (Denmark); Parisi, J. [University of Oldenburg, Energy and Semiconductor Research Laboratory, Institute of Physics, Carl-von-Ossietzky-Str. 9-11, D-26111 Oldenburg (Germany); Rubahn, H.-G. [University of Southern Denmark, Mads Clausen Institute, Alsion 2, DK-6400 Sønderborg (Denmark); Lützen, A. [University of Bonn, Kekulé Institute of Organic Chemistry and Biochemistry, Gerhard-Domagk-Str. 1, D-53121 Bonn (Germany); Schiek, M. [University of Oldenburg, Energy and Semiconductor Research Laboratory, Institute of Physics, Carl-von-Ossietzky-Str. 9-11, D-26111 Oldenburg (Germany)

    2015-12-31

    The epitaxial growth of the methoxy functionalized para-quaterphenylene (MOP4) on the (001) faces of the alkali halides NaCl and KCl and on glass is investigated by a combination of low energy electron diffraction (LEED), polarized light microscopy (PLM), atomic force microscopy (AFM), and X-ray diffraction (XRD). Both domains from upright molecules as well as fiber-like crystallites from lying molecules form. Neither a wetting layer from lying molecules nor widespread epitaxial fiber growth on the substrates is detected. Our results focus on the upright standing molecules, which condense into a thin film phase with an enlarged layer spacing compared to the bulk phase. - Highlights: • Growth of a methoxy-functionalized para-phenylene on dielectric surfaces is investigated. • Low-energy electron diffraction and X-ray diffraction techniques are employed for structural characterization. • Epitaxial growth of upright molecules only is documented. • Polarized optical microscopy together with atomic force microscopy complements the findings.

  7. Epitaxial growth of a methoxy-functionalized quaterphenylene on alkali halide surfaces

    International Nuclear Information System (INIS)

    Balzer, F.; Sun, R.; Parisi, J.; Rubahn, H.-G.; Lützen, A.; Schiek, M.

    2015-01-01

    The epitaxial growth of the methoxy functionalized para-quaterphenylene (MOP4) on the (001) faces of the alkali halides NaCl and KCl and on glass is investigated by a combination of low energy electron diffraction (LEED), polarized light microscopy (PLM), atomic force microscopy (AFM), and X-ray diffraction (XRD). Both domains from upright molecules as well as fiber-like crystallites from lying molecules form. Neither a wetting layer from lying molecules nor widespread epitaxial fiber growth on the substrates is detected. Our results focus on the upright standing molecules, which condense into a thin film phase with an enlarged layer spacing compared to the bulk phase. - Highlights: • Growth of a methoxy-functionalized para-phenylene on dielectric surfaces is investigated. • Low-energy electron diffraction and X-ray diffraction techniques are employed for structural characterization. • Epitaxial growth of upright molecules only is documented. • Polarized optical microscopy together with atomic force microscopy complements the findings.

  8. Lasing in robust cesium lead halide perovskite nanowires

    Science.gov (United States)

    Eaton, Samuel W.; Lai, Minliang; Gibson, Natalie A.; Wong, Andrew B.; Dou, Letian; Ma, Jie; Wang, Lin-Wang; Leone, Stephen R.; Yang, Peidong

    2016-01-01

    The rapidly growing field of nanoscale lasers can be advanced through the discovery of new, tunable light sources. The emission wavelength tunability demonstrated in perovskite materials is an attractive property for nanoscale lasers. Whereas organic–inorganic lead halide perovskite materials are known for their instability, cesium lead halides offer a robust alternative without sacrificing emission tunability or ease of synthesis. Here, we report the low-temperature, solution-phase growth of cesium lead halide nanowires exhibiting low-threshold lasing and high stability. The as-grown nanowires are single crystalline with well-formed facets, and act as high-quality laser cavities. The nanowires display excellent stability while stored and handled under ambient conditions over the course of weeks. Upon optical excitation, Fabry–Pérot lasing occurs in CsPbBr3 nanowires with an onset of 5 μJ cm−2 with the nanowire cavity displaying a maximum quality factor of 1,009 ± 5. Lasing under constant, pulsed excitation can be maintained for over 1 h, the equivalent of 109 excitation cycles, and lasing persists upon exposure to ambient atmosphere. Wavelength tunability in the green and blue regions of the spectrum in conjunction with excellent stability makes these nanowire lasers attractive for device fabrication. PMID:26862172

  9. Quantum confinement effect of two-dimensional all-inorganic halide perovskites

    KAUST Repository

    Cai, Bo; Li, Xiaoming; Gu, Yu; Harb, Moussab; Li, Jianhai; Xie, Meiqiu; Cao, Fei; Song, Jizhong; Zhang, Shengli; Cavallo, Luigi; Zeng, Haibo

    2017-01-01

    Quantum confinement effect (QCE), an essential physical phenomenon of semiconductors when the size becomes comparable to the exciton Bohr radius, typically results in quite different physical properties of low-dimensional materials from their bulk counterparts and can be exploited to enhance the device performance in various optoelectronic applications. Here, taking CsPbBr3 as an example, we reported QCE in all-inorganic halide perovskite in two-dimensional (2D) nanoplates. Blue shifts in optical absorption and photoluminescence spectra were found to be stronger in thinner nanoplates than that in thicker nanoplates, whose thickness lowered below ∼7 nm. The exciton binding energy results showed similar trend as that obtained for the optical absorption and photoluminescence. Meanwile, the function of integrated intensity and full width at half maximum and temperature also showed similar results, further supporting our conclusions. The results displayed the QCE in all-inorganic halide perovskite nanoplates and helped to design the all-inorganic halide perovskites with desired optical properties.

  10. Quaternary oxide halides of group 15 with zinc and cadmium

    International Nuclear Information System (INIS)

    Rueck, Nadia

    2014-01-01

    The present thesis ''Quaternary oxide halides of group 15 with zinc and cadmium'' deals with the chemical class of oxide halides, which contain d-block element cations and pnicogens. Over the past few years compounds containing pnicogene cations are intensively investigated. The reason for this is the free electron pair of the Pn"3"+ cation, which is responsible for some interesting properties. Free electron pairs do not only impact the spatial structure of molecules but also the properties of materials. The object of this work was the synthesis and characterization of compounds containing Pn"3"+ cations with free electron pairs. Due to the structure-determining effect of these free electron pairs and in combination with halides it is possible to synthesize compounds with low-dimensional structures like chains and layers. In these compounds the structure is separated into halophilic and chalcophilic sub-structures, which are held together only by weak Van der Waals forces.

  11. Quantum confinement effect of two-dimensional all-inorganic halide perovskites

    KAUST Repository

    Cai, Bo

    2017-09-07

    Quantum confinement effect (QCE), an essential physical phenomenon of semiconductors when the size becomes comparable to the exciton Bohr radius, typically results in quite different physical properties of low-dimensional materials from their bulk counterparts and can be exploited to enhance the device performance in various optoelectronic applications. Here, taking CsPbBr3 as an example, we reported QCE in all-inorganic halide perovskite in two-dimensional (2D) nanoplates. Blue shifts in optical absorption and photoluminescence spectra were found to be stronger in thinner nanoplates than that in thicker nanoplates, whose thickness lowered below ∼7 nm. The exciton binding energy results showed similar trend as that obtained for the optical absorption and photoluminescence. Meanwile, the function of integrated intensity and full width at half maximum and temperature also showed similar results, further supporting our conclusions. The results displayed the QCE in all-inorganic halide perovskite nanoplates and helped to design the all-inorganic halide perovskites with desired optical properties.

  12. Heterogeneous Monolithic Integration of Single-Crystal Organic Materials.

    Science.gov (United States)

    Park, Kyung Sun; Baek, Jangmi; Park, Yoonkyung; Lee, Lynn; Hyon, Jinho; Koo Lee, Yong-Eun; Shrestha, Nabeen K; Kang, Youngjong; Sung, Myung Mo

    2017-02-01

    Manufacturing high-performance organic electronic circuits requires the effective heterogeneous integration of different nanoscale organic materials with uniform morphology and high crystallinity in a desired arrangement. In particular, the development of high-performance organic electronic and optoelectronic devices relies on high-quality single crystals that show optimal intrinsic charge-transport properties and electrical performance. Moreover, the heterogeneous integration of organic materials on a single substrate in a monolithic way is highly demanded for the production of fundamental organic electronic components as well as complex integrated circuits. Many of the various methods that have been designed to pattern multiple heterogeneous organic materials on a substrate and the heterogeneous integration of organic single crystals with their crystal growth are described here. Critical issues that have been encountered in the development of high-performance organic integrated electronics are also addressed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Thorium valency in molten alkali halides in equilibrium with metallic thorium

    International Nuclear Information System (INIS)

    Smirnov, M.V.; Kudyakov, V.Ya.

    1983-01-01

    Metallic thorium is shown to corrode in molten alkali halides even in the absence of external oxidizing agents, alkali cations acting as oxidizing agents. Its corrosion rate grows in the series of alkali chlorides from LiCl to CsCl at constant temperature. Substituting halide anions for one another exerts a smaller influence, the rate rising slightly in going from chlorides to bromides and iodides, having the same alkali cations. Thorium valency is determined coulometrically, the metal being dissolved anodically in molten alkali halides and their mixtures. In fluoride melts it is equal to 4 but in chloride, bromide and iodide ones, as a rule, it has non-integral values between 4 and 2 which diminish as the temperature is raised, as the thorium concentration is lowered, as the radii of alkali cations decrease and those of halide anions increase. The emf of cells Th/N ThHlsub(n) + (1-N) MHl/MHl/C, Hlsub(2(g)) where Hl is Cl, Br or I, M is Li, Na, K, Cs or Na + K, and N < 0.05, is measured as a function of concentration at several temperatures. Expressions are obtained for its concentration dependence. The emf grows in the series of alkali chlorides from LiCl to CsCl, other conditions being equal. (author)

  14. Transfer Hydro-dehalogenation of Organic Halides Catalyzed by Ruthenium(II) Complex.

    Science.gov (United States)

    You, Tingjie; Wang, Zhenrong; Chen, Jiajia; Xia, Yuanzhi

    2017-02-03

    A simple and efficient Ru(II)-catalyzed transfer hydro-dehalogenation of organic halides using 2-propanol solvent as the hydride source was reported. This methodology is applicable for hydro-dehalogenation of a variety of aromatic halides and α-haloesters and amides without additional ligand, and quantitative yields were achieved in many cases. The potential synthetic application of this method was demonstrated by efficient gram-scale transformation with catalyst loading as low as 0.5 mol %.

  15. Tolerance of GaAs as an original substrate for HVPE growth of free standing GaN

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Mio; Sato, T.; Suemasu, T.; Hasegawa, F. [University of Tsukuba, Institute of Applied Physics, Tsukuba, Ibaraki 305-8573 (Japan)

    2004-09-01

    In order to investigate possibility of thick GaN growth on a GaAs substrate by halide vapar phase epitaxy (HVPE), GaN was grown on GaAs(111)/Ti wafer with Ti deposited by E-gun. It was found that surface treatment of the GaAs substrate by HF solution deteriorated greatly the tolerance of GaAs and that Ti can protected GaAs from erosion by NH{sub 3}. By depositing Ti on GaAs(111)A surface, a mirror-like GaN layer could be grown at 1000 C for 1 hour without serious deterioration of the original GaAs substrate. By increasing the growth rate, a thick free standing GaN will be obtained with GaAs as an original substrate in near future. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Hydroformylation of olefins and reductive carbonylation of aryl halides with syngas formed ex situ from dehydrogenative decarbonylation of hexane-1,6-diol

    DEFF Research Database (Denmark)

    Christensen, Stig Holden; Olsen, Esben Paul Krogh; Rosenbaum, Jascha

    2014-01-01

    A variety of primary alcohols have been investigated as convenient substrates for the ex situ delivery of carbon monoxide and molecular hydrogen in a two-chamber reactor. The gaseous mixture is liberated in one chamber by an iridium-catalysed dehydrogenative decarbonylation of the alcohol...... and then consumed in the other chamber in either a rhodium-catalysed hydroformylation of olefins or a palladium-catalysed reductive carbonylation of aryl halides. Hexane-1,6-diol was found to be the optimum alcohol for both reactions where moderate to excellent yields were obtained of the product aldehydes...

  17. Environmental Effects on the Photophysics of Organic-Inorganic Halide Perovskites.

    Science.gov (United States)

    Galisteo-López, Juan F; Anaya, M; Calvo, M E; Míguez, H

    2015-06-18

    The photophysical properties of films of organic-inorganic lead halide perovskites under different ambient conditions are herein reported. We demonstrate that their luminescent properties are determined by the interplay between photoinduced activation and darkening processes, which strongly depend on the atmosphere surrounding the samples. We have isolated oxygen and moisture as the key elements in each process, activation and darkening, both of which involve the interaction with photogenerated carriers. These findings show that environmental factors play a key role in the performance of lead halide perovskites as efficient luminescent materials.

  18. Advancement on Lead-Free Organic-Inorganic Halide Perovskite Solar Cells: A Review.

    Science.gov (United States)

    Sani, Faruk; Shafie, Suhaidi; Lim, Hong Ngee; Musa, Abubakar Ohinoyi

    2018-06-14

    Remarkable attention has been committed to the recently discovered cost effective and solution processable lead-free organic-inorganic halide perovskite solar cells. Recent studies have reported that, within five years, the reported efficiency has reached 9.0%, which makes them an extremely promising and fast developing candidate to compete with conventional lead-based perovskite solar cells. The major challenge associated with the conventional perovskite solar cells is the toxic nature of lead (Pb) used in the active layer of perovskite material. If lead continues to be used in fabricating solar cells, negative health impacts will result in the environment due to the toxicity of lead. Alternatively, lead free perovskite solar cells could give a safe way by substituting low-cost, abundant and non toxic material. This review focuses on formability of lead-free organic-inorganic halide perovskite, alternative metal cations candidates to replace lead (Pb), and possible substitutions of organic cations, as well as halide anions in the lead-free organic-inorganic halide perovskite architecture. Furthermore, the review gives highlights on the impact of organic cations, metal cations and inorganic anions on stability and the overall performance of lead free perovskite solar cells.

  19. Effects of Substrate and Polymer Encapsulation on CO

    NARCIS (Netherlands)

    Birdja, Yuvraj Y.; Vos, Rafaël E.; Wezendonk, T.A.; Jiang, Lin; Kapteijn, F.; Koper, M.T.M.

    2018-01-01

    Heterogenization of molecular catalysts for CO2 electroreduction has attracted significant research activity, due to the combined advantages of homogeneous and heterogeneous catalysts. In this work, we demonstrate the strong influence of the nature of the substrate on the selectivity

  20. Metal induced gap states at alkali halide/metal interface

    International Nuclear Information System (INIS)

    Kiguchi, Manabu; Yoshikawa, Genki; Ikeda, Susumu; Saiki, Koichiro

    2004-01-01

    The electronic state of a KCl/Cu(0 0 1) interface was investigated using the Cl K-edge near-edge X-ray absorption fine structure (NEXAFS). A pre-peak observed on the bulk edge onset of thin KCl films has a similar feature to the peak at a LiCl/Cu(0 0 1) interface, which originates from the metal induced gap state (MIGS). The present result indicates that the MIGS is formed universally at alkali halide/metal interfaces. The decay length of MIGS to an insulator differs from each other, mainly due to the difference in the band gap energy of alkali halide

  1. Metal halides vapor lasers with inner reactor and small active volume.

    Science.gov (United States)

    Shiyanov, D. V.; Sukhanov, V. B.; Evtushenko, G. S.

    2018-04-01

    Investigation of the energy characteristics of copper, manganese, lead halide vapor lasers with inner reactor and small active volume 90 cm3 was made. The optimal operating pulse repetition rates, temperatures, and buffer gas pressure for gas discharge tubes with internal and external electrodes are determined. Under identical pump conditions, such systems are not inferior in their characteristics to standard metal halide vapor lasers. It is shown that the use of a zeolite halogen generator provides lifetime laser operation.

  2. Silver halide photographic material providing an image and an unsharp mask

    International Nuclear Information System (INIS)

    Broadhead, P.; Farnell, G.C.

    1981-01-01

    Desirable edge effects are produced by normal imagewise exposure and processing of a sensitive radiographic film comprising a transparent film support bearing a layer of a direct-positive silver halide emulsion and a layer of a negative silver halide emulsion and wherein the film comprises means to reduce crossover between the two emulsion layers, one of said emulsion layers being adapted to record a primary image and the other being adapted to record an unsharp mask image. (author)

  3. Monocrystalline halide perovskite nanostructures for optoelectronic applications

    NARCIS (Netherlands)

    Khoram, P.

    2018-01-01

    Halide perovskites are a promising class of materials for incorporation in optoelectronics with higher efficiency and lower cost. The solution processability of these materials provides unique opportunities for simple nanostructure fabrication. In the first half of the thesis (chapter 2 and 3) we

  4. Reactivity of halide and pseudohalide ligands

    International Nuclear Information System (INIS)

    Kukushkin, Yu.N.

    1987-01-01

    Reactivity of halide and pseudohalide (cyanide, azide, thiocyanate, cyanate) ligands tending to form bridge bonds in transition metal (Re, Mo, W) complexes is considered. Complexes where transition metal salts are ligands of other, complex-forming ion, are described. Transformation of innerspheric pseudohalide ligands is an important way of directed synthesis of these metal coordination compounds

  5. Vibrational Spectra of Discrete UO22+ Halide Complexes in the Gas Phase

    International Nuclear Information System (INIS)

    Groenewold, G.S.; Van Stipdonk, Michael J.; Oomens, Jos; De Jong, Wibe A.; Gresham, Garold L.; Mcilwain, Michael

    2010-01-01

    The intrinsic binding of halide ions to the metal center in the uranyl molecule is a topic of ongoing research interest in both the actinide separations and theoretical communities. Investigations of structure in the condensed phases is frequently obfuscated by solvent interactions that can alter ligand binding and spectroscopic properties. The approach taken in this study is to move the uranyl halide complexes into the gas phase where they are free from solvent interactions, and then interrogate their vibrational spectroscopy using infrared multiple photon dissociation (IRMPD). The spectra of cationic coordination complexes having the composition (UO 2 (X)(ACO) 3 ) + (where X = F, Cl, Br and I; ACO = acetone) were acquired using electrospray for ion formation, and monitoring the ion signal from the photoelimination of ACO ligands. The studies showed that the asymmetric ν 3 UO 2 frequency was insensitive to halide identity as X was varied from Cl to I, suggesting that in these pseudo-octahedral complexes, changing the nucleophilicity of the halide did not appreciably alter its binding in the complex. The ν 3 peak in the spectrum of the F-containing complex was 9 cm -1 lower indicating stronger coordination in this complex. Similarly the ACO carbonyl stretches showed that the C=O frequency was relatively insensitive to the identity of the halide, although a modest shift to higher wavenumber was seen for the complexes with the more nucleophilic anions, consistent with the idea that they loosen solvent binding. Surprisingly, the ν 1 stretch was activated when the softer anions Cl, Br and I were present in the complexes. IR studies of the anionic complexes (UO 2 X 3 ) - (where X = Cl - , Br - and I - ) compared the ν 3 UO 2 modes versus halide, and showed that the ν 3 values decreased with increasing anion nucleophilicity. This observation was consistent with DFT calculations that indicated that (UO 2 X 2 ) - -X, and (UO 2 X 2 )·-X - dissociation energies

  6. Direct ToF-SIMS analysis of organic halides and amines on TLC plates

    Energy Technology Data Exchange (ETDEWEB)

    Parent, Alexander A. [Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602 (United States); Anderson, Thomas M. [Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602 (United States); Michaelis, David J. [Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602 (United States); Jiang, Guilin [Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602 (United States); Savage, Paul B. [Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602 (United States); Linford, Matthew R. [Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602 (United States)]. E-mail: mrlinford@chem.byu.edu

    2006-07-30

    It has been reported that: 'direct analysis of thin layer chromatography (TLC) plates with secondary ion mass spectrometry (SIMS) yields no satisfactory results' (J. Chromatogr. A 1084 (2005) 113-118). While this statement appears to be true in general, we have identified two important classes of compounds, organic halides and amines, that appear to yield to such direct analyses. For example, five organic halides with diverse structures were eluted on normal phase TLC plates. In all cases the halide signals in the negative ion time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra were notably stronger than the background signals. Similarly, a series of five organic amines with diverse structures were directly analyzed by positive ion ToF-SIMS. In all but one of the spectra characteristic, and sometimes even quasi-molecular ions, were observed. Most likely, the good halide ion yields are largely a function of the electronegativity of the halogens. We also propose that direct analysis of amines on normal phase silica gel is facilitated by the acidity, i.e., proton donation, of surface silanol groups.

  7. Direct ToF-SIMS analysis of organic halides and amines on TLC plates

    International Nuclear Information System (INIS)

    Parent, Alexander A.; Anderson, Thomas M.; Michaelis, David J.; Jiang, Guilin; Savage, Paul B.; Linford, Matthew R.

    2006-01-01

    It has been reported that: 'direct analysis of thin layer chromatography (TLC) plates with secondary ion mass spectrometry (SIMS) yields no satisfactory results' (J. Chromatogr. A 1084 (2005) 113-118). While this statement appears to be true in general, we have identified two important classes of compounds, organic halides and amines, that appear to yield to such direct analyses. For example, five organic halides with diverse structures were eluted on normal phase TLC plates. In all cases the halide signals in the negative ion time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra were notably stronger than the background signals. Similarly, a series of five organic amines with diverse structures were directly analyzed by positive ion ToF-SIMS. In all but one of the spectra characteristic, and sometimes even quasi-molecular ions, were observed. Most likely, the good halide ion yields are largely a function of the electronegativity of the halogens. We also propose that direct analysis of amines on normal phase silica gel is facilitated by the acidity, i.e., proton donation, of surface silanol groups

  8. Radiation damage in the alkali halide crystals

    International Nuclear Information System (INIS)

    Diller, K.M.

    1975-10-01

    A general review is given of the experimental data on radiation damage in the alkali halide crystals. A report is presented of an experimental investigation of irradiation produced interstitial dislocation loops in NaCl. These loops are found to exhibit the usual growth and coarsening behaviour during thermal annealing which operates by a glide and self-climb mechanism. It is shown that the recombination of defects in these crystals is a two stage process, and that the loss of interstitials stabilized at the loops is caused by extrinsic vacancies. The theoretical techniques used in simulating point defects in ionic crystals are described. Shell model potentials are derived for all the alkali halide crystals by fitting to bulk crystal data. The fitting is supplemented by calculations of the repulsive second neighbour interactions using methods based on the simple electron gas model. The properties of intrinsic and substitutional impurity defects are calculated. The HADES computer program is used in all the defect calculations. Finally the report returns to the problems of irradiation produced interstitial defects. The properties of H centres are discussed; their structure, formation energies, trapping at impurities and dimerization. The structure, formation energies and mobility of the intermediate and final molecular defects are then discussed. The thermodynamics of interstitial loop formation is considered for all the alklai halide crystals. The nucleation of interstitial loops in NaCl and NaBr is discussed, and the recombination of interstitial and vacancy defects. The models are found to account for all the main features of the experimental data. (author)

  9. Silver chloride as a heterogeneous nucleant for the growth of silver nanowires.

    Science.gov (United States)

    Schuette, Waynie M; Buhro, William E

    2013-05-28

    Various additives are employed in the polyol synthesis of silver nanowires (Ag NWs), which are typically halide salts such as NaCl. A variety of mechanistic roles have been suggested for these additives. We now show that the early addition of NaCl in the polyol synthesis of Ag NWs from AgNO3 in ethylene glycol results in the rapid formation of AgCl nanocubes, which induce the heterogeneous nucleation of metallic Ag upon their surfaces. Ag NWs subsequently grow from these nucleation sites. The conclusions are supported by studies using ex situ generated AgCl nanocubes.

  10. Local coordination of polyvalent metal ions in molten halide mixtures

    International Nuclear Information System (INIS)

    Akdeniz, Z.; Tosi, M.P.

    1989-07-01

    Ample experimental evidence is available in the literature on the geometry and the stability of local coordination for polyvalent metal ions in molten mixtures of their halides with alkali halides. Recent schemes for classifying this evidence are discussed. Dissociation of tetrahedral halocomplexes in good ionic systems can be viewed as a classical Mott problem of bound-state stability in a conducting matrix. More generally, structural coordinates can be constructed from properties of the component elements, to separate out systems with long-lived fourfold or sixfold coordination and to distinguish between these. (author). 11 refs, 1 fig

  11. Development and melt growth of novel scintillating halide crystals

    Science.gov (United States)

    Yoshikawa, Akira; Yokota, Yuui; Shoji, Yasuhiro; Kral, Robert; Kamada, Kei; Kurosawa, Shunsuke; Ohashi, Yuji; Arakawa, Mototaka; Chani, Valery I.; Kochurikhin, Vladimir V.; Yamaji, Akihiro; Andrey, Medvedev; Nikl, Martin

    2017-12-01

    Melt growth of scintillating halide crystals is reviewed. The vertical Bridgman growth technique is still considered as very popular method that enables production of relatively large and commercially attractive crystals. On the other hand, the micro-pulling-down method is preferable when fabrication of small samples, sufficient for preliminary characterization of their optical and/or scintillation performance, is required. Moreover, bulk crystal growth is also available using the micro-pulling-down furnace. The examples of growths of various halide crystals by industrially friendly melt growth techniques including Czochralski and edge-defined film-fed growth methods are also discussed. Finally, traveling molten zone growth that in some degree corresponds to horizontal zone melting is briefly overviewed.

  12. Alkali Halide Microstructured Optical Fiber for X-Ray Detection

    Science.gov (United States)

    DeHaven, S. L.; Wincheski, R. A.; Albin, S.

    2014-01-01

    Microstructured optical fibers containing alkali halide scintillation materials of CsI(Na), CsI(Tl), and NaI(Tl) are presented. The scintillation materials are grown inside the microstructured fibers using a modified Bridgman-Stockbarger technique. The x-ray photon counts of these fibers, with and without an aluminum film coating are compared to the output of a collimated CdTe solid state detector over an energy range from 10 to 40 keV. The photon count results show significant variations in the fiber output based on the materials. The alkali halide fiber output can exceed that of the CdTe detector, dependent upon photon counter efficiency and fiber configuration. The results and associated materials difference are discussed.

  13. Formation of structured nanophases in halide crystals

    Czech Academy of Sciences Publication Activity Database

    Kulveit, Jan; Demo, Pavel; Polák, Karel; Sveshnikov, Alexey; Kožíšek, Zdeněk

    2013-01-01

    Roč. 5, č. 6 (2013), s. 561-564 ISSN 2164-6627 R&D Projects: GA ČR GAP108/12/0891 Institutional support: RVO:68378271 Keywords : halide crystals * nucleation Subject RIV: BM - Solid Matter Physics ; Magnetism http://www.aspbs.com/asem.html#v5n6

  14. Determination of the structural phase and octahedral rotation angle in halide perovskites

    Science.gov (United States)

    dos Reis, Roberto; Yang, Hao; Ophus, Colin; Ercius, Peter; Bizarri, Gregory; Perrodin, Didier; Shalapska, Tetiana; Bourret, Edith; Ciston, Jim; Dahmen, Ulrich

    2018-02-01

    A key to the unique combination of electronic and optical properties in halide perovskite materials lies in their rich structural complexity. However, their radiation sensitive nature limits nanoscale structural characterization requiring dose efficient microscopic techniques in order to determine their structures precisely. In this work, we determine the space-group and directly image the Br halide sites of CsPbBr3, a promising material for optoelectronic applications. Based on the symmetry of high-order Laue zone reflections of convergent-beam electron diffraction, we identify the tetragonal (I4/mcm) structural phase of CsPbBr3 at cryogenic temperature. Electron ptychography provides a highly sensitive phase contrast measurement of the halide positions under low electron-dose conditions, enabling imaging of the elongated Br sites originating from the out-of-phase octahedral rotation viewed along the [001] direction of I4/mcm persisting at room temperature. The measurement of these features and comparison with simulations yield an octahedral rotation angle of 6.5°(±1.5°). The approach demonstrated here opens up opportunities for understanding the atomic scale structural phenomena applying advanced characterization tools on a wide range of radiation sensitive halide-based all-inorganic and hybrid organic-inorganic perovskites.

  15. Solvation structures of lithium halides in methanol–water mixtures

    International Nuclear Information System (INIS)

    Sarkar, Atanu; Dixit, Mayank Kumar; Tembe, B.L.

    2015-01-01

    Highlights: • Potentials of mean force for Li + -halides are calculated in methanol–water mixtures. • Stable CIP for x methanol = 1.0 becomes unstable at and below x methanol = 0.75. • The Li + ion is preferentially solvated by methanol molecules. • The halide ions are preferentially solvated by water molecules. - Abstract: The potentials of mean force (PMFs) for the ion pairs, Li + −Cl − , Li + −Br − and Li + −I − have been calculated in five methanol–water compositions. The results obtained are verified by trailing the trajectories and calculating the ion pair distance residence times. Local structures around the ions are studied using the radial distribution functions, density profiles, orientational correlation functions, running coordination numbers and excess coordination numbers. The major change in PMF is observed as the methanol mole fraction (x methanol ) is changed from 1.0 to 0.75. The stable contact ion pair occurring for x methanol = 1.0 becomes unstable at and below x methanol = 0.75. The preferential solvation data show that the halide ions are always preferentially solvated by water molecules. Although the lithium ion is preferentially solvated by methanol molecules, there is significant affinity towards water molecules as well

  16. Chemical vapor deposition growth of single-crystalline cesium lead halide microplatelets and heterostructures for optoelectronic applications

    Institute of Scientific and Technical Information of China (English)

    Yiliu Wang; Xun Guan; Dehui Li; Hung-Chieh Cheng; Xidong Duan; Zhaoyang Lin; Xiangfeng Duan

    2017-01-01

    Orgaruc-inorganic hybrid halide perovskites,such as CH3NH3PbI3,have emerged as an exciting class of materials for solar photovoltaic applications;however,they are currently plagued by insufficient environmental stability.To solve this issue,all-inorganic halide perovskites have been developed and shown to exhibit significantly improved stability.Here,we report a single-step chemical vapor deposition growth of cesium lead halide (CsPbX3) microcrystals.Optical microscopy studies show that the resulting perovskite crystals predominantly adopt a square-platelet morphology.Powder X-ray diffraction (PXRD) studies of the resulting crystals demonstrate a highly crystalline nature,with CsPbC13,CsPbBr3,and CsPbI3 showing tetragonal,monoclinic,and orthorhombic phases,respectively.Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies show that the resulting platelets exhibit well-faceted structures with lateral dimensions of the order of 10-50 μm,thickness around 1 μm,and ultra-smooth surface,suggesting the absence of obvious grain boundaries and the single-crystalline nature of the individual microplatelets.Photoluminescence (PL) images and spectroscopic studies show a uniform and intense emission consistent with the expected band edge transition.Additionally,PL images show brighter emission around the edge of the platelets,demonstrating a wave-guiding effect in high-quality crystals.With a well-defined geometry and ultra-smooth surface,the square platelet structure can function as a whispering gallery mode cavity with a quality factor up to 2,863 to support laser emission at room temperature.Finally,we demonstrate that such microplatelets can be readily grown on a variety of substrates,including silicon,graphene,and other two-dimensional materials such as molybdenum disulfide,which can readily allow the construction of heterostructure optoelectronic devices,including a graphene/perovskite/ graphene vertically-stacked photodetector with

  17. Electron detachment energies in high-symmetry alkali halide solvated-electron anions

    Science.gov (United States)

    Anusiewicz, Iwona; Berdys, Joanna; Simons, Jack; Skurski, Piotr

    2003-07-01

    We decompose the vertical electron detachment energies (VDEs) in solvated-electron clusters of alkali halides in terms of (i) an electrostatic contribution that correlates with the dipole moment (μ) of the individual alkali halide molecule and (ii) a relaxation component that is related to the polarizability (α) of the alkali halide molecule. Detailed numerical ab initio results for twelve species (MX)n- (M=Li,Na; X=F,Cl,Br; n=2,3) are used to construct an interpolation model that relates the clusters' VDEs to their μ and α values as well as a cluster size parameter r that we show is closely related to the alkali cation's ionic radius. The interpolation formula is then tested by applying it to predict the VDEs of four systems [i.e., (KF)2-, (KF)3-, (KCl)2-, and (KCl)3-] that were not used in determining the parameters of the model. The average difference between the model's predicted VDEs and the ab initio calculated electron binding energies is less than 4% (for the twelve species studied). It is concluded that one can easily estimate the VDE of a given high-symmetry solvated electron system by employing the model put forth here if the α, μ and cation ionic radii are known. Alternatively, if VDEs are measured for an alkali halide cluster and the α and μ values are known, one can estimate the r parameter, which, in turn, determines the "size" of the cluster anion.

  18. Local Polar Fluctuations in Lead Halide Perovskite Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yaffe, Omer; Guo, Yinsheng; Tan, Liang Z.; Egger, David A.; Hull, Trevor; Stoumpos, Constantinos C.; Zheng, Fan; Heinz, Tony F.; Kronik, Leeor; Kanatzidis, Mercouri G.; Owen, Jonathan S.; Rappe, Andrew M.; Pimenta, Marcos A.; Brus, Louis E.

    2017-03-01

    Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH3NH3PbBr3) and all-inorganic (CsPbBr3) leadhalide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. MD simulations indicate that head-tohead Cs motion coupled to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr3.

  19. Methyl halide fluxes from tropical plants under controlled radiation and temperature regimes

    Science.gov (United States)

    Blei, Emanuel; Yokouchi, Yoko; Saito, Takuya; Nozoe, Susumu

    2015-04-01

    Methyl halides (CH3Cl, CH3Br, CH3I) contribute significantly to the halogen burden of the atmosphere and have the potential to influence the stratospheric ozone layer through their catalytic effect in the Chapman cycle. As such they have been studied over the years, and many plants and biota have been examined for their potential to act as a source of these gases. One of the potentially largest terrestrial sources identified was tropical vegetation such as tropical ferns and Dipterocarp trees. Most of these studies concentrated on the identification and quantification of such fluxes rather than their characteristics and often the chambers used in these studies were either opaque or only partially transparent to the full solar spectrum. Therefore it is not certain to which degree emissions of methyl halides are innate to the plants and how much they might vary due to radiation or temperature conditions inside the enclosures. In a separate development it had been proposed that UV-radiation could cause live plant materials to be become emitters of methane even under non-anoxic conditions. As methane is chemically very similar to methyl halides and had been proposed to be produced from methyl-groups ubiquitously found in plant cell material there is a relatively good chance that such a production mechanism would also apply to methyl halides. To test whether radiation can affect elevated emissions of methyl halides from plant materials and to distinguish this from temperature effects caused by heat build-up in chambers a set of controlled laboratory chamber enclosures under various radiation and temperature regimes was conducted on four different tropical plant species (Magnolia grandiflora, Cinnamonum camphora, Cyathea lepifera, Angiopteris lygodiifolia), the latter two of which had previously been identified as strong methyl halide emitters. Abscised leaf samples of these species were subjected to radiation treatments such UV-B, UV-A and broad spectrum radiation

  20. Role of substrate morphology in ion induced dewetting of thin solid films

    Energy Technology Data Exchange (ETDEWEB)

    Repetto, Luca, E-mail: luca.repetto@unige.it [Physics Department and Nanomed Labs, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Lo Savio, Roberto [Physics Department and Nanomed Labs, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Šetina Batič, Barbara [Inštitut Za Kovinske Materiale in Tehnologije, Lepi pot 11, 1000 Ljubljana (Slovenia); Firpo, Giuseppe; Valbusa, Ugo [Physics Department and Nanomed Labs, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy)

    2014-10-01

    Highlights: • We have created by ion bombardment silicon substrates with different topographies. • The substrates have been characterized by ellipsometry, AFM, SEM and EDX. • The substrates have been used for experiments of ion induced Cr films. • We show that different substrate topographies can induce different dewetted patterns. • Substrate topography can favor spinodal dewetting against heterogeneous nucleations. - Abstract: We investigate the role of the substrate morphology in the dewetting of ultrathin chromium films irradiated with 30 keV Ga ions. Silicon surfaces with different roughness were used as substrates for the films. The results of the irradiation experiments and of related simulations indicate that the chromium films can undergo a dewetting-like process through the two standard channels that show up for liquids, namely the spinodal channel, and the dewetting by heterogeneous nucleation. The two processes are competitive, and the prevailing one can be predicted and selected according to the characteristics of the substrate.

  1. Role of substrate morphology in ion induced dewetting of thin solid films

    International Nuclear Information System (INIS)

    Repetto, Luca; Lo Savio, Roberto; Šetina Batič, Barbara; Firpo, Giuseppe; Valbusa, Ugo

    2014-01-01

    Highlights: • We have created by ion bombardment silicon substrates with different topographies. • The substrates have been characterized by ellipsometry, AFM, SEM and EDX. • The substrates have been used for experiments of ion induced Cr films. • We show that different substrate topographies can induce different dewetted patterns. • Substrate topography can favor spinodal dewetting against heterogeneous nucleations. - Abstract: We investigate the role of the substrate morphology in the dewetting of ultrathin chromium films irradiated with 30 keV Ga ions. Silicon surfaces with different roughness were used as substrates for the films. The results of the irradiation experiments and of related simulations indicate that the chromium films can undergo a dewetting-like process through the two standard channels that show up for liquids, namely the spinodal channel, and the dewetting by heterogeneous nucleation. The two processes are competitive, and the prevailing one can be predicted and selected according to the characteristics of the substrate

  2. Thermal battery. [solid metal halide electrolytes with enhanced electrical conductance after a phase transition

    Science.gov (United States)

    Carlsten, R.W.; Nissen, D.A.

    1973-03-06

    The patent describes an improved thermal battery whose novel design eliminates various disadvantages of previous such devices. Its major features include a halide cathode, a solid metal halide electrolyte which has a substantially greater electrical conductance after a phase transition at some temperature, and a means for heating its electrochemical cells to activation temperature.

  3. Probing the Catalytic Mechanism of S-Ribosylhomocysteinase (LuxS) with Catalytic Intermediates and Substrate Analogues

    Energy Technology Data Exchange (ETDEWEB)

    Gopishetty, Bhaskar; Zhu, Jinge; Rajan, Rakhi; Sobczak, Adam J.; Wnuk, Stanislaw F.; Bell, Charles E.; Pei, Dehua; (OSU); (FIU)

    2009-05-12

    S-Ribosylhomocysteinase (LuxS) cleaves the thioether bond in S-ribosylhomocysteine (SRH) to produce homocysteine (Hcys) and 4,5-dihydroxy-2,3-pentanedione (DPD), the precursor of the type II bacterial quorum sensing molecule (AI-2). The catalytic mechanism of LuxS comprises three distinct reaction steps. The first step involves carbonyl migration from the C1 carbon of ribose to C2 and the formation of a 2-ketone intermediate. The second step shifts the C=O group from the C2 to C3 position to produce a 3-ketone intermediate. In the final step, the 3-ketone intermediate undergoes a {beta}-elimination reaction resulting in the cleavage of the thioether bond. In this work, the 3-ketone intermediate was chemically synthesized and shown to be chemically and kinetically competent in the LuxS catalytic pathway. Substrate analogues halogenated at the C3 position of ribose were synthesized and reacted as time-dependent inhibitors of LuxS. The time dependence was caused by enzyme-catalyzed elimination of halide ions. Examination of the kinetics of halide release and decay of the 3-ketone intermediate catalyzed by wild-type and mutant LuxS enzymes revealed that Cys-84 is the general base responsible for proton abstraction in the three reaction steps, whereas Glu-57 likely facilitates substrate binding and proton transfer during catalysis.

  4. Analysis and modeling of alkali halide aqueous solutions

    DEFF Research Database (Denmark)

    Kim, Sun Hyung; Anantpinijwatna, Amata; Kang, Jeong Won

    2016-01-01

    on calculations for various electrolyte properties of alkali halide aqueous solutions such as mean ionic activity coefficients, osmotic coefficients, and salt solubilities. The model covers highly nonideal electrolyte systems such as lithium chloride, lithium bromide and lithium iodide, that is, systems...

  5. A study on the localized corrosion of cobalt in bicarbonate solutions containing halide ions

    Energy Technology Data Exchange (ETDEWEB)

    Gallant, Danick [Departement de Biologie, Chimie et Sciences de la Sante, Universite du Quebec a Rimouski, 300, Allee des Ursulines, Rimouski, Que., G5L 3A1 (Canada); Departement de Chimie, Universite Laval, Quebec, Que., G1K 7P4 (Canada); Simard, Stephan [Departement de Biologie, Chimie et Sciences de la Sante, Universite du Quebec a Rimouski, 300, Allee des Ursulines, Rimouski, Que., G5L 3A1 (Canada)]. E-mail: stephan_simard@uqar.qc.ca

    2005-07-01

    The localized attack of cobalt in bicarbonate aqueous solutions containing halide ions was investigated using electrochemical techniques, scanning electron microscopy, UV-visible and Raman spectroscopies. Rotating disc and rotating ring-disc electrodes were used to determine the effect of bicarbonate concentration, solution pH, nature and concentration of the halide ions, convection and potential sweep rate on the corrosion processes. These parameters were found to play a key role on the localized attack induced by halide ions by influencing the production of a Co(HCO{sub 3}){sub 2} precipitate on the pit surface. Potentiostatically generated cobalt oxide films (CoO and Co{sub 3}O{sub 4}) were found to be efficient to reduce pitting corrosion of cobalt.

  6. Grafting heterogeneous catalyst with gamma radiation

    International Nuclear Information System (INIS)

    Garnett, J.L.; Long, M.A.; Levot, R.G.

    1984-01-01

    A process for the production of a heterogeneous catalyst comprises the steps of: irradiating an organic macromolecular substrate or a metal substrate with ionising or ultra violet radiation in the presence of a monomer selected from the group consisting of o-, m-, or p- styryl diphenyl phosphine and o-, m- or p- phenyl acrylyl diphenyl phosphine, to graft the monomer to the substrate; and reacting the graft copolymer with a homogeneous catalyst selected from the group consisting of catalytic metal salts and catalytic organometallic complexes such that the graft copolymer conjugate becomes a ligand of the catalyst

  7. Precise Control of Quantum Confinement in Cesium Lead Halide Perovskite Quantum Dots via Thermodynamic Equilibrium.

    Science.gov (United States)

    Dong, Yitong; Qiao, Tian; Kim, Doyun; Parobek, David; Rossi, Daniel; Son, Dong Hee

    2018-05-09

    Cesium lead halide (CsPbX 3 ) nanocrystals have emerged as a new family of materials that can outperform the existing semiconductor nanocrystals due to their superb optical and charge-transport properties. However, the lack of a robust method for producing quantum dots with controlled size and high ensemble uniformity has been one of the major obstacles in exploring the useful properties of excitons in zero-dimensional nanostructures of CsPbX 3 . Here, we report a new synthesis approach that enables the precise control of the size based on the equilibrium rather than kinetics, producing CsPbX 3 quantum dots nearly free of heterogeneous broadening in their exciton luminescence. The high level of size control and ensemble uniformity achieved here will open the door to harnessing the benefits of excitons in CsPbX 3 quantum dots for photonic and energy-harvesting applications.

  8. 2D halide perovskite-based van der Waals heterostructures: contact evaluation and performance modulation

    Science.gov (United States)

    Guo, Yaguang; Saidi, Wissam A.; Wang, Qian

    2017-09-01

    Halide perovskites and van der Waals (vdW) heterostructures are both of current interest owing to their novel properties and potential applications in nano-devices. Here, we show the great potential of 2D halide perovskite sheets (C4H9NH3)2PbX4 (X  =  Cl, Br and I) that were synthesized recently (Dou et al 2015 Science 349 1518-21) as the channel materials contacting with graphene and other 2D metallic sheets to form van der Waals heterostructures for field effect transistor (FET). Based on state-of-the-art theoretical simulations, we show that the intrinsic properties of the 2D halide perovskites are preserved in the heterojunction, which is different from the conventional contact with metal surfaces. The 2D halide perovskites form a p-type Schottky barrier (Φh) contact with graphene, where tunneling barrier exists, and a negative band bending occurs at the lateral interface. We demonstrate that the Schottky barrier can be turned from p-type to n-type by doping graphene with nitrogen atoms, and a low-Φh or an Ohmic contact can be realized by doping graphene with boron atoms or replacing graphene with other high-work-function 2D metallic sheets such as ZT-MoS2, ZT-MoSe2 and H-NbS2. This study not only predicts a 2D halide perovskite-based FETs, but also enhances the understanding of tuning Schottky barrier height in device applications.

  9. Structures of butyl ions formed by electron impact ionization of isomeric butyl halides and alkanes

    International Nuclear Information System (INIS)

    Shold, D.M.; Ausloos, P.

    1978-01-01

    Using a pulsed ion cyclotron resonance (ICR) spectrometer, it is demonstrated that at pressures of about 10 -6 Torr and at observation times ranging from 10 -3 to 0.5 s, isobutane, neopentane, 2,2-dimethylbutane, isobutyl halides, and tert-butyl halides form C 4 H 9 + ions having the tertiary structure. In n-alkanes, 2-methylbutane, 3-methylpentane, n-butyl halides, and sec-butyl halides, both sec-C 4 H 9 + and t-C 4 H 9 + ions are observed, the sec-C 4 H 9 + ions surviving without rearrangement for at least 0.1 s. However, in the case of the halides, a collision-induced isomerization of the sec-C 4 H 9 + to the t-C 4 H 9 + ions occurs. The efficiency of this process increases with the basicity of the alkyl halide. Radiolysis experiments carried out at atmospheric pressures indicate, in agreement with ICR and solution experiments, that at times as short as 10 -10 s the majority of the i-C 4 H 9 + ions from isobutyl bromide rearrange to the t-C 4 H 9 + structure. On the other hand, in the radiolysis of both n-hexane and 3-methylpentane, the abundance of t-C 4 H 9 + relative to sec-C 4 H 9 + is substantially smaller than that observed in the ICR experiments, and decreases with decreasing collision interval. It is suggested that about 90% of the i-C 4 H 9 + can rearrange to t-C 4 H 9 + by simple 1,2-hydride shift without involving secondary or protonated methylcyclopropane structures as intermediates. 4 figures, 2 tables

  10. Dipole-dipole van der Waals interaction in alkali halides

    International Nuclear Information System (INIS)

    Thakur, B.N.; Thakur, K.P.

    1978-01-01

    Values of van der Waals dipole-dipole constants and interaction energetics of alkali halides are reported using the recent data. The values obtained are somewhat larger than those of earlier workers. (orig.) [de

  11. Depletion-mode vertical Ga2O3 trench MOSFETs fabricated using Ga2O3 homoepitaxial films grown by halide vapor phase epitaxy

    Science.gov (United States)

    Sasaki, Kohei; Thieu, Quang Tu; Wakimoto, Daiki; Koishikawa, Yuki; Kuramata, Akito; Yamakoshi, Shigenobu

    2017-12-01

    We developed depletion-mode vertical Ga2O3 trench metal-oxide-semiconductor field-effect transistors by using n+ contact and n- drift layers. These epilayers were grown on an n+ (001) Ga2O3 single-crystal substrate by halide vapor phase epitaxy. Cu and HfO2 were used for the gate metal and dielectric film, respectively. The mesa width and gate length were approximately 2 and 1 µm, respectively. The devices showed good DC characteristics, with a specific on-resistance of 3.7 mΩ cm2 and clear current modulation. An on-off ratio of approximately 103 was obtained.

  12. Lead Halide Perovskite Nanocrystals in the Research Spotlight: Stability and Defect Tolerance

    Science.gov (United States)

    2017-01-01

    This Perspective outlines basic structural and optical properties of lead halide perovskite colloidal nanocrystals, highlighting differences and similarities between them and conventional II–VI and III–V semiconductor quantum dots. A detailed insight into two important issues inherent to lead halide perovskite nanocrystals then follows, namely, the advantages of defect tolerance and the necessity to improve their stability in environmental conditions. The defect tolerance of lead halide perovskites offers an impetus to search for similar attributes in other related heavy metal-free compounds. We discuss the origins of the significantly blue-shifted emission from CsPbBr3 nanocrystals and the synthetic strategies toward fabrication of stable perovskite nanocrystal materials with emission in the red and infrared parts of the optical spectrum, which are related to fabrication of mixed cation compounds guided by Goldschmidt tolerance factor considerations. We conclude with the view on perspectives of use of the colloidal perovskite nanocrystals for applications in backlighting of liquid-crystal TV displays. PMID:28920080

  13. Calcium phosphate cements with strontium halides as radiopacifiers.

    Science.gov (United States)

    López, Alejandro; Montazerolghaem, Maryam; Engqvist, Håkan; Ott, Marjam Karlsson; Persson, Cecilia

    2014-02-01

    High radiopacity is required to monitor the delivery and positioning of injectable implants. Inorganic nonsoluble radiopacifiers are typically used in nondegradable bone cements; however, their usefulness in resorbable cements is limited due to their low solubility. Strontium halides, except strontium fluoride, are ionic water-soluble compounds that possess potential as radiopacifiers. In this study, we compare the radiopacity, mechanical properties, composition, and cytotoxicity of radiopaque brushite cements prepared with strontium fluoride (SrF2 ), strontium chloride (SrCl2 ·6H2 O), strontium bromide (SrBr2 ), or strontium iodide (SrI2 ). Brushite cements containing 10 wt % SrCl2 ·6H2 O, SrBr2 , or SrI2 exhibited equal to or higher radiopacity than commercial radiopaque cements. Furthermore, the brushite crystal lattice in cements that contained the ionic radiopacifiers was larger than in unmodified cements and in cements that contained SrF2 , indicating strontium substitution. Despite the fact that the strontium halides increased the solubility of the cements and affected their mechanical properties, calcium phosphate cements containing SrCl2 ·6H2 O, SrBr2 , and SrI2 showed no significant differences in Saos-2 cell viability and proliferation with respect to the control. Strontium halides: SrCl2 ·6H2 O, SrBr2 , and SrI2 may be potential candidates as radiopacifiers in resorbable biomaterials although their in vivo biocompatibility, when incorporated into injectable implants, is yet to be assessed. Copyright © 2013 Wiley Periodicals, Inc.

  14. Sodium-metal halide and sodium-air batteries.

    Science.gov (United States)

    Ha, Seongmin; Kim, Jae-Kwang; Choi, Aram; Kim, Youngsik; Lee, Kyu Tae

    2014-07-21

    Impressive developments have been made in the past a few years toward the establishment of Na-ion batteries as next-generation energy-storage devices and replacements for Li-ion batteries. Na-based cells have attracted increasing attention owing to low production costs due to abundant sodium resources. However, applications of Na-ion batteries are limited to large-scale energy-storage systems because of their lower energy density compared to Li-ion batteries and their potential safety problems. Recently, Na-metal cells such as Na-metal halide and Na-air batteries have been considered to be promising for use in electric vehicles owing to good safety and high energy density, although less attention is focused on Na-metal cells than on Na-ion cells. This Minireview provides an overview of the fundamentals and recent progress in the fields of Na-metal halide and Na-air batteries, with the aim of providing a better understanding of new electrochemical systems. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Local polar fluctuations in lead halide perovskites

    Science.gov (United States)

    Tan, Liang; Yaffe, Omer; Guo, Yinsheng; Brus, Louis; Rappe, Andrew; Egger, David; Kronik, Leeor

    The lead halide perovskites have recently attracted much attention because of their large and growing photovoltaic power conversion efficiencies. However, questions remain regarding the temporal and spatial correlations of the structural fluctuations, their atomistic nature, and how they affect electronic and photovoltaic properties. To address these questions, we have performed a combined ab initio molecular dynamics (MD) and density functional theory (DFT) study on CsPbBr3. We have observed prevalent anharmonic motion in our MD trajectories, with local polar fluctuations involving head-to-head motion of A-site Cs cations coupled with Br window opening. We calculate Raman spectra from the polarizability auto-correlation functions obtained from these trajectories and show that anharmonic A-site cation motion manifests as a broad central peak in the Raman spectrum, which increases in intensity with temperature. A comparison of the experimental Raman spectrum of hybrid organometallic MAPbBr3 and fully inorganic CsPbBr3 suggests that structural fluctuations in lead-halide perovskites is more general than rotation of polar organic cations and is intimately coupled to the inorganic framework.

  16. The role of halide ions on the electrochemical behaviour of iron in alkali solutions

    Science.gov (United States)

    Begum, S. Nathira; Muralidharan, V. S.; Basha, C. Ahmed

    2008-02-01

    Active dissolution and passivation of transition metals in alkali solutions is of technological importance in batteries. The performance of alkaline batteries is decided by the presence of halides as they influence passivation. Cyclic voltammetric studies were carried out on iron in different sodium hydroxide solutions in presence of halides. In alkali solutions iron formed hydroxo complexes and their polymers in the interfacial diffusion layer. With progress of time they formed a cation selective layer. The diffusion layer turned into bipolar ion selective layer consisted of halides, a selective inner sublayer to the metal side and cation selective outer layer to the solution side. At very high anodic potentials, dehydration and deprotonation led to the conversion of salt layer into an oxide.

  17. Abiotic Formation of Methyl Halides in the Terrestrial Environment

    Science.gov (United States)

    Keppler, F.

    2011-12-01

    Methyl chloride and methyl bromide are the most abundant chlorine and bromine containing organic compounds in the atmosphere. Since both compounds have relatively long tropospheric lifetimes they can effectively transport halogen atoms from the Earth's surface, where they are released, to the stratosphere and following photolytic oxidation form reactive halogen gases that lead to the chemical destruction of ozone. Methyl chloride and methyl bromide account for more than 20% of the ozone-depleting halogens delivered to the stratosphere and are predicted to grow in importance as the chlorine contribution to the stratosphere from anthropogenic CFCs decline. Today methyl chloride and methyl bromide originate mainly from natural sources with only a minor fraction considered to be of anthropogenic origin. However, until as recently as 2000 most of the methyl chloride and methyl bromide input to the atmosphere was considered to originate from the oceans, but investigations in recent years have clearly demonstrated that terrestrial sources such as biomass burning, wood-rotting fungi, coastal salt marshes, tropical vegetation and organic matter degradation must dominate the atmospheric budgets of these trace gases. However, many uncertainties still exist regarding strengths of both sources and sinks, as well as the mechanisms of formation of these naturally occurring halogenated gases. A better understanding of the atmospheric budget of both methyl chloride and methyl bromide is therefore required for reliable prediction of future ozone depletion. Biotic and abiotic methylation processes of chloride and bromide ion are considered to be the dominant pathways of formation of these methyl halides in nature. In this presentation I will focus on abiotic formation processes in the terrestrial environment and the potential parameters that control their emissions. Recent advances in our understanding of the abiotic formation pathway of methyl halides will be discussed. This will

  18. The impact of alkali metal halide electron donor complexes in the photocatalytic degradation of pentachlorophenol

    Energy Technology Data Exchange (ETDEWEB)

    Khuzwayo, Z., E-mail: zack.khuzwayo@up.ac.za; Chirwa, E.M.N

    2017-01-05

    Highlights: • Facilitation of photocatalysis using simple metal-halides as VB hole scavengers. • Recombination prevention by coupled valence and conduction band approaches. • Determination of anions critical levels beyond which process retardation occurs. • Determination of the photocatalytic process rate of reaction kinetics. - Abstract: The performance of photocatalytic oxidation of chemical pollutants is subjected to the presence of anion complexes in natural waters. This study investigated the influence of alkali metal (Na{sup +} (sodium), K{sup +} (potassium)) halides (Cl{sup −} (chloride), Br{sup −} (bromide), F{sup −} (fluoride)) as inorganic ion sources in the photocatalytic degradation of pentachlorophenol (PCP) in batch systems. It was found that the exclusive presence of halides in the absence of an electron acceptor adequately facilitated the photocatalyst process below critical levels of anion populations, where beyond the critical point the process was significantly hindered. Below the determined critical point, the performance in some cases near matches that of the facilitation of the photocatalytic process by exclusive oxygen, acting as an electron scavenger. The coupling of halide ions and oxygenation presented significantly improved photo-oxidation of PCP, this was confirmed by the inclusion of formic acid as a comparative electron donor. The Langmuir-Hinshelwood kinetic expression was used to calculate the performance rate kinetics. The probable impact of the halide anions was discussed with regards to the process of electron hole pair recombination prevention.

  19. Solution-Phase Synthesis of Cesium Lead Halide Perovskite Nanowires.

    Science.gov (United States)

    Zhang, Dandan; Eaton, Samuel W; Yu, Yi; Dou, Letian; Yang, Peidong

    2015-07-29

    Halide perovskites have attracted much attention over the past 5 years as a promising class of materials for optoelectronic applications. However, compared to hybrid organic-inorganic perovskites, the study of their pure inorganic counterparts, like cesium lead halides (CsPbX3), lags far behind. Here, a catalyst-free, solution-phase synthesis of CsPbX3 nanowires (NWs) is reported. These NWs are single-crystalline, with uniform growth direction, and crystallize in the orthorhombic phase. Both CsPbBr3 and CsPbI3 are photoluminescence active, with composition-dependent temperature and self-trapping behavior. These NWs with a well-defined morphology could serve as an ideal platform for the investigation of fundamental properties and the development of future applications in nanoscale optoelectronic devices based on all-inorganic perovskites.

  20. Development of alkali halide-optics for high power-IR laser

    International Nuclear Information System (INIS)

    Pohl, L.

    1989-01-01

    In this work 'Development of Alkali Halide-Optics for High Power-IR Laser' we investigated the purification of sodiumchloride-, potassiumchloride- and potassiumbromide-raw materials. We succeeded to reduce the content of impurities like Cu, Pb, V, Cr, Mn, Fe, Co and Ni in these raw materials to the lower of ppb's by a Complex-Adsorption-Method (CAM). Crystals were grown from purified substances by 'Kyropoulos' method'. Windows were cur thereof, polished and measured by FTIR-spectroscopy. Analytical data showed, that the resulting crystals were of lower quality than the raw materials. Because of this fact crystal-growing-conditions have to undergo a special improvement. Alkali halide windows from other sources on the market had been tested. (orig.) [de

  1. Spectroscopic investigation of indium halides as substitudes of mercury in low pressure discharges for lighting applications

    Energy Technology Data Exchange (ETDEWEB)

    Briefi, Stefan

    2012-05-22

    Low pressure discharges with indium halides as radiator are discussed as substitutes for hazardous mercury in conventional fluorescent lamps. In this work, the applicability of InBr and InCl in a low pressure discharge light source is investigated. The aim is to identify and understand the physical processes which determine the discharge characteristics and the efficiency of the generated near-UV emission of the indium halide molecule and of the indium atom which is created due to dissociation processes in the plasma. As discharge vessels sealed cylindrical quartz glass tubes which contain a defined amount of indium halide and a rare gas are used. Preliminary investigations showed that for a controlled variation of the indium halide density a well-defined cold spot setup is mandatory. This was realized in the utilized experimental setup. The use of metal halides raises the issue, that power coupling by internal electrodes is not possible as the electrodes would quickly be eroded by the halides. The comparison of inductive and capacitive RF-coupling with external electrodes revealed that inductively coupled discharges provide higher light output and much better long term stability. Therefore, all investigations are carried out using inductive RF-coupling. The diagnostic methods optical emission and white light absorption spectroscopy are applied. As the effects of absorption-signal saturation and reabsorption of emitted radiation within the plasma volume could lead to an underestimation of the determined population densities by orders of magnitude, these effects are considered in the data evaluation. In order to determine the electron temperature and the electron density from spectroscopic measurements, an extended corona model as population model of the indium atom has been set up. A simulation of the molecular emission spectra has been implemented to investigate the rovibrational population processes of the indium halide molecules. The impact of the cold spot

  2. Thermomechanical measurements of lead halide single crystals

    Czech Academy of Sciences Publication Activity Database

    Nitsch, Karel; Rodová, Miroslava

    2002-01-01

    Roč. 234, č. 2 (2002), s. 701-709 ISSN 0370-1972 R&D Projects: GA AV ČR IAA2010926 Institutional research plan: CEZ:AV0Z1010914 Keywords : PbX 2 (X=Cl, Br, I) * coefficients of linear thermal expansion * polymorphism in lead halides Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.930, year: 2002

  3. Dislocation unpinning model of acoustic emission from alkali halide ...

    Indian Academy of Sciences (India)

    The present paper reports the dislocation unpinning model of acoustic emis- sion (AE) from ... Acoustic emission; dislocation; alkali halide crystals; plastic deformation. ..... [5] T Nishimura, A Tahara and T Kolama, Jpn. Metal Inst. 64, 339 (2000).

  4. Effect of tissue heterogeneity on quantification in positron emission tomography

    International Nuclear Information System (INIS)

    Blomqvist, G.; Lammertsma, A.A.; Mazoyer, B.; Wienhard, K.

    1995-01-01

    As a result of the limited spatial resolution of positron emission tomographic scanners, the measurements of physiological parameters are compromised by tissue heterogeneity. The effect of tissue heterogeneity on a number of parameters was studied by simulation and an analytical method. Five common tracer models were assessed. The input and tissue response functions were assumed to be free from noise and systematic errors. The kinetic model was assumed to be perfect. Two components with different kinetics were mixed in different proportions and contrast with respect to the model parameters. Different experimental protocols were investigated. Of three methods investigated for the measurement of cerebral blood flow (CBF) (steady state, dynamic, integral), the second one was least sensitive to errors caused by tissue heterogeneity and the main effect was an underestimation of the distribution volume. With the steady state method, errors in oxygen extraction fraction caused by tissue heterogeneity were always found to be less than the corresponding errors in CBF. For myocardial blood flow the steady state method was found to perform better than the bolus method. The net accumulation of substrate (i.e. rCMR glc in the case of glucose analogs) was found to be comparatively insensitive to tissue heterogeneity. Individual rate constans such as k 2 and k 3 for efflux and metabolism of the substrate in the pool of unmetabolized substrate in the tissue, respectively, were found to be more sensitive. In studies of radioligand binding, using only tracer doses, the effect of tissue heterogeneity on the parameter k on .B max could be considerable. In studies of radioligand binding using a protocol with two experiments, one with high and one with low specific activity, B max was found to be insensitive while K d was very sensitive to tissue heterogeneity. (orig.)

  5. Effect of tissue heterogeneity on quantification in positron emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Blomqvist, G [Dept. of Clinical Neuroscience, Experimental Alcohol and Drug Addiction Research Section, Karolinska Hospital, Stockholm (Sweden); Lammertsma, A A [PET Methodology Group, Cyclotron Unit, MRC Clinical Sciences Centre, Royal Postgraduate Medical School, Hammersmith Hospital, London (United Kingdom); Mazoyer, B [Service Hospitalier Frederic Joliot CEA/Dept. de Biologie, Hopital d` Orsay and Antenne d` Informatique Medicale, Hopital Robert Debre, Paris (France); Wienhard, K [Max-Planck-Inst. fuer Neurologische Forschung, Koeln (Germany)

    1995-07-01

    As a result of the limited spatial resolution of positron emission tomographic scanners, the measurements of physiological parameters are compromised by tissue heterogeneity. The effect of tissue heterogeneity on a number of parameters was studied by simulation and an analytical method. Five common tracer models were assessed. The input and tissue response functions were assumed to be free from noise and systematic errors. The kinetic model was assumed to be perfect. Two components with different kinetics were mixed in different proportions and contrast with respect to the model parameters. Different experimental protocols were investigated. Of three methods investigated for the measurement of cerebral blood flow (CBF) (steady state, dynamic, integral), the second one was least sensitive to errors caused by tissue heterogeneity and the main effect was an underestimation of the distribution volume. With the steady state method, errors in oxygen extraction fraction caused by tissue heterogeneity were always found to be less than the corresponding errors in CBF. For myocardial blood flow the steady state method was found to perform better than the bolus method. The net accumulation of substrate (i.e. rCMR{sub glc} in the case of glucose analogs) was found to be comparatively insensitive to tissue heterogeneity. Individual rate constans such as k{sub 2} and k{sub 3} for efflux and metabolism of the substrate in the pool of unmetabolized substrate in the tissue, respectively, were found to be more sensitive. In studies of radioligand binding, using only tracer doses, the effect of tissue heterogeneity on the parameter k{sub on}.B{sub max} could be considerable. In studies of radioligand binding using a protocol with two experiments, one with high and one with low specific activity, B{sub max} was found to be insensitive while K{sub d} was very sensitive to tissue heterogeneity. (orig.)

  6. Alternative route to metal halide free ionic liquids

    International Nuclear Information System (INIS)

    Takao, Koichiro; Ikeda, Yasuhisa

    2008-01-01

    An alternative synthetic route to metal halide free ionic liquids using trialkyloxonium salt is proposed. Utility of this synthetic route has been demonstrated by preparing 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid through the reaction between 1-methylimidazole and triethyloxonium tetra-fluoroborate in anhydrous ether. (author)

  7. The thermo-elastic instability model of melting of alkali halides in the Debye approximation

    Science.gov (United States)

    Owens, Frank J.

    2018-05-01

    The Debye model of lattice vibrations of alkali halides is used to show that there is a temperature below the melting temperature where the vibrational pressure exceeds the electrostatic pressure. The onset temperature of this thermo-elastic instability scales as the melting temperature of NaCl, KCl, and KBr, suggesting its role in the melting of the alkali halides in agreement with a previous more rigorous model.

  8. Wetting of heterogeneous substrates. A classical density-functional-theory approach

    Science.gov (United States)

    Yatsyshin, Peter; Parry, Andrew O.; Rascón, Carlos; Duran-Olivencia, Miguel A.; Kalliadasis, Serafim

    2017-11-01

    Wetting is a nucleation of a third phase (liquid) on the interface between two different phases (solid and gas). In many experimentally accessible cases of wetting, the interplay between the substrate structure, and the fluid-fluid and fluid-substrate intermolecular interactions leads to the appearance of a whole ``zoo'' of exciting interface phase transitions, associated with the formation of nano-droplets/bubbles, and thin films. Practical applications of wetting at small scales are numerous and include the design of lab-on-a-chip devices and superhydrophobic surfaces. In this talk, we will use a fully microscopic approach to explore the phase space of a planar wall, decorated with patches of different hydrophobicity, and demonstrate the highly non-trivial behaviour of the liquid-gas interface near the substrate. We will present fluid density profiles, adsorption isotherms and wetting phase diagrams. Our analysis is based on a formulation of statistical mechanics, commonly known as classical density-functional theory. It provides a computationally-friendly and rigorous framework, suitable for probing small-scale physics of classical fluids and other soft-matter systems. EPSRC Grants No. EP/L027186,EP/K503733;ERC Advanced Grant No. 247031.

  9. Large polarons in lead halide perovskites

    Science.gov (United States)

    Miyata, Kiyoshi; Meggiolaro, Daniele; Trinh, M. Tuan; Joshi, Prakriti P.; Mosconi, Edoardo; Jones, Skyler C.; De Angelis, Filippo; Zhu, X.-Y.

    2017-01-01

    Lead halide perovskites show marked defect tolerance responsible for their excellent optoelectronic properties. These properties might be explained by the formation of large polarons, but how they are formed and whether organic cations are essential remain open questions. We provide a direct time domain view of large polaron formation in single-crystal lead bromide perovskites CH3NH3PbBr3 and CsPbBr3. We found that large polaron forms predominantly from the deformation of the PbBr3− frameworks, irrespective of the cation type. The difference lies in the polaron formation time, which, in CH3NH3PbBr3 (0.3 ps), is less than half of that in CsPbBr3 (0.7 ps). First-principles calculations confirm large polaron formation, identify the Pb-Br-Pb deformation modes as responsible, and explain quantitatively the rate difference between CH3NH3PbBr3 and CsPbBr3. The findings reveal the general advantage of the soft [PbX3]− sublattice in charge carrier protection and suggest that there is likely no mechanistic limitations in using all-inorganic or mixed-cation lead halide perovskites to overcome instability problems and to tune the balance between charge carrier protection and mobility. PMID:28819647

  10. Nanostructure of propylammonium nitrate in the presence of poly(ethylene oxide) and halide salts

    Science.gov (United States)

    Stefanovic, Ryan; Webber, Grant B.; Page, Alister J.

    2018-05-01

    Nanoscale structure of protic ionic liquids is critical to their utility as molecular electrochemical solvents since it determines the capacity to dissolve salts and polymers such as poly(ethylene oxide) (PEO). Here we use quantum chemical molecular dynamics simulations to investigate the impact of dissolved halide anions on the nanostructure of an archetypal nanostructured protic ionic liquid, propylammonium nitrate (PAN), and how this impacts the solvation of a model PEO polymer. At the molecular level, PAN is nanostructured, consisting of charged/polar and uncharged/nonpolar domains. The charged domain consists of the cation/anion charge groups, and is formed by their electrostatic interaction. This domain solvophobically excludes the propyl chains on the cation, which form a distinct, self-assembled nonpolar domain within the liquid. Our simulations demonstrate that the addition of Cl- and Br- anions to PAN disrupts the structure within the PAN charged domain due to competition between nitrate and halide anions for the ammonium charge centre. This disruption increases with halide concentration (up to 10 mol. %). However, at these concentrations, halide addition has little effect on the structure of the PAN nonpolar domain. Addition of PEO to pure PAN also disrupts the structure within the charged domain of the liquid due to hydrogen bonding between the charge groups and the terminal PEO hydroxyl groups. There is little other association between the PEO structure and the surrounding ionic liquid solvent, with strong PEO self-interaction yielding a compact, coiled polymer morphology. Halide addition results in greater association between the ionic liquid charge centres and the ethylene oxide components of the PEO structure, resulting in reduced conformational flexibility, compared to that observed in pure PAN. Similarly, PEO self-interactions increase in the presence of Cl- and Br- anions, compared to PAN, indicating that the addition of halide salts to PAN

  11. Resonant halide perovskite nanoparticles

    Science.gov (United States)

    Tiguntseva, Ekaterina Y.; Ishteev, Arthur R.; Komissarenko, Filipp E.; Zuev, Dmitry A.; Ushakova, Elena V.; Milichko, Valentin A.; Nesterov-Mueller, Alexander; Makarov, Sergey V.; Zakhidov, Anvar A.

    2017-09-01

    The hybrid halide perovskites is a prospective material for fabrication of cost-effective optical devices. Unique perovskites properties are used for solar cells and different photonic applications. Recently, perovskite-based nanophotonics has emerged. Here, we consider perovskite like a high-refractive index dielectric material, which can be considered to be a basis for nanoparticles fabrication with Mie resonances. As a result, we fabricate and study resonant perovskite nanoparticles with different sizes. We reveal, that spherical nanoparticles show enhanced photoluminescence signal. The achieved results lay a cornerstone in the field of novel types of organic-inorganic nanophotonics devices with optical properties improved by Mie resonances.

  12. A Cluster-Bethe lattice treatment for the F-center in alkali-halides

    International Nuclear Information System (INIS)

    Queiroz, S.L.A. de; Koiller, B.; Maffeo, B.; Brandi, H.S.

    1977-01-01

    The electronic structure of the F-center in alkali-halides with the NaCl structure has been studied using the Cluster-Bethe lattice method. The central cluster has been taken as constituted by the vacancy and the nearest- and second- neighbors to it, respectively, cations and anions. The optical transitions have been calculated and compared to experimental data on the location of the peak of the F-absorption band. The agreement obtained indicates that this method may be used to study properties of this defect in alkali halides [pt

  13. Electrochemical specific adsorption of halides on Cu 111, 100, and 211: A Density Functional Theory study

    International Nuclear Information System (INIS)

    McCrum, Ian T.; Akhade, Sneha A.; Janik, Michael J.

    2015-01-01

    The specific adsorption of ions onto electrode surfaces can affect electrocatalytic reactions. Density functional theory is used to investigate the specific adsorption of aqueous F − , Cl − , Br − , and I − onto Cu (111), (100), and (211) surfaces. The adsorption is increasingly favorable in the order of F − < Cl − < Br − < I − . The adsorption has a weak dependence on the surface facet, with adsorption most favorable on Cu (100) and least favorable on Cu (111). Potential ranges where specific adsorption would be expected on each facet are reported. The thermodynamics of bulk copper halide (CuX, CuX 2 ) formation are also investigated as a function of potential. CuX formation occurs at potentials slightly more positive of halide specific adsorption and of copper oxidation in aqueous electrolytes. Specifically adsorbed halides and bulk CuX may be present during a variety of electrochemical reactions carried out over a Cu electrode in halide containing electrolyte solutions

  14. First-principles study of γ-ray detector materials in perovskite halides

    Science.gov (United States)

    Im, Jino; Jin, Hosub; Stoumpos, Constantinos; Chung, Duck; Liu, Zhifu; Peters, John; Wessels, Bruce; Kanatzidis, Mercouri; Freeman, Arthur

    2013-03-01

    In an effort to search for good γ-ray detector materials, perovskite halide compounds containing heavy elements were investigated. Despite the three-dimensional network of the corner shared octahedra and the extended nature of the outermost shell, its strong ionic character leads to a large band gap, which is one of the essential criteria for γ-ray detector materials. Thus, considering high density and high atomic number, these pervoskite halides are possible candidate for γ-ray detector materials. We performed first-principles calculations to investigate electronic structures and thermodynamic properties of intrinsic defects in the selected perovskite halide, CsPbBr3. The screened-exchange local density approximation scheme was employed to correct the underestimation of the band gap in the LDA method. As a result, the calculated band gap of CsPbBr3 is found to be suitable for γ-ray detection. Furthermore, defect formation energy calculations allow us to predict thermodynamic and electronic properties of possible intrinsic defects, which affect detector efficiency and energy resolution. Supported by the office of Nonproliferation and Verification R &D under Contract No. DE-AC02-06CH11357

  15. Single Crystals of Organolead Halide Perovskites: Growth, Characterization, and Applications

    KAUST Repository

    Peng, Wei

    2017-01-01

    Despite their outstanding charge transport characteristics, organolead halide perovskite single crystals grown by hitherto reported crystallization methods are not suitable for most optoelectronic devices due to their small aspect ratios

  16. Highly Efficient Broadband Yellow Phosphor Based on Zero-Dimensional Tin Mixed-Halide Perovskite.

    Science.gov (United States)

    Zhou, Chenkun; Tian, Yu; Yuan, Zhao; Lin, Haoran; Chen, Banghao; Clark, Ronald; Dilbeck, Tristan; Zhou, Yan; Hurley, Joseph; Neu, Jennifer; Besara, Tiglet; Siegrist, Theo; Djurovich, Peter; Ma, Biwu

    2017-12-27

    Organic-inorganic hybrid metal halide perovskites have emerged as a highly promising class of light emitters, which can be used as phosphors for optically pumped white light-emitting diodes (WLEDs). By controlling the structural dimensionality, metal halide perovskites can exhibit tunable narrow and broadband emissions from the free-exciton and self-trapped excited states, respectively. Here, we report a highly efficient broadband yellow light emitter based on zero-dimensional tin mixed-halide perovskite (C 4 N 2 H 14 Br) 4 SnBr x I 6-x (x = 3). This rare-earth-free ionically bonded crystalline material possesses a perfect host-dopant structure, in which the light-emitting metal halide species (SnBr x I 6-x 4- , x = 3) are completely isolated from each other and embedded in the wide band gap organic matrix composed of C 4 N 2 H 14 Br - . The strongly Stokes-shifted broadband yellow emission that peaked at 582 nm from this phosphor, which is a result of excited state structural reorganization, has an extremely large full width at half-maximum of 126 nm and a high photoluminescence quantum efficiency of ∼85% at room temperature. UV-pumped WLEDs fabricated using this yellow emitter together with a commercial europium-doped barium magnesium aluminate blue phosphor (BaMgAl 10 O 17 :Eu 2+ ) can exhibit high color rendering indexes of up to 85.

  17. Correlations between entropy and volume of melting in halide salts

    International Nuclear Information System (INIS)

    Akdeniz, Z.; Tosi, M.P.

    1991-09-01

    Melting parameters and transport coefficients in the melt are collated for halides of monovalent, divalent and trivalent metals. A number of systems show a deficit of entropy of melting relative to the linear relationships between entropy change and relative volume change on melting that are found to be approximately obeyed by a majority of halides. These behaviours are discussed on the basis of structural and transport data. The deviating systems are classified into three main classes, namely (i) fast-ion conductors in the high-temperature crystal phase such as AgI, (ii) strongly structured network-like systems such as ZnCl 2 , and (iii) molecular systems melting into associated molecular liquids such as SbCl 3 . (author). 35 refs, 1 fig., 3 tabs

  18. A signal-substrate match in the substrate-borne component of a multimodal courtship display

    Directory of Open Access Journals (Sweden)

    Damian O. ELIAS, Andrew C. MASON, Eileen A. HEBETS

    2010-06-01

    Full Text Available The environment can impose strong limitations on the efficacy of signal transmission. In particular, for vibratory communication, the signaling environment is often extremely heterogeneous at very small scales. Nevertheless, natural selection is expected to select for signals well-suited to effective transmission. Here, we test for substrate-dependent signal efficacy in the wolf spider Schizocosa stridulans Stratton 1991. We first explore the transmission characteristics of this important signaling modality by playing recorded substrate-borne signals through three different substrates (leaf litter, pine litter, and red clay and measuring the propagated signal. We found that the substrate-borne signal of S. stridulans attenuates the least on leaf litter, the substrate upon which the species is naturally found. Next, by assessing mating success with artificially muted and non-muted males across different signaling substrates (leaf litter, pine litter, and sand, we explored the relationship between substrate-borne signaling and substrate for mating success. We found that muted males were unsuccessful in obtaining copulations regardless of substrate, while mating success was dependent on the signaling substrate for non-muted males. For non-muted males, more males copulated on leaf litter than any other substrate. Taken together, these results confirm the importance of substrate-borne signaling in S. stridulans and suggest a match between signal properties and signal efficacy – leaf litter transmits the signal most effectively and males are most successful in obtaining copulations on leaf litter [Current Zoology 56 (3: 370–378, 2010].

  19. Influence of electrode, buffer gas and control gear on metal halide lamp performance

    International Nuclear Information System (INIS)

    Lamouri, A; Naruka, A; Sulcs, J; Varanasi, C V; Brumleve, T R

    2005-01-01

    In this paper the influence of electrode composition, buffer gas fill pressure and control gear on the performance of metal halide lamps is investigated. It is shown that pure tungsten electrodes improve lumen maintenance and reduce voltage rise over lamp life. An optimum buffer gas fill pressure condition is discovered which allows for reduced electrode erosion during lamp starting as well as under normal operating conditions. Use of electronic control gear is shown to improve the performance of metal halide lamps

  20. Reversible photo-induced trap formation in mixed-halide hybrid perovskites for photovoltaics.

    Science.gov (United States)

    Hoke, Eric T; Slotcavage, Daniel J; Dohner, Emma R; Bowring, Andrea R; Karunadasa, Hemamala I; McGehee, Michael D

    2015-01-01

    We report on reversible, light-induced transformations in (CH 3 NH 3 )Pb(Br x I 1- x ) 3 . Photoluminescence (PL) spectra of these perovskites develop a new, red-shifted peak at 1.68 eV that grows in intensity under constant, 1-sun illumination in less than a minute. This is accompanied by an increase in sub-bandgap absorption at ∼1.7 eV, indicating the formation of luminescent trap states. Light soaking causes a splitting of X-ray diffraction (XRD) peaks, suggesting segregation into two crystalline phases. Surprisingly, these photo-induced changes are fully reversible; the XRD patterns and the PL and absorption spectra revert to their initial states after the materials are left for a few minutes in the dark. We speculate that photoexcitation may cause halide segregation into iodide-rich minority and bromide-enriched majority domains, the former acting as a recombination center trap. This instability may limit achievable voltages from some mixed-halide perovskite solar cells and could have implications for the photostability of halide perovskites used in optoelectronics.

  1. On the Boiling Points of the Alkyl Halides.

    Science.gov (United States)

    Correia, John

    1988-01-01

    Discusses the variety of explanations in organic chemistry textbooks of a physical property of organic compounds. Focuses on those concepts explaining attractive forces between molecules. Concludes that induction interactions play a major role in alkyl halides and other polar organic molecules and should be given wider exposure in chemistry texts.…

  2. Binuclear trivalent and tetravalent uranium halides and cyanides supported by cyclooctatetraene ligands

    International Nuclear Information System (INIS)

    Wang, Cong-Zhi; Wu, Qun-Yan; Lan, Jian-Hui; Shi, Wei-Qun; Gibson, John K.

    2017-01-01

    Although the first organoactinide chloride Cp_3UCl (Cp = η"5-C_5H_5) was synthesized more than 50 years ago, binuclear uranium halides remain very rare in organoactinide chemistry. Herein, a series of binuclear trivalent and tetravalent uranium halides and cyanides with cyclooctatetraene ligands, (COT)_2U_2X_n (COT = η"8-C_8H_8; X=F, Cl, CN; n=2, 4), have been systematically studied using scalar-relativistic density functional theory (DFT). The structures with bridging halide or cyanide ligands were predicted to be the most stable complexes of (COT)_2U_2X_n, and all the complexes show weak antiferromagnetic interactions between the uranium centers. However, for each species, there is no significant uranium-uranium bonding interaction. The bonding between the metal and the ligands shows some degree of covalent character, especially between the metal and terminal halide or cyanide ligands. The U-5f and 6d orbitals are predominantly involved in the metal-ligand bonding. All the (COT)_2U_2X_n species were predicted to be more stable compared to the mononuclear half-sandwich complexes at room temperature in the gas phase such that (COT)_2U_2X_4 might be accessible through the known (COT)_2U complex. The tetravalent derivatives (COT)_2U_2X_4 are more energetically favorable than the trivalent (COT)_2U_2X_2 analogs, which may be attributed to the greater number of strong metal-ligand bonds in the former complexes.

  3. Physicochemical properties of mixed phosphorus halides

    International Nuclear Information System (INIS)

    Sladkov, I.B.; Tugarinova, N.S.

    1996-01-01

    Certain physicochemical properties (thermodynamic characteristics at boiling point, critical constants, density of liquid on the saturation line) of mixed phosphorus halides (PI 3 , PI 2 F, PIF 2 , PI 2 Cl, PICl 2 , PI 1 Br, PIBr 2 , PIClF, PIBrCl, etc.) are determined by means of approximate methods. Reliability of the results obtained is confirmed by comparison of calculated and experimental data for phosphorus compounds of the same type. 7 refs., 3 figs., 4 tabs

  4. A SUBSTRATE AND A METHOD FOR DETERMINING AND/OR MONITORING ELECTROPHYSIOLOGICAL PROPERTIES OF ION CHANNELS

    DEFF Research Database (Denmark)

    2001-01-01

    The present invention relates to a substrate and a method for obtaining an electrophysiological measuring configuration in which a cell forms a high resistive seal (giga-seal) around a measuring electrode making it suitable for determining and monitoring a current flow through the cell membrane...... and reference electrodes formed by wafer processing technology. The electrodes are adapted to conduct a current between them by delivery of ions by one electrode and receipt of ions by the other electrode and are typically silver/silver halide electrodes. This allows for effective and fast measuring of cells...

  5. Chemical Origin of the Stability Difference between Copper(I)- and Silver(I)-Based Halide Double Perovskites.

    Science.gov (United States)

    Xiao, Zewen; Du, Ke-Zhao; Meng, Weiwei; Mitzi, David B; Yan, Yanfa

    2017-09-25

    Recently, Cu I - and Ag I -based halide double perovskites have been proposed as promising candidates for overcoming the toxicity and instability issues inherent within the emerging Pb-based halide perovskite absorbers. However, up to date, only Ag I -based halide double perovskites have been experimentally synthesized; there are no reports on successful synthesis of Cu I -based analogues. Here we show that, owing to the much higher energy level for the Cu 3d 10 orbitals than for the Ag 4d 10 orbitals, Cu I atoms energetically favor 4-fold coordination, forming [CuX 4 ] tetrahedra (X=halogen), but not 6-fold coordination as required for [CuX 6 ] octahedra. In contrast, Ag I atoms can have both 6- and 4-fold coordinations. Our density functional theory calculations reveal that the synthesis of Cu I halide double perovskites may instead lead to non-perovskites containing [CuX 4 ] tetrahedra, as confirmed by our material synthesis efforts. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Heterogeneous composite bodies with isolated lenticular shaped cermet regions

    Science.gov (United States)

    Sherman, Andrew J [Cirtland Hills, OH

    2009-12-22

    A heterogeneous body having ceramic rich cermet regions in a more ductile metal matrix. The heterogeneous bodies are formed by thermal spray operations on metal substrates. The thermal spray operations apply heat to a cermet powder and project it onto a solid substrate. The cermet powder is composed of complex composite particles in which a complex ceramic-metallic core particle is coated with a matrix precursor. The cermet regions are generally comprised of complex ceramic-metallic composites that correspond approximately to the core particles. The cermet regions are approximately lenticular shaped with an average width that is at least approximately twice the average thickness. The cermet regions are imbedded within the matrix phase and generally isolated from one another. They have obverse and reverse surfaces. The matrix phase is formed from the matrix precursor coating on the core particles. The amount of heat applied during the formation of the heterogeneous body is controlled so that the core particles soften but do not become so fluid that they disperse throughout the matrix phase. The force of the impact on the surface of the substrate tends to flatten them. The flattened cermet regions tend to be approximately aligned with one another in the body.

  7. Emerging heterogeneous integrated photonic platforms on silicon

    Directory of Open Access Journals (Sweden)

    Fathpour Sasan

    2015-05-01

    Full Text Available Silicon photonics has been established as a mature and promising technology for optoelectronic integrated circuits, mostly based on the silicon-on-insulator (SOI waveguide platform. However, not all optical functionalities can be satisfactorily achieved merely based on silicon, in general, and on the SOI platform, in particular. Long-known shortcomings of silicon-based integrated photonics are optical absorption (in the telecommunication wavelengths and feasibility of electrically-injected lasers (at least at room temperature. More recently, high two-photon and free-carrier absorptions required at high optical intensities for third-order optical nonlinear effects, inherent lack of second-order optical nonlinearity, low extinction ratio of modulators based on the free-carrier plasma effect, and the loss of the buried oxide layer of the SOI waveguides at mid-infrared wavelengths have been recognized as other shortcomings. Accordingly, several novel waveguide platforms have been developing to address these shortcomings of the SOI platform. Most of these emerging platforms are based on heterogeneous integration of other material systems on silicon substrates, and in some cases silicon is integrated on other substrates. Germanium and its binary alloys with silicon, III–V compound semiconductors, silicon nitride, tantalum pentoxide and other high-index dielectric or glass materials, as well as lithium niobate are some of the materials heterogeneously integrated on silicon substrates. The materials are typically integrated by a variety of epitaxial growth, bonding, ion implantation and slicing, etch back, spin-on-glass or other techniques. These wide range of efforts are reviewed here holistically to stress that there is no pure silicon or even group IV photonics per se. Rather, the future of the field of integrated photonics appears to be one of heterogenization, where a variety of different materials and waveguide platforms will be used for

  8. Photovoltaic Rudorffites: Lead-Free Silver Bismuth Halides Alternative to Hybrid Lead Halide Perovskites.

    Science.gov (United States)

    Turkevych, Ivan; Kazaoui, Said; Ito, Eisuke; Urano, Toshiyuki; Yamada, Koji; Tomiyasu, Hiroshi; Yamagishi, Hideo; Kondo, Michio; Aramaki, Shinji

    2017-10-09

    Hybrid CPbX 3 (C: Cs, CH 3 NH 3 ; X: Br, I) perovskites possess excellent photovoltaic properties but are highly toxic, which hinders their practical application. Unfortunately, all Pb-free alternatives based on Sn and Ge are extremely unstable. Although stable and non-toxic C 2 ABX 6 double perovskites based on alternating corner-shared AX 6 and BX 6 octahedra (A=Ag, Cu; B=Bi, Sb) are possible, they have indirect and wide band gaps of over 2 eV. However, is it necessary to keep the corner-shared perovskite structure to retain good photovoltaic properties? Here, we demonstrate another family of photovoltaic halides based on edge-shared AX 6 and BX 6 octahedra with the general formula A a B b X x (x=a+3 b) such as Ag 3 BiI 6 , Ag 2 BiI 5 , AgBiI 4 , AgBi 2 I 7 . As perovskites were named after their prototype oxide CaTiO 3 discovered by Lev Perovski, we propose to name these new ABX halides as rudorffites after Walter Rüdorff, who discovered their prototype oxide NaVO 2 . We studied structural and optoelectronic properties of several highly stable and promising Ag-Bi-I photovoltaic rudorffites that feature direct band gaps in the range of 1.79-1.83 eV and demonstrated a proof-of-concept FTO/c-m-TiO 2 /Ag 3 BiI 6 /PTAA/Au (FTO: fluorine-doped tin oxide, PTAA: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], c: compact, m: mesoporous) solar cell with photoconversion efficiency of 4.3 %. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Advances and Promises of Layered Halide Hybrid Perovskite Semiconductors

    NARCIS (Netherlands)

    Pedesseau, Laurent; Sapori, Daniel; Traore, Boubacar; Robles, Roberto; Fang, Hong-Hua; Loi, Maria Antonietta; Tsai, Hsinhan; Nie, Wanyi; Blancon, Jean-Christophe; Neukirch, Amanda; Tretiak, Sergei; Mohite, Aditya D.; Katan, Claudine; Even, Jacky; Kepenekian, Mikael

    2016-01-01

    Layered halide hybrid organic inorganic perovskites (HOP) have been the subject of intense investigation before the rise of three-dimensional (3D) HOP and their impressive performance in solar cells. Recently, layered HOP have also been proposed as attractive alternatives for photostable solar cells

  10. Strong Carrier-Phonon Coupling in Lead Halide Perovskite Nanocrystals

    NARCIS (Netherlands)

    Iaru, Claudiu M; Geuchies, Jaco J|info:eu-repo/dai/nl/370526090; Koenraad, Paul M; Vanmaekelbergh, Daniël|info:eu-repo/dai/nl/304829137; Silov, Andrei Yu

    2017-01-01

    We highlight the importance of carrier-phonon coupling in inorganic lead halide perovskite nanocrystals. The low-temperature photoluminescence (PL) spectrum of CsPbBr3 has been investigated under a nonresonant and a nonstandard, quasi-resonant excitation scheme, and phonon replicas of the main PL

  11. Homocoupling of aryl halides in flow: Space integration of lithiation and FeCl3 promoted homocoupling

    Directory of Open Access Journals (Sweden)

    Aiichiro Nagaki

    2011-08-01

    Full Text Available The use of FeCl3 resulted in a fast homocoupling of aryllithiums, and this enabled its integration with the halogen–lithium exchange reaction of aryl halides in a flow microreactor. This system allows the homocoupling of two aryl halides bearing electrophilic functional groups, such as CN and NO2, in under a minute.

  12. Self-trapped holes in alkali silver halide crystals

    International Nuclear Information System (INIS)

    Awano, T.; Ikezawa, M.; Matsuyama, T.

    1995-01-01

    γ-Ray irradiation at 77 K induces defects in M 2 AgX 3 (M=Rb, K and NH 4 ; X=Br and I) crystals. The irradiation induces self-trapped holes of the form of I 0 in the case of alkali silver iodides, and (halogen) 2 - and (halogen) 0 in the case of ammonium silver halides. The (halogen) 0 is weakly coupled with the nearest alkali metal ion or ammonium ion. It is able to be denoted as RbI + , KI + , NH 4 I + or NH 4 Br + . The directions of hole distribution of (halogen) 2 - and (halogen) 0 were different in each case of the alkali silver iodides, ammonium silver halides and mixed crystal of them. The (halogen) 0 decayed at 160 K in annealing process. The (halogen) 2 - was converted into another form of (halogen) 2 - at 250 K and this decayed at 310 K. A formation of metallic layers was observed on the crystal surface parallel with the c-plane of (NH 4 ) 2 AgI 3 irradiated at room temperature. (author)

  13. Large polarons in lead halide perovskites

    OpenAIRE

    Miyata, Kiyoshi; Meggiolaro, Daniele; Trinh, M. Tuan; Joshi, Prakriti P.; Mosconi, Edoardo; Jones, Skyler C.; De Angelis, Filippo; Zhu, X.-Y.

    2017-01-01

    Lead halide perovskites show marked defect tolerance responsible for their excellent optoelectronic properties. These properties might be explained by the formation of large polarons, but how they are formed and whether organic cations are essential remain open questions. We provide a direct time domain view of large polaron formation in single-crystal lead bromide perovskites CH3NH3PbBr3 and CsPbBr3. We found that large polaron forms predominantly from the deformation of the PbBr3 ? framewor...

  14. Halide peroxidase in tissues that interact with bacteria in the host squid Euprymna scolopes.

    Science.gov (United States)

    Small, A L; McFall-Ngai, M J

    1999-03-15

    An enzyme with similarities to myeloperoxidase, the antimicrobial halide peroxidase in mammalian neutrophils, occurs abundantly in the light organ tissue of Euprymna scolopes, a squid that maintains a beneficial association with the luminous bacterium Vibrio fischeri. Using three independent assays typically applied to the analysis of halide peroxidase enzymes, we directly compared the activity of the squid enzyme with that of human myeloperoxidase. One of these methods, the diethanolamine assay, confirmed that the squid peroxidase requires halide ions for its activity. The identification of a halide peroxidase in a cooperative bacterial association suggested that this type of enzyme can function not only to control pathogens, but also to modulate the interactions of host animals with their beneficial partners. To determine whether the squid peroxidase functions under both circumstances, we examined its distribution in a variety of host tissues, including those that typically interact with bacteria and those that do not. Tissues interacting with bacteria included those that have specific cooperative associations with bacteria (i.e., the light organ and accessory nidamental gland) and those that have transient nonspecific interactions with bacteria (i.e., the gills, which clear the cephalopod circulatory system of invading microorganisms). These bacteria-associated tissues were compared with the eye, digestive gland, white body, and ink-producing tissues, which do not typically interact directly with bacteria. Peroxidase enzyme assays, immunocytochemical localization, and DNA-RNA hybridizations showed that the halide-dependent peroxidase is consistently expressed in high concentration in tissues that interact bacteria. Elevated levels of the peroxidase were also found in the ink-producing tissues, which are known to have enzymatic pathways associated with antimicrobial activity. Taken together, these data suggest that the host uses a common biochemical response to

  15. Effect of annealing on metastable shallow acceptors in Mg-doped GaN layers grown on GaN substrates

    OpenAIRE

    Pozina, Galia; Hemmingsson, Carl; Paskov, Plamen P.; Bergman, Peder; Monemar, Bo; Kawashima, T.; Amano, H.; Akasaki, I.; Usui, A.

    2008-01-01

    Mg-doped GaN layers grown by metal-organic vapor phase epitaxy on GaN substrates produced by the halide vapor phase technique demonstrate metastability of the near-band-gap photoluminescence (PL). The acceptor bound exciton (ABE) line possibly related to the C acceptor vanishes in as-grown samples within a few minutes under UV laser illumination. Annealing activates the more stable Mg acceptors and passivates C acceptors. Consequently, only the ABE line related to Mg is dominant in PL spectra...

  16. Molecular Active Sites in Heterogeneous Ir-La/C-Catalyzed Carbonylation of Methanol to Acetates.

    Science.gov (United States)

    Kwak, Ja Hun; Dagle, Robert; Tustin, Gerald C; Zoeller, Joseph R; Allard, Lawrence F; Wang, Yong

    2014-02-06

    We report that when Ir and La halides are deposited on carbon, exposure to CO spontaneously generates a discrete molecular heterobimetallic structure, containing an Ir-La covalent bond that acts as a highly active, selective, and stable heterogeneous catalyst for the carbonylation of methanol to produce acetic acid. This catalyst exhibits a very high productivity of ∼1.5 mol acetyl/mol Ir·s with >99% selectivity to acetyl (acetic acid and methyl acetate) without detectable loss in activity or selectivity for more than 1 month of continuous operation. The enhanced activity can be mechanistically rationalized by the presence of La within the ligand sphere of the discrete molecular Ir-La heterobimetallic structure, which acts as a Lewis acid to accelerate the normally rate-limiting CO insertion in Ir-catalyzed carbonylation. Similar approaches may provide opportunities for attaining molecular (single site) behavior similar to homogeneous catalysis on heterogeneous surfaces for other industrial applications.

  17. Binuclear trivalent and tetravalent uranium halides and cyanides supported by cyclooctatetraene ligands

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Cong-Zhi; Wu, Qun-Yan; Lan, Jian-Hui; Shi, Wei-Qun [Chinese Academy of Sciences, Beijing (China). Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety; Chai, Zhi-Fang [Chinese Academy of Sciences, Beijing (China). Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety; Soochow Univ., Suzhou (China). School of Radiological and Interdisciplinary Sciences (RAD-X); Gibson, John K. [Lawrence Berkeley National Laboratory, CA (United States). Chemical Sciences Division

    2017-03-01

    Although the first organoactinide chloride Cp{sub 3}UCl (Cp = η{sup 5}-C{sub 5}H{sub 5}) was synthesized more than 50 years ago, binuclear uranium halides remain very rare in organoactinide chemistry. Herein, a series of binuclear trivalent and tetravalent uranium halides and cyanides with cyclooctatetraene ligands, (COT){sub 2}U{sub 2}X{sub n} (COT = η{sup 8}-C{sub 8}H{sub 8}; X=F, Cl, CN; n=2, 4), have been systematically studied using scalar-relativistic density functional theory (DFT). The structures with bridging halide or cyanide ligands were predicted to be the most stable complexes of (COT){sub 2}U{sub 2}X{sub n}, and all the complexes show weak antiferromagnetic interactions between the uranium centers. However, for each species, there is no significant uranium-uranium bonding interaction. The bonding between the metal and the ligands shows some degree of covalent character, especially between the metal and terminal halide or cyanide ligands. The U-5f and 6d orbitals are predominantly involved in the metal-ligand bonding. All the (COT){sub 2}U{sub 2}X{sub n} species were predicted to be more stable compared to the mononuclear half-sandwich complexes at room temperature in the gas phase such that (COT){sub 2}U{sub 2}X{sub 4} might be accessible through the known (COT){sub 2}U complex. The tetravalent derivatives (COT){sub 2}U{sub 2}X{sub 4} are more energetically favorable than the trivalent (COT){sub 2}U{sub 2}X{sub 2} analogs, which may be attributed to the greater number of strong metal-ligand bonds in the former complexes.

  18. Estrogen response of MCF-7 cells grown on diverse substrates and in suspension culture: promotion of morphological heterogeneity, modulation of progestin receptor induction; cell-substrate interactions on collagen gels.

    Science.gov (United States)

    Pourreau-Schneider, N; Berthois, Y; Mittre, H; Charpin, C; Jacquemier, J; Martin, P M

    1984-12-01

    In this study we observed the incidence of hormone sensitivity in the response of MCF-7 cells to estrogen stimulation when the cells were cultured in different contact environments (hydrophilic plastic, bovine corneal extracellular matrix, type I collagen and in suspension culture). The major purpose was to describe the influence of cell to cell and cell to substrate contacts on the morphological response to estrogen treatment. However, other parameters including growth and induction of progestin receptor were also explored, keeping in mind that the MCF-7 cell line, although representative of normal mammary epithelium in that it contains a similar hormone receptivity, was selected in vitro from a metastatic population in a pleural effusion. Although substrate conditions did not modify growth enhancement by estrogens, progestin receptor levels were significantly higher in three-dimensional spheroid cultures in which cell to cell contacts were optimal due to elimination of basal contact. A careful morphological survey of large surfaces lead to an objective opinion of the overall effect of the hormone treatment on the non-cloned cell line in which a marked heterogeneity in the response of individual cells was observed. In terms of morphofunctional differentiation, the edification of acini with dense microvillus coating was best in suspension culture. When sections were made perpendicular to the plane of cultures on collagen gel rafts two other phenomena were noted: decrease in intercellular junctions, resulting in reduced cell to cell cohesion, and accumulation biodegradation products in the collagen lattice. This suggested a hormone-mediated interaction between the metastatic cells and the fibrillar substrate, collagen I, one of the major constituents of tissue stroma. This estrogen response might be related to the metastatic phenotype and must be distinct from their hormone sensitivity in terms of growth and differentiation since hormone receptivity is generally

  19. Empirical formula for the parameters of metallic monovalent halides ...

    African Journals Online (AJOL)

    By collating the data on melting properties and transport coefficients obtained from various experiments and theories for certain halides of monovalent metals, allinclusive linear relationship has been fashioned out. This expression holds between the change in entropy and volume on melting; it is approximately obeyed by ...

  20. Spectroscopy on metal-halide lamps under varying gravity conditions

    NARCIS (Netherlands)

    Flikweert, A.J.

    2008-01-01

    Worldwide, 20% of all electricity is used for lighting. For this reason, efficient lamps are economically and ecologically important. High intensity discharge (HID) lamps are efficient lamps. The most common HID lamp these days is the metal-halide (MH) lamp. MH lamps have a good colour rendering

  1. Dislocation unpinning model of acoustic emission from alkali halide ...

    Indian Academy of Sciences (India)

    AE) from alkali halide crystals. Equations are derived for the strain dependence of the transient AE pulse rate, peak value of the AE pulse rate and the total number of AE pulse emitted. It is found that the AE pulse rate should be maximum for a ...

  2. Halide Perovskites: New Science or ``only'' future Energy Converters?

    Science.gov (United States)

    Cahen, David

    Over the years many new ideas and systems for photovoltaic, PV, solar to electrical energy conversion have been explored, but only a few have really impacted PV's role as a more sustainable, environmentally less problematic and safer source of electrical power than fossil or nuclear fuel-based generation. Will Halide Perovskites, HaPs, be able to join the very select group of commercial PV options? To try to address this question, we put Halide Perovskite(HaP) cells in perspective with respect to other PV cells. Doing so also allows to identify fundamental scientific issues that can be important for PV and beyond. What remains to be seen is if those issues lead to new science or scientific insights or additional use of existing models. Being more specific is problematic, given the fact that this will be 4 months after writing this abstract. Israel National Nano-initiative, Weizmann Institute of Science's Alternative sustainable Energy Research Initiative; Israel Ministries of -Science and of -Infrastructure, Energy & Water.

  3. Double Charged Surface Layers in Lead Halide Perovskite Crystals

    KAUST Repository

    Sarmah, Smritakshi P.

    2017-02-01

    Understanding defect chemistry, particularly ion migration, and its significant effect on the surface’s optical and electronic properties is one of the major challenges impeding the development of hybrid perovskite-based devices. Here, using both experimental and theoretical approaches, we demonstrated that the surface layers of the perovskite crystals may acquire a high concentration of positively charged vacancies with the complementary negatively charged halide ions pushed to the surface. This charge separation near the surface generates an electric field that can induce an increase of optical band gap in the surface layers relative to the bulk. We found that the charge separation, electric field, and the amplitude of shift in the bandgap strongly depend on the halides and organic moieties of perovskite crystals. Our findings reveal the peculiarity of surface effects that are currently limiting the applications of perovskite crystals and more importantly explain their origins, thus enabling viable surface passivation strategies to remediate them.

  4. Aluminum Pitting Corrosion in Halide Media: A Quantum Model and Empirical Evidence

    Science.gov (United States)

    Lashgari, Mohsen; Kianpour, Effat; Mohammadi, Esmaeil

    2013-12-01

    The phenomenon of localized damage of aluminum oxide surface in the presence of halide anions was scrutinized at an atomistic level, through the cluster approach and density functional theory. The phenomenon was also investigated empirically through Tafel polarization plots and scanning electron microscopy. A distinct behavior witnessed in the fluoride medium was justified through the hard-soft acid-base principle. The atomistic investigations revealed the greatest potency for chloride entrance into the metal oxide lattice and rationalized to the severity of damage. The interaction of halide anions with the oxide surface causing some displacements on the position of Al atoms provides a mechanistic insight of the phenomenon.

  5. The nature of dynamic disorder in lead halide perovskite crystals (Conference Presentation)

    Science.gov (United States)

    Yaffe, Omer; Guo, Yinsheng; Hull, Trevor; Stoumpos, Costas; Tan, Liang Z.; Egger, David A.; Zheng, Fan; Szpak, Guilherme; Semonin, Octavi E.; Beecher, Alexander N.; Heinz, Tony F.; Kronik, Leeor; Rappe, Andrew M.; Kanatzidis, Mercouri G.; Owen, Jonathan S.; Pimenta, Marcos A.; Brus, Louis E.

    2016-09-01

    We combine low frequency Raman scattering measurements with first-principles molecular dynamics (MD) to study the nature of dynamic disorder in hybrid lead-halide perovskite crystals. We conduct a comparative study between a hybrid (CH3NH3PbBr3) and an all-inorganic lead-halide perovskite (CsPbBr3). Both are of the general ABX3 perovskite formula, and have a similar band gap and structural phase sequence, orthorhombic at low temperature, changing first to tetragonal and then to cubic symmetry as temperature increases. In the high temperature phases, we find that both compounds show a pronounced Raman quasi-elastic central peak, indicating that both are dynamically disordered.

  6. Organometallic halide perovskite single crystals having low deffect density and methods of preparation thereof

    KAUST Repository

    Bakr, Osman M.

    2016-02-18

    The present disclosure presents a method of making a single crystal organometallic halide perovskites, with the formula: AMX3, wherein A is an organic cation, M is selected from the group consisting of: Pb, Sn, Cu, Ni, Co, Fe, Mn, Pd, Cd, Ge, and Eu, and X is a halide. The method comprises the use of two reservoirs containing different precursors and allowing the vapor diffusion from one reservoir to the other one. A solar cell comprising said crystal is also disclosed.

  7. Infrared Dielectric Screening Determines the Low Exciton Binding Energy of Metal-Halide Perovskites.

    Science.gov (United States)

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

    2018-02-01

    The performance of lead-halide perovskites in optoelectronic devices is due to a unique combination of factors, including highly efficient generation, transport, and collection of photogenerated charge carriers. The mechanism behind efficient charge generation in lead-halide perovskites is still largely unknown. Here, we investigate the factors that influence the exciton binding energy (E b ) in a series of metal-halide perovskites using accurate first-principles calculations based on solution of the Bethe-Salpeter equation, coupled to ab initio molecular dynamics simulations. We find that E b is strongly modulated by screening from low-energy phonons, which account for a factor ∼2 E b reduction, while dynamic disorder and rotational motion of the organic cations play a minor role. We calculate E b = 15 meV for MAPbI 3 , in excellent agreement with recent experimental estimates. We then explore how different material combinations (e.g., replacing Pb → Pb:Sn→ Sn; and MA → FA → Cs) may lead to different E b values and highlight the mechanisms underlying E b tuning.

  8. Third-order elastic moduli for alkali-halide crystals possessing the sodium chloride structure

    International Nuclear Information System (INIS)

    Ray, U.

    2010-01-01

    The values of third-order elastic moduli for alkali halides, having NaCl-type crystal structure are calculated according to the Born-Mayer potential model, considering the repulsive interactions up to the second nearest neighbours and calculating the values of the potential parameters for each crystal, independently, from the compressibility data. This work presents the first published account of the calculation of the third-order elastic moduli taking the actual value of the potential parameter unlike the earlier works. Third-order elastic constants have been computed for alkali halides at 0 and 300 K. The results of the third-order elastic constants are compared with the available experimental and theoretical data. Very good agreement between experimental and theoretical third-order elastic constant data (except C 123 ) is found. We have also computed the values of the pressure derivatives of second-order elastic constants and Anderson-Grueneisen parameter for alkali halides, which agree reasonably well with the experimental values, indicating the satisfactory nature of our computed data for third-order elastic constants.

  9. Beyond Cassie equation: Local structure of heterogeneous surfaces determines the contact angles of microdroplets

    Science.gov (United States)

    Zhang, Bo; Wang, Jianjun; Liu, Zhiping; Zhang, Xianren

    2014-01-01

    The application of Cassie equation to microscopic droplets is recently under intense debate because the microdroplet dimension is often of the same order of magnitude as the characteristic size of substrate heterogeneities, and the mechanism to describe the contact angle of microdroplets is not clear. By representing real surfaces statistically as an ensemble of patterned surfaces with randomly or regularly distributed heterogeneities (patches), lattice Boltzmann simulations here show that the contact angle of microdroplets has a wide distribution, either continuous or discrete, depending on the patch size. The origin of multiple contact angles observed is ascribed to the contact line pinning effect induced by substrate heterogeneities. We demonstrate that the local feature of substrate structure near the contact line determines the range of contact angles that can be stabilized, while the certain contact angle observed is closely related to the contact line width. PMID:25059292

  10. Inhibition of mild steel corrosion in acidic medium using synthetic and naturally occurring polymers and synergistic halide additives

    Energy Technology Data Exchange (ETDEWEB)

    Umoren, S.A. [Department of Chemistry, Faculty of Science, University of Uyo, P.M.B 1017 Uyo (Nigeria)], E-mail: saviourumoren@yahoo.com; Ogbobe, O.; Igwe, I.O. [Department of Polymer and Textile Engineering, School of Engineering and Engineering Technology, Federal University of Technology, P.M.B. 1526 Owerri (Nigeria); Ebenso, E.E. [Department of Chemistry and Chemical Technology, National University of Lesotho, P. O. Roma180, Lesotho (South Africa)

    2008-07-15

    The corrosion inhibition of mild steel in H{sub 2}SO{sub 4} in the presence of gum arabic (GA) (naturally occurring polymer) and polyethylene glycol (PEG) (synthetic polymer) was studied using weight loss, hydrogen evolution and thermometric methods at 30-60 deg. C. PEG was found to be a better inhibitor for mild steel corrosion in acidic medium than GA. The effect of addition of halides (KCl, KBr and KI) was also studied. Results obtained showed that inhibition efficiency (I%) increased with increase in GA and PEG concentration, addition of halides and with increase in temperature. Increase in inhibition efficiency (I%) and degree of surface coverage ({theta}) was found to follow the trend Cl{sup -} < Br{sup -} < I{sup -} which indicates that the radii and electronegativity of the halide ions play a significant role in the adsorption process. GA and PEG alone and in combination with halides were found to obey Temkin adsorption isotherm. Phenomenon of chemical adsorption is proposed from the trend of inhibition efficiency with temperature and values {delta}G{sub ads}{sup 0} obtained. The synergism parameter, S{sub I} evaluated is found to be greater than unity indicating that the enhanced inhibition efficiency caused by the addition of halides is only due to synergism.

  11. Preparation of gold microparticles using halide ions in bulk block copolymer phases via photoreduction

    International Nuclear Information System (INIS)

    Cha, Sang-Ho; Kim, Ki-Hyun; Lee, Won-Ki; Lee, Jong-Chan

    2009-01-01

    Gold microparticles were prepared from the gold salt in the solid bulk phase of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer via a photoreduction process in the presence of halide ions. The shapes and sizes of the gold microparticles were found to be dependent on the types and amount of halide ions as well as the types of cations used due to the combined effects of the adsorption power and oxidative dissolution ability of the additives on gold surfaces. Gold nanorods were obtained when poly(ethylene oxide) was used instead of the block copolymer. This suggests that the poly(propylene oxide) (PPO) parts in the block copolymer are essential for the formation of gold microparticles, even though the degree of the direct interaction between the PPO blocks and gold salt is not significant. - Graphical abstract: Gold microparticles were successfully prepared using halide ions as additives in the polymeric bulk phase via photoreduction with the glow lamp irradiation.

  12. Demixing in a metal halide lamp, results from modeling

    NARCIS (Netherlands)

    Beks, M.L.; Hartgers, A.; Mullen, van der J.J.A.M.; Veldhuizen, van E.M.

    2005-01-01

    Metal Halide (MH) lamps are high pressure discharge devices, containing a complex chemical mixture, to emit light on a broad spectrum while maintaining good efficacies. Lamps of this type were first exhibited by General Electric at the 1964 World Fair in New York [1]. They typically consist of an

  13. Crystal growth, structure and phase studies on gold halides

    NARCIS (Netherlands)

    Janssen, Eugenius Maria Wilhelmus Janssen

    1977-01-01

    Only very corrosive substances attack gold, the most noble metal. In this study the reactivity and the phase diagrams of gold with the halogens chlorine, bromine and iodine have been investigated. owing to the noble behaviour of gold, its halides are sensitive to heat; on heating they decompose into

  14. Growth and Characterization of PDMS-Stamped Halide Perovskite Single Microcrystals

    NARCIS (Netherlands)

    Khoram, P.; Brittman, S.; Dzik, W.I.; Reek, J.N.H.; Garneett, E.C.

    2016-01-01

    Recently, halide perovskites have attracted considerable attention for optoelectronic applications, but further progress in this field requires a thorough understanding of the fundamental properties of these materials. Studying perovskites in their single-crystalline form provides a model system for

  15. Synergistic effect of halide ions on the corrosion inhibition of aluminium in H2SO4 using 2-acetylphenothiazine

    International Nuclear Information System (INIS)

    Ebenso, E.E.

    2003-01-01

    The corrosion inhibition of aluminium in H 2 SO 4 in the presence of 2-acetylphenothiazine (2APTZ) at temperature range of 30-60 deg. C was studied using the weight loss and thermometric techniques. The effect of addition of halides (KCl, KBr, KI) is also reported. The inhibition efficiency (I, %) increased with increase in concentration of 2APTZ. The addition of the halides increased the inhibition efficiency to a considerable extent. The temperature increased the corrosion rate and inhibition efficiency in the range 30-60 deg. C in the absence and presence of the inhibitor and halides. Phenomenon of chemical adsorption is proposed. Flory-Huggins adsorption isotherm equation was obeyed at all the concentrations studied. The decrease in inhibition efficiency (and surface coverage values) was found to be in the order I - >Br - >Cl - which clearly indicates that the radii and the electronegativity of halides play a significant role in the adsorption process. All the data acquired reveal that 2APTZ acts as an inhibitor in the acid environment from the two techniques used. The synergistic effect of 2APTZ and halide ions is discussed

  16. Trap-Free Hot Carrier Relaxation in Lead–Halide Perovskite Films

    KAUST Repository

    Bretschneider, Simon A.; Laquai, Fré dé ric; Bonn, Mischa

    2017-01-01

    Photovoltaic devices that employ lead-halide perovskites as photoactive materials exhibit power conversion efficiencies of 22%. One of the potential routes to go beyond the current efficiencies is to extract charge carriers that carry excess energy, that is, nonrelaxed or

  17. Trap-Free Hot Carrier Relaxation in Lead–Halide Perovskite Films

    KAUST Repository

    Bretschneider, Simon A.

    2017-05-08

    Photovoltaic devices that employ lead-halide perovskites as photoactive materials exhibit power conversion efficiencies of 22%. One of the potential routes to go beyond the current efficiencies is to extract charge carriers that carry excess energy, that is, nonrelaxed or

  18. Halides of BET-TTF: novel hydrated molecular metals

    Energy Technology Data Exchange (ETDEWEB)

    Laukhina, E.; Ribera, E.; Vidal-Gancedo, J.; Canadell, E.; Veciana, J.; Rovira, C. [Universidad Autonoma de Barcelona, Bellaterra (Spain). Inst. de Ciencia de Materials; Khasanov, S.; Zorina, L.; Shibaeva, R. [Rossijskaya Akademiya Nauk, Chernogolovka (Russian Federation). Inst. Fiziki Tverdogo Tela; Laukhin, V. [Inst. of Problems of Chemical Physics, RAS, Chernogolovka (Russian Federation); Honold, M.; Nam, M.-S.; Singleton, J. [Clarendon Lab., Univ. of Oxford (United Kingdom)

    2000-01-07

    A hint of superconducting transition has been observed for the first time in a cation radical salt derived from bisethylenethio-tetrathiafulvalene (BET-TTF), the salt (BET-TTF){sub 2}Br.3H{sub 2}O. Here the synthesis, X-ray structure, and physical properties of two hydrated halides of BET-TTF that are isostructural and present stable metallic properties are described. (orig.)

  19. The Electrical and Optical Properties of Organometal Halide Perovskites Relevant to Optoelectronic Performance

    KAUST Repository

    Adinolfi, Valerio

    2017-10-12

    Organometal halide perovskites are under intense study for use in optoelectronics. Methylammonium and formamidinium lead iodide show impressive performance as photovoltaic materials; a premise that has spurred investigations into light-emitting devices and photodetectors. Herein, the optical and electrical material properties of organometal halide perovskites are reviewed. An overview is given on how the material composition and morphology are tied to these properties, and how these properties ultimately affect device performance. Material attributes and techniques used to estimate them are analyzed for different perovskite materials, with a particular focus on the bandgap, mobility, diffusion length, carrier lifetime, and trap-state density.

  20. Building up an electrocatalytic activity scale of cathode materials for organic halide reductions

    International Nuclear Information System (INIS)

    Bellomunno, C.; Bonanomi, D.; Falciola, L.; Longhi, M.; Mussini, P.R.; Doubova, L.M.; Di Silvestro, G.

    2005-01-01

    A wide investigation on the electrochemical activity of four model organic bromides has been carried out in acetonitrile on nine cathodes of widely different affinity for halide anions (Pt, Zn, Hg, Sn, Bi, Pb, Au, Cu, Ag), and the electrocatalytic activities of the latter have been evaluated with respect to three possible inert reference cathode materials, i.e. glassy carbon, boron-doped diamond, and fluorinated boron-doped diamond. A general electrocatalytic activity scale for the process is proposed, with a discussion on its modulation by the configuration of the reacting molecule, and its connection with thermodynamic parameters accounting for halide adsorption

  1. Demixing in a metal halide lamp, results from modelling

    NARCIS (Netherlands)

    Beks, M.L.; Hartgers, A.; Mullen, van der J.J.A.M.

    2006-01-01

    Convection and diffusion in the discharge region of a metal halide lamp is studied using a computer model built with the plasma modeling package Plasimo. A model lamp contg. mercury and sodium iodide is studied. The effects of the total lamp pressure on the degree of segregation of the light

  2. Fullerenes doped with metal halides

    International Nuclear Information System (INIS)

    Martin, T.P.; Heinebrodt, M.; Naeher, U.; Goehlich, H.; Lange, T.; Schaber, H.

    1993-01-01

    The cage-like structure of fullerenes is a challenge to every experimental to put something inside - to dope the fullerenes. In fact, the research team that first identified C 60 as a football-like molecule quickly succeeded in trapping metal atoms inside and in shrinking the cage around this atom by photofragmentation. In this paper we report the results of ''shrink-wrapping'' the fullerenes around metal halide molecules. Of special interest is the critical size (the minimum number of carbon atoms) that can still enclose the dopant. A rough model for the space available inside a carbon cage gives good agreement with the measured shrinking limits. (author). 8 refs, 6 figs

  3. Iron halide mediated atom transfer radical polymerization of methyl methacrylate with N-Alkyl-2-pyridylmethanimine as the ligand

    NARCIS (Netherlands)

    Zhang, H.; Schubert, U.S.

    2004-01-01

    The controlled atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) catalyzed by iron halide/N-(n-hexyl)-2-pyridylmethanimine (NHPMI) is described. The ethyl 2-bromoisobutyrate (EBIB)-initiated ATRP with [MMA]0/[EBIB]0/[iron halide]0/[NHPMI]0 = 150/1/1/2 was better controlled in

  4. Solution enthalpies of alkali metal halides in water and heavy water mixtures with dimethyl sulfoxide

    International Nuclear Information System (INIS)

    Egorov, G.I.

    1994-01-01

    Solution enthalpies of CsF, LiCl, NaI, CsI and some other halides of alkali metals and tetrabutylammonium have been measured by the method of calorimetry. Standard solution enthalpies of all alkali metals (except rubidium) halides in water and heavy water mixtures with dimethylsulfoxide at 298.15 K have been calculated. Isotopic effects in solvation enthalpy of the electrolytes mentioned in aqueous solutions of dimethylsulfoxide have been discussed. 29 refs., 2 figs., 4 tabs

  5. Barium halide nanocrystals in fluorozirconate based glass ceramics for scintillation application

    Energy Technology Data Exchange (ETDEWEB)

    Selling, J.

    2007-07-01

    Europium (Eu)-activated barium halide nanocrystals in fluorozirconate based glass ceramics represent a promising class of Xray scintillators. The scintillation in these glass ceramics is mainly caused by the emission of divalent Eu incorporated in hexagonal BaCl{sub 2} nanocrystals which are formed in the glass matrix upon appropriate annealing. Experiments with cerium (Ce)-activated fluorozironate glass ceramics showed that Ce is an interesting alternative. In order to get a better understanding of the scintillation mechanism in Eu- or Ce-activated barium halide nanocrystals, an investigation of the processes in the corresponding bulk material is essential. The objective of this thesis is the investigation of undoped, Eu-, and Ce-doped barium halides by X-ray excited luminescence (XL), pulse height, and scintillation decay spectra. That will help to figure out which of these crystals has the most promising scintillation properties and would be the best nanoparticles for the glass ceramics. Furthermore, alternative dopants like samarium (Sm) and manganese (Mn) were also investigated. Besides the above-mentioned optical investigation electron paramagnetic resonance (EPR) and Moessbauer measurements were carried out in order to complete the picture of Eu-doped barium halides. The EPR data of Eu-doped BaI{sub 2} is anticipated to yield more information about the crystal field and crystal structure that will help to understand the charge carrier process during the scintillation process. The main focus of the Moessbauer investigations was set on the Eu-doped fluorochlorozirconate glass ceramics. The results of this investigation should help to improve the glass ceramics. The Eu{sup 2+}/Eu{sup 3+} ratio in the glass ceramics should be determined and optimize favor of the Eu{sup 2+}. We also want to distinguish between Eu{sup 2+} in the glass matrix and Eu{sup 2+} in the nanocrystals. For a better understanding of Moessbauer spectroscopy on Eu also measurements on Eu in a

  6. Barium halide nanocrystals in fluorozirconate based glass ceramics for scintillation application

    International Nuclear Information System (INIS)

    Selling, J.

    2007-01-01

    Europium (Eu)-activated barium halide nanocrystals in fluorozirconate based glass ceramics represent a promising class of Xray scintillators. The scintillation in these glass ceramics is mainly caused by the emission of divalent Eu incorporated in hexagonal BaCl 2 nanocrystals which are formed in the glass matrix upon appropriate annealing. Experiments with cerium (Ce)-activated fluorozironate glass ceramics showed that Ce is an interesting alternative. In order to get a better understanding of the scintillation mechanism in Eu- or Ce-activated barium halide nanocrystals, an investigation of the processes in the corresponding bulk material is essential. The objective of this thesis is the investigation of undoped, Eu-, and Ce-doped barium halides by X-ray excited luminescence (XL), pulse height, and scintillation decay spectra. That will help to figure out which of these crystals has the most promising scintillation properties and would be the best nanoparticles for the glass ceramics. Furthermore, alternative dopants like samarium (Sm) and manganese (Mn) were also investigated. Besides the above-mentioned optical investigation electron paramagnetic resonance (EPR) and Moessbauer measurements were carried out in order to complete the picture of Eu-doped barium halides. The EPR data of Eu-doped BaI 2 is anticipated to yield more information about the crystal field and crystal structure that will help to understand the charge carrier process during the scintillation process. The main focus of the Moessbauer investigations was set on the Eu-doped fluorochlorozirconate glass ceramics. The results of this investigation should help to improve the glass ceramics. The Eu 2+ /Eu 3+ ratio in the glass ceramics should be determined and optimize favor of the Eu 2+ . We also want to distinguish between Eu 2+ in the glass matrix and Eu 2+ in the nanocrystals. For a better understanding of Moessbauer spectroscopy on Eu also measurements on Eu in a CaF 2 host lattice were carried

  7. Metal Halide Perovskite Polycrystalline Films Exhibiting Properties of Single Crystals

    NARCIS (Netherlands)

    Brenes, Roberto; Guo, D.; Osherov, Anna; Noel, Nakita K.; Eames, Christopher; Hutter, E.M.; Pathak, Sandeep K.; Niroui, Farnaz; Friend, Richard H.; Islam, M. Saiful; Snaith, Henry J.; Bulović, Vladimir; Savenije, T.J.; Stranks, Samuel D.

    2017-01-01

    Metal halide perovskites are generating enormous excitement for use in solar cells and light-emission applications, but devices still show substantial non-radiative losses. Here, we show that by combining light and atmospheric treatments, we can increase the internal luminescence quantum

  8. Photoinduced, copper-catalyzed alkylation of amides with unactivated secondary alkyl halides at room temperature.

    Science.gov (United States)

    Do, Hien-Quang; Bachman, Shoshana; Bissember, Alex C; Peters, Jonas C; Fu, Gregory C

    2014-02-05

    The development of a mild and general method for the alkylation of amides with relatively unreactive alkyl halides (i.e., poor substrates for SN2 reactions) is an ongoing challenge in organic synthesis. We describe herein a versatile transition-metal-catalyzed approach: in particular, a photoinduced, copper-catalyzed monoalkylation of primary amides. A broad array of alkyl and aryl amides (as well as a lactam and a 2-oxazolidinone) couple with unactivated secondary (and hindered primary) alkyl bromides and iodides using a single set of comparatively simple and mild conditions: inexpensive CuI as the catalyst, no separate added ligand, and C-N bond formation at room temperature. The method is compatible with a variety of functional groups, such as an olefin, a carbamate, a thiophene, and a pyridine, and it has been applied to the synthesis of an opioid receptor antagonist. A range of mechanistic observations, including reactivity and stereochemical studies, are consistent with a coupling pathway that includes photoexcitation of a copper-amidate complex, followed by electron transfer to form an alkyl radical.

  9. Melting and liquid structure of polyvalent metal halides

    International Nuclear Information System (INIS)

    Tosi, M.P.

    1992-08-01

    A short review is given of recent progress in determining and understanding liquid structure types and melting mechanisms for halides of polyvalent metals. The nature of the preferred local coordination for the polyvalent metal ion in the melt can usually be ascertained from data on liquid mixtures with halogen-donating alkali halides. The stability of these local coordination states and the connectivity that arises between them in the approach to the pure melt determines the character of its short-range and possible medium-range order. A broad classification of structural and melting behaviours can be given on the basis of measured melting parameters and transport coefficients for many compounds, in combination with the available diffraction data on the liquid structure of several compounds. Correlations have been shown to exist with a simple indicator of the nature of the chemical bond and also with appropriate parameters of ionic models, wherever the latter are usefully applicable for semiquantitative calculations of liquid structure. Consequences on the mechanisms for valence electron localization in solutions of metallic elements into strongly structured molten salts are also briefly discussed. (author). 46 refs, 4 figs, 2 tabs

  10. Mechanoluminescence response to the plastic flow of coloured alkali halide crystals

    International Nuclear Information System (INIS)

    Chandra, B.P.; Bagri, A.K.; Chandra, V.K.

    2010-01-01

    The present paper reports the luminescence induced by plastic deformation of coloured alkali halide crystals using pressure steps. When pressure is applied onto a γ-irradiated alkali halide crystal, then initially the mechanoluminescence (ML) intensity increases with time, attains a peak value and later on it decreases with time. The ML of diminished intensity also appears during the release of applied pressure. The intensity I m corresponding to the peak of ML intensity versus time curve and the total ML intensity I T increase with increase in value of the applied pressure. The time t m corresponding to the ML peak slightly decreases with the applied pressure. After t m , initially the ML intensity decreases at a fast rate and later on it decreases at a slow rate. The decay time of the fast decrease in the ML intensity is equal to the pinning time of dislocations and the decay time for the slow decrease of ML intensity is equal to the diffusion time of holes towards the F-centres. The ML intensity increases with the density of F-centres and it is optimum for a particular temperature of the crystals. The ML spectra of coloured alkali halide crystals are similar to the thermoluminescence and afterglow spectra. The peak ML intensity and the total ML intensity increase drastically with the applied pressure following power law, whereby the pressure dependence of the ML intensity is related to the work-hardening exponent of the crystals. The ML also appears during the release of the applied pressure because of the movement of dislocation segments and movements of dislocation lines blocked under pressed condition. On the basis of the model based on the mechanical interaction between dislocation and F-centres, expressions are derived for the ML intensity, which are able to explain different characteristics of the ML. From the measurements of the plastico ML induced by the application of loads on γ-irradiated alkali halide crystals, the pinning time of dislocations

  11. The electronic structure of the F-center in alkali-halides-The Bethe cluster - lattice

    International Nuclear Information System (INIS)

    Queiroz, S.L.A. de.

    1977-07-01

    The electronic structure of the F-center in alkali-halides with the NaCl structure has been studied using the Bethe Cluster lattice method. The central cluster has been taken as constituted by the vacancy and the nearest- and second-neighbors to it, respectively cations and anions. The optical transitions have been calculated and compared to experimental data on the location of the peak of the F-absorption band. The agreement obtained indicates that this method may be used to study properties of this defect in alkali halides. (Author) [pt

  12. Reaction between aminoalkyl radicals and akyl halides: Dehalogenation by electron transfer?

    Science.gov (United States)

    Lalevée, J.; Fouassier, J. P.; Blanchard, N.; Ingold, K. U.

    2011-07-01

    Aminoalkyl radicals, such as Et2NCrad HCH3, have low oxidation potentials and are therefore powerful reducing agents. We have found that Et2NCrad HCH3 reacts with CCl4 and CBr4 in di-tert-butyl peroxide with bimolecular rate constants (measured by LFP) close, or equal, to the diffusion-controlled limit. For the less reactive halide, CH2Br2, the reaction rate is increased substantially by the addition of acetonitrile as a co-solvent. It is tentatively concluded that these reactions occur by electron-transfer from the aminoalkyl to the organohalide with formation of the iminium ion, Et2N+dbnd CHCH3 (NMR detection), halide ion and a halomethyl radical, e.g., rad CCl3 and rad CHCl2 (ESR, spin-trapping detection).

  13. Hybrid Lead Halide Perovskites for Ultrasensitive Photoactive Switching in Terahertz Metamaterial Devices.

    Science.gov (United States)

    Manjappa, Manukumara; Srivastava, Yogesh Kumar; Solanki, Ankur; Kumar, Abhishek; Sum, Tze Chien; Singh, Ranjan

    2017-08-01

    The recent meteoric rise in the field of photovoltaics with the discovery of highly efficient solar-cell devices is inspired by solution-processed organic-inorganic lead halide perovskites that exhibit unprecedented light-to-electricity conversion efficiencies. The stunning performance of perovskites is attributed to their strong photoresponsive properties that are thoroughly utilized in designing excellent perovskite solar cells, light-emitting diodes, infrared lasers, and ultrafast photodetectors. However, optoelectronic application of halide perovskites in realizing highly efficient subwavelength photonic devices has remained a challenge. Here, the remarkable photoconductivity of organic-inorganic lead halide perovskites is exploited to demonstrate a hybrid perovskite-metamaterial device that shows extremely low power photoswitching of the metamaterial resonances in the terahertz part of the electromagnetic spectrum. Furthermore, a signature of a coupled phonon-metamaterial resonance is observed at higher pump powers, where the Fano resonance amplitude is extremely weak. In addition, a low threshold, dynamic control of the highly confined electric field intensity is also observed in the system, which could tremendously benefit the new generation of subwavelength photonic devices as active sensors, low threshold optically controlled lasers, and active nonlinear devices with enhanced functionalities in the infrared, optical, and the terahertz parts of the electromagnetic spectrum. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Band Gap Tuning and Defect Tolerance of Atomically Thin Two- Dimensional Organic-Inorganic Halide Perovskites

    OpenAIRE

    Pandey, Mohnish; Jacobsen, Karsten Wedel; Thygesen, Kristian Sommer

    2016-01-01

    Organic−inorganic halide perovskites have proven highly successful for photovoltaics but suffer from low stability, which deteriorates their performance over time. Recent experiments have demonstrated that low dimensional phases of the hybrid perovskites may exhibit improved stability. Here we report first-principles calculations for isolated monolayers of the organometallic halide perovskites (C4H9NH3)2MX2Y2, where M = Pb, Ge, Sn and X,Y = Cl, Br, I. The band gaps computed using the GLLB-SC ...

  15. Sequential One-Pot Ruthenium-Catalyzed Azide−Alkyne Cycloaddition from Primary Alkyl Halides and Sodium Azide

    KAUST Repository

    Johansson, Johan R.

    2011-04-01

    An experimentally simple sequential one-pot RuAAC reaction, affording 1,5-disubstituted 1H-1,2,3-triazoles in good to excellent yields starting from an alkyl halide, sodium azide, and an alkyne, is reported. The organic azide is formed in situ by treating the primary alkyl halide with sodium azide in DMA under microwave heating. Subsequent addition of [RuClCp*(PPh 3) 2] and the alkyne yielded the desired cycloaddition product after further microwave irradiation. © 2011 American Chemical Society.

  16. Analisa Teknis Pemakaian Kombinasi Lampu Metal Halide Dan Led Sebagai Pemikat Ikan Pada Kapal Pukat Cincin (Purse Seine Dan Pengaruhnya Terhadap Konsumsi Bahan Bakar Genset

    Directory of Open Access Journals (Sweden)

    Septian Ragil Wibisono

    2017-01-01

    Full Text Available Saat ini lampu Metal Halide dipakai sebagai pemikat ikan  oleh nelayan Purse Seine. Peggunaan lampu tersebut memerlukan daya Genset yang besar karena satu lampu Metal Halide berdaya 1500 Watt. Semakin banyak lampu Metal Halide yang digunakan semakin besar pula konsumsi bahan bakar Genset. Dalam upaya penghematan energi bahan bakar maka digunakan lampu LED sebagai alternatif pemikat ikan. Lampu LED dikenal sebagai lampu yang hemat energi. Penelitian ini ditujukan untuk mengetahui dan membandingkan konsumsi bahan bakar Genset saat menggunakan kombinasi lampu Metal Halide dan LED. Penelitian ini dilakukan dengan mengambil data konsumsi bahan bakar Genset untuk menyalakan sejumlah lampu Metal Halide dan lampu LED, kemudian dilakukan analisa regresi untuk mendapatkan model persaamaan konsumsi bahan bakar Genset. Selanjutnya dilakukan ekstrapolasi untuk memprediksi konsumsi bahan bakar saat Genset dengan jumlah lampu tertentu. Hasilnya dengan besar fluks cahaya yang hampir sama, saat penggunaan 6 lampu Metal Halide konsumsi bahan bakar sebesar 13.606,03 liter, dan saat menggunakan kombinasi lampu 1 Metal Halide dan 25 lampu LED konsumsi bahan bakar sebesar 13.255,63 liter, yang artinya terjadi penghematan bahan bakar sebesar 2,58%.

  17. Finding New Perovskite Halides via Machine learning

    Directory of Open Access Journals (Sweden)

    Ghanshyam ePilania

    2016-04-01

    Full Text Available Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach towards rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning via building a support vector machine (SVM based classifier that uses elemental features (or descriptors to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br or I anion in the perovskite crystal structure. The classification model is built by learning from a dataset of 181 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. The trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

  18. Finding New Perovskite Halides via Machine learning

    Science.gov (United States)

    Pilania, Ghanshyam; Balachandran, Prasanna V.; Kim, Chiho; Lookman, Turab

    2016-04-01

    Advanced materials with improved properties have the potential to fuel future technological advancements. However, identification and discovery of these optimal materials for a specific application is a non-trivial task, because of the vastness of the chemical search space with enormous compositional and configurational degrees of freedom. Materials informatics provides an efficient approach towards rational design of new materials, via learning from known data to make decisions on new and previously unexplored compounds in an accelerated manner. Here, we demonstrate the power and utility of such statistical learning (or machine learning) via building a support vector machine (SVM) based classifier that uses elemental features (or descriptors) to predict the formability of a given ABX3 halide composition (where A and B represent monovalent and divalent cations, respectively, and X is F, Cl, Br or I anion) in the perovskite crystal structure. The classification model is built by learning from a dataset of 181 experimentally known ABX3 compounds. After exploring a wide range of features, we identify ionic radii, tolerance factor and octahedral factor to be the most important factors for the classification, suggesting that steric and geometric packing effects govern the stability of these halides. The trained and validated models then predict, with a high degree of confidence, several novel ABX3 compositions with perovskite crystal structure.

  19. Conformational isomerism in mixed-ligand complexes of 2,2'-bipyridine and triphenylphosphine with copper(I) halides

    International Nuclear Information System (INIS)

    Barron, P.F.; Engelhardt, L.M.; Healy, P.C.; Kildea, J.D.; White, A.H.

    1988-01-01

    Mixed-ligand complexes of triphenylphosphine and 2,2'-bipyridine and copper(I) halides have been synthesized. The 31 P NMR spectra of the complexes were measured and are reported along with data for complete structural characterization of the complexes. The results indicate a novel dichotomy of conformational isomers to be present in the chloride lattice. The Cu-P bond length was found to not vary with different halides. 8 refs., 4 figs., 6 tabs

  20. THERMODYNAMICS OF MICELLE FORMATION BY 1-METHYL-4-ALKYLPYRIDINIUM HALIDES

    NARCIS (Netherlands)

    BIJMA, K; ENGBERTS, JBFN; HAANDRIKMAN, G; VANOS, NM; BLANDAMER, MJ; BUTT, MD; CULLIS, PM

    This paper reports enthalpies of micellization for a series of 1-methyl-4-alkylpyridinium halide surfactants at 303.2 K with different lengths and degrees of branching of the 4-alkyl chain and different sizes of counterions using two microcalorimeters (LKB 2277 and Omega Microcal). The standard

  1. Chemistry of gaseous lower-valent actinide halides. Technical progress report

    International Nuclear Information System (INIS)

    Hildenbrand, D.L.

    1984-01-01

    Objective is to provide thermochemical data for key actinide halide and oxyhalide systems. Progress is reported on bond dissociation energies of gaseous ThCl 4 , ThCl 3 , ThCl 2 , and ThCl; bond dissociation energies of ruthenium fluorides; and mass spectroscopy of UF 6

  2. Students' Understanding of Alkyl Halide Reactions in Undergraduate Organic Chemistry

    Science.gov (United States)

    Cruz-Ramirez de Arellano, Daniel

    2013-01-01

    Organic chemistry is an essential subject for many undergraduate students completing degrees in science, engineering, and pre-professional programs. However, students often struggle with the concepts and skills required to successfully solve organic chemistry exercises. Since alkyl halides are traditionally the first functional group that is…

  3. Halide salts accelerate degradation of high explosives by zerovalent iron

    International Nuclear Information System (INIS)

    Kim, Jong Sung; Shea, Patrick J.; Yang, Jae E.; Kim, Jang-Eok

    2007-01-01

    Zerovalent iron (Fe 0 , ZVI) has drawn great interest as an inexpensive and effective material to promote the degradation of environmental contaminants. A focus of ZVI research is to increase degradation kinetics and overcome passivation for long-term remediation. Halide ions promote corrosion, which can increase and sustain ZVI reactivity. Adding chloride or bromide salts with Fe 0 (1% w/v) greatly enhanced TNT, RDX, and HMX degradation rates in aqueous solution. Adding Cl or Br salts after 24 h also restored ZVI reactivity, resulting in complete degradation within 8 h. These observations may be attributed to removal of the passivating oxide layer and pitting corrosion of the iron. While the relative increase in degradation rate by Cl - and Br - was similar, TNT degraded faster than RDX and HMX. HMX was most difficult to remove using ZVI alone but ZVI remained effective after five HMX reseeding cycles when Br - was present in solution. - The addition of halide ions promotes the degradation of high explosives by zerovalent iron

  4. Exciton-relaxation dynamics in lead halides

    International Nuclear Information System (INIS)

    Iwanaga, Masanobu; Hayashi, Tetsusuke

    2003-01-01

    We survey recent comprehensive studies of exciton relaxation in the crystals of lead halides. The luminescence and electron-spin-resonance studies have revealed that excitons in lead bromide spontaneously dissociate and both electrons and holes get self-trapped individually. Similar relaxation has been also clarified in lead chloride. The electron-hole separation is ascribed to repulsive correlation via acoustic phonons. Besides, on the basis of the temperature profiles of self-trapped states, we discuss the origin of luminescence components which are mainly induced under one-photon excitation into the exciton band in lead fluoride, lead chloride, and lead bromide

  5. Plasmonic characterization of photo-induced silver nanoparticles extracted from silver halide based TEM film

    Energy Technology Data Exchange (ETDEWEB)

    Sudheer,, E-mail: sudheer@rrcat.gov.in; Tiwari, P.; Rai, V. N.; Srivastava, A. K. [Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology Indore, Madhya Pradesh 452013 (India); Varshney, G. K. [Laser Bio-medical Applications & Instrumentation Division, Raja Ramanna Centre for Advanced Technology Indore, Madhya Pradesh 452013 (India)

    2016-05-23

    The plasmonic responses of silver nanoparticles extracted from silver halide based electron microscope film are investigated. Photo-reduction process is carried out to convert the silver halide grains into the metallic silver. The centrifuge technique is used for separating the silver nanoparticles from the residual solution. Morphological study performed by field emission scanning electron microscope (FESEM) shows that all the nanoparticles have an average diameter of ~120 nm with a high degree of mono dispersion in size. The localized surface plasmon resonance (LSPR) absorption peak at ~537 nm confirms the presence of large size silver nanoparticles.

  6. Clinical heterogeneity in Fabry disease

    Directory of Open Access Journals (Sweden)

    G. N. Salogub

    2015-01-01

    Full Text Available Fabry disease is an X-linked, lysosomal storage disease (OMIM: 301500, caused by α-galactosidase A deficiency, resulting in accumulation of its substrates, glycosphingolipids, primarily – globotriaosylceramide, in the lysosomes of multiple cell types with multi-system clinical manifestations, even within the same family, including abnormalities of the central and peripheral nervous system, kidneys, heart, gastrointestinal tract, lungs, organ of vision. Clinical heterogeneity is often the reason of the delayed diagnosis. Nowadays enzyme replacement therapy has proved its efficiency in the treatment of Fabry disease. Including Fabry disease in the differential diagnosis of a large range of disorders is important because of its wide clinical heterogeneity and the possibility of an earlier intervention with a beneficial treatment.

  7. White-Light Emission from Layered Halide Perovskites.

    Science.gov (United States)

    Smith, Matthew D; Karunadasa, Hemamala I

    2018-03-20

    With nearly 20% of global electricity consumed by lighting, more efficient illumination sources can enable massive energy savings. However, effectively creating the high-quality white light required for indoor illumination remains a challenge. To accurately represent color, the illumination source must provide photons with all the energies visible to our eye. Such a broad emission is difficult to achieve from a single material. In commercial white-light sources, one or more light-emitting diodes, coated by one or more phosphors, yield a combined emission that appears white. However, combining emitters leads to changes in the emission color over time due to the unequal degradation rates of the emitters and efficiency losses due to overlapping absorption and emission energies of the different components. A single material that emits broadband white light (a continuous emission spanning 400-700 nm) would obviate these problems. In 2014, we described broadband white-light emission upon near-UV excitation from three new layered perovskites. To date, nine white-light-emitting perovskites have been reported by us and others, making this a burgeoning field of study. This Account outlines our work on understanding how a bulk material, with no obvious emissive sites, can emit every color of the visible spectrum. Although the initial discoveries were fortuitous, our understanding of the emission mechanism and identification of structural parameters that correlate with the broad emission have now positioned us to design white-light emitters. Layered hybrid halide perovskites feature anionic layers of corner-sharing metal-halide octahedra partitioned by organic cations. The narrow, room-temperature photoluminescence of lead-halide perovskites has been studied for several decades, and attributed to the radiative recombination of free excitons (excited electron-hole pairs). We proposed that the broad white emission we observed primarily stems from exciton self-trapping. Here, the

  8. Diffraction efficiency of plasmonic gratings fabricated by electron beam lithography using a silver halide film

    Energy Technology Data Exchange (ETDEWEB)

    Sudheer,, E-mail: sudheer@rrcat.gov.in, E-mail: sudheer.rrcat@gmail.com; Tiwari, P.; Srivastava, Himanshu; Rai, V. N.; Srivastava, A. K.; Naik, P. A. [Homi Bhabha National Institute, Mumbai, Maharashtra 400094 (India); Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Porwal, S. [Solid State Lasers Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Bhartiya, S. [Homi Bhabha National Institute, Mumbai, Maharashtra 400094 (India); Laser Materials Development and Device Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Rao, B. T. [Homi Bhabha National Institute, Mumbai, Maharashtra 400094 (India); Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Sharma, T. K. [Homi Bhabha National Institute, Mumbai, Maharashtra 400094 (India); Solid State Lasers Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India)

    2016-07-28

    The silver nanoparticle surface relief gratings of ∼10 μm period are fabricated using electron beam lithography on the silver halide film substrate. Morphological characterization of the gratings shows that the period, the shape, and the relief depth in the gratings are mainly dependent on the number of lines per frame, the spot size, and the accelerating voltage of electron beam raster in the SEM. Optical absorption of the silver nanoparticle gratings provides a broad localized surface plasmon resonance peak in the visible region, whereas the intensity of the peaks depends on the number density of silver nanoparticles in the gratings. The maximum efficiency of ∼7.2% for first order diffraction is observed for the grating fabricated at 15 keV. The efficiency is peaking at 560 nm with ∼380 nm bandwidth. The measured profiles of the diffraction efficiency for the gratings are found in close agreement with the Raman-Nath diffraction theory. This technique provides a simple and efficient method for the fabrication of plasmonic nanoparticle grating structures with high diffraction efficiency having broad wavelength tuning.

  9. Synergistic effect of halide ions on the corrosion inhibition of aluminium in H{sub 2}SO{sub 4} using 2-acetylphenothiazine

    Energy Technology Data Exchange (ETDEWEB)

    Ebenso, E.E

    2003-03-05

    The corrosion inhibition of aluminium in H{sub 2}SO{sub 4} in the presence of 2-acetylphenothiazine (2APTZ) at temperature range of 30-60 deg. C was studied using the weight loss and thermometric techniques. The effect of addition of halides (KCl, KBr, KI) is also reported. The inhibition efficiency (I, %) increased with increase in concentration of 2APTZ. The addition of the halides increased the inhibition efficiency to a considerable extent. The temperature increased the corrosion rate and inhibition efficiency in the range 30-60 deg. C in the absence and presence of the inhibitor and halides. Phenomenon of chemical adsorption is proposed. Flory-Huggins adsorption isotherm equation was obeyed at all the concentrations studied. The decrease in inhibition efficiency (and surface coverage values) was found to be in the order I{sup -}>Br{sup -}>Cl{sup -} which clearly indicates that the radii and the electronegativity of halides play a significant role in the adsorption process. All the data acquired reveal that 2APTZ acts as an inhibitor in the acid environment from the two techniques used. The synergistic effect of 2APTZ and halide ions is discussed.

  10. The Role of Surface Tension in the Crystallization of Metal Halide Perovskites

    KAUST Repository

    Zhumekenov, Ayan A.; Burlakov, Victor M.; Saidaminov, Makhsud I.; Alofi, Abdulilah; Haque, Mohammed; Turedi, Bekir; Davaasuren, Bambar; Dursun, Ibrahim; Cho, Nam Chul; El-Zohry, Ahmed M.; de Bastiani, Michele; Giugni, Andrea; Torre, Bruno; Di Fabrizio, Enzo M.; Mohammed, Omar F.; Rothenberger, Alexander; Wu, Tao; Goriely, Alain; Bakr, Osman

    2017-01-01

    The exciting intrinsic properties discovered in single crystals of metal halide perovskites still await their translation into optoelectronic devices. The poor understanding and control of the crystallization process of these materials are current

  11. A quenched-flow system for measuring heterogeneous enzyme kinetics with sub-second time resolution

    DEFF Research Database (Denmark)

    Olsen, Johan Pelck; Kari, Jeppe; Borch, Kim

    2017-01-01

    of insoluble substrate. Perhaps for this reason, transient kinetics has rarely been reported for heterogeneous enzyme reactions. Here, we describe a quenched-flow system using peristaltic pumps and stirred substrate suspensions with a dead time below 100 ms. The general performance was verified by alkali...

  12. Postsynthetic Doping of MnCl2 Molecules into Preformed CsPbBr3 Perovskite Nanocrystals via a Halide Exchange-Driven Cation Exchange.

    Science.gov (United States)

    Huang, Guangguang; Wang, Chunlei; Xu, Shuhong; Zong, Shenfei; Lu, Ju; Wang, Zhuyuan; Lu, Changgui; Cui, Yiping

    2017-08-01

    Unlike widely used postsynthetic halide exchange for CsPbX 3 (X is halide) perovskite nanocrystals (NCs), cation exchange of Pb is of a great challenge due to the rigid nature of the Pb cationic sublattice. Actually, cation exchange has more potential for rendering NCs with peculiar properties. Herein, a novel halide exchange-driven cation exchange (HEDCE) strategy is developed to prepare dually emitting Mn-doped CsPb(Cl/Br) 3 NCs via postsynthetic replacement of partial Pb in preformed perovskite NCs. The basic idea for HEDCE is that the partial cation exchange of Pb by Mn has a large probability to occur as a concomitant result for opening the rigid halide octahedron structure around Pb during halide exchange. Compared to traditional ionic exchange, HEDCE is featured by proceeding of halide exchange and cation exchange at the same time and lattice site. The time and space requirements make only MnCl 2 molecules (rather than mixture of Mn and Cl ions) capable of doping into perovskite NCs. This special molecular doping nature results in a series of unusual phenomenon, including long reaction time, core-shell structured mid states with triple emission bands, and dopant molecules composition-dependent doping process. As-prepared dual-emitting Mn-doped CsPb(Cl/Br) 3 NCs are available for ratiometric temperature sensing. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Monocrystallomimicry in the aerosols of ammonium and cesium halides

    International Nuclear Information System (INIS)

    Melikhov, I.V.; Kitova, E.N.; Kozlovskaya, EhD.; Kamenskaya, A.N.; Mikheev, N.B.; Kulyukhin, S.A.

    1997-01-01

    It is experimentally shown that initial CsI and NH 4 Hal nanocrystals combining into mixed aggregates of polyhedral form (pseudo monocrystals) are formed in the process of cocrystallization of ammonium halide and cesium iodide. The origination and growth of the pseudo monocrystals on the account of successive addition of initial crystals is described by the Fokker-Plank equation [ru

  14. Line emissions from sonoluminescence in aqueous solutions of halide salts without noble gases

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Jinfu, E-mail: liang.shi2007@163.com [The Key Laboratory of Modern Acoustics, Ministry of Education, Institution of Acoustics, Nanjing University, Nanjing 210093 (China); School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550001 (China); Chen, Weizhong, E-mail: wzchen@nju.edu.cn [The Key Laboratory of Modern Acoustics, Ministry of Education, Institution of Acoustics, Nanjing University, Nanjing 210093 (China); Zhou, Chao; Cui, Weicheng; Chen, Zhan [The Key Laboratory of Modern Acoustics, Ministry of Education, Institution of Acoustics, Nanjing University, Nanjing 210093 (China)

    2015-02-20

    Line emissions of trivalent terbium (Tb{sup 3+}) ion were observed from single-bubble sonoluminescence (SL) in an aqueous solution of terbium chloride (TbCl{sub 3}) that contained no noble gas. In addition, sodium (Na) lines were observed in multi-bubble SL in aqueous solutions of various halide salts that contained no noble gas. These observations show that the halide ions, such as Cl{sup −}, Br{sup −}, and I{sup −}, help for line emissions as the noble gases. The intensity of a line emission depends on both the chemical species produced by cavitation bubbles and the temperature of SL bubble that responds to the driving ultrasound pressure. With the increase of driving pressure, some line emissions attached to the continuous spectrum may become increasingly clear, while other line emissions gradually become indistinct. - Highlights: • Line emissions of Tb(III) ions were observed without the presence of noble gases. • The halide ions help to generate a line emission during sonoluminescence. • The intensity of a line emission mainly depends on the bubble's temperature. • The definition of a line emission is related to the temperature of caviation bubble and the kind of host liquid.

  15. Unveiling the Shape Evolution and Halide-Ion-Segregation in Blue-Emitting Formamidinium Lead Halide Perovskite Nanocrystals Using an Automated Microfluidic Platform.

    Science.gov (United States)

    Lignos, Ioannis; Protesescu, Loredana; Emiroglu, Dilara Börte; Maceiczyk, Richard; Schneider, Simon; Kovalenko, Maksym V; deMello, Andrew J

    2018-02-14

    Hybrid organic-inorganic perovskites and in particular formamidinium lead halide (FAPbX 3 , X = Cl, Br, I) perovskite nanocrystals (NCs) have shown great promise for their implementation in optoelectronic devices. Specifically, the Br and I counterparts have shown unprecedented photoluminescence properties, including precise wavelength tuning (530-790 nm), narrow emission linewidths (photoluminescence quantum yields (70-90%). However, the controlled formation of blue emitting FAPb(Cl 1-x Br x ) 3 NCs lags behind their green and red counterparts and the mechanism of their formation remains unclear. Herein, we report the formation of FAPb(Cl 1-x Br x ) 3 NCs with stable emission between 440 and 520 nm in a fully automated droplet-based microfluidic reactor and subsequent reaction upscaling in conventional laboratory glassware. The thorough parametric screening allows for the elucidation of parametric zones (FA-to-Pb and Br-to-Cl molar ratios, temperature, and excess oleic acid) for the formation of nanoplatelets and/or NCs. In contrast to CsPb(Cl 1-x Br x ) 3 NCs, based on online parametric screening and offline structural characterization, we demonstrate that the controlled synthesis of Cl-rich perovskites (above 60 at% Cl) with stable emission remains a challenge due to fast segregation of halide ions.

  16. Charge-charge liquid structure factor and the freezing of alkali halides

    International Nuclear Information System (INIS)

    March, N.H.; Tosi, M.P.

    1980-10-01

    The peak height of the charge-charge liquid structure factor Ssub(QQ) in molten alkali halides is proposed as a criterion for freezing. Available data on molten alkali chlorides, when extrapolated to the freezing point suggests Ssub(QQ)sup(max) approximately 5. (author)

  17. Superconducting nitride halides MNX (M = Ti, Zr, Hf; X = Cl, Br, I)

    Energy Technology Data Exchange (ETDEWEB)

    Schurz, Christian M.; Shlyk, Larysa; Schleid, Thomas; Niewa, Rainer [Stuttgart Univ. (Germany). Inst. fuer Anorganische Chemie

    2011-07-01

    Two different polymorphs of the metal nitride halides MNX (M = Ti, Zr, Hf; X = Cl, Br, I) are known to crystallize in layered structures. The two crystal structures differ in the way {sub {infinity}}{sup 2}{l_brace}X[M{sub 2}N{sub 2}]X{r_brace} slabs are stacked along the c-axes. Metal atoms and/or organic molecules can be intercalated into the van-der-Waals gap between these layers. After such an electron-doping via intercalation the prototypic band insulators change into superconductors with moderate high critical temperatures T{sub c} up to 25.5 K. This review gathers information on synthesis routes, structural characteristics and properties of the prototypic nitride halides and the derivatives after electron-doping with a focus on superconductivity. (orig.)

  18. Manipulating Ion Migration for Highly Stable Light-Emitting Diodes with Single-Crystalline Organometal Halide Perovskite Microplatelets.

    Science.gov (United States)

    Chen, Mingming; Shan, Xin; Geske, Thomas; Li, Junqiang; Yu, Zhibin

    2017-06-27

    Ion migration has been commonly observed as a detrimental phenomenon in organometal halide perovskite semiconductors, causing the measurement hysteresis in solar cells and ultrashort operation lifetimes in light-emitting diodes. In this work, ion migration is utilized for the formation of a p-i-n junction at ambient temperature in single-crystalline organometal halide perovskites. The junction is subsequently stabilized by quenching the ionic movement at a low temperature. Such a strategy of manipulating the ion migration has led to efficient single-crystalline light-emitting diodes that emit 2.3 eV photons starting at 1.8 V and sustain a continuous operation for 54 h at ∼5000 cd m -2 without degradation of brightness. In addition, a whispering-gallery-mode cavity and exciton-exciton interaction in the perovskite microplatelets have both been observed that can be potentially useful for achieving electrically driven laser diodes based on single-crystalline organometal halide perovskite semiconductors.

  19. Holographic Optical Elements Recorded in Silver Halide Sensitized Gelatin Emulsions. Part I. Transmission Holographic Optical Elements

    Science.gov (United States)

    Kim, Jong Man; Choi, Byung So; Kim, Sun Il; Kim, Jong Min; Bjelkhagen, Hans I.; Phillips, Nicholas J.

    2001-02-01

    Silver halide sensitized gelatin (SHSG) holograms are similar to holograms recorded in dichromated gelatin (DCG), the main recording material for holographic optical elements (HOE s). The drawback of DCG is its low sensitivity and limited spectral response. Silver halide materials can be processed in such a way that the final hologram will have properties like a DCG hologram. Recently this technique has become more interesting since the introduction of new ultra-high-resolution silver halide emulsions. An optimized processing technique for transmission HOE s recorded in these materials is introduced. Diffraction efficiencies over 90% can be obtained for transmissive diffraction gratings. Understanding the importance of the selective hardening process has made it possible to obtain results similar to conventional DCG processing. The main advantage of the SHSG process is that high-sensitivity recording can be performed with laser wavelengths anywhere within the visible spectrum. This simplifies the manufacturing of high-quality, large-format HOE s.

  20. Transport phenomena in metal-halide lamps : a poly-diagnostic study

    NARCIS (Netherlands)

    Nimalasuriya, T.

    2007-01-01

    Worldwide about 20% of all electricity is used for lighting. It is therefore of great interest to develop a lamp that has high e±cacy, good colour rendering and long lifetime. The metal-halide lamp is a gas discharge lamp that meets all these demands. Unfortunately there are still issues with this

  1. Thin Film Magnetless Faraday Rotators for Compact Heterogeneous Integrated Optical Isolators (Postprint)

    Science.gov (United States)

    2017-06-15

    AFRL-RX-WP-JA-2017-0348 THIN-FILM MAGNETLESS FARADAY ROTATORS FOR COMPACT HETEROGENEOUS INTEGRATED OPTICAL ISOLATORS (POSTPRINT) Dolendra Karki...Interim 9 May 2016 – 1 December 2016 4. TITLE AND SUBTITLE THIN-FILM MAGNETLESS FARADAY ROTATORS FOR COMPACT HETEROGENEOUS INTEGRATED OPTICAL...transfer of ultra-compact thin-film magnetless Faraday rotators to silicon photonic substrates. Thin films of magnetization latching bismuth

  2. Inorganic Lead Halide Perovskite Single Crystals: Phase-Selective Low-Temperature Growth, Carrier Transport Properties, and Self-Powered Photodetection

    KAUST Repository

    Saidaminov, Makhsud I.

    2016-12-06

    A rapid, low-temperature, and solution-based route is developed for growing large-sized cesium lead halide perovskite single crystals under ambient conditions. An ultralow minority carrier concentration was measured in CsPbBr3 (≈108 holes per cm3, much lower than in any other lead halide perovskite and crystalline silicon), which enables to realize self-powered photodetectors with a high ON/OFF ratio (105).

  3. Research Update: Physical and electrical characteristics of lead halide perovskites for solar cell applications

    Directory of Open Access Journals (Sweden)

    Simon A. Bretschneider

    2014-04-01

    Full Text Available The field of thin-film photovoltaics has been recently enriched by the introduction of lead halide perovskites as absorber materials, which allow low-cost synthesis of solar cells with efficiencies exceeding 16%. The exact impact of the perovskite crystal structure and composition on the optoelectronic properties of the material are not fully understood. Our progress report highlights the knowledge gained about lead halide perovskites with a focus on physical and optoelectronic properties. We discuss the crystal and band structure of perovskite materials currently implemented in solar cells and the impact of the crystal properties on ferroelectricity, ambipolarity, and the properties of excitons.

  4. Research Update: Luminescence in lead halide perovskites

    Directory of Open Access Journals (Sweden)

    Ajay Ram Srimath Kandada

    2016-09-01

    Full Text Available Efficiency and dynamics of radiative recombination of carriers are crucial figures of merit for optoelectronic materials. Following the recent success of lead halide perovskites in efficient photovoltaic and light emitting technologies, here we review some of the noted literature on the luminescence of this emerging class of materials. After outlining the theoretical formalism that is currently used to explain the carrier recombination dynamics, we review a few significant works which use photoluminescence as a tool to understand and optimize the operation of perovskite based optoelectronic devices.

  5. Metal-halide lamp design: atomic and molecular data needed

    International Nuclear Information System (INIS)

    Lapatovich, Walter P

    2009-01-01

    Metal-halide lamps are a subset of high intensity discharge (HID) lamps so named because of their high radiance. These lamps are low temperature (∼0.5 eV), weakly ionized plasmas sustained in refractory but light transmissive envelopes by the passage of electric current through atomic and molecular vapors. For commercial applications, the conversion of electric power to light must occur with good efficiency and with sufficient spectral content throughout the visible (380-780 nm) to permit the light so generated to render colors comparable to natural sunlight. This is achieved by adding multiple metals to a basic mercury discharge. Because the vapor pressure of most metals is very much lower than mercury itself, metal-halide salts of the desired metals, having higher vapor pressures, are used to introduce the material into the basic discharge. The metal compounds are usually polyatomic iodides, which vaporize and subsequently dissociate as they diffuse into the bulk plasma. Metals with multiple visible transitions are necessary to achieve high photometric efficiency (efficacy) and good color. Compounds of Sc, Dy, Ho, Tm, Ce, Pr, Yb and Nd are commonly used. The electrons, atoms and radicals are in local thermodynamic equilibrium (LTE), but not with the radiation field. Strong thermal (10 6 K m -1 ) and density gradients are sustained in the discharge. Atomic radiation produced in the high-temperature core transits through colder gas regions where it interacts with cold atoms and un-dissociated molecules before exiting the lamp. Power balance and spectral output of the lamp are directly affected by the strength of atomic transitions. Attempts to simulate the radiative output of functional metal-halide lamps have been successful only in very simple cases. More data (e.g. the atomic transition probabilities of Ce i) are necessary to improve lamp performance, to select appropriate radiators and in scaling the lamp geometry to various wattages for specific applications.

  6. Thermoluminescence response of a mixed ternary alkali halide crystals exposed to gamma rays

    International Nuclear Information System (INIS)

    Rodriguez M, R.; Perez S, R.; Vazquez P, G.; Riveros, H.; Gonzalez M, P.

    2014-08-01

    Ionic crystals, mainly alkali halide crystals have been the subject of intense research for a better understanding of the luminescence properties of defects induced by ionizing radiation. The defects in crystals can be produced in appreciable concentration due to elastic stresses, radiation, and addition of impurities. These defects exhibit remarkable thermoluminescence properties. This work is concerned with the Tl properties of a ternary alkali halide crystal after being irradiated with gamma and beta rays. It has been found that the Tl glow peak of the crystal follows a rule of average associated to the Tl Temperatures of the components of the mixture, similarly to the response of europium doped binary mixed crystals KCl x KBr 1-x and KBr x RbBr 1-x . (Author)

  7. Possible configuration of two-knot auto-localized exciton in strainless and deformed alkali halide crystals

    International Nuclear Information System (INIS)

    Dzhumanov, S.; Tulepbergenov, S.K.; Shunkeev, K.Sh.

    2002-01-01

    In the paper molecular component of two-knot auto-localized exciton (TALE) occupying centrosymmetric state in alkali halide crystal cubic lattice with local D 2h symmetry is considered. In is suggested that the symmetry lowering of forming small radius auto-localized exciton (ALE) is realizing in order configuration transformation by the scenario: multi-knot continual ALE (with O h symmetry)→six-halide ALE (with O h symmetry)→TALE (with O h symmetry) or by the scenario O h →D 2h . Then for TALE with local D 2h symmetry normal molecular ion shifts are considered as well

  8. Students' Understanding of Alkyl Halide Reactions in Undergraduate Organic Chemistry

    Science.gov (United States)

    Cruz-Ramírez de Arellano, Daniel; Towns, Marcy H.

    2014-01-01

    Organic chemistry is an essential subject for many undergraduate students completing degrees in science, engineering, and pre-professional programs. However, students often struggle with the concepts and skills required to successfully solve organic chemistry exercises. Since alkyl halides are traditionally the first functional group that is…

  9. Epitaxial Growth of a Methoxy-Functionalized Quaterphenylene on Alkali Halide Surfaces

    DEFF Research Database (Denmark)

    Balzer, Frank; Sun, Rong; Parisi, Jürgen

    2015-01-01

    The epitaxial growth of the methoxy functionalized para-quaterphenylene (MOP4) on the (001) faces of the alkali halides NaCl and KCl and on glass is investigated by a combination of lowenergy electron diffraction (LEED), polarized light microscopy (PLM), atomic force microscopy (AFM), and X...

  10. Structural stability, acidity, and halide selectivity of the fluoride riboswitch recognition site

    KAUST Repository

    Chawla, Mohit

    2015-01-14

    Using static and dynamics DFT methods we show that the Mg2+/F-/phosphate/water cluster at the center of the fluoride riboswitch is stable by its own and, once assembled, does not rely on any additional factor from the overall RNA fold. Further, we predict that the pKa of the water molecule bridging two Mg cations is around 8.4. We also demonstrate that the halide selectivity of the fluoride riboswitch is determined by the stronger Mg-F bond, which is capable of keeping together the cluster. Replacing F- with Cl- results in a cluster that is unstable under dynamic conditions. Similar conclusions on the structure and energetics of the cluster in the binding pocket of fluoride-inhibited pyrophosphatase suggest that the peculiarity of fluoride is in its ability to establish much stronger metal-halide bonds.

  11. Structural stability, acidity, and halide selectivity of the fluoride riboswitch recognition site

    KAUST Repository

    Chawla, Mohit; Credendino, Raffaele; Poater, Albert; Oliva, Romina M.; Cavallo, Luigi

    2015-01-01

    Using static and dynamics DFT methods we show that the Mg2+/F-/phosphate/water cluster at the center of the fluoride riboswitch is stable by its own and, once assembled, does not rely on any additional factor from the overall RNA fold. Further, we predict that the pKa of the water molecule bridging two Mg cations is around 8.4. We also demonstrate that the halide selectivity of the fluoride riboswitch is determined by the stronger Mg-F bond, which is capable of keeping together the cluster. Replacing F- with Cl- results in a cluster that is unstable under dynamic conditions. Similar conclusions on the structure and energetics of the cluster in the binding pocket of fluoride-inhibited pyrophosphatase suggest that the peculiarity of fluoride is in its ability to establish much stronger metal-halide bonds.

  12. Stereodirection of an α-ketoester at sub-molecular sites on chirally modified Pt(111): Heterogeneous asymmetric catalysis

    DEFF Research Database (Denmark)

    Demers-Carpentier, V.; Rasmussen, A.M.H.; Goubert, G.

    2013-01-01

    Chirally modified Pt catalysts are used in the heterogeneous asymmetric hydrogenation of α-ketoesters. Stereoinduction is believed to occur through the formation of chemisorbed modifier–substrate complexes. In this study, the formation of diastereomeric complexes by coadsorbed methyl 3,3,3-triflu......Chirally modified Pt catalysts are used in the heterogeneous asymmetric hydrogenation of α-ketoesters. Stereoinduction is believed to occur through the formation of chemisorbed modifier–substrate complexes. In this study, the formation of diastereomeric complexes by coadsorbed methyl 3...

  13. Practical chemical analysis of Pt and Pd based heterogeneous catalysts with hard X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yoshikawa, H., E-mail: YOSHIKAWA.Hideki@nims.go.jp [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Matolínová, I.; Matolín, V. [Charles University in Prague, Faculty of Mathematics and Physics, V Holešovičkách 2, 18000 Prague 8 (Czech Republic)

    2013-10-15

    Highlights: •Hard X-ray photoelectron spectroscopy (HAXPES) enables interface analysis of catalyst. •HAXPES enables overall analysis of porous film of Pt-doped CeO{sub 2} and related catalyst. •HAXPES enables analysis of trace elements for Pd and Pt{sub 3}Ni nanoparticle catalysts. -- Abstract: Interfacial properties including configuration, porosity, chemical states, and atomic diffusion greatly affect the performance of supported heterogeneous catalysts. Hard X-ray photoelectron spectroscopy (HAXPES) can be used to analyze the interfaces of heterogeneous catalysts because of its large information depth of more than 20 nm. We use HAXPES to examine Pt-doped CeO{sub 2} and related thin film catalysts evaporated on Si, carbon, and carbon nanotube substrates, because Pt-doped CeO{sub 2} has great potential as a noble metal-based heterogeneous catalyst for fuel cells. The HAXPES measurements clarify that the dopant material, substrate material, and surface pretreatment of substrate are important parameters that affect the interfacial properties of Pt-doped CeO{sub 2} and related thin film catalysts. Another advantage of HAXPES measurement of heterogeneous catalysts is that it can be used for chemical analysis of trace elements by detecting photoelectrons from deep core levels, which have large photoionization cross-sections in the hard X-ray region. We use HAXPES for chemical analysis of trace elements in Pd nanoparticle catalysts immobilized on sulfur-terminated substrates and Pt{sub 3}Ni nanoparticle catalysts enveloped by dendrimer molecules.

  14. Tailoring Mixed-Halide, Wide-Gap Perovskites via Multistep Conversion Process

    NARCIS (Netherlands)

    Bae, D.; Palmstrom, A.; Roelofs, K.; Mei, Bastian Timo; Chorkendorf, I.; Bent, S.F.; Vesborg, P.C.

    2016-01-01

    Wide-band-gap mixed-halide CH3NH3PbI3–XBrX-based solar cells have been prepared by means of a sequential spin-coating process. The spin-rate for PbI2 as well as its repetitive deposition are important in determining the cross-sectional shape and surface morphology of perovskite, and, consequently,

  15. Homocoupling of benzyl halides catalyzed by POCOP-nickel pincer complexes

    KAUST Repository

    Chen, Tao

    2012-08-01

    Two types of POCOP-nickel(II) pincer complexes were prepared by mixing POCOP pincer ligands and NiX 2 in toluene at reflux. The resulting nickel complexes efficiently catalyze the homocoupling reactions of benzyl halides in the presence of zinc. The coupled products were obtained in excellent to quantitative yields. © 2012 Elsevier Ltd. All rights reserved.

  16. Parity-Forbidden Transitions and Their Impact on the Optical Absorption Properties of Lead-Free Metal Halide Perovskites and Double Perovskites.

    Science.gov (United States)

    Meng, Weiwei; Wang, Xiaoming; Xiao, Zewen; Wang, Jianbo; Mitzi, David B; Yan, Yanfa

    2017-07-06

    Using density functional theory calculations, we analyze the optical absorption properties of lead (Pb)-free metal halide perovskites (AB 2+ X 3 ) and double perovskites (A 2 B + B 3+ X 6 ) (A = Cs or monovalent organic ion, B 2+ = non-Pb divalent metal, B + = monovalent metal, B 3+ = trivalent metal, X = halogen). We show that if B 2+ is not Sn or Ge, Pb-free metal halide perovskites exhibit poor optical absorptions because of their indirect band gap nature. Among the nine possible types of Pb-free metal halide double perovskites, six have direct band gaps. Of these six types, four show inversion symmetry-induced parity-forbidden or weak transitions between band edges, making them not ideal for thin-film solar cell applications. Only one type of Pb-free double perovskite shows optical absorption and electronic properties suitable for solar cell applications, namely, those with B + = In, Tl and B 3+ = Sb, Bi. Our results provide important insights for designing new metal halide perovskites and double perovskites for optoelectronic applications.

  17. First-principles thermodynamics study of phase stability in inorganic halide perovskite solid solutions

    Science.gov (United States)

    Bechtel, Jonathon S.; Van der Ven, Anton

    2018-04-01

    Halide substitution gives rise to a tunable band gap as a function of composition in halide perovskite materials. However, photoinduced phase segregation, observed at room temperature in mixed halide A Pb (IxBr1-x) 3 systems, limits open circuit voltages and decreases photovoltaic device efficiencies. We investigate equilibrium phase stability of orthorhombic P n m a γ -phase CsM (XxY1-x) 3 perovskites where M is Pb or Sn, and X and Y are Br, Cl, or I. Finite-temperature phase diagrams are constructed using a cluster expansion effective Hamiltonian parameterized from first-principles density-functional-theory calculations. Solid solution phases for CsM (IxBr1-x) 3 and CsM (BrxCl1-x) 3 are predicted to be stable well below room temperature while CsM (IxCl1-x) 3 systems have miscibility gaps that extend above 400 K. The height of the miscibility gap correlates with the difference in volume between end members. Also layered ground states are found on the convex hull at x =2 /3 for CsSnBr2Cl ,CsPbI2Br , and CsPbBrCl2. The impact of these ground states on the finite temperature phase diagram is discussed in the context of the experimentally observed photoinduced phase segregation.

  18. Design of Lead-Free Inorganic Halide Perovskites for Solar Cells via Cation-Transmutation.

    Science.gov (United States)

    Zhao, Xin-Gang; Yang, Ji-Hui; Fu, Yuhao; Yang, Dongwen; Xu, Qiaoling; Yu, Liping; Wei, Su-Huai; Zhang, Lijun

    2017-02-22

    Hybrid organic-inorganic halide perovskites with the prototype material of CH 3 NH 3 PbI 3 have recently attracted intense interest as low-cost and high-performance photovoltaic absorbers. Despite the high power conversion efficiency exceeding 20% achieved by their solar cells, two key issues-the poor device stabilities associated with their intrinsic material instability and the toxicity due to water-soluble Pb 2+ -need to be resolved before large-scale commercialization. Here, we address these issues by exploiting the strategy of cation-transmutation to design stable inorganic Pb-free halide perovskites for solar cells. The idea is to convert two divalent Pb 2+ ions into one monovalent M + and one trivalent M 3+ ions, forming a rich class of quaternary halides in double-perovskite structure. We find through first-principles calculations this class of materials have good phase stability against decomposition and wide-range tunable optoelectronic properties. With photovoltaic-functionality-directed materials screening, we identify 11 optimal materials with intrinsic thermodynamic stability, suitable band gaps, small carrier effective masses, and low excitons binding energies as promising candidates to replace Pb-based photovoltaic absorbers in perovskite solar cells. The chemical trends of phase stabilities and electronic properties are also established for this class of materials, offering useful guidance for the development of perovskite solar cells fabricated with them.

  19. Rocksalt or cesium chloride: Investigating the relative stability of the cesium halide structures with random phase approximation based methods

    Science.gov (United States)

    Nepal, Niraj K.; Ruzsinszky, Adrienn; Bates, Jefferson E.

    2018-03-01

    The ground state structural and energetic properties for rocksalt and cesium chloride phases of the cesium halides were explored using the random phase approximation (RPA) and beyond-RPA methods to benchmark the nonempirical SCAN meta-GGA and its empirical dispersion corrections. The importance of nonadditivity and higher-order multipole moments of dispersion in these systems is discussed. RPA generally predicts the equilibrium volume for these halides within 2.4% of the experimental value, while beyond-RPA methods utilizing the renormalized adiabatic LDA (rALDA) exchange-correlation kernel are typically within 1.8%. The zero-point vibrational energy is small and shows that the stability of these halides is purely due to electronic correlation effects. The rAPBE kernel as a correction to RPA overestimates the equilibrium volume and could not predict the correct phase ordering in the case of cesium chloride, while the rALDA kernel consistently predicted results in agreement with the experiment for all of the halides. However, due to its reasonable accuracy with lower computational cost, SCAN+rVV10 proved to be a good alternative to the RPA-like methods for describing the properties of these ionic solids.

  20. Ground state depletion – A step towards mid-IR lasing of doped silver halides

    Energy Technology Data Exchange (ETDEWEB)

    Tsur, Yuval, E-mail: yuvaltsu@post.tau.ac.il [Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 6997801 (Israel); Goldring, Sharone [Applied Physics Division, Soreq NRC, Yavne 81800 (Israel); Galun, Ehud [DDR& D, Ministry of Defense (Israel); Katzir, Abraham [Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 6997801 (Israel)

    2016-07-15

    We show for the first time ground state absorption saturation in a doped silver halide crystal (AgCl{sub x}Br{sub 1−x}), specifically with cobalt. Spectroscopic studies showed absorption bands in the 1.4–2.5 μm region and emission bands in the 3.8–5.0 μm region, with a 1.5 ms lifetime at low temperatures. Absorption saturation indicates a good low and room temperature lasing feasibility at 4.1 μm. In addition, a comparison of cobalt, nickel and iron as dopants is presented. These doped silver halide crystals can be extruded to form optical fibers, possibly introducing a new family of fiber lasers for the middle infrared.

  1. A mild and efficient procedure for the synthesis of ethers from various alkyl halides

    Directory of Open Access Journals (Sweden)

    Mosstafa Kazemi

    2013-10-01

    Full Text Available A simple, mild and practical procedure has been developed for the synthesis of symmetrical and unsymmetrical ethers by using DMSO, TBAI in the presence of K2CO3. We extended the utility of Potassium carbonate as an efficient base for the preparation of ethers. A wide range of alkyl aryl and dialkyl ethers are synthezied from treatment of aliphatic alcohols and phenols with various alkyl halides in the prescence of efficient base Potassium carbonate. Secondary alkyl halides were easily converted to corresponding ethers in releatively good yields . This is a mild, simple and practical procedure for the preparation of ethers in high yields and suitable times under mild condition.

  2. Investigation of sodalites for conditioning halide salts (NaCl and NaI): Comparison of two synthesis routes

    Energy Technology Data Exchange (ETDEWEB)

    Bardez, Isabelle; Campayo, Lionel; Rigaud, Danielle; Chartier, Myriam; Calvet, Aurelie [CEA, Laboratoire d' Etudes des Materiaux Ceramiques pour le Conditionnement, Site de Marcoule, Batiment 208, B.P. 17171, 30207 Bagnols sur Ceze cedex (France)

    2008-07-01

    Sodalites with the general formula Na{sub 8}Al{sub 6}Si{sub 6}O{sub 24}X{sub 2} (where X = Cl or I) were investigated for ceramic conditioning of halide salts (NaCl and NaI). Because of the tendency of halides to volatilize at high temperature, two synthesis routes were tested to optimize the halide content in the sodalite phase. The first is based on heating at high temperature of a [nepheline NaAlSiO{sub 4} + salt] mixture prepared by a dry process. The second, performed at low temperature, consists of the reaction in aqueous media between kaolinite (Al{sub 2}Si{sub 2}O{sub 5}(OH){sub 4}), sodium hydroxide (NaOH) and the salt. The present study compares these two syntheses and examines differences between chloro-sodalite and iodo-sodalite based on X-ray diffraction and infrared spectroscopy. The next step will consist in sintering the resulting powder samples to obtain dense ceramics. (authors)

  3. Corrosion inhibition of iron in 0.5 mol L-1 H2SO4 by halide ions

    Directory of Open Access Journals (Sweden)

    Jeyaprabha C.

    2006-01-01

    Full Text Available The inhibition effect of halide ions such as iodide, bromide and chloride ions on the corrosion of iron in 0.5 mol L-1 H2SO4 and the adsorption behaviour of these ions on the electrode surface have been studied by polarization and impedance methods. It has been found that the inhibition of nearly 90% has been observed for iodide ions at 2.5 10-3 mol L-1, for bromide ions at 10 10-3 mol L-1 and 80% for chloride ions at 2.5 10-3 mol L-1. The inhibition effect is increased with increase of halide ions concentration in the case of I- and Br- ions, whereas it has decreased in the case of Cl- ion at concentrations higher than 5 10-3 mol L-1. The double layer capacitance values have decreased considerably in the presence of halide ions which indicate that these anions are adsorbed on iron at the corrosion potential.

  4. Impact of the organic halide salt on final perovskite composition for photovoltaic applications

    KAUST Repository

    Moore, David T.; Sai, Hiroaki; Wee Tan, Kwan; Estroff, Lara A.; Wiesner, Ulrich

    2014-01-01

    The methylammonium lead halide perovskites have shown significant promise as a low-cost, second generation, photovoltaic material.Despite recent advances, however, there are still a number of fundamental aspects of their formation as well

  5. (e,2e) momentum spectroscopic study of the C=C π orbitals of the vinyl halides

    International Nuclear Information System (INIS)

    Gorunganthu, R.R.; Coplan, M.A.; Leung, K.T.; Tossell, J.A.; Moore, J.H.; Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada; Department of Chemistry, University of Maryland, College Park, Maryland 20742)

    1989-01-01

    The distribution of electron momentum density has been measured for the outermost occupied orbitals of the vinyl halides and ethylene using the (e,2e) technique. In contrast to the ionization potentials for these π orbitals which decrease monotonically from vinyl fluoride to vinyl iodide, the values of the momenta where the distributions are a maximum, p max , increase from the fluoride through the bromide and then shift back to a lower value for the iodide. This observation can be analyzed in terms of B(r), the Fourier transform of the observed momentum distribution, and ΔB(r), the difference between B(r) functions. The shape of ΔB(r) for the fluoride, chloride, and bromide in comparison to ethylene reflects the effect of the carbon--halogen antibonding interaction in these vinyl halides. On the other hand, in vinyl iodide the antibonding interaction is compensated for by the diffuse iodine 5p character of the molecular orbital. The relation of these observations to chemical properties of the vinyl halides is discussed along with differences between experiment and calculations at low momentum

  6. Thermoluminescence response of a mixed ternary alkali halide crystals exposed to gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez M, R.; Perez S, R. [Universidad de Sonora, Departamento de Investigacion en Fisica, Apdo. Postal 5-088, 83190 Hermosillo, Sonora (Mexico); Vazquez P, G.; Riveros, H. [UNAM, Instituto de Fisica, Apdo. Postal 20-364, 01000 Mexico D. F. (Mexico); Gonzalez M, P., E-mail: mijangos@cifus.uson.mx [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2014-08-15

    Ionic crystals, mainly alkali halide crystals have been the subject of intense research for a better understanding of the luminescence properties of defects induced by ionizing radiation. The defects in crystals can be produced in appreciable concentration due to elastic stresses, radiation, and addition of impurities. These defects exhibit remarkable thermoluminescence properties. This work is concerned with the Tl properties of a ternary alkali halide crystal after being irradiated with gamma and beta rays. It has been found that the Tl glow peak of the crystal follows a rule of average associated to the Tl Temperatures of the components of the mixture, similarly to the response of europium doped binary mixed crystals KCl{sub x}KBr{sub 1-x} and KBr{sub x}RbBr{sub 1-x}. (Author)

  7. Design nanocrack patterns in heterogeneous films

    International Nuclear Information System (INIS)

    Salac, David; Lu Wei

    2006-01-01

    Nanowires have significant potential in future technologies such as nanomechanical devices and electronics. Recent experiments suggest that nanowires with sub-100 nm diameters may be fabricated by filling cracks with various materials. The geometry of cracks becomes important on such a length scale, and the practical application of the approach requires an understanding of crack evolution in heterogeneous films. This paper proposes a level-set approach to model directed nanocracks on pre-patterned substrates. The approach does not require the explicit tracking of crack fronts and thus allows the simulation of complex crack patterns. Results indicate that pre-patterning a substrate can lead to various well controlled nanocrack patterns, suggesting a possibility to make designed and complex nanowires difficult to obtain with other methods

  8. Designing mixed metal halide ammines for ammonia storage using density functional theory and genetic algorithms

    DEFF Research Database (Denmark)

    Jensen, Peter Bjerre; Lysgaard, Steen; Quaade, Ulrich J.

    2014-01-01

    electrolyte membrane fuel cells (PEMFC). We use genetic algorithms (GAs) to search for materials containing up to three different metals (alkaline-earth, 3d and 4d) and two different halides (Cl, Br and I) – almost 27000 combinations, and have identified novel mixtures, with significantly improved storage......Metal halide ammines have great potential as a future, high-density energy carrier in vehicles. So far known materials, e.g. Mg(NH3)6Cl2 and Sr(NH3)8Cl2, are not suitable for automotive, fuel cell applications, because the release of ammonia is a multi-step reaction, requiring too much heat...

  9. Hyphal heterogeneity in Aspergillus niger

    OpenAIRE

    de Bekker, A.M.

    2011-01-01

    Mycelial fungi use hyphae to colonize substrates. These hyphae secrete enzymes that convert complex polymers into breakdown products that can be taken up to serve as nutrients. Using GFP as a reporter it has been shown that exploring hyphae of Aspergillus niger are heterogenic with respect to expression of the glucoamylase gene glaA; some hyphae strongly express the glucoamylase gene glaA, while others express it lowly. This was a surprising finding considering the fact that all hyphae were e...

  10. Modulation of electronic and optical properties in mixed halide perovskites CsPbCl3xBr3(1-x) and CsPbBr3xI3(1-x)

    Science.gov (United States)

    Zhou, Ziqi; Cui, Yu; Deng, Hui-Xiong; Huang, Le; Wei, Zhongming; Li, Jingbo

    2017-03-01

    The recent discovery of lead halide perovskites with band gaps in the visible presents important potential in the design of high efficient solar cells. CsPbCl3, CsPbBr3 and CsPbI3 are stable compounds within this new family of semiconductors. By performing the first-principles calculation, we explore the structural, electronic and optical properties of CsPbCl3xBr3(1-x) and CsPbBr3xI3(1-x) with various compositions of halide atoms. Structural stability is demonstrated with halide atoms distributing randomly at the halide atomic sites. CsPbCl3xBr3(1-x) and CsPbBr3xI3(1-x) exhibit the modulation of their band gaps by varying the halide composition. Our results also indicate that CsPbCl3xBr3(1-x) and CsPbBr3xI3(1-x) with different halide compositions are suitable to application to solar cells for the general features are well preserved. Good absorption to lights of different wavelengths has been obtained in these mixed halide perovskites.

  11. The importance of moisture in hybrid lead halide perovskite thin film fabrication

    NARCIS (Netherlands)

    Eperon, G.E.; Habisreutinger, S.N.; Leijtens, T.; Bruijnaers, B.J.; van Franeker, J.J.; deQuilettes, D.W.; Pathak, S.; Sutton, R.J.; Grancini, G.; Ginger, D.S.; Janssen, R.A.J.; Petrozza, A.; Snaith, H.J.

    2015-01-01

    Moisture, in the form of ambient humidity, has a significant impact on methylammonium lead halide perovskite films. In particular, due to the hygroscopic nature of the methylammonium component, moisture plays a significant role during film formation. This issue has so far not been well understood

  12. 40 CFR 63.2465 - What requirements must I meet for process vents that emit hydrogen halide and halogen HAP or HAP...

    Science.gov (United States)

    2010-07-01

    ... process vents that emit hydrogen halide and halogen HAP or HAP metals? 63.2465 Section 63.2465 Protection... and halogen HAP or HAP metals? (a) You must meet each emission limit in Table 3 to this subpart that... section. (b) If any process vents within a process emit hydrogen halide and halogen HAP, you must...

  13. [BMIM][PF(6)] promotes the synthesis of halohydrin esters from diols using potassium halides.

    Science.gov (United States)

    Oromí-Farrús, Mireia; Eras, Jordi; Villorbina, Gemma; Torres, Mercè; Llopis-Mestre, Veronica; Welton, Tom; Canela, Ramon

    2008-10-01

    Haloesterification of diverse diols with various carboxylic acids was achieved using potassium halides (KX) as the only halide source in ionic liquids. The best yield was obtained in [BMIM][PF(6)] when 1,2-octanediol, palmitic acid and KBr were used. This yield was 85% and the regioisomer with the bromine in primary position was present in a 75:25 ratio. The regioisomeric ratio could be improved using either KCl or some phenylcarboxylic acids. [BMIM][PF(6)] acts as both reaction media and catalyst of the reaction. To the best of our knowledge, this type of combined reaction using an ionic liquid is unprecedented. The other solvents tested did not lead either to the same yield or to the same regioisomeric ratio.

  14. Alloying effects on superionic conductivity in lithium indium halides for all-solid-state batteries

    Science.gov (United States)

    Zevgolis, Alysia; Wood, Brandon C.; Mehmedović, Zerina; Hall, Alex T.; Alves, Thomaz C.; Adelstein, Nicole

    2018-04-01

    Alloying of anions is a promising engineering strategy for tuning ionic conductivity in halide-based inorganic solid electrolytes. We explain the alloying effects in Li3InBr6-xClx, in terms of strain, chemistry, and microstructure, using first-principles molecular dynamics simulations and electronic structure analysis. We find that strain and bond chemistry can be tuned through alloying and affect the activation energy and maximum diffusivity coefficient. The similar conductivities of the x = 3 and x = 6 compositions can be understood by assuming that the alloy separates into Br-rich and Cl-rich regions. Phase-separation increases diffusivity at the interface and in the expanded Cl-region, suggesting microstructure effects are critical. Similarities with other halide superionic conductors are highlighted.

  15. Protonation of octadecylamine Langmuir monolayer by adsorption of halide counterions

    Science.gov (United States)

    Sung, Woongmo; Avazbaeva, Zaure; Lee, Jonggwan; Kim, Doseok

    Langmuir monolayer consisting of octadecylamine (C18H37NH2, ODA) was investigated by heterodyne vibrational sum-frequency generation (HD-VSFG) spectroscopy in conjunction with surface pressure-area (π- A) isotherm, and the result was compared with that from cationic-lipid (DPTAP) Langmuir monolayer. In case of ODA monolayer on pure water, both SF intensity of water OH band and the surface pressure were significantly smaller than those of the DPTAP monolayer implying that only small portion of the amine groups (-NH3+ is protonated in the monolayer. In the presence of sodium halides (NaCl and NaI) in the subphase water, it was found that the sign of Imχ (2) of water OH band remained the same as that of the ODA monolayer on pure water, but there was a substantial increase in the SF amplitude. From this, we propose that surface excess of the halide counterions (Cl- and I-) makes the solution condition near the ODA monolayer/water interface more acidic so that ODA molecules in the monolayer are more positively charged, which works to align the water dipoles at the interface.

  16. Spatially resolved microrheology of heterogeneous biopolymer hydrogels using covalently bound microspheres

    NARCIS (Netherlands)

    Wong, L.H.; Kurniawan, Nicholas A.; Too, H.-P.; Rajagopalan, R.

    2014-01-01

    Characterization of the rheological properties of heterogeneous biopolymers is important not only to understand the effect of substrate elasticity on cell behaviors, but also to provide insights into mechanical changes during cellular remodeling of the environment. Conventional particle-tracking

  17. Heterogeneity in magnetic complex oxides

    Science.gov (United States)

    Arenholz, Elke

    Heterogeneity of quantum materials on the nanoscale can result from the spontaneous formation of regions with distinct atomic, electronic and/or magnetic order, and indicates coexistence of competing quantum phases. In complex oxides, the subtle interplay of lattice, charge, orbital, and spin degrees of freedom gives rise to especially rich phase diagrams. For example, coexisting conducting and insulating phases can occur near metal-insulator transitions, colossal magnetoresistance can emerge where ferromagnetic and antiferromagnetic domains compete, and charge-ordered and superconducting regions are present simultaneously in materials exhibiting high-temperature superconductivity. Additionally, externally applied fields (electric, magnetic, or strain) or other external excitations (light or heat) can tip the energy balance towards one phase, or support heterogeneity and phase coexistence and provide the means to perturb and tailor quantum heterogeneity at the nanoscale. Engineering nanomaterials, with structural, electronic and magnetic characteristics beyond what is found in bulk materials, is possible today through the technique of thin film epitaxy, effectively a method of `spray painting' atoms on single crystalline substrates to create precisely customized layered structures with atomic arrangements defined by the underlying substrate. Charge transfer and spin polarization across interfaces as well as imprinting nanoscale heterogeneity between adjacent layers lead to intriguing and important new phenomena testing our understanding of basic physics and creating new functionalities. Moreover, the abrupt change of orientation of an order parameter between nanoscale domains can lead to unique phases that are localized at domain walls, including conducting domain walls in insulating ferroelectrics, and ferromagnetic domain walls in antiferromagnets. Here we present our recent results on tailoring the electronic anisotropy of multiferroic heterostructures by

  18. Combinatorial screening of halide perovskite thin films and solar cells by mask-defined IR laser molecular beam epitaxy

    OpenAIRE

    Kawashima, Kazuhiro; Okamoto, Yuji; Annayev, Orazmuhammet; Toyokura, Nobuo; Takahashi, Ryota; Lippmaa, Mikk; Itaka, Kenji; Suzuki, Yoshikazu; Matsuki, Nobuyuki; Koinuma, Hideomi

    2017-01-01

    Abstract As an extension of combinatorial molecular layer epitaxy via ablation of perovskite oxides by a pulsed excimer laser, we have developed a laser molecular beam epitaxy (MBE) system for parallel integration of nano-scaled thin films of organic?inorganic hybrid materials. A pulsed infrared (IR) semiconductor laser was adopted for thermal evaporation of organic halide (A-site: CH3NH3I) and inorganic halide (B-site: PbI2) powder targets to deposit repeated A/B bilayer films where the thic...

  19. Analogy between temperature dependent radiation effects in alkali halide crystals and crystalline ammonia

    International Nuclear Information System (INIS)

    Blum, A.

    1977-01-01

    Pikaev, Ershov, and Makarov recently reported the characteristic shape of Arrhenius-type dependence for F-centers slow part (millisecond) decay in alkali halide crystals irradiated at different temperatures. The decay rate is constant when the temperature is below the limiting value (T/sub lim/) and exhibits constant activation energy (E/sub A/) at temperatures above T/sub lim/ up to the melting point. A similar dependence has been observed for crystalline ammonia radiolysis yields (H 2 and N 2 ) in the temperature range from 77 to 195 0 K (ammonia melting point) with a limiting value of 105 0 K for N 2 and 119 0 K for H 2 . The coincidence between the alkali halide and ammonia data does not seem to be formal and there are indications showing a closer analogy between these two cases

  20. Intrinsic Defect Physics in Indium-based Lead-free Halide Double Perovskites.

    Science.gov (United States)

    Xu, Jian; Liu, Jian-Bo; Liu, Bai-Xin; Huang, Bing

    2017-09-21

    Lead-free halide double perovskites (HDPs) are expected to be promising photovoltaic (PV) materials beyond organic-inorganic halide perovskite, which is hindered by its structural instability and toxicity. The defect- and stability-related properties of HDPs are critical for the use of HDPs as important PV absorbers, yet their reliability is still unclear. Taking Cs 2 AgInBr 6 as a representative, we have systemically investigated the defect properties of HDPs by theoretical calculations. First, we have determined the stable chemical potential regions to grow stoichiometric Cs 2 AgInBr 6 without structural decomposition. Second, we reveal that Ag-rich and Br-poor are the ideal chemical potential conditions to grow n-type Cs 2 AgInBr 6 with shallow defect levels. Third, we find the conductivity of Cs 2 AgInBr 6 can change from good n-type, to poorer n-type, to intrinsic semiconducting depending on the growth conditions. Our studies provided important guidance for experiments to fabricate Pb-free perovskite-based solar cell devices with superior PV performances.

  1. Sodium-Metal-Halide Battery Energy Storage for DoD Installations

    Science.gov (United States)

    2017-10-24

    electrical equipment for AC interface PDE Pacific Data Electric V&F Voltage and Frequency, power quality measurements VA Volt-Amp, units for apparent...Metal-Halide technology could operate at extreme ambient temperatures, but the early prototypes did struggle with managing sand ingress.  The...peak power Not tested 3. PV smoothing Measure improvement in power quality Power meter measurements Power quality improvements 15-min

  2. Rapid Microwave-Assisted Copper-Catalyzed Nitration of Aromatic Halides with Nitrite Salts

    Energy Technology Data Exchange (ETDEWEB)

    Paik, Seung Uk; Jung, Myoung Geun [Keimyung University, Daegu (Korea, Republic of)

    2012-02-15

    A rapid and efficient copper-catalyzed nitration of aryl halides has been established under microwave irradiation. The catalytic systems were found to be the most effective with 4-substituted aryl iodides leading to nearly complete conversions. Nitration of aromatic compounds is one of the important industrial processes as underlying intermediates in the manufacture of a wide range of chemicals such as dyes, pharmaceuticals, agrochemicals and explosives. General methods for the nitration of aromatic compounds utilize strongly acidic conditions employing nitric acid or a mixture of nitric and sulfuric acids, sometimes leading to problems with poor regioselectivity, overnitration, oxidized byproducts and excess acid waste in many cases of functionalized aromatic compounds. Several other nitrating agents or methods avoiding harsh reaction conditions have been explored using metal nitrates, nitrite salts, and ionic liquid-mediated or microwave-assisted nitrations. Recently, copper or palladium compounds have been successfully used as efficient catalysts for the arylation of amines with aryl halides under mild conditions.

  3. Efficient Photon Recycling and Radiation Trapping in Cesium Lead Halide Perovskite Waveguides

    KAUST Repository

    Dursun, Ibrahim

    2018-05-26

    Cesium lead halide perovskite materials have attracted considerable attention for potential applications in lasers, light emitting diodes and photodetectors. Here, we provide the experimental and theoretical evidence for photon recycling in CsPbBr3 perovskite microwires. Using two-photon excitation, we recorded photoluminescence (PL) lifetimes and emission spectra as a function of the lateral distance between PL excitation and collection positions along the microwire, with separations exceeding 100 µm. At longer separations, the PL spectrum develops a red-shifted emission peak accompanied by an appearance of well-resolved rise times in the PL kinetics. We developed quantitative modeling that accounts for bimolecular recombination and photon recycling within the microwire waveguide and is sufficient to account for the observed decay modifications. It relies on a high radiative efficiency in CsPbBr3 perovskite microwires and provides crucial information about the potential impact of photon recycling and waveguide trapping on optoelectronic properties of cesium lead halide perovskite materials.

  4. Rapid Microwave-Assisted Copper-Catalyzed Nitration of Aromatic Halides with Nitrite Salts

    International Nuclear Information System (INIS)

    Paik, Seung Uk; Jung, Myoung Geun

    2012-01-01

    A rapid and efficient copper-catalyzed nitration of aryl halides has been established under microwave irradiation. The catalytic systems were found to be the most effective with 4-substituted aryl iodides leading to nearly complete conversions. Nitration of aromatic compounds is one of the important industrial processes as underlying intermediates in the manufacture of a wide range of chemicals such as dyes, pharmaceuticals, agrochemicals and explosives. General methods for the nitration of aromatic compounds utilize strongly acidic conditions employing nitric acid or a mixture of nitric and sulfuric acids, sometimes leading to problems with poor regioselectivity, overnitration, oxidized byproducts and excess acid waste in many cases of functionalized aromatic compounds. Several other nitrating agents or methods avoiding harsh reaction conditions have been explored using metal nitrates, nitrite salts, and ionic liquid-mediated or microwave-assisted nitrations. Recently, copper or palladium compounds have been successfully used as efficient catalysts for the arylation of amines with aryl halides under mild conditions

  5. Radiation processes in organic halides (Cl, Br, I) studied by ESR spectroscopy

    International Nuclear Information System (INIS)

    Symons, M.C.R.

    1980-01-01

    Electron-loss from alkyl halides (Cl, Br, I) gives Rhal. + which may dimerise to give (Rhal-halR) + σ* radicals with characteristic ESR spectra, or may lose H + to give α-halo radicals (R 2 Chal) also with well characterised ESR spectra. Electron-capture gives dissociation, but there may be weak residual charge-transfer interaction between R. and hal - which gives rise to well defined hyperfine coupling from the halide nuclei. Loss of β-hydrogen gives β-halo radicals, R 2 C-CH 2 hal (Cl,Br) whose conformation, established by ESR spectroscopy, is such that the halogen atom lies out of the radical plane so that overlap between the half-filled 2p(π) orbital and the C-hal (σ) orbital is maximised. Electron addition to α-halocarboxylates and related compounds probably gives β-halo radical anions, (R 2 C[hal]CO 2 H) - with a similar preferred conformation. Alternative structures are considered for these species. (author)

  6. Energetics and dynamics in organic–inorganic halide perovskite photovoltaics and light emitters

    International Nuclear Information System (INIS)

    Sum, Tze Chien; Chen, Shi; Xing, Guichuan; Liu, Xinfeng; Wu, Bo

    2015-01-01

    The rapid transcendence of organic–inorganic metal halide perovskite solar cells to above the 20% efficiency mark has captivated the broad photovoltaic community. As the efficiency race continues unabated, it is essential that fundamental studies keep pace with these developments. Further gains in device efficiencies are expected to be increasingly arduous and harder to come by. The key to driving the perovskite solar cell efficiencies towards their Shockley–Queisser limit is through a clear understanding of the interfacial energetics and dynamics between perovskites and other functional materials in nanostructured- and heterojunction-type devices. In this review, we focus on the current progress in basic characterization studies to elucidate the interfacial energetics (energy-level alignment and band bending) and dynamical processes (from the ultrafast to the ultraslow) in organic–inorganic metal halide perovskite photovoltaics and light emitters. Major findings from these studies will be distilled. Open questions and scientific challenges will also be highlighted. (topical review)

  7. Relationship between thermoluminescence and X-ray induced luminescence in alkali halides

    International Nuclear Information System (INIS)

    Aguilar, M.; Lopez, F.J.; Jaque, F.

    1978-01-01

    The wavelength spectra of thermoluminescence and X-ray induced luminescence in pure and divalent cation doped alkali halides, in the temperature range LNT-RT have been studied. The more important conclusion is that the wavelength spectra in both cases are very similar. This allows a new point of view to be presented on thermoluminescence mechanisms. (author)

  8. A review on bis-hydrazonoyl halides: Recent advances in their synthesis and their diverse synthetic applications leading to bis-heterocycles of biological interest

    Directory of Open Access Journals (Sweden)

    Ahmad Sami Shawali

    2016-11-01

    Full Text Available This review covers a summary of the literature data published on the chemistry of bis-hydrazonoyl halides over the last four decades. The biological activities of some of the bis-heterocyclic compounds obtained from these bis-hydrazonoyl halides are also reviewed and discussed.

  9. Special features of the formation of high-conductivity phases of halides of alkali metals at superhigh pressures

    International Nuclear Information System (INIS)

    Babushkin, A.N.; Babushkina, G.V.

    1999-01-01

    The halides of alkali metals are the simplest crystals with the ionic nature of chemical bonds and are used widely as modelling materials in high-pressure physics. As a result of previous theoretical and experimental (optical, structural, electro-physical and shock-waves) investigations it was shown that these materials may be characterised by the overlapping of the valency and conduction bands and by the formation of groups of free charge carriers at pressures of the megabaric level. However, the authors know of no data on the direct investigations of the electrophysical properties of the halides of alkali metals at such high static pressures. The end of this investigation was to examine the temperature dependences of the electrical conductivity and thermal EMF of halides of alkali metals AX (A = Na, K, Rb, Cs, X = Cl, Br, I) in a wide temperature range at pressures from 10 to 50 GPa in order to reveal the general leisure since governing the change of their electronic structures, in particular, the transition to the state with the activation-type or metallic conductivity

  10. Calcium looping process for high purity hydrogen production integrated with capture of carbon dioxide, sulfur and halides

    Science.gov (United States)

    Ramkumar, Shwetha; Fan, Liang-Shih

    2013-07-30

    A process for producing hydrogen comprising the steps of: (i) gasifying a fuel into a raw synthesis gas comprising CO, hydrogen, steam, sulfur and halide contaminants in the form of H.sub.2S, COS, and HX, wherein X is a halide; (ii) passing the raw synthesis gas through a water gas shift reactor (WGSR) into which CaO and steam are injected, the CaO reacting with the shifted gas to remove CO.sub.2, sulfur and halides in a solid-phase calcium-containing product comprising CaCO.sub.3, CaS and CaX.sub.2; (iii) separating the solid-phase calcium-containing product from an enriched gaseous hydrogen product; and (iv) regenerating the CaO by calcining the solid-phase calcium-containing product at a condition selected from the group consisting of: in the presence of steam, in the presence of CO.sub.2, in the presence of synthesis gas, in the presence of H.sub.2 and O.sub.2, under partial vacuum, and combinations thereof.

  11. Designing mixed metal halide ammines for ammonia storage using density functional theory and genetic algorithms.

    Science.gov (United States)

    Jensen, Peter Bjerre; Lysgaard, Steen; Quaade, Ulrich J; Vegge, Tejs

    2014-09-28

    Metal halide ammines have great potential as a future, high-density energy carrier in vehicles. So far known materials, e.g. Mg(NH3)6Cl2 and Sr(NH3)8Cl2, are not suitable for automotive, fuel cell applications, because the release of ammonia is a multi-step reaction, requiring too much heat to be supplied, making the total efficiency lower. Here, we apply density functional theory (DFT) calculations to predict new mixed metal halide ammines with improved storage capacities and the ability to release the stored ammonia in one step, at temperatures suitable for system integration with polymer electrolyte membrane fuel cells (PEMFC). We use genetic algorithms (GAs) to search for materials containing up to three different metals (alkaline-earth, 3d and 4d) and two different halides (Cl, Br and I) - almost 27,000 combinations, and have identified novel mixtures, with significantly improved storage capacities. The size of the search space and the chosen fitness function make it possible to verify that the found candidates are the best possible candidates in the search space, proving that the GA implementation is ideal for this kind of computational materials design, requiring calculations on less than two percent of the candidates to identify the global optimum.

  12. NMR longitudinal relaxation enhancement in metal halides by heteronuclear polarization exchange during magic-angle spinning

    Energy Technology Data Exchange (ETDEWEB)

    Shmyreva, Anna A. [Center for Magnetic Resonance, St. Petersburg State University, St. Petersburg 198504 (Russian Federation); Safdari, Majid; Furó, István [Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm (Sweden); Dvinskikh, Sergey V., E-mail: sergeid@kth.se [Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm (Sweden); Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg 199034 (Russian Federation)

    2016-06-14

    Orders of magnitude decrease of {sup 207}Pb and {sup 199}Hg NMR longitudinal relaxation times T{sub 1} upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX{sub 2} (Me = Pb, Hg and X = Cl, Br, I). In lead(II) halides, the most dramatic decrease of T{sub 1} relative to that in a static sample is in PbI{sub 2}, while it is smaller but still significant in PbBr{sub 2}, and not detectable in PbCl{sub 2}. The effect is magnetic-field dependent but independent of the spinning speed in the range 200–15 000 Hz. The observed relaxation enhancement is explained by laboratory-frame heteronuclear polarization exchange due to crossing between energy levels of spin-1/2 metal nuclei and adjacent quadrupolar-spin halogen nuclei. The enhancement effect is also present in lead-containing organometal halide perovskites. Our results demonstrate that in affected samples, it is the relaxation data recorded under non-spinning conditions that characterize the local properties at the metal sites. A practical advantage of fast relaxation at slow MAS is that spectral shapes with orientational chemical shift anisotropy information well retained can be acquired within a shorter experimental time.

  13. Luminescent decay and spectra of impurity-activated alkali halides under high pressure

    International Nuclear Information System (INIS)

    Klick, D.I.

    1977-01-01

    The effect of high pressure on the luminescence of alkali halides doped with the transition-metal ions Cu + and Ag + and the heavy-metal ions In + and Tl + was investigated to 140 kbar. Measurement of spectra allowed the prediction of kinetic properties, and the predictions agree with lifetime data

  14. Holographic Optical Elements Recorded in Silver Halide Sensitized Gelatin Emulsions. Part 2. Reflection Holographic Optical Elements

    Science.gov (United States)

    Kim, Jong Man; Choi, Byung So; Choi, Yoon Sun; Kim, Jong Min; Bjelkhagen, Hans I.; Phillips, Nicholas J.

    2002-03-01

    Silver halide sensitized gelatin (SHSG) holograms are similar to holograms recorded in dichromated gelatin (DCG), the main recording material for holographic optical elements (HOEs). The drawback of DCG is its low energetic sensitivity and limited spectral response. Silver halide materials can be processed in such a way that the final hologram will have properties like a DCG hologram. Recently this technique has become more interesting since the introduction of new ultra-fine-grain silver halide (AgHal) emulsions. In particular, high spatial-frequency fringes associated with HOEs of the reflection type are difficult to construct when SHSG processing methods are employed. Therefore an optimized processing technique for reflection HOEs recorded in the new AgHal materials is introduced. Diffraction efficiencies over 90% can be obtained repeatably for reflection diffraction gratings. Understanding the importance of a selective hardening process has made it possible to obtain results similar to conventional DCG processing. The main advantage of the SHSG process is that high-sensitivity recording can be performed with laser wavelengths anywhere within the visible spectrum. This simplifies the manufacturing of high-quality, large-format HOEs, also including high-quality display holograms of the reflection type in both monochrome and full color.

  15. 40 CFR Table 3 to Subpart Ffff of... - Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP Metals Emissions From...

    Science.gov (United States)

    2010-07-01

    ... Halogen HAP Emissions or HAP Metals Emissions From Process Vents 3 Table 3 to Subpart FFFF of Part 63... to Subpart FFFF of Part 63—Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP... following table that applies to your process vents that contain hydrogen halide and halogen HAP emissions or...

  16. Quantitative positron annihilation studies in citrates, halides and oxyhalides chemisorbed on γ-alumina catalyst

    International Nuclear Information System (INIS)

    Luo, X.H.; Jean, Y.C.; Cheng, K.L.

    1987-01-01

    A quantitative study of the γ-alumina catalyst chemisorbed by nitrates, halides, and oxyhalides has been conducted with the positron annihilation spectroscopy (PAS). Catalysts containing Fe, Co, or Ni have been extensively used in chemical industry and petroleum refining. The positron or Ps annihilation can provide a profile information about the bulk, near surface, and void. It is an in-situ surface technique. The PAS technique has shown its capability to determine the nitrate or chloride in γ-alumina as low as 0.02% in solids. It is interesting to note that the PAS may offer the oxidation state information in solids. This is not surprising because the positron annihilation is sensitive to the electron density variation in environments. Positron annihilation models for halides and oxyhalides are proposed

  17. Linear chrono-amperometry using re-dissolution: application to halides

    International Nuclear Information System (INIS)

    Perchard, J.-P.; Buvet, M.; Molina, R.

    1966-06-01

    The possibility of applying linear chrono-amperometry to analysis was studied using a falling-drop mercury electrode. Measurements of the cations were carried out by direct reduction or by prior formation of an amalgam, which is then oxidized. Using the first technique, the minimum concentration that can be attained is about 10 -6 M and the reproducibility of the results is of the order of 2%. With the second method the sensitivity is much improved: in the concentration range of 10 -7 to 10 -8 M, the scatter of the results is less than 10% if the agitation and temperature conditions are kept constant. The halides are determined by re-dissolving the mercurous halide deposit formed by electrolysis. From the analytical point of view, the sensitivity is limited in the domain where the phenomena can be interpreted and used. In the case of the chloride ion the lower limit of this zone is close to 10 -5 M; it is 10 -6 M for the bromide and less than 10 -7 M for the iodide. For lower concentrations, simple laws that might be applied in analysis are no longer valid. However, the splitting of the peak observed during the reduction of the mercurous iodide deposit was interpreted as showing that the mono-molecular Hg 2 I 2 layer formed on the drop has particular electrochemical properties. (authors) [fr

  18. Radiophotoluminescence of alkali-halide crystals stimulated by Bessel laser beam

    CERN Document Server

    Lyakh, V V; Kochubey, D I; Gyunsburg, K E; Zvezdova, N P; Kochubey, D I; Sedova, Y G; Koronkevich, V P; Poleschuk, A G; Sedukhin, A G

    2000-01-01

    A new approach to realization of optimal high-resolution reading of deep X-ray images in X-ray-sensitive materials on the base of alkali-halide crystals modified with admixtures has been suggested and investigated experimentally. A possibility to use diffraction axicons with ring aperture for forming micron bright light beams (spatially truncated Bessel beams) which can efficiently de-excite radiophotoluminescence centers lying at large depth in crystals is also presented.

  19. F-center and self-trapped exciton formation in strongly excited alkali halide crystals

    International Nuclear Information System (INIS)

    Kravchenko, V.A.; Yakovlev, V.Yu.

    1988-01-01

    Method of luminescent and absorption spectroscopy with time resolution was used to study the effect of density of electron pulse excitation (t p =10 -8 s, P=(10 5 -10 8 ) WXcm -2 ) on efficiency of η ε two-halide autolocalized exciton (TALE) and F-centers (η F ) formation in CsI, CsBr, KBr, KI alkali halide crystals. It was established that for all studied systems the elevation of P power of electron beam (EB) from 10 5 up to 5X10 7 WXcm -2 resulted to sufficient decrease of production efficiency and yield of TALE luminescence. In the case when F-centers of colour are induced predominantly by pulsed irradiation in crystals, F-center yield is independent of P. If F-centers and TALE are produced in comparable amounts (CsBr crystals, T=80 K), η ε decrease with P growth is accompanied by η F growth

  20. A Simple Halide-to-Anion Exchange Method for Heteroaromatic Salts and Ionic Liquids

    Directory of Open Access Journals (Sweden)

    Neus Mesquida

    2012-04-01

    Full Text Available A broad and simple method permitted halide ions in quaternary heteroaromatic and ammonium salts to be exchanged for a variety of anions using an anion exchange resin (A− form in non-aqueous media. The anion loading of the AER (OH− form was examined using two different anion sources, acids or ammonium salts, and changing the polarity of the solvents. The AER (A− form method in organic solvents was then applied to several quaternary heteroaromatic salts and ILs, and the anion exchange proceeded in excellent to quantitative yields, concomitantly removing halide impurities. Relying on the hydrophobicity of the targeted ion pair for the counteranion swap, organic solvents with variable polarity were used, such as CH3OH, CH3CN and the dipolar nonhydroxylic solvent mixture CH3CN:CH2Cl2 (3:7 and the anion exchange was equally successful with both lipophilic cations and anions.

  1. Surface passivation of mixed-halide perovskite CsPb(BrxI1-x)3 nanocrystals by selective etching for improved stability.

    Science.gov (United States)

    Jing, Qiang; Zhang, Mian; Huang, Xiang; Ren, Xiaoming; Wang, Peng; Lu, Zhenda

    2017-06-08

    In recent years, there has been an unprecedented rise in the research of halide perovskites because of their important optoelectronic applications, including photovoltaic cells, light-emitting diodes, photodetectors and lasers. The most pressing question concerns the stability of these materials. Here faster degradation and PL quenching are observed at higher iodine content for mixed-halide perovskite CsPb(Br x I 1-x ) 3 nanocrystals, and a simple yet effective method is reported to significantly enhance their stability. After selective etching with acetone, surface iodine is partially etched away to form a bromine-rich surface passivation layer on mixed-halide perovskite nanocrystals. This passivation layer remarkably stabilizes the nanocrystals, making their PL intensity improved by almost three orders of magnitude. It is expected that a similar passivation layer can also be applied to various other kinds of perovskite materials with poor stability issues.

  2. Diversity of band gap and photoluminescence properties of lead halide perovskite: A halogen-dependent spectroscopic study

    Science.gov (United States)

    Yu, Wenlei; Jiang, Yunfeng; Zhu, Xiuwei; Luo, Chunhua; Jiang, Kai; Chen, Liangliang; Zhang, Juan

    2018-05-01

    The effects of halogen substitution on microstructure, optical absorption, and phonon modes for perovskite CH3NH3PbX3 (MAPbX3, X = I/Br/Cl) films grown on FTO substrates have been investigated. The X-ray diffraction analysis exhibited good crystallization, and the strong diffraction peak assigned to (1 0 0) c for X = Br/Cl shifted toward a higher angle compared to (1 1 0) t of MAPbI3. Band-gap tuning from 1.63 to 2.37 to 3.11 eV in the I-Br-Cl series can be found due to the halogen effects. These energy values closely match the positions of peak determined from photoluminescence experiments. The remarkable absorption dip and emission peak appear for the MAPbBr3, suggesting higher crystallinity under the same preparation conditions. The wavenumbers of main IR-vibrations slightly decrease with ionic radius of the halogen increasing (in the order of Cl-Br-I), which related to the increasing polarizability. These results provide important progress towards the understanding of the halide role in the realization of high performance MAPbX3-based solar cells.

  3. Conversion of Sugars to Lactic Acid Derivatives Using Heterogeneous Zeotype Catalysts

    DEFF Research Database (Denmark)

    Holm, Martin Spangsberg; Shunmugavel, Saravanamurugan; Taarning, Esben

    2010-01-01

    of mono-and disaccharides that are dissolved in methanol to methyl lactate at 160 C. With sucrose as the substrate, methyl lactate yield reaches 68%, and the heterogeneous catalyst can be easily recovered by filtration and reused multiple times after calcination without any substantial change...

  4. Nature of the superionic transition in Ag+ and Cu+ halides

    International Nuclear Information System (INIS)

    Keen, D.A.; Hull, S.; Barnes, A.C.; Berastegui, P.; Crichton, W.A.; Madden, P.A.; Tucker, M.G.; Wilson, M.

    2003-01-01

    Silver and copper halides generally display an abrupt (first-order) transition to the superionic state. However, powder diffraction studies and molecular dynamics (MD) simulations of AgI under hydrostatic pressure both indicate that a continuous superionic transition occurs on heating. The gradual onset of the highly conducting state is accompanied by an increasing fraction of dynamic Frenkel defects, a peak in the specific heat and anomalous behavior of the lattice expansion. Similar methods have been employed to investigate the proposed continuous superionic transition between the two ambient pressure face centered cubic phases of CuI. This is difficult to examine experimentally, because the hexagonal β phase exists over a narrow temperature range between the γ (cation ordered) and α (cation disordered) phases. MD simulations performed with the simulation box constrained to remain cubic at all temperatures show that, although limited Cu + Frenkel disorder occurs within γ-CuI, CuI undergoes an abrupt superionic transition at 670 K to the superionic α phase. This is supported by powder neutron diffraction studies of CuI lightly doped with Cs + to prevent stabilization of the β phase. The implications of these results on the phase transitions of other copper and silver halide superionic conductors are discussed

  5. Kinetics of halide release of haloalkane dehalogenase : Evidence for a slow conformational change

    NARCIS (Netherlands)

    Schanstra, JP; Janssen, DB; Schanstra, Joost P.

    1996-01-01

    Haloalkane dehalogenase converts haloalkanes to their corresponding alcohols and halides, The reaction mechanism involves the formation of a covalent alkyl-enzyme complex which is hydrolyzed by water. The active site is a hydrophobic cavity buried between the main domain and the cap domain of the

  6. 2-D images of the metal-halide lamp obtained by experiment and model

    NARCIS (Netherlands)

    Flikweert, A.J.; Beks, M.L.; Nimalasuriya, T.; Kroesen, G.M.W.; Mullen, van der J.J.A.M.; Stoffels, W.W.

    2008-01-01

    The metal-halide lamp shows color segregation caused by diffusion and convection. Two-dimensional imaging of the arc discharge under varying gravity conditions aids in the understanding of the flow phenomena. In this paper, we show results obtained by experiments and by numerical simulations in

  7. Behaviour of alkali halides as materials for optical components of high power lasers

    International Nuclear Information System (INIS)

    Apostol, D.I.; Mihailescu, N.I.; Ghiordanescu, V.; Nistor, C.L.; Nistor, V.S.; Teodorescu, V.; Voda, M.

    1978-01-01

    The physical phenomena taking place in alkali halides when a CO 2 laser radiation is passing through have been reviewed. A special emphasis has been put on the specific qualities which such materials should have for being used as components for high power lasers. (author)

  8. Hard substrate in the deep ocean: How sediment features influence epibenthic megafauna on the eastern Canadian margin

    Science.gov (United States)

    Lacharité, Myriam; Metaxas, Anna

    2017-08-01

    Benthic habitats on deep continental margins (> 1000 m) are now considered heterogeneous - in particular because of the occasional presence of hard substrate in a matrix of sand and mud - influencing the distribution of megafauna which can thrive on both sedimented and rocky substrates. At these depths, optical imagery captured with high-definition cameras to describe megafauna can also describe effectively the fine-scale sediment properties in the immediate vicinity of the fauna. In this study, we determined the relationship between local heterogeneity (10-100 sm) in fine-scale sediment properties and the abundance, composition, and diversity of megafauna along a large depth gradient (1000-3000 m) in a previously-unexplored habitat: the Northeast Fan, which lies downslope of submarine canyons off the Gulf of Maine (northwest Atlantic). Substrate heterogeneity was quantified using a novel approach based on principles of computer vision. This approach proved powerful in detecting gradients in sediment, and sporadic complex features (i.e. large boulders) in an otherwise homogeneous environment because it characterizes sediment properties on a continuous scale. Sediment heterogeneity influenced megafaunal diversity (morphospecies richness and Shannon-Wiener Index) and community composition, with areas of higher substrate complexity generally supported higher diversity. However, patterns in abundance were not influenced by sediment properties, and may be best explained by gradients in food supply. Our study provides a new approach to quantify fine-scale sediment properties and assess their role in shaping megafaunal communities in the deep sea, which should be included into habitat studies given their potential ecological importance.

  9. Decomposition of heterogeneous organic matterand its long-term stabilization in soils

    Science.gov (United States)

    Sierra, Carlos A.; Harmon, Mark E.; Perakis, Steven S.

    2011-01-01

    Soil organic matter is a complex mixture of material with heterogeneous biological, physical, and chemical properties. Decomposition models represent this heterogeneity either as a set of discrete pools with different residence times or as a continuum of qualities. It is unclear though, whether these two different approaches yield comparable predictions of organic matter dynamics. Here, we compare predictions from these two different approaches and propose an intermediate approach to study organic matter decomposition based on concepts from continuous models implemented numerically. We found that the disagreement between discrete and continuous approaches can be considerable depending on the degree of nonlinearity of the model and simulation time. The two approaches can diverge substantially for predicting long-term processes in soils. Based on our alternative approach, which is a modification of the continuous quality theory, we explored the temporal patterns that emerge by treating substrate heterogeneity explicitly. The analysis suggests that the pattern of carbon mineralization over time is highly dependent on the degree and form of nonlinearity in the model, mostly expressed as differences in microbial growth and efficiency for different substrates. Moreover, short-term stabilization and destabilization mechanisms operating simultaneously result in long-term accumulation of carbon characterized by low decomposition rates, independent of the characteristics of the incoming litter. We show that representation of heterogeneity in the decomposition process can lead to substantial improvements in our understanding of carbon mineralization and its long-term stability in soils.

  10. INTERRELATION OF ACIDITY-BASICITY, SOLUBILITY AND ABILITY TO INTERACTION OF HALIDES OF MX AND M'X2 (M - Li ÷ Cs, M' - Be ÷ Ba, X - Cl ÷ I TYPES

    Directory of Open Access Journals (Sweden)

    V. F. Zinchenko

    2015-11-01

    Full Text Available The size-charge factor of basicity for definition of the acid-base properties of alkaline both alkaline-earth metals and Be halides is offered. The certain interrelation of the specified factor, and also the magnitudes connected with energy of a crystal lattice (temperature of boiling and enthalpy of evaporation of salt with its solubility in water, and also with enthalpy of hydration is established. It is shown that the minimum solubility possess alkaline metals halides (KCl for chlorides, RbBr for Rubidium halides and CsI for alkaline metals halides as a whole at which value of the factor of basicity is equal to 0.83, i.e. it is slightly less than 1. Among alkaline-earth metals halides the lowest solubility has BaCl2 with the highest value of the factor of basicity (0.4. An absolute value of enthalpy of hydration for salts crystal-hydrates possesses tens kJ/mol H2O and increases with reduction of the factor of basicity at transition from metals chlorides to iodides, and also at cationic substitution by easier analogue. Qualitative correlation between a difference of basicity of binary halides and their ability to interaction with formation of complex compounds of various degree of durability is established. At an average difference of basicities 0.4 in halide systems are formed incongruently melting, and at 0.6-0.8 and more – congruently melting compounds. Forecasting of solubility of complex halide of CsSrCl3 composition on the basis of its value of equalized basicity is carried out.

  11. Quaternary oxide halides of group 15 with zinc and cadmium; Quaternaere Oxidhalogenide der Gruppe 15 mit Zink und Cadmium

    Energy Technology Data Exchange (ETDEWEB)

    Rueck, Nadia

    2014-07-30

    The present thesis ''Quaternary oxide halides of group 15 with zinc and cadmium'' deals with the chemical class of oxide halides, which contain d-block element cations and pnicogens. Over the past few years compounds containing pnicogene cations are intensively investigated. The reason for this is the free electron pair of the Pn{sup 3+} cation, which is responsible for some interesting properties. Free electron pairs do not only impact the spatial structure of molecules but also the properties of materials. The object of this work was the synthesis and characterization of compounds containing Pn{sup 3+} cations with free electron pairs. Due to the structure-determining effect of these free electron pairs and in combination with halides it is possible to synthesize compounds with low-dimensional structures like chains and layers. In these compounds the structure is separated into halophilic and chalcophilic sub-structures, which are held together only by weak Van der Waals forces.

  12. Simplified nonplanar wafer bonding for heterogeneous device integration

    Science.gov (United States)

    Geske, Jon; Bowers, John E.; Riley, Anton

    2004-07-01

    We demonstrate a simplified nonplanar wafer bonding technique for heterogeneous device integration. The improved technique can be used to laterally integrate dissimilar semiconductor device structures on a lattice-mismatched substrate. Using the technique, two different InP-based vertical-cavity surface-emitting laser active regions have been integrated onto GaAs without compromising the quality of the photoluminescence. Experimental and numerical simulation results are presented.

  13. Hot working alkali halides for laser window applications

    International Nuclear Information System (INIS)

    Koepke, B.G.; Anderson, R.H.; Stokes, R.J.

    1975-01-01

    The techniques used to hot work alkali halide crystals into laser window blanks are reviewed. From the point of view of high power laser window applications one of the materials with a high figure of merit is KCl. Thus the materials examined are KCl and alloys of KCl-KBr containing 5 mole percent KBr. The fabrication techniques include conventional and constrained press forging, isostatic press forging and hot rolling. Optical properties are paramount to the ultimate usefulness of these materials. Results on the optical properties of the hot worked material are included together with mechanical properties and microstructural data

  14. Synthesis of halide- and solvent free metal borohydrides

    DEFF Research Database (Denmark)

    Grinderslev, Jakob; Møller, Kasper Trans; Richter, Bo

    have challenges due to their high desorption kinetics and limited reversibility at moderate conditions.[2],[3],[4] In this work, we present a new approach to synthesize halide- and solvent free metal borohydrides starting from the respective metal hydride. The synthetic strategy ensures that no metal...... to the metal. Hence, the powdered M(BH4)3∙DMS is heated to 140 °C for 4 hours to obtain pure M(BH4)3. The rare-earth metal borohydrides have been investigated by infrared spectroscopy and thermal analysis (TGA-DSC-MS). Furthermore, the structural trends are investigated by synchrotron radiation powder X...

  15. Composition-Dependent Energy Splitting between Bright and Dark Excitons in Lead Halide Perovskite Nanocrystals.

    Science.gov (United States)

    Chen, Lan; Li, Bin; Zhang, Chunfeng; Huang, Xinyu; Wang, Xiaoyong; Xiao, Min

    2018-03-14

    Perovskite semiconductor nanocrystals with different compositions have shown promise for applications in light-emitting devices. Dark excitonic states may suppress light emission from such nanocrystals by providing an additional nonradiative recombination channel. Here, we study the composition dependence of dark exciton dynamics in nanocrystals of lead halides by time-resolved photoluminescence spectroscopy at cryogenic temperatures. The presence of a spin-related dark state is revealed by magneto-optical spectroscopy. The energy splitting between bright and dark states is found to be highly sensitive to both halide elements and organic cations, which is explained by considering the effects of size confinement and charge screening, respectively, on the exchange interaction. These findings suggest the possibility of manipulating dark exciton dynamics in perovskite semiconductor nanocrystals by composition engineering, which will be instrumental in the design of highly efficient light-emitting devices.

  16. Monitoring of heavy/toxic metals and halides in surface/ground water (abstract)

    International Nuclear Information System (INIS)

    Viqar-un-Nisa; Ahmed, R.; Husain, M.

    1999-01-01

    Water is essential for maintaining physical and social life. Human and animal consumption is perhaps the most evident essential use of water. Water quality and quantity have become critical issues, affecting all life. The importance of water in our lives, combined with the threats, make water resources use a global problem. Among the different pollutants toxic metals, metalloids and halides have special significance. Industrial effluents and municipal wastewater are normally drained into water streams, rivers and other reservoirs thus polluting these significantly. Quality of our water resources especially is an issue, which continues to arouse the attention of concerned scientists, legislators and the general public. Among various pollutant chemicals, the heavy metals and metalloids are present at trace levels in various compartments of the environment. Some metals become toxic even at trace levels because of the important features that distinguishes metals from other pollutants is that they are not biodegradable. The halides like Cl, Br, and I from different sources can enter easily into water systems and then they make their way directly into the human body. The intake of toxic as wells as essential elements through water and other food items like vegetables, milk wheat flour etc. is significant. The abundance or deficiency of these meals as well as halides results in abnormal metabolic functions. Due to excessive demand for trace analysis in water and other materials a variety of techniques and instrumentation has been developed. Determination of heavy metals ions is of the highest interest in environmental analysis. Among the food materials water is most important because of their large consumption by man. Also toxic metals in water may be in dissolved ionic form, which directly go into human metabolism and start their toxic action. Presence of even small amounts of toxic metals in drinking water can produce serious health hazards. (author)

  17. Thermochromic halide perovskite solar cells.

    Science.gov (United States)

    Lin, Jia; Lai, Minliang; Dou, Letian; Kley, Christopher S; Chen, Hong; Peng, Fei; Sun, Junliang; Lu, Dylan; Hawks, Steven A; Xie, Chenlu; Cui, Fan; Alivisatos, A Paul; Limmer, David T; Yang, Peidong

    2018-03-01

    Smart photovoltaic windows represent a promising green technology featuring tunable transparency and electrical power generation under external stimuli to control the light transmission and manage the solar energy. Here, we demonstrate a thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide. The solar cells undergo thermally-driven, moisture-mediated reversible transitions between a transparent non-perovskite phase (81.7% visible transparency) with low power output and a deeply coloured perovskite phase (35.4% visible transparency) with high power output. The inorganic perovskites exhibit tunable colours and transparencies, a peak device efficiency above 7%, and a phase transition temperature as low as 105 °C. We demonstrate excellent device stability over repeated phase transition cycles without colour fade or performance degradation. The photovoltaic windows showing both photoactivity and thermochromic features represent key stepping-stones for integration with buildings, automobiles, information displays, and potentially many other technologies.

  18. Thermochromic halide perovskite solar cells

    Science.gov (United States)

    Lin, Jia; Lai, Minliang; Dou, Letian; Kley, Christopher S.; Chen, Hong; Peng, Fei; Sun, Junliang; Lu, Dylan; Hawks, Steven A.; Xie, Chenlu; Cui, Fan; Alivisatos, A. Paul; Limmer, David T.; Yang, Peidong

    2018-03-01

    Smart photovoltaic windows represent a promising green technology featuring tunable transparency and electrical power generation under external stimuli to control the light transmission and manage the solar energy. Here, we demonstrate a thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide. The solar cells undergo thermally-driven, moisture-mediated reversible transitions between a transparent non-perovskite phase (81.7% visible transparency) with low power output and a deeply coloured perovskite phase (35.4% visible transparency) with high power output. The inorganic perovskites exhibit tunable colours and transparencies, a peak device efficiency above 7%, and a phase transition temperature as low as 105 °C. We demonstrate excellent device stability over repeated phase transition cycles without colour fade or performance degradation. The photovoltaic windows showing both photoactivity and thermochromic features represent key stepping-stones for integration with buildings, automobiles, information displays, and potentially many other technologies.

  19. Spatial coupling in heterogeneous catalysis

    Science.gov (United States)

    Yamamoto, S. Y.; Surko, C. M.; Maple, M. B.

    1995-11-01

    Spatial coupling mechanisms are studied in the heterogeneous catalytic oxidation of carbon monoxide over platinum at atmospheric pressure under oscillatory conditions. Experiments are conducted in a continuous flow reactor, and the reaction rate is monitored using both infrared imaging and thermocouples. The catalysts are in the form of platinum annular thin films on washer-shaped quartz substrates, and they provide highly repeatable oscillatory behavior. Oscillations are typically spatially synchronized with the entire catalyst ``flashing'' on and off uniformly. Spatial coupling is investigated by introducing various barriers which split the annular ring in half. Infrared images show that coupling through the gas phase dominates coupling via the diffusion of CO on the surface or heat diffusion through the substrate. The introduction of a localized heat perturbation to the catalyst surface does not induce a transition in the reaction rate. Thus, it is likely that the primary mode of communication is through the gas-phase diffusion of reactants.

  20. Surface and zeta-potentials of silver halide single crystals: pH-dependence in comparison to particle systems

    International Nuclear Information System (INIS)

    Selmani, Atiða; Kallay, Nikola; Preočanin, Tajana; Lützenkirchen, Johannes

    2014-01-01

    We have carried out surface and zeta-potential measurements on AgCl and AgBr single crystals. As for particle systems we find that, surprisingly and previously unnoted, the zeta-potential exhibits pH-dependence, while the surface potential does not. A possible interpretation of these observations is the involvement of water ions in the interfacial equilibria and in particular, stronger affinity of the hydroxide ion compared to the proton. The pH-dependence of the zeta-potential can be suppressed at sufficiently high silver concentrations, which agrees with previous measurements in particle systems where no pH-dependence was found at high halide ion concentrations. The results suggest a subtle interplay between the surface potential determining the halide and silver ion concentrations, and the water ions. Whenever the charge due to the halide and silver ions is sufficiently high, the influence of the proton/hydroxide ion on the zeta-potential vanishes. This might be related to the water structuring at the relevant interfaces which should be strongly affected by the surface potential. Another interesting observation is accentuation of the assumed water ion effect on the zeta-potential at the flat single crystal surfaces compared to the corresponding silver halide colloids. Previous generic MD simulations have indeed predicted that hydroxide ion adsorption is accentuated on flat/rigid surfaces. A thermodynamic model for AgI single crystals was developed to describe the combined effects of iodide, silver and water ions, based on two independently previously published models for AgI (that only consider constituent and background electrolyte ions) and inert surfaces (that only consider water and background electrolyte ions). The combined model correctly predicts all the experimentally observed trends. (paper)

  1. A comparative study of semi-empirical interionic potentials for alkali halides - II

    International Nuclear Information System (INIS)

    Khwaja, F.A.; Naqvi, S.H.

    1985-08-01

    A comprehensive study of some semi-empirical interionic potentials is carried out through the calculation of the cohesive energy, relative stability and pressure induced solid-solid phase transformations in alkali halides. The theoretical values of these properties of the alkali halides are obtained using a new set of van der Waals coefficients and zero-point energy in the expression for interionic potential. From the comparison of the present calculations with some previous sophisticated ab-initio quantum-mechanical calculations and other semi-empirical approaches, it is concluded that the present calculations in the simplest central pairwise interaction description with the new values of the van der Waals coefficients and zero-point energy are in better agreement with the experimental data than the previous calculations. It is also concluded that in some cases the better choice of the interionic potential alone in the simplest semi-empirical picture of interaction gives an agreement of the theoretical predictions with the experimental data much superior to the ab-initio quantum mechanical approaches. (author)

  2. Resonance Raman and excitation energy dependent charge transfer mechanism in halide-substituted hybrid perovskite solar cells.

    Science.gov (United States)

    Park, Byung-wook; Jain, Sagar M; Zhang, Xiaoliang; Hagfeldt, Anders; Boschloo, Gerrit; Edvinsson, Tomas

    2015-02-24

    Organo-metal halide perovskites (OMHPs) are materials with attractive properties for optoelectronics. They made a recent introduction in the photovoltaics world by methylammonium (MA) lead triiodide and show remarkably improved charge separation capabilities when chloride and bromide are added. Here we show how halide substitution in OMHPs with the nominal composition CH3NH3PbI2X, where X is I, Br, or Cl, influences the morphology, charge quantum yield, and local interaction with the organic MA cation. X-ray diffraction and photoluminescence data demonstrate that halide substitution affects the local structure in the OMHPs with separate MAPbI3 and MAPbCl3 phases. Raman spectroscopies as well as theoretical vibration calculations reveal that this at the same time delocalizes the charge to the MA cation, which can liberate the vibrational movement of the MA cation, leading to a more adaptive organic phase. The resonance Raman effect together with quantum chemical calculations is utilized to analyze the change in charge transfer mechanism upon electronic excitation and gives important clues for the mechanism of the much improved photovoltage and photocurrent also seen in the solar cell performance for the materials when chloride compounds are included in the preparation.

  3. 7YSZ coating prepared by PS-PVD based on heterogeneous nucleation

    Directory of Open Access Journals (Sweden)

    Ziqian DENG

    2018-04-01

    Full Text Available Plasma spray-physical vapor deposition (PS-PVD as a novel coating process based on low-pressure plasma spray (LPPS has been significantly used for thermal barrier coatings (TBCs. A coating can be deposited from liquid splats, nano-sized clusters, and the vapor phase forming different structured coatings, which shows obvious advantages in contrast to conventional technologies like atmospheric plasma spray (APS and electron beam-physical vapor deposition (EB-PVD. In addition, it can be used to produce thin, dense, and porous ceramic coatings for special applications because of its special characteristics, such as high power, very low pressure, etc. These provide new opportunities to obtain different advanced microstructures, thus to meet the growing requirements of modern functional coatings. In this work, focusing on exploiting the potential of gas-phase deposition from PS-PVD, a series of 7YSZ coating experiments with various process conditions was performed in order to better understand the deposition process in PS-PVD, where coatings were deposited on different substrates including graphite and zirconia. Meanwhile, various substrate temperatures were investigated for the same substrate. As a result, a deposition mechanism of heterogeneous nucleation has been presented showing that surface energy is an important influencing factor for coating structures. Besides, undercooling of the interface between substrate and vapor phase plays an important role in coating structures. Keywords: 7YSZ, Deposition mechanism, Heterogeneous nucleation, PS-PVD, TBC

  4. HETEROGENEITY OF POLYCLONAL IMMUNOGLOBULINS NUCLEASE ACTIVITY IN RHEUMATOID AND REACTIVE ARTHRITIS

    Directory of Open Access Journals (Sweden)

    M. V. Volkova

    2017-01-01

    Full Text Available Catalytic properties of immunoglobulins are widely studied within recent years. It was found that nuclease activity of immunoglobulins is increased in systemic autoimmune diseases. Given some pathogenetic features of rheumatoid arthritis and reactive arthritis, it is appropriate to clarify the nature of nuclease activity in these diseases. Determination of DNAse activity of immunoglobulins with different DNA substrates, and search for specific substrates for distinct clinical entities could serve these purposes. The aim of present work is to determine DNase activity of the polyclonal class G immunoglobulins in rheumatoid and reactive arthritis using various methods.Different methods are used to evaluate nuclease activity. In this paper we present newly developed and modified techniques for determination of DNAse activity of polyclonal IgGs. Particular attention was paid to the electrophoretic method of DNase activity assessment. Polyclonal IgG isolated from blood serum of patients with rheumatoid arthritis and reactive arthritis were used for assays. In this study, we demonstrated the presence of an inhomogeneous DNase activity of immunoglobulins in relation to different substrates.Along with calf thymus DNA, we used bacterial plasmid DNA and PCR products based on bacterial gene sequences. Levels of DNase activity by rivanol clot method with calf thymus DNA as substrate proved to be higher in patients with rheumatoid arthritis than the control values (p < 0.01. DNase abzyme activity in patients with rheumatoid arthritis was elevated, as compared to the patients with reactive arthritis (p < 0.01.When examining ability of the IgG to hydrolyze procaryotic DNA (bacterial plasmid DNA and PCR products, based on bacterial genes, we obtained heterogeneous results. Different Ig samples showed varying degrees of DNA hydrolysis. Abzyme hydrolysis of DNA substrates longer than 700 bp was more pronounced, as compared to short DNA substrates (100 base pairs

  5. Facile Synthesis of Photofunctional Nanolayer Coatings on Titanium Substrates

    Directory of Open Access Journals (Sweden)

    Kyong-Hoon Choi

    2016-01-01

    Full Text Available We developed a two-step chemical bonding process using photosensitizer molecules to fabricate photofunctional nanolayer coatings on hematoporphyrin- (HP- coated Ti substrates. In the first step, 3-aminopropyltriethoxysilane was covalently functionalized onto the surface of the Ti substrates to provide heterogeneous sites for immobilizing the HP molecules. Then, HP molecules with carboxyl groups were chemically attached to the amine-terminated nanolayer coatings via a carbodiimide coupling reaction. The microstructure and elemental and phase composition of the HP-coated Ti substrates were investigated using field-emission scanning electron microscopy and energy-dispersive X-ray spectrometry. The photophysical properties of the photofunctional nanolayer coatings were confirmed using reflectance ultraviolet-visible absorption and emission spectrophotometry. The singlet oxygen generation efficiency of the photofunctional nanolayer coatings was determined using the decomposition reaction of 1,3-diphenylisobenzofuran. The HP-coated Ti substrates exhibited good biocompatibility without any cytotoxicity, and these nanolayer coatings generated singlet oxygen, which can kill microorganisms using only visible light.

  6. Polyol Synthesis of Silver Nanowires by Heterogeneous Nucleation and Mechanistic Aspects Influencing its Length and Diameter

    Science.gov (United States)

    Schuette, Waynie Mark

    Various additives are employed in the polyol synthesis of silver nanowires (Ag NWs), which are typically halide salts such as NaCl. A variety of mechanistic roles have been suggested for these additives. My research showed that the early addition of NaCl in the polyol synthesis of Ag NWs from AgNO3 in ethylene glycol results in the rapid formation of AgCl nanocubes, which induce the heterogeneous nucleation of metallic Ag upon their surfaces. Ag NWs subsequently grow from these nucleation sites. The conclusions are supported by studies using ex-situ generated AgCl nanocubes. Additionally, the final mean silver nanowire diameter is found to be independent of the size of the heterogeneous nucleant, showing that the diameter is not significantly influenced by the nucleation event. Kinetics studies determine that nanowire diameter, length, and aspect ratio grow in parallel to one another and with the extent of the Ag+ reduction reaction, demonstrating that growth is reduction-rate limited. The results are interpreted to support nanowire growth by a surface-catalyzed reduction process occurring on all nanowire surfaces, and to exclude nanoparticle aggregation or Ostwald ripening as primary components of the growth mechanism.

  7. Amination of Aryl Halides and Esters Using Intensified Continuous Flow Processing

    Directory of Open Access Journals (Sweden)

    Thomas M. Kohl

    2015-09-01

    Full Text Available Significant process intensification of the amination reactions of aryl halides and esters has been demonstrated using continuous flow processing. Using this technology traditionally difficult amination reactions have been performed safely at elevated temperatures. These reactions were successfully conducted on laboratory scale coil reactor modules with 1 mm internal diameter (ID and on a preparatory scale tubular reactor with 6 mm ID containing static mixers.

  8. REPLACEMENT OF TRYPTOPHAN RESIDUES IN HALOALKANE DEHALOGENASE REDUCES HALIDE BINDING AND CATALYTIC ACTIVITY

    NARCIS (Netherlands)

    KENNES, C; PRIES, F; KROOSHOF, GH; BOKMA, E; Kingma, Jacob; JANSSEN, DB

    1995-01-01

    Haloalkane dehalogenase catalyzes the hydrolytic cleavage of carbon-halogen bonds in short-chain haloalkanes. Two tryptophan residues of the enzyme (Trp125 and Trp175) form a halide-binding site in the active-site cavity, and were proposed to play a role in catalysis. The function of these residues

  9. Kinetics of cesium lead halide perovskite nanoparticle growth; focusing and de-focusing of size distribution

    Science.gov (United States)

    Koolyk, Miriam; Amgar, Daniel; Aharon, Sigalit; Etgar, Lioz

    2016-03-01

    In this work we study the kinetics of cesium lead halide perovskite nanoparticle (NP) growth; the focusing and de-focusing of the NP size distribution. Cesium lead halide perovskite NPs are considered to be attractive materials for optoelectronic applications. Understanding the kinetics of the formation of these all-inorganic perovskite NPs is critical for reproducibly and reliably generating large amounts of uniformly sized NPs. Here we investigate different growth durations for CsPbI3 and CsPbBr3 NPs, tracking their growth by high-resolution transmission electron microscopy and size distribution analysis. As a result, we are able to provide a detailed model for the kinetics of their growth. It was observed that the CsPbI3 NPs exhibit focusing of the size distribution in the first 20 seconds of growth, followed by de-focusing over longer growth durations, while the CsPbBr3 NPs show de-focusing of the size distribution starting from the beginning of the growth. The monomer concentration is depleted faster in the case of CsPbBr3 than in the case of CsPbI3, due to faster diffusion of the monomers, which increases the critical radius and results in de-focusing of the population. Accordingly, focusing is not observed within 40 seconds of growth in the case of CsPbBr3. This study provides important knowledge on how to achieve a narrow size distribution of cesium lead halide perovskite NPs when generating large amounts of these promising, highly luminescent NPs.In this work we study the kinetics of cesium lead halide perovskite nanoparticle (NP) growth; the focusing and de-focusing of the NP size distribution. Cesium lead halide perovskite NPs are considered to be attractive materials for optoelectronic applications. Understanding the kinetics of the formation of these all-inorganic perovskite NPs is critical for reproducibly and reliably generating large amounts of uniformly sized NPs. Here we investigate different growth durations for CsPbI3 and CsPbBr3 NPs, tracking

  10. Dynamics in population heterogeneity during batch and continuous fermentation of Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Heins, Anna-Lena; Lencastre Fernandes, Rita; Lundin, L.

    2012-01-01

    Traditionally, microbial populations in optimization studies of fermentation processes have been considered homogeneous. However, research has shown that a typical microbial population in fermentation is heterogeneous. There are indications that this heterogeneity may be both beneficial...... (facilitates quick adaptation to new conditions) and harmful (reduces yields and productivities)[1,2]. Typically, gradients of e.g. dissolved oxygen, substrates, and pH are observed in industrial scale fermentation processes. Consequently, microbial cells circulating throughout a bioreactor experience rapid...... distribution during different growth stages. To further simulate which effect gradients have on population heterogeneity, glucose and ethanol perturbations during continuous cultivation were performed. Physiological changes were analyzed on single cell level by using flow cytometry followed by cell sorting...

  11. Development of semi-synthetic bread substrates for examination of bread spoilage organisms

    DEFF Research Database (Denmark)

    Enk, Michael; Nielsen, Per Væggemose

    1998-01-01

    Shelf life studies of bread are highly irreproducible due to the very heterogenous structure of bread and the difficulties in obtaining sterile bread. We hypothesize that novel semi-synthetic bread substrates with chemical and microbial properties similar to those of bread can be developed....... The bread based substrates can prove valuable in predicting shelf life of bread and in the routine hygienic control of bread factories.Our objective was to develop substrates with properties, which both chemically and microbiologically resembles those of dark and white bread respectively.Nineteen dark (DB......) and 19 white (WB) bread based substrates were made based on a factorial design. Lactic acid, acetic acid, propionic acid, ethanol and glucose were added in amounts found in different brand of bread by chemical analysis. Water activity was adjusted by polyethylene glycol. The substrates were evaluated...

  12. Radiation chemistry of the alkali halides

    International Nuclear Information System (INIS)

    Robinson, V.J.; Chandratillake, M.R.

    1987-01-01

    By far the most thoroughly investigated group of compounds in solid-state radiation chemistry are the alkali halides. Some of the reasons are undoubtedly practical: large single crystals of high purity are readily prepared. The crystals are transparent over a wide range of wavelengths. They are more sensitive to radiation damage than most other ionic solids. The crystals have simple well-defined structures, and the products of radiolysis have also in many cases been clearly identified by a variety of experimental techniques, the most important being optical methods and electron paramagnetic resonance (EPR). In recent years the application of pulse techniques-radiolysis and laser photolysis-has yielded a wealth of information concerning the mechanisms of the primary processes of radiation damage, on the one hand, and of thermal and photolytic reactions that the radiolysis products undergo, on the other

  13. Phase space investigation of the lithium amide halides

    Energy Technology Data Exchange (ETDEWEB)

    Davies, Rosalind A. [Hydrogen Storage Chemistry Group, School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Hydrogen and Fuel Cell Group, School of Chemical Engineering, University of Birmingham, Edgbaston B15 2TT (United Kingdom); Hewett, David R.; Korkiakoski, Emma [Hydrogen Storage Chemistry Group, School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Thompson, Stephen P. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX (United Kingdom); Anderson, Paul A., E-mail: p.a.anderson@bham.ac.uk [Hydrogen Storage Chemistry Group, School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

    2015-10-05

    Highlights: • The lower limits of halide incorporation in lithium amide have been investigated. • The only amide iodide stoichiometry observed was Li{sub 3}(NH{sub 2}){sub 2}I. • Solid solutions were observed in both the amide chloride and amide bromide systems. • A 46% reduction in chloride content resulted in a new phase: Li{sub 7}(NH{sub 2}){sub 6}Cl. • New low-chloride phase maintained improved H{sub 2} desorption properties of Li{sub 4}(NH{sub 2}){sub 3}Cl. - Abstract: An investigation has been carried out into the lower limits of halide incorporation in lithium amide (LiNH{sub 2}). It was found that the lithium amide iodide Li{sub 3}(NH{sub 2}){sub 2}I was unable to accommodate any variation in stoichiometry. In contrast, some variation in stoichiometry was accommodated in Li{sub 7}(NH{sub 2}){sub 6}Br, as shown by a decrease in unit cell volume when the bromide content was reduced. The amide chloride Li{sub 4}(NH{sub 2}){sub 3}Cl was found to adopt either a rhombohedral or a cubic structure depending on the reaction conditions. Reduction in chloride content generally resulted in a mixture of phases, but a new rhombohedral phase with the stoichiometry Li{sub 7}(NH{sub 2}){sub 6}Cl was observed. In comparison to LiNH{sub 2}, this new low-chloride phase exhibited similar improved hydrogen desorption properties as Li{sub 4}(NH{sub 2}){sub 3}Cl but with a much reduced weight penalty through addition of chloride. Attempts to dope lithium amide with fluoride ions have so far proved unsuccessful.

  14. Halide based MBE of crystalline metals and oxides

    Energy Technology Data Exchange (ETDEWEB)

    Greenlee, Jordan D.; Calley, W. Laws; Henderson, Walter; Doolittle, W. Alan [Georgia Institute of Technology, School of Electrical and Computer Engineering, Atlanta, Georgia (United States)

    2012-02-15

    A halide based growth chemistry has been demonstrated which can deliver a range of transition metals using low to moderate effusion cell temperatures (30-700 C) even for high melting point metals. Previously, growth with transition metal species required difficult to control electron beam or impurity inducing metal organic sources. Both crystalline oxide and metal films exhibiting excellent crystal quality are grown using this halide-based growth chemistry. Films are grown using a plasma assisted Molecular Beam Epitaxy (MBE) system with metal-chloride precursors. Crystalline niobium, cobalt, iron, and nickel were grown using this chemistry but the technology can be generalized to almost any metal for which a chloride precursor is available. Additionally, the oxides LiNbO{sub 3} and LiNbO{sub 2} were grown with films exhibiting X-ray diffraction (XRD) rocking curve full-widths at half maximum of 150 and 190 arcseconds respectively. LiNbO{sub 2} films demonstrate a memristive response due to the rapid movement of lithium in the layered crystal structure. The rapid movement of lithium ions in LiNbO{sub 2} memristors is characterized using impedance spectroscopy measurements. The impedance spectroscopy measurements suggest an ionic current of.1 mA for a small drive voltage of 5 mV AC or equivalently an ionic current density of {proportional_to}87 A/cm{sup 2}. This high ionic current density coupled with low charge transfer resistance of {proportional_to}16.5 {omega} and a high relaxation frequency (6.6 MHz) makes this single crystal material appealing for battery applications in addition to memristors. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Correlated linear response calculations of the C6 dispersion coefficients of hydrogen halides

    Czech Academy of Sciences Publication Activity Database

    Sauer, S. P. A.; Paidarová, Ivana

    2007-01-01

    Roč. 3, 2-4 (2007), s. 399-421 ISSN 1574-0404 R&D Projects: GA AV ČR IAA401870702 Institutional research plan: CEZ:AV0Z40400503 Keywords : hydrogen halides * C6 dospersion coefficients * van der Waals coefficients * polarizability at imaginary frequences * SOPPA Subject RIV: CF - Physical ; Theoretical Chemistry

  16. Can Ferroelectric Polarization Explain the High Performance of Hybrid Halide Perovskite Solar Cells?

    NARCIS (Netherlands)

    Sherkar, Tejas; Koster, L. Jan Anton

    The power conversion efficiency of photovoltaic cells based on the use of hybrid halide perovskites, CH3NH3PbX3 (X = Cl, Br, I), now exceeds 20%. Recently, it was suggested that this high performance originates from the presence of ferroelectricity in the perovskite, which is hypothesized to lower

  17. Spectral and Dynamical Properties of Single Excitons, Biexcitons, and Trions in Cesium-Lead-Halide Perovskite Quantum Dots.

    Science.gov (United States)

    Makarov, Nikolay S; Guo, Shaojun; Isaienko, Oleksandr; Liu, Wenyong; Robel, István; Klimov, Victor I

    2016-04-13

    Organic-inorganic lead-halide perovskites have been the subject of recent intense interest due to their unusually strong photovoltaic performance. A new addition to the perovskite family is all-inorganic Cs-Pb-halide perovskite nanocrystals, or quantum dots, fabricated via a moderate-temperature colloidal synthesis. While being only recently introduced to the research community, these nanomaterials have already shown promise for a range of applications from color-converting phosphors and light-emitting diodes to lasers, and even room-temperature single-photon sources. Knowledge of the optical properties of perovskite quantum dots still remains vastly incomplete. Here we apply various time-resolved spectroscopic techniques to conduct a comprehensive study of spectral and dynamical characteristics of single- and multiexciton states in CsPbX3 nanocrystals with X being either Br, I, or their mixture. Specifically, we measure exciton radiative lifetimes, absorption cross-sections, and derive the degeneracies of the band-edge electron and hole states. We also characterize the rates of intraband cooling and nonradiative Auger recombination and evaluate the strength of exciton-exciton coupling. The overall conclusion of this work is that spectroscopic properties of Cs-Pb-halide quantum dots are largely similar to those of quantum dots of more traditional semiconductors such as CdSe and PbSe. At the same time, we observe some distinctions including, for example, an appreciable effect of the halide identity on radiative lifetimes, considerably shorter biexciton Auger lifetimes, and apparent deviation of their size dependence from the "universal volume scaling" previously observed for many traditional nanocrystal systems. The high efficiency of Auger decay in perovskite quantum dots is detrimental to their prospective applications in light-emitting devices and lasers. This points toward the need for the development of approaches for effective suppression of Auger

  18. Organometallic halide perovskite single crystals having low deffect density and methods of preparation thereof

    KAUST Repository

    Bakr, Osman; Shi, Dong

    2016-01-01

    The present disclosure presents a method of making a single crystal organometallic halide perovskites, with the formula: AMX3, wherein A is an organic cation, M is selected from the group consisting of: Pb, Sn, Cu, Ni, Co, Fe, Mn, Pd, Cd, Ge, and Eu

  19. Halide salts and their structural properties in presence of secondary amine based molecule: A combined experimental and theoretical analysis

    Science.gov (United States)

    Ghosh, Pritam; Hazra, Abhijit; Ghosh, Meenakshi; Chandra Murmu, Naresh; Banerjee, Priyabrata

    2018-04-01

    Biologically relevant halide salts and its solution state structural properties are always been significant. In general, exposure of halide salts into polar solution medium results in solvation which in turn separates the cationic and anionic part of the salt. However, the conventional behaviour of salts might alter in presence of any secondary amine based compound, i.e.; moderately strong Lewis acid. In its consequence, to investigate the effect of secondary amine based compound in the salt solution, novel (E)-2-(4-bromobenzylidene)-1-(perfluorophenyl) hydrazine has been synthesized and used as secondary amine source. The secondary amine compound interestingly shows a drastic color change upon exposure to fluoride salts owing to hydrogen bonding interaction. Several experimental methods, e.g.; SCXRD, UV-Vis, FT-IR, ESI-MS and DLS together with modern DFT (i.e.; DFT-D3) have been performed to explore the structural properties of the halide salts upon exposure to secondary amine based compound. The effect of counter cation of the fluoride salt in binding with secondary amine source has also been investigated.

  20. NEW THIO S2- ADDUCTS WITH ANTIMONY (III AND V HALIDE: SYNTHESIS AND INFRARED STUDY

    Directory of Open Access Journals (Sweden)

    HASSAN ALLOUCH

    2013-12-01

    Full Text Available Five new S2- adducts with SbIII and SbV halides have been synthesized and studied by infrared. Discrete structures have been suggested, the environment around the antimony being tetrahedral, trigonal bipyramidal or octahedral.

  1. Band Gap Tuning and Defect Tolerance of Atomically Thin Two-Dimensional Organic-Inorganic Halide Perovskites.

    Science.gov (United States)

    Pandey, Mohnish; Jacobsen, Karsten W; Thygesen, Kristian S

    2016-11-03

    Organic-inorganic halide perovskites have proven highly successful for photovoltaics but suffer from low stability, which deteriorates their performance over time. Recent experiments have demonstrated that low dimensional phases of the hybrid perovskites may exhibit improved stability. Here we report first-principles calculations for isolated monolayers of the organometallic halide perovskites (C 4 H 9 NH 3 ) 2 MX 2 Y 2 , where M = Pb, Ge, Sn and X,Y = Cl, Br, I. The band gaps computed using the GLLB-SC functional are found to be in excellent agreement with experimental photoluminescence data for the already synthesized perovskites. Finally, we study the effect of different defects on the band structure. We find that the most common defects only introduce shallow or no states in the band gap, indicating that these atomically thin 2D perovskites are likely to be defect tolerant.

  2. Energy distributions of atoms sputtered from alkali halides by 540 eV electrons, Ch.1

    International Nuclear Information System (INIS)

    Overeijnder, H.; Szymonski, M.; Haring, A.; Vries, A.E. de

    1978-01-01

    The emission of halogen and alkali atoms, occurring under bombardment of alkali halides with electrons has been investigated. The electron energy was 540 eV and the temperature of the target was varied between room temperature and 400 0 C. The energy distribution of the emitted neutral particles was measured with a time of flight method. It was found that either diffusing interstitial halogen atoms or moving holes dominate the sputtering process above 200 0 C. Below 150 0 C alkali halides with lattice parameters s/d >= 0.33 show emission of non-thermal halogen atoms. s is the interionic space between two halogen ions in a direction and d is the diameter of a halogen atom. In general the energy distribution of the alkali and halogen atoms is thermal above 200 0 C, but not Maxwellian. (Auth.)

  3. Band Gap Tuning and Defect Tolerance of Atomically Thin Two- Dimensional Organic-Inorganic Halide Perovskites

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Jacobsen, Karsten Wedel; Thygesen, Kristian Sommer

    2016-01-01

    Organic−inorganic halide perovskites have proven highly successful for photovoltaics but suffer from low stability, which deteriorates their performance over time. Recent experiments have demonstrated that low dimensional phases of the hybrid perovskites may exhibit improved stability. Here we...... report first-principles calculations for isolated monolayers of the organometallic halide perovskites (C4H9NH3)2MX2Y2, where M = Pb, Ge, Sn and X,Y = Cl, Br, I. The band gaps computed using the GLLB-SC functional are found to be in excellent agreement with experimental photoluminescence data...... for the already synthesized perovskites. Finally, we study the effect of different defects on the band structure. We find that the most common defects only introduce shallow or no states in the band gap, indicating that these atomically thin 2D perovskites are likely to be defect tolerant....

  4. Nanoscale-Agglomerate-Mediated Heterogeneous Nucleation.

    Science.gov (United States)

    Cha, Hyeongyun; Wu, Alex; Kim, Moon-Kyung; Saigusa, Kosuke; Liu, Aihua; Miljkovic, Nenad

    2017-12-13

    Water vapor condensation on hydrophobic surfaces has received much attention due to its ability to rapidly shed water droplets and enhance heat transfer, anti-icing, water harvesting, energy harvesting, and self-cleaning performance. However, the mechanism of heterogeneous nucleation on hydrophobic surfaces remains poorly understood and is attributed to defects in the hydrophobic coating exposing the high surface energy substrate. Here, we observe the formation of high surface energy nanoscale agglomerates on hydrophobic coatings after condensation/evaporation cycles in ambient conditions. To investigate the deposition dynamics, we studied the nanoscale agglomerates as a function of condensation/evaporation cycles via optical and field emission scanning electron microscopy (FESEM), microgoniometric contact angle measurements, nucleation statistics, and energy dispersive X-ray spectroscopy (EDS). The FESEM and EDS results indicated that the nanoscale agglomerates stem from absorption of sulfuric acid based aerosol particles inside the droplet and adsorption of volatile organic compounds such as methanethiol (CH 3 SH), dimethyl disulfide (CH 3 SSCH), and dimethyl trisulfide (CH 3 SSSCH 3 ) on the liquid-vapor interface during water vapor condensation, which act as preferential sites for heterogeneous nucleation after evaporation. The insights gained from this study elucidate fundamental aspects governing the behavior of both short- and long-term heterogeneous nucleation on hydrophobic surfaces, suggest previously unexplored microfabrication and air purification techniques, and present insights into the challenges facing the development of durable dropwise condensing surfaces.

  5. Cell-substrate interaction with cell-membrane-stress dependent adhesion.

    Science.gov (United States)

    Jiang, H; Yang, B

    2012-01-10

    Cell-substrate interaction is examined in a two-dimensional mechanics model. The cell and substrate are treated as a shell and an elastic solid, respectively. Their interaction through adhesion is treated using nonlinear springs. Compared to previous cell mechanics models, the present model introduces a cohesive force law that is dependent not only on cell-substrate distance but also on internal cell-membrane stress. It is postulated that a living cell would establish focal adhesion sites with density dependent on the cell-membrane stress. The formulated mechanics problem is numerically solved using coupled finite elements and boundary elements for the cell and the substrate, respectively. The nodes in the adhesion zone from either side are linked by the cohesive springs. The specific cases of a cell adhering to a homogeneous substrate and a heterogeneous bimaterial substrate are examined. The analyses show that the substrate stiffness affects the adhesion behavior significantly and regulates the direction of cell adhesion, in good agreement with the experimental results in the literature. By introducing a reactive parameter (i.e., cell-membrane stress) linking biological responses of a living cell to a mechanical environment, the present model offers a unified mechanistic vehicle for characterization and prediction of living cell responses to various kinds of mechanical stimuli including local extracellular matrix and neighboring cells. Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. Inorganic hole conductor-based lead halide perovskite solar cells with 12.4% conversion efficiency

    KAUST Repository

    Qin, Peng

    2014-05-12

    Organo-lead halide perovskites have attracted much attention for solar cell applications due to their unique optical and electrical properties. With either low-temperature solution processing or vacuum evaporation, the overall conversion efficiencies of perovskite solar cells with organic hole-transporting material were quickly improved to over 15% during the last 2 years. However, the organic hole-transporting materials used are normally quite expensive due to complicated synthetic procedure or high-purity requirement. Here, we demonstrate the application of an effective and cheap inorganic p-type hole-transporting material, copper thiocyanate, on lead halide perovskite-based devices. With low-temperature solution-process deposition method, a power conversion efficiency of 12.4% was achieved under full sun illumination. This work represents a well-defined cell configuration with optimized perovskite morphology by two times of lead iodide deposition, and opens the door for integration of a class of abundant and inexpensive material for photovoltaic application. © 2014 Macmillan Publishers Limited.

  7. Excitonic and electron-hole mechanisms of the creation of Frenkel defect in alkali halides

    International Nuclear Information System (INIS)

    Lushchik, A.; Kirm, M.; Lushchik, Ch.; Vasil'chenko, E.

    2000-01-01

    Excitonic and electron-hole (e-h) mechanisms of stable F centre creation by VUV radiation in alkali halide crystals are discussed. In KCl at 4.2 K, the efficiency of stable F-H pair creation is especially high at the direct optical formation of triplet excitons with n=1. At 200-400 K, the creation processes of stable F centres in KCl are especially efficient at the formation of one-halide exciton in the Urbach tail of an exciton absorption. In KCl and KBr, the decay of a cation exciton (∼20 eV) causes the formation of two e-h pairs, while in NaCl a cation exciton (33.5 eV) decays into two e-h and an anion exciton. An elastic uniaxial stress of a crystal excited by VUV radiation decreases the mean free path of excitons before their self-trapping (KI) and increases the mean free path of hot holes before self-trapping (NaCl)

  8. Inorganic hole conductor-based lead halide perovskite solar cells with 12.4% conversion efficiency

    KAUST Repository

    Qin, Peng; Tanaka, Soichiro; Ito, Seigo; Tetreault, Nicolas; Manabe, Kyohei; Nishino, Hitoshi; Nazeeruddin, Mohammad Khaja; Grä tzel, Michael

    2014-01-01

    Organo-lead halide perovskites have attracted much attention for solar cell applications due to their unique optical and electrical properties. With either low-temperature solution processing or vacuum evaporation, the overall conversion efficiencies of perovskite solar cells with organic hole-transporting material were quickly improved to over 15% during the last 2 years. However, the organic hole-transporting materials used are normally quite expensive due to complicated synthetic procedure or high-purity requirement. Here, we demonstrate the application of an effective and cheap inorganic p-type hole-transporting material, copper thiocyanate, on lead halide perovskite-based devices. With low-temperature solution-process deposition method, a power conversion efficiency of 12.4% was achieved under full sun illumination. This work represents a well-defined cell configuration with optimized perovskite morphology by two times of lead iodide deposition, and opens the door for integration of a class of abundant and inexpensive material for photovoltaic application. © 2014 Macmillan Publishers Limited.

  9. High Pressure Optical Studies of the Thallous Halides and of Charge-Transfer Complexes

    Science.gov (United States)

    Jurgensen, Charles Willard

    High pressure was used to study the insulator -to-metal transition in sulfur and the thallous halides and to study the intermolecular interactions in charge -transfer complexes. The approach to the band overlap insulator -to-metal transition was studied in three thallous halides and sulfur by optical absorption measurements of the band gap as a function of pressure. The band gap of sulfur continuously decreases with pressure up to the insulator -to-metal transition which occurs between 450 and 485 kbars. The results on the thallous halides indicate that the indirect gap decreases more rapidly than the direct gap; the closing of the indirect gap is responsible for the observed insulator -to-metal transitions. High pressure electronic and vibrational spectroscopic measurements on the solid-state complexes of HMB-TCNE were used to study the intermolecular interactions of charge -transfer complexes. The vibrational frequency shifts indicate that the degree of charge transfer increases with pressure which is independently confirmed by an increase in the molar absorptivity of the electronic charge-transfer peak. Induction and dispersion forces contribute towards a red shift of the charge-transfer peak; however, charge-transfer resonance contributes toward a blue shift and this effect is dominant for the HMB-TCNE complexes. High pressure electronic spectra were used to study the effect of intermolecular interactions on the electronic states of TCNQ and its complexes. The red shifts with pressure of the electronic spectra of TCNQ and (TCNQ)(' -) in polymer media and of crystalline TCNQ can be understood in terms of Van der Waals interactions. None of the calculations which considered intradimer distance obtained the proper behavior for either the charge-transfer of the locally excited states of the complexes. The qualitative behavior of both states can be interpreted as the effect of increased mixing of the locally excited and charge transfer states.

  10. Gradient simulation experiments for targeting population heterogeneity in continuous Saccharomyces cerevisiae fermentation

    DEFF Research Database (Denmark)

    Heins, Anna-Lena; Lencastre Fernandes, Rita; Lundin, L.

    Traditionally, a microbial population has been considered homogeneous in optimization studies of fermentation processes. However, research has shown that a typical microbial population in a fermenter is heterogeneous. There are indications that such heterogeneity may be both beneficial (facilitates...... quick adaptation to new conditions) and harmful (reduces yields and productivities) (Bylund et al. (1998); Enfors et al. (2001)). Significant gradients of e.g. dissolved oxygen, substrates, and pH are typically observed in many industrial scale fermentation processes. Consequently, the microbial cells...... reporter strain demonstrated a highly dynamic behaviour with regards to subpopulation distribution during the different growth stages. To simulate which effect glucose gradients, often seen in large scale cultivations, have on population heterogeneity, glucose perturbations during continuous cultivation...

  11. Targeting population heterogeneity in Saccharomyces cerevisiae batch fermentation for optimal cell factories

    DEFF Research Database (Denmark)

    Heins, Anna-Lena; Lencastre Fernandes, Rita; Lundin, L.

    )). Significant gradients of e.g. dissolved oxygen, substrates, and pH are typically observed in many industrial scale fermentation processes. Consequently, the microbial cells experience rapid changes in environmental conditions as they circulate throughout the reactor, which might pose stress on the cells...... and affect their metabolism and consequently affect the heterogeneity level of the population. To further investigate these phenomena and gain a deeper understanding of population heterogeneity, Saccharomyces cerevisiae growth reporter strains based on the expression of green fluorescent protein (GFP) were...... environmental factors on heterogeneity level and amount of living cells. A highly dynamic behavior with regard to subpopulation distribution during the different growth stages was seen for the batch cultivations. Moreover, it could be demonstrated that the glucose concentration had a clear influence...

  12. Molecular dispersion energy parameters for alkali and halide ions in aqueous solution

    International Nuclear Information System (INIS)

    Reiser, S.; Deublein, S.; Hasse, H.; Vrabec, J.

    2014-01-01

    Thermodynamic properties of aqueous solutions containing alkali and halide ions are determined by molecular simulation. The following ions are studied: Li + , Na + , K + , Rb + , Cs + , F − , Cl − , Br − , and I − . The employed ion force fields consist of one Lennard-Jones (LJ) site and one concentric point charge with a magnitude of ±1 e. The SPC/E model is used for water. The LJ size parameter of the ion models is taken from Deublein et al. [J. Chem. Phys. 136, 084501 (2012)], while the LJ energy parameter is determined in the present study based on experimental self-diffusion coefficient data of the alkali cations and the halide anions in aqueous solutions as well as the position of the first maximum of the radial distribution function of water around the ions. On the basis of these force field parameters, the electric conductivity, the hydration dynamics of water molecules around the ions, and the enthalpy of hydration is predicted. Considering a wide range of salinity, this study is conducted at temperatures of 293.15 and 298.15 K and a pressure of 1 bar

  13. Structural and Chemical Analysis of Gadolinium Halides Encapsulated within WS 2 Nanotubes

    KAUST Repository

    Anumol, E A

    2016-05-18

    The hollow cavities of nanotubes could serve as templates for the growth of size- and shape-confined functional nanostructures, giving rise to novel materials and properties. In this work, considering their potential application as MRI contrast agents, gadolinium halides are encapsulated within the hollow cavities of inorganic nanotubes of WS2 by capillary filling to obtain GdX3@WS2 nanotubes (where X = Cl, Br or I and @ means encapsulated in). Aberration corrected scanning/transmission electron microscopy (S/TEM) and spectroscopy is employed to understand the morphology and composition of the GdI3@WS2 nanotubes. The three dimensional morphology is studied with STEM tomography but understanding the compositional information is a non-trivial matter due to the presence of multiple high atomic number elements. Therefore, energy dispersive X-ray spectroscopy (EDS) tomography was employed revealing the three dimensional chemical composition. Molecular dynamics simulations of the filling procedure shed light into the mechanics behind the formation of the confined gadolinium halide crystals. The quasi-1D system employed here serves as an example of a TEM-based chemical nanotomography method that could be extended to other materials, including beam-sensitive soft materials.

  14. Structural and Chemical Analysis of Gadolinium Halides Encapsulated within WS 2 Nanotubes

    KAUST Repository

    Anumol, E A; Enyashin, Andrey; Batra, Nitin M; Da Costa, Pedro M. F. J.; Francis, Leonard Deepak

    2016-01-01

    The hollow cavities of nanotubes could serve as templates for the growth of size- and shape-confined functional nanostructures, giving rise to novel materials and properties. In this work, considering their potential application as MRI contrast agents, gadolinium halides are encapsulated within the hollow cavities of inorganic nanotubes of WS2 by capillary filling to obtain GdX3@WS2 nanotubes (where X = Cl, Br or I and @ means encapsulated in). Aberration corrected scanning/transmission electron microscopy (S/TEM) and spectroscopy is employed to understand the morphology and composition of the GdI3@WS2 nanotubes. The three dimensional morphology is studied with STEM tomography but understanding the compositional information is a non-trivial matter due to the presence of multiple high atomic number elements. Therefore, energy dispersive X-ray spectroscopy (EDS) tomography was employed revealing the three dimensional chemical composition. Molecular dynamics simulations of the filling procedure shed light into the mechanics behind the formation of the confined gadolinium halide crystals. The quasi-1D system employed here serves as an example of a TEM-based chemical nanotomography method that could be extended to other materials, including beam-sensitive soft materials.

  15. Substrate-Related Factors Affecting Enzymatic Saccharification of Lignocelluloses: Our Recent Understanding

    Science.gov (United States)

    Shao-Yuan Leu; J.Y. Zhu

    2013-01-01

    Enzymatic saccharification of cellulose is a key step in conversion of plant biomass to advanced biofuel and chemicals. Many substrate-related factors affect saccharification. Rather than examining the role of each individual factor on overall saccharification efficiency, this study examined how each factor affects the three basic processes of a heterogeneous...

  16. The Study of Reducing Krypton-85 Activity in Metal Halide Lamp%降低金卤灯内氪-85活度的研究

    Institute of Scientific and Technical Information of China (English)

    叶碧君

    2012-01-01

    通过测试及分析不同氪-85活度填充气体的同规格金卤灯的各项性能参数,研究了在确保金卤灯各项性能的前提下,降低金卤灯中氪-85活度的可行性及金卤灯中氪-85存在的必要性,可以为今后确定金卤灯中需添加的最低氪-85活度提供参考。%By analyzing the parameters of metal halide lamps which are filled with gas with different activity of krypton-85, the paper studies the feasibility of reducing krypton-85 activity in metal halide lamp while ensuring the lamp performance, and proves the necessity of its existence of krypton-85 in metal halide lamp. it can provide us a reference to determine the minimum krypton-85 activity to he added in metal halide lamps.

  17. Structural, dynamical, and transport properties of the hydrated halides: How do At{sup −} bulk properties compare with those of the other halides, from F{sup −} to I{sup −}?

    Energy Technology Data Exchange (ETDEWEB)

    Réal, Florent, E-mail: florent.real@univ-lille1.fr; Severo Pereira Gomes, André; Guerrero Martínez, Yansel Omar; Vallet, Valérie [Université de Lille, CNRS, UMR 8523–PhLAM–Physique des Lasers Atomes et Molécules, F-59000 Lille (France); Ayed, Tahra; Galland, Nicolas [CEISAM UMR CNRS 6230, Université de Nantes, 2 Rue de la Houssinière, BP 92208 F-44322 Nantes Cedex 3 (France); Masella, Michel [Laboratoire de Biologie Structurale et Radiobiologie, Service de Bioénergétique, Biologie Structurale et Mécanismes, Institut de Biologie et de Technologies de Saclay, CEA Saclay, F-91191 Gif sur Yvette Cedex (France)

    2016-03-28

    The properties of halides from the lightest, fluoride (F{sup −}), to the heaviest, astatide (At{sup −}), have been studied in water using a polarizable force-field approach based on molecular dynamics (MD) simulations at the 10 ns scale. The selected force-field explicitly treats the cooperativity within the halide-water hydrogen bond networks. The force-field parameters have been adjusted to ab initio data on anion/water clusters computed at the relativistic Möller-Plesset second-order perturbation theory level of theory. The anion static polarizabilities of the two heaviest halides, I{sup −} and At{sup −}, were computed in the gas phase using large and diffuse atomic basis sets, and taking into account both electron correlation and spin-orbit coupling within a four-component framework. Our MD simulation results show the solvation properties of I{sup −} and At{sup −} in aqueous phase to be very close. For instance, their first hydration shells are structured and encompass 9.2 and 9.1 water molecules at about 3.70 ± 0.05 Å, respectively. These values have to be compared to the F{sup −}, Cl{sup −}, and Br{sup −} ones, i.e., 6.3, 8.4, and 9.0 water molecules at 2.74, 3.38, and 3.55 Å, respectively. Moreover our computations predict the solvation free energy of At{sup −} in liquid water at ambient conditions to be 68 kcal mol{sup −1}, a value also close the I{sup −} one, about 70 kcal mol{sup −1}. In all, our simulation results for I{sup −} are in excellent agreement with the latest neutron- and X-ray diffraction studies. Those for the At{sup −} ion are predictive, as no theoretical or experimental data are available to date.

  18. Inhibition performance of a gemini surfactant and its co-adsorption effect with halides on mild steel in 0.25 M H{sub 2}SO{sub 4} solution

    Energy Technology Data Exchange (ETDEWEB)

    Wang Xiumei [State Key Laboratory for Corrosion and Protection, Institute of Metal Research Chinese Academy of Sciences, Shenyang 110016 (China); School of Materials Science and Engineering, Shenyang Jianzhu University, Shenyang 110168 (China); Yang Huaiyu, E-mail: hyyang@imr.ac.cn [State Key Laboratory for Corrosion and Protection, Institute of Metal Research Chinese Academy of Sciences, Shenyang 110016 (China); Wang Fuhui [State Key Laboratory for Corrosion and Protection, Institute of Metal Research Chinese Academy of Sciences, Shenyang 110016 (China)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer 1,4-Bis (1-chlorobenzyl-benzimidazolyl)-butane has good inhibition effect for mild steel in H{sub 2}SO{sub 4}. Black-Right-Pointing-Pointer The compound acts as a mixed-type inhibitor and obeys Langmuir adsorption isotherm. Black-Right-Pointing-Pointer Halide ions can improve the inhibition property of compound via the co-adsorption effect. Black-Right-Pointing-Pointer The adsorbed halides play an important intermediate bridge role in co-adsorption process. Black-Right-Pointing-Pointer The obtained results can supply the bases for the future using of cationic inhibitor. - Abstract: The inhibition performance of a cationic gemini-surfactant (CBB) and its co-adsorption behavior with halides on mild steel in 0.25 M H{sub 2}SO{sub 4} solution was studied by weight loss and electrochemical techniques. Results showed that the compound could effectively inhibit the mild steel corrosion and acted as a mixed-type inhibitor by suppressing simultaneously anodic and cathodic reactions. Addition of the halides improve the inhibition efficiency of CBB and the synergistic effect increase in the order of I{sup -} > Br{sup -} > Cl{sup -}, revealing that halides radii and their electronegativity may play significant roles in co-adsorption with the cationic inhibitor.

  19. Evaluation of field test equipment for halide and DOP testing

    International Nuclear Information System (INIS)

    Schreiber, K.L.; Kovach, J.L.

    1975-01-01

    The Nucon Testing Services Department, field testing at power reactor sites, has performed tests using R-11, R-12, and R-112 in conjunction with gas chromatographs and direct reading halide detectors. The field operational experience with these detector systems, thus sensitivity, precision, and manner of field calibration, are presented. Laboratory experiments regarding 3 H-tagged methyl iodide for in place leak testing of adsorber systems indicate a low hazard, high reliability process for leak testing in facilities where atmospheric cross contamination occurs. (U.S.)

  20. Conceptual design of an angular multiplexed rare-gas-halide laser-fusion driver. Final technical report, 1 August 1979-31 May 1980

    International Nuclear Information System (INIS)

    Parks, J.H.

    1980-11-01

    A conceptual definition for angular multiplexed rare gas halide drivers was formulated and several design examples analyzed. Angular multiplexed rare gas-halide lasers, in particular the KrF* laser, can be designed to meet ICF requirements. These lasers are scalable, emit at short wavelengths (KrF* 250 nm), and through the use of optical angular multiplexing, produce the required high energy (approx. 1 to 5 MJ) in a short pulse (approx. 10 nsec) with projected overall efficiency in the range of 5 to 7%

  1. Solution and solid-state studies on the halide binding affinity of perfluorophenyl-armed uranyl-salophen receptors enhanced by anion-π interactions

    Energy Technology Data Exchange (ETDEWEB)

    Leoni, Luca; Mele, Andrea; Giannicchi, Ilaria; Mihan, Francesco Yafteh; Dalla Cort, Antonella [Dipartimento di Chimica and IMC-CNR, Universita di Roma La Sapienza (Italy); Puttreddy, Rakesh; Jurcek, Ondrej; Rissanen, Kari [University of Jyvaeskylae, Department of Chemistry, Nanoscience Center (Finland)

    2016-12-23

    The enhancement of the binding between halide anions and a Lewis acidic uranyl-salophen receptor has been achieved by the introduction of pendant electron-deficient arene units into the receptor skeleton. The association and the occurrence of the elusive anion-π interaction with halide anions (as tetrabutylammonium salts) have been demonstrated in solution and in the solid state, providing unambiguous evidence on the interplay of the concerted interactions responsible for the anion binding. (copyright 2016 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Pressure-Induced Metallization of the Halide Perovskite (CH 3 NH 3 )PbI 3

    Energy Technology Data Exchange (ETDEWEB)

    Jaffe, Adam; Lin, Yu [Photon; Mao, Wendy L. [Photon; Karunadasa, Hemamala I.

    2017-03-10

    We report the metallization of the hybrid perovskite semiconductor (MA)PbI3 (MA = CH3NH3+) with no apparent structural transition. We tracked its bandgap evolution during compression in diamond-anvil cells using absorption spectroscopy and observed strong absorption over both visible and IR wavelengths at pressures above ca. 56 GPa, suggesting the imminent closure of its optical bandgap. The metallic character of (MA)PbI3 above 60 GPa was confirmed using both IR reflectivity and variable-temperature dc conductivity measurements. The impressive semiconductor properties of halide perovskites have recently been exploited in a multitude of optoelectronic applications. Meanwhile, the study of metallic properties in oxide perovskites has revealed diverse electronic phenomena. Importantly, the mild synthetic routes to halide perovskites and the templating effects of the organic cations allow for fine structural control of the inorganic lattice. Pressure-induced closure of the 1.6 eV bandgap in (MA)PbI3 demonstrates the promise of the continued study of halide perovskites under a range of thermodynamic conditions, toward realizing wholly new electronic properties.

  3. Ligand-free, palladium-catalyzed dihydrogen generation from TMDS: dehalogenation of aryl halides on water.

    Science.gov (United States)

    Bhattacharjya, Anish; Klumphu, Piyatida; Lipshutz, Bruce H

    2015-03-06

    A mild and environmentally attractive dehalogenation of functionalized aryl halides has been developed using nanoparticles formed from PdCl2 in the presence of tetramethyldisiloxane (TMDS) on water. The active catalyst and reaction medium can be recycled. This method can also be applied to cascade reactions in a one-pot sequence.

  4. An air-stable copper reagent for nucleophilic trifluoromethylthiolation of aryl halides

    KAUST Repository

    Weng, Zhiqiang

    2012-12-12

    A series of copper(I) trifluoromethyl thiolate complexes have been synthesized from the reaction of CuF2 with Me3SiCF 3 and S8 (see scheme; Cu red, F green, N blue, S yellow). These air-stable complexes serve as reagents for the efficient conversion of a wide range of aryl halides into the corresponding aryl trifluoromethyl thioethers in excellent yields. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. An air-stable copper reagent for nucleophilic trifluoromethylthiolation of aryl halides

    KAUST Repository

    Weng, Zhiqiang; He, Weiming; Chen, Chaohuang; Lee, Richmond; Tan, Davin; Lai, Zhiping; Kong, Dedao; Yuan, Yaofeng; Huang, Kuo-Wei

    2012-01-01

    A series of copper(I) trifluoromethyl thiolate complexes have been synthesized from the reaction of CuF2 with Me3SiCF 3 and S8 (see scheme; Cu red, F green, N blue, S yellow). These air-stable complexes serve as reagents for the efficient conversion of a wide range of aryl halides into the corresponding aryl trifluoromethyl thioethers in excellent yields. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Ca-Fe and Alkali-Halide Alteration of an Allende Type B CAI: Aqueous Alteration in Nebular or Asteroidal Settings

    Science.gov (United States)

    Ross, D. K.; Simon, J. I.; Simon, S. B.; Grossman, L.

    2012-01-01

    Ca-Fe and alkali-halide alteration of CAIs is often attributed to aqueous alteration by fluids circulating on asteroidal parent bodies after the various chondritic components have been assembled, although debate continues about the roles of asteroidal vs. nebular modification processes [1-7]. Here we report de-tailed observations of alteration products in a large Type B2 CAI, TS4 from Allende, one of the oxidized subgroup of CV3s, and propose a speculative model for aqueous alteration of CAIs in a nebular setting. Ca-Fe alteration in this CAI consists predominantly of end-member hedenbergite, end-member andradite, and compositionally variable, magnesian high-Ca pyroxene. These phases are strongly concentrated in an unusual "nodule" enclosed within the interior of the CAI (Fig. 1). The Ca, Fe-rich nodule superficially resembles a clast that pre-dated and was engulfed by the CAI, but closer inspection shows that relic spinel grains are enclosed in the nodule, and corroded CAI primary phases interfinger with the Fe-rich phases at the nodule s margins. This CAI also contains abundant sodalite and nepheline (alkali-halide) alteration that occurs around the rims of the CAI, but also penetrates more deeply into the CAI. The two types of alteration (Ca-Fe and alkali-halide) are adjacent, and very fine-grained Fe-rich phases are associated with sodalite-rich regions. Both types of alteration appear to be replacive; if that is true, it would require substantial introduction of Fe, and transport of elements (Ti, Al and Mg) out of the nodule, and introduction of Na and Cl into alkali-halide rich zones. Parts of the CAI have been extensively metasomatized.

  7. Catalytic performance of heterogeneous Rh/C3N4 for the carbonylation of methanol

    Science.gov (United States)

    Budiman, Anatta Wahyu; Choi, Myoung Jae; Nur, Adrian

    2018-02-01

    The excess of water in homogeneous the carbonylation of methanol system could increase the amount of by-products formed through water-gas shift reaction and could accelerate the rusting of equipment. Many scientists tried to decrease the content of water in the carbonylation of methanol system by using lithium and iodide promoter that results a moderate catalytic activity in the water content at 2wt%. The heterogenized catalyst offers several distinct advantages such as it was enables increased catalyst concentration in the reaction mixture, which is directly proportional to acetic acid production rate, without the addition of an alkali iodide salt promoter. The heterogeneous catalyst also results in reduced by-product formation. This study is aimed to produce a novel catalyst (Rh/C3N4) with a high selectivity of acetic acid in a relatively lower water and halide content. This novel catalyst performs high conversion and selectivity of acetic acid as the result of the strong ionic bonding of melamine and rhodium complex species that was caused by the presence of methyl iodide species. The CO2 in feed gas significantly decreases the catalytic activity of Rh-melamine because of its inert characteristics. The kinetic test was performed as that the first order kinetic equation. The kinetic tests revealed the reaction route of the the carbonylation of methanol in this system was performed trough the methyl acetate.

  8. Photoinduced intramolecular substitution reaction of aryl halide with carbonyl oxygen of amide group

    CERN Document Server

    Park, Y T; Kim, M S; Kwon, J H

    2002-01-01

    Photoreaction of N-(o-halophenyl)acetamide in basic acetonitrile produces an intramolecular substituted product, 2-methylbenzoxazole in addition to reduced product, acetanilide, whereas photoreaction of N-(o-halobenzyl)acetamide affords a reduced product, N-benzylacetamide only. On the basis of preparative reaction, kinetics, and UV/vis absorption behavior, an electrophilic aromatic substitution of aryl halide with oxygen of its amide bond are proposed.

  9. Photoinduced intramolecular substitution reaction of aryl halide with carbonyl oxygen of amide group

    Energy Technology Data Exchange (ETDEWEB)

    Park, Yong Tae; Song, Myong Geun; Kim, Moon Sub; Kwon, Jeong Hee [Kyungpook National Univ., Daegu (Korea, Republic of)

    2002-09-01

    Photoreaction of N-(o-halophenyl)acetamide in basic acetonitrile produces an intramolecular substituted product, 2-methylbenzoxazole in addition to reduced product, acetanilide, whereas photoreaction of N-(o-halobenzyl)acetamide affords a reduced product, N-benzylacetamide only. On the basis of preparative reaction, kinetics, and UV/vis absorption behavior, an electrophilic aromatic substitution of aryl halide with oxygen of its amide bond are proposed.

  10. Photoinduced intramolecular substitution reaction of aryl halide with carbonyl oxygen of amide group

    International Nuclear Information System (INIS)

    Park, Yong Tae; Song, Myong Geun; Kim, Moon Sub; Kwon, Jeong Hee

    2002-01-01

    Photoreaction of N-(o-halophenyl)acetamide in basic acetonitrile produces an intramolecular substituted product, 2-methylbenzoxazole in addition to reduced product, acetanilide, whereas photoreaction of N-(o-halobenzyl)acetamide affords a reduced product, N-benzylacetamide only. On the basis of preparative reaction, kinetics, and UV/vis absorption behavior, an electrophilic aromatic substitution of aryl halide with oxygen of its amide bond are proposed

  11. Electron-stimulated desorption of lithium ions from lithium halide thin films

    International Nuclear Information System (INIS)

    Markowski, Leszek

    2007-01-01

    Electron-stimulated desorption of positive lithium ions from thin layers of lithium halides deposited onto Si(1 1 1) are investigated by the time-of-flight technique. The determined values of isotope effect of the lithium ( 6 Li + / 7 Li + ) are 1.60 ± 0.04, 1.466 ± 0.007, 1.282 ± 0.004, 1.36 ± 0.01 and 1.33 ± 0.01 for LiH, LiF, LiCl, LiBr and LiI, respectively. The observed most probable kinetic energies of 7 Li + are 1.0, 1.9, 1.1, 0.9 and 0.9 eV for LiH, LiF, LiCl, LiBr and LiI, respectively, and seem to be independent of the halide component mass. The values of lithium ion emission yield, lithium kinetic energy and lithium isotope effect suggest that the lattice relaxation is only important in the lithium ion desorption process from the LiH system. In view of possible mechanisms and processes involved into lithium ion desorption the obtained results indicate that for LiH, LiCl, LiBr and LiI the ions desorb in a rather classical way. However, for LiF, ion desorption has a more quantum character and the modified wave packet squeezing model has to be taken into account

  12. Photoluminescence properties of Er-doped Ge–In(Ga)–S glasses modified by caesium halides

    Czech Academy of Sciences Publication Activity Database

    Ivanova, Z.G.; Zavadil, Jiří; Kostka, P.; Djouama, T.; Reinfelde, M.

    2017-01-01

    Roč. 254, č. 6 (2017), č. článku 1600662. ISSN 0370-1972 Institutional support: RVO:67985882 Keywords : caesium halides * chalcohalide glasses * erbium doping * transmission spectroscopy * photoluminiscence Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass OBOR OECD: Ceramics Impact factor: 1.674, year: 2016

  13. Photoluminescence properties of Er-doped Ge–In(Ga)–S glasses modified by caesium halides

    Czech Academy of Sciences Publication Activity Database

    Ivanova, Z.G.; Zavadil, Jiří; Kostka, Petr; Djouama, T.; Reinfelde, M.

    2017-01-01

    Roč. 254, č. 6 (2017), č. článku 1600662. ISSN 0370-1972 Institutional support: RVO:67985891 Keywords : caesium halides * chalcohalide glasses * erbium doping * transmission spectroscopy * photoluminiscence Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass OBOR OECD: Ceramics Impact factor: 1.674, year: 2016

  14. A model for additive transport in metal halide lamps containing mercury and dysprosium tri-iodide

    NARCIS (Netherlands)

    Beks, M.L.; Haverlag, M.; Mullen, van der J.J.A.M.

    2008-01-01

    The distribution of additives in a metal halide lamp is examined through numerical modelling. A model for a lamp containing sodium iodide additives has been modified to study a discharge containing dysprosium tri-iodide salts. To study the complex chemistry the method of Gibbs minimization is used

  15. Radiation chemistry of hydrocarbon and alkyl halide systems. Progress report, August 1, 1977--August 1, 1978

    International Nuclear Information System (INIS)

    Hanrahan, R.J.

    1978-01-01

    Progress of experimental work is reported on pulse radiolysis of simple alkyl halides in the gas phase, gas phase radiolysis of CHF 3 -CH 3 I mixtures, gamma radiolysis of the system CO/H 2 , and improvements in equipment and facilities

  16. Effect of chromone-substituted benzothiazolium halides on photosynthetic processes

    International Nuclear Information System (INIS)

    Kralova, K.; Sersen, F.; Gasparova, R.; Lacova, M.

    1998-01-01

    The effects of 3-R 2 -2[2-(6-R 1 -chromone-3-yl)ethenyl]benzothiazolium halides (CBH) on photosynthetic electron transport in spinach chloroplasts and in the legal suspension of Chlorella vulgaris were investigated. Using EPR spectroscopy it was confirmed that these compounds containing in their molecules two heterocyclic skeletons, namely benzothiazole and chromone, interact with the intermediate D + , corresponding to the tyrosine radical Tyr D situated in D 2 protein on the donor side of photosystem 2. Consequently, higher concentrations of CBH inhibited oxygen evolution rate in Chlorella vulgaris and the inhibitory effectiveness depended on the lipophilicity of the of the compound. (authors)

  17. Nanocrystals of Cesium Lead Halide Perovskites (CsPbX₃, X = Cl, Br, and I): Novel Optoelectronic Materials Showing Bright Emission with Wide Color Gamut.

    Science.gov (United States)

    Protesescu, Loredana; Yakunin, Sergii; Bodnarchuk, Maryna I; Krieg, Franziska; Caputo, Riccarda; Hendon, Christopher H; Yang, Ruo Xi; Walsh, Aron; Kovalenko, Maksym V

    2015-06-10

    Metal halides perovskites, such as hybrid organic-inorganic CH3NH3PbI3, are newcomer optoelectronic materials that have attracted enormous attention as solution-deposited absorbing layers in solar cells with power conversion efficiencies reaching 20%. Herein we demonstrate a new avenue for halide perovskites by designing highly luminescent perovskite-based colloidal quantum dot materials. We have synthesized monodisperse colloidal nanocubes (4-15 nm edge lengths) of fully inorganic cesium lead halide perovskites (CsPbX3, X = Cl, Br, and I or mixed halide systems Cl/Br and Br/I) using inexpensive commercial precursors. Through compositional modulations and quantum size-effects, the bandgap energies and emission spectra are readily tunable over the entire visible spectral region of 410-700 nm. The photoluminescence of CsPbX3 nanocrystals is characterized by narrow emission line-widths of 12-42 nm, wide color gamut covering up to 140% of the NTSC color standard, high quantum yields of up to 90%, and radiative lifetimes in the range of 1-29 ns. The compelling combination of enhanced optical properties and chemical robustness makes CsPbX3 nanocrystals appealing for optoelectronic applications, particularly for blue and green spectral regions (410-530 nm), where typical metal chalcogenide-based quantum dots suffer from photodegradation.

  18. Comparative study of energy-efficiency and conservation systems for ceramic metal-halide discharge lamps

    International Nuclear Information System (INIS)

    Hermoso Orzáez, Manuel Jesús; Andrés Díaz, José Ramón de

    2013-01-01

    Interest in energy savings in urban lighting is gaining traction and has become a priority for municipal administrations. LED (light-emitting diode) technology appears to be the clear future lighting choice. However, this technology is still rapidly developing and has not been sufficiently tested. As an intermediate step, alternative proposals for energy-saving equipment for traditional discharge lamps are desirable so that the current technologies can coexist with the new LED counterparts for the short and medium term. This article provides a comparative study between two efficiency and energy-saving systems for discharge lamps with metal-halide and ceramic technologies, i.e., a lighting flow dimmer-stabilizer and a double-level electronic ballast. - Highlights: ► It has been demonstrated the possibility of regulating ceramic metal-halide lamps with lighting flow dimmer-stabilizer. ► Electronic ballasts can save approximately double quantity of energy than lighting flow dimmer-stabilizers. ► The use of lighting flow dimmer-stabilizer is more profitable than electronic ballasts due to costs and reliability

  19. Progress on Perovskite Materials and Solar Cells with Mixed Cations and Halide Anions.

    Science.gov (United States)

    Ono, Luis K; Juarez-Perez, Emilio J; Qi, Yabing

    2017-09-13

    Organic-inorganic halide perovskite materials (e.g., MAPbI 3 , FAPbI 3 , etc.; where MA = CH 3 NH 3 + , FA = CH(NH 2 ) 2 + ) have been studied intensively for photovoltaic applications. Major concerns for the commercialization of perovskite photovoltaic technology to take off include lead toxicity, long-term stability, hysteresis, and optimal bandgap. Therefore, there is still need for further exploration of alternative candidates. Elemental composition engineering of MAPbI 3 and FAPbI 3 has been proposed to address the above concerns. Among the best six certified power conversion efficiencies reported by National Renewable Energy Laboratory on perovskite-based solar cells, five are based on mixed perovskites (e.g., MAPbI 1-x Br x , FA 0.85 MA 0.15 PbI 2.55 Br 0.45 , Cs 0.1 FA 0.75 MA 0.15 PbI 2.49 Br 0.51 ). In this paper, we review the recent progress on the synthesis and fundamental aspects of mixed cation and halide perovskites correlating with device performance, long-term stability, and hysteresis. In the outlook, we outline the future research directions based on the reported results as well as related topics that warrant further investigation.

  20. Interplay between organic cations and inorganic framework and incommensurability in hybrid lead-halide perovskite CH3NH3PbBr3

    Science.gov (United States)

    Guo, Yinsheng; Yaffe, Omer; Paley, Daniel W.; Beecher, Alexander N.; Hull, Trevor D.; Szpak, Guilherme; Owen, Jonathan S.; Brus, Louis E.; Pimenta, Marcos A.

    2017-09-01

    Organic-inorganic coupling in the hybrid lead-halide perovskite is a central issue in rationalizing the outstanding photovoltaic performance of these emerging materials. Here, we compare and contrast the evolution of the structure and dynamics of hybrid CH3NH3PbBr3 and inorganic CsPbBr3 lead-halide perovskites with temperature, using Raman spectroscopy and single-crystal x-ray diffraction. Results reveal a stark contrast between their order-disorder transitions, which are abrupt for the hybrid whereas smooth for the inorganic perovskite. X-ray diffraction observes an intermediate incommensurate phase between the ordered and the disordered phases in CH3NH3PbBr3 . Low-frequency Raman scattering captures the appearance of a sharp soft mode in the incommensurate phase, ascribed to the theoretically predicted amplitudon mode. Our work highlights the interaction between the structural dynamics of organic cation CH3NH3+ and the lead-halide framework, and unravels the competition between tendencies for the organic and inorganic moieties to minimize energy in the incommensurate phase of the hybrid perovskite structure.

  1. Hydrodynamic boundary conditions for one-component liquid-gas flows on non-isothermal solid substrates

    KAUST Repository

    Xu, Xinpeng; Liu, Chun; Qian, Tiezheng

    2012-01-01

    profiles of liquid-gas flows on non-isothermal, heterogeneous solid substrates is still absent. The purpose of this work is to construct a continuum model for simulating the liquid-gas flows on solid surfaces that are flat and rigid, and may involve

  2. Electrochemical Exfoliation of Graphite in Aqueous Sodium Halide Electrolytes toward Low Oxygen Content Graphene for Energy and Environmental Applications.

    Science.gov (United States)

    Munuera, J M; Paredes, J I; Enterría, M; Pagán, A; Villar-Rodil, S; Pereira, M F R; Martins, J I; Figueiredo, J L; Cenis, J L; Martínez-Alonso, A; Tascón, J M D

    2017-07-19

    Graphene and graphene-based materials have shown great promise in many technological applications, but their large-scale production and processing by simple and cost-effective means still constitute significant issues in the path of their widespread implementation. Here, we investigate a straightforward method for the preparation of a ready-to-use and low oxygen content graphene material that is based on electrochemical (anodic) delamination of graphite in aqueous medium with sodium halides as the electrolyte. Contrary to previous conflicting reports on the ability of halide anions to act as efficient exfoliating electrolytes in electrochemical graphene exfoliation, we show that proper choice of both graphite electrode (e.g., graphite foil) and sodium halide concentration readily leads to the generation of large quantities of single-/few-layer graphene nanosheets possessing a degree of oxidation (O/C ratio down to ∼0.06) lower than that typical of anodically exfoliated graphenes obtained with commonly used electrolytes. The halide anions are thought to play a role in mitigating the oxidation of the graphene lattice during exfoliation, which is also discussed and rationalized. The as-exfoliated graphene materials exhibited a three-dimensional morphology that was suitable for their practical use without the need to resort to any kind of postproduction processing. When tested as dye adsorbents, they outperformed many previously reported graphene-based materials (e.g., they adsorbed ∼920 mg g -1 for methyl orange) and were useful sorbents for oils and nonpolar organic solvents. Supercapacitor cells assembled directly from the as-exfoliated products delivered energy and power density values (up to 15.3 Wh kg -1 and 3220 W kg -1 , respectively) competitive with those of many other graphene-based devices but with the additional advantage of extreme simplicity of preparation.

  3. Formation of random and regular relief-phase structures on silver halide photographic emulsions by holographic methods

    Science.gov (United States)

    Ganzherli, N. M.; Gulyaev, S. N.; Gurin, A. S.; Kramushchenko, D. D.; Maurer, I. A.; Chernykh, D. F.

    2009-07-01

    The formation of diffusers and microlens rasters on silver halide emulsions by holographic methods is considered. Two techniques for converting amplitude holographic recording to relief-phase recording, selective curing and irradiation of the emulsion gelatin by short-wavelength UV radiation, are compared.

  4. UV and X radiation effects on the stability of calcium halide phosphate phosphors. 2

    International Nuclear Information System (INIS)

    Tews, W.; Getter, R.; Kleemann, M.

    1983-01-01

    Sb(V) and Sb(III) concentrations in calcium halide phosphate phosphors have been investigated as a function of time of irradiation with near UV and X radiation. It was found that the reduction of both Sb(V) and Sb(III) to elemental Sb results in intensity losses. The reductions follow consecutive first-order kinetics and first-order kinetics, respectively

  5. Phase recording for formation of holographic optical elements on silver-halide photographic emulsions

    Science.gov (United States)

    Ganzherli, Nina M.; Gulyaev, Sergey N.; Maurer, Irina A.; Chernykh, Dmitrii F.

    2009-05-01

    Holographic fabrication methods of regular and nonregular relief-phase structures on silver-halide photographic emulsions are considered. Methods of gelatin photodestruction under short-wave ultra-violet radiation and chemical hardening with the help of dichromated solutions were used as a technique for surface relief formation. The developed techniques permitted us to study specimens of holographic diffusers and microlens rasters with small absorption and high light efficiency.

  6. Substrate-Based Noble-Metal Nanomaterials: Shape Engineering and Applications

    Science.gov (United States)

    Hajfathalian, Maryam

    Nanostructures have potential for use in state-of-the-art applications such as sensing, imaging, therapeutics, drug delivery, and electronics. The ability to fabricate and engineer these nanoscale materials is essential for the continued development of such devices. Because the morphological features of nanomaterials play a key role in determining chemical and physical properties, there is great interest in developing and improving methods capable of controlling their size, shape, and composition. While noble nanoparticles have opened the door to promising applications in fields such as imaging, cancer targeting, photothermal treatment, drug delivery, catalysis and sensing, the synthetic processes required to form these nanoparticles on surfaces are not well-developed. Herein is a detailed account on efforts for adapting established solution-based seed-mediated synthetic protocols to structure in a substrate-based platform. These syntheses start by (i) defining heteroepitaxially oriented nanostructured seeds at site-specific locations using lithographic or directed-assembly techniques, and then (ii) transforming the seeds using either a solution or vapor phase processing route to activate kinetically- or thermodynamically-driven growth modes, to arrive at nanocrystals with complex and useful geometries. The first series of investigations highlight synthesis-routes based on heterogeneous nucleation, where templates serve as nucleation sites for metal atoms arriving in the vapor phase. In the first research direction, the vapor-phase heterogeneous nucleation of Ag on Au was carried out at high temperatures, where the Ag vapor was sourced from a sublimating foil onto adjacent Au templates. This process transformed both the composition and morphology of the initial Au Wulff-shaped nanocrystals to a homogeneous AuAg nanoprism. In the second case, the vapor-phase heterogeneous nucleation of Cu atoms on Au nanocrystal templates was investigated by placing a Cu foil next

  7. All-Inorganic Colloidal Quantum Dot Photovoltaics Employing Solution-Phase Halide Passivation

    KAUST Repository

    Ning, Zhijun

    2012-09-12

    A new solution-phase halide passivation strategy to improve the electronic properties of colloidal quantum dot films is reported. We prove experimentally that the approach leads to an order-of-magnitude increase in mobility and a notable reduction in trap state density. We build solar cells having the highest efficiency (6.6%) reported using all-inorganic colloidal quantum dots. The improved photocurrent results from increased efficiency of collection of infrared-generated photocarriers. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. All-Inorganic Colloidal Quantum Dot Photovoltaics Employing Solution-Phase Halide Passivation

    KAUST Repository

    Ning, Zhijun; Ren, Yuan; Hoogland, Sjoerd; Voznyy, Oleksandr; Levina, Larissa; Stadler, Philipp; Lan, Xinzheng; Zhitomirsky, David; Sargent, Edward H.

    2012-01-01

    A new solution-phase halide passivation strategy to improve the electronic properties of colloidal quantum dot films is reported. We prove experimentally that the approach leads to an order-of-magnitude increase in mobility and a notable reduction in trap state density. We build solar cells having the highest efficiency (6.6%) reported using all-inorganic colloidal quantum dots. The improved photocurrent results from increased efficiency of collection of infrared-generated photocarriers. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Genesis, challenges and opportunities for colloidal lead halide perovskite nanocrystals

    Science.gov (United States)

    Akkerman, Quinten A.; Rainò, Gabriele; Kovalenko, Maksym V.; Manna, Liberato

    2018-05-01

    Lead halide perovskites (LHPs) in the form of nanometre-sized colloidal crystals, or nanocrystals (NCs), have attracted the attention of diverse materials scientists due to their unique optical versatility, high photoluminescence quantum yields and facile synthesis. LHP NCs have a `soft' and predominantly ionic lattice, and their optical and electronic properties are highly tolerant to structural defects and surface states. Therefore, they cannot be approached with the same experimental mindset and theoretical framework as conventional semiconductor NCs. In this Review, we discuss LHP NCs historical and current research pursuits, challenges in applications, and the related present and future mitigation strategies explored.

  10. Status quo of ceramic material for metal halide discharge lamps

    International Nuclear Information System (INIS)

    Kappen, Theo G M M

    2005-01-01

    Polycrystalline alumina is an excellent ceramic material for use as the envelope for metal halide discharge lamps. Although this material was introduced in the mid-1960s, and is thus already known for several decades, recent years have seen considerable effort aimed at further development of these ceramic envelope materials. Developments are not only in the field of ceramic shaping technologies, but are also concentrated on the material properties of the ceramic material itself. Optical, mechanical as well as the chemical properties of the ceramic envelope are strongly controlled by the shape as well as the microstructure of the ceramics used

  11. Structure and energetics of trivalent metal halides

    International Nuclear Information System (INIS)

    Hutchinson, F.

    1999-01-01

    Metal trihalide (MX 3 ) systems represent a stern challenge in terms of constructing transferable potential models. Starting from a previously published set of potentials, 'extended' ionic models are developed which, at the outset, include only anion polarization. Deficiencies in these models, particularly for smaller (highly polarizing) cations, axe shown to be significant. For example, crystal structures different to those observed experimentally axe adopted. The potentials axe improved upon by reference to ab initio information available for alkali halides with the 'constraint' that the parameters transfer systematically in a physically transparent manner, for example, in terms of ion radii. The possible influence of anion compression ('breathing') and the relative abundance of anion-anion interactions are considered. Simulation techniques axe developed to allow for the effective simulation of any system symmetry and for the study of transitions between different crystals (constant stress). The developed models are fully tested for a large range of metal trichloride (MCl 3 ) systems. Particular attention is paid to the comparison with recent neutron and X-ray diffraction data on the liquid state. Polarization effects axe shown to be vital in reproducing strong experimental features. The excellent agreement between simulation and experiment allows for differences in experimental procedures to be highlighted. The transferability is further tested by modelling mixtures of the lanthanides with alkali halides with potentials unchanged from the pure systems. The complex evolution of the melt structure is highlighted as the concentration of MCl 3 increases. The effectiveness of the models is tested by reference to dynamical properties. Particular attention is paid to the comparison with Raman scattering data available for a wide range of systems and mixture concentrations. The simulated spectra are generated both by a simple molecular picture of the underlying

  12. Variable Charge and Electrical Double Layer of Mineral-Water Interfaces: Silver Halides versus Metal (Hydr)Oxides

    NARCIS (Netherlands)

    Hiemstra, T.

    2012-01-01

    Classically, silver (Ag) halides have been used to understand thermodynamic principles of the charging process and the corresponding development of the electrical double layer (EDL). A mechanistic approach to the processes on the molecular level has not yet been carried out using advanced surface

  13. Drift mechanism of mass transfer on heterogeneous reaction in crystalline silicon substrate

    Energy Technology Data Exchange (ETDEWEB)

    Kukushkin, S.A. [Institute of Problems of Mechanical Engineering, Russian Academy of Science, St Petersburg, 199178 (Russian Federation); St. Petersburg National Research University of Information Technologies, Mechanics and Optics, 197101 (Russian Federation); Osipov, A.V., E-mail: Andrey.V.Osipov@gmail.com [Institute of Problems of Mechanical Engineering, Russian Academy of Science, St Petersburg, 199178 (Russian Federation); St. Petersburg National Research University of Information Technologies, Mechanics and Optics, 197101 (Russian Federation)

    2017-05-01

    This work aims to study the pressure dependence of the thickness of the epitaxial silicon carbide film growing from crystalline silicon due to the heterogeneous reaction with gaseous carbon monoxide. It turned out that this dependence exhibits the clear maximum. On further pressure increasing the film thickness decreases. The theoretical model has been developed which explains such a character of the dependence by the fact that the gaseous silicon monoxide reaction product inhibits the drift of the gaseous reagent through the channels of a crystal lattice, thus decreasing their hydraulic diameter. In the proposed hydraulic model, the dependences of the film thickness both on the gas pressure and time have been calculated. It was shown that not only the qualitative but also quantitative correspondence between theoretical and experimental results takes place. As one would expect, due to the Einstein relation, at short growth times the drift model coincides with the diffusion one. Consequences of this drift mechanism of epitaxial film growing are discussed. - Graphical abstract: This work aims to study the pressure dependence of the thickness of the epitaxial silicon carbide film growing from crystalline silicon due to the heterogeneous reaction with gaseous carbon monoxide. It turned out that this dependence exhibits the clear maximum. On further pressure increasing the film thickness decreases. The theoretical model has been developed which explains such a character of the dependence by the fact that the gaseous silicon monoxide reaction product inhibits the drift of the gaseous reagent through the channels of a crystal lattice, thus decreasing their hydraulic diameter. - Highlights: • It is established that the greater pressure, the smaller is the reaction rate. • The reaction product prevents penetration of the reagent into a reaction zone. • For description the hydraulic model of crystal lattice channels is developed. • Theoretical results for polytropic

  14. Transformation of Sintered CsPbBr3 Nanocrystals to Cubic CsPbI3 and Gradient CsPbBrxI3-x through Halide Exchange.

    Science.gov (United States)

    Hoffman, Jacob B; Schleper, A Lennart; Kamat, Prashant V

    2016-07-13

    All-inorganic cesium lead halide (CsPbX3, X = Br(-), I(-)) perovskites could potentially provide comparable photovoltaic performance with enhanced stability compared to organic-inorganic lead halide species. However, small-bandgap cubic CsPbI3 has been difficult to study due to challenges forming CsPbI3 in the cubic phase. Here, a low-temperature procedure to form cubic CsPbI3 has been developed through a halide exchange reaction using films of sintered CsPbBr3 nanocrystals. The reaction was found to be strongly dependent upon temperature, featuring an Arrhenius relationship. Additionally, film thickness played a significant role in determining internal film structure at intermediate reaction times. Thin films (50 nm) showed only a small distribution of CsPbBrxI3-x species, while thicker films (350 nm) exhibited much broader distributions. Furthermore, internal film structure was ordered, featuring a compositional gradient within film. Transient absorption spectroscopy showed the influence of halide exchange on the excited state of the material. In thicker films, charge carriers were rapidly transferred to iodide-rich regions near the film surface within the first several picoseconds after excitation. This ultrafast vectorial charge-transfer process illustrates the potential of utilizing compositional gradients to direct charge flow in perovskite-based photovoltaics.

  15. Evaluated kinetic and photochemical data for atmospheric chemistry: Volume V – heterogeneous reactions on solid substrates

    Directory of Open Access Journals (Sweden)

    J. N. Crowley

    2010-09-01

    Full Text Available This article, the fifth in the ACP journal series, presents data evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the heterogeneous processes on surfaces of solid particles present in the atmosphere, for which uptake coefficients and adsorption parameters have been presented on the IUPAC website in 2010. The article consists of an introduction and guide to the evaluation, giving a unifying framework for parameterisation of atmospheric heterogeneous processes. We provide summary sheets containing the recommended uptake parameters for the evaluated processes. Four substantial appendices contain detailed data sheets for each process considered for ice, mineral dust, sulfuric acid hydrate and nitric acid hydrate surfaces, which provide information upon which the recommendations are made.

  16. Energy transfer and infrared-to-visible upconversion luminescence of Er3+/Yb3+-codoped halide modified tellurite glasses

    International Nuclear Information System (INIS)

    Zhang, Q.Y.; Feng, Z.M.; Yang, Z.M.; Jiang, Z.H.

    2006-01-01

    We report on the energy transfer and frequency upconversion spectroscopic properties of Er 3+ -doped and Er 3+ /Yb 3+ -codoped TeO 2 -ZnO-Na 2 O-PbCl 2 halide modified tellurite glasses upon excitation with 808 and 978 nm laser diode. Three intense emissions centered at around 529, 546 and 657 nm, alongwith a very weak blue emission at 410 nm have clearly been observed for the Er 3+ /Yb 3+ -codoped halide modified tellurite glasses upon excitation at 978 nm and the involved mechanisms are explained. The quadratic dependence of fluorescence on excitation laser power confirms the fact that the two-photon contribute to the infrared to green-red upconversion emissions. And the blue upconversion at 410 nm involved a sequential three-photon absorption process

  17. Synthesis of E-Alkyl Alkenes from Terminal Alkynes via Ni-Catalyzed Cross-Coupling of Alkyl Halides with B-Alkenyl-9-borabicyclo[3.3.1]nonanes.

    Science.gov (United States)

    Di Franco, Thomas; Epenoy, Alexandre; Hu, Xile

    2015-10-02

    The first Ni-catalyzed Suzuki-Miyaura coupling of alkyl halides with alkenyl-(9-BBN) reagents is reported. Both primary and secondary alkyl halides including alkyl chlorides can be coupled. The coupling method can be combined with hydroboration of terminal alkynes, allowing the expedited synthesis of functionalized alkyl alkenes from readily available alkynes with complete (E)-selectivity in one pot. The method was applied to the total synthesis of (±)-Recifeiolide, a natural macrolide.

  18. Absorption lineshape of FA centers in alkali halides

    International Nuclear Information System (INIS)

    Baldacchini, G.; Giovenale, E.; De Matteis, F.; Scacco, A.; Somma, F.; Grassano, U.M.

    1988-01-01

    The line shape of the absorption bands of F A centers in alkali halides have been studied for the first time. The new method used for this investigation is based on the determination of the overlap between the F A1 and F A2 bands from luminescence measurements. The experimental results have been compared with calculated values deduced from the theoretical F A bands of different shapes. For both F A (I) centers in KCl:Na + and F A (II) centers in KCl:Li + and RbCl:Li + the absorption lineshape at low temperature is much closer to a sum of two Lorentzian curves than that of two Gaussian or Poissonian bands. This results shows an unexpected difference with the F centers, whose absorption lineshape is known to be Poissonian at the same temperatures

  19. Water-Induced Dimensionality Reduction in Metal-Halide Perovskites

    KAUST Repository

    Turedi, Bekir

    2018-03-30

    Metal-halide perovskite materials are highly attractive materials for optoelectronic applications. However, the instability of perovskite materials caused by moisture and heat-induced degradation impairs future prospects of using these materials. Here we employ water to directly transform films of the three-dimensional (3D) perovskite CsPbBr3 to stable two-dimensional (2D) perovskite-related CsPb2Br5. A sequential dissolution-recrystallization process governs this water induced transformation under PbBr2 rich condition. We find that these post-synthesized 2D perovskite-related material films exhibit excellent stability against humidity and high photoluminescence quantum yield. We believe that our results provide a new synthetic method to generate stable 2D perovskite-related materials that could be applicable for light emitting device applications.

  20. Pressure-Induced Structural Evolution and Band Gap Shifts of Organometal Halide Perovskite-Based Methylammonium Lead Chloride.

    Science.gov (United States)

    Wang, Lingrui; Wang, Kai; Xiao, Guanjun; Zeng, Qiaoshi; Zou, Bo

    2016-12-15

    Organometal halide perovskites are promising materials for optoelectronic devices. Further development of these devices requires a deep understanding of their fundamental structure-property relationships. The effect of pressure on the structural evolution and band gap shifts of methylammonium lead chloride (MAPbCl 3 ) was investigated systematically. Synchrotron X-ray diffraction and Raman experiments provided structural information on the shrinkage, tilting distortion, and amorphization of the primitive cubic unit cell. In situ high pressure optical absorption and photoluminescence spectra manifested that the band gap of MAPbCl 3 could be fine-tuned to the ultraviolet region by pressure. The optical changes are correlated with pressure-induced structural evolution of MAPbCl 3 , as evidenced by band gap shifts. Comparisons between Pb-hybrid perovskites and inorganic octahedra provided insights on the effects of halogens on pressure-induced transition sequences of these compounds. Our results improve the understanding of the structural and optical properties of organometal halide perovskites.

  1. Structural, optical, and electronic studies of wide-bandgap lead halide perovskites

    KAUST Repository

    Comin, Riccardo; Walters, Grant; Thibau, Emmanuel Sol; Voznyy, Oleksandr; Lu, Zheng-Hong; Sargent, Edward H.

    2015-01-01

    © The Royal Society of Chemistry 2015. We investigate the family of mixed Br/Cl organolead halide perovskites which enable light emission in the blue-violet region of the visible spectrum. We report the structural, optical and electronic properties of this air-stable family of perovskites, demonstrating full bandgap tunability in the 400-550 nm range and enhanced exciton strength upon Cl substitution. We complement this study by tracking the evolution of the band levels across the gap, thereby providing a foundational framework for future optoelectronic applications of these materials.

  2. Genetic heterogeneity of L-Zagreb mumps virus vaccine strain.

    Science.gov (United States)

    Kosutic-Gulija, Tanja; Forcic, Dubravko; Santak, Maja; Ramljak, Ana; Mateljak-Lukacevic, Sanja; Mazuran, Renata

    2008-07-10

    The most often used mumps vaccine strains Jeryl Lynn (JL), RIT4385, Urabe-AM9, L-Zagreb and L-3 differ in immunogenicity and reactogenicity. Previous analyses showed that JL, Urabe-AM9 and L-3 are genetically heterogeneous. We identified the heterogeneity of L-Zagreb throughout the entire genome. Two major variants were defined: variant A being identical to the consensus sequence of viral seeds and vaccine(s) and variant B which differs from variant A in three nucleotide positions. The difference between viral variants in L-Zagreb strain is insufficient for distinct viral strains to be defined. We demonstrated that proportion of variants in L-Zagreb viral population depends on cell substrate used for viral replication in vitro and in vivo. L-Zagreb strain should be considered as a single strain composed of at least two variant viral genomes.

  3. Variation in stonefly (Nemoura cinerea Retzius) growth and development in response to hydraulic and substrate conditions

    NARCIS (Netherlands)

    Franken, R.J.M.; Gardeniers, J.J.P.; Beijer, J.A.J.; Peeters, E.T.H.M.

    2008-01-01

    Spatial heterogeneity among microhabitat patches in aquatic ecosystems creates refuges (e.g., substrate interstices) that protect organisms against a variety of environmental constraints. Aquatic insects have evolved the ability to alter their life-history traits in response to environmental

  4. CuI-Catalyzed: One-Pot Synthesis of Diaryl Disulfides from Aryl Halides and Carbon Disulfide

    Directory of Open Access Journals (Sweden)

    Mohammad Soleiman-Beigi

    2013-01-01

    Full Text Available A new application of carbon disulfide in the presence of KF/Al2O3 is reported for the synthesis of organic symmetrical diaryl disulfides. These products were synthesized by one-pot reaction of aryl halides with the in situ generated trithiocarbonate ion in the presence of copper under air atmosphere.

  5. Touching is believing: interrogating halide perovskite solar cells at the nanoscale via scanning probe microscopy

    Science.gov (United States)

    Li, Jiangyu; Huang, Boyuan; Nasr Esfahani, Ehsan; Wei, Linlin; Yao, Jianjun; Zhao, Jinjin; Chen, Wei

    2017-10-01

    Halide perovskite solar cells based on CH3NH3PbI3 and related materials have emerged as the most exciting development in the next generation photovoltaic technologies, yet the microscopic phenomena involving photo-carriers, ionic defects, spontaneous polarization, and molecular vibration and rotation interacting with numerous grains, grain boundaries, and interfaces are still inadequately understood. In fact, there is still need for an effective method to interrogate the local photovoltaic properties of halide perovskite solar cells that can be directly traced to their microstructures on one hand and linked to their device performance on the other hand. In this perspective, we propose that scanning probe microscopy (SPM) techniques have great potential to realize such promises at the nanoscale, and highlight some of the recent progresses and challenges along this line of investigation toward local probing of photocurrent, work function, ionic activities, polarization switching, and chemical degradation. We also emphasize the importance of multi-modality imaging, in-operando scanning, big data analysis, and multidisciplinary collaboration for further studies toward fully understanding of these complex systems.

  6. An objective protocol for comparing the noise performance of silver halide film and digital sensor

    Science.gov (United States)

    Cao, Frédéric; Guichard, Frédéric; Hornung, Hervé; Tessière, Régis

    2012-01-01

    Digital sensors have obviously invaded the photography mass market. However, some photographers with very high expectancy still use silver halide film. Are they only nostalgic reluctant to technology or is there more than meets the eye? The answer is not so easy if we remark that, at the end of the golden age, films were actually scanned before development. Nowadays film users have adopted digital technology and scan their film to take advantage from digital processing afterwards. Therefore, it is legitimate to evaluate silver halide film "with a digital eye", with the assumption that processing can be applied as for a digital camera. The article will describe in details the operations we need to consider the film as a RAW digital sensor. In particular, we have to account for the film characteristic curve, the autocorrelation of the noise (related to film grain) and the sampling of the digital sensor (related to Bayer filter array). We also describe the protocol that was set, from shooting to scanning. We then present and interpret the results of sensor response, signal to noise ratio and dynamic range.

  7. Hydrolysis in the organic phase during the extraction of alkali metal halides and water by copper bis(2-ethylhexyl)phosphate

    International Nuclear Information System (INIS)

    Golovanov, V.I.; Kuznetsov, S.M.

    2001-01-01

    Experimental data on extraction of halides, among which are LiCl and CsCl, and water by copper di-(2-ethylhexyl)phosphate solutions in respect to hydrolysis mechanism of reaction are generalized. Copper di-(2-ethylhexyl)phosphate manifests properties of ionogen colloidal surfactant in water. Extraction of halides by copper di-(2-ethylhexyl)phosphate was shown to be visualized by the process of capsule formation in MHal molecules, as well as in hydrolyzed MOH and HHal forms of electrolyte by Cu 4 (D2EHF) 8 · hH 2 O clathrate-like micellar associates. The model of hydrolysis mechanism is not different from proposed earlier model of electrolyte extraction with their partial dissociation in organic phase [ru

  8. Effects of Halide Ions on the Carbamidocyclophane Biosynthesis in Nostoc sp. CAVN2

    Science.gov (United States)

    Preisitsch, Michael; Heiden, Stefan E.; Beerbaum, Monika; Niedermeyer, Timo H. J.; Schneefeld, Marie; Herrmann, Jennifer; Kumpfmüller, Jana; Thürmer, Andrea; Neidhardt, Inga; Wiesner, Christoph; Daniel, Rolf; Müller, Rolf; Bange, Franz-Christoph; Schmieder, Peter; Schweder, Thomas; Mundt, Sabine

    2016-01-01

    In this study, the influence of halide ions on [7.7]paracyclophane biosynthesis in the cyanobacterium Nostoc sp. CAVN2 was investigated. In contrast to KI and KF, supplementation of the culture medium with KCl or KBr resulted not only in an increase of growth but also in an up-regulation of carbamidocyclophane production. LC-MS analysis indicated the presence of chlorinated, brominated, but also non-halogenated derivatives. In addition to 22 known cylindrocyclophanes and carbamidocyclophanes, 27 putative congeners have been detected. Nine compounds, carbamidocyclophanes M−U, were isolated, and their structural elucidation by 1D and 2D NMR experiments in combination with HRMS and ECD analysis revealed that they are brominated analogues of chlorinated carbamidocyclophanes. Quantification of the carbamidocyclophanes showed that chloride is the preferably utilized halide, but incorporation is reduced in the presence of bromide. Evaluation of the antibacterial activity of 30 [7.7]paracyclophanes and related derivatives against selected pathogenic Gram-positive and Gram-negative bacteria exhibited remarkable effects especially against methicillin- and vancomycin-resistant staphylococci and Mycobacterium tuberculosis. For deeper insights into the mechanisms of biosynthesis, the carbamidocyclophane biosynthetic gene cluster in Nostoc sp. CAVN2 was studied. The gene putatively coding for the carbamoyltransferase has been identified. Based on bioinformatic analyses, a possible biosynthetic assembly is discussed. PMID:26805858

  9. UV-VIS absorption spectra of molten AgCl and AgBr and of their mixtures with group I and II halide salts

    Energy Technology Data Exchange (ETDEWEB)

    Greening, Giorgio G.W. [Technische Universitaet Darmstadt (Germany). Eduard-Zintl-Institut fuer Anorganische und Physikalische Chemie

    2015-07-01

    The UV-VIS absorption spectra of (Ag{sub 1-X}[Li-Cs, Ba]{sub X})Cl and of (Ag{sub 1-X}[Na, K, Cs]{sub X})Br at 823 K at the concentrations X=0.0, 0.1, 0.2 have been measured. The findings show that on adding the respective halides to molten silver chloride and silver bromide, shifts of the fundamental absorption edge to shorter wavelengths result. A correlation between the observed shifts and the expansion of the silver sub-lattice is found, which is valid for both silver halide systems studied in this work.

  10. Transport, Optical, and Magnetic Properties of the Conducting Halide Perovskite CH 3NH 3SnI 3

    Science.gov (United States)

    Mitzi, D. B.; Feild, C. A.; Schlesinger, Z.; Laibowitz, R. B.

    1995-01-01

    A low-temperature ( T ≤ 100°C) solution technique is described for the preparation of polycrystalline and single crystal samples of the conducting halide perovskite, CH 3NH 3SnI 3. Transport, Hall effect, magnetic, and optical properties are examined over the temperature range 1.8-300 K, confirming that this unusual conducting halide perovskite is a low carrier density p-type metal with a Hall hole density, 1/ RHe ≃ 2 × 10 19 cm -3. The resistivity of pressed pellet samples decreases with decreasing temperature with resistivity ratio ρ(300 K)/ρ(2 K) ≃ 3 and room temperature resistivity ρ(300 K) ≃ 7 mΩ-cm. A free-carrier infrared reflectivity spectrum with a plasma edge observed at approximately 1600 cm -1 further attests to the metallic nature of this compound and suggests a small optical effective mass, m* ≃ 0.2.

  11. Investigation on thermodynamics of ion-slicing of GaN and heterogeneously integrating high-quality GaN films on CMOS compatible Si(100) substrates.

    Science.gov (United States)

    Huang, Kai; Jia, Qi; You, Tiangui; Zhang, Runchun; Lin, Jiajie; Zhang, Shibin; Zhou, Min; Zhang, Bo; Yu, Wenjie; Ou, Xin; Wang, Xi

    2017-11-08

    Die-to-wafer heterogeneous integration of single-crystalline GaN film with CMOS compatible Si(100) substrate using the ion-cutting technique has been demonstrated. The thermodynamics of GaN surface blistering is in-situ investigated via a thermal-stage optical microscopy, which indicates that the large activation energy (2.5 eV) and low H ions utilization ratio (~6%) might result in the extremely high H fluence required for the ion-slicing of GaN. The crystalline quality, surface topography and the microstructure of the GaN films are characterized in detail. The full width at half maximum (FWHM) for GaN (002) X-ray rocking curves is as low as 163 arcsec, corresponding to a density of threading dislocation of 5 × 10 7  cm -2 . Different evolution of the implantation-induced damage was observed and a relationship between the damage evolution and implantation-induced damage is demonstrated. This work would be beneficial to understand the mechanism of ion-slicing of GaN and to provide a platform for the hybrid integration of GaN devices with standard Si CMOS process.

  12. Fabrication of large area plasmonic nanoparticle grating structure on silver halide based transmission electron microscope film and its application as a surface enhanced Raman spectroscopy substrate

    International Nuclear Information System (INIS)

    Sudheer,; Tiwari, P.; Singh, M. N.; Sinha, A. K.; Rai, V. N.; Srivastava, A. K.; Bhartiya, S.; Mukherjee, C.

    2015-01-01

    The plasmonic responses of silver nanoparticle grating structures of different periods made on silver halide based electron microscope film are investigated. Raster scan of the conventional scanning electron microscope (SEM) is used to carry out electron beam lithography for fabricating the plasmonic nanoparticle grating (PNG) structures. Morphological characterization of the PNG structures, carried out by the SEM and the atomic force microscope, indicates that the depth of the groove decreases with a decrease in the grating period. Elemental characterization performed by the energy dispersive spectroscopy and the x-ray diffraction shows the presence of nanoparticles of silver in the PNG grating. The optical characterization of the gratings shows that the localized surface plasmon resonance peak shifts from 366 to 378 nm and broadens with a decrease in grating period from 10 to 2.5 μm. The surface enhanced Raman spectroscopy of the Rhodamine-6G dye coated PNG structure shows the maximum enhancement by two orders of magnitude in comparison to the randomly distributed silver nanoparticles having similar size and shape as the PNG structure

  13. Excitonic Effects in Methylammonium Lead Halide Perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Beard, Matthew C [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Chen, Xihan [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Lu, Haipeng [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Yang, Ye [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2018-05-01

    The exciton binding energy in methylammonium lead iodide (MAPbI3) is about 10 meV, around 1/3 of the available thermal energy (kBT ~ 26 meV) at room temperature. Thus, exciton populations are not stable at room temperature at moderate photoexcited carrier densities. However, excitonic resonances dominate the absorption onset. Furthermore, these resonances determine the transient absorbance and transient reflectance spectra. The exciton binding energy is a reflection of the Coulomb interaction energy between photoexcited electrons and holes. As such, it serves as a marker for the strength of electron/hole interactions and impacts a variety of phenomena, such as, absorption, radiative recombination, and Auger recombination. In this Perspective, we discuss the role of excitons and excitonic resonances in the optical properties of lead-halide perovskite semiconductors. Finally, we discuss how the strong light-matter interactions induce an optical stark effect splitting the doubly spin degenerate ground exciton states and are easily observed at room temperature.

  14. Tailoring Mixed-Halide, Wide-Gap Perovskites via Multistep Conversion Process

    DEFF Research Database (Denmark)

    Bae, Dowon; Palmstrom, Axel; Roelofs, Katherine

    2016-01-01

    Wide-band-gap mixed-halide CH3NH3PbI3–XBrX-based solar cells have been prepared by means of a sequential spin-coating process. The spin-rate for PbI2 as well as its repetitive deposition are important in determining the cross-sectional shape and surface morphology of perovskite, and, consequently......, J–V performance. A perovskite solar cell converted from PbI2 with a dense bottom layer and porous top layer achieved higher device performance than those of analogue cells with a dense PbI2 top layer. This work demonstrates a facile way to control PbI2 film configuration and morphology simply...

  15. Elucidating the impact of micro-scale heterogeneous bacterial distribution on biodegradation

    Science.gov (United States)

    Schmidt, Susanne I.; Kreft, Jan-Ulrich; Mackay, Rae; Picioreanu, Cristian; Thullner, Martin

    2018-06-01

    Groundwater microorganisms hardly ever cover the solid matrix uniformly-instead they form micro-scale colonies. To which extent such colony formation limits the bioavailability and biodegradation of a substrate is poorly understood. We used a high-resolution numerical model of a single pore channel inhabited by bacterial colonies to simulate the transport and biodegradation of organic substrates. These high-resolution 2D simulation results were compared to 1D simulations that were based on effective rate laws for bioavailability-limited biodegradation. We (i) quantified the observed bioavailability limitations and (ii) evaluated the applicability of previously established effective rate concepts if microorganisms are heterogeneously distributed. Effective bioavailability reductions of up to more than one order of magnitude were observed, showing that the micro-scale aggregation of bacterial cells into colonies can severely restrict the bioavailability of a substrate and reduce in situ degradation rates. Effective rate laws proved applicable for upscaling when using the introduced effective colony sizes.

  16. Non-halide sediments from the Loule diapir salt mine: characterization and environmental significance

    Science.gov (United States)

    Ribeiro, Carlos; Terrinha, Pedro; Andrade, Alexandre; Fonseca, Bruno; Caetano, Miguel; Neres, Marta; Font, Eric; Mirão, José; Dias, Cristina; Rosado, Lúcia; Maurer, Anne-France; Manhita, Ana

    2017-04-01

    The sedimentary record of the Mesozoic Algarve Basin (south Portugal) spans from the Triassic to the Lower Cretaceous. Following the initial phase of Pangaea breakup and the related continental sedimentation during the Triassic, the sedimentation evolved through transitional (Triassic-Jurassic transition) to marine (Jurassic) environments. During the Hettangian a thick sequence of evaporites deposited in the basin. Most of the occurrences of these deposits have undetermined volumes, due to the post depositional diapiric movements. At the central Algarve, under the town of Loulé, a salt wall of up to > 1 km across, > 3 km in length and > 2 km in height has been exploited for the chemical industry (Loulé Diapir - LD). Most of the sediments that constitute LD are halides (> 99% halite), the exception being a package of non-halide sediments, constituted by carbonates (dolomite and magnesite) and sulphates (anhydrite) in various proportions with a maximum thickness of 3 meters. This package has a distinctive mesoscopic aspect of three layers of approximately the same thickness, different colours and primary sedimentary structures: black-brow-grey, from bottom to top. The sediments of this package were studied with a multidisciplinary approach aiming their mineralogical and chemical characterization, the determination of the organic matter content and origin, as well as the characterization and understanding of the chemical processes that occurred during the emplacement and compression of the LD: (i) X-ray diffraction for the determination of the mineral phases present and semi-quantification using the RIR-Reference Intensity Ratio method; (ii) micro analysis of the mineralogical samples by Scanning Electron Microscopy coupled to Energy Dispersive Spectroscopy; (iii) REE content determination by ICP-MS; (iv) determination of the carbon content by CHN Elemental analysis; (v) determination of the organic matter content by elemental analysis and their composition by

  17. Structure of some complex halides of uranium(III)

    International Nuclear Information System (INIS)

    Volkov, V.A.; Suglobova, I.G.; Chirkst, D.E.

    1987-01-01

    Polycrystals of some halide complexes of uranium(III) were obtained and investigated by x-ray diffraction. The M 2 UCl 5 compounds (M = K, Rb) are isostructural with K 2 PrCl 5 ; RbU 2 Cl 7 is of the same type as RbDy 2 Cl 7 or KDy 2 Cl 7 . The coordination number of the uranium is 7. The M 2 UBr 5 compounds (M = K-Cs) are isostructural with Cs 2 DyCl 5 , and the coordination number of the uranium is 6. Rb 2 NaUCl 6 is a 12L-hexagonal polytype, the structural analog of Cs 2 NaCrF 6 . The most characteristic coordination number of uranium in the UHal 3 -MHal systems is 8 for Hal = F, 7 for Hal = Cl, and 6 for Hal = Br

  18. Irradiation damage of alkali halide crystals during positron bombardment

    International Nuclear Information System (INIS)

    Arefiev, K.P.; Arefiev, V.P.; Vorobiev, S.A.

    1978-01-01

    The bleaching effect of positron irradiation of KCl and KBr single crystals previously coloured with electrons or protons was investigated. Positrons injection in the coloured alkali halide samples reduced the F-centres concentration considerably. For KCl crystals thicker than the positrons range the appearance of additional bands in the absorption spectra is noticeable. The experimental data show that the bleaching phenomenon should be observed merely throughout the positron exposure both for irradiated and non-irradiated regions of the sample. Irradiation effects, due to positron source, on the peak counting rate of (γ-γ) angular correlation in KCl crystals under applied magnetic field were also investigated. The growth of peak counting rate shows the increase of positronium-like states formation near defects of cation sublattice. (author)

  19. EPR study of electron bombarded alkali- and alkaline-earth halide crystal surfaces

    Science.gov (United States)

    Fryburg, G. C.; Lad, R. A.

    1975-01-01

    An EPR study of electron bombarded LiF, NaCl, KCl, CaF2 and BaF2 polycrystalline surfaces has shown that small metal particles are formed on the surfaces of the crystals. Identification was made from CESR signals. The symmetric line-shape of the signals, even at 77 K, indicated that the particles were less than 0.5 micron in diameter. Signals due to F centers were observed in LiF but not in the other halides. Implications to metal deposition are considered.

  20. Ultrahigh Detective Heterogeneous Photosensor Arrays with In-Pixel Signal Boosting Capability for Large-Area and Skin-Compatible Electronics.

    Science.gov (United States)

    Kim, Jaehyun; Kim, Jaekyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Myungwon; Moon, Juhyuk; Yang, Lin; Kim, Myung-Gil; Kim, Yong-Hoon; Park, Sung Kyu

    2016-04-01

    An ultra-thin and large-area skin-compatible heterogeneous organic/metal-oxide photosensor array is demonstrated which is capable of sensing and boosting signals with high detectivity and signal-to-noise ratio. For the realization of ultra-flexible and high-sensitive heterogeneous photosensor arrays on a polyimide substrate having organic sensor arrays and metal-oxide boosting circuitry, solution-processing and room-temperature alternating photochemical conversion routes are applied. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Interaction of 3D dewetting nanodroplets on homogeneous and chemically heterogeneous substrates

    International Nuclear Information System (INIS)

    Asgari, M; Moosavi, A

    2014-01-01

    Long-time interaction of dewetting nanodroplets is investigated using a long-wave approximation method. Although three-dimensional (3D) droplets evolution dynamics exhibits qualitative behavior analogous to two-dimensional (2D) dynamics, there is an extensive quantitative difference between them. 3D dynamics is substantially faster than 2D dynamics. This can be related to the larger curvature and, as a consequence, the larger Laplace pressure difference between the droplets in 3D systems. The influence of various chemical heterogeneities on the behavior of droplets has also been studied. In the case of gradient surfaces, it is shown how the gradient direction could change the dynamics. For a chemical step located between the droplets, the dynamics is enhanced or weakened depending on the initial configuration of the system. (paper)

  2. Genetic heterogeneity of L-Zagreb mumps virus vaccine strain

    Directory of Open Access Journals (Sweden)

    Mateljak-Lukacevic Sanja

    2008-07-01

    Full Text Available Abstract Background The most often used mumps vaccine strains Jeryl Lynn (JL, RIT4385, Urabe-AM9, L-Zagreb and L-3 differ in immunogenicity and reactogenicity. Previous analyses showed that JL, Urabe-AM9 and L-3 are genetically heterogeneous. Results We identified the heterogeneity of L-Zagreb throughout the entire genome. Two major variants were defined: variant A being identical to the consensus sequence of viral seeds and vaccine(s and variant B which differs from variant A in three nucleotide positions. The difference between viral variants in L-Zagreb strain is insufficient for distinct viral strains to be defined. We demonstrated that proportion of variants in L-Zagreb viral population depends on cell substrate used for viral replication in vitro and in vivo. Conclusion L-Zagreb strain should be considered as a single strain composed of at least two variant viral genomes.

  3. Genetic heterogeneity of L-Zagreb mumps virus vaccine strain

    Science.gov (United States)

    Kosutic-Gulija, Tanja; Forcic, Dubravko; Šantak, Maja; Ramljak, Ana; Mateljak-Lukacevic, Sanja; Mazuran, Renata

    2008-01-01

    Background The most often used mumps vaccine strains Jeryl Lynn (JL), RIT4385, Urabe-AM9, L-Zagreb and L-3 differ in immunogenicity and reactogenicity. Previous analyses showed that JL, Urabe-AM9 and L-3 are genetically heterogeneous. Results We identified the heterogeneity of L-Zagreb throughout the entire genome. Two major variants were defined: variant A being identical to the consensus sequence of viral seeds and vaccine(s) and variant B which differs from variant A in three nucleotide positions. The difference between viral variants in L-Zagreb strain is insufficient for distinct viral strains to be defined. We demonstrated that proportion of variants in L-Zagreb viral population depends on cell substrate used for viral replication in vitro and in vivo. Conclusion L-Zagreb strain should be considered as a single strain composed of at least two variant viral genomes. PMID:18616793

  4. Inhibitory action of quaternary ammonium bromide on mild steel and synergistic effect with other halide ions in 0.5 M H2SO4

    Directory of Open Access Journals (Sweden)

    A. Khamis

    2014-11-01

    Full Text Available The corrosion inhibition of mild steel in 0.5 M H2SO4 solution has been investigated using electrochemical methods, X-ray diffraction (XRD and scanning electron microscope (SEM. The adsorption and inhibition action of acid corrosion of mild steel using cetyltrimethylammonium bromide (CTABr and different halides (NaCl, NaBr and NaI has shown synergetic effect. The results showed that the protection efficiency (P% has high values at considerable high concentration of CTABr. However, in the presence of the different halides, the P increases dramatically at low concentration of CTABr. Physisorption was proposed from the the values of ΔGads0. The synergism parameter (Sθ is found to be greater than unity indicating that the enhanced P% caused by the addition of the halides to the CTABr is due to a co-operative adsorption of both species. Corrosion products phases and surface morphology were studied using X-ray diffraction (XRD and scanning electron microscopy (SEM, respectively.

  5. Optical emission spectroscopy of metal-halide lamps: Radially resolved atomic state distribution functions of Dy and Hg

    NARCIS (Netherlands)

    Nimalasuriya, T.; Flikweert, A.J.; Stoffels, W.W.; Haverlag, M.; Mullen, van der J.J.A.M.; Pupat, N.B.M.

    2006-01-01

    Absolute line intensity measurements are performed on a metal-halide lamp. Several transitions of atomic and ionic Dy and atomic Hg are measured at different radial positions from which we obtain absolute atomic and ionic Dy intensity profiles. From these profiles we construct the radially resolved

  6. Deposition of tantalum carbide coatings on graphite by laser interactions

    Science.gov (United States)

    Veligdan, James; Branch, D.; Vanier, P. E.; Barietta, R. E.

    1994-01-01

    Graphite surfaces can be hardened and protected from erosion by hydrogen at high temperatures by refractory metal carbide coatings, which are usually prepared by chemical vapor deposition (CVD) or chemical vapor reaction (CVR) methods. These techniques rely on heating the substrate to a temperature where a volatile metal halide decomposes and reacts with either a hydrocarbon gas or with carbon from the substrate. For CVR techniques, deposition temperatures must be in excess of 2000 C in order to achieve favorable deposition kinetics. In an effort to lower the bulk substrate deposition temperature, the use of laser interactions with both the substrate and the metal halide deposition gas has been employed. Initial testing involved the use of a CO2 laser to heat the surface of a graphite substrate and a KrF excimer laser to accomplish a photodecomposition of TaCl5 gas near the substrate. The results of preliminary experiments using these techniques are described.

  7. Deposition and modification of tantalum carbide coatings on graphite by laser interactions

    International Nuclear Information System (INIS)

    Veligdan, J.; Branch, D.; Vanier, P.E.; Barletta, R.E.

    1992-01-01

    Graphite surfaces can be hardened and protected from erosion by hydrogen at high temperatures by refractory metal carbide coatings, which are usually prepared by chemical vapor deposition (CVD) or chemical vapor reaction (CVR) methods. These techniques rely on heating the substrate to a temperature where a volatile metal halide decomposes and reacts with either a hydrocarbon gas or with carbon from the substrate. For CVR techniques, deposition temperatures must be in excess of 2000 degrees C in order to achieve favorable deposition kinetics. In an effort to lower the bulk substrate deposition temperature, the use of laser interactions with both the substrate and the metal halide deposition gas has been employed. Initial testing, involved the use of a CO 2 laser to heat the surface of a graphite substrate and a KrF excimer laser to accomplish a photodecomposition of TaCl 5 gas near the substrate. Results of preliminary experiments using these techniques are described

  8. A PEG/copper(i) halide cluster as an eco-friendly catalytic system for C-N bond formation.

    Science.gov (United States)

    Li, Cheng-An; Ji, Wei; Qu, Jian; Jing, Su; Gao, Fei; Zhu, Dun-Ru

    2018-05-22

    The catalytic activities of eight copper(i) halide clusters assembled from copper(i) halide and ferrocenyltelluroethers, 1-8, were investigated in C-N formation under various conditions. A catalytic procedure using poly(ethylene glycol) (PEG-400) as a greener alternative organic solvent has been developed. The PEG-400/5 system can achieve 99% targeted yield with a mild reaction temperature and short reaction time. After the isolation of the products by extraction with diethyl ether, this PEG-400/cluster system could be easily recycled. Spectroscopic studies elucidate a stepwise mechanism: firstly, proton-coupled electron transfer (PCET) involving the transfer of an electron from Cu+ and a proton from imidazole results in the formation of a labile penta-coordinated Cu2+ and aryl radical; the following effective electron transfer from the ferrocene unit reduces Cu2+ and forms the target product; finally, the ferrocenium unit is reduced by the I- anion. The merits of this eco-friendly synthesis are the efficient utilization of reagents and easy recyclability.

  9. Volatile Gas Production by Methyl Halide Transferase: An In Situ Reporter Of Microbial Gene Expression In Soil.

    Science.gov (United States)

    Cheng, Hsiao-Ying; Masiello, Caroline A; Bennett, George N; Silberg, Jonathan J

    2016-08-16

    Traditional visual reporters of gene expression have only very limited use in soils because their outputs are challenging to detect through the soil matrix. This severely restricts our ability to study time-dependent microbial gene expression in one of the Earth's largest, most complex habitats. Here we describe an approach to report on dynamic gene expression within a microbial population in a soil under natural water levels (at and below water holding capacity) via production of methyl halides using a methyl halide transferase. As a proof-of-concept application, we couple the expression of this gas reporter to the conjugative transfer of a bacterial plasmid in a soil matrix and show that gas released from the matrix displays a strong correlation with the number of transconjugant bacteria that formed. Gas reporting of gene expression will make possible dynamic studies of natural and engineered microbes within many hard-to-image environmental matrices (soils, sediments, sludge, and biomass) at sample scales exceeding those used for traditional visual reporting.

  10. Experimental demonstration of correlated flux scaling in photoconductivity and photoluminescence of lead-halide perovskites

    OpenAIRE

    Yi, Hee Taek; Irkhin, Pavel; Joshi, Prakriti P.; Gartstein, Yuri N.; Zhu, Xiaoyang; Podzorov, Vitaly

    2018-01-01

    Lead-halide perovskites attracted attention as materials for high-efficiency solar cells and light emitting applications. Among their attributes are solution processability, high absorbance in the visible spectral range and defect tolerance, as manifested in long photocarrier lifetimes and diffusion lengths. The microscopic origin of photophysical properties of perovskites is, however, still unclear and under debate. Here, we have observed an interesting universal scaling behavior in a series...

  11. Substrate homogenization affects survival and fitness in the lowland stream caddisflies Micropterna sequax and Potamophylax rotundipennis

    NARCIS (Netherlands)

    Westveer, Judith J.; Verdonschot, Piet F.M.; Verdonschot, Ralf C.M.

    2017-01-01

    Loss of substrate heterogeneity or patchiness is common in lowland streams with disturbed hydrological regimes. At the reach scale, peak discharges tend to homogenize the stream bed and decrease the availability of specific microhabitat types. This spatial shift in habitats toward a more

  12. Degradation of 17α-ethinylestradiol in water by heterogeneous photocatalysis

    Directory of Open Access Journals (Sweden)

    Wilton Silva Lopes

    2015-11-01

    Full Text Available We investigated the degradation of 17α-ethynylestradiol in an aqueous solution using a batch heterogeneous photocatalytic (HPC reactor with ultraviolet (UV light and TiO2 catalyst. In order to determine appropriate operating conditions, a 23 factorial experiment was conducted with initial an substrate concentration of 15 or 30 mg L-1, TiO2 concentration of 0.02 or 0.05%, pH of 5.0 or 9.0 and total reaction time 240 min. Degradation profiles and kinetic parameters were determined with an initial substrate concentration of 15 or 30 mg L-1, 0.02% TiO2 and pH 7.0.With17α-ethynylestradiol at 15 mg L-1, degradation efficiency was 100% after 120 min independent of TiO2 concentration and pH. However, less than 50% of the substrate was degraded when the initial concentration was 30 mg L-1 (0.05% TiO2 and pH 5.0. Initial substrate concentration was a limiting factor for HPC, although the reaction was also strongly influenced by TiO2 concentration and the interaction between initial substrate concentration and TiO2 concentration. All degradations followed first-order kinetics. With 17α-ethynylestradiol at 15 mg L-1, the half-life time (t½ was 64.16 min and the rate constant was 0.108 min-1, while at 30 mg L-1, substrate degradation proceeded in two stages, the t½ values of which were 44.71 and 433.12 min.

  13. Grazer diversity interacts with biogenic habitat heterogeneity to accelerate intertidal algal succession.

    Science.gov (United States)

    Whalen, Matthew A; Aquilino, Kristin M; Stachowicz, John J

    2016-08-01

    Environmental heterogeneity contributes to coexistence by allowing species with different traits to persist when different species perform best at different times or places. This interaction between niche differences and environmental variability may also help explain relationships between biodiversity and ecosystem functioning, but few data are available to rigorously evaluate this hypothesis. We assessed how a biologically relevant aspect of environmental heterogeneity interacts with species diversity to determine ecosystem processes in a natural rocky intertidal community. We used field removals to factorially manipulate biogenic habitat heterogeneity (barnacles, bare rock, and plots that were 50/50 mixes of the two habitat types) and gastropod grazer species richness and then tracked algal community succession and recovery over the course of 1 yr. We found that herbivore diversity, substrate heterogeneity, and their interaction played unique roles in the peak abundance and timing of occurrence of different algal functional groups. Early successional microalgae were most heavily grazed in diverse herbivore assemblages and those with barnacles present, which was likely due to complementary feeding strategies among all three grazers. In contrast, late successional macroalgae were strongly influenced by the presence of a habitat generalist limpet. In this herbivore's absence, heterogeneous habitats (i.e., mixtures of bare rock and barnacles) experienced the greatest algal accumulation, which was partly a result of complementary habitat use by the remaining herbivores. The complex way habitat identity and heterogeneity altered grazer-algal interactions in our study suggests species' differences and environmental heterogeneity both separately and interactively contribute to the relationship between biodiversity and ecosystem functions. © 2016 by the Ecological Society of America.

  14. Coulometric thermometric titration of halides in molten calcium nitrate tetrahydrate.

    Science.gov (United States)

    Zsigrai, I J; Bartusz, D B

    1983-01-01

    A method for coulometric thermometric precipitation titrations of chloride, bromide and iodide in molten calcium nitrate tetrahydrate at 55 degrees with coulometrically generated silver ions has been developed. The change in temperature during the titration is followed with the aid of a thermistor bridge coupled to a recorder. To minimize the temperature effect of the passage of current through the melt, two thermistors are connected in opposition in the bridge, with one in the anodic and the other in the cathodic cell compartment. Amounts of 62-80 mumole of halide have been determined with relative error below 0.4% and relative standard deviation less than 2.7%. The relative error in determination of 40 mumole of iodide was + 2%.

  15. Magnetic properties of nickel halide hydrates including deuteration effects

    Energy Technology Data Exchange (ETDEWEB)

    DeFotis, G.C., E-mail: gxdefo@wm.edu [Chemistry Department, College of William & Mary, Williamsburg, VA, 23187 United States (United States); Van Dongen, M.J.; Hampton, A.S.; Komatsu, C.H.; Trowell, K.T.; Havas, K.C.; Davis, C.M.; DeSanto, C.L. [Chemistry Department, College of William & Mary, Williamsburg, VA, 23187 United States (United States); Hays, K.; Wagner, M.J. [Chemistry Department, George Washington University, Washington, DC, 20052 United States (United States)

    2017-01-01

    Magnetic measurements on variously hydrated nickel chlorides and bromides, including deuterated forms, are reported. Results include locations and sizes of susceptibility maxima, T{sub max} and χ{sub max}, ordering temperatures T{sub c}, Curie constants and Weiss theta in the paramagnetic regime, and primary and secondary exchange interactions from analysis of low temperature data. For the latter a 2D Heisenberg model augmented by interlayer exchange in a mean-field approximation is applied. Magnetization data to 16 kG as a function of temperature show curvature and hysteresis characteristics quite system dependent. For four materials high field magnetization data to 70 kG at 2.00 K are also obtained. Comparison is made with theoretical relations for spin-1 models. Trends are apparent, primarily that T{sub max} of each bromide hydrate is less than for the corresponding chloride, and that for a given halide nD{sub 2}O (n=1 or 2) deuterates exhibit lesser T{sub max} than do nH{sub 2}O hydrates. A monoclinic unit cell determined from powder X-ray diffraction data on NiBr{sub 2}·2D{sub 2}O is different from and slightly larger than that of NiBr{sub 2}·2H{sub 2}O. This provides some rationale for the difference in magnetic properties between these. - Highlights: • The magnetism of Ni(II) chloride and bromide dihydrates and monohydrates is studied. • Effects of replacing H{sub 2}O by D{sub 2}O are examined for both hydration states and both halides. • Exchange interactions in bromides are weaker than in corresponding chlorides. • Exchange interactions are weaker in D{sub 2}O than in corresponding H{sub 2}O containing systems. • The unit cell of NiBr{sub 2}·2D{sub 2}O is different from and slightly larger than that of NiBr{sub 2}·2H{sub 2}O.

  16. High Quantum Yield Blue Emission from Lead-Free Inorganic Antimony Halide Perovskite Colloidal Quantum Dots.

    Science.gov (United States)

    Zhang, Jian; Yang, Ying; Deng, Hui; Farooq, Umar; Yang, Xiaokun; Khan, Jahangeer; Tang, Jiang; Song, Haisheng

    2017-09-26

    Colloidal quantum dots (QDs) of lead halide perovskite have recently received great attention owing to their remarkable performances in optoelectronic applications. However, their wide applications are hindered from toxic lead element, which is not environment- and consumer-friendly. Herein, we utilized heterovalent substitution of divalent lead (Pb 2+ ) with trivalent antimony (Sb 3+ ) to synthesize stable and brightly luminescent Cs 3 Sb 2 Br 9 QDs. The lead-free, full-inorganic QDs were fabricated by a modified ligand-assisted reprecipitation strategy. A photoluminescence quantum yield (PLQY) was determined to be 46% at 410 nm, which was superior to that of other reported halide perovskite QDs. The PL enhancement mechanism was unraveled by surface composition derived quantum-well band structure and their large exciton binding energy. The Br-rich surface and the observed 530 meV exciton binding energy were proposed to guarantee the efficient radiative recombination. In addition, we can also tune the inorganic perovskite QD (Cs 3 Sb 2 X 9 ) emission wavelength from 370 to 560 nm via anion exchange reactions. The developed full-inorganic lead-free Sb-perovskite QDs with high PLQY and stable emission promise great potential for efficient emission candidates.

  17. TG-FTIR, DSC and quantum chemical studies of the thermal decomposition of quaternary methylammonium halides

    International Nuclear Information System (INIS)

    Sawicka, Marlena; Storoniak, Piotr; Skurski, Piotr; Blazejowski, Jerzy; Rak, Janusz

    2006-01-01

    The thermal decomposition of quaternary methylammonium halides was studied using thermogravimetry coupled to FTIR (TG-FTIR) and differential scanning calorimetry (DSC) as well as the DFT, MP2 and G2 quantum chemical methods. There is almost perfect agreement between the experimental IR spectra and those predicted at the B3LYP/6-311G(d,p) level: this has demonstrated for the first time that an equimolar mixture of trimethylamine and a methyl halide is produced as a result of decomposition. The experimental enthalpies of dissociation are 153.4, 171.2, and 186.7 kJ/mol for chloride, bromide and iodide, respectively, values that correlate well with the calculated enthalpies of dissociation based on crystal lattice energies and quantum chemical thermodynamic barriers. The experimental activation barriers estimated from the least-squares fit of the F1 kinetic model (first-order process) to thermogravimetric traces - 283, 244 and 204 kJ/mol for chloride, bromide and iodide, respectively - agree very well with theoretically calculated values. The theoretical approach assumed in this work has been shown capable of predicting the relevant characteristics of the thermal decomposition of solids with experimental accuracy

  18. Electrochemistry and Spectroelectrochemistry of Lead Halide Perovskite Films: Materials Science Aspects and Boundary Conditions

    KAUST Repository

    Samu, Gergely F.; Scheidt, Rebecca A; Kamat, Prashant V.; Janá ky, Csaba

    2017-01-01

    The unique optoelectronic properties of lead halide perovskites have triggered a new wave of excitement in materials chemistry during the past five years. Electrochemistry, spectroelectrochemistry, and photoelectrochemistry could be viable tools both for analyzing the optoelectronic features of these materials and to assemble their hybrid architectures (e.g., solar cells). At the same time, the instability of these materials limits the pool of solvents and electrolytes that can be employed in such experiments. The focus of our study is to establish a stability window for electrochemical tests for all-inorganic CsPbBr3 and hybrid organic-inorganic MaPbI3 perovskites. In addition, we aimed to understand the reduction and oxidation events that occur and to assess the damage done during these processes at extreme electrochemical conditions. In this vein, we demonstrated the chemical, structural, and morphological changes of the films in both reductive and oxidative environments. Taking all these results together as a whole, we propose a set of boundary conditions and protocols for how electrochemical experiments with lead halide perovskites should be carried out and interpreted. We believe that the presented results will contribute to the understanding of the electrochemical response of these materials and lead to a standardization of results in the literature so that easier comparisons can be made.

  19. Electrochemistry and Spectroelectrochemistry of Lead Halide Perovskite Films: Materials Science Aspects and Boundary Conditions.

    Science.gov (United States)

    Samu, Gergely F; Scheidt, Rebecca A; Kamat, Prashant V; Janáky, Csaba

    2018-02-13

    The unique optoelectronic properties of lead halide perovskites have triggered a new wave of excitement in materials chemistry during the past five years. Electrochemistry, spectroelectrochemistry, and photoelectrochemistry could be viable tools both for analyzing the optoelectronic features of these materials and for assembling them into hybrid architectures (e.g., solar cells). At the same time, the instability of these materials limits the pool of solvents and electrolytes that can be employed in such experiments. The focus of our study is to establish a stability window for electrochemical tests for all-inorganic CsPbBr 3 and hybrid organic-inorganic MAPbI 3 perovskites. In addition, we aimed to understand the reduction and oxidation events that occur and to assess the damage done during these processes at extreme electrochemical conditions. In this vein, we demonstrated the chemical, structural, and morphological changes of the films in both reductive and oxidative environments. Taking all these results together as a whole, we propose a set of boundary conditions and protocols for how electrochemical experiments with lead halide perovskites should be carried out and interpreted. The presented results will contribute to the understanding of the electrochemical response of these materials and lead to a standardization of results in the literature so that comparisons can more easily be made.

  20. Electrochemistry and Spectroelectrochemistry of Lead Halide Perovskite Films: Materials Science Aspects and Boundary Conditions

    KAUST Repository

    Samu, Gergely F.

    2017-12-06

    The unique optoelectronic properties of lead halide perovskites have triggered a new wave of excitement in materials chemistry during the past five years. Electrochemistry, spectroelectrochemistry, and photoelectrochemistry could be viable tools both for analyzing the optoelectronic features of these materials and to assemble their hybrid architectures (e.g., solar cells). At the same time, the instability of these materials limits the pool of solvents and electrolytes that can be employed in such experiments. The focus of our study is to establish a stability window for electrochemical tests for all-inorganic CsPbBr3 and hybrid organic-inorganic MaPbI3 perovskites. In addition, we aimed to understand the reduction and oxidation events that occur and to assess the damage done during these processes at extreme electrochemical conditions. In this vein, we demonstrated the chemical, structural, and morphological changes of the films in both reductive and oxidative environments. Taking all these results together as a whole, we propose a set of boundary conditions and protocols for how electrochemical experiments with lead halide perovskites should be carried out and interpreted. We believe that the presented results will contribute to the understanding of the electrochemical response of these materials and lead to a standardization of results in the literature so that easier comparisons can be made.

  1. Evaluation of quaternary ammonium halides for removal of methyl iodide from flowing air streams

    International Nuclear Information System (INIS)

    Freeman, W.P.; Mohacsi, T.G.; Kovach, J.L.

    1985-01-01

    The quaternary ammonium halides of several tertiary amines were used as impregnants on activated carbon and were tested for methyl iodide penetration in accordance with test Method A, ASTM D3803, 1979, ''Standard Test Methods for Radio-iodine Testing of Nuclear Grade Gas Phase Adsorbents''. The results suggest that the primary removal mechanism for methyl iodide-131 is isotopic exchange with the quaternary ammonium halide. For example, a 5 wt% impregnation of each of the tetramethyl, tetraethyl, tetrapropyl and tetrabutyl ammonium iodides on activated carbon yielded percent penetrations of 0.47, 0.53, 0.78, and 0.08 respectively when tested according to Method A of ASTM D3803. A sample impregnated with 5% tetramethyl ammonium hydroxide gave a methyl iodide penetration of 64.87%, thus supporting the isotopic exchange mechanism for removal. It has been a generally held belief that the success of tertiary amines as impregnants for radioiodine removal is a result of their ability to complex with the methyl iodide. The results of the work indicates that the superiority of the tertiary amines similar to triethylene diamine and quinuclidine, when compared to their straight chain analogs, is a result of their ease in reacting with methyl iodide-127 to form the quaternary ammonium iodide followed by isotopic exchange

  2. Electrochemistry and Spectroelectrochemistry of Lead Halide Perovskite Films: Materials Science Aspects and Boundary Conditions

    Science.gov (United States)

    2017-01-01

    The unique optoelectronic properties of lead halide perovskites have triggered a new wave of excitement in materials chemistry during the past five years. Electrochemistry, spectroelectrochemistry, and photoelectrochemistry could be viable tools both for analyzing the optoelectronic features of these materials and for assembling them into hybrid architectures (e.g., solar cells). At the same time, the instability of these materials limits the pool of solvents and electrolytes that can be employed in such experiments. The focus of our study is to establish a stability window for electrochemical tests for all-inorganic CsPbBr3 and hybrid organic–inorganic MAPbI3 perovskites. In addition, we aimed to understand the reduction and oxidation events that occur and to assess the damage done during these processes at extreme electrochemical conditions. In this vein, we demonstrated the chemical, structural, and morphological changes of the films in both reductive and oxidative environments. Taking all these results together as a whole, we propose a set of boundary conditions and protocols for how electrochemical experiments with lead halide perovskites should be carried out and interpreted. The presented results will contribute to the understanding of the electrochemical response of these materials and lead to a standardization of results in the literature so that comparisons can more easily be made. PMID:29503507

  3. Thermal annealing of high dose radiation induced damage at room temperature in alkali halides. Stored energy, thermoluminiscence and colouration

    International Nuclear Information System (INIS)

    Delgado, L.

    1980-01-01

    The possible relation between stored energy, thermoluminiscence and colour centre annealing in gamma and electron irradiated alkali halides is studied. Thermoluminiscence occurs at temperature higher than the temperature at which the main stored energy peak appears. No stored energy release is detected in additively coloured KCl samples. Plastic deformation and doping with Ca and Sr induce a stored energy spectrum different from the spectrum observed in pure and as cleaved samples, but the amount of stored energy does not change for a given irradiation dose. Capacity of alkali halides to sotore energy by irradiation increases as the cation size decreases. It appears that most of the observed release is not related to annealing processes of the radiation induced anion Frenkel pairs. The existence of damage in the cation sublattice with which this energy release might be related is considered. (auth.)

  4. The Effect of Radiation "Memory" in Alkali-Halide Crystals

    Science.gov (United States)

    Korovkin, M. V.; Sal'nikov, V. N.

    2017-01-01

    The exposure of the alkali-halide crystals to ionizing radiation leads to the destruction of their structure, the emergence of radiation defects, and the formation of the electron and hole color centers. Destruction of the color centers upon heating is accompanied by the crystal bleaching, luminescence, and radio-frequency electromagnetic emission (REME). After complete thermal bleaching of the crystal, radiation defects are not completely annealed, as the electrons and holes released from the color centers by heating leave charged and locally uncompensated defects. Clusters of these "pre centers" lead to electric microheterogeneity of the crystal, the formation of a quasi-electret state, and the emergence of micro-discharges accompanied by radio emission. The generation of REME associated with residual defectiveness, is a manifestation of the effect of radiation "memory" in dielectrics.

  5. The chemistry of positronium. Part VI: inhibition and enhancement of positronium formation in aqueous solutions of halides, sulfide and thiocyanate

    International Nuclear Information System (INIS)

    Duplatre, G.; Abbe, J.C.; Maddock, A.G.; Haessler, A.

    1977-01-01

    The formation of positronium in aqueous solutions of halides, sulfide and thiocyanate has been investigated. Inhibiting and enhancing reactions of positronium formation are found. The results are discussed in terms of the spur model

  6. Development of processes for the production of solar grade silicon from halides and alkali metals

    Science.gov (United States)

    Dickson, C. R.; Gould, R. K.

    1980-01-01

    High temperature reactions of silicon halides with alkali metals for the production of solar grade silicon in volume at low cost were studied. Experiments were performed to evaluate product separation and collection processes, measure heat release parameters for scaling purposes, determine the effects of reactants and/or products on materials of reactor construction, and make preliminary engineering and economic analyses of a scaled-up process.

  7. Preparation, infrared, raman and nmr spectra of N,N'-diethylthiourea complexes with zinc(II), cadmium(II) and mercury(II) halides

    Energy Technology Data Exchange (ETDEWEB)

    Marcotrigiano, G [Bari Univ. (Italy). Cattedra di Chimica, Facolta di Medicina-Veterinaria

    1976-05-01

    Several complexes of N,N'-diethylthiourea (Dietu) with zinc(II), cadmium(II) and mercury(II) halides were prepared and characterized by i.r. (4000-60 cm/sup -1/), raman (400-60 cm/sup -1/), in the solid state and n.m.r. and conductometric methods in solution. The complexes Zn(Dietu)/sub 2/X/sub 2/, Cd(Dietu)/sub 2/X/sub 2/ (X=Cl, Br, I) and Hg(Dietu)/sub 2/X/sub 2/ (X=Br, I) are tetrahedral species in which intramolecular -NH...X interactions have been observed. The 1:1 mercury(II) complexes, Hg(Dietu)X/sub 2/ (X=Cl, Br), appear to have a dimeric tetrahedral halide-bridged structure in the solid state. In all these complexes N,N'-diethylthiourea is sulphur-bonded to the metal.

  8. In-situ EC-STM studies on the influence of halide anions on structure and reactivity of dibenzylviologen on Cu(100)

    Energy Technology Data Exchange (ETDEWEB)

    Gentz, Knud; Wandelt, Klaus [Institute of Physical and Theoretical Chemistry, Bonn University (Germany); Broekmann, Peter [University of Bern (Switzerland)

    2009-07-01

    Copper has become a focus of research activities over the last two decades due to its use as interconnect material in microchip design. Nitrogen-containing cationic organic molecules have been studied as additives for the so-called copper damascene process. In the present investigation the structures and reactivity of a dibenzylviologen (DBV) layer adsorbed on a bromide-modified Cu(100) surface have been studied by in-situ electrochemical STM and will be compared to the results on the chloride-modified substrate and the related Diphenylviologen (DPV). N,N'-dibenzyl-4,4'-bipyridinium molecules (dibenzylviologen, DBV) spontaneously adsorb on a halide-modified Cu(100)-surface, forming distinctive patterns, which have been characterized by in-situ scanning tunneling microscopy. Depending on the adsorption potential a striped phase, a cavitand phase and an amorphous phase have been identified. Cyclic voltammetry indicates that even more processes take place on the surface, because if the potential is decreased beyond a range of fully reversible processes, an irreversible surface phase formation is observed at -450 mV vs. RHE. This surface phase passivates the surface against adsorption of the dicationic phase, so the charge reversal of the interface in the outer Helmholtz layer seems to be reduced.

  9. Cluster harvesting by successive reduction of a metal halide with a nonconventional reduction agent: a benefit for the exploration of metal-rich halide systems.

    Science.gov (United States)

    Ströbele, Markus; Mos, Agnieszka; Meyer, Hans-Jürgen

    2013-06-17

    The preparation of thermally labile compounds is a great temptation in chemistry which requires a careful selection of reaction media and reaction conditions. With a new scanning technique denoted here as Cluster Harvesting, a whole series of metal halide compounds is detected by differential thermal analysis (DTA) in fused silica tubes and structurally characterized by X-ray powder diffraction. Experiments of the reduction of tungsten hexahalides with elemental antimony and iron are presented. A cascade of six compounds is identified during the reduction with antimony, and five compounds or phases are monitored following the reduction with iron. The crystal structure of Fe2W2Cl10 is reported, and two other phases in the Fe-W-Cl system are discussed.

  10. Modeling cell-substrate de-adhesion dynamics under fluid shear

    Science.gov (United States)

    Maan, Renu; Rani, Garima; Menon, Gautam I.; Pullarkat, Pramod A.

    2018-07-01

    Changes in cell-substrate adhesion are believed to signal the onset of cancer metastasis, but such changes must be quantified against background levels of intrinsic heterogeneity between cells. Variations in cell-substrate adhesion strengths can be probed through biophysical measurements of cell detachment from substrates upon the application of an external force. Here, we investigate, theoretically and experimentally, the detachment of cells adhered to substrates when these cells are subjected to fluid shear. We present a theoretical framework within which we calculate the fraction of detached cells as a function of shear stress for fast ramps as well as the decay in this fraction at fixed shear stress as a function of time. Using HEK and 3T3 fibroblast cells as experimental model systems, we extract characteristic force scales for cell adhesion as well as characteristic detachment times. We estimate force-scales of  ∼500 pN associated to a single focal contact, and characteristic time-scales of s representing cell-spread-area dependent mean first passage times to the detached state at intermediate values of the shear stress. Variations in adhesion across cell types are especially prominent when cell detachment is probed by applying a time-varying shear stress. These methods can be applied to characterizing changes in cell adhesion in a variety of contexts, including metastasis.

  11. Hybrid lead halide perovskites for light energy conversion: Excited state properties and photovoltaic applications

    Science.gov (United States)

    Manser, Joseph S.

    The burgeoning class of metal halide perovskites constitutes a paradigm shift in the study and application of solution-processed semiconductors. Advancements in thin film processing and our understanding of the underlying structural, photophysical, and electronic properties of these materials over the past five years have led to development of perovskite solar cells with power conversion efficiencies that rival much more mature first and second-generation commercial technologies. It seems only a matter of time before the real-world impact of these compounds is put to the test. Like oxide perovskites, metal halide perovskites have ABX3 stoichiometry, where typically A is a monovalent cation, B a bivalent post-transition metal, and X a halide anion. Characterizing the behavior of photogenerated charges in metal halide perovskites is integral for understanding the operating principles and fundamental limitations of perovskite optoelectronics. The majority of studies outlined in this dissertation involve fundamental study of the prototypical organic-inorganic compound methylammonium lead iodide (CH3NH3PbI 3). Time-resolved pump-probe spectroscopy serves as a principle tool in these investigations. Excitation of a semiconductor can lead to formation of a number different excited state species and electronic complexes. Through analysis of excited state decay kinetics and optical nonlinearities in perovskite thin films, we identify spontaneous formation of a large fraction of free electrons and holes, whose presence is requisite for efficient photovoltaic operation. Following photogeneration of charge carriers in a semiconductor absorber, these species must travel large distances across the thickness of the material to realize large external quantum efficiencies and efficient carrier extraction. Using a powerful technique known as transient absorption microscopy, we directly image long-range carrier diffusion in a CH3NH3PbI 3 thin film. Charges are unambiguously shown to

  12. Organometal halide perovskite light-emitting diodes with laminated carbon nanotube electrodes

    Science.gov (United States)

    Shan, Xin; Bade, Sri Ganesh R.; Geske, Thomas; Davis, Melissa; Smith, Rachel; Yu, Zhibin

    2017-08-01

    Organometal halide perovskite light-emitting diodes (LEDs) with laminated carbon nanotube (CNT) electrodes are reported. The LEDs have an indium tin oxide (ITO) bottom electrode, a screen printed methylammonium lead tribromide (MAPbBr3)/polymer composite thin film as the emissive layer, and laminated CNT as the top electrode. The devices can be turned on at 2.2 V, reaching a brightness of 4,960 cd m-2 and a current efficiency of 1.54 cd A-1 at 6.9 V. The greatly simplified fabrication process in this work can potentially lead to the scalable manufacturing of large size and low cost LED panels in the future.

  13. High Photoluminescence Quantum Yield in Band Gap Tunable Bromide Containing Mixed Halide Perovskites

    OpenAIRE

    Carolin M. Sutter-Fella Yanbo Li Matin Amani Joel W. Ager III Francesca M. Toma; Eli Yablonovitch Ian D. Sharp and Ali Javey

    2016-01-01

    Hybrid organic–inorganic halide perovskite based semiconductor materials are attractive for use in a wide range of optoelectronic devices because they combine the advantages of suitable optoelectronic attributes and simultaneously low cost solution processability. Here we present a two step low pressure vapor assisted solution process to grow high quality homogeneous CH3NH3PbI3–xBrx perovskite films over the full band gap range of 1.6–2.3 eV. Photoluminescence light in versus light out charac...

  14. Phase-field model for deposition process of platinum nanoparticles on carbon substrate

    International Nuclear Information System (INIS)

    Yamakawa, S; Hyodo, S; Okazaki-Maeda, K; Kohyama, M

    2008-01-01

    Platinum supported on a carbon carrier is widely used as a catalyst for polymer electrolyte membrane fuel cells. The catalytic activity is significantly affected by the size distribution and morphologies of the platinum particles. The objective of this study is to extend the phase-field approach to describe the formation process of platinum particles onto the substrate. The microstructural evolution of a nanoparticle was represented by the temporal evolution of the field variables related to the platinum concentration, long-range crystallographic ordering and phase transition. First-principles calculations were performed in order to estimate the interaction energies between several different types of platinum clusters and a graphene sheet. The platinum density profile concentrated over the substrate surface led to the formation of three-dimensional islands in accordance with the Volmer-Weber mode of growth. The size distributions of the platinum particles were sensitive to the heterogeneity of the substrate surface and to the competitive nucleation and growth processes

  15. Low-Temperature Electron Beam-Induced Transformations of Cesium Lead Halide Perovskite Nanocrystals

    Science.gov (United States)

    2017-01-01

    Cesium lead halide perovskite (CsPbX3, with X = Br, Cl, I) nanocrystals have been found to undergo severe modifications under the high-energy electron beam irradiation of a transmission electron microscope (80/200 keV). In particular, in our previous work, together with halogen desorption, Pb2+ ions were found to be reduced to Pb0 and then diffused to form lead nanoparticles at temperatures above −40 °C. Here, we present a detailed irradiation study of CsPbBr3 nanocrystals at temperatures below −40 °C, a range in which the diffusion of Pb0 atoms/clusters is drastically suppressed. Under these conditions, the irradiation instead induces the nucleation of randomly oriented CsBr, CsPb, and PbBr2 crystalline domains. In addition to the Br desorption, which accompanies Pb2+ reduction at all the temperatures, Br is also desorbed from the CsBr and PbBr2 domains at low temperatures, leading to a more pronounced Br loss, thus the final products are mainly composed of Cs and Pb. The overall transformation involves the creation of voids, which coalesce upon further exposure, as demonstrated in both nanosheets and nanocuboids. Our results show that although low temperatures hinder the formation of Pb nanoparticles in CsPbBr3 nanocrystals when irradiated, the nanocrystals are nevertheless unstable. Consequently, we suggest that an optimum combination of temperature range, electron energy, and dose rate needs to be carefully chosen for the characterization of halide perovskite nanocrystals to minimize both the Pb nanoparticle formation and the structural decomposition. PMID:28983524

  16. A new fundamental hydrogen defect in alkali halides

    International Nuclear Information System (INIS)

    Morato, S.P.; Luety, F.

    1978-01-01

    Atom hydrogen in neutral (H 0 ) and negative (H - ) form on substitutional and interstitial lattice sites gives rise to well characterized model defects in alkali-halides (U,U 1 ,U 2 ,U 3 centers), which have been extensively investigated in the past. When studying the photo-decomposition of OH - defects, a new configuration of atomic charged hidrogen was discovered, which can be produced in large quantities in the crystal and is apparently not connected to any other impurity. This new hidrogen defect does not show any pronounced electronic absorption, but displays a single sharp local mode band (at 1114cm -1 in KCl) with a perfect isotope shift. The defect can be produced by various UV or X-ray techniques in crystais doped with OH - , Sh - or H - defects. A detailed study of its formation kinetics at low temperature shows that it is primarily formed by the reaction of a mobile CI 2 - crowdion (H-center) with hidrogen defects [pt

  17. Silver nanoparticles from silver halide photography to plasmonics

    CERN Document Server

    Tani, Tadaaki

    2015-01-01

    This book provides systematic knowledge and ideas on nanoparticles of Ag and related materials. While Ag and metal nanoparticles are essential for plasmonics, silver halide (AgX) photography relies to a great extent on nanoparticles of Ag and AgX which have the same crystal structure and have been studied extensively for many years. This book has been written to combine the knowledge of nanoparticles of Ag and related materials in plasmonics and AgX photography in order to provide new ideas for metal nanoparticles in plasmonics. Chapters 1–3 of this book describe the structure and formation of nanoparticles of Ag and related materials. Systematic descriptions of the structure and preparation of Ag, Au, and noble-metal nanoparticles for plasmonics are followed by and related to those of nanoparticles of Ag and AgX in AgX photography. Knowledge of the structure and preparation of Ag and AgX nanoparticles in photography covers nanoparticles with widely varying sizes, shapes, and structures, and formation proce...

  18. Phase-resolved response of a metal-halide lamp

    International Nuclear Information System (INIS)

    Flikweert, A J; Beks, M L; Nimalasuriya, T; Kroesen, G M W; Van der Mullen, J J A M; Stoffels, W W

    2009-01-01

    The metal-halide (MH) lamp sometimes shows unwanted colour segregation, caused by a combination of convection and diffusion. In the past we investigated the lamp, running on a switched dc ballast of 120 Hz, using a dc approximation for the distribution of the radiating species. Here we present phase-resolved intensity measurements to verify this approximation. The MH lamp contains Hg as buffer gas and DyI 3 as salt additive; we measure the light emitted by Dy and by Hg atoms. An intensity fluctuation of ∼25% close to the electrodes is found only. The observed fluctuations are explained by the cataphoresis effect and temperature fluctuations; the time scales are in the same order. Furthermore, measurements at higher gravity in a centrifuge (up to 10g) show that the effect becomes smaller at increasing gravity levels. From these results it is concluded that a dc approximation, which is generally assumed by lamp developers, is allowed for this MH lamp.

  19. Temperature-dependent excitonic photoluminescence of hybrid organometal halide perovskite films

    KAUST Repository

    Wu, Kewei; Bera, Ashok; Ma, Chun; Du, Yuanmin; Yang, Yang; LI, LIANG; Wu, Tao

    2014-01-01

    Organometal halide perovskites have recently attracted tremendous attention due to their potential for photovoltaic applications, and they are also considered as promising materials in light emitting and lasing devices. In this work, we investigated in detail the cryogenic steady state photoluminescence properties of a prototypical hybrid perovskite CH3NH3PbI3-xClx. The evolution of the characteristics of two excitonic peaks coincides with the structural phase transition around 160 K. Our results further revealed an exciton binding energy of 62.3 ± 8.9 meV and an optical phonon energy of 25.3 ± 5.2 meV, along with an abnormal blue-shift of the band gap in the high-temperature tetragonal phase. This journal is

  20. X-ray induced fluorescence measurement of segregation in a DyI{sub 3}-Hg metal-halide lamp

    Energy Technology Data Exchange (ETDEWEB)

    Nimalasuriya, T [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Curry, J J [National Institute of Standards and Technology, 100 Bureau Drive, Stop 8422, Gaithersburg, MD 20899-8422 (United States); Sansonetti, C J [National Institute of Standards and Technology, 100 Bureau Drive, Stop 8422, Gaithersburg, MD 20899-8422 (United States); Ridderhof, E J [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Shastri, S D [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States); Flikweert, A J [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Stoffels, W W [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Haverlag, M [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Mullen, J J A M van der [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands)

    2007-05-07

    Segregation of elemental Dy in a DyI{sub 3}-Hg metal-halide high-intensity discharge lamp has been observed with x-ray induced fluorescence. Significant radial and axial Dy segregation are seen, with the axial segregation characterized by a Fischer parameter value of {lambda} = 0.215 {+-} 0.002 mm{sup -1}. This is within 7% of the value ({lambda} = 0.20 {+-} 0.01 mm{sup -1}) obtained by Flikweert et al (2005 J. Appl. Phys. 98 073301) based on laser absorption by neutral Dy atoms. Elemental I is seen to exhibit considerably less axial and radial segregation. Some aspects of the observed radial segregation are compatible with a simplified fluid picture describing two main transition regions in the radial coordinate. The first transition occurs in the region where DyI{sub 3} molecules are in equilibrium with neutral Dy atoms. The second transition occurs where neutral Dy atoms are in equilibrium with ionized Dy. These measurements are part of a larger study on segregation in metal-halide lamps under a variety of conditions.

  1. Development and Application of TiO2 Nanoparticles Coupled with Silver Halide

    Directory of Open Access Journals (Sweden)

    Xiaojia Wan

    2014-01-01

    Full Text Available Titanium dioxide (TiO2 is proposed to be effective photocatalyst for wastewater treatment, air purification, and self-cleaning ability, because of its strong oxidation and superhydrophilicity. In order to conquer the limits of TiO2, a variety of methods have been used. This paper presents a critical review of novel research and achievements in the modification of TiO2 nanoparticles with silver halide (AgX, X=Cl, Br, I, which aims at enhancing the visible light absorption and photosensitivity. Herein we study the synthesis, physical and chemical properties, and the mechanism of this composite photocatalyst.

  2. Basic mechanisms of color centres production by excitons in activated alkali halides

    International Nuclear Information System (INIS)

    Vale, G.

    1981-01-01

    The paper deals with some peculiarities of colour centers formation which are caused by introduction of the activator in alkali halide crystals. The crystals of KBr and KI activated with Tl + , In + , Sn ++ in concentrations 10 17 -10 18 cm -3 and irradiated with ultraviolet light are studied. Excitation spectra of photostimulated activator luminescence and thermoluminescence were measured. The kinetics of the photostimulated activator luminescence is studied. The conclusion is made that the activator does not affect the primary reaction of exciton decay with F-H pair generation, but only the secondary reactions of colour center production [ru

  3. Biophysically inspired rational design of structured chimeric substrates for DNAzyme cascade engineering.

    Directory of Open Access Journals (Sweden)

    Matthew R Lakin

    Full Text Available The development of large-scale molecular computational networks is a promising approach to implementing logical decision making at the nanoscale, analogous to cellular signaling and regulatory cascades. DNA strands with catalytic activity (DNAzymes are one means of systematically constructing molecular computation networks with inherent signal amplification. Linking multiple DNAzymes into a computational circuit requires the design of substrate molecules that allow a signal to be passed from one DNAzyme to another through programmed biochemical interactions. In this paper, we chronicle an iterative design process guided by biophysical and kinetic constraints on the desired reaction pathways and use the resulting substrate design to implement heterogeneous DNAzyme signaling cascades. A key aspect of our design process is the use of secondary structure in the substrate molecule to sequester a downstream effector sequence prior to cleavage by an upstream DNAzyme. Our goal was to develop a concrete substrate molecule design to achieve efficient signal propagation with maximal activation and minimal leakage. We have previously employed the resulting design to develop high-performance DNAzyme-based signaling systems with applications in pathogen detection and autonomous theranostics.

  4. Halide-Enhanced Catalytic Activity of Palladium Nanoparticles Comes at the Expense of Catalyst Recovery

    Directory of Open Access Journals (Sweden)

    Azzedine Bouleghlimat

    2017-09-01

    Full Text Available In this communication, we present studies of the oxidative homocoupling of arylboronic acids catalyzed by immobilised palladium nanoparticles in aqueous solution. This reaction is of significant interest because it shares a key transmetallation step with the well-known Suzuki-Miyaura cross-coupling reaction. Additives can have significant effects on catalysis, both in terms of reaction mechanism and recovery of catalytic species, and our aim was to study the effect of added halides on catalytic efficiency and catalyst recovery. Using kinetic studies, we have shown that added halides (added as NaCl and NaBr can increase the catalytic activity of the palladium nanoparticles more than 10-fold, allowing reactions to be completed in less than half a day at 30 °C. However, this increased activity comes at the expense of catalyst recovery. The results are in agreement with a reaction mechanism in which, under conditions involving high concentrations of chloride or bromide, palladium leaching plays an important role. Considering the evidence for analogous reactions occurring on the surface of palladium nanoparticles under different reaction conditions, we conclude that additives can exert a significant effect on the mechanism of reactions catalyzed by nanoparticles, including switching from a surface reaction to a solution reaction. The possibility of this switch in mechanism may also be the cause for the disagreement on this topic in the literature.

  5. Visualizing Carrier Transport in Metal Halide Perovskite Nanoplates via Electric Field Modulated Photoluminescence Imaging.

    Science.gov (United States)

    Hu, Xuelu; Wang, Xiao; Fan, Peng; Li, Yunyun; Zhang, Xuehong; Liu, Qingbo; Zheng, Weihao; Xu, Gengzhao; Wang, Xiaoxia; Zhu, Xiaoli; Pan, Anlian

    2018-05-09

    Metal halide perovskite nanostructures have recently been the focus of intense research due to their exceptional optoelectronic properties and potential applications in integrated photonics devices. Charge transport in perovskite nanostructure is a crucial process that defines efficiency of optoelectronic devices but still requires a deep understanding. Herein, we report the study of the charge transport, particularly the drift of minority carrier in both all-inorganic CsPbBr 3 and organic-inorganic hybrid CH 3 NH 3 PbBr 3 perovskite nanoplates by electric field modulated photoluminescence (PL) imaging. Bias voltage dependent elongated PL emission patterns were observed due to the carrier drift at external electric fields. By fitting the drift length as a function of electric field, we obtained the carrier mobility of about 28 cm 2 V -1 S -1 in the CsPbBr 3 perovskite nanoplate. The result is consistent with the spatially resolved PL dynamics measurement, confirming the feasibility of the method. Furthermore, the electric field modulated PL imaging is successfully applied to the study of temperature-dependent carrier mobility in CsPbBr 3 nanoplates. This work not only offers insights for the mobile carrier in metal halide perovskite nanostructures, which is essential for optimizing device design and performance prediction, but also provides a novel and simple method to investigate charge transport in many other optoelectronic materials.

  6. Photoinduced oxidation of sea salt halides by aromatic ketones: a source of halogenated radicals

    Directory of Open Access Journals (Sweden)

    A. Jammoul

    2009-07-01

    Full Text Available The interactions between triplet state benzophenone and halide anion species (Cl, Br and I have been studied by laser flash photolysis (at 355 nm in aqueous solutions at room temperature. The decay of the triplet state of benzophenone was followed at 525 nm. Triplet lifetime measurements gave rate constants, kq (M−1 s, close to diffusion controlled limit for iodide (~8×109 M−1 s, somewhat less for bromide (~3×108 M−1 s and much lower for chloride (<106 M−1 s. The halide (X quenches the triplet state; the resulting product has a transient absorption at 355 nm and a lifetime much longer than that of the benzophenone triplet state, is formed. This transient absorption feature matches those of the corresponding radical anion (X2. We therefore suggest that such reactive quenching is a photosensitized source of halogen in the atmosphere or the driving force for the chemical oxidation of the oceanic surface micro layer.

  7. Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes

    Science.gov (United States)

    Yang, Hui; Tang, Ming; Gross, Thilo

    2015-08-01

    One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that network heterogeneity, i.e. a broad degree distribution, can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

  8. Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes.

    Science.gov (United States)

    Yang, Hui; Tang, Ming; Gross, Thilo

    2015-08-21

    One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that network heterogeneity, i.e. a broad degree distribution, can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

  9. Amine-Free Synthesis of Cesium Lead Halide Perovskite Quantum Dots for Efficient Light-Emitting Diodes

    KAUST Repository

    Yassitepe, Emre; Yang, Zhenyu; Voznyy, Oleksandr; Kim, Younghoon; Walters, Grant; Castañ eda, Juan Andres; Kanjanaboos, Pongsakorn; Yuan, Mingjian; Gong, Xiwen; Fan, Fengjia; Pan, Jun; Hoogland, Sjoerd; Comin, Riccardo; Bakr, Osman; Padilha, Lazaro A.; Nogueira, Ana F.; Sargent, Edward H.

    2016-01-01

    Cesium lead halide perovskite quantum dots (PQDs) have attracted significant interest for optoelectronic applications in view of their high brightness and narrow emission linewidth at visible wavelengths. A remaining challenge is the degradation of PQDs during purification from the synthesis solution. This is attributed to proton transfer between oleic acid and oleylamine surface capping agents that leads to facile ligand loss. Here, a new synthetic method is reported that enhances the colloidal stability of PQDs by capping them solely using oleic acid (OA). Quaternary alkylammonium halides are used as precursors, eliminating the need for oleylamine. This strategy enhances the colloidal stability of OA capped PQDs during purification, allowing us to remove excess organic content in thin films. Inverted red, green, and blue PQD light-emitting diodes (LED) are fabricated for the first time with solution-processed polymer-based hole transport layers due to higher robustness of OA capped PQDs to solution processing. The blue and green LEDs exhibit threefold and tenfold improved external quantum efficiency (EQE), respectively, compared to prior related reports for amine/ammonium capped cross-linked PQDs. The brightest blue LED based on all inorganic CsPb(Br1- xClx)3 PQDs is also reported. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Amine-Free Synthesis of Cesium Lead Halide Perovskite Quantum Dots for Efficient Light-Emitting Diodes

    KAUST Repository

    Yassitepe, Emre

    2016-10-31

    Cesium lead halide perovskite quantum dots (PQDs) have attracted significant interest for optoelectronic applications in view of their high brightness and narrow emission linewidth at visible wavelengths. A remaining challenge is the degradation of PQDs during purification from the synthesis solution. This is attributed to proton transfer between oleic acid and oleylamine surface capping agents that leads to facile ligand loss. Here, a new synthetic method is reported that enhances the colloidal stability of PQDs by capping them solely using oleic acid (OA). Quaternary alkylammonium halides are used as precursors, eliminating the need for oleylamine. This strategy enhances the colloidal stability of OA capped PQDs during purification, allowing us to remove excess organic content in thin films. Inverted red, green, and blue PQD light-emitting diodes (LED) are fabricated for the first time with solution-processed polymer-based hole transport layers due to higher robustness of OA capped PQDs to solution processing. The blue and green LEDs exhibit threefold and tenfold improved external quantum efficiency (EQE), respectively, compared to prior related reports for amine/ammonium capped cross-linked PQDs. The brightest blue LED based on all inorganic CsPb(Br1- xClx)3 PQDs is also reported. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Time Domain View of Liquid-like Screening and Large Polaron Formation in Lead Halide Perovskites

    Science.gov (United States)

    Joshi, Prakriti Pradhan; Miyata, Kiyoshi; Trinh, M. Tuan; Zhu, Xiaoyang

    The structural softness and dynamic disorder of lead halide perovskites contributes to their remarkable optoelectronic properties through efficient charge screening and large polaron formation. Here we provide a direct time-domain view of the liquid-like structural dynamics and polaron formation in single crystal CH3NH3PbBr3 and CsPbBr3 using femtosecond optical Kerr effect spectroscopy in conjunction with transient reflectance spectroscopy. We investigate structural dynamics as function of pump energy, which enables us to examine the dynamics in the absence and presence of charge carriers. In the absence of charge carriers, structural dynamics are dominated by over-damped picosecond motions of the inorganic PbBr3- sub-lattice and these motions are strongly coupled to band-gap electronic transitions. Carrier injection from across-gap optical excitation triggers additional 0.26 ps dynamics in CH3NH3PbBr3 that can be attributed to the formation of large polarons. In comparison, large polaron formation is slower in CsPbBr3 with a time constant of 0.6 ps. We discuss how such dynamic screening protects charge carriers in lead halide perovskites. US Department of Energy, Office of Science - Basic Energy Sciences.

  12. Linkage of molecular units in the chemistry of niobium and tantalum cluster halides

    International Nuclear Information System (INIS)

    Perrin, C.; Sergent, M.

    1991-01-01

    In low valency niobium and tantalum halides, interunit linkages are observed between the (Me 6 X 12 )X 6 units. They are insulators and interesting magnetic properties are observed, due to the intrinsic potential magnetism of the Me 6 cluster and depending on the inserted cations, for instance rare earths in MM'Nb 6 Cl 18 (M = monovalent cation, M' = rare earth). Of special interest are the niobium iodides which exhibit (Me 6 X 8 )X 6 units, an exception in the niobium chemistry; interesting properties have been reported for some of these iodides

  13. Habitat heterogeneity of hadal trenches: Considerations and implications for future studies

    Science.gov (United States)

    Stewart, Heather A.; Jamieson, Alan J.

    2018-02-01

    The hadal zone largely comprises a series of subduction trenches that do not form part of the continental shelf-slope rise to abyssal plain continuum. Instead they form geographically isolated clusters of deep-sea (6000-11,000 m water depth) environments. There is a growing realization in hadal science that ecological patterns and processes are not driven solely by responses to hydrostatic pressure, with comparable levels of habitat heterogeneity as observed in other marine biozones. Furthermore, this heterogeneity can be expressed at multiple scales from inter-trench levels (degrees of geographical isolation, and biochemical province), to intra-trench levels (variation between trench flanks and axis), topographical features within the trench interior (sedimentary basins, ridges, escarpments, 'deeps', seamounts) to the substrate of the trench floor (seabed-sediment composition, mass movement deposits, bedrock outcrop). Using best available bathymetry data combined with the largest lander-derived imaging dataset that spans the full depth range of three hadal trenches (including adjacent slopes); the Mariana, Kermadec and New Hebrides trenches, the topographic variability, fine-scale habitat heterogeneity and distribution of seabed sediments of these three trenches have been assessed for the first time. As well as serving as the first descriptive study of habitat heterogeneity at hadal depths, this study also provides guidance for future hadal sampling campaigns taking into account geographic isolation, total trench particulate organic matter flux, maximum water depth and area.

  14. Entropy-driven crystal formation on highly strained substrates

    KAUST Repository

    Savage, John R.

    2013-05-20

    In heteroepitaxy, lattice mismatch between the deposited material and the underlying surface strongly affects nucleation and growth processes. The effect of mismatch is well studied in atoms with growth kinetics typically dominated by bond formation with interaction lengths on the order of one lattice spacing. In contrast, less is understood about how mismatch affects crystallization of larger particles, such as globular proteins and nanoparticles, where interparticle interaction energies are often comparable to thermal fluctuations and are short ranged, extending only a fraction of the particle size. Here, using colloidal experiments and simulations, we find particles with short-range attractive interactions form crystals on isotropically strained lattices with spacings significantly larger than the interaction length scale. By measuring the free-energy cost of dimer formation on monolayers of increasing uniaxial strain, we show the underlying mismatched substrate mediates an entropy-driven attractive interaction extending well beyond the interaction length scale. Remarkably, because this interaction arises from thermal fluctuations, lowering temperature causes such substrate-mediated attractive crystals to dissolve. Such counterintuitive results underscore the crucial role of entropy in heteroepitaxy in this technologically important regime. Ultimately, this entropic component of lattice mismatched crystal growth could be used to develop unique methods for heterogeneous nucleation and growth of single crystals for applications ranging from protein crystallization to controlling the assembly of nanoparticles into ordered, functional superstructures. In particular, the construction of substrates with spatially modulated strain profiles would exploit this effect to direct self-assembly, whereby nucleation sites and resulting crystal morphology can be controlled directly through modifications of the substrate.

  15. Palladium-Catalyzed Decarboxylative γ-Olefination of 2,5-Cyclohexadiene-1-carboxylic Acid Derivatives with Vinyl Halides.

    Science.gov (United States)

    Chang, Chi-Hao; Chou, Chih-Ming

    2018-04-06

    This study explores a Pd-catalyzed decarboxylative Heck-type Csp 3 -Csp 2 coupling reaction of 2,5-cyclohexadiene-1-carboxylic acid derivatives with vinyl halides to provide γ-olefination products. The olefinated 1,3-cyclohexadienes can be further oxidized to produce meta-alkylated stilbene derivatives. Additionally, the conjugated diene products can also undergo a Diels-Alder reaction to produce a bicyclo[2.2.2]octadiene framework.

  16. Collective Motion in Behaviorally Heterogeneous Systems

    Science.gov (United States)

    Copenhagen, Katherine

    Collective motion is a widespread phenomenon in nature where individuals actively propel themselves, gather together and move as a group. Some examples of collective motion are bird flocks, fish schools, bacteria swarms, cell clusters, and crowds of people. Many models seek to understand the effects of activity in collective systems including things such as environmental disorder, density, and interaction details primarily at infinite size limits and with uniform populations. In this dissertation I investigate the effects of finite sizes and behavioral heterogeneity as it exists in nature. Behavioral heterogeneity can originate from several different sources. Mixed populations of individuals can have inherently different behaviors such as mutant bacteria, injured fish, or agents that prefer individualistic behavior over coordinated motion. Alternatively, agents may modify their own behavior based on some local environmental dependency, such as local substrate, or density. In cases such as mutant cheaters in bacteria or malfunctioning drones in swarms, mixed populations of behaviorally heterogeneous agents can be modelled as arising in the form of aligning and non-aligning agents. When this kind of heterogeneity is introduced, there is a critical carrying capacity of non-aligners above which the system is unable to form a cohesive ordered group. However, if the cohesion of the group is relaxed to allow for fracture, the system will actively sort out non-aligning agents the system will exist at a critical non-aligner fraction. A similar heterogeneity could result in a mixture of high and low noise individuals. In this case there is also a critical carry capacity beyond which the system is unable to reach an ordered state, however the nature of this transition depends on the model details. Agents which are part of an ordered collective may vary their behavior as the group changes environments such as a flock of birds flying into a cloud. Using a unique model of a

  17. Competition between convection and diffusion in a metal halide lamp, investigated by numerical simulations and imaging laser absorption spectroscopy

    NARCIS (Netherlands)

    Beks, M.L.; Flikweert, A.J.; Nimalasuriya, T.; Stoffels, W.W.; Mullen, van der J.J.A.M.

    2008-01-01

    The effect of the competition between convection and diffusion on the distribution of metal halide additives in a high pressure mercury lamp has been examined by placing COST reference lamps with mercury fillings of 5 and 10 mg in a centrifuge. By subjecting them to different accelerational

  18. X-ray absorption tomography of a high-pressure metal-halide lamp with a bent arc due to Lorentz-forces

    NARCIS (Netherlands)

    Denisova, N.; Haverlag, M.; Ridderhof, E.J.; Nimalasuriya, T.; Mullen, van der J.J.A.M.

    2007-01-01

    The arc temperature is one of the most important characteristics which cotrol the emission properties of plasma light sources. X-ray absorption technique has received some attention as a powerful method to determine the temperature in high-pressure metal-halide lamps. An important advantage of x-ray

  19. Ligand-Enabled Reactivity and Selectivity in a Synthetically Versatile Aryl C–H Olefination*

    Science.gov (United States)

    Wang, Dong-Hui; Engle, Keary M.; Shi, Bing-Feng; Yu, Jin-Quan

    2010-01-01

    The Mizoroki–Heck reaction, which couples aryl halides with olefins, has been widely used to stitch together the carbogenic cores of numerous complex organic molecules. Given that the position-selective introduction of a halide onto an arene is not always straightforward, direct olefination of aryl C–H bonds would obviate the inefficiencies associated with generating halide precursors or their equivalents; however, methods for carrying out such a reaction have suffered from narrow substrate scope and low positional selectivity. Here we report an operationally simple, atom-economical, carboxylate-directed Pd(II)-catalyzed C–H olefination reaction with phenylacetic acid and 3-phenylpropionic acid substrates, using oxygen at atmospheric pressure as the oxidant. The positional selectivity can be tuned by introducing amino acid derivatives as ligands. We demonstrate the versatility of the method through direct elaboration of commercial drug scaffolds and efficient synthesis of 2-tetralone and naphthoic acid natural product cores. PMID:19965380

  20. Structure and function of vanadium haloperoxidases

    NARCIS (Netherlands)

    Wever, R.; Michibata, H.

    2012-01-01

    Vanadium haloperoxidases contain the bare metal oxide vanadate as a prosthetic group and differ strongly from the heme peroxidases in substrate specificity and molecular properties. The substrates of these enzymes are limited to halides and sulfides, which in the presence of hydrogen peroxide are