WorldWideScience

Sample records for calcium halides

  1. The Antimicrobial Action of Silver Halides in Calcium Phosphate

    OpenAIRE

    Kalniņa, D; Gross, K; Onufrijevs, P.; Daukšta, E; Nikolajeva, V; Stankeviciute, Z; Kareiva, A.

    2015-01-01

    Silver halides represent a yet unexplored avenue for imparting antimicrobial activity to calcium phosphates. Negtively charged silver halide colloids (AgI, AgBr and AgCl) were added to synthesized amorphous calcium phosphate. Concurrent melting of silver halides and crystallization to carbonated apatite at 700 oC increased the silver halide surface area available to bacteria and formed a lower solubility apatite. The effect of the matrix solubility on antimicrobial response could ...

  2. UV and X radiation effects on the stability of calcium halide phosphate phosphors. 1

    International Nuclear Information System (INIS)

    Intensity losses of several calcium halide phosphate phosphors have been investigated as a function of the time of irradiation with near UV and X radiation. The results show that antimony-containing foreign phases increase such losses. The directly excited manganese centre emission is much more lowered than the sensitized one. Detrimental effects of the 185 nm UV radiation are observable not only in the first minutes of irradiation but also over considerably extended periods. The sensitization effect caused by irradiation in different gases depends on the phosphor, especially on the content of antimony, and can be explained by the sorption of gaseous impurities at the phosphor surface so that the diffusion of photochemical reaction products from the surface is inhibited

  3. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ramkumar, Shwetha; Fan, Liang-Shih

    2015-11-04

    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.

  5. Calcium manganate: A promising candidate as buffer layer for hybrid halide perovskite photovoltaic-thermoelectric systems

    International Nuclear Information System (INIS)

    We have systematically studied the feasibility of CaMnO3 thin film, an n-type perovskite, to be utilized as the buffer layer for hybrid halide perovskite photovoltaic-thermoelectric device. Locations of the conduction band and the valence band, spontaneous polarization performance, and optical properties were investigated. Results indicate the energy band of CaMnO3 can match up well with that of CH3NH3PbI3 on separating electron-hole pairs. In addition, the consistent polarization angle helps enlarge the open circuit voltage of the composite system. Besides, CaMnO3 film shows large absorption coefficient and low extinction coefficient under visible irradiation, demonstrating high carrier concentration, which is beneficial to the current density. More importantly, benign thermoelectric properties enable CaMnO3 film to assimilate phonon vibration from CH3NH3PbI3. All the above features lead to a bright future of CaMnO3 film, which can be a promising candidate as a buffer layer for hybrid halide perovskite photovoltaic-thermoelectric systems

  6. Calcium manganate: A promising candidate as buffer layer for hybrid halide perovskite photovoltaic-thermoelectric systems

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Pengjun; Wang, Hongguang; Kong, Wenwen [Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi 830011 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xu, Jinbao, E-mail: xujb@ms.xjb.ac.cn; Wang, Lei; Ren, Wei; Bian, Liang; Chang, Aimin [Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi 830011 (China)

    2014-11-21

    We have systematically studied the feasibility of CaMnO{sub 3} thin film, an n-type perovskite, to be utilized as the buffer layer for hybrid halide perovskite photovoltaic-thermoelectric device. Locations of the conduction band and the valence band, spontaneous polarization performance, and optical properties were investigated. Results indicate the energy band of CaMnO{sub 3} can match up well with that of CH{sub 3}NH{sub 3}PbI{sub 3} on separating electron-hole pairs. In addition, the consistent polarization angle helps enlarge the open circuit voltage of the composite system. Besides, CaMnO{sub 3} film shows large absorption coefficient and low extinction coefficient under visible irradiation, demonstrating high carrier concentration, which is beneficial to the current density. More importantly, benign thermoelectric properties enable CaMnO{sub 3} film to assimilate phonon vibration from CH{sub 3}NH3PbI{sub 3}. All the above features lead to a bright future of CaMnO{sub 3} film, which can be a promising candidate as a buffer layer for hybrid halide perovskite photovoltaic-thermoelectric systems.

  7. Effect of the calcium halides, CaCl{sub 2} and CaBr{sub 2}, on hydrogen desorption in the Li–Mg–N–H system

    Energy Technology Data Exchange (ETDEWEB)

    Bill, Rachel F. [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Reed, Daniel; Book, David [School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Anderson, Paul A., E-mail: p.a.anderson@bham.ac.uk [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

    2015-10-05

    Highlights: • H{sub 2} desorption from 2LiNH{sub 2}–MgH{sub 2}–xCaX{sub 2} (x = 0, 0.1, 0.15; X = Cl, Br) samples studied. • Addition of calcium halides reduced the desorption temperature in all samples. • Peak H{sub 2} release was around 150 °C lower in ball-milled than in hand-ground samples. • The 2LiNH{sub 2}–MgH{sub 2}–0.15CaBr{sub 2} sample showed the lowest peak desorption temperature. • CaBr{sub 2} reduced the activation energy to 78.8 kJ mol{sup −1}, 24% less than the undoped sample. - Abstract: Calcium-halide-doped lithium amide–magnesium hydride samples were prepared both by hand-grinding and ball-milling 2LiNH{sub 2}–MgH{sub 2}–xCaX{sub 2} (x = 0, 0.1, and 0.15; X = Cl or Br). The addition of calcium halides reduced the hydrogen desorption temperature in all samples. The ball-milled undoped sample (2LiNH{sub 2}–MgH{sub 2}) began to desorb hydrogen at around 125 °C and peaked at 170 °C. Hydrogen desorption from the 0.15 mol CaCl{sub 2}-containing sample began ca 30 °C lower than that of the undoped sample and peaked at 150 °C. Both the onset and peak temperatures of the CaBr{sub 2} sample (x = 0.15) were reduced by 15 °C compared to the chloride. Kissinger’s method was used to calculate the effective activation energy (E{sub a}) for the systems: E{sub a} for the 0.15 mol CaCl{sub 2}-containing sample was found to be 91.8 kJ mol{sup −1} and the value for the 0.15 mol CaBr{sub 2}-containing sample was 78.8 kJ mol{sup −1}.

  8. The Silver Halides

    Science.gov (United States)

    Sahyun, M. R. V.

    1977-01-01

    Illustrates the type of fractional bonding for solid silver halides. Treats the silver halides as electron excess compounds, and develops a model of a localized bonding unit that may be iterated in three dimensions to describe the bulk phase. (MLH)

  9. Method for calcining nuclear waste solutions containing zirconium and halides

    Science.gov (United States)

    Newby, Billie J.

    1979-01-01

    A reduction in the quantity of gelatinous solids which are formed in aqueous zirconium-fluoride nuclear reprocessing waste solutions by calcium nitrate added to suppress halide volatility during calcination of the solution while further suppressing chloride volatility is achieved by increasing the aluminum to fluoride mole ratio in the waste solution prior to adding the calcium nitrate.

  10. Photofragmentation of metal halides

    International Nuclear Information System (INIS)

    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.)

  11. PREPARATION OF HALIDES OF PLUTONIUM

    Science.gov (United States)

    Garner, C.S.; Johns, I.B.

    1958-09-01

    A dry chemical method is described for preparing plutonium halides, which consists in contacting plutonyl nitrate with dry gaseous HCl or HF at an elevated temperature. The addition to the reaction gas of a small quantity of an oxidizing gas or a reducing gas will cause formation of the tetra- or tri-halide of plutonium as desired.

  12. METHOD OF PREPARING METAL HALIDES

    Science.gov (United States)

    Hendrickson, A.V.

    1958-11-18

    The conversion of plutonium halides from plutonium peroxide can be done by washing the peroxide with hydrogen peroxide, drying the peroxide, passing a dry gaseous hydrohalide over the surface of the peroxide at a temperature of about lOO icient laborato C until the reaction rate has stabillzed, and then ralsing the reaction temperature to between 400 and 600 icient laborato C until the conversion to plutonium halide is substantially complete.

  13. Radiochemical synthesis of pure anhydrous metal halides

    Science.gov (United States)

    Philipp, W. H.; Marsik, S. J.; May, C. E.

    1973-01-01

    Method uses radiation chemistry as practical tool for inorganic preparations and in particular deposition of metals by irradiation of their aqueous metal salt solutions with high energy electrons. Higher valence metal halide is dissolved in organic liquid and exposed to high energy electrons. This causes metal halide to be reduced to a lower valence metal halide.

  14. Preparation of cerium halide solvate complexes

    Science.gov (United States)

    Vasudevan, Kalyan V; Smith, Nickolaus A; Gordon, John C; McKigney, Edward A; Muenchaussen, Ross E

    2013-08-06

    Crystals of a solvated cerium(III) halide solvate complex resulted from a process of forming a paste of a cerium(III) halide in an ionic liquid, adding a solvent to the paste, removing any undissolved solid, and then cooling the liquid phase. Diffusing a solvent vapor into the liquid phase also resulted in crystals of a solvated cerium(III) halide complex.

  15. Saucy-Marbet Rearrangements of Alkynyl Halides in the Synthesis of Highly Enantiomerically Enriched Allenyl Halides

    OpenAIRE

    Tang, Yu; Shen, Lichun; Dellaria, Becky J.; Richard P. Hsung

    2008-01-01

    A stereospecific Saucy-Marbet rearrangement of alkynyl halides is described here. These rearrangements provide an entry to highly enantiomerically enriched allenyl bromides and chlorides through excellent chirality transfer and the reservation of optical integrity of alkynyl halides.

  16. 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.

  17. 40 CFR 721.4095 - Quaternary ammonium alkyltherpropyl trialkylamine halides.

    Science.gov (United States)

    2010-07-01

    ... trialkylamine halides. 721.4095 Section 721.4095 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.4095 Quaternary ammonium alkyltherpropyl trialkylamine halides. (a... generically as quaternary ammonium alkyltherpropyl trialkylamine halides (PMNs...

  18. Halogen versus halide electronic structure

    Institute of Scientific and Technical Information of China (English)

    Willem-Jan; van; Zeist; F.Matthias; Bickelhaupt

    2010-01-01

    Halide anions X-are known to show a decreasing proton affinity(PA),as X descends in the periodic table along series F,Cl,Br and I.But it is also well-known that,along this series,the halogen atom X becomes less electronegative(or more electropositive).This corresponds to an increasing energy of the valence np atomic orbital(AO) which,somewhat contradictorily,suggests that the electron donor capability and thus the PA of the halides should increase along the series F,Cl,Br,I.To reconcile these contradictory observations,we have carried out a detailed theoretical analysis of the electronic structure and bonding capability of the halide anions X-as well as the halogen radicals X-,using the molecular orbital(MO) models contained in Kohn-Sham density functional theory(DFT,at SAOP/TZ2P as well as OLYP/TZ2P levels) and ab initio theory(at the HF/TZ2P level).We also resolve an apparent intrinsic contradiction in Hartree-Fock theory between orbital-energy and PA trends.The results of our analyses are of direct relevance for understanding elementary organic reactions such as nucleophilic substitution(SN2) and base-induced elimination(E2) reactions.

  19. Cohesive Energy-Lattice Constant and Bulk Modulus-Lattice Constant Relationships: Alkali Halides, Ag Halides, Tl Halides

    Science.gov (United States)

    Schlosser, Herbert

    1992-01-01

    In this note we present two expressions relating the cohesive energy, E(sub coh), and the zero pressure isothermal bulk modulus, B(sub 0), of the alkali halides. Ag halides and TI halides, with the nearest neighbor distances, d(sub nn). First, we show that the product E(sub coh)d(sub 0) within families of halide crystals with common crystal structure is to a good approximation constant, with maximum rms deviation of plus or minus 2%. Secondly, we demonstrate that within families of halide crystals with a common cation and common crystal structure the product B(sub 0)d(sup 3.5)(sub nn) is a good approximation constant, with maximum rms deviation of plus or minus 1.36%.

  20. PREPARATION OF ALKYL HALIDES VIA ORGANOTELLURIUMS

    OpenAIRE

    チカマツ, キヨフミ; オオツボ, テツオ; オグラ, フミオ; ヤマグチ, ハチロウ; Kiyofumi, CHIKAMATSU; Tetsuo, OTSUBO; Fumio, OGURA; Hachiro, YAMAGUCHI

    1982-01-01

    The conversion of phenyltelluroalkanes to haloalkanes was studied in connection with the homologation of alkyl halides. Similar reactions of 1,1-bis(phenyltelluro)alkanes provided a new synthetic method of aldehydes.

  1. Toxicity of organometal halide perovskite solar cells

    Science.gov (United States)

    Babayigit, Aslihan; Ethirajan, Anitha; Muller, Marc; Conings, Bert

    2016-03-01

    In the last few years, the advent of metal halide perovskite solar cells has revolutionized the prospects of next-generation photovoltaics. As this technology is maturing at an exceptional rate, research on its environmental impact is becoming increasingly relevant.

  2. Copper Catalyzed Oceanic Methyl Halide Production

    OpenAIRE

    Robin Kim, Jae Yun; Rhew, Robert

    2014-01-01

    Methyl halides are found in all of Earth’s biomes, produced naturally or through manmade means. Their presence in the atmosphere is problematic, as they catalyze depletion of stratospheric ozone. To understand the full environmental impact of these compounds, it is important to identify their chemical cycling processes. Iron increases methyl halide production in soils and oceans, yet copper’s influence remains unknown despite its similar chemical oxidation properties to iron. I experimentally...

  3. Method for recovering hydrocarbons from molten metal halides

    Science.gov (United States)

    Pell, Melvyn B.

    1979-01-01

    In a process for hydrocracking heavy carbonaceous materials by contacting such carbonaceous materials with hydrogen in the presence of a molten metal halide catalyst to produce hydrocarbons having lower molecular weights and thereafter recovering the hydrocarbons so produced from the molten metal halide, an improvement comprising injecting into the spent molten metal halide, a liquid low-boiling hydrocarbon stream is disclosed.

  4. 40 CFR 721.575 - Substituted alkyl halide.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted alkyl halide. 721.575... Substances § 721.575 Substituted alkyl halide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as substituted alkyl halide (PMN P-83-1222)...

  5. Harmonic dynamical behaviour of thallous halides

    Indian Academy of Sciences (India)

    Sarvesh K Tiwari; L J Shukla; K S Upadhyaya

    2010-05-01

    Harmonic dynamical behaviour of thallous halides (TlCl and TlBr) have been studied using the new van der Waals three-body force shell model (VTSM), which incorporates the effects of the van der Waals interaction along with long-range Coulomb interactions, three-body interactions and short-range second neighbour interactions in the framework of rigid shell model (RSM). Phonon dispersion curves (PDC), variations of Debye temperature with absolute temperature and phonon density of state (PDS) curves have been reported for thallous halides using VTSM. Comparison of experimental values with those of VTSM and TSM are also reported in the paper and a good agreement between experimental and VTSM values has been found, from which it may be inferred that the incorporation of van der Waals interactions is essential for the complete harmonic dynamical behaviour of thallous halides.

  6. Computational screening of mixed metal halide ammines

    DEFF Research Database (Denmark)

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

    . In this project we are searching for improved mixed materials with optimal desorption temperatures and kinetics, optimally releasing all ammonia in one step. We apply Density Functional Theory, DFT, calculations on mixed compounds selected by a Genetic Algorithm (GA), relying on biological principles of natural......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...

  7. Calcium - urine

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/003603.htm Calcium - urine To use the sharing features on this ... enable JavaScript. This test measures the amount of calcium in urine. All cells need calcium in order ...

  8. Calcium supplements

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/007477.htm Calcium supplements To use the sharing features on this page, please enable JavaScript. WHO SHOULD TAKE CALCIUM SUPPLEMENTS? Calcium is an important mineral for the ...

  9. Incidental Polymorphism, Non-Isomorphic and Isomorphic Substitution in Calcium-Valine Coordination Polymers

    OpenAIRE

    Kevin Lamberts; Ulli Englert

    2015-01-01

    Five coordination polymers with the stoichiometry CaX2(valine)2(H2O)2 (X = Cl, Br) were obtained from the corresponding calcium halides and either racemic and enantiopure valine. In all cases the zwitterionic amino acid is exclusively O coordinated and the halides act as counteranions for the resulting one-dimensional cationic chains. The enantiopure chloride shows dimorphism; both forms differ in connectivity from the bromide. In contrast to this structural variability for L-valine, the deri...

  10. The Additive Coloration of Alkali Halides

    Science.gov (United States)

    Jirgal, G. H.; and others

    1969-01-01

    Describes the construction and use of an inexpensive, vacuum furnace designed to produce F-centers in alkali halide crystals by additive coloration. The method described avoids corrosion or contamination during the coloration process. Examination of the resultant crystals is discussed and several experiments using additively colored crystals are…

  11. Infrared spectra of FHF - in alkali halides

    Science.gov (United States)

    Chunnilall, C. J.; Sherman, W. F.

    1982-03-01

    The bifluoride ion, FHF -, has been substitutionally isolated within single crystal samples of several different alkali halides. Infrared spectra of these crystals have been studied for sample temperatures down to 8K when half-bandwidths of less than 1 cm -1 have been observed. (Note that at room temperature ν 3 is observed to have a half-bandwidth of about 40 cm -1). The frequency shifts and half-bandwidth changes caused by cooling are considered together with the frequency shifts caused by pressures up to 10 k bar. The low temperature spectra clearly indicate that FHF - is a linear symmetrical ion when substitutionally isolated within alkali halides of either the NaCl or CsCl structure.

  12. Lanthanide-halide based humidity indicators

    Science.gov (United States)

    Beitz, James V.; Williams, Clayton W.

    2008-01-01

    The present invention discloses a lanthanide-halide based humidity indicator and method of producing such indicator. The color of the present invention indicates the humidity of an atmosphere to which it is exposed. For example, impregnating an adsorbent support such as silica gel with an aqueous solution of the europium-containing reagent solution described herein, and dehydrating the support to dryness forms a substance with a yellow color. When this substance is exposed to a humid atmosphere the water vapor from the air is adsorbed into the coating on the pore surface of the silica gel. As the water content of the coating increases, the visual color of the coated silica gel changes from yellow to white. The color change is due to the water combining with the lanthanide-halide complex on the pores of the gel.

  13. Process and composition for drying of gaseous hydrogen halides

    Science.gov (United States)

    Tom, Glenn M.; Brown, Duncan W.

    1989-08-01

    A process for drying a gaseous hydrogen halide of the formula HX, wherein X is selected from the group consisting of bromine, chlorine, fluorine, and iodine, to remove water impurity therefrom, comprising: contacting the water impurity-containing gaseous hydrogen halide with a scavenger including a support having associated therewith one or more members of the group consisting of: (a) an active scavenging moiety selected from one or more members of the group consisting of: (i) metal halide compounds dispersed in the support, of the formula MX.sub.y ; and (ii) metal halide pendant functional groups of the formula -MX.sub.y-1 covalently bonded to the support, wherein M is a y-valent metal, and y is an integer whose value is from 1 to 3; (b) corresponding partially or fully alkylated compounds and/or pendant functional groups, of the metal halide compounds and/or pendant functional groups of (a); wherein the alkylated compounds and/or pendant functional groups, when present, are reactive with the gaseous hydrogen halide to form the corresponding halide compounds and/or pendant functional groups of (a); and M being selected such that the heat of formation, .DELTA.H.sub.f of its hydrated halide, MX.sub.y.(H.sub.2 O).sub.n, is governed by the relationship: .DELTA.H.sub.f .gtoreq.n.times.10.1 kilocalories/mole of such hydrated halide compound wherein n is the number of water molecules bound to the metal halide in the metal halide hydrate. Also disclosed is an appertaining scavenger composition and a contacting apparatus wherein the scavenger is deployed in a bed for contacting with the water impurity-containing gaseous hydrogen halide.

  14. Iridium-catalyzed intramolecular [4 + 2] cycloadditions of alkynyl halides

    OpenAIRE

    Andrew Tigchelaar; William Tam

    2012-01-01

    Iridium-catalyzed intramolecular [4 + 2] cycloadditions of diene-tethered alkynyl halides were investigated by using [IrCl(cod)]2 as catalyst, and dppe was found to be the most suitable phosphine ligand for the reaction. No oxidative insertion of the iridium into the carbon–halide bond was observed, and the reactions proceeded to provide the halogenated cycloadducts in good yield (75–94%). These results are the first examples of cycloadditions of alkynyl halides using an iridium c...

  15. Lanthanide doped strontium-barium cesium halide scintillators

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Mechanism and Selectivity in Nickel-Catalyzed Cross-Electrophile Coupling of Aryl Halides with Alkyl Halides

    OpenAIRE

    Biswas, Soumik; Weix, Daniel J.

    2013-01-01

    The direct cross-coupling of two different electrophiles, such as an aryl halide with an alkyl halide, offers many advantages over conventional cross-coupling methods that require a carbon nucleophile. Despite its promise as a versatile synthetic strategy, a limited understanding of the mechanism and origin of cross selectivity has hindered progress in reaction development and design. Herein, we shed light on the mechanism for the nickel-catalyzed cross-electrophile coupling of aryl halides w...

  17. 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

  18. Making and Breaking of Lead Halide Perovskites.

    Science.gov (United States)

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

    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. Efficient destruction of CF4 through in situ generation of alkali metals from heated alkali halide reducing mixtures.

    Science.gov (United States)

    Lee, Myung Churl; Choi, Wonyong

    2002-03-15

    Perfluorocarbons (PFCs) are the most potent green house gases that are very recalcitrant at destruction. An effective way of converting PFCs using hot solid reagents into safe products has been recently introduced. By investigating the thermal reductive destruction of tetrafluoromethane (CF4) we provided new insight and more physicochemical consideration on this novel process. The complete destruction of CF4was successfully achieved by flowing the gas through a heated reagent bed (400-950 degrees C) that contained powder mixtures of alkali halides, CaO, and Si. The silicon acted as a reducing agent of alkali halides for the in-situ production of alkali metals, and the calcium oxide played the role of a halide ion acceptor. The absence of any single component in this ternary mixture drastically reduced the destruction efficiency of CF4. The CF4 destruction efficiencies with the solid reagent containing the alkali halide, MX, increased in the order of Li approximately Na < K < Cs for alkali cations and I < Br < Cl < F for halide anions. This trend agreed with the endothermicity of the alkali metal generation reaction: the higher the endothermicity, the lower the destruction efficiency. Alkali metal generation was indirectly detected by monitoring H2 production from its reaction with water. The production of alkali metals increased with NaF, KF, and CsF in this order. The CsF/CaO/Si system exhibited the complete destruction of CF4 at as low as 600 degrees C. The solid product analysis by X-ray diffraction (XRD) showed the formation of CaF2 and the depletion of Si with black carbon particles formed in the solid reagent residue. No CO/CO2 and toxic HF and SiF4 formation were detected in the exhaust gas. PMID:11944694

  20. [Emissions of methyl halides from coastal salt marshes: A review].

    Science.gov (United States)

    Xie, Wen-xia; Zhao, Quan-sheng; Cui, Yu-qian; Du, Hui-na; Ye, Si-yuan

    2015-11-01

    Methyl halides are the major carrier of halogens in the atmosphere, and they play an important role in tropospheric and stratospheric ozone depletion. Meanwhile, methyl halides can act as greenhouse gases in the atmosphere, and they are also environmentally significant because of their toxicity. Coastal salt marshes, the important intertidal ecosystems at the land-ocean interface, have been considered to be a large potential natural source of methyl halides. In this paper, the research status of the natural source or sink of methyl halides, the mechanisms of their emission from coastal salt marshes and affecting factors were summarized. In view of this, the following research fields need to be strengthened in the future: 1) Long time-scale and large region-range researches about the emission of methyl halides and the evaluation of their source and sink function, 2) Accurate quantification of contribution rates of different plant species and various biological types to fluxes of methyl halides, 3) Further researches on effects of the tidal fluctuation process and flooding duration on methyl halides emission, 4) Effects of the global change and human activities on methyl halides emission. PMID:26915215

  1. How specific halide adsorption varies hydrophobic interactions.

    Science.gov (United States)

    Stock, Philipp; Müller, Melanie; Utzig, Thomas; Valtiner, Markus

    2016-03-11

    Hydrophobic interactions (HI) are driven by the water structure around hydrophobes in aqueous electrolytes. How water structures at hydrophobic interfaces and how this influences the HI was subject to numerous studies. However, the effect of specific ion adsorption on HI and hydrophobic interfaces remains largely unexplored or controversial. Here, the authors utilized atomic force microscopy force spectroscopy at well-defined nanoscopic hydrophobic interfaces to experimentally address how specific ion adsorption of halide ions as well as NH4 (+), Cs(+), and Na(+) cations alters interaction forces across hydrophobic interfaces. Our data demonstrate that iodide adsorption at hydrophobic interfaces profoundly varies the hydrophobic interaction potential. A long-range and strong hydration repulsion at distances D > 3 nm, is followed by an instability which could be explained by a subsequent rapid ejection of adsorbed iodides from approaching hydrophobic interfaces. In addition, the authors find only a weakly pronounced influence of bromide, and as expected no influence of chloride. Also, all tested cations do not have any significant influence on HI. Complementary, x-ray photoelectron spectroscopy and quartz-crystal-microbalance with dissipation monitoring showed a clear adsorption of large halide ions (Br(-)/I(-)) onto hydrophobic self-assembled monolayers (SAMs). Interestingly, iodide can even lead to a full disintegration of SAMs due to specific and strong interactions of iodide with gold. Our data suggest that hydrophobic surfaces are not intrinsically charged negatively by hydroxide adsorption, as it was generally believed. Hydrophobic surfaces rather interact strongly with negatively charged large halide ions, leading to a surface charging and significant variation of interaction forces.

  2. Research Update: Luminescence in lead halide perovskites

    Science.gov (United States)

    Srimath Kandada, Ajay Ram; Petrozza, Annamaria

    2016-09-01

    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.

  3. Ultraviolet absorption spectra of mercuric halides.

    Science.gov (United States)

    Templet, P.; Mcdonald, J. R.; Mcglynn, S. P.; Kendrow, C. H.; Roebber, J. L.; Weiss, K.

    1972-01-01

    The gas phase transitions of the mercuric halides were observed in the UV region by operating at temperatures above 400 K and at vapor pressures on the order of 0.5 mm. Spectral features exhibited by the chloride, bromide, and iodide of mercury correlate energetically with bands previously designated as intermolecular charge transfer transitions. The solution spectra of mercuric iodide and deep color of the crystals (if not due to some solid state interactions) indicate that this molecule may also have longer wavelength transitions.

  4. Elastic Properties of Potassium Halides under Pressure

    Institute of Scientific and Technical Information of China (English)

    K.Haddadi; L.Louail; D.Maouche

    2008-01-01

    The moderate-pressure elastic properties of potassium halides KX (X=F, CI, Br) was studied theoretically using the density functional theory (DFT) with normconserving pseudopotentials method. The phase transfor- mation from the B1 phase (NaCl-type structure) to the denser B2 phase (CsCl-type structure) occurred at 7.7, 3.46 and 2.96 GPa for KF, KCl and KBr, respectively. The elastic stiffness coefficients and bulk modulus of these materials were calculated as function of hydrostatic pressure and compared with both the experimental and theoretical values.

  5. Studies of rare gas halide lasers

    OpenAIRE

    Hogan, Daniel Christopher.; Webb, Colin E.; Dr. C. E. Webb

    1983-01-01

    This thesis presents the results of a study of the mechanisms responsible for limiting the laser pulse duration obtainable in xenon chloride lasers which are excited by UV-preionized, self-sustained gas discharges. The xenon chloride laser system, the principal emission band of which is centred around 308 nm, belongs to the class of high pressure gas lasers known as 'rare-gas halides'(RGH). RGH lasers are now well known for their high peak power output at a number of wavelen...

  6. Computational Screening of Mixed Metal Halide Ammines

    DEFF Research Database (Denmark)

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

    selected by a Genetic Algorithm (GA), relying on biological principles of natural selection. The GA is evolving from an initial (random) population and selecting those with highest fitness, e.g. stability, release temperature and storage capacity. The search space includes all alkaline, alkaline earth, 3d......Metal halide ammines, e.g. Mg(NH3)6Cl2 and Sr(NH3)8Cl2, can reversibly store ammonia, with high volumetric hydrogen storage capacities. In this project we are searching for improved mixed materials with optimal desorption temperature and kinetics. We apply DFT calculations on mixed compounds...

  7. 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.

  8. 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.

  9. Alkali metal and alkali earth metal gadolinium halide scintillators

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. Halide-Substituted Electronic Properties of Organometal Halide Perovskite Films: Direct and Inverse Photoemission Studies.

    Science.gov (United States)

    Li, Chi; Wei, Jian; Sato, Mikio; Koike, Harunobu; Xie, Zhong-Zhi; Li, Yan-Qing; Kanai, Kaname; Kera, Satoshi; Ueno, Nobuo; Tang, Jian-Xin

    2016-05-11

    Solution-processed perovskite solar cells are attracting increasing interest due to their potential in next-generation hybrid photovoltaic devices. Despite the morphological control over the perovskite films, quantitative information on electronic structures and interface energetics is of paramount importance to the optimal photovoltaic performance. Here, direct and inverse photoemission spectroscopies are used to determine the electronic structures and chemical compositions of various methylammonium lead halide perovskite films (MAPbX3, X = Cl, Br, and I), revealing the strong influence of halide substitution on the electronic properties of perovskite films. Precise control over halide compositions in MAPbX3 films causes the manipulation of the electronic properties, with a qualitatively blue shift along the I → Br → Cl series and showing the increase in ionization potentials from 5.96 to 7.04 eV and the change of transport band gaps in the range from 1.70 to 3.09 eV. The resulting light absorption of MAPbX3 films can cover the entire visible region from 420 to 800 nm. The results presented here provide a quantitative guide for the analysis of perovskite-based solar cell performance and the selection of optimal carrier-extraction materials for photogenerated electrons and holes. PMID:27101940

  11. Metal halide perovskites for energy applications

    Science.gov (United States)

    Zhang, Wei; Eperon, Giles E.; Snaith, Henry J.

    2016-06-01

    Exploring prospective materials for energy production and storage is one of the biggest challenges of this century. Solar energy is one of the most important renewable energy resources, due to its wide availability and low environmental impact. Metal halide perovskites have emerged as a class of semiconductor materials with unique properties, including tunable bandgap, high absorption coefficient, broad absorption spectrum, high charge carrier mobility and long charge diffusion lengths, which enable a broad range of photovoltaic and optoelectronic applications. Since the first embodiment of perovskite solar cells showing a power conversion efficiency of 3.8%, the device performance has been boosted up to a certified 22.1% within a few years. In this Perspective, we discuss differing forms of perovskite materials produced via various deposition procedures. We focus on their energy-related applications and discuss current challenges and possible solutions, with the aim of stimulating potential new applications.

  12. Calcium Carbonate

    Science.gov (United States)

    ... before being swallowed; do not swallow them whole. Drink a full glass of water after taking either the regular or chewable tablets or capsules. Some liquid forms of calcium carbonate must be shaken well before use.Do not ...

  13. Calcium Calculator

    Science.gov (United States)

    ... Latvia - Lebanon - Libya - Lithuania - Luxembourg - Macedonia, Republic of - Malaysia - Malta - Mexico - Moldova - Morocco - Netherlands - New Zealand - Nigeria - ... and Statistics Popular content Calcium content of common foods What is Osteoporosis? The Board Introduction to Bone ...

  14. Calcium Electroporation

    DEFF Research Database (Denmark)

    Frandsen, Stine Krog; Gibot, Laure; Madi, Moinecha;

    2015-01-01

    BACKGROUND: Calcium electroporation describes the use of high voltage electric pulses to introduce supraphysiological calcium concentrations into cells. This promising method is currently in clinical trial as an anti-cancer treatment. One very important issue is the relation between tumor cell kill...... efficacy-and normal cell sensitivity. METHODS: Using a 3D spheroid cell culture model we have tested the effect of calcium electroporation and electrochemotherapy using bleomycin on three different human cancer cell lines: a colorectal adenocarcinoma (HT29), a bladder transitional cell carcinoma (SW780......), and a breast adenocarcinoma (MDA-MB231), as well as on primary normal human dermal fibroblasts (HDF-n). RESULTS: The results showed a clear reduction in spheroid size in all three cancer cell spheroids three days after treatment with respectively calcium electroporation (p

  15. Silver-catalyzed coupling reactions of alkyl halides with indenyllithiums

    OpenAIRE

    Someya, Hidenori; Yorimitsu, Hideki; Oshima, Koichiro

    2010-01-01

    Coupling reactions of tertiary and secondary alkyl halides with indenyllithiums proceeded effectively in the presence of a catalytic amount of silver bromide to provide tertiary- and secondary-alkyl-substituted indene derivatives in good yields.

  16. Novel Silver Cobaltacarborane Complexes with a Linearly Bridging Halide

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hyun Seo; Bae, Hye Jin; Do, Youngkyu [KAIST, Daejeon (Korea, Republic of); Park, Youngwhan [LG Chem/Research Park, Daejeon (Korea, Republic of); Go, Min Jeong; Lee, Junseong [Chonnam National Univ., Gwangju (Korea, Republic of)

    2013-10-15

    The structural versatility of halides mainly originates from their coordinating abilities of adopting a bridging bond between two or more metal atoms, as well as a terminal bond. Moreover, a halide bridging bond angle is so flexible that thermodynamic stability can be endowed with proper geometry, which conceptually varies from acute to right, obtuse, and linear. In spite of innumerable reports on molecular metal halides, examples of the linearly bridging fashion are very scarce. The reason for the rarity of the linear M. X. M arrangement can be easily explained by the VSEPR (Valence Shell Electron Pair Repulsion) concept. The linear M. X. M formation has only been achieved by adopting a macrocyclic chelate ligand, which is structurally demanding, so that the VSEPR repulsions among lone-pair electrons on the halide atom could be overcome.

  17. Radiative properties of ceramic metal-halide high intensity discharge lamps containing additives in argon plasma

    Science.gov (United States)

    Cressault, Yann; Teulet, Philippe; Zissis, Georges

    2016-07-01

    The lighting represents a consumption of about 19% of the world electricity production. We are thus searching new effective and environment-friendlier light sources. The ceramic metal-halide high intensity lamps (C-MHL) are one of the options for illuminating very high area. The new C-MHL lamps contain additives species that reduce mercury inside and lead to a richer spectrum in specific spectral intervals, a better colour temperature or colour rendering index. This work is particularly focused on the power radiated by these lamps, estimated using the net emission coefficient, and depending on several additives (calcium, sodium, tungsten, dysprosium, and thallium or strontium iodides). The results show the strong influence of the additives on the power radiated despite of their small quantity in the mixtures and the increase of visible radiation portion in presence of dysprosium.

  18. Theory of the late stage of radiolysis of alkali halides

    OpenAIRE

    Dubinko, V. I.; Turkin, A.A.; Vainshtein, D.I.; Hartog, H.W. den

    2000-01-01

    Recent results on heavily irradiated natural and synthetic NaCl crystals give evidence for the formation of large vacancy voids, which were not addressed by the conventional Jain-Lidiard model of radiation damage ill alkali halides. This model was constructed to describe metal colloids and dislocation loops formed in alkali halides during earlier stages of irradiation. We present a theory based on a new mechanism of dislocation climb, which involves the production of Vt centers (self-trapped ...

  19. Observation of color center peaks in calcium fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, T. [LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, AZ 85287-1704, USA (United States); Garvie, L.A.J. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404 (United States); Rez, P., E-mail: Peter.Rez@asu.edu [Department of Physics, Arizona State University, Tempe, AZ 85287-1504 (United States)

    2015-06-15

    Alkali halides such as calcium fluoride all have color center defects that absorb light in the visible region. Using a moncochromator equipped, aberration corrected, scanning transmission electron microscope (STEM) we recorded spectra showing the time evolution of the generation of F and H centers in calcium fluoride. The final stage of electron beam irradiation is the formation of metallic calcium nanoparticles. High resolution low loss spectra for the Vacuum Ultraviolet region were also recorded. - Highlights: • Color center defects clearly identified by high resolution EELS of CaF{sub 2}. • Both F Centers and H Centers produced by electron beam irradiation. • Ultimately metallic calcium is left as evidenced by plasmon and density of states. • High resolution low loss (VUV) spectra also recorded.

  20. Observation of color center peaks in calcium fluoride

    International Nuclear Information System (INIS)

    Alkali halides such as calcium fluoride all have color center defects that absorb light in the visible region. Using a moncochromator equipped, aberration corrected, scanning transmission electron microscope (STEM) we recorded spectra showing the time evolution of the generation of F and H centers in calcium fluoride. The final stage of electron beam irradiation is the formation of metallic calcium nanoparticles. High resolution low loss spectra for the Vacuum Ultraviolet region were also recorded. - Highlights: • Color center defects clearly identified by high resolution EELS of CaF2. • Both F Centers and H Centers produced by electron beam irradiation. • Ultimately metallic calcium is left as evidenced by plasmon and density of states. • High resolution low loss (VUV) spectra also recorded

  1. Synthesis of methyl halides from biomass using engineered microbes.

    Science.gov (United States)

    Bayer, Travis S; Widmaier, Daniel M; Temme, Karsten; Mirsky, Ethan A; Santi, Daniel V; Voigt, Christopher A

    2009-05-13

    Methyl halides are used as agricultural fumigants and are precursor molecules that can be catalytically converted to chemicals and fuels. Plants and microorganisms naturally produce methyl halides, but these organisms produce very low yields or are not amenable to industrial production. A single methyl halide transferase (MHT) enzyme transfers the methyl group from the ubiquitous metabolite S-adenoyl methionine (SAM) to a halide ion. Using a synthetic metagenomic approach, we chemically synthesized all 89 putative MHT genes from plants, fungi, bacteria, and unidentified organisms present in the NCBI sequence database. The set was screened in Escherichia coli to identify the rates of CH(3)Cl, CH(3)Br, and CH(3)I production, with 56% of the library active on chloride, 85% on bromide, and 69% on iodide. Expression of the highest activity MHT and subsequent engineering in Saccharomyces cerevisiae results in productivity of 190 mg/L-h from glucose and sucrose. Using a symbiotic co-culture of the engineered yeast and the cellulolytic bacterium Actinotalea fermentans, we are able to achieve methyl halide production from unprocessed switchgrass (Panicum virgatum), corn stover, sugar cane bagasse, and poplar (Populus sp.). These results demonstrate the potential of producing methyl halides from non-food agricultural resources.

  2. Incidental Polymorphism, Non-Isomorphic and Isomorphic Substitution in Calcium-Valine Coordination Polymers

    Directory of Open Access Journals (Sweden)

    Kevin Lamberts

    2015-05-01

    Full Text Available Five coordination polymers with the stoichiometry CaX2(valine2(H2O2 (X = Cl, Br were obtained from the corresponding calcium halides and either racemic and enantiopure valine. In all cases the zwitterionic amino acid is exclusively O coordinated and the halides act as counteranions for the resulting one-dimensional cationic chains. The enantiopure chloride shows dimorphism; both forms differ in connectivity from the bromide. In contrast to this structural variability for L-valine, the derivatives of the racemic amino acid are isomorphous.

  3. Seasonal variations in halides in marine brown algae from Porbandar and Okha coasts (NW coast of India)

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, Ch.K.; Singbal, S.Y.S.

    percentage of enrichment factor) of halides shows that the tissue concentration of each halide was independent of other halides accumulation. The extent of bioaccumulation could be related to intrinsic property such as x space (spectroscopic electronegativity...

  4. Color silver halide hologram production and mastering

    Science.gov (United States)

    Bjelkhagen, Hans I.; Huang, Qiang

    1997-04-01

    Color reflection holograms recorded with the Denisyuk geometry have been demonstrated by the recently formed HOLOS Corporation in New Hampshire. The Slavich red-green-blue (RGB) sensitized ultra-high resolution silver halide emulsion was used for the hologram recording. The employed laser wavelengths were 647 nm, 532 nm, and 476 nm, generated by an argon ion, a frequency doubled Nd:YAG, and a krypton ion laser, respectively. A beam combination mechanism with dichroic filters enabled a simultaneous RGB exposure, which made the color balance and overall exposure energy easy to control as well as simplifying the recording procedure. HOLOS has been producing limited edition color holograms in various sizes from 4' X 5' to 12' X 16'. A 30 foot long optical table and high power lasers will enable HOLOS to record color holograms up to the size of one meter square in the near future. Various approaches have been investigated in generating color hologram masters which have sufficiently high diffraction efficiency to contact copy the color images onto photopolymer materials. A specially designed test object including the 1931 CIE chromaticity diagram, a rainbow ribbon cable, pure yellow dots, and a cloisonne elephant was used for color recording experiments. In addition, the Macbeth Color Checker chart was used. Both colorimetric evaluation and scattering noise measurements were performed using the PR-650 Photo Research SpectraScan SpectraCalorimeter.

  5. Calcium and bones

    Science.gov (United States)

    Bone strength and calcium ... calcium (as well as phosphorus) to make healthy bones. Bones are the main storage site of calcium in ... your body does not absorb enough calcium, your bones can get weak or will not grow properly. ...

  6. Calcium carbonate overdose

    Science.gov (United States)

    Tums overdose; Calcium overdose ... Calcium carbonate can be dangerous in large amounts. ... Some products that contain calcium carbonate are certain: ... and mineral supplements Other products may also contain calcium ...

  7. Get Enough Calcium

    Science.gov (United States)

    ... Calcium Print This Topic En español Get Enough Calcium Browse Sections The Basics Overview Foods and Vitamins ... 2 of 4 sections Take Action! Take Action: Calcium Sources Protect your bones – get plenty of calcium ...

  8. Halide Perovskites: Poor Man's High-Performance Semiconductors.

    Science.gov (United States)

    Stoumpos, Constantinos C; Kanatzidis, Mercouri G

    2016-07-01

    Halide perovskites are a rapidly developing class of medium-bandgap semiconductors which, to date, have been popularized on account of their remarkable success in solid-state heterojunction solar cells raising the photovoltaic efficiency to 20% within the last 5 years. As the physical properties of the materials are being explored, it is becoming apparent that the photovoltaic performance of the halide perovskites is just but one aspect of the wealth of opportunities that these compounds offer as high-performance semiconductors. From unique optical and electrical properties stemming from their characteristic electronic structure to highly efficient real-life technological applications, halide perovskites constitute a brand new class of materials with exotic properties awaiting discovery. The nature of halide perovskites from the materials' viewpoint is discussed here, enlisting the most important classes of the compounds and describing their most exciting properties. The topics covered focus on the optical and electrical properties highlighting some of the milestone achievements reported to date but also addressing controversies in the vastly expanding halide perovskite literature. PMID:27174223

  9. Halide Perovskites: Poor Man's High-Performance Semiconductors.

    Science.gov (United States)

    Stoumpos, Constantinos C; Kanatzidis, Mercouri G

    2016-07-01

    Halide perovskites are a rapidly developing class of medium-bandgap semiconductors which, to date, have been popularized on account of their remarkable success in solid-state heterojunction solar cells raising the photovoltaic efficiency to 20% within the last 5 years. As the physical properties of the materials are being explored, it is becoming apparent that the photovoltaic performance of the halide perovskites is just but one aspect of the wealth of opportunities that these compounds offer as high-performance semiconductors. From unique optical and electrical properties stemming from their characteristic electronic structure to highly efficient real-life technological applications, halide perovskites constitute a brand new class of materials with exotic properties awaiting discovery. The nature of halide perovskites from the materials' viewpoint is discussed here, enlisting the most important classes of the compounds and describing their most exciting properties. The topics covered focus on the optical and electrical properties highlighting some of the milestone achievements reported to date but also addressing controversies in the vastly expanding halide perovskite literature.

  10. Two Dimensional Organometal Halide Perovskite Nanorods with Tunable Optical Properties.

    Science.gov (United States)

    Aharon, Sigalit; Etgar, Lioz

    2016-05-11

    Organo-metal halide perovskite is an efficient light harvester in photovoltaic solar cells. Organometal halide perovskite is used mainly in its "bulk" form in the solar cell. Confined perovskite nanostructures could be a promising candidate for efficient optoelectronic devices, taking advantage of the superior bulk properties of organo-metal halide perovskite, as well as the nanoscale properties. In this paper, we present facile low-temperature synthesis of two-dimensional (2D) lead halide perovskite nanorods (NRs). These NRs show a shift to higher energies in the absorbance and in the photoluminescence compared to the bulk material, which supports their 2D structure. X-ray diffraction (XRD) analysis of the NRs demonstrates their 2D nature combined with the tetragonal 3D perovskite structure. In addition, by alternating the halide composition, we were able to tune the optical properties of the NRs. Fast Fourier transform, and electron diffraction show the tetragonal structure of these NRs. By varying the ligands ratio (e.g., octylammonium to oleic acid) in the synthesis, we were able to provide the formation mechanism of these novel 2D perovskite NRs. The 2D perovskite NRs are promising candidates for a variety of optoelectronic applications, such as light-emitting diodes, lasing, solar cells, and sensors. PMID:27089497

  11. 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. This is...

  12. 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.

  13. Calcium paradox and calcium entry blockers

    NARCIS (Netherlands)

    Ruigrok, T.J.C.; Slade, A.M.; Nayler, W.G.; Meijler, F.L.

    1984-01-01

    Reperfusion of isolated hearts with calcium-containing solution after a short period of calcium-free perfusion results in irreversible cell damage (calcium paradox). This phenomenon is characterized by an excessive influx of calcium into the cells, the rapid onset of myocardial contracture, exhausti

  14. Semiempirical and DFT Investigations of the Dissociation of Alkyl Halides

    Science.gov (United States)

    Waas, Jack R.

    2006-01-01

    Enthalpy changes corresponding to the gas phase heats of dissociation of 12 organic halides were calculated using two semiempirical methods, the Hartree-Fock method, and two DFT methods. These calculated values were compared to experimental values where possible. All five methods agreed generally with the expected empirically known trends in the…

  15. Kinetic Studies of the Solvolysis of Two Organic Halides

    Science.gov (United States)

    Duncan, J. A.; Pasto, D. J.

    1975-01-01

    Describes an undergraduate organic chemistry laboratory experiment which utilizes the solvolysis of organic halides to demonstrate first and second order reaction kinetics. The experiment also investigates the effect of a change of solvent polarity on reaction rate, common-ion and noncommon-ion salt effects, and the activation parameters of a…

  16. 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.…

  17. A new mechanism for radiation damage processes in alkali halides

    NARCIS (Netherlands)

    Dubinko, V.I.; Turkin, A.A.; Vainshtein, D.I.; Hartog, H.W. den

    1999-01-01

    We present a theory of radiation damage formation in alkali halides based on a new mechanism of dislocation climb, which involves the production of VF centers (self-trapped hole neighboring a cation vacancy) as a result of the absorption of H centers of dislocation lines. We consider the evolution o

  18. 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…

  19. Halide glass containing trivalent uranium ions and its fabrication process

    International Nuclear Information System (INIS)

    This halide glass, showing an optical attenuation -1 in the near infrared from 2.2 to 304 micrometers, is prepared with a glass containing uranium ions as U4+ and/or U5+ reduced by ionizing radiations in U3+. Application is made to the fabrication of optical fibers and lasers doped with trivalent uranium

  20. Theory of the late stage of radiolysis of alkali halides

    NARCIS (Netherlands)

    Dubinko, V.I.; Turkin, A.A.; Vainshtein, D.I.; Hartog, H.W. den

    2000-01-01

    Recent results on heavily irradiated natural and synthetic NaCl crystals give evidence for the formation of large vacancy voids, which were not addressed by the conventional Jain-Lidiard model of radiation damage ill alkali halides. This model was constructed to describe metal colloids and dislocati

  1. Iron-catalysed Negishi coupling of benzyl halides and phosphates.

    Science.gov (United States)

    Bedford, Robin B; Huwe, Michael; Wilkinson, Mark C

    2009-02-01

    Iron-based catalysts containing either 1,2-bis(diphenylphosphino)benzene or 1,3-bis(diphenylphosphino)propane give excellent activity and good selectivity in the Negishi coupling of aryl zinc reagents with a range of benzyl halides and phosphates.

  2. Calcium source (image)

    Science.gov (United States)

    Getting enough calcium to keep bones from thinning throughout a person's life may be made more difficult if that person has ... as a tendency toward kidney stones, for avoiding calcium-rich food sources. Calcium deficiency also effects the ...

  3. Calcium hydroxide poisoning

    Science.gov (United States)

    Hydrate - calcium; Lime milk; Slaked lime ... Calcium hydroxide ... These products contain calcium hydroxide: Cement Limewater Many industrial solvents and cleaners (hundreds to thousands of construction products, flooring strippers, brick cleaners, cement ...

  4. Calcium and bones (image)

    Science.gov (United States)

    Calcium is one of the most important minerals for the growth, maintenance, and reproduction of the human ... body, are continually being re-formed and incorporate calcium into their structure. Calcium is essential for the ...

  5. Coronary Calcium Scan

    Science.gov (United States)

    ... the NHLBI on Twitter. What Is a Coronary Calcium Scan? A coronary calcium scan is a test ... you have calcifications in your coronary arteries. Coronary Calcium Scan Figure A shows the position of the ...

  6. Calcium Pyrophosphate Deposition (CPPD)

    Science.gov (United States)

    ... Patient / Caregiver Diseases & Conditions Calcium Pyrophosphate Deposition (CPPD) Calcium Pyrophosphate Deposition (CPPD) Fast Facts The risk of ... young people, too. Proper diagnosis depends on detecting calcium pyrophosphate crystals in the fluid of an affected ...

  7. Matrix isolation infrared spectra of hydrogen halide and halogen complexes with nitrosyl halides

    Science.gov (United States)

    Allamandola, Louis J.; Lucas, Donald; Pimentel, George C.

    1982-01-01

    Matrix isolation infrared spectra of nitrosyl halide (XNO) complexes with HX and X2 (X = Cl, Br) are presented. The relative frequency shifts of the HX mode are modest (ClNO H-Cl, delta-nu/nu = -0.045; BrNO H-Br, delta-nu/nu = -0.026), indicating weak hydrogen bonds 1-3 kcal/mol. These shifts are accompanied by significant shifts to higher frequencies in the XN-O stretching mode (CIN-O HCl, delta-nu/nu = +0.016; BrN-O HBr, delta-nu/nu = +0.011). Similar shifts were observed for the XN-O X2 complexes (ClN-O Cl2, delta-nu/nu = +0.009; BrN-O-Br2, delta-nu/nu = +0.013). In all four complexes, the X-NO stretching mode relative shift is opposite in sign and about 1.6 times that of the NO stretching mode. These four complexes are considered to be similar in structure and charge distribution. The XN-O frequency shift suggests that complex formation is accompanied by charge withdrawal from the NO bond ranging from about .04 to .07 electron charges. The HX and X2 molecules act as electron acceptors, drawing electrons out of the antibonding orbital of NO and strengthening the XN-O bond. The implications of the pattern of vibrational shifts concerning the structure of the complexes are discussed.

  8. Electrolytic systems and methods for making metal halides and refining metals

    Energy Technology Data Exchange (ETDEWEB)

    Holland, Justin M.; Cecala, David M.

    2015-05-26

    Disclosed are electrochemical cells and methods for producing a halide of a non-alkali metal and for electrorefining the halide. The systems typically involve an electrochemical cell having a cathode structure configured for dissolving a hydrogen halide that forms the halide into a molten salt of the halogen and an alkali metal. Typically a direct current voltage is applied across the cathode and an anode that is fabricated with the non-alkali metal such that the halide of the non-alkali metal is formed adjacent the anode. Electrorefining cells and methods involve applying a direct current voltage across the anode where the halide of the non-alkali metal is formed and the cathode where the non-alkali metal is electro-deposited. In a representative embodiment the halogen is chlorine, the alkali metal is lithium and the non-alkali metal is uranium.

  9. Large methyl halide emissions from south Texas salt marshes

    Directory of Open Access Journals (Sweden)

    R. C. Rhew

    2014-06-01

    Full Text Available Coastal salt marshes are natural sources of methyl chloride (CH3Cl and methyl bromide (CH3Br to the atmosphere, but measured emission rates vary widely by geography. Here we report large methyl halide fluxes from subtropical salt marshes of south Texas. Sites with the halophytic plant, Batis maritima, emitted methyl halides at rates that are orders of magnitude greater than sites containing other vascular plants or macroalgae. B. maritima emissions were generally highest at midday; however, diurnal variability was more pronounced for CH3Br than CH3Cl, and surprisingly high nighttime CH3Cl fluxes were observed in July. Seasonal and intra-site variability were large, even taking into account biomass differences. Overall, these subtropical salt marsh sites show much higher emission rates than temperate salt marshes at similar times of the year, supporting the contention that low-latitude salt marshes are significant sources of CH3Cl and CH3Br.

  10. 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.

  11. Facile Preparation of Silver Halide Nanoparticles as Visible Light Photocatalysts

    Directory of Open Access Journals (Sweden)

    Linfan Cui

    2015-07-01

    Full Text Available In this study, highly efficient silver halide (AgX-based photocatalysts were successfully fabricated using a facile and template-free direct-precipitation method. AgX nanoparticles, which included silver chloride (AgCl, silver bromide (AgBr and silver iodide (AgI, were synthesized using different potassium halides and silver acetate as reactive sources. The size distribution of the AgX nanopar‐ ticles was determined by the reaction time and ratio of the reagents, which were monitored by UV-vis spectra. The as- prepared AgX nanoparticles exhibited different photoca‐ talytic properties. This shows the differences for the photodegradation of methyl orange and Congo red dyes. In addition, the AgCl nanoparticle-based photocatalyst exhibited the best photocatalytic property among all three types of AgX nanoparticles that are discussed in this study. Therefore, it is a good candidate for removing organic pollutants.

  12. Chemical Reactivity Perspective into the Group 2B Metals Halides.

    Science.gov (United States)

    Özen, Alimet Sema; Akdeniz, Zehra

    2016-06-30

    Chemical reactivity descriptors within the conceptual density functional theory can be used to understand the nature of the interactions between two monomers of the Group 2B metal halides. This information might be valuable in the development of adequate force law parameters for simulations in the liquid state. In this study, MX2 monomers and dimers, where M = Zn, Cd, Hg and X = F, Cl, Br, I, were investigated in terms of chemical reactivity descriptors. Relativistic effects were taken into account using the effective core potential (ECP) approach. Correlations were produced between global and local reactivity descriptors and dimerization energies. Results presented in this work represent the first systematic investigation of Group 2B metal halides in the literature from a combined point of view of both relativistic effects and chemical reactivity descriptors. Steric effects were found to be responsible for the deviation from the chemical reactivity principles. They were introduced into the chemical reactivity descriptors such as local softness.

  13. Alkali halide microstructured optical fiber for X-ray detection

    International Nuclear Information System (INIS)

    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

  14. Copper-catalyzed arylation of alkyl halides with arylaluminum reagents

    Directory of Open Access Journals (Sweden)

    Bijay Shrestha

    2015-12-01

    Full Text Available We report a Cu-catalyzed coupling between triarylaluminum reagents and alkyl halides to form arylalkanes. The reaction proceeds in the presence of N,N,N’,N’-tetramethyl-o-phenylenediamine (NN-1 as a ligand in combination with CuI as a catalyst. This catalyst system enables the coupling of primary alkyl iodides and bromides with electron-neutral and electron-rich triarylaluminum reagents and affords the cross-coupled products in good to excellent yields.

  15. Study of methyl halide fluxes in temperate and tropical ecosystems

    OpenAIRE

    Blei, Emanuel

    2010-01-01

    CH3Br and CH3Cl (methyl halides) are the most abundant natural vectors of bromine and chlorine into the stratosphere and play an important role in stratospheric ozone destruction. The current knowledge of their respective natural sources is incomplete leading to large uncertainties in their global budgets. Beside the issue of quantification, characterisation of possible sources is needed to assist modelling of future environmental change impacts on these sources and hence the s...

  16. Semiphysical development of holograms recorded in silver halide emulsions

    Science.gov (United States)

    Banyasz, Istvan; Belendez, Augusto; Pascual, Inmaculada V.; Fimia, Antonio

    2000-10-01

    In the course of experiments on measurement of the effects of processing on nonlinear characteristics of silver halide holograms recorded in Agfa-gevaert 8E75HD emulsions we found that, under certain circumstances, the AAC developer acted as a semi-physical developer instead of the normal chemical developing action. The developed and fixed holograms were of low optical density (carbonate of purest grade with that of for analysis grade of the same company.

  17. Influence of the Print Run on Silver Halide Printing Plates

    Directory of Open Access Journals (Sweden)

    Tomislav Cigula

    2010-09-01

    Full Text Available The most common printing technique today is lithography. The difference between printing and nonprinting areason a printing plate is accomplished by opposite physical and chemical properties of those areas (MacPhee, 1998.The printing areas are made of photoactive layer that attracts oil and chemical substances with oil solvent – printinginks. The nonprinting areas are made of aluminium-oxide which attracts water based substances – the fountainsolution.There are many of various types of photoactive layer which are used for production of offset printing plates, amongothers is silver halide layer. The usage of the silver halide technology in the graphic reproduction is not a novelty.The filmmaking phase is based on the usage of the silver halide as the photographically active ingredient, for instance,AgBr (silver bromide. The new, digital plate making technology (Computer to Plate, CtP eliminates thefilmmaking phase and therefore enables control of the printing plate’s exposure made by computer. CtP technologyeliminates the filmmaking phase, but it also results with the reduction of needed material quantities and requiredtime for the production (Limburg, 1994; Seydel, 1996.In this paper the basis of the graphic reproduction by using the silver halide digital printing plates was described.The changes of the AgX copying layer and the surface of the aluminium base in the printing process have beenobserved. The surface characteristics were determined by measuring the relevant surface roughness parameters. Inaddition, measurements of coverage values on the prints, detailed at smaller print run, were conducted.Results showed that surface changes on the printing plate are changing during printing process and that thesechanges influence transfer of the printing ink on the printing substrate. These measurements proved to be of greatinterest in the graphic reproduction as they enable us to determine consistency of the printing plates during theprinting

  18. Oxidative alkoxylation of phosphine in alcohol solutions of copper halides

    Science.gov (United States)

    Polimbetova, G. S.; Borangazieva, A. K.; Ibraimova, Zh. U.; Bugubaeva, G. O.; Keynbay, S.

    2016-08-01

    The phosphine oxidation reaction with oxygen in alcohol solutions of copper (I, II) halides is studied. Kinetic parameters, intermediates, and by-products are studied by means of NMR 31P-, IR-, UV-, and ESR- spectroscopy; and by magnetic susceptibility, redox potentiometry, gas chromatography, and elemental analysis. A reaction mechanism is proposed, and the optimum conditions are found for the reaction of oxidative alkoxylation phosphine.

  19. Calcium and Vitamin D

    Science.gov (United States)

    ... Home › Patients › Treatment › Calcium/Vitamin D Calcium/Vitamin D Getting enough calcium and vitamin D is essential ... counter medications and calcium supplements. What is Vitamin D and What Does it Do? Vitamin D plays ...

  20. Effects of Halides on Plasmid-Mediated Silver Resistance in Escherichia coli

    OpenAIRE

    Gupta, Amit; Maynes, Maria; Silver, Simon

    1998-01-01

    Silver resistance of sensitive Escherichia coli J53 and resistance plasmid-containing J53(pMG101) was affected by halides in the growth medium. The effects of halides on Ag+ resistance were measured with AgNO3 and silver sulfadiazine, both on agar and in liquid. Low concentrations of chloride made the differences in MICs between sensitive and resistant strains larger. High concentrations of halides increased the sensitivities of both strains to Ag+.

  1. Methods and Mechanisms for Cross-Electrophile Coupling of Csp2 Halides with Alkyl Electrophiles

    OpenAIRE

    Weix, Daniel J.

    2015-01-01

    Conspectus Cross-electrophile coupling, the cross-coupling of two different electrophiles, avoids the need for preformed carbon nucleophiles, but development of general methods has lagged behind cross-coupling and C–H functionalization. A central reason for this slow development is the challenge of selectively coupling two substrates that are alike in reactivity. This Account describes the discovery of generally cross-selective reactions of aryl halides and acyl halides with alkyl halides, th...

  2. 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...

  3. Quantum Size Effect in Organometal Halide Perovskite Nanoplatelets.

    Science.gov (United States)

    Sichert, Jasmina A; Tong, Yu; Mutz, Niklas; Vollmer, Mathias; Fischer, Stefan; Milowska, Karolina Z; García Cortadella, Ramon; Nickel, Bert; Cardenas-Daw, Carlos; Stolarczyk, Jacek K; Urban, Alexander S; Feldmann, Jochen

    2015-10-14

    Organometal halide perovskites have recently emerged displaying a huge potential for not only photovoltaic, but also light emitting applications. Exploiting the optical properties of specifically tailored perovskite nanocrystals could greatly enhance the efficiency and functionality of applications based on this material. In this study, we investigate the quantum size effect in colloidal organometal halide perovskite nanoplatelets. By tuning the ratio of the organic cations used, we can control the thickness and consequently the photoluminescence emission of the platelets. Quantum mechanical calculations match well with the experimental values. We find that not only do the properties of the perovskite, but also those of the organic ligands play an important role. Stacking of nanoplatelets leads to the formation of minibands, further shifting the bandgap energies. In addition, we find a large exciton binding energy of up to several hundreds of meV for nanoplatelets thinner than three unit cells, partially counteracting the blueshift induced by quantum confinement. Understanding of the quantum size effects in perovskite nanoplatelets and the ability to tune them provide an additional method with which to manipulate the optical properties of organometal halide perovskites. PMID:26327242

  4. 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.

  5. Systematic analysis of the unique band gap modulation of mixed halide perovskites.

    Science.gov (United States)

    Kim, Jongseob; Lee, Sung-Hoon; Chung, Choong-Heui; Hong, Ki-Ha

    2016-02-14

    Solar cells based on organic-inorganic hybrid metal halide perovskites have been proven to be one of the most promising candidates for the next generation thin film photovoltaic cells. Mixing Br or Cl into I-based perovskites has been frequently tried to enhance the cell efficiency and stability. One of the advantages of mixed halides is the modulation of band gap by controlling the composition of the incorporated halides. However, the reported band gap transition behavior has not been resolved yet. Here a theoretical model is presented to understand the electronic structure variation of metal mixed-halide perovskites through hybrid density functional theory. Comparative calculations in this work suggest that the band gap correction including spin-orbit interaction is essential to describe the band gap changes of mixed halides. In our model, both the lattice variation and the orbital interactions between metal and halides play key roles to determine band gap changes and band alignments of mixed halides. It is also presented that the band gap of mixed halide thin films can be significantly affected by the distribution of halide composition. PMID:26791587

  6. Formal Nucleophilic Boryl Substitution of Organic Halides with Silylborane/Alkoxy Base System

    OpenAIRE

    Yamamoto, Eiji; Izumi, Kiyotaka; Horita, Yuko; Ukigai, Satoshi; Ito, Hajime

    2014-01-01

    Boryl substitution of organohalides with a silylborane and alkoxy bases is described. This reaction can be applied to various functionalized aryl halides. Alkyl and alkenyl halides, and even sterically congested aryl bromides also provided the corresponding borylated products in high yields. Mechanistic studies indicated that neither trace transition-metal impurities nor aryl radical species involved in this reaction.

  7. Temperature effects in the absorption spectra and exciton luminescence in ammonium halides

    International Nuclear Information System (INIS)

    Warm-up behavior of the first maximum exciton absorption bands in ammonium halides is explored. Under phase transition occurs offset of bands, bound both with changing a parameter of lattice, and efficient mass of exciton. Warm-up dependency of quantum leaving a luminescence of self-trapped excitons in ammonium halides is measured. (author)

  8. Artificial Synapses: Organometal Halide Perovskite Artificial Synapses (Adv. Mater. 28/2016).

    Science.gov (United States)

    Xu, Wentao; Cho, Himchan; Kim, Young-Hoon; Kim, Young-Tae; Wolf, Christoph; Park, Chan-Gyung; Lee, Tae-Woo

    2016-07-01

    A synapse-emulating electronic device based on organometal halide perovskite thin films is described by T.-W. Lee and co-workers on page 5916. The device successfully emulates important characteristics of a biological synapse. This work extends the application of organometal halide perovskites to bioinspired electronic devices, and contributes to the development of neuromorphic electronics. PMID:27442971

  9. 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).

  10. 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.

  11. Calcium channel blocker overdose

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002580.htm Calcium channel blocker overdose To use the sharing features on this page, please enable JavaScript. Calcium channel blockers are a type of medicine used ...

  12. Fenoprofen calcium overdose

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/002649.htm Fenoprofen calcium overdose To use the sharing features on this page, please enable JavaScript. Fenoprofen calcium is a type of medicine called a nonsteroidal ...

  13. Optical Properties of Photovoltaic Organic-Inorganic Lead Halide Perovskites.

    Science.gov (United States)

    Green, Martin A; Jiang, Yajie; Soufiani, Arman Mahboubi; Ho-Baillie, Anita

    2015-12-01

    Over the last several years, organic-inorganic lead halide perovskites have rapidly emerged as a new photovoltaic contender. Although energy conversion efficiency above 20% has now been certified, improved understanding of the material properties contributing to these high performance levels may allow the progression to even higher efficiency, stable cells. The optical properties of these new materials are important not only to device design but also because of the insight they provide into less directly accessible properties, including energy-band structures, binding energies, and likely impact of excitons, as well as into absorption and inverse radiative recombination processes.

  14. Silylaryl Halides Can Replace Triflates as Aryne Precursors.

    Science.gov (United States)

    Mesgar, Milad; Daugulis, Olafs

    2016-08-01

    Silylaryl bromides and iodides can be prepared in one step from commercially available starting materials. Arynes can be generated from these compounds under conditions nearly identical to those employed for silylaryl triflates. Three distinct transformations, ortho-arylation of N-tritylanilines, intermolecular addition of arynes to amides, and reaction of ureas with arynes, were shown to be successful for the new aryne precursors. The main advantage of silylaryl halides relative to silyl aryl triflates is their one-step preparation from commercially available starting materials. PMID:27415183

  15. A new mechanism for radiation damage processes in alkali halides

    OpenAIRE

    Dubinko, V. I.; Turkin, A.A.; Vainshtein, D.I.; Hartog, H.W. den

    1999-01-01

    We present a theory of radiation damage formation in alkali halides based on a new mechanism of dislocation climb, which involves the production of VF centers (self-trapped hole neighboring a cation vacancy) as a result of the absorption of H centers of dislocation lines. We consider the evolution of all experimentally observed extended defects: metal colloids, gas bubbles, and vacancy voids. Voids are shown to arise and grow large due to the reaction between F and VF centers at the surface o...

  16. Thermal conductivity of halide solid solutions: measurement and prediction.

    Science.gov (United States)

    Gheribi, Aïmen E; Poncsák, Sándor; St-Pierre, Rémi; Kiss, László I; Chartrand, Patrice

    2014-09-14

    The composition dependence of the lattice thermal conductivity in NaCl-KCl solid solutions has been measured as a function of composition and temperature. Samples with systematically varied compositions were prepared and the laser flash technique was used to determine the thermal diffusivity from 373 K to 823 K. A theoretical model, based on the Debye approximation of phonon density of state (which contains no adjustable parameters) was used to predict the thermal conductivity of both stoichiometric compounds and fully disordered solid solutions. The predictions obtained with the model agree very well with our measurement. A general method for predicting the thermal conductivity of different halide systems is discussed. PMID:25217938

  17. Optical Properties of Photovoltaic Organic-Inorganic Lead Halide Perovskites.

    Science.gov (United States)

    Green, Martin A; Jiang, Yajie; Soufiani, Arman Mahboubi; Ho-Baillie, Anita

    2015-12-01

    Over the last several years, organic-inorganic lead halide perovskites have rapidly emerged as a new photovoltaic contender. Although energy conversion efficiency above 20% has now been certified, improved understanding of the material properties contributing to these high performance levels may allow the progression to even higher efficiency, stable cells. The optical properties of these new materials are important not only to device design but also because of the insight they provide into less directly accessible properties, including energy-band structures, binding energies, and likely impact of excitons, as well as into absorption and inverse radiative recombination processes. PMID:26560862

  18. Structural, dynamical, and transport properties of the hydrated halides: How do At− bulk properties compare with those of the other halides, from F− to I−?

    OpenAIRE

    Réal, Florent; Severo Pereira Gomes, Andre; Guerrero Martínez, Yansel Omar; Galland, Nicolas; Vallet, Valérie; Masella, Michel; Ayed, Tarah

    2016-01-01

    International audience The properties of halides from the lightest, uoride (F−), to the heaviest, astatide (At−), have been studied in water using a polarizable force- eld approach based on molecular dynamics (MD) simulations at the 10 ns scale. The selected force- eld explicitly treats the cooperativity within the halide-water hydrogen bond networks. The force- eld parameters have been adjusted to ab initio data on anion/water clusters computed at the relativistic Möller-Plesset second-o...

  19. Calcium and Mitosis

    Science.gov (United States)

    Hepler, P.

    1983-01-01

    Although the mechanism of calcium regulation is not understood, there is evidence that calcium plays a role in mitosis. Experiments conducted show that: (1) the spindle apparatus contains a highly developed membrane system that has many characteristics of sarcoplasmic reticulum of muscle; (2) this membrane system contains calcium; and (3) there are ionic fluxes occurring during mitosis which can be seen by a variety of fluorescence probes. Whether the process of mitosis can be modulated by experimentally modulating calcium is discussed.

  20. Calcium en cardioplegie

    NARCIS (Netherlands)

    Ruigrok, T.J.C.; Meijler, F.L.

    1985-01-01

    Coronary perfusion with a calcium-free solution, followed by reperfusion with a calcium containing solution, may result in acute myocardial cell death and in irreversible loss of the e1ectrical and mechanical activity of the heart. This phenomenon is known as the calcium paradox. A number of cardiop

  1. Structure and Bonding in Small Neutral Alkali-Halide Clusters

    CERN Document Server

    Aguado, A; López, J M; Alonso, J A

    1997-01-01

    The structural and bonding properties of small neutral alkali-halide clusters (AX)n, with n less than or equal to 10, A=Li, Na, K, Rb and X=F, Cl, Br, I, are studied using the ab initio Perturbed Ion (aiPI) model and a restricted structural relaxation criterion. A trend of competition between rock-salt and hexagonal ring-like isomers is found and discussed in terms of the relative ionic sizes. The main conclusion is that an approximate value of r_C/r_A=0.5 (where r_C and r_A are the cationic and anionic radii) separates the hexagonal from the rock-salt structures. The classical electrostatic part of the total energy at the equilibrium geometry is enough to explain these trends. The magic numbers in the size range studied are n= 4, 6 and 9, and these are universal since they occur for all alkali-halides and do not depend on the specific ground state geometry. Instead those numbers allow for the formation of compact clusters. Full geometrical relaxations are considered for (LiF)n (n=3-7) and (AX)_3 clusters, an...

  2. Tunable Near-Infrared Luminescence in Tin Halide Perovskite Devices.

    Science.gov (United States)

    Lai, May L; Tay, Timothy Y S; Sadhanala, Aditya; Dutton, Siân E; Li, Guangru; Friend, Richard H; Tan, Zhi-Kuang

    2016-07-21

    Infrared emitters are reasonably rare in solution-processed materials. Recently, research into hybrid organo-lead halide perovskite, originally popular in photovoltaics,1-3 has gained traction in light-emitting diodes (LED) due to their low-cost solution processing and good performance.4-9 The lead-based electroluminescent materials show strong colorful emission in the visible region, but lack emissive variants further in the infrared. The concerns with the toxicity of lead may, additionally, limit their wide-scale applications. Here, we demonstrate tunable near-infrared electroluminescence from a lead-free organo-tin halide perovskite, using an ITO/PEDOT:PSS/CH3NH3Sn(Br1-xIx)3/F8/Ca/Ag device architecture. In our tin iodide (CH3NH3SnI3) LEDs, we achieved a 945 nm near-infrared emission with a radiance of 3.4 W sr(-1) m(-2) and a maximum external quantum efficiency of 0.72%, comparable with earlier lead-based devices. Increasing the bromide content in these tin perovskite devices widens the semiconductor bandgap and leads to shorter wavelength emissions, tunable down to 667 nm. These near-infrared LEDs could find useful applications in a range of optical communication, sensing and medical device applications. PMID:27336412

  3. Two-Dimensional Halide Perovskites: Tuning Electronic Activities of Defects.

    Science.gov (United States)

    Liu, Yuanyue; Xiao, Hai; Goddard, William A

    2016-05-11

    Two-dimensional (2D) halide perovskites are emerging as promising candidates for nanoelectronics and optoelectronics. To realize their full potential, it is important to understand the role of those defects that can strongly impact material properties. In contrast to other popular 2D semiconductors (e.g., transition metal dichalcogenides MX2) for which defects typically induce harmful traps, we show that the electronic activities of defects in 2D perovskites are significantly tunable. For example, even with a fixed lattice orientation one can change the synthesis conditions to convert a line defect (edge or grain boundary) from electron acceptor to inactive site without deep gap states. We show that this difference originates from the enhanced ionic bonding in these perovskites compared with MX2. The donors tend to have high formation energies and the harmful defects are difficult to form at a low halide chemical potential. Thus, we unveil unique properties of defects in 2D perovskites and suggest practical routes to improve them. PMID:27100910

  4. Dislocation unpinning model of acoustic emission from alkali halide crystals

    Indian Academy of Sciences (India)

    B P Chandra; Anubha S Gour; Vivek K Chandra; Yuvraj Patil

    2004-06-01

    The present paper reports the dislocation unpinning model of acoustic emission (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 particular strain of the crystals. The peak value of the AE pulse rate should depend on the volume and strain rate of the crystals, and also on the pinning time of dislocations. Since the pinning time of dislocations decreases with increasing strain rate, the AE pulse rate should be weakly dependent on the strain rate of the crystals. The total number of AE should increase linearly with deformation and then it should attain a saturation value for the large deformation. By measuring the strain dependence of the AE pulse rate at a fixed strain rate, the time constant $_{\\text{s}}$ for surface annihilation of dislocations and the pinning time $_{\\text{p}}$ of the dislocations can be determined. A good agreement is found between the theoretical and experimental results related to the AE from alkali halide crystals.

  5. Calcium signaling and epilepsy.

    Science.gov (United States)

    Steinlein, Ortrud K

    2014-08-01

    Calcium signaling is involved in a multitude of physiological and pathophysiological mechanisms. Over the last decade, it has been increasingly recognized as an important factor in epileptogenesis, and it is becoming obvious that the excess synchronization of neurons that is characteristic for seizures can be linked to various calcium signaling pathways. These include immediate effects on membrane excitability by calcium influx through ion channels as well as delayed mechanisms that act through G-protein coupled pathways. Calcium signaling is able to cause hyperexcitability either by direct modulation of neuronal activity or indirectly through calcium-dependent gliotransmission. Furthermore, feedback mechanisms between mitochondrial calcium signaling and reactive oxygen species are able to cause neuronal cell death and seizures. Unravelling the complexity of calcium signaling in epileptogenesis is a daunting task, but it includes the promise to uncover formerly unknown targets for the development of new antiepileptic drugs.

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

    Science.gov (United States)

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

    2008-12-01

    In this study a total of 186 complex halide systems were collected; the formabilities of ABX3 (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-MnF2) without perovskite structure and six systems (RbF-PbF2, CsF-BeF2, KCl-FeCl2, TlI-MnI2, RbI-SnI2, TlI-PbI2) 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 ABX3 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 ABO3 oxide perovskite, and may be helpful to design novel halide materials with the perovskite structure. PMID:19029699

  7. Investigation of change regularity of energy states of Mn2+ in halides

    International Nuclear Information System (INIS)

    Data on 4E, 4A1 (4G) and 4T1 (4G) energy states of Mn2+ ion in some halides have been obtained and analyzed. With use of the dielectric theory of the chemical bond for complex crystals, several chemical bond parameters were calculated. The change regularity of the energy states of Mn2+ in halides has been studied. The results show that the covalence, the coordination number and the radius of the central ion are the main factors influencing the energy states of Mn2+ ion in halides. The relationships between these factors and the energy state 4T1 (4G), the energy difference ΔE (ΔE=4E, 4A1 (4G)→4T1 (4G)) of Mn2+ ion in halides were established: E=2.0898+0.8618 exp (−F/0.2431); ΔE=0.3201+0.9713⁎F. These relationships allow us to predict the position of energy state 4T1 (4G) and the energy difference ΔE of Mn2+ in halides. This work can be significant for further understanding the luminescent properties of Mn2+ and can be used to develop new Mn2+-doped phosphors. - Highlights: ► Relationship between F and energy state 4T1(4G) of Mn2+ in halides was set up. ► Relationship between F and energy difference ΔE of Mn2+ in halides was set up. ► Site occupation of Mn2+-doped halides with two or more cations can be made clear. ► Energy state 4T1(4G) and emission band of Mn2+ in halides can be predicted.

  8. Smoking, calcium, calcium antagonists, and aging.

    Science.gov (United States)

    Nicita-Mauro, V

    1990-01-01

    Aging is characterized, besides other changes, by a progressive increase in calcium content in the arterial wall, which is enhanced by diabetes mellitus, osteoporosis, arterial hypertension, and tabagism. As to tabagism, experiments in animals have shown that nicotine can increase calcium content of the arterial wall, and clinical studies have demonstrated that cigarette smoking induces peripheral vasoconstriction, with consequent increase in blood pressure levels. In order to study the role of calcium ions in the pathogenesis of the vasoconstrictive lesions caused by "acute" smoking, the author has studied the peripheral vascular effects of the calcium-channel antagonist nifedipine, a dihydropyridine derivative, and calcitonin, a hypocalcemizing hormone which possess vasoactive actions on 12 elderly regular smokers (mean age 65.8 years). The results demonstrated that both nifedipine (10 mg sublingually 20 min before smoking) and salmon calcitonin (100 MRC U/daily intramuscularly for three days) are able to prevent peripheral vasoconstriction evaluated by Doppler velocimetry, as well as the increase of blood pressure induced by smoking. On the basis of our results, the author proposes that cigarette smoking-induced vasoconstriction is a calcium-mediated process, which can be hindered by drugs with calcium antagonist action. PMID:2226675

  9. Calcium absorption and achlorhydria

    International Nuclear Information System (INIS)

    Defective absorption of calcium has been thought to exist in patients with achlorhydria. The author compared absorption of calcium in its carbonate form with that in a pH-adjusted citrate form in a group of 11 fasting patients with achlorhydria and in 9 fasting normal subjects. Fractional calcium absorption was measured by a modified double-isotope procedure with 0.25 g of calcium used as the carrier. Mean calcium absorption (+/- S.D.) in the patients with achlorhydria was 0.452 +/- 0.125 for citrate and 0.042 +/- 0.021 for carbonate (P less than 0.0001). Fractional calcium absorption in the normal subjects was 0.243 +/- 0.049 for citrate and 0.225 +/- 0.108 for carbonate (not significant). Absorption of calcium from carbonate in patients with achlorhydria was significantly lower than in the normal subjects and was lower than absorption from citrate in either group; absorption from citrate in those with achlorhydria was significantly higher than in the normal subjects, as well as higher than absorption from carbonate in either group. Administration of calcium carbonate as part of a normal breakfast resulted in completely normal absorption in the achlorhydric subjects. These results indicate that calcium absorption from carbonate is impaired in achlorhydria under fasting conditions. Since achlorhydria is common in older persons, calcium carbonate may not be the ideal dietary supplement

  10. Mild Palladium-Catalyzed Cyanation of (Hetero)aryl Halides and Triflates in Aqueous Media

    OpenAIRE

    Cohen, Daniel T.; Buchwald, Stephen L.

    2015-01-01

    A mild, efficient, and low-temperature palladium-catalyzed cyanation of (hetero)aryl halides and triflates is reported. Previous palladium-catalyzed cyanations of (hetero)aryl halides have required higher temperatures to achieve good catalytic activity. This current reaction allows the cyanation of a general scope of (hetero)aryl halides and triflates at 2–5 mol % catalyst loadings with temperatures ranging from rt to 40 °C. This mild method was applied to the synthesis of lersivirine, a reve...

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

    KAUST Repository

    Falivene, Laura

    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.

  12. Giant photostriction in organic-inorganic lead halide perovskites

    Science.gov (United States)

    Zhou, Yang; You, Lu; Wang, Shiwei; Ku, Zhiliang; Fan, Hongjin; Schmidt, Daniel; Rusydi, Andrivo; Chang, Lei; Wang, Le; Ren, Peng; Chen, Liufang; Yuan, Guoliang; Chen, Lang; Wang, Junling

    2016-04-01

    Among the many materials investigated for next-generation photovoltaic cells, organic-inorganic lead halide perovskites have demonstrated great potential thanks to their high power conversion efficiency and solution processability. Within a short period of about 5 years, the efficiency of solar cells based on these materials has increased dramatically from 3.8 to over 20%. Despite the tremendous progress in device performance, much less is known about the underlying photophysics involving charge-orbital-lattice interactions and the role of the organic molecules in this hybrid material remains poorly understood. Here, we report a giant photostrictive response, that is, light-induced lattice change, of >1,200 p.p.m. in methylammonium lead iodide, which could be the key to understand its superior optical properties. The strong photon-lattice coupling also opens up the possibility of employing these materials in wireless opto-mechanical devices.

  13. Theoretical study of the scandium and yttrium halides

    Science.gov (United States)

    Langhoff, Stephen R.; Bauschlicher, Charles W., Jr.; Partridge, Harry

    1988-01-01

    The X1Sigma(+) ground states and a3Delta excited states of the diatomic halides of Sc and Y are characterized theoretically, using the SDCI coupled-pair functional method and the state-averaged CASSCF method to determine the spectroscopic constants and related properties. The techniques employed are discussed, and the results are presented in extensive tables. The dissociation energies are given as D0 = 6.00 eV for ScF, 4.55 eV for ScCl, 3.90 eV for ScBr, 6.72 eV for YF, 5.36 eV for YCl, and 4.74 eV for YBr.

  14. Material Innovation in Advancing Organometal Halide Perovskite Functionality.

    Science.gov (United States)

    Zheng, Fan; Saldana-Greco, Diomedes; Liu, Shi; Rappe, Andrew M

    2015-12-01

    Organometal halide perovskites (OMHPs) have garnered much attention recently for their unprecedented rate of increasing power conversion efficiency (PCE), positioning them as a promising basis for the next-generation photovoltaic devices. However, the gap between the rapid increasing PCE and the incomplete understanding of the structure-property-performance relationship prevents the realization of the true potential of OMHPs. This Perspective aims to provide a concise overview of the current status of OMHP research, highlighting the unique properties of OMHPs that are critical for solar applications but still not adequately explained. Stability and performance challenges of OMHP solar cells are discussed, calling upon combined experimental and theoretical efforts to address these challenges for pioneering commercialization of OMHP solar cells. Various material innovation strategies for improving the performance and stability of OMHPs are surveyed, showing that the OMHP architecture can serve as a promising and robust platform for the design and optimization of materials with desired functionalities. PMID:26631361

  15. Quasielastic neutron scattering study of silver selenium halides

    CERN Document Server

    Major, A G; Barnes, A C; Howells, W S

    2002-01-01

    Both silver chalcogenides (Ag sub 2 S, Ag sub 2 Se, and Ag sub 2 Te) and silver halides (AgCl, AgBr, and AgI) are known to be fast-ion solids in which the silver ions can diffuse quickly in a sublattice formed by the other ions. To clarify whether mixtures of these materials (such as Ag sub 3 SeI) possess comparable properties and whether a systematic dependence on the cation-to-anion ratio can be observed, some of these mixtures were studied by quasielastic neutron scattering both in the solid and the liquid phases. To identify the diffusion mechanisms and constants, a new data-analysis method based on a two-dimensional maximum-likelihood fit is proposed. This method has the potential to give more reliable information on the diffusion mechanism than the traditional Bayesian method. (orig.)

  16. Strong Turbulence in Alkali Halide Negative Ion Plasmas

    Science.gov (United States)

    Sheehan, Daniel

    1999-11-01

    Negative ion plasmas (NIPs) are charge-neutral plasmas in which the negative charge is dominated by negative ions rather than electrons. They are found in laser discharges, combustion products, semiconductor manufacturing processes, stellar atmospheres, pulsar magnetospheres, and the Earth's ionosphere, both naturally and man-made. They often display signatures of strong turbulence^1. Development of a novel, compact, unmagnetized alkali halide (MX) NIP source will be discussed, it incorporating a ohmically-heated incandescent (2500K) tantulum solenoid (3cm dia, 15 cm long) with heat shields. The solenoid ionizes the MX vapor and confines contaminant electrons, allowing a very dry (electron-free) source. Plasma densities of 10^10 cm-3 and positive to negative ion mass ratios of 1 Fusion 4, 91 (1978).

  17. Games people play with interstitials (in alkali halides)

    International Nuclear Information System (INIS)

    A survey is given of the various ways in which interstitial halogen atoms produced by ionising radiation can be trapped in alkali halides. First, the fundamental interstitial halogen atom center, the H-center, is discussed. Then, interstitial centers trapped by, or in the neighbourhood of, various impurities are presented. Particular attention is given to trapping by the following impurities: foreign halogen ions, foreign alkali ions or pairs of both. The discussion is limited to a description of the production and the models of these H-type centers and little is said about their sometimes interesting physical properties. A few speculations are offered why certain interstitial centers have not yet been observed. The models of a few paramagnetic diinterstitial centers are also presented

  18. Analysis and modeling of alkali halide aqueous solutions

    DEFF Research Database (Denmark)

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

    2016-01-01

    A new model is proposed for correlation and prediction of thermodynamic properties of electrolyte solutions. In the proposed model, terms of a second virial coefficient-type and of a KT-UNIFAC model are used to account for a contribution of binary interactions between ion and ion, and water and ion...... 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......, respectively, with a Debye-Hückel term for electrostatic interactions. In a second approach of the model, additional parameters for interactions of ion pairs in the KT-UNIFAC are introduced as a correction to get better agreement with data. Structural parameters of ions used in the framework of UNIFAC...

  19. Theory of freezing of alkali halides and binary alloys

    International Nuclear Information System (INIS)

    Using the basic equations of classical statistical mechanics relating the singlet densities rho1 and rho2 of a binary system to the three partial direct correlation functions csub(ij), a theory of freezing is developed. Though the theory is set up for arbitrary concentration, we focus on the freezing of the alkali halides. In particular, we show that periodic solutions of the equations for rho1 and rho2 can coexist with homogeneous solutions. The difference in free energy between periodic and homogeneous phases is built up in terms of (i) the volume difference and (ii) the Fourier components of rho1, rho2 and csub(ij). To lowest order, it is stressed that the freezing transition is determined by the charge-charge structure factor at the principal peak and by the compressibility. (author)

  20. Fabrication of alkali halide UV photocathodes by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Brendel' , V M; Bukin, V V; Garnov, Sergei V; Bagdasarov, V Kh; Denisov, N N; Garanin, Sergey G; Terekhin, V A; Trutnev, Yurii A

    2012-12-31

    A technique has been proposed for the fabrication of atmospheric corrosion resistant alkali halide UV photocathodes by pulsed laser deposition. We produced photocathodes with a highly homogeneous photoemissive layer well-adherent to the substrate. The photocathodes were mounted in a vacuum photodiode, and a tungsten grid was used as an anode. Using pulsed UV lasers, we carried out experiments aimed at evaluating the quantum efficiency of the photocathodes. With a dc voltage applied between the photocathode and anode grid, we measured a shunt signal proportional to the total charge emitted by the cathode exposed to UV laser light. The proposed deposition technique enables one to produce photocathodes with photoemissive layers highly uniform in quantum efficiency, which is its main advantage over thin film growth by resistive evaporation. (laser technologies)

  1. Fabrication of alkali halide UV photocathodes by pulsed laser deposition

    Science.gov (United States)

    Brendel', V. M.; Bukin, V. V.; Garnov, Sergei V.; Bagdasarov, V. Kh; Denisov, N. N.; Garanin, Sergey G.; Terekhin, V. A.; Trutnev, Yurii A.

    2012-12-01

    A technique has been proposed for the fabrication of atmospheric corrosion resistant alkali halide UV photocathodes by pulsed laser deposition. We produced photocathodes with a highly homogeneous photoemissive layer well-adherent to the substrate. The photocathodes were mounted in a vacuum photodiode, and a tungsten grid was used as an anode. Using pulsed UV lasers, we carried out experiments aimed at evaluating the quantum efficiency of the photocathodes. With a dc voltage applied between the photocathode and anode grid, we measured a shunt signal proportional to the total charge emitted by the cathode exposed to UV laser light. The proposed deposition technique enables one to produce photocathodes with photoemissive layers highly uniform in quantum efficiency, which is its main advantage over thin film growth by resistive evaporation.

  2. Two-photon pumped lead halide perovskite nanowire lasers

    CERN Document Server

    Gu, Zhiyuan; Sun, Wenzhao; Li, Jinakai; Liu, Shuai; Song, Qinghai; Xiao, Shumin

    2015-01-01

    Solution-processed lead halide perovskites have shown very bright future in both solar cells and microlasers. Very recently, the nonlinearity of perovskites started to attract considerable research attention. Second harmonic generation and two-photon absorption have been successfully demonstrated. However, the nonlinearity based perovskite devices such as micro- & nano- lasers are still absent. Here we demonstrate the two-photon pumped nanolasers from perovskite nanowires. The CH3NH3PbBr3 perovskite nanowires were synthesized with one-step solution self-assembly method and dispersed on glass substrate. Under the optical excitation at 800 nm, two-photon pumped lasing actions with periodic peaks have been successfully observed at around 546 nm. The obtained quality (Q) factors of two-photon pumped nanolasers are around 960, and the corresponding thresholds are about 674?J=cm2. Both the Q factors and thresholds are comparable to conventional whispering gallery modes in two-dimensional polygon microplates. Ou...

  3. Measurements of intracellular calcium

    International Nuclear Information System (INIS)

    Intracellular calcium concentration ([Ca2+]i) has been measured in cultured cells by using Fura-2 load cells and a computer-controlled Perkin Elmer LS-5B spectrofluorometer. Increased [Ca2+]i in cells exposed to extracellular bilirubin was observed both with and without extracellular calcium. However, the increase was considerable larger with extracellular calcium. The enhancement of [Ca2+]i became smaller with decreasing bilirubin/BSA (bovine serum albumine) ratio. 5 refs., 5 figs

  4. 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.

  5. The Structure and Thermodynamics of Alkali Halide Vapors.

    Science.gov (United States)

    Hartley, John George

    A comprehensive set of electron diffraction experiments were performed on 16 of the alkali halides in the vapor phase. A 40kev electron beam was scattered from the vapor effusing out of the nozzle of a temperature controlled gas cell. The resulting data were analyzed at the University of Edinburgh with the program ED80. This resulted in values for the bond lengths of monomers and the dimers, the bond angle of the dimers and the monomer-dimer ratios. In several cases, it was possible to further refine the data to obtain information on the mean amplitudes of vibration. As a check on the accuracy of the results, the monomer bond distances obtained by electron diffraction were compared to values obtained previously by microwave spectroscopy. The average monomer bond length r_{a} is corrected to obtain the equilibrium bond distance r_{e}. This value is then compared to the value of r_{e } obtained from microwave spectroscopy and found to be in excellent agreement. The bond lengths and angles of the dimers were compared against model calculations. While no one model was found to accurately predict the dimer structure parameters of all of the alkali halides, the Rittner model of Gowda et al was found to accurately predict the structure of six of the dimers. Thermodynamical calculations were performed on the model data which resulted in theoretical curves of the monomer-dimer ratios. Comparison of these curves with the experimental monomer-dimer ratio permits an evaluation of the model vibration frequencies. The enthalpy of formation of the dimer, Delta H_sp{2}{f}(298) is examined with regard to the size of the variation necessary to bring about agreement of the experimental and model monomer-dimer ratios.

  6. Phase space investigation of the lithium amide halides

    International Nuclear Information System (INIS)

    Highlights: • The lower limits of halide incorporation in lithium amide have been investigated. • The only amide iodide stoichiometry observed was Li3(NH2)2I. • Solid solutions were observed in both the amide chloride and amide bromide systems. • A 46% reduction in chloride content resulted in a new phase: Li7(NH2)6Cl. • New low-chloride phase maintained improved H2 desorption properties of Li4(NH2)3Cl. - Abstract: An investigation has been carried out into the lower limits of halide incorporation in lithium amide (LiNH2). It was found that the lithium amide iodide Li3(NH2)2I was unable to accommodate any variation in stoichiometry. In contrast, some variation in stoichiometry was accommodated in Li7(NH2)6Br, as shown by a decrease in unit cell volume when the bromide content was reduced. The amide chloride Li4(NH2)3Cl 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 Li7(NH2)6Cl was observed. In comparison to LiNH2, this new low-chloride phase exhibited similar improved hydrogen desorption properties as Li4(NH2)3Cl but with a much reduced weight penalty through addition of chloride. Attempts to dope lithium amide with fluoride ions have so far proved unsuccessful

  7. Methods for synthesizing alane without the formation of adducts and free of halides

    Science.gov (United States)

    Zidan, Ragaiy; Knight, Douglas A; Dinh, Long V

    2013-02-19

    A process is provided to synthesize an alane without the formation of alane adducts as a precursor. The resulting product is a crystallized .alpha.-alane and is a highly stable product and is free of halides.

  8. 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.

  9. Approaching Bulk Carrier Dynamics in Organo-Halide Perovskite Nanocrystalline Films by Surface Passivation.

    Science.gov (United States)

    Stewart, Robert J; Grieco, Christopher; Larsen, Alec V; Maier, Joshua J; Asbury, John B

    2016-04-01

    The electronic properties of organo-halide perovskite absorbers described in the literature have been closely associated with their morphologies and processing conditions. However, the underlying origins of this dependence remain unclear. A combination of inorganic synthesis, surface chemistry, and time-resolved photoluminescence spectroscopy was used to show that charge recombination centers in organo-halide perovskites are almost exclusively localized on the surfaces of the crystals rather than in the bulk. Passivation of these surface defects causes average charge carrier lifetimes in nanocrystalline thin films to approach the bulk limit reported for single-crystal organo-halide perovskites. These findings indicate that the charge carrier lifetimes of perovskites are correlated with their thin-film processing conditions and morphologies through the influence these have on the surface chemistry of the nanocrystals. Therefore, surface passivation may provide a means to decouple the electronic properties of organo-halide perovskites from their thin-film processing conditions and corresponding morphologies. PMID:26966792

  10. Palladium-catalyzed Cascade Cyclization-Coupling Reaction of Benzyl Halides with N,N-Diallylbenzoylamide

    Institute of Scientific and Technical Information of China (English)

    Yi Min HU; Yu ZHANG; Jian Lin HAN; Cheng Jian ZHU; Yi PAN

    2003-01-01

    A novel type of palladium-catalyzed cascade cyclization-coupling reaction has been found. Reaction of N, N-diallylbenzoylamide 1 with benzyl halides 2 afforded the corresponding dihydropyrroles 3 in moderate to excellent yields.

  11. Space-dependent self-diffusion processes in molten copper halides: a molecular dynamics study

    OpenAIRE

    Alcaraz Sendra, Olga; Trullàs Simó, Joaquim

    2001-01-01

    This work is concerned with single ion dynamics in molten copper halides (CuI and CuCl) which exhibit fast ionic conduction before melting. The self-dynamic structure factor of the two ionic species in each melt have been calculated by molecular dynamics simulations and the corresponding effective wavelength-dependent self-diffusion coefficients have been studied. The results have been compared with those obtained for molten alkali halides (KCl and RbCl).

  12. Atomistic simulation of ion solvation in water explains surface preference of halides

    OpenAIRE

    Caleman, C.; Hub, J. S.; van Maaren, P.; van der Spoel, D

    2011-01-01

    Water is a demanding partner. It strongly attracts ions, yet some halide anions—chloride, bromide, and iodide—are expelled to the air/water interface. This has important implications for chemistry in the atmosphere, including the ozone cycle. We present a quantitative analysis of the energetics of ion solvation based on molecular simulations of all stable alkali and halide ions in water droplets. The potentials of mean force for Cl-, Br-, and I- have shallow minima near the surface. We demons...

  13. 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.

  14. The effect of low solublility organic acids on the hygroscopicity of sodium halide aerosols

    OpenAIRE

    L. Miñambres; Méndez, E; Sánchez, M. N.; Castaño, F.; F. J. Basterretxea

    2014-01-01

    In order to accurately assess the influence of fatty acids on the hygroscopic and other physicochemical properties of sea salt aerosols, hexanoic, octanoic or lauric acid together with sodium halide salts (NaCl, NaBr and NaI) have been chosen to be performed in this study. The hygroscopic properties of sodium halide submicrometer particles covered with organic acids have been examined by Fourier-transform infrared spectroscopy in an aerosol flow cell. Covered particles were gen...

  15. The effect of low solubility organic acids on the hygroscopicity of sodium halide aerosols

    OpenAIRE

    L. Miñambres; Méndez, E; Sánchez, M. N.; Castaño, F.; F. J. Basterretxea

    2014-01-01

    In order to accurately assess the influence of fatty acids on the hygroscopic and other physicochemical properties of sea salt aerosols, hexanoic, octanoic or lauric acid together with sodium halide salts (NaCl, NaBr and NaI) have been chosen to be investigated in this study. The hygroscopic properties of sodium halide sub-micrometre particles covered with organic acids have been examined by Fourier-transform infrared spectroscopy in an aerosol flow cell. Covered particles w...

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

    OpenAIRE

    Bretschneider, Simon A.; Jonas Weickert; James A. Dorman; Lukas Schmidt-Mende

    2014-01-01

    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...

  17. The effect of low solublility organic acids on the hygroscopicity of sodium halide aerosols

    Science.gov (United States)

    Miñambres, L.; Méndez, E.; Sánchez, M. N.; Castaño, F.; Basterretxea, F. J.

    2014-02-01

    In order to accurately assess the influence of fatty acids on the hygroscopic and other physicochemical properties of sea salt aerosols, hexanoic, octanoic or lauric acid together with sodium halide salts (NaCl, NaBr and NaI) have been chosen to be performed in this study. The hygroscopic properties of sodium halide submicrometer particles covered with organic acids have been examined by Fourier-transform infrared spectroscopy in an aerosol flow cell. Covered particles were generated by flowing atomized sodium halide particles (either dry or aqueous) through a heated oven containing the gaseous acid. The obtained results indicate that gaseous organic acids easily nucleate onto dry and aqueous sodium halide particles. On the other hand, Scanning Electron Microscopy (SEM) images indicate that lauric acid coating on NaCl particles makes them to aggregate in small clusters. The hygroscopic behaviour of covered sodium halide particles in deliquescence mode shows different features with the exchange of the halide ion: whereas the organic covering has little effect in NaBr particles, NaCl and NaI covered particles change their deliquescence relative humidities, with different trends observed for each of the acids studied. In efflorescence mode, the overall effect of the organic covering is to retard the loss of water in the particles. It has been observed that the presence of gaseous water in heterogeneously nucleated particles tends to displace the cover of hexanoic acid to energetically stabilize the system.

  18. The effect of low solubility organic acids on the hygroscopicity of sodium halide aerosols

    Science.gov (United States)

    Miñambres, L.; Méndez, E.; Sánchez, M. N.; Castaño, F.; Basterretxea, F. J.

    2014-10-01

    In order to accurately assess the influence of fatty acids on the hygroscopic and other physicochemical properties of sea salt aerosols, hexanoic, octanoic or lauric acid together with sodium halide salts (NaCl, NaBr and NaI) have been chosen to be investigated in this study. The hygroscopic properties of sodium halide sub-micrometre particles covered with organic acids have been examined by Fourier-transform infrared spectroscopy in an aerosol flow cell. Covered particles were generated by flowing atomized sodium halide particles (either dry or aqueous) through a heated oven containing the gaseous acid. The obtained results indicate that gaseous organic acids easily nucleate onto dry and aqueous sodium halide particles. On the other hand, scanning electron microscopy (SEM) images indicate that lauric acid coating on NaCl particles makes them to aggregate in small clusters. The hygroscopic behaviour of covered sodium halide particles in deliquescence mode shows different features with the exchange of the halide ion, whereas the organic surfactant has little effect in NaBr particles, NaCl and NaI covered particles experience appreciable shifts in their deliquescence relative humidities, with different trends observed for each of the acids studied. In efflorescence mode, the overall effect of the organic covering is to retard the loss of water in the particles. It has been observed that the presence of gaseous water in heterogeneously nucleated particles tends to displace the cover of hexanoic acid to energetically stabilize the system.

  19. Mechanistic Aspects of Aryl-Halide Oxidative Addition, Coordination Chemistry, and Ring-Walking by Palladium.

    Science.gov (United States)

    Zenkina, Olena V; Gidron, Ori; Shimon, Linda J W; Iron, Mark A; van der Boom, Milko E

    2015-11-01

    This contribution describes the reactivity of a zero-valent palladium phosphine complex with substrates that contain both an aryl halide moiety and an unsaturated carbon-carbon bond. Although η(2) -coordination of the metal center to a C=C or C≡C unit is kinetically favored, aryl halide bond activation is favored thermodynamically. These quantitative transformations proceed under mild reaction conditions in solution or in the solid state. Kinetic measurements indicate that formation of η(2) -coordination complexes are not nonproductive side-equilibria, but observable (and in several cases even isolated) intermediates en route to aryl halide bond cleavage. At the same time, DFT calculations show that the reaction with palladium may proceed through a dissociation-oxidative addition mechanism rather than through a haptotropic intramolecular process (i.e., ring walking). Furthermore, the transition state involves coordination of a third phosphine to the palladium center, which is lost during the oxidative addition as the C-halide bond is being broken. Interestingly, selective activation of aryl halides has been demonstrated by adding reactive aryl halides to the η(2) -coordination complexes. The product distribution can be controlled by the concentration of the reactants and/or the presence of excess phosphine.

  20. Calcium in plant cells

    Directory of Open Access Journals (Sweden)

    V. V. Schwartau

    2014-04-01

    Full Text Available The paper gives the review on the role of calcium in many physiological processes of plant organisms, including growth and development, protection from pathogenic influences, response to changing environmental factors, and many other aspects of plant physiology. Initial intake of calcium ions is carried out by Ca2+-channels of plasma membrane and they are further transported by the xylem owing to auxins’ attractive ability. The level of intake and selectivity of calcium transport to ove-ground parts of the plant is controlled by a symplast. Ca2+enters to the cytoplasm of endoderm cells through calcium channels on the cortical side of Kaspary bands, and is redistributed inside the stele by the symplast, with the use of Ca2+-АТPases and Ca2+/Н+-antiports. Owing to regulated expression and activity of these calcium transporters, calclum can be selectively delivered to the xylem. Important role in supporting calcium homeostasis is given to the vacuole which is the largest depo of calcium. Regulated quantity of calcium movement through the tonoplast is provided by a number of potential-, ligand-gated active transporters and channels, like Ca2+-ATPase and Ca2+/H+ exchanger. They are actively involved in the inactivation of the calcium signal by pumping Ca2+ to the depo of cells. Calcium ATPases are high affinity pumps that efficiently transfer calcium ions against the concentration gradient in their presence in the solution in nanomolar concentrations. Calcium exchangers are low affinity, high capacity Ca2+ transporters that are effectively transporting calcium after raising its concentration in the cell cytosol through the use of protons gradients. Maintaining constant concentration and participation in the response to stimuli of different types also involves EPR, plastids, mitochondria, and cell wall. Calcium binding proteins contain several conserved sequences that provide sensitivity to changes in the concentration of Ca2+ and when you

  1. Calcium D-saccharate

    DEFF Research Database (Denmark)

    Garcia, André Castilho; Hedegaard, Martina Vavrusova; Skibsted, Leif Horsfelt

    2016-01-01

    Molar conductivity of saturated aqueous solutions of calcium d-saccharate, used as a stabilizer of beverages fortified with calcium d-gluconate, increases strongly upon dilution, indicating complex formation between calcium and d-saccharate ions, for which, at 25 °C, Kassoc = 1032 ± 80, ΔHassoc......° = -34 ± 6 kJ mol-1, and ΔSassoc° = -55 ± 9 J mol-1 K-1, were determined electrochemically. Calcium d-saccharate is sparingly soluble, with a solubility product, Ksp, of (6.17 ± 0.32) × 10-7 at 25 °C, only moderately increasing with the temperature: ΔHsol° = 48 ± 2 kJ mol-1, and ΔSassoc° = 42 ± 7 J mol-1...... K-1. Equilibria in supersaturated solutions of calcium d-saccharate seem only to adjust slowly, as seen from calcium activity measurements in calcium d-saccharate solutions made supersaturated by cooling. Solutions formed by isothermal dissolution of calcium d-gluconate in aqueous potassium d...

  2. Reactivity of TEMPO anion as a nucleophile and its applications for selective transformations of haloalkanes or acyl halides to aldehydes

    OpenAIRE

    Inokuchi, Tsutomu; Kawafuchi, Hiroyuki

    2004-01-01

    Sodium 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO−Na+), generated by reduction of TEMPO· with sodium naphthalenide in THF, reacted with alkyl halides or acyl halides to produce O-alkylated or acylated TEMPOs, which were in turn oxidized with mCPBA or reduced with DIBAL-H to afford the corresponding aldehydes, thus accomplishing a new protocol for the halides-carbonyls conversion.

  3. HYPERTHERMIA, INTRACELLULAR FREE CALCIUM AND CALCIUM IONOPHORES

    NARCIS (Netherlands)

    STEGE, GJJ; WIERENGA, PK; KAMPINGA, HH; KONINGS, AWT

    1993-01-01

    It is shown that heat-induced increase of intracellular calcium does not correlate with hyperthermic cell killing. Six different cell lines were investigated; in four (EAT, HeLa S3, L5178Y-R and L5178Y-S) heat treatments killing 90% of the cells did not affect the levels of intracellular free calciu

  4. Double-Diffusive Convection During Growth of Halides and Selenides

    Science.gov (United States)

    Singh, N. B.; Su, Ching-Hua; Duval, Walter M. B.

    2015-01-01

    Heavy metal halides and selenides have unique properties which make them excellent materials for chemical, biological and radiological sensors. Recently it has been shown that selenohalides are even better materials than halides or selenides for gamma-ray detection. These materials also meet the strong needs of a wide band imaging technology to cover ultra-violet (UV), midwave infrared wavelength (MWIR) to very long wavelength infrared (VLWIR) region for hyperspectral imager components such as etalon filters and acousto-optic tunable filters (AO). In fact AOTF based imagers based on these materials have some superiority than imagers based on liquid crystals, FTIR, Fabry-Perot, grating, etalon, electro-optic modulation, piezoelectric and several other concepts. For example, broadband spectral and imagers have problems of processing large amount of information during real-time observation. Acousto-Optic Tunable Filter (AOTF) imagers are being developed to fill the need of reducing processing time of data, low cost operation and key to achieving the goal of covering long-wave infrared (LWIR). At the present time spectral imaging systems are based on the use of diffraction gratings are typically used in a pushbroom or whiskbroom mode. They are mostly used in systems and acquire large amounts of hyperspectral data that is processed off-line later. In contrast, acousto-optic tunable filter spectral imagers require very little image processing, providing new strategies for object recognition and tracking. They are ideally suited for tactical situations requiring immediate real-time image processing. But the performance of these imagers depends on the quality and homogeneity of acousto-optic materials. In addition for many systems requirements are so demanding that crystals up to sizes of 10 cm length are desired. We have studied several selenides and halide crystals for laser and AO imagers for MWIR and LWIR wavelength regions. We have grown and fabricated crystals of

  5. STUDY ON THE CATIONIC POLYMERIZATION OF 1,3-PENTADIENE INITIATED BY AlCl3/ALKYL HALIDE SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    PENG Yuxing; LIU Jialin; DAI Hansong; CUN Linfeng

    1996-01-01

    The cationic polymerizations of 1, 3-pentadiene were initiated by AlCl3 in n-hexane at 30℃ in the presence of alkyl halides, i.e., tert-butyl chloride, tert-butyl bromide and isobutyl chloride. The effects of these halides on the polymer yield, molecular weight,crosslinking reaction, cyclization and polymer microstructure, have been investigated. Two main side reactions, crosslinking and cyclization, were suppressed and reduced by the addition of the halides. The proportion of 1, 4 units of polymer chains was increased by the presence of the halides, which reduced the polymer yield and the molecular weight of polymers.

  6. Photophysics of Hybrid Lead Halide Perovskites: The Role of Microstructure.

    Science.gov (United States)

    Srimath Kandada, Ajay Ram; Petrozza, Annamaria

    2016-03-15

    Since the first reports on high efficiency, solution processed solar cells based on hybrid lead halide perovskites, there has been an explosion of activities on these materials. Researchers with interests spanning the full range from conventional inorganic to emerging organic and hybrid optoelectronic technologies have been contributing to the prolific research output. This has led to solar cell power conversion efficiencies now exceeding 20% and the demonstration of proofs of concept for electroluminescent and lasing devices. Hybrid perovskites can be self-assembled by a simple chemical deposition of the constituent units, with the possibility of integrating the useful properties of organic and inorganic compounds at the molecular scale within a single crystalline material, thus enabling a fine-tuning of the electronic properties. Tellingly, the fundamental properties of these materials may make us think of a new, solution processable, GaAs-like semiconductor. While this can be true to a first approximation, hybrid perovskites are intrinsically complex materials, where the presence of various types of interactions and structural disorder may strongly affect their properties. In particular, a clear understanding and control of the relative interactions between the organic and inorganic moieties is of paramount importance to properly disentangle their innate physics. In this Account we review our recent studies which aim to clarify the relationship between structural and electronic properties from a molecular to mesoscopic level. First we identify the markers for local disorder at the molecular level by using Raman spectroscopy as a probe. Then, we exploit such a tool to explore the role of microstructure on the absorption and luminescence properties of the semiconductor. Finally we address the controversy surrounding electron-hole interactions and excitonic effects. We show that in hybrid lead-halide perovskites dielectric screening also depends on the local

  7. Effects of isoelectronic and halide surfactants on compound semiconductors

    Science.gov (United States)

    Howard, Alexander David

    Isoelectronic surfactants Sb, Bi, and N, have proven to increase the doping efficiency of Zn while concurrently reducing the unintentional impurities C, Si, and S in GaP. Additionally, surfactant Sb and N have demonstrated that altering the incorporation efficiency in GaP is also possible with a surfactant surface coverage of less than one. Halide surfactants Br and Cl were shown to systematically destroy ordering in GaInP. Furthermore, a distinct correlation between increasing surfactant Br or Cl in the vapor and surface roughness was evident. This work is presented in three main sections. First, surfactants Sb and Bi, from the pyrolysis of TMSb and TMBi, were examined to determine the effect on Zn doping in GaP. The data demonstrate that the incorporation of Zn can be increased by an order of magnitude in GaP to a value of approximately 1020 cm-3, the highest value reported to date. Additionally, these same surfactants lead to significant decreases in carbon contamination during growth. At high growth temperatures, the reduction can be as large as 100 x in GaP. Second, the role of steps versus the singular surface between steps was studied by using a surfactant fractional surface coverage of less than one. When surfactant Sb was used, the Zn concentration was increased and C was reduced. However, there was no discernable change in incorporation efficiency over the entire range of surfactant Sb studied. Interestingly, surfactant N showed a linear increase in the Zn doping the with amount of surfactant present during growth resulting in an increase of 2 x at the highest flow rate used. Third, halide surfactants Br and Cl, carbon-tetrabromide and carbon-tetrachloride, were studied for their effects on ordering in GaInP. Bromine systematically decreased the amount of CuPt ordering observed by photoluminescence and transmission electron microscopy. Both surfactants Br and Cl were shown to significantly increase the surface roughness, which is postulated to be the

  8. Hysteresis, Stability, and Ion Migration in Lead Halide Perovskite Photovoltaics.

    Science.gov (United States)

    Miyano, Kenjiro; Yanagida, Masatoshi; Tripathi, Neeti; Shirai, Yasuhiro

    2016-06-16

    Ion migration has been suspected as the origin of various irreproducible and unstable properties, most notably the hysteresis, of lead halide perovskite photovoltaic (PV) cells since the early stage of the research. Although many evidence of ionic movement have been presented both numerically and experimentally, a coherent and quantitative picture that accounts for the observed irreproducible phenomena is still lacking. At the same time, however, it has been noticed that in certain types of PV cells, the hysteresis is absent or at least within the measurement reproducibility. We have previously shown that the electronic properties of hysteresis-free cells are well represented in terms of the conventional inorganic semiconductors. The reproducibility of these measurements was confirmed typically within tens of minutes under the biasing field of -1 V to +1.5 V. In order to probe the effect of ionic motion in the hysteresis-free cells, we extended the time scale and the biasing rage in the electronic measurements, from which we conclude the following: (1) From various evidence, it appears that ion migration is inevitable. However, it does not cause detrimental effects to the PV operation. (2) We propose, based on the quantitative characterization, that the degradation is more likely due to the chemical change at the interfaces between the carrier selective layers and perovskite rather than the compositional change of the lead iodide perovskite bulk. Together, they give much hope in the use of the lead iodide perovskite in the use of actual application. PMID:27227427

  9. Emission Enhancement and Intermittency in Polycrystalline Organolead Halide Perovskite Films

    Directory of Open Access Journals (Sweden)

    Cheng Li

    2016-08-01

    Full Text Available Inorganic-organic halide organometal perovskites have demonstrated very promising performance for opto-electronic applications, such as solar cells, light-emitting diodes, lasers, single-photon sources, etc. However, the little knowledge on the underlying photophysics, especially on a microscopic scale, hampers the further improvement of devices based on this material. In this communication, correlated conventional photoluminescence (PL characterization and wide-field PL imaging as a function of time are employed to investigate the spatially- and temporally-resolved PL in CH3NH3PbI3−xClx perovskite films. Along with a continuous increase of the PL intensity during light soaking, we also observe PL blinking or PL intermittency behavior in individual grains of these films. Combined with significant suppression of PL blinking in perovskite films coated with a phenyl-C61-butyric acid methyl ester (PCBM layer, it suggests that this PL intermittency is attributed to Auger recombination induced by photoionized defects/traps or mobile ions within grains. These defects/traps are detrimental for light conversion and can be effectively passivated by the PCBM layer. This finding paves the way to provide a guideline on the further improvement of perovskite opto-electronic devices.

  10. Electron–phonon coupling in hybrid lead halide perovskites

    Science.gov (United States)

    Wright, Adam D.; Verdi, Carla; Milot, Rebecca L.; Eperon, Giles E.; Pérez-Osorio, Miguel A.; Snaith, Henry J.; Giustino, Feliciano; Johnston, Michael B.; Herz, Laura M.

    2016-01-01

    Phonon scattering limits charge-carrier mobilities and governs emission line broadening in hybrid metal halide perovskites. Establishing how charge carriers interact with phonons in these materials is therefore essential for the development of high-efficiency perovskite photovoltaics and low-cost lasers. Here we investigate the temperature dependence of emission line broadening in the four commonly studied formamidinium and methylammonium perovskites, HC(NH2)2PbI3, HC(NH2)2PbBr3, CH3NH3PbI3 and CH3NH3PbBr3, and discover that scattering from longitudinal optical phonons via the Fröhlich interaction is the dominant source of electron–phonon coupling near room temperature, with scattering off acoustic phonons negligible. We determine energies for the interacting longitudinal optical phonon modes to be 11.5 and 15.3 meV, and Fröhlich coupling constants of ∼40 and 60 meV for the lead iodide and bromide perovskites, respectively. Our findings correlate well with first-principles calculations based on many-body perturbation theory, which underlines the suitability of an electronic band-structure picture for describing charge carriers in hybrid perovskites. PMID:27225329

  11. Superconducting state in bromium halide at high pressure

    Science.gov (United States)

    Szczȩśniak, R.; Zemła, T. P.; Szczȩśniak, D.

    2016-08-01

    The thermodynamic properties of the superconducting state in bromium halide (HBr) compound have been analyzed in the framework of the Eliashberg formalism. In particular, for the range of the pressure (p) from 140 GPa to 200 GPa, it has been shown that the critical temperature increases significantly: TC(p) ∈ K, whereas the Coulomb pseudopotential (μ⋆) is equal to 0.1. Together with the increase of p, the values of the thermodynamic parameters such as: the ratio of the energy gap at the temperature of zero Kelvin to the critical temperature (RΔ ≡ 2 Δ (0) /kB TC), the ratio of the specific heat jump at the critical temperature to the electronic specific heat of the normal state (RC ≡ ΔC (TC) /CN (TC)), and the ratio related to the thermodynamic critical field (RH ≡TC CN (TC) / HC2 (0)) increasingly deviate from the predictions of the BCS model: RΔ(p) ∈ , RC(p) ∈ , and RH(p) ∈ . It should be noted that the increase of μ⋆ visibly lowers TC and significantly reduces the difference between the results of the Eliashberg and BCS theory.

  12. Two dimensional condensation of argon adsorbed on lamellar halides

    International Nuclear Information System (INIS)

    Lamellar halides such as NiCl2, FeCl2, NiBr2, MnBr2, MgBr2, CdBr2, CoI2, FeI2, MnI2, CaI2 and PbI2 were sublimed in a rapid stream of dry nitrogen. The adsorption of argon on such materials shows stepped isotherms which reveal two dimensional condensations. From sets of isotherms the Helmholtz free energy, the internal energy and the entropy of the successive layers are determined. From the entropy of the first layer the role of the potential relief of the adsorbent surface on the structure of the adsorbed layer may be determined while the Helmholtz free energy reveals how the ionic character of the adsorbent governs the attractive force of adsorption. The study of the second third and fourth layers shows that their growth follows quite a different behaviour depending on whether the Van der Waals diameter of argon is greater or smaller than the distance between adjacent anions on the crystal surface. A proposition is made to account for the difference in the critical temperatures of the first and second dense layers in terms of the vibrationnal state of their respective substrate. The occurence for the maximum critical temperature observed of corresponding to a triangular layer 3% more expanded than the (111) plane of solid argon is discussed

  13. Synthetic and structural chemistry of amidinate-substituted boron halides.

    Science.gov (United States)

    Hill, Nicholas J; Findlater, Michael; Cowley, Alan H

    2005-10-01

    The following new amidinate-substituted boron halides are reported: [PhC{N(SiMe(3))}(2)]BCl(2)(6), [MeC{NCy}(2)]BCl(2)(10), [Mes*C{NCy}(2)]BCl(2)(11), [MeC{N(i)Pr}(2)]BCl(2)(12), and [FcC{NCy}(2)]BBr(2)(13). Compound 6 was prepared via the trimethylsilyl chloride elimination reaction of BCl(3) with N,N,N'-tris(trimethylsilyl)benzamidine, and compounds 10-12 were prepared by salt metathesis between the lithium amidinates [RC(NR')(2)]Li and BX(3). Compound 13 was prepared via the insertion of 1,3-dicyclohexylcarbodiimide into the B-C bond of ferrocenyldibromoborane FcBBr(2). The molecular structures of 6, 10, 11, 13 and the known compound [PhC{N(SiMe(3))}(2)]BBr(2)(1) were established by single-crystal X-ray diffraction. PMID:16172649

  14. Effects of halides on reaction of nucleosides with ozone.

    Science.gov (United States)

    Suzuki, Toshinori; Kaya, Eriko; Inukai, Michiyo

    2012-01-01

    Ozone (O(3)), a major component of photochemical oxidants, is used recently as a deodorizer in living spaces. It has been reported that O(3) can directly react with DNA, causing mutagenesis in human cells and carcinogenesis in mice. However, little is known about the effects of coexistent ions in the reaction of O(3). In the present study, we analyzed the effects of halides on the reaction of O(3) with nucleosides using reversed-phase high-performance liquid chromatography with ultraviolet detection. When aqueous O(3) solution was added to a nucleoside mixture in potassium phosphate buffer (pH 7.3), the nucleosides were consumed with the following decreasing order of importance: dGuo > Thd > dCyd > dAdo. The effects of addition of fluoride and chloride in the system were slight. Bromide suppressed the reactions of dGuo, Thd, and dAdo but enhanced the reaction of dCyd. The major products were 5-hydroxy-2'-deoxycytidine, 5-bromo-2'-deoxycytidine, and 8-bromo-2'-deoxyguanosine. The time course and pH dependence of the product yield indicated formation of hypobromous acid as the reactive agent. Iodide suppressed all the reactions effectively. The results suggest that bromide may alter the mutation spectrum by O(3) in humans. PMID:22646086

  15. Phase holograms in silver halide emulsions without a bleaching step

    Science.gov (United States)

    Belendez, Augusto; Madrigal, Roque F.; Pascual, Inmaculada V.; Fimia, Antonio

    2000-03-01

    Phase holograms in holographic emulsions are usually obtained by two bath processes (developing and bleaching). In this work we present a one step method to reach phase holograms with silver-halide emulsions. Which is based on the variation of the conditions of the typical developing processes of amplitude holograms. For this, we have used the well-known chemical developer, AAC, which is composed by ascorbic acid as a developing agent and sodium carbonate anhydrous as accelerator. Agfa 8E75 HD and BB-640 plates were used to obtain these phase gratings, whose colors are between yellow and brown. In function of the parameters of this developing method the resulting diffraction efficiency and optical density of the diffraction gratings were studied. One of these parameters studied is the influence of the grain size. In the case of Agfa plates diffraction efficiency around 18% with density emulsion, whose grain is smaller than that of the Agfa, diffraction efficiency near 30% has been obtained. The resulting gratings were analyzed through X-ray spectroscopy showing the differences of the structure of the developed silver when amplitude and transmission gratings are obtained. The angular response of both (transmission and amplitude) gratings were studied, where minimal transmission is showed at the Braggs angle in phase holograms, whilst a maximal value is obtained in amplitude gratings.

  16. Coordination Chemistry Dictates the Structural Defects in Lead Halide Perovskites.

    Science.gov (United States)

    Rahimnejad, Sara; Kovalenko, Alexander; Forés, Sergio Martí; Aranda, Clara; Guerrero, Antonio

    2016-09-19

    We show the influence of species present in precursor solution during formation of lead halide perovskite materials on the structural defects of the films. The coordination of lead by competing solvent molecules and iodide ions dictate the type of complexes present in the films. Depending on the processing conditions all PbIS5 (+) , PbI2 S4, PbI3 S3 (-) , PbI4 S2 (2-) , PbI5 S2 (3-) , PbI6 (4-) and 1D (Pb2 I4 )n chains are observed by absorption measurements. Different parameters are studied such as polarity of the solvent, concentration of iodide ions, concentration of solvent molecules and temperature. It is concluded that strongly coordinating solvents will preferentially form species with a low number of iodide ions and less coordinative solvents generate high concentration of PbI6 (-) . We furthermore propose that all these plumbate ions may act as structural defects determining electronic properties of the photovoltaic films.

  17. Hysteresis, Stability, and Ion Migration in Lead Halide Perovskite Photovoltaics.

    Science.gov (United States)

    Miyano, Kenjiro; Yanagida, Masatoshi; Tripathi, Neeti; Shirai, Yasuhiro

    2016-06-16

    Ion migration has been suspected as the origin of various irreproducible and unstable properties, most notably the hysteresis, of lead halide perovskite photovoltaic (PV) cells since the early stage of the research. Although many evidence of ionic movement have been presented both numerically and experimentally, a coherent and quantitative picture that accounts for the observed irreproducible phenomena is still lacking. At the same time, however, it has been noticed that in certain types of PV cells, the hysteresis is absent or at least within the measurement reproducibility. We have previously shown that the electronic properties of hysteresis-free cells are well represented in terms of the conventional inorganic semiconductors. The reproducibility of these measurements was confirmed typically within tens of minutes under the biasing field of -1 V to +1.5 V. In order to probe the effect of ionic motion in the hysteresis-free cells, we extended the time scale and the biasing rage in the electronic measurements, from which we conclude the following: (1) From various evidence, it appears that ion migration is inevitable. However, it does not cause detrimental effects to the PV operation. (2) We propose, based on the quantitative characterization, that the degradation is more likely due to the chemical change at the interfaces between the carrier selective layers and perovskite rather than the compositional change of the lead iodide perovskite bulk. Together, they give much hope in the use of the lead iodide perovskite in the use of actual application.

  18. Emission Enhancement and Intermittency in Polycrystalline Organolead Halide Perovskite Films.

    Science.gov (United States)

    Li, Cheng; Zhong, Yu; Luna, Carlos Andres Melo; Unger, Thomas; Deichsel, Konstantin; Gräser, Anna; Köhler, Jürgen; Köhler, Anna; Hildner, Richard; Huettner, Sven

    2016-01-01

    Inorganic-organic halide organometal perovskites have demonstrated very promising performance for opto-electronic applications, such as solar cells, light-emitting diodes, lasers, single-photon sources, etc. However, the little knowledge on the underlying photophysics, especially on a microscopic scale, hampers the further improvement of devices based on this material. In this communication, correlated conventional photoluminescence (PL) characterization and wide-field PL imaging as a function of time are employed to investigate the spatially- and temporally-resolved PL in CH₃NH₃PbI3-xClx perovskite films. Along with a continuous increase of the PL intensity during light soaking, we also observe PL blinking or PL intermittency behavior in individual grains of these films. Combined with significant suppression of PL blinking in perovskite films coated with a phenyl-C61-butyric acid methyl ester (PCBM) layer, it suggests that this PL intermittency is attributed to Auger recombination induced by photoionized defects/traps or mobile ions within grains. These defects/traps are detrimental for light conversion and can be effectively passivated by the PCBM layer. This finding paves the way to provide a guideline on the further improvement of perovskite opto-electronic devices. PMID:27548128

  19. 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...

  20. Robust quantum anomalous Hall effect in ferromagnetic transition metal halides

    CERN Document Server

    Huang, Chengxi; Wu, Haiping; Deng, Kaiming; Jena, Puru; Kan, Erjun

    2016-01-01

    The quantum anomalous Hall (QAH) effect is a novel topological spintronic phenomenon arising from inherent magnetization and spin-orbit coupling. Various theoretical and experimental efforts have been devoted in search of robust intrinsic QAH insulators. However, up to now, it has only been observed in Cr or V doped (Bi,Sb)2Te3 film in experiments with very low working temperature. Based on the successful synthesis of transition metal halides, we use first-principles calculations to predict that RuI3 monolayer is an intrinsic ferromagnetic QAH insulator with a topologically nontrivial global band gap of 11 meV. This topologically nontrivial band gap at the Fermi level is due to its crystal symmetry, thus the QAH effect is robust. Its Curie temperature, estimated to be ~360 K using Monte-Carlo simulation, is above room temperature and higher than most of two-dimensional ferromagnetic thin films. We also discuss the manipulation of its exchange energy and nontrivial band gap by applying in-plane strain. Our wor...

  1. Experimental and theoretical optical properties of methylammonium lead halide perovskites.

    Science.gov (United States)

    Leguy, Aurélien M A; Azarhoosh, Pooya; Alonso, M Isabel; Campoy-Quiles, Mariano; Weber, Oliver J; Yao, Jizhong; Bryant, Daniel; Weller, Mark T; Nelson, Jenny; Walsh, Aron; van Schilfgaarde, Mark; Barnes, Piers R F

    2016-03-28

    The optical constants of methylammonium lead halide single crystals CH3NH3PbX3 (X = I, Br, Cl) are interpreted with high level ab initio calculations using the relativistic quasiparticle self-consistent GW approximation (QSGW). Good agreement between the optical constants derived from QSGW and those obtained from spectroscopic ellipsometry enables the assignment of the spectral features to their respective inter-band transitions. We show that the transition from the highest valence band (VB) to the lowest conduction band (CB) is responsible for almost all the optical response of MAPbI3 between 1.2 and 5.5 eV (with minor contributions from the second highest VB and the second lowest CB). The calculations indicate that the orientation of [CH3NH3](+) cations has a significant influence on the position of the bandgap suggesting that collective orientation of the organic moieties could result in significant local variations of the optical properties. The optical constants and energy band diagram of CH3NH3PbI3 are then used to simulate the contributions from different optical transitions to a typical transient absorption spectrum (TAS). PMID:26477295

  2. Effects of halide ions on photodegradation of sulfonamide antibiotics: Formation of halogenated intermediates.

    Science.gov (United States)

    Li, Yingjie; Qiao, Xianliang; Zhang, Ya-Nan; Zhou, Chengzhi; Xie, Huaijun; Chen, Jingwen

    2016-10-01

    The occurrence of sulfonamide antibiotics (SAs) in estuarine waters urges insights into their environmental fate for ecological risk assessment. Although many studies focused on the photochemical behavior of SAs, yet the effects of halide ions relevant to estuarine and marine environments on their photodegradation have been poorly understood. Here, we investigated the effects of halide ions on the photodegradation of SAs with sulfapyridine, sulfamethazine, and sulfamethoxazole as representative compounds. Results showed that halide ions did not significantly impact the photodegradation of sulfapyridine and sulfamethoxazole, while they significantly promoted the photodegradation of sulfamethazine. Further experiments found that ionic strength applied with NaClO4 significantly enhanced the photodegradation of the SAs, which was attributed to the decreased quenching rate constant of the triplet-excited SAs ((3)SA(∗)). Compared with ionic strength, specific Cl(-) effects retarded the photodegradation of the SAs. Our study found that triplet-excited sulfamethazine can oxidize halide ions to produce halogen radicals, subsequently leading to the halogenation of sulfamethazine, which was confirmed by the identification of both chlorinated and brominated intermediates. These results indicate that halide ions play an important role in the photochemical behavior of some SAs in estuarine waters and seawater. The occurrence of halogenation for certain organic pollutants can be predicted by comparing the oxidation potentials of triplet-excited contaminants with those of halogen radicals. Our findings are helpful in understanding the photochemical behavior and assessing the ecological risks of SAs and other organic pollutants in estuarine and marine environment. PMID:27393965

  3. Influence of Halide Solutions on Collagen Networks: Measurements of Physical Properties by Atomic Force Microscopy

    Science.gov (United States)

    Kempe, André; Lackner, Maximilian

    2016-01-01

    The influence of aqueous halide solutions on collagen coatings was tested. The effects on resistance against indentation/penetration on adhesion forces were measured by atomic force microscopy (AFM) and the change of Young's modulus of the coating was derived. Comparative measurements over time were conducted with halide solutions of various concentrations. Physical properties of the mesh-like coating generally showed large variability. Starting with a compact set of physical properties, data disperse after minutes. A trend of increase in elasticity and permeability was found for all halide solutions. These changes were largest in NaI, displaying a logical trend with ion size. However a correlation with concentration was not measured. Adhesion properties were found to be independent of mechanical properties. The paper also presents practical experience for AFM measurements of soft tissue under liquids, particularly related to data evaluation. The weakening in physical strength found after exposure to halide solutions may be interpreted as widening of the network structure or change in the chemical properties in part of the collagen fibres (swelling). In order to design customized surface coatings at optimized conditions also for medical applications, halide solutions might be used as agents with little impact on the safety of patients.

  4. Calcium binding by dietary fibre

    International Nuclear Information System (INIS)

    Dietary fibre from plants low in phytate bound calcium in proportion to its uronic-acid content. This binding by the non-cellulosic fraction of fibre reduces the availability of calcium for small-intestinal absorption, but the colonic microbial digestion of uronic acids liberates the calcium. Thus the ability to maintain calcium balance on high-fibre diets may depend on the adaptive capacity on the colon for calcium. (author)

  5. Acidosis and Urinary Calcium Excretion

    DEFF Research Database (Denmark)

    Alexander, R Todd; Cordat, Emmanuelle; Chambrey, Régine;

    2016-01-01

    Metabolic acidosis is associated with increased urinary calcium excretion and related sequelae, including nephrocalcinosis and nephrolithiasis. The increased urinary calcium excretion induced by metabolic acidosis predominantly results from increased mobilization of calcium out of bone...... and inhibition of calcium transport processes within the renal tubule. The mechanisms whereby acid alters the integrity and stability of bone have been examined extensively in the published literature. Here, after briefly reviewing this literature, we consider the effects of acid on calcium transport...

  6. [Calcium suppletion for patients who use gastric acid inhibitors: calcium citrate or calcium carbonate?].

    NARCIS (Netherlands)

    Jonge, H.J. de; Gans, R.O.; Huls, G.A.

    2012-01-01

    Various calcium supplements are available for patients who have an indication for calcium suppletion. American guidelines and UpToDate recommend prescribing calcium citrate to patients who use antacids The rationale for this advice is that water-insoluble calcium carbonate needs acid for adequate ab

  7. Alkaline and alkaline earth metal phosphate halides and phosphors

    Science.gov (United States)

    Lyons, Robert Joseph; Setlur, Anant Achyut; Cleaver, Robert John

    2012-11-13

    Compounds, phosphor materials and apparatus related to nacaphite family of materials are presented. Potassium and rubidium based nacaphite family compounds and phosphors designed by doping divalent rare earth elements in the sites of alkaline earth metals in the nacaphite material families are descried. An apparatus comprising the phosphors based on the nacaphite family materials are presented herein. The compounds presented is of formula A.sub.2B.sub.1-yR.sub.yPO.sub.4X where the elements A, B, R, X and suffix y are defined such that A is potassium, rubidium, or a combination of potassium and rubidium and B is calcium, strontium, barium, or a combination of any of calcium, strontium and barium. X is fluorine, chlorine, or a combination of fluorine and chlorine, R is europium, samarium, ytterbium, or a combination of any of europium, samarium, and ytterbium, and y ranges from 0 to about 0.1.

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

    OpenAIRE

    Aiichiro Nagaki; Yuki Uesugi; Yutaka Tomida; Jun-ichi Yoshida

    2011-01-01

    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.

  9. Copper(I)-catalyzed carbon-halogen bond-selective boryl substitution of alkyl halides bearing terminal alkene moieties

    OpenAIRE

    Iwamoto, Hiroaki; Kubota, Koji; Yamamoto, Eiji; Ito, Hajime

    2015-01-01

    The selective boryl substitution of alkyl halides bearing terminal C=C double bonds has been achieved using a copper(I)/tricyclohexylphosphine or copper(I)/o-diphenylphosphinophenol catalyst. This reaction represents a useful complementary approach to conventional procedures for the hydroboration of C=C double bonds or the borylative cyclization of alkyl halides bearing terminal alkenes.

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

    OpenAIRE

    Nagaki, Aiichiro; Uesugi, Yuki; Tomida, Yutaka; Yoshida, Jun-ichi

    2011-01-01

    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.

  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. 10 CFR 431.324 - Uniform test method for the measurement of energy efficiency of metal halide ballasts.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Uniform test method for the measurement of energy efficiency of metal halide ballasts. 431.324 Section 431.324 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY PROGRAM FOR CERTAIN COMMERCIAL AND INDUSTRIAL EQUIPMENT Metal Halide Lamp Ballasts...

  13. Holographic optical elements recorded in silver halide sensitized gelatin emulsions. Part I. Transmission holographic optical elements.

    Science.gov (United States)

    Kim, J M; Choi, B S; Kim, S I; Kim, J M; Bjelkhagen, H I; Phillips, N J

    2001-02-10

    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.

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

    Directory of Open Access Journals (Sweden)

    Sourish Chatterjee

    2013-11-01

    Full Text Available 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 CMH lamp demands the use of current control device in the lamp circuit and perfect matching of lamp ballast combination is required for efficient lamp operation. The electrical and photometric performance of two sets of commercial 70 watt CMH lamp and intregated ballast units were measured to investigate their compatibility for optimum lamp operation. The measured data were utilized to develop an electrical model for lamp ballast combination. Using this model a compatibility index is proposed which can be used for assessment of lamp performance.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun; Wang, Yafeng; Hu, Tao; Wu, Lin; Shen, Xuechu; Chen, Zhanghai, E-mail: lujian@fudan.edu.cn, E-mail: zhanghai@fudan.edu.cn [State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433 (China); Cao, Runan; Xu, Fei [Department of Physics, Shanghai University, Shanghai 200444 (China); Da, Peimei; Zheng, Gengfeng [Laboratory of Advanced Materials, Department of Chemistry, Fudan University, Shanghai 200433 (China); Lu, Jian, E-mail: lujian@fudan.edu.cn, E-mail: zhanghai@fudan.edu.cn [State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433 (China); Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210 (China)

    2016-01-11

    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.

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

    International Nuclear Information System (INIS)

    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

  17. High-Efficiency Flexible Solar Cells Based on Organometal Halide Perovskites.

    Science.gov (United States)

    Wang, Yuming; Bai, Sai; Cheng, Lu; Wang, Nana; Wang, Jianpu; Gao, Feng; Huang, Wei

    2016-06-01

    Flexible and light-weight solar cells are important because they not only supply power to wearable and portable devices, but also reduce the transportation and installation cost of solar panels. High-efficiency organometal halide perovskite solar cells can be fabricated by a low-temperature solution process, and hence are promising for flexible-solar-cell applications. Here, the development of perovskite solar cells is briefly discussed, followed by the merits of organometal halide perovskites as promising candidates as high-efficiency, flexible, and light-weight photovoltaic materials. Afterward, recent developments of flexible solar cells based on perovskites are reviewed.

  18. Surface tension of molten alkali metal halides as a function of ion sizes

    International Nuclear Information System (INIS)

    The analysis of the experimental data on the surface tension of the liquid/vapor interphase boundary of the molten alkali metal halides MX (M Li-Cs, X = F-I) near the melting temperature, accounting for the cation and anion dimensional differences, is presented. The main attention is focused at the manifestation of the effects of the interphase boundary of the effects of the interphase boundary thickness and twofold electric layer. It is shown, that the experimental data on the whole MX series may be represented in the form of the electrocapillary curve on the graph of the surface tension dependence on the degree of the halides dimensional asymmetry

  19. 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.

  20. Study of alkali halide/FHF - systems at 10 - 290 K, 0 - 8 kBAR

    Science.gov (United States)

    Chunnilall, C. J.; Sherman, W. F.; Wilkinson, G. R.

    1984-03-01

    The bifluoride ion FHF -, (and FDF -), has been substitutionally isolated within single crystal samples of several alkali halides. Infrared and Raman spectra of these crystals have been studied at variable temperature and pressure. The infrared absorptions are strong, whereas the Raman is weak. At low temperatures the bands are very sharp with halfwidths less than 1 cm -1. On applying pressure, ν3 increases in frequency whereas ν2 decreases. On reducing temperature, ν3 decreases in frequency whereas ν2 increases. Hence the effect of volume contraction is overridden in the temperature dependent case. The deuterated spectra confirm that the bifluoride ion is well isolated within the alkali halide matrix.

  1. Visible-Light-Promoted Trifluoromethylthiolation of Styrenes by Dual Photoredox/Halide Catalysis.

    Science.gov (United States)

    Honeker, Roman; Garza-Sanchez, R Aleyda; Hopkinson, Matthew N; Glorius, Frank

    2016-03-18

    Herein, we report a new visible-light-promoted strategy to access radical trifluoromethylthiolation reactions by combining halide and photoredox catalysis. This approach allows for the synthesis of vinyl-SCF3 compounds of relevance in pharmaceutical chemistry directly from alkenes under mild conditions with irradiation from household light sources. Furthermore, alkyl-SCF3-containing cyclic ketone and oxindole derivatives can be accessed by radical-polar crossover semi-pinacol and cyclization processes. Inexpensive halide salts play a crucial role in activating the trifluoromethylthiolating reagent towards photoredox catalysis and aid the formation of the SCF3 radical.

  2. 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.

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

    Science.gov (United States)

    Sudheer, Tiwari, P.; Varshney, G. K.; Rai, V. N.; Srivastava, A. K.

    2016-05-01

    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.

  4. High-Efficiency Flexible Solar Cells Based on Organometal Halide Perovskites.

    Science.gov (United States)

    Wang, Yuming; Bai, Sai; Cheng, Lu; Wang, Nana; Wang, Jianpu; Gao, Feng; Huang, Wei

    2016-06-01

    Flexible and light-weight solar cells are important because they not only supply power to wearable and portable devices, but also reduce the transportation and installation cost of solar panels. High-efficiency organometal halide perovskite solar cells can be fabricated by a low-temperature solution process, and hence are promising for flexible-solar-cell applications. Here, the development of perovskite solar cells is briefly discussed, followed by the merits of organometal halide perovskites as promising candidates as high-efficiency, flexible, and light-weight photovoltaic materials. Afterward, recent developments of flexible solar cells based on perovskites are reviewed. PMID:26669326

  5. CALCIUM-INDUCED SUPRAMOLECULAR STRUCTURES IN THE CALCIUM CASEINATE SYSTEM

    Science.gov (United States)

    The molecular details deciphering the spontaneous calcium-induced protein aggregation process in the calcium caseinate system remain obscure. Understanding this complex process could lead to potential new applications of this important food ingredient. In this work, we studied calcium-induced supra...

  6. GaN nanotubes grown by halide vapor phase epitaxy

    International Nuclear Information System (INIS)

    Full text: Wide-band gap GaN nanostructures such as quantum dots, nanorods, nanowires, nano columns and nanotubes have a strong potential within areas of biochemical sensing, nanofluidics, and optoelectronics. GaN nanotubes play a role of the building blocks for several applications such as solution-based transistors and highly sensitive nanotube molecular sensors. We have studied non-catalytic and Au-assisted growth of GaN nanotubes using halide vapor phase epitaxy (HVPE) technique. The growth was performed in the temperature range 480 degrees Celsius to 520 degrees Celsius using pure N2 as a carrier gas at atmospheric pressure. The nanotubes size, shape, density and the selectivity of growth have been studied depending on V/III ratio, growth temperature and substrate material. By increasing the GaCl partial pressure, the structure changed from dot-like to nanotubes. The nanotubes were about 1 μm long with a diameter of typically 200 nm. In addition, it was observed that the nanostructures were spontaneously nucleated at droplets of Ga or, when using Au-coated Al2O3, on droplets of Au/Ga alloy. By varying the growth temperature, the inner diameter of the nanotubes could be controlled. A growth model is suggested, where the nanotubes are nucleated at droplets of Ga or an Au/Ga alloy. Our experimental results suggest that the approach with pre-patterned Au-coated Al2O3 substrates has the potential for fabrication of well-organized nanotubes with a high density. Nanostructures were characterized using electron microscopy methods and by low temperature time-resolved photoluminescence (TRPL). Studies were performed on samples with different wall thickness in the range of 35-75 nm. Two recombination processes with different dynamics contribute to the emission spectra of the GaN nanotubes. The photoluminescence peak shifts rapidly to the higher energy from 3.47 eV to 3.75 eV within a very short time of 30 ps. The origin of the emission having a short lifetime is related

  7. A sensor for calcium uptake

    OpenAIRE

    Collins, Sean; Meyer, Tobias

    2010-01-01

    Mitochondria — the cell’s power plants — increase their energy production in response to calcium signals in the cytoplasm. A regulator of the elusive mitochondrial calcium channel has now been identified.

  8. Children's Bone Health and Calcium

    Science.gov (United States)

    ... Trials Resources and Publications Children's Bone Health and Calcium: Condition Information Skip sharing on social media links ... straight, walk, run, and lead an active life. Calcium is one of the key dietary building blocks ...

  9. Calcium ion channel and epilepsy

    Institute of Scientific and Technical Information of China (English)

    Yudan Lü; Weihong Lin; Dihui Ma

    2006-01-01

    OBJECTIVE: To review the relationship between calcium ion channel and epilepsy for well investigating the pathogenesis of epilepsy and probing into the new therapeutic pathway of epilepsy.DATA SOURCES: A computer-based online research Calcium ion channel and epilepsy related articles published between January 1994 and December 2006 in the CKNI and Wanfang database with the key words of "calcium influxion, epilepsy, calcium-channel blocker". The language was limited to Chinese. At the same time,related articles published between January 1993 and December 2006 in Pubmed were searched for on online with the key words of "calcium influxion, epilepsy" in English.STUDY SELECTION: The materials were selected firstly. Inclusive criteria: ① Studies related to calcium ion channel and the pat1hogenesis of epilepsy. ② Studies on the application of calcium ion channel blocker in the treatment of epilepsy. Exclusive criteria: repetitive or irrelated studies.DATA EXTRACTION: According to the criteria, 123 articles were retrieved and 93 were excluded due to repetitive or irrelated studies. Altogether 30 articles met the inclusive criteria, 11 of them were about the structure and characters of calcium ion channel, 10 about calcium ion channel and the pathogenesis of epilepsy and 9 about calcium blocker and the treatment of epilepsy.DATA SYNTHESIS: Calcium ion channels mainly consist of voltage dependent calcium channel and receptor operated calcium channel. Depolarization caused by voltage gating channel-induced influxion is the pathological basis of epileptic attack, and it is found in many studies that many anti-epileptic drugs have potential and direct effect to rivalizing voltage-dependent calcium ion channel.CONCLUSION: Calcium influxion plays an important role in the seizure of epilepsy. Some calcium antagonists seen commonly are being tried in the clinical therapy of epilepsy that is being explored, not applied in clinical practice. If there are enough evidences to

  10. Solar Imagery - Chromosphere - Calcium

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset consists of full-disk images of the sun in Calcium (Ca) II K wavelength (393.4 nm). Ca II K imagery reveal magnetic structures of the sun from about...

  11. An Improved Protocol for the Pd-catalyzed α-Arylation of Aldehydes with Aryl Halides

    OpenAIRE

    Martín, Rubén; Buchwald, Stephen L.

    2008-01-01

    An improved protocol for the Pd-catalyzed α-arylation of aldehydes with aryl halides has been developed. The new catalytic system allows for the coupling of an array of substrates including challenging electron-rich aryl bromides and less reactive aryl chlorides. The utility of this method has been demonstrated in a new total synthesis of (±)-sporochnol.

  12. Regioselective chlorination and bromination of unprotected anilines under mild conditions using copper halides in ionic liquids

    OpenAIRE

    Han Wang; Kun Wen; Nurbiya Nurahmat; Yan Shao; He Zhang; Chao Wei; Ya Li; Yongjia Shen; Zhihua Sun

    2012-01-01

    By using ionic liquids as solvents, the chlorination or bromination of unprotected anilines at the para-position can be achieved in high yields with copper halides under mild conditions, without the need for potentially hazardous operations such as supplementing oxygen or gaseous HCl.

  13. α-Regioselective Barbier Reaction of Carbonyl Compounds and Allyl Halides Mediated by Praseodymium.

    Science.gov (United States)

    Wu, San; Li, Ying; Zhang, Songlin

    2016-09-01

    The first utility of praseodymium as a mediating metal in the Barbier reaction of carbonyl compounds with allyl halides was reported in this paper. In contrast to the traditional metal-mediated or catalyzed Barbier reactions, exclusive α-adducts were obtained in this one-pot reaction with a broad scope of substrates and feasible reaction conditions. PMID:27490708

  14. Magnetic Silica Supported Copper: A Modular Approach to Aqueous Ullmann-type Amination of Aryl Halides

    Science.gov (United States)

    One-pot synthesis of magnetic silica supported copper catalyst has been described via in situ generated magnetic silica (Fe3O4@SiO2); the catalyst can be used for the efficacious amination of aryl halides in aqueous medium under microwave irradiation.

  15. Regioselective chlorination and bromination of unprotected anilines under mild conditions using copper halides in ionic liquids

    Directory of Open Access Journals (Sweden)

    Han Wang

    2012-05-01

    Full Text Available By using ionic liquids as solvents, the chlorination or bromination of unprotected anilines at the para-position can be achieved in high yields with copper halides under mild conditions, without the need for potentially hazardous operations such as supplementing oxygen or gaseous HCl.

  16. Amination of Aryl Halides and Esters Using Intensified Continuous Flow Processing

    OpenAIRE

    Thomas M. Kohl; Christian H. Hornung; John Tsanaktsidis

    2015-01-01

    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.

  17. Iron-Catalyzed Acylation of Polyfunctionalized Aryl- and Benzylzinc Halides with Acid Chlorides.

    Science.gov (United States)

    Benischke, Andreas D; Leroux, Marcel; Knoll, Irina; Knochel, Paul

    2016-08-01

    FeCl2 (5 mol %) catalyzes a smooth and convenient acylation of functionalized arylzinc halides at 50 °C (2-4 h) and benzylic zinc chlorides at 25 °C (0.5-4 h) with a variety of acid chlorides leading to polyfunctionalized diaryl and aryl heteroaryl ketones. PMID:27457108

  18. Enhancement of Exciton Emission in Lead Halide-Based Layered Perovskites by Cation Mixing.

    Science.gov (United States)

    Era, Masanao; Komatsu, Yumeko; Sakamoto, Naotaka

    2016-04-01

    Spin-coated films of a lead halide, PbX: X = I and Br, layered perovskites having cyclohexenylethyl ammonium molecule as an organic layer, which were mixed with other metal halide-based layered perovskites consisting of various divalent metal halides (for example, Ca2, Cdl2, FeI2, SnBr2 and so on), were prepared. The results of X-ray diffraction measurements exhibited that solid solution formation between PbX-based layered perovskite and other divalent metal halide-based layered perovskites was observed up to very high molar concentration of 50 molar% in the mixed film samples when divalent cations having ionic radius close to that of Pb2+ were employed. In the solid solution films, the exciton emission was much enhanced at room temperature. Exciton emission intensity of Pbl-based layered perovskite mixed with Cal-based layered perovskite (20 molar%) is about 5 times large that of the pristine Pbl-based layered perovskite, and that of PbBr-based layered perovskite mixed with SnBr-based layered perovskite (20 molar%) was also about 5 times large that of the pristine PbBr-based layered perovskite at room temperature. PMID:27451628

  19. 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

  20. Correlation between standard enthalpy of formation, structural parameters and ionicity for alkali halides

    Directory of Open Access Journals (Sweden)

    Nasar Abu

    2013-01-01

    Full Text Available The standard enthalpy of formation (ΔHo has been considered to be an interesting and useful parameter for the correlation of various properties of alkali halides. The interrelation between ΔHo and structural parameters for the halides of Li, Na, K and Rb has been thoroughly analyzed. When cationic component element is kept constant in a homologous series of alkali halides, the negative value of ΔHo has been observed to decrease linearly with increase of interionic distance (d and accordingly following empirical equation ΔHo = α + βd (where α and β are empirical constants has been established. However, for common anionic series of alkali halides an opposite nonlinear trend has been observed with the exception of common fluorides. The correlation study on the standard enthalpy of formation has been extended in term of radius ratio and also discussed in the light of ionization energy of the metal, electron affinity of the halogen, size of the ions, ionic character of bond and lattice energy of the compound.

  1. A Simple Empirical Analysis of the Enthalpies of Formation of Lanthanide Halides and Oxides.

    Science.gov (United States)

    Smith, Derek W.

    1986-01-01

    Proposes a simple and general method whereby the lattice energies of lanthanide(II) and (IV) compounds are derived directly from those found experimentally for the corresponding lanthanide(III) compounds. The method is applicable to all lanthanide halides and oxides and involves calculations which can be easily and quickly performed by students.…

  2. Non-conventional halide oxidation pathways : oxidation by imidazole triplet and surface specific oxidation by ozone

    Science.gov (United States)

    Ammann, Markus; Corral-Arroyo, Pablo; Aellig, Raphael; Orlando, Fabrizio; Lee, Ming-Tao; Artiglia, Luca

    2016-04-01

    Oxidation of halide ions (chloride, bromide, iodide) are the starting point of halogen release mechanisms out of sea water, marine aerosol or other halide containing continental aerosols. Slow oxidation of chloride and bromide by ozone in the bulk aqueous phase is of limited relevance. Faster surface specific oxidation has been suggested based on heterogeneous kinetics experiments. We provide first insight into very efficient bromide oxidation by ozone at the aqueous solution - air interface by surface sensitive X-ray photoelectron spectroscopy indicating significant build-up of an oxidized intermediate at the surface within millisecond time scales. The second source of oxidants in the condensed we have considered is the absorption of light by triplet forming photosensitizers at wavelengths longer than needed for direct photolysis and radical formation. We have performed coated wall flow tube experiments with mixtures of citric acid (CA) and imidazole-2-carboxaldehyde (IC) to represent secondary organic material rich marine aerosol. The halide ions bromide and iodide have been observed to act as efficient electron donors leading to their oxidation, HO2 formation and finally release of molecular halogen compounds. The photosensitization of imidazole-2-carboxaldehyde (IC) involves a well-known mechanism where the triplet excited state of IC is reduced by citric acid to a reduced ketyl radical that reacts with halide ions. A competition kinetics approach has been used to evaluate the rate limiting steps and to assess the significance of this source of halogens to the gas phase.

  3. Palladium-catalyzed Coupling between Aryl Halides and Trimethylsilylacetylene Assisted by Dimethylaminotrimethyltin

    Institute of Scientific and Technical Information of China (English)

    Cai Liangzhen; Yang Dujuan; Sun Zhonghua; Tao Xiaochun; Cai Lisheng; Pike Victor W

    2011-01-01

    Palladium-catalyzed coupling between aryl halides, especially less reactive ones or N-heteroaryls, and trimethylsilylacetylene in the presence of dimethylaminotrimethyltin generated the coupled products in high yields. The reaction does not need CuI and base as auxiliary agents.

  4. New Condensation Reaction of β-keto-δ-valerolactones, Carbon Disulfide and Alkyl Halides

    Institute of Scientific and Technical Information of China (English)

    You Ming WANG; Yu Xin LI; Su Hua WANG; Zheng Ming LI

    2004-01-01

    β-Keto-δ-valerolactones, which were obtained by reaction of acetoacetate with aldehydes or ketones, reacted with carbon disulfide, alkyl halides and a new condensation reaction was developed. The structures of the products 3 were confirmed by 1HNMR spectra and elemental analysis.

  5. Ionic liquids as solvent for efficient esterification of carboxylic acids with alkyl halides

    OpenAIRE

    carboxylic, Ionic liquids as solvent for efficient e

    2010-01-01

    The selective esterification of carboxylic acid derivatives with a variety of alkyl halides was carried out using ionic liquid as solvent in the presence of triethylamine. The reaction was found to proceed under relatively mild conditions with excellent conversions (up to 99%) and selectivities. The ionic liquid was recycled and reused.

  6. Halogen bonding-enhanced electrochemical halide anion sensing by redox-active ferrocene receptors.

    Science.gov (United States)

    Lim, Jason Y C; Cunningham, Matthew J; Davis, Jason J; Beer, Paul D

    2015-10-01

    The first examples of halogen bonding redox-active ferrocene receptors and their anion electrochemical sensing properties are reported. Halogen bonding was found to significantly amplify the magnitude of the receptor's metallocene redox-couple's voltammetric responses for halide sensing compared to their hydrogen bonding analogues in both acetonitrile and aqueous-acetonitrile solvent media. PMID:26289779

  7. Halocyclization of Unsaturated Guanidines Mediated by Koser's Reagent and Lithium Halides.

    Science.gov (United States)

    Daniel, Marion; Blanchard, Florent; Nocquet-Thibault, Sophie; Cariou, Kevin; Dodd, Robert H

    2015-11-01

    The synthesis of halogenated cyclic guanidines through iodine(III)-mediated umpolung of halide salts is described. Cyclic guanidines of various sizes can be obtained with generally excellent regioselectivities through either a chloro- or a bromocyclization, using Koser's reagent and the corresponding lithium salt. PMID:26492553

  8. 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...

  9. Synthesis of Cyclic Carbonates from CO2 and Epoxides Catalyzed by Hexaalkylguanidinium Halides

    Institute of Scientific and Technical Information of China (English)

    DUAN Hai-feng; LI Sheng-hai; LIN Ying-jie; XIE Hai-bo; ZHANG Suo-bo; WANG Zong-mu

    2004-01-01

    Hexaalkylguanidinium halides exhibit an efficient catalytic activity in the synthesis of cyclic carbonates from epoxides and carbon dioxide. By this method cyclic carbonates can be obtained in a high yield and a high selectivity at a low temperature and atmospheric pressure. This procedure is easy for the product isolation and recycling of the catalyst.

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

    International Nuclear Information System (INIS)

    Objective is to provide thermochemical data for key actinide halide and oxyhalide systems. Progress is reported on bond dissociation energies of gaseous ThCl4, ThCl3, ThCl2, and ThCl; bond dissociation energies of ruthenium fluorides; and mass spectroscopy of UF6

  11. 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.

  12. Exciton Binding Energy in Organic-Inorganic Tri-Halide Perovskites.

    Science.gov (United States)

    Askar, Abdelrahman M; Shankar, Karthik

    2016-06-01

    The recent dramatic increase in the power conversion efficiencies of organic-inorganic tri-halide perovskite solar cells has triggered intense research worldwide and created a paradigm shift in the photovoltaics field. It is crucial to develop a solid understanding of the photophysical processes underlying solar cell operation in order to both further improve the photovoltaic performance of perovskite solar cells as well as to exploit the broader optoelectronic applications of the tri-halide perovskites. In this short review, we summarize the main research findings about the binding energy of excitons in tri-halide perovskite materials and find that a value in the range of 2-22 meV at room temperature would be a safe estimate. Spontaneous free carrier generation is the dominant process taking place directly after photoexcitation in organic-inorganic tri-halide perovskites at room temperature, which eliminates the exciton diffusion bottleneck present in organic solar cells and constitutes a major contributing factor to the high photovoltaic performance of this material. PMID:27427650

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

    International Nuclear Information System (INIS)

    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. Microwave assisted, ligand free, copper catalyzed reaction of aryl halides with phenyl urea

    Institute of Scientific and Technical Information of China (English)

    Sandip N. Gavade; Ravi S. Balaskar; Madhav S. Mane; Pramod N. Pabrekar; Murlidhar S. Shingare; Dhananjay V. Mane

    2011-01-01

    The ligand free coupling reaction of phenyl urea with different functionalized aryl halides in the presence of air stable Cu2O and t-BuOK as a base gives symmetrical and unsymmetrical diarylureas in relatively high yields. This method is milder than the palladium catalyzed arylation and avoids the use of toxic phosphine ligand.

  15. Viabilization of a new aluminium grain refiner based on Zirconium halide salt

    International Nuclear Information System (INIS)

    A new aluminium grain refiner based on Zirconium halide salt is proposed. Its efficiency, as grain refiner is analysed varying the salt amount, the inoculation temperature and holding time. The grain size reduction shows to be dependent on the salt amount and independent on the inoculation temperature. The holding time effects is dependent on the innoculated salt amount. (Author)

  16. Calcium aluminate in alumina

    Science.gov (United States)

    Altay, Arzu

    The properties of ceramic materials are determined not only by the composition and structure of the phases present, but also by the distribution of impurities, intergranular films and second phases. The phase distribution and microstructure both depend on the fabrication techniques, the raw materials used, the phase-equilibrium relations, grain growth and sintering processes. In this dissertation research, various approaches have been employed to understand fundamental phenomena such as grain growth, impurity segregation, second-phase formation and crystallization. The materials system chosen was alumina intentionally doped with calcium. Atomic-scale structural analyses of grain boundaries in alumina were carried on the processed samples. It was found that above certain calcium concentrations, CA6 precipitated as a second phase at all sintering temperatures. The results also showed that abnormal grain growth can occur after precipitation and it is not only related to the calcium level, but it is also temperature dependent. In order to understand the formation mechanism of CA6 precipitates in calcium doped alumina samples, several studies have been carried out using either bulk materials or thin films The crystallization of CA2 and CA6 powders has been studied. Chemical processing techniques were used to synthesize the powders. It was observed that CA2 powders crystallized directly, however CA6 powders crystallized through gamma-Al 2O3 solid solution. The results of energy-loss near-edge spectrometry confirmed that gamma-Al2O3 can dissolve calcium. Calcium aluminate/alumina reaction couples have also been investigated. All reaction couples were heat treated following deposition. It was found that gamma-Al2O3 was formed at the interface as a result of the interfacial reaction between the film and the substrate. gamma-Al 2O3 at the interface was stable at much higher temperatures compared to the bulk gamma-Al2O3 formed prior to the CA6 crystallization. In order to

  17. Effects of Alloying on the Optical Properties of Organic-Inorganic Lead Halide Perovskite Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Ndione, Paul F.; Li, Zhen; Zhu, Kai

    2016-09-07

    Complex refractive index and dielectric function spectra of organic-inorganic lead halide perovskite alloy thin films are presented, together with the critical-point parameter analysis (energy and broadening) of the respective composition. Thin films of methylammonium lead halide alloys (MAPbI3, MAPbBr3, MAPbBr2I, and MAPbBrI2), formamidinium lead halide alloys (FAPbI3, FAPbBr3, and FAPbBr2I), and formamidinium cesium lead halide alloys [FA0.85Cs0.15PbI3, FA0.85Cs0.15PbBrI2, and FA0.85Cs0.15Pb(Br0.4I0.6)3] were studied. The complex refractive index and dielectric functions were determined by spectroscopic ellipsometry (SE) in the photon energy range of 0.7-6.5 eV. Critical point energies and optical transitions were obtained by lineshape fitting to the second-derivative of the complex dielectric function data of these thin films as a function of alloy composition. Absorption onset in the vicinity of the bandgap, as well as critical point energies and optical band transition shift toward higher energies as the concentration of Br in the films increases. Cation alloying (Cs+) has less effect on the optical properties of the thin films compared to halide mixed alloys. The reported optical properties can help to understand the fundamental properties of the perovskite materials and also be used for optimizing or designing new devices.

  18. Calcium signaling in taste cells.

    Science.gov (United States)

    Medler, Kathryn F

    2015-09-01

    The sense of taste is a common ability shared by all organisms and is used to detect nutrients as well as potentially harmful compounds. Thus taste is critical to survival. Despite its importance, surprisingly little is known about the mechanisms generating and regulating responses to taste stimuli. All taste responses depend on calcium signals to generate appropriate responses which are relayed to the brain. Some taste cells have conventional synapses and rely on calcium influx through voltage-gated calcium channels. Other taste cells lack these synapses and depend on calcium release to formulate an output signal through a hemichannel. Beyond establishing these characteristics, few studies have focused on understanding how these calcium signals are formed. We identified multiple calcium clearance mechanisms that regulate calcium levels in taste cells as well as a calcium influx that contributes to maintaining appropriate calcium homeostasis in these cells. Multiple factors regulate the evoked taste signals with varying roles in different cell populations. Clearly, calcium signaling is a dynamic process in taste cells and is more complex than has previously been appreciated. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.

  19. Fruit Calcium: Transport and Physiology

    Directory of Open Access Journals (Sweden)

    Bradleigh eHocking

    2016-04-01

    Full Text Available Calcium has well-documented roles in plant signaling, water relations and cell wall interactions. Significant research into how calcium impacts these individual processes in various tissues has been carried out; however, the influence of calcium on fruit ripening has not been thoroughly explored. Here, we review the current state of knowledge on how calcium may impact fruit development, physical traits and disease susceptibility through facilitating developmental and stress response signaling, stabilizing membranes, influencing water relations and modifying cell wall properties through cross-linking of de-esterified pectins. We explore the involvement of calcium in hormone signaling integral to ripening and the physiological mechanisms behind common disorders that have been associated with fruit calcium deficiency (e.g. blossom end rot in tomatoes or bitter pit in apples. This review works towards an improved understanding of how the many roles of calcium interact to influence fruit ripening, and proposes future research directions to fill knowledge gaps. Specifically, we focus mostly on grapes and present a model that integrates existing knowledge around these various functions of calcium in fruit, which provides a basis for understanding the physiological impacts of sub-optimal calcium nutrition in grapes. Calcium accumulation and distribution in fruit is shown to be highly dependent on water delivery and cell wall interactions in the apoplasm. Localized calcium deficiencies observed in particular species or varieties can result from differences in xylem morphology, fruit water relations and pectin composition, and can cause leaky membranes, irregular cell wall softening, impaired hormonal signaling and aberrant fruit development. We propose that the role of apoplasmic calcium-pectin crosslinking, particularly in the xylem, is an understudied area that may have a key influence on fruit water relations. Furthermore, we believe that improved

  20. DISTILLATION OF CALCIUM

    Science.gov (United States)

    Barton, J.

    1954-07-27

    This invention relates to an improvement in the process for the purification of caicium or magnesium containing an alkali metal as impurity, which comprises distiiling a batch of the mixture in two stages, the first stage distillation being carried out in the presence of an inert gas at an absolute pressure substantially greater than the vapor pressure of calcium or maguesium at the temperature of distillation, but less than the vaper pressure at that temperature of the alkali metal impurity so that only the alkali metal is vaporized and condensed on a condensing surface. A second stage distilso that substantially only the calcium or magnesium distills under its own vapor pressure only and condenses in solid form on a lower condensing surface.

  1. Models of calcium signalling

    CERN Document Server

    Dupont, Geneviève; Kirk, Vivien; Sneyd, James

    2016-01-01

    This book discusses the ways in which mathematical, computational, and modelling methods can be used to help understand the dynamics of intracellular calcium. The concentration of free intracellular calcium is vital for controlling a wide range of cellular processes, and is thus of great physiological importance. However, because of the complex ways in which the calcium concentration varies, it is also of great mathematical interest.This book presents the general modelling theory as well as a large number of specific case examples, to show how mathematical modelling can interact with experimental approaches, in an interdisciplinary and multifaceted approach to the study of an important physiological control mechanism. Geneviève Dupont is FNRS Research Director at the Unit of Theoretical Chronobiology of the Université Libre de Bruxelles;Martin Falcke is head of the Mathematical Cell Physiology group at the Max Delbrück Center for Molecular Medicine, Berlin;Vivien Kirk is an Associate Professor in the Depar...

  2. A composite light-harvesting layer from photoactive polymer and halide perovskite for planar heterojunction solar cells

    Science.gov (United States)

    Wang, Heming; Rahaq, Yaqub; Kumar, Vikas

    2016-07-01

    A new route for fabrication of photoactive materials in organic-inorganic hybrid solar cells is presented in this report. Photoactive materials by blending a semiconductive conjugated polymer with an organolead halide perovskite were fabricated for the first time. The composite active layer was then used to make planar heterojunction solar cells with the PCBM film as the electron-acceptor. Photovoltaic performance of solar cells was investigated by J-V curves and external quantum efficiency spectra. We demonstrated that the incorporation of the conjugated photoactive polymer into organolead halide perovskites did not only contribute to the generation of charges, but also enhance stability of solar cells by providing a barrier protection to halide perovskites. It is expected that versatile of conjugated semi-conductive polymers and halide perovskites in photoactive properties enables to create various combinations, forming composites with advantages offered by both types of photoactive materials.

  3. A composite light-harvesting layer from photoactive polymer and halide perovskite for planar heterojunction solar cells

    Science.gov (United States)

    Wang, Heming; Rahaq, Yaqub; Kumar, Vikas

    2016-01-01

    A new route for fabrication of photoactive materials in organic-inorganic hybrid solar cells is presented in this report. Photoactive materials by blending a semiconductive conjugated polymer with an organolead halide perovskite were fabricated for the first time. The composite active layer was then used to make planar heterojunction solar cells with the PCBM film as the electron-acceptor. Photovoltaic performance of solar cells was investigated by J-V curves and external quantum efficiency spectra. We demonstrated that the incorporation of the conjugated photoactive polymer into organolead halide perovskites did not only contribute to the generation of charges, but also enhance stability of solar cells by providing a barrier protection to halide perovskites. It is expected that versatile of conjugated semi-conductive polymers and halide perovskites in photoactive properties enables to create various combinations, forming composites with advantages offered by both types of photoactive materials. PMID:27411487

  4. Alkali Metal Halide Salts as Interface Additives to Fabricate Hysteresis-Free Hybrid Perovskite-Based Photovoltaic Devices.

    Science.gov (United States)

    Wang, Lili; Moghe, Dhanashree; Hafezian, Soroush; Chen, Pei; Young, Margaret; Elinski, Mark; Martinu, Ludvik; Kéna-Cohen, Stéphane; Lunt, Richard R

    2016-09-01

    A new method was developed for doping and fabricating hysteresis-free hybrid perovskite-based photovoltaic devices by using alkali metal halide salts as interface layer additives. Such salt layers introduced at the perovskite interface can provide excessive halide ions to fill vacancies formed during the deposition and annealing process. A range of solution-processed halide salts were investigated. The highest performance of methylammonium lead mixed-halide perovskite device was achieved with a NaI interlayer and showed a power conversion efficiency of 12.6% and a hysteresis of less than 2%. This represents a 90% improvement compared to control devices without this salt layer. Through depth-resolved mass spectrometry, optical modeling, and photoluminescence spectroscopy, this enhancement is attributed to the reduction of iodide vacancies, passivation of grain boundaries, and improved hole extraction. Our approach ultimately provides an alternative and facile route to high-performance and hysteresis-free perovskite solar cells.

  5. An Efficient Synthesis of Diaryl Ethers by Coupling Aryl Halides with Substituted Phenoxytrimethylsilane in the Presence of TBAF

    Institute of Scientific and Technical Information of China (English)

    Jian Kui ZHAO; Yan Guang WANG

    2003-01-01

    A general synthesis of diaryl ethers via coupling of aryl halides with substitutedphenoxytrimethylsilane in the presence of TBAF is described. The protocol is simple and mild,and gives good to excellent yields.

  6. A composite light-harvesting layer from photoactive polymer and halide perovskite for planar heterojunction solar cells.

    Science.gov (United States)

    Wang, Heming; Rahaq, Yaqub; Kumar, Vikas

    2016-01-01

    A new route for fabrication of photoactive materials in organic-inorganic hybrid solar cells is presented in this report. Photoactive materials by blending a semiconductive conjugated polymer with an organolead halide perovskite were fabricated for the first time. The composite active layer was then used to make planar heterojunction solar cells with the PCBM film as the electron-acceptor. Photovoltaic performance of solar cells was investigated by J-V curves and external quantum efficiency spectra. We demonstrated that the incorporation of the conjugated photoactive polymer into organolead halide perovskites did not only contribute to the generation of charges, but also enhance stability of solar cells by providing a barrier protection to halide perovskites. It is expected that versatile of conjugated semi-conductive polymers and halide perovskites in photoactive properties enables to create various combinations, forming composites with advantages offered by both types of photoactive materials. PMID:27411487

  7. Synthesis and structural characterization of a calcium coordination polymer based on a 3-bridging tetradentate binding mode of glycine

    Indian Academy of Sciences (India)

    Subramanian Natarajan; Bikshandarkoil R Srinivasan; J Kalyana Sundar; K Ravikumar; R V Krishnakumar; J Suresh

    2012-07-01

    A new coordination polymer namely [[Ca6(H-gly)12(H2O)18]Cl12·6H2O] (1) (H-gly = glycine) has been isolated from the calcium chloride-glycine-water system and structurally characterized. Each Ca(II) in 1 is eight-coordinated and is bonded to eight oxygen atoms three of which are from terminal water molecules and five oxygen atoms from four symmetry related zwitterionic glycine ligands. The H-gly ligands exhibit two different binding modes viz. a monodentate carboxylate ligation and a 3-tetradentate bridging carboxylate binding mode, which results in the formation of a one-dimensional coordination polymer. In the infinite chain the Ca(II) atoms are organized in a zigzag fashion. A comparative study reveals a rich and diverse structural chemistry of calcium halide-glycine compounds.

  8. Spectral Features and Charge Dynamics of Lead Halide Perovskites: Origins and Interpretations.

    Science.gov (United States)

    Sum, Tze Chien; Mathews, Nripan; Xing, Guichuan; Lim, Swee Sien; Chong, Wee Kiang; Giovanni, David; Dewi, Herlina Arianita

    2016-02-16

    Lead halide perovskite solar cells are presently the forerunner among the third generation solution-processed photovoltaic technologies. With efficiencies exceeding 20% and low production costs, they are prime candidates for commercialization. Critical insights into their light harvesting, charge transport, and loss mechanisms have been gained through time-resolved optical probes such as femtosecond transient absorption spectroscopy (fs-TAS), transient photoluminescence spectroscopy, and time-resolved terahertz spectroscopy. Specifically, the discoveries of long balanced electron-hole diffusion lengths and gain properties in halide perovskites underpin their significant roles in uncovering structure-function relations and providing essential feedback for materials development and device optimization. In particular, fs-TAS is becoming increasingly popular in perovskite characterization studies, with commercial one-box pump-probe systems readily available as part of a researcher's toolkit. Although TAS is a powerful probe in the study of charge dynamics and recombination mechanisms, its instrumentation and data interpretation can be daunting even for experienced researchers. This issue is exacerbated by the sensitive nature of halide perovskites where the kinetics are especially susceptible to pump fluence, sample preparation and handling and even degradation effects that could lead to disparate conclusions. Nonetheless, with end-users having a clear understanding of TAS's capabilities, subtleties, and limitations, cutting-edge work with deep insights can still be performed using commercial setups as has been the trend for ubiquitous spectroscopy instruments like absorption, fluorescence, and transient photoluminescence spectrometers. Herein, we will first briefly examine the photophysical processes in lead halide perovskites, highlighting their novel properties. Next, we proceed to give a succinct overview of the fundamentals of pump-probe spectroscopy in relation

  9. Structural, dynamical, and transport properties of the hydrated halides: How do At- bulk properties compare with those of the other halides, from F- to I-?

    Science.gov (United States)

    Réal, Florent; Severo Pereira Gomes, André; Guerrero Martínez, Yansel Omar; Ayed, Tahra; Galland, Nicolas; Masella, Michel; Vallet, Valérie

    2016-03-01

    The properties of halides from the lightest, fluoride (F-), to the heaviest, astatide (At-), 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- and At-, 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- and At- 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-, Cl-, and Br- 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- in liquid water at ambient conditions to be 68 kcal mol-1, a value also close the I- one, about 70 kcal mol-1. In all, our simulation results for I- are in excellent agreement with the latest neutron- and X-ray diffraction studies. Those for the At- ion are predictive, as no theoretical or experimental data are available to date.

  10. Structural, dynamical, and transport properties of the hydrated halides: How do At(-) bulk properties compare with those of the other halides, from F(-) to I(-)?

    Science.gov (United States)

    Réal, Florent; Gomes, André Severo Pereira; Guerrero Martínez, Yansel Omar; Ayed, Tahra; Galland, Nicolas; Masella, Michel; Vallet, Valérie

    2016-03-28

    The properties of halides from the lightest, fluoride (F(-)), to the heaviest, astatide (At(-)), 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(-) and At(-), 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(-) and At(-) 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(-), Cl(-), and Br(-) 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(-) in liquid water at ambient conditions to be 68 kcal mol(-1), a value also close the I(-) one, about 70 kcal mol(-1). In all, our simulation results for I(-) are in excellent agreement with the latest neutron- and X-ray diffraction studies. Those for the At(-) ion are predictive, as no theoretical or experimental data are available to date. PMID:27036467

  11. Mild and Phosphine-Free Iron-Catalyzed Cross-Coupling of Nonactivated Secondary Alkyl Halides with Alkynyl Grignard Reagents

    OpenAIRE

    Cheung, Chi Wai; Ren, Peng; Hu, Xile

    2014-01-01

    A simple protocol for iron-catalyzed cross-coupling of nonactivated secondary alkyl bromides and iodides with alkynyl Grignard reagents at room temperature has been developed. A wide range of secondary alkyl halides and terminal alkynes are tolerated to afford the substituted alkynes in good yields. A slight modification of the reaction protocol also allows for cross-coupling with a variety of primary alkyl halides.

  12. Palladium-Catalyzed Hydroxylation of Aryl and Heteroaryl Halides Enabled by the Use of a Palladacycle Precatalyst

    OpenAIRE

    Cheung, Chi Wai; Buchwald, Stephen L.

    2014-01-01

    A method for the hydroxylation of aryl and heteroaryl halides, promoted by a catalyst based on a biarylphosphine ligand tBuBrettPhos (L5) and its corresponding palladium precatalyst (1), is described. The reactions allow the cross-coupling of both potassium and cesium hydroxides with (hetero)aryl halides to afford a variety of phenols and hydroxylated heteroarenes in high to excellent yield.

  13. Fine structures in the optical absorption spectra of photochemical silver in silver halides? A call for further research

    OpenAIRE

    Georgiev, Mladen

    2007-01-01

    A survey is presented of the work done so far to check earlier claims that a fine structure may be observed to occur under certain circumstances in the impurity spectral range of the optical absorption spectra of silver halides following photostimulation in the intrinsic range. This structure, associated with the photochemical formation of silver specks, has been questioned over the years. We now weigh carefully the experimental evidence on the silver halides against a background of similar d...

  14. Fluorogenic derivatization of aryl halides based on the formation of biphenyl by Suzuki coupling reaction with phenylboronic acid.

    OpenAIRE

    Kishikawa, Naoya; Kubo, Kimiko; Hammad, Sherin Farouk; Mabrouk, Mokhtar Mohamed; Habib, Ahmed; Elfatatry, Hamed; Ohyama, Kaname; Nakashima, Kenichiro; Kuroda, Naotaka

    2009-01-01

    The fluorogenic derivatization method for aryl halide was developed for the first time. This method was based on the formation of fluorescent biphenyl structure by Suzuki coupling reaction between aryl halides and non-fluorescent phenylboronic acid (PBA). We measured the fluorescence spectra of the products obtained by the reaction of p-substituted aryl bromides (i.e., 4-bromobenzonitrile, 4-bromoanisole, 4-bromobenzoic acid ethyl ester and 4-bromotoluene) with PBA in the presence of palladiu...

  15. Spacial Structure of Cationic Phosphorus Ligand-Ru (Ⅱ) Halide Complexes-by DFT Study

    Institute of Scientific and Technical Information of China (English)

    Yi Xin ZHAO; Shu Guang WANG

    2005-01-01

    The full-parameter geometry optimization of cationic (S)-BINAP-Ru (Ⅱ) halide complex was performed by DFT method using B3LYP, PW91 and PBE potentials with several basis sets. PW91 with 3-21G / SDD basis sets is found to be the most suitable method with consideration of both precision and efficiency. The dihedral angles (θ) of the binaphthyl or biphenyl with different phosphorus ligand-Ru (Ⅱ) halide complexes were found changing from 59.9 to 79.3 degree, while the natural bite angle (βn) of those complexes only changes from 87.4to 90.3 degree. It is different from the common view of asymmetric organic chemists' that θ directly influences βn.

  16. Reactions between cold methyl halide molecules and alkali-metal atoms

    CERN Document Server

    Lutz, Jesse J

    2013-01-01

    We investigate the potential energy surfaces and activation energies for reactions between methyl halide molecules CH$_{3}X$ ($X$ = F, Cl, Br, I) and alkali-metal atoms $A$ ($A$ = Li, Na, K, Rb) using high-level {\\it ab initio} calculations. We examine the anisotropy of each intermolecular potential energy surface (PES) and the mechanism and energetics of the only available exothermic reaction pathway, ${\\rm CH}_{3}X+A\\rightarrow{\\rm CH}_{3}+AX$. The region of the transition state is explored using two-dimensional PES cuts and estimates of the activation energies are inferred. Nearly all combinations of methyl halide and alkali-metal atom have positive barrier heights, indicating that reactions at low temperatures will be slow.

  17. Relationships between Lead Halide Perovskite Thin-Film Fabrication, Morphology, and Performance in Solar Cells.

    Science.gov (United States)

    Sharenko, Alexander; Toney, Michael F

    2016-01-20

    Solution-processed lead halide perovskite thin-film solar cells have achieved power conversion efficiencies comparable to those obtained with several commercial photovoltaic technologies in a remarkably short period of time. This rapid rise in device efficiency is largely the result of the development of fabrication protocols capable of producing continuous, smooth perovskite films with micrometer-sized grains. Further developments in film fabrication and morphological control are necessary, however, in order for perovskite solar cells to reliably and reproducibly approach their thermodynamic efficiency limit. This Perspective discusses the fabrication of lead halide perovskite thin films, while highlighting the processing-property-performance relationships that have emerged from the literature, and from this knowledge, suggests future research directions.

  18. 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)

  19. Correlations for calculating the surface tension and enthalpies of sublimation of alkali halides

    International Nuclear Information System (INIS)

    The capability of a new model on predicting the surface tension of molten alkali halides is described. A relationship, with a simple form of calculation, exists between the surface tension (γ) at the melting point, molar volume (V), inter-nuclear distance (D) and the enthalpy of sublimation (Es). The basic idea results from the assumption that all the parameters are constants that are usually easy to acquire. Moreover, two previous models (Furth and Schytil equations) were also checked and applied for calculating surface tension of molten salts. The three formulas have been examined for 20 salts and showed remarkable agreement between calculated and experimental data with a difference of less than 10% for most of the salts studied. The heats of sublimation of alkali halides were, theoretically, calculated and compared to literature values.

  20. Enhanced phosphorescence emission by incorporating aromatic halides into an entangled coordination framework based on naphthalenediimide.

    Science.gov (United States)

    Martínez-Martínez, Virginia; Sola Llano, Rebeca; Furukawa, Shuhei; Takashima, Yohei; López Arbeloa, Iñigo; Kitagawa, Susumu

    2014-08-25

    Phosphorescence emission at room temperature is turned on in an entangled porous coordination polymer (PCP) with naphthalenediimide (NDI) as chromophore, by incorporating halogenated guests into the pores. The phosphorescent efficiency is drastically increased by the incorporation of aromatic halide guests in comparison with the incorporation of nonaromatic derivatives. Aromatic halide guests trigger a structural transformation, which allows a strong interaction with the NDI ligand in the framework through charge-transfer complexation, and provides an extra population process of the triplet state. The long-lived photoinduced triplet states, with an emission wavelength in the red region of the visible spectrum, demonstrated by this PCP, may open the door for potential uses, for example, as singlet-oxygen generators or for bio-imaging applications. PMID:24953198

  1. Amine synthesis via iron-catalysed reductive coupling of nitroarenes with alkyl halides.

    Science.gov (United States)

    Cheung, Chi Wai; Hu, Xile

    2016-01-01

    (Hetero)Aryl amines, an important class of organic molecules in medicinal chemistry, are most commonly synthesized from anilines, which are in turn synthesized by hydrogenation of nitroarenes. Amine synthesis directly from nitroarenes is attractive due to improved step economy and functional group compatibility. Despite these potential advantages, there is yet no general method for the synthesis of (hetero)aryl amines by carbon-nitrogen cross-coupling of nitroarenes. Here we report the reductive coupling of nitroarenes with alkyl halides to yield (hetero)aryl amines. A simple iron catalyst enables the coupling with numerous primary, secondary and tertiary alkyl halides. Broad scope and high functional group tolerance are demonstrated. Mechanistic study suggests that nitrosoarenes and alkyl radicals are involved as intermediates. This new C-N coupling method provides general and step-economical access to aryl amines. PMID:27515391

  2. Reactions between cold methyl halide molecules and alkali-metal atoms

    International Nuclear Information System (INIS)

    We investigate the potential energy surfaces and activation energies for reactions between methyl halide molecules CH3X (X = F, Cl, Br, I) and alkali-metal atoms A (A = Li, Na, K, Rb) using high-level ab initio calculations. We examine the anisotropy of each intermolecular potential energy surface (PES) and the mechanism and energetics of the only available exothermic reaction pathway, CH3X + A → CH3 + AX. The region of the transition state is explored using two-dimensional PES cuts and estimates of the activation energies are inferred. Nearly all combinations of methyl halide and alkali-metal atom have positive barrier heights, indicating that reactions at low temperatures will be slow

  3. Solvation structures and dynamics of alkaline earth metal halides in supercritical water: A molecular dynamics study

    Science.gov (United States)

    Keshri, Sonanki; Mandal, Ratnamala; Tembe, B. L.

    2016-09-01

    Constrained molecular dynamics simulations of alkaline earth metal halides have been carried out to investigate their structural and dynamical properties in supercritical water. Potentials of mean force (PMFs) for all the alkaline earth metal halides in supercritical water have been computed. Contact ion pairs (CIPs) are found to be more stable than all other configurations of the ion pairs except for MgI2 where solvent shared ion pair (SShIP) is more stable than the CIP. There is hardly any difference in the PMFs between the M2+ (M = Mg, Ca, Sr, Ba) and the X- (X = F, Cl, Br, I) ions whether the second X- ion is present in the first coordination shell of the M2+ ion or not. The solvent molecules in the solvation shells diffuse at a much slower rate compared to the bulk. Orientational distribution functions of solvent molecules are sharper for smaller ions.

  4. 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.

  5. Solid-State Nanopore Confinement for Band Gap Engineering of Metal-Halide Perovskites

    CERN Document Server

    Demchyshyn, Stepan; Groiss, Heiko; Heilbrunner, Herwig; Ulbricht, Christoph; Apaydin, Dogukan; Rütt, Uta; Bertram, Florian; Hesser, Günter; Scharber, Markus; Nickel, Bert; Sariciftci, Niyazi Serdar; Bauer, Siegfried; Głowacki, Eric Daniel; Kaltenbrunner, Martin

    2016-01-01

    Tuning the band gap of semiconductors via quantum size effects launched a technological revolution in optoelectronics, advancing solar cells, quantum dot light-emitting displays, and solid state lasers. Next generation devices seek to employ low-cost, easily processable semiconductors. A promising class of such materials are metal-halide perovskites, currently propelling research on emerging photovoltaics. Their narrow band emission permits very high colour purity in light-emitting devices and vivid life-like displays paired with low-temperature processing through printing-compatible methods. Success of perovskites in light-emitting devices is conditional upon finding reliable strategies to obtain tunability of the band gap. So far, colour can be tuned chemically by mixed halide stoichiometry, or by synthesis of colloidal particles. Here we introduce a general strategy of controlling shape and size of perovskite nanocrystallites (less than 10 nm) in domains that exhibit strong quantum size effects. Without ma...

  6. Tuning the thermal conductivity of methylammonium lead halide by the molecular substructure.

    Science.gov (United States)

    Caddeo, Claudia; Melis, Claudio; Saba, Maria Ilenia; Filippetti, Alessio; Colombo, Luciano; Mattoni, Alessandro

    2016-09-21

    By using state-of-the-art atomistic methods we provide an accurate estimate of thermal conductivity of methylammonium lead halide as a function of sample size and temperature, in agreement with experimental works. We show that the thermal conductivity of methylammonium lead halide is intrinsically low, due to the low sound velocity of the PbI lattice. Furthermore, by selectively analyzing the effect of different molecular degrees of freedom, we clarify the role of the molecular substructure by showing that the internal modes above 150 cm(-1) (in addition to rotations) are effective in reducing the thermal conductivity of hybrid perovskites. This analysis suggests strategies to tailor the thermal conductivity by modifying the internal structure of organic cations. PMID:27531063

  7. Coloration of cadmium halide crystals due to reactor irradiation at low temperature

    International Nuclear Information System (INIS)

    The optical absorption spectra and ESR spectra of cadmium halide crystals were measured after the reactor irradiation at low temperature to study the coloration. The irradiated neutron dose was about 5 x 1017 n/cm2. In the measurement of ESR spectra, the crystal was rotated around the v-axis (the two-fold axis) in the magnetic field of fixed direction. The optical absorption spectra showed that the Cd3+ center was generated. From the analysis of the angular dependence of ESR spectra, the centers of C(2h) symmetry and the centers of D(3d) symmetry were considered to be generated. The models of these centers were considered, and the angular dependence was analyzed. It can be concluded from the present experiment that the coloration of cadmium halide crystals is recognized as the results of the reactor irradiation at low temperature. (Kato, T.)

  8. Energetics and dynamics in organic-inorganic halide perovskite photovoltaics and light emitters.

    Science.gov (United States)

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

    2015-08-28

    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. PMID:26234397

  9. Calcium – how and why?

    Indian Academy of Sciences (India)

    J K Jaiswal

    2001-09-01

    Calcium is among the most commonly used ions, in a multitude of biological functions, so much so that it is impossible to imagine life without calcium. In this article I have attempted to address the question as to how calcium has achieved this status with a brief mention of the history of calcium research in biology. It appears that during the origin and early evolution of life the Ca2+ ion was given a unique opportunity to be used in several biological processes because of its unusual physical and chemical properties.

  10. Calcium Phosphate Biomaterials: An Update

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Current calcium phosphate (CaP) biomaterials for bone repair, substitution, augmentation and regeneration include hydroxyapatite ( HA ) from synthetic or biologic origin, beta-tricalcium phosphate ( β-TCP ) , biphasic calcium phosphate (BCP), and are available as granules, porous blocks, components of composites (CaP/polymer) cements, and as coatings on orthopedic and dental implants. Experimental calcium phosphate biomaterials include CO3- and F-substituted apatites, Mg-and Zn-substituted β-TCP, calcium phosphate glasses. This paper is a brief review of the different types of CaP biomaterials and their properties such as bioactivity, osteoconductivity, osteoinductivity.

  11. Cardiovascular Effects of Calcium Supplements

    Directory of Open Access Journals (Sweden)

    Ian R. Reid

    2013-07-01

    Full Text Available Calcium supplements reduce bone turnover and slow the rate of bone loss. However, few studies have demonstrated reduced fracture incidence with calcium supplements, and meta-analyses show only a 10% decrease in fractures, which is of borderline statistical and clinical significance. Trials in normal older women and in patients with renal impairment suggest that calcium supplements increase the risk of cardiovascular disease. To further assess their safety, we recently conducted a meta-analysis of trials of calcium supplements, and found a 27%–31% increase in risk of myocardial infarction, and a 12%–20% increase in risk of stroke. These findings are robust because they are based on pre-specified analyses of randomized, placebo-controlled trials and are consistent across the trials. Co-administration of vitamin D with calcium does not lessen these adverse effects. The increased cardiovascular risk with calcium supplements is consistent with epidemiological data relating higher circulating calcium concentrations to cardiovascular disease in normal populations. There are several possible pathophysiological mechanisms for these effects, including effects on vascular calcification, vascular cells, blood coagulation and calcium-sensing receptors. Thus, the non-skeletal risks of calcium supplements appear to outweigh any skeletal benefits, and are they appear to be unnecessary for the efficacy of other osteoporosis treatments.

  12. 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...... by modification of spin-coating parameters without any additional chemical or thermal post-treatment....

  13. Seed-mediated growth of palladium nanocrystals: The effect of pseudo-halide thiocyanate ions

    Science.gov (United States)

    Zhang, Ling; Niu, Wenxin; Xu, Guobao

    2011-02-01

    In synthesis in a solution phase, adsorbates such as halides can interact selectively with different metal crystal facets and affect the final morphology of nanocrystals. Pseudo-halide thiocyanate ions (SCN-) can also adsorb on the metal surface, but they have never been used for the synthesis of shape-controlled colloidal metal nanocrystals. In this study, we first investigated the effect of SCN- on the morphology of palladium nanocrystals through a seed-mediated growth method. The presence of 1 µM SCN- in the growth solutions could lead to the formation of palladium polyhedra: truncated rhombic dodecahedra enclosed by twelve {110}, eight {111} and six {100} facets. The products were nanocubes enclosed with six {100} facets if cetyltrimethylammonium bromide (CTAB) was the only capping agent. Meanwhile, the mechanism of the effect of SCN- on the morphology of Pd nanocrystals is discussed.In synthesis in a solution phase, adsorbates such as halides can interact selectively with different metal crystal facets and affect the final morphology of nanocrystals. Pseudo-halide thiocyanate ions (SCN-) can also adsorb on the metal surface, but they have never been used for the synthesis of shape-controlled colloidal metal nanocrystals. In this study, we first investigated the effect of SCN- on the morphology of palladium nanocrystals through a seed-mediated growth method. The presence of 1 µM SCN- in the growth solutions could lead to the formation of palladium polyhedra: truncated rhombic dodecahedra enclosed by twelve {110}, eight {111} and six {100} facets. The products were nanocubes enclosed with six {100} facets if cetyltrimethylammonium bromide (CTAB) was the only capping agent. Meanwhile, the mechanism of the effect of SCN- on the morphology of Pd nanocrystals is discussed. Electronic supplementary information (ESI) available: Additional SEM, TEM and XRD data. See DOI: 10.1039/c0nr00622j

  14. Calculation of shear angles in holographic gratings recorded in bleached silver-halide emulsions

    OpenAIRE

    Beléndez Vázquez, Augusto; Pascual Villalobos, Inmaculada; Fuentes Rosillo, Rosa; Fimia Gil, Antonio

    1993-01-01

    Shearing phenomena in holographic gratings formed in bleached silver-halide emulsions due to chemical processing are evaluated. These effects are introduced because of the inability of emulsion-thickness changes to explain the anomalous detuning of the peak diffraction efficiency from the expected Bragg condition. Experimental results obtained with transmission and reflection gratings are presented and discussed considering shearing effects, and the values of the shear angles calculated from ...

  15. Temperature Dependence of Interatomic Separation and Bulk Modulus for Alkali Halides

    Science.gov (United States)

    Liu, Quan

    2016-07-01

    The values of interatomic separation r with the change of temperature T for seven alkali halides have been investigated with the help of an isobaric equation of state. The calculated results are used to predict the values of bulk modulus at different temperatures. The results are compared with the available experimental data and other theoretical results and are further discussed in view of recent research in the field of high temperature physics.

  16. Mössbauer Emission-Spectra of Impurity Cobalt-57 in a Halide Matrix

    DEFF Research Database (Denmark)

    Maddock, A. G.; Williams, A. F.; Siekierska, K. E.;

    1976-01-01

    The Mössbauer emission spectra of 57Co in low concentrations in KF, NaCl, NaF, LiF, and MgF2, and the effects of doping NaF and LiF with La3+ ions are reported. The monovalent halides all give similar spectra showing a broad single line or a doublet at 2.19mm/s and two overlapping doublets at 0...

  17. Theoretical analysis of the kinetics of low-temperature defect recombination in alkali halide crystals

    Science.gov (United States)

    Kuzovkov, V. N.; Popov, A. I.; Kotomin, E. A.; Moskina, A. M.; Vasilchenko, E.; Lushchik, A.

    2016-07-01

    We analyzed carefully the experimental kinetics of the low-temperature diffusion-controlled F, H center recombination in a series of irradiated alkali halides and extracted the migration energies and pre-exponential parameters for the hole H centers. The migration energy for the complementary electronic F centers in NaCl was obtained from the colloid formation kinetics observed above room temperature. The obtained parameters were compared with data available from the literature.

  18. Dielectric relaxation of alkyl chains in graphite oxide and n-alkylammonium halides

    OpenAIRE

    Xiaoqian Ai; Yuchen Tian; Min Gu; Ji Yu; Tong B. Tang

    2016-01-01

    The dynamic of n-alkylammonium halides and n-alkylammonium cations (n = 12, 14, 16, 18) intercalated in graphite oxide (GO) have been investigated with complex impedance spectroscopy. X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, elemental analysis and thermogravimetry served to characterize the materials. The intercalated alkylammonium cations distributes as monolayers (when n = 12, 14 or 16) or bilayers (when n = 18), with their long axis para...

  19. Dehalogenation of Aryl Halides Catalyzed by Montmorillonite Immobilized Bimetal Catalyst in Aqueous System

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A novel bisupported bimetal catalyst PVP-PdCl2-FeSO4/Al-Mont-PEG600 was prepared by immobilization of PVP (poly (N-vinyl-2-pyrrolidone)) supported bimetallic catalyst using alumina pillared inartificial montmorillonite as the carrier. This catalyst has good dehalogenation activity and selectivity to aryl halides-o-chlorotoluene in aqueous system in the presence of phase transfer catalyst (PEG) and sodium formate as hydrogen source. The catalyst also shows good reusability.

  20. Three-Component Halo Aldol Condensation of Thioacrylates with Aldehydes Mediated by Titanium (IV Halide

    Directory of Open Access Journals (Sweden)

    Guigen Li

    2002-01-01

    Full Text Available a,b-Ethyl thioacrylate was difuctionalized by a tandem X-C/C=C bond formation reaction. The new system uses Ti (IV halide as both the Lewis acidic promoter and the halogen source for the Michael-type addition onto the thioacrylate. The titanium enolate species resulting from Michael-type addition react with aldehydes followed by dehydration to afford trisubstituted olefin products. Complete geometric selectivity (>95% and up to 72% yield have been obtained for 7 examples.

  1. Bright Light-Emitting Diodes Based on Organometal Halide Perovskite Nanoplatelets.

    Science.gov (United States)

    Ling, Yichuan; Yuan, Zhao; Tian, Yu; Wang, Xi; Wang, Jamie C; Xin, Yan; Hanson, Kenneth; Ma, Biwu; Gao, Hanwei

    2016-01-13

    Bright light-emitting diodes based on solution-processable organometal halide perovskite nanoplatelets are demonstrated. The nanoplatelets created using a facile one-pot synthesis exhibit narrow-band emissions at 529 nm and quantum yield up to 85%. Using these nanoparticles as emitters, efficient electroluminescence is achieved with a brightness of 10 590 cd m(-2) . These ligand-capped nanoplatelets appear to be quite stable in moisture, allowing out-of-glovebox device fabrication.

  2. 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.

  3. Three-Component Halo Aldol Condensation of Thioacrylates with Aldehydes Mediated by Titanium (IV) Halide

    OpenAIRE

    Guigen Li; Gao, Joe J.; Han-Xun Wei; Sun Hee Kim

    2002-01-01

    a,b-Ethyl thioacrylate was difuctionalized by a tandem X-C/C=C bond formation reaction. The new system uses Ti (IV) halide as both the Lewis acidic promoter and the halogen source for the Michael-type addition onto the thioacrylate. The titanium enolate species resulting from Michael-type addition react with aldehydes followed by dehydration to afford trisubstituted olefin products. Complete geometric selectivity (>95%) and up to 72% yield have been obtained for 7 examples.

  4. Circular Photogalvanic Effect in Organometal Halide Perovskite CH$_3$NH$_3$PbI$_3$

    OpenAIRE

    Li, Junwen; Haney, Paul M.

    2016-01-01

    We study the circular photogalvanic effect in the organometal halide perovskite solar cell absorber CH$_3$NH$_3$PbI$_3$. For crystal structures which lack inversion symmetry, the calculated photocurrent density is about $10^{-9}$ A/W, comparable to the previously studied quantum well and bulk Rashba systems. Because of the dependence of the circular photogalvanic effect on inversion symmetry breaking, the degree of inversion asymmetry at different depths from the surface can be probed by tuni...

  5. Can Ferroelectric Polarization Explain the High Performance of Hybrid Halide Perovskite Solar Cells?

    OpenAIRE

    Sherkar, Tejas; Koster, L Jan Anton

    2016-01-01

    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 charge recombination in the device. Here, we investigate and quantify the influence of mesoscale ferroelectric polarization on the device performance of perovskite solar cells. We implement a 3D dri...

  6. Intrinsic femtosecond charge generation dynamics in a single crystal organometal halide perovskite

    OpenAIRE

    Valverde-Chávez, David A.; Ponseca Jr., Carlito; Stoumpos, Constantinos; Yartsev, Arkady; Kanatzidis, Mercouri G.; Sundström, Villy; Cooke, David G.

    2015-01-01

    Hybrid metal-organic perovskite solar cells have astounded the solar cell community with their rapid rise in efficiency over the past three years. Despite this success, the basic processes governing the photogeneration of free charges, particularly their dynamics and efficiency, remain unknown. Here we use ultrabroadband pulses of THz frequency light to see the intrinsic photophysical properties of single crystal lead halide perovskite just femtoseconds after a photon is first absorbed. Our s...

  7. Optical Description of Mesostructured Organic¿Inorganic Halide Perovskite Solar Cells

    OpenAIRE

    Anaya, Miguel; Lozano, Gabriel; Calvo, Mauricio E.; Zhang, Wei; Johnston, Michael B; Snaith, Henry J.; Míguez, Hernán

    2015-01-01

    Herein we describe both theoretically and experimentally the optical response of solution-processed organic¿inorganic halide perovskite solar cells based on mesostructured scaffolds. We develop a rigorous theoretical model using a method based on the propagation of waves in layered media, which allows visualizing the way in which light is spatially distributed across the device and serves to quantify the fraction of light absorbed by each medium comprising the cell. The discrimination between...

  8. 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.

  9. Non-linear composition dependence of the conductivity parameters in alkali halides mixed crystals

    Energy Technology Data Exchange (ETDEWEB)

    Zardas, Georgios E., E-mail: gzardas@phys.uoa.g [Department of Solid State Physics, Faculty of Physics, University of Athens, Panepistimiopolis, 157 84 Zografos (Greece)

    2009-06-01

    Since mixed alkali halides were found to have applications in optical, optoelectronic and electronic devices, a strong interest has recently expressed for the study of their physical properties. Here, we discuss the experimental finding that a maximum conductivity enhancement with respect to pure constituents is obtained at a certain composition. We show that this composition can be predicted from the bulk properties of the end members.

  10. Palladium-Catalyzed Suzuki-Miyaura Type Coupling Reaction of Aryl Halides with Triphenylborane-Pyridine

    Institute of Scientific and Technical Information of China (English)

    杨明华; 顾勇冰; 王艳; 赵玺玉; 严国兵

    2012-01-01

    The Suzuki-Miyaura type coupling reaction of aryl halides with triphenylborane-pyridine was described. The reaction can be catalyzed by Pd(OAc)2 (5 mol%) in presence of Cs2CO3 at 50 ℃ or 80 ℃, and functionalized biaryls were obtained in good to excellent yields. This protocol is general and can tolerate a wide range of func- tional groups.

  11. Novel Distance-Related Matrix Index and QSPR Research for Thermodynamics of Methyl Halides

    Institute of Scientific and Technical Information of China (English)

    YANG Hai-lang; WANG Zhen-dong; HUANG Yun-ping; YANG Feng

    2004-01-01

    A novel topological index WF is defined by the matrices X, W and L as WF = XWL. The topological index WF based on the distance-related matrix of molecular graphs is used to code the structural environ-ment of each atom- type in a molecular graph. Good QSPR models have been obtained for standard formation en-thalpy of methyl halides. The result indicates that the idea of using multiple matrices to define the distance- relatedmatrix topological index is valid.

  12. Photokeratitis Linked to Metal Halide Bulbs in Two Gymnasiums - Philadelphia, Pennsylvania, 2011 and 2013.

    Science.gov (United States)

    Finn, Lauren E; Gutowski, Jennifer; Alles, Steve; Mirowitz, Naomi; Johnson, Caroline; Osterhoudt, Kevin C; Patel, Ami

    2016-01-01

    In December 2011 and December 2013, the Philadelphia Department of Public Health (PDPH) received separate reports of clusters of photokeratitis linked to gymnasium events. Photokeratitis, a painful eye condition resulting from unprotected exposure to ultraviolet radiation, has previously been linked to metal halide lamps with broken outer envelopes (1,2). To investigate the cause of these clusters and further characterize patients with photokeratitis, PDPH administered questionnaires to potentially exposed persons, established a case definition, and conducted environmental assessments of both gymnasiums. Because event attendee registration information was available, a cohort study was conducted to evaluate the 2011 cluster of 242 persons who met the photokeratitis case definition. A case-series investigation was conducted to evaluate the 2013 cluster of 20 persons who met the photokeratitis case definition for that event. These investigations indicated that Type R metal halide bulbs with broken outer envelopes found in both gymnasiums were the probable cause of the photokeratitis. The Food and Drug Administration has made a number of recommendations regarding the use of metal halide bulbs in facilities where bulbs are at elevated risk for breaking, such as schools and indoor sports facilities (3). Because Type R metal halide lamps do not self-extinguish once the outer envelope is broken, these bulbs should be removed from settings with a high risk for outer envelope rupture, such as gymnasiums, or should be placed within enclosed fixtures. In instances where these bulbs cannot be exchanged for self-extinguishing lamps, Type R lamps with a broken outer envelope should be replaced immediately to limit exposure to ultraviolet radiation. A broken outer envelope can be detected by the presence of glass on the floor, or visual examination of the bulb when the power is turned off. A broken outer envelope is difficult to detect when the lamp is emitting light. PMID

  13. Simultaneous Analyses and Applications of Multiple Fluorobenzoate and Halide Tracers in Hydrologic Studies

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Q; Moran, J E

    2004-01-22

    An analytical method that employs ion chromatography has been developed to more fully exploit the use of fluorobenzoic acids (FBAs) and halides as hydrologic tracers. In a single run, this reliable, sensitive, and robust method can simultaneously separate and quantify halides (fluoride, chloride, bromide, and iodide) and up to seven FBAs from other common groundwater constituents (e.g., nitrate and sulfate). The usefulness of this ion chromatographic (IC) analytical method is demonstrated in both field and laboratory tracer experiments. Field experiments in unsaturated tuff featuring fractures or a fault show that this efficient and cost-effective method helps achieve the objectives of tracer studies that use multiple FBAs and/or diffusivity tracers (simultaneous use of one or more FBA and halide). The field study examines the hydrologic response of fractures and the matrix to different flow rates and the contribution of matrix diffusion in chemical transport. Laboratory tracer experiments with eight geologic media from across the United States--mostly from Department of Energy facilities where groundwater contamination is prevalent and where subsurface characterization employing tracers has been ongoing or is in need--reveal several insights about tracer transport behavior: (1) Bromide and FBAs are not always transported conservatively. (2) The delayed transport of these anionic tracers is likely related to geologic media characteristics, such as organic matter, pH, iron oxide content, and clay mineralogy. (3) Any use of iodine as a hydrologic tracer should take into account the different sorption behaviors of iodide and iodate and the possible conversion of iodine's initial chemical form. (4) The transport behavior of potential FBA and halide tracers under relevant geochemical conditions should be evaluated before beginning ambitious, large-scale field tracer experiments.

  14. Mechanoluminescence produced during cleavage of γ-irradiated alkali halide crystals

    International Nuclear Information System (INIS)

    When g-irradiated alkali halide crystals are cleaved, then in their mechanoluminescence (ML) intensity versus time curve, two peak intensities Im1 and Im2 are observed at time tm1 and tm2 respectively. The ML intensity both beyond tm1 and tm2 decrease exponentially. It is shown that ML provides a new technique for determining the pinning time of dislocations and lifetime of the electrons in dislocation band. (author)

  15. Calcium measurement methods

    Directory of Open Access Journals (Sweden)

    CarloAlberto Redi

    2010-09-01

    Full Text Available Rightly stressed by prof. Wolfgang Walz in the Preface to the series Neuromethods series, the “careful application of methods is probably the most important step in the process of scientific inquiry”. Thus, I strongly suggest to all those interested in calcium signaling and especially to the new-comers in the hot topic of neuroscience (which has so much space even in science-society debate for its implications in legal issues and in the judge-decision process to take profit from this so well edited book. I am saying this since prof. Verkhratsky and prof. Petersen......

  16. 21 CFR 573.240 - Calcium periodate.

    Science.gov (United States)

    2010-04-01

    ... with calcium hydroxide or calcium oxide to form a substance consisting of not less than 60 percent by... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium periodate. 573.240 Section 573.240 Food... Additive Listing § 573.240 Calcium periodate. The food additive calcium periodate may be safely used...

  17. 21 CFR 573.260 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 573.260 Section 573.260 Food and... Listing § 573.260 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used as an anticaking agent in animal feed, provided that the amount of calcium silicate does...

  18. On the Thermal and Thermodynamic (In)Stability of Methylammonium Lead Halide Perovskites

    Science.gov (United States)

    Brunetti, Bruno; Cavallo, Carmen; Ciccioli, Andrea; Gigli, Guido; Latini, Alessandro

    2016-08-01

    The interest of the scientific community on methylammonium lead halide perovskites (MAPbX3, X = Cl, Br, I) for hybrid organic-inorganic solar cells has grown exponentially since the first report in 2009. This fact is clearly justified by the very high efficiencies attainable (reaching 20% in lab scale devices) at a fraction of the cost of conventional photovoltaics. However, many problems must be solved before a market introduction of these devices can be envisaged. Perhaps the most important to be addressed is the lack of information regarding the thermal and thermodynamic stability of the materials towards decomposition, which are intrinsic properties of them and which can seriously limit or even exclude their use in real devices. In this work we present and discuss the results we obtained using non-ambient X-ray diffraction, Knudsen effusion-mass spectrometry (KEMS) and Knudsen effusion mass loss (KEML) techniques on MAPbCl3, MAPbBr3 and MAPbI3. The measurements demonstrate that all the materials decompose to the corresponding solid lead (II) halide and gaseous methylamine and hydrogen halide, and the decomposition is well detectable even at moderate temperatures (~60 °C). Our results suggest that these materials may be problematic for long term operation of solar devices.

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

    Science.gov (United States)

    Shmyreva, Anna A; Safdari, Majid; Furó, István; Dvinskikh, Sergey V

    2016-06-14

    Orders of magnitude decrease of (207)Pb and (199)Hg NMR longitudinal relaxation times T1 upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX2 (Me = Pb, Hg and X = Cl, Br, I). In lead(ii) halides, the most dramatic decrease of T1 relative to that in a static sample is in PbI2, while it is smaller but still significant in PbBr2, and not detectable in PbCl2. 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.

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

    Science.gov (United States)

    Shmyreva, Anna A; Safdari, Majid; Furó, István; Dvinskikh, Sergey V

    2016-06-14

    Orders of magnitude decrease of (207)Pb and (199)Hg NMR longitudinal relaxation times T1 upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX2 (Me = Pb, Hg and X = Cl, Br, I). In lead(ii) halides, the most dramatic decrease of T1 relative to that in a static sample is in PbI2, while it is smaller but still significant in PbBr2, and not detectable in PbCl2. 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. PMID:27306000

  1. On the Thermal and Thermodynamic (In)Stability of Methylammonium Lead Halide Perovskites

    Science.gov (United States)

    Brunetti, Bruno; Cavallo, Carmen; Ciccioli, Andrea; Gigli, Guido; Latini, Alessandro

    2016-01-01

    The interest of the scientific community on methylammonium lead halide perovskites (MAPbX3, X = Cl, Br, I) for hybrid organic-inorganic solar cells has grown exponentially since the first report in 2009. This fact is clearly justified by the very high efficiencies attainable (reaching 20% in lab scale devices) at a fraction of the cost of conventional photovoltaics. However, many problems must be solved before a market introduction of these devices can be envisaged. Perhaps the most important to be addressed is the lack of information regarding the thermal and thermodynamic stability of the materials towards decomposition, which are intrinsic properties of them and which can seriously limit or even exclude their use in real devices. In this work we present and discuss the results we obtained using non-ambient X-ray diffraction, Knudsen effusion-mass spectrometry (KEMS) and Knudsen effusion mass loss (KEML) techniques on MAPbCl3, MAPbBr3 and MAPbI3. The measurements demonstrate that all the materials decompose to the corresponding solid lead (II) halide and gaseous methylamine and hydrogen halide, and the decomposition is well detectable even at moderate temperatures (~60 °C). Our results suggest that these materials may be problematic for long term operation of solar devices. PMID:27545661

  2. 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.

  3. Lanthanum halide scintillators for time-of-flight 3-D pet

    Science.gov (United States)

    Karp, Joel S.; Surti, Suleman

    2008-06-03

    A Lanthanum Halide scintillator (for example LaCl.sub.3 and LaBr.sub.3) with fast decay time and good timing resolution, as well as high light output and good energy resolution, is used in the design of a PET scanner. The PET scanner includes a cavity for accepting a patient and a plurality of PET detector modules arranged in an approximately cylindrical configuration about the cavity. Each PET detector includes a Lanthanum Halide scintillator having a plurality of Lanthanum Halide crystals, a light guide, and a plurality of photomultiplier tubes arranged respectively peripherally around the cavity. The good timing resolution enables a time-of-flight (TOF) PET scanner to be developed that exhibits a reduction in noise propagation during image reconstruction and a gain in the signal-to-noise ratio. Such a PET scanner includes a time stamp circuit that records the time of receipt of gamma rays by respective PET detectors and provides timing data outputs that are provided to a processor that, in turn, calculates time-of-flight (TOF) of gamma rays through a patient in the cavity and uses the TOF of gamma rays in the reconstruction of images of the patient.

  4. 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

    2002-03-10

    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 away 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.

  5. High-Efficiency Light-Emitting Diodes of Organometal Halide Perovskite Amorphous Nanoparticles.

    Science.gov (United States)

    Xing, Jun; Yan, Fei; Zhao, Yawen; Chen, Shi; Yu, Huakang; Zhang, Qing; Zeng, Rongguang; Demir, Hilmi Volkan; Sun, Xiaowei; Huan, Alfred; Xiong, Qihua

    2016-07-26

    Organometal halide perovskite has recently emerged as a very promising family of materials with augmented performance in electronic and optoelectronic applications including photovoltaic devices, photodetectors, and light-emitting diodes. Herein, we propose and demonstrate facile solution synthesis of a series of colloidal organometal halide perovskite CH3NH3PbX3 (X = halides) nanoparticles with amorphous structure, which exhibit high quantum yield and tunable emission from ultraviolet to near-infrared. The growth mechanism and photoluminescence properties of the perovskite amorphous nanoparticles were studied in detail. A high-efficiency green-light-emitting diode based on amorphous CH3NH3PbBr3 nanoparticles was demonstrated. The perovskite amorphous nanoparticle-based light-emitting diode shows a maximum luminous efficiency of 11.49 cd/A, a power efficiency of 7.84 lm/W, and an external quantum efficiency of 3.8%, which is 3.5 times higher than that of the best colloidal perovskite quantum-dot-based light-emitting diodes previously reported. Our findings indicate the great potential of colloidal perovskite amorphous nanoparticles in light-emitting devices.

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

    Science.gov (United States)

    Shmyreva, Anna A.; Safdari, Majid; Furó, István; Dvinskikh, Sergey V.

    2016-06-01

    Orders of magnitude decrease of 207Pb and 199Hg NMR longitudinal relaxation times T1 upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX2 (Me = Pb, Hg and X = Cl, Br, I). In lead(ii) halides, the most dramatic decrease of T1 relative to that in a static sample is in PbI2, while it is smaller but still significant in PbBr2, and not detectable in PbCl2. 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.

  7. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Ray, U., E-mail: ray_ugrasen@yahoo.co [Department of Physics, Bhaktapur Multiple Campus, Tribhuvan University, Kathmandu (Nepal)

    2010-08-01

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

    International Nuclear Information System (INIS)

    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 C123) 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.

  10. 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. PMID:25115581

  11. Extracellular calcium sensing and extracellular calcium signaling

    Science.gov (United States)

    Brown, E. M.; MacLeod, R. J.; O'Malley, B. W. (Principal Investigator)

    2001-01-01

    , localized changes in Ca(o)(2+) within the ECF can originate from several mechanisms, including fluxes of calcium ions into or out of cellular or extracellular stores or across epithelium that absorb or secrete Ca(2+). In any event, the CaR and other receptors/sensors for Ca(o)(2+) and probably for other extracellular ions represent versatile regulators of numerous cellular functions and may serve as important therapeutic targets.

  12. Preparation of Polybutylene Oxides Bearing Terminal Ester Groups by Treatment of H[(CH_2)_4O]_nSiR_3 with Acyl Halides

    OpenAIRE

    Iura, Takafumi; Matsubara, Kouki; Nagashima,Hideo

    2000-01-01

    Treatment of H[(CH_2)_4O]_nSiR_3, which were prepared by the silane induced polymerization of THF with acyl halides catalyzed by (μ_3:η^2:η^3:η^5-acenaphthylene)Ru_3(CO)_7, provides a novel synthetic method for polybutylene oxides bearing terminal ester groups. Various acyl halides such as acetyl chloride, benzoyl bromide, adipoyl chloride, acryloyl chloride, and 2-bromoisobutyryl bromide could be used as the acyl halide component; the reactivity of acyl halides increased in the order RCOBr>R...

  13. Calcium, vitamin D, and your bones

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/patientinstructions/000490.htm Calcium, vitamin D, and your bones To use the sharing ... and maintain strong bones. How Much Calcium and Vitamin D Do I Need? Amounts of calcium are ...

  14. Vitamin D, Calcium, and Bone Health

    Science.gov (United States)

    ... Balance › Vitamin D, Calcium, and Bone Health Vitamin D, Calcium, and Bone Health March 2012 Download PDFs ... helps keep your bones strong. Why are vitamin D and calcium important to bone health? Vitamin D ...

  15. CALCIUM ENHANCES ANTIINFLAMMATORY ACTIVITY OF ASPIRIN

    OpenAIRE

    Choksi Krishna; Shenoy Ashoka M; A. R. Shabharaya; Lala Minaxi

    2011-01-01

    The objective of present study is to evaluate the effects of calcium carbonate and calcium gluconate on acute and subacute inflammation and to study their possible interactions with Aspirin. Calcium carbonate (10 mg/kg) and calcium gluconate (5 mg/kg) were administered individually and also co-administered along with sub therapeutic dose Aspirin (50mg/kg) to study their interaction. The inflammation was induced by carrageenan or a foreign body. Both calcium carbonate and calcium gluconate cou...

  16. Calcium addition in straw gasification

    DEFF Research Database (Denmark)

    Risnes, H.; Fjellerup, Jan Søren; Henriksen, Ulrik Birk;

    2003-01-01

    The present work focuses on the influence of calcium addition in gasification. The inorganic¿organic element interaction as well as the detailed inorganic¿inorganic elements interaction has been studied. The effect of calcium addition as calcium sugar/molasses solutions to straw significantly...... affected the ash chemistry and the ash sintering tendency but much less the char reactivity. Thermo balance test are made and high-temperature X-ray diffraction measurements are performed, the experimental results indicate that with calcium addition major inorganic¿inorganic reactions take place very late...... in the char conversion process. Comprehensive global equilibrium calculations predicted important characteristics of the inorganic ash residue. Equilibrium calculations predict the formation of liquid salt if sufficient amounts of Ca are added and according to experiments as well as calculations calcium binds...

  17. Evolution of the Calcium Paradigm: The Relation between Vitamin D, Serum Calcium and Calcium Absorption

    Directory of Open Access Journals (Sweden)

    Borje E. Christopher Nordin

    2010-09-01

    Full Text Available Osteoporosis is the index disease for calcium deficiency, just as rickets/osteomalacia is the index disease for vitamin D deficiency, but there is considerable overlap between them. The common explanation for this overlap is that hypovitaminosis D causes malabsorption of calcium which then causes secondary hyperparathyroidism and is effectively the same thing as calcium deficiency. This paradigm is incorrect. Hypovitaminosis D causes secondary hyperparathyroidism at serum calcidiol levels lower than 60 nmol/L long before it causes malabsorption of calcium because serum calcitriol (which controls calcium absorption is maintained until serum calcidiol falls below 20 nmol/L. This secondary hyperparathyroidism, probably due to loss of a “calcaemic” action of vitamin D on bone first described in 1957, destroys bone and explains why vitamin D insufficiency is a risk factor for osteoporosis. Vitamin D thus plays a central role in the maintenance of the serum (ionised calcium, which is more important to the organism than the preservation of the skeleton. Bone is sacrificed when absorbed dietary calcium does not match excretion through the skin, kidneys and bowel which is why calcium deficiency causes osteoporosis in experimental animals and, by implication, in humans.

  18. Sensitivity to calcium intake in calcium stone forming patients.

    Science.gov (United States)

    Heilberg, I P; Martini, L A; Draibe, S A; Ajzen, H; Ramos, O L; Schor, N

    1996-01-01

    The absorptive or renal origin of hypercalciuria can be discriminated using an acute oral calcium load test (ACLT). Of 86 patients with calcium oxalate kidney stones, 28 (23%) were found to be hypercalciuric (HCa) and 58 (67%) normocalciuric (NCa) on their customary free diet, containing 542 +/- 29 mg/day (mean +/- SE) of calcium. Since the apparently normal 24-hour calcium excretion of many calcium stone formers (CSF) may be due to a combination of high calcium absorption with moderately low calcium intake, all patients were investigated by ACLT. Of 28 HCa patients, 13 (46%) were classified as absorptive (AH) and 15 (54%) as renal hypercalciuria (RH). Of the 58 NCa patients, 38 (65%) presented features of intestinal hyperabsorption and were therefore designated as AH-like, and 20 (35%) as RH-like. To further elucidate the role of dietary calcium in these CSF, a chronic calcium load test (CCLT), consisting of 1 g/day of oral Ca for 7 days, was designed. A positive response to the CCLT was considered to occur when urinary calcium (uCa) was > or = 4 mg/ kg/24 h on the 7th day. Among NCa patients, 29% of AH-like subjects responded to the CCLT and 71% did not; 50% of RH-like subjects also responded and 50% did not. In HCa patients, 85% of AH and 67% of RH subjects maintained uCa > or = 4 mg/kg/24 h after the CCLT and 15% of AH and 23% of RH subjects did not. However, a significant additional increase in mean uCa was not observed among HCa patients. All patients were submitted to a second evaluation of fasting calciuria (Ca/Cr). A modification of this parameter was noticed in 89% of RH-like and 78% of RH patients. In conclusion, these data suggest the presence of subpopulations of patients sensitive or not to calcium intake, regardless of whether the acute response to a calcium overload test suggested AH or RH. The CCLT disclosed dietary hypercalciuria in 21/58 (36%) of previously NCa patients. In these NCa patients, the ACLT may be replaced by the CCLT. The distinction

  19. Limestone reaction in calcium aluminate cement–calcium sulfate systems

    Energy Technology Data Exchange (ETDEWEB)

    Bizzozero, Julien, E-mail: julien.bizzozero@gmail.com; Scrivener, Karen L.

    2015-10-15

    This paper reports a study of ternary blends composed of calcium aluminate cement, calcium sulfate hemihydrate and limestone. Compressive strength tests and hydration kinetics were studied as a function of limestone and calcium sulfate content. The phase evolution and the total porosity were followed and compared to thermodynamic simulation to understand the reactions involved and the effect of limestone on these binders. The reaction of limestone leads to the formation of hemicarboaluminate and monocarboaluminate. Increasing the ratio between sulfate and aluminate decreases the extent of limestone reaction.

  20. Calcium binding protein-mediated regulation of voltage-gated calcium channels linked to human diseases

    Institute of Scientific and Technical Information of China (English)

    Nasrin NFJATBAKHSH; Zhong-ping FENG

    2011-01-01

    Calcium ion entry through voltage-gated calcium channels is essential for cellular signalling in a wide variety of cells and multiple physiological processes. Perturbations of voltage-gated calcium channel function can lead to pathophysiological consequences. Calcium binding proteins serve as calcium sensors and regulate the calcium channel properties via feedback mechanisms. This review highlights the current evidences of calcium binding protein-mediated channel regulation in human diseases.

  1. Calcium signals in olfactory neurons.

    Science.gov (United States)

    Tareilus, E; Noé, J; Breer, H

    1995-11-01

    Laser scanning confocal microscopy in combination with the fluorescent calcium indicators Fluo-3 and Fura-Red was employed to estimate the intracellular concentration of free calcium ions in individual olfactory receptor neurons and to monitor temporal and spatial changes in the Ca(2+)-level upon stimulation. The chemosensory cells responded to odorants with a significant increase in the calcium concentration, preferentially in the dendritic knob. Applying various stimulation paradigma, it was found that in a population of isolated cells, subsets of receptor neurons display distinct patterns of responsiveness. PMID:7488645

  2. Calcium signals in olfactory neurons.

    Science.gov (United States)

    Tareilus, E; Noé, J; Breer, H

    1995-11-01

    Laser scanning confocal microscopy in combination with the fluorescent calcium indicators Fluo-3 and Fura-Red was employed to estimate the intracellular concentration of free calcium ions in individual olfactory receptor neurons and to monitor temporal and spatial changes in the Ca(2+)-level upon stimulation. The chemosensory cells responded to odorants with a significant increase in the calcium concentration, preferentially in the dendritic knob. Applying various stimulation paradigma, it was found that in a population of isolated cells, subsets of receptor neurons display distinct patterns of responsiveness.

  3. Fine structures in the optical absorption spectra of photochemical silver in silver halides? A call for further research

    CERN Document Server

    Georgiev, Mladen

    2007-01-01

    A survey is presented of the work done so far to check earlier claims that a fine structure may be observed to occur under certain circumstances in the impurity spectral range of the optical absorption spectra of silver halides following photostimulation in the intrinsic range. This structure, associated with the photochemical formation of silver specks, has been questioned over the years. We now weigh carefully the experimental evidence on the silver halides against a background of similar data on the alkali halides, where competing processes run slower. We come to the conclusion that present day advances in experimental techniques may be quite adequate for providing a solid experimental basis to solve the problem unambiguously.

  4. Metallaphotoredox-catalysed sp3-sp3 cross-coupling of carboxylic acids with alkyl halides

    Science.gov (United States)

    Johnston, Craig P.; Smith, Russell T.; Allmendinger, Simon; MacMillan, David W. C.

    2016-08-01

    In the past 50 years, cross-coupling reactions mediated by transition metals have changed the way in which complex organic molecules are synthesized. The predictable and chemoselective nature of these transformations has led to their widespread adoption across many areas of chemical research. However, the construction of a bond between two sp3-hybridized carbon atoms, a fundamental unit of organic chemistry, remains an important yet elusive objective for engineering cross-coupling reactions. In comparison to related procedures with sp2-hybridized species, the development of methods for sp3-sp3 bond formation via transition metal catalysis has been hampered historically by deleterious side-reactions, such as β-hydride elimination with palladium catalysis or the reluctance of alkyl halides to undergo oxidative addition. To address this issue, nickel-catalysed cross-coupling processes can be used to form sp3-sp3 bonds that utilize organometallic nucleophiles and alkyl electrophiles. In particular, the coupling of alkyl halides with pre-generated organozinc, Grignard and organoborane species has been used to furnish diverse molecular structures. However, the manipulations required to produce these activated structures is inefficient, leading to poor step- and atom-economies. Moreover, the operational difficulties associated with making and using these reactive coupling partners, and preserving them through a synthetic sequence, has hindered their widespread adoption. A generically useful sp3-sp3 coupling technology that uses bench-stable, native organic functional groups, without the need for pre-functionalization or substrate derivatization, would therefore be valuable. Here we demonstrate that the synergistic merger of photoredox and nickel catalysis enables the direct formation of sp3-sp3 bonds using only simple carboxylic acids and alkyl halides as the nucleophilic and electrophilic coupling partners, respectively. This metallaphotoredox protocol is suitable for

  5. Metallaphotoredox-catalysed sp(3)-sp(3) cross-coupling of carboxylic acids with alkyl halides.

    Science.gov (United States)

    Johnston, Craig P; Smith, Russell T; Allmendinger, Simon; MacMillan, David W C

    2016-08-18

    In the past 50 years, cross-coupling reactions mediated by transition metals have changed the way in which complex organic molecules are synthesized. The predictable and chemoselective nature of these transformations has led to their widespread adoption across many areas of chemical research. However, the construction of a bond between two sp(3)-hybridized carbon atoms, a fundamental unit of organic chemistry, remains an important yet elusive objective for engineering cross-coupling reactions. In comparison to related procedures with sp(2)-hybridized species, the development of methods for sp(3)-sp(3) bond formation via transition metal catalysis has been hampered historically by deleterious side-reactions, such as β-hydride elimination with palladium catalysis or the reluctance of alkyl halides to undergo oxidative addition. To address this issue, nickel-catalysed cross-coupling processes can be used to form sp(3)-sp(3) bonds that utilize organometallic nucleophiles and alkyl electrophiles. In particular, the coupling of alkyl halides with pre-generated organozinc, Grignard and organoborane species has been used to furnish diverse molecular structures. However, the manipulations required to produce these activated structures is inefficient, leading to poor step- and atom-economies. Moreover, the operational difficulties associated with making and using these reactive coupling partners, and preserving them through a synthetic sequence, has hindered their widespread adoption. A generically useful sp(3)-sp(3) coupling technology that uses bench-stable, native organic functional groups, without the need for pre-functionalization or substrate derivatization, would therefore be valuable. Here we demonstrate that the synergistic merger of photoredox and nickel catalysis enables the direct formation of sp(3)-sp(3) bonds using only simple carboxylic acids and alkyl halides as the nucleophilic and electrophilic coupling partners, respectively. This metallaphotoredox

  6. Solvation structure of the halides from x-ray absorption spectroscopy

    Science.gov (United States)

    Antalek, Matthew; Pace, Elisabetta; Hedman, Britt; Hodgson, Keith O.; Chillemi, Giovanni; Benfatto, Maurizio; Sarangi, Ritimukta; Frank, Patrick

    2016-07-01

    Three-dimensional models for the aqueous solvation structures of chloride, bromide, and iodide are reported. K-edge extended X-ray absorption fine structure (EXAFS) and Minuit X-ray absorption near edge (MXAN) analyses found well-defined single shell solvation spheres for bromide and iodide. However, dissolved chloride proved structurally distinct, with two solvation shells needed to explain its strikingly different X-ray absorption near edge structure (XANES) spectrum. Final solvation models were as follows: iodide, 8 water molecules at 3.60 ± 0.13 Å and bromide, 8 water molecules at 3.40 ± 0.14 Å, while chloride solvation included 7 water molecules at 3.15 ± 0.10 Å, and a second shell of 7 water molecules at 4.14 ± 0.30 Å. Each of the three derived solvation shells is approximately uniformly disposed about the halides, with no global asymmetry. Time-dependent density functional theory calculations simulating the chloride XANES spectra following from alternative solvation spheres revealed surprising sensitivity of the electronic state to 6-, 7-, or 8-coordination, implying a strongly bounded phase space for the correct structure during an MXAN fit. MXAN analysis further showed that the asymmetric solvation predicted from molecular dynamics simulations using halide polarization can play no significant part in bulk solvation. Classical molecular dynamics used to explore chloride solvation found a 7-water solvation shell at 3.12 (-0.04/+0.3) Å, supporting the experimental result. These experiments provide the first fully three-dimensional structures presenting to atomic resolution the aqueous solvation spheres of the larger halide ions.

  7. Solubility of alkali metal halides in the ionic liquid [C4C1im][OTf].

    Science.gov (United States)

    Kuzmina, O; Bordes, E; Schmauck, J; Hunt, P A; Hallett, J P; Welton, T

    2016-06-28

    The solubilities of the metal halides LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbCl, CsCl, CsI, were measured at temperatures ranging from 298.15 to 378.15 K in the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([C4C1im][OTf]). Li(+), Na(+) and K(+) salts with anions matching the ionic liquid have also been investigated to determine how well these cations dissolve in [C4C1im][OTf]. This study compares the influence of metal cation and halide anion on the solubility of salts within this ionic liquid. The highest solubility found was for iodide salts, and the lowest solubility for the three fluoride salts. There is no outstanding difference in the solubility of salts with matching anions in comparison to halide salts. The experimental data were correlated employing several phase equilibria models, including ideal mixtures, van't Hoff, the λh (Buchowski) equation, the modified Apelblat equation, and the non-random two-liquid model (NRTL). It was found that the van't Hoff model gave the best correlation results. On the basis of the experimental data the thermodynamic dissolution parameters (ΔH, ΔS, and ΔG) were determined for the studied systems together with computed gas phase metathesis parameters. Dissolution depends on the energy difference between enthalpies of fusion and dissolution of the solute salt. This demonstrates that overcoming the lattice energy of the solid matrix is the key to the solubility of inorganic salts in ionic liquids. PMID:27264676

  8. Novel estimated surface tension data of actinide halide salts in the molten state

    Energy Technology Data Exchange (ETDEWEB)

    Aqra, Fathi, E-mail: fathiaqra2009@hotmail.com

    2014-05-01

    The surface tension of ThF{sub 4}, UF{sub 4} and UF{sub 6} is theoretically estimated, as function of temperature, whereas eight other halide salts only for temperature equal to their melting points. Calculations are based on a model, using statistical thermodynamics of Eyring theory. It is observed that the surface tension decreases linearly with temperature. The results are strictly compared with the available experimental data. The technique can be applied for conditions where experimental data are currently missing. The compressibility and surface tension products, of all salts under study, were also calculated.

  9. 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

    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...... 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...

  10. Measurements of prompt fission gamma-rays and neutrons with lanthanide halide scintillation detectors

    CERN Document Server

    Oberstedt, A; Billnert, R; Borcea, R; Brys, T; Chaves, C; Gamboni, T; Geerts, W; Göök, A; Guerrero, C; Hambsch, F-J; Kis, Z; Martinez, T; Oberstedt, S; Szentmiklosi, L; Takács, K; Vivaldi, M

    2014-01-01

    Photons have been measured with lanthanide halide scintillation detectors in coincidence with fission fragments. Using the time-of-flight information, reactions from γ-rays and neutrons could easily be distinguished. In several experiments on $^{252}$Cf(sf), $^{235}$U(n$_{th}$,f) and $^{241}$Pu(n$_{th}$,f) prompt fission γ-ray spectra characteristics were determined with high precision and the results are presented here. Moreover, a measured prompt fission neutron spectrum for $^{235}$U(n$_{th}$,f) is shown in order to demonstrate a new detection technique.

  11. Solvated Positron Chemistry - Positron Reactions with Pseudo-Halide Ions in Water

    DEFF Research Database (Denmark)

    Mogensen, O. E.; Pedersen, Niels Jørgen; Andersen, Jan Rud

    1982-01-01

    The hydrated positron e+aq reactions with SCN−, OCN−, CN−, S2− were studied by means of the angular correlation technique. The positron forms bound states with SCN−, CN−, and S2− but not with OCN−. Apparently, the e+aq reaction with SH− results in a positron bound state with S2−. It was difficult...... to determine the shapes of the bound-state angular correlation curves. Only in the SCN− case could a very rough estimate of the rate constant be obtained. Estimates of the binding energies relative to those of the corresponding halide ion states could be determined for SCN− and S2−....

  12. Organic-inorganic interactions of single crystalline organolead halide perovskites studied by Raman spectroscopy.

    Science.gov (United States)

    Xie, Li-Qiang; Zhang, Tai-Yang; Chen, Liang; Guo, Nanjie; Wang, Yu; Liu, Guo-Kun; Wang, Jia-Rui; Zhou, Jian-Zhang; Yan, Jia-Wei; Zhao, Yi-Xin; Mao, Bing-Wei; Tian, Zhong-Qun

    2016-07-21

    Organolead halide perovskites exhibit superior photoelectric properties, which have given rise to the perovskite-based solar cells whose power conversion efficiency has rapidly reached above 20% in the past few years. However, perovskite-based solar cells have also encountered problems such as current-voltage hysteresis and degradation under practical working conditions. Yet investigations into the intrinsic chemical nature of the perovskite material and its role on the performance of the solar cells are relatively rare. In this work, Raman spectroscopy is employed together with CASTEP calculations to investigate the organic-inorganic interactions in CH3NH3PbI3 and CH3NH3PbBr3-xClx perovskite single crystals with comparison to those having ammonic acid as the cations. For Raman measurements of CH3NH3PbI3, a low energy line of 1030 nm is used to avoid excitation of strong photoluminescence of CH3NH3PbI3. Raman spectra covering a wide range of wavenumbers are obtained, and the restricted rotation modes of CH3-NH3(+) embedded in CH3NH3PbBr3 (325 cm(-1)) are overwhelmingly stronger over the other vibrational bands of the cations. However, the band intensity diminishes dramatically in CH3NH3PbBr3-xClx and most of the bands shift towards high frequency, indicating the interaction with the halides. The details of such an interaction are further revealed by inspecting the band shift of the restricted rotation mode as well as the C-N, NH3(+) and CH3 stretching of the CH3NH3(+) as a function of Cl composition and length of the cationic ammonic acids. The results show that the CH3NH3(+) interacts with the PbX3(-) octahedral framework via the NH3(+) end through N(+)-HX hydrogen bonding whose strength can be tuned by the composition of halides but is insensitive to the size of the organic cations. Moreover, an increase of the Cl content strengthens the hydrogen bonding and thus blueshifts the C-N stretching bands. This is due to the fact that Cl is more electronegative than Br

  13. Nickel-Catalyzed Methylation of Aryl Halides with Deuterated Methyl Iodide.

    Science.gov (United States)

    Hu, Lu; Liu, Xin; Liao, Xuebin

    2016-08-01

    A nickel-catalyzed methylation of aryl halides with cheap and readily available CH3 I or CD3 I is described. The reaction is applicable to a wide range of substrates and allows installation of a CD3 group under mild reaction conditions without deuterium scrambling to other carbon atoms. Initial mechanistic studies on the stoichiometric and catalytic reactions of the isolated [(dppp)Ni(C6 H4 -4-CO2 Et)Br] [dppp=1,3-bis(diphenylphosphanyl)propane] suggest that a Ni(0) /Ni(II) catalytic cycle is favored. PMID:27381725

  14. The super-super exchange mechanism in iron-based antiperovskite chalco-halides

    OpenAIRE

    Liu, Kai; LU, Zhong-Yi

    2016-01-01

    By using the first-principles electronic structure calculations, we have systematically studied the magnetism in three recently synthesized iron-based antiperovskite chalco-halides: Ba$_3$(FeS$_4$)Cl, Ba$_3$(FeS$_4$)Br, and Ba$_3$(FeSe$_4$)Br. These compounds consist of edge-sharing Ba$Q_6$ ($Q$=Cl or Br) octahedra intercalated with isolated Fe$X_4$ ($X$=S or Se) tetrahedra. We find that even though the shortest distances between the nearest-neighboring Fe atoms in these three compounds alrea...

  15. High-Pressure Low-Symmetry Phases of Cesium Halides from First Principle Techniques

    OpenAIRE

    Nardelli, M. Buongiorno; Baroni, S.; Giannozzi, P.

    1994-01-01

    The relative stability of different high-pressure phases of various Cesium Halides is studied from first principles and analyzed using the Landau theory of phase transitions. We present results for CsI, CsBr, and CsCl up to pressures of about 100 GPa. A cubic-to-orthorhombic transition, driven by the softening of an acoustic phonon at the M point of the Brillouin zone, is competing with the cubic-to-tetragonal martensitic transition typical of these compounds. The phonon softening takes place...

  16. Methyl halides in surface seawater and marine boundary layer of the northwest Pacific

    OpenAIRE

    Ooki, Atsushi; Tsuda, Atsushi; Kameyama, Sohiko; Takeda, Shigenobu; Itoh, Sachihiko; SUGA, Toshio; Tazoe, Hirofumi; Okubo, Ayako; Yokouchi, Yoko

    2010-01-01

    The partial pressures of methyl halides (CH3X; X = Cl, Br, or I) and of CHClF2 (HCFC‐22), which are all volatile organic compounds (VOCs), were measured in the air of the marine boundary layer (pVOCair) and in surface seawater (pVOCwater) during a cruise from the subarctic to subtropical regions of the northwest Pacific in summer of 2008. In the northern transition water (TWN) with high biological activity, high levels of the three CH3Xs in surface seawater were frequently obse...

  17. Concentration Effects of Silver Ions on Ionic Conductivities of Molten Silver Halides

    OpenAIRE

    Okada T.; Kawakita Y.; Tahara S.; Ohno S.; Takeda S

    2011-01-01

    Ionic conductivities of molten (RbX)c(AgX)1-c (X = Cl and I) mixtures were measured to clarify the concentration effects of silver ions on ionic conductivities of molten silver halides. It is found that the addition of RbX to molten AgX rapidly reduces the ionic conductivity with 0 ≤ c ≤ 0.4. It suggests that strong Ag-Ag correlation is necessary to fast conduction of Ag ions in molten state. The absolute values of ionic conductivity for (RbCl)c(AgCl)1-c are larger than those for (R...

  18. Copper Complexes of Anionic Nitrogen Ligands in the Amidation and Imidation of Aryl Halides

    OpenAIRE

    Tye, Jesse W.; Weng, Zhiqiang; Johns, Adam M.; Incarvito, Christopher D.; Hartwig, John F.

    2008-01-01

    Copper(I) imidate and amidate complexes of chelating N,N-donor ligands, which are proposed intermediates in copper-catalyzed amidations of aryl halides, have been synthesized and characterized by X-ray diffraction and detailed solution-phase methods. In some cases, the complexes adopt neutral, three-coordinate trigonal planar structures in the solid state, but in other cases they adopt an ionic form consisting of an L2Cu+ cation and a CuX2− anion. A tetraalkylammonium salt of the CuX2− anion ...

  19. Novel estimated surface tension data of actinide halide salts in the molten state

    International Nuclear Information System (INIS)

    The surface tension of ThF4, UF4 and UF6 is theoretically estimated, as function of temperature, whereas eight other halide salts only for temperature equal to their melting points. Calculations are based on a model, using statistical thermodynamics of Eyring theory. It is observed that the surface tension decreases linearly with temperature. The results are strictly compared with the available experimental data. The technique can be applied for conditions where experimental data are currently missing. The compressibility and surface tension products, of all salts under study, were also calculated

  20. First-principles study on the electronic and optical properties of cubic ABX3 halide perovskites

    International Nuclear Information System (INIS)

    The electronic properties of ABX3 type compounds in the cubic phase are systematically studied using the first-principles calculations. The chemical trend of their properties as A or B or X varies is fully investigated. The optical properties of the ABX3 compounds are also investigated. Our calculations show that taking into account the spin–orbit coupling effect is crucial for predicting the accurate band gap of these halide perovskites. We predict that CH3NH3SnBr3 is a promising material for solar cells absorber with a perfect band gap and good optical absorption.

  1. Palladium-catalyzed cross-coupling reactions of aryl boronic acids with aryl halides in water.

    Science.gov (United States)

    Wang, Shaoyan; Zhang, Zhiqiang; Hu, Zhizhi; Wang, Yue; Lei, Peng; Chi, Haijun

    2009-01-01

    An efficient Suzuki cross-coupling reaction using a variety of aryl halides in neat water was developed. The Pd-catalyzed reaction between aryl bromides or chlorides and phenyl boronic acids was compatible with various functional groups and affords biphenyls in good to excellent yields without requirement of organic cosolvents. The air stability and solubility in water of the palladium-phosphinous acid complexes were considered to facilitate operation of the coupling reaction and product isolation. The reaction conditions including Pd catalyst selection, temperature, base and catalyst recoverability were also investigated. PMID:25084408

  2. Structural, optical, and electronic studies of wide-bandgap lead halide perovskites

    KAUST Repository

    Comin, Riccardo

    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.

  3. Exploration geochemical technique for the determination of preconcentrated organometallic halides by ICP-AES

    Science.gov (United States)

    Motooka, J.M.

    1988-01-01

    An atomic absorption extraction technique which is widely used in geochemical exploration for the determination of Ag, As, Au, Bi, Cd, Cu, Mo, Pb, Sb, and Zn has been modified and adapted to a simultaneous inductively coupled plasma-atomic emission instrument. the experimental and operating parameters are described for the preconcentration of the metals into their organometallic halides and for the determination of the metals. Lower limits of determination are equal to or improved over those for flame atomic absorption (except Au) and ICP results are very similar to the accepted AA values, with precision for the ICP data in excess of that necessary for exploration purposes.

  4. Structural and chemical analysis of gadolinium halides encapsulated within WS2 nanotubes

    Science.gov (United States)

    Anumol, E. A.; Enyashin, Andrey N.; Batra, Nitin M.; Costa, Pedro M. F. J.; Deepak, Francis Leonard

    2016-06-01

    The hollow cavities of nanotubes 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 WS2 nanotubes 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 non-trivial 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.The hollow cavities of nanotubes 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 WS2 nanotubes 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 non-trivial due to the

  5. Nickel-catalyzed Electrochemical Coupling of Phenyl Halide and Study of Mechanism

    Institute of Scientific and Technical Information of China (English)

    ZHAO, Peng; LUO, Yi-Wen; XUE, Teng; ZHANG, Ai-Jian; LU, Jia-Xing

    2006-01-01

    Electrochemical coupling of phenyl halide catalyzed by NiCl2bpy in DMF has been investigated in this paper.Stainless steel was used as cathode and zinc as anode. Effects of potential, temperature and catalyst on electrolyses were studied to optimize the electrolytic conditions, with the maximal isolated yield under potentiostatic electrolysis to be 85%. Cyclic voltammetry of NiCl2bpy in the presence of phenyl bromide has been studied and mechanisms,concerned with several kinds of nickel complex, have been summarized.

  6. Charge transfer dynamics from organometal halide perovskite to polymeric hole transport materials in hybrid solar cells

    OpenAIRE

    Brauer, Jan C.; Lee, Yong Hui; Nazeeruddin, Mohammad Khaja; Banerji, Natalie

    2016-01-01

    Organometal halide perovskites have emerged as promising next-generation solar cell technologies presenting outstanding efficiencies. However, many questions concerning their working principles remain to be answered. Here, we present a detailed study of hole transfer dynamics into polymeric hole transporting materials (HTMs), poly(triarylamine) (PTAA), poly(3-hexylthiophee-2,5-diyl (P3HT), and poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-benzothiadiaz...

  7. Physics and Nanofriction of Alkali Halide Solid Surfaces at the Melting Point

    OpenAIRE

    Zykova-Timan, T.; Ceresoli, D.; Tartaglino, U.; Tosatti, E.

    2006-01-01

    Alkali halide (100) surfaces are anomalously poorly wetted by their own melt at the triple point. We carried out simulations for NaCl(100) within a simple (BMHFT) model potential. Calculations of the solid-vapor, solid-liquid and liquid-vapor free energies showed that solid NaCl(100) is a nonmelting surface, and that the incomplete wetting can be traced to the conspiracy of three factors: surface anharmonicities stabilizing the solid surface; a large density jump causing bad liquid-solid adhe...

  8. Why Are Alkali Halide Solid Surfaces Not Wetted By Their Own Melt?

    OpenAIRE

    Zykova-Timan, T.; Ceresoli, D.; Tartaglino, U.; Tosatti, E.

    2005-01-01

    Alkali halide (100) crystal surfaces are anomalous, being very poorly wetted by their own melt at the triple point. We present extensive simulations for NaCl, followed by calculations of the solid-vapor, solid-liquid, and liquid-vapor free energies showing that solid NaCl(100) is a nonmelting surface, and that its full behavior can quantitatively be accounted for within a simple Born-Meyer-Huggins-Fumi-Tosi model potential. The incomplete wetting is traced to the conspiracy of three factors: ...

  9. D301 resin as a solid base for phosphine-free Heck reactions with heteroaryl halides

    Institute of Scientific and Technical Information of China (English)

    Wen Pei; Xiang Mei Wu

    2008-01-01

    A new and practical method of the D301 resin,a weak basic anion exchange resin with secondary amine functionality (Grade Matrix Structure:Styrene-DVB D301R),used as base to Heck reactions catalyzed by palladium reagent without phosphine compound as ligand is described.It was found that the D301 resin used as base is an efficient and reusable base and can be regenerated and recycled in the reaction.The olefination of heteroaryl halides prepared the corresponding products in good yields using D301 resin as base.

  10. 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.

  11. The Renaissance of Halide Perovskites and Their Evolution as Emerging Semiconductors.

    Science.gov (United States)

    Stoumpos, Constantinos C; Kanatzidis, Mercouri G

    2015-10-20

    The recent re-emergence of the halide perovskites, of the type AMX3, derives from a sea-changing breakthrough in the field of photovoltaics that has led to a whole new generation of solar devices with remarkable power conversion efficiency. The success in the field of photovoltaics has led to intense, combined research efforts to better understand these materials both from the fundamental chemistry and physics points of view and for the improvement of applied functional device engineering. This groundswell of activity has breathed new life into this long-known but largely "forgotten" class of perovskites. The impressive achievements of halide perovskites in photovoltaics, as well as other optoelectronic applications, stem from an unusually favorable combination of optical and electronic properties, with the ability to be solution processed into films. This defines them as a brand new class of semiconductors that can rival or exceed the performance of the venerable classes of III-V and II-IV semiconductors, which presently dominate the industries of applied optoelectronics. Our aim in this Account is to highlight the basic pillars that define the chemistry of the halide perovskites and their unconventional electronic properties through the prism of structure-property relationships. We focus on the synthetic requirements under which a halide perovskite can exist and emphasize how the synthetic conditions can determine the structural integrity and the bulk properties of the perovskites. Then we proceed to discuss the origins of the optical and electronic phenomena, using the perovskite crystal structure as a guide. Some of the most remarkable features of the perovskites dealt with in this Account include the evolution of a unique type of defect, which gives rise to superlattices. These can enhance or diminish the fluorescence properties of the perovskites. For example, the exotic self-doping ability of the Sn-based perovskites allows them to adopt electrical

  12. 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.

  13. High Efficiency Infrared to Visible Upconversion in Er3+/Yb3+-Doped Lead Halide Tellurite Glass

    Institute of Scientific and Technical Information of China (English)

    张丽艳; 杨建虎; 胡丽丽; 姜中宏

    2003-01-01

    Strong upconversion luminescence of Er3+/yb3+-doped lead halide tellurite glass under 976nm excitation is demonstrated. Three emission bands centred at 525nm, 545nm, and 655nm resulting from the transitions from the excited states 2H11/2, 4Ss/2, and 4F9/2 to the ground state 4I15/2, respectively, are observed even at 60mW pumping power. The power dependent intensity and the upconversion mechanisms responsible for the luminescence are evaluated and discussed. The obtained results might provide useful information for the developments of upconversion lasers.

  14. A First-Principles Study on the Structural and Electronic Properties of Sn-Based Organic-Inorganic Halide Perovskites

    Science.gov (United States)

    Ma, Zi-Qian; Pan, Hui; Wong, Pak Kin

    2016-08-01

    Organic-inorganic halide perovskites have attracted increasing interest on solar-energy harvesting because of their outstanding electronic properties. In this work, we systematically investigate the structural and electronic properties of Sn-based hybrid perovskites MASnX3 and FASnX3 (X = I, Br) based on density-functional-theory calculations. We find that their electronic properties strongly depend on the organic molecules, halide atoms, and structures. We show that there is a general rule to predict the band gap of the Sn-based hybrid perovskite: its band gap increases as the size of halide atom decreases as well as that of organic molecule increase. The band gap of high temperature phase (cubic structure) is smaller than that of low temperature phase (orthorhombic structure). The band gap of tetragonal structure (medium-temperature phase) may be larger or smaller than that of cubic phase, depending on the orientation of the molecule. Tunable band gap within a range of 0.73-1.53 eV can be achieved by choosing halide atom and organic molecule, and controlling structure. We further show that carrier effective mass also reduces as the size of halide atom increases and that of molecule decreases. By comparing with Pb-based hybrid perovskites, the Sn-based systems show enhanced visible-light absorption and carrier mobility due to narrowed band gap and reduced carrier effective mass. These Sn-based organic-inorganic halide perovskites may find applications in solar energy harvesting with improved performance.

  15. A First-Principles Study on the Structural and Electronic Properties of Sn-Based Organic-Inorganic Halide Perovskites

    Science.gov (United States)

    Ma, Zi-Qian; Pan, Hui; Wong, Pak Kin

    2016-11-01

    Organic-inorganic halide perovskites have attracted increasing interest on solar-energy harvesting because of their outstanding electronic properties. In this work, we systematically investigate the structural and electronic properties of Sn-based hybrid perovskites MASnX3 and FASnX3 (X = I, Br) based on density-functional-theory calculations. We find that their electronic properties strongly depend on the organic molecules, halide atoms, and structures. We show that there is a general rule to predict the band gap of the Sn-based hybrid perovskite: its band gap increases as the size of halide atom decreases as well as that of organic molecule increase. The band gap of high temperature phase (cubic structure) is smaller than that of low temperature phase (orthorhombic structure). The band gap of tetragonal structure (medium-temperature phase) may be larger or smaller than that of cubic phase, depending on the orientation of the molecule. Tunable band gap within a range of 0.73-1.53 eV can be achieved by choosing halide atom and organic molecule, and controlling structure. We further show that carrier effective mass also reduces as the size of halide atom increases and that of molecule decreases. By comparing with Pb-based hybrid perovskites, the Sn-based systems show enhanced visible-light absorption and carrier mobility due to narrowed band gap and reduced carrier effective mass. These Sn-based organic-inorganic halide perovskites may find applications in solar energy harvesting with improved performance.

  16. Variability of calcium absorption

    International Nuclear Information System (INIS)

    Variability in calcium absorption was estimated in three groups of normal subjects in whom Ca absorption was measured by standard isotopic-tracer methods at interstudy intervals ranging from 1 to 4 mo. Fifty absorption tests were performed in 22 subjects. Each was done in the morning after an overnight fast with an identical standard breakfast containing a Ca load of approximately 250 mg. Individual fractional absorption values were normalized to permit pooling of the data. The coefficient of variation (CVs) for absorption for the three groups ranged from 10.57 to 12.79% with the size of the CV increasing with interstudy duration. One other published study presenting replicate absorption values was analyzed in a similar fashion and was found to have a CV of absorption of 9.78%. From these data we estimate that when the standard double-isotope method is used to measure Ca absorption there is approximately 10% variability around any given absorption value within an individual human subject and that roughly two-thirds of this represents real biological variability in absorption

  17. Suzuki-Miyaura Cross-Coupling Reactions of Unactivated Alkyl Halides Catalyzed by a Nickel Pincer Complex

    OpenAIRE

    Di Franco, Thomas; Boutin, Nicolas; Hu, Xile

    2013-01-01

    A nickel(II) pincer complex, [((N2N)-N-Me)Ni-Cl], was used to catalyze alkyl-alkyl and alkyl-aryl Suzuki-Miyaura coupling reactions of unactivated alkyl halides. The coupling of 9-alkyl-9-borabicyclo[3.3.1]nonane and 9-phenyl-9-borabicyclo[3.3.1]nonane reagents with alkyl halides was achieved in modest to good yields. The reactions tolerated a variety of useful functional groups including ester, ether, furan, thioether, acetal, and Boc groups.

  18. Grand Canonical Monte Carlo coupled multiscale simulation for electrochemical and solvent parameters of silver halide systems in water.

    Science.gov (United States)

    Sudha, V; Harinipriya, S; Sangaranarayanan, M V

    2016-07-01

    Grand Canonical Monte Carlo methods in conjunction with continuum Multiscale simulation to estimate the hydration energies and surface potentials of silver halides as demonstrated elsewhere is employed by incorporating random distribution of molecules, nearest neighbor distances and hydration numbers. The extent of dehydration during each step and the corresponding variation in the hydration numbers are evaluated, assuming the validity of hard spheres. These estimates are then employed to deduce the redox potential of the reaction viz. 2AgX(solution)⇔2Ag(solid)+X2(gas). The dependence of these values on the nature of the halides and solvation characteristics is indicated. PMID:27442589

  19. Off-center impurity in alkali halides: reorientation, electric polarization and pairing to F center. III. Numerical calculations

    CERN Document Server

    Baldacchini, G; Grassano, U M; Scacco, A; Petrova, P; Mladenova, M; Ivanovich, M; Georgiev, M

    2007-01-01

    We carried out numerical calculations by an extended-Hueckel program in order to check the analytical results reported in the preceding Part I and Part II. We typically consider alkali halide clusters composed of some tens of constituent atoms to calculate electronic energies under static conditions or versus the displacements of particular atoms. Among other things, the off-center displacement of substitutional Li+ impurity in most alkali halides is evidenced. The trigonometric profile of the rotational barriers is also confirmed for KCl.

  20. Research Update: Challenges for high-efficiency hybrid lead-halide perovskite LEDs and the path towards electrically pumped lasing

    Science.gov (United States)

    Li, Guangru; Price, Michael; Deschler, Felix

    2016-09-01

    Hybrid lead-halide perovskites have emerged as promising solution-processed semiconductor materials for thin-film optoelectronics. In this review, we discuss current challenges in perovskite LED performance, using thin-film and nano-crystalline perovskite as emitter layers, and look at device performance and stability. Fabrication of electrically pumped, optical-feedback devices with hybrid lead halide perovskites as gain medium is a future challenge, initiated by the demonstration of optically pumped lasing structures with low gain thresholds. We explain the material parameters affecting optical gain in perovskites and discuss the challenges towards electrically pumped perovskite lasers.

  1. Z-Selective Olefin Synthesis via Iron-Catalyzed Reductive Coupling of Alkyl Halides with Terminal Arylalkynes.

    Science.gov (United States)

    Cheung, Chi Wai; Zhurkin, Fedor E; Hu, Xile

    2015-04-22

    Selective catalytic synthesis of Z-olefins has been challenging. Here we describe a method to produce 1,2-disubstituted olefins in high Z selectivity via reductive cross-coupling of alkyl halides with terminal arylalkynes. The method employs inexpensive and nontoxic catalyst (iron(II) bromide) and reductant (zinc). The substrate scope encompasses primary, secondary, and tertiary alkyl halides, and the reaction tolerates a large number of functional groups. The utility of the method is demonstrated in the synthesis of several pharmaceutically relevant molecules. Mechanistic study suggests that the reaction proceeds through an iron-catalyzed anti-selective carbozincation pathway.

  2. 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.

  3. Mitochondrial calcium uptake.

    Science.gov (United States)

    Williams, George S B; Boyman, Liron; Chikando, Aristide C; Khairallah, Ramzi J; Lederer, W J

    2013-06-25

    Calcium (Ca(2+)) uptake into the mitochondrial matrix is critically important to cellular function. As a regulator of matrix Ca(2+) levels, this flux influences energy production and can initiate cell death. If large, this flux could potentially alter intracellular Ca(2+) ([Ca(2+)]i) signals. Despite years of study, fundamental disagreements on the extent and speed of mitochondrial Ca(2+) uptake still exist. Here, we review and quantitatively analyze mitochondrial Ca(2+) uptake fluxes from different tissues and interpret the results with respect to the recently proposed mitochondrial Ca(2+) uniporter (MCU) candidate. This quantitative analysis yields four clear results: (i) under physiological conditions, Ca(2+) influx into the mitochondria via the MCU is small relative to other cytosolic Ca(2+) extrusion pathways; (ii) single MCU conductance is ∼6-7 pS (105 mM [Ca(2+)]), and MCU flux appears to be modulated by [Ca(2+)]i, suggesting Ca(2+) regulation of MCU open probability (P(O)); (iii) in the heart, two features are clear: the number of MCU channels per mitochondrion can be calculated, and MCU probability is low under normal conditions; and (iv) in skeletal muscle and liver cells, uptake per mitochondrion varies in magnitude but total uptake per cell still appears to be modest. Based on our analysis of available quantitative data, we conclude that although Ca(2+) critically regulates mitochondrial function, the mitochondria do not act as a significant dynamic buffer of cytosolic Ca(2+) under physiological conditions. Nevertheless, with prolonged (superphysiological) elevations of [Ca(2+)]i, mitochondrial Ca(2+) uptake can increase 10- to 1,000-fold and begin to shape [Ca(2+)]i dynamics.

  4. Correlation between deformation bleaching and mechanoluminescence in coloured alkali halide crystals

    Indian Academy of Sciences (India)

    B P Chandra; M Ramrakhiani; P Sahu; A M Rastogi

    2000-02-01

    The present paper reports the correlation between deformation bleaching of coloration and mechanoluminescence (ML) in coloured alkali halide crystals. When the -centre electrons captured by moving dislocations are picked up by holes, deep traps and other compatible traps, then deformation bleaching occurs. At the same time, radiative recombination of dislocation captured electrons with the holes gives rise to the mechanoluminescence. Expressions are derived for the strain dependence of the density of colour centres in deformed crystals and also for the number of colour centres bleached. So far as strain, temperature, density of colour centres, a and volume dependence are concerned, there exists a correlation between the deformation bleaching and ML in coloured alkali halide crystals. From the strain dependence of the density of colour centres in deformed crystals, the value of coefficient of deformation bleaching is determined and it is found to be 1.93 and 2.00 for KCl and KBr crystals, respectively. The value of $(D + \\mathcal{X})$ is determined from the strain dependence of the ML intensity and it is found to be 2.6 and 3.7 for KCl and KBr crystals, respectively. This gives the value of coefficient of deformation generated compatible traps $\\mathcal{X}$ to be 0.67 and 1.7 for KCl and KBr crystals, respectively.

  5. Evaluation of quaternary ammonium halides for removal of methyl iodide from flowing air streams

    International Nuclear Information System (INIS)

    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

  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. Dielectric relaxation of alkyl chains in graphite oxide and n-alkylammonium halides

    Directory of Open Access Journals (Sweden)

    Xiaoqian Ai

    2016-05-01

    Full Text Available The dynamic of n-alkylammonium halides and n-alkylammonium cations (n = 12, 14, 16, 18 intercalated in graphite oxide (GO have been investigated with complex impedance spectroscopy. X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, elemental analysis and thermogravimetry served to characterize the materials. The intercalated alkylammonium cations distributes as monolayers (when n = 12, 14 or 16 or bilayers (when n = 18, with their long axis parallel to GO layers, and with cations of headgroups bonded ionically to C-O- groups of GO; backbones of the confined molecules remain free. All halides and intercalation compounds suffer dielectric loss at low temperature. Arrhenius plots of the thermal dependence of the loss peaks, which are asymmetric, produce apparent activation energies that rise with increasing n. Ngai’s correlated-state model helps to correct for effects of dipole-dipole interaction, leading to virtually identical values for actual activation energy of 110 meV ± 5%; the values are also almost the same as the barrier energy for internal rotation in the alkyl macromolecule. We conclude that the relaxation of the alkylammonium cations arises not from C3 reorientation of the CH3 at its headgroup, but from small-angle wobbling around its major axis, an intrinsic motion.

  8. Rhodium-catalysed asymmetric allylic arylation of racemic halides with arylboronic acids

    Science.gov (United States)

    Sidera, Mireia; Fletcher, Stephen P.

    2015-11-01

    Csp2-Csp2 cross-coupling reactions between arylboronic acid and aryl halides are widely used in both academia and industry and are strategically important in the development of new agrochemicals and pharmaceuticals. Csp2-Csp3 cross-coupling reactions have been developed, but enantioselective variations are rare and simply retaining the stereochemistry is a problem. Here we report a highly enantioselective Csp2-Csp3 bond-forming method that couples arylboronic acids to racemic allyl chlorides. Both enantiomers of a cyclic chloride are converted into a single enantiomer of product via a dynamic kinetic asymmetric transformation. This Rh-catalysed method uses readily available and inexpensive building blocks and is mild and broadly applicable. For electron-deficient, electron-rich or ortho-substituted boronic acids better results are obtained with racemic allyl bromides. Oxygen substitution in the allyl halide is tolerated and the products can be functionalized to provide diverse building blocks. The approach fills a significant gap in the methods for catalytic asymmetric synthesis.

  9. Color-Pure Violet-Light-Emitting Diodes Based on Layered Lead Halide Perovskite Nanoplates.

    Science.gov (United States)

    Liang, Dong; Peng, Yuelin; Fu, Yongping; Shearer, Melinda J; Zhang, Jingjing; Zhai, Jianyuan; Zhang, Yi; Hamers, Robert J; Andrew, Trisha L; Jin, Song

    2016-07-26

    Violet electroluminescence is rare in both inorganic and organic light-emitting diodes (LEDs). Low-cost and room-temperature solution-processed lead halide perovskites with high-efficiency and color-tunable photoluminescence are promising for LEDs. Here, we report room-temperature color-pure violet LEDs based on a two-dimensional lead halide perovskite material, namely, 2-phenylethylammonium (C6H5CH2CH2NH3(+), PEA) lead bromide [(PEA)2PbBr4]. The natural quantum confinement of two-dimensional layered perovskite (PEA)2PbBr4 allows for photoluminescence of shorter wavelength (410 nm) than its three-dimensional counterpart. By converting as-deposited polycrystalline thin films to micrometer-sized (PEA)2PbBr4 nanoplates using solvent vapor annealing, we successfully integrated this layered perovskite material into LEDs and achieved efficient room-temperature violet electroluminescence at 410 nm with a narrow bandwidth. This conversion to nanoplates significantly enhanced the crystallinity and photophysical properties of the (PEA)2PbBr4 samples and the external quantum efficiency of the violet LED. The solvent vapor annealing method reported herein can be generally applied to other perovskite materials to increase their grain size and, ultimately, improve the performance of optoelectronic devices based on perovskite materials. PMID:27336850

  10. Metallotropic liquid crystals formed by surfactant templating of molten metal halides.

    Science.gov (United States)

    Martin, James D; Keary, Cristin L; Thornton, Todd A; Novotnak, Mark P; Knutson, Jeremey W; Folmer, Jacob C W

    2006-04-01

    Liquid crystals consist of anisotropic molecular units, and most are organic molecules. Materials incorporating metals into anisotropic molecules, described as metallomesogens, have been prepared. Anisotropic structures such as one-dimensional chains and two-dimensional layers are frequently observed in solid-state inorganic materials, however, little is understood about structural organization in melts of such materials. Achieving liquid-crystalline behaviour in inorganic fluids should be possible if the anisotropic structure can be retained or designed into the molten phase. We demonstrated the ability to engineer zeolite-type structures into metal halide glasses and liquids. In this work we have engineered lamellar, cubic and hexagonal liquid-crystalline structure in metal-halide melts by controlling the volume fraction and nature of the inorganic block (up to 80 mol%) with respect to alkylammonium surfactants. The high metal content of these liquid-crystalline systems significantly advances the field of metallomesogens, which seeks to combine magnetic, electronic, optical, redox and catalytic properties common to inorganic materials with the fluid properties of liquid crystals. PMID:16547520

  11. 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.

  12. Light-Matter Interactions in Cesium Lead Halide Perovskite Nanowire Lasers.

    Science.gov (United States)

    Park, Kidong; Lee, Jong Woon; Kim, Jun Dong; Han, Noh Soo; Jang, Dong Myung; Jeong, Seonghyun; Park, Jeunghee; Song, Jae Kyu

    2016-09-15

    Light-matter interactions in inorganic perovskite nanolasers are investigated using single-crystalline cesium lead halide (CsPbX3, X = Cl, Br, and I) nanowires synthesized by the chemical vapor transport method. The perovskite nanowires exhibit a uniform growth direction, smooth surfaces, straight end facets, and homogeneous composition distributions. Lasing occurs in the perovskite nanowires at low thresholds (3 μJ/cm(2)) with high quality factors (Q = 1200-1400) under ambient atmospheric environments. The wavelengths of the nanowire lasers are tunable by controlling the stoichiometry of the halide, allowing the lasing of the inorganic perovskite nanowires from blue to red. The unusual spacing of the Fabry-Pérot modes suggests strong light-matter interactions in the reduced mode volume of the nanowires, while the polarization of the lasing indicates that the Fabry-Pérot modes belong to the same fundamental transverse mode. The dispersion curve of the exciton-polariton model suggests that the group refractive index of the polariton is significantly enhanced. PMID:27594046

  13. 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.

  14. Ab initio modeling of the optical properties in organometallic halide perovskites for photovoltaic applications

    Science.gov (United States)

    Neukirch, Amanda; Nei, Wanyi; Pedesseau, Laurent; Even, Jacky; Katan, Claudine; Mohite, Aditya; Tretiak, Segrei

    2015-03-01

    The need for an inexpensive, clean, and plentiful source of energy has generated large amounts of research in an assortment of solution processed organic and hybrid organic-inorganic solar cells. A relative newcomer to the field of solution processed photovoltaics is the lead halide perovskite solar cell. In the past 5 years, the efficiencies of devices made from this material have increased from 3.5% to nearly 20%. Despite the rapid development of organic-inorganic perovskite solar cells, a thorough understanding of the fundamental photophysical processes driving the high performance of these devices is not well understood. I am using state-of-the-art ab initio computational techniques in order to characterize the properties at the interface of perovskite devices in order to aide in materials design and device engineering. I will present an in-depth analysis of the electronic and optical properties of bulk and surface states of pure and mixed halide systems. The high-level static quantum mechanical calculations, including spin-orbit-coupling and the many body GW approach, identify the key electronic states involved in photoinduced dynamics. This knowledge provides important information on how the optical properties change with variations to the system. Supported by the DOE, the LANL LDRD program XW11, and CNLS.

  15. Direct synthesis of Z-alkenyl halides through catalytic cross-metathesis

    Science.gov (United States)

    Koh, Ming Joo; Nguyen, Thach T.; Zhang, Hanmo; Schrock, Richard R.; Hoveyda, Amir H.

    2016-03-01

    Olefin metathesis has had a large impact on modern organic chemistry, but important shortcomings remain: for example, the lack of efficient processes that can be used to generate acyclic alkenyl halides. Halo-substituted ruthenium carbene complexes decompose rapidly or deliver low activity and/or minimal stereoselectivity, and our understanding of the corresponding high-oxidation-state systems is limited. Here we show that previously unknown halo-substituted molybdenum alkylidene species are exceptionally reactive and are able to participate in high-yielding olefin metathesis reactions that afford acyclic 1,2-disubstituted Z-alkenyl halides. Transformations are promoted by small amounts of a catalyst that is generated in situ and used with unpurified, commercially available and easy-to-handle liquid 1,2-dihaloethene reagents, and proceed to high conversion at ambient temperature within four hours. We obtain many alkenyl chlorides, bromides and fluorides in up to 91 per cent yield and complete Z selectivity. This method can be used to synthesize biologically active compounds readily and to perform site- and stereoselective fluorination of complex organic molecules.

  16. Amorphous TiO2 Compact Layers via ALD for Planar Halide Perovskite Photovoltaics.

    Science.gov (United States)

    Kim, In Soo; Haasch, Richard T; Cao, Duyen H; Farha, Omar K; Hupp, Joseph T; Kanatzidis, Mercouri G; Martinson, Alex B F

    2016-09-21

    A low-temperature (<120 °C) route to pinhole-free amorphous TiO2 compact layers may pave the way to more efficient, flexible, and stable inverted perovskite halide device designs. Toward this end, we utilize low-temperature thermal atomic layer deposition (ALD) to synthesize ultrathin (12 nm) compact TiO2 underlayers for planar halide perovskite PV. Although device performance with as-deposited TiO2 films is poor, we identify room-temperature UV-O3 treatment as a route to device efficiency comparable to crystalline TiO2 thin films synthesized by higher temperature methods. We further explore the chemical, physical, and interfacial properties that might explain the improved performance through X-ray diffraction, spectroscopic ellipsometry, Raman spectroscopy, and X-ray photoelectron spectroscopy. These findings challenge our intuition about effective electron selective layers as well as point the way to a greater selection of flexible substrates and more stable inverted device designs.

  17. Photo-induced halide redistribution in organic-inorganic perovskite films

    Science.gov (United States)

    Dequilettes, Dane W.; Zhang, Wei; Burlakov, Victor M.; Graham, Daniel J.; Leijtens, Tomas; Osherov, Anna; Bulović, Vladimir; Snaith, Henry J.; Ginger, David S.; Stranks, Samuel D.

    2016-05-01

    Organic-inorganic perovskites such as CH3NH3PbI3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH3NH3PbI3 films under illumination. We demonstrate that the photo-induced `brightening' of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging the same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. Our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance.

  18. Photo-induced halide redistribution in organic–inorganic perovskite films

    Science.gov (United States)

    deQuilettes, Dane W.; Zhang, Wei; Burlakov, Victor M.; Graham, Daniel J.; Leijtens, Tomas; Osherov, Anna; Bulović, Vladimir; Snaith, Henry J.; Ginger, David S.; Stranks, Samuel D.

    2016-01-01

    Organic–inorganic perovskites such as CH3NH3PbI3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH3NH3PbI3 films under illumination. We demonstrate that the photo-induced ‘brightening' of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging the same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. Our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance. PMID:27216703

  19. Dielectric relaxation of alkyl chains in graphite oxide and n-alkylammonium halides

    Science.gov (United States)

    Ai, Xiaoqian; Tian, Yuchen; Gu, Min; Yu, Ji; Tang, Tong B.

    2016-05-01

    The dynamic of n-alkylammonium halides and n-alkylammonium cations (n = 12, 14, 16, 18) intercalated in graphite oxide (GO) have been investigated with complex impedance spectroscopy. X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, elemental analysis and thermogravimetry served to characterize the materials. The intercalated alkylammonium cations distributes as monolayers (when n = 12, 14 or 16) or bilayers (when n = 18), with their long axis parallel to GO layers, and with cations of headgroups bonded ionically to C-O- groups of GO; backbones of the confined molecules remain free. All halides and intercalation compounds suffer dielectric loss at low temperature. Arrhenius plots of the thermal dependence of the loss peaks, which are asymmetric, produce apparent activation energies that rise with increasing n. Ngai's correlated-state model helps to correct for effects of dipole-dipole interaction, leading to virtually identical values for actual activation energy of 110 meV ± 5%; the values are also almost the same as the barrier energy for internal rotation in the alkyl macromolecule. We conclude that the relaxation of the alkylammonium cations arises not from C3 reorientation of the CH3 at its headgroup, but from small-angle wobbling around its major axis, an intrinsic motion.

  20. 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

    2015-05-01

    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.

  1. Enthalpic Interaction for α-Amino Acid with Alkali Metal Halides in Water

    Institute of Scientific and Technical Information of China (English)

    LU,Yan(卢雁)

    2004-01-01

    The studies of the enthalpic interaction parameters, hxy, hxyy and hxxv, of alkali metal halides with glycine,α-alanine and α-aminobutyric acid were published. Synthetic considering of the results of the studies, some interesting behaviors of the interaction between alkali metal halides and the α-amino acids have been found. The values of hxy will increase with the increase of the number of carbon atoms in alkyl side chain of amino acid molecules and decrease with the increase of the radius of the ions. The increasing of the salt's effect on the hydrophobic hydration structure as the radii of anion is more obvious than as that of cation. The value of hxxy will regularly decrease with the increase of the number of carbon atoms in the alkyl chain of amino acids and linear increase with the increase of the radius. But the relation of hxxy with the radius of cations is not evident. The value of hxyy will increase with the increase of the radii of the ions. As the increase of the number of carbon atoms of amino acids, hxyy is decreas for the ions which have lager size and there is a maximum value at α-alanine for the ions which have small size. The behaviors of the interaction mentioned above were further discussed in view of electrostatic and structural interactions.

  2. Comparative study of energy-efficiency and conservation systems for ceramic metal-halide discharge lamps

    International Nuclear Information System (INIS)

    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

  3. Assignment of photoelectron spectra of halide-water clusters: Contrasting patterns of delocalization in Dyson orbitals

    Science.gov (United States)

    Dolgounitcheva, O.; Zakrzewski, V. G.; Ortiz, J. V.

    2013-04-01

    Ab initio electron propagator calculations in various self-energy approximations provide accurate assignments of peaks observed in the photoelectron spectra of complexes that comprise a fluoride or chloride anion and two or three water molecules. More than one minimum structure is found in all four cases. When the halide anion is Cl-, the first three final states may be described as quasi-degenerate 2P chlorine atoms coordinated to water molecules. Higher final states consist of a chloride anion juxtaposed to a positive charge that is delocalized over the water molecules. For the clusters with fluoride anions, most of the final states correspond to Dyson orbitals that are delocalized over the F and O nuclei. A variety of F-O σ and π bonding and antibonding patterns are evident in the Dyson orbitals. The assignment of low-lying spectral peaks to halide p orbital vacancies or to delocalized solvent orbitals is more valid for the chloride clusters than for the fluoride clusters, where a delocalized picture arises from strong bonding interactions between F 2p and H2O 1b1 orbitals.

  4. Aging and calcium as an environmental factor.

    Science.gov (United States)

    Fujita, T

    1985-12-01

    Calcium deficiency is a constant menace to land-abiding animals, including mammals. Humans enjoying exceptional longevity on earth are especially susceptible to calcium deficiency in old age. Low calcium and vitamin D intake, short solar exposure, decreased intestinal absorption, and falling renal function with insufficient 1,25(OH)2 vitamin D biosynthesis all contribute to calcium deficiency, secondary hyperparathyroidism, bone loss and possibly calcium shift from the bone to soft tissue, and from the extracellular to the intracellular compartment, blunting the sharp concentration gap between these compartments. The consequences of calcium deficiency might thus include not only osteoporosis, but also arteriosclerosis and hypertension due to the increase of calcium in the vascular wall, amyotrophic lateral sclerosis and senile dementia due to calcium deposition in the central nervous system, and a decrease in cellular function, because of blunting of the difference in extracellular-intracellular calcium, leading to diabetes mellitus, immune deficiency and others (Fig. 6). PMID:2943880

  5. Optimizing calcium selective fluorimetric nanospheres.

    Science.gov (United States)

    Kisiel, Anna; Kłucińska, Katarzyna; Gniadek, Marianna; Maksymiuk, Krzysztof; Michalska, Agata

    2015-11-01

    Recently it was shown that optical nanosensors based on alternating polymers e.g. poly(maleic anhydride-alt-1-octadecene) were characterized by a linear dependence of emission intensity on logarithm of concentration over a few of orders of magnitude range. In this work we focus on the material used to prepare calcium selective nanosensors. It is shown that alternating polymer nanosensors offer competitive performance in the absence of calcium ionophore, due to interaction of the nanospheres building blocks with analyte ions. The emission increase corresponds to increase of calcium ions contents in the sample within the range from 10(-4) to 10(-1) M. Further improvement in sensitivity (from 10(-6) to 10(-1) M) and selectivity can be achieved by incorporating calcium ionophore in the nanospheres. The optimal results were obtained for core-shell nanospheres, where the core was prepared from poly(styrene-co-maleic anhydride) and the outer layer from poly(maleic anhydride-alt-1-octadecene). Thus obtained chemosensors were showing linear dependence of emission on logarithm of calcium ions concentration within the range from 10(-7) to 10(-1) M. PMID:26452839

  6. Using Group-Inquiry to Study Differing Reaction Conditions in the E2 Elimination of Cyclohexyl Halides

    Science.gov (United States)

    Long, Robert D.

    2012-01-01

    In this experiment, students individually conduct one of several variations of an E2 dehydrohalogenation reaction on a cyclohexyl halide substrate for 30 min, which is sufficient only for a partial reaction to occur. The variations examine reaction conditions including different leaving groups, decreased reaction temperature, or reduced base…

  7. CuI-Catalyzed: One-Pot Synthesis of Diaryl Disulfides from Aryl Halides and Carbon Disulfide

    OpenAIRE

    Mohammad Soleiman-Beigi; Azadeh Izadi

    2013-01-01

    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.

  8. N-Arylation of azaheterocycles with aryl and heteroaryl halides catalyzed by iminodiacetic acid resin-chelated copper complex

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Iminodiacetic acid resin-chelated copper(Ⅱ) complex is effective in cross-coupling reactions between azaheterocycles and aryl or heteroaryl halides,providing N-arylated products in good to excellent yields.The copper catalyst is air stable and can be readily recovered and reused with minimal loss of activity for three runs.

  9. Halide (Cl(super -)) Quenching of Quinine Sulfate Fluorescence: A Time-Resolved Fluorescence Experiment for Physical Chemistry

    Science.gov (United States)

    Gutow, Jonathan H.

    2005-01-01

    The time-resolved fluorescence experiment investigating the halide quenching of fluorescence from quinine sulfate in water is described. The objectives of the experiment include reinforcing student understanding of the kinetics of competing pathways, making connections with microscopic theories of kinetics through comparison of experimental and…

  10. 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 co

  11. Green Synthesis and Regioselective Control of Sn/I2 Mediated Allylation of Carbonyl Compounds with Crotyl Halide in Water

    Institute of Scientific and Technical Information of China (English)

    ZHANG,Yan; ZHA,Zhang-Gen; ZHOU,Yu-Qing; WANG,Zhi-Yong

    2004-01-01

    @@ Barbier-type carbonyl allylation is particularly useful due to ease of operation and the availability and tractability of allylic substrates,[1] Metals such as indium, zinc and tin are often used as the mediator. Here we present a green approach toward the synthesis, that is, Sn/I2 mediated allylation of carbonyl compounds with crotyl halide in water.

  12. Calcium release-activated calcium current in rat mast cells.

    Science.gov (United States)

    Hoth, M; Penner, R

    1993-06-01

    1. Whole-cell patch clamp recordings of membrane currents and fura-2 measurements of free intracellular calcium concentration ([Ca2+]i) were used to study the biophysical properties of a calcium current activated by depletion of intracellular calcium stores in rat peritoneal mast cells. 2. Calcium influx through an inward calcium release-activated calcium current (ICRAC) was induced by three independent mechanisms that result in store depletion: intracellular infusion of inositol 1,4,5-trisphosphate (InsP3) or extracellular application of ionomycin (active depletion), and intracellular infusion of calcium chelators (ethylene glycol bis-N,N,N',N'-tetraacetic acid (EGTA) or 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA)) to prevent reuptake of leaked-out calcium into the stores (passive depletion). 3. The activation of ICRAC induced by active store depletion has a short delay (4-14 s) following intracellular infusion of InsP3 or extracellular application of ionomycin. It has a monoexponential time course with a time constant of 20-30 s and, depending on the complementary Ca2+ buffer, a mean normalized amplitude (at 0 mV) of 0.6 pA pF-1 (with EGTA) and 1.1 pA pF-1 (with BAPTA). 4. After full activation of ICRAC by InsP3 in the presence of EGTA (10 mM), hyperpolarizing pulses to -100 mV induced an instantaneous inward current that decayed by 64% within 50 ms. This inactivation is probably mediated by [Ca2+]i, since the decrease of inward current in the presence of the fast Ca2+ buffer BAPTA (10 mM) was only 30%. 5. The amplitude of ICRAC was dependent on the extracellular Ca2+ concentration with an apparent dissociation constant (KD) of 3.3 mM. Inward currents were nonsaturating up to -200 mV. 6. The selectivity of ICRAC for Ca2+ was assessed by using fura-2 as the dominant intracellular buffer (at a concentration of 2 mM) and relating the absolute changes in the calcium-sensitive fluorescence (390 nm excitation) with the calcium current integral

  13. The effect of variable calcium and very low calcium diets on human calcium metabolism. Ph.D. Thesis. Final Report

    Science.gov (United States)

    Chu, J.

    1971-01-01

    The effects of a very low calcium diet, with variable high and low protein intake, on the dynamics of calcium metabolism and the mechanism of calciuretics, are examined. The experiment, using male subjects, was designed to study the role of intestinal calcium absorption on urinary calcium excretion, and the rate of production of endogeneously secreted calcium in the gastrointestinal tract. The study showed an average of 70% fractional absorption rate during very low calcium intake, and that a decrease in renal tubular reabsorption of calcium is responsible for calciuretic effects of high protein intake. The study also indicates that there is a tendency to develop osteoporosis after long periods of low calcium intake, especially with a concurrent high protein intake.

  14. An experimental study of formation of the mercury mixed halides HgClBr and HgBrI and of their purity

    OpenAIRE

    Rabia Ahmad; Jamshed Ali; Qamer Faisal

    2015-01-01

    Claims to have produced the mixed halides of mercury are very old. However, their stability or even their very existence was seriously questioned by Ammlung and Brill several decades back, on the basis of their study, in several solvents, of what was thought to be HgBrI. The mixed halide HgClI was already known to be unstable. On the basis of these facts, which were also lent some theoretical support, it was strongly conjectured that the mixed halides of mercury and similar elements, were...

  15. Halide Scintillators

    NARCIS (Netherlands)

    Van Loef, E.V.D.

    2003-01-01

    Scintillators have been used for decades to make ionising radiation visible. Either by direct observation of the light flash produced by the material when it is exposed to radiation, or indirect by use of a photomultiplier tube or photodiode. Despite the enormous amount of commercially available sci

  16. The effect of calcium gluconate and other calcium supplements as a dietary calcium source on magnesium absorption in rats.

    Science.gov (United States)

    Chonan, O; Takahashi, R; Yasui, H; Watanuki, M

    1997-01-01

    The effects of commercially available calcium supplements (calcium carbonate, calcium gluconate, oyster shell preparation and bovine bone preparation) and gluconic acid on the absorption of calcium and magnesium were evaluated for 30 days in male Wistar rats. There were no differences in the apparent absorption ratio of calcium among rats fed each calcium supplement; however, the rats fed the calcium gluconate diet had a higher apparent absorption ratio of magnesium than the rats fed the other calcium supplements. Dietary gluconic acid also more markedly stimulated magnesium absorption than the calcium carbonate diet, and the bone (femur and tibia) magnesium contents of rats fed the gluconic acid diet were significantly higher than those of the rats fed the calcium carbonate diet. Furthermore, the weight of cecal tissue and the concentrations of acetic acid and butyric acid in cecal digesta of rats fed the calcium gluconate diet or the gluconic acid diet were significantly increased. We speculate that the stimulation of magnesium absorption in rats fed the calcium gluconate diet is a result of the gluconic acid component and the effect of gluconic acid on magnesium absorption probably results from cecal hypertrophy, magnesium solubility in the large intestine and the effects of volatile fatty acids on magnesium absorption.

  17. Decalcification of calcium polycarbophil in rats.

    Science.gov (United States)

    Yamada, T; Saito, T; Takahara, E; Nagata, O; Tamai, I; Tsuji, A

    1997-03-01

    The in vivo decalcification of calcium polycarbophil was examined. The decalcification ratio of [45Ca]calcium polycarbophil in the stomach after oral dosing to rats was more than 70% at each designated time and quite closely followed in the in vitro decalcification curve, indicating that the greater part of the calcium ion is released from calcium polycarbophil under normal gastric acidic conditions. The residual radioactivity in rat gastrointestine was nearly equal to that after oral administration of either [45Ca]calcium chloride + polycarbophil. The serum level of radioactivity was nearly equal to that after oral dosing of [45Ca]calcium lactate. These results indicate that the greater part of orally administered calcium polycarbophil released calcium ions to produce polycarbophil in vivo.

  18. Familial hypocalciuric hypercalcemia and calcium sensing receptor

    DEFF Research Database (Denmark)

    Mrgan, Monija; Nielsen, Sanne; Brixen, Kim

    2014-01-01

    Familial hypocalciuric hypercalcemia (FHH) is a lifelong, benign autosomal dominant disease characterized by hypercalcemia, normal to increased parathyroid hormone level, and a relatively low renal calcium excretion. Inactivation of the calcium-sensing receptor in heterozygous patients results in...

  19. Calcium, vitamin D, and your bones

    Science.gov (United States)

    ... can break easily, even without an obvious injury. Vitamin D helps your body absorb calcium. Eat foods that provide the right amounts of calcium, vitamin D, and protein. This kind of diet will give ...

  20. Dairy Dilemma: Are You Getting Enough Calcium?

    Science.gov (United States)

    ... Dairy Dilemma Dairy Dilemma Are You Getting Enough Calcium? You may be avoiding dairy products because of ... But dairy products are a major source of calcium, vitamin D and other nutrients that are important ...

  1. Mechanism of store-operated calcium entry

    Indian Academy of Sciences (India)

    Devkanya Dutta

    2000-12-01

    Activation of receptors coupled to the phospholipase C/IP3 signalling pathway results in a rapid release of calcium from its intracellular stores, eventually leading to depletion of these stores. Calcium store depletion triggers an influx of extracellular calcium across the plasma membrane, a mechanism known as the store-operated calcium entry or capacitative calcium entry. Capacitative calcium current plays a key role in replenishing calcium stores and activating various physiological processes. Despite considerable efforts, very little is known about the molecular nature of the capacitative channel and the signalling pathway that activates it. This review summarizes our current knowledge about store operated calcium entry and suggests possible hypotheses for its mode of activation.

  2. Solvation structure around ruthenium(II tris(bipyridine in lithium halide solutions

    Directory of Open Access Journals (Sweden)

    Ida Josefsson

    2016-03-01

    Full Text Available The solvation of the ruthenium(II tris(bipyridine ion ([Ru(bpy3]2+ is investigated with molecular dynamics simulations of lithium halide solutions in polar solvents. The anion distribution around the [Ru(bpy3]2+ complex exhibits a strong solvent dependence. In aqueous solution, the iodide ion forms a solvent shared complex with [Ru(bpy3]2+, but not in the other solvents. Between Cl– and [Ru(bpy3]2+, the strong hydration of the chloride ion results in a solvent separated complex where more than one solvent molecule separates the anion from the metal center. Hence, tailored solvation properties in electrolytes is a route to influence ion-ion interactions and related electron transfer processes.

  3. Solvation structure around ruthenium(II) tris(bipyridine) in lithium halide solutions

    Science.gov (United States)

    Josefsson, Ida; Eriksson, Susanna K.; Rensmo, Håkan; Odelius, Michael

    2016-01-01

    The solvation of the ruthenium(II) tris(bipyridine) ion ([Ru(bpy)3]2+) is investigated with molecular dynamics simulations of lithium halide solutions in polar solvents. The anion distribution around the [Ru(bpy)3]2+ complex exhibits a strong solvent dependence. In aqueous solution, the iodide ion forms a solvent shared complex with [Ru(bpy)3]2+, but not in the other solvents. Between Cl– and [Ru(bpy)3]2+, the strong hydration of the chloride ion results in a solvent separated complex where more than one solvent molecule separates the anion from the metal center. Hence, tailored solvation properties in electrolytes is a route to influence ion-ion interactions and related electron transfer processes. PMID:26798838

  4. A Photoferroelectric Perovskite-Type Organometallic Halide with Exceptional Anisotropy of Bulk Photovoltaic Effects.

    Science.gov (United States)

    Sun, Zhihua; Liu, Xitao; Khan, Tariq; Ji, Chengmin; Asghar, Muhammad Adnan; Zhao, Sangen; Li, Lina; Hong, Maochun; Luo, Junhua

    2016-05-23

    Perovskite-type ferroelectrics composed of organometallic halides are emerging as a promising alternative to conventional photovoltaic devices because of their unique photovoltaic effects (PVEs). A new layered perovskite-type photoferroelectric, bis(cyclohexylaminium) tetrabromo lead (1), is presented. The material exhibits an exceptional anisotropy of bulk PVEs. Upon photoexcitation, superior photovoltaic behaviors are created along its inorganic layers, which are composed of corner-sharing PbBr6 octahedra. Semiconducting activity with remarkable photoconductivity is achieved in the vertical direction, showing sizeable on/off current ratios (>10(4) ), which compete with the most active photovoltaic material CH3 NH3 PbI3 . In 1 the temperature-dependence of photovoltage coincides fairly well with that of polarization, confirming the dominant role of ferroelectricity in such highly anisotropic PVEs. This finding sheds light on bulk PVEs in ferroelectric materials, and promotes their application in optoelectronic devices.

  5. Tunable Crystal-to-Crystal Phase Transition in a Cadmium Halide Chain Polymer

    Directory of Open Access Journals (Sweden)

    Ulli Englert

    2011-07-01

    Full Text Available The chain polymer [{Cd(μ-X2py2}1∞] (X = Cl, Br; py = pyridine undergoes a fully reversible phase transition between a monoclinic low-temperature and an orthorhombic high-temperature phase. The transformation can be directly monitored in single crystals and can be confirmed for the bulk by powder diffraction. The transition temperature can be adjusted by tuning the composition of the mixed-halide phase: Transition temperatures between 175 K up to the decomposition of the material at ca. 350 K are accessible. Elemental analysis, ion chromatography and site occupancy refinements from single-crystal X-ray diffraction agree with respect to the stoichiometric composition of the samples.

  6. Lithium halide monolayers: Structural, electronic and optical properties by first principles study

    Science.gov (United States)

    Safari, Mandana; Maskaneh, Pegah; Moghadam, Atousa Dashti; Jalilian, Jaafar

    2016-09-01

    Using first principle study, we investigate the structural, electronic and optical properties of lithium halide monolayers (LiF, LiCl, LiBr). In contrast to graphene and other graphene-like structures that form hexagonal rings in plane, these compounds can form and stabilize in cubic shape interestingly. The type of band structure in these insulators is identified as indirect type and ionic nature of their bonds are illustrated as well. The optical properties demonstrate extremely transparent feature for them as a result of wide band gap in the visible range; also their electron transitions are indicated for achieving a better vision on the absorption mechanism in these kinds of monolayers.

  7. Impurity segregation in zone-refined precursors for crystalline halide scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Swider, S., E-mail: swider@capesym.com [CapSym, Inc., Natick, MA (United States); Lam, S.; Motakef, S. [CapSym, Inc., Natick, MA (United States); Donohoe, E.; Coers, L.; Taylor, S.; Spencer, S. [SAFC-Hitech, Urbana, IL (United States)

    2015-06-01

    Successful growth of halide scintillator crystals depends on a supply of ultra-high purity (UHP) precursor materials. Metallic interstitials and substitutions may provide traps that quench luminescence. Oxygen impurities can create competing compounds within a matrix, such as oxyhalides, that disrupt crystallinity and nucleate cracks. Using mass spectroscopy and oxygen combustion analysis, we analyzed impurities in SrI{sub 2}, EuI{sub 2}, and YCl{sub 3} precursors before and after zone refining. The data show most alkali and alkali earth impurities segregated easily. However, with the exception of iron, many transition metals were incorporated into the solid. Reliable oxygen measurements proved difficult to achieve. Additional oxygen was measured in nitrates and sulfates, via ion chromatography. Zone refining reduced the overall impurity content, but levels remained above a 10 ppm target.

  8. Concentration Effects of Silver Ions on Ionic Conductivities of Molten Silver Halides

    Directory of Open Access Journals (Sweden)

    Okada T.

    2011-05-01

    Full Text Available Ionic conductivities of molten (RbXc(AgX1-c (X = Cl and I mixtures were measured to clarify the concentration effects of silver ions on ionic conductivities of molten silver halides. It is found that the addition of RbX to molten AgX rapidly reduces the ionic conductivity with 0 ≤ c ≤ 0.4. It suggests that strong Ag-Ag correlation is necessary to fast conduction of Ag ions in molten state. The absolute values of ionic conductivity for (RbClc(AgCl1-c are larger than those for (RbIc(AgI1-c mixtures at all compositions. These differences might relate to difference of diffusion constant between Cl- and I- and difference of effective charge carried by an ion between molten AgCl and AgI

  9. Minimal electronic model for a layered nitride halide superconductor β-ZrNCl

    International Nuclear Information System (INIS)

    We construct tight-binding models of the layered nitride halide superconductor LixZrNCl by first-principles calculation. 14-, 10-, 8-, and 4-orbital models are constructed, all of which reproduce the Fermi surface by the first-principles calculation, and the band structure away from the Fermi level at various levels. On the basis of the tight-binding parameters in real space, it is found that bilayer coupling is relatively strong, suggesting that a single-layer approximation may not be valid. Taking into account the on-site and nearest-neighbor electron-electron interactions, and calculating the spin and charge susceptibilities for each model, we conclude that the 8 (= Zrdx2-y2, dxy, Npx, py × bilayer)-orbital model is the minimal model for describing low-energy physics. (author)

  10. Structure and bonding in metal-rich compounds: pnictides, chalcides and halides

    International Nuclear Information System (INIS)

    The subject is reviewed under the following headings: introduction (compounds included in the review; purpose of the review); MX compounds with M = transition metal and X = O,N,S or P; sulfides and selenides of the transition metals; transition-metal phosphides; alkali oxides; transition-metal oxides and nitrides with X/M < 1; metal-rich halides; conclusion. The references number 238. Compounds of the following principal elements of nuclear interest are included in the tables and text: Am, Ce, Cs, Eu, Gd, Hf, La, Mo, Np, Nb, Pu, Pr, Pa, Re, Ru, Sc, Ta, Tb, Th, W, U, V, Y, Zr. The information in the tables is presented under: structure type, space group, lattice parameters and remarks. (U.K.)

  11. Temperature-dependent excitonic photoluminescence of hybrid organometal halide perovskite films

    KAUST Repository

    Wu, Kewei

    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

  12. Role of Microstructure in the Electron-Hole Interaction of Hybrid Lead-Halide Perovskites

    Science.gov (United States)

    Frost, Jarvist M.; Barker, Alex J.; De Bastiani, Michele; Gandini, Marina; Marras, Sergio; Lanzani, Guglielmo; Walsh, Aron; Petrozza, Annamaria

    2015-01-01

    Solar cells based on hybrid inorganic-organic halide perovskites have demonstrated high power conversion efficiencies in a range of architectures. The existence and stability of bound electron-hole pairs in these materials, and their role in the exceptional performance of optoelectronic devices, remains a controversial issue. Here we demonstrate, through a combination of optical spectroscopy and multiscale modeling as a function of the degree of polycrystallinity and temperature, that the electron-hole interaction is sensitive to the microstructure of the material. The long-range order is disrupted by polycrystalline disorder and the variations in electrostatic potential found for smaller crystals suppress exciton formation, while larger crystals of the same composition demonstrate an unambiguous excitonic state. We conclude that fabrication procedures and morphology strongly influence perovskite behaviour, with both free carrier and excitonic regimes possible, with strong implications for optoelectronic devices. PMID:26442125

  13. Luminescent and thermochromic properties of tellurium(IV) halide complexes with cesium

    Science.gov (United States)

    Sedakova, T. V.; Mirochnik, A. G.

    2016-02-01

    The spectral-luminescent and thermochromic properties of complex compounds of the composition Cs2TeHal6 (Hal = Cl, Br, I) are studied. The interrelation between the geometric structure and spectral-luminescent properties is studied using the example on complex compounds of tellurium(IV) halides with cesium. The Stokes shift and the luminescence intensity of Te(IV) ions with island octahedral coordination are found to depend on the position of the A band in the luminescence excitation spectra, the diffuse reflection, and the energy of the luminescent 3 P 1 → 1 S 0 transition of the tellurium(IV) ion. The maximum luminescence intensity and the minimum Stokes shift at 77 and 300 K are observed for Cs2TeCl6. The geometrical and electronic factors responsible for luminescence intensification in Te(IV) complexes under study are analyzed.

  14. Ab initio and DFT studies on vibrational spectra of some halides of group IIIB elements

    Science.gov (United States)

    Zhang, Yu; Zhao, Jianying; Tang, Guodong; Zhu, Longgen

    2005-11-01

    The vibrational spectra of some group IIIB elements halides MX 3 and their dimmers, M 2X 6 (M = Sc(III), Y(III), La(III); X = F, Cl, Br, I), have been systematically investigated by ab initio restricted Hartree-Fock (RHF) and density functional B3LYP methods with LanL2DZ and SDD basis sets. The optimized geometries and calculated vibrational frequencies are evaluated via comparison with experimental values. The vibrational frequencies, calculated by two methods with different basis sets, are compared to each other. The effect of the methods and the basis sets used on the calculated vibrational frequencies are discussed. Some vibrational frequencies of these complexes are also predicted.

  15. Halide based shock-wave treatment of fluid-rich natural phases

    Science.gov (United States)

    Schlothauer, T.; Schimpf, C.; Brendler, E.; Keller, K.; Kroke, E.; Heide, G.

    2015-11-01

    For the synthesis of high pressure phases from natural minerals and the shock wave treatment of fluid bearing phases a halide based method was developed. The experiments were performed in the pressure range between 25 and 162 GPa with a success rate for the new method of 100% for the new method. Based on the Impedance Corrected Sample Recovery Capsule under avoiding the adiabatic decompression a direct comparison between different loading paths and sample holder geometries is possible. The recovered samples show neither indications of melting in the case of kaolinite and very limited degassing in the case of carbonates. The recovery of amorphous water bearing Al-Si-phases with Aluminum in four-, five- and six-fold coordination was possible. The samples were analyzed with scanning electron microscopy, x-ray diffraction, nuclear-magnetic-resonance- and infra-red-spectroscopy and the results were directly compared.

  16. Hydrophobic Organic Hole Transporters for Improved Moisture Resistance in Metal Halide Perovskite Solar Cells.

    Science.gov (United States)

    Leijtens, Tomas; Giovenzana, Tommaso; Habisreutinger, Severin N; Tinkham, Jonathan S; Noel, Nakita K; Kamino, Brett A; Sadoughi, Golnaz; Sellinger, Alan; Snaith, Henry J

    2016-03-01

    Solar cells based on organic-inorganic perovskite semiconductor materials have recently made rapid improvements in performance, with the best cells performing at over 20% efficiency. With such rapid progress, questions such as cost and solar cell stability are becoming increasingly important to address if this new technology is to reach commercial deployment. The moisture sensitivity of commonly used organic-inorganic metal halide perovskites has especially raised concerns. Here, we demonstrate that the hygroscopic lithium salt commonly used as a dopant for the hole transport material in perovskite solar cells makes the top layer of the devices hydrophilic and causes the solar cells to rapidly degrade in the presence of moisture. By using novel, low cost, and hydrophobic hole transporters in conjunction with a doping method incorporating a preoxidized salt of the respective hole transporters, we are able to prepare efficient perovskite solar cells with greatly enhanced water resistance. PMID:26859777

  17. Metal-encapsulated organolead halide perovskite photocathode for solar-driven hydrogen evolution in water

    Science.gov (United States)

    Crespo-Quesada, Micaela; Pazos-Outón, Luis M.; Warnan, Julien; Kuehnel, Moritz F.; Friend, Richard H.; Reisner, Erwin

    2016-09-01

    Lead-halide perovskites have triggered the latest breakthrough in photovoltaic technology. Despite the great promise shown by these materials, their instability towards water even in the presence of low amounts of moisture makes them, a priori, unsuitable for their direct use as light harvesters in aqueous solution for the production of hydrogen through water splitting. Here, we present a simple method that enables their use in photoelectrocatalytic hydrogen evolution while immersed in an aqueous solution. Field's metal, a fusible InBiSn alloy, is used to efficiently protect the perovskite from water while simultaneously allowing the photogenerated electrons to reach a Pt hydrogen evolution catalyst. A record photocurrent density of -9.8 mA cm-2 at 0 V versus RHE with an onset potential as positive as 0.95+/-0.03 V versus RHE is obtained. The photoelectrodes show remarkable stability retaining more than 80% of their initial photocurrent for ~1 h under continuous illumination.

  18. Crystal lattice properties fully determine short-range interaction parameters for alkali and halide ions

    CERN Document Server

    Mao, Albert H; 10.1063/1.4742068

    2012-01-01

    Accurate models of alkali and halide ions in aqueous solution are necessary for computer simulations of a broad variety of systems. Previous efforts to develop ion force fields have generally focused on reproducing experimental measurements of aqueous solution properties such as hydration free energies and ion-water distribution functions. This dependency limits transferability of the resulting parameters because of the variety and known limitations of water models. We present a solvent-independent approach to calibrating ion parameters based exclusively on crystal lattice properties. Our procedure relies on minimization of lattice sums to calculate lattice energies and interionic distances instead of equilibrium ensemble simulations of dense fluids. The gain in computational efficiency enables simultaneous optimization of all parameters for Li+, Na+, K+, Rb+, Cs+, F-, Cl-, Br-, and I- subject to constraints that enforce consistency with periodic table trends. We demonstrate the method by presenting lattice-d...

  19. Fully Printed Halide Perovskite Light-Emitting Diodes with Silver Nanowire Electrodes.

    Science.gov (United States)

    Bade, Sri Ganesh R; Li, Junqiang; Shan, Xin; Ling, Yichuan; Tian, Yu; Dilbeck, Tristan; Besara, Tiglet; Geske, Thomas; Gao, Hanwei; Ma, Biwu; Hanson, Kenneth; Siegrist, Theo; Xu, Chengying; Yu, Zhibin

    2016-02-23

    Printed organometal halide perovskite light-emitting diodes (LEDs) are reported that have indium tin oxide (ITO) or carbon nanotubes (CNTs) as the transparent anode, a printed composite film consisting of methylammonium lead tribromide (Br-Pero) and poly(ethylene oxide) (PEO) as the emissive layer, and printed silver nanowires as the cathode. The fabrication can be carried out in ambient air without humidity control. The devices on ITO/glass have a low turn-on voltage of 2.6 V, a maximum luminance intensity of 21014 cd m(-2), and a maximum external quantum efficiency (EQE) of 1.1%, surpassing previous reported perovskite LEDs. The devices on CNTs/polymer were able to be strained to 5 mm radius of curvature without affecting device properties.

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

    Science.gov (United States)

    Bae, Dowon; Palmstrom, Axel; Roelofs, Katherine; Mei, Bastian; Chorkendorff, Ib; Bent, Stacey F; Vesborg, Peter C K

    2016-06-15

    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 by modification of spin-coating parameters without any additional chemical or thermal post-treatment. PMID:27227816

  1. Multicolor fluorescent light-emitting diodes based on cesium lead halide perovskite quantum dots

    Science.gov (United States)

    Wang, Peng; Bai, Xue; Sun, Chun; Zhang, Xiaoyu; Zhang, Tieqiang; Zhang, Yu

    2016-08-01

    High quantum yield, narrow full width at half-maximum and tunable emission color of perovskite quantum dots (QDs) make this kind of material good prospects for light-emitting diodes (LEDs). However, the relatively poor stability under high temperature and air condition limits the device performance. To overcome this issue, the liquid-type packaging structure in combination with blue LED chip was employed to fabricate the fluorescent perovskite quantum dot-based LEDs. A variety of monochromatic LEDs with green, yellow, reddish-orange, and red emission were fabricated by utilizing the inorganic cesium lead halide perovskite quantum dots as the color-conversion layer, which exhibited the narrow full width at half-maximum (color stability against the various working currents. Furthermore, we demonstrated the potential prospects of all-inorganic perovskite QDs for the liquid-type warm white LEDs.

  2. A two-accelerator facility and its use for radiation damage studies in alkali halides

    International Nuclear Information System (INIS)

    An experimental system is described in which heavy ions, of energies 50-100 MeV, and light ions of energies 0.5-2 MeV, may be transported alternately from different accelerators into a common scattering chamber. The beam-transport and scattering-chamber details are described, the latter being designed to make in-beam studies of different modes of radiation damage in the target material. Experimental studies are described of simultaneous detection of back-scattered helium ions, X-rays and optical absorption in single-crystal alkali halide samples, done during continuous irradiation by a 1 MeV He beam; also back-scattered protons following intermittent irradiation by a 60 MeV oxygen beam. Analysis of the relative damage by these two beams is discussed in relation to a damage mechanism due to Pooley

  3. Rapid yet accurate first principle based predictions of alkali halide crystal phases using alchemical perturbation

    CERN Document Server

    Solovyeva, Alisa

    2016-01-01

    We assess the predictive power of alchemical perturbations for estimating fundamental properties in ionic crystals. Using density functional theory we have calculated formation energies, lattice constants, and bulk moduli for all sixteen iso-valence-electronic combinations of pure pristine alkali halides involving elements $A \\in \\{$Na, K, Rb, Cs$\\}$ and $X \\in \\{$F, Cl, Br, I$\\}$. For rock salt, zincblende and cesium chloride symmetry, alchemical Hellmann-Feynman derivatives, evaluated along lattice scans of sixteen reference crystals, have been obtained for all respective 16$\\times$15 combinations of reference and predicted target crystals. Mean absolute errors (MAE) are on par with density functional theory level of accuracy for energies and bulk modulus. Predicted lattice constants are less accurate. NaCl is the best reference salt for alchemical estimates of relative energies (MAE $<$ 40 meV/atom) while alkali fluorides are the worst. By contrast, lattice constants are predicted best using NaF as a re...

  4. Calcium channel blockers and Alzheimer's disease

    Institute of Scientific and Technical Information of China (English)

    Yi Tan; Yulin Deng; Hong Qing

    2012-01-01

    Alzheimer's disease is characterized by two pathological hallmarks: amyloid plaques and neurofi-brillary tangles. In addition, calcium homeostasis is disrupted in the course of human aging. Recent research shows that dense plaques can cause functional alteration of calcium signals in mice with Alzheimer's disease. Calcium channel blockers are effective therapeutics for treating Alzheimer's disease. This review provides an overview of the current research of calcium channel blockers in-volved in Alzheimer's disease therapy.

  5. 21 CFR 184.1210 - Calcium oxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium oxide. 184.1210 Section 184.1210 Food and... Substances Affirmed as GRAS § 184.1210 Calcium oxide. (a) Calcium oxide (CaO, CAS Reg. No. 1305-78-8) is also known as lime, quick lime, burnt lime, or calx. It is produced from calcium carbonate, limestone,...

  6. 21 CFR 184.1185 - Calcium acetate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium acetate. 184.1185 Section 184.1185 Food and... Substances Affirmed as GRAS § 184.1185 Calcium acetate. (a) Calcium acetate (Ca (C2H3O2)2, CAS Reg. No. 62-54-4), also known as acetate of lime or vinegar salts, is the calcium salt of acetic acid. It may...

  7. Halide impact on emission of mononuclear copper(I) complexes with pyrazolylpyrimidine and triphenylphosphine.

    Science.gov (United States)

    Vinogradova, Katerina A; Plyusnin, Victor F; Kupryakov, Arkady S; Rakhmanova, Marianna I; Pervukhina, Natalia V; Naumov, Dmitrii Yu; Sheludyakova, Lilia A; Nikolaenkova, Elena B; Krivopalov, Viktor P; Bushuev, Mark B

    2014-02-21

    A series of mononuclear heteroleptic copper(I) halide complexes, [CuL(PPh3)X] (X = Cl, Br, I), based on 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L) and triphenylphosphine, have been synthesized by reaction between CuX (X = Cl, Br, I), L and PPh3 in a molar ratio of 1/1/1 in MeCN solutions. The copper atom, showing the distorted tetrahedral environment, is bound by the N,N-chelating ligand L, triphenylphosphine and a halide ion. The complexes [CuL(PPh3)Cl] and [CuL(PPh3)Br] are isostructural. In CH2Cl2 solutions, L and the complexes [CuL(PPh3)X] (X = Cl, Br, I) display a luminescence band with λ(max) = 377 nm and a lifetime of 1.9 ns (ligand-based luminescence (LL*)). However, the complex [CuL(PPh3)I] has an additional weak luminescence band with λ(max) = 681 nm and a lifetime of 96 ns of (3)MLCT origin. In the solid state, L shows the splitting of the luminescence band to λ(max) = 365 and 384 nm and a slight increase of the lifetime to 2.66 ns. Solid samples of the complexes [CuL(PPh3)X] demonstrate (3)MLCT luminescence bands at 620 nm (X = Cl), 605 nm (X = Br) and 559 nm (X = I) with lifetimes in the range 3.6-11.2 μs, whereas the LL* band (377 nm) is absent. Quantum yields and rate constants of radiative and nonradiative processes were determined in CH2Cl2 solutions and in the solid state for all complexes. The luminescence quantum yield and lifetimes for the solid samples increase in the order [CuL(PPh3)Cl] lifetime of 11.2 μs.

  8. Concentration Effects and Ion Properties Controlling the Fractionation of Halides during Aerosol Formation

    Science.gov (United States)

    Guzman, Marcelo I.; Athalye, Richa R.; Rodriguez, Jose M.

    2012-01-01

    During the aerosolization process at the sea surface, halides are incorporated into aerosol droplets, where they may play an important role in tropospheric ozone chemistry. Although this process may significantly contribute to the formation of reactive gas phase molecular halogens, little is known about the environmental factors that control how halides selectively accumulate at the air-water interface. In this study, the production of sea spray aerosol is simulated using electrospray ionization (ESI) of 100 nM equimolar solutions of NaCl, NaBr, NaI, NaNO2, NaNO3, NaClO4, and NaIO4. The microdroplets generated are analyzed by mass spectrometry to study the comparative enrichment of anions (f (Isub x-)) and their correlation with ion properties. Although no correlation exists between f (sub x-) and the limiting equivalent ionic conductivity, the correlation coefficient of the linear fit with the size of the anions R(sub x-), dehydration free-energy ?Gdehyd, and polarizability alpha, follows the order: (R(sub x-)(exp -2)) > (R(sub x-)(exp -1)) >(R(sub x-) > delta G(sub dehyd) > alpha. The same pure physical process is observed in H2O and D2O. The factor f (sub x-) does not change with pH (6.8-8.6), counterion (Li+, Na+, K+, and Cs+) substitution effects, or solvent polarity changes in methanol - and ethanol-water mixtures (0 concentration effects in sea spray aerosol formation.

  9. 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.

  10. The Electronic Structure of Calcium

    DEFF Research Database (Denmark)

    Jan, J.-P.; Skriver, Hans Lomholt

    1981-01-01

    The electronic structure of calcium under pressure is re-examined by means of self-consistent energy band calculations based on the local density approximation and using the linear muffin-tin orbitals (LMTO) method with corrections to the atomic sphere approximation included. At zero pressure...

  11. Teaching Calcium-Induced Calcium Release in Cardiomyocytes Using a Classic Paper by Fabiato

    Science.gov (United States)

    Liang, Willmann

    2008-01-01

    This teaching paper utilizes the materials presented by Dr. Fabiato in his review article entitled "Calcium-induced release of calcium from the cardiac sarcoplasmic reticulum." In the review, supporting evidence of calcium-induced calcium release (CICR) is presented. Data concerning potential objections to the CICR theory are discussed as well. In…

  12. 21 CFR 582.1205 - Calcium hydroxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium hydroxide. 582.1205 Section 582.1205 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1205 Calcium hydroxide. (a) Product. Calcium hydroxide. (b) Conditions of use....

  13. 21 CFR 182.2227 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2227 Calcium silicate. (a) Product. Calcium silicate....

  14. 21 CFR 582.2227 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  15. 21 CFR 582.5210 - Calcium oxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium oxide. 582.5210 Section 582.5210 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS... 1 § 582.5210 Calcium oxide. (a) Product. Calcium oxide. (b) Conditions of use. This substance...

  16. Lactulose stimulates calcium absorption in postmenopausal women

    NARCIS (Netherlands)

    Heuvel, E.G.H.M. van den; Muijs, T.; Dokkum, W. van; Schaafsma, G.

    1999-01-01

    Animal studies have indicated that calcium absorption is increased by lactulose, a synthetic disaccharide. Therefore, the influence of lactulose on calcium absorption was measured in postmenopausal women who may benefit from the possible enhancing effect of lactulose on calcium absorption. Twelve po

  17. 21 CFR 582.1210 - Calcium oxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium oxide. 582.1210 Section 582.1210 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS....1210 Calcium oxide. (a) Product. Calcium oxide. (b) Conditions of use. This substance is...

  18. 21 CFR 582.6185 - Calcium acetate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium acetate. 582.6185 Section 582.6185 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium acetate. (a) Product. Calcium acetate. (b) Conditions of use. This substance is...

  19. 21 CFR 582.1217 - Calcium phosphate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium phosphate. 582.1217 Section 582.1217 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1217 Calcium phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic)....

  20. 21 CFR 182.1217 - Calcium phosphate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium phosphate. 182.1217 Section 182.1217 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Substances § 182.1217 Calcium phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic)....

  1. 21 CFR 582.5217 - Calcium phosphate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium phosphate. 582.5217 Section 582.5217 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Supplements 1 § 582.5217 Calcium phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic)....

  2. Synthesis of Mixed Carbonates via a Three-Component Coupling of Alcohols, CO2, and Alkyl Halides in the Presence of K2CO3 and Tetrabutylammonium Iodide

    OpenAIRE

    Yu-Mei Shen; Min Shi

    2002-01-01

    Various mixed carbonates can be conveniently prepared in good yields using the corresponding alcohols, alkyl halides under CO2 atmosphere in the presence of potassium carbonate or sodium carbonate and tetrabutylammonium iodide.

  3. Insight of DFT and atomistic thermodynamics on the adsorption and insertion of halides onto the hydroxylated NiO(1 1 1) surface

    Energy Technology Data Exchange (ETDEWEB)

    Bouzoubaa, A. [Laboratoire de Physico-Chimie des surfaces, CNRS-ENSCP (UMR 7045), Ecole Nationale Superieure de Chimie de Paris, Chimie-ParisTech, 11 rue Pierre et Marie Curie, 75005 Paris (France); Costa, D., E-mail: dominique-costa@chimie-paristech.f [Laboratoire de Physico-Chimie des surfaces, CNRS-ENSCP (UMR 7045), Ecole Nationale Superieure de Chimie de Paris, Chimie-ParisTech, 11 rue Pierre et Marie Curie, 75005 Paris (France); Diawara, B., E-mail: boubakar-diawara@chimie-paristech.f [Laboratoire de Physico-Chimie des surfaces, CNRS-ENSCP (UMR 7045), Ecole Nationale Superieure de Chimie de Paris, Chimie-ParisTech, 11 rue Pierre et Marie Curie, 75005 Paris (France); Audiffren, N. [CINES, Centre Informatique National de l' Enseignement Superieur, 950 rue de Saint Priest, 34097 Montpellier Cedex 5 (France); Marcus, P. [Laboratoire de Physico-Chimie des surfaces, CNRS-ENSCP (UMR 7045), Ecole Nationale Superieure de Chimie de Paris, Chimie-ParisTech, 11 rue Pierre et Marie Curie, 75005 Paris (France)

    2010-08-15

    Spin polarized, DFT + U periodic calculations have been used to study the interaction of halides (X) with a (1 x 1)-hydroxylated NiO(1 1 1) surface, a model of passivated nickel. The exchange of surface OH groups by the X ions and the insertion of the halides in the anionic sub-surface layer have been investigated. The substitution of OH by halides is favored by a smaller size of the halide ions and by a lower substitution proportion. An atomistic thermodynamic approach including solvent effects allows us to construct phase diagrams of the surface terminations as a function of the Cl and F concentrations in the aqueous solution. The higher proportion of OH substitution by F, and the lower insertion energy, as compared to Cl, may be related to stronger corrosion caused by F as compared to Cl.

  4. Calcium electroporation in three cell lines; a comparison of bleomycin and calcium, calcium compounds, and pulsing conditions

    DEFF Research Database (Denmark)

    Frandsen, Stine Krog; Gissel, Hanne; Hojman, Pernille;

    2013-01-01

    BACKGROUND: Electroporation with calcium (calcium electroporation) can induce ATP depletion-associated cellular death. In the clinical setting, the cytotoxic drug bleomycin is currently used with electroporation (electrochemotherapy) for palliative treatment of tumors. Calcium electroporation...... offers several advantages over standard treatment options: calcium is inexpensive and may readily be applied without special precautions, as is the case with cytostatic drugs. Therefore, details on the use of calcium electroporation are essential for carrying out clinical trials comparing calcium...... electroporation and electrochemotherapy. METHODS: The effects of calcium electroporation and bleomycin electroporation (alone or in combination) were compared in three different cell lines (DC-3F, transformed Chinese hamster lung fibroblast; K-562, human leukemia; and murine Lewis Lung Carcinoma). Furthermore...

  5. Polystyrene-supported triphenylarsines: Useful ligands in palladium-catalyzed aryl halide homocoupling reactions and a catalyst for alkene epoxidation using hydrogen peroxide

    OpenAIRE

    Song He, H; Zhang, C; Ng, CKW; Toy, PH

    2005-01-01

    The utility of both soluble (non-cross-linked) and insoluble (cross-linked) polystyrene-supported triphenylarsine reagents were examined. These reagents were prepared by standard radical polymerization methodology and used in palladium-catalyzed homocoupling reactions of aryl halides. The insoluble reagent was also used as a catalyst precursor in heterogeneous alkene epoxidation reactions in which aqueous hydrogen peroxide was the stoichiometric oxidant. For the aryl halide homocoupling react...

  6. 2-aminopyrimidine-4,6-diol as an efficient ligand for solvent-free copper-catalyzed N-arylations of imidazoles with aryl and heteroaryl halides.

    Science.gov (United States)

    Xie, Ye-Xiang; Pi, Shao-Feng; Wang, Jian; Yin, Du-Lin; Li, Jin-Heng

    2006-10-13

    Efficient and solvent-free copper-catalyzed N-arylations of imidazoles with aryl and heteroaryl halides have been demonstrated. In the presence of CuBr, 2-aminopyrimidine-4,6-diol, and TBAF (n-Bu4NF), a variety of imidazoles underwent the N-arylation reaction with aryl and heteroaryl halides smoothly in moderate to excellent yields. Noteworthy is that the reaction is conducted under solvent-free conditions. PMID:17025338

  7. Calcium signals and calcium channels in osteoblastic cells

    Science.gov (United States)

    Duncan, R. L.; Akanbi, K. A.; Farach-Carson, M. C.

    1998-01-01

    Calcium (Ca2+) channels are present in non-excitable as well as in excitable cells. In bone cells of the osteoblast lineage, Ca2+ channels play fundamental roles in cellular responses to external stimuli including both mechanical forces and hormonal signals. They are also proposed to modulate paracrine signaling between bone-forming osteoblasts and bone-resorbing osteoclasts at local sites of bone remodeling. Calcium signals are characterized by transient increases in intracellular Ca2+ levels that are associated with activation of intracellular signaling pathways that control cell behavior and phenotype, including patterns of gene expression. Development of Ca2+ signals is a tightly regulated cellular process that involves the concerted actions of plasma membrane and intracellular Ca2+ channels, along with Ca2+ pumps and exchangers. This review summarizes the current state of knowledge concerning the structure, function, and role of Ca2+ channels and Ca2+ signals in bone cells, focusing on the osteoblast.

  8. Computational study of a calcium release-activated calcium channel

    Science.gov (United States)

    Talukdar, Keka; Shantappa, Anil

    2016-05-01

    The naturally occurring proteins that form hole in membrane are commonly known as ion channels. They play multiple roles in many important biological processes. Deletion or alteration of these channels often leads to serious problems in the physiological processes as it controls the flow of ions through it. The proper maintenance of the flow of ions, in turn, is required for normal health. Here we have investigated the behavior of a calcium release-activated calcium ion channel with pdb entry 4HKR in Drosophila Melanogaster. The equilibrium energy as well as molecular dynamics simulation is performed first. The protein is subjected to molecular dynamics simulation to find their energy minimized value. Simulation of the protein in the environment of water and ions has given us important results too. The solvation energy is also found using Charmm potential.

  9. Store-operated calcium signaling in neutrophils.

    Science.gov (United States)

    Clemens, Regina A; Lowell, Clifford A

    2015-10-01

    Calcium signals in neutrophils are initiated by a variety of cell-surface receptors, including formyl peptide and other GPCRs, FcRs, and integrins. The predominant pathway by which calcium enters immune cells is termed SOCE, whereby plasma membrane CRAC channels allow influx of extracellular calcium into the cytoplasm when intracellular ER stores are depleted. The identification of 2 key families of SOCE regulators, STIM calcium "sensors" and ORAI calcium channels, has allowed for genetic manipulation of SOCE pathways and provided valuable insight into the molecular mechanism of calcium signaling in immune cells, including neutrophils. This review focuses on our current knowledge of the molecules involved in neutrophil SOCE and how study of these molecules has further informed our understanding of the role of calcium signaling in neutrophil activation.

  10. CALCIUM ENHANCES ANTIINFLAMMATORY ACTIVITY OF ASPIRIN

    Directory of Open Access Journals (Sweden)

    Choksi Krishna

    2011-03-01

    Full Text Available The objective of present study is to evaluate the effects of calcium carbonate and calcium gluconate on acute and subacute inflammation and to study their possible interactions with Aspirin. Calcium carbonate (10 mg/kg and calcium gluconate (5 mg/kg were administered individually and also co-administered along with sub therapeutic dose Aspirin (50mg/kg to study their interaction. The inflammation was induced by carrageenan or a foreign body. Both calcium carbonate and calcium gluconate could not show significant anti-inflammatory activity on their own in acute as well as subacute inflammation models. Aspirin at sub-anti-inflammatory dose (50mg/Kg when co-administered along with calcium salts produced the significant anti-inflammatory response which was comparable to anti-inflammatory response of aspirin at therapeutic dose (200mg/Kg. Also co-adminostration minimized the gastro-toxicity of aspirin.

  11. Reproducible formation of uniform CH3NH3PbI3-xClx mixed halide perovskite film by separation of the powder formation and spin-coating process

    Science.gov (United States)

    Song, Dae-ho; Heo, Jin Hyuck; Han, Hye Ji; You, Myoung Sang; Im, Sang Hyuk

    2016-04-01

    To deposit uniform CH3NH3PbI3-xClx (MAPbI3-xClx) mixed halide perovskite film reproducibly, we separated the conventional process to formation of MAPbI3-xClx mixed halide perovskite powder by heat-treatment process and deposition of MAPbI3-xClx mixed halide perovskite film by single step spin-coating. The deviation of power conversion efficiency of MAPbI3-xClx mixed halide perovskite solar cells prepared by currently proposed method and conventional method was 13.75 ± 0.88% and 8.02 ± 1.65%, respectively, because more uniform MAPbI3-xClx mixed halide perovskite film could be reproducibly formed by separating the formation process of mixed halide perovskite powder and the single step spin-coating process.

  12. First-principles study of the local structure and crystal field of Yb2+ in sodium and potassium halides

    Institute of Scientific and Technical Information of China (English)

    Wen Jun; Duan Chang-Kui; Yin Min; Yu.V.Orlovskii; Xia Shang-Da; Zhang Yong-Fan

    2012-01-01

    The local coordination structures around the doping Yb2+ ions in sodium and potassium halides were calculated by using the first-principles supercell model.Both the cases with and without the charge compensation vacancy in the local environment of the doping Yb2+ were calculated to study the effect of the doping on the local coordination structures of Yb2+.Using the calculated local structures,we obtained the crystal-field parameters for the Yb2+ ions doped in sodium and potassium halides by a method based on the combination of the quantum-chemical calculations and the effective Hamiltonian method.The calculated crystal-field parameters were analyzed and compared with the fitted results.

  13. Development of a 2-Channel Embedded Infrared Fiber-Optic Temperature Sensor Using Silver Halide Optical Fibers

    Directory of Open Access Journals (Sweden)

    Bongsoo Lee

    2011-10-01

    Full Text Available A 2-channel embedded infrared fiber-optic temperature sensor was fabricated using two identical silver halide optical fibers for accurate thermometry without complicated calibration processes. In this study, we measured the output voltages of signal and reference probes according to temperature variation over a temperature range from 25 to 225 °C. To decide the temperature of the water, the difference between the amounts of infrared radiation emitted from the two temperature sensing probes was measured. The response time and the reproducibility of the fiber-optic temperature sensor were also obtained. Thermometry with the proposed sensor is immune to changes if parameters such as offset voltage, ambient temperature, and emissivity of any warm object. In particular, the temperature sensing probe with silver halide optical fibers can withstand a high temperature/pressure and water-chemistry environment. It is expected that the proposed sensor can be further developed to accurately monitor temperature in harsh environments.

  14. Synthesis of alkenyl sulfides through the iron-catalyzed cross-coupling reaction of vinyl halides with thiols.

    Science.gov (United States)

    Lin, Yun-Yung; Wang, Yu-Jen; Lin, Che-Hung; Cheng, Jun-Hao; Lee, Chin-Fa

    2012-07-20

    We report here the iron-catalyzed cross-coupling reaction of alkyl vinyl halides with thiols. While many works are devoted to the coupling of thiols with alkyl vinyl iodides, interestingly, the known S-vinylation of vinyl bromides and chlorides is limited to 1-(2-bromovinyl)benzene and 1-(2-chlorovinyl)benzene. Investigation on the coupling reaction of challenging alkyl vinyl bromides and chlorides with thiols is rare. Since the coupling of 1-(2-bromovinyl)benzene and 1-(2-chlorovinyl)benzene with thiols can be performed in the absence of any catalyst, here we focus on the coupling of thiols with alkyl vinyl halides. This system is generally reactive for alkyl vinyl iodides and bromides to provide the products in good yields. 1-(Chloromethylidene)-4-tert-butyl-cyclohexane was also coupled with thiols, giving the targets in moderate yields. PMID:22708836

  15. [Calcium pyrophosphate dihydrate deposition disease].

    Science.gov (United States)

    Koitschev, C; Kaiserling, E; Koitschev, A

    2003-08-01

    Calcium pyrophosphate dihydrate deposition disease (CPPD) of the temporomandibular joint is rare. The disorder is characterized by the presence of crystal deposits within the affected joint. The deposition of crystals in adjacent soft tissue may lead to the formation of pseudotumors. This form of the disease is called tophaceous pseudogout and typically affects the temporomandibular joint. It is difficult to differentiate the disease, particularly from malignant tumors, on the clinical and radiographic findings alone. The diagnosis is based on histological identification of the calcium pyrophosphate crystals. We present an unusually advanced case of tophaceous pseudogout of the temporomandibular joint. The etiology, clinical and diagnostic criteria as well as treatment options are discussed on the basis of our own experience and a review of the literature. PMID:12942180

  16. Serum calcium in pulmonary tuberculosis

    OpenAIRE

    Subhash C. Sharma

    1981-01-01

    Serum calcium was studied serially in 94 patients with active pulmonary tuberculosis. An equal number of age- and sex-matched patients with chronic obstructive pulmonary disease were controls. Seventy patients in the study group were normocalcaemic and 10 were hypercalcaemic. These 10 were on a higher supplement of vitamin D than the 70 normocalcaemic patients. There was a positive correlation between the daily vitamin intake and the degree and duration of hypercalcaemia. None of the controls...

  17. Modeling and investigation of heavy oxide and alkali-halide scintillators for potential use in neutron and gamma detection systems

    OpenAIRE

    Cadiente, Jeremy S.

    2015-01-01

    Approved for public release; distribution is unlimited Heavy inorganic oxide and alkali-halide crystals, which previous experimental research has indicated to have fast neutron detection efficiencies well over 40%, were investigated for potential use as highly efficient gamma-neutron radiation detectors. The Monte Carlo N-Particle radiation transport code (MCNP) was used to characterize the radiation interactions in a candidate set of crystals, including Bismuth Germanate (BGO), Lead Tungs...

  18. Quasicharacteristic radiation of relativistic electrons at orientation motion in lithium halides crystals along charged planes and axes

    Science.gov (United States)

    Maksyuta, N. V.; Vysotskii, V. I.; Efimenko, S. V.

    2016-07-01

    The paper deals with the investigation of the orientation motion of relativistic electrons in charged (111) planes and charged [110] axes of lithium halides ionic crystals of LiF, LiCl, LiBr and LiI. On the basis of these investigations the spectra of quasicharacteristic radiation for the electron beams with various Lorentz-factors both in planar and axial cases have been calculated numerically.

  19. Ab Initio Calculation of the Lattice Distortions induced by Substitutional Ag- and Cu- Impurities in Alkali Halide Crystals

    OpenAIRE

    Aguado, Andrés; López, José M.; Alonso, Julio A.

    2000-01-01

    An ab initio study of the doping of alkali halide crystals (AX: A = Li, Na, K, Rb; X = F, Cl, Br, I) by ns2 anions (Ag- and Cu-) is presented. Large active clusters with 179 ions embedded in the surrounding crystalline lattice are considered in order to describe properly the lattice relaxation induced by the introduction of substitutional impurities. In all the cases considered, the lattice distortions imply the concerted movement of several shells of neighbors. The shell displacements are sm...

  20. The use of halides for stabilisation of iron gall ink containing paper - the pronounced effect of cation.

    OpenAIRE

    Malešič, J.; Kolar, J.; Strlic, M.; Polanc, S.

    2005-01-01

    It has long been known that transitional metal ions and acids in iron gall inks induce degradation of paper support, thus endangering numerous historical materials. Stabilization treatment should therefore consist of deacidification and addition of antioxidants that could be used for stabilization of all historical material, regardless to their iron gall ink composition. This contribution discusses the effects of various quaternary ammonium and phosphonium halides on iron gall ink corrosion o...

  1. Resting State and Elementary Steps of the Coupling of Aryl Halides with Thiols Catalyzed by Alkylbisphosphine Complexes of Palladium

    OpenAIRE

    Alvaro, Elsa; Hartwig, John F.

    2009-01-01

    Detailed mechanistic studies on the coupling of aryl halides with thiols catalyzed by palladium complexes of the alkylbisphosphine ligand CyPF-tBu (1-dicyclohexylphosphino-2-di-tert-butylphosphinoethylferrocene) are reported. The elementary steps that constitute the catalytic cycle, i.e. oxidative addition, transmetalation and reductive elimination, have been studied, and their relative rates are reported. Each of the steps of the catalytic process occurs at temperatures that are much lower t...

  2. SN2-type ring opening of substituted--tosylaziridines with zinc (II) halides: Control of racemization by quaternary ammonium salt

    Indian Academy of Sciences (India)

    Manas K Ghorai; Deo Prakash Tiwari; Amit Kumar; Kalpataru Das

    2011-11-01

    Quaternary ammonium salt mediated highly regioselective ring opening of aziridines with zinc(II) halides to racemic and non-racemic -halo amines in excellent yield and selectivity is described. The reaction proceeds via an SN2-type pathway and the partial racemization of the starting substrate and the product was effectively controlled by using quaternary ammonium salts to afford the enantioenriched products (er up to 95:5).

  3. A Novel Palladium-catalyzed Amination of Aryl Halides with Amines Using rac-P-Phos as the Ligand

    Institute of Scientific and Technical Information of China (English)

    CHEN, Huansheng; WANG, Quanrui; TAO, Fenggang

    2009-01-01

    An efficient palladium-catalyzed amination of aryl halides with amines, using rac-P-Phos as the ancillary ligand and Pd(OAc)2 as the palladium source is developed. The ligand and all of the synthetic intermediates are stable to air and moisture, allowing the easy handling. The catalyst system performed well for a large number of different substrate combinations in 80-110 ℃ to furnish aromatic amines in high yields.

  4. Development of a 2-Channel Embedded Infrared Fiber-Optic Temperature Sensor Using Silver Halide Optical Fibers

    OpenAIRE

    Bongsoo Lee; Byung Gi Park; Jang-Yeon Park; Ki-Tek Han; Jinsoo Moon; Wook Jae Yoo; Kyoung Won Jang; Jeong Ki Seo

    2011-01-01

    A 2-channel embedded infrared fiber-optic temperature sensor was fabricated using two identical silver halide optical fibers for accurate thermometry without complicated calibration processes. In this study, we measured the output voltages of signal and reference probes according to temperature variation over a temperature range from 25 to 225 °C. To decide the temperature of the water, the difference between the amounts of infrared radiation emitted from the two temperature sensing probes wa...

  5. Influence of calcium oxalate crystal accumulation on the calcium content of seeds from Medicago truncatula.

    Science.gov (United States)

    Nakata, Paul A

    2012-04-01

    Crystals of calcium oxalate often form in cells adjacent to the vascular bundles in the tissues along the xylem stream. This spatial crystal pattern suggests a role for calcium oxalate formation in regulating calcium transport and partitioning to edible organs such as seeds. To investigate this potential role, microscopic and biochemical comparisons were conducted on the different tissues of Medicago truncatula wild-type and the calcium oxalate defective (cod) 5 which lacks the ability to accumulate prismatic crystals in the cells adjacent to the vascular bundles. Calcium measurements showed that cod5 seeds had more calcium and cod5 pods contained less calcium than the corresponding wild-type tissues. Roots, stems, and leaves from cod5 and wild-type had similar calcium content. Although cod5 was devoid of prismatic crystals, cod5 pods were observed to form druse crystals of calcium oxalate not found in wild-type pods. Taken together these findings suggest a functional role for calcium oxalate formation in regulating calcium transport to the seeds. Regulating calcium uptake at the roots also appeared to be another point of control in determining seed calcium content. Overall, regulating the long distance transport and partitioning of calcium to the seeds appears to be a complex process with multiple points of control. PMID:22325887

  6. CCN3 and calcium signaling

    Directory of Open Access Journals (Sweden)

    Li Chang Long

    2003-08-01

    Full Text Available Abstract The CCN family of genes consists presently of six members in human (CCN1-6 also known as Cyr61 (Cystein rich 61, CTGF (Connective Tissue Growth Factor, NOV (Nephroblastoma Overexpressed gene, WISP-1, 2 and 3 (Wnt-1 Induced Secreted Proteins. Results obtained over the past decade have indicated that CCN proteins are matricellular proteins, which are involved in the regulation of various cellular functions, such as proliferation, differentiation, survival, adhesion and migration. The CCN proteins have recently emerged as regulatory factors involved in both internal and external cell signaling. CCN3 was reported to physically interact with fibulin-1C, integrins, Notch and S100A4. Considering that, the conformation and biological activity of these proteins are dependent upon calcium binding, we hypothesized that CCN3 might be involved in signaling pathways mediated by calcium ions. In this article, we review the data showing that CCN3 regulates the levels of intracellular calcium and discuss potential models that may account for the biological effects of CCN3.

  7. Growth of high quality mercurous halide single crystals by physical vapor transport method for AOM and radiation detection applications

    Science.gov (United States)

    Amarasinghe, Priyanthi M.; Kim, Joo-Soo; Chen, Henry; Trivedi, Sudhir; Qadri, Syed B.; Soos, Jolanta; Diestler, Mark; Zhang, Dajie; Gupta, Neelam; Jensen, Janet L.; Jensen, James

    2016-09-01

    Single crystals of mercurous halide were grown by physical vapor transport method (PVT). The orientation and the crystalline quality of the grown crystals were determined using high resolution x-ray diffraction (HRXRD) technique. The full width at half maximum (FWHM) of the grown mercurous bromide crystals was measured to be 0.13 degrees for (004) reflection, which is the best that has been achieved so far for PVT grown mercurous halide single crystals. The extended defects of the crystals were also analyzed using high resolution x-ray diffraction topography. Preliminary studies were carried out to evaluate the performance of the crystals on acousto-optic modulator (AOM) and gamma-ray detector applications. The results indicate the grown mercurous halide crystals are excellent materials for acousto-optic modulator device fabrication. The diffraction efficiencies of the fabricated AOM device with 1152 and 1523 nm wavelength lasers polarizing parallel to the acoustic wave were found to be 35% and 28%, respectively. The results also indicate the grown crystals are a promising material for gamma-ray detector application with a very high energy resolution of 1.86% FWHM.

  8. Halide effects on formation and physicochemical properties of mercury(II) complexes containing Y-type tridentate N-donor

    Science.gov (United States)

    Choi, Eunkyung; Kwon, Nam; Kim, Jeong Gyun; Jung, Ok-Sang; Lee, Young-A.

    2016-08-01

    Self-assembly of HgX2 (X- = Cl-, Br-, and I-) with Y-type 2,6-bis[(2-isonicotinoyloxy-5-methylphenyl)methyl]-1-isonicotinoyloxy-4-methylbenzene (L) yields 2D consisting of alternate prismatic P- and M-helical-linked-layers, 1D consisting of P- and M-helices, and simple 2D sheet in a unique Y-type mode, respectively. The L/Hg(II) ratio of each product (3/3 for Cl-; 2/3 for Br-; 1/3 for I-) is dependent on the nature of the halide anions. The coordinating environments around of Hg(II) ion approximate to a square pyramid for Cl-, a square planar and a distorted tetrahedral geometry for Br-, and distorted tetrahedral arrangement for I-, respectively. Photoluminescence wavelengths are strongly depending on the halide anions, and coordination ability to L is in the order of X- = Cl- > Br- > I-. Such physicochemical properties were explained by electronic and steric natures of halide anions.

  9. Halide Free M(BH4)2 (M = Sr, Ba, and Eu) Synthesis, Structure, and Decomposition.

    Science.gov (United States)

    Sharma, Manish; Didelot, Emilie; Spyratou, Alexandra; Lawson Daku, Latévi Max; Černý, Radovan; Hagemann, Hans

    2016-07-18

    Borohydrides have attained high interest in the past few years due to their high volumetric and gravimetric hydrogen content. Synthesis of di/trimetallic borohydride is a way to alter the thermodynamics of hydrogen release from borohydrides. Previously reported preparations of M(BH4)2 involved chloride containing species such as SrCl2. The presence of residual chloride (or other halide) ions in borohydrides may change their thermodynamic behavior and their decomposition pathway. Pure monometallic borohydrides are needed to study decomposition products without interference from halide impurities. They can also be used as precursors for synthesizing di/trimetallic borohydrides. In this paper we present a way to synthesize halide free alkaline earth metal (Sr, Ba) and europium borohydrides starting with the respective hydrides as precursors. Two novel high temperature polymorphs of Sr and Eu borohydrides and four polymorphs of Ba borohydride have been characterized by synchrotron X-ray powder diffraction, thermal analysis, and Raman and infrared spectroscopy and supported by periodic DFT calculations. The decomposition routes of these borohydrides have also been investigated. In the case of the decomposition of strontium and europium borohydrides, the metal borohydride hydride (M(BH4)H3, M = Sr, Eu) is observed and characterized. Periodic DFT calculations performed on room temperature Ba(BH4)2 revealed the presence of bidentate and tridentate borohydrides. PMID:27351948

  10. Nanostructured Lanthanum Halides and CeBr3 for Nuclear Radiation and Detection

    International Nuclear Information System (INIS)

    Scintillator materials are used to detect, and in some cases identify, gamma rays. Higher performance scintillators are expensive, hard to manufacture, fragile, and sometimes require liquid nitrogen or cooling engines. But whereas lower-quality scintillators are cheap, easy to manufacture, and more rugged, their performance is lower. At issue: can the desirable qualities of high-and low-performance scintillators be combined to achieve better performance at lower cost? Preliminary experiments show that a LaF3:Ce oleic acid-based nanocomposite exhibits a photopeak when exposed to 137Cs source gamma-radiation. The chemical synthesis of the cerium-doped lanthanum halide nanoparticles are scalable and large quantities of material can be produced at a time, unlike typical crystal growth processes such as the Bridgeman process. Using a polymer composite (Figure 1), produced by LANL, initial measurements of the unloaded and 8% LaF3:Ce-loaded sample have been made using 137Cs sources. Figure 2 shows an energy spectrum acquired for CeF3. The lighter plot is the measured polymer-only spectrum and the black plot is the spectrum from the nanocomposite scintillator. As the development of this material continues, the energy resolution is expected to improve and the photopeak-to-Compton ratio will become greater at higher loadings. These measurements show the expected Compton edge in the polymer-only sample, and the Compton edge and photo-peak expected in the nanophosphor composites that LANL has produced. Using a porous VYCORR with CdSe/ZnS core shell quantum dots, Letant has demonstrated that he has obtained signatures of the 241Am photopeak with energy resolution as good at NaI (Figure 3). We begin with the fact that CeBr3 crystals do not have a self-activity component as strong as the lanthanum halides. The radioactive 0.090% 138La component of lanthanum leads to significant self-activity, which will be a problem for very large detector volumes. Yet a significant strength of

  11. Calcium channel as a potential anticancer agent.

    Science.gov (United States)

    Kriazhev, L

    2009-11-01

    Anticancer treatment in modern clinical practices includes chemotherapy and radiation therapy with or without surgical interventions. Efficiency of both methods varies greatly depending on cancer types and stages. Besides, chemo- and radiotherapy are toxic and damaging that causes serious side effects. This fact prompts the search for alternative methods of antitumor therapy. It is well known that prolonged or high increase of intracellular calcium concentration inevitably leads to the cell death via apoptosis or necrosis. However, stimulation of cell calcium level by chemical agents is hardly achievable because cells have very sophisticated machinery for maintaining intracellular calcium in physiological ranges. This obstacle can be overridden, nevertheless. It was found that calcium channels in so called calcium cells in land snails are directly regulated by extracellular calcium concentration. The higher the concentration the higher the calcium intake is through the channels. Bearing in mind that extracellular/intracellular calcium concentration ratio in human beings is 10,000-12,000 fold the insertion of the channel into cancer cells would lead to fast and uncontrollable by the cells calcium intake and cell death. Proteins composing the channel may be extracted from plasma membrane of calcium cells and sequenced by mass-spectrometry or N-terminal sequencing. Either proteins or corresponding genes could be used for targeted delivery into cancer cells.

  12. Long-lived charge carrier dynamics in polymer/quantum dot blends and organometal halide perovskites

    Science.gov (United States)

    Nagaoka, Hirokazu

    Solution-processable semiconductors offer a potential route to deploy solar panels on a wide scale, based on the possibility of reduced manufacturing costs by using earth-abundant materials and inexpensive production technologies, such as inkjet or roll-to-roll printing. Understanding the fundamental physics underlying device operation is important to realize this goal. This dissertation describes studies of two kinds of solar cells: hybrid polymer/PbS quantum dot solar cells and organometal halide perovskite solar cells. Chapter two discusses details of the experimental techniques. Chapter three and four explore the mechanisms of charge transfer and energy transfer spectroscopically, and find that both processes contribute to the device photocurrent. Chapter four investigates the important question of how the energy level alignment of quantum dot acceptors affects the operation of hybrid polymer/quantum dot solar cells, by making use of the size-tunable energy levels of PbS quantum dots. We observe that long-lived charge transfer yield is diminished at larger dot sizes as the energy level offset at the polymer/quantum dot interface is changed through decreasing quantum confinement using a combination of spectroscopy and device studies. Chapter five discusses the effects of TiO2 surface chemistry on the performance of organometal halide perovskite solar cells. Specifically, chapter five studies the effect of replacing the conventional TiO2 electrode with Zr-doped TiO2 (Zr-TiO2). We aim to explore the correlation between charge carrier dynamics and device studies by incorporating zirconium into TiO2. We find that, compared to Zr-free controls, solar cells employing Zr-TiO2 give rise to an increase in overall power conversion efficiency, and a decrease in hysteresis. We also observe longer carrier lifetimes and higher charge carrier densities in devices on Zr-TiO2 electrodes at microsecond times in transient photovoltage experiments, as well as at longer persistent

  13. Calcium signals can freely cross the nuclear envelope in hippocampal neurons: somatic calcium increases generate nuclear calcium transients

    Directory of Open Access Journals (Sweden)

    Bading Hilmar

    2007-07-01

    Full Text Available Abstract Background In hippocampal neurons, nuclear calcium signaling is important for learning- and neuronal survival-associated gene expression. However, it is unknown whether calcium signals generated by neuronal activity at the cell membrane and propagated to the soma can unrestrictedly cross the nuclear envelope to invade the nucleus. The nuclear envelope, which allows ion transit via the nuclear pore complex, may represent a barrier for calcium and has been suggested to insulate the nucleus from activity-induced cytoplasmic calcium transients in some cell types. Results Using laser-assisted uncaging of caged calcium compounds in defined sub-cellular domains, we show here that the nuclear compartment border does not represent a barrier for calcium signals in hippocampal neurons. Although passive diffusion of molecules between the cytosol and the nucleoplasm may be modulated through changes in conformational state of the nuclear pore complex, we found no evidence for a gating mechanism for calcium movement across the nuclear border. Conclusion Thus, the nuclear envelope does not spatially restrict calcium transients to the somatic cytosol but allows calcium signals to freely enter the cell nucleus to trigger genomic events.

  14. Binding of calcium and carbonate to polyacrylates.

    Science.gov (United States)

    Tribello, Gareth A; Liew, CheeChin; Parrinello, Michele

    2009-05-21

    Polyacrylate molecules can be used to slow the growth of calcium carbonate. However, little is known about the mechanism by which the molecules impede the growth rate. A recent computational study (Bulo et al. Macromolecules 2007, 40, 3437) used metadynamics to investigate the binding of calcium to polyacrylate chains and has thrown some light on the coiling and precipitation of these polymers. We extend these simulations to examine the binding of calcium and carbonate to polyacrylate chains. We show that calcium complexed with both carbonate and polyacrylate is a very stable species. The free energies of calcium-carbonate-polyacrylate complexes, with different polymer configurations, are calculated, and differences in the free energy of the binding of carbonate are shown to be due to differences in the amount of steric hindrance about the calcium, which prevents the approach of the carbonate ion. PMID:19400592

  15. Altered calcium signaling in cancer cells.

    Science.gov (United States)

    Stewart, Teneale A; Yapa, Kunsala T D S; Monteith, Gregory R

    2015-10-01

    It is the nature of the calcium signal, as determined by the coordinated activity of a suite of calcium channels, pumps, exchangers and binding proteins that ultimately guides a cell's fate. Deregulation of the calcium signal is often deleterious and has been linked to each of the 'cancer hallmarks'. Despite this, we do not yet have a full understanding of the remodeling of the calcium signal associated with cancer. Such an understanding could aid in guiding the development of therapies specifically targeting altered calcium signaling in cancer cells during tumorigenic progression. Findings from some of the studies that have assessed the remodeling of the calcium signal associated with tumorigenesis and/or processes important in invasion and metastasis are presented in this review. The potential of new methodologies is also discussed. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

  16. Dominant factors limiting the optical gain in layered two-dimensional halide perovskite thin films.

    Science.gov (United States)

    Chong, Wee Kiang; Thirumal, Krishnamoorthy; Giovanni, David; Goh, Teck Wee; Liu, Xinfeng; Mathews, Nripan; Mhaisalkar, Subodh; Sum, Tze Chien

    2016-05-25

    Semiconductors are ubiquitous gain media for coherent light sources. Solution-processed three-dimensional (3D) halide perovskites (e.g., CH3NH3PbI3) with their outstanding room temperature optical gain properties are the latest members of this family. Their two-dimensional (2D) layered perovskite counterparts with natural multiple quantum well structures exhibit strong light-matter interactions and intense excitonic luminescence. However, despite such promising traits, there have been no reports on room temperature optical gain in 2D layered perovskites. Herein, we reveal the challenges towards achieving amplified spontaneous emission (ASE) in the archetypal (C6H5C2H4NH3)2PbI4 (or PEPI) system. Temperature-dependent transient spectroscopy uncovers the dominant free exciton trapping and bound biexciton formation pathways that compete effectively with biexcitonic gain. Phenomenological rate equation modeling predicts a large biexciton ASE threshold of ∼1.4 mJ cm(-2), which is beyond the damage threshold of these materials. Importantly, these findings would rationalize the difficulties in achieving optical gain in 2D perovskites and provide new insights and suggestions for overcoming these challenges.

  17. A survey of infrared continuum versus line radiation from metal halide lamps

    Science.gov (United States)

    Kato, M.; Herd, M. T.; Lawler, J. E.

    2008-07-01

    Near-infrared radiation (near-IR) losses from the arcs of six commercial metal halide high intensity discharge (MH-HID) lamps with various power levels and with both Na/Sc and rare earth doses were surveyed in this paper. A radiometrically calibrated Fourier transform infrared spectrometer was used. Lamps with rare earth doses have appreciably better color rendering indices (CRIs) than lamps with Na/Sc doses. The ratios of near-IR continuum emission over near-IR line emission from these six lamps were compared. The near-IR continuum dominates near-IR losses from lamps with rare earth doses and the continuum is significant, but not dominant, from lamps with Na/Sc doses. There was no strong dependence of this ratio on input power or color temperature (Tc). Total near-IR losses were estimated using absolutely calibrated, horizontal irradiance measurements. Estimated total near-IR losses were correlated with CRI. The lamps with rare earth doses yield the best CRIs, but have appreciably higher near-IR losses due primarily to continuum processes. One of these rare earth MH-HID lamps was used in a more detailed study of the microscopic physics of the continuum mechanism (Herd M T and Lawler E 2007 J. Phys. D: Appl. Phys. 40 3386).

  18. A Survey of Infrared Continuum verses Line Radiation from Metal Halide

    Science.gov (United States)

    Kato, M.; Herd, M. T.; Lawler, J. E.

    2007-10-01

    Near-infrared radiation (near-IR) losses from the arc of six commercial Metal Halide High Intensity Discharge (MH-HID) lamps with various power levels and with both Na/Sc and rare earth doses were surveyed in this paper. A radiometrically calibrated Fourier transform infrared spectrometer was used. Lamps with rare earth doses have appreciably better Color Rendering Indices (CRI's) than lamps with Na/Sc doses. The ratios of near-IR continuum emission over near-IR line emission from these six lamps were compared. The near-IR continuum dominates near-IR losses from lamps with rare earth doses and the continuum is significant, but not dominant, from lamps with Na/Sc doses. There was no strong dependence of this ratio on input power or Color Temperature (Tc). Total near-IR losses were estimated using absolutely calibrated, horizontal irradiance measurements. Estimated total near-IR losses were correlated with CRI. The lamps with rare earth doses yield the best CRI's, but have appreciably higher near-IR losses due primarily to continuum processes. One of these rare earth MH-HID lamps was used in a more detailed study of the microscopic physics of the continuum mechanism[M. T. Herd & J. E. Lawler, J. Phys. D 40, 3386 (2007)].

  19. Halides with Fifteen Aliphatic C–H···Anion Interaction Sites

    Science.gov (United States)

    Shi, Genggongwo; Aliakbar Tehrani, Zahra; Kim, Dongwook; Cho, Woo Jong; Youn, Il-Seung; Lee, Han Myoung; Yousuf, Muhammad; Ahmed, Nisar; Shirinfar, Bahareh; Teator, Aaron J.; Lastovickova, Dominika N.; Rasheed, Lubna; Lah, Myoung Soo; Bielawski, Christopher W.; Kim, Kwang S.

    2016-07-01

    Since the aliphatic C–H···anion interaction is relatively weak, anion binding using hydrophobic aliphatic C–H (Cali–H) groups has generally been considered not possible without the presence of additional binding sites that contain stronger interactions to the anion. Herein, we report X-ray structures of organic crystals that feature a chloride anion bound exclusively by hydrophobic Cali–H groups. An X-ray structure of imidazolium-based scaffolds using Cali–H···A‑ interactions (A‑ = anion) shows that a halide anion is directly interacting with fifteen Cali–H groups (involving eleven hydrogen bonds, two bidentate hydrogen-bond-type binding interactions and two weakly hydrogen-bonding-like binding interactions). Additional supporting interactions and/or other binding sites are not observed. We note that such types of complexes may not be rare since such high numbers of binding sites for an anion are also found in analogous tetraalkylammonium complexes. The Cali–H···A‑ interactions are driven by the formation of a near-spherical dipole layer shell structure around the anion. The alternating layers of electrostatic charge around the anion arise because the repulsions between weakly positively charged H atoms are reduced by the presence of the weakly negatively charged C atoms connected to H atoms.

  20. Halides with Fifteen Aliphatic C-H···Anion Interaction Sites.

    Science.gov (United States)

    Shi, Genggongwo; Aliakbar Tehrani, Zahra; Kim, Dongwook; Cho, Woo Jong; Youn, Il-Seung; Lee, Han Myoung; Yousuf, Muhammad; Ahmed, Nisar; Shirinfar, Bahareh; Teator, Aaron J; Lastovickova, Dominika N; Rasheed, Lubna; Lah, Myoung Soo; Bielawski, Christopher W; Kim, Kwang S

    2016-01-01

    Since the aliphatic C-H···anion interaction is relatively weak, anion binding using hydrophobic aliphatic C-H (Cali-H) groups has generally been considered not possible without the presence of additional binding sites that contain stronger interactions to the anion. Herein, we report X-ray structures of organic crystals that feature a chloride anion bound exclusively by hydrophobic Cali-H groups. An X-ray structure of imidazolium-based scaffolds using Cali-H···A(-) interactions (A(-) = anion) shows that a halide anion is directly interacting with fifteen Cali-H groups (involving eleven hydrogen bonds, two bidentate hydrogen-bond-type binding interactions and two weakly hydrogen-bonding-like binding interactions). Additional supporting interactions and/or other binding sites are not observed. We note that such types of complexes may not be rare since such high numbers of binding sites for an anion are also found in analogous tetraalkylammonium complexes. The Cali-H···A(-) interactions are driven by the formation of a near-spherical dipole layer shell structure around the anion. The alternating layers of electrostatic charge around the anion arise because the repulsions between weakly positively charged H atoms are reduced by the presence of the weakly negatively charged C atoms connected to H atoms. PMID:27444513

  1. Comparison of boron halide, decaborane and B implants in Si from Molecular Dynamics simulations

    CERN Document Server

    Webb, R P; Gwilliam, R M; Sealy, B J; Boudreault, G; Jeynes, C; Kirkby, K J

    2003-01-01

    Ultra shallow junctions (depths <0.1 mu m) are required for future generations of silicon devices. This requires either very low energy ion implantation (<1 keV for B for the shallowest of implants) or the use of heavier implanted species (either elemental or molecular). Many commercial implanters have problems operating at such low terminal voltages. For many years molecular ions, in particular BF sub 2 sup + , have been used to transport low velocity boron at higher energies, enabling the use of conventional implanters in the production of shallow junctions. However, with ever shrinking scales the energies required even for BF sub 2 are becoming too low. The investigation here is to look at the alternative heavier halides and decaborane as possible alternatives to allow continued use of conventional ion implanters. We use a molecular dynamics simulation to see if we can find any evidence of non-linear behaviour from the use of such molecular species for implantation, thereby making the modelling and s...

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

    Science.gov (United States)

    Sudheer, Porwal, S.; Bhartiya, S.; Rao, B. T.; Tiwari, P.; Srivastava, Himanshu; Sharma, T. K.; Rai, V. N.; Srivastava, A. K.; Naik, P. A.

    2016-07-01

    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.

  3. Two-dimensional condensation of physi-sorbed methane on layer-like halides

    International Nuclear Information System (INIS)

    Two-dimensional condensation of methane in physi-sorbed layers has been studied from sets of stepped isotherms of methane on the cleavage plane of layer-like halides (FeCl2, CdCl2, NiBr2, CdBr2, FeI2, CaI2, CaI2 and PbI2) in most cases prepared by sublimation in a rapid current of inert gas. The vertical parts of the steps of adsorption isotherms correspond to the formation of successive monomolecular layers by two-dimensional condensation. Thermodynamic analysis of experimental results, has mainly emphasized the important effect of the potential relief of adsorbent surfaces, on both the structure of the physi-sorbed layers and the two-dimensional critical temperature. From its entropy, we conclude that the first layer is a (111) plane of f.c.c.: methane which becomes more loosely packed as the dimensional compatibility of the lattices of the adsorbent and adsorbate becomes poorer. Experimental values of the two-dimensional critical temperatures in the first, second and third layers have been determined, and interpreted on the following basis. An expansion of the layer induces a lowering of the two-dimensional critical temperature by decreasing the lateral interaction energy, while a localisation of the adsorbed molecules in potential wells, when possible, induces a rise of the two-dimensional critical temperature. (author)

  4. Metal-encapsulated organolead halide perovskite photocathode for solar-driven hydrogen evolution in water.

    Science.gov (United States)

    Crespo-Quesada, Micaela; Pazos-Outón, Luis M; Warnan, Julien; Kuehnel, Moritz F; Friend, Richard H; Reisner, Erwin

    2016-01-01

    Lead-halide perovskites have triggered the latest breakthrough in photovoltaic technology. Despite the great promise shown by these materials, their instability towards water even in the presence of low amounts of moisture makes them, a priori, unsuitable for their direct use as light harvesters in aqueous solution for the production of hydrogen through water splitting. Here, we present a simple method that enables their use in photoelectrocatalytic hydrogen evolution while immersed in an aqueous solution. Field's metal, a fusible InBiSn alloy, is used to efficiently protect the perovskite from water while simultaneously allowing the photogenerated electrons to reach a Pt hydrogen evolution catalyst. A record photocurrent density of -9.8 mA cm(-2) at 0 V versus RHE with an onset potential as positive as 0.95±0.03 V versus RHE is obtained. The photoelectrodes show remarkable stability retaining more than 80% of their initial photocurrent for ∼1 h under continuous illumination. PMID:27595974

  5. Atomically thin two-dimensional materials as hole extraction layers in organolead halide perovskite photovoltaic cells

    Science.gov (United States)

    Kim, Yu Geun; Kwon, Ki Chang; Le, Quyet Van; Hong, Kootak; Jang, Ho Won; Kim, Soo Young

    2016-07-01

    Atomically thin two-dimensional materials such as MoS2, WS2, and graphene oxide (GO) are used as hole extraction layers (HEL) in organolead halide perovskites solar cells (PSCs) instead of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HEL. MoS2 and WS2 layers with a polycrystalline structure were synthesized by a chemical deposition method using a uniformly spin-coated (NH4)MoS4 and (NH4)WS4 precursor solution. GO was synthesized by the oxidation of natural graphite powder using Hummers' method. The work functions of MoS2, WS2, and GO are measured to be 5.0, 4.95, and 5.1 eV, respectively. The X-ray diffraction spectrum indicated that the synthesized perovskite material is CH3NH3PbI3-xClx. The PSCs with the p-n junction structure were fabricated based on the CH3NH3PbI3-xClx perovskite layer. The power conversion efficiencies of the MoS2, WS2, and GO-based PSCs were 9.53%, 8.02%, and 9.62%, respectively, which are comparable to those obtained from PEDOT:PSS-based devices (9.93%). These results suggest that two-dimensional materials such as MoS2, WS2, and GO can be promising candidates for the formation of HELs in the PSCs.

  6. Bio-analytical applications of mid-infrared spectroscopy using silver halide fiber-optic probes

    International Nuclear Information System (INIS)

    Infrared-spectroscopy has proved to be a powerful method for the study of various biomedical samples, in particular for in-vitro analysis in the clinical laboratory and for non-invasive diagnostics. In general, the analysis of biofluids such as whole blood, urine, microdialysates and bioreactor broth media takes advantage of the fact that a multitude of analytes can be quantified simultaneously and rapidly without the need for reagents. Progress in the quality of infrared silver halide fibers enabled us to construct several flexible fiber-optic probes of different geometries, which are particularly suitable for the measurement of small biosamples. Recent trends show that dry film measurements by mid-infrared spectroscopy could revolutionize analytical tools in the clinical chemistry laboratory, and an example is given. Infrared diagnostic tools show a promising potential for patients, and minimal-invasive blood glucose assays or skin tissue pathology in particular cannot be left out using mid-infrared fiber-based probes. Other applications include the measurement of skin samples including penetration studies of vitamins and constituents of cosmetic cream formulations. A further field is the micro-domain analysis of biopsy samples from bog mummified corpses, and recent results on the chemistry of dermis and hair samples are reported. Another field of application, for which results are reported, is food analysis and bio-reactor monitoring

  7. Role of hydrogen bonding in solubility of poly(N-isopropylacrylamide) brushes in sodium halide solutions

    Science.gov (United States)

    Xin-Jun, Zhao; Zhi-Fu, Gao

    2016-07-01

    By employing molecular theory, we systematically investigate the shift of solubility of poly(N-isopropylacrylamide) (PNIPAM) brushes in sodium halide solutions. After considering PNIPAM–water hydrogen bonds, water–anion hydrogen bonds, and PNIPAM–anion bonds and their explicit coupling to the PNIPAM conformations, we find that increasing temperature lowers the solubility of PNIPAM, and results in a collapse of the layer at high enough temperatures. The combination of the three types of bonds would yield a decrease in the solubility of PNIPAM following the Hofmeister series: NaCl>NaBr>NaI. PNIPAM–water hydrogen bonds are affected by water–anion hydrogen bonds and PNIPAM–anion bonds. The coupling of polymer conformations and the competition among the three types of bonds are essential for describing correctly a decrease in the solubility of PNIPAM brushes, which is determined by the free energy associated with the formation of the three types of bonds. Our results agree well with the experimental observations, and would be very important for understanding the shift of the lower critical solution temperature of PNIPAM brushes following the Hofmeister series. Project supported by the National Natural Science Foundation of China (Grant Nos. 21264016, 11464047, and 21364016) and the Joint Funds of Xinjiang Natural Science Foundation, China (Grant No. 2015211C298).

  8. Role of hydrogen bonding in solubility of poly(N-isopropylacrylamide) brushes in sodium halide solutions

    Institute of Scientific and Technical Information of China (English)

    赵新军; 高志福

    2016-01-01

    By employing molecular theory, we systematically investigate the shift of solubility of poly(N-isopropylacrylamide) (PNIPAM) brushes in sodium halide solutions. After considering PNIPAM–water hydrogen bonds, water–anion hydro-gen bonds, and PNIPAM–anion bonds and their explicit coupling to the PNIPAM conformations, we find that increasing temperature lowers the solubility of PNIPAM, and results in a collapse of the layer at high enough temperatures. The combination of the three types of bonds would yield a decrease in the solubility of PNIPAM following the Hofmeister se-ries:NaCl>NaBr>NaI. PNIPAM–water hydrogen bonds are affected by water–anion hydrogen bonds and PNIPAM–anion bonds. The coupling of polymer conformations and the competition among the three types of bonds are essential for de-scribing correctly a decrease in the solubility of PNIPAM brushes, which is determined by the free energy associated with the formation of the three types of bonds. Our results agree well with the experimental observations, and would be very im-portant for understanding the shift of the lower critical solution temperature of PNIPAM brushes following the Hofmeister series.

  9. Temperature dependent halogen activation by N2O5 reactions on halide-doped ice surfaces

    Directory of Open Access Journals (Sweden)

    J. A. Thornton

    2012-06-01

    Full Text Available We examined the reaction of N2O5 on frozen halide salt solutions as a function of temperature and composition using a coated wall flow tube technique coupled to a chemical ionization mass spectrometer (CIMS. The molar yield of photo-labile halogen compounds was near unity for almost all conditions studied, with the observed reaction products being nitryl chloride (ClNO2 and/or molecular bromine (Br2. The relative yield of ClNO2 and Br2 depended on the ratio of bromide to chloride ions in the solutions used to form the ice. At a bromide to chloride ion molar ratio greater than 1/30 in the starting solution, Br2 was the dominant product otherwise ClNO2 was primarily produced on these near pH-neutral brines. We demonstrate that the competition between chlorine and bromine activation is a function of the ice/brine temperature presumably due to the preferential precipitation of NaCl hydrates from the brine below 250 K. Our results provide new experimental confirmation that the chemical environment of the brine layer changes with temperature and that these changes can directly affect multiphase chemistry. These findings have implications for modeling air-snow-ice interactions in polar regions and likely in polluted mid-latitude regions during winter as well.

  10. Modified Becke-Johnson exchange potential: improved modeling of lead halides for solar cell applications

    Directory of Open Access Journals (Sweden)

    Radi A. Jishi

    2016-01-01

    Full Text Available We report first-principles calculations, within density functional theory, on the lead halide compounds PbCl2, PbBr2, and CH3NH3PbBr3−xClx, taking into account spin-orbit coupling. We show that, when the modified Becke-Johnson exchange potential is used with a suitable choice of defining parameters, excellent agreement between calculations and experiment is obtained. The computational model is then used to study the effect of replacing the methylammonium cation in CH3NH3PbI3 and CH3NH3PbBr3 with either N2H5+or N2H3+, which have slightly smaller ionic radii than methylammonium. We predict that a considerable downshift in the values of the band gaps occurs with this replacement. The resulting compounds would extend optical absorption down to the near-infrared region, creating excellent light harvesters for solar cells.

  11. New niobium and rhenium halides synthesis routes by atomic vaporization. X-ray absorption spectroscopy characterization

    International Nuclear Information System (INIS)

    New synthetic route as the so called 'chimie douce' or MVS (Metal Vapor Synthesis) has been an increasing field lately to synthesize new kind of solid state structures. Our interest is the assembly of small molecular building blocks of early transition metal halides. We illustrate the use of vaporized rare earth metals to condense NbCls units. We probed the local order around the Nb atom with X-Ray Absorption Spectroscopy, far Infra-Red and XPS in order to better understand the mechanisms involved. A first EXAFS, IR and XPS study on solid state products has shown the evolution of the NbCl5 dimer towards a chain like structure. However, the condensation patterns depends on the rare earth atoms vaporized. These results have been confirmed by X-ray Absorption ab initio calculations. Because our compounds are extremely air sensitive we have developed in situ MVS reactor to take 'snapshots' of the structural intermediates by EXAFS. This study showed the condensation of the initial NbCl5 building blocks by reduction of the Nb oxidation state by rare earth vaporization. This method is a new way of looking at condensation mechanisms via structural evolution observed by EXAFS. (author)

  12. Multicolor fluorescent light-emitting diodes based on cesium lead halide perovskite quantum dots

    Science.gov (United States)

    Wang, Peng; Bai, Xue; Sun, Chun; Zhang, Xiaoyu; Zhang, Tieqiang; Zhang, Yu

    2016-08-01

    High quantum yield, narrow full width at half-maximum and tunable emission color of perovskite quantum dots (QDs) make this kind of material good prospects for light-emitting diodes (LEDs). However, the relatively poor stability under high temperature and air condition limits the device performance. To overcome this issue, the liquid-type packaging structure in combination with blue LED chip was employed to fabricate the fluorescent perovskite quantum dot-based LEDs. A variety of monochromatic LEDs with green, yellow, reddish-orange, and red emission were fabricated by utilizing the inorganic cesium lead halide perovskite quantum dots as the color-conversion layer, which exhibited the narrow full width at half-maximum (<35 nm), the relatively high luminous efficiency (reaching 75.5 lm/W), and the relatively high external quantum efficiency (14.6%), making it the best-performing perovskite LEDs so far. Compared to the solid state LED device, the liquid-type LED devices exhibited excellent color stability against the various working currents. Furthermore, we demonstrated the potential prospects of all-inorganic perovskite QDs for the liquid-type warm white LEDs.

  13. Emergence of Hysteresis and Transient Ferroelectric Response in Organo-Lead Halide Perovskite Solar Cells.

    Science.gov (United States)

    Chen, Hsin-Wei; Sakai, Nobuya; Ikegami, Masashi; Miyasaka, Tsutomu

    2015-01-01

    Although there has been rapid progress in the efficiency of perovskite-based solar cells, hysteresis in the current-voltage performance is not yet completely understood. Owing to its complex structure, it is not easy to attribute the hysteretic behavior to any one of different components, such as the bulk of the perovskite or different heterojunction interfaces. Among organo-lead halide perovskites, methylammonium lead iodide perovskite (CH3NH3PbI3) is known to have a ferroelectric property. The present investigation reveals a strong correlation between transient ferroelectric polarization of CH3NH3PbI3 induced by an external bias in the dark and hysteresis enhancement in photovoltaic characteristics. Our results demonstrate that the reverse bias poling (-0.3 to -1.1 V) of CH3NH3PbI3 photovoltaic layers prior to the photocurrent-voltage measurement generates stronger hysteresis whose extent changes significantly by the cell architecture. The phenomenon is interpreted as the effect of remanent polarization in the perovskite film on the photocurrent, which is most enhanced in planar perovskite structures without mesoporous scaffolds.

  14. The nature of free-carrier transport in organometal halide perovskites

    Science.gov (United States)

    Hakamata, Tomoya; Shimamura, Kohei; Shimojo, Fuyuki; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

    2016-01-01

    Organometal halide perovskites are attracting great attention as promising material for solar cells because of their high power conversion efficiency. The high performance has been attributed to the existence of free charge carriers and their large diffusion lengths, but the nature of carrier transport at the atomistic level remains elusive. Here, nonadiabatic quantum molecular dynamics simulations elucidate the mechanisms underlying the excellent free-carrier transport in CH3NH3PbI3. Pb and I sublattices act as disjunct pathways for rapid and balanced transport of photoexcited electrons and holes, respectively, while minimizing efficiency-degrading charge recombination. On the other hand, CH3NH3 sublattice quickly screens out electrostatic electron-hole attraction to generate free carriers within 1 ps. Together this nano-architecture lets photoexcited electrons and holes dissociate instantaneously and travel far away to be harvested before dissipated as heat. This work provides much needed structure-property relationships and time-resolved information that potentially lead to rational design of efficient solar cells. PMID:26781627

  15. Organic-inorganic hybrid lead halide perovskites for optoelectronic and electronic applications.

    Science.gov (United States)

    Zhao, Yixin; Zhu, Kai

    2016-02-01

    Organic and inorganic hybrid perovskites (e.g., CH(3)NH(3)PbI(3)), with advantages of facile processing, tunable bandgaps, and superior charge-transfer properties, have emerged as a new class of revolutionary optoelectronic semiconductors promising for various applications. Perovskite solar cells constructed with a variety of configurations have demonstrated unprecedented progress in efficiency, reaching about 20% from multiple groups after only several years of active research. A key to this success is the development of various solution-synthesis and film-deposition techniques for controlling the morphology and composition of hybrid perovskites. The rapid progress in material synthesis and device fabrication has also promoted the development of other optoelectronic applications including light-emitting diodes, photodetectors, and transistors. Both experimental and theoretical investigations on organic-inorganic hybrid perovskites have enabled some critical fundamental understandings of this material system. Recent studies have also demonstrated progress in addressing the potential stability issue, which has been identified as a main challenge for future research on halide perovskites. Here, we review recent progress on hybrid perovskites including basic chemical and crystal structures, chemical synthesis of bulk/nanocrystals and thin films with their chemical and physical properties, device configurations, operation principles for various optoelectronic applications (with a focus on solar cells), and photophysics of charge-carrier dynamics. We also discuss the importance of further understanding of the fundamental properties of hybrid perovskites, especially those related to chemical and structural stabilities. PMID:26645733

  16. Third-order nonlinear optical properties of methylammonium lead halide perovskite films

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Justin C.; Li, Zhen; Ndione, Paul F.; Zhu, Kai

    2016-01-01

    We report third-order nonlinear coefficient values and decay time kinetics vs. halide composition (CH3NH3PbBr3 and CH3NH3PbBr2I), temperature, and excitation wavelength. The maximum values of the third-order nonlinear susceptibility X(3) (-1.6 x 10-6 esu) are similar to or larger than many common third-order materials. The source of the nonlinearity is shown to be primarily excitonic in the tribromide film by virtue of its strong enhancement near the exciton resonance. Nonresonant excitation reduces the nonlinearity significantly, as does increasing the temperature. Substitution of one I for one Br also reduces the nonlinearity by at least one order of magnitude, presumably due to the lack of strong exciton resonance in the substituted form. The thin films are stable, highly homogenous (lacking significant light scattering), and simple and inexpensive to fabricate, making them potentially useful in a variety of optoelectronic applications in which wavelength selectivity is important.

  17. Dominant factors limiting the optical gain in layered two-dimensional halide perovskite thin films.

    Science.gov (United States)

    Chong, Wee Kiang; Thirumal, Krishnamoorthy; Giovanni, David; Goh, Teck Wee; Liu, Xinfeng; Mathews, Nripan; Mhaisalkar, Subodh; Sum, Tze Chien

    2016-05-25

    Semiconductors are ubiquitous gain media for coherent light sources. Solution-processed three-dimensional (3D) halide perovskites (e.g., CH3NH3PbI3) with their outstanding room temperature optical gain properties are the latest members of this family. Their two-dimensional (2D) layered perovskite counterparts with natural multiple quantum well structures exhibit strong light-matter interactions and intense excitonic luminescence. However, despite such promising traits, there have been no reports on room temperature optical gain in 2D layered perovskites. Herein, we reveal the challenges towards achieving amplified spontaneous emission (ASE) in the archetypal (C6H5C2H4NH3)2PbI4 (or PEPI) system. Temperature-dependent transient spectroscopy uncovers the dominant free exciton trapping and bound biexciton formation pathways that compete effectively with biexcitonic gain. Phenomenological rate equation modeling predicts a large biexciton ASE threshold of ∼1.4 mJ cm(-2), which is beyond the damage threshold of these materials. Importantly, these findings would rationalize the difficulties in achieving optical gain in 2D perovskites and provide new insights and suggestions for overcoming these challenges. PMID:27184073

  18. NHC-Copper(I) Halide-Catalyzed Direct Alkynylation of Trifluoromethyl Ketones on Water

    KAUST Repository

    Czerwiński, Paweł

    2016-05-04

    An efficient and easily scalable NHC-copper(I) halide-catalyzed addition of terminal alkynes to 1,1,1-trifluoromethyl ketones, carried out on water for the first time, is reported. A series of addition reactions were performed with as little as 0.1-2.0mol% of [(NHC)CuX] (X=Cl, Br, I, OAc, OTf) complexes, providing tertiary propargylic trifluoromethyl alcohols in high yields and with excellent chemoselectivity from a broad range of aryl- and more challenging alkyl-substituted trifluoromethyl ketones (TFMKs). DFT calculations were performed to rationalize the correlation between the yield of catalytic alkynylation and the sterics of N-heterocyclic carbenes (NHCs), expressed as buried volume (%VBur), indicating that steric effects dominate the yield of the reaction. Additional DFT calculations shed some light on the differential reactivity of [(NHC)CuX] complexes in the alkynylation of TFMKs. The first enantioselective version of a direct alkynylation in the presence of C1-symmetric NHC-copper(I) complexes is also presented. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Charge-Carrier Dynamics in Organic-Inorganic Metal Halide Perovskites

    Science.gov (United States)

    Herz, Laura M.

    2016-05-01

    Hybrid organic-inorganic metal halide perovskites have recently emerged as exciting new light-harvesting and charge-transporting materials for efficient photovoltaic devices. Yet knowledge of the nature of the photogenerated excitations and their subsequent dynamics is only just emerging. This article reviews the current state of the field, focusing first on a description of the crystal and electronic band structure that give rise to the strong optical transitions that enable light harvesting. An overview is presented of the numerous experimental approaches toward determining values for exciton binding energies, which appear to be small (a few milli-electron volts to a few tens of milli-electron volts) and depend significantly on temperature because of associated changes in the dielectric function. Experimental evidence for charge-carrier relaxation dynamics within the first few picoseconds after excitation is discussed in terms of thermalization, cooling, and many-body effects. Charge-carrier recombination mechanisms are reviewed, encompassing trap-assisted nonradiative recombination that is highly specific to processing conditions, radiative bimolecular (electron-hole) recombination, and nonradiative many-body (Auger) mechanisms.

  20. Pressure-Induced Structural and Optical Properties of Organometal Halide Perovskite-Based Formamidinium Lead Bromide.

    Science.gov (United States)

    Wang, Lingrui; Wang, Kai; Zou, Bo

    2016-07-01

    Organometal halide perovskites (OMHPs) are attracting an ever-growing scientific interest as photovoltaic materials with moderate cost and compelling properties. In this Letter, pressure-induced optical and structural changes of OMHP-based formamidinium lead bromide (FAPbBr3) were systematically investigated. We studied the pressure dependence of optical absorption and photoluminescence, both of which showed piezochromism. Synchrotron X-ray diffraction indicated that FAPbBr3 underwent two phase transitions and subsequent amorphization, leading directly to the bandgap evolution with redshift followed by blueshift during compression. Raman experiments illustrated the high pressure behavior of organic cation and the surrounding inorganic octahedra. Additionally, the effect of cation size and the different intermolecular interactions between organic cation and inorganic octahedra result in the fact that FAPbBr3 is less compressible than the reported methylammonium lead bromide (MAPbBr3). High pressure studies of the structural evolution and optical properties of OMHPs provide important clues in optimizing photovoltaic performance and help to design novel OMHPs with higher stimuli-resistant ability. PMID:27321024