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Sample records for fluorescent metal halide

  1. X-ray Methods in High-Intensity Discharges and Metal-Halide Lamps: X-ray Induced Fluorescence

    SciTech Connect

    Curry, John J.; Lapatovich, Walter P.; Henins, Albert

    2011-12-09

    We describe the use of x-ray induced fluorescence to study metal-halide high-intensity discharge lamps and to measure equilibrium vapor pressures of metal-halide salts. The physical principles of metal-halide lamps, relevant aspects of x-ray-atom interactions, the experimental method using synchrotron radiation, and x-ray induced fluorescence measurements relevant to metal-halide lamps are covered.

  2. Growth and yield characteristics of 'Waldmann's Green' leaf lettuce under different photon fluxes from metal halide or incandescent + fluorescent radiation

    NASA Technical Reports Server (NTRS)

    Knight, Sharon L.; Mitchell, Cary A.

    1988-01-01

    Growth of 'Waldmann's Green' leaf lettuce under metal halide radiation was compared with that under In = Fl at the same photosynthetic photon flux (920 micromol/s/sq m) to evaluate the influence of lamp type on growth. No differences in leaf dry weight, leaf area, relative growth rate or photosynthesis occurred after 8 days of exposure to these radiation treatments for 20 h/day.

  3. Metal halide perovskite light emitters

    PubMed Central

    Kim, Young-Hoon; Cho, Himchan; Lee, Tae-Woo

    2016-01-01

    Twenty years after layer-type metal halide perovskites were successfully developed, 3D metal halide perovskites (shortly, perovskites) were recently rediscovered and are attracting multidisciplinary interest from physicists, chemists, and material engineers. Perovskites have a crystal structure composed of five atoms per unit cell (ABX3) with cation A positioned at a corner, metal cation B at the center, and halide anion X at the center of six planes and unique optoelectronic properties determined by the crystal structure. Because of very narrow spectra (full width at half-maximum ≤20 nm), which are insensitive to the crystallite/grain/particle dimension and wide wavelength range (400 nm ≤ λ ≤ 780 nm), perovskites are expected to be promising high-color purity light emitters that overcome inherent problems of conventional organic and inorganic quantum dot emitters. Within the last 2 y, perovskites have already demonstrated their great potential in light-emitting diodes by showing high electroluminescence efficiency comparable to those of organic and quantum dot light-emitting diodes. This article reviews the progress of perovskite emitters in two directions of bulk perovskite polycrystalline films and perovskite nanoparticles, describes current challenges, and suggests future research directions for researchers to encourage them to collaborate and to make a synergetic effect in this rapidly emerging multidisciplinary field. PMID:27679844

  4. Multiple-Wavelength Metal/Halide Laser

    NASA Technical Reports Server (NTRS)

    Nerheim, N. M.

    1984-01-01

    Single device produces multiple lasing lines. Laser capable of producing many lasing lines has several reservoirs of halide lasant mixed with chlorides of copper, manganese and iron. Convection-control technique possible to rapidly change from one metal halide to another at maximum energy.

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

    DOEpatents

    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.

  6. Dimming of metal halide lamps

    NASA Technical Reports Server (NTRS)

    Schurer, Kees

    1994-01-01

    We ran some tests on the effect of dimming of metal halide (MH) lamps upon the stability and the spectral quality of the light output. Lamps used were a new Philips lamp HPI-T 250W, a similar Philips lamp with a few thousand burning hours and a new Osram lamp HQI-T 250W/D. The ballast was a BBC type DJ 250/2KS, the starter a BAS TORGI type MZN 250 SE and the dimmer an Elstrom Control System type ERHQ-T 250. Power was derived from a Philips stabilizer, type PE 1602. Lamp output was monitored with a PAR meter. Spectra were taken at 100% and at 50% output as measured with the PAR meter. Lamps were allowed to stabilize at any setting for 30 minutes before measurements were made. Lamp manufacturers advise against dimming for fear of poor stability and intolerable changes of the spectrum. However, none of the lamps showed a decrease in stability, no flicker or wandering of the discharge, and the changes of the spectrum were not negligible, but certainly not dramatic. Lamps of either manufacture retain their white color, relative peak heights of spectral lines did shift, but no gaps in the spectrum occurred. Spectra taken at 50% with 30 minutes intervals coincided. Differences between the new and the older Philips lamp were noticeable, but not really significant.

  7. METHOD OF PREPARING METAL HALIDES

    DOEpatents

    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.

  8. Method for recovering hydrocarbons from molten metal halides

    DOEpatents

    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.

  9. Alkali metal and alkali earth metal gadolinium halide scintillators

    DOEpatents

    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. Metal induced gap states at alkali halide/metal interface

    NASA Astrophysics Data System (ADS)

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

    2004-10-01

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

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

    SciTech Connect

    Curry, J. J.; Henins, A.; Hardis, J. E.; Estupinan, E. G.; Lapatovich, W. P.; Shastri, S. D.

    2012-02-20

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

  12. Metal halide perovskites for energy applications

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    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.

  14. 10 CFR 431.322 - Definitions concerning metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... is produced by radiation of metal halides and their products of dissociation, possibly in combination... electromagnetic ballast that starts a pulse-start metal halide lamp with high voltage pulses, where lamps shall...

  15. Infrared Laser-Induced Breakdown Spectroscopy of Alkali Metal Halides

    NASA Astrophysics Data System (ADS)

    Brown, Ei; Hommerich, Uwe; Yang, Clayton; Trivedi, Sudhir; Samuels, Alan; Snyder, Peter

    2008-10-01

    Laser-induced breakdown spectroscopy (LIBS) is a powerful diagnostic tool for detection of trace elements by monitoring the atomic and ionic emission from laser-induced plasmas. LIBS is a relatively simple technique and has been successfully employed in applications such as environmental monitoring, materials analysis, medical diagnostics, industrial process control, and homeland security. Most LIBS applications are limited to emission features in the ultraviolet-visible-near infrared (UV-VIS-NIR) region arising from atoms and simple molecular fragments. In the present work, we report on the observation of mid- infrared emission lines from alkali metal halides due to laser-induced breakdown processes. The studied alkali metal halides included LiCl, NaCl, NaBr, KCl, KBr, KF, RbCl, and RbBr. The laser-induced plasma was produced by focusing a 16 mJ pulsed Nd:YAG laser (1064 nm) on the target. The LIBS infrared emission from alkali halides showed intense and narrow bands located in the region from 2-8 μm. The observed emission features were assigned to atomic transitions between higher-lying Rydberg states of neutral alkali atoms. More detailed results of the performed IR LIBS studies on alkali metal halides will be discussed at the conference.

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

    PubMed

    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.

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

    ERIC Educational Resources Information Center

    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…

  18. Method for producing hydrocarbon fuels from heavy polynuclear hydrocarbons by use of molten metal halide catalyst

    DOEpatents

    Gorin, Everett

    1979-01-01

    In a process for hydrocracking heavy polynuclear carbonaceous feedstocks to produce lighter hydrocarbon fuels by contacting the heavy feedstocks with hydrogen in the presence of a molten metal halide catalyst, thereafter separating at least a substantial portion of the carbonaceous material associated with the reaction mixture from the spent molten metal halide and thereafter regenerating the metal halide catalyst, an improvement comprising contacting the spent molten metal halide catalyst after removal of a major portion of the carbonaceous material therefrom with an additional quantity of hydrogen is disclosed.

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

    PubMed

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

    2014-07-21

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

  20. 75 FR 5544 - Energy Conservation Program: Energy Conservation Standards for Metal Halide Lamp Fixtures: Public...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-03

    ... public meeting and availability of the Framework Document in the Federal Register (74 FR 69036) for... for Metal Halide Lamp Fixtures: Public Meeting and Availability of the Framework Document AGENCY... conservation standards for certain metal halide lamp fixtures. This document announces that the period...

  1. Secondary alkyl halides in transition-metal-catalyzed cross-coupling reactions.

    PubMed

    Rudolph, Alena; Lautens, Mark

    2009-01-01

    Enormous effort has gone into the development of metal-catalyzed cross-coupling reactions with alkyl halides as electrophilic coupling partners. Whereas a wide array of primary alkyl halides can now be used effectively in cross-coupling reactions, the synthetic potential of secondary alkyl halides is just beginning to be revealed. This Minireview summarizes selected examples of the use of secondary alkyl halides as electrophiles in cross-coupling reactions. Emphasis is placed on the transition metals employed, the mechanistic pathways involved, and implications in terms of the stereochemical outcome of reactions.

  2. New generation of medium wattage metal halide lamps and spectroscopic tools for their diagnostics

    NASA Astrophysics Data System (ADS)

    Dunaevsky, A.; Tu, J.; Gibson, R.; Steere, T.; Graham, K.; van der Eyden, J.

    2010-11-01

    A new generation of ceramic metal halide high intensity discharge (HID) lamps has achieved high efficiencies by implementing new design concepts. The shape of the ceramic burner is optimized to withstand high temperatures with minimal thermal stress. Corrosion processes with the ceramic walls are slowed down via adoption of non-aggressive metal halide chemistry. Light losses over life due to tungsten deposition on the walls are minimized by maintaining a self-cleaning chemical process, known as tungsten cycle. All these advancements have made the new ceramic metal halide lamps comparable to high pressure sodium lamps for luminous efficacy, life, and maintenance while providing white light with high color rendering. Direct replacement of quartz metal halide lamps and systems results in the energy saving from 18 up to 50%. High resolution spectroscopy remains the major non-destructive tool for the ceramic metal halide lamps. Approaches to reliable measurements of relative partial pressures of the arc species are discussed.

  3. Method for producing hydrocarbon fuels and fuel gas from heavy polynuclear hydrocarbons by the use of molten metal halide catalysts

    DOEpatents

    Gorin, Everett

    1979-01-01

    In a process for hydrocracking heavy polynuclear carbonaceous feedstocks to produce lighter hydrocarbon fuels by contacting the heavy feedstocks with hydrogen in the presence of a molten metal halide catalyst in a hydrocracking zone, thereafter separating at least a major portion of the lighter hydrocarbon fuels from the spent molten metal halide and thereafter regenerating the spent molten metal halide by incinerating the spent molten metal halide by combustion of carbon and sulfur compounds in the spent molten metal halide in an incineration zone, the improvement comprising: (a) contacting the heavy feedstocks and hydrogen in the presence of the molten metal halide in the hydrocracking zone at reaction conditions effective to convert from about 60 to about 90 weight percent of the feedstock to lighter hydrocarbon fuels; (b) separating at least a major portion of the lighter hydrocarbon fuels from the spent molten metal halide; (c) contacting the spent molten metal halide with oxygen in a liquid phase gasification zone at a temperature and pressure sufficient to vaporize from about 25 to about 75 weight percent of the spent metal halide, the oxygen being introduced in an amount sufficient to remove from about 60 to about 90 weight percent of the carbon contained in the spent molten metal halide to produce a fuel gas and regenerated metal halide; and (d) incinerating the spent molten metal halide by combusting carbon and sulfur compounds contained therein.

  4. Electronic properties of metal-induced gap states formed at alkali-halide/metal interfaces

    NASA Astrophysics Data System (ADS)

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

    2005-04-01

    The spatial distribution and site distribution of metal-induced gap states (MIGS) are studied by thickness-dependent near-edge x-ray absorption fine structure (NEXAFS) and by comparing the cation and anion-edge NEXAFS. The thickness-dependent NEXAFS shows that the decay length of MIGS depends on an alkali-halide rather than a metal, and it is larger for alkali-halides with smaller band gap energies. By comparing the Cl-edge and K-edge NEXAFS for KCl/Cu (001) , MIGS are found to be states localizing at anion sites.

  5. Fluorescent noble metal nanoclusters

    NASA Astrophysics Data System (ADS)

    Zheng, Jie

    Water-soluble fluorescent metallic clusters at sizes comparable to the Fermi wavelength of an electron (˜0.5 nm for gold and silver) were created and their photophysical properties were investigated at the bulk and single molecule levels. We employed biocompatible dendrimer and peptide to prepare a series of strong fluorescent gold and silver clusters with chemical or photo reduction methods. Facilitated by the well-defined dendrimer size, electrospray ionization mass spectrometry indicates that the fluorescent silver nanocluster size ranges from 2 to 8 Ag atoms. The correlation of emission energy with the number of atoms, N, in each gold nanocluster is quantitatively fit for the smallest nanoclusters with no adjustable parameters by the simple scaling relation of EFermi/N1/3, in which EFermi is the Fermi energy of bulk gold. The transition energy scaling inversely with cluster radius indicates that electronic structure can be well described with the spherical jellium model and further demonstrates that these nanomaterials are "multi-electron artificial atoms". Fluorescence from these small metal clusters can be considered protoplasmonic, molecular transitions of the free conduction electrons before the onset of collective dipole oscillations occurring when a continuous density of states is reached. In addition, very strong single molecular Stokes and anti-Stokes Raman enhancement by fluorescent silver clusters was observed. Pushing to larger sizes, we also created ˜2nm diameter glutathione encapsulated luminescent gold nanoparticles. Distinct from similarly sized but nonluminescent gold nanoparticles, these 2 nm gold nanoparticles show bright, long lifetime emission but no plasmon absorption. The emission might arise from charge transfer between gold atoms and the thiol ligand. Providing the "missing link" between atomic and nanoparticle behavior in noble metals, these highly fluorescent, water-soluble gold and silver nanoclusters offer complementary transition

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

    DOEpatents

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

    1973-03-06

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

  7. First examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands

    SciTech Connect

    Wang Lamei; Fan Yong; Wang Yan; Xiao Lina; Hu Yangyang; Peng Yu; Wang Tiegang; Gao Zhongmin; Zheng Dafang; Cui Xiaobing; Xu Jiqing

    2012-07-15

    Two new organic-inorganic compounds based on polyoxometalates, metal halide clusters and organic ligands: [BW{sub 12}O{sub 40}]{sub 2}[Cu{sub 2}(Phen){sub 4}Cl](H{sub 2}4, 4 Prime -bpy){sub 4}{center_dot}H{sub 3}O{center_dot}5H{sub 2}O (1) and [HPW{sub 12}O{sub 40}][Cd{sub 2}(Phen){sub 4}Cl{sub 2}](4, 4 Prime -bpy) (2) (Phen=1, 10-phenanthroline, bpy=bipyridine), have been prepared and characterized by IR, UV-vis, XPS, XRD and single crystal X-ray diffraction analyses. Crystal structure analyses reveal that compound 1 is constructed from [BW{sub 12}O{sub 40}]{sup 5-}, metal halide clusters [Cu{sub 2}(Phen){sub 4}Cl]{sup +}and 4, 4 Prime -bpy ligands, while compound 2 is constructed from [PW{sub 12}O{sub 40}]{sup 3-}, metal halide cluster [Cd{sub 2}(Phen){sub 4}Cl{sub 2}]{sup 2+} and 4, 4 Prime -bpy ligands. Compound 1 and compound 2 are not common hybrids based on polyoxometalates and metal halide clusters, they also contain dissociated organic ligands, therefore, compound 1 and 2 are the first examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands. - Graphical Abstract: Two new compounds have been synthesized and characterized. Structure analyses revealed that the two compounds are the first examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands. Highlights: Black-Right-Pointing-Pointer First examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands. Black-Right-Pointing-Pointer Two different kinds of metal halide clusters. Black-Right-Pointing-Pointer Supramolecular structures based on polyoxometalates, metal halide clusters and organic ligands. Black-Right-Pointing-Pointer Hybridization of three different of building blocks.

  8. Metal halide arc discharge lamp having short arc length

    NASA Technical Reports Server (NTRS)

    Muzeroll, Martin E. (Inventor)

    1994-01-01

    A metal halide arc discharge lamp includes a sealed light-transmissive outer jacket, a light-transmissive shroud located within the outer jacket and an arc tube assembly located within the shroud. The arc tube assembly includes an arc tube, electrodes mounted within the arc tube and a fill material for supporting an arc discharge. The electrodes have a spacing such that an electric field in a range of about 60 to 95 volts per centimeter is established between the electrodes. The diameter of the arc tube and the spacing of the electrodes are selected to provide an arc having an arc diameter to arc length ratio in a range of about 1.6 to 1.8. The fill material includes mercury, sodium iodide, scandium tri-iodide and a rare gas, and may include lithium iodide. The lamp exhibits a high color rendering index, high lumen output and high color temperature.

  9. Direct current ballast circuit for metal halide lamp

    NASA Technical Reports Server (NTRS)

    Lutus, P. (Inventor)

    1981-01-01

    A direct current ballast circuit for a two electrode metal halide lamp is described. Said direct current ballast circuit includes a low voltage DC input and a high frequency power amplifier and power transformer for developing a high voltage output. The output voltage is rectified by diodes and filtered by inductor and capacitor to provide a regulated DC output through commutating diodes to one terminal of the lamp at the output terminal. A feedback path from the output of the filter capacitor through the bias resistor to power the high frequency circuit which includes the power amplifier and the power transformer for sustaining circuit operations during low voltage transients on the input DC supply is described. A current sensor connected to the output of the lamp through terminal for stabilizing lamp current following breakdown of the lamp is described.

  10. Optical and Spectral Studies on β Alanine Metal Halide Hybrid Crystals

    NASA Astrophysics Data System (ADS)

    Sweetlin, M. Daniel; Selvarajan, P.; Perumal, S.; Ramalingom, S.

    2011-10-01

    We have synthesized and grown β alanine metal halide hybrid crystals viz. β alanine cadmium chloride (BACC), an amino acid transition metal halide complex crystal and β alanine potassium chloride (BAPC), an amino acid alkali metal halide complex crystal by slow evaporation method. The grown crystals were found to be transparent and have well defined morphology. The optical characteristics of the grown crystals were carried out with the help of UV-Vis Spectroscopy. The optical transmittances of the spectrums show that BAPC is more transparent than BACC. The Photoluminescence of the materials were determined by the Photoluminescent Spectroscopy

  11. Reactivity of halide and pseudohalide ligands in transition-metal complexes

    SciTech Connect

    Kukushkin, Yu.N.; Kukushkin, V.Yu.

    1985-10-01

    The experimental material on the reactions of coordinated halide ligands, as well as cyanide, azido, thiocyanato, and cyanato ligands, in transition-metal complexes has been generalized in this review.

  12. High power metallic halide laser. [amplifying a copper chloride laser

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J. (Inventor)

    1982-01-01

    A laser amplification system is disclosed whereby a metallic halide vapor such as copper chloride is caused to flow through a laser amplifier and a heat exchanger in a closed loop system so that the flow rate is altered to control the temperature rise across the length of the laser amplifier. The copper atoms within the laser amplifier should not exceed a temperature of 3000 K, so that the number of copper atoms in the metastable state will not be high enough to prevent amplification in the amplifier. A molecular dissociation apparatus is provided at the input to the laser amplifier for dissociating the copper chloride into copper atoms and ions and chlorine atoms and ions. The dissociation apparatus includes a hollow cathode tube and an annular ring spaced apart from the tube end. A voltage differential is applied between the annular ring and the hollow cathode tube so that as the copper chloride flows through, it is dissociated into copper and chlorine ions and atoms.

  13. 10 CFR 431.324 - Uniform test method for the measurement of energy efficiency of metal halide ballasts.

    Code of Federal Regulations, 2010 CFR

    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 and Fixtures Test Procedures § 431.324...

  14. 10 CFR Appendix C to Subpart S of... - Enforcement for Performance Standards; Compliance Determination Procedure for Metal Halide Lamp...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Determination Procedure for Metal Halide Lamp Ballasts C Appendix C to Subpart S of Part 431 Energy DEPARTMENT... EQUIPMENT Metal Halide Lamp Ballasts and Fixtures Pt. 431, Subpt. S, App. C Appendix C to Subpart S of Part... additional units DOE has tested at the manufacturer's request.) DOE will determine compliance...

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

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 3 2014-01-01 2014-01-01 false Definitions concerning metal halide lamp ballasts and fixtures. 431.322 Section 431.322 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY PROGRAM... ballast and putting the ballast in standby mode. Active mode means the condition in which an...

  16. 10 CFR 431.322 - Definitions concerning metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 3 2011-01-01 2011-01-01 false Definitions concerning metal halide lamp ballasts and fixtures. 431.322 Section 431.322 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY PROGRAM... ballast and putting the ballast in standby mode. Active mode means the condition in which an...

  17. 10 CFR 431.322 - Definitions concerning metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 3 2013-01-01 2013-01-01 false Definitions concerning metal halide lamp ballasts and fixtures. 431.322 Section 431.322 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY PROGRAM... ballast and putting the ballast in standby mode. Active mode means the condition in which an...

  18. 10 CFR 431.322 - Definitions concerning metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 3 2012-01-01 2012-01-01 false Definitions concerning metal halide lamp ballasts and fixtures. 431.322 Section 431.322 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY PROGRAM... ballast and putting the ballast in standby mode. Active mode means the condition in which an...

  19. 10 CFR Appendix A to Subpart S of... - Compliance Statement for Metal Halide Lamp Ballasts

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...”) submits this Compliance Statement under 10 CFR Part 431 (Energy Efficiency Program for Certain Commercial... Appendix A to Subpart S of Part 431 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY... models of metal halide lamp ballasts subject to energy conservation standards specified in 10 CFR...

  20. 10 CFR 429.54 - Metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 3 2012-01-01 2012-01-01 false Metal halide lamp ballasts and fixtures. 429.54 Section 429.54 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION CERTIFICATION, COMPLIANCE, AND ENFORCEMENT FOR... and fixtures. (a) Sampling plan for selection of units for testing. (1) The requirements of §...

  1. 10 CFR 429.54 - Metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 3 2014-01-01 2014-01-01 false Metal halide lamp ballasts and fixtures. 429.54 Section 429.54 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION CERTIFICATION, COMPLIANCE, AND ENFORCEMENT FOR... and fixtures. (a) Sampling plan for selection of units for testing. (1) The requirements of §...

  2. 10 CFR 429.54 - Metal halide lamp ballasts and fixtures.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 3 2013-01-01 2013-01-01 false Metal halide lamp ballasts and fixtures. 429.54 Section 429.54 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION CERTIFICATION, COMPLIANCE, AND ENFORCEMENT FOR... and fixtures. (a) Sampling plan for selection of units for testing. (1) The requirements of §...

  3. Stability diagrams for fourfold coordination of polyvalent metal ions in molten mixtures of halide salts

    SciTech Connect

    Akdeniz, Z. Istanbul Univ. . Dept. of Physics); Tosi, M.P. . Dipt. di Fisica Teorica Argonne National Lab., IL )

    1988-11-01

    The stability of local fourfold coordination for divalent and trivalent metal ions in liquid mixtures of polyvalent metal halides and alkali halides is classified by means of structural coordinates obtained from properties of the elements. In parallel with earlier classifications of compound crystal structures and molecular shapes, the elemental properties are taken from first-principles calculations of valence electron orbitals in atoms, in the form of (i) the nodal radii of Andreoni, Baldereschi and Guizzetti or (ii) the pseudopotential radii or Zunger and Cohen. As a third alternative a classification based on Pettifor's phenomenological chemical scale of the elements is also considered. The alternative structural classification schemes that are developed from these elemental properties are generally successfully in distinguishing molten mixtures in which the available experimental evidence indicates long-lived fourfold coordination of polyvalent metal ions. In addition, Pettifor's chemical scale scheme is useful in sorting out finer details of local coordination in the liquid state. 3 figs., 71 refs.

  4. Promotion of Organic Reactions by Ultrasound: Coupling of Alkyl and Aryl Halides in the Presence of Lithium Metal and Ultrasound.

    ERIC Educational Resources Information Center

    Lash, Timothy D.; Berry, Donna

    1985-01-01

    Experiments involving the coupling of alkyl and aryl halides in the presence of lithium metal and ultrasound are described. The experiments illustrate classical Wurtz and Fittig reactions in addition to being a convenient application of organic sonochemistry. (JN)

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

    SciTech Connect

    Lutz, Jesse J.; Hutson, Jeremy M.

    2014-01-07

    We investigate the potential energy surfaces and activation energies for reactions between methyl halide molecules CH{sub 3}X (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, CH{sub 3}X + A → CH{sub 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.

  6. Theory of metal atom-water interactions and alkali halide dimers

    NASA Technical Reports Server (NTRS)

    Jordan, K. D.; Kurtz, H. A.

    1982-01-01

    Theoretical studies of the interactions of metal atoms with water and some of its isoelectronic analogs, and of the properties of alkali halides and their aggregates are discussed. Results are presented of ab initio calculations of the heats of reaction of the metal-water adducts and hydroxyhydrides of Li, Be, B, Na, Mg, and Al, and of the bond lengths and angles an; the heats of reaction for the insertion of Al into HF, H2O, NH3, H2S and CH3OH, and Be and Mg into H2O. Calculations of the electron affinities and dipole moments and polarizabilities of selected gas phase alkali halide monomers and dimers are discussed, with particular attention given to results of calculations of the polarizability of LiF taking into account electron correlation effects, and the polarizability of the dimer (LiF)2.

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

    NASA Astrophysics Data System (ADS)

    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.

  8. Sub-millimeter Spectroscopy of Astrophysically Important Molecules and Ions: Metal Hydrides, Halides, and Cyanides

    NASA Technical Reports Server (NTRS)

    Ziurys, L. M.; Flory, M. A.; Halfen, D. T.

    2006-01-01

    With the advent of SOFIA, Herschel, and SAFIR, new wavelength regions will become routinely accessible for astronomical spectroscopy, particularly at submm frequencies (0.5-1.1 THz). Molecular emission dominates the spectra of dense interstellar gas at these wavelengths. Because heterodyne detectors are major instruments of these missions, accurate knowledge of transition frequencies is crucial for their success. The Ziurys spectroscopy laboratory has been focusing on the measurement of the pure rotational transitions of astrophysically important molecules in the sub-mm regime. Of particular interest have been metal hydride species and their ions, as well as metal halides and cyanides. A new avenue of study has included metal bearing molecular ions.

  9. Development of processes for the production of solar grade silicon from halides and alkali metals

    NASA Technical Reports Server (NTRS)

    Dickson, C. R.; Gould, R. K.

    1980-01-01

    High temperature reactions of silicon halides with alkali metals for the production of solar grade silicon in volume at low cost were studied. Experiments were performed to evaluate product separation and collection processes, measure heat release parameters for scaling purposes, determine the effects of reactants and/or products on materials of reactor construction, and make preliminary engineering and economic analyses of a scaled-up process.

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

    PubMed

    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

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

    PubMed

    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

  12. Multicolor fluorescent light-emitting diodes based on cesium lead halide perovskite quantum dots

    NASA Astrophysics Data System (ADS)

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

  15. Metal-Catalyzed Carboxylation of Organic (Pseudo)halides with CO2

    PubMed Central

    2016-01-01

    The recent years have witnessed the development of metal-catalyzed reductive carboxylation of organic (pseudo)halides with CO2 as C1 source, representing potential powerful alternatives to existing methodologies for preparing carboxylic acids, privileged motifs in a myriad of pharmaceuticals and molecules displaying significant biological properties. While originally visualized as exotic cross-coupling reactions, a close look into the literature data indicates that these processes have become a fertile ground, allowing for the utilization of a variety of coupling partners, even with particularly challenging substrate combinations. As for other related cross-electrophile scenarios, the vast majority of reductive carboxylation of organic (pseudo)halides are characterized by their simplicity, mild conditions, and a broad functional group compatibility, suggesting that these processes could be implemented in late-stage diversification. This perspective describes the evolution of metal-catalyzed reductive carboxylation of organic (pseudo)halides from its inception in the pioneering stoichiometric work of Osakada to the present. Specific emphasis is devoted to the reactivity of these coupling processes, with substrates ranging from aryl-, vinyl-, benzyl- to unactivated alkyl (pseudo)halides. Despite the impressive advances realized, a comprehensive study detailing the mechanistic intricacies of these processes is still lacking. Some recent empirical evidence reveal an intriguing dichotomy exerted by the substitution pattern on the ligands utilized; still, however, some elementary steps within the catalytic cycle of these reactions remain speculative, in many instances invoking a canonical cross-coupling process. Although tentative, we anticipate that these processes might fall into more than one distinct mechanistic category depending on the substrate utilized, suggesting that investigations aimed at unraveling the mechanistic underpinnings of these processes will likely

  16. Metal halide solid-state surface treatment for nanocrystal materials

    DOEpatents

    Luther, Joseph M.; Crisp, Ryan; Beard, Matthew C.

    2016-04-26

    Methods of treating nanocrystal and/or quantum dot devices are described. The methods include contacting the nanocrystals and/or quantum dots with a solution including metal ions and halogen ions, such that the solution displaces native ligands present on the surface of the nanocrystals and/or quantum dots via ligand exchange.

  17. Antimicrobial properties of metal and metal-halide nanoparticles and their potential applications

    NASA Astrophysics Data System (ADS)

    Torrey, Jason Robert

    Heavy metals, including silver and copper, have been known to possess antimicrobial properties against bacterial, fungal, and viral pathogens. Metal nanoparticles (aggregations of metal atoms 1-200 nm in size) have recently become the subject of intensive study for their increased antimicrobial properties. In the current studies, metal and metal-halide nanoparticles were evaluated for their antibacterial efficacy. Silver (Ag), silver bromide (AgBr), silver iodide (AgI), and copper iodide (CuI) nanoparticles significantly reduced bacterial numbers of the Gram-negative Pseudomonas aeruginosa and the Gram-positive Staphylococcus aureus within 24 hours and were more effective against P. aeruginosa. CuI nanoparticles were found to be highly effective, reducing both organisms by >4.43 log 10 within 15 minutes at 60 ppm Cu. CuI nanoparticles formulated with different stabilizers (sodium dodecyl sulfate, SDS; polyvinyl pyrrolidone, PVP) were further tested against representative Gram-positive and Gram-negative bacteria, Mycobacteria, a fungus (Candida albicans ), and a non-enveloped virus (poliovirus). Both nanoparticles caused significant reductions in most of the Gram-negative bacteria within five minutes (>5.09-log10). The Gram-positive bacterial species and C. albicans were more sensitive to the CuI-SDS than the CuI-PVP nanoparticles. In contrast, the acid-fast Mycobacterium smegmatis was more resistant to CuI-SDS than CuI-PVP nanoparticles. Poliovirus was more resistant than the other organisms tested except for Mycobacterium fortuitum, which displayed the greatest resistance to CuI nanoparticles. As an example of a real world antimicrobial application, polymer coatings embedded with various concentrations of CuI nanoparticles were tested for antibacterial efficacy against P. aeruginosa and S. aureus. Polyester-epoxy powder coatings were found to display superior uniformity, stability and antimicrobial properties against both organisms (>4.92 log 10 after six hours at

  18. Evaluation of Metal Halide, Plasma, and LED Lighting Technologies for a Hydrogen Fuel Cell Mobile Light (H 2 LT)

    DOE PAGES

    Miller, L. B.; Donohoe, S. P.; Jones, M. H.; White, W. A.; Klebanoff, L. E.; Velinsky, S. A.

    2015-04-22

    This article reports on the testing and comparison of a prototype hydrogen fuel cell light tower (H2LT) and a conventional diesel-powered metal halide light trailer for use in road maintenance and construction activities. The prototype was originally outfitted with plasma lights and then with light-emitting diode (LED) luminaires. Light output and distribution, lighting energy efficiency (i.e., efficacy), power source thermal efficiency, and fuel costs are compared. The metal halide luminaires have 2.2 and 3.1 times more light output than the plasma and LED luminaires, respectively, but they require more power/lumen to provide that output. The LED luminaires have 1.6 timesmore » better light efficacy than either the metal halide or plasma luminaires. The light uniformity ratios produced by the plasma and LED towers are acceptable. The fuel cell thermal efficiency at the power required to operate the plasma lights is 48%, significantly higher than the diesel generator efficiency of 23% when operating the metal halide lights. Due to the increased efficiency of the fuel cell and the LED lighting, the fuel cost per lumen-hour of the H2LT is 62% of the metal halide diesel light tower assuming a kilogram of hydrogen is twice the cost of a gallon of diesel fuel.« less

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

    PubMed

    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

  20. Alkali metal/halide thermal energy storage systems performance evaluation

    NASA Technical Reports Server (NTRS)

    Phillips, W. M.; Stearns, J. W.

    1986-01-01

    A pseudoheat-pipe heat transfer mechanism has been demonstrated effective in terms of both total heat removal efficiency and rate, on the one hand, and system isothermal characteristics, on the other, for solar thermal energy storage systems of the kind being contemplated for spacecraft. The selection of appropriate salt and alkali metal substances for the system renders it applicable to a wide temperature range. The rapid heat transfer rate obtainable makes possible the placing of the thermal energy storage system around the solar receiver canister, and the immersing of heat transfer fluid tubes in the phase change salt to obtain an isothermal heat source.

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

    PubMed

    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. PMID:27532662

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

    PubMed

    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.

  3. Highly Tunable Colloidal Perovskite Nanoplatelets through Variable Cation, Metal, and Halide Composition.

    PubMed

    Weidman, Mark C; Seitz, Michael; Stranks, Samuel D; Tisdale, William A

    2016-08-23

    Colloidal perovskite nanoplatelets are a promising class of semiconductor nanomaterials-exhibiting bright luminescence, tunable and spectrally narrow absorption and emission features, strongly confined excitonic states, and facile colloidal synthesis. Here, we demonstrate the high degree of spectral tunability achievable through variation of the cation, metal, and halide composition as well as nanoplatelet thickness. We synthesize nanoplatelets of the form L2[ABX3]n-1BX4, where L is an organic ligand (octylammonium, butylammonium), A is a monovalent metal or organic molecular cation (cesium, methylammonium, formamidinium), B is a divalent metal cation (lead, tin), X is a halide anion (chloride, bromide, iodide), and n-1 is the number of unit cells in thickness. We show that variation of n, B, and X leads to large changes in the absorption and emission energy, while variation of the A cation leads to only subtle changes but can significantly impact the nanoplatelet stability and photoluminescence quantum yield (with values over 20%). Furthermore, mixed halide nanoplatelets exhibit continuous spectral tunability over a 1.5 eV spectral range, from 2.2 to 3.7 eV. The nanoplatelets have relatively large lateral dimensions (100 nm to 1 μm), which promote self-assembly into stacked superlattice structures-the periodicity of which can be adjusted based on the nanoplatelet surface ligand length. These results demonstrate the versatility of colloidal perovskite nanoplatelets as a material platform, with tunability extending from the deep-UV, across the visible, into the near-IR. In particular, the tin-containing nanoplatelets represent a significant addition to the small but increasingly important family of lead- and cadmium-free colloidal semiconductors.

  4. Highly Tunable Colloidal Perovskite Nanoplatelets through Variable Cation, Metal, and Halide Composition.

    PubMed

    Weidman, Mark C; Seitz, Michael; Stranks, Samuel D; Tisdale, William A

    2016-08-23

    Colloidal perovskite nanoplatelets are a promising class of semiconductor nanomaterials-exhibiting bright luminescence, tunable and spectrally narrow absorption and emission features, strongly confined excitonic states, and facile colloidal synthesis. Here, we demonstrate the high degree of spectral tunability achievable through variation of the cation, metal, and halide composition as well as nanoplatelet thickness. We synthesize nanoplatelets of the form L2[ABX3]n-1BX4, where L is an organic ligand (octylammonium, butylammonium), A is a monovalent metal or organic molecular cation (cesium, methylammonium, formamidinium), B is a divalent metal cation (lead, tin), X is a halide anion (chloride, bromide, iodide), and n-1 is the number of unit cells in thickness. We show that variation of n, B, and X leads to large changes in the absorption and emission energy, while variation of the A cation leads to only subtle changes but can significantly impact the nanoplatelet stability and photoluminescence quantum yield (with values over 20%). Furthermore, mixed halide nanoplatelets exhibit continuous spectral tunability over a 1.5 eV spectral range, from 2.2 to 3.7 eV. The nanoplatelets have relatively large lateral dimensions (100 nm to 1 μm), which promote self-assembly into stacked superlattice structures-the periodicity of which can be adjusted based on the nanoplatelet surface ligand length. These results demonstrate the versatility of colloidal perovskite nanoplatelets as a material platform, with tunability extending from the deep-UV, across the visible, into the near-IR. In particular, the tin-containing nanoplatelets represent a significant addition to the small but increasingly important family of lead- and cadmium-free colloidal semiconductors. PMID:27471862

  5. Alkaline and alkaline earth metal phosphate halides and phosphors

    SciTech Connect

    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.

  6. Metal Hydride and Alkali Halide Opacities in Extrasolar Giant Planets and Cool Stellar Atmospheres

    NASA Technical Reports Server (NTRS)

    Weck, Philippe F.; Stancil, Phillip C.; Kirby, Kate; Schweitzer, Andreas; Hauschildt, Peter H.

    2006-01-01

    The lack of accurate and complete molecular line and continuum opacity data has been a serious limitation to developing atmospheric models of cool stars and Extrasolar Giant Planets (EGPs). We report our recent calculations of molecular opacities resulting from the presence of metal hydrides and alkali halides. The resulting data have been included in the PHOENIX stellar atmosphere code (Hauschildt & Baron 1999). The new models, calculated using spherical geometry for all gravities considered, also incorporate our latest database of nearly 670 million molecular lines, and updated equations of state.

  7. Light emission of metal halide lamps under micro- and hypergravity conditions

    SciTech Connect

    Stoffels, W.W.; Kemps, P.C.M.; Beckers, J.; Kroesen, G.M.W.; Haverlag, M.

    2005-12-12

    The wavelength-integrated light output from a metal halide discharge lamp is measured for gravity conditions varying from 0 to 1.8 g during parabolic flights. The results show that the changing gravity affects the convection flow in the lamp, which in turn changes the total light output. For vertically burning lamps, the sign and magnitude of the effect can be predicted using the demixing parameter: the ratio of typical diffusion to convection times. In horizontally burning lamps at 0 g, the absence of convective mixing results in a reduced light emission.

  8. Helical instability in metal halide lamps under micro and hypergravity conditions

    SciTech Connect

    Stoffels, W.W.; Hout, F. van den; Kroesen, G.M.W.; Haverlag, M.; Keijser, R.

    2006-02-27

    The onset and rotation frequency of a helical instability in a metal halide lamp is studied for gravity conditions varying from microgravity to 1.8g during parabolic flights and at microgravity in the International Space Station. The results show that gravity-induced convection seriously alters the onset and behavior of the instability. Hypergravity and low lamp power increase the rotation frequency of the instability, which seems independent of the arc pressure. At microgravity conditions, only arc bending and no rotation has been observed. The arc bending increases with lamp power, allowing one to monitor the driving and damping forces of the instability.

  9. AMO Physics of Metal-Halide High-Intensity-Discharge Lamps

    NASA Astrophysics Data System (ADS)

    Lawler, J. E.

    2003-05-01

    Metal Halide High Intensity Discharge (MH-HID) lamps are widely used today, and are being studied for continued development, because of their superior color and efficacy [1]. MH-HID lamps are high pressure (many bar) mercury arc lamps with metal halide additives such as ScI3 or rare earth iodides. These additive salts evaporate at arc tube temperatures, the salt molecules dissociate in the arc, and the metal atoms and ions radiate strongly from the arc core to produce a pleasing white light with an excellent color temperature and color rendering index. Transition metals (e.g. Sc) and rare earth metals (e.g. Dy) have rich visible spectra. Although the plasma in these lamps is in local thermodynamic equilibrium, it is by no means easy to model due to huge temperature gradients, plasma segregation of additives, free convection cells, complex radiation transport, and other effects. Diagnostic experiments, especially in the lamps with translucent poly-crystalline alumina arc tubes [1], are equally challenging. Recent progress in the development of X-ray and optical-UV diagnostic experiments using synchrotron radiation will be summarized [2,3,4]. A possibility for combining these diagnostics to get a first look at the molecules and molecular radicals in the mantle of the arc will be described. The spectra of the metal halide molecules and radicals are almost completely unknown, but the formation of these species in the mantle is thought to protect the arc tube from chemical attack by reactive metal atoms. Recent progress toward the development of a quantitative microscopic understanding of infrared losses from the arc will be reported. [1] W. J. van den Hoek, A. G. Jack, & G. M. J. F. Luijks 2001, in Ullmann's Encyclopedia of Industrial Chemistry, 6th Ed. (Weinheim: Wiley-VCH) [2] J. J. Curry, M. Sakai, and J. E. Lawler, J. Appl. Phys. 84, 3066 (1998) [3] J. J. Curry, H. Adler, S. D. Shastri, and J. E. Lawler, Appl. Phys. Lett. 79, 1974 (2001) [4] G. A. Bonvallet, D. J

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

    PubMed

    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

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

    PubMed

    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.

  12. Chemical bonding topology of ternary transition metal-centered bismuth cluster halides: from molecules to metals.

    PubMed

    King, R Bruce

    2003-12-29

    The bismuth polyhedra in ternary transition metal-centered bismuth cluster halides may form discrete molecules or ions, infinite chains, and/or infinite layers. The chemical bonding in many of these diverse structures is related to that in deltahedral boranes exhibiting three-dimensional aromaticity by replacing the multicenter core bond in the boranes with two-center two-electron (2c-2e) bonds from the central transition metal to the nearest neighbor bismuth vertices. Examples of discrete molecules or ions include octahedral MBi(6)(micro-X)(12)(z)()(-) (X = Br, I; M = Rh, Ir, z = 3; M = Ru, z = 4) with exclusively 2c-2e bonds and pentagonal bipyramidal RhBi(7)Br(8) with a 5c-4e bond in the equatorial pentagonal plane indicative of Möbius aromaticity. The compound Ru(3)Bi(24)Br(20) contains a more complicated discrete bismuth cluster ion Ru(2)Bi(17)(micro-Br)(4)(5+), which can be dissected into a RuBi(5) closo octahedron and a RuBi(8) nido capped square antiprism bridged by a Ru(2)Bi(4)(micro-Br)(4) structural unit. In RuBi(4)X(2) (X = Br, I), the same Ru(2)Bi(4)(micro-Br)(4) structural unit bridges Bi(4) squares similar to those found in the known Zintl ion Bi(4)(2)(-) to give infinite chains of Ru(2)Bi(4) octahedra. The electron counts of the RuBi(5), RuBi(8), and Ru(2)Bi(4) polyhedra in these structures follow the Wade-Mingos rules. A different infinite chain structure is constructed from fused RhBi(7/2)Bi bicapped trigonal prisms in Rh(2)Bi(9)Br(3). This Rh(2)Bi(9)Br(3) structure can alternatively be derived from alternating Rh(2/2)Bi(4) octahedra and Rh(2/)(2)Bi(5) pentagonal bipyramids with electron counts obeying the Wade-Mingos rules. Related chemical bonding principles appear to apply to more complicated layer structures such as Pt(3)Bi(13)I(7) containing Kagomé nets of PtBi(8/2) cubes and Ni(4)Bi(12)X(3) containing linked chains of NiBi(6/3)Bi capped trigonal prisms.

  13. High-efficiency metal halide lighting systems for compact LCD projectors

    NASA Astrophysics Data System (ADS)

    Stewart, Charles N.; Rutan, Douglas M.; Savage, Daniel J.

    1997-05-01

    Compact LCD projectors require a high efficiency light source that has the smallest possible spatial extent. The objective of the lamp design must be to preserve the system etendue to ensure excellent screen illuminance. We present the results of the development of projection lighting systems that produce 1,500 to 3,000 lumens, have luminous efficacious of >= 1m/W and source sizes of metal halide lamps with very small source sizes. We have identified a series of designs for lamp/ballast systems that give the user an option of performance sets. We will describe recent work on the design and characterization of a long life 50 Watt, 1.2 m arc gap metal halide lighting system that produces 3,200 lumens. A theoretical characterization of the optical efficiency of an arbitrary projection optical system through discussion of the arc efficiency and the system etendue will be presented.

  14. Transition metal ion-assisted photochemical generation of alkyl halides and hydrocarbons from carboxylic acids

    SciTech Connect

    Carraher, Jack; Pestovsky, Oleg; Bakac, Andreja

    2012-03-14

    Near-UV photolysis of aqueous solutions of propionic acid and aqueous Fe3+ in the absence of oxygen generates a mixture of hydrocarbons (ethane, ethylene and butane), carbon dioxide, and Fe2+. The reaction becomes mildly catalytic (about five turnovers) in the presence of oxygen which converts a portion of alkyl radicals to oxidizing intermediates that reoxidize Fe2+. The photochemistry in the presence of halide ions (X− = Cl−, Br−) generates ethyl halides via halogen atom abstraction from FeXn3−n by ethyl radicals. Near-quantitative yields of C2H5X are obtained at ≥0.05 M X−. Competition experiments with Co(NH3)5Br2+ provided kinetic data for the reaction of ethyl radicals with FeCl2+ (k = (4.0 ± 0.5) × 106 M−1 s−1) and with FeBr2+ (k = (3.0 ± 0.5) × 107 M−1 s−1). Photochemical decarboxylation of propionic acid in the presence of Cu2+ generates ethylene and Cu+. Longer-chain acids also yield alpha olefins as exclusive products. These reactions become catalytic under constant purge with oxygen which plays a dual role. It reoxidizes Cu+ to Cu2+, and removes gaseous olefins to prevent accumulation of Cu+(olefin) complexes and depletion of Cu2+. The results underscore the profound effect that the choice of metal ions, the medium, and reaction conditions exert on the photochemistry of carboxylic acids.

  15. Metal-encapsulated organolead halide perovskite photocathode for solar-driven hydrogen evolution in water

    NASA Astrophysics Data System (ADS)

    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.

  16. Silicon Halide-alkali Metal Flames as a Source of Solar Grade Silicon

    NASA Technical Reports Server (NTRS)

    Olson, D. B.; Gould, R. K.

    1979-01-01

    A program is presented which was aimed at determining the feasibility of using high temperature reactions of alkali metals and silicon halides to produce low cost solar-grade silicon. Experiments are being conducted to evaluate product separation and collection processes, measure heat release parameters for scaling purposes, and determine the effects of the reactants and/or products on materials of reactor construction. During the current reporting period, the results of heat release experiments were used to design and construct a new type of thick-wall graphite reactor to produce larger quantities of silicon. A reactor test facility was constructed. Material compatibility tests were performed for Na in contact with graphite and several coated graphites. All samples were rapidly degraded at T = 1200K, while samples retained structural strength at 1700K. Pyrolytic graphite coatings cracked and separated from substances in all cases.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Extremely bulky amido first row transition metal(II) halide complexes: potential precursors to low coordinate metal-metal bonded systems.

    PubMed

    Hicks, Jamie; Jones, Cameron

    2013-04-01

    Reactions of the extremely bulky potassium amide complexes, [KL'(η(6)-toluene)] or [KL"] (L'/L" = N(Ar*)(SiR3), Ar* = C6H2{C(H)Ph2}2Me-2,6,4; R = Me (L') or Ph (L")), with a series of first row transition metal(II) halides have yielded 10 rare examples of monodentate amido first row transition metal(II) halide complexes, all of which were crystallographically characterized. They encompass the dimeric, square-planar chromium complexes, [{CrL'(THF)(μ-Cl)}2] and [{CrL"(μ-Cl)}2], the latter of which displays intramolecular η(2)-Ph···Cr interactions; the dimeric tetrahedral complexes, [{ML'(THF)(μ-Br)}2] (M = Mn or Fe), [{ML"(THF)(μ-X)}2] (M = Mn, Fe or Co; X = Cl or Br) and [{CoL"(μ-Cl)}2] (which displays intramolecular η(2)-Ph···Co interactions); and the monomeric zinc amides, [L'ZnBr(THF)] (three-coordinate) and [L"ZnBr] (two-coordinate). Solution state magnetic moment determinations on all but one of the paramagnetic compounds show them to be high-spin systems. Throughout, comparisons are made with related bulky terphenyl transition metal(II) halide complexes, and the potential for the use of the prepared complexes as precursors to low-valent transition metal systems is discussed.

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

    PubMed

    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.

  1. Transient Absorption and Time-Resolved Fluorescence Studies of Solvated Ruthenium Di-Bipyridine Pseudo-Halide Complexes

    NASA Astrophysics Data System (ADS)

    Compton, R.; Weidinger, D.; Owrutsky, J. C.

    2012-06-01

    Time-resolved IR and fluorescence measurements were performed to probe the vibrational and electronic properties, respectively, of ruthenium di-bipyridine pseudo-halide (Ru(Bpy){_2}(X){_2} (where X = CN, N{_3} or NCS)) complexes. Vibrational energy relaxation (VER) times were determined for the complexes dissolved in dimethyl sulfoxide (DMSO) with a trend in VER time of NCS > CN > N{_3}. A similar trend and comparable absolute rates for NCS- and N3- were previously observed by our group and others for simple inorganic anions in solution, suggesting a minimal contribution due to complexation. Measurements of the VER time of the CN complex in various solvents provide VER times in ethanol (42.3 ps) and DMSO (53.3 ps), which shows that protic solvents promote the relaxation. Time-resolved fluorescence measurements indicate a strong ligand dependence, with a factor of five decrease in the excited electronic state decay time from the CN (215 ns) to the NCS (39 ns) complex. A solvent dependence of the CN complex reveals a nearly 3-fold increase in the fluorescence decay time from acetonitrile (70 ns) to DMSO (215 ns).

  2. Effects and mechanism of sodium loss in quartz metal halide lamps

    NASA Astrophysics Data System (ADS)

    van Erk, W.; Tu, J.; Suijker, J.

    2005-09-01

    Several analytical techniques have been used to obtain a detailed mass balance of a test series of metal halide lamps, containing sodium and scandium iodide. The lamps were made to burn for 5000 h and showed appreciable sodium loss, up to 45% at the end of 5000 h. In burners dosed with an excess of scandium metal the loss of sodium caused an increase in the amount of scandium iodide. Thermodynamic modelling showed that scandium, present as a silicate, is converted into scandium iodide. This implies that the loss of sodium will cause a significant shift in the composition of the salt pool in the burner and this will affect the light technical properties and lifetime determining phenomena. Sodium that has escaped from the arc tube has a certain propensity for being deposited on the metal frame in the outer bulb. Since it is a very effective electron emitter, the emission of electrons by photo- and thermionic emission will be strongly enhanced. It is argued that this must have a significant effect on the sodium loss process and on the interpretation of experiments done in the past to reveal the mechanism of sodium loss. A two-phase model for sodium loss is proposed.

  3. Metal-enhanced fluorescence of single green fluorescent protein (GFP)

    SciTech Connect

    Fu Yi; Zhang Jian; Lakowicz, Joseph R.

    2008-11-28

    The green fluorescent protein (GFP) has emerged as a powerful reporter molecule for monitoring gene expression, protein localization, and protein-protein interaction. However, the detection of low concentrations of GFPs is limited by the weakness of the fluorescent signal and the low photostability. In this report, we observed the proximity of single GFPs to metallic silver nanoparticles increases its fluorescence intensity approximately 6-fold and decreases the decay time. Single protein molecules on the silvered surfaces emitted 10-fold more photons as compared to glass prior to photobleaching. The photostability of single GFP has increased to some extent. Accordingly, we observed longer duration time and suppressed blinking. The single-molecule lifetime histograms indicate the relatively heterogeneous distributions of protein mutants inside the structure.

  4. Electronic properties of metal-induced gap states at insulator/metal interfaces: Dependence on the alkali halide and the possibility of excitonic mechanism of superconductivity

    NASA Astrophysics Data System (ADS)

    Arita, Ryotaro; Tanida, Yoshiaki; Kuroki, Kazuhiko; Aoki, Hideo

    2004-03-01

    Motivated from the experimental observation of metal-induced gap states (MIGS) at insulator/metal interfaces by Kiguchi et al. [Phys. Rev. Lett. 90, 196803 (2003)], we have theoretically investigated the electronic properties of MIGS at interfaces between various alkali halides and a metal represented by a jellium with the first-principles density-functional method. We have found that, on top of the usual evanescent state, MIGS generally have appreciable amplitudes on halogen sites with a pz-like character, whose penetration depth (λ) is as large as half the lattice constant of bulk alkali halides. This implies that λ, while little dependent on the carrier density in the jellium, is dominated by the energy gap of the alkali halide, and is scaled by the lattice constant, where λLiF<λLiCl<λLiI. We also propose a possibility of the MIGS working favorably for the exciton-mediated superconductivity, especially in a system where ˜10 Å of metal is sandwiched by alkali halide substrates.

  5. Silicon halide-alkali metal flames as a source of solar grade silicon. Final report

    SciTech Connect

    Olson, D.B.; Miller, W.J.; Gould, R.K.

    1980-01-01

    The object of this program was to determine the feasibility of using continuous high-temperature reactions of alkali metals and silicon halides to produce silicon in large quantities and of suitable purity for use in the production of photovoltaic solar cells. Equilibrium calculations showed that a range of conditions were available where silicon was produced as a condensed phase but the byproduct alkali metal salt was a vapor. A process was proposed using the vapor phase reaction of Na with SiCl/sub 4/. Low pressure experiments were performed demonstrating that free silicon was produced and providing experience with the construction of reactant vapor generators. Further experiments at higher reagent flow rates were performed in a low temperature flow tube configuration with co-axial injection of reagents. Relatively pure silicon was produced in these experiments. A high temperature graphite flow tube was built and continuous separation of Si from NaCl was demonstrated. A larger-scaled well-stirred reactor was built. Experiments were performed to investigate the compatibility of graphite-based reactor materials of construction with sodium. At 1100 to 1200 K none of these materials were found to be suitable. At 1700 K the graphites performed well with little damage except to coatings of pyrolytic graphite and silicon carbide which were damaged.

  6. The molten state of trivalent metal halides and oxides : recent progress.

    SciTech Connect

    Akdeniz, Z.; Price, D. L.; Saboungi, M.-L.; Tosi, M. P.; Materials Science Division; International Centre for Theoretical Physics; Univ. of istanbul; Istituto Nazionale di Fisica della Materia and Classe di Scienze

    1998-01-01

    The structures of trivalent metal halides and oxides have been reviewed with emphasis on the stability of a six-fold coordination of metal ions, e.g. in YCl{sub 3} and YO{sub 3}, and its competition with a four-fold coordination, e.g. in AlCl{sub 3} and AlO{sub 3}. Upon melting in some cases the crystalline coordination is preserved, leading to the formation of either an ionic network or a molecular structure, while in other cases a transition to a different kind of structure occurs, such as that from an ionic to a molecular-type structure. Specific examples will be selected from recent experiments in which structural information at the partial level and Raman spectra have been obtained, and the X-ray average structure has been complemented by electrical transport data. Directions for future work with a potential impact on our understanding of the complex structure-property relations in the crystalline and liquid state have been proposed.

  7. Metallic halide lights and lighting systems. (Latest citations from the US Patent Bibliographic file with exemplary claims). Published Search

    SciTech Connect

    Not Available

    1994-11-01

    The bibliography contains citations of selected patents concerning the design and operation of metallic halide lights and lighting systems. High pressure, high intensity, and low wattage discharge lamps are described. Citations discuss power sources, lamp life, lamp control circuits, thermal switches, and heat reflective coatings. Applications in sport stadium lighting, vehicle headlights, and crop-lighting are included. (Contains a minimum of 170 citations and includes a subject term index and title list.)

  8. Enhanced Organo-Metal Halide Perovskite Photoluminescence from Nanosized Defect-Free Crystallites and Emitting Sites.

    PubMed

    Tian, Yuxi; Merdasa, Aboma; Unger, Eva; Abdellah, Mohamed; Zheng, Kaibo; McKibbin, Sarah; Mikkelsen, Anders; Pullerits, Tõnu; Yartsev, Arkady; Sundström, Villy; Scheblykin, Ivan G

    2015-10-15

    Photoluminescence (PL) of organo-metal halide perovskite semiconductors can be enhanced by several orders of magnitude by exposure to visible light. We applied PL microscopy and super-resolution optical imaging to investigate this phenomenon with spatial resolution better than 10 nm using films of CH3NH3PbI3 prepared by the equimolar solution-deposition method, resulting in crystals of different sizes. We found that PL of ∼100 nm crystals enhances much faster than that of larger, micrometer-sized ones. This crystal-size dependence of the photochemical light passivation of charge traps responsible for PL quenching allowed us to conclude that traps are present in the entire crystal volume rather than at the surface only. Because of this effect, "dark" micrometer-sized perovskite crystals can be converted into highly luminescent smaller ones just by mechanical grinding. Super-resolution optical imaging shows spatial inhomogeneity of the PL intensity within perovskite crystals and the existence of <100 nm-sized localized emitting sites. The possible origin of these sites is discussed. PMID:26722793

  9. Charge-Carrier Dynamics in Organic-Inorganic Metal Halide Perovskites

    NASA Astrophysics Data System (ADS)

    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.

  10. Charge-Carrier Dynamics in Organic-Inorganic Metal Halide Perovskites.

    PubMed

    Herz, Laura M

    2016-05-27

    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.

  11. Metal-encapsulated organolead halide perovskite photocathode for solar-driven hydrogen evolution in water

    PubMed Central

    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

  12. Silicon halide-alkali metal flames as a source of solar grade silicon

    NASA Technical Reports Server (NTRS)

    Olsen, D. B.; Miller, W. J.

    1979-01-01

    The feasibility of using alkali metal-silicon halide diffusion flames to produce solar-grade silicon in large quantities and at low cost is demonstrated. Prior work shows that these flames are stable and that relatively high purity silicon can be produced using Na + SiCl4 flames. Silicon of similar purity is obtained from Na + SiF4 flames although yields are lower and product separation and collection are less thermochemically favored. Continuous separation of silicon from the byproduct alkali salt was demonstrated in a heated graphite reactor. The process was scaled up to reduce heat losses and to produce larger samples of silicon. Reagent delivery systems, scaled by a factor of 25, were built and operated at a production rate of 0.5 kg Si/h. Very rapid reactor heating rates are observed with wall temperatures reaching greater than 2000 K. Heat release parameters were measured using a cooled stainless steel reactor tube. A new reactor was designed.

  13. Silicon halide-alkali metal flames as a source of solar grade silicon

    NASA Technical Reports Server (NTRS)

    Olson, D. B.; Miller, W. J.; Gould, R. K.

    1980-01-01

    The feasibility of using continuous high-temperature reactions of alkali metals and silicon halides to produce silicon in large quantities and of suitable purity for use in the production of photovoltaic solar cells was demonstrated. Low pressure experiments were performed demonstrating the production of free silicon and providing experience with the construction of reactant vapor generators. Further experiments at higher reagent flow rates were performed in a low temperature flow tube configuration with co-axial injection of reagents and relatively pure silicon was produced. A high temperature graphite flow tube was built and continuous separation of Si from NaCl was demonstrated. A larger scaled well stirred reactor was built. Experiments were performed to investigate the compatability of graphite based reactor materials of construction with sodium. At 1100 to 1200 K none of these materials were found to be suitable. At 1700 K the graphites performed well with little damage except to coatings of pyrolytic graphite and silicon carbide which were damaged.

  14. Assessment of metal halide lamp for the illumination of LCD-based projection display

    NASA Astrophysics Data System (ADS)

    Wang, K. C.; Huang, C. H.; Chen, How-More; Chiang, Cyril C.

    1995-04-01

    Apparatus consists of a short-arc metal halide lamp and a dichroic mirror in parabolic-like shape has been widely employed in portable projection TV (PTV) as the light source to illuminate liquid crystal display (LCD) panels. Advantages include high luminous efficacy, near-daylight color temperature, and superior color rendering index. At MRL or ITRI we have successfully developed such light sources of 150 W input power, using Dy-Nd-Cs iodides in appropriate amount. Nominal efficiency exceeds 73 lm/w with color temperature of 6500 K. Higher efficiency better than 80 lm/w was possible at the cost of color temperature. Continuous lifetime test has been conducted for 3000 hours, compared to effective `ON' history in ON/OFF start-ups longer than 2300 hours. Luminous decay in the ON/OFF test was observed lower than 35%. A 70% reduction of the initial value is estimated around 2000 hours, better than most of the commercial counterparts. Quality of image in display is improved by matching illumination spectrum to the characteristics of flat panel devices. Monochromes after being projected are compared using (u,v) coordinates against NTSC data. Computer simulation was integrated to resolve the brightness distribution on a 3.6-inch (diagonal) LCD panel, with which lamp fixture was precisely determined. Know-hows leading to more favorable PTV systems lie in the combination of lamp spectra and color filters that comprises of the core interests in lamp assessment.

  15. Liquid-crystal luminaire consisting of an optical shutter and a metal halide lamp.

    PubMed

    Takizawa, K; Fujii, T; Fujikake, H; Hirabayashi, T; Tanaka, Y; Hara, K; Takano, S; Asakawa, H; Kita, H

    1999-04-20

    We made a liquid-crystal (LC) luminaire for the first time to our knowledge by combining a metal halide lamp and an optical shutter composed of a compound of a very high nematic-isotropic point (172 degrees C) LC and a polymer (CLCP). The shutter can modulate high-power light independently of the state of polarization because the CLCP film becomes transparent or opalescent when either sufficiently high or no voltage is applied to it. To solve the problem, which is peculiar to CLCP films, that the color temperature of light modulated by the film changes with the film's transmittance, a pulse-width modulation method that varies the time ratio of the on and off states of the shutter was developed. The performance characteristics of the luminaire were as follows: illuminance range, 192 to 10,400 lx at a distance of 5 m from the luminaire; rise and decay times, 1.4 and 1.5 ms; color temperature, 4060-5600 K; operation room temperature, approximately 150 degrees C; stable operation time, more than 2000 h. Experimental results show the feasibility of applications of this luminaire in various fields, including television, movie, and stage lighting. PMID:18319829

  16. Spectral Changes in Metal Halide and High-Pressure Sodium Lamps Equipped with Electronic Dimming

    NASA Technical Reports Server (NTRS)

    Bubenheim, David L.; Sargis, Raman; Wilson, David

    1995-01-01

    Electronic dimming of high-intensity discharge lamps offers control of Photosynthetic Photon Flux (PPF) but is often characterized as causing significant spectral changes. Growth chambers with 400-W Metal Halide (MH) and High-Pressure Sodium (HPS) lamps were equipped with a dimmer system using Silicon-Controlled Rectifiers (SCR) as high-speed switches. Phase control operation turned the line power off for some period of the alternating current cycle. At full power, the electrical input to HPS and MH lamps was 480 W (root mean squared) and could be decreased to 267 W and 428 W, respectively, before the arc was extinguished. Concomitant with this decrease in input power, PPF decreased by 60% in HPS and 50% in MH. The HPS lamp has characteristic spectral peaks at 589 and 595 nm. As power to the HPS lamps was decreased, the 589-nm peak remained constant while the 595-nm peak decreased, equaling the 589-nm peak at 345-W input, and 589-nm peak was almost absent at 270-W input. The MH lamp has a broader spectral output but also has a peak at 589 nm and another smaller peak at 545 nm. As input power approached 428 W, the 589-nm peak shifted to 570 nm. While the spectrum changed as input power was decreased in the MH and HPS lamps, the phytochrome equilibrium ratio (P(sub ft):P(sub tot)) remains unchanged for both lamp types.

  17. Metal-encapsulated organolead halide perovskite photocathode for solar-driven hydrogen evolution in water.

    PubMed

    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

  18. Temperature measurements using selected Tm and Dy lines in Metal Halide Lamps

    NASA Astrophysics Data System (ADS)

    Aiura, Y.; Lawler, J. E.

    2003-10-01

    The 1 m Fourier transform spectrometer (FTS) at the National Solar Observatory on Kitt Peak was used to record UV to IR emission spectra of Metal Halide-High Intensity Discharge (MH-HID) lamps with doses containing rare earth salts. All intrinsic structure is fully resolved in these spectra. Many additive lines were found to have nearly perfect Lorentzian profiles and to be surprisingly narrow (FWHM < 1 cm-1) [1]. Fitting these profiles to Lorentzian functions provides a sensitive test for radiation trapping and line blending [1]. We have used this fitting approach along with recently measured absolute transition probabilities [2,3] to select sets of lines in Tm I, Tm II, Dy I, and Dy II which are good for temperature determinations in MH-HID lamps. [1 ] H. Adler, L. Riley, & J. E. Lawler in Proceedings of the Ninth International Symposium on the Science and Technology of Light Sources LS:9 ed: R S Bergman (2001, Ithaca: Cornell University Press) p 129. [2] M. E. Wickliffe & J. E. Lawler, J. Opt. Soc. Am. B 14, 737 (1997) [3] M. E. Wickliffe, J. E. Lawler, & G. Nave, J. Quant. Spectrosc. Radiat. Transfer 66, 363 (2000).

  19. Spectral Changes in Metal Halide and High-pressure Sodium Lamps Equipped with Electronic Dimming

    NASA Technical Reports Server (NTRS)

    Bubenheim, David L.; Sargis, Raman; Wilson, David

    1995-01-01

    Electronic dimming of high-intensity discharge lamps offers control of photosynthetic photon flux (PPF) but is often characterized as causing significant spectral changes. Growth chambers with 400-W metal halide (MH) and high-pressure sodium (HPS) lamps were equipped with a dimmer system using silicon-controlled rectifiers (SCR) as high-speed switches. Phase control operation turned the line power off for some period of the alternating current cycle. At full power, the electrical input to HPS and MH lamps was 480 W (root mean squared) and could be decreased to 267 W and 428 W, respectively, before the arc was extinguished. Concomitant with this decrease in input power, PPF decreased by 60% in HPS and 50% in MH. The HPS lamp has characteristic spectral peaks at 589 and 595 nm. As power to the HPS lamps was decreased, the 589-nm peak remained constant while the 595-nm peak decreased, equaling the 589-nm peak at 345-W input, and the 589-nm peak was almost absent at 270-W input. The MH lamp has a broader spectral output but also has a peak at 589 nm and another smaller peak at 545 nm. As input power to the MH lamps decreased, the peak at 589 diminished to equal the 545-nm peak. As input power approached 428 W, the 589-nm peak shifted to 570 nm. While the spectrum changed as input power was decreased in the MH and HPS lamps, the phytochrome equilibrium ratio (P(sub fr):P(sub tot)) remains unchanged for both lamp types.

  20. Metal-Induced Gap States at Well Defined Alkali-Halide/Metal Interfaces

    NASA Astrophysics Data System (ADS)

    Kiguchi, Manabu; Arita, Ryotaro; Yoshikawa, Genki; Tanida, Yoshiaki; Katayama, Masao; Saiki, Koichiro; Koma, Atsushi; Aoki, Hideo

    2003-05-01

    In order to search for states specific to insulator/metal interfaces, we have studied epitaxially grown interfaces with element-selective near edge x-ray absorption fine structure. An extra peak is observed below the bulk edge onset for LiCl films on Cu and Ag substrates. The nature of chemical bonds as probed by x-ray photoemission spectroscopy and Auger electron spectroscopy remains unchanged, so we regard this as evidence for metal-induced gap states (MIGS) formed by the proximity to a metal, rather than local bonds at the interface. The dependence on the film thickness shows that the MIGS are as thin as one monolayer. An ab initio electronic structure calculation supports the existence of the MIGS that are strongly localized at the interface.

  1. Metal-induced gap states at well defined alkali-halide/metal interfaces.

    PubMed

    Kiguchi, Manabu; Arita, Ryotaro; Yoshikawa, Genki; Tanida, Yoshiaki; Katayama, Masao; Saiki, Koichiro; Koma, Atsushi; Aoki, Hideo

    2003-05-16

    In order to search for states specific to insulator/metal interfaces, we have studied epitaxially grown interfaces with element-selective near edge x-ray absorption fine structure. An extra peak is observed below the bulk edge onset for LiCl films on Cu and Ag substrates. The nature of chemical bonds as probed by x-ray photoemission spectroscopy and Auger electron spectroscopy remains unchanged, so we regard this as evidence for metal-induced gap states (MIGS) formed by the proximity to a metal, rather than local bonds at the interface. The dependence on the film thickness shows that the MIGS are as thin as one monolayer. An ab initio electronic structure calculation supports the existence of the MIGS that are strongly localized at the interface.

  2. Technetium Dichloride: A New Binary Halide Containing Metal-Metal Multiple Bonds

    SciTech Connect

    Poineau, Frederic; Malliakas, Christos D.; Weck, Philippe F.; Scott, Brian L.; Johnstone, Erik V.; Forster, Paul M.; Kim, Eunja; Kanatzidis, Mercouri G.; Czerwinski, Kenneth R.; Sattelberge, Alfred P.

    2011-10-19

    Technetium dichloride has been discovered. It was synthesized from the elements and characterized by several physical techniques, including single crystal X-ray diffraction. In the solid state, technetium dichloride exhibits a new structure type consisting of infinite chains of face sharing [Tc{sub 2}Cl{sub 8}] rectangular prisms that are packed in a commensurate supercell. The metal-metal separation in the prisms is 2.127(2) {angstrom}, a distance consistent with the presence of a Tc {triple_bond} Tc triple bond that is also supported by electronic structure calculations.

  3. Technetium dichloride : a new binary halide containing metal-metal multiple bonds.

    SciTech Connect

    Poineau, F.; Malliakas, C. D.; Weck, P. F.; Scott, B. L.; Johnstone, E. V.; Forster, P. M.; Kim, E.; Kanatzidis, M. G.; Czerwinski, K. R.; Sattelberger, A. P.

    2011-06-15

    Technetium dichloride has been discovered. It was synthesized from the elements and characterized by several physical techniques, including single crystal X-ray diffraction. In the solid state, technetium dichloride exhibits a new structure type consisting of infinite chains of face sharing [Tc{sub 2}Cl{sub 8}] rectangular prisms that are packed in a commensurate supercell. The metal-metal separation in the prisms is 2.127(2) {angstrom}, a distance consistent with the presence of a Tc {triple_bond} Tc triple bond that is also supported by electronic structure calculations.

  4. Evaluation of Metal Halide, Plasma, and LED Lighting Technologies for a Hydrogen Fuel Cell Mobile Light (H 2 LT)

    SciTech Connect

    Miller, L. B.; Donohoe, S. P.; Jones, M. H.; White, W. A.; Klebanoff, L. E.; Velinsky, S. A.

    2015-04-22

    This article reports on the testing and comparison of a prototype hydrogen fuel cell light tower (H2LT) and a conventional diesel-powered metal halide light trailer for use in road maintenance and construction activities. The prototype was originally outfitted with plasma lights and then with light-emitting diode (LED) luminaires. Light output and distribution, lighting energy efficiency (i.e., efficacy), power source thermal efficiency, and fuel costs are compared. The metal halide luminaires have 2.2 and 3.1 times more light output than the plasma and LED luminaires, respectively, but they require more power/lumen to provide that output. The LED luminaires have 1.6 times better light efficacy than either the metal halide or plasma luminaires. The light uniformity ratios produced by the plasma and LED towers are acceptable. The fuel cell thermal efficiency at the power required to operate the plasma lights is 48%, significantly higher than the diesel generator efficiency of 23% when operating the metal halide lights. Due to the increased efficiency of the fuel cell and the LED lighting, the fuel cost per lumen-hour of the H2LT is 62% of the metal halide diesel light tower assuming a kilogram of hydrogen is twice the cost of a gallon of diesel fuel.

  5. Release of halide ions from the buried active site of the haloalkane dehalogenase LinB revealed by stopped-flow fluorescence analysis and free energy calculations.

    PubMed

    Hladilkova, Jana; Prokop, Zbynek; Chaloupkova, Radka; Damborsky, Jiri; Jungwirth, Pavel

    2013-11-21

    Release of halide ions is an essential step of the catalytic cycle of haloalkane dehalogenases. Here we describe experimentally and computationally the process of release of a halide anion from the buried active site of the haloalkane dehalogenase LinB. Using stopped-flow fluorescence analysis and umbrella sampling free energy calculations, we show that the anion binding is ion-specific and follows the ordering I(-) > Br(-) > Cl(-). We also address the issue of the protonation state of the catalytic His272 residue and its effect on the process of halide release. While deprotonation of His272 increases binding of anions in the access tunnel, we show that the anionic ordering does not change with the switch of the protonation state. We also demonstrate that a sodium cation could relatively easily enter the active site, provided the His272 residue is singly protonated, and replace thus the missing proton. In contrast, Na(+) is strongly repelled from the active site containing the doubly protonated His272 residue. Our study contributes toward understanding of the reaction mechanism of haloalkane dehalogenase enzyme family. Determination of the protonation state of the catalytic histidine throughout the catalytic cycle remains a challenge for future studies.

  6. Antenna induced hot restrike of a ceramic metal halide lamp recorded by high-speed photography

    NASA Astrophysics Data System (ADS)

    Hermanns, P.; Hoebing, T.; Bergner, A.; Ruhrmann, C.; Awakowicz, P.; Mentel, J.

    2016-03-01

    The hot restrike is one of the biggest challenges in operating ceramic metal halide lamps with mercury as buffer gas. Compared to a cold lamp, the pressure within a ceramic burner is two orders of magnitude higher during steady state operation due to the high temperature of the ceramic tube and the resulting high mercury vapour pressure. Room temperature conditions are achieved after 300 s of cooling down in a commercial burner, enclosed in an evacuated outer bulb. At the beginning of the cooling down, ignition voltage rises up to more than 14 kV. A significant reduction of the hot-restrike voltage can be achieved by using a so called active antenna. It is realized by a conductive sleeve surrounding the burner at the capillary of the upper electrode. The antenna is connected to the lower electrode of the lamp, so that its potential is extended to the vicinity of the upper electrode. An increased electric field in front of the upper electrode is induced, when an ignition pulse is applied to the lamp electrodes. A symmetrically shaped ignition pulse is applied with an amplitude, which is just sufficient to re-ignite the hot lamp. The re-ignition, 60 s after switching off the lamp, when the mercury pressure starts to be saturated, is recorded for both polarities of the ignition pulse with a high-speed camera, which records four pictures within the symmetrically shaped ignition pulse with exposure times of 100 ns and throws of 100 ns. The pictures show that the high electric field and its temporal variation establish a local dielectric barrier discharge in front of the upper electrode inside the burner, which covers the inner wall of the burner with a surface charge. It forms a starting point of streamers, which may induce the lamp ignition predominantly within the second half cycle of the ignition pulse. It is found out that an active antenna is more effective when the starting point of the surface streamer in front of the sleeve is a negative surface charge on the

  7. Universal scaling of potential energy functions describing intermolecular interactions. II. The halide-water and alkali metal-water interactions

    SciTech Connect

    Werhahn, Jasper C.; Akase, Dai; Xantheas, Sotiris S.

    2014-08-14

    The scaled versions of the newly introduced [S. S. Xantheas and J. C. Werhahn, J. Chem. Phys.141, 064117 (2014)] generalized forms of some popular potential energy functions (PEFs) describing intermolecular interactions – Mie, Lennard-Jones, Morse, and Buckingham exponential-6 – have been used to fit the ab initio relaxed approach paths and fixed approach paths for the halide-water, X-(H2O), X = F, Cl, Br, I, and alkali metal-water, M+(H2O), M = Li, Na, K, Rb, Cs, interactions. The generalized forms of those PEFs have an additional parameter with respect to the original forms and produce fits to the ab initio data that are between one and two orders of magnitude better in the χ2 than the original PEFs. They were found to describe both the long-range, minimum and repulsive wall of the respective potential energy surfaces quite accurately. Overall the 4-parameter extended Morse (eM) and generalized Buckingham exponential-6 (gBe-6) potentials were found to best fit the ab initio data for these two classes of ion-water interactions. Finally, the fitted values of the parameter of the (eM) and (gBe-6) PEFs that control the repulsive wall of the potential correlate remarkably well with the ionic radii of the halide and alkali metal ions.

  8. Spectral variation of fluorescence lifetime near single metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Jia; Krasavin, Alexey V.; Webster, Linden; Segovia, Paulina; Zayats, Anatoly V.; Richards, David

    2016-02-01

    We explore the spectral dependence of fluorescence enhancement and the associated lifetime modification of fluorescent molecules coupled to single metal nanoparticles. Fluorescence lifetime imaging microscopy and single-particle dark-field spectroscopy are combined to correlate the dependence of fluorescence lifetime reduction on the spectral overlap between the fluorescence emission and the localised surface plasmon (LSP) spectra of individual gold nanoparticles. A maximum lifetime reduction is observed when the fluorescence and LSP resonances coincide, with good agreement provided by numerical simulations. The explicit comparison between experiment and simulation, that we obtain, offers an insight into the spectral engineering of LSP mediated fluorescence and may lead to optimized application in sensing and biomedicine.

  9. Mesoscopic photosystems for solar light harvesting and conversion: facile and reversible transformation of metal-halide perovskites.

    PubMed

    Harms, Hauke Arne; Tétreault, Nicolas; Pellet, Norman; Bensimon, Michaël; Grätzel, Michael

    2014-01-01

    Recently, hybrid organic-inorganic metal halide perovskites have gained prominence as potent light harvesters in thin film solid-state photovoltaics. In particular the solar-to-electric power conversion efficiency (PCE) of devices using CH(3)NH(3)PbI(3) as sensitizer has increased from 3 to 20.1% within only a few years. This key material can be prepared by solution processing from PbI(2) and CH(3)NH(3)I in one step or by sequential deposition. In the latter case an electron capturing support such as TiO(2) is first covered with PbI(2), which upon exposure to a CH(3)NH(3)I solution is converted to the perovskite. Here we apply for the first time quartz crystal microbalance (QCMD) measurements in conjunction with X-ray diffraction and scanning electron microscopy to analyse the dynamics of the conversion of PbI(2) to CH(3)NH(3)PbI(3). Employing 200 nm thick PbI(2) films as substrates we discover that the CH(3)NH(3)I insertion in the PbI(2) is reversible, with the extraction into the solvent isopropanol occurring on the same time scale of seconds as the intercalation process. This offers an explanation for the strikingly rapid and facile exchange of halide ions in CH(3)NH(3)PbX(3) by solution processing at room temperature. PMID:25643832

  10. Metal Halide Solid-State Surface Treatment for High Efficiency PbS and PbSe QD Solar Cells

    SciTech Connect

    Crisp, R. W.; Kroupa, D. M.; Marshall, A. R.; Miller, E. M.; Zhang, J.; Beard, M. C.; Luther, J. M.

    2015-04-24

    We developed a layer-by-layer method of preparing PbE (E = S or Se) quantum dot (QD) solar cells using metal halide (PbI2, PbCl2, CdI2, or CdCl2) salts dissolved in dimethylformamide to displace oleate surface ligands and form conductive QD solids. The resulting QD solids have a significant reduction in the carbon content compared to films treated with thiols and organic halides. We find that the PbI2 treatment is the most successful in removing alkyl surface ligands and also replaces most surface bound Cl- with I-. The treatment protocol results in PbS QD films exhibiting a deeper work function and band positions than other ligand exchanges reported previously. The method developed here produces solar cells that perform well even at film thicknesses approaching a micron, indicating improved carrier transport in the QD films. We demonstrate QD solar cells based on PbI2 with power conversion efficiencies above 7%.

  11. Mesoscopic photosystems for solar light harvesting and conversion: facile and reversible transformation of metal-halide perovskites.

    PubMed

    Harms, Hauke Arne; Tétreault, Nicolas; Pellet, Norman; Bensimon, Michaël; Grätzel, Michael

    2014-01-01

    Recently, hybrid organic-inorganic metal halide perovskites have gained prominence as potent light harvesters in thin film solid-state photovoltaics. In particular the solar-to-electric power conversion efficiency (PCE) of devices using CH(3)NH(3)PbI(3) as sensitizer has increased from 3 to 20.1% within only a few years. This key material can be prepared by solution processing from PbI(2) and CH(3)NH(3)I in one step or by sequential deposition. In the latter case an electron capturing support such as TiO(2) is first covered with PbI(2), which upon exposure to a CH(3)NH(3)I solution is converted to the perovskite. Here we apply for the first time quartz crystal microbalance (QCMD) measurements in conjunction with X-ray diffraction and scanning electron microscopy to analyse the dynamics of the conversion of PbI(2) to CH(3)NH(3)PbI(3). Employing 200 nm thick PbI(2) films as substrates we discover that the CH(3)NH(3)I insertion in the PbI(2) is reversible, with the extraction into the solvent isopropanol occurring on the same time scale of seconds as the intercalation process. This offers an explanation for the strikingly rapid and facile exchange of halide ions in CH(3)NH(3)PbX(3) by solution processing at room temperature.

  12. Valence and Conduction Band Densities of States of Metal Halide Perovskites: A Combined Experimental–Theoretical Study

    PubMed Central

    2016-01-01

    We report valence and conduction band densities of states measured via ultraviolet and inverse photoemission spectroscopies on three metal halide perovskites, specifically methylammonium lead iodide and bromide and cesium lead bromide (MAPbI3, MAPbBr3, CsPbBr3), grown at two different institutions on different substrates. These are compared with theoretical densities of states (DOS) calculated via density functional theory. The qualitative agreement achieved between experiment and theory leads to the identification of valence and conduction band spectral features, and allows a precise determination of the position of the band edges, ionization energy and electron affinity of the materials. The comparison reveals an unusually low DOS at the valence band maximum (VBM) of these compounds, which confirms and generalizes previous predictions of strong band dispersion and low DOS at the MAPbI3 VBM. This low DOS calls for special attention when using electron spectroscopy to determine the frontier electronic states of lead halide perovskites. PMID:27364125

  13. Metal Halide Solid-State Surface Treatment for High Efficiency PbS and PbSe QD Solar Cells

    DOE PAGES

    Crisp, R. W.; Kroupa, D. M.; Marshall, A. R.; Miller, E. M.; Zhang, J.; Beard, M. C.; Luther, J. M.

    2015-04-24

    We developed a layer-by-layer method of preparing PbE (E = S or Se) quantum dot (QD) solar cells using metal halide (PbI2, PbCl2, CdI2, or CdCl2) salts dissolved in dimethylformamide to displace oleate surface ligands and form conductive QD solids. The resulting QD solids have a significant reduction in the carbon content compared to films treated with thiols and organic halides. We find that the PbI2 treatment is the most successful in removing alkyl surface ligands and also replaces most surface bound Cl- with I-. The treatment protocol results in PbS QD films exhibiting a deeper work function and bandmore » positions than other ligand exchanges reported previously. The method developed here produces solar cells that perform well even at film thicknesses approaching a micron, indicating improved carrier transport in the QD films. We demonstrate QD solar cells based on PbI2 with power conversion efficiencies above 7%.« less

  14. Valence and Conduction Band Densities of States of Metal Halide Perovskites: A Combined Experimental-Theoretical Study.

    PubMed

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

    2016-07-21

    We report valence and conduction band densities of states measured via ultraviolet and inverse photoemission spectroscopies on three metal halide perovskites, specifically methylammonium lead iodide and bromide and cesium lead bromide (MAPbI3, MAPbBr3, CsPbBr3), grown at two different institutions on different substrates. These are compared with theoretical densities of states (DOS) calculated via density functional theory. The qualitative agreement achieved between experiment and theory leads to the identification of valence and conduction band spectral features, and allows a precise determination of the position of the band edges, ionization energy and electron affinity of the materials. The comparison reveals an unusually low DOS at the valence band maximum (VBM) of these compounds, which confirms and generalizes previous predictions of strong band dispersion and low DOS at the MAPbI3 VBM. This low DOS calls for special attention when using electron spectroscopy to determine the frontier electronic states of lead halide perovskites. PMID:27364125

  15. The impacts of new street light technologies: experimentally testing the effects on bats of changing from low-pressure sodium to white metal halide.

    PubMed

    Stone, Emma Louise; Wakefield, Andrew; Harris, Stephen; Jones, Gareth

    2015-05-01

    Artificial light at night is a major feature of anthropogenic global change and is increasingly recognized as affecting biodiversity, often negatively. On a global scale, newer technology white lights are replacing orange sodium lights to reduce energy waste. In 2009, Cornwall County Council (UK) commenced replacement of existing low-pressure sodium (LPS) high intensity discharge (HID) street lights with new Phillips CosmoPolis white ceramic metal halide street lights to reduce energy wastage. This changeover provided a unique collaborative opportunity to implement a before-after-control-impact field experiment to investigate the ecological effects of newly installed broad spectrum light technologies. Activity of the bat species Pipistrellus pipistrellus, P. pygmaeus and Nyctalus/Eptesicus spp. was significantly higher at metal halide than LPS lights, as found in other studies of bat activity at old technology (i.e. mercury vapour) white light types. No significant difference was found in feeding attempts per bat pass between light types, though more passes overall were recorded at metal halide lights. Species-specific attraction of bats to the metal halide lights could have cascading effects at lower trophic levels. We highlight the need for further research on possible ecosystem-level effects of light technologies before they are installed on a wide scale. PMID:25780239

  16. New Family of Quantum Spin Hall Insulators in Two-dimensional Transition-Metal Halide with Large Nontrivial Band Gaps.

    PubMed

    Zhou, Liujiang; Kou, Liangzhi; Sun, Yan; Felser, Claudia; Hu, Feiming; Shan, Guangcun; Smith, Sean C; Yan, Binghai; Frauenheim, Thomas

    2015-12-01

    Topological insulators (TIs) are promising for achieving dissipationless transport devices due to the robust gapless states inside the insulating bulk gap. However, currently realized two-dimensional (2D) TIs, quantum spin Hall (QSH) insulators, suffer from ultrahigh vacuum and extremely low temperature. Thus, seeking for desirable QSH insulators with high feasibility of experimental preparation and large nontrivial gap is of great importance for wide applications in spintronics. On the basis of the first-principles calculations, we predict a novel family of 2D QSH insulators in transition-metal halide MX (M = Zr, Hf; X = Cl, Br, and I) monolayers, especially, which is the first case based on transition-metal halide-based QSH insulators. MX family has the large nontrivial gaps of 0.12-0.4 eV, comparable with bismuth (111) bilayer (0.2 eV), stanene (0.3 eV), and larger than ZrTe5 (0.1 eV) monolayers and graphene-based sandwiched heterstructures (30-70 meV). Their corresponding 3D bulk materials are weak topological insulators from stacking QSH layers, and some of bulk compounds have already been synthesized in experiment. The mechanism for 2D QSH effect in this system originates from a novel d-d band inversion, significantly different from conventional band inversion between s-p, p-p, or d-p orbitals. The realization of pure layered MX monolayers may be prepared by exfoliation from their 3D bulk phases, thus holding great promise for nanoscale device applications and stimulating further efforts on transition metal-based QSH materials.

  17. Variable charge and electrical double layer of mineral-water interfaces: silver halides versus metal (hydr)oxides.

    PubMed

    Hiemstra, Tjisse

    2012-11-01

    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 complexation modeling (SCM) as applied to metal (hydr)oxide interfaces. Ag halides and metal (hydr)oxides behave quite differently in some respect. The location of charge in the interface of Ag halides is not a priori obvious. For AgI(s), SCM indicates the separation of interfacial charge in which the smaller silver ions are apparently farther away from the surface than iodide. This charge separation can be understood from the surface structure of the relevant crystal faces. Charge separation with positive charge above the surface is due to monodentate surface complex formation of Ag(+) ions binding to I sites located at the surface. Negative surface charge is due to the desorption of Ag(+) ions out of the lattice. These processes can be described with the charge distribution (CD) model. The MO/DFT optimized geometry of the complex is used to estimate the value of the CD. SCM reveals the EDL structure of AgI(s), having two Stern layers in series. The inner Stern layer has a very low capacitance (C(1) = 0.15 ± 0.01 F/m(2)) in comparison to that of metal (hydr)oxides, and this can be attributed to the strong orientation of the (primary) water molecules on the local electrostatic field of the Ag(+) and I(-) ions of the surface (relative dielectric constant ε(r) ≈ 6). Depending on the extent of water ordering, mineral surfaces may in principle develop a second Stern layer. The corresponding capacitance (C(2)) will depend on the degree of water ordering that may decrease in the series AgI (C(2) = 0.57 F/m(2)), goethite (C(2) = 0.74 F/m(2)), and rutile (C(2) = ∞), as discussed. The charging principles of AgI minerals iodargyrite and miersite may also be applied to minerals

  18. Hydrogen Interaction with Metal Halides: the Nuclear Quadrupole Coupling Constant of Gold in the {p}{-H}_2{-AuCl} Complex and Trends in the Other Hydrogen-Coinage Metal Halide Interactions

    NASA Astrophysics Data System (ADS)

    Obenchain, Daniel A.; Grubbs, G. S. Grubbs, Ii; Pickett, Herbert M.; Novick, Stewart E.

    2013-06-01

    The rotational spectrum of p-H_2-AuCl has been measured using a laser ablation equipped FTMW cavity spectrometer. The predicted structure, using a 60 electron core potential and an aug-cc-pVQZ at the MP2 level of theory, shows that H_2 has an r_e = 0.91Å. A predicted value for the eQq(χ_{aa}) of gold required a semi-empirical method using the results of previous AuCl complexes in the gas phase. Transitions have been measured across multiple J levels, and have been used to determine the rotational constants, centrifugal distortion constants, and nuclear quadrupole coupling constants of multiple isotopologues. The o-H_2-AuCl has also been observed. While the monomer value of the eQq of ^{197}Au was determined to be 9.63112(13) MHz in ^{197}Au^{35}Cl, we observed a significant change in the eQq of ^{197}Au in p-H_2-^{197}Au^{35}Cl to a value of -817.9983(36) MHz [0.02728556(12) cm^{-1}], giving rise to a Au hyperfine component splittings of approximately 220 MHz [0.007 cm^{-1}] and suggesting a change in electronic structure with the interaction of H_2. We will present a summary of the hydrogen-coinage metal halide talks given at this conference, including trends in eQq and hydrogen metal halide dissociation energies. D. Figgen, G. Rauhut, M. Dolh, H. Stoll J. Chem. Phys. 311(2005) 227. K. A. Peterson, C. Puzzarini, Theor. Chem. Acc. 114 (2005) 283. C. J. Evans, C. L. Gerry J. Mol. Spectrosc. 203 (2000) 105.

  19. Three dimensional dynamic study of a metal halide thallium iodine discharge plasma powered by a sinusoidal and square signal

    NASA Astrophysics Data System (ADS)

    Bechir Ben Hamida, Mohamed; Charrada, Kamel

    2016-01-01

    The purpose of this paper is to study the dynamic of a metal halide thallium iodine discharge lamp fed by a sinusoidal and square power supply. For this, a chemical model under Local Thermodynamic Equilibrium conditions has been developed to compute the plasma composition and transport coefficients such as thermal conductivity, viscosity and electric conductivity. This is then coupled with a three-dimensional time-dependent code that solves the system of the mass, energy and momentum equations, as well as the Laplace equation for the plasma using Comsol Multiphysics with Matlab. After validation with the experimental results, this model was applied to analyze the influence of the key parameters on the discharge behavior such as frequency for an AC arc current and the atomic ratio for square arc-current wave form on the convective process.

  20. Development of processes for the production of solar grade silicon from halides and alkali metals, phase 1 and phase 2

    NASA Astrophysics Data System (ADS)

    Dickson, C. R.; Gould, R. K.; Felder, W.

    1981-03-01

    High temperature reactions of silicon halides with alkali metals for the production of solar grade silicon are described. Product separation and collection processes were evaluated, measure heat release parameters for scaling purposes and effects of reactants and/or products on materials of reactor construction were determined, and preliminary engineering and economic analysis of a scaled up process were made. The feasibility of the basic process to make and collect silicon was demonstrated. The jet impaction/separation process was demonstrated to be a purification process. The rate at which gas phase species from silicon particle precursors, the time required for silane decomposition to produce particles, and the competing rate of growth of silicon seed particles injected into a decomposing silane environment were determined. The extent of silane decomposition as a function of residence time, temperature, and pressure was measured by infrared absorption spectroscopy. A simplistic model is presented to explain the growth of silicon in a decomposing silane enviroment.

  1. Revealing the ultrafast charge carrier dynamics in organo metal halide perovskite solar cell materials using time resolved THz spectroscopy.

    PubMed

    Ponseca, C S; Sundström, V

    2016-03-28

    Ultrafast charge carrier dynamics in organo metal halide perovskite has been probed using time resolved terahertz (THz) spectroscopy (TRTS). Current literature on its early time characteristics is unanimous: sub-ps charge carrier generation, highly mobile charges and very slow recombination rationalizing the exceptionally high power conversion efficiency for a solution processed solar cell material. Electron injection from MAPbI3 to nanoparticles (NP) of TiO2 is found to be sub-ps while Al2O3 NPs do not alter charge dynamics. Charge transfer to organic electrodes, Spiro-OMeTAD and PCBM, is sub-ps and few hundreds of ps respectively, which is influenced by the alignment of energy bands. It is surmised that minimizing defects/trap states is key in optimizing charge carrier extraction from these materials.

  2. Development of processes for the production of solar grade silicon from halides and alkali metals, phase 1 and phase 2

    NASA Technical Reports Server (NTRS)

    Dickson, C. R.; Gould, R. K.; Felder, W.

    1981-01-01

    High temperature reactions of silicon halides with alkali metals for the production of solar grade silicon are described. Product separation and collection processes were evaluated, measure heat release parameters for scaling purposes and effects of reactants and/or products on materials of reactor construction were determined, and preliminary engineering and economic analysis of a scaled up process were made. The feasibility of the basic process to make and collect silicon was demonstrated. The jet impaction/separation process was demonstrated to be a purification process. The rate at which gas phase species from silicon particle precursors, the time required for silane decomposition to produce particles, and the competing rate of growth of silicon seed particles injected into a decomposing silane environment were determined. The extent of silane decomposition as a function of residence time, temperature, and pressure was measured by infrared absorption spectroscopy. A simplistic model is presented to explain the growth of silicon in a decomposing silane enviroment.

  3. Optical emission spectroscopy of metal-halide lamps: Radially resolved atomic state distribution functions of Dy and Hg

    NASA Astrophysics Data System (ADS)

    Nimalasuriya, T.; Flikweert, A. J.; Stoffels, W. W.; Haverlag, M.; van der Mullen, J. J. A. M.; Pupat, N. B. M.

    2006-03-01

    Absolute line intensity measurements are performed on a metal-halide lamp. Several transitions of atomic and ionic Dy and atomic Hg are measured at different radial positions from which we obtain absolute atomic and ionic Dy intensity profiles. From these profiles we construct the radially resolved atomic state distribution function (ASDF) of the atomic and ionic Dy and the atomic Hg. From these ASDFs several quantities are determined as functions of radial position, such as the (excitation) temperature, the ion ratio Hg+/Dy+, the electron density, the ground state, and the total density of Dy atoms and ions. Moreover, these ASDFs give us insight about the departure from equilibrium. The measurements show a hollow density profile for the atoms and the ionization of atoms in the center. In the outer parts of the lamp molecules dominate.

  4. Optical emission spectroscopy of metal-halide lamps: Radially resolved atomic state distribution functions of Dy and Hg

    SciTech Connect

    Nimalasuriya, T.; Flikweert, A.J.; Stoffels, W.W.; Haverlag, M.; Mullen, J.J.A.M. van der; Pupat, N.B.M.

    2006-03-01

    Absolute line intensity measurements are performed on a metal-halide lamp. Several transitions of atomic and ionic Dy and atomic Hg are measured at different radial positions from which we obtain absolute atomic and ionic Dy intensity profiles. From these profiles we construct the radially resolved atomic state distribution function (ASDF) of the atomic and ionic Dy and the atomic Hg. From these ASDFs several quantities are determined as functions of radial position, such as the (excitation) temperature, the ion ratio Hg{sup +}/Dy{sup +}, the electron density, the ground state, and the total density of Dy atoms and ions. Moreover, these ASDFs give us insight about the departure from equilibrium. The measurements show a hollow density profile for the atoms and the ionization of atoms in the center. In the outer parts of the lamp molecules dominate.

  5. Metal enhanced fluorescence with gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Mattingly, Shaina LaRissa Strating

    A novel hybrid nanocomposite of Au nanoparticle-modified silicon nanowire was developed for surface enhanced fluorescence applications. The designed nanocomposite contained a silicon nanowire, gold nanoparticles and a silica layer doped with dye molecules. The hybrid nanomaterial was characterized using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), fluorescence measurements, Fourier transform infrared (FT-IR) spectroscopy, and energy-dispersive X-ray spectroscopy (EDS). The results showed that the gold nanoparticles were uniformly adhered on the silicon nanowires and covered by a thin silica layer. The nanostructure exhibited strong capacity for surface enhanced fluorescence. Different enhancement factors were obtained by changing synthetic conditions. The second goal of the project was to determine if the shape of gold nanoparticles affects the extent of its fluorescence enhancement under constant external factors. Two shapes of gold nanoparticles were synthesized and characterized by SEM, STEM, zeta potential and absorbance measurements. Then they were coated with fluorescent dye-doped silica and the fluorescence intensity was measured and compared to the pure fluorescent dye. Gold nanorods enhanced fluorescence more than gold nanostars and that the fluorescent dye Alexafluor 700 showed a greater fluorescence intensity change in the presence of nanoparticles than methylene blue.

  6. On the transfer of protective coating elements on a metal surface from halide gaseous media

    NASA Astrophysics Data System (ADS)

    Abraimov, N. V.

    2016-06-01

    The processes occurring during the formation of multicomponent diffusion coatings on nickel alloys at the stage of delivery of elements on the article surface when chlorine, bromine, and iodine halides are used as activators are considered. Balance equations and calculated values are given for the partial pressures in the composition of a gas phase of components participating in chemical transport reaction; the possible reactions of delivering elements on the article surfaces and the structures of Ni-Al, Ni-Cr, Ni-Cr-Al, Co-Cr-Al coatings deposited on the ZhS26, ZhS6U, ZhS32, and VZhL12U alloys are presented.

  7. Spectral variation of fluorescence lifetime near single metal nanoparticles

    PubMed Central

    Li, Jia; Krasavin, Alexey V.; Webster, Linden; Segovia, Paulina; Zayats, Anatoly V.; Richards, David

    2016-01-01

    We explore the spectral dependence of fluorescence enhancement and the associated lifetime modification of fluorescent molecules coupled to single metal nanoparticles. Fluorescence lifetime imaging microscopy and single-particle dark-field spectroscopy are combined to correlate the dependence of fluorescence lifetime reduction on the spectral overlap between the fluorescence emission and the localised surface plasmon (LSP) spectra of individual gold nanoparticles. A maximum lifetime reduction is observed when the fluorescence and LSP resonances coincide, with good agreement provided by numerical simulations. The explicit comparison between experiment and simulation, that we obtain, offers an insight into the spectral engineering of LSP mediated fluorescence and may lead to optimized application in sensing and biomedicine. PMID:26876780

  8. Tuning Fluorescence Direction with Plasmonic Metal–Dielectric– Metal Substrates

    PubMed Central

    Choudhury, Sharmistha Dutta; Badugu, Ramachandram; Nowaczyk, Kazimierz; Ray, Krishanu; Lakowicz, Joseph R.

    2013-01-01

    Controlling the emission properties of fluorophores is essential for improving the performance of fluorescence-based techniques in modern biochemical research, medical diagnosis, and sensing. Fluorescence emission is isotropic in nature, which makes it difficult to capture more than a small fraction of the total emission. Metal– dielectric–metal (MDM) substrates, discussed in this Letter, convert isotropic fluorescence into beaming emission normal to the substrate. This improves fluorescence collection efficiency and also opens up new avenues for a wide range of fluorescence-based applications. We suggest that MDM substrates can be readily adapted for multiple uses, such as in microarray formats, for directional fluorescence studies of multiple probes or for molecule-specific sensing with a high degree of spatial control over the fluorescence emission. SECTION: Physical Processes in Nanomaterials and Nanostructures PMID:24013521

  9. Transition metal-mediated donor-acceptor coordination of low-oxidation state Group 14 element halides.

    PubMed

    Swarnakar, Anindya K; Ferguson, Michael J; McDonald, Robert; Rivard, Eric

    2016-04-14

    The reactivity of tungsten carbonyl adducts of Group 14 element (Ge, Sn and Pb) dihalides towards the metal-based donors (η(5)-C5H5)Rh(PMe2Ph)2 and Pt(PCy3)2 was examined. When (η(5)-C5H5)Rh(PMe2Ph)2 was treated with the Lewis acid supported Ge(ii) complex, THF·GeCl2·W(CO)5, cyclopentadienyl ring activation occurred, whereas the analogous Lewis acidic units SnCl2·W(CO)5 and PbCl2 form direct adducts with the Rh complex to yield Rh-Sn and Rh-Pb dative bonds. Attempts to prepare metal coordinated element(ii) hydrides by adding hydride sources to the above mentioned rhodium-E(ii) halide complexes were unsuccessful; in each case insoluble products were formed along with regeneration of free (η(5)-C5H5)Rh(PMe2Ph)2. In a parallel study, ECl2·W(CO)5 (E = Ge or Sn) groups were shown to participate in E-Cl oxidation addition chemistry with (Cy3P)2Pt to give the formal Pt(ii) complexes ClPt(PCy3)2ECl·W(CO)5.

  10. Fluorescence enhancement in visible light: dielectric or noble metal?

    PubMed

    Sun, S; Wu, L; Bai, P; Png, C E

    2016-07-28

    A high permittivity dielectric gives the impression of outperforming plasmonic noble metal in visible light fluorescence enhancement primarily because of its small loss. Nonetheless, the performances of these two platforms in various situations remain obscure due to the different optical confinement mechanisms as well as the complexity in the fluorescence enhancement process. This study presents a comprehensive comparison between these two platforms based on nanoparticles (NPs) to evaluate their capability and applicability in fluorescence enhancement by taking into account the fluorescence excitation rate, the quantum yield, the fluorophore wavelengths and Stokes shifts as well as the far field intensity. In a low permittivity sensing medium (e.g. air), the dielectric NP can achieve comparable or higher fluorescence enhancement than the metal NP due to its decent NP-enhanced excitation rate and larger quantum yield. In a relatively high permittivity sensing medium (e.g. water), however, there is a significant decrement of the excitation rate of the dielectric NP as the permittivity contrast decreases, leading to a smaller fluorescence enhancement compared to the metallic counterpart. Combining the fluorescence enhancement and the far field intensity studies, we further conclude that for both dielectric and plasmonic NPs, the optimal situation occurs when the fluorescence excitation wavelength, the fluorescence emission wavelength and the electric-dipole-mode of the dielectric NP (or the plasmonic resonance of the metal NP) are the same and all fall in the low conductivity region of the NP material. We also find that the electric-dipole-mode of the dielectric NP performs better than the magnetic-dipole-mode for fluorescence enhancement applications because only the electric-dipole-mode can be strongly excited by the routinely used fluorescent dyes and quantum dots, which behave as electric dipoles by nature.

  11. Fluorescence enhancement in visible light: dielectric or noble metal?

    PubMed

    Sun, S; Wu, L; Bai, P; Png, C E

    2016-07-28

    A high permittivity dielectric gives the impression of outperforming plasmonic noble metal in visible light fluorescence enhancement primarily because of its small loss. Nonetheless, the performances of these two platforms in various situations remain obscure due to the different optical confinement mechanisms as well as the complexity in the fluorescence enhancement process. This study presents a comprehensive comparison between these two platforms based on nanoparticles (NPs) to evaluate their capability and applicability in fluorescence enhancement by taking into account the fluorescence excitation rate, the quantum yield, the fluorophore wavelengths and Stokes shifts as well as the far field intensity. In a low permittivity sensing medium (e.g. air), the dielectric NP can achieve comparable or higher fluorescence enhancement than the metal NP due to its decent NP-enhanced excitation rate and larger quantum yield. In a relatively high permittivity sensing medium (e.g. water), however, there is a significant decrement of the excitation rate of the dielectric NP as the permittivity contrast decreases, leading to a smaller fluorescence enhancement compared to the metallic counterpart. Combining the fluorescence enhancement and the far field intensity studies, we further conclude that for both dielectric and plasmonic NPs, the optimal situation occurs when the fluorescence excitation wavelength, the fluorescence emission wavelength and the electric-dipole-mode of the dielectric NP (or the plasmonic resonance of the metal NP) are the same and all fall in the low conductivity region of the NP material. We also find that the electric-dipole-mode of the dielectric NP performs better than the magnetic-dipole-mode for fluorescence enhancement applications because only the electric-dipole-mode can be strongly excited by the routinely used fluorescent dyes and quantum dots, which behave as electric dipoles by nature. PMID:27374052

  12. Photodeposition of Silver Can Result in Metal-Enhanced Fluorescence

    PubMed Central

    GEDDES, CHRIS D.; PARFENOV, ALEXANDR

    2009-01-01

    Chemically deposited silver particles are widely used for surface-enhanced Raman scattering (SERS) and more recently for surface-enhanced fluorescence (SEF), also known as metal-enhanced fluorescence (MEF). We now show that metallic silver deposited by laser illumination results in an ~7-fold increased intensity of locally bound indocyanine green. The increased intensity is accompanied by a decreased lifetime and increased photostability. These results demonstrate the possibility of photolithographic preparation of surfaces for enhanced fluorescence in microfluidics, medical diagnostics, and other applications. PMID:14658678

  13. Use of Nanoconfinement to Control Metal-Halide Perovskite Crystallization and Stability

    NASA Astrophysics Data System (ADS)

    Lee, Sangchul; Feldman, Joshua; Lee, Stephanie

    We present a systematic study of the effect of nanoconfinement on the crystallization of methylammonium lead halide (MAPbI3) perovskite crystallization. MAPbI3 was spin coated onto anodized aluminum oxide (AAO) templates with uniaxially-aligned pores ranging from 20 - 200 nm in diameter and examined using 2-D X-ray diffraction and scanning electron microscopy. X-ray diffraction patterns revealed the presence of a transient precursor phase that converts to the MAPbI3 crystal structure upon thermal annealing. The orientation of the precursor phase and conversion rate to the MAPbI3 crystal structure were found to depend on the pore size of the AAO template. The stability of MAPbI3 in air also depends on the extent of nanoconfinement. When deposited on flat SiO2 surfaces, MAPbI3 degraded into PbI2 and MA after 21 days. When deposited in AAO templates exhibiting 20-nm pore sizes, however, MAPbI3 crystals were stable for longer than 16 days. These findings suggest that nanoconfinement of MAPbI3 crystals may be a promising strategy for improving the stability of perovskite-based solar cells.

  14. Fluorescence Spectroscopy with Metal-Dielectric Waveguides

    PubMed Central

    Badugu, Ramachandram; Szmacinski, Henryk; Ray, Krishanu; Descrovi, Emiliano; Ricciardi, Serena; Zhang, Douguo; Chen, Junxue; Huo, Yiping; Lakowicz, Joseph R.

    2015-01-01

    We describe a hybrid metal-dielectric waveguide structures (MDWs) with numerous potential applications in the biosciences. These structures consist of a thin metal film coated with a dielectric layer. Depending on the thickness of the dielectric layer, the modes can be localized near the metal, within the dielectric, or at the top surface of the dielectric. The optical modes in a metal-dielectric waveguide can have either S (TE) or P (TM) polarization. The dielectric spacer avoids the quenching, which usually occurs for fluorophores within about 5 nm from the metal. Additionally, the resonances display a sharp angular dependence and can exhibit several hundred-fold increases in intensity (E2) at the silica-air interface relative to the incident intensity. Fluorophores placed on top of the silica layer couple efficiently with the metal, resulting in a sharp angular distribution of emission through the metal and down from the bottom of the structure. This coupling occurs over large distances to several hundred nm away from the metal and was found to be consistent with simulations of the reflectivity of the metal-dielectric waveguides. Remarkably, for some silica thicknesses, the emission is almost completely coupled through the structure with little free-space emission away from the metal-dielectric waveguide. The efficiency of fluorophore coupling is related to the quality of the resonant modes sustained by the metal-dielectric waveguide, resulting in coupling of most of the emission through the metal into the underlying glass substrates. Metal-dielectric waveguides also provide a method to resolve the emission from surface-bound fluorophores from the bulk-phase fluorophores. Metal-dielectric waveguides are simple to fabricate for large surface areas, the resonance wavelength can be adjusted by the dielectric thickness, and the silica surface is suitable for coupling to biomolecules. Metal-dielectric waveguides can have numerous applications in diagnostics and high

  15. Single molecule fluorescence studies of ribosome dynamics: An application of metal enhanced fluorescence

    NASA Astrophysics Data System (ADS)

    Bharill, Shashank

    Metal enhanced fluorescence (MEF), in which a surface plasmon near a noble metal alters the spectral properties of an organic fluorophore, has been reported to increase fluorescence intensity without a concomitant increase in photobleaching rate. The fluorescence intensities of Cy3- and Cy5-labeled ribosomal initiation complexes (ICs) near 50 nm silver particles were increased 4 - 7-fold compared to ICs in the absence of silver colloids. Photobleaching lifetime was not significantly decreased, resulting in 4 - 5.5-fold enhancement in total photon emission prior to photobleaching. Fluorophores showing enhanced fluorescence were located within ˜280 nm of the colloidal particles, as detected by light scattering and scanning probe microscopy. Aggregates of silver particles or larger colloids themselves produced wavelength-shifted luminescence similar to fluorescence, presumably due to resonant extinction between nearby metal particles. Intensity fluctuations above shot noise, at 0.1 - 5 Hz, were greater from slides containing colloidal particles than from plain glass. Overall signal to noise ratio was similar or slightly better near the silver particles. Proximity to silver particles did not compromise ribosome function, as measured by codon-dependent binding of fluorescent tRNA to the A site of fluorescent labeled ribosomes, dynamics of fluorescence resonance energy transfer between adjacent tRNAs in the ribosomal A and P sites, and elongation factor G catalyzed translocation.

  16. Thioureas as reporting elements for metal-responsive fluorescent chemosensors.

    PubMed

    Vonlanthen, Mireille; Finney, Nathaniel S

    2013-04-19

    Proof that sulfur is a viable reporting element for the development of fluorescent chemosensors for metal ions is presented. To date, the majority of metal-responsive fluorescent chemosensors have relied on metal-nitrogen coordination to provide a fluorescence response, most commonly by suppressing photoinduced electron transfer (PET) quenching. While chemosensors with direct application to biology, medicine, and analytical chemistry have been so developed, reliance on the coordination chemistry of nitrogen remains a practical and conceptual limitation. Building on the fact that thioureas can quench fluorescence emission by PET, it is shown that the quenched emission of thiourea-appended naphthalimides can be restored by metal binding and that metal affinity and selectivity can be controlled through structural modification of the thiourea substituents. Further, such chemosensors can function in aqueous media and, unlike nitrogen-based chemosensors, are unresponsive to increases in [H(+)]. Given that the coordination properties of sulfur are distinct from those of nitrogen, this work lays the foundation for the development of a new class of interesting and useful metal-responsive fluorescent probes. PMID:23470031

  17. Charge-transfer gap closure in transition-metal halides under pressure

    SciTech Connect

    Chen, A.L.; Yu, P.Y.

    1995-01-01

    Insulator-to-metal transition induced by pressure has been studied in three transition metal iodides: NiI{sub 2}, CoI{sub 2} and FeI{sub 2} using optical absorption and resistivity measurements at room temperature. Comparisons between the results obtained by these two techniques suggested that the closure of the charge-transfer gap is the principal mechanism responsible for the insulator-to-metal transition in these materials.

  18. Metal ion influence on eumelanin fluorescence and structure

    NASA Astrophysics Data System (ADS)

    Sutter, Jens-Uwe; Birch, David J. S.

    2014-06-01

    Melanin has long been thought to have an unworkably weak and complex fluorescence, but here we study its intrinsic fluorescence in order to demonstrate how metal ions can be used to control the rate of formation, constituents and structure of eumelanin formed from the well-known laboratory auto-oxidation of 3,4-dihydroxy-L-phenylalanine (L-DOPA). The effect on eumelanin absorption and fluorescence of a range of solvated metal ions is reported including Cu, Zn, Ni, Na and K. Monovalent cations and Zn have little effect, but the effect of transition metal cations can be considerable. For example, at pH 10, copper ions are shown to accelerate the onset of eumelanin formation, but not the rate of formation once it commences, and simplify the usual complex structure and intrinsic fluorescence of eumelanin in a way that is consistent with an increased abundance of 5,5-dihydroxyindole-2-carboxylic acid (DHICA). The presence of a dominant 6 ns fluorescence decay time at 480 nm, when excited at 450 nm describes a distinct photophysical species, which we tentatively assign to small oligomers. Copper is well-known to normally quench fluorescence, but increasing amounts of copper surprisingly leads to an increase in the fluorescence decay time of eumelanin, while reducing the fluorescence intensity, suggesting copper modification of the excited state. Such results have bearing on diverse areas. The most accepted morphology for melanin is that of a graphite-like sheet structure, and one which readily binds metal ions, an interaction that is thought to have an important, though as yet unclear bearing on several areas of medicine including neurology. There is also increasing interest in bio-mimicry by preparing and labelling sheet structures with metal ions for new electronic and photonic materials.

  19. Diode-Pumped Organo-Lead Halide Perovskite Lasing in a Metal-Clad Distributed Feedback Resonator.

    PubMed

    Jia, Yufei; Kerner, Ross A; Grede, Alex J; Brigeman, Alyssa N; Rand, Barry P; Giebink, Noel C

    2016-07-13

    Organic-inorganic lead halide perovskite semiconductors have recently reignited the prospect of a tunable, solution-processed diode laser, which has the potential to impact a wide range of optoelectronic applications. Here, we demonstrate a metal-clad, second-order distributed feedback methylammonium lead iodide perovskite laser that marks a significant step toward this goal. Optically pumping this device with an InGaN diode laser at low temperature, we achieve lasing above a threshold pump intensity of 5 kW/cm(2) for durations up to ∼25 ns at repetition rates exceeding 2 MHz. We show that the lasing duration is not limited by thermal runaway and propose instead that lasing ceases under continuous pumping due to a photoinduced structural change in the perovskite that reduces the gain on a submicrosecond time scale. Our results indicate that the architecture demonstrated here could provide the foundation for electrically pumped lasing with a threshold current density Jth < 5 kA/cm(2) under sub-20 ns pulsed drive. PMID:27331618

  20. Diode-Pumped Organo-Lead Halide Perovskite Lasing in a Metal-Clad Distributed Feedback Resonator.

    PubMed

    Jia, Yufei; Kerner, Ross A; Grede, Alex J; Brigeman, Alyssa N; Rand, Barry P; Giebink, Noel C

    2016-07-13

    Organic-inorganic lead halide perovskite semiconductors have recently reignited the prospect of a tunable, solution-processed diode laser, which has the potential to impact a wide range of optoelectronic applications. Here, we demonstrate a metal-clad, second-order distributed feedback methylammonium lead iodide perovskite laser that marks a significant step toward this goal. Optically pumping this device with an InGaN diode laser at low temperature, we achieve lasing above a threshold pump intensity of 5 kW/cm(2) for durations up to ∼25 ns at repetition rates exceeding 2 MHz. We show that the lasing duration is not limited by thermal runaway and propose instead that lasing ceases under continuous pumping due to a photoinduced structural change in the perovskite that reduces the gain on a submicrosecond time scale. Our results indicate that the architecture demonstrated here could provide the foundation for electrically pumped lasing with a threshold current density Jth < 5 kA/cm(2) under sub-20 ns pulsed drive.

  1. Metal-Enhanced Fluorescence: Ultrafast Energy Transfer from Dyes in a Polymer Film to Metal Nanoparticles.

    PubMed

    Lee, Jaebeom; Pang, Yoonsoo

    2016-02-01

    Fluorescence from dye molecules dispersed in thin polymer layers increases by 20-25 times when a silver island film exists beneath the layer. Polymer layers of <100 nm thick cover the silver island film to minimize emission quenching from direct contact and also keep the dye molecules in close proximity to the metal nanosurface for possible fluorescence enhancements by silver island film. We report an ultrafast radiation process of ~400 ps lifetime from the surface plasmons of silver nanoparticles observed in time-resolved fluorescence of rhodamine 6G and DCM in thin polymer films coated on silver island surface. The ultrafast energy transfer and fluorescence from metal nanoparticles might be strongly related to the efficiency of metal-enhanced fluorescence. PMID:27433635

  2. Pathways toward high-performance perovskite solar cells: review of recent advances in organo-metal halide perovskites for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Song, Zhaoning; Watthage, Suneth C.; Phillips, Adam B.; Heben, Michael J.

    2016-04-01

    Organo-metal halide perovskite-based solar cells have been the focus of intense research over the past five years, and power conversion efficiencies have rapidly been improved from 3.8 to >21%. This article reviews major advances in perovskite solar cells that have contributed to the recent efficiency enhancements, including the evolution of device architecture, the development of material deposition processes, and the advanced device engineering techniques aiming to improve control over morphology, crystallinity, composition, and the interface properties of the perovskite thin films. The challenges and future directions for perovskite solar cell research and development are also discussed.

  3. A study of the convective flow as a function of external parameters in a high-pressure metal halide discharge lamp (HgDyI3)

    NASA Astrophysics Data System (ADS)

    Hajji, S.; HadjSalah, S.; Benhalima, A.; Charrada, K.; Zissis, G.

    2016-06-01

    This paper deals with the modelling of the convection processes in metal-halide lamp discharges (HgDyI3). For this, we realized a 3D model, a steady, direct current powered and time-depending model for the solution of conservation equations relative to mass, momentum, and energy. After validation, this model was applied to the study of the effect of some parameters that have appeared on major transport phenomena of mass and energy in studying the lamp. Indeed, the electric current, the atomic ratio (Hg/Dy), and the effect of the convective transport have been studied.

  4. Spectral dependence of fluorescence near plasmon resonant metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Yeechi

    The optical properties of fluorophores are significantly modified when placed within the near field (0--100 nm) of plasmon resonant metal nanostructures, due to the competition between increased decay rates and "hotspots" of concentrated electric fields. The decay rates and effective electric field intensities are highly dependent on the relative position of dye and metal and the overlap between plasmon resonance and dye absorption and emission. Understanding these dependencies can greatly improve the performance of biosensing and nanophotonic devices. In this dissertation, the fluorescence intensity of organic dyes and CdSe quantum dots near single metal nanoparticles is studied as a function of the local surface plasmon resonance (LSPR) of the nanoparticle. Single metal nanoparticles have narrow, well-defined, intense local surface plasmon resonances that are tunable across the visible spectrum by changes in size and shape. First, we show that organic dyes can be self-assembled on single silver nanoprisms into known configurations by the hybridization of thiolated DNA oligomers. We correlate the fluorescence intensity of the dyes to the LSPR of the individual nanoprism to which they are attached. For each of three different organic dyes, we observe a strong correlation between the fluorescence intensity of the dye and the degree of spectral overlap with the plasmon resonance of the nanoparticle. On average, we observe the brightest fluorescence from dyes attached to metal nanoparticles that have a LSPR scattering peak 40--120 meV higher in energy than the emission peak of the fluorophore. Second, the plasmon-enhanced fluorescence from CdSe/CdS/CdZnS/ZnS core/shell quantum dots is studied near a variety of silver and gold nanoparticles. With single-particle scattering spectroscopy, the localized surface plasmon resonance spectra of single metal nanoparticles is correlated with the photoluminescence excitation (PLE) spectra of the nearby quantum dots. The PLE

  5. Fluorescent probes and bioimaging: alkali metals, alkaline earth metals and pH.

    PubMed

    Yin, Jun; Hu, Ying; Yoon, Juyoung

    2015-07-21

    All living species and life forms have an absolute requirement for bio-functional metals and acid-base equilibrium chemistry owing to the critical roles they play in biological processes. Hence, a great need exists for efficient methods to detect and monitor biometals and acids. In the last few years, great attention has been paid to the development of organic molecule based fluorescent chemosensors. The availability of new synthetic fluorescent probes has made fluorescence microscopy an indispensable tool for tracing biologically important molecules and in the area of clinical diagnostics. This review highlights the recent advances that have been made in the design and bioimaging applications of fluorescent probes for alkali metals and alkaline earth metal cations, including lithium, sodium and potassium, magnesium and calcium, and for pH determination within biological systems. PMID:25317749

  6. Fluorescent probes and bioimaging: alkali metals, alkaline earth metals and pH.

    PubMed

    Yin, Jun; Hu, Ying; Yoon, Juyoung

    2015-07-21

    All living species and life forms have an absolute requirement for bio-functional metals and acid-base equilibrium chemistry owing to the critical roles they play in biological processes. Hence, a great need exists for efficient methods to detect and monitor biometals and acids. In the last few years, great attention has been paid to the development of organic molecule based fluorescent chemosensors. The availability of new synthetic fluorescent probes has made fluorescence microscopy an indispensable tool for tracing biologically important molecules and in the area of clinical diagnostics. This review highlights the recent advances that have been made in the design and bioimaging applications of fluorescent probes for alkali metals and alkaline earth metal cations, including lithium, sodium and potassium, magnesium and calcium, and for pH determination within biological systems.

  7. Sensing Metal Ions with DNA Building Blocks: Fluorescent Pyridobenzimidazole Nucleosides

    PubMed Central

    Kim, Su Jeong; Kool, Eric T.

    2008-01-01

    We describe novel fluorescent N-deoxyribosides (1 and 2) having 2-pyrido-2-benzimidazole and 2-quino-2-benzimidazole as aglycones. The compounds were prepared from the previously unknown heterocyclic precursors and Hoffer’s chlorosugar, yielding alpha anomers as the chief products. X-ray crystal structures confirmed the geometry, and showed that the pyridine and benzimidazole ring systems deviated from coplanarity in the solid state by 154° and 140°, respectively. In methanol the compounds 1 and 2 had absorption maxima at 360 and 370 nm respectively, and emission maxima at 494 and 539 nm. Experiments revealed varied fluorescence responses of the nucleosides to a panel of seventeen monovalent, divalent and trivalent metal ions in methanol. One or both of the nucleosides showed significant changes with ten of the metal ions. The most pronounced spectral changes for ligand-nucleoside 1 included red shifts in fluorescence (Au+, Au3+), strong quenching (Cu2+, Ni2+, Pt2+), and in substantial enhancements in emission intensity coupled with redshifts (Ag+, Cd2+, Zn2+). The greatest spectral changes for ligand-nucleoside 2 included a redshift in fluorescence (Ag+), a blueshift (Cd2+), strong quenching (Pd2+, Pt2+), and in substantial enhancements in emission intensity coupled with a blueshift (Zn2+). The compounds could be readily incorporated into oligodeoxynucleotides, where an initial study revealed that they retained sensitivity to metal ions in aqueous solution, and demonstrated possible cooperative sensing behavior with several ions. The two free nucleosides alone can act as differential sensors for at multiple metal ions, and they are potentially useful monomers for contributing metal ion sensing capability to DNAs. PMID:16669686

  8. Metal-atom fluorescence from the quenching of metastable rare gases by metal carbonyls

    SciTech Connect

    Hollingsworth, W.E.

    1982-11-01

    A flowing afterglow apparatus was used to study the metal fluorescence resulting from the quenching of metastable rare-gas states by metal carbonyls. The data from the quenching or argon, neon, and helium by iron and nickel carbonyl agreed well with a restricted degree of freedom model indicating a concerted bond-breaking dissociation.

  9. Modeling of catalytically active metal complex species and intermediates in reactions of organic halides electroreduction.

    PubMed

    Lytvynenko, Anton S; Kolotilov, Sergey V; Kiskin, Mikhail A; Eremenko, Igor L; Novotortsev, Vladimir M

    2015-02-28

    The results of quantum chemical modeling of organic and metal-containing intermediates that occur in electrocatalytic dehalogenation reactions of organic chlorides are presented. Modeling of processes that take place in successive steps of the electrochemical reduction of representative C1 and C2 chlorides - CHCl3 and Freon R113 (1,1,2-trifluoro-1,2,2-trichloroethane) - was carried out by density functional theory (DFT) and second-order Møller-Plesset perturbation theory (MP2). It was found that taking solvation into account using an implicit solvent model (conductor-like screening model, COSMO) or considering explicit solvent molecules gave similar results. In addition to modeling of simple non-catalytic dehalogenation, processes with a number of complexes and their reduced forms, some of which were catalytically active, were investigated by DFT. Complexes M(L1)2 (M = Fe, Co, Ni, Cu, Zn, L1H = Schiff base from 2-pyridinecarbaldehyde and the hydrazide of 4-pyridinecarboxylic acid), Ni(L2) (H2L2 is the Schiff base from salicylaldehyde and 1,2-ethylenediamine, known as salen) and Co(L3)2Cl2, representing a fragment of a redox-active coordination polymer [Co(L3)Cl2]n (L3 is the dithioamide of 1,3-benzenedicarboxylic acid), were considered. Gradual changes in electronic structure in a series of compounds M(L1)2 were observed, and correlations between [M(L1)2](0) spin-up and spin-down LUMO energies and the relative energies of the corresponding high-spin and low-spin reduced forms, as well as the shape of the orbitals, were proposed. These results can be helpful for determination of the nature of redox-processes in similar systems by DFT. No specific covalent interactions between [M(L1)2](-) and the R113 molecule (M = Fe, Co, Ni, Zn) were found, which indicates that M(L1)2 electrocatalysts act rather like electron transfer mediators via outer-shell electron transfer. A relaxed surface scan of the adducts {M(L1)2·R113}(-) (M = Ni or Co) versus the distance between the

  10. Designer metal-nanoantennae/dye complexes for maximum fluorescence enhancement

    NASA Astrophysics Data System (ADS)

    Meng, Xiang; Yang, Hao; Grote, Richard R.; Dadap, Jerry I.; Panoiu, Nicolae C.; Osgood, Richard M.

    2015-09-01

    We theoretically investigate the fluorescence enhancement of a representative set of dye-molecules excited by three classes of nanoantennae, using a fully vectorial three-dimensional finite-difference time-domain (3D FDTD) method. Through these 3D FDTD calculations, in conjunction with analytic guidance using temporal coupled-mode (TCM) theory, we develop a design procedure for antennae assemblies that allow achieving fluorescence enhancements of 200-900 over the emission intensity in the bare dye molecule. The enhancement from these commercially available fluorochrome conjugates, namely, CFTM568, CFTM660R and CFTM790 are fully investigated using spherical-dimer, elliptical-dimer, and bowtie nanoantennae. These results demonstrate a method for rationally designing arbitrary metallic nanoparticle/emitter assemblies prior to their synthesis and assembly to achieve optimum fluorescence enhancement.

  11. Structure of fluorescent metal clusters on a DNA template.

    NASA Astrophysics Data System (ADS)

    Vdovichev, A. A.; Sych, T. S.; Reveguk, Z. V.; Smirnova, A. A.; Maksimov, D. A.; Ramazanov, R. R.; Kononov, A. I.

    2016-08-01

    Luminescent metal clusters are a subject of growing interest in recent years due to their bright emission from visible to near infrared range. Detailed structure of the fluorescent complexes of Ag and other metal clusters with ligands still remains a challenging task. In this joint experimental and theoretical study we synthesized Ag-DNA complexes on a DNA oligonucleotide emitting in violet- green spectral range. The structure of DNA template was determined by means of various spectral measurements (CD, MS, XPS). Comparison of the experimental fluorescent excitation spectra and calculated absorption spectra for different QM/MM optimized structures allowed us to determine the detailed structure of the green cluster containing three silver atoms in the stem of the DNA hairpin structure stabilized by cytosine-Ag+-cytosine bonds.

  12. In Vivo Metal Ion Imaging Using Fluorescent Sensors.

    PubMed

    Van de Bittner, Genevieve C; Hirayama, Tasuku

    2016-01-01

    In vivo imaging in living animals provides the ability to monitor alterations of signaling molecules, ions, and other biological components during various life stages and in disease. The data gained from in vivo imaging can be used for biological discovery or to determine elements of disease progression and can inform the development and translation of therapeutics. Herein, we present theories behind small-molecule, fluorescent, metal ion sensors as well as the methods for their successful application to in vivo metal ion imaging, including ex vivo validation. PMID:27283424

  13. The electronic structure of metal oxide/organo metal halide perovskite junctions in perovskite based solar cells

    PubMed Central

    Dymshits, Alex; Henning, Alex; Segev, Gideon; Rosenwaks, Yossi; Etgar, Lioz

    2015-01-01

    Cross-sections of a hole-conductor-free CH3NH3PbI3 perovskite solar cell were characterized with Kelvin probe force microscopy. A depletion region width of about 45 nm was determined from the measured potential profiles at the interface between CH3NH3PbI3 and nanocrystalline TiO2, whereas a negligible depletion was measured at the CH3NH3PbI3/Al2O3 interface. A complete solar cell can be realized with the CH3NH3PbI3 that functions both as light harvester and hole conductor in combination with a metal oxide. The band diagrams were estimated from the measured potential profile at the interfaces, and are critical findings for a better understanding and further improvement of perovskite based solar cells. PMID:25731963

  14. Ore metal redistribution by hydrocarbon-brine and hydrocarbon-halide melt phases, North Range footwall of the Sudbury Igneous Complex, Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Hanley, J. J.; Mungall, J. E.; Pettke, T.; Spooner, E. T. C.; Bray, C. J.

    2005-11-01

    We report methane-dominant hydrocarbon (fluid) inclusions (CH4±C2H6-C2H2, C3H8) coexisting with primary brine inclusions and secondary halide melt (solid NaCl) inclusions in Au-Pt-rich quartz-sulfide-epidote alteration veins associated with the footwall-style Cu-PGE (platinum-group element)-Au deposits at the Fraser Mine (North Range of the Sudbury Igneous Complex). Evidence for coentrapment of immiscible hydrocarbon-brine, and hydrocarbon-halide melt mixtures is demonstrated. A primary CH4-brine assemblage was trapped during quartz growth at relatively low T (min. T trapping˜145-315°C) and P (max. P trapping˜500 bar), prior to the crystallization of sulfide minerals in the veins. Secondary inclusions contain solid halite and a mixture of CH4, C2H6-C2H2 and C3H8 and were trapped at a minimum T of ˜710°C. The halite inclusions may represent halide melt that exsolved from crystallizing sulfide ores that texturally postdate (by replacement) early alteration quartz hosting the primary, lower T brine-CH4 assemblage. Laser ablation ICP-MS analyses show that the brine, hydrocarbon and halide melt inclusions contain significant concentrations of Cu (0.1-1 wt% range), Au, Bi, Ag and Pt (all 0.1-10 ppm range). Cu:Pt and Cu:Au ratios in the inclusions are significantly (up to 4 log units) lower than in the host alteration veins and adjacent massive sulfide ore veins, suggesting either (1) early Cu loss from the volatiles by chalcopyrite precipitation or (2) enhanced Au and Pt solubilities relative to Cu at the temperatures of entrapment. Concentration ratios between coexisting brine and CH4 inclusions [C^{elem}_{brine}/C^{elem}_{CH4}] are lower for Cu, Au, Bi and Ag than for other elements (Na, Ca, Fe, Mn, Zn, Pb) indicating that during interaction with the brine, the hydrocarbon phase was enriched in ore metals. The high concentrations of ore metals in hydrocarbon, brine and halide melt phases confirm that both aqueous and non-aqueous volatiles were carriers of

  15. Metal-Enhanced Fluorescence of Phycobiliproteins from Heterogeneous Plasmonic Nanostructures.

    PubMed

    Chowdhury, Mustafa H; Ray, Krishanu; Aslan, Kadir; Lakowicz, Joseph R; Geddes, Chris D

    2007-12-01

    We report here the use of plasmonic metal nanostructures in the form of silver island films (SiFs) to enhance the fluorescence emission of five different phycobiliproteins. Our findings clearly show that the phycobiliproteins display up to a 9-fold increase in fluorescence emission intensity, with a maximum 7-fold decrease in lifetime when they are assembled as a monolayer above SiFs, as compared to a monolayer assembled on the surface of amine-terminated glass slides of the control sample. The study was also repeated with a thin liquid layer of the phycobiliproteins sandwiched between two glass substrates (and a SiFs and a glass substrate) clamped together. Similarly, the results show a maximum 10-fold increase in fluorescence emission intensity coupled with a 2-fold decrease in lifetime of the phycobiliproteins in the SiF-glass setup as compared to the glass control sample, implying that near-field enhancement of phycobiliprotein emission can be attained both with and without chemical linkage of the proteins to the SiFs. Hence, our results clearly show that metal-enhanced fluorescence (MEF) can potentially be employed to increase the sensitivity and detection limit of the plethora of bioassays that employ phycobiliproteins as fluorescence labels, such as in fluoro-immunoassays where the assay can be tethered on the surface of SiFs, and also in flow cytometry where analytes in the liquid phase could potentially flow through channels coated with SiFs without actually being attached to the silver.

  16. Noble metal superparticles and methods of preparation thereof

    DOEpatents

    Sun, Yugang; Hu, Yongxing

    2016-07-12

    A method comprises heating an aqueous solution of colloidal silver particles. A soluble noble metal halide salt is added to the aqueous solution which undergoes a redox reaction on a surface of the silver particles to form noble metal/silver halide SPs, noble metal halide/silver halide SPs or noble metal oxide/silver halide SPs on the surface of the silver particles. The heat is maintained for a predetermined time to consume the silver particles and release the noble metal/silver halide SPs, the noble metal halide/silver halide SPs or the noble metal oxide/silver halide SPs into the aqueous solution. The aqueous solution is cooled. The noble metal/silver halide SPs, the noble metal halide/silver halide SPs or noble metal oxide/silver halide SPs are separated from the aqueous solution. The method optionally includes adding a soluble halide salt to the aqueous solution.

  17. 40 CFR Table 3 to Subpart Ffff of... - Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP Metals Emissions From...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 12 2010-07-01 2010-07-01 true Emission Limits for Hydrogen Halide and... to Subpart FFFF of Part 63—Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP... following table that applies to your process vents that contain hydrogen halide and halogen HAP emissions...

  18. 40 CFR Table 3 to Subpart Ffff of... - Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP Metals Emissions From...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 13 2014-07-01 2014-07-01 false Emission Limits for Hydrogen Halide.... FFFF, Table 3 Table 3 to Subpart FFFF of Part 63—Emission Limits for Hydrogen Halide and Halogen HAP... limit in the following table that applies to your process vents that contain hydrogen halide and...

  19. 40 CFR Table 3 to Subpart Ffff of... - Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP Metals Emissions From...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 12 2011-07-01 2009-07-01 true Emission Limits for Hydrogen Halide and... to Subpart FFFF of Part 63—Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP... following table that applies to your process vents that contain hydrogen halide and halogen HAP emissions...

  20. 40 CFR Table 3 to Subpart Ffff of... - Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP Metals Emissions From...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 13 2013-07-01 2012-07-01 true Emission Limits for Hydrogen Halide and..., Table 3 Table 3 to Subpart FFFF of Part 63—Emission Limits for Hydrogen Halide and Halogen HAP Emissions... limit in the following table that applies to your process vents that contain hydrogen halide and...

  1. 40 CFR Table 3 to Subpart Ffff of... - Emission Limits for Hydrogen Halide and Halogen HAP Emissions or HAP Metals Emissions From...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 13 2012-07-01 2012-07-01 false Emission Limits for Hydrogen Halide.... FFFF, Table 3 Table 3 to Subpart FFFF of Part 63—Emission Limits for Hydrogen Halide and Halogen HAP... limit in the following table that applies to your process vents that contain hydrogen halide and...

  2. Bimetallic Nanoshells for Metal - Enhanced Fluorescence with Broad Band Fluorophores.

    PubMed

    Zhang, Jian; Fu, Yi; Mahdavi, Farhad

    2012-11-15

    In this article, we reported the near-field interactions between the Ru(bpy)(3) (2+) complexes and plasmon resonances from the bimetallic nanoshells. The metallic nanoshells were fabricated on 20 nm silica spheres as cores by depositing 10 nm monometallic or bimetallic shells. There were approx. 15 Ru(bpy)(3) (2+) complexes in the silica core. The metal shells were constituted of silver or/and gold. The bimetallic shells could be generated in homogeneous or heterogeneous geometries. The homogeneous bimetallic shells contained 10 nm silver-gold alloys. The heterogeneous bimetallic shells contained successive 5 nm gold and 5 nm silver shells, or alternatively, 5 nm silver and 5 nm gold shells. Optical properties of metal nanoshells were studied on both the ensemble spectra and single nanoparticle imaging measurements. The heterogeneous bimetallic shells were found to have a large scale of metal-enhanced emission relative to the monometallic or homogeneous bimetallic shells. It is because the heterogeneous bimetallic shells may display split dual plasmon resonances which can interact with the excitation and emission bands of the Ru(bpy)(3) (2+) complexes in the silica cores leading to more efficient near-field interactions. The prediction can be demonstrated by the lifetimes. Therefore, it is suggested that both the compositions and geometries of the metal shells can influence the interactions with the fluorophores in the cores. This observation also offers us an opportunity for developing plasmon-based fluorescence metal nanoparticles as novel nanoparticle imaging agents which have high performances in fluorescence cell or tissue imaging. PMID:23230456

  3. Metal-induced fluorescence properties of three-dimensionally ordered macroporous silver inverse opal platforms

    NASA Astrophysics Data System (ADS)

    Chae, Weon-Sik; Lee, Myung-Jin; Kim, Kisun; Hyun, Jerome K.; Jeon, Seokwoo

    2016-02-01

    This study examined the metal-induced fluorescence properties of three-dimensionally ordered macroporous silver inverse opal (IO) films. Electrochemically synthesized silver IO films with a micrometer cavity exhibited notable fluorescence enhancement at the silver frame, and a decrease in fluorescence lifetime. Numerical calculations supported the observations of a higher fluorescence efficiency at the frame than in the cavity.

  4. Fluorescence from a quantum dot and metallic nanosphere hybrid system

    SciTech Connect

    Schindel, Daniel G.; Singh, Mahi R.

    2014-03-31

    We present energy absorption and interference in a quantum dot-metallic nanosphere system embedded on a dielectric substrate. A control field is applied to induce dipole moments in the nanosphere and the quantum dot, and a probe field is applied to monitor absorption. Dipole moments in the quantum dot or the metal nanosphere are induced, both by the external fields and by each other's dipole fields. Thus, in addition to direct polarization, the metal nanosphere and the quantum dot will sense one another via the dipole-dipole interaction. The density matrix method was used to show that the absorption spectrum can be split from one peak to two peaks by the control field, and this can also be done by placing the metal sphere close to the quantum dot. When the two are extremely close together, a self-interaction in the quantum dot produces an asymmetry in the absorption peaks. In addition, the fluorescence efficiency can be quenched by the addition of a metal nanosphere. This hybrid system could be used to create ultra-fast switching and sensing nanodevices.

  5. Fluorescence from a quantum dot and metallic nanosphere hybrid system

    NASA Astrophysics Data System (ADS)

    Schindel, Daniel G.; Singh, Mahi R.

    2014-03-01

    We present energy absorption and interference in a quantum dot-metallic nanosphere system embedded on a dielectric substrate. A control field is applied to induce dipole moments in the nanosphere and the quantum dot, and a probe field is applied to monitor absorption. Dipole moments in the quantum dot or the metal nanosphere are induced, both by the external fields and by each other's dipole fields. Thus, in addition to direct polarization, the metal nanosphere and the quantum dot will sense one another via the dipole-dipole interaction. The density matrix method was used to show that the absorption spectrum can be split from one peak to two peaks by the control field, and this can also be done by placing the metal sphere close to the quantum dot. When the two are extremely close together, a self-interaction in the quantum dot produces an asymmetry in the absorption peaks. In addition, the fluorescence efficiency can be quenched by the addition of a metal nanosphere. This hybrid system could be used to create ultra-fast switching and sensing nanodevices.

  6. Colorimetric Fluorescent Nanosensor Based on Hexamethylene Diisocyanate for Fluorescent Responses and Adsorption of Heavy Metal Ions.

    PubMed

    Xu, Yaohui; Zhou, Yang; Li, Ruixing

    2016-03-01

    An inorganic-organic hybrid material based on magnetic Fe3O4@SiO2 nanoparticles was synthesized for fluorescent responses and removal of heavy metal ions, in which superparamagnetic Fe3O4@SiO2 nanoparticles were firstly prepared and modified with hexamethylene diisocyanate (HDI) instead of 3-isocyanatopropyltriethoxysilane (IPTES) as the organic coupling agent, and then a rhodamine derivative with spirolactam structure (Rho-en) was conjugated on the HDI functionalized Fe3O4@SiO2 nanoparticles through isocyanate groups. Both of functionalized Fe3O4@SiO2 nanoparticles based on IPTES and HDI were characterized by FT-IR and XPS, and the results indicated that HDI was a good alternative as chemical bridge for surface modification on the surface of Fe3O4@SiO2 nanoparticles. The inorganic-organic hybrid composites synthesized based HDI showed naked-eye color changes and fluorescent responses towards Zn2+, Cd2+, Mn2+, Pb2+, Hg2+ and Fe3+, which could serve as the available proofs for the qualitative analysis. Moreover, the as-obtained composites not only had excellent adsorption capability for Pb2+ and Hg2+, but also showed strong magnetic sensitivity, which could help to the removal and separation of functionalized magnetic nanocomposites after capturing the heavy metal ions. In addition, the plausible interaction mode of functionalized Fe3O4@SiO2 nanoparticles with heavy metal ions was discussed. PMID:27455720

  7. Effect of metal cation replacement on the electronic structure of metalorganic halide perovskites: Replacement of lead with alkaline-earth metals

    NASA Astrophysics Data System (ADS)

    Pazoki, Meysam; Jacobsson, T. Jesper; Hagfeldt, Anders; Boschloo, Gerrit; Edvinsson, Tomas

    2016-04-01

    Organic and inorganic lead halogen perovskites, and in particular, C H3N H3Pb I3 , have during the last years emerged as a class of highly efficient solar cell materials. Herein we introduce metalorganic halogen perovskite materials for energy-relevant applications based on alkaline-earth metals. Based on the classical notion of Goldschmidt's rules and quantum mechanical considerations, the three alkaline-earth metals, Ca, Sr, and Ba, are shown to be able to exchange lead in the perovskite structure. The three alkaline-earth perovskites, C H3N H3Ca I3,C H3N H3Sr I3 , and C H3N H3Ba I3 , as well as the reference compound, C H3N H3Pb I3 , are in this paper investigated with density functional theory (DFT) calculations, which predict these compounds to exist as stable perovskite materials, and their electronic properties are explored. A detailed analysis of the projected molecular orbital density of states and electronic band structure from DFT calculations were used for interpretation of the band-gap variations in these materials and for estimation of the effective masses of the electrons and holes. Neglecting spin-orbit effects, the band gap of MACa I3,MASr I3 , and MABa I3 were estimated to be 2.95, 3.6, and 3.3 eV, respectively, showing the relative change expected for metal cation exchange. The shifts in the conduction band (CB) edges for the alkaline-earth perovskites were quantified using scalar relativistic DFT calculations and tight-binding analysis, and were compared to the situation in the more extensively studied lead halide perovskite, C H3N H3Pb I3 , where the change in the work function of the metal is the single most important factor in tuning the CB edge and band gap. The results show that alkaline-earth-based organometallic perovskites will not work as an efficient light absorber in photovoltaic applications but instead could be applicable as charge-selective contact materials. The rather high CB edge and the wide band gap together with the large

  8. Fluorescent bioassays for toxic metals in milk and yoghurt

    PubMed Central

    2012-01-01

    Background From a human health viewpoint, contaminated milk and its products could be a source of long-term exposure to toxic metals. Simple, inexpensive, and on-site assays would enable constant monitoring of their contents. Bioassays that can measure toxic metals in milk or yoghurt might reduce the risk. For this purpose, the green fluorescent protein (GFP)-tagged trans factors, ArsR-GFP and CadC-GFP, together with their cis elements were used to develop such bioassays. Results ArsR-GFP or CadC-GFP, which binds either toxic metal or DNA fragment including cis element, was directly mixed with cow’s milk or yoghurt within a neutral pH range. The fluorescence of GFP, which is reflected by the association/dissociation ratio between cis element and trans factor, significantly changed with increasing externally added As (III) or Cd (II) whereas smaller responses to externally added Pb (II) and Zn (II) were found. Preparation and dilution of whey fraction at low pH were essential to intrinsic zinc quantification using CadC-GFP. Using the extraction procedure and bioassay, intrinsic Zn (II) concentrations ranging from 1.4 to 4.8 mg/l for milk brands and from 1.2 to 2.9 mg/kg for yoghurt brands were determined, which correlated to those determined using inductively coupled plasma atomic emission spectroscopy. Conclusions GFP-tagged bacterial trans factors and cis elements can work in the neutralized whole composition and diluted whey fraction of milk and yoghurt. The feature of regulatory elements is advantageous for establishment of simple and rapid assays of toxic metals in dairy products. PMID:23098077

  9. Actinide halide complexes

    SciTech Connect

    Avens, L.R.; Zwick, B.D.; Sattelberger, A.P.; Clark, D.L.; Watkin, J.G.

    1991-02-07

    A compound of the formula MX{sub n}L{sub m} wherein M = Th, Pu, Np,or Am thorium, X = a halide atom, n = 3 or 4, L is a coordinating ligand selected from the group consisting of aprotic Lewis bases having an oxygen-, nitrogen-, sulfur-, or phosphorus-donor, and m is 3 or 4 for monodentate ligands or is 2 for bidentate ligands, where n + m = 7 or 8 for monodentate ligands or 5 or 6 for bidentate ligands, a compound of the formula MX{sub n} wherein M, X, and n are as previously defined, and a process of preparing such actinide metal compounds including admixing the actinide metal in an aprotic Lewis base as a coordinating solvent in the presence of a halogen-containing oxidant, are provided.

  10. A theoretical investigation of single-molecule fluorescence detection on thin metallic layers.

    PubMed Central

    Enderlein, J

    2000-01-01

    In the present paper, the excitation and detection of single-molecule fluorescence over thin metallic films is studied theoretically within the framework of classical electrodynamics. The model takes into account the specific conditions of surface plasmon-assisted optical excitation, fluorescence quenching by the metal film, and detection geometry. Extensive numerical results are presented for gold, silver, and aluminum films, showing the detectable fluorescence intensities and their dependence on film thickness and the fluorescent molecule's position under optimal excitation conditions. PMID:10733992

  11. A theoretical investigation of single-molecule fluorescence detection on thin metallic layers.

    PubMed

    Enderlein, J

    2000-04-01

    In the present paper, the excitation and detection of single-molecule fluorescence over thin metallic films is studied theoretically within the framework of classical electrodynamics. The model takes into account the specific conditions of surface plasmon-assisted optical excitation, fluorescence quenching by the metal film, and detection geometry. Extensive numerical results are presented for gold, silver, and aluminum films, showing the detectable fluorescence intensities and their dependence on film thickness and the fluorescent molecule's position under optimal excitation conditions.

  12. Excitation volumetric effects (EVE) in metal-enhanced fluorescence.

    PubMed

    Dragan, A I; Geddes, C D

    2011-03-01

    Metal-Enhanced Fluorescence (MEF) effects from different density silver island films (SiFs) and the effects of far-field excitation irradiance on the observed enhancement of fluorescence were studied. It is shown that MEF non-linearly depends on silver nanoparticle (NP) size/density, reaching a maximum value for SiFs made at a deposition time (DT) of ∼5 minutes, i.e. just before SiFs become continuous. Numerical simulations of the silver-islands growing on glass revealed that the near-field magnitude depends non-linearly on size and interparticle distance exhibiting dramatic enhancement at ∼10 nm distance between the NPs. In addition, a remarkable effect of modulation in MEF efficiency by far-field excitation irradiance has been observed, which can be correlated well with numerical simulations that show an excitation power volume dependence. The near-field volume changes non-linearly with far-field power. This unique observation has profound implications in MEF, which has rapidly emerged as a powerful tool in the biosciences and ultimately allows for tunable fluorescence enhancement factors.

  13. Process and composition for drying of gaseous hydrogen halides

    DOEpatents

    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. Oxidation of hydrogen halides to elemental halogens

    DOEpatents

    Rohrmann, Charles A.; Fullam, Harold T.

    1985-01-01

    A process for oxidizing hydrogen halides having substantially no sulfur impurities by means of a catalytically active molten salt is disclosed. A mixture of the subject hydrogen halide and an oxygen bearing gas is contacted with a molten salt containing an oxidizing catalyst and alkali metal normal sulfates and pyrosulfates to produce an effluent gas stream rich in the elemental halogen and substantially free of sulfur oxide gases.

  15. Containerless study of metal evaporation by laser induced fluorescence

    NASA Technical Reports Server (NTRS)

    Schiffman, Robert A.; Nordine, Paul C.

    1987-01-01

    Laser induced fluorescence (LIF) detection of atomic vapors was used to study evaporation from electromagnetically levitated and CW CO2 laser-heated molybdenum spheres and resistively-heated tungsten filaments. Electromagnetic (EM) levitation in combination with laser heating of tungsten, zirconium, and aluminum specimens was also investigated. LIF intensity vs temperature data were obtained for molybdenum atoms and six electronic states of atomic tungsten, at temperatures up to the melting point of each metal. The detected fraction of the emitted radiation was reduced by self-absorption effects at the higher experimental temperatures. Vaporization enthalpies derived from data for which less than half the LIF intensity was self-absorbed were -636 + or - 24 kJ/g-mol for Mo and 831 + or - 32 kJ/g-mol for W. Space-based applications of EM levitation in combination with radiative heating are discussed.

  16. Fluorescent chelates for monitoring metal binding with macromolecules.

    PubMed

    Islam, M; Khanin, M; Sadik, O A

    2003-01-01

    Metals and radionuclides are usually coupled with proteins together with suitable ligands for therapeutic, tumor-imaging, pharmaceuticals, and biocompatibility applications. Several ligands that can strongly coordinate a given nuclide in a specific valency are already known. However, the demand for bifunctionality has limited the applications of these ligands. We hereby report the molecular design of a receptor system based on the linkage of protein to monoazo ligands. By use of basic coordination chemistry, 4-(3-quinolinoazo)hydroxybenzoic acid (QABA) and derivatives were successfully conjugated to ovalbumin, bovine serum albumin, and alkaline phosphatase at a site that was distinct from the metal binding site. The presence of carboxylic acid linkage in the QABA served as a convenient bridge for protein conjugation and may allow the generic application of these ligands for bioconjugate synthesis while ensuring a high in vivo stability. The ligand-protein conjugates were characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy, thin layer chromatography, NMR, and surface-enhanced laser desorption ionization time-of-flight mass spectrometry. The conjugate was tested for the ability to recognize nonradioactive Ga(3+) at a physiological pH, and a binding constant of 1 x 10(20) was recorded. Also, the in vitro testing results indicated that the fluorescent conjugates exhibited significant selectivity for gallium compared to Pb(2+), Hg(2+), Zn(2+), Cu(2+), Fe(3+), and Co(2+) while no responses were obtained for alkaline and alkaline earth metals. These attributes could allow these conjugates to be used as a model for imaging sensors and for metal detection. PMID:12523855

  17. Selective fluorescence sensors for detection of nitroaniline and metal Ions based on ligand-based luminescent metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Yu, Zongchao; Wang, Fengqin; Lin, Xiangyi; Wang, Chengmiao; Fu, Yiyuan; Wang, Xiaojun; Zhao, Yongnan; Li, Guodong

    2015-12-01

    Metal-organic frameworks (MOFs) are porous crystalline materials with high potential for applications in fluorescence sensors. In this work, two solvent-induced Zn(II)-based metal-organic frameworks, Zn3L3(DMF)2 (1) and Zn3L3(DMA)2(H2O)3 (2) (L=4,4‧-stilbenedicarboxylic acid), were investigated as selective sensing materials for detection of nitroaromatic compounds and metal ions. The sensing experiments show that 1 and 2 both exhibit selective fluorescence quenching toward nitroaniline with a low detection limit. In addition, 1 exhibits high selectivity for detection of Fe3+ and Al3+ by significant fluorescence quenching or enhancement effect. While for 2, it only exhibits significant fluorescence quenching effect for Fe3+. The results indicate that 1 and 2 are both promising fluorescence sensors for detecting and recognizing nitroaniline and metal ions with high sensitivity and selectivity.

  18. The gas phase emitter effect of lanthanum within ceramic metal halide lamps and its dependence on the La vapor pressure and operating frequency

    SciTech Connect

    Ruhrmann, C.; Hoebing, T.; Bergner, A.; Groeger, S.; Awakowicz, P.; Mentel, J.; Denissen, C.; Suijker, J.

    2015-08-07

    The gas phase emitter effect increases the lamp lifetime by lowering the work function and, with it, the temperature of the tungsten electrodes of metal halide lamps especially for lamps in ceramic vessels due to their high rare earth pressures. It is generated by a monolayer on the electrode surface of electropositive atoms of certain emitter elements, which are inserted into the lamp bulb by metal iodide salts. They are vaporized, dissociated, ionized, and deposited by an emitter ion current onto the electrode surface within the cathodic phase of lamp operation with a switched-dc or ac-current. The gas phase emitter effect of La and the influence of Na on the emitter effect of La are studied by spatially and phase-resolved pyrometric measurements of the electrode tip temperature, La atom, and ion densities by optical emission spectroscopy as well as optical broadband absorption spectroscopy and arc attachment images by short time photography. An addition of Na to the lamp filling increases the La vapor pressure within the lamp considerably, resulting in an improved gas phase emitter effect of La. Furthermore, the La vapor pressure is raised by a heating of the cold spot. In this way, conditions depending on the La vapor pressure and operating frequency are identified, at which the temperature of the electrodes becomes a minimum.

  19. The gas phase emitter effect of lanthanum within ceramic metal halide lamps and its dependence on the La vapor pressure and operating frequency

    NASA Astrophysics Data System (ADS)

    Ruhrmann, C.; Hoebing, T.; Bergner, A.; Groeger, S.; Denissen, C.; Suijker, J.; Awakowicz, P.; Mentel, J.

    2015-08-01

    The gas phase emitter effect increases the lamp lifetime by lowering the work function and, with it, the temperature of the tungsten electrodes of metal halide lamps especially for lamps in ceramic vessels due to their high rare earth pressures. It is generated by a monolayer on the electrode surface of electropositive atoms of certain emitter elements, which are inserted into the lamp bulb by metal iodide salts. They are vaporized, dissociated, ionized, and deposited by an emitter ion current onto the electrode surface within the cathodic phase of lamp operation with a switched-dc or ac-current. The gas phase emitter effect of La and the influence of Na on the emitter effect of La are studied by spatially and phase-resolved pyrometric measurements of the electrode tip temperature, La atom, and ion densities by optical emission spectroscopy as well as optical broadband absorption spectroscopy and arc attachment images by short time photography. An addition of Na to the lamp filling increases the La vapor pressure within the lamp considerably, resulting in an improved gas phase emitter effect of La. Furthermore, the La vapor pressure is raised by a heating of the cold spot. In this way, conditions depending on the La vapor pressure and operating frequency are identified, at which the temperature of the electrodes becomes a minimum.

  20. Analysis of molecular structure, spectroscopic properties (FT-IR, micro-Raman and UV-vis) and quantum chemical calculations of free and ligand 2-thiopheneglyoxylic acid in metal halides (Cd, Co, Cu, Ni and Zn)

    NASA Astrophysics Data System (ADS)

    Gökce, Halil; Bahçeli, Semiha

    2013-12-01

    In this study, molecular geometries, experimental vibrational wavenumbers, electronic properties and quantum chemical calculations of 2-thiopheneglyoxylic acid molecule, (C6H4O3S), and its metal halides (Cd, Co, Cu, Ni and Zn) which are used as pharmacologic agents have been investigated experimentally by FT-IR, micro-Raman and UV-visible spectroscopies and elemental analysis. Meanwhile the vibrational calculations were verified by DFT/B3LYP method with 6-311++G(d,p) and LANL2DZ basis sets in the ground state, for free TPGA molecule and its metal halide complexes, respectively, for the first time. The calculated fundamental vibrational frequencies for the title compounds are in a good agreement with the experimental data.

  1. Fluorescence quenching of water-soluble conjugated polymer by metal cations and its application in sensor.

    PubMed

    Chen, Yan-Guo; Zhao, Dan; He, Zhi-Ke; Ai, Xin-Ping

    2007-02-01

    The effects of different metal cations on the fluorescence of water-soluble conjugated polymer (CP) and their quenching mechanism have been explored. Most transition metal cations, especially noble metal cations, such as Pd2+, Ru3+, and Pt2+ possessed higher quenching efficiency to CP fluorescence than that of the main group metal cations and other transition metal cations, which have filled or half-full outmost electron layer configurations. Base on this, rapid, sensitive detection of noble metal cations can be realized and a novel quencher-tether-ligand (QTL) probe was developed to detect avidin and streptavidin.

  2. Actinide halide complexes

    DOEpatents

    Avens, Larry R.; Zwick, Bill D.; Sattelberger, Alfred P.; Clark, David L.; Watkin, John G.

    1992-01-01

    A compound of the formula MX.sub.n L.sub.m wherein M is a metal atom selected from the group consisting of thorium, plutonium, neptunium or americium, X is a halide atom, n is an integer selected from the group of three or four, L is a coordinating ligand selected from the group consisting of aprotic Lewis bases having an oxygen-, nitrogen-, sulfur-, or phosphorus-donor, and m is an integer selected from the group of three or four for monodentate ligands or is the integer two for bidentate ligands, where the sum of n+m equals seven or eight for monodentate ligands or five or six for bidentate ligands, a compound of the formula MX.sub.n wherein M, X, and n are as previously defined, and a process of preparing such actinide metal compounds including admixing the actinide metal in an aprotic Lewis base as a coordinating solvent in the presence of a halogen-containing oxidant, are provided.

  3. Actinide halide complexes

    DOEpatents

    Avens, L.R.; Zwick, B.D.; Sattelberger, A.P.; Clark, D.L.; Watkin, J.G.

    1992-11-24

    A compound is described of the formula MX[sub n]L[sub m] wherein M is a metal atom selected from the group consisting of thorium, plutonium, neptunium or americium, X is a halide atom, n is an integer selected from the group of three or four, L is a coordinating ligand selected from the group consisting of aprotic Lewis bases having an oxygen-, nitrogen-, sulfur-, or phosphorus-donor, and m is an integer selected from the group of three or four for monodentate ligands or is the integer two for bidentate ligands, where the sum of n+m equals seven or eight for monodentate ligands or five or six for bidentate ligands. A compound of the formula MX[sub n] wherein M, X, and n are as previously defined, and a process of preparing such actinide metal compounds are described including admixing the actinide metal in an aprotic Lewis base as a coordinating solvent in the presence of a halogen-containing oxidant.

  4. A combined metal-halide/metal flux synthetic route towards type-I clathrates: crystal structures and thermoelectric properties of A8Al8Si38 (A = K, Rb, and Cs).

    PubMed

    Baran, Volodymyr; Senyshyn, Anatoliy; Karttunen, Antti J; Fischer, Andreas; Scherer, Wolfgang; Raudaschl-Sieber, Gabriele; Fässler, Thomas F

    2014-11-10

    Single-phase samples of the compounds K8Al8Si38 (1), Rb8Al8Si38 (2), and Cs7.9Al7.9Si38.1 (3) were obtained with high crystallinity and in good quantities by using a novel flux method with two different flux materials, such as Al and the respective alkali-metal halide salt (KBr, RbCl, and CsCl). This approach facilitates the removal of the product mixture from the container and also allows convenient extraction of the flux media due to the good solubility of the halide salts in water. The products were analyzed by means of single-crystal X-ray structure determination, powder X-ray and neutron diffraction experiments, (27)Al-MAS NMR spectroscopy measurements, quantum chemical calculations, as well as magnetic and transport measurements (thermal conductivity, electrical resistivity, and Seebeck coefficient). Due to the excellent quality of the neutron diffraction data, the difference between the nuclear scattering factors of silicon and aluminum atoms was sufficient to refine their mixed occupancy at specific sites. The role of variable-range hopping for the interpretation of the resistivity and the Seebeck coefficient is discussed. PMID:25267571

  5. Recent advances in technetium halide chemistry.

    PubMed

    Poineau, Frederic; Johnstone, Erik V; Czerwinski, Kenneth R; Sattelberger, Alfred P

    2014-02-18

    Transition metal binary halides are fundamental compounds, and the study of their structure, bonding, and other properties gives chemists a better understanding of physicochemical trends across the periodic table. One transition metal whose halide chemistry is underdeveloped is technetium, the lightest radioelement. For half a century, the halide chemistry of technetium has been defined by three compounds: TcF6, TcF5, and TcCl4. The absence of Tc binary bromides and iodides in the literature was surprising considering the existence of such compounds for all of the elements surrounding technetium. The common synthetic routes that scientists use to obtain binary halides of the neighboring elements, such as sealed tube reactions between elements and flowing gas reactions between a molecular complex and HX gas (X = Cl, Br, or I), had not been reported for technetium. In this Account, we discuss how we used these routes to revisit the halide chemistry of technetium. We report seven new phases: TcBr4, TcBr3, α/β-TcCl3, α/β-TcCl2, and TcI3. Technetium tetrachloride and tetrabromide are isostructural to PtX4 (X = Cl or Br) and consist of infinite chains of edge-sharing TcX6 octahedra. Trivalent technetium halides are isostructural to ruthenium and molybdenum (β-TcCl3, TcBr3, and TcI3) and to rhenium (α-TcCl3). Technetium tribromide and triiodide exhibit the TiI3 structure-type and consist of infinite chains of face-sharing TcX6 (X = Br or I) octahedra. Concerning the trichlorides, β-TcCl3 crystallizes with the AlCl3 structure-type and consists of infinite layers of edge-sharing TcCl6 octahedra, while α-TcCl3 consists of infinite layers of Tc3Cl9 units. Both phases of technetium dichloride exhibit new structure-types that consist of infinite chains of [Tc2Cl8] units. For the technetium binary halides, we studied the metal-metal interaction by theoretical methods and magnetic measurements. The change of the electronic configuration of the metal atom from d(3) (Tc

  6. Recent advances in technetium halide chemistry.

    PubMed

    Poineau, Frederic; Johnstone, Erik V; Czerwinski, Kenneth R; Sattelberger, Alfred P

    2014-02-18

    Transition metal binary halides are fundamental compounds, and the study of their structure, bonding, and other properties gives chemists a better understanding of physicochemical trends across the periodic table. One transition metal whose halide chemistry is underdeveloped is technetium, the lightest radioelement. For half a century, the halide chemistry of technetium has been defined by three compounds: TcF6, TcF5, and TcCl4. The absence of Tc binary bromides and iodides in the literature was surprising considering the existence of such compounds for all of the elements surrounding technetium. The common synthetic routes that scientists use to obtain binary halides of the neighboring elements, such as sealed tube reactions between elements and flowing gas reactions between a molecular complex and HX gas (X = Cl, Br, or I), had not been reported for technetium. In this Account, we discuss how we used these routes to revisit the halide chemistry of technetium. We report seven new phases: TcBr4, TcBr3, α/β-TcCl3, α/β-TcCl2, and TcI3. Technetium tetrachloride and tetrabromide are isostructural to PtX4 (X = Cl or Br) and consist of infinite chains of edge-sharing TcX6 octahedra. Trivalent technetium halides are isostructural to ruthenium and molybdenum (β-TcCl3, TcBr3, and TcI3) and to rhenium (α-TcCl3). Technetium tribromide and triiodide exhibit the TiI3 structure-type and consist of infinite chains of face-sharing TcX6 (X = Br or I) octahedra. Concerning the trichlorides, β-TcCl3 crystallizes with the AlCl3 structure-type and consists of infinite layers of edge-sharing TcCl6 octahedra, while α-TcCl3 consists of infinite layers of Tc3Cl9 units. Both phases of technetium dichloride exhibit new structure-types that consist of infinite chains of [Tc2Cl8] units. For the technetium binary halides, we studied the metal-metal interaction by theoretical methods and magnetic measurements. The change of the electronic configuration of the metal atom from d(3) (Tc

  7. Metal-clad optical waveguide fluorescence device for the detection of heavy metal ions

    NASA Astrophysics Data System (ADS)

    Margheri, Giancarlo; Giorgetti, Emilia; Marsili, Paolo; Zoppi, Angela; Lascialfari, Luisa; Cicchi, Stefano

    2014-07-01

    We developed Hg-sensing chips by decorating the external surface of metal-clad optical waveguides with a monolayer of Hg-sensitive fluorescent molecular probes. The emission properties of the original water-soluble form of the molecule were previously found to be selectively quenched in the presence of Hg ions. The fabricated samples were tested with optical waveguide fluorescence spectroscopy by putting them in contact with a 5-μM water solution of Hg ions and recording the emission spectra versus incubation time. The estimate of the limit of detection was 150 nM. A preliminary evaluation of the selectivity of the structure was also performed by using Cd as possible interfering analytes.

  8. Chemistry of soluble β-diketiminatoalkaline-earth metal complexes with M-X bonds (M=Mg, Ca, Sr; X=OH, Halides, H).

    PubMed

    Sarish, Sankaranarayana Pillai; Nembenna, Sharanappa; Nagendran, Selvarajan; Roesky, Herbert W

    2011-03-15

    Victor Grignard's Nobel Prize-winning preparation of organomagnesium halides (Grignard reagents) marked the formal beginning of organometallic chemistry with alkaline earth metals. Further development of this invaluable synthetic route, RX+Mg→RMgX, with the heavier alkaline earth metals (Ca and Sr) was hampered by limitations in synthetic methodologies. Moreover, the lack of suitable ligands for stabilizing the reactive target molecules, particularly with the more electropositive Ca and Sr, was another obstacle. The absence in the literature, until just recently, of fundamental alkaline earth metal complexes with M-H, M-F, and M-OH (where M is the Group 2 metal Mg, Ca, or Sr) bonds amenable for organometallic reactions is remarkable. The progress in isolating various unstable compounds of p-block elements with β-diketiminate ligands was recently applied to Group 2 chemistry. The monoanionic β-diketiminate ligands are versatile tools for addressing synthetic challenges, as amply demonstrated with alkaline earth complexes: the synthesis and structural characterization of soluble β-diketiminatocalcium hydroxide, β-diketiminatostrontium hydroxide, and β-diketiminatocalcium fluoride are just a few examples of our contribution to this area of research. To advance the chemistry beyond synthesis, we have investigated the reactivity and potential for applications of these species, for example, through the demonstration of dip coating surfaces with CaCO(3) and CaF(2) with solutions of the calcium hydroxide and calcium fluoride complexes, respectively. In this Account, we summarize some recent developments in alkaline earth metal complex chemistry, particularly of Mg, Ca, and Sr, through the utilization of β-diketiminate ligands. We focus on results generated in our laboratory but give due mention to work from other groups as well. We also highlight the closely related chemistry of the Group 12 element Zn, as well as the important chemistry developed by other groups

  9. Complete-velocity-range description of negative-ion conversion of neutral atoms on an alkali-metal-halide surface under grazing geometry

    NASA Astrophysics Data System (ADS)

    Zhou, Hu; Zhou, Wang; Zhang, Meixiao; Zhou, Lihua; Ma, Yulong; Wang, Guangyi; Wu, Yong; Li, Bowen; Chen, Ximeng

    2016-06-01

    We propose a simple theoretical approach to consider negative-ion conversion of neutral atoms grazing on alkali-metal-halide crystal surfaces over the complete velocity range. The conversion process is viewed as a series of successive binary collisions between the projectile and the negatively charged sites on the surface along their trajectories due to localization of valence-band electrons at the anionic sites of the crystal. Conversion from F0 to F- via grazing scattering in LiF(100) and KI(100) is demonstrated with this model, which incorporates the key factors of image interaction and Mott-Littleton polarization interaction for electron capture. It also incorporates the decrease in the electron affinity due to Coulomb barrier tunneling of large-velocity negative ions to the vacuum level near surface anion sites. The pronounced differences in the efficiency of F- formation at LiF(100) and KI(100) surfaces are well explained by the proposed model. The relative efficiency and related saturation of the negative-ion formation for LiF and KI crystals compare well with experimental results.

  10. [Studies on toxicity of four kinds of heavy metals in water by synchronous-scan fluorescence].

    PubMed

    Duan, Jing-Bo; Liu, Wen-Qing; Zhang, Yu-Jun; Zhao, Nan-Jing; Wang, Zhi-Gang; Yin, Gao-Fang; Fang, Li; Liu, Jing

    2013-05-01

    Spectrofluorometry of chlorella pyrenoidosa was studied by three dimensional excitation-emission (3DEEM) fluorescence spectroscopy and synchronous scan fluorescence spectroscopy with Delta gamma = 20 nm in the stress of Hg+, Cd2+, Cu2+ and Zn2+. The conclusion from two kinds of Spectrofluorometry was the same: after 96h stress by heavy metals, the maximum fluorescence values reduced obviously, chlorophyll-a and chlorophyll-b in the photosynthetic system were seriously damaged by heavy metal. Further analysis of the correlations between heavy metal concentration and fluorescence quenching efficiency I0/I can conclude that the toxicity of heavy metal and the fluorescence quenching efficiency I0/I were positively correlated, and they all increased with the heavy metal concentration and stress time. For one kind of heavy metals, synchronous scan fluorometry is a sensitive method for its toxicity assessment. Compared to 3DEEM fluorescence spectroscopy, synchronous scan fluorescence spectroscopy is less time consuming and of higher selectivity. It is suitable to assess the toxicity of pollutions in water.

  11. Rigidifying Fluorescent Linkers by Metal-Organic Framework Formation for Fluorescence Blue Shift and Quantum Yield Enhancement

    SciTech Connect

    Wei, ZW; Gu, ZY; Arvapally, RK; Chen, YP; McDougald, RN; Ivy, JF; Yakovenko, AA; Feng, DW; Omary, MA; Zhou, HC

    2014-06-11

    We demonstrate that rigidifying the structure of fluorescent linkers by structurally constraining them in metal-organic frameworks (MOFs) to control their conformation effectively tunes the fluorescence energy and enhances the quantum yield. Thus, a new tetraphenylethylene-based zirconium MOF exhibits a deep-blue fluorescent emission at 470 nm with a unity quantum yield (99.9 +/- 0.5%) under Ar, representing ca. 3600 cm(-1) blue shift and doubled radiative decay efficiency vs the linker precursor. An anomalous increase in the fluorescence lifetime and relative intensity takes place upon heating the solid MOF from cryogenic to ambient temperatures. The origin of these unusual photoluminescence properties is attributed to twisted linker conformation, intramolecular hindrance, and framework rigidity.

  12. APPARATUS FOR THE PRODUCTION OF LITHIUM METAL

    DOEpatents

    Baker, P.S.; Duncan, F.R.; Greene, H.B.

    1961-08-22

    Methods and apparatus for the production of high-purity lithium from lithium halides are described. The apparatus is provided for continuously contacting a molten lithium halide with molten barium, thereby forming lithium metal and a barium halide, establishing separate layers of these reaction products and unreacted barium and lithium halide, and continuously withdrawing lithium and barium halide from the reaction zone. (AEC)

  13. Fluorescent metal nanoshell and CK19 detection on single cell image

    SciTech Connect

    Zhang, Jian; Fu, Yi; Li, Ge; Lakowicz, Joseph R.; Zhao, Richard Y.

    2011-09-16

    Highlights: {yields} Novel metal nanoshell as fluorescence imaging agent. {yields} Fluorescent mAb-metal complex with enhanced intensity and shortened lifetime. {yields} Immuno-interactions of mAb-metal complexes with CK19 molecules on CNCAP and HeLa cell surfaces. {yields} Isolation of conjugated mAb-metal complexes from cellular autofluorescence on cell image. -- Abstract: In this article, we report the synthesis strategy and optical properties of a novel type of fluorescence metal nanoshell when it was used as imaging agent for fluorescence cell imaging. The metal nanoshells were made with 40 nm silica cores and 10 nm silver shells. Unlike typical fluorescence metal nanoshells which contain the organic dyes in the cores, novel metal nanoshells were composed of Cy5-labelled monoclonal anti-CK19 antibodies (mAbs) on the external surfaces of shells. Optical measurements to the single nanoparticles showed that in comparison with the metal free labelled mAbs, the mAb-Ag complexes displayed significantly enhanced emission intensity and dramatically shortened lifetime due to near-field interactions of fluorophores with metal. These metal nanoshells were found to be able to immunoreact with target cytokeratin 19 (CK19) molecules on the surfaces of LNCAP and HeLa cells. Fluorescence cell images were recorded on a time-resolved confocal microscope. The emissions from the metal nanoprobes could be clearly isolated from the cellular autofluorescence backgrounds on the cell images as either individuals or small clusters due to their stronger emission intensities and shorter lifetimes. These emission signals could also be precisely counted on single cell images. The count number may provide an approach for quantifying the target molecules in the cells.

  14. Complementary Metal-Oxide-Semiconductor Image Sensor with Microchamber Array for Fluorescent Bead Counting

    NASA Astrophysics Data System (ADS)

    Sasagawa, Kiyotaka; Ando, Keisuke; Kobayashi, Takuma; Noda, Toshihiko; Tokuda, Takashi; Kim, Soo Hyeon; Iino, Ryota; Noji, Hiroyuki; Ohta, Jun

    2012-02-01

    We fabricated a complementary metal-oxide-semiconductor image sensor with a femtoliter microchamber array. The microchamber array plate is used for trapping microbeads and limiting the incident angle of light detected by the sensor. The sensor has an interference filter for fluorescent microbeads imaging. We detected fluorescent and nonfluorescent microbead with this sensor and showed its capability for counting the number of fluorescent chambers.

  15. An artificial tongue fluorescent sensor array for identification and quantitation of various heavy metal ions.

    PubMed

    Xu, Wang; Ren, Changliang; Teoh, Chai Lean; Peng, Juanjuan; Gadre, Shubhankar Haribhau; Rhee, Hyun-Woo; Lee, Chi-Lik Ken; Chang, Young-Tae

    2014-09-01

    Herein, a small-molecule fluorescent sensor array for rapid identification of seven heavy metal ions was designed and synthesized, with its sensing mechanism mimicking that of a tongue. The photoinduced electron transfer and intramolecular charge transfer mechanism result in combinatorial interactions between sensor array and heavy metal ions, which lead to diversified fluorescence wavelength shifts and emission intensity changes. Upon principle component analysis (PCA), this result renders clear identification of each heavy metal ion on a 3D spatial dispersion graph. Further exploration provides a concentration-dependent pattern, allowing both qualitative and quantitative measurements of heavy metal ions. On the basis of this information, a "safe-zone" concept was proposed, which provides rapid exclusion of versatile hazardous species from clean water samples based on toxicity characteristic leaching procedure standards. This type of small-molecule fluorescent sensor array could open a new avenue for multiple heavy metal ion detection and simplified water quality analysis.

  16. An artificial tongue fluorescent sensor array for identification and quantitation of various heavy metal ions.

    PubMed

    Xu, Wang; Ren, Changliang; Teoh, Chai Lean; Peng, Juanjuan; Gadre, Shubhankar Haribhau; Rhee, Hyun-Woo; Lee, Chi-Lik Ken; Chang, Young-Tae

    2014-09-01

    Herein, a small-molecule fluorescent sensor array for rapid identification of seven heavy metal ions was designed and synthesized, with its sensing mechanism mimicking that of a tongue. The photoinduced electron transfer and intramolecular charge transfer mechanism result in combinatorial interactions between sensor array and heavy metal ions, which lead to diversified fluorescence wavelength shifts and emission intensity changes. Upon principle component analysis (PCA), this result renders clear identification of each heavy metal ion on a 3D spatial dispersion graph. Further exploration provides a concentration-dependent pattern, allowing both qualitative and quantitative measurements of heavy metal ions. On the basis of this information, a "safe-zone" concept was proposed, which provides rapid exclusion of versatile hazardous species from clean water samples based on toxicity characteristic leaching procedure standards. This type of small-molecule fluorescent sensor array could open a new avenue for multiple heavy metal ion detection and simplified water quality analysis. PMID:25144824

  17. Molecular compressibility of some halides in alcohols

    NASA Technical Reports Server (NTRS)

    Serban, C.; Auslaender, D.

    1974-01-01

    After measuring ultrasonic velocity and density, the molecular compressibility values from Wada's formula were calculated, for alkali metal halide solutions in methyl, ethyl, butyl, and glycol alcohol. The temperature and concentration dependence were studied, finding deviations due to the hydrogen bonds of the solvent.

  18. Radiative decay engineering 5: metal-enhanced fluorescence and plasmon emission

    PubMed Central

    Lakowicz, Joseph R.

    2009-01-01

    Metallic particles and surfaces display diverse and complex optical properties. Examples include the intense colors of noble metal colloids, surface plasmon resonance absorption by thin metal films, and quenching of excited fluorophores near the metal surfaces. Recently, the interactions of fluorophores with metallic particles and surfaces (metals) have been used to obtain increased fluorescence intensities, to develop assays based on fluorescence quenching by gold colloids, and to obtain directional radiation from fluorophores near thin metal films. For metal-enhanced fluorescence it is difficult to predict whether a particular metal structure, such as a colloid, fractal, or continuous surface, will quench or enhance fluorescence. In the present report we suggest how the effects of metals on fluorescence can be explained using a simple concept, based on radiating plasmons (RPs). The underlying physics may be complex but the concept is simple to understand. According to the RP model, the emission or quenching of a fluorophore near the metal can be predicted from the optical properties of the metal structures as calculated from electrodynamics, Mie theory, and/or Maxwell’s equations. For example, according to Mie theory and the size and shape of the particle, the extinction of metal colloids can be due to either absorption or scattering. Incident energy is dissipated by absorption. Far-field radiation is created by scattering. Based on our model small colloids are expected to quench fluorescence because absorption is dominant over scattering. Larger colloids are expected to enhance fluorescence because the scattering component is dominant over absorption. The ability of a metal’s surface to absorb or reflect light is due to wavenumber matching requirements at the metal–sample interface. Wavenumber matching considerations can also be used to predict whether fluorophores at a given distance from a continuous planar surface will be emitted or quenched. These

  19. Metal-enhanced fluorescence and FRET on nanohole arrays excited at angled incidence.

    PubMed

    Poirier-Richard, H-P; Couture, M; Brule, T; Masson, J-F

    2015-07-21

    The influence of experimental parameters on the performance of plasmonic sensors is of great importance in analytical sciences. The plasmon coupling conditions (angle of incidence, metal composition, laser frequency and excitation/emission properties of fluorophores) were thus investigated for surface plasmon-enhanced fluorescence on metallic nanohole arrays. Optimal fluorescence enhancements were achieved when the plasmon resonance, the excitation laser and the fluorophore's excitation wavelengths were matched. The enhancement of the acceptor emission of a rhodamine 6G(Rh6G)-Quasar670™ FRET pair was achieved on the nanohole arrays by tuning the plasmon wavelength with the maximal overlap of the donor's emission and acceptor excitation. Silver nanohole arrays achieved larger fluorescence enhancement than gold nanohole arrays at 532 nm, while gold nanohole arrays led to larger fluorescence enhancement at 635 nm. These results demonstrate the importance of tuning the plasmon coupling conditions for surface plasmon-enhanced fluorescence sensing.

  20. Recognition- and reactivity-based fluorescent probes for studying transition metal signaling in living systems.

    PubMed

    Aron, Allegra T; Ramos-Torres, Karla M; Cotruvo, Joseph A; Chang, Christopher J

    2015-08-18

    Metals are essential for life, playing critical roles in all aspects of the central dogma of biology (e.g., the transcription and translation of nucleic acids and synthesis of proteins). Redox-inactive alkali, alkaline earth, and transition metals such as sodium, potassium, calcium, and zinc are widely recognized as dynamic signals, whereas redox-active transition metals such as copper and iron are traditionally thought of as sequestered by protein ligands, including as static enzyme cofactors, in part because of their potential to trigger oxidative stress and damage via Fenton chemistry. Metals in biology can be broadly categorized into two pools: static and labile. In the former, proteins and other macromolecules tightly bind metals; in the latter, metals are bound relatively weakly to cellular ligands, including proteins and low molecular weight ligands. Fluorescent probes can be useful tools for studying the roles of transition metals in their labile forms. Probes for imaging transition metal dynamics in living systems must meet several stringent criteria. In addition to exhibiting desirable photophysical properties and biocompatibility, they must be selective and show a fluorescence turn-on response to the metal of interest. To meet this challenge, we have pursued two general strategies for metal detection, termed "recognition" and "reactivity". Our design of transition metal probes makes use of a recognition-based approach for copper and nickel and a reactivity-based approach for cobalt and iron. This Account summarizes progress in our laboratory on both the development and application of fluorescent probes to identify and study the signaling roles of transition metals in biology. In conjunction with complementary methods for direct metal detection and genetic and/or pharmacological manipulations, fluorescent probes for transition metals have helped reveal a number of principles underlying transition metal dynamics. In this Account, we give three recent

  1. Fluorescent metal nanoshell and CK19 detection on single cell image.

    PubMed

    Zhang, Jian; Fu, Yi; Li, Ge; Lakowicz, Joseph R; Zhao, Richard Y

    2011-09-16

    In this article, we report the synthesis strategy and optical properties of a novel type of fluorescence metal nanoshell when it was used as imaging agent for fluorescence cell imaging. The metal nanoshells were made with 40 nm silica cores and 10nm silver shells. Unlike typical fluorescence metal nanoshells which contain the organic dyes in the cores, novel metal nanoshells were composed of Cy5-labelled monoclonal anti-CK19 antibodies (mAbs) on the external surfaces of shells. Optical measurements to the single nanoparticles showed that in comparison with the metal free labelled mAbs, the mAb-Ag complexes displayed significantly enhanced emission intensity and dramatically shortened lifetime due to near-field interactions of fluorophores with metal. These metal nanoshells were found to be able to immunoreact with target cytokeratin 19 (CK19) molecules on the surfaces of LNCAP and HeLa cells. Fluorescence cell images were recorded on a time-resolved confocal microscope. The emissions from the metal nanoprobes could be clearly isolated from the cellular autofluorescence backgrounds on the cell images as either individuals or small clusters due to their stronger emission intensities and shorter lifetimes. These emission signals could also be precisely counted on single cell images. The count number may provide an approach for quantifying the target molecules in the cells. PMID:21867692

  2. Floating AC-DEP (dielectrophoretic) manipulations of fluorescent nanoparticle at metal nanostructure for plasmonic applications

    NASA Astrophysics Data System (ADS)

    Kim, J.; Shin, H. J.; Hwang, K. S.; Park, J. H.

    2014-11-01

    We propose the fluorescent nanoparticle manipulations at nano-metal structures with floating AC-DEP force for plasmonic applications. The electrode gap was optimized to induce enough DEP force around the nano-structure for manipulation of the nanoparticles. 10um wide gap of electrode was acquired to apply the floating AC-DEP force at various designed metal nano-structure such as nanowire, y-branch and vortex. The all shape of nano-metal structures are formed at the gap of microelectrode and not connected with microelectrode. The gold nano-structures in the gap of microelectrode were fabricated with e-beam lithography and lift-off process. Before the formation of metal nanostructure, micro electrodes for applying the electric field around the metal nano-structures were fabricated with photolithography and lift-off process. Cadmium selenide (CdSe/ZnS) QDs (0.8 nM, emission wavelength of 605 nm) with a 25 nm zinc sulfide capping layer and 100nm polystyrene nano bead (1 nM, emission wavelength of 610nm) were used as fluorescent nanoparticles. We applied the 8 Vpp, 3 MHz sine wave for the positive DEP force, and it resulted in 108 V/m electric field and 1011 V/m electric field gradient around gold nanowire with floating AC. The fluorescent nanoparticle's attachment at the nanowire is confirmed by the fluorescent optical analysis. The fluorescent nanoparticles are located successfully at designed metal nano-structures for plasmonic applications.

  3. Highly selectively monitoring heavy and transition metal ions by a fluorescent sensor based on dipeptide.

    PubMed

    Neupane, Lok Nath; Thirupathi, Ponnaboina; Jang, Sujung; Jang, Min Jung; Kim, Jung Hwa; Lee, Keun-Hyeung

    2011-09-15

    Fluorescent sensor (DMH) based on dipeptide was efficiently synthesized in solid phase synthesis. The dipeptide sensor shows sensitive response to Ag(I), Hg(II), and Cu(II) among 14 metal ions in 100% aqueous solution. The fluorescent sensor differentiates three heavy metal ions by response type; turn on response to Ag(I), ratiometric response to Hg(II), and turn off detection of Cu(II). The detection limits of the sensor for Ag(I) and Cu(II) were much lower than the EPA's drinking water maximum contaminant levels (MCL). Specially, DMH penetrated live cells and detected intracellular Ag(+) by turn on response. We described the fluorescent change, binding affinity, detection limit for the metal ions. The study of a heavy metal-responsive sensor based on dipeptide demonstrates its potential utility in the environment field.

  4. Quenching of tryptophan fluorescence of bovine serum albumin under the effect of ions of heavy metals

    NASA Astrophysics Data System (ADS)

    Plotnikova, O. A.; Mel'nikov, A. G.; Mel'nikov, G. V.; Gubina, T. I.

    2016-01-01

    The interaction of heavy metals with bovine serum albumin (BSA) has been studied using data of quenching of intrinsic fluorescence of the protein by the ions of the heavy metals. Under the assumption of static quenching with formation of nonfluorescent complexes of fluorophores of BSA with heavy metals, conclusions have been drawn on the peculiarities of binding of the heavy metals to the protein. The values of the Stern-Volmer constants of association and those of the constants of BSA binding to the heavy metals decrease in the order Cu(II) > Pb(II) > Cd(II). It has been experimentally found that the copper ions have greater capacity to bind to the protein with the formation of the nonfluorescent complexes, which results in a significant decrease in the fluorescence intensity of the protein.

  5. Metal-enhanced intrinsic fluorescence of nucleic acids using platinum nanostructured substrates

    NASA Astrophysics Data System (ADS)

    Akbay, Nuriye; Mahdavi, Farhad; Lakowicz, Joseph R.; Ray, Krishanu

    2012-10-01

    We investigated the feasibility of using platinum nanostructures to accomplish the metal-enhanced fluorescence (MEF) in the UV spectral region. We examine the possibility for detection of the intrinsic fluorescence from nucleotides and G-quadruplex DNA on platinum nanoparticles. Guanosine monophosphate (GMP) showed significant increases (˜20-fold) in fluorescence intensities in the presence of platinum nanostructures when compared to quartz controls. G-quadruplex DNA demonstrated ˜5-fold increase in fluorescence intensity and higher photostability in the presence of Pt nanostructures. We performed Finite Element Method simulations to explore how Pt nanoparticles interact with plane waves and conformed that the Pt nanostructures are promising for enhancing the fluorescence emission in the UV region.

  6. UV-Fluorescent Sensing for Primary Selection of Metal-rich Seafloor Massive Sulfide Ore

    NASA Astrophysics Data System (ADS)

    Yamazaki, T.; Nakatani, T.; Nakatani, N.; Arai, R.

    2012-12-01

    Seafloor massive sulfides (SMS) in the western Pacific have received much attention as resources for Au, Ag, Cu, Zn, and Pb. Because of the higher metal contents, the venture commercial mining project may start in 2013 in the East Manus Basin, Papua New Guinea. One of important problems to be solved is reducing the waste rock disposal costs for the economy. The best location for the reducing is on seafloor just after the excavation of SMS ores. The authors select UV-fluorescent sensing for primary selection of the ores, because no additional environmental impact is created with the application of the method. First of all, the effectiveness of the UV-fluorescent sensing by a combination system with a UV-light and a camera (See attached figure) in deep water condition is clarified. Then many UV-fluorescent data of SMS ore, SMS accompanied rock, and seafloor rock samples are collected. In the analyses phase, the ore and rock samples are classified into some groups by applying the cluster analysis to the metal contents at first. Then, using the UV fluorescent color brightness and contrasts of the ore and rock samples, the discriminant analysis based on Mahalanobis distance is applied. The higher possibility to identify the SMS ores containing valuable metals from camera image is suggested from the analyses. When additional UV-fluorescent and chemical assay data are obtained, the renewal of discriminant analysis is necessary. Therefore, the results and conclusions described in this study are tentative ones.; UV-fluorescent sensing

  7. Metal enhanced fluorescence of flavin mononucleotide using new plasmonic platform

    NASA Astrophysics Data System (ADS)

    Synak, Anna; Grobelna, Beata; Raut, Sangram; Bojarski, Piotr; Gryczyński, Ignacy; Karczewski, Jakub; Shtoyko, Tanya

    2016-09-01

    New plasmonic platform was successfully obtained to investigate the increase of fluorescence intensity of a fluorophore in the presence of silver nanoparticles. A flavin mononucleotide, was selected by us as a fluorophore for this study as a very important biological compound playing a key role in many biochemical process. Plasmonic platforms were characterized by means of luminescence spectroscopy. Flavin mononucleotide deposited on plasmonic platform exhibits dramatic emission enhancements in presence of silver nanoparticles deposited on gold mirror.

  8. Protein-gold nanoclusters for identification of amino acids by metal ions modulated ratiometric fluorescence.

    PubMed

    Wang, Min; Mei, Qingsong; Zhang, Kui; Zhang, Zhongping

    2012-04-01

    Here we report that the dual fluorescence emissions from protein-gold (Au) nanoclusters can greatly be modulated by metal ions and the resultant fluorescence ratiometric responses provide a novel sensory method for the identification of amino acids. The protein-gold (Au) nanoclusters were simply synthesized by the reduction of chloroauric acid with bovine serum albumin (BSA), which exhibit dual emissions: the blue at 425 nm from the oxides of BSA, and the red at 635 nm from Au nanoclusters. It has been demonstrated that different metal ions react with BSA-Au nanoclusters and thus greatly affect the two emissions in different ways by fluorescence enhancement or quenching. Interestingly, the addition of amino acids leads to fluorescence ratiometric changes through the interactions with the bound metal ions. When BSA-Au nanocluster probes modulated by four different metal ions were used together to construct a sensor array, different amino acids were clearly discriminated by the distinctive patterns of four ratiometric fluorescence responses. Results and methods reported here provide a unique strategy for the determination of amino acids.

  9. Large-scale detection of metals with a small set of fluorescent DNA-like chemosensors.

    PubMed

    Yuen, Lik Hang; Franzini, Raphael M; Tan, Samuel S; Kool, Eric T

    2014-10-15

    An important advantage of pattern-based chemosensor sets is their potential to detect and differentiate a large number of analytes with only few sensors. Here we test this principle at a conceptual limit by analyzing a large set of metal ion analytes covering essentially the entire periodic table, employing fluorescent DNA-like chemosensors on solid support. A tetrameric "oligodeoxyfluoroside" (ODF) library of 6561 members containing metal-binding monomers was screened for strong responders to 57 metal ions in solution. Our results show that a set of 9 chemosensors could successfully discriminate the 57 species, including alkali, alkaline earth, post-transition, transition, and lanthanide metals. As few as 6 ODF chemosensors could detect and differentiate 50 metals at 100 μM; sensitivity for some metals was achieved at midnanomolar ranges. A blind test with 50 metals further confirmed the discriminating power of the ODFs. PMID:25255102

  10. Heterogeneity in metal binding by individual fluorescent components in a eutrophic algae-rich lake.

    PubMed

    Xu, Huacheng; Yan, Zaisheng; Cai, Haiyuan; Yu, Guanghui; Yang, Liuyan; Jiang, Helong

    2013-12-01

    Dissolved organic matter (DOM) affects the toxicity, mobility and bioavailability of metals in aquatic environment. In this study, the interactions between two metals of environmental concern [Cu(II) and Fe(III)] with DOM in a euthrophic algae-rich lake (Lake Taihu, China), including dissolved natural organic matter (NOM) and algal extracellular polymeric substance (EPS), were studied using fluorescence excitation-emission matrix (EEM) quenching titration combined with parallel factor (PARAFAC) analysis. Obvious protein-like peaks were detected in algal EPS matrix, while both protein- and humic-like peaks can be found in NOM. PARAFAC analysis identified four fluorescent components, including one humic-, one tryptophan- and two tyrosine-like components, from 114 EEM samples. It was shown that fluorescent tyrosine- (log K(M) > 5.21) and humic-like substances (log K(M) > 4.84) in NOM fraction exhibited higher metal binding capacities than those in EPS matrix, while algal EPS was characterized with a high metal-tryptophan-like substances affinity (log K(M) > 5.08). Moreover, for the eutrophic algae-rich lakes, fluorescent tryptophan- and humic-like substances were responsible for Cu transportation, whereas the mobility of Fe would be related with the tyrosine-like substances. The results facilitate a further insight into the biogeochemical behaviors of metals in eutrophic algae-rich ecosystems as well as other related aquatic environments.

  11. Shape assisted fabrication of fluorescent cages of squarate based metal-organic coordination frameworks.

    PubMed

    Jayaramulu, Kolleboyina; Krishna, Katla Sai; George, Subi J; Eswaramoorthy, Muthuswamy; Maji, Tapas Kumar

    2013-05-11

    Micronic cage structures of squarate based metal-organic coordination frameworks (MOCFs) have been fabricated for the first time by specific anion selective etching of metal squarate cubes. Time and stoichiometry dependent synthesis and the corresponding microscopic studies have provided mechanistic insight into the cage formation. Furthermore, a non-covalent post-synthetic strategy has been adopted to functionalize the micronic cubes or cages with chromophores rendering the resulting hybrids green fluorescent.

  12. Development of a fluorescent transgenic zebrafish biosensor for sensing aquatic heavy metal pollution.

    PubMed

    Pawar, Nilambari; Gireesh-Babu, P; Sabnis, Supriya; Rasal, Kiran; Murthy, Renuka; Zaidi, S G S; Sivasubbu, Sridhar; Chaudhari, Aparna

    2016-10-01

    We report a transgenic zebrafish (Danio rerio) designed to respond to heavy metals using a metal-responsive promoter linked to a fluorescent reporter gene (DsRed2). The metallothionein MT-Ia1 promoter containing metal-responsive elements was derived from the Asian green mussel, Perna viridis. The promoter is known to be induced by a broad spectrum of heavy metals. The promoter-reporter cassette cloned into the Tol2 transposon vector was microinjected into zebrafish embryos that were then reared to maturity. A transgene integration rate of 28 % was observed. The confirmed transgenics were mated with wild-type counterparts, and pools of F1 embryos were exposed to sub-lethal doses of Cd(2+), Cu(2+), Hg(2+), Pb(2+) and Zn(2+). The red fluorescence response of zebrafish embryos was observed 8 h post- exposure to these sub-lethal doses of heavy metals using a fluorescence microscope. Reporter expression estimated by real-time PCR revealed eightfold, sixfold and twofold increase on exposure to highest concentrations of Hg(2+), Cd(2+) and Cu(2+), while Pb(2+) and Zn(2+) had no effect. This biosensor could be a first-level screening method for confirming aquatic heavy metal bio-toxicity to eukaryotes. PMID:27120052

  13. Metal-Enhanced Fluorescence of Chlorophylls in Light-Harvesting Complexes Coupled to Silver Nanowires

    PubMed Central

    Kowalska, Dorota; Krajnik, Bartosz; Olejnik, Maria; Czechowski, Nikodem; Mackowski, Sebastian

    2013-01-01

    We investigate metal-enhanced fluorescence of peridinin-chlorophyll protein coupled to silver nanowires using optical microscopy combined with spectrally and time-resolved fluorescence techniques. In particular we study two different sample geometries: first, in which the light-harvesting complexes are deposited onto silver nanowires, and second, where solution of both nanostructures are mixed prior deposition on a substrate. The results indicate that for the peridinin-chlorophyll complexes placed in the vicinity of the silver nanowires we observe higher intensities of fluorescence emission as compared to the reference sample, where no nanowires are present. Enhancement factors estimated for the sample where the light-harvesting complexes are mixed together with the silver nanowires prior deposition on a substrate are generally larger in comparison to the other geometry of a hybrid nanostructure. While fluorescence spectra are identical both in terms of overall shape and maximum wavelength for peridinin-chlorophyll-protein complexes both isolated and coupled to metallic nanostructures, we conclude that interaction with plasmon excitations in the latter remains neutral to the functionality of the biological system. Fluorescence transients measured for the PCP complexes coupled to the silver nanowires indicate shortening of the fluorescence lifetime pointing towards modifications of radiative rate due to plasmonic interactions. Our results can be applied for developing ways to plasmonically control the light-harvesting capability of photosynthetic complexes. PMID:23533354

  14. Metal-enhanced fluorescence of chlorophylls in light-harvesting complexes coupled to silver nanowires.

    PubMed

    Kowalska, Dorota; Krajnik, Bartosz; Olejnik, Maria; Twardowska, Magdalena; Czechowski, Nikodem; Hofmann, Eckhard; Mackowski, Sebastian

    2013-01-01

    We investigate metal-enhanced fluorescence of peridinin-chlorophyll protein coupled to silver nanowires using optical microscopy combined with spectrally and time-resolved fluorescence techniques. In particular we study two different sample geometries: first, in which the light-harvesting complexes are deposited onto silver nanowires, and second, where solution of both nanostructures are mixed prior deposition on a substrate. The results indicate that for the peridinin-chlorophyll complexes placed in the vicinity of the silver nanowires we observe higher intensities of fluorescence emission as compared to the reference sample, where no nanowires are present. Enhancement factors estimated for the sample where the light-harvesting complexes are mixed together with the silver nanowires prior deposition on a substrate are generally larger in comparison to the other geometry of a hybrid nanostructure. While fluorescence spectra are identical both in terms of overall shape and maximum wavelength for peridinin-chlorophyll-protein complexes both isolated and coupled to metallic nanostructures, we conclude that interaction with plasmon excitations in the latter remains neutral to the functionality of the biological system. Fluorescence transients measured for the PCP complexes coupled to the silver nanowires indicate shortening of the fluorescence lifetime pointing towards modifications of radiative rate due to plasmonic interactions. Our results can be applied for developing ways to plasmonically control the light-harvesting capability of photosynthetic complexes.

  15. Laser-induced fluorescence of metal-atom impurities in a neutral beam

    SciTech Connect

    Burrell, C.F.; Pyle, R.V.; Sabetimani, Z.; Schlachter, A.S.

    1984-10-01

    The need to limit impurities in fusion devices to low levels is well known. We have investigated, by the technique of laser-induced fluorescence, the concentration of heavy-metal atoms in a neutral beam caused by their evaporation from the hot filaments in a conventional high-current multifilament hydrogen-ion source.

  16. Mapping metals in Parkinson's and normal brain using rapid-scanning x-ray fluorescence.

    PubMed

    Popescu, Bogdan F Gh; George, Martin J; Bergmann, Uwe; Garachtchenko, Alex V; Kelly, Michael E; McCrea, Richard P E; Lüning, Katharina; Devon, Richard M; George, Graham N; Hanson, Akela D; Harder, Sheri M; Chapman, L Dean; Pickering, Ingrid J; Nichol, Helen

    2009-02-01

    Rapid-scanning x-ray fluorescence (RS-XRF) is a synchrotron technology that maps multiple metals in tissues by employing unique hardware and software to increase scanning speed. RS-XRF was validated by mapping and quantifying iron, zinc and copper in brain slices from Parkinson's disease (PD) and unaffected subjects. Regions and structures in the brain were readily identified by their metal complement and each metal had a unique distribution. Many zinc-rich brain regions were low in iron and vice versa. The location and amount of iron in brain regions known to be affected in PD agreed with analyses using other methods. Sample preparation is simple and standard formalin-fixed autopsy slices are suitable. RS-XRF can simultaneously and non-destructively map and quantify multiple metals and holds great promise to reveal metal pathologies associated with PD and other neurodegenerative diseases as well as diseases of metal metabolism.

  17. Metal plasmon-coupled fluorescence imaging and label free coenzyme detection in cells

    SciTech Connect

    Zhang, Jian; Fu, Yi; Li, Ge; Zhao, Richard Y.

    2012-08-31

    Highlights: Black-Right-Pointing-Pointer Metal nanoparticle for fluorescence cell imaging. Black-Right-Pointing-Pointer Non-invasive emission detection of coenzyme in cell on time-resolved confocal microscope. Black-Right-Pointing-Pointer Near-field interaction of flavin adenine dinucleotide with silver substrate. Black-Right-Pointing-Pointer Isolation of emissions by coenzymes from cellular autofluorescence on fluorescence cell imaging. -- Abstract: Flavin adenine dinucleotide (FAD) is a key metabolite in cellular energy conversion. Flavin can also bind with some enzymes in the metabolic pathway and the binding sites may be changed due to the disease progression. Thus, there is interest on studying its expression level, distribution, and redox state within the cells. FAD is naturally fluorescent, but it has a modest extinction coefficient and quantum yield. Hence the intrinsic emission from FAD is generally too weak to be isolated distinctly from the cellular backgrounds in fluorescence cell imaging. In this article, the metal nanostructures on the glass coverslips were used as substrates to measure FAD in cells. Particulate silver films were fabricated with an optical resonance near the absorption and the emission wavelengths of FAD which can lead to efficient coupling interactions. As a result, the emission intensity and quantum yield by FAD were greatly increased and the lifetime was dramatically shortened resulting in less interference from the longer lived cellular background. This feature may overcome the technical limits that hinder the direct observation of intrinsically fluorescent coenzymes in the cells by fluorescence microscopy. Fluorescence cell imaging on the metallic particle substrates may provide a non-invasive strategy for collecting the information of coenzymes in cells.

  18. Use of algal fluorescence for determination of phytotoxicity of heavy metals and pesticides as environmental pollutants

    SciTech Connect

    Samson, G.; Popovic, R.

    1988-12-01

    The phytotoxicity of heavy metals and pesticides was studied by using the fluorescence induction from the alga Dunaliella tertiolecta. The complementary area calculated from the variable fluorescence induction was used as a direct parameter to estimate phytotoxicity. The value of this parameter was affected when algae were treated with different concentrations of mercury, copper, atrazine, DCMU, Dutox, and Soilgard. The toxic effect of these pollutants was estimated by monitoring the decrease in the complementary area, which reflects photosystem II photochemistry. Further, the authors have demonstrated the advantage of using the complementary area as a parameter of phytotoxicity over using variable fluorescence yield. The complementary area of algal fluorescence can be used as a simple and sensitive parameter in the estimation of the phytotoxicity of polluted water.

  19. Application of three-coordinate copper(I) complexes with halide ligands in organic light-emitting diodes that exhibit delayed fluorescence.

    PubMed

    Osawa, Masahisa; Hoshino, Mikio; Hashimoto, Masashi; Kawata, Isao; Igawa, Satoshi; Yashima, Masataka

    2015-05-14

    A series of three-coordinate copper(I) complexes (L(Me))CuX [X = Cl (1), Br (2), I (3)], (L(Et))CuBr (4), and (L(iPr))CuBr (5) [L(Me) = 1,2-bis[bis(2-methylphenyl)phosphino]benzene, L(Et) = 1,2-bis[bis(2-ethylphenyl)phosphino]benzene, and L(iPr) = 1,2-bis[bis(2-isopropylphenyl)phosphino]benzene] exhibit efficient blue-green emission in the solid state at ambient temperature with peak wavelengths between 473 and 517 nm. The emission quantum yields were 0.38-0.95. The emission lifetimes were measured in the temperature range of 77-295 K using a nanosecond laser technique. The temperature dependence of the emission lifetimes was explained using a model with two excited states: a singlet and a triplet state. The small energy gaps (<830 cm(-1)) between the two states suggest that efficient emission from 1-5 was thermally activated delayed fluorescence (TADF). Alkyl substituents at ortho positions of peripheral phenyl groups were found to have little effect on the electronic excited states. Because the origin of the emission of complexes 2, 4, and 5 was thought to be a (σ + Br)→π* transition, photoluminescence characteristics of these complexes were dominated by the diphosphine ligands. Complexes 2, 4, and 5 had similar emission properties. Complexes 1-5 had efficient green TADF in amorphous films at 293 K with maximum emission wavelengths of 508-520 nm and quantum yields of 0.61-0.71. Organic light-emitting devices that contained complexes 1-5 and exhibited TADF exhibit bright green luminescence with current efficiencies of 55.6-69.4 cd A(-1) and maximum external quantum efficiencies of 18.6-22.5%.

  20. Fluorescent copper nanoparticles: recent advances in synthesis and applications for sensing metal ions

    NASA Astrophysics Data System (ADS)

    Guo, Yongming; Cao, Fengpu; Lei, Xiaoling; Mang, Lianghong; Cheng, Shengjuan; Song, Jintong

    2016-02-01

    Fluorescent copper nanoparticles (F-CuNPs) have received great attention due to their attractive features, such as water solubility, wide availability, ease of functionalization and good biocompatibility, and considerable efforts have been devoted to the preparation and applications of F-CuNPs. This review article comprises three main parts. In the first part, we briefly present the fluorescence properties of F-CuNPs. Then we cover the fabrication strategies of various F-CuNPs functionalized by different ligands. In the third part, we focus on the applications of F-CuNPs for sensing metal ions, including Hg2+, Pb2+, Cu2+, Fe3+ and other metal ions. Lastly, we further discuss the opportunities and challenges of F-CuNPs in the synthetic strategies and applications for sensing metal ions.

  1. Fluorescent copper nanoparticles: recent advances in synthesis and applications for sensing metal ions.

    PubMed

    Guo, Yongming; Cao, Fengpu; Lei, Xiaoling; Mang, Lianghong; Cheng, Shengjuan; Song, Jintong

    2016-03-01

    Fluorescent copper nanoparticles (F-CuNPs) have received great attention due to their attractive features, such as water solubility, wide availability, ease of functionalization and good biocompatibility, and considerable efforts have been devoted to the preparation and applications of F-CuNPs. This review article comprises three main parts. In the first part, we briefly present the fluorescence properties of F-CuNPs. Then we cover the fabrication strategies of various F-CuNPs functionalized by different ligands. In the third part, we focus on the applications of F-CuNPs for sensing metal ions, including Hg(2+), Pb(2+), Cu(2+), Fe(3+) and other metal ions. Lastly, we further discuss the opportunities and challenges of F-CuNPs in the synthetic strategies and applications for sensing metal ions. PMID:26879547

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

    PubMed

    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

  3. Metal plasmon-coupled fluorescence imaging and label free coenzyme detection in cells.

    PubMed

    Zhang, Jian; Fu, Yi; Li, Ge; Zhao, Richard Y

    2012-08-31

    Flavin adenine dinucleotide (FAD) is a key metabolite in cellular energy conversion. Flavin can also bind with some enzymes in the metabolic pathway and the binding sites may be changed due to the disease progression. Thus, there is interest on studying its expression level, distribution, and redox state within the cells. FAD is naturally fluorescent, but it has a modest extinction coefficient and quantum yield. Hence the intrinsic emission from FAD is generally too weak to be isolated distinctly from the cellular backgrounds in fluorescence cell imaging. In this article, the metal nanostructures on the glass coverslips were used as substrates to measure FAD in cells. Particulate silver films were fabricated with an optical resonance near the absorption and the emission wavelengths of FAD which can lead to efficient coupling interactions. As a result, the emission intensity and quantum yield by FAD were greatly increased and the lifetime was dramatically shortened resulting in less interference from the longer lived cellular background. This feature may overcome the technical limits that hinder the direct observation of intrinsically fluorescent coenzymes in the cells by fluorescence microscopy. Fluorescence cell imaging on the metallic particle substrates may provide a non-invasive strategy for collecting the information of coenzymes in cells.

  4. Atomic layer deposition to prevent metal transfer from implants: An X-ray fluorescence study

    NASA Astrophysics Data System (ADS)

    Bilo, Fabjola; Borgese, Laura; Prost, Josef; Rauwolf, Mirjam; Turyanskaya, Anna; Wobrauschek, Peter; Kregsamer, Peter; Streli, Christina; Pazzaglia, Ugo; Depero, Laura E.

    2015-12-01

    We show that Atomic Layer Deposition is a suitable coating technique to prevent metal diffusion from medical implants. The metal distribution in animal bone tissue with inserted bare and coated Co-Cr alloys was evaluated by means of micro X-ray fluorescence mapping. In the uncoated implant, the migration of Co and Cr particles from the bare alloy in the biological tissues is observed just after one month and the number of particles significantly increases after two months. In contrast, no metal diffusion was detected in the implant coated with TiO2. Instead, a gradient distribution of the metals was found, from the alloy surface going into the tissue. No significant change was detected after two months of aging. As expected, the thicker is the TiO2 layer, the lower is the metal migration.

  5. Noninvasive Evaluation of Heavy Metal Uptake and Storage in Micoralgae Using a Fluorescence Resonance Energy Transfer-Based Heavy Metal Biosensor1[C][W][OPEN

    PubMed Central

    Rajamani, Sathish; Torres, Moacir; Falcao, Vanessa; Ewalt Gray, Jaime; Coury, Daniel A.; Colepicolo, Pio; Sayre, Richard

    2014-01-01

    We have developed a fluorescence resonance energy transfer (FRET)-based heavy metal biosensor for the quantification of bioavailable free heavy metals in the cytoplasm of the microalga Chlamydomonas reinhardtii. The biosensor is composed of an end-to-end fusion of cyan fluorescent protein (CFP), chicken metallothionein II (MT-II), and yellow fluorescent protein (YFP). In vitro measurements of YFP/CFP fluorescence emission ratios indicated that the addition of metals to the purified biosensor enhanced FRET between CFP and YFP, consistent with heavy metal-induced folding of MT-II. A maximum YFP/CFP FRET ratio of 2.8 was observed in the presence of saturating concentrations of heavy metals. The sensitivity of the biosensor was greatest for Hg2+ followed by Cd2+ ≈ Pb2+ > Zn2+ > Cu2+. The heavy metal biosensor was unresponsive to metals that do not bind to MT-II (Na+ and Mg2+). When expressed in C. reinhardtii, we observed a differential metal-dependent response to saturating external concentrations (1.6 mm) of heavy metals (Pb2+ > Cd2+) that was unlike that observed for the isolated biosensor (in vitro). Significantly, analysis of metal uptake kinetics indicated that equilibration of the cytoplasm with externally applied heavy metals occurred within seconds. Our results also indicated that algae have substantial buffering capacity for free heavy metals in their cytosol, even at high external metal concentrations. PMID:24368336

  6. Noninvasive evaluation of heavy metal uptake and storage in micoralgae using a fluorescence resonance energy transfer-based heavy metal biosensor.

    PubMed

    Rajamani, Sathish; Torres, Moacir; Falcao, Vanessa; Ewalt Gray, Jaime; Coury, Daniel A; Colepicolo, Pio; Sayre, Richard

    2014-02-01

    We have developed a fluorescence resonance energy transfer (FRET)-based heavy metal biosensor for the quantification of bioavailable free heavy metals in the cytoplasm of the microalga Chlamydomonas reinhardtii. The biosensor is composed of an end-to-end fusion of cyan fluorescent protein (CFP), chicken metallothionein II (MT-II), and yellow fluorescent protein (YFP). In vitro measurements of YFP/CFP fluorescence emission ratios indicated that the addition of metals to the purified biosensor enhanced FRET between CFP and YFP, consistent with heavy metal-induced folding of MT-II. A maximum YFP/CFP FRET ratio of 2.8 was observed in the presence of saturating concentrations of heavy metals. The sensitivity of the biosensor was greatest for Hg2+ followed by Cd2+≈Pb2+>Zn2+>Cu2+. The heavy metal biosensor was unresponsive to metals that do not bind to MT-II (Na+ and Mg2+). When expressed in C. reinhardtii, we observed a differential metal-dependent response to saturating external concentrations (1.6 mm) of heavy metals (Pb2+>Cd2+) that was unlike that observed for the isolated biosensor (in vitro). Significantly, analysis of metal uptake kinetics indicated that equilibration of the cytoplasm with externally applied heavy metals occurred within seconds. Our results also indicated that algae have substantial buffering capacity for free heavy metals in their cytosol, even at high external metal concentrations.

  7. A distance-dependent metal-enhanced fluorescence sensing platform based on molecular beacon design.

    PubMed

    Zhou, Zhenpeng; Huang, Hongduan; Chen, Yang; Liu, Feng; Huang, Cheng Zhi; Li, Na

    2014-02-15

    A new metal-enhanced fluorescence (MEF) based platform was developed on the basis of distance-dependent fluorescence quenching-enhancement effect, which combined the easiness of Ag-thiol chemistry with the MEF property of noble-metal structures as well as the molecular beacon design. For the given sized AgNPs, the fluorescence enhancement factor was found to increase with a d(6) dependency in agreement with fluorescence resonance energy transfer mechanism at shorter distance and decrease with a d(-3) dependency in agreement with plasmonic enhancement mechanism at longer distance between the fluorophore and the AgNP surface. As a proof of concept, the platform was demonstrated by a sensitive detection of mercuric ions, using thymine-containing molecular beacon to tune silver nanoparticle (AgNP)-enhanced fluorescence. Mercuric ions were detected via formation of a thymine-mercuric-thymine structure to open the hairpin, facilitating fluorescence recovery and AgNP enhancement to yield a limit of detection of 1 nM, which is well below the U.S. Environmental Protection Agency regulation of the Maximum Contaminant Level Goal (10nM) in drinking water. Since the AgNP functioned as not only a quencher to reduce the reagent blank signal but also an enhancement substrate to increase fluorescence of the open hairpin when target mercuric ions were present, the quenching-enhancement strategy can greatly improve the detection sensitivity and can in principle be a universal approach for various targets when combined with molecular beacon design.

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

    SciTech Connect

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

    2014-12-08

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

  9. Mapping Metal Elements of Shuangbai Dinosaur Fossil by Synchrotron X-ray Fluorescence Microprobe

    SciTech Connect

    Wang, Y.; Qun, Y; Ablett, J

    2008-01-01

    The metal elements mapping of Shuangbai dinosaur fossil, was obtained by synchrotron x-ray fluorescence (SXRF). Eight elements, Ca, Mn, Fe, Cu, Zn, As, Y and Sr were determined. Elements As and Y were detected for the first time in the dinosaur fossil. The data indicated that metal elements are asymmetrical on fossil section. This is different from common minerals. Mapping metals showed that metal element As is few. The dinosaur most likely belongs to natural death. This is different from Zigong dinosaurs which were found dead from poisoning. This method has been used to find that metals Fe and Mn are accrete, and the same is true for Sr and Y. This study indicated that colloid granule Fe and Mn, as well as Sr and Y had opposite electric charges in lithification process of fossils. By this analysis, compound forms can be ascertained. Synchrotron light source x-ray fluorescence is a complementary method that shows mapping of metal elements at the dinosaur fossil, and is rapid, exact and intuitionist. This study shows that dinosaur fossil mineral imaging has a potential in reconstructing the paleoenvironment and ancient geology.

  10. Epi-Fluorescence Microscopy

    PubMed Central

    Webb, Donna J.; Brown, Claire M.

    2012-01-01

    Epi-fluorescence microscopy is available in most life sciences research laboratories, and when optimized can be a central laboratory tool. In this chapter, the epi-fluorescence light path is introduced and the various components are discussed in detail. Recommendations are made for incident lamp light sources, excitation and emission filters, dichroic mirrors, objective lenses, and charge-coupled device (CCD) cameras in order to obtain the most sensitive epi-fluorescence microscope. The even illumination of metal-halide lamps combined with new “hard” coated filters and mirrors, a high resolution monochrome CCD camera, and a high NA objective lens are all recommended for high resolution and high sensitivity fluorescence imaging. Recommendations are also made for multicolor imaging with the use of monochrome cameras, motorized filter turrets, individual filter cubes, and corresponding dyes that are the best choice for sensitive, high resolution multicolor imaging. Images should be collected using Nyquist sampling and should be corrected for background intensity contributions and nonuniform illumination across the field of view. Photostable fluorescent probes and proteins that absorb a lot of light (i.e., high extinction co-efficients) and generate a lot of fluorescence signal (i.e., high quantum yields) are optimal. A neuronal immune-fluorescence labeling protocol is also presented. Finally, in order to maximize the utility of sensitive wide-field microscopes and generate the highest resolution images with high signal-to-noise, advice for combining wide-field epi-fluorescence imaging with restorative image deconvolution is presented. PMID:23026996

  11. METAL-CONTAINING CONJUGATED POLYMERS AS FLUORESCENT CHEMOSENSORS IN THE DETECTION OF TOXICANTS.

    PubMed

    Fegley, Megan E A; Pinnock, Sherryllene S; Malele, Catherine N; Jones, Wayne E

    2012-02-15

    Fluorescent conjugated polymers have received a great deal of recent interest due to their ability to act as chemosensors to detect various chemical species in both environmental and biological systems with sensitivity and selectivity. Examples from the literature include polymer chemosensors that operate on either fluorescence "turn-on" or "turn-off" as mechanisms of sensor response. These responses can be related to either photoinduced electron transfer or electronic energy transfer mechanisms. Recently, a series of metal-containing polymers or metallopolymers have been explored by various research groups for their use as chemosensors. In many cases, these metallopolymers have been shown to be more sensitive and selective for specific chemical species. This review focuses on fluorescent conjugated polymers as chemosensors, with a specific concentration on recent advances in metallopolymer chemosensors. PMID:22711916

  12. METAL-CONTAINING CONJUGATED POLYMERS AS FLUORESCENT CHEMOSENSORS IN THE DETECTION OF TOXICANTS

    PubMed Central

    Fegley, Megan E. A.; Pinnock, Sherryllene S.; Malele, Catherine N.; Jones, Wayne E.

    2012-01-01

    Fluorescent conjugated polymers have received a great deal of recent interest due to their ability to act as chemosensors to detect various chemical species in both environmental and biological systems with sensitivity and selectivity. Examples from the literature include polymer chemosensors that operate on either fluorescence “turn-on” or “turn-off” as mechanisms of sensor response. These responses can be related to either photoinduced electron transfer or electronic energy transfer mechanisms. Recently, a series of metal-containing polymers or metallopolymers have been explored by various research groups for their use as chemosensors. In many cases, these metallopolymers have been shown to be more sensitive and selective for specific chemical species. This review focuses on fluorescent conjugated polymers as chemosensors, with a specific concentration on recent advances in metallopolymer chemosensors. PMID:22711916

  13. Visualizing Metal Content and Intracellular Distribution in Primary Hippocampal Neurons with Synchrotron X-Ray Fluorescence

    PubMed Central

    2016-01-01

    Increasing evidence suggests that metal dyshomeostasis plays an important role in human neurodegenerative diseases. Although distinctive metal distributions are described for mature hippocampus and cortex, much less is known about metal levels and intracellular distribution in individual hippocampal neuronal somata. To solve this problem, we conducted quantitative metal analyses utilizing synchrotron radiation X-Ray fluorescence on frozen hydrated primary cultured neurons derived from rat embryonic cortex (CTX) and two regions of the hippocampus: dentate gyrus (DG) and CA1. Comparing average metal contents showed that the most abundant metals were calcium, iron, and zinc, whereas metals such as copper and manganese were less than 10% of zinc. Average metal contents were generally similar when compared across neurons cultured from CTX, DG, and CA1, except for manganese that was larger in CA1. However, each metal showed a characteristic spatial distribution in individual neuronal somata. Zinc was uniformly distributed throughout the cytosol, with no evidence for the existence of previously identified zinc-enriched organelles, zincosomes. Calcium showed a peri-nuclear distribution consistent with accumulation in endoplasmic reticulum and/or mitochondria. Iron showed 2–3 distinct highly concentrated puncta only in peri-nuclear locations. Notwithstanding the small sample size, these analyses demonstrate that primary cultured neurons show characteristic metal signatures. The iron puncta probably represent iron-accumulating organelles, siderosomes. Thus, the metal distributions observed in mature brain structures are likely the result of both intrinsic neuronal factors that control cellular metal content and extrinsic factors related to the synaptic organization, function, and contacts formed and maintained in each region. PMID:27434052

  14. Visualizing Metal Content and Intracellular Distribution in Primary Hippocampal Neurons with Synchrotron X-Ray Fluorescence.

    PubMed

    Colvin, Robert A; Jin, Qiaoling; Lai, Barry; Kiedrowski, Lech

    2016-01-01

    Increasing evidence suggests that metal dyshomeostasis plays an important role in human neurodegenerative diseases. Although distinctive metal distributions are described for mature hippocampus and cortex, much less is known about metal levels and intracellular distribution in individual hippocampal neuronal somata. To solve this problem, we conducted quantitative metal analyses utilizing synchrotron radiation X-Ray fluorescence on frozen hydrated primary cultured neurons derived from rat embryonic cortex (CTX) and two regions of the hippocampus: dentate gyrus (DG) and CA1. Comparing average metal contents showed that the most abundant metals were calcium, iron, and zinc, whereas metals such as copper and manganese were less than 10% of zinc. Average metal contents were generally similar when compared across neurons cultured from CTX, DG, and CA1, except for manganese that was larger in CA1. However, each metal showed a characteristic spatial distribution in individual neuronal somata. Zinc was uniformly distributed throughout the cytosol, with no evidence for the existence of previously identified zinc-enriched organelles, zincosomes. Calcium showed a peri-nuclear distribution consistent with accumulation in endoplasmic reticulum and/or mitochondria. Iron showed 2-3 distinct highly concentrated puncta only in peri-nuclear locations. Notwithstanding the small sample size, these analyses demonstrate that primary cultured neurons show characteristic metal signatures. The iron puncta probably represent iron-accumulating organelles, siderosomes. Thus, the metal distributions observed in mature brain structures are likely the result of both intrinsic neuronal factors that control cellular metal content and extrinsic factors related to the synaptic organization, function, and contacts formed and maintained in each region. PMID:27434052

  15. Polyacrylonitrile/noble metal/SiO₂ nanofibers as substrates for the amplified detection of picomolar amounts of metal ions through plasmon-enhanced fluorescence.

    PubMed

    Zhang, Han; Cao, Minhua; Wu, Wei; Xu, Haibo; Cheng, Si; Fan, Li-Juan

    2015-01-28

    Electrospun polymer/noble metal hybrid nanofibers have developed rapidly as surface-enhanced Raman scattering (SERS)-active substrates over the last few years. However, polymer/noble metal nanofibers with plasmon-enhanced fluorescence (PEF) activity have received no attention to date. Herein, we show a general and facile approach for the preparation of polyacrylonitrile (PAN)/noble metal/SiO2 nanofibrous mats with PEF activity for the first time by combining electrospinning and controlled silica coatings. These PEF-active nanofibrous mats can selectively improve the fluorescence intensity of conjugated polyelectrolytes (CPEs). Importantly, the CPE solution in the presence of a PAN/noble metal/SiO2 nanofibrous mat showed dramatic fluorescence quenching towards picomolar (pM) amounts of heavy metal ions, while the fluorescence of the CPE solution without the nanofibrous mat had no apparent quenching towards micromolar (μM) amounts of metal ions. The combination of the distance-dependent fluorescence enhancement performance of metal NPs and the ionic characteristics of the CPE solution makes the polymer/noble metal nanofibers promising substrates for greatly improving the detection sensitivity towards metal ions. We believe that this work provides a general strategy for preparing plasmon band-tuned PEF-active substrates with advantages including good selectivity, remarkable sensitivity and recyclability, which make them a preferable choice for practical sensing applications. PMID:25494487

  16. Novel laser atomic fluorescence spectrometer for environmental and biomedical analyses of heavy metals

    NASA Astrophysics Data System (ADS)

    Dergachev, Alex Y.; Mirov, Sergey B.; Pitt, Robert E.; Parmer, Keith D.

    1997-05-01

    We report on the development of a novel experimental set-up using laser atomic fluorescence for detection and concentration measurements of heavy metal atoms for environmental and biomedical analyses. This spectrometer is based on the application of tunable LiF:F2+** and LiF:F2- color center and alexandrite lasers with nonlinear converters for narrowband excitation of atomic fluorescence and the use of gated multichannel CCD detectors for fluorescence measurements. A standard graphite furnace module was used for sample atomization. The laser sources used provide narrowband selective laser excitation continuously tunable in the 200 - 400 nm range and are therefore suitable for resonant excitation of atomic transitions in practically all known heavy metal atoms. In the first experiments, water samples containing Cu, Pb and Fe impurities were studied and detection levels of less than 1 ppb were observed. Comparison of the results of atomic laser fluorescence analysis and traditional atomic absorption spectrometry showed good qualitative agreement between these two methods. It is projected that full optimization of our experimental set up will allow for improved detection levels of several orders of magnitude. Possible optimization and simplification of the spectrometer are discussed in the context of developing a portable instrument for field use.

  17. Metal enhanced fluorescence in rare earth doped plasmonic core-shell nanoparticles.

    PubMed

    Derom, S; Berthelot, A; Pillonnet, A; Benamara, O; Jurdyc, A M; Girard, C; Colas des Francs, G

    2013-12-13

    We theoretically and numerically investigate metal enhanced fluorescence of plasmonic core-shell nanoparticles doped with rare earth (RE) ions. Particle shape and size are engineered to maximize the average enhancement factor (AEF) of the overall doped shell. We show that the highest enhancement (11 in the visible and 7 in the near-infrared) is achieved by tuning either the dipolar or the quadrupolar particle resonance to the rare earth ion's excitation wavelength. Additionally, the calculated AEFs are compared to experimental data reported in the literature, obtained in similar conditions (plasmon mediated enhancement) or when a metal-RE energy transfer mechanism is involved.

  18. Fluorescent, MRI, and colorimetric chemical sensors for the first-row d-block metal ions.

    PubMed

    Zhu, Hao; Fan, Jiangli; Wang, Benhua; Peng, Xiaojun

    2015-07-01

    Transition metals (d-blocks) are recognized as playing critical roles in biology, and they most often act as cofactors in diverse enzymes; however, improper regulation of transition metal stores is also connected to serious disorders. Therefore, the monitoring and imaging of transition metals are significant for biological research as well as clinical diagnosis. In this article, efforts have been made to review the chemical sensors that have been developed for the detection of the first-row d-block metals (except Cu and Zn): Cr, Mn, Fe, Co, and Ni. We focus on the development of fluorescent sensors (fall into three classes: "turn-off", "turn-on", and ratiometric), colorimetric sensors, and responsive MRI contrast agents for these transition metals (242 references). Future work will be likely to fill in the blanks: (1) sensors for Sc, Ti, and V; (2) MRI sensors for Cr, Mn, Co, Ni; (3) ratiometric fluorescent sensors for Cr(6+), Mn(2+), and Ni(2+), explore new ways of sensing Fe(3+) or Cr(3+) without the proton interference, as well as extend applications of MRI sensors to living systems.

  19. Light trapping to amplify metal enhanced fluorescence with application for sensing TNT.

    PubMed

    Matoian, Meredith A; Sweetman, Richard; Hall, Emily C; Albanese, Shayna; Euler, William B

    2013-09-01

    Metal Enhanced Fluorescence (MEF) typically produces enhancement factors of 10 to 50. By using a polymer layer as the dielectric spacer enhancements as high as 1,600 can be observed. The effect occurs with a variety of different polymers and substrates, all of which act to trap light in the dielectric layer. This allows the fabrication of sensors with improved sensitivity as demonstrated for detection of trinitrotoluene (TNT).

  20. Polyacrylamide hydrogel encapsulated E. coli expressing metal-sensing green fluorescent protein as a potential tool for copper ion determination

    PubMed Central

    Tantimongcolwat, Tanawut; Isarankura-Na-Ayudhya, Chartchalerm; Srisarin, Apapan; Galla, Hans-Joachim; Prachayasittikul, Virapong

    2014-01-01

    A simple, inexpensive and field applicable metal determination system would be a powerful tool for the efficient control of metal ion contamination in various sources e.g. drinking-water, water reservoir and waste discharges. In this study, we developed a cell-based metal sensor for specific and real-time detection of copper ions. E. coli expressing metal-sensing green fluorescent protein (designated as TG1/(CG)6GFP and TG1/H6CdBP4GFP) were constructed and served as a metal analytical system. Copper ions were found to exert a fluorescence quenching effect, while zinc and cadmium ions caused minor fluorescence enhancement in the engineered bacterial suspension. To construct a user-friendly and reagentless metal detection system, TG1/H6CdBP4GFP and TG1/(CG)6GFP were encapsulated in polyacrylamide hydrogels that were subsequently immobilized on an optical fiber equipped with a fluorescence detection module. The sensor could be applied to measure metal ions by simply dipping the encapsulated bacteria into a metal solution and monitoring fluorescence changes in real time as a function of the metal concentration in solution. The sensor system demonstrated high specificity toward copper ions. The fluorescence intensities of the encapsulated TG1/(CG)6GFP and TG1/H6CdBP4GFP were quenched by approximately 70 % and 80 % by a high-dose of copper ions (50 mM), respectively. The level of fluorescence quenching exhibited a direct correlation with the copper concentration, with a linear correlation coefficient (r) of 0.99. The cell-based metal sensor was able to efficiently monitor copper concentrations ranging between 5 M and 50 mM, encompassing the maximum allowed copper contamination in drinking water (31.15 M) established by the WHO. Furthermore, the cell-based metal sensor could undergo prolonged storage for at least 2 weeks without significantly influencing the copper sensitivity. PMID:26417267

  1. Polyacrylamide hydrogel encapsulated E. coli expressing metal-sensing green fluorescent protein as a potential tool for copper ion determination.

    PubMed

    Tantimongcolwat, Tanawut; Isarankura-Na-Ayudhya, Chartchalerm; Srisarin, Apapan; Galla, Hans-Joachim; Prachayasittikul, Virapong

    2014-01-01

    A simple, inexpensive and field applicable metal determination system would be a powerful tool for the efficient control of metal ion contamination in various sources e.g. drinking-water, water reservoir and waste discharges. In this study, we developed a cell-based metal sensor for specific and real-time detection of copper ions. E. coli expressing metal-sensing green fluorescent protein (designated as TG1/(CG)6GFP and TG1/H6CdBP4GFP) were constructed and served as a metal analytical system. Copper ions were found to exert a fluorescence quenching effect, while zinc and cadmium ions caused minor fluorescence enhancement in the engineered bacterial suspension. To construct a user-friendly and reagentless metal detection system, TG1/H6CdBP4GFP and TG1/(CG)6GFP were encapsulated in polyacrylamide hydrogels that were subsequently immobilized on an optical fiber equipped with a fluorescence detection module. The sensor could be applied to measure metal ions by simply dipping the encapsulated bacteria into a metal solution and monitoring fluorescence changes in real time as a function of the metal concentration in solution. The sensor system demonstrated high specificity toward copper ions. The fluorescence intensities of the encapsulated TG1/(CG)6GFP and TG1/H6CdBP4GFP were quenched by approximately 70 % and 80 % by a high-dose of copper ions (50 mM), respectively. The level of fluorescence quenching exhibited a direct correlation with the copper concentration, with a linear correlation coefficient (r) of 0.99. The cell-based metal sensor was able to efficiently monitor copper concentrations ranging between 5 M and 50 mM, encompassing the maximum allowed copper contamination in drinking water (31.15 M) established by the WHO. Furthermore, the cell-based metal sensor could undergo prolonged storage for at least 2 weeks without significantly influencing the copper sensitivity. PMID:26417267

  2. Infrared spectra of the CH3-MX, CH2=MHX, and CH[triple bond]MH2X- complexes formed by reaction of methyl halides with laser-ablated group 5 metal atoms.

    PubMed

    Cho, Han-Gook; Andrews, Lester

    2006-08-24

    Reactions of group 5 metal atoms and methyl halides give carbon-metal single, double, and triple bonded complexes that are identified from matrix IR spectra and vibrational frequencies computed by DFT. Two different pairs of complexes are prepared in reactions of methyl fluoride with laser-ablated vanadium and tantalum atoms. The two vanadium complexes (CH(3)-VF and CH(2)=VHF) are persistently photoreversible and show a kinetic isotope effect on the yield of CD(2)=VDF. Identification of CH(2)=TaHF and CH[triple bond]TaH(2)F(-), along with the similar anionic Nb complex, suggests that the anionic methylidyne complex is a general property of the heavy group 5 metals. Reactions of Nb and Ta with CH(3)Cl and CH(3)Br have also been carried out to understand the ligand effects on the calculated structures and the vibrational characteristics. The methylidene complexes become more distorted with increasing halogen size, while the calculated C=M bond lengths and stretching frequencies decrease and increase, respectively. The anionic methylidyne complexes are less favored with increasing halogen size. Infrared spectra show a dramatic increase of the Ta methylidenes upon annealing, suggesting that the formation of CH(3)-TaX and its conversion to CH(2)=TaHX require essentially no activation energy.

  3. Infrared spectra of the CH3-MX, CH2=MHX, and CH[triple bond]MH2X- complexes formed by reaction of methyl halides with laser-ablated group 5 metal atoms.

    PubMed

    Cho, Han-Gook; Andrews, Lester

    2006-08-24

    Reactions of group 5 metal atoms and methyl halides give carbon-metal single, double, and triple bonded complexes that are identified from matrix IR spectra and vibrational frequencies computed by DFT. Two different pairs of complexes are prepared in reactions of methyl fluoride with laser-ablated vanadium and tantalum atoms. The two vanadium complexes (CH(3)-VF and CH(2)=VHF) are persistently photoreversible and show a kinetic isotope effect on the yield of CD(2)=VDF. Identification of CH(2)=TaHF and CH[triple bond]TaH(2)F(-), along with the similar anionic Nb complex, suggests that the anionic methylidyne complex is a general property of the heavy group 5 metals. Reactions of Nb and Ta with CH(3)Cl and CH(3)Br have also been carried out to understand the ligand effects on the calculated structures and the vibrational characteristics. The methylidene complexes become more distorted with increasing halogen size, while the calculated C=M bond lengths and stretching frequencies decrease and increase, respectively. The anionic methylidyne complexes are less favored with increasing halogen size. Infrared spectra show a dramatic increase of the Ta methylidenes upon annealing, suggesting that the formation of CH(3)-TaX and its conversion to CH(2)=TaHX require essentially no activation energy. PMID:16913680

  4. Algal photosynthetic responses to toxic metals and herbicides assessed by chlorophyll a fluorescence.

    PubMed

    Kumar, K Suresh; Dahms, Hans-Uwe; Lee, Jae-Seong; Kim, Hyung Chul; Lee, Won Chan; Shin, Kyung-Hoon

    2014-06-01

    Chlorophyll a fluorescence is established as a rapid, non-intrusive technique to monitor photosynthetic performance of plants and algae, as well as to analyze their protective responses. Apart from its utility in determining the physiological status of photosynthesizers in the natural environment, chlorophyll a fluorescence-based methods are applied in ecophysiological and toxicological studies to examine the effect of environmental changes and pollutants on plants and algae (microalgae and seaweeds). Pollutants or environmental changes cause alteration of the photosynthetic capacity which could be evaluated by fluorescence kinetics. Hence, evaluating key fluorescence parameters and assessing photosynthetic performances would provide an insight regarding the probable causes of changes in photosynthetic performances. This technique quintessentially provides non-invasive determination of changes in the photosynthetic apparatus prior to the appearance of visible damage. It is reliable, economically feasible, time-saving, highly sensitive, versatile, accurate, non-invasive and portable; thereby comprising an excellent alternative for detecting pollution. The present review demonstrates the applicability of chlorophyll a fluorescence in determining photochemical responses of algae exposed to environmental toxicants (such as toxic metals and herbicides). PMID:24632123

  5. Algal photosynthetic responses to toxic metals and herbicides assessed by chlorophyll a fluorescence.

    PubMed

    Kumar, K Suresh; Dahms, Hans-Uwe; Lee, Jae-Seong; Kim, Hyung Chul; Lee, Won Chan; Shin, Kyung-Hoon

    2014-06-01

    Chlorophyll a fluorescence is established as a rapid, non-intrusive technique to monitor photosynthetic performance of plants and algae, as well as to analyze their protective responses. Apart from its utility in determining the physiological status of photosynthesizers in the natural environment, chlorophyll a fluorescence-based methods are applied in ecophysiological and toxicological studies to examine the effect of environmental changes and pollutants on plants and algae (microalgae and seaweeds). Pollutants or environmental changes cause alteration of the photosynthetic capacity which could be evaluated by fluorescence kinetics. Hence, evaluating key fluorescence parameters and assessing photosynthetic performances would provide an insight regarding the probable causes of changes in photosynthetic performances. This technique quintessentially provides non-invasive determination of changes in the photosynthetic apparatus prior to the appearance of visible damage. It is reliable, economically feasible, time-saving, highly sensitive, versatile, accurate, non-invasive and portable; thereby comprising an excellent alternative for detecting pollution. The present review demonstrates the applicability of chlorophyll a fluorescence in determining photochemical responses of algae exposed to environmental toxicants (such as toxic metals and herbicides).

  6. Using Synchrotron X-ray Fluorescence Microprobes in the Study of Metal Homeostasis in Plants

    SciTech Connect

    Punshon, T.; Guerinot, M; Lanzirotti, A

    2009-01-01

    Background and Aims: This Botanical Briefing reviews the application of synchrotron X-ray fluorescence (SXRF) microprobes to the plant sciences; how the technique has expanded our knowledge of metal(loid) homeostasis, and how it can be used in the future. Scope: The use of SXRF microspectroscopy and microtomography in research on metal homeostasis in plants is reviewed. The potential use of SXRF as part of the ionomics toolbox, where it is able to provide fundamental information on the way that plants control metal homeostasis, is recommended. Conclusions: SXRF is one of the few techniques capable of providing spatially resolved in-vivo metal abundance data on a sub-micrometre scale, without the need for chemical fixation, coating, drying or even sectioning of samples. This gives researchers the ability to uncover mechanisms of plant metal homeostasis that can potentially be obscured by the artefacts of sample preparation. Further, new generation synchrotrons with smaller beam sizes and more sensitive detection systems will allow for the imaging of metal distribution within single living plant cells. Even greater advances in our understanding of metal homeostasis in plants can be gained by overcoming some of the practical boundaries that exist in the use of SXRF analysis.

  7. PREPARATION OF HALIDES OF PLUTONIUM

    DOEpatents

    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.

  8. Well dispersed single-walled carbon nanotubes with strong visible fluorescence in water for metal ions sensing.

    PubMed

    Qian, Zhaosheng; Wang, Chen; Feng, Hui; Chen, Congcong; Zhou, Jin; Chen, Jianrong

    2011-07-01

    A novel and simple method to prepare well dispersed single-walled carbon nanotubes with strong visible fluorescence in water is reported. The visible fluorescence was found to be responsive to pH value and metal ions, and tunable emission ability of oxidized SWCNTs depending on the excitation wavelength and a novel self-excitation and emission process were found.

  9. Screening heavy metals levels in hair of sanitation workers by X-ray fluorescence analysis.

    PubMed

    Md Khudzari, Jauharah; Wagiran, Husin; Hossain, I; Ibrahim, Noorddin

    2013-01-01

    This work presents a study of human hair as a bio-indicator for detection of heavy metals as part of environmental health surveillance programs project to develop a subject of interest in the biomedical and environmental sciences. A total of 34 hair samples were analyzed that consisting of 29 samples from sanitation workers and five samples from students. The hair samples were prepared and treated in accordance to the International Atomic Energy Agency (IAEA) recommendations. The concentrations of heavy metals were analyzed using the energy dispersive X-ray fluorescence (EDXRF) technique by X-50 Mobile X-ray Fluorescence (XRF) at Oceanography Institute, Universiti Malaysia Terengganu. The performance of EDXRF analyzer was tested by Standard Reference Material (SRM 2711) Montana Soil which was in good agreement with certified value within 14% deviations except for Hg. While seven heavy metals: Mn, Fe, Ni, Cu, Zn, Se, and Sb were detected in both groups, three additional elements, i.e. As, Hg and Pb, were detected only in sanitation workers group. For sanitation workers group, the mean concentration of six elements, Mn, Fe, Cu, Zn, Se, and Sb, shows elevated concentration as compared to the control samples concentration. Results from both groups were compared and discussed in relation to their respective heavy metals concentrations. PMID:22846873

  10. Comprehensive Screen of Metal Oxide Nanoparticles for DNA Adsorption, Fluorescence Quenching, and Anion Discrimination.

    PubMed

    Liu, Biwu; Liu, Juewen

    2015-11-11

    Although DNA has been quite successful in metal cation detection, anion detectioin remains challenging because of the charge repulsion. Metal oxides represent a very important class of materials, and different oxides might interact with anions differently. In this work, a comprehensive screen of common metal oxide nanoparticles (MONPs) was carried out for their ability to adsorb DNA, quench fluorescence, and release adsorbed DNA in the presence of target anions. A total of 19 MONPs were studied, including Al2O3, CeO2, CoO, Co3O4, Cr2O3, Fe2O3, Fe3O4, In2O3, ITO, Mn2O3, NiO, SiO2, SnO2, a-TiO2 (anatase), r-TiO2 (rutile), WO3, Y2O3, ZnO, ZrO2. These MONPs have different DNA adsorption affinity. Some adsorb DNA without quenching the fluorescence, while others strongly quench adsorbed fluorophores. They also display different affinity toward anions probed by DNA desorption. Finally, CeO2, Fe3O4, and ZnO were used to form a sensor array to discriminate phosphate, arsenate, and arsenite from the rest using linear discriminant analysis. This study not only provides a solution for anion discrimination using DNA as a signaling molecule but also provides insights into the interface of metal oxides and DNA.

  11. Detection of CXCR4 receptors on cell surface using a fluorescent metal nanoshell

    NASA Astrophysics Data System (ADS)

    Zhang, Jian; Fu, Yi; Li, Ge; Zhao, Richard Y.; Lakowicz, Joseph R.

    2011-01-01

    Fluorescence cell imaging can be used for disease diagnosis and cellular signal transduction. Using a metal nanoshell as molecular imaging agent, we develop a cellular model system to detect CXCR4 chemokine receptor on T-lymphatic cell surface. These metal nanoshells are observed to express enhanced emission intensity and shortened lifetimes due to the near-field interactions. They are covalently bound with anti-CXCR4 monoclonal antibodies for immunoreactions with the target sites of the CXCR4 receptors on the CEM-SS cells. The fluorescence intensity and lifetime cell images are recorded with a time-resolved confocal microscopy. As expected, the emission signals from the metal nanoshells are clearly isolated from the cellular autofluorescence due to strong intensities and distinctive lifetimes. The number of emission spots on the single cell image is estimated by direct count to the emission signals. Analyzing a pool of cell images, a maximal count number is obtained in a range of 200+/-50. Because there is an average of ~6000 binding sites on the cell surface, we estimate that one emission spot from the metal nanoshell may represent ~30 CXCR5 receptors. In addition, the CXCR4 receptors are estimated to distribute on ~70% area of the cell surface.

  12. Laser-induced fluorescence in doped metal oxide planar waveguides deposited from aqueous solutions

    SciTech Connect

    Hess, N.J.; Exarhos, G.J. ); Wood, S.M. . Shock Dynamics Lab.)

    1991-12-01

    An aqueous route to the deposition of complex metal oxide films is based upton the complexation of the corresponding metal nitrate salts by glycine, followed by spin-casting the concentrated solution onto silica substrates. The presence of glycine serves to frustrate precipitation and leads to the formation of a glassy matrix through which metal cations are homogeneously dispersed. Subsequent heating of coated substrates initiates an oxidation-reduction reaction which removes the organic matrix and residual nitrate leaving behind a film of the desired oxide composition. Using this method, ruby (Cr:Al{sub 2}O{sub 3}) and Sm:YAG (Sm:Y{sub 3}Al{sub 5}O{sub 12}) films on the order of 150 nm thick have been deposited. The respective phase have been confirmed by XRD data and from the measured fluorescence spectra. The red fluorescence exhibited by these materials under 488 nm excitation is dependent upon the ambient temperature and pressure. A marked shift in wavelength is observed as a function of increasing pressure. Ruby also exhibits a temperature dependent wavelength shift in contrast to Sm:YAG where a negligible shift is seen to temperatures near 1200 K. Fluorescence lifetimes of both materials exhibit a temperature dependence which varies with dopant concentration. This work suggests the possible application of these films as pressure-temperature sensors in a planar waveguide configuration or as a coating material for optical fibers. Details of the deposition process will be reviewed and the fluorescence response of both types of films will be summarized. 15 refs., 4 figs.

  13. A cross-reactive sensor array for the fluorescence qualitative analysis of heavy metal ions.

    PubMed

    Kang, Huaizhi; Lin, Liping; Rong, Mingcong; Chen, Xi

    2014-11-01

    A cross-reactive sensor array using mercaptopropionic acid modified cadmium telluride (CdTe), glutathione modified CdTe, poly(methacrylic acid) modified silver nanoclusters, bovine serum albumin modified gold nanoclusters, rhodamine derivative and calcein blue as fluorescent indicators has been designed for the detection of seven heavy metal ions (Ag(+), Hg(2+), Pb(2+), Cu(2+), Cr(3+), Mn(2+) and Cd(2+)). The discriminatory capacity of the sensor array to different heavy metal ions in different pH solutions has been tested and the results have been analyzed with linear discriminant analysis. Results showed that the sensor array could be used to qualitatively analyze the selected heavy metal ions. The array performance was also evaluated in the identification of known and unknown samples and the preliminary results suggested the promising practicability of the designed sensor assay.

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

    PubMed

    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

  15. Process for oxidation of hydrogen halides to elemental halogens

    DOEpatents

    Lyke, Stephen E.

    1992-01-01

    An improved process for generating an elemental halogen selected from chlorine, bromine or iodine, from a corresponding hydrogen halide by absorbing a molten salt mixture, which includes sulfur, alkali metals and oxygen with a sulfur to metal molar ratio between 0.9 and 1.1 and includes a dissolved oxygen compound capable of reacting with hydrogen halide to produce elemental halogen, into a porous, relatively inert substrate to produce a substrate-supported salt mixture. Thereafter, the substrate-supported salt mixture is contacted (stage 1) with a hydrogen halide while maintaining the substrate-supported salt mixture during the contacting at an elevated temperature sufficient to sustain a reaction between the oxygen compound and the hydrogen halide to produce a gaseous elemental halogen product. This is followed by purging the substrate-supported salt mixture with steam (stage 2) thereby recovering any unreacted hydrogen halide and additional elemental halogen for recycle to stage 1. The dissolved oxygen compound is regenerated in a high temperature (stage 3) and an optical intermediate temperature stage (stage 4) by contacting the substrate-supported salt mixture with a gas containing oxygen whereby the dissolved oxygen compound in the substrate-supported salt mixture is regenerated by being oxidized to a higher valence state.

  16. Cross-Reactive Sensor Array for Metal Ion Sensing Based on Fluorescent SAMs

    PubMed Central

    Basabe-Desmonts, Lourdes; van der Baan, Frederieke; Zimmerman, Rebecca S.; Reinhoudt, David N.; Crego-Calama, Mercedes

    2007-01-01

    Fluorescent self assembled monolayers (SAMs) on glass were previously developed in our group as new sensing materials for metal ions. These fluorescent SAMs are comprised by fluorophores and small molecules sequentially deposited on a monolayer on glass. The preorganization provided by the surface avoids the need for complex receptor design, allowing for a combinatorial approach to sensing systems based on small molecules. Now we show the fabrication of an effective microarray for the screening of metal ions and the properties of the sensing SAMs. A collection of fluorescent sensing SAMs was generated by combinatorial methods and immobilized on the glass surfaces of a custom-made 140 well microtiter-plate. The resulting libraries are easily measured and show varied responses to a series cations such as Cu2+, Co2+, Pb2+, Ca2+ and Zn2+. These surfaces are not designed to complex selectively a unique analyte but rather they are intended to produce fingerprint type responses to a range of analytes by less specific interactions. The unselective responses of the library to the presence of different cations generate a characteristic pattern for each analyte, a “finger print” response.

  17. Metal-Enhanced Near-Infrared Fluorescence by Micropatterned Gold Nanocages

    PubMed Central

    2015-01-01

    In metal-enhanced fluorescence (MEF), the localized surface plasmon resonances of metallic nanostructures amplify the absorption of excitation light and assist in radiating the consequent fluorescence of nearby molecules to the far-field. This effect is at the base of various technologies that have strong impact on fields such as optics, medical diagnostics, and biotechnology. Among possible emission bands, those in the near-infrared (NIR) are particularly intriguing and widely used in proteomics and genomics due to its noninvasive character for biomolecules, living cells, and tissues, which greatly motivates the development of effective and, eventually, multifunctional NIR-MEF platforms. Here, we demonstrate NIR-MEF substrates based on Au nanocages micropatterned with a tight spatial control. The dependence of the fluorescence enhancement on the distance between the nanocage and the radiating dipoles is investigated experimentally and modeled by taking into account the local electric field enhancement and the modified radiation and absorption rates of the emitting molecules. At a distance around 80 nm, a maximum enhancement up to 2–7 times with respect to the emission from pristine dyes (in the region 660–740 nm) is estimated for films and electrospun nanofibers. Due to their chemical stability, finely tunable plasmon resonances, and large light absorption cross sections, Au nanocages are ideal NIR-MEF agents. When these properties are integrated with the hollow interior and controllable surface porosity, it is feasible to develop a nanoscale system for targeted drug delivery with the diagnostic information encoded in the fluorophore. PMID:26397166

  18. Imaging metals in proteins by combining electrophoresis with rapid x-ray fluorescence mapping.

    SciTech Connect

    Finney, L.; Chishti, Y.; Khare, T.; Giometti, C.; Levina, A.; Lay, P. A.; Vogt, S.; Univ. of Sydney; Northwestern Univ.

    2010-01-01

    Growing evidence points toward a very dynamic role for metals in biology. This suggests that physiological circumstance may mandate metal ion redistribution among ligands. This work addresses a critical need for technology that detects, identifies, and measures the metal-containing components of complex biological matrixes. We describe a direct, user-friendly approach for identifying and quantifying metal?protein adducts in complex samples using native- or SDS-PAGE, blotting, and rapid synchrotron X-ray fluorescence mapping with micro-XANES (X-ray absorption near-edge structure) of entire blots. The identification and quantification of each metal bound to a protein spot has been demonstrated, and the technique has been applied in two exemplary cases. In the first, the speciation of the in vitro binding of exogenous chromium to blood serum proteins was influenced markedly by both the oxidation state of chromium exposed to the serum proteins and the treatment conditions, which is of relevance to the biochemistry of Cr dietary supplements. In the second case, in vivo changes in endogenous metal speciation were examined to probe the influence of oxygen depletion on iron speciation in Shewanella oneidensis.

  19. Differential transition metal uptake and fluorescent probe localization in hippocampal slices.

    PubMed

    Kay, Alan R; Rumschik, Sean M

    2011-08-01

    Metals are taken up by the combined action of metal transporters and ion channels. In this communication we have measured the uptake of the biologically important transition metals Mn, Fe, Co, Ni, Cu, Zn and Cd by rat and mouse hippocampal slices using the fluorescent probes FluoZin-3 (FZ3) and Newport Green (NPG), introduced by acetoxymethyl ester (AM) loading. The combination of metals and probes is also used to attempt to localize cellular sites into which metals translocate. We show that FZ3 and NPG partition into different cellular compartments; FZ3 into neuropil, whereas NPG localizes in neuropil and compartments within the cell bodies of neurons. Ni, Zn and Cd pass across the plasma membrane and then accumulate in intracellular vesicles and within intracellular membranes of cell bodies. The latter accumulate Cd, while synaptic vesicles take up Co. The passage of Mn, Cu and Fe into cells can be detected but there is some uncertainty about their disposition within the cell. All of our experiments are consistent with metals accumulating in intracellular compartments rather than the cytoplasm. Whether and to what extent there are transient elevations of free zinc levels in the cytoplasm remains unclear.

  20. Differentiating between fluorescence-quenching metal ions with polyfluorophore sensors built on a DNA backbone.

    PubMed

    Tan, Samuel S; Kim, Su Jeong; Kool, Eric T

    2011-03-01

    A common problem in detecting metal ions with fluorescentchemosensors is the emission-suppressing effects of fluorescence-quenching metal ions. This quenching tendency makes it difficult to design sensors with turn-on signal, and differentiate between several metal ions that may yield a strong quenching response. To address these challenges, we investigate a new sensor design strategy, incorporating fluorophores and metal ligands as DNA base replacements in DNA-like oligomers, for generating a broader range of responses for quenching metal ions. The modular molecular design enabled rapid synthesis and discovery of sensors from libraries on PEG-polystyrene beads. Using this approach, water-soluble sensors 1-5 were identified as strong responders to a set of eight typically quenching metal ions (Co(2+), Ni(2+), Cu(2+), Hg(2+), Pb(2+), Ag(+), Cr(3+), and Fe(3+)). They were synthesized and characterized for sensing responses in solution. Cross-screening with the full set of metal ions showed that they have a wide variety of responses, including emission enhancements and red- and blue-shifts. The diversity of sensor responses allows as few as two sensors (1 and 2) to be used together to successfully differentiate these eight metals. As a test, a set of unknown metal ion solutions in blind studies were also successfully identified based on the response pattern of the sensors. The modular nature of the sensor design strategy suggests a broadly applicable approach to finding sensors for differentiating many different cations by pattern-based recognition, simply by varying the sequence and composition of ligands and fluorophores on a DNA synthesizer.

  1. Metal-Enhanced Fluorescence Lifetime Imaging and Spectroscopy on a Modified SERS Substrate

    PubMed Central

    Ray, Krishanu; Lakowicz, Joseph R.

    2013-01-01

    In this paper, we developed a metal-enhanced fluorescence (MEF) substrate by modification of the commercially available surface enhanced Raman spectroscopy (SERS) substrate that may meet the reproducibility and sensitivity challenge of MEF. In spite of many studies and interest on MEF from a number of research groups, application to real-world situations and its commercial use remain challenging mainly due to the difficulties in fabricating reproducible MEF substrates. Specifically, one of the challenges is achieving a standardized MEF substrate for reproducible fluorescence intensity enhancement and/or changes in lifetime. The gold standard klarite substrates for SERS were coated with a thin layer of silver nanoparticles for MEF studies. To test the newly developed MEF substrates, a monolayer of streptavidin conjugated Alexa-647 was assembled on biotinylated-glass or MEF substrates. We observed over 50-fold increase in the fluorescence intensity from a monolayer of streptavidin conjugated Alexa-647 on the biotinylated MEF substrate compared to the same on glass substrate. A significant reduction in the lifetime and increased photostability of Alexa-647 on MEF substrate was observed. Fluorescence lifetime imaging was performed on the monolayer of dye assembled on the modified SERS substrates. We expect this study will serve as a platform to encourage the future use of a standardized MEF substrate for a plethora of sensing applications. PMID:24416457

  2. Multicomponent assembly of fluorescent-tag functionalized ligands in metal-organic frameworks for sensing explosives.

    PubMed

    Gole, Bappaditya; Bar, Arun Kumar; Mukherjee, Partha Sarathi

    2014-10-01

    Detection of trace amounts of explosive materials is significantly important for security concerns and pollution control. Four multicomponent metal-organic frameworks (MOFs-12, 13, 23, and 123) have been synthesized by employing ligands embedded with fluorescent tags. The multicomponent assembly of the ligands was utilized to acquire a diverse electronic behavior of the MOFs and the fluorescent tags were strategically chosen to enhance the electron density in the MOFs. The phase purity of the MOFs was established by PXRD, NMR spectroscopy, and finally by single-crystal XRD. Single-crystal structures of the MOFs-12 and 13 showed the formation of three-dimensional porous networks with the aromatic tags projecting inwardly into the pores. These electron-rich MOFs were utilized for detection of explosive nitroaromatic compounds (NACs) through fluorescence quenching with high selectivity and sensitivity. The rate of fluorescence quenching for all the MOFs follows the order of electron deficiency of the NACs. We also showed the detection of picric acid (PA) by luminescent MOFs is not always reliable and can be misleading. This attracts our attention to explore these MOFs for sensing picryl chloride (PC), which is as explosive as picric acid and used widely to prepare more stable explosives like 2,4,6-trinitroaniline from PA. Moreover, the recyclability and sensitivity studies indicated that these MOFs can be reused several times with parts per billion (ppb) levels of sensitivity towards PC and 2,4,6-trinitrotoluene (TNT).

  3. Hybrid silver nanoparticle/conjugated polyelectrolyte nanocomposites exhibiting controllable metal-enhanced fluorescence

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoyu; He, Fang; Zhu, Xi; Tang, Fu; Li, Lidong

    2014-03-01

    Metal-enhanced fluorescence of conjugated polyelectrolytes (CPs) is realized using a simple, green hybrid Ag nanocomposite film. Ag nanoparticles (Ag NPs) are pre-prepared by sodium citrate reduction and incorporated into agarose by mixing to form an Ag-containing agarose film (Ag@agarose). Through variation of the amount of Ag NPs in the Ag@agarose film as well as the thickness of the interlayer between CPs and the Ag@agarose film prepared of layer-by-layer assembly of chitosan and sodium alginate, a maximum 8.5-fold increase in the fluorescence of CPs is obtained. After introducing tyrosinase, this system also can be used to detect phenolic compounds with high sensitivity and good visualization under ultraviolet light.

  4. Hybrid silver nanoparticle/conjugated polyelectrolyte nanocomposites exhibiting controllable metal-enhanced fluorescence

    PubMed Central

    Wang, Xiaoyu; He, Fang; Zhu, Xi; Tang, Fu; Li, Lidong

    2014-01-01

    Metal-enhanced fluorescence of conjugated polyelectrolytes (CPs) is realized using a simple, green hybrid Ag nanocomposite film. Ag nanoparticles (Ag NPs) are pre-prepared by sodium citrate reduction and incorporated into agarose by mixing to form an Ag-containing agarose film (Ag@agarose). Through variation of the amount of Ag NPs in the Ag@agarose film as well as the thickness of the interlayer between CPs and the Ag@agarose film prepared of layer-by-layer assembly of chitosan and sodium alginate, a maximum 8.5-fold increase in the fluorescence of CPs is obtained. After introducing tyrosinase, this system also can be used to detect phenolic compounds with high sensitivity and good visualization under ultraviolet light. PMID:24638208

  5. Ratiometric and turn-on monitoring for heavy and transition metal ions in aqueous solution with a fluorescent peptide sensor.

    PubMed

    Joshi, Bishnu Prasad; Park, Junwon; Lee, Wan In; Lee, Keun-Hyeung

    2009-05-15

    A novel fluorescent peptide sensor containing tryptophan (donor) and dansyl fluorophore (acceptor) was synthesized for monitoring heavy and transition metal (HTM) ions on the basis of metal ion binding motif (Cys-X-X-X-Cys). The peptide probe successfully exhibited a turn on and ratiometric response for several heavy metal ions such as Hg(2+), Cd(2+), Pb(2+), Zn(2+), and Ag(+) in aqueous solution. The enhancements of emission intensity were achieved in the presence of the HTM ions by fluorescent resonance energy transfer (FRET) and chelation enhanced fluorescence (CHEF) effects. The detection limits of the sensor for Cd(2+), Pb(2+), Zn(2+), and Ag(+) were lower than the EPA's drinking water maximum contaminant levels (MCL). We described the fluorescent enhancement, binding affinity, and detection limit of the peptide probe for HTM ions.

  6. Fluorescence properties of riboflavin-functionalized mesoporous silica SBA-15 and riboflavin solutions in presence of different metal and organic cations

    NASA Astrophysics Data System (ADS)

    Lewandowski, Dawid; Schroeder, Grzegorz; Sawczak, Mirosław; Ossowski, Tadeusz

    2015-10-01

    Riboflavin was covalently linked to mesoporous SBA-15 silica surface via grafting technique. Then fluorescence properties of the system obtained were analyzed in the presence of several metal and organic cations. Both quenching and strengthening of fluorescence as well as significant changes in the maximum fluorescence wavelength were observed. The results were compared with absorption and fluorescence data obtained for riboflavin water solutions.

  7. Polyacrylonitrile/noble metal/SiO2 nanofibers as substrates for the amplified detection of picomolar amounts of metal ions through plasmon-enhanced fluorescence

    NASA Astrophysics Data System (ADS)

    Zhang, Han; Cao, Minhua; Wu, Wei; Xu, Haibo; Cheng, Si; Fan, Li-Juan

    2015-01-01

    Electrospun polymer/noble metal hybrid nanofibers have developed rapidly as surface-enhanced Raman scattering (SERS)-active substrates over the last few years. However, polymer/noble metal nanofibers with plasmon-enhanced fluorescence (PEF) activity have received no attention to date. Herein, we show a general and facile approach for the preparation of polyacrylonitrile (PAN)/noble metal/SiO2 nanofibrous mats with PEF activity for the first time by combining electrospinning and controlled silica coatings. These PEF-active nanofibrous mats can selectively improve the fluorescence intensity of conjugated polyelectrolytes (CPEs). Importantly, the CPE solution in the presence of a PAN/noble metal/SiO2 nanofibrous mat showed dramatic fluorescence quenching towards picomolar (pM) amounts of heavy metal ions, while the fluorescence of the CPE solution without the nanofibrous mat had no apparent quenching towards micromolar (μM) amounts of metal ions. The combination of the distance-dependent fluorescence enhancement performance of metal NPs and the ionic characteristics of the CPE solution makes the polymer/noble metal nanofibers promising substrates for greatly improving the detection sensitivity towards metal ions. We believe that this work provides a general strategy for preparing plasmon band-tuned PEF-active substrates with advantages including good selectivity, remarkable sensitivity and recyclability, which make them a preferable choice for practical sensing applications.Electrospun polymer/noble metal hybrid nanofibers have developed rapidly as surface-enhanced Raman scattering (SERS)-active substrates over the last few years. However, polymer/noble metal nanofibers with plasmon-enhanced fluorescence (PEF) activity have received no attention to date. Herein, we show a general and facile approach for the preparation of polyacrylonitrile (PAN)/noble metal/SiO2 nanofibrous mats with PEF activity for the first time by combining electrospinning and controlled silica

  8. Surface-enhanced fluorescence from metal sculptured thin films with application to biosensing in water

    NASA Astrophysics Data System (ADS)

    Abdulhalim, I.; Karabchevsky, Alina; Patzig, Christian; Rauschenbach, Bernd; Fuhrmann, Bodo; Eltzov, Evgeni; Marks, Robert; Xu, Jian; Zhang, Fan; Lakhtakia, Akhlesh

    2009-02-01

    Surface-enhanced fluorescence from porous, metallic sculptured thin films (STFs) was demonstrated for sensing of bacteria in water. Enhancement factors larger than 15 were observed using STFs made of silver, aluminum, gold, and copper with respect to their dense film counterparts. The STFs used are assemblies of tilted, shaped, parallel nanowires prepared with several variants of the oblique-angle-deposition technique. Comparison between the different films indicates that the enhancement factor is higher when the tilt is either small (<30 deg) or large (>80 deg); thus, the enhancement is higher when only a single resonance in the nanowires is excited.

  9. Exploring metal detoxification and accumulation potential during vermicomposting of Tea factory coal ash: sequential extraction and fluorescence probe analysis

    PubMed Central

    Goswami, Linee; Pratihar, Sanjay; Dasgupta, Suman; Bhattacharyya, Pradip; Mudoi, Pronab; Bora, Jayanta; Bhattacharya, Satya Sundar; Kim, Ki Hyun

    2016-01-01

    Metal contamination from coal ashes (CAs) is widely recognized as a significant environmental concern. To learn more about metal detoxification and accumulation potential of earthworm species, metal-rich tea factory coal ashes (TFCA) were fed to Eisenia fetida and Lampito mauritii by employing a fluorescent tag detection method. Fascinatingly, on feeding fluorescence probed Zn and Cd along with cow dung to Eisenia fetida, the detection of the gut-proteins with a molecular mass higher than 100 kDa was a distinct evidence of metal binding. Significant increases were observed in the content of humified organic C [humic acid (HAC) and fulvic acid C (FAC)] and degree of humification during vermicomposting. Concurrently, considerably large amount of toxic metals (Cr, Cd, Pb, and Zn) was transformed from exchangeable to recalcitrant (organic matter and mineral bound) fractions. Moreover, total metal concentrations were reduced with high removal efficiency upon vermicomposting. PMID:27456167

  10. Exploring metal detoxification and accumulation potential during vermicomposting of Tea factory coal ash: sequential extraction and fluorescence probe analysis

    NASA Astrophysics Data System (ADS)

    Goswami, Linee; Pratihar, Sanjay; Dasgupta, Suman; Bhattacharyya, Pradip; Mudoi, Pronab; Bora, Jayanta; Bhattacharya, Satya Sundar; Kim, Ki Hyun

    2016-07-01

    Metal contamination from coal ashes (CAs) is widely recognized as a significant environmental concern. To learn more about metal detoxification and accumulation potential of earthworm species, metal-rich tea factory coal ashes (TFCA) were fed to Eisenia fetida and Lampito mauritii by employing a fluorescent tag detection method. Fascinatingly, on feeding fluorescence probed Zn and Cd along with cow dung to Eisenia fetida, the detection of the gut-proteins with a molecular mass higher than 100 kDa was a distinct evidence of metal binding. Significant increases were observed in the content of humified organic C [humic acid (HAC) and fulvic acid C (FAC)] and degree of humification during vermicomposting. Concurrently, considerably large amount of toxic metals (Cr, Cd, Pb, and Zn) was transformed from exchangeable to recalcitrant (organic matter and mineral bound) fractions. Moreover, total metal concentrations were reduced with high removal efficiency upon vermicomposting.

  11. Exploring metal detoxification and accumulation potential during vermicomposting of Tea factory coal ash: sequential extraction and fluorescence probe analysis.

    PubMed

    Goswami, Linee; Pratihar, Sanjay; Dasgupta, Suman; Bhattacharyya, Pradip; Mudoi, Pronab; Bora, Jayanta; Bhattacharya, Satya Sundar; Kim, Ki Hyun

    2016-01-01

    Metal contamination from coal ashes (CAs) is widely recognized as a significant environmental concern. To learn more about metal detoxification and accumulation potential of earthworm species, metal-rich tea factory coal ashes (TFCA) were fed to Eisenia fetida and Lampito mauritii by employing a fluorescent tag detection method. Fascinatingly, on feeding fluorescence probed Zn and Cd along with cow dung to Eisenia fetida, the detection of the gut-proteins with a molecular mass higher than 100 kDa was a distinct evidence of metal binding. Significant increases were observed in the content of humified organic C [humic acid (HAC) and fulvic acid C (FAC)] and degree of humification during vermicomposting. Concurrently, considerably large amount of toxic metals (Cr, Cd, Pb, and Zn) was transformed from exchangeable to recalcitrant (organic matter and mineral bound) fractions. Moreover, total metal concentrations were reduced with high removal efficiency upon vermicomposting. PMID:27456167

  12. Release of the self-quenching of fluorescence near silver metallic surfaces.

    PubMed

    Lakowicz, Joseph R; Malicka, Joanna; D'Auria, Sabato; Gryczynski, Ignacy

    2003-09-01

    Fluorescein is one of the most widely used fluorescent probes in microscopy, biotechnology, and clinical assays. One difficulty with fluorescein is its self-quenching, which results in decreased intensities with increasing labeling density. In this study we examined human serum albumin (HSA), which contained one to nine covalently linked fluorescein molecules per molecule of HSA. The occurrence of homo resonance energy transfer for labeling ratios greater than 1 were confirmed by decreases in the relative quantum yields, anisotropies, and lifetimes. We found that most of the self-quenching can be partially eliminated by proximity of the labeled protein to metallic silver particles. These results suggest the use of heavily labeled proteins and metallic colloids to obtain ultrabright reagents for use in immunoassays, imaging, and other applications. PMID:12895465

  13. Heat capacity of molten halides.

    PubMed

    Redkin, Alexander A; Zaikov, Yurii P; Korzun, Iraida V; Reznitskikh, Olga G; Yaroslavtseva, Tatiana V; Kumkov, Sergey I

    2015-01-15

    The heat capacities of molten salts are very important for their practical use. Experimental investigation of this property is challenging because of the high temperatures involved and the corrosive nature of these materials. It is preferable to combine experimental investigations with empirical relationships, which allows for the evaluation of the heat capacity of molten salt mixtures. The isobaric molar heat capacities of all molten alkali and alkaline-earth halides were found to be constant for each group of salts. The value depends on the number of atoms in the salt, and the molar heat capacity per atom is constant for all molten halide salts with the exception of the lithium halides. The molar heat capacities of molten halides do not change when the anions are changed.

  14. Heat capacity of molten halides.

    PubMed

    Redkin, Alexander A; Zaikov, Yurii P; Korzun, Iraida V; Reznitskikh, Olga G; Yaroslavtseva, Tatiana V; Kumkov, Sergey I

    2015-01-15

    The heat capacities of molten salts are very important for their practical use. Experimental investigation of this property is challenging because of the high temperatures involved and the corrosive nature of these materials. It is preferable to combine experimental investigations with empirical relationships, which allows for the evaluation of the heat capacity of molten salt mixtures. The isobaric molar heat capacities of all molten alkali and alkaline-earth halides were found to be constant for each group of salts. The value depends on the number of atoms in the salt, and the molar heat capacity per atom is constant for all molten halide salts with the exception of the lithium halides. The molar heat capacities of molten halides do not change when the anions are changed. PMID:25530462

  15. Giant increase in the metal-enhanced fluorescence of organic molecules in nanoporous alumina templates and large molecule-specific red/blue-shift of the fluorescence peak.

    PubMed

    Sarkar, S; Kanchibotla, B; Nelson, J D; Edwards, J D; Anderson, J; Tepper, G C; Bandyopadhyay, S

    2014-10-01

    The fluorescence of organic fluorophore molecules is enhanced when they are placed in contact with certain metals (Al, Ag, Cu, Au, etc.) whose surface plasmon waves couple into the radiative modes of the molecules and increase the radiative efficiency. Here, we report a hitherto unknown size dependence of this metal-enhanced fluorescence (MEF) effect in the nanoscale. When the molecules are deposited in nanoporous anodic alumina films with exposed aluminum at the bottom of the pores, they form organic nanowires standing on aluminum nanoparticles whose plasmon waves have much larger amplitudes. This increases the MEF strongly, resulting in several orders of magnitude increase in the fluorescence intensity of the organic fluorophores. The increase in intensity shows an inverse superlinear dependence on nanowire diameter because the nanowires also act as plasmonic "waveguides" that concentrate the plasmons and increase the coupling of the plasmons with the radiative modes of the molecules. Furthermore, if the nanoporous template housing the nanowires has built-in electric fields due to space charges, a strong molecule-specific red- or blue-shift is induced in the fluorescence peak owing to a renormalization of the dipole moment of the molecule. This can be exploited to detect minute amounts of target molecules in a mixture using their optical signature (fluorescence) despite the presence of confounding background signals. It can result in a unique new technology for biosensing and chemical sensing.

  16. Vitrification of IFR and MSBR halide salt reprocessing wastes

    SciTech Connect

    Siemer, D.D.

    2013-07-01

    Both of the genuinely sustainable (breeder) nuclear fuel cycles (IFR - Integral Fast Reactor - and MSBR - Molten Salt Breeder Reactor -) studied by the USA's national laboratories would generate high level reprocessing waste (HLRW) streams consisting of a relatively small amount ( about 4 mole %) of fission product halide (chloride or fluoride) salts in a matrix comprised primarily (about 95 mole %) of non radioactive alkali metal halide salts. Because leach resistant glasses cannot accommodate much of any of the halides, most of the treatment scenarios previously envisioned for such HLRW have assumed a monolithic waste form comprised of a synthetic analog of an insoluble crystalline halide mineral. In practice, this translates to making a 'substituted' sodalite ('Ceramic Waste Form') of the IFR's chloride salt-based wastes and fluoroapatite of the MSBR's fluoride salt-based wastes. This paper discusses my experimental studies of an alternative waste management scenario for both fuel cycles that would separate/recycle the waste's halide and immobilize everything else in iron phosphate (Fe-P) glass. It will describe both how the work was done and what its results indicate about how a treatment process for both of those wastes should be implemented (fluoride and chloride behave differently). In either case, this scenario's primary advantages include much higher waste loadings, much lower overall cost, and the generation of a product (glass) that is more consistent with current waste management practices. (author)

  17. Metal enhanced fluorescence improved protein and DNA detection by zigzag Ag nanorod arrays.

    PubMed

    Ji, Xiaofan; Xiao, Chenyu; Lau, Wai-Fung; Li, Jianping; Fu, Junxue

    2016-08-15

    As metal nano-arrays show great potential on metal enhanced fluorescence (MEF) than random nanostructures, MEF of Ag zigzag nanorod (ZNR) arrays made by oblique angle deposition has been studied for biomolecule-protein interaction and DNA hybridization. By changing the folding number and the deposition substrate temperature, a 14-fold enhancement factor (EF) is obtained for biotin-neutravidin detection. The optimal folding number is decided as Z=7, owing to the high scattering intensity of Ag ZNRs. The substrate temperature T=25°C and 0°C slightly alters the morphology of Ag ZNRs but has no big difference in EF. Further, Ag ZNRs deposited on a layer of Ag film have been introduced to the DNA hybridization and a significant signal enhancement has been observed through the fluorescence microscope. Through a detailed quantitative EF analysis, which excludes the enhancing effect from the increased surface area of ZNRs and only considers the contribution of MEF, an EF of 28 is achieved for the hybridization of two single-stranded oligonucleotides with 33 bases. Furthermore, a limit of detection is determined as 0.01pM. We believe that the Ag ZNR arrays can serve as a universal and sensitive bio-detection platform. PMID:27088369

  18. Photophysical characterization of fluorescent metal nanoclusters sythesized using oligonucleotides, proteins and small reagent moleucles

    SciTech Connect

    Yeh, Hsin-chih; Jaswinder, Sharma K; Martinez, Jennifer S; Werner, James H; Yoo, Hyojong

    2009-01-01

    The size transition from bulk metals to insulating nanoparticles and eventually to single atoms passes through the relatively unexplored few-atom nanocluster region. With climensions close to the Fermi wavelength, these nanoclusters demonstrate molecule-like properties distinct from bulk metals or atoms, such as discrete and size-tunable electronic transitions which lead to photoluminescence. Current research aims to elucidate the fundamental photophysical properties of the existing metal nanoclusters made by different means and based on different encapsulation agents. Here, we report the study of the photophysical properties, including quantum yields, lifetimes, extinction coefficients, blinking dynamics and sizes, of silver and gold nanoclusters synthesized using oligonucleotides, a protein (bovine serum albumin) and a Good's buffer molecule (MES, 2-(N-morpholino)ethanesulfonic acid) as encapsulation agents. We also investigate the change of photoluminescence under varying conditions (time, temperature and salt). Furthermore, it is demonstrated here that fluorescent metal clusters can be used as a donor in forming resonance energy transfer pairs with a commercial organic quenching dye.

  19. Photophysical characterization of fluorescent metal nanoclusters synthesized using oligonucleotides, proteins and small molecule ligands

    NASA Astrophysics Data System (ADS)

    Yeh, Hsin-Chih; Sharma, Jaswinder; Yoo, Hyojong; Martinez, Jennifer S.; Werner, James H.

    2010-02-01

    The size transition from bulk conducting metals to insulating nanoparticles and eventually to single atoms passes through the relatively unexplored few-atom nanocluster region. With dimensions close to the Fermi wavelength, these nanoclusters demonstrate molecule-like properties distinct from bulk metals or atoms, such as discrete and size-tunable electronic transitions which lead to photoluminescence. Current research aims to elucidate the fundamental photophysical properties of metal nanoclusters made by different means and based on different encapsulation agents. Here, we report the study of the photophysical properties, including quantum yields, lifetimes, extinction coefficients, blinking dynamics and sizes, of silver and gold nanoclusters synthesized using oligonucleotides, a protein (bovine serum albumin) and a Good's buffer molecule (MES, 2-(N-morpholino) ethanesulfonic acid) as encapsulation agents. We also investigate the change of photoluminescence as a function of temperature. Furthermore, we show that the fluorescent metal clusters can be used as a donor in forming a resonance energy transfer pair with a commercial organic quencher. These new fluorophores have great potential as versatile tools for a broad range of applications in biological and chemical detection.

  20. ELECTROLYTIC PROCESS FOR PRODUCING METALS

    DOEpatents

    Kopelman, B.; Holden, R.B.

    1961-06-01

    A method is described for reducing beryllium halides to beryllium. The beryllfum halide fs placed in an eutectic mixture of alkali halides and alkaline earth halides. The constituents of this eutectic bath are so chosen that it has a melting point less than the boiling point of mercury, which acts as a cathode for the system. The beryllium metal is then deposited in the mercury upon electrolysis.

  1. Recyclables recovery of europium and yttrium metals and some salts from spent fluorescent lamps.

    PubMed

    Rabah, Mahmoud A

    2008-01-01

    Europium and yttrium metals and some valuable salts were recovered from the powder coating the inner surface of the glass tubes of fluorescent lamps. The tubes were broken under 30% aqueous acetone to avoid emission of mercury vapor to the atmosphere, and the powder was collected by brushing. Metals available in the powder were pressure leached using sulfuric/nitric acid mixture. Sulphate salt of europium and yttrium so obtained was converted to thiocyanate. Trimethyl-benzylammonium chloride solvent was used to selectively extract Eu and Y from the thiocyanate solution. The metal loaded in the organic solvent was recovered by N-tributylphosphate in 1M nitric acid to produce nitrate salts of Eu and Y. Europium nitrate was separated from yttrium nitrate by dissolving in ethyl alcohol. The isolated powder contained 1.62% europium oxide, 1.65% yttrium oxide, 34.48% calcium sulphate, 61.52% Ca orthophosphate and 0.65% other impurity metals by weight. Autoclave digestion of the powder in the acid mixture for 4h at approximately 125 degrees C and 5 MPa dissolved 96.4% of the yttrium and 92.8% of the europium. Conversion of the sulphate to thiocyanate is favoured at low temperature. Extraction of Eu and Y from the thiocyanate solution attained its maximum at approximately 80 degrees C. N-tributylphosphate in 1N nitric acid at 125 degrees C achieved a stripping extent of 99%. Thermal reduction using hydrogen gas at 850 degrees C and 1575 degrees C produced europium and yttrium metals, respectively. A metal separation factor of 9.4 was achieved. Economic estimation revealed that the suggested method seemed feasible for industrial applications.

  2. Site-specific control of N7-metal coordination in DNA by a fluorescent purine derivative.

    PubMed

    Dumas, Anaëlle; Luedtke, Nathan W

    2012-01-01

    A synthetic strategy that utilizes O6-protected 8-bromoguanosine gives broad access to C8-guanine derivatives with phenyl, pyridine, thiophene, and furan substituents. The resulting 8-substituted 2'-deoxyguanosines are push-pull fluorophores that can exhibit environmentally sensitive quantum yields (Φ=0.001-0.72) due to excited-state proton-transfer reactions with bulk solvent. Changes in nucleoside fluorescence were used to characterize metal-binding affinity and specificity of 8-substituted 2'-deoxyguanosines. One derivative, 8-(2-pyridyl)-2'-deoxyguanosine (2PyG), exhibits selective binding of Cu(II), Ni(II), Cd(II), and Zn(II) through a bidentate effect provided by the N7 position of guanine and the 2-pyridyl nitrogen atom. Upon incorporation into DNA, 2-pyridine-modified guanine residues selectively bind to Cu(II) and Ni(II) with equilibrium dissociation constants (K(d)) that range from 25 to 850 nM; the affinities depend on the folded state of the oligonucleotide (duplex>G-quadruplex) as well as the identity of the metal ion (Cu>Ni≫Cd). These binding affinities are approximately 10 to 1 000 times higher than for unmodified metal binding sites in DNA, thereby providing site-specific control of metal localization in alternatively folded nucleic acids. Temperature-dependent circular-dichroism studies reveal metal-dependent stabilization of duplexes, but destabilization of G-quadruplex structures upon adding Cu(II) to 2PyG-modified oligonucleotides. These results demonstrate how the addition of a single pyridine group to the C8 position of guanine provides a powerful new tool for studying the effects of N7 metalation on the structure, stability, and electronic properties of nucleic acids.

  3. The low temperature electrochemical growth of iron, nickel and other metallic single crystals from halide eutectic fluxes in a temperature gradient

    NASA Astrophysics Data System (ADS)

    Chareev, Dmitriy A.

    2015-11-01

    Single crystals of metallic Fe, Ni, Co, Cr, Al, Cu, Ag, Au, Pd, Pt and a few alloys were grown using the AlCl3/KCl and CsCl/NaCl/KCl fluxes for Men+ transport and an inert metallic wire for electron transport in a permanent temperature gradient from 350-600 °C that produced single crystalline samples with dimensions of approximately 2×2×2 mm3. Energy dispersive X-ray spectroscopy established crystal formation of pure metals.

  4. Switch-On Fluorescence of a Perylene-Dye-Functionalized Metal-Organic Framework through Postsynthetic Modification.

    PubMed

    Dietl, Christian; Hintz, Henrik; Rühle, Bastian; Schmedt Auf der Günne, Jörn; Langhals, Heinz; Wuttke, Stefan

    2015-07-20

    A perylene dye was introduced directly as a linker into a metal-organic framework (MOF) during synthesis. Depending on the dye concentration in the MOF synthesis mixture, different fluorescent materials were generated. The successful incorporation of the dye was proven by using (13) C and (27) Al MAS NMR spectroscopy, by solution NMR spectroscopy after digestion of the MOF sample, and by synthesizing a reference dye without connecting groups, which could coordinate on the metal-oxo cluster inside the MOF. Fluorescence quenching effects of the MOF linker, 2-aminoterephthalate, were observed and overcome by postsynthetic modification with acetic anhydride. We show here for the first time that amino groups, which can be used as anchoring points for covalent attachment of other molecules, are responsible for fluorescence quenching. Thus, a very promising strategy to implement switchable fluorescence into MOFs is shown here.

  5. Dependence of Purcell effect on fluorescence wavelength in dye molecules on metal-dielectric multilayer hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Tsurumachi, Noriaki; Izawa, Hayato; Tomioka, Ryo; Sakata, Tomohiro; Suzuki, Makoto; Tanaka, Yasuhiro; Shimokawa, Fusao; Nakanishi, Shunsuke

    2016-02-01

    Recently, the enhancement of spontaneous emission, i.e., broadband Purcell effect, has been achieved using hyperbolic metamaterials. Hyperbolic metamaterials, which can be realized using a metal-dielectric multilayer structure, have an extremely large optical anisotropy of permittivity in both the parallel and perpendicular directions to the propagation of light, especially when the signs of permittivities in both directions differ. In this study, we investigated the conditions for realizing the broadband Purcell effect using dye molecules with different fluorescence wavelengths. Our fabricated metal-dielectric multilayer structure exhibited hyperbolic dispersion at wavelengths beyond 500 nm. In the case of coumarin 500 whose fluorescence peak is located at 500 nm, no broadband Purcell effect was observed. However, in the case of pyridine 1 whose fluorescence peak is located at 650 nm, we observed the successfull fluorescence lifetime shortening, i.e., the broadband Purcell effect.

  6. Turn-on fluorescence in tetraphenylethylene-based metal-organic frameworks: an alternative to aggregation-induced emission.

    PubMed

    Shustova, Natalia B; McCarthy, Brian D; Dincă, Mircea

    2011-12-21

    Coordinative immobilization of functionalized tetraphenylethylene within rigid porous metal-organic frameworks (MOFs) turns on fluorescence in the typically non-emissive tetraphenylethylene core. The matrix coordination-induced emission effect (MCIE) is complementary to aggregation-induced emission. Despite the large interchromophore distances imposed by coordination to metal ions, a carboxylate analogue of tetraphenylethylene anchored by Zn(2+) and Cd(2+) ions inside MOFs shows fluorescence lifetimes in line with those of close-packed molecular aggregates. Turn-on fluorescence by coordinative ligation in a porous matrix is a powerful approach that may lead to new materials made from chromophores with molecular rotors. The potential utility of MCIE toward building new sensing materials is demonstrated by tuning the fluorescence response of the porous MOFs as a function of adsorbed small analytes.

  7. Significant metal enhanced fluorescence of Ag2S quantum dots in the second near-infrared window

    NASA Astrophysics Data System (ADS)

    Theodorou, I. G.; Jawad, Z. A. R.; Qin, H.; Aboagye, E. O.; Porter, A. E.; Ryan, M. P.; Xie, F.

    2016-06-01

    The amplification of light in NIR-II from Ag2S QDs via metal enhanced fluorescence (MEF) is reported for the first time. Significant fluorescence enhancement of over 100 times for Ag2S QDs deposited on Au-nanostructured arrays, paves the way for novel sensing and imaging applications based on Ag2S QDs, with improved detection sensitivity and contrast enhancement.The amplification of light in NIR-II from Ag2S QDs via metal enhanced fluorescence (MEF) is reported for the first time. Significant fluorescence enhancement of over 100 times for Ag2S QDs deposited on Au-nanostructured arrays, paves the way for novel sensing and imaging applications based on Ag2S QDs, with improved detection sensitivity and contrast enhancement. Electronic supplementary information (ESI) available: Detailed description of experimental methods. See DOI: 10.1039/c6nr03220f

  8. Making and Breaking of Lead Halide Perovskites.

    PubMed

    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

  9. Correlation of photobleaching, oxidation and metal induced fluorescence quenching of DNA-templated silver nanoclusters

    NASA Astrophysics Data System (ADS)

    Morishita, Kiyoshi; Maclean, James L.; Liu, Biwu; Jiang, Hui; Liu, Juewen

    2013-03-01

    Few-atom noble metal nanoclusters have attracted a lot of interest due to their potential applications in biosensor development, imaging and catalysis. DNA-templated silver nanoclusters (AgNCs) are of particular interest as different emission colors can be obtained by changing the DNA sequence. A popular analytical application is fluorescence quenching by Hg2+, where d10-d10 metallophilic interaction has often been proposed for associating Hg2+ with nanoclusters. However, it cannot explain the lack of response to other d10 ions such as Zn2+ and Cd2+. In our effort to elucidate the quenching mechanism, we studied a total of eight AgNCs prepared by different hairpin DNA sequences; they showed different sensitivity to Hg2+, and DNA with a larger cytosine loop size produced more sensitive AgNCs. In all the cases, samples strongly quenched by Hg2+ were also more easily photobleached. Light of shorter wavelengths bleached AgNCs more potently, and photobleached samples can be recovered by NaBH4. Strong fluorescence quenching was also observed with high redox potential metal ions such as Ag+, Au3+, Cu2+ and Hg2+, but not with low redox potential ions. Such metal induced quenching cannot be recovered by NaBH4. Electronic absorption and mass spectrometry studies offered further insights into the oxidation reaction. Our results correlate many important experimental observations and will fuel the further growth of this field.Few-atom noble metal nanoclusters have attracted a lot of interest due to their potential applications in biosensor development, imaging and catalysis. DNA-templated silver nanoclusters (AgNCs) are of particular interest as different emission colors can be obtained by changing the DNA sequence. A popular analytical application is fluorescence quenching by Hg2+, where d10-d10 metallophilic interaction has often been proposed for associating Hg2+ with nanoclusters. However, it cannot explain the lack of response to other d10 ions such as Zn2+ and Cd2+. In

  10. Significant metal enhanced fluorescence of Ag2S quantum dots in the second near-infrared window.

    PubMed

    Theodorou, I G; Jawad, Z A R; Qin, H; Aboagye, E O; Porter, A E; Ryan, M P; Xie, F

    2016-07-14

    The amplification of light in NIR-II from Ag2S QDs via metal enhanced fluorescence (MEF) is reported for the first time. Significant fluorescence enhancement of over 100 times for Ag2S QDs deposited on Au-nanostructured arrays, paves the way for novel sensing and imaging applications based on Ag2S QDs, with improved detection sensitivity and contrast enhancement. PMID:27314986

  11. Methyl Halide Production by Fungi

    NASA Astrophysics Data System (ADS)

    Dailey, G. D.; Varner, R. K.; Blanchard, R. O.; Sive, B. C.; Crill, P. M.

    2005-12-01

    Methyl chloride (CH3Cl), methyl bromide (CH3Br) and methyl iodide (CH3I) are methyl halide gases that contribute significant amounts of halogen radicals to the atmosphere. In an effort to better understand the global budget of methyl halides and their impact on the atmosphere, we need to identify the natural sources in addition to the known anthropogenic sources of these compounds. We are investigating the role of fungi in the production of methyl halides in the soils and wetlands in southern New Hampshire, USA. Previous research has shown that wood decay fungi and ectomycorrhizal fungi, which are within a group of fungi called basidiomycetes, emit methyl halides. In our study, measurements of headspace gas extracted from flasks containing fungi grown in culture demonstrate that a variety of fungi, including basidiomycetes and non-basidiomycetes, emit methyl halides. Our research sites include four ecosystems: an agricultural field, a temperate forest, a fresh water wetland, and coastal salt marshes. We have collected and isolated fungi at each site by culturing tissue samples of fruiting bodies and plant material, by using wood baits, and from the direct culture of soil. We compared the rates of methyl halide emissions from the fungi in the four ecosystems. In addition, we measured emissions from previously assayed fungal isolates after reintroducing them to sterilized soils that were collected from their original environments. Fungal biomass was determined by substrate-induced respiration (SIR). The emission rate by the fungus was determined by a linear regression of the concentration of methyl halide in the sample headspace over time divided by the fungal biomass.

  12. Mapping of Heavy Metal Ion Sorption to Cell-Extracellular Polymeric Substance-Mineral Aggregates by Using Metal-Selective Fluorescent Probes and Confocal Laser Scanning Microscopy

    PubMed Central

    Li, Jianli; Kappler, Andreas; Obst, Martin

    2013-01-01

    Biofilms, organic matter, iron/aluminum oxides, and clay minerals bind toxic heavy metal ions and control their fate and bioavailability in the environment. The spatial relationship of metal ions to biomacromolecules such as extracellular polymeric substances (EPS) in biofilms with microbial cells and biogenic minerals is complex and occurs at the micro- and submicrometer scale. Here, we review the application of highly selective and sensitive metal fluorescent probes for confocal laser scanning microscopy (CLSM) that were originally developed for use in life sciences and propose their suitability as a powerful tool for mapping heavy metals in environmental biofilms and cell-EPS-mineral aggregates (CEMAs). The benefit of using metal fluorescent dyes in combination with CLSM imaging over other techniques such as electron microscopy is that environmental samples can be analyzed in their natural hydrated state, avoiding artifacts such as aggregation from drying that is necessary for analytical electron microscopy. In this minireview, we present data for a group of sensitive fluorescent probes highly specific for Fe3+, Cu2+, Zn2+, and Hg2+, illustrating the potential of their application in environmental science. We evaluate their application in combination with other fluorescent probes that label constituents of CEMAs such as DNA or polysaccharides and provide selection guidelines for potential combinations of fluorescent probes. Correlation analysis of spatially resolved heavy metal distributions with EPS and biogenic minerals in their natural, hydrated state will further our understanding of the behavior of metals in environmental systems since it allows for identifying bonding sites in complex, heterogeneous systems. PMID:23974141

  13. Highly Fluorescent Group 13 Metal Complexes with Cyclic, Aromatic Hydroxamic Acid Ligands

    SciTech Connect

    Seitz, Michael; Moore, Evan G.; Raymond, Kenneth N.

    2008-02-11

    The neutral complexes of two ligands based on the 1-oxo-2-hydroxy-isoquinoline (1,2-HOIQO) motif with group 13 metals (Al, Ga, In) show bright blue-violet luminescence in organic solvents. The corresponding transition can be attributed to ligand-centered singlet emission, characterized by a small Stokes shifts of only a few nm combined with lifetimes in the range between 1-3 ns. The fluorescence efficiency is high, with quantum yields of up to 37% in benzene solution. The crystal structure of one of the indium(III) complexes (trigonal space group R-3, a = b = 13.0384(15) {angstrom}, c = 32.870(8) {angstrom}, ? = {beta} = 90{sup o}, {gamma} = 120{sup o}, V = 4839.3(14) {angstrom}{sup 3}, Z = 6) shows a six-coordinate geometry around the indium center which is close to trigonal-prismatic, with a twist angle between the two trigonal faces of 20.7{sup o}. Time-dependent density functional theory (TD-DFT) calculations (Al and Ga: B3LYP/6-31G(d)); In: B3LYP/LANL2DZ of the fac and mer isomers with one of the two ligands indicate that there is no clear preference for either one of the isomeric forms of the metal complexes. In addition, the metal centers do not have a significant influence on the electronic structure, and as a consequence, on the predominant intraligand optical transitions.

  14. In vivo monitoring of toxic metals: assessment of neutron activation and x-ray fluorescence techniques

    SciTech Connect

    Ellis, K.J.

    1986-01-01

    To date, cadmium, lead, aluminum, and mercury have been measured in vivo in humans. The possibilities of monitoring other toxic metals have also been demonstrated, but no human studies have been performed. Neutron activation analysis appears to be most suitable for Cd and Al measurements, while x-ray fluorescence is ideally suited for measurement of lead in superficial bone. Filtered neutron beams and polarized x-ray sources are being developed which will improve in vivo detection limits. Even so, several of the current facilities are already suitable for use in epidemiological studies of selected populations with suspected long-term low-level ''environmental'' exposures. Evaluation and diagnosis of patients presenting with general clinical symptoms attributable to possible toxic metal exposure may be assisted by in vivo examination. Continued in vivo monitoring of industrial workers, especially follow-up measurements, will provide the first direct assessment of changes in body burden and a direct measure of the biological life-times of these metals in humans. 50 refs., 4 figs., 2 tabs.

  15. Microfluidic-based metal enhanced fluorescence for capillary electrophoresis by Ag nanorod arrays

    NASA Astrophysics Data System (ADS)

    Xiao, Chenyu; Cao, Zhen; Deng, Junhong; Huang, Zhifeng; Xu, Zheng; Fu, Junxue; Yobas, Levent

    2014-06-01

    As metal nanorods show much higher metal enhanced fluorescence (MEF) than metal nanospheres, microfluidic-based MEF is first explored with Ag nanorod (ND) arrays made by oblique angle deposition. By measuring the fluorescein isothiocyanate (FITC) solution sandwiched between the Ag NDs and a piece of cover slip, the enhancement factors (EFs) are found as 3.7 ± 0.64 and 6.74 ± 2.04, for a solution thickness at 20.8 μm and 10 μm, respectively. Because of the strong plasmonic coupling between the adjacent Ag NDs, only the emission of the fluorophores present in the three-dimensional NDs array gets enhanced. Thus, the corresponding effective enhancement factors (EEFs) are revealed to be relatively close, 259 ± 92 and 340 ± 102, respectively. To demonstrate the application of MEF in microfluidic systems, a multilayer of SiO2 NDs/Ag NDs is integrated with a capillary electrophoresis device. At a microchannel depth of 10 μm, an enhancement of 6.5 fold is obtained for amino acids separation detection. These results are very encouraging and open the possibility of MEF applications for the Ag ND arrays decorated microchannels. With the miniaturization of microfluidic devices, microfluidic-based MEF by Ag ND arrays will likely find more applications with further enhancement.

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

    PubMed

    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

  17. RARE-EARTH METAL FISSION PRODUCTS FROM LIQUID U-Bi

    DOEpatents

    Wiswall, R.H.

    1960-05-10

    Fission product metals can be removed from solution in liquid bismuth without removal of an appreciable quantity of uranium by contacting the liquid metal solution with fused halides, as for example, the halides of sodium, potassium, and lithium and by adding to the contacted phases a quantity of a halide which is unstable relative to the halides of the fission products, a specific unstable halide being MgCl/sub 3/.

  18. Molecules for Fluorescence Detection of Specific Chemicals

    NASA Technical Reports Server (NTRS)

    Fedor, Steve

    2008-01-01

    A family of fluorescent dye molecules has been developed for use in on-off fluorescence detection of specific chemicals. By themselves, these molecules do not fluoresce. However, when exposed to certain chemical analytes in liquid or vapor forms, they do fluoresce (see figure). These compounds are amenable to fixation on or in a variety of substrates for use in fluorescence-based detection devices: they can be chemically modified to anchor them to porous or non-porous solid supports or can be incorporated into polymer films. Potential applications for these compounds include detection of chemical warfare agents, sensing of acidity or alkalinity, and fluorescent tagging of proteins in pharmaceutical research and development. These molecules could also be exploited for use as two-photon materials for photodynamic therapy in the treatment of certain cancers and other diseases. A molecule in this family consists of a fluorescent core (such as an anthracene or pyrene) attached to two end groups that, when the dye is excited by absorption of light, transfer an electron to the core, thereby quenching the fluorescence. The end groups can be engineered so that they react chemically with certain analytes. Upon reaction, electrons on the end groups are no longer available for transfer to the core and, consequently, the fluorescence from the core is no longer quenched. The chemoselectivity of these molecules can be changed by changing the end groups. For example, aniline end groups afford a capability for sensing acids or acid halides (including those contained in chemical warfare agents). Pyridine or bipyridyl end groups would enable sensing of metal ions. Other chemicals that can be selectively detected through suitable choice of end groups include glucose and proteins. Moreover, the fluorescent cores can be changed to alter light-absorption and -emission characteristics: anthracene cores fluoresce at wavelengths around 500 nm, whereas perylene cores absorb and emit at

  19. Fluorescent DNAzyme biosensors for metal ions based on catalytic molecular beacons.

    PubMed

    Liu, Juewen; Lu, Yi

    2006-01-01

    In this chapter, methods for designing metal ion sensors using fluorophore- and quencher-labeled DNAzymes are discussed. In contrast to the classical molecular beacon method based on binding, the methods described here utilize catalytic cleavage to release the fluorophore for detection and quantification, making it possible to take advantage of catalytic turnovers for signal amplification. Unlike classical molecular beacons that detect only nucleic acids, catalytic molecular beacons can be applied to different DNAzymes to detect a broad range of analytes. The methods described are based on the finding that almost all known trans-cleaving DNAzymes share a similar structure comprised of a catalytic DNAzyme core flanked by two substrate recognition arms. Using a typical DNAzyme called the "8-17" DNAzyme as an example, the design of highly sensitive and selective Pb2+ sensors is described in detail. The initial design employs a single fluorophore-quencher pair in close proximity, with the fluorophore on the 5'-end of the substrate and the quencher on the 3'-end of the enzyme. Although this sensor is highly sensitive and selective at 4 degrees C, high background fluorescence is observed at higher temperatures. Therefore a new design with an additional quencher attached to the 3'-end of the substrate is employed to suppress background fluorescence. The dual quencher method allows the sensor to perform at ambient temperatures with a high signal-to-noise ratio.

  20. Recent progress in fluorescent and colorimetric chemosensors for detection of precious metal ions (silver, gold and platinum ions).

    PubMed

    Zhang, Jun Feng; Zhou, Ying; Yoon, Juyoung; Kim, Jong Seung

    2011-07-01

    Due to the wide range of applications and biological significance, the development of optical probes for silver, gold and platinum ions has been an active research area in the past few years. This tutorial review focuses on the recent contributions concerning the fluorescent or colorimetric sensors for these metal ions, and is organized according to their structural classifications (for Ag(+) detection) and unique mechanisms between the sensors and metal ions (for Au(3+) and Pt(2+) detection).

  1. Preparation of cerium halide solvate complexes

    DOEpatents

    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.

  2. Theoretical analysis of NMR shieldings of group-11 metal halides on MX (M = Cu, Ag, Au; X = H, F, Cl, Br, I) molecular systems, and the appearance of quasi instabilities on AuF.

    PubMed

    Maldonado, Alejandro F; Melo, Juan I; Aucar, Gustavo A

    2015-10-14

    Accurate calculations of nuclear magnetic shieldings of group-11 metal halides, σ(M; MX) (M = Cu, Ag, Au; X = H, F, Cl, Br, I), were performed with relativistic and nonrelativistic theoretical schemes in order to learn more about the importance of the involved electronic mechanisms that underlie such shieldings. We applied state of the art schemes: polarization propagators at a random phase level of approach (PP-RPA); spin-free Hamiltonian (SF); linear response elimination of small component (LRESC) and density functional theory (DFT) with two different functionals: B3LYP and PBE0. The results from DFT calculations are not close to those from the relativistic polarization propagator calculations at the RPA level of approach (RelPP-RPA), in line with previous results. The spin-orbit (SO) contribution to a shielding constant is important only for MF molecules (M = Cu, Ag, Au). Different electronic mechanisms are considered within the LRESC method, bunched into two groups: core- and ligand-dependent. For the analysed shieldings the core-dependent electronic mechanisms are the most important ones; the ligand-dependent being only important for MF molecules. An out of range value for σ(Au) is found in AuF. It was previously reported in the literature, either originated in the large fluorine electronegativity together with large spin-orbit coupling contributions; or, due to Fermi-contact contributions. We argue here that such an unexpected large value is an artifact originated in the appearance of quasi instabilities, and show how to handle this apparent problem.

  3. Oxidation of hydrogen halides to elemental halogens with catalytic molten salt mixtures

    DOEpatents

    Rohrmann, Charles A.

    1978-01-01

    A process for oxidizing hydrogen halides by means of a catalytically active molten salt is disclosed. The subject hydrogen halide is contacted with a molten salt containing an oxygen compound of vanadium and alkali metal sulfates and pyrosulfates to produce an effluent gas stream rich in the elemental halogen. The reduced vanadium which remains after this contacting is regenerated to the active higher valence state by contacting the spent molten salt with a stream of oxygen-bearing gas.

  4. Metal ions diffusion through polymeric matrices: A total reflection X-ray fluorescence study

    NASA Astrophysics Data System (ADS)

    Boeykens, S.; Caracciolo, N.; D'Angelo, M. V.; Vázquez, C.

    2006-11-01

    This work proposes the use of X-ray fluorescence with total reflection geometry to explore the metal ions transport in aqueous hydrophilic polymer solutions. It is centered in the study of polymer concentration influence on ion diffusion. This subject is relevant to various and diverse applications, such as drug controlled release, microbiologic corrosion protection and enhanced oil recovery. It is anticipated that diffusion is influenced by various factors in these systems, including those specific to the diffusing species, such as charge, shape, molecular size, and those related to the structural complexity of the matrix as well as any specific interaction between the diffusing species and the matrix. The diffusion of nitrate salts of Ba and Mn (same charge, different hydrodynamic radii) through water-swollen polymeric solutions and gels in the 0.01% to 1% concentration ranges was investigated. The measurements of the metal concentration were performed by TXRF analysis using the scattered radiation by the sample as internal standard. Results are discussed according to different physical models for solute diffusion in polymeric solutions.

  5. Design of fluorescent assays for cyanide and hydrogen peroxide based on the inner filter effect of metal nanoparticles.

    PubMed

    Shang, Li; Dong, Shaojun

    2009-02-15

    We have demonstrated the design of a new type fluorescent assay based on the inner filter effect (IFE) of metal nanoparticles (NPs), which is conceptually different from the previously reported metal NPs-based fluorescent assays. With a high extinction coefficient and tunable plasmon absorption feature, metal NPs are expected to be capable of functioning as a powerful absorber to tune the emission of the fluorophore in the IFE-based fluorescent assays. In this work, we presented two proof-of-concept examples based on the IFE of Au NPs by choosing MDMO-PPV as a model fluorophore, whose fluorescence could be tuned by the absorbance of Au NPs with a much higher sensitivity than the corresponding absorbance approach. While the first assay worked in a turn-on mode upon the etching of Au NPs by the analyte, CN(-), the second one functioned in a turn-off mode upon the catalytic growth of Au NPs by the analyte, H(2)O(2). As a result, the present IFE-based approach can detect cyanide ranging from 1.0 x 10(-6) to 6.0 x 10(-4) M with a detection limit of 6.0 x 10(-7) M and H(2)O(2) ranging from 1.5 x 10(-7) to 2.2 x 10(-5) M with a detection limit of 8.5 x 10(-8) M, respectively. Notably, the present IFE-based approach allows the design of fluorescent assays in a more simple, time-saving, and economical approach when compared with conventional metal NPs-based fluorescent assays, since no modification step of the fluorophore was needed any more.

  6. Silver-Gold Nanocomposite Substrates for Metal-Enhanced Fluorescence: Ensemble and Single-Molecule Spectroscopic Studies.

    PubMed

    Choudhury, Sharmistha Dutta; Badugu, Ramachandram; Ray, Krishanu; Lakowicz, Joseph R

    2012-03-01

    In recent years, there has been a growing interest in the studies involving the interactions of fluorophores with plasmonic nanostructures or nanoparticles. These interactions lead to several favorable effects such as increase in the fluorescence intensities, increased photostabilities, and reduced excited-state lifetimes that can be exploited to improve the capabilities of present fluorescence methodologies. In this regard, we report the use of newly developed silver-gold nanocomposite (Ag-Au-NC) structures as substrates for metal-enhanced fluorescence (MEF). The Ag-Au-NC substrates have been prepared by a one-step galvanic replacement reaction from thin silver films coated on glass slides. This approach is simple and suitable for the fabrication of MEF substrates with large area. We have observed about 15-fold enhancement in the fluorescence intensity of ATTO655 from ensemble fluorescence measurements using these substrates. The fluorescence enhancement on the Ag-Au-NC substrates is also accompanied by a reduction in the fluorescence lifetime of ATTO655, which is consistent with the fluorophore-plasmon coupling mechanism. Single-molecule fluorescence measurements have been performed to gain more insight into the metal-fluorophore interactions and to unravel the heterogeneity in the interaction of individual fluorophores with the fabricated substrates. The single-molecule studies are in good agreement with the ensemble measurements and show maximum enhancements of ~50-fold for molecules located in proximity to the "hotspots" on the substrates. In essence, the Ag-Au-NC substrates have a very good potential for various MEF applications.

  7. Fast Monitoring Soil Environmental Qualities of Heavy Metal by Portable X-Ray Fluorescence Spectrometer.

    PubMed

    Wang, Bao; Yu, Jian-xin; Huang, Biao; Hu, Wen-you; Chang, Qing

    2015-06-01

    Portable X-ray fluorescence (PXRF) spectrometer as a new type of equipment for quick test has a prominent prospect, but there are also shortcomings of detection range and limition, therefore this paper studied the suitability of PXRF spectrometer in monitoring soil environmental qualities of heavy metals included Cr, Ni, Cu, Zn, Pb, Cd, As and Hg, the aim of this paper is to screen elements which can be detected by this kind of instrument and evaluate the accuracy of test results. The research method is to test heavy metals contaminated soil samples by PXRF spectrometer, evaluate the accuracy of test results of PXRF compared with inductively coupled plasma mass(ICP-MS), then establish linear regression relationship between analysis results of PXRF and ICP-MS method. The results show that, (1) When measuring the soil environmental quality, PXRF spectrometer is appropriate to measure the content of Pb, Zn, Cr and Cu, except Ni, Cd, As and Hg. (2) Compared with the test value of ICP-MS, the test value of Pb and Zn is lower, the test value of Cu is higher, the test value of Cr is too high, all the results of PXRF spectrometer should be linear corrected according to standard analysis method. In conclusion, PXRF spectrometer is suitable for monitoring environmental quality of soil which is polluted by heavy metal such as Pb, Zn, Cr and Cu, it is an analysis means with characteristics of simple and rapid, accurate and reliable. The innovation of this article is that reasonable avoiding the shortcomings of PXRF spectrometer as using the instrument to monitor soil environmental quality, at last improved the application value of test results.

  8. Hydrogel-based protein and oligonucleotide microchips on metal-coated surfaces: enhancement of fluorescence and optimization of immunoassay.

    PubMed

    Zubtsova, Zh I; Zubtsov, D A; Savvateeva, E N; Stomakhin, A A; Chechetkin, V R; Zasedatelev, A S; Rubina, A Yu

    2009-10-26

    Manufacturing of hydrogel-based microchips on metal-coated substrates significantly enhances fluorescent signals upon binding of labeled target molecules. This observation holds true for both oligonucleotide and protein microchips. When Cy5 is used as fluorophore, this enhancement is 8-10-fold in hemispherical gel elements and 4-5-fold in flattened gel pads, as compared with similar microchips manufactured on uncoated glass slides. The effect also depends on the hydrophobicity of metal-coated substrate and on the presence of a layer of liquid over the gel pads. The extent of enhancement is insensitive to the nature of formed complexes and immobilized probes and remains linear within a wide range of fluorescence intensities. Manufacturing of gel-based protein microarrays on metal-coated substrates improves their sensitivity using the same incubation time for immunoassay. Sandwich immunoassay using these microchips allows shortening the incubation time without loss of sensitivity. Unlike microchips with probes immobilized directly on a surface, for which the plasmon mechanism is considered responsible for metal-enhanced fluorescence, the enhancement effect observed using hydrogel-based microchips on metal-coated substrates might be explained within the framework of geometric optics.

  9. Asymmetri Distribution of Metals in the Xenopus Laevis Oocyte: a Synchrotron X-Ray Fluorescence Microprobe Study

    SciTech Connect

    Popescu, B.F.G.; Belak, Z.R.; Ignatyev, K.; Ovsenek, N.; Nichol, H.; /Saskatchewan U. /SLAC, SSRL

    2009-04-29

    The asymmetric distribution of many components of the Xenopus oocyte, including RNA, proteins, and pigment, provides a framework for cellular specialization during development. During maturation, Xenopus oocytes also acquire metals needed for development, but apart from zinc, little is known about their distribution. Synchrotron X-ray fluorescence microprobe was used to map iron, copper, and zinc and the metalloid selenium in a whole oocyte. Iron, zinc, and copper were asymmetrically distributed in the cytoplasm, while selenium and copper were more abundant in the nucleus. A zone of high copper and zinc was seen in the animal pole cytoplasm. Iron was also concentrated in the animal pole but did not colocalize with zinc, copper, or pigment accumulations. This asymmetry of metal deposition may be important for normal development. Synchrotron X-ray fluorescence microprobe will be a useful tool to examine how metals accumulate and redistribute during fertilization and embryonic development.

  10. Asymmetric Distribution of Metals in the Xenopus Laevis Oocyte: a Synchrotron X-Ray Fluorescence Microprobe Study

    SciTech Connect

    Popescu, B.F.Gh.; Belak, Z.R.; Ignatyev, K.; Ovsenek, N.; Nichol, H.

    2009-06-04

    The asymmetric distribution of many components of the Xenopus oocyte, including RNA, proteins, and pigment, provides a framework for cellular specialization during development. During maturation, Xenopus oocytes also acquire metals needed for development, but apart from zinc, little is known about their distribution. Synchrotron X-ray fluorescence microprobe was used to map iron, copper, and zinc and the metalloid selenium in a whole oocyte. Iron, zinc, and copper were asymmetrically distributed in the cytoplasm, while selenium and copper were more abundant in the nucleus. A zone of high copper and zinc was seen in the animal pole cytoplasm. Iron was also concentrated in the animal pole but did not colocalize with zinc, copper, or pigment accumulations. This asymmetry of metal deposition may be important for normal development. Synchrotron X-ray fluorescence microprobe will be a useful tool to examine how metals accumulate and redistribute during fertilization and embryonic development.

  11. Real-time thermal imaging of microwave accelerated metal-enhanced fluorescence (MAMEF) based assays on sapphire plates.

    PubMed

    Previte, Michael J R; Zhang, Yongxia; Aslan, Kadir; Geddes, Chris D

    2007-11-01

    In this paper, we describe an optical geometry that facilitates our further characterization of the temperature changes above silver island films (SiFs) on sapphire plates, when exposed to microwave radiation. Since sapphire transmits IR, we designed an optical scheme to capture real-time temperature images of a thin water film on sapphire plates with and without SiFs during the application of a short microwave pulse. Using this optical scheme, we can accurately determine the temperature profile of solvents in proximity to metal structures when exposed to microwave irradiation. We believe that this optical scheme will provide us with a basis for further studies in designing metal structures to further improve plasmonic-fluorescence clinical sensing applications, such as those used in microwave accelerated metal-enhanced fluorescence (MAMEF). PMID:17902038

  12. Performance of a Cyanobacteria Whole Cell-Based Fluorescence Biosensor for Heavy Metal and Pesticide Detection

    PubMed Central

    Shing, Wong Ling; Heng, Lee Yook; Surif, Salmijah

    2013-01-01

    Whole cell biosensors always face the challenge of low stability of biological components and short storage life. This paper reports the effects of poly(2-hydroxyethyl methacrylate) (pHEMA) immobilization on a whole cell fluorescence biosensor for the detection of heavy metals (Cu, Pb, Cd), and pesticides (dichlorophenoxyacetic acid (2,4-D), and chlorpyrifos). The biosensor was produced by entrapping the cyanobacterium Anabaena torulosa on a cellulose membrane, followed by applying a layer of pHEMA, and attaching it to a well. The well was then fixed to an optical probe which was connected to a fluorescence spectrophotometer and an electronic reader. The optimization of the biosensor using several factors such as amount of HEMA and drying temperature were undertaken. The detection limits of biosensor without pHEMA for Cu, Cd, Pb, 2,4-D and chlorpyrifos were 1.195, 0.027, 0.0100, 0.025 and 0.025 μg/L respectively. The presence of pHEMA increased the limits of detection to 1.410, 0.250, 0.500, 0.235 and 0.117 μg/L respectively. pHEMA is known to enhance the reproducibility of the biosensor with average relative standard deviation (RSD) of ±1.76% for all the pollutants tested, 48% better than the biosensor without pHEMA (RSD = ±3.73%). In storability test with Cu 5 μg/L, the biosensor with pHEMA performed 11.5% better than the test without pHEMA on day-10 and 5.2% better on day-25. pHEMA is therefore a good candidate to be used in whole cell biosensors as it increases reproducibility and enhances biosensor storability. PMID:23673679

  13. Performance of a cyanobacteria whole cell-based fluorescence biosensor for heavy metal and pesticide detection.

    PubMed

    Shing, Wong Ling; Heng, Lee Yook; Surif, Salmijah

    2013-05-14

    Whole cell biosensors always face the challenge of low stability of biological components and short storage life. This paper reports the effects of poly(2-hydroxyethyl methacrylate) (pHEMA) immobilization on a whole cell fluorescence biosensor for the detection of heavy metals (Cu, Pb, Cd), and pesticides (dichlorophenoxyacetic acid (2,4-D), and chlorpyrifos). The biosensor was produced by entrapping the cyanobacterium Anabaena torulosa on a cellulose membrane, followed by applying a layer of pHEMA, and attaching it to a well. The well was then fixed to an optical probe which was connected to a fluorescence spectrophotometer and an electronic reader. The optimization of the biosensor using several factors such as amount of HEMA and drying temperature were undertaken. The detection limits of biosensor without pHEMA for Cu, Cd, Pb, 2,4-D and chlorpyrifos were 1.195, 0.027, 0.0100, 0.025 and 0.025 µg/L respectively. The presence of pHEMA increased the limits of detection to 1.410, 0.250, 0.500, 0.235 and 0.117 µg/L respectively. pHEMA is known to enhance the reproducibility of the biosensor with average relative standard deviation (RSD) of ±1.76% for all the pollutants tested, 48% better than the biosensor without pHEMA (RSD = ±3.73%). In storability test with Cu 5 µg/L, the biosensor with pHEMA performed 11.5% better than the test without pHEMA on day-10 and 5.2% better on day-25. pHEMA is therefore a good candidate to be used in whole cell biosensors as it increases reproducibility and enhances biosensor storability.

  14. Quantification and localization of trace metals in natural plancton using a synchrotron x-ray fluorescence microprobe.

    SciTech Connect

    Twining, B. S.; Baines, S. B.; Fisher, N. S.; Jacobsen, C.; Maser, J.; State Univ. of New York at Stony Brook

    2003-03-01

    The accumulation of trace metals by planktonic protists influences the growth of primary producers, metal biogeochemical cycling, and metal bioaccumulation in aquatic food chains. Despite their importance, unequivocal measurements of trace element concentrations in individual plankton cells have not been possible to date. We have used the 2-ID-E side-branch hard x-ray microprobe at the Advanced Photon Source to measure trace elements in individual marine plankton cells. This microprobe employs zoneplate optics to produce the sub-micron spatial resolution and low background fluorescence required to produce trace element maps of planktonic protist cells ranging in size from 3 to >50 {micro}m. We have developed preservation, rinsing, and mounting protocols that remove most of the salt from our marine samples, thus simplifying the identification of unknown cells and reducing high Cl-related background fluorescence. We have also developed spectral modeling techniques that account for the frequent overlap of adjacent fluorescence peaks and non-uniform detector response. Finally, we have used parallel soft x-ray transmission and epifluorescence microscopy images to estimate C normalized trace element concentrations, identify functional cell types (e.g., photosynthetic vs. non-photosynthetic), and correlate cell structures with spatial patterns in trace element fluorescence.

  15. Analysis of settled dust with X-ray Fluorescence for exposure assessment of metals in the province of Brescia, Italy.

    PubMed

    Zacco, Annalisa; Resola, Sergio; Lucchini, Roberto; Albini, Elisa; Zimmerman, Neil; Guazzetti, Stefano; Bontempi, Elza

    2009-09-01

    Ferroalloy industries have been active for more than a century in the province of Brescia, Northern Italy. Air emission and water discharge have contaminated the environment in the surroundings of four plants with several metals including manganese. The presence of manganese in this region is especially interesting, because of the observed relationship between manganese exposure and Parkinsonism in a previous epidemiological survey. The aim of this study was represented by an initial screening of metal exposure in this area, using a geographic information system. X-ray fluorescence (XRF) was applied to identify heavy metals in deposited dust samples, collected in representative residential households throughout the province. The results were interpreted through a systematic mapping of all municipal districts of the Brescia province. A more frequent distribution of manganese and other metals was observed in the municipalities where the plants were located and differences in the geochemical and anthropogenic origin of metals were discussed, according to the point sources. PMID:19724825

  16. Atomic structure of metal-halide perovskites from first principles: The chicken-and-egg paradox of the organic-inorganic interaction

    NASA Astrophysics Data System (ADS)

    Li, Jingrui; Rinke, Patrick

    2016-07-01

    We have studied the prototype hybrid organic-inorganic perovskite CH3NH3PbI3 and its three close relatives, CH3NH3SnI3 ,CH3NH3PbCl3 , and CsPbI3, using relativistic density function theory. The long-range van der Waals (vdW) interactions were incorporated into the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional using the Tkatchenko-Scheffler pairwise scheme. Our results reveal that hydrogen bonding, which is well described by the PBE functional, plays a decisive role for the structural parameters of these systems, including the position and orientation of the organic cation as well as the deformation of the inorganic framework. The magnitude of the inorganic-framework deformation depends sensitively on the orientation of the organic cation, and directly influences the stability of the hybrid perovskites. Our results suggest that the organic and the inorganic components complement each other; the low symmetry of the organic cation is the origin of the inorganic-framework deformation, which then aids the overall stabilization of the hybrid perovskite structure. This stabilization is indirectly affected by vdW interactions, which lead to smaller unit-cell volumes than in PBE and therefore modulate the interaction between the organic cation and the inorganic framework. The vdW-induced lattice-constant corrections are system dependent and lead to PBE+vdW lattice constants in good agreement with experiment. Further insight is gained by analyzing the vdW contributions. In all iodide-based hybrid perovskites, the interaction between the organic cation and the iodide anions provides the largest lattice-constant change, followed by iodine-iodine and the organic cation—heavy-metal cation interaction. These corrections follow an almost linear dependence on the lattice constant within the range considered in our study and are therefore approximately additive.

  17. Electrochemical X-ray fluorescence spectroscopy for trace heavy metal analysis: enhancing X-ray fluorescence detection capabilities by four orders of magnitude.

    PubMed

    Hutton, Laura A; O'Neil, Glen D; Read, Tania L; Ayres, Zoë J; Newton, Mark E; Macpherson, Julie V

    2014-05-01

    The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales). Large area free-standing boron doped diamond grown using microwave plasma chemical vapor deposition techniques is found to be ideal as the electrode material for both electrodeposition and XRF due to its wide solvent window, transparency to the XRF beam, and ability to be produced in mechanically robust freestanding thin film form. During electrodeposition it is possible to vary both the deposition potential (Edep) and deposition time (tdep). For the metals Cu(2+) and Pb(2+) the highest detection sensitivities were found for Edep = -1.75 V and tdep (=) 4000 s with LODs of 0.05 and 0.04 ppb achieved, respectively. In mixed Cu(2+)/Pb(2+) solutions, EC-XRF shows that Cu(2+) deposition is unimpeded by Pb(2+), across a broad concentration range, but this is only true for Pb(2+) when both metals are present at low concentrations (10 nM), boding well for trace level measurements. In a dual mixed metal solution, EC-XRF can also be employed to either selectively deposit the metal which has the most positive formal reduction potential, E(0), or exhaustively deplete it from solution, enabling uninhibited detection of the metal with the more negative E(0).

  18. Integrated Fluorescence

    NASA Technical Reports Server (NTRS)

    Tuma, Margaret (Inventor); Gruhlke, Russell W. (Inventor)

    1998-01-01

    A detection method is integrated with a filtering method and an enhancement method to create a fluorescence sensor that can be miniaturized. The fluorescence sensor comprises a thin film geometry including a waveguide layer, a metal film layer and sensor layer. The thin film geometry of the fluorescence sensor allows the detection of fluorescent radiation over a narrow wavelength interval. This enables wavelength discrimination and eliminates the detection of unwanted light from unknown or spurious sources.

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

    SciTech Connect

    Leigh R. Martin; Aaron T. Johnson; Jana Pfeiffer; Martha R. Finck

    2014-10-01

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

  20. PROCESSING OF URANIUM-METAL-CONTAINING FUEL ELEMENTS

    DOEpatents

    Moore, R.H.

    1962-10-01

    A process is given for recovering uranium from neutronbombarded uranium- aluminum alloys. The alloy is dissolved in an aluminum halide--alkali metal halide mixture in which the halide is a mixture of chloride and bromide, the aluminum halide is present in about stoichiometric quantity as to uranium and fission products and the alkali metal halide in a predominant quantity; the uranium- and electropositive fission-products-containing salt phase is separated from the electronegative-containing metal phase; more aluminum halide is added to the salt phase to obtain equimolarity as to the alkali metal halide; adding an excess of aluminum metal whereby uranium metal is formed and alloyed with the excess aluminum; and separating the uranium-aluminum alloy from the fission- productscontaining salt phase. (AEC)

  1. Sensitive detection of Ochratoxin A in food and drinks using metal-enhanced fluorescence.

    PubMed

    Todescato, Francesco; Antognoli, Agnese; Meneghello, Anna; Cretaio, Erica; Signorini, Raffaella; Bozio, Renato

    2014-07-15

    Easy, sensitive, rapid and low cost ochratoxin biosensors are strongly demanded in food analysis since Ochratoxin A (OTA) is a widely diffused food contaminant, highly detrimental for human health. In this work, a novel plasmonic based optical biosensor prototype for ochratoxin A is described. It exploits the metal-enhanced fluorescence phenomenon due to the silver film over nanosphere plasmonic substrate. Since ochratoxin A could be present in different food commodities, sensor performances have been tested on three different matrices (dried milk, juices, and wheat mix). Firstly, a common OTA extraction solvent and a labeling and detection protocol were defined for the analyzed matrices. Then, the efficiency of the Ag-FON surfaces in signal amplification for the detection of low ochratoxin A concentrations was defined. Using samples spiked with OTA-AF 647 or with unlabeled OTA we were able to detect the mycotoxin at concentrations lower than E.U. specifications of 0.5 μg/kg in wheat, milk and apple juice. The test performances are comparable to those of ELISA kits but the platform presented here, once optimized, present some perspective advantages, such as: low cost and time consuming, versatility of the protocol for the investigation of different matrices, employment also in non-qualified laboratories, small dimensions that allow its integration in a compact device for OTA on-site detection. PMID:24583316

  2. Sensitive detection of Ochratoxin A in food and drinks using metal-enhanced fluorescence.

    PubMed

    Todescato, Francesco; Antognoli, Agnese; Meneghello, Anna; Cretaio, Erica; Signorini, Raffaella; Bozio, Renato

    2014-07-15

    Easy, sensitive, rapid and low cost ochratoxin biosensors are strongly demanded in food analysis since Ochratoxin A (OTA) is a widely diffused food contaminant, highly detrimental for human health. In this work, a novel plasmonic based optical biosensor prototype for ochratoxin A is described. It exploits the metal-enhanced fluorescence phenomenon due to the silver film over nanosphere plasmonic substrate. Since ochratoxin A could be present in different food commodities, sensor performances have been tested on three different matrices (dried milk, juices, and wheat mix). Firstly, a common OTA extraction solvent and a labeling and detection protocol were defined for the analyzed matrices. Then, the efficiency of the Ag-FON surfaces in signal amplification for the detection of low ochratoxin A concentrations was defined. Using samples spiked with OTA-AF 647 or with unlabeled OTA we were able to detect the mycotoxin at concentrations lower than E.U. specifications of 0.5 μg/kg in wheat, milk and apple juice. The test performances are comparable to those of ELISA kits but the platform presented here, once optimized, present some perspective advantages, such as: low cost and time consuming, versatility of the protocol for the investigation of different matrices, employment also in non-qualified laboratories, small dimensions that allow its integration in a compact device for OTA on-site detection.

  3. 3D Imaging of Transition Metals in the Zebrafish Embryo by X-ray Fluorescence Microtomography

    PubMed Central

    Bourassa, Daisy; Gleber, Sophie-Charlotte; Vogt, Stefan; Yi, Hong; Will, Fabian; Richter, Heiko; Shin, Chong Hyun; Fahrni, Christoph J.

    2014-01-01

    Synchrotron X-ray fluorescence (SXRF) microtomography has emerged as a powerful technique for the 3D visualization of the elemental distribution in biological samples. The mechanical stability, both of the instrument and the specimen, is paramount when acquiring tomographic projection series. By combining the progressive lowering of temperature method (PLT) with femtosecond laser sectioning, we were able to embed, excise, and preserve a zebrafish embryo at 24 hours post fertilization in an X-ray compatible, transparent resin for tomographic elemental imaging. Based on a data set comprised of 60 projections, acquired with a step size of 2 μm during 100 hours of beam time, we reconstructed the 3D distribution of zinc, iron, and copper using the iterative maximum likelihood expectation maximization (MLEM) reconstruction algorithm. The volumetric elemental maps, which entail over 124 million individual voxels for each transition metal, revealed distinct elemental distributions that could be correlated with characteristic anatomical features at this stage of embryonic development. PMID:24992831

  4. Silver–Gold Nanocomposite Substrates for Metal-Enhanced Fluorescence: Ensemble and Single-Molecule Spectroscopic Studies

    PubMed Central

    Choudhury, Sharmistha Dutta; Badugu, Ramachandram; Ray, Krishanu; Lakowicz, Joseph R.

    2012-01-01

    In recent years, there has been a growing interest in the studies involving the interactions of fluorophores with plasmonic nanostructures or nanoparticles. These interactions lead to several favorable effects such as increase in the fluorescence intensities, increased photostabilities, and reduced excited-state lifetimes that can be exploited to improve the capabilities of present fluorescence methodologies. In this regard, we report the use of newly developed silver–gold nanocomposite (Ag–Au–NC) structures as substrates for metal-enhanced fluorescence (MEF). The Ag–Au–NC substrates have been prepared by a one-step galvanic replacement reaction from thin silver films coated on glass slides. This approach is simple and suitable for the fabrication of MEF substrates with large area. We have observed about 15-fold enhancement in the fluorescence intensity of ATTO655 from ensemble fluorescence measurements using these substrates. The fluorescence enhancement on the Ag–Au–NC substrates is also accompanied by a reduction in the fluorescence lifetime of ATTO655, which is consistent with the fluorophore–plasmon coupling mechanism. Single-molecule fluorescence measurements have been performed to gain more insight into the metal–fluorophore interactions and to unravel the heterogeneity in the interaction of individual fluorophores with the fabricated substrates. The single-molecule studies are in good agreement with the ensemble measurements and show maximum enhancements of ~50-fold for molecules located in proximity to the “hotspots” on the substrates. In essence, the Ag–Au–NC substrates have a very good potential for various MEF applications. PMID:22707999

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

    PubMed

    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.

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

    PubMed

    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

  7. METHOD OF ALLOYING REACTIVE METALS WITH ALUMINUM OR BERYLLIUM

    DOEpatents

    Runnalls, O.J.C.

    1957-10-15

    A halide of one or more of the reactive metals, neptunium, cerium and americium, is mixed with aluminum or beryllium. The mass is heated at 700 to 1200 deg C, while maintaining a substantial vacuum of above 10/sup -3/ mm of mercury or better, until the halide of the reactive metal is reduced and the metal itself alloys with the reducing metal. The reaction proceeds efficiently due to the volatilization of the halides of the reducing metal, aluminum or beryllium.

  8. Detecting weak fluorescence turn-on in the presence of Pb2+ heavy metal ion using coaxial fiber optic sensor

    NASA Astrophysics Data System (ADS)

    Ma, Jianjun; Chiniforooshan, Yasser; Hao, Wenhui; Bock, Wojtek J.; Wang, Zhi Yuan

    2013-10-01

    This paper is devoted to examining the ability of a coaxial fiber-optic sensor (FOS) in detecting weak fluorescent light and weak fluorescence "turn-on" in the presence of trace heavy metal ion Pb2+. The captured fluorescent signal is detected by the Ocean Optics QE65000 spectrometer. The stock solutions include Pb2+ acetate in water (0.01 M) and a small molecule probe in water. The preliminary experiment shows that this FOS offers the Pb2+ detection limit (DL) of 1.26×10-4 mg/mL. The advantages, limitations and further improvements of this coaxial FOS are discussed in comparison with the bench-top instruments in terms of the abilities of signal light capture and stray excitation light suppression.

  9. Affinity binding-guided fluorescent nanobiosensor for acetylcholinesterase inhibitors via distance modulation between the fluorophore and metallic nanoparticle.

    PubMed

    Zhang, Yaodong; Hei, Tingting; Cai, Yanan; Gao, Qunqun; Zhang, Qi

    2012-03-20

    The magnitude of fluorescence enhancement was found to depend strongly on the distance between fluorophores and metal nanostructures in metal-enhanced fluorescence (MEF). However, the precise placement of the particle in front of the molecule with nanometer accuracy and distance control is a great challenge. We describe a method using acetylcholinesterase (AChE) to modulate the distance between a gold nanoparticle (AuNP) and the fluorophore 7-hydroxy-9H-(1,3-dichloro-9,9-dimethylacridin-2-one) (DDAO). We found that DDAO is a reversible mixed type-I AChE inhibitor. DDAO binds to the peripheral anionic site and penetrates into the active gorge site of AChE via inhibition kinetics test and molecular docking study. The affinity ligand DDAO bound to AChE which was immobilized onto AuNPs, and its fluorescence was sharply enhanced due to MEF. The fluorescence was reduced by distance variations between the AuNP and DDAO, which resulted from other inhibitors competitively binding with AChE and partly or completely displacing DDAO. Experimental results show that changes in fluorescence intensity are related to the concentration of inhibitors present in the solution. In addition, the nanobiosensor has high sensitivity, with detection limits as low as 0.4 μM for paraoxon and 10 nM for tacrine, and also exhibits different reduction efficiencies for the two types of inhibitor. Thus, instead of an inhibition test, a new type of affinity binding-guided fluorescent nanobiosensor was fabricated to detect AChE inhibitors, determine AChE inhibitor binding mode, and screen more potent AChE inhibitors. The proposed strategy may be applied to other proteins or protein domains via changes in the affinity ligand.

  10. DEPOSITION OF METAL ON NONMETAL FILAMENT

    DOEpatents

    Magel, T.T.

    1959-02-10

    A method is described for purifying metallic uranium by passing a halogen vapor continuously over the impure uranium to form uranium halide vapor and immediately passing the halide vapor into contact with a nonmetallic refractory surface which is at a temperature above the melting point of uranium metal. The halide is decomposed at the heated surface depositing molten metal, which collects and falls into a receiver below.

  11. Determination of metal components in marine sediments using energy-dispersive X-ray fluorescence (ED-XRF) spectrometry.

    PubMed

    Tung, Joanne Wai Ting

    2004-11-01

    A rapid energy-dispersive X-ray fluorescence (ED-XRF) spectrometric method for the analysis of metal components of marine sediments has been presented. Calibrations were made using synthetic matrix. The agreement of the results for sediment standard reference materials with reference values is satisfactory. Major advantages of the non-destructive ED-XRF technique over conventional chemical digestion methods include the applicability to analyzing the major oxide components, as well as to trace metals, and the avoidance of hazardous chemicals. The method has been applied to the routine analysis of Hong Kong marine sediment.

  12. Selective extraction and recovery of rare earth metals from phosphor powders in waste fluorescent lamps using an ionic liquid system.

    PubMed

    Yang, Fan; Kubota, Fukiko; Baba, Yuzo; Kamiya, Noriho; Goto, Masahiro

    2013-06-15

    The recycling of rare earth metals from phosphor powders in waste fluorescent lamps by solvent extraction using ionic liquids was studied. Acid leaching of rare earth metals from the waste phosphor powder was examined first. Yttrium (Y) and europium (Eu) dissolved readily in the acid solution; however, the leaching of other rare earth metals required substantial energy input. Ionization of target rare earth metals from the waste phosphor powders into the leach solution was critical for their successful recovery. As a high temperature was required for the complete leaching of all rare earth metals, ionic liquids, for which vapor pressure is negligible, were used as an alternative extracting phase to the conventional organic diluent. An extractant, N, N-dioctyldiglycol amic acid (DODGAA), which was recently developed, showed a high affinity for rare earth metal ions in liquid-liquid extraction although a conventional commercial phosphonic extractant did not. An effective recovery of the rare earth metals, Y, Eu, La and Ce, from the metal impurities, Fe, Al and Zn, was achieved from the acidic leach solution of phosphor powders using an ionic liquid containing DODGAA as novel extractant system.

  13. A library-screening approach for developing a fluorescence sensing array for the detection of metal ions.

    PubMed

    Smith, David G; Sajid, Naveed; Rehn, Simone; Chandramohan, Ramya; Carney, Isaac J; Khan, Misbahul A; New, Elizabeth J

    2016-08-01

    Detection of individual metal ions is of importance across a range of fields of chemistry including environmental monitoring, and health and disease. Fluorescence is a highly sensitive technique and small fluorescent molecules are widely used for the detection and quantification of metal ions in various applications. Achieving specificity for a single metal from a single sensor is always a challenge. An alternative to selective sensing is the use of a number of non-specific sensors, in an array, which together respond in a unique pattern to each analyte. Here we show that screening a library of compounds can give a small sensor set that can be used to identify a range of metal ions following PCA and LDA. We explore a method for screening the initial compounds to identify the best performing sensors. We then present our method for reducing the size of the sensor array, resulting in a four-membered system, which is capable of identifying nine distinct metal ion species in lake water. PMID:27291513

  14. Selective turn-on ammonia sensing enabled by high-temperature fluorescence in metal-organic frameworks with open metal sites.

    PubMed

    Shustova, Natalia B; Cozzolino, Anthony F; Reineke, Sebastian; Baldo, Marc; Dincă, Mircea

    2013-09-11

    We show that fluorescent molecules incorporated as ligands in rigid, porous metal-organic frameworks (MOFs) maintain their fluorescence response to a much higher temperature than in molecular crystals. The remarkable high-temperature ligand-based fluorescence, demonstrated here with tetraphenylethylene- and dihydroxyterephthalate-based linkers, is essential for enabling selective and rapid detection of analytes in the gas phase. Both Zn2(TCPE) (TCPE = tetrakis(4-carboxyphenyl)ethylene) and Mg(H2DHBDC) (H2DHBDC(2-) = 2,5-dihydroxybenzene-1,4-dicarboxylate) function as selective sensors for ammonia at 100 °C, although neither shows NH3 selectivity at room temperature. Variable-temperature diffuse-reflectance infrared spectroscopy, fluorescence spectroscopy, and X-ray crystallography are coupled with density-functional calculations to interrogate the temperature-dependent guest-framework interactions and the preferential analyte binding in each material. These results describe a heretofore unrecognized, yet potentially general property of many rigid, fluorescent MOFs and portend new applications for these materials in selective sensors, with selectivity profiles that can be tuned as a function of temperature.

  15. Selective turn-on ammonia sensing enabled by high-temperature fluorescence in metal-organic frameworks with open metal sites.

    PubMed

    Shustova, Natalia B; Cozzolino, Anthony F; Reineke, Sebastian; Baldo, Marc; Dincă, Mircea

    2013-09-11

    We show that fluorescent molecules incorporated as ligands in rigid, porous metal-organic frameworks (MOFs) maintain their fluorescence response to a much higher temperature than in molecular crystals. The remarkable high-temperature ligand-based fluorescence, demonstrated here with tetraphenylethylene- and dihydroxyterephthalate-based linkers, is essential for enabling selective and rapid detection of analytes in the gas phase. Both Zn2(TCPE) (TCPE = tetrakis(4-carboxyphenyl)ethylene) and Mg(H2DHBDC) (H2DHBDC(2-) = 2,5-dihydroxybenzene-1,4-dicarboxylate) function as selective sensors for ammonia at 100 °C, although neither shows NH3 selectivity at room temperature. Variable-temperature diffuse-reflectance infrared spectroscopy, fluorescence spectroscopy, and X-ray crystallography are coupled with density-functional calculations to interrogate the temperature-dependent guest-framework interactions and the preferential analyte binding in each material. These results describe a heretofore unrecognized, yet potentially general property of many rigid, fluorescent MOFs and portend new applications for these materials in selective sensors, with selectivity profiles that can be tuned as a function of temperature. PMID:23981174

  16. High Pressure Electrochemistry: Application to silver halides

    NASA Astrophysics Data System (ADS)

    Havens, K.; Kavner, A.

    2007-12-01

    Electron and ion charge transfer processes help govern electrical conductivity and diffusive mass and heat transport properties in deep Earth minerals. In an attempt to understand how pressure influences charge transfer behavior, the halide silver bromide (AgBr) was studied under the influence of an electric potential difference applied across two electrodes in a diamond anvil cell. This study follows our previous work on AgI, which was found to dissociate to molecular iodine and silver metal due to pressure and voltage influences. We performed two sets of experiments on AgBr at high pressure in a diamond anvil cell: electrochemical dissociation and electrical resistance measurements. In our study, we were able to electrochemically dissociate AgBr at pressures of 0.25-1.6 GPa by applying a voltage across the electrodes in the diamond cell sample chamber. Ag metal grew visibly on the negatively-charged electrode when voltages varying from 0.1 V to 5 V were applied. Additionally, a dark blue color appeared in low pressure areas of the diamond cell and grew darker from both voltage application and light exposure, indicating photochemical effects. We found that the reaction area and growth rate of both metal and dark blue color strongly increased as voltage increased, but tended to decrease with greater pressure. The resistance across the cell was observed to be influenced by both pressure and light exposure. As the AgBr sample was exposed to visible light, the resistance dropped instantaneously, and after the light was turned off, the resistance increased on a timescale of 10's of seconds to minutes. Notably, at higher pressures, the AgBr showed less photosensitivity. Exploration of these metal halide systems has many potential applications. First, these experiments explore the pressure-dependence of photochemical and photovoltaic processes, and may spur development of pressure-tuned microscale electronic devices. Second, these experimental results can be used to

  17. An Optical Biosensor from Green Fluorescent Escherichia coli for the Evaluation of Single and Combined Heavy Metal Toxicities

    PubMed Central

    Futra, Dedi; Heng, Lee Yook; Ahmad, Asmat; Surif, Salmijah; Ling, Tan Ling

    2015-01-01

    A fluorescence-based fiber optic toxicity biosensor based on genetically modified Escherichia coli (E. coli) with green fluorescent protein (GFP) was developed for the evaluation of the toxicity of several hazardous heavy metal ions. The toxic metals include Cu(II), Cd(II), Pb(II), Zn(II), Cr(VI), Co(II), Ni(II), Ag(I) and Fe(III). The optimum fluorescence excitation and emission wavelengths of the optical biosensor were 400 ± 2 nm and 485 ± 2 nm, respectively. Based on the toxicity observed under optimal conditions, the detection limits of Cu(II), Cd(II), Pb(II), Zn(II), Cr(VI), Co(II), Ni(II), Ag(I) and Fe(III) that can be detected using the toxicity biosensor were at 0.04, 0.32, 0.46, 2.80, 100, 250, 400, 720 and 2600 μg/L, respectively. The repeatability and reproducibility of the proposed biosensor were 3.5%–4.8% RSD (relative standard deviation) and 3.6%–5.1% RSD (n = 8), respectively. The biosensor response was stable for at least five weeks, and demonstrated higher sensitivity towards metal toxicity evaluation when compared to a conventional Microtox assay. PMID:26029952

  18. An optical biosensor from green fluorescent Escherichia coli for the evaluation of single and combined heavy metal toxicities.

    PubMed

    Futra, Dedi; Heng, Lee Yook; Ahmad, Asmat; Surif, Salmijah; Ling, Tan Ling

    2015-05-28

    A fluorescence-based fiber optic toxicity biosensor based on genetically modified Escherichia coli (E. coli) with green fluorescent protein (GFP) was developed for the evaluation of the toxicity of several hazardous heavy metal ions. The toxic metals include Cu(II), Cd(II), Pb(II), Zn(II), Cr(VI), Co(II), Ni(II), Ag(I) and Fe(III). The optimum fluorescence excitation and emission wavelengths of the optical biosensor were 400 ± 2 nm and 485 ± 2 nm, respectively. Based on the toxicity observed under optimal conditions, the detection limits of Cu(II), Cd(II), Pb(II), Zn(II), Cr(VI), Co(II), Ni(II), Ag(I) and Fe(III) that can be detected using the toxicity biosensor were at 0.04, 0.32, 0.46, 2.80, 100, 250, 400, 720 and 2600 μg/L, respectively. The repeatability and reproducibility of the proposed biosensor were 3.5%-4.8% RSD (relative standard deviation) and 3.6%-5.1% RSD (n = 8), respectively. The biosensor response was stable for at least five weeks, and demonstrated higher sensitivity towards metal toxicity evaluation when compared to a conventional Microtox assay.

  19. Gaseous NH3 Confers Porous Pt Nanodendrites Assisted by Halides

    PubMed Central

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

    2016-01-01

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

  20. Gaseous NH3 Confers Porous Pt Nanodendrites Assisted by Halides

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  1. Laser ablation laser induced fluorescence for sensitive detection of heavy metals in water

    NASA Astrophysics Data System (ADS)

    Godwal, Yogesh

    Laser Induced Breakdown Spectroscopy LIBS is a fast non-contact technique for the analysis of the elemental composition using spectral information of the emission from a laser-induced plasma. For the LIBS studies in this thesis the focus has been in using very low energy, microjoule pulses in order to give high spatial resolution and minimize the laser system requirements. This is a regime that we refer to as microLIBS. Under such conditions it is important to maximize the signal detected to give the lowest limit of detection LOD possible. One technique to improve the signal to noise ratios is by coupling LIBS with Laser Induced Fluorescence. This is a technique where the first pulse creates a vapor plume and the second pulse tuned to a resonant absorption line of the species of interest re-excites the plume. We term this technique as Laser ablation Laser Induced Fluorescence LA-LIF. We have been investigating the performance of LA-LIF at low pulse energies (≤ 1 mJ for both pulses) for the detection of elemental contaminants in water. This technique allows reasonable performance compared to high energy single-pulse LIBS, but at a much reduced total energy expenditure. This allows LODs in the parts per billion range ppb range which typically cannot be obtained with low energy single pulse probing of the systems. This approach or exceeds the sensitivities which can be obtained with many shots using much larger energy systems. In this thesis we investigated the performance of LIBS at low pulse energies for the detection of Pb as a contaminant in water. An LOD of 70 ppb was obtained for an accumulation of 100 shots with the ablation laser pulse energy of 250 muJ and an excitation laser pulse energy of 8 muJ. A systematic study of the detector conditions was made for the system for the detection of Pb. Scaling laws for the LOD in terms of the pump and probe energies were measured and also the effect of detector gain, the gate delay and the gate width were studied. In

  2. Heavy metal stress detection and monitoring via LED-induced chlorophyll fluorescence analysis of Zea mays L. seedlings aimed at polluted soil phytoremediation

    NASA Astrophysics Data System (ADS)

    Gouveia-Neto, Artur S.; Silva, Elias A., Jr.; da Silva, Airon José; do Nascimento, Clístenes W. A.

    2012-03-01

    Chlorophyll fluorescence spectroscopy is employed to detect and study the time evolution of metal stress of Zea mays L. seedlings aiming polluted soil phytoremediation. The chlorophyll fluorescence spectra of intact leaves are analyzed using 405 nm LED excitation. Red (Fr) and far-red (FFr) emissions around 685 nm and 735 nm, respectively, are examined as a function of the heavy metal concentration. The fluorescence ratio Fr/FFr was employed to monitor the effect of heavy metal upon the physiological state of the plants before signs of visual stress became apparent. The chlorophyll fluorescence analysis permitted detection and evaluation of the damage caused by heavy metal soil contamination in the early stages of the plants growing process, which is not feasible using conventional in vitro spectral analysis.

  3. Catalysts for cross-coupling reactions with non-activated alkyl halides.

    PubMed

    Frisch, Anja C; Beller, Matthias

    2005-01-21

    Despite the problems inherent to metal-catalyzed cross-coupling reactions with alkyl halides, these reactions have become increasingly important during the last few years. Detailed mechanistic investigations have led to a variety of novel procedures for the selective cross-coupling of non-activated alkyl halides bearing beta hydrogen atoms with a variety of organometallic nucleophiles under mild reaction conditions. This Minireview highlights selected examples of metal-catalyzed coupling methods and is intended to encourage chemists to exploit the potential of these approaches in organic synthesis.

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

    PubMed

    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.

  5. Protein-based fluorescent metal nanoclusters for small molecular drug screening.

    PubMed

    Yu, Yong; New, Siu Yee; Xie, Jianping; Su, Xiaodi; Tan, Yen Nee

    2014-11-18

    A facile drug screening method based on synthesis of fluorescent gold nanoclusters inside albumin proteins loaded with small molecular drugs and comparing the relative fluorescence intensities of the resultant gold nanoclusters has been developed and successfully applied for the quantitative measurement of drug-protein binding constants. PMID:25253537

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

    NASA Technical Reports Server (NTRS)

    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%.

  7. Synthesis and characterization of fluorescence-labelled silica core-shell and noble metal-decorated ceria nanoparticles

    PubMed Central

    Rennhak, Markus; Reller, Armin

    2014-01-01

    Summary The present review article covers work done in the cluster NPBIOMEM in the DFG priority programme SPP 1313 and focuses on synthesis and characterization of fluorescent silica and ceria nanoparticles. Synthetic methods for labelling of silica and polyorganosiloxane/silica core–shell nanoparticles with perylenediimide derivatives are described, as well as the modification of the shell with thiol groups. Photometric methods for the determination of the number of thiol groups and an estimate for the number of fluorescent molecules per nanoparticles, including a scattering correction, have been developed. Ceria nanoparticles decorated with noble metals (Pt, Pd, Rh) are models for the decomposition products of automobile catalytic converters which appear in the exhaust gases and finally interact with biological systems including humans. The control of the degree of agglomeration of small ceria nanoparticles is the basis for their synthesis. Almost monodisperse agglomerates (40 ± 4–260 ± 40 nm diameter) can be prepared and decorated with noble metal nanoparticles (2–5 nm diameter). Fluorescence labelling with ATTO 647N gave the model particles which are now under biophysical investigation. PMID:25671137

  8. A microscale solid-phase extraction poly(dimethylsiloxane) chip for enrichment and fluorescent detection of metal ions.

    PubMed

    Xue, Shuhua; Liu, Yan; Li, Hai-Fang; Uchiyama, Katsumi; Lin, Jin-Ming

    2013-11-15

    A rapid and simple enrichment system was developed on microfluidic chip which was integrated with on-line complexing and fluorescence detection. Microparticles of ion-exchange resin were trapped into the microchannel by a fabricated weir-structure in the end of the microchannel to construct a micro-solid-phase extraction (μ-SPE) device. Some commonly existing metal ions in environment were served as models to evaluate the performance of the proposed microdevice, in combination with on-line derivatization with 8-hydroxyquinolin-5-sulfonic acid (HQS) and fluorescence detection. The concentration and pH value of HQS solution were optimized for metal-HQS fluorescent derivatization. The parameters, which affected the efficiency of the developed method, including composition and concentration of eluent, pH value and the flow rate of HQS solution and elution, were also investigated. Under the optimal conditions, Ca(2+), Mg(2+), Zn(2+) and Pb(2+) were successfully determined by the μ-SPE device on-chip. The experimental enrichment factors for Ca(2+), Mg(2+), Zn(2+) and Pb(2+) were up to 520, 565, 578 and 487 folds, respectively.

  9. Tunable Two-color Luminescence and Host-guest Energy Transfer of Fluorescent Chromophores Encapsulated in Metal-Organic Frameworks

    NASA Astrophysics Data System (ADS)

    Yan, Dongpeng; Tang, Yanqun; Lin, Heyang; Wang, Dan

    2014-03-01

    Co-assembly of chromophore guests with host matrices can afford materials which have photofunctionalities different from those of individual components. Compared with clay and zeolite materials, the use of metal-organic frameworks (MOFs) as a host structure for fabricating luminescent host-guest materials is still at an early stage. Herein, we report the incorporation of a laser dye, 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), into stilbene-based and naphthalene-based MOF systems. The resulting materials exhibit blue/red two-color emission, and the intensity ratio of blue to red fluorescence varies in different planes within the MOF crystal as detected by 3D confocal fluorescence microscopy. The observed changes in ratiometric fluorescence suggest the occurrence of energy transfer from MOF host to DCM molecules, which can be further confirmed by periodic density functional theoretical (DFT) calculations. Moreover, selective changes in luminescence behavior are observed on treating the guest@MOF samples with volatile organic compounds (methanol, acetone and toluene), indicating that these host-guest systems have potential applications as fluorescence sensors. It can be expected that by rational selection of MOF hosts and guest chromophores with suitable emissive colors and energy levels, a wide variety of multi-color luminescent and energy-transfer systems can readily be prepared in a similar manner.

  10. A sensitive fluorescent assay for thiamine based on metal-organic frameworks with intrinsic peroxidase-like activity.

    PubMed

    Tan, Hongliang; Li, Qian; Zhou, Zhengchen; Ma, Chanjiao; Song, Yonghai; Xu, Fugang; Wang, Li

    2015-01-26

    Metal-organic frameworks (MOFs) with tunable structures and properties have recently been emerged as very interesting functional materials. However, the catalytic properties of MOFs as enzymatic mimics remain to be further investigated. In this work, we for the first time demonstrated the peroxidase-like activity of copper-based MOFs (HKUST-1) by employing thiamine (TH) as a peroxidase substrate. In the presence of H2O2, HKUST-1 can catalyze efficiently the conversion of non-fluorescent TH to strong fluorescent thiochrome. The catalytic activity of HKUST-1 is highly dependent on the temperature, pH and H2O2 concentrations. As a peroxidase mimic, HKUST-1 not only has the features of low cost, high stability and easy preparation, but also follows Michaelis-Menten behaviors and shows stronger affinity to TH than horseradish peroxidase (HRP). Based on the peroxidase-like activity of HKUST-1, a simple and sensitive fluorescent method for TH detection has been developed. As low as 1 μM TH can be detected with a linear range from 4 to 700 μM. The detection limit for TH is about 50 fold lower than that of HRP-based fluorescent assay. The proposed method was successfully applied to detect TH in tablets and urine samples and showed a satisfactory result. We believed that the present work could improve the understanding of catalytic behaviors of MOFs as enzymatic mimics and find out a wider application in bioanalysis.

  11. Tunable two-color luminescence and host-guest energy transfer of fluorescent chromophores encapsulated in metal-organic frameworks.

    PubMed

    Yan, Dongpeng; Tang, Yanqun; Lin, Heyang; Wang, Dan

    2014-03-11

    Co-assembly of chromophore guests with host matrices can afford materials which have photofunctionalities different from those of individual components. Compared with clay and zeolite materials, the use of metal-organic frameworks (MOFs) as a host structure for fabricating luminescent host-guest materials is still at an early stage. Herein, we report the incorporation of a laser dye, 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), into stilbene-based and naphthalene-based MOF systems. The resulting materials exhibit blue/red two-color emission, and the intensity ratio of blue to red fluorescence varies in different planes within the MOF crystal as detected by 3D confocal fluorescence microscopy. The observed changes in ratiometric fluorescence suggest the occurrence of energy transfer from MOF host to DCM molecules, which can be further confirmed by periodic density functional theoretical (DFT) calculations. Moreover, selective changes in luminescence behavior are observed on treating the guest@MOF samples with volatile organic compounds (methanol, acetone and toluene), indicating that these host-guest systems have potential applications as fluorescence sensors. It can be expected that by rational selection of MOF hosts and guest chromophores with suitable emissive colors and energy levels, a wide variety of multi-color luminescent and energy-transfer systems can readily be prepared in a similar manner.

  12. Hygroscopicity Evaluation of Halide Scintillators

    SciTech Connect

    Zhuravleva, M; Stand, L; Wei, H; Hobbs, C. L.; Boatner, Lynn A; Ramey, Joanne Oxendine; Burger, Arnold; Rowe, E; Bhattacharya, P.; Tupitsyn, E; Melcher, Charles L

    2014-01-01

    A collaborative study of relative hygroscopicity of anhydrous halide scintillators grown at various laboratories is presented. We have developed a technique to evaluate moisture sensitivity of both raw materials and grown crystals, in which the moisture absorption rate is measured using a gravimetric analysis. Degradation of the scintillation performance was investigated by recording gamma-ray spectra and monitoring the photopeak position, count rate and energy resolution. The accompanying physical degradation of the samples exposed to ambient atmosphere was photographically recorded as well. The results were compared with ben

  13. Investigation of the Co-Dependence of Morphology and Fluorescence Lifetime in a Metal-Organic Framework.

    PubMed

    Schrimpf, Waldemar; Ossato, Giulia; Hirschle, Patrick; Wuttke, Stefan; Lamb, Don C

    2016-07-01

    Porous materials, due to their large surface-to-volume ratio, are important for a broad range of applications and are the subject of intense research. Most studies investigate the bulk properties of these materials, which are not sensitive to the effect of heterogeneities within the sample. Herein, a new strategy based on correlative fluorescence lifetime imaging and scanning electron microscopy is presented that allows the detection and localization of those heterogeneities, and connects them to morphological and structural features of the material. By applying this method to a dye-modified metal-organic framework (MOF), two independent fluorescence quenching mechanisms in the MOF scaffold are identified and quantified. The first mechanism is based on quenching via amino groups, while the second mechanism is influenced by morphology. Furthermore, a similar correlation between the inherent luminescence lifetime and the morphology of the unmodified MOF structure is demonstrated.

  14. Efficient stray-light suppression for resonance fluorescence in quantum dot micropillars using self-aligned metal apertures

    NASA Astrophysics Data System (ADS)

    Hopfmann, Caspar; Musiał, Anna; Maier, Sebastian; Emmerling, Monika; Schneider, Christian; Höfling, Sven; Kamp, Martin; Reitzenstein, Stephan

    2016-09-01

    Within this work we propose and demonstrate a technological approach to efficiently suppress excitation laser stray-light in resonance fluorescence experiments on quantum dot micropillars. To ensure efficient stray-light suppression, their fabrication process includes a planarization step and subsequent covering with a titanium mask to fabricate self-aligned apertures at the micropillar positions. These apertures aim to limit laser stray-light in the side-excitation vertical-detection configuration, while enabling detection of the optical signal through the top facet of the micropillars. The beneficial effects of these apertures are proven and quantitatively evaluated within a statistical study in which we determine and compare the stray-light suppression of 48 micropillars with and without metal apertures. Actual resonance fluorescence experiments on single quantum dots coupled to the cavity mode prove the relevance of the proposed approach and demonstrate that it will foster further studies on cavity quantum electrodynamics phenomena under coherent optical excitation.

  15. Unsymmetrical Schiff base (ON) ligand on complexation with some transition metal ions: synthesis, spectral characterization, antibacterial, fluorescence and thermal studies.

    PubMed

    Ali, Omyma A M; El-Medani, Samir M; Abu Serea, Maha R; Sayed, Abeer S S

    2015-02-01

    A series of eight metal Schiff base complexes were synthesized by the thermal reaction of Cu(II), Ni(II), Fe(III), Co(II), Zn(II), Hg(II), La(III) or Sm(III) with a Schiff base "L" produced by the condensation of furfuraldehyde and 1,2-diaminobenzene. These compounds were characterized by elemental analysis, UV-Vis, FT-IR, molar conductance, mass spectrometry, thermal and fluorescence studies. The studies suggested the coordination of the ligand L to metal through azomethine imine nitrogen and furan oxygen atoms of Schiff base moiety. Thermogravimetric (TG/DTG) analyses data were studied and indicated high stability for all complexes and suggested the presence of lattice and/or coordinated water molecules in the complexes. Coats-Redfern method has been used to calculate the kinetic and thermodynamic parameters of the metal complexes. The spectral and thermal analysis reveal that all complexes have octahedral geometry except Cu(II) and Ni(II) complexes which can attain a square planner arrangements. The ligand and its complexes exhibited intraligand (π-π(∗)) fluorescence and can potentially serve as photoactive materials. Both the ligand and its complexes have been screened for antibacterial activities.

  16. Unsymmetrical Schiff base (ON) ligand on complexation with some transition metal ions: Synthesis, spectral characterization, antibacterial, fluorescence and thermal studies

    NASA Astrophysics Data System (ADS)

    Ali, Omyma A. M.; El-Medani, Samir M.; Abu Serea, Maha R.; Sayed, Abeer S. S.

    2015-02-01

    A series of eight metal Schiff base complexes were synthesized by the thermal reaction of Cu(II), Ni(II), Fe(III), Co(II), Zn(II), Hg(II), La(III) or Sm(III) with a Schiff base "L" produced by the condensation of furfuraldehyde and 1,2-diaminobenzene. These compounds were characterized by elemental analysis, UV-Vis, FT-IR, molar conductance, mass spectrometry, thermal and fluorescence studies. The studies suggested the coordination of the ligand L to metal through azomethine imine nitrogen and furan oxygen atoms of Schiff base moiety. Thermogravimetric (TG/DTG) analyses data were studied and indicated high stability for all complexes and suggested the presence of lattice and/or coordinated water molecules in the complexes. Coats-Redfern method has been used to calculate the kinetic and thermodynamic parameters of the metal complexes. The spectral and thermal analysis reveal that all complexes have octahedral geometry except Cu(II) and Ni(II) complexes which can attain a square planner arrangements. The ligand and its complexes exhibited intraligand (π-π∗) fluorescence and can potentially serve as photoactive materials. Both the ligand and its complexes have been screened for antibacterial activities.

  17. Permeation of halide anions through phospholipid bilayers occurs by the solubility-diffusion mechanism

    NASA Technical Reports Server (NTRS)

    Paula, S.; Volkov, A. G.; Deamer, D. W.

    1998-01-01

    Two alternative mechanisms are frequently used to describe ionic permeation of lipid bilayers. In the first, ions partition into the hydrophobic phase and then diffuse across (the solubility-diffusion mechanism). The second mechanism assumes that ions traverse the bilayer through transient hydrophilic defects caused by thermal fluctuations (the pore mechanism). The theoretical predictions made by both models were tested for halide anions by measuring the permeability coefficients for chloride, bromide, and iodide as a function of bilayer thickness, ionic radius, and sign of charge. To vary the bilayer thickness systematically, liposomes were prepared from monounsaturated phosphatidylcholines (PC) with chain lengths between 16 and 24 carbon atoms. The fluorescent dye MQAE (N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide) served as an indicator for halide concentration inside the liposomes and was used to follow the kinetics of halide flux across the bilayer membranes. The observed permeability coefficients ranged from 10(-9) to 10(-7) cm/s and increased as the bilayer thickness was reduced. Bromide was found to permeate approximately six times faster than chloride through bilayers of identical thickness, and iodide permeated three to four times faster than bromide. The dependence of the halide permeability coefficients on bilayer thickness and on ionic size were consistent with permeation of hydrated ions by a solubility-diffusion mechanism rather than through transient pores. Halide permeation therefore differs from that of a monovalent cation such as potassium, which has been accounted for by a combination of the two mechanisms depending on bilayer thickness.

  18. Meditating metal coenhanced fluorescence and SERS around gold nanoaggregates in nanosphere as bifunctional biosensor for multiple DNA targets.

    PubMed

    Liu, Yong; Wu, Peiyi

    2013-06-26

    Gold nanoparticles (Au NPs) are very attractive candidate nanoparticles in biological assay because of their high chemical stabilities, high homogeneities, good biocompatibilities, and low toxicities. However, molecular beacon assays via encapsulating the combined fluorescence or surface-enhanced Raman scattering (SERS) signals of reporters and Au NPs in nanobarcodes particles usually suffer from fluorescence quenching or weak Raman enhancement when Au NPs are employed (especially with size smaller than 15 nm). Herein, we present a new design of simultaneously realizing metal-enhanced fluorescence and coenhanced surface-enhanced Raman scattering by facilely embedding Ag nanoparticle into the shell of two kinds of Au nanoaggregate (5 and 10 nm), meanwhile, fluorophore is located between the silver core and gold nanoparticle layers and the distance among them is adjusted by SiO2 spacer (Ag@first SiO2 spacer@FiTC+SiO2@second SiO2 spacer@Au nanoaggregate). In this architecture, Ag nanoparticle not only is utilized as an efficient fluorescence enhancer to overcome the common fluorescence quenching around Au nanoaggregates but also behaves like a mirror. Thus, incident light that passes through the SERS-active Au nanoaggregate and the intervening dielectric layer of SiO2 could be reflected multiply from the surface of Ag nanoparticle and coupled with the light at the nanogap between the Au nanoaggregates to further amplify Raman intensity. This results in enhancement factors for fluorescence and SERS ~1.6-fold and more than 300-fold higher than the control samples without silver core under identical experimental conditions, respectively. Moreover, fluorophore and SERS reporters are assembled onto different layers of the concentric hybrid microsphere, resulting in a feasible fabrication protocol when a large number of agents need to be involved into the dual-mode nanobarcodes. A proof-of-concept chip-based DNA sandwich hybridization assay using genetically modified

  19. APPARATUS FOR HIGH PURITY METAL RECOVERY

    DOEpatents

    Magel, T.T.

    1959-02-10

    An apparatus is described for preparing high purity metal such as uranium, plutonium and the like from an impure mass of the same metal. The apparatus is arranged so that the impure metal is heated and swept by a stream of hydrogen gas bearing a halogen such as iodine. The volatiie metal halide formed is carried on to a hot filament where the metal halide is decomposed and the molten high purity metal is collected in a rceeiver below

  20. Detection of heavy metals in water by fluorescence spectroscopy: on the way to a suitable sensor system.

    PubMed

    Prestel, H; Gahr, A; Niessner, R

    2000-01-01

    In order to develop a fiber optical heavy metal ion detection system, the applicability of selected complexing agents with fluorescent properties has been studied. Beginning with the application of known chelators, like BTC-5N, Newport Green, neocuproine, and chromotropic acid, a sensor configuration has been found, which allows the detection of Cd2+, Ni2+, and Cu2+ well below the chemical parameter threshold values of the new Water Quality Directive 98/83/EU. The sensor itself uses a membrane separation of the chelator flow from the sample volume. The diffusion across the membrane limits the response time to about 15 to 20 min. Applications are seen in monitoring networks.

  1. A novel fluorescence-quenching immunochromatographic sensor for detection of the heavy metal chromium.

    PubMed

    Fu, QiangQiang; Tang, Yong; Shi, CongYing; Zhang, XiaoLi; Xiang, JunJian; Liu, Xi

    2013-11-15

    A novel fluorescence quenching immunochromatographic sensor (ICS) was developed for detecting chromium (Cr(3+)) within 15 min utilizing the fluorescence quenching function of gold nanoparticles (Au-NPs). The sensor performed with a positive readout. When the low concentrations of Cr(3+) samples were applied, detection signals of the test line (T line) were quenched, whereas when higher concentration Cr(3+) samples (1.56 ng/mL) were applied, the detection signal of the T line appeared. The detection signal intensity of the T line increased with increasing concentrations of Cr(3+). The low detection limit of developed fluorescence quenching ICS was 1.56 ng/mL. The fluorescence quenching ICS has a linear range of detection of Cr(3+) comprising between 6.25 ng/mL to 800 ng/mL. The recoveries of the fluorescence quenching ICS to detect Cr(3+) in tap water ranged from 94.7% to 101.7%. This result indicated that the developed sensor gave higher sensitivity and reliable reproducibility. It could provide a general detection method for small analyte in water samples.

  2. A novel fluorescence-quenching immunochromatographic sensor for detection of the heavy metal chromium.

    PubMed

    Fu, QiangQiang; Tang, Yong; Shi, CongYing; Zhang, XiaoLi; Xiang, JunJian; Liu, Xi

    2013-11-15

    A novel fluorescence quenching immunochromatographic sensor (ICS) was developed for detecting chromium (Cr(3+)) within 15 min utilizing the fluorescence quenching function of gold nanoparticles (Au-NPs). The sensor performed with a positive readout. When the low concentrations of Cr(3+) samples were applied, detection signals of the test line (T line) were quenched, whereas when higher concentration Cr(3+) samples (1.56 ng/mL) were applied, the detection signal of the T line appeared. The detection signal intensity of the T line increased with increasing concentrations of Cr(3+). The low detection limit of developed fluorescence quenching ICS was 1.56 ng/mL. The fluorescence quenching ICS has a linear range of detection of Cr(3+) comprising between 6.25 ng/mL to 800 ng/mL. The recoveries of the fluorescence quenching ICS to detect Cr(3+) in tap water ranged from 94.7% to 101.7%. This result indicated that the developed sensor gave higher sensitivity and reliable reproducibility. It could provide a general detection method for small analyte in water samples. PMID:23800612

  3. Shallow halogen vacancies in halide optoelectronic materials

    NASA Astrophysics Data System (ADS)

    Shi, Hongliang; Du, Mao-Hua

    2014-11-01

    Halogen vacancies (VH ) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep VH contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., C H3N H3Pb I3 and TlBr. Both C H3N H3Pb I3 and TlBr have been found to have shallow VH , in contrast to commonly seen deep VH in halides. In this paper, several halide optoelectronic materials, i.e., C H3N H3Pb I3 , C H3N H3Sn I3 (photovoltaic materials), TlBr, and CsPbB r3 (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether VH is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of n s2 ions both play important roles in creating shallow VH in halides such as C H3N H3Pb I3 , C H3N H3Sn I3 , and TlBr. The key to identifying halides with shallow VH is to find the right crystal structures and compounds that suppress cation orbital hybridization at VH , such as those with large cation-cation distances and low anion coordination numbers and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at VH . The results of this paper provide insight and guidance to identifying halides with shallow VH as good electronic and optoelectronic materials.

  4. Shallow halogen vacancies in halide optoelectronic materials

    DOE PAGES

    Shi, Hongliang; Du, Mao -Hua

    2014-11-05

    Halogen vacancies (VH) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep VH contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., CH3NH3PbI3 and TlBr. Both CH3NH3PbI3 and TlBr have been found to have shallow VH, in contrast to commonly seen deep VH in halides. In this paper, several halide optoelectronic materials, i.e., CH3NH3PbI3, CH3NH3SnI3 (photovoltaic materials), TlBr, and CsPbBr3, (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether VHmore » is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of ns2 ions both play important roles in creating shallow VH in halides such as CH3NH3PbI3, CH3NH3SnI3, and TlBr. The key to identifying halides with shallow VH is to find the right crystal structures and compounds that suppress cation orbital hybridization at VH, such as those with long cation-cation distances and low anion coordination numbers, and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at VH. Furthermore, the results of this paper provide insight and guidance to identifying halides with shallow VH as good electronic and optoelectronic materials.« less

  5. Triplet state magnetic resonance and fluorescence spectroscopy of metal-substituted hemoglobins.

    PubMed Central

    Polm, M W; Schaafsma, T J

    1997-01-01

    Fluorescence detected magnetic resonance (FDMR) spectra detected at 596 nm of zinc-substituted hemoglobins at 4.2 K show a split D-E transition, which is not observed for zinc protoporphyrins ligated by methylimidazole in glasses. Incorporation of the zinc heme into the globin pocket is also accompanied by a blue shift of the fluorescence of 20 nm at 4.2 K. FDMR spectra recorded at 576 nm do not show the D-E splitting. The D-E splitting and the huge blue shift are not observed for the magnesium-substituted hemoglobins. Fluorescence measurements at 4.2 K and 77 K, and EPR measurements at 110 K, were carried out to obtain information about the ligation states of the zinc and magnesium protoporphyrins in glasses and in hemoglobin. The results are explained by considering ligation effects and distortion of the porphyrin plane. Images FIGURE 12 PMID:8994622

  6. Polarization control of metal-enhanced fluorescence in hybrid assemblies of photosynthetic complexes and gold nanorods.

    PubMed

    Bujak, Ł; Olejnik, M; Brotosudarmo, T H P; Schmidt, M K; Czechowski, N; Piatkowski, D; Aizpurua, J; Cogdell, R J; Heiss, W; Mackowski, S

    2014-05-21

    Fluorescence imaging of hybrid nanostructures composed of a bacterial light-harvesting complex LH2 and Au nanorods with controlled coupling strength is employed to study the spectral dependence of the plasmon-induced fluorescence enhancement. Perfect matching of the plasmon resonances in the nanorods with the absorption bands of the LH2 complexes facilitates a direct comparison of the enhancement factors for longitudinal and transverse plasmon frequencies of the nanorods. We find that the fluorescence enhancement due to excitation of longitudinal resonance can be up to five-fold stronger than for the transverse one. We attribute this result, which is important for designing plasmonic functional systems, to a very different distribution of the enhancement of the electric field due to the excitation of the two characteristic plasmon modes in nanorods.

  7. Magnetic porous carbon nanocomposites derived from metal-organic frameworks as a sensing platform for DNA fluorescent detection.

    PubMed

    Tan, Hongliang; Tang, Gonge; Wang, Zhixiong; Li, Qian; Gao, Jie; Wu, Shimeng

    2016-10-12

    Metal-organic frameworks (MOFs) have emerged as very fascinating functional materials due to their tunable nature and diverse applications. In this work, we prepared a magnetic porous carbon (MPC) nanocomposite by employing iron-containing MOFs (MIL-88A) as precursors through a one-pot thermolysis method. It was found that the MPC can absorb selectively single-stranded DNA (ssDNA) probe to form MPC/ssDNA complex and subsequently quench the labelled fluorescent dye of the ssDNA probe, which is resulted from the synergetic effect of magnetic nanoparticles and carbon matrix. Upon the addition of complementary target DNA, however, the absorbed ssDNA probe could be released from MPC surface by forming double-stranded DNA with target DNA, and accompanied by the recovery of the fluorescence of ssDNA probe. Based on these findings, a sensing platform with low background signal for DNA fluorescent detection was developed. The proposed sensing platform exhibits high sensitivity with detection limit of 1 nM and excellent selectivity to specific target DNA, even single-base mismatched nucleotide can be distinguished. We envision that the presented study would provide a new perspective on the potential applications of MOF-derived nanocomposites in biomedical fields.

  8. Metal-free phthalocyanine aggregation and binding with amines: Specific and general solvent effects on absorption and fluorescence properties

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Zhang, Xian-Fu; Lu, Xulin

    2015-03-01

    The fluorescence and absorption properties of a metal-free phthalocyanine (Pc) H2PcR4 and its zinc-centered complex ZnPcR4 (R is the isopropyloxy at the β-position of a Pc ring) were measured and compared in protic and aprotic solvents. H2PcR4 shows strong bonding interaction with amines and aggregation in alcohols in addition to the general solvent effect in aprotic solvents due to polarity change. The specific solvent effect leads to substantial changes in its spectra, fluorescence quantum yield (Φf) and fluorescence lifetime (τf) values. In contrast, ZnPcR4 does not show the specific effects due to the presence of a central element in a Pc cavity. For H2PcR4 the change of solvents caused a large variation of Φf (0.050-0.48) and τf (3.45-6.88 ns), in contrast to the slight changes for ZnPcR4. On the other hand, the general solvent effect of H2PcR4 due to polarity is also more significant than that of ZnPcR4. The increase of solvent polarity decreases both Φf and τf, but increases the Stoke's shift.

  9. Magnetic porous carbon nanocomposites derived from metal-organic frameworks as a sensing platform for DNA fluorescent detection.

    PubMed

    Tan, Hongliang; Tang, Gonge; Wang, Zhixiong; Li, Qian; Gao, Jie; Wu, Shimeng

    2016-10-12

    Metal-organic frameworks (MOFs) have emerged as very fascinating functional materials due to their tunable nature and diverse applications. In this work, we prepared a magnetic porous carbon (MPC) nanocomposite by employing iron-containing MOFs (MIL-88A) as precursors through a one-pot thermolysis method. It was found that the MPC can absorb selectively single-stranded DNA (ssDNA) probe to form MPC/ssDNA complex and subsequently quench the labelled fluorescent dye of the ssDNA probe, which is resulted from the synergetic effect of magnetic nanoparticles and carbon matrix. Upon the addition of complementary target DNA, however, the absorbed ssDNA probe could be released from MPC surface by forming double-stranded DNA with target DNA, and accompanied by the recovery of the fluorescence of ssDNA probe. Based on these findings, a sensing platform with low background signal for DNA fluorescent detection was developed. The proposed sensing platform exhibits high sensitivity with detection limit of 1 nM and excellent selectivity to specific target DNA, even single-base mismatched nucleotide can be distinguished. We envision that the presented study would provide a new perspective on the potential applications of MOF-derived nanocomposites in biomedical fields. PMID:27662768

  10. Metal-enhanced fluorescence platforms based on plasmonic ordered copper arrays: wavelength dependence of quenching and enhancement effects.

    PubMed

    Sugawa, Kosuke; Tamura, Takahiro; Tahara, Hironobu; Yamaguchi, Daisuke; Akiyama, Tsuyoshi; Otsuki, Joe; Kusaka, Yasuyuki; Fukuda, Nobuko; Ushijima, Hirobumi

    2013-11-26

    Ordered arrays of copper nanostructures were fabricated and modified with porphyrin molecules in order to evaluate fluorescence enhancement due to the localized surface plasmon resonance. The nanostructures were prepared by thermally depositing copper on the upper hemispheres of two-dimensional silica colloidal crystals. The wavelength at which the surface plasmon resonance of the nanostructures was generated was tuned to a longer wavelength than the interband transition region of copper (>590 nm) by controlling the diameter of the underlying silica particles. Immobilization of porphyrin monolayers onto the nanostructures was achieved via self-assembly of 16-mercaptohexadecanoic acid, which also suppressed the oxidation of the copper surface. The maximum fluorescence enhancement of porphyrin by a factor of 89.2 was achieved as compared with that on a planar Cu plate (CuP) due to the generation of the surface plasmon resonance. Furthermore, it was found that while the fluorescence from the porphyrin was quenched within the interband transition region, it was efficiently enhanced at longer wavelengths. It was demonstrated that the enhancement induced by the proximity of the fluorophore to the nanostructures was enough to overcome the highly efficient quenching effects of the metal. From these results, it is speculated that the surface plasmon resonance of copper has tremendous potential for practical use as high functional plasmonic sensor and devices.

  11. Multimodal Complementary Metal-Oxide-Semiconductor Sensor Device for Imaging of Fluorescence and Electrical Potential in Deep Brain of Mouse

    NASA Astrophysics Data System (ADS)

    Tagawa, Ayato; Minami, Hiroki; Mitani, Masahiro; Noda, Toshihiko; Sasagawa, Kiyotaka; Tokuda, Takashi; Tamura, Hideki; Hatanaka, Yumiko; Ishikawa, Yasuyuki; Shiosaka, Sadao; Ohta, Jun

    2010-01-01

    We have developed a multimodal complementary metal-oxide-semiconductor (CMOS) sensor device for observing neural activities in the deep brain of a mouse. The CMOS sensor includes an image sensor, electrodes, and a light-emitting diode (LED). The image sensor was designed to be operated using only four inputs/outputs (I/Os) to reduce the number of connecting wires. The electrodes were placed on the pixel array of the sensor. Windows were opened in the electrode over the photodiodes to enable the fluorescence to be imaged using the pixels under the electrodes. An LED was mounted on the chip. The sensor chip was shaped like a shank to facilitate smooth insertion into the brain tissue. The entire device was coated with a parylene layer to make it biocompatible. The experimental results showed that the green fluorescent beads on the pixel array were successfully imaged using the LED on the chip as a light source. In a brain phantom, the change in the electrical potential was successfully sensed by the electrode, and green fluorescent beads were simultaneously imaged using the pixels under the electrode. We also demonstrated that the CMOS sensor device could successfully operate in the hippocampal area of an anesthetized mouse.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Formation of tungsten monocarbide from a molten tungstate-halide phase by gas sparging

    SciTech Connect

    Gomes, J.M.; Raddatz, A.E.; Baglin, E.G.

    1988-02-23

    A process for preparation of tungsten monocarbide is described comprising: (a) providing a molten composition comprising an alkali metal halide and an oxygen compound of tungsten; (b) sparging the composition with a gas comprising a gaseous hydrocarbon which is selected from the group consisting of natural gas, methane, ethane, acetylene, propane, butane, mixtures thereof, and admixtures of these gases with H/sub 2/ or CO, at a temperature of about 900/sup 0/ to 1100/sup 0/C for a sufficient time for the tungsten compound to be substantially converted to tungsten carbide; and (c) decanting the molten halide from the tungsten carbide product.

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

    NASA Astrophysics Data System (ADS)

    Lashgari, Mohsen; Kianpour, Effat; Mohammadi, Esmaeil

    2013-12-01

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

  15. The use of total reflectance X-ray fluorescence (TXRF) for the determination of metals in the pharmaceutical industry.

    PubMed

    Antosz, Frederick J; Xiang, Yanqiao; Diaz, Angel R; Jensen, Andrew J

    2012-03-25

    The control of residual metals in active pharmaceutical ingredients (API's) and intermediates is critical because of their potential toxic effects. A variety of technologies are available to measure residual metals in pharmaceutical compounds including, AAS, ICP-AES, and ICP-MS. The newest technology is total reflectance X-ray fluorescence spectroscopy (TXRF) which uses primary X-rays to excite atoms which then emit secondary X-rays. The emitted X-rays are characteristic of the individual elements present, and the intensities of the emitted X-rays are proportional to the concentrations of the elements present in the sample. The benefits of TXRF are that it is essentially unaffected by matrix effects, is very sensitive (ppb's), requires small amounts of sample (5-10 mg), and requires very little sample preparation time. During this study, TXRF was used to quantitatively measure residual metals in API's and intermediates and such topics as sample preparation, sensitivity, linearity, reproducibility and accuracy are discussed. The results obtained by TXRF were compared with those obtained by ICP-MS for the same samples for Pd and Cu measurement, and statistical analysis indicated that the results obtained by the two technologies are equivalent at the 95% confidence level. A comparison is also made of the capabilities of the instruments using a tungsten (W) or a molybdenum (Mo) source for excitation. Both instruments could be used for the quantitative determination of residual metals in pharmaceuticals.

  16. A study of heavy metal pollution in Lake Victoria sediments by Energy Dispersive X-Ray Fluorescence.

    PubMed

    Makundi, I N

    2001-01-01

    Sources of heavy metal pollution of Lake Victoria is of interest due to its economic and domestic implication in East Africa. Sediments from the shore of Lake Victoria and from some streams flowing into the lake have been analyzed for their heavy metal content using Energy Dispersive X-Ray Fluorescence (EDXRF) analysis. The samples were collected from seventeen different locations around the Municipality of Mwanza divided into three zones according to their activities. The results show that sediments from Mwanza North, which is least in anthropogenic activities, contains Cr and Co in addition to metals of terrestrial origin (K, Ca, Ti, Mn, Fe, Rb, Sr, Y, and Zr), samples from Mwanza Central, which is the town center, contains high concentrations of V, Cu, Zn and Pb, and samples collected from Mwanza South, which is the industrial area, contains the highest concentrations of V, Cu, Zn, As and Pb. It is concluded that the industrial and sewage wastes discharged into the lake are the main sources of the heavy metal contamination of Lake Victoria. Further studies will be required to assess detriments of these pollutants to human and aquatic life before policy for the factories responsible is put in place. PMID:11501314

  17. Development of energy-dispersive X-ray fluorescence as a mobile analysis method for hazardous metals in transuranic waste

    SciTech Connect

    Goldstein, S.J.

    1998-09-01

    Energy-dispersive X-ray fluorescence (EDXRF) is a widely applied technique for both laboratory and field-based characterization of metals in complex matrices. Here an EDXRF method is described for analysis of 13 hazardous (RCRA) metals in Portland cement, a typical matrix for transuranic (TRU) waste from US Department of Energy (DOE) sites. Samples are analyzed as homogeneous powders prepared by simple drying, mixing, and milling. Analyses are performed using a commercial EDXRF spectrometer equipped with an X-ray tube, a high-resolution Si(Li) detector, and fundamental parameters software for data reduction. The spectrometer is rugged and suitable for use in either mobile or fixed-based laboratories. Standardization is accomplished using fundamental parameters techniques for several prepared standards which bracket the expected range in metal concentrations, and typical standardization uncertainties are < 10%. Detection limits range from 2--20 ppm and meet required action levels with a few exceptions including Be, Hg and V. Accuracy is evaluated from a series of unknown quality control samples and ranges from 85--102%, whereas the total method uncertainty is typically < 10%. Consequently, this simple, rapid, and inexpensive technique can provide quantitative characterization of virtually all of the RCRA metals in TRU waste cement samples.

  18. Surface-plasmon cross coupling in molecular fluorescence near a corrugated thin metal film

    NASA Technical Reports Server (NTRS)

    Gruhlke, R. W.; Holland, W. R.; Hall, D. G.

    1968-01-01

    Surface plasmons on opposite sides of a thin metal film can cross couple in the presence of a surface corrugation, or grating. The observation of this cross-coupling phenomenon as a radiative-decay mechanism for molecules near a corrugated thin metal film is reported.

  19. [Comparison of soil heavy metals determined by AAS/AFS and portable X-ray fluorescence analysis].

    PubMed

    Ran, Jing; Wang, De-Jian; Wang, Can; Bo, Lu-Ji; Zheng, Ji-Cheng; Yao, Li-Peng

    2014-11-01

    Total concentrations of Cu, Pb, As, Cr, Ni and Zn were determined for 53 soil samples using portable X-ray fluorescence (PXRF) system in in-situ and ex-situ (Lab.) conditions. PXRF metal concentrations were statistically compared with analytical results from traditional AAS/AFS analysis. The ability of PXRF instrument to produce comparable analytical results to the reference method was assessed by linear regression. To investgate the effects of soil moisture on PXRF, the in-situ moisture content of all soil samples was quantified and the metal concentrations of selected samples with known moisture contents were measured too. The results showed that the detection limits of PXRF for Cu, Pb, As, Cr, Ni and Zn were 10.6, 8.1, 5.7, 22.5, 21.6 and 10.4 mg kg(-1) respectively. A good degree of linearity was found for Pb, Cr, Ni and Zn in in-situ condition. While in ex-situ condition, quantitative level data were achieved across the entire range of samples tested for Cu, Pb, Cr, Ni and Zn. X-ray fluorescence spectrometry was shown to be an effective tool for quantification and rapid assessment of heavy metals in soils. Soil moisture content did affected the performance of PXRF, the mean percent difference for soil samples in-situ with moisture content less than 15% and higher than 25% was -17% and -31% respectively. In ex-situ condition, as the soil moisture content increased from air dried level to 30%, the mean percent difference decreased from 10% to -24%. The dilution effect of moisture in soils may cause discrepancies with conventional analytical results and induce worse data quality, and it should be controlled within 0-25% in in-situ condition.

  20. Low-threshold amplified spontaneous emission and lasing from colloidal nanocrystals of caesium lead halide perovskites

    PubMed Central

    Yakunin, Sergii; Protesescu, Loredana; Krieg, Franziska; Bodnarchuk, Maryna I.; Nedelcu, Georgian; Humer, Markus; De Luca, Gabriele; Fiebig, Manfred; Heiss, Wolfgang; Kovalenko, Maksym V.

    2015-01-01

    Metal halide semiconductors with perovskite crystal structures have recently emerged as highly promising optoelectronic materials. Despite the recent surge of reports on microcrystalline, thin-film and bulk single-crystalline metal halides, very little is known about the photophysics of metal halides in the form of uniform, size-tunable nanocrystals. Here we report low-threshold amplified spontaneous emission and lasing from ∼10 nm monodisperse colloidal nanocrystals of caesium lead halide perovskites CsPbX3 (X=Cl, Br or I, or mixed Cl/Br and Br/I systems). We find that room-temperature optical amplification can be obtained in the entire visible spectral range (440–700 nm) with low pump thresholds down to 5±1 μJ cm−2 and high values of modal net gain of at least 450±30 cm−1. Two kinds of lasing modes are successfully observed: whispering-gallery-mode lasing using silica microspheres as high-finesse resonators, conformally coated with CsPbX3 nanocrystals and random lasing in films of CsPbX3 nanocrystals. PMID:26290056

  1. X-ray fluorescence analysis of metal concentration in an alloy electroplating bath

    SciTech Connect

    Hines, R.A.

    1980-06-01

    An energy-dispersive x-ray fluorescence analysis system has been developed for rapid, simultaneous analysis of gold and copper concentrations in an aqueous electroplating bath. The speed and repeatability of the system make it well suited for in-process control. Data collection and reduction are automatic. The analysis requires less than 10 minutes from taking the sample to printing the gold and copper concentrations.

  2. Soil Heavy Metal Pollution along Subin River in Kumasi, Ghana; Using X-Ray Fluorescence (XRF) Analysis

    NASA Astrophysics Data System (ADS)

    Kodom, K.; Wiafe-Akenten, J.; Boamah, D.

    2010-04-01

    This study is aimed to analyze and assess the existence of heavy metal pollution in the surface soils along Subin River in the Kumasi metropolis using X-Ray Fluorescence (XRF) analysis. Twenty (20) soil samples were collected along the River at regular interval of 5 m (covering entire area of about 100 m2), with the aid of a core sampler. The samples were suitably packaged and conveyed into the laboratory for sample preparation and analysis. The concentration of heavy metals (Cr, Cu, Pb, Hg, Ni, Zn, Tl, V and Cd) were measured and quantified (mgkg-1) after the elemental analysis using XRF spectrometry, and their respective average concentrations (121.89 mgkg-1, 49.24 mgkg-1, 80.84 mgkg-1, 2.52 mgkg-1, 17.01 mgkg-1, 148.08 mgkg-1, 3.21 mgkg-1, 84.40 mgkg-1, and 4.05 mgkg-1) were attained. According to these results, the presence of heavy metals such as (Pb, Cd and Hg) present in the soil, were highly recorded above their threshold limit values (TLVs) by an amount of 60.84 mgkg-1, 3.05 mgkg-1 and 1.52 mgkg-1 respectively. These metals are highly toxic even in very low concentrations and their toxicity and poisoning in living organisms often occur through exchange and co-ordination mechanisms in the soft tissues. These high excess concentration values alarmingly depict that, the study site is highly polluted with those metals, and the Subin river-body and the inhabitants who reside closely to the polluted river, are at serious risk. The extent to which the study area is polluted, was successfully and statistically analyzed from the standard deviation (σ) and difference between the average concentration values recorded, and the TLVs.

  3. One-Pot Ketone Synthesis with Alkylzinc Halides Prepared from Alkyl Halides via a Single Electron Transfer (SET) Process: New Extension of Fukuyama Ketone Synthesis.

    PubMed

    Lee, Jung Hwa; Kishi, Yoshito

    2016-06-01

    One-pot ketone synthesis has been developed with in situ activation of alkyl halides to alkylzinc halides in the presence of thioesters and Pd-catalyst. The new method provides us with a reliable option for a coupling at a late stage in a convergent synthesis of complex molecules, with use of a near 1:1 molar ratio of coupling partners. First, two facile, orthogonal methods have been developed for preparation of alkylzinc halides: (1) direct insertion of zinc dust to 1°- and 2°-alkyl halides in the presence of LiI in DMI and (2) early transition-metal assisted activation of alkyl halides via a single electron transfer (SET) process. CrCl2 has been found as an unprecedented, inevitable mediator for preparation of alkylzinc halides from alkyl halides, where CrCl2 likely functions to trap R·, generated via a SET process, and transfer it to Zn(II) to form RZnX. In addition to a commonly used CoPc, a new radical initiator NbCpCl4 has been discovered through the study. Second, with use of the two orthogonal methods, three sets of coupling conditions have been developed to complete one-pot ketone synthesis, with Condition A (Pd2dba3, PR3, Zn, LiI, TESCl, DMI), Condition B (A + CrCl2), and Condition C (B + NbCpCl4 or CoPc) being useful for simple linear and α-substituted substrates, simple linear and β-substituted substrates, and complex substrates, respectively. Condition C is applicable to the broadest range of substrates. Overall, one-pot ketone synthesis gives excellent yields, with good functional group tolerance. Controlled formation of alkylzinc halides by a combination of CrCl2 and NbCpCl4 or CoPc is crucial for its application to complex substrates. Interestingly, one-pot ketone synthesis does not suffer from the chemical instability due to the inevitable radical pathway(s), for example a 1,5-H shift. Notably, even with the increase in molecular size, no significant decrease in coupling efficiency has been noticed. To illustrate the synthetic value at a late

  4. Hybrid magnetic nanoparticle/nanogold clusters and their distance-dependent metal-enhanced fluorescence effect via DNA hybridization

    NASA Astrophysics Data System (ADS)

    GuThese Authors Contributed Equally To This Study., Xuefan; Wu, Youshen; Zhang, Lingze; Liu, Yongchun; Li, Yan; Yan, Yongli; Wu, Daocheng

    2014-07-01

    To improve the metal-enhanced fluorescence (MEF) effect of nanogolds (AuNPs) and accurately detect specific DNA sequences via DNA hybridization, novel hybrid magnetic nanoparticles/nanogold clusters (HMNCs) were designed based on finite-difference time-domain simulation results and prepared by using Fe3O4 and nanogolds. The nanogolds outside the HMNC were then conjugated with thiol-terminated DNA molecules, thus DNA modified-HMNCs (DNA-HMNCs) were obtained. The size distributions of these nanostructures were measured by a Malvern size analyzer, and their morphology was observed via transmission electron microscopy (TEM). The ultraviolet (UV)-visible (vis) absorption spectra of the samples were recorded with a UV-2600 spectrophotometer. Fluorescence spectra and the MEF effect were recorded using a spectrophotofluorometer, and lifetimes were determined using a time-correlated single photon counting apparatus. The prepared HMNCs were stable in aqueous solutions and had an average diameter of 87 +/- 3.2 nm, with six to eight AuNPs around a single Fe3O4 nanoparticle. Fluorescein isothiocyanate (FITC) tagged DNA-HMNC conjugates exhibited a significant MEF effect and could accurately detect specific DNA sequences after DNA hybridization. This result indicates their various potential applications in sensors and biomedical fields.To improve the metal-enhanced fluorescence (MEF) effect of nanogolds (AuNPs) and accurately detect specific DNA sequences via DNA hybridization, novel hybrid magnetic nanoparticles/nanogold clusters (HMNCs) were designed based on finite-difference time-domain simulation results and prepared by using Fe3O4 and nanogolds. The nanogolds outside the HMNC were then conjugated with thiol-terminated DNA molecules, thus DNA modified-HMNCs (DNA-HMNCs) were obtained. The size distributions of these nanostructures were measured by a Malvern size analyzer, and their morphology was observed via transmission electron microscopy (TEM). The ultraviolet (UV

  5. Atomically precise arrays of fluorescent silver clusters: a modular approach for metal cluster photonics on DNA nanostructures.

    PubMed

    Copp, Stacy M; Schultz, Danielle E; Swasey, Steven; Gwinn, Elisabeth G

    2015-03-24

    The remarkable precision that DNA scaffolds provide for arraying nanoscale optical elements enables optical phenomena that arise from interactions of metal nanoparticles, dye molecules, and quantum dots placed at nanoscale separations. However, control of ensemble optical properties has been limited by the difficulty of achieving uniform particle sizes and shapes. Ligand-stabilized metal clusters offer a route to atomically precise arrays that combine desirable attributes of both metals and molecules. Exploiting the unique advantages of the cluster regime requires techniques to realize controlled nanoscale placement of select cluster structures. Here we show that atomically monodisperse arrays of fluorescent, DNA-stabilized silver clusters can be realized on a prototypical scaffold, a DNA nanotube, with attachment sites separated by <10 nm. Cluster attachment is mediated by designed DNA linkers that enable isolation of specific clusters prior to assembly on nanotubes and preserve cluster structure and spectral purity after assembly. The modularity of this approach generalizes to silver clusters of diverse sizes and DNA scaffolds of many types. Thus, these silver cluster nano-optical elements, which themselves have colors selected by their particular DNA templating oligomer, bring unique dimensions of control and flexibility to the rapidly expanding field of nano-optics.

  6. Determination of trace metals in drinking water using solid-phase extraction disks and X-ray fluorescence spectrometry.

    PubMed

    Hou, Xiandeng; Peters, Heather L; Yang, Zheng; Wagner, Karl A; Batchelor, James D; Daniel, Meredith M; Jones, Bradley T

    2003-03-01

    A convenient method is described for monitoring Cd, Ni, Cu, and Pb at trace levels in drinking water samples. These metals are preconcentrated on a chelating solid-phase extraction disk and then determined by X-ray fluorescence spectrometry. The method tolerates a wide pH range (pH 6-14) and a large amount of alkaline and alkaline earth elements. The preconcentration factor is well over 1600, assuming a 1 L water sample volume. The limits of detection for Cd, Ni, Cu, and Pb are 3.8, 0.6, 0.4, and 0.3 ng/mL, respectively. These are well below the federal maximum contaminant level values, which are 5, 100, 1300, and 15 ng/mL, respectively. The proposed method has many advantages including ease of operation, multielement capability, nondestructiveness, high sensitivity, and relative cost efficiency. The solid-phase extraction step can be conducted in the field and then the disks can be mailed to a laboratory for the analysis, eliminating the cost of transporting large volumes of water samples. Furthermore, the color of the used extraction disk provides an initial estimate of the degree of contamination for some transition metals (for example, Ni and Cu). Thus, the overall cost for analysis of metals in drinking water can be minimized by implementing the method, and small water supply companies with limited budgets will be better able to comply with the Safe Drinking Water Act. PMID:14658627

  7. Determination of some heavy metals (Fe, Cu, Zn and Pb) in blood by total reflection X-ray fluorescence

    NASA Astrophysics Data System (ADS)

    Bounakhla, M.; Doukkali, A.; Lalaoui, K.; Aguenaou, H.; Mokhtar, N.; Attrassi, B.

    2003-05-01

    The main purpose of this study is the interaction between nutrition (micronutrients heavy metals: Fe, Zn, Cu) and toxic heavy metals such as Pb in blood of children living in Gharb region of Morocco. This region receives all pollution carried by the Sebou river coming mainly from industrial activities. A rapid and simple analytical procedure was used for the determination of Fe, Cu and Zn trace amounts in blood by total-reflection X-ray fluorescence technique. This method is an energy dispersive XRF technique in a special geometry of primary beam, sample and detector. The sample is deposited on a plane polished surface of a suitable reflector material. It is presented as a few drops (25 μl) from a solution of blood digested in a mixture of HNO3 and H2O2 using a microwaves accelerated reaction system. The accuracy of measurements has been investigated by using certified materials. The concentration of Cu was found to be normal in all samples (\\cong1 ppm) which ruled out any interaction between this element and the others. On the other hand, amounts of Fe and Zn are very variables, suggesting an interaction between Fe and Zn. However, amounts of Pb in blood are inferior to 50 ppb, suggesting that no interaction exist with this metal and micronutrients.

  8. Vapor phase decomposition droplet collection total reflection X-ray fluorescence spectrometry for metallic contamination analysis on Ge wafers

    NASA Astrophysics Data System (ADS)

    Hellin, D.; Geens, V.; Teerlinck, I.; Van Steenbergen, J.; Rip, J.; Laureyn, W.; Raskin, G.; Mertens, P. W.; De Gendt, S.; Vinckier, C.

    2005-02-01

    Ge substrates are recently being reconsidered as a candidate material for the replacement of Si substrates in advanced semiconductor devices. The reintroduction of this material requires reengineering of the standard IC processing steps. In this paper, we present the extension of the methodology of vapor phase decomposition-droplet collection-total reflection X-ray fluorescence spectrometry (VPD-DC-TXRF) for metallic contamination analysis towards Ge substrates. A first step that asked for adaptation was the collection chemistry as the Ge wafers surface is not hydrophobic after the VPD treatment. The contact angle could be significantly increased using a concentrated HCl solution. This chemistry has been proved to perform well in the collection of metals from intentionally contaminated Ge wafers. A second step that needed optimization was the matrix removal method as a sample preparation step prior to the TXRF analysis. First, the upper limits of TXRF on Ge containing solutions have been characterized. The accuracy of TXRF is found to be acceptable for Ge contents lower than 1×10 14 atoms (250 ppb in 50 μL) but decreases systematically with higher Ge contents. Fortunately, Ge can be volatilized at low temperatures as GeCl 4 by the addition of HCl. The parameters within this method have been investigated with respect to the removal of Ge and the recovery of metal traces. Finally, the full VPD-DC-TXRF method has been applied on intentionally contaminated Ge wafers and proved to be very accurate.

  9. Assessment of occupational exposure to manganese and other metals in welding fumes by portable X-ray fluorescence spectrometer.

    PubMed

    Laohaudomchok, Wisanti; Cavallari, Jennifer M; Fang, Shona C; Lin, Xihong; Herrick, Robert F; Christiani, David C; Weisskopf, Marc G

    2010-08-01

    Elemental analysis of welding fume samples can be done using several laboratory-based techniques. However, portable measurement techniques could offer several advantages. In this study, we sought to determine whether the portable X-ray fluorescence spectrometer (XRF) is suitable for analysis of five metals (manganese, iron, zinc, copper, and chromium) on 37-mm polytetrafluoroethylene filters. Using this filter fitted on a cyclone in line with a personal pump, gravimetric samples were collected from a group of boilermakers exposed to welding fumes. We assessed the assumption of uniform deposition of these metals on the filters, and the relationships between measurement results of each metal obtained from traditional laboratory-based XRF and the portable XRF. For all five metals of interest, repeated measurements with the portable XRF at the same filter area showed good consistency (reliability ratios are equal or close to 1.0 for almost all metals). The portable XRF readings taken from three different areas of each filter were not significantly different (p-values = 0.77 to 0.98). This suggested that the metal rich PM(2.5) deposits uniformly on the samples collected using this gravimetric method. For comparison of the two XRFs, the results from the portable XRF were well correlated and highly predictive of those from the laboratory XRF. The Spearman correlation coefficients were from 0.325 for chromium, to 0.995 for manganese and 0.998 for iron. The mean differences as a percent of the mean laboratory XRF readings were also small (<5%) for manganese, iron, and copper. The differences were greater for zinc and chromium, which were present at very low amounts in our samples and below the limits of detection of the portable XRF for many of the samples. These five metals were moderately to strongly correlated with the total fine particle fraction on filters (Spearman rho = 0.41 for zinc to 0.97 for iron). Such strong correlations and comparable results suggested that

  10. Assessment of occupational exposure to manganese and other metals in welding fumes by portable X-ray fluorescence spectrometer.

    PubMed

    Laohaudomchok, Wisanti; Cavallari, Jennifer M; Fang, Shona C; Lin, Xihong; Herrick, Robert F; Christiani, David C; Weisskopf, Marc G

    2010-08-01

    Elemental analysis of welding fume samples can be done using several laboratory-based techniques. However, portable measurement techniques could offer several advantages. In this study, we sought to determine whether the portable X-ray fluorescence spectrometer (XRF) is suitable for analysis of five metals (manganese, iron, zinc, copper, and chromium) on 37-mm polytetrafluoroethylene filters. Using this filter fitted on a cyclone in line with a personal pump, gravimetric samples were collected from a group of boilermakers exposed to welding fumes. We assessed the assumption of uniform deposition of these metals on the filters, and the relationships between measurement results of each metal obtained from traditional laboratory-based XRF and the portable XRF. For all five metals of interest, repeated measurements with the portable XRF at the same filter area showed good consistency (reliability ratios are equal or close to 1.0 for almost all metals). The portable XRF readings taken from three different areas of each filter were not significantly different (p-values = 0.77 to 0.98). This suggested that the metal rich PM(2.5) deposits uniformly on the samples collected using this gravimetric method. For comparison of the two XRFs, the results from the portable XRF were well correlated and highly predictive of those from the laboratory XRF. The Spearman correlation coefficients were from 0.325 for chromium, to 0.995 for manganese and 0.998 for iron. The mean differences as a percent of the mean laboratory XRF readings were also small (<5%) for manganese, iron, and copper. The differences were greater for zinc and chromium, which were present at very low amounts in our samples and below the limits of detection of the portable XRF for many of the samples. These five metals were moderately to strongly correlated with the total fine particle fraction on filters (Spearman rho = 0.41 for zinc to 0.97 for iron). Such strong correlations and comparable results suggested that

  11. Assessment of Occupational Exposure to Manganese and Other Metals in Welding Fumes by Portable X-ray Fluorescence Spectrometer

    PubMed Central

    Laohaudomchok, Wisanti; Cavallari, Jennifer M.; Fang, Shona C.; Lin, Xihong; Herrick, Robert F.; Christiani, David C.; Weisskopf, Marc G.

    2011-01-01

    Elemental analysis of welding fume samples can be done using several laboratory-based techniques. However, portable measurement techniques could offer several advantages. In this study, we sought to determine whether the portable X-ray fluorescence spectrometer (XRF) is suitable for analysis of five metals (manganese, iron, zinc, copper, and chromium) on 37-mm polytetrafluoroethylene filters. Using this filter fitted on a cyclone in line with a personal pump, gravimetric samples were collected from a group of boilermakers exposed to welding fumes. We assessed the assumption of uniform deposition of these metals on the filters, and the relationships between measurement results of each metal obtained from traditional laboratory-based XRF and the portable XRF. For all five metals of interest, repeated measurements with the portable XRF at the same filter area showed good consistency (reliability ratios are equal or close to 1.0 for almost all metals). The portable XRF readings taken from three different areas of each filter were not significantly different (p-values = 0.77 to 0.98). This suggested that the metal rich PM2.5 deposits uniformly on the samples collected using this gravimetric method. For comparison of the two XRFs, the results from the portable XRF were well correlated and highly predictive of those from the laboratory XRF. The Spearman correlation coefficients were from 0.325 for chromium, to 0.995 for manganese and 0.998 for iron. The mean differences as a percent of the mean laboratory XRF readings were also small (<5%) for manganese, iron, and copper. The differences were greater for zinc and chromium, which were present at very low amounts in our samples and below the limits of detection of the portable XRF for many of the samples. These five metals were moderately to strongly correlated with the total fine particle fraction on filters (Spearman ρ = 0.41 for zinc to 0.97 for iron). Such strong correlations and comparable results suggested that the

  12. Synthesis of fluorescent metal nanoparticles in aqueous solution by photochemical reduction

    NASA Astrophysics Data System (ADS)

    Kshirsagar, Prakash; Shankar Sangaru, Shiv; Brunetti, Virgilio; Malvindi, Maria Ada; Pompa, Pier Paolo

    2014-01-01

    A facile green chemistry approach for the synthesis of sub-5 nm silver and gold nanoparticles is reported. The synthesis was achieved by a photochemical method using tyrosine as the photoreducing agent. The size of the gold and silver nanoparticles was about 3 and 4 nm, respectively. The nanoparticles were characterized using x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and photoluminescence spectroscopy. Both silver and gold nanoparticles synthesized by this method exhibited fluorescence properties and their use for cell imaging applications has been demonstrated.

  13. Effect of metal films on the photostabilities of emissive organic layers as probed by fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Abbas, Sikandar; Peteanu, Linda A.

    2015-09-01

    Realization of energy efficient and cost effective electroluminescence applications of conjugated polymers, like organic light emitting diodes (OLEDs), requires a complete understanding of photo-chemical processes at metal-polymer interfaces. Therefore it is useful to study the effects of metal films on the photoluminescence of emissive organic layer fabricated on it. While investigating these processes we observed an interesting and unexpected phenomenon that, when conjugated polymer is deposited on thin gold film substrates, it exhibits remarkable photo-stability relative to that deposited on glass, even in the presence of molecular oxygen. This paper addresses the photo-stability enhancement by thin Au films and explores the photochemical mechanism behind it.

  14. Method and apparatus for convection control of metallic halide vapor density in a metallic halide laser

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J. (Inventor)

    1982-01-01

    An apparatus is disclosed in which a reservoir containing copper chloride is heated so that the copper chloride is maintained in a liquid form. The apparatus includes a means for flowing a buffer gas (which in the exemplary embodiment is neon) over the liquid copper chloride to provide a mixture of copper chloride vapor and neon above the liquid copper chloride. A conduit provides fluid communication between the reservoir containing the copper chloride vapor/neon mixture and the laser. The copper chloride vapor density in the laser is related to the liquid copper chloride temperature and the neon flow rate through the reservoir. In accordance with a further feature of the exemplary embodiment, neon is also provided directly to the laser in order to provide a further means of controlling the copper chloride vapor density in the laser.

  15. Design of ratiometric fluorescent probes based on arene-metal-ion interactions and their application to Cd(II) and hydrogen sulfide imaging in living cells.

    PubMed

    Takashima, Ippei; Kinoshita, Miyuki; Kawagoe, Ryosuke; Nakagawa, Saika; Sugimoto, Manabu; Hamachi, Itaru; Ojida, Akio

    2014-02-17

    Non-coordinative interactions between a metal ion and the aromatic ring of a fluorophore can act as a versatile sensing mechanism for the detection of metal ions with a large emission change of fluorophores. We report the design of fluorescent probes based on arene-metal-ion interactions and their biological applications. This study found that various probes having different fluorophores and metal binding units displayed significant emission redshift upon complexation with metal ions, such as Ag(I), Cd(II), Hg(II), and Pb(II). X-ray crystallography of the complexes confirmed that the metal ions were held in close proximity to the fluorophore to form an arene-metal-ion interaction. Electronic structure calculations based on TDDFT offered a theoretical basis for the sensing mechanism, thus showing that metal ions electrostatically modulate the energy levels of the molecular orbitals of the fluorophore. A fluorescent probe was successfully applied to the ratiometric detection of the uptake of Cd(II) ions and hydrogen sulfide (H2S) in living cells. These results highlight the utility of interactions between arene groups and metal ions in biological analyses.

  16. Detection of heavy metals in water by fluorescence spectroscopy: on the way to a suitable sensor system.

    PubMed

    Prestel, H; Gahr, A; Niessner, R

    2000-01-01

    In order to develop a fiber optical heavy metal ion detection system, the applicability of selected complexing agents with fluorescent properties has been studied. Beginning with the application of known chelators, like BTC-5N, Newport Green, neocuproine, and chromotropic acid, a sensor configuration has been found, which allows the detection of Cd2+, Ni2+, and Cu2+ well below the chemical parameter threshold values of the new Water Quality Directive 98/83/EU. The sensor itself uses a membrane separation of the chelator flow from the sample volume. The diffusion across the membrane limits the response time to about 15 to 20 min. Applications are seen in monitoring networks. PMID:11220577

  17. Using Nondestructive Portable X-ray Fluorescence Spectrometers on Stone, Ceramics, Metals, and Other Materials in Museums: Advantages and Limitations.

    PubMed

    Tykot, Robert H

    2016-01-01

    Elemental analysis is a fundamental method of analysis on archaeological materials to address their overall composition or identify the source of their geological components, yet having access to instrumentation, its often destructive nature, and the time and cost of analyses have limited the number and/or size of archaeological artifacts tested. The development of portable X-ray fluorescence (pXRF) instruments over the past decade, however, has allowed nondestructive analyses to be conducted in museums around the world, on virtually any size artifact, producing data for up to several hundred samples per day. Major issues have been raised, however, about the sensitivity, precision, and accuracy of these devices, and the limitation of performing surface analysis on potentially heterogeneous objects. The advantages and limitations of pXRF are discussed here regarding archaeological studies of obsidian, ceramics, metals, bone, and painted materials. PMID:26767632

  18. Using Nondestructive Portable X-ray Fluorescence Spectrometers on Stone, Ceramics, Metals, and Other Materials in Museums: Advantages and Limitations.

    PubMed

    Tykot, Robert H

    2016-01-01

    Elemental analysis is a fundamental method of analysis on archaeological materials to address their overall composition or identify the source of their geological components, yet having access to instrumentation, its often destructive nature, and the time and cost of analyses have limited the number and/or size of archaeological artifacts tested. The development of portable X-ray fluorescence (pXRF) instruments over the past decade, however, has allowed nondestructive analyses to be conducted in museums around the world, on virtually any size artifact, producing data for up to several hundred samples per day. Major issues have been raised, however, about the sensitivity, precision, and accuracy of these devices, and the limitation of performing surface analysis on potentially heterogeneous objects. The advantages and limitations of pXRF are discussed here regarding archaeological studies of obsidian, ceramics, metals, bone, and painted materials.

  19. Rapid detection of toxic metals in non-crushed oyster shells by portable X-ray fluorescence spectrometry.

    PubMed

    Chou, Ju; Clement, Garret; Bursavich, Bradley; Elbers, Don; Cao, Baobao; Zhou, Weilie

    2010-06-01

    The aim of this study was the multi-elemental detection of toxic metals such as lead (Pb) in non-crushed oyster shells by using a portable X-ray fluorescence (XRF) spectrometer. A rapid, simultaneous multi-element analytical methodology for non-crushed oyster shells has been developed using a portable XRF which provides a quick, quantitative, non-destructive, and cost-effective mean for assessment of oyster shell contamination from Pb. Pb contamination in oyster shells was further confirmed by scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The results indicated that Pb is distributed in-homogeneously in contaminated shells. Oyster shells have a lamellar structure that could contribute to the high accumulation of Pb on oyster shells.

  20. Halide Ion Enhancement of Nitrate Ion Photolysis

    NASA Astrophysics Data System (ADS)

    Richards, N. K.; Wingen, L. M.; Callahan, K. M.; Tobias, D. J.; Finlayson-Pitts, B. J.

    2009-12-01

    Nitrate ion photochemistry is an important source of NOx in the polar regions. It is uncertain whether coexisting ions such as halides play a role in nitrate photochemistry. The effect of halides on NO3 photolysis was investigated using photolysis experiments in 230 L Teflon chambers that contain deliquesced aerosols of NaBr:NaNO3, KBr:KNO3 and ternary mixtures of NaCl:NaBr:NaNO3. Gas phase NO2 and gaseous halogen products were measured as a function of photolysis time using long path FTIR, NOx chemiluminescence and API-MS (atmospheric pressure ionization mass spectrometry). Experiments were conducted with NO3- held at a constant 0.5 M and with the amount of total halide concentration varying from 0.25 M to 4 M. Studies on NaBr:NaNO3 mixtures suggest that as the bromide ion to nitrate ion ratio increases, there is an enhancement in the rate of production of NO2 in the nitrate-bromide mixtures over that formed in the photolysis of NaNO3. Molecular dynamic (MD) simulations provide molecular level insight into the ions near the air-water interface in the aqueous halide-nitrate mixtures. These studies suggest that the presence of sodium halides at the air-water interface may encourage some nitrate ions to approach the top layers of water, allowing for more efficient escape of photoproducts than is seen in the absence of halides. Experiments on mixtures of KBr:KNO3 are being conducted to determine potential cation effects. In addition, ternary mixtures of NaCl:NaBr:NaNO3 are being examined to determine the effects of mixtures of halides on production of NO2 and gaseous halogen products. The implications of this photochemistry for tropospheric chemistry will be discussed.

  1. X-ray Fluorescence Tomography of Aged Fluid-Catalytic-Cracking Catalyst Particles Reveals Insight into Metal Deposition Processes

    PubMed Central

    Kalirai, Sam; Boesenberg, Ulrike; Falkenberg, Gerald; Meirer, Florian; Weckhuysen, Bert M

    2015-01-01

    Microprobe X-ray fluorescence tomography was used to investigate metal poison deposition in individual, intact and industrially deactivated fluid catalytic cracking (FCC) particles at two differing catalytic life-stages. 3 D multi-element imaging, at submicron resolution was achieved by using a large-array Maia fluorescence detector. Our results show that Fe, Ni and Ca have significant concentration at the exterior of the FCC catalyst particle and are highly co-localized. As concentrations increase as a function of catalytic life-stage, the deposition profiles of Fe, Ni, and Ca do not change significantly. V has been shown to penetrate deeper into the particle with increasing catalytic age. Although it has been previously suggested that V is responsible for damaging the zeolite components of FCC particles, no spatial correlation was found for V and La, which was used as a marker for the embedded zeolite domains. This suggests that although V is known to be detrimental to zeolites in FCC particles, a preferential interaction does not exist between the two. PMID:26613011

  2. Hybrid magnetic nanoparticle/nanogold clusters and their distance-dependent metal-enhanced fluorescence effect via DNA hybridization.

    PubMed

    Gu, Xuefan; Wu, Youshen; Zhang, Lingze; Liu, Yongchun; Li, Yan; Yan, Yongli; Wu, Daocheng

    2014-08-01

    To improve the metal-enhanced fluorescence (MEF) effect of nanogolds (AuNPs) and accurately detect specific DNA sequences via DNA hybridization, novel hybrid magnetic nanoparticles/nanogold clusters (HMNCs) were designed based on finite-difference time-domain simulation results and prepared by using Fe3O4 and nanogolds. The nanogolds outside the HMNC were then conjugated with thiol-terminated DNA molecules, thus DNA modified-HMNCs (DNA-HMNCs) were obtained. The size distributions of these nanostructures were measured by a Malvern size analyzer, and their morphology was observed via transmission electron microscopy (TEM). The ultraviolet (UV)-visible (vis) absorption spectra of the samples were recorded with a UV-2600 spectrophotometer. Fluorescence spectra and the MEF effect were recorded using a spectrophotofluorometer, and lifetimes were determined using a time-correlated single photon counting apparatus. The prepared HMNCs were stable in aqueous solutions and had an average diameter of 87 ± 3.2 nm, with six to eight AuNPs around a single Fe3O4 nanoparticle. Fluorescein isothiocyanate (FITC) tagged DNA-HMNC conjugates exhibited a significant MEF effect and could accurately detect specific DNA sequences after DNA hybridization. This result indicates their various potential applications in sensors and biomedical fields.

  3. Blue fluorescence of three metal-organic zinc polymers containing tetrazinc units and asymmetric ligand of btc{sup 3-}

    SciTech Connect

    Xu Ling; Liu Bing; Zheng Fakun; Guo Guocong . E-mail: gcguo@ms.fjirsm.ac.cn; Huang Jinshun

    2005-11-15

    Three new zinc coordination polymers [Zn{sub 2}(btc){sub 2}(H{sub 2}O){sub 2}] {sub n} .n[Zn(H{sub 2}O){sub 6}] (1), [Zn{sub 3}(btc){sub 2}(2,2'-bipy){sub 2}(H{sub 2}O){sub 3}] {sub n} .2nH{sub 2}O (2) and [Zn{sub 3}(btc){sub 2}(H{sub 2}O){sub 6}] {sub n} .nH{sub 2}O (3) (H{sub 3}btc=1,2,4-benzenetricarboxylic acid, 2,2'-bipy=2,2'-bipyridine) were obtained by the diffusion method and their crystal structures were determined by single-crystal X-ray diffraction. Compounds 1-3 have the similar tetrametallic unit [Zn{sub 4}(btc){sub 2}] SBUs and these SBUs are further connected into stair-like structure, 2-D layer and 3-D framework for 1, 2 and 3, in which the btc{sup 3-} ligands adopt {mu} {sub 3}, {mu} {sub 4} and {mu} {sub 5} coordination modes, respectively. The title compounds show strong blue fluorescence, which may be assigned as {pi}*{sup {yields}}n transition of the ligand mixed with the ligand-to-metal change transfer (LMCT), indicating the fluorescence, indicates the title compounds may be good candidates for blue-light photoactive materials.

  4. A tong-like fluorescence sensor for metal ions: perfect conformational switch of hinge sugar by pyrene stacking.

    PubMed

    Yuasa, Hideya; Miyagawa, Naofusa; Nakatani, Masatoshi; Izumi, Masayuki; Hashimoto, Hironobu

    2004-12-21

    Carbohydrates are among the potential materials for molecular devices, since they are abundant natural resources. However, their rigidity has restricted their use for movable devices. Hinge sugars, 2,4-diamino-2,4-dideoxy-xylopyranosides, shed light on the use of carbohydrates as movable components, as demonstrated by the motion by which all four equatorial substituents can change to an axial orientation in synchronization with a chelation-driven 4C1-1C4 ring flip. In this study, we synthesized a tong-like metal ion sensor, 1,3-di-O-pyrenylmethylated hinge sugar (1), and its model compound, methyl 2,4-di-O-pyrenecarbonyl-xylopyranoside (2), to extend the abilities of hinge sugars as molecular components. From observations of the solvent-dependent conformational and fluorescent behavior of 2, we found that the pyrene stacking assists the 1C4 formation of xylopyranoside by 1.7 kcal mol(-1). We also found that compound 1 produced excimer fluorescence by chelation to Pt2+, Zn2+, Cd2+, Mg2+ or Mn2+, and unexpectedly by addition of acids. 1H NMR measurements ascribed this behavior to the 4C1-1C4 ring flip of hinge sugar in response to chelation or protonation at N2, and revealed rapid and perfect 1C4 formation in the case of Zn2+. These findings will extend the scope of hinge sugars as movable components.

  5. Online X-ray Fluorescence (XRF) Analysis of Heavy Metals in Pulverized Coal on a Conveyor Belt.

    PubMed

    Yan, Zhang; XinLei, Zhang; WenBao, Jia; Qing, Shan; YongSheng, Ling; DaQian, Hei; Da, Chen

    2016-02-01

    Heavy metals in haze episode will continue to threaten the quality of public health around the world. In order to decrease the emission of heavy metals produced from coal burning, an online X-ray fluorescence (XRF) analyzer system, consisting of an XRF analyzer with data acquisition software and a laser rangefinder, was developed to carry out the measurement of heavy metals in pulverized coal. The XRF analyzer was mounted on a sled, which can effectively smooth the surface of pulverized coal and reduce the impact of surface roughness during online measurement. The laser rangefinder was mounted over the sled for measuring the distance between a pulverized coal sample and the analyzer. Several heavy metals and other elements in pulverized coal were online measured by the XRF analyzer directly above a conveyor belt. The limits of detection for Hg, Pb, Cr, Ti, Fe, and Ca by the analyzer were 44 ± 2, 34 ± 2, 17 ± 3, 41 ± 4, 19 ± 3, and 65 ± 2 mg·kg(-1), respectively. The relative standard deviation (%RSD) for the elements mentioned was less than 7.74%. By comparison with the results by inductively-coupled plasma mass spectrometry (ICP-MS), relative deviation (%D) of the online XRF analyzer was less than 10% for Cr, Ti, and Ca, in the range of 0.8-24.26% for Fe, and greater than 20% for Hg and Pb. PMID:26787706

  6. Study of heavy metals in wild edible mushrooms under different pollution conditions by X-ray fluorescence spectrometry.

    PubMed

    Carvalho, M L; Pimentel, A C; Fernandes, B

    2005-07-01

    In this work we studied and compared the metal uptake in edible mushrooms (Lepiota procera, Boletus badius, Boletus edulis, Tricholoma equestry, Lactarius deliciosus, Cantarelus tubalformis and Cantarelus edulis), relative to sampling sites submitted to different pollution conditions: car traffic, soil pollution due to pesticides and fertilizers used in old vineyards, and incineration of hospital waste. Soil was also collected in some places, and its content was correlated to the corresponding one in some mushrooms species. All samples, without any chemical treatment, were analyzed by an X-ray fluorescence set-up. This technique is based on a monochromatic X-ray beam ionizing the atoms of the sample. Following this ionization, the emitted radiation is characteristic of the element, allowing its identification and quantification. Vineyards are normally submitted to very high amounts of sulfating, containing high copper concentrations. This metal is accumulated on the soil, and can be up-taken by vegetation. Very high levels of Fe and Cu were found in Lepiota procera species in old vineyards. Zinc was found to be always higher than Cu by factors ranging from 1.5 to 8 in clean wood taken as a reference for the whole analyzed species, while in old vineyards the ratio Zn/Cu reach 0.25 for Lepiota procera. This is correlated to the soil content for both elements. In addition, pollution induced by car traffic was checked in some samples, collected in the proximity of highways. Pb was the main contaminant in these areas, and presenting values 10 times higher than the corresponding ones in sites not submitted to pollution, for some species. Mushrooms contamination due to incineration of hospital waste was also studied, but we did not observe any contamination involving heavy metals in the several analyzed species around these areas. This is in agreement with what was expected, taking into account that hospital waste is mostly organic and, in principle, no heavy metals would

  7. Online X-ray Fluorescence (XRF) Analysis of Heavy Metals in Pulverized Coal on a Conveyor Belt.

    PubMed

    Yan, Zhang; XinLei, Zhang; WenBao, Jia; Qing, Shan; YongSheng, Ling; DaQian, Hei; Da, Chen

    2016-02-01

    Heavy metals in haze episode will continue to threaten the quality of public health around the world. In order to decrease the emission of heavy metals produced from coal burning, an online X-ray fluorescence (XRF) analyzer system, consisting of an XRF analyzer with data acquisition software and a laser rangefinder, was developed to carry out the measurement of heavy metals in pulverized coal. The XRF analyzer was mounted on a sled, which can effectively smooth the surface of pulverized coal and reduce the impact of surface roughness during online measurement. The laser rangefinder was mounted over the sled for measuring the distance between a pulverized coal sample and the analyzer. Several heavy metals and other elements in pulverized coal were online measured by the XRF analyzer directly above a conveyor belt. The limits of detection for Hg, Pb, Cr, Ti, Fe, and Ca by the analyzer were 44 ± 2, 34 ± 2, 17 ± 3, 41 ± 4, 19 ± 3, and 65 ± 2 mg·kg(-1), respectively. The relative standard deviation (%RSD) for the elements mentioned was less than 7.74%. By comparison with the results by inductively-coupled plasma mass spectrometry (ICP-MS), relative deviation (%D) of the online XRF analyzer was less than 10% for Cr, Ti, and Ca, in the range of 0.8-24.26% for Fe, and greater than 20% for Hg and Pb.

  8. "Turn on" and label-free core-shell Ag@SiO2 nanoparticles-based metal-enhanced fluorescent (MEF) aptasensor for Hg2+

    NASA Astrophysics Data System (ADS)

    Pang, Yuanfeng; Rong, Zhen; Xiao, Rui; Wang, Shengqi

    2015-03-01

    A turn on and label-free fluorescent apasensor for Hg2+ with high sensitivity and selectivity has been demonstrated in this report. Firstly, core-shell Ag@SiO2 nanoparticles (NPs) were synthetized as a Metal-Enhanced Fluorescent (MEF) substrate, T-rich DNA aptamers were immobilized on the surface of Ag@SiO2 NPs and thiazole orange (TO) was selected as fluorescent reporter. After Hg2+ was added to the aptamer-Ag@SiO2 NPs and TO mixture buffer solution, the aptamer strand can bind Hg2+ to form T-Hg2+-T complex with a hairpin structure which TO can insert into. When clamped by the nucleic acid bases, the fluorescence quanta yield of TO will be increased under laser excitation and emitted a fluorescence emission. Furthermore, the fluorescence emission can be amplified largely by the MEF effect of the Ag@SiO2 NPs. The whole experiment can be finished within 30 min and the limit of detection is 0.33 nM even with interference by high concentrations of other metal ions. Finally, the sensor was applied for detecting Hg2+ in different real water samples with satisfying recoveries over 94%.

  9. "Turn on" and label-free core−shell Ag@SiO2 nanoparticles-based metal-enhanced fluorescent (MEF) aptasensor for Hg2+

    PubMed Central

    Pang, Yuanfeng; Rong, Zhen; Xiao, Rui; Wang, Shengqi

    2015-01-01

    A turn on and label-free fluorescent apasensor for Hg2+ with high sensitivity and selectivity has been demonstrated in this report. Firstly, core−shell Ag@SiO2 nanoparticles (NPs) were synthetized as a Metal-Enhanced Fluorescent (MEF) substrate, T-rich DNA aptamers were immobilized on the surface of Ag@SiO2 NPs and thiazole orange (TO) was selected as fluorescent reporter. After Hg2+ was added to the aptamer-Ag@SiO2 NPs and TO mixture buffer solution, the aptamer strand can bind Hg2+ to form T-Hg2+-T complex with a hairpin structure which TO can insert into. When clamped by the nucleic acid bases, the fluorescence quanta yield of TO will be increased under laser excitation and emitted a fluorescence emission. Furthermore, the fluorescence emission can be amplified largely by the MEF effect of the Ag@SiO2 NPs. The whole experiment can be finished within 30 min and the limit of detection is 0.33 nM even with interference by high concentrations of other metal ions. Finally, the sensor was applied for detecting Hg2+ in different real water samples with satisfying recoveries over 94%. PMID:25819733

  10. Shallow halogen vacancies in halide optoelectronic materials

    SciTech Connect

    Shi, Hongliang; Du, Mao -Hua

    2014-11-05

    Halogen vacancies (VH) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep VH contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., CH3NH3PbI3 and TlBr. Both CH3NH3PbI3 and TlBr have been found to have shallow VH, in contrast to commonly seen deep VH in halides. In this paper, several halide optoelectronic materials, i.e., CH3NH3PbI3, CH3NH3SnI3 (photovoltaic materials), TlBr, and CsPbBr3, (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether VH is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of ns2 ions both play important roles in creating shallow VH in halides such as CH3NH3PbI3, CH3NH3SnI3, and TlBr. The key to identifying halides with shallow VH is to find the right crystal structures and compounds that suppress cation orbital hybridization at VH, such as those with long cation-cation distances and low anion coordination numbers, and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at VH. Furthermore, the results of this paper provide insight and guidance to identifying halides with shallow VH as good electronic and optoelectronic materials.

  11. The Remarkable Reactivity of Aryl Halides with Nucleophiles

    ERIC Educational Resources Information Center

    Bunnett, Joseph F.

    1974-01-01

    Discusses the reactivity of aryl halides with nucleophilic or basic reagents, including nucleophilic attacks on carbon, hydrogen, halogen, and arynes. Suggestions are made concerning revisions of the sections on aryl halide chemistry courses and the corresponding chapters in textbooks. (CC)

  12. 40 CFR 721.4095 - Quaternary ammonium alkyltherpropyl trialkylamine halides.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Quaternary ammonium alkyltherpropyl... Specific Chemical Substances § 721.4095 Quaternary ammonium alkyltherpropyl trialkylamine halides. (a... generically as quaternary ammonium alkyltherpropyl trialkylamine halides (PMNs...

  13. 40 CFR 721.4095 - Quaternary ammonium alkyltherpropyl trialkylamine halides.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Quaternary ammonium alkyltherpropyl... Specific Chemical Substances § 721.4095 Quaternary ammonium alkyltherpropyl trialkylamine halides. (a... generically as quaternary ammonium alkyltherpropyl trialkylamine halides (PMNs...

  14. Fluorescence imaging and chlorophyll fluorescence to evaluate the role of EDU in UV-B protection in cucumber

    NASA Astrophysics Data System (ADS)

    Sandhu, Ravinder K.; Kim, Moon S.; Krizek, Donald T.; Middleton, Elizabeth M.

    1997-07-01

    A fluorescence imaging system and chlorophyll fluorescence emissions were used to evaluate whether EDU, N-[2-(2-oxo-1- imidazolidinyl) ethyl]-N'-phenylurea, provided protection against ultraviolet-B (UV-B) irradiation (290 - 320 nm) in cucumber (Cucumis sativus L.) leaves. Plants were grown in growth chambers illuminated for 14 h per day with 400 W high pressure sodium and metal halide lamps. Photosynthetically active radiation (PAR) for 1 hr at the beginning and end of each cycle was provided at 270 micrometers ol m-2 s-1 PAR; during the other 12 hr of the photoperiod, the plants received 840 micrometers ol m-2 s-1 PAR. Beginning on the twelfth day, the plants were exposed to UV-B radiation (0.2 & 18.0 kJ m-2d-1) for 2 days at 8 h per day centered in the photoperiod. Rapidly acquired (less than 1 s), high spatial resolution (less than 1 mm2) images were obtained for whole adaxial leaf surfaces using a fluorescence imaging system. The steady-state fluorescence images were acquired in four spectral regions: blue (F450 nm), green (F550 nm), red (F680 nm), and far-red (F740 nm). Fluorescence emission spectra for leaf pigments extracted in dimethyl sulfoxide (DMSO) were obtained by excitation at 280 and 380 nm (280EX 300 - 530 nm; 380EX 400 - 800 nm). Both UV-B and EDU induced stress responses in cucumber leaves that altered the fluorescence emissions obtained from extracts. In the fluorescence images only UV-B induced stress responses were observed but this damage was detected before it was visually apparent. There was no evidence that EDU afforded protection against UV-B irradiation. Use of fluorescence imaging may provide an early stress detection capability for helping to assess damage to the photosynthetic apparatus of plants.

  15. Fabrication of freestanding silk fibroin films containing Ag nanowires/NaYF4:Yb,Er nanocomposites with metal-enhanced fluorescence behavior.

    PubMed

    Zhao, Bing; Qi, Ning; Zhang, Ke-Qin; Gong, Xiao

    2016-06-01

    Solar cells containing upconversion nanoparticles (UCNPs) used as a power source in biomedical nanosystems have attracted great interest. However, such solar cells further need to be developed because their substrate materials should be biocompatible, flexible and highly luminescent. Here, we report that freestanding silk fibroin (SF) films containing a mesh of silver nanowires (AgNWs) and β-NaYF4:Yb,Er nanocrystals with metal-enhanced fluorescence behavior can be fabricated. The freestanding composite films exhibit properties such as good optical transparency, conductivity and flexibility. Furthermore, they show significantly enhanced upconversion fluorescence due to surface plasmon polaritons (SPPs) of AgNWs compared to the SF-UCNP films without AgNWs. The freestanding composite films with metal-enhanced fluorescence behavior show great promise for future applications in self-powered nanodevices such as cardiac pacemakers, biosensors and nanorobots.

  16. Quantitation and localization of intracellular redox active metals by X-ray fluorescence microscopy in cortical neurons derived from APP and APLP2 knockout tissue

    SciTech Connect

    Ciccotosto, Giuseppe D.; James, Simon A.; Altissimo, Matteo; Paterson, David; Vogt, Stefan; Lai, Barry; de Jonge, Martin D.; Howard, Daryl L.; Bush, Ashley I.; Cappai, Roberto

    2014-10-01

    The amyloid precursor protein (APP) gene family includes APP and the amyloid precursor-like proteins, APLP1 and APLP2. These proteins contain metal binding sites for copper, zinc and iron and are known to have physiological roles in modulating the metal homeostasis in brain cells. Here we report the application of X-ray fluorescence microscopy (XFM) to investigate the subcellular distribution patterns of the metal ions Cu, Zn, Fe, and Ca in individual neurons derived from APP and APLP2 knockout mice brains to further define their role in metal homeostasis. These studies add to the growing body of data that the APP family of proteins are metalloproteins that have shared as well as distinct effects on metals. As we continue to delineate the cellular effects of the APP family of proteins it is important to consider how metals are involved in their actions.

  17. Quantitation and localization of intracellular redox active metals by X-ray fluorescence microscopy in cortical neurons derived from APP and APLP2 knockout tissue

    DOE PAGES

    Ciccotosto, Giuseppe D.; James, Simon A.; Altissimo, Matteo; Paterson, David; Vogt, Stefan; Lai, Barry; de Jonge, Martin D.; Howard, Daryl L.; Bush, Ashley I.; Cappai, Roberto

    2014-10-01

    The amyloid precursor protein (APP) gene family includes APP and the amyloid precursor-like proteins, APLP1 and APLP2. These proteins contain metal binding sites for copper, zinc and iron and are known to have physiological roles in modulating the metal homeostasis in brain cells. Here we report the application of X-ray fluorescence microscopy (XFM) to investigate the subcellular distribution patterns of the metal ions Cu, Zn, Fe, and Ca in individual neurons derived from APP and APLP2 knockout mice brains to further define their role in metal homeostasis. These studies add to the growing body of data that the APP familymore » of proteins are metalloproteins that have shared as well as distinct effects on metals. As we continue to delineate the cellular effects of the APP family of proteins it is important to consider how metals are involved in their actions.« less

  18. X-ray fluorescence analysis of wear metals in used lubricating oils

    NASA Technical Reports Server (NTRS)

    Maddox, W. E.; Kelliher, W. C.

    1986-01-01

    Used oils from several aircraft at NASA's Langley Research Center were analyzed over a three year period using X-ray fluorescence (XRF) and atomic emission spectrometry. The results of both analyses are presented and comparisons are made. Fe and Cu data for oil from four internal combustion engines are provided and XRF and atomic emission spectrometry measurements were found to be in perfect agreement. However, distributions were found in the case of oil from a jet aircraft engine whereby the latter method gave values for total iron concentration in the oil and did not distinguish between suspended particles and oil additives. XRF does not have these particle-size limitations; moreover, it is a faster process. It is concluded that XRF is the preferred method in the construction of a man-portable oil wear analysis instrument.

  19. Correlative super-resolution fluorescence and metal replica transmission electron microscopy

    PubMed Central

    Sochacki, Kem A.; Shtengel, Gleb; van Engelenburg, Schuyler B.; Hess, Harald F.; Taraska, Justin W.

    2014-01-01

    Super-resolution localization microscopy is combined with a complementary imaging technique, transmission electron microscopy of metal replicas, to locate proteins on the landscape of the cellular plasma membrane at the nanoscale. Robust correlation on the scale of 20 nm is validated by imaging endogenous clathrin (with 2D and 3D PALM/TEM) and the method is further used to find the previously unknown 3D position of epsin on clathrin coated structures. PMID:24464288

  20. Intelligent simultaneous quantitative online analysis of environmental trace heavy metals with total-reflection X-ray fluorescence.

    PubMed

    Ma, Junjie; Wang, Yeyao; Yang, Qi; Liu, Yubing; Shi, Ping

    2015-05-06

    Total-reflection X-ray fluorescence (TXRF) has achieved remarkable success with the advantages of simultaneous multi-element analysis capability, decreased background noise, no matrix effects, wide dynamic range, ease of operation, and potential of trace analysis. Simultaneous quantitative online analysis of trace heavy metals is urgently required by dynamic environmental monitoring and management, and TXRF has potential in this application domain. However, it calls for an online analysis scheme based on TXRF as well as a robust and rapid quantification method, which have not been well explored yet. Besides, spectral overlapping and background effects may lead to loss of accuracy or even faulty results during practical quantitative TXRF analysis. This paper proposes an intelligent, multi-element quantification method according to the established online TXRF analysis platform. In the intelligent quantification method, collected characteristic curves of all existing elements and a pre-estimated background curve in the whole spectrum scope are used to approximate the measured spectrum. A novel hybrid algorithm, PSO-RBFN-SA, is designed to solve the curve-fitting problem, with offline global optimization and fast online computing. Experimental results verify that simultaneous quantification of trace heavy metals, including Cr, Mn, Fe, Co, Ni, Cu and Zn, is realized on the online TXRF analysis platform, and both high measurement precision and computational efficiency are obtained.

  1. Intelligent Simultaneous Quantitative Online Analysis of Environmental Trace Heavy Metals with Total-Reflection X-Ray Fluorescence

    PubMed Central

    Ma, Junjie; Wang, Yeyao; Yang, Qi; Liu, Yubing; Shi, Ping

    2015-01-01

    Total-reflection X-ray fluorescence (TXRF) has achieved remarkable success with the advantages of simultaneous multi-element analysis capability, decreased background noise, no matrix effects, wide dynamic range, ease of operation, and potential of trace analysis. Simultaneous quantitative online analysis of trace heavy metals is urgently required by dynamic environmental monitoring and management, and TXRF has potential in this application domain. However, it calls for an online analysis scheme based on TXRF as well as a robust and rapid quantification method, which have not been well explored yet. Besides, spectral overlapping and background effects may lead to loss of accuracy or even faulty results during practical quantitative TXRF analysis. This paper proposes an intelligent, multi-element quantification method according to the established online TXRF analysis platform. In the intelligent quantification method, collected characteristic curves of all existing elements and a pre-estimated background curve in the whole spectrum scope are used to approximate the measured spectrum. A novel hybrid algorithm, PSO-RBFN-SA, is designed to solve the curve-fitting problem, with offline global optimization and fast online computing. Experimental results verify that simultaneous quantification of trace heavy metals, including Cr, Mn, Fe, Co, Ni, Cu and Zn, is realized on the online TXRF analysis platform, and both high measurement precision and computational efficiency are obtained. PMID:25954949

  2. Intelligent simultaneous quantitative online analysis of environmental trace heavy metals with total-reflection X-ray fluorescence.

    PubMed

    Ma, Junjie; Wang, Yeyao; Yang, Qi; Liu, Yubing; Shi, Ping

    2015-01-01

    Total-reflection X-ray fluorescence (TXRF) has achieved remarkable success with the advantages of simultaneous multi-element analysis capability, decreased background noise, no matrix effects, wide dynamic range, ease of operation, and potential of trace analysis. Simultaneous quantitative online analysis of trace heavy metals is urgently required by dynamic environmental monitoring and management, and TXRF has potential in this application domain. However, it calls for an online analysis scheme based on TXRF as well as a robust and rapid quantification method, which have not been well explored yet. Besides, spectral overlapping and background effects may lead to loss of accuracy or even faulty results during practical quantitative TXRF analysis. This paper proposes an intelligent, multi-element quantification method according to the established online TXRF analysis platform. In the intelligent quantification method, collected characteristic curves of all existing elements and a pre-estimated background curve in the whole spectrum scope are used to approximate the measured spectrum. A novel hybrid algorithm, PSO-RBFN-SA, is designed to solve the curve-fitting problem, with offline global optimization and fast online computing. Experimental results verify that simultaneous quantification of trace heavy metals, including Cr, Mn, Fe, Co, Ni, Cu and Zn, is realized on the online TXRF analysis platform, and both high measurement precision and computational efficiency are obtained. PMID:25954949

  3. X-ray fluorescence as a method of monitoring metal catalyst content during the purification of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Cavness, Brandon; Heimbecker, Joshua; Velasquez, Joe; Williams, S.

    2012-02-01

    There have been several studies that suggest that catalyst metals in carbon nanotubes (CNTs) may pose a health threat. As there are many potential applications of CNTs in medicine, it is important to be able to quantitatively determine the amount of metal catalyst contained in a CNT sample. The relative catalyst content of carbon nanotube samples synthesized via arc-discharge has been determined at various stages of the purification process using X-ray fluorescence (XRF) analysis. Purification was achieved by immersing samples in heated nitric acid. The intensities of the nickel K α X-rays were studied to determine the relative catalyst content in the samples. Scanning electron microscopy (SEM) images of purified nanotubes have been compared to the images of a sample that has been irradiated by 0-15 keV bremsstrahlung in order to determine if the XRF analysis of the nanotubes is in any way destructive. No obvious structural defects were observed as the result of irradiation.

  4. Determining heavy metals in spent compact fluorescent lamps (CFLs) and their waste management challenges: Some strategies for improving current conditions

    SciTech Connect

    Taghipour, Hassan; Amjad, Zahra; Jafarabadi, Mohamad Asghari; Gholampour, Akbar; Norouz, Prviz

    2014-07-15

    Highlights: • Heavy metals in spent compact fluorescent lamps (CFLs) determined. • Current waste management condition of CFLs in Iran assessed. • Currently, waste of CFLs is disposed by municipal waste stream in waste landfills. • We propose extended producer responsibility (EPR) for CFLs waste management. - Abstract: From environmental viewpoint, the most important advantage of compact fluorescent lamps (CFLs) is reduction of green house gas emissions. But their significant disadvantage is disposal of spent lamps because of containing a few milligrams of toxic metals, especially mercury and lead. For a successful implementation of any waste management plan, availability of sufficient and accurate information on quantities and compositions of the generated waste and current management conditions is a fundamental prerequisite. In this study, CFLs were selected among 20 different brands in Iran. Content of heavy metals including mercury, lead, nickel, arsenic and chromium was determined by inductive coupled plasma (ICP). Two cities, Tehran and Tabriz, were selected for assessing the current waste management condition of CFLs. The study found that waste generation amount of CFLs in the country was about 159.80, 183.82 and 153.75 million per year in 2010, 2011 and 2012, respectively. Waste generation rate of CFLs in Iran was determined to be 2.05 per person in 2012. The average amount of mercury, lead, nickel, arsenic and chromium was 0.417, 2.33, 0.064, 0.056 and 0.012 mg per lamp, respectively. Currently, waste of CFLs is disposed by municipal waste stream in waste landfills. For improving the current conditions, we propose by considering the successful experience of extended producer responsibility (EPR) in other electronic waste management. The EPR program with advanced recycling fee (ARF) is implemented for collecting and then recycling CFLs. For encouraging consumers to take the spent CFLs back at the end of the products’ useful life, a proportion of

  5. 40 CFR 721.575 - Substituted alkyl halide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 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)...

  6. 40 CFR 721.575 - Substituted alkyl halide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 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)...

  7. 40 CFR 721.575 - Substituted alkyl halide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 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)...

  8. 40 CFR 721.10698 - Polyfluorinated alkyl halide (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Polyfluorinated alkyl halide (generic... Specific Chemical Substances § 721.10698 Polyfluorinated alkyl halide (generic). (a) Chemical substance and... polyfluorinated alkyl halide (PMN P-11-527) is subject to reporting under this section for the significant...

  9. 40 CFR 721.575 - Substituted alkyl halide.

    Code of Federal Regulations, 2010 CFR

    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)...

  10. 40 CFR 721.575 - Substituted alkyl halide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 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)...

  11. Parallel factor analysis of excitation-emission matrix fluorescence spectra of water soluble soil organic matter as basis for the determination of conditional metal binding parameters.

    PubMed

    Ohno, Tsutomu; Amirbahman, Aria; Bro, Rasmus

    2008-01-01

    Organic matter-metal complexes in soil solution and aquatic systems are involved in important environmental and ecological processes such as plant nutrient availability and the solubilization and transport of metals. Our work presented here extends the use of fluorescence spectrometry for determining conditional stability constants for such complexes. We combine the use of excitation-emission matrix (EEM) fluorescence spectrometry and parallel factor analysis (PARAFAC) to determine the stability constants of the chemically meaningful components modeled by PARAFAC. Water-soluble organic matter (WSOM) from O-horizon soils of deciduous and coniferous forest stands were extracted and titrated at pH = 4.7 with iron(lll) (Fe) and aluminum (Al) which are important metals in acid soil systems. The EEM spectra were then recorded and PARAFAC analysis showed that the WSOM contained three humic-substance-like components. Fe titration led to fluorescence quenching of the three components, while Al titration enhanced fluorescence for two components and quenched one of the components. The average Ryan-Weber stability constants at pH 4.7 ranged from log K of 4.28 to 4.91 for Fe and 4.84 to 5.96 for Al. The conditional stability constants were similar for Fe binding for deciduous and coniferous stand-derived WSOM, while they were stronger for Al binding with coniferous stand-derived WSOM. This difference in binding strengths for Al may affect the chemical behavior of Al in soil and aquatic systems. Determining the individual binding parameters of organic matter components with metals represents a significant advance over current approaches that utilize fluorescence quenching at a single excitation-emission wavelength pair to characterize organic matter-metal interactions.

  12. Characterization of quaternary metal oxide films by synchrotron x-ray fluorescence microprobe

    SciTech Connect

    Perry, D.L.; Thompson, A.C.; Russo, R.E.

    1997-04-01

    A high demand for thin films in industrial technology has been responsible for the creation of new techniques for the fabrication of such films. One highly effective method for the syntheses of variable composition thin films is pulsed-laser deposition (PLD). The technique has a large number of characteristics which make it an attractive approach for making films. It offers rapid deposition rates, congruent material transfer, simple target requirements from which to make the films, in situ multilayer deposition, and no gas composition or pressure requirements. Additionally, the technique can also afford crystalline films and films with novel structures. Pulsed-laser deposition can be used to make films of semiconductors, insulators, high-temperature superconductors, diamond-like films, and piezoelectric materials. Quaternary metal oxides involving calcium, nickel, and potassium have been shown to be quite effective in the catalysis of coal gasification and methane coupling. One approach to incorporating all three of the metal oxides into one phase is the use of laser ablation to prepare films of the catalysts so that they may be used for coatings, smooth surfaces on which to conduct detailed studies of gas-solid interface reactions that are involved in catalytic processes, and other applications. The problem of dissimilar boiling points of the three metal oxides system is overcome, since the laser ablation process effects the volatilization of all three components from the laser target essentially simultaneously. There is strong interest in gaining an understanding of the chemical and morphological aspects of the films that are deposited. Phenomena such as lattice defects and chemical heterogeneity are of interest. The experimental data discussed here are restricted to the matrix homogeneity of the films themselves for films which were void of microparticles.

  13. Interactions between fluorescence of atomically layered graphene oxide and metallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Li, Shao-Sian; Yeh, Yun-Chieh; Yu, Chen-Chieh; Chen, Hsuen-Li; Li, Feng-Chieh; Chang, Yu-Ming; Chen, Chun-Wei

    2013-01-01

    Graphene oxide (GO) demonstrates interesting photoluminescence (PL) because of its unique heterogeneous atomic structure, which consists of variable sp2- and sp3-bonded carbons. In this study, we report the interaction between the luminescence of GO ranging from a single atomic layer to few-layered thin films and localized surface plasmon resonance (LSPR) from silver nanoparticles (Ag NPs). The photoluminescence of GO in the vicinity of the Ag NPs is enhanced significantly due to the near-field plasmonic effect by coupling electron-hole pairs of GO with oscillating electrons in Ag NPs, leading to an increased PL intensity and a decreased PL decay lifetime. The maxima 30-fold enhancement in PL intensity is obtained with an optimized film thickness of GO, and the luminescence image from a single atomic layer GO sheet is successfully observed with the assistance of the LSPR effect. The results provide an ideal platform for exploring the interactions between the fluorescence of two-dimensional layered materials and the LSPR effect.Graphene oxide (GO) demonstrates interesting photoluminescence (PL) because of its unique heterogeneous atomic structure, which consists of variable sp2- and sp3-bonded carbons. In this study, we report the interaction between the luminescence of GO ranging from a single atomic layer to few-layered thin films and localized surface plasmon resonance (LSPR) from silver nanoparticles (Ag NPs). The photoluminescence of GO in the vicinity of the Ag NPs is enhanced significantly due to the near-field plasmonic effect by coupling electron-hole pairs of GO with oscillating electrons in Ag NPs, leading to an increased PL intensity and a decreased PL decay lifetime. The maxima 30-fold enhancement in PL intensity is obtained with an optimized film thickness of GO, and the luminescence image from a single atomic layer GO sheet is successfully observed with the assistance of the LSPR effect. The results provide an ideal platform for exploring the

  14. Pd-catalyzed cross-coupling reactions of alkyl halides.

    PubMed

    Kambe, Nobuaki; Iwasaki, Takanori; Terao, Jun

    2011-10-01

    Cross-coupling reactions have become indispensable tools for creating carbon-carbon (or heteroatom) bonds in organic synthesis. Like in other important transition metal catalyzed reactions, such as metathesis, addition, and polymerization, unsaturated compounds are usually employed as substrates for cross-coupling reactions. However during the past decade, a great deal of effort has been devoted to the use of alkyl halides as saturated compounds in cross-coupling reactions, which has resulted in significant progress in this undeveloped area by introducing new effective ligands. Many useful catalytic systems are now available for synthetic transformations based on C(sp(3))-C(sp(3)), C(sp(3))-C(sp(2)) and C(sp(3))-C(sp) bond formation as complementary methods to conventional C(sp(2))-C(sp(2)), C(sp(2))-C(sp) and C(sp)-C(sp) coupling. This tutorial review summarizes recent advances in cross-coupling reactions of alkyl halides and pseudohalides catalyzed by a palladium complex.

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

    PubMed

    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.

  16. Treatability study for removal of leachable mercury in crushed fluorescent lamps

    SciTech Connect

    Bostick, W.D.; Beck, D.E.; Bowser, K.T.

    1996-02-01

    Nonserviceable fluorescent lamps removed from radiological control areas at the Oak Ridge Department of Energy facilities have been crushed and are currently managed as mixed waste (hazardous and radiologically contaminated). We present proposed treatment flowsheets and supporting treatability study data for conditioning this solid waste residue so that it can qualify for disposal in a sanitary landfill. Mercury in spent fluorescent lamps occurs primarily as condensate on high-surface-area phosphor material. It can be solubilized with excess oxidants (e.g., hypochlorite solution) and stabilized by complexation with halide ions. Soluble mercury in dechlorinated saline solution is effectively removed by cementation with zero-valent iron in the form of steel wool. In packed column dynamic flow testing, soluble mercury was reduced to mercury metal and insoluble calomel, loading > 1.2 g of mercury per grain of steel wool before an appreciable breakthrough of soluble mercury in the effluent.

  17. Interactions between fluorescence of atomically layered graphene oxide and metallic nanoparticles.

    PubMed

    Wang, Yu; Li, Shao-Sian; Yeh, Yun-Chieh; Yu, Chen-Chieh; Chen, Hsuen-Li; Li, Feng-Chieh; Chang, Yu-Ming; Chen, Chun-Wei

    2013-02-21

    Graphene oxide (GO) demonstrates interesting photoluminescence (PL) because of its unique heterogeneous atomic structure, which consists of variable sp(2)- and sp(3)-bonded carbons. In this study, we report the interaction between the luminescence of GO ranging from a single atomic layer to few-layered thin films and localized surface plasmon resonance (LSPR) from silver nanoparticles (Ag NPs). The photoluminescence of GO in the vicinity of the Ag NPs is enhanced significantly due to the near-field plasmonic effect by coupling electron-hole pairs of GO with oscillating electrons in Ag NPs, leading to an increased PL intensity and a decreased PL decay lifetime. The maxima 30-fold enhancement in PL intensity is obtained with an optimized film thickness of GO, and the luminescence image from a single atomic layer GO sheet is successfully observed with the assistance of the LSPR effect. The results provide an ideal platform for exploring the interactions between the fluorescence of two-dimensional layered materials and the LSPR effect. PMID:23340692

  18. X-ray fluorescence analysis of low concentrations metals in geological samples and technological products

    NASA Astrophysics Data System (ADS)

    Lagoida, I. A.; Trushin, A. V.

    2016-02-01

    For the past several years many nuclear physics methods of quantitative elemental analysis have been designed. Many of these methods have applied in different devices which have become useful and effective instrument in many industrial laboratories. Methods of a matter structure analysis are based on the intensity detection of the X-ray radiation from the nuclei of elements which are excited by external X-ray source. The production of characteristic X-rays involves transitions of the orbital electrons of atoms in the target material between allowed orbits, or energy states, associated with ionization of the inner atomic shells. One of these methods is X-ray fluorescence analysis, which is widespread in metallurgical and processing industries and is used to identify and measure the concentration of the elements in ores and minerals on a conveyor belt. Samples of copper ore with known concentrations of elements, were taken from the Ural deposit. To excite the characteristic X-rays radionuclide sources 109Cd, with half-life 461.4 days were used. After finding the calibration coefficients, control measurements of samples and averaging of overall samples were made. The measurement error did not exceed 3%.

  19. X-ray Fluorescence Spectroscopy Study of Coating Thickness and Base Metal Composition

    NASA Technical Reports Server (NTRS)

    Rolin, T. D.; Leszczuk, Y.

    2008-01-01

    For electrical, electronic, and electromechanical (EEE) parts to be approved for space use, they must be able to meet safety standards approved by NASA. A fast, reliable, and precise method is needed to make sure these standards are met. Many EEE parts are coated in gold (Au) and nickel (Ni), and the thickness coating is crucial to a part s performance. A nondestructive method that is efficient in measuring coating thickness is x-ray fluorescence (XRF) spectroscopy. The XRF spectrometer is a machine designed to measure layer thickness and composition of single or multilayered samples. By understanding the limitations in the collection of the data by this method, accurate composition and thickness measurements can be obtained for samples with Au and Ni coatings. To understand the limitations of data found, measurements were taken with the XRF spectrometer and compared to true values of standard reference materials (SRM) that were National Institute of Standards and Technology (NIST) traceable. For every sample, six different parameters were varied to understand measurement error: coating/substrate combination, number of layers, counting interval, collimator size, coating thickness, and test area location. Each measurement was taken in accordance with standards set by the American Society for Testing and Materials (ASTM) International Standard B 568.

  20. Fluorescent probes for tracking the transfer of iron-sulfur cluster and other metal cofactors in biosynthetic reaction pathways.

    PubMed

    Vranish, James N; Russell, William K; Yu, Lusa E; Cox, Rachael M; Russell, David H; Barondeau, David P

    2015-01-14

    Iron-sulfur (Fe-S) clusters are protein cofactors that are constructed and delivered to target proteins by elaborate biosynthetic machinery. Mechanistic insights into these processes have been limited by the lack of sensitive probes for tracking Fe-S cluster synthesis and transfer reactions. Here we present fusion protein- and intein-based fluorescent labeling strategies that can probe Fe-S cluster binding. The fluorescence is sensitive to different cluster types ([2Fe-2S] and [4Fe-4S] clusters), ligand environments ([2Fe-2S] clusters on Rieske, ferredoxin (Fdx), and glutaredoxin), and cluster oxidation states. The power of this approach is highlighted with an extreme example in which the kinetics of Fe-S cluster transfer reactions are monitored between two Fdx molecules that have identical Fe-S spectroscopic properties. This exchange reaction between labeled and unlabeled Fdx is catalyzed by dithiothreitol (DTT), a result that was confirmed by mass spectrometry. DTT likely functions in a ligand substitution reaction that generates a [2Fe-2S]-DTT species, which can transfer the cluster to either labeled or unlabeled Fdx. The ability to monitor this challenging cluster exchange reaction indicates that real-time Fe-S cluster incorporation can be tracked for a specific labeled protein in multicomponent assays that include several unlabeled Fe-S binding proteins or other chromophores. Such advanced kinetic experiments are required to untangle the intricate networks of transfer pathways and the factors affecting flux through branch points. High sensitivity and suitability with high-throughput methodology are additional benefits of this approach. We anticipate that this cluster detection methodology will transform the study of Fe-S cluster pathways and potentially other metal cofactor biosynthetic pathways.

  1. Tailoring Oxygen Sensitivity with Halide Substitution in Difluoroboron Dibenzoylmethane Polylactide Materials

    PubMed Central

    DeRosa, Christopher A.; Kerr, Caroline; Fan, Ziyi; Kolpaczynska, Milena; Mathew, Alexander S.; Evans, Ruffin E.; Zhang, Guoqing; Fraser, Cassandra L.

    2015-01-01

    The dual-emissive properties of solid-state difluoroboron β-diketonate-poly(lactic acid) (BF2bdkPLA) materials have been utilized for biological oxygen sensing. In this work, BF2dbm(X)PLA materials were synthesized, where X = H, F, Cl, Br, and I. The effects of changing the halide substituent and PLA polymer chain length on the optical properties in dilute CH2Cl2 solutions and solid-state polymer films were studied. These luminescent materials show fluorescence, phosphorescence, and lifetime tunability on the basis of molecular weight, as well as lifetime modulation via the halide substituent. Short BF2dbm(Br)PLA (6.0 kDa) and both short and long BF2dbm(I)PLA polymers (6.0 or 20.3 kDa) have fluorescence and intense phosphorescence ideal for ratiometric oxygen sensing. The lighter halide-dye polymers with hydrogen, fluorine, and chlorine substitution have longer phosphorescence lifetimes and can be utilized as ultrasensitive oxygen sensors. Photostability was also analyzed for the polymer films. PMID:26480236

  2. Tailoring Oxygen Sensitivity with Halide Substitution in Difluoroboron Dibenzoylmethane Polylactide Materials.

    PubMed

    DeRosa, Christopher A; Kerr, Caroline; Fan, Ziyi; Kolpaczynska, Milena; Mathew, Alexander S; Evans, Ruffin E; Zhang, Guoqing; Fraser, Cassandra L

    2015-10-28

    The dual-emissive properties of solid-state difluoroboron β-diketonate-poly(lactic acid) (BF2bdkPLA) materials have been utilized for biological oxygen sensing. In this work, BF2dbm(X)PLA materials were synthesized, where X = H, F, Cl, Br, and I. The effects of changing the halide substituent and PLA polymer chain length on the optical properties in dilute CH2Cl2 solutions and solid-state polymer films were studied. These luminescent materials show fluorescence, phosphorescence, and lifetime tunability on the basis of molecular weight, as well as lifetime modulation via the halide substituent. Short BF2dbm(Br)PLA (6.0 kDa) and both short and long BF2dbm(I)PLA polymers (6.0 or 20.3 kDa) have fluorescence and intense phosphorescence ideal for ratiometric oxygen sensing. The lighter halide-dye polymers with hydrogen, fluorine, and chlorine substitution have longer phosphorescence lifetimes and can be utilized as ultrasensitive oxygen sensors. Photostability was also analyzed for the polymer films. PMID:26480236

  3. Microwave-Accelerated Metal-Enhanced Fluorescence (MAMEF) with silver colloids in 96-well plates: Application to ultra fast and sensitive immunoassays, High Throughput Screening and drug discovery.

    PubMed

    Aslan, Kadir; Holley, Patrick; Geddes, Chris D

    2006-05-30

    Fluorescence detection is the basis of most assays used in drug discovery and High Throughput Screening (HTS) today. In all of these assays, assay rapidity and sensitivity is a primary concern, the sensitivity determined by both the quantum yield of the fluorophores and efficiency of the detection system, while rapidity is determined by the physical and biophysical parameters of temperature, concentration, assay bioaffinity, etc. In this paper we describe a platform technology that promises to fundamentally address these two physical constraints of sensitivity and rapidity. By combining the use of Metal-Enhanced Fluorescence (MEF), a near-field effect that can significantly enhance fluorescence signatures, with low power microwave heating, we can significantly increase the sensitivity of surface assays as well as >95% kinetically complete the assay within a few seconds. In addition, the metallic nanostructures used to facilitate MEF appear to be preferentially heated as compared to the surface assay fluid, advantageously localizing the MEF and heating around the nanostructures. To demonstrate proof of principle, a 96-well plate has been functionalized with silver nanostructures, and a model protein avidin-biotin assay studied. In our findings, a greater than 5-fold fluorescence enhancement coupled with a approximately 90-fold increase in assay kinetics was observed, but with no assay washing steps needed due to the silver-enhanced evanescent field mode of excitation. These findings promise to strongly facilitate high throughput fluorescence-based processes, such as in biology, drug discovery and general compound screening.

  4. PROCESS OF PRODUCING ACTINIDE METALS

    DOEpatents

    Magel, T.T.

    1959-07-14

    The preparation of actinide metals in workable, coherent form is described. In general, the objects of the invention are achieved by heating a mixture of an oxide and a halide of an actinide metal such as uranium with an alkali metal on alkaline earth metal reducing agent in the presence of iodine.

  5. Development of a flow injection analysis (FIA) system for the measurement of heavy metals using a fiber optic chemical sensor based on laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Zhang, Jingdong; Prestel, Harald; Gahr, Achim; Niessner, Reinhard

    2000-05-01

    The development of a fiber optic sensor system is described, for the on-line detection of heavy metal ions in water. This is based on laser-induced fluorescence spectroscopy of suitable metal-ligand complexes. The sensor system is designed to measure heavy metal ions in the field. Flow injection analysis (FIA) is coupled with the sensor system, to overcome problems of a slow diffusion rate of heavy metals through the membrane of an in situ sensor head. Preliminary experiments show the new FIA system has good reproducibility, a high sample analysis rate and it can measure heavy metal ions (Cu(II), Ni(II), Cd(II) and Zn(II)) at the ppb level, when using the appropriate ligands.

  6. Tetrazine chromophore-based metal-organic frameworks with unusual configurations: synthetic, structural, theoretical, fluorescent, and nonlinear optical studies.

    PubMed

    Li, Jianghua; Jia, Ding; Meng, Suci; Zhang, Jinfang; Cifuentes, Marie P; Humphrey, Mark G; Zhang, Chi

    2015-05-18

    Three unusual three-dimensional (3D) tetrazine chromophore-based metal-organic frameworks (MOFs) {(Et4 N)[WS4 Cu3 (CN)2 (4,4'-pytz)0.5 ]}n (1), {[MoS4 Cu4 (CN)2 (4,4'-pytz)2 ]⋅CH2 Cl2 }n (2), and {[WS4 Cu3 (4,4'-pytz)3 ]⋅[N(CN)2 ]}n (3; 4,4'-pytz=3,6-bis(4-pyridyl)tetrazine) have been synthesized and characterized by using FTIR and UV/Vis spectroscopy, elemental analysis, powder X-ray diffraction, gel permeation chromatography, steady-state fluorescence, and thermogravimetric analysis; their identities were confirmed by single-crystal X-ray diffraction studies. MOF 1 possesses the first five-connected M/S/Cu (M=Mo, W) framework with an unusual 3D (4(4) ⋅6(6) ) topology constructed from T-shaped [WS4 Cu3 ](+) clusters as nodes and single CN(-) /4,4'-pytz bridges as linkers. MOF 2 features a novel 3D MOF structure with (4(20) ⋅6(8) ) topology, in which the bridging 4,4'-pytz ligands exhibit unique distorted arch structures. MOF 3 displays the first 3D MOF structure based on flywheel-shaped [WS4 Cu3 ](+) clusters with a non-interpenetrating honeycomb-like framework and a heavily distorted "ACS" topology. Steady-state fluorescence studies of 1-3 reveal significant fluorescence emissions. The nonlinear optical (NLO) properties of 1-3 were investigated by using a Z-scan technique with 5 ns pulses at λ=532 nm. The Z-scan experimental results show that the π-delocalizable tetrazine-based 4,4'-pytz ligands contribute to the strong third-order NLO properties exhibited by 1-3. Time-dependent density functional theory studies afforded insight into the electronic transitions and spectral characterization of these functionalized NLO molecular materials. PMID:25877804

  7. Merging photoredox with nickel catalysis: Coupling of α-carboxyl sp3-carbons with aryl halides

    PubMed Central

    Zuo, Zhiwei; Ahneman, Derek T.; Chu, Lingling; Terrett, Jack A.; Doyle, Abigail G.; MacMillan, David W. C.

    2015-01-01

    Over the past 40 years, transition metal catalysis has enabled bond formation between aryl and olefinic (sp2) carbons in a selective and predictable manner with high functional group tolerance. Couplings involving alkyl (sp3) carbons have proven more challenging. Here, we demonstrate that the synergistic combination of photoredox catalysis and nickel catalysis provides an alternative cross-coupling paradigm, in which simple and readily available organic molecules can be systematically used as coupling partners. By using this photoredox-metal catalysis approach, we have achieved a direct decarboxylative sp3–sp2 cross-coupling of amino acids, as well as α-O– or phenyl-substituted carboxylic acids, with aryl halides. Moreover, this mode of catalysis can be applied to direct cross-coupling of Csp3–H in dimethylaniline with aryl halides via C–H functionalization. PMID:24903563

  8. The Additive Coloration of Alkali Halides

    ERIC Educational Resources Information Center

    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…

  9. Graphene oxide and metal-mediated base pairs based "molecular beacon" integrating with exonuclease I for fluorescence turn-on detection of biothiols.

    PubMed

    Xing, Xiaojing; Zhou, Ying; Liu, Xueguo; Pang, Daiwen; Tang, Hongwu

    2014-08-27

    A novel fluorescence turn-on strategy, based on the resistance of metal-mediated molecular-beacons (MBs) toward nuclease digestion and the remarkable difference in the affinity of graphene oxide (GO) with MBs and the mononucleotides, is designed for the biothiols assay. Specifically, the metal-mediated base pairs facilitate the dye labeled MBs to fold into a hairpin structure preventing the digestion by exonuclease I, and thus allow the fluorescence quenching. The competition binding by biothiols removes metal ions from the base pairs, causing the nuclease reaction, and less decrease in the fluorescence is obtained after incubating with GO due to the weak affinity of the product-mononucleotides to GO. Hg(2+)-mediated MBs were firstly designed for the biothiols detection, and glutathione (GSH) was applied as the model target. Under the optimal conditions, the approach exhibits high sensitivity to GSH with a detection limit of 1.53 nM. Ag(+)-mediated MBs based sensor was also constructed to demonstrate its versatility, and cysteine was studied as the model target. The satisfactory results in the determination of biothiols in serum demonstrate that the method possesses great potential for detecting thiols in biological fluids. This new approach is expected to promote the exploitation of metal-mediated base pairs-based biosensors in biochemical and biomedical studies.

  10. Determination of metal-cofactors in enzyme complexes by total-reflection X-ray fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Wittershagen, A.; Rostam-Khani, P.; Klimmek, O.; Groß, R.; Zickermann, V.; Zickermann, I.; Gemeinhardt, S.; Kröger, A.; Ludwig, B.; Kolbesen, B. O.

    1997-07-01

    The determination of metal-cofactors and their molar concentrations is an important requirement for the characterisation of metalloproteins and a challenge regarding the capabilities of trace analytical methods. In this respect, total-reflection X-ray fluorescence spectrometry offers many advantages for the determination of trace elements in enzymes, as compared to other well known analytical techniques such as flame atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry (ICP-AES), because of the significantly smaller amounts of sample required. Without any decomposition, elements like P, S, Fe, Ni, Cu, Zn, Mn and Mo could be determined with high accuracy, in spite of the large bio-organic matrix. The enzymes (polysulphide reductase and hydrogenase of the rumen bacterium Wolinella succinogenes, and the cytochrome c oxidase and quinol oxidase of the soil bacterium Paracoccus denitrificans) were transferred from their usual salt-buffer into a solution of 100 mmol l -1 tris(hydroxymethyl)aminomethane (tris)-acetate containing an appropriate detergent. By this procedure, an improved signal-to-noise ratio is obtained. The polysulphide reductase was found to contain copper as a hitherto existing unknown cofactor. The enzyme contains a stretch of amino acids that are typical of copper proteins and thus confirm the presence of this element. Furthermore, the data concerning cytochrome c oxidase from Paracoccus denitrificans are in good agreement with published values obtained by ICP-AES. Also, results from measurements with the quinol oxidase from the same bacterium agree with the expected values. The investigations lead to the conclusion that the method is well suited to the quantitative determination of metals in enzymes, in particular their molar fractions, and requires only small amounts of the biological sample without any extensive pretreatment.

  11. Determining heavy metals in spent compact fluorescent lamps (CFLs) and their waste management challenges: some strategies for improving current conditions.

    PubMed

    Taghipour, Hassan; Amjad, Zahra; Jafarabadi, Mohamad Asghari; Gholampour, Akbar; Norouz, Prviz

    2014-07-01

    From environmental viewpoint, the most important advantage of compact fluorescent lamps (CFLs) is reduction of green house gas emissions. But their significant disadvantage is disposal of spent lamps because of containing a few milligrams of toxic metals, especially mercury and lead. For a successful implementation of any waste management plan, availability of sufficient and accurate information on quantities and compositions of the generated waste and current management conditions is a fundamental prerequisite. In this study, CFLs were selected among 20 different brands in Iran. Content of heavy metals including mercury, lead, nickel, arsenic and chromium was determined by inductive coupled plasma (ICP). Two cities, Tehran and Tabriz, were selected for assessing the current waste management condition of CFLs. The study found that waste generation amount of CFLs in the country was about 159.80, 183.82 and 153.75 million per year in 2010, 2011 and 2012, respectively. Waste generation rate of CFLs in Iran was determined to be 2.05 per person in 2012. The average amount of mercury, lead, nickel, arsenic and chromium was 0.417, 2.33, 0.064, 0.056 and 0.012 mg per lamp, respectively. Currently, waste of CFLs is disposed by municipal waste stream in waste landfills. For improving the current conditions, we propose by considering the successful experience of extended producer responsibility (EPR) in other electronic waste management. The EPR program with advanced recycling fee (ARF) is implemented for collecting and then recycling CFLs. For encouraging consumers to take the spent CFLs back at the end of the products' useful life, a proportion of ARF (for example, 50%) can be refunded. On the other hand, the government and Environmental Protection Agency should support and encourage recycling companies of CFLs both technically and financially in the first place.

  12. Determining heavy metals in spent compact fluorescent lamps (CFLs) and their waste management challenges: some strategies for improving current conditions.

    PubMed

    Taghipour, Hassan; Amjad, Zahra; Jafarabadi, Mohamad Asghari; Gholampour, Akbar; Norouz, Prviz

    2014-07-01

    From environmental viewpoint, the most important advantage of compact fluorescent lamps (CFLs) is reduction of green house gas emissions. But their significant disadvantage is disposal of spent lamps because of containing a few milligrams of toxic metals, especially mercury and lead. For a successful implementation of any waste management plan, availability of sufficient and accurate information on quantities and compositions of the generated waste and current management conditions is a fundamental prerequisite. In this study, CFLs were selected among 20 different brands in Iran. Content of heavy metals including mercury, lead, nickel, arsenic and chromium was determined by inductive coupled plasma (ICP). Two cities, Tehran and Tabriz, were selected for assessing the current waste management condition of CFLs. The study found that waste generation amount of CFLs in the country was about 159.80, 183.82 and 153.75 million per year in 2010, 2011 and 2012, respectively. Waste generation rate of CFLs in Iran was determined to be 2.05 per person in 2012. The average amount of mercury, lead, nickel, arsenic and chromium was 0.417, 2.33, 0.064, 0.056 and 0.012 mg per lamp, respectively. Currently, waste of CFLs is disposed by municipal waste stream in waste landfills. For improving the current conditions, we propose by considering the successful experience of extended producer responsibility (EPR) in other electronic waste management. The EPR program with advanced recycling fee (ARF) is implemented for collecting and then recycling CFLs. For encouraging consumers to take the spent CFLs back at the end of the products' useful life, a proportion of ARF (for example, 50%) can be refunded. On the other hand, the government and Environmental Protection Agency should support and encourage recycling companies of CFLs both technically and financially in the first place. PMID:24726659

  13. Ionic alkali halide XUV laser feasibility study

    SciTech Connect

    Yang, T.T.; Gylys, V.T.; Bower, R.D.; Harris, D.G.; Blauer, J.A.; Turner, C.E.; Hindy, R.N.

    1989-11-10

    The objective of this work is to assess the feasibility of a select set of ionic alkali halide XUV laser concepts by obtaining the relevant kinetic and spectroscopic parameters required for a proof-of-principle and conceptual design. The proposed lasers operate in the 80--200 nm spectral region and do not require input from outside radiation sources for their operation. Frequency up-conversion and frequency mixing techniques and therefore not considered in the work to be described. An experimental and theoretical study of a new type of laser operating in the extreme ultraviolet wavelength region has been conducted. The lasing species are singly ionized alkali halide molecules such as Rb{sup 2+}F{sub {minus}}, Rb{sup 2+}Br{sup {minus}} and Cs{sup 2+}F{sup {minus}}. These species are similar in electronic structure to the rare gas halide excimers, such as XeF and Krf, except that the ionic molecules emit at wavelengths of 80--200 nm, much shorter than the conventional rare-gas halide excimer laser. The radiative lifetime of these molecules are typically near 1 ns, which is about an order of magnitude shorter than that for rare-gas halide systems. The values of the cross section for stimulated emission are on the order of 1 {times} 10{sup {minus}16}cm{sup 2}. Because of the fundamental similarity to existing UV lasers, these systems show promise as a high power, efficient XUV lasers. 55 refs., 50 figs., 5 tabs.

  14. Fluorescence sensor array for metal ion detection based on various coordination chemistries: general performance and potential application.

    PubMed

    Wang, Zhuo; Palacios, Manuel A; Anzenbacher, Pavel

    2008-10-01

    A sensor array containing 9 cross-reactive sensing fluorescent elements with different affinity and selectivity to 10 metal cations (Ca(2+), Mg(2+), Cd(2+), Hg(2+), Co(2+), Zn(2+), Cu(2+), Ni(2+), Al(3+), Ga(3+)) is described. The discriminatory capacity of the array was tested at different ranges of pH and at different cation concentrations using linear discriminant analysis (LDA). Qualitative identification of cations can be determined with over 96% of accuracy in a concentration range covering 3 orders of a magnitude (5-5000 microM). Quantitative analysis can be achieved with over 90% accuracy in the concentration range between 10 and 5000 microM. The array performance was also tested in identification of nine different mineral water brands utilizing their various electrolyte compositions and their Ca(2+), Mg(2+), and Zn(2+) levels. LDA cross-validation routine shows 100% correct classification for all trials. Preliminary results suggest that similar arrays could be used in testing of the consistency of the purification and manufacturing process of purified and mineral waters. PMID:18778035

  15. Enhanced quantum efficiency from hybrid cesium halide/copper photocathodes

    SciTech Connect

    Kong, Lingmei; Joly, Alan G.; Droubay, Timothy C.; Gong, Yu; Hess, Wayne P.

    2014-04-28

    The quantum efficiency (QE) of Cu is found to increase dramatically when coated by a CsI film and then irradiated by a UV laser. Over three orders of magnitude quantum efficiency enhancement at 266 nm is observed in CsI/Cu(100), indicating potential application in future photocathode devices. Upon laser irradiation, a large work function reduction to a value less than 2 eV is also observed, significantly greater than for similarly treated CsBr/Cu(100). The initial QE enhancement, prior to laser irradiation, is attributed to interface interaction and the intrinsic properties of the Cs halide film. Further QE enhancement following activation is attributed to formation of inter-band states and Cs metal accumulation at the interface induced by laser irradiation.

  16. Potential environmental impacts from the metals in incandescent, compact fluorescent lamp (CFL), and light-emitting diode (LED) bulbs.

    PubMed

    Lim, Seong-Rin; Kang, Daniel; Ogunseitan, Oladele A; Schoenung, Julie M

    2013-01-15

    Artificial lighting systems are transitioning from incandescent to compact fluorescent lamp (CFL) and light-emitting diode (LED) bulbs in response to the U.S. Energy Independence and Security Act and the EU Ecodesign Directive, which leads to energy savings and reduced greenhouse gas emissions. Although CFLs and LEDs are more energy-efficient than incandescent bulbs, they require more metal-containing components. There is uncertainty about the potential environmental impacts of these components and whether special provisions must be made for their disposal at the end of useful life. Therefore, the objective of this study is to analyze the resource depletion and toxicity potentials from the metals in incandescent, CFL, and LED bulbs to complement the development of sustainable energy policy. We assessed the potentials by examining whether the lighting products are to be categorized as hazardous waste under existing U.S. federal and California state regulations and by applying life cycle impact-based and hazard-based assessment methods (note that "life cycle impact-based method" does not mean a general life cycle assessment (LCA) but rather the elements in LCA used to quantify toxicity potentials). We discovered that both CFL and LED bulbs are categorized as hazardous, due to excessive levels of lead (Pb) leachability (132 and 44 mg/L, respectively; regulatory limit: 5) and the high contents of copper (111,000 and 31,600 mg/kg, respectively; limit: 2500), lead (3860 mg/kg for the CFL bulb; limit: 1000), and zinc (34,500 mg/kg for the CFL bulb; limit: 5000), while the incandescent bulb is not hazardous (note that the results for CFL bulbs excluded mercury vapor not captured during sample preparation). The CFLs and LEDs have higher resource depletion and toxicity potentials than the incandescent bulb due primarily to their high aluminum, copper, gold, lead, silver, and zinc. Comparing the bulbs on an equivalent quantity basis with respect to the expected lifetimes of

  17. Potential environmental impacts from the metals in incandescent, compact fluorescent lamp (CFL), and light-emitting diode (LED) bulbs.

    PubMed

    Lim, Seong-Rin; Kang, Daniel; Ogunseitan, Oladele A; Schoenung, Julie M

    2013-01-15

    Artificial lighting systems are transitioning from incandescent to compact fluorescent lamp (CFL) and light-emitting diode (LED) bulbs in response to the U.S. Energy Independence and Security Act and the EU Ecodesign Directive, which leads to energy savings and reduced greenhouse gas emissions. Although CFLs and LEDs are more energy-efficient than incandescent bulbs, they require more metal-containing components. There is uncertainty about the potential environmental impacts of these components and whether special provisions must be made for their disposal at the end of useful life. Therefore, the objective of this study is to analyze the resource depletion and toxicity potentials from the metals in incandescent, CFL, and LED bulbs to complement the development of sustainable energy policy. We assessed the potentials by examining whether the lighting products are to be categorized as hazardous waste under existing U.S. federal and California state regulations and by applying life cycle impact-based and hazard-based assessment methods (note that "life cycle impact-based method" does not mean a general life cycle assessment (LCA) but rather the elements in LCA used to quantify toxicity potentials). We discovered that both CFL and LED bulbs are categorized as hazardous, due to excessive levels of lead (Pb) leachability (132 and 44 mg/L, respectively; regulatory limit: 5) and the high contents of copper (111,000 and 31,600 mg/kg, respectively; limit: 2500), lead (3860 mg/kg for the CFL bulb; limit: 1000), and zinc (34,500 mg/kg for the CFL bulb; limit: 5000), while the incandescent bulb is not hazardous (note that the results for CFL bulbs excluded mercury vapor not captured during sample preparation). The CFLs and LEDs have higher resource depletion and toxicity potentials than the incandescent bulb due primarily to their high aluminum, copper, gold, lead, silver, and zinc. Comparing the bulbs on an equivalent quantity basis with respect to the expected lifetimes of

  18. Influences of pH, urea and metal ions on the interaction of sinomenine with Lysozyme by steady state fluorescence spectroscopy.

    PubMed

    Li, Daojin; Zhang, Tian; Ji, Baoming

    2014-09-15

    The interaction between sinomenine and Lysozyme (Lys) in aqueous solution has been systemically investigated by fluorescence spectroscopic techniques at pH 7.4. The quenching rate constants and binding constants calculated indicated the static quenching mechanism and medium binding force. The effect of sinomenine on the conformation of Lys was analyzed using synchronous fluorescence and three-dimensional (3D) fluorescence. In addition, influence of pH on the binding of sinomenine to Lys was investigated and the binding ability of the drug to Lys deceased under other pH conditions (pH 9.0, 3.5, and 1.9) as compared with that at pH 7.4. As compared with the binding ability of sinomenine to native Lys, that of sinomenine to denatured Lys deceases dramatically. Furthermore, the effect of many metal ions on the binding constant of sinomenine with Lys was investigated.

  19. Influences of pH, urea and metal ions on the interaction of sinomenine with Lysozyme by steady state fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Daojin; Zhang, Tian; Ji, Baoming

    2014-09-01

    The interaction between sinomenine and Lysozyme (Lys) in aqueous solution has been systemically investigated by fluorescence spectroscopic techniques at pH 7.4. The quenching rate constants and binding constants calculated indicated the static quenching mechanism and medium binding force. The effect of sinomenine on the conformation of Lys was analyzed using synchronous fluorescence and three-dimensional (3D) fluorescence. In addition, influence of pH on the binding of sinomenine to Lys was investigated and the binding ability of the drug to Lys deceased under other pH conditions (pH 9.0, 3.5, and 1.9) as compared with that at pH 7.4. As compared with the binding ability of sinomenine to native Lys, that of sinomenine to denatured Lys deceases dramatically. Furthermore, the effect of many metal ions on the binding constant of sinomenine with Lys was investigated.

  20. Fluorescence quenching study of 2,6-bis(5-(4-methylphenyl)-1-H-pyrazol-3-yl)pyridine with metal ions.

    PubMed

    Liu, Hua; Li, Fang-Xiong; Pi, Yan; Wang, Dun-Jia; Hu, Yan-Jun; Zheng, Jing

    2015-06-15

    A novel bispyrazole derivative 2,6-bis(5-(4-methylphenyl)-1-H-pyrazol-3-yl)pyridine was synthesized and its structure was confirmed by (1)H NMR, FTIR, MS techniques and elemental analysis. The binding interactions of BMPP with Cd(2+), Co(2+), Pb(2+) and Cu(2+) ions were investigated in MeOH-H2O solution by fluorescence quenching technique at two temperatures (25 and 35°C). Their quenching constants KSV, binding constants K, binding sites n and thermodynamic parameters (ΔH, ΔG and ΔS) were determined. The results indicated that the metal ions quenched the intrinsic fluorescence of the bispyrazole by forming the bispyrazole-metal complexes and their quenching process was a static quenching mechanism. In addition, the process of interaction was spontaneous and mainly ΔS-driven.

  1. Mapping the Microstructural Location of Salts and Metals in Sea Ice with X-Ray Micro-Fluorescence Spectroscopy

    NASA Astrophysics Data System (ADS)

    Lieb-Lappen, R.; Leonard, J.; Obbard, R. W.

    2015-12-01

    Sea ice forms a permeable boundary between the ocean and the atmosphere, mediating chemical, physical, and transport processes that can have large impacts on a changing climate. It is a complex media composed of ice, brine, air pockets, and salt precipitates whose fine microstructure is constantly evolving with time and temperature. To gain insight of the processes occurring within the sea ice, it is key to have an understanding of how the different phases interact. Using synchrotron x-ray micro-fluorescence (XRF) at Argonne National Laboratory's Advanced Photon Source (APS), we examined the microstructural location of different salts and metals in Antarctic sea ice. In particular, we sought to determine whether these elements are found solely in brine channels and at grain boundaries or exist ubiquitously throughout the crystal lattice of ice. Further, we also investigated the spatial distribution of each impurity to determine how microstructure may vary within the sea ice column. Although it is well known that salts are expelled from the ice matrix during the freezing process and the bulk of impurities lies in brine inclusions and channels, providing quantitative and visual evidence with high resolution remains an ongoing process. XRF enables us to detect and map the precise microstructural and stratigraphic location of the constituent salts in sea ice. Cores were cut into 0.5 cm-thick slices every ten cm along the length of the core. At APS, a 2 mm x 2 mm region of each sample was scanned by an 18 kV X-ray beam and the resulting fluorescence signal detected using a silicon drift detector. By integrating the detected signal for the respective characteristic energy, we were able to obtain two-dimensional elemental maps with ten micron resolution for bromide, chloride, potassium, calcium, strontium, iron, copper, and zinc. Maps were compared to thin sections obtained under cross-polarizing lenses to identify particular features. We were able to show that salts

  2. Vibrational spectra of discrete UO22+ halide complexes in the gas phase

    SciTech Connect

    Gary S. Groenewold; Michael J. van Stipdonk; Wibe A. de Jong; Jos Oomens; Garold L. Gresham

    2010-11-01

    The intrinsic binding of halide ions to the metal center in the uranyl molecule is a topic of ongoing research interest in both the actinide separations and theoretical communities. Investigations of structure in the condensed phases is frequently obfuscated by solvent interactions, that can alter ligand binding and spectroscopic properties. The approach taken in this study is to move the uranyl halide complexes into the gas phase where they are free from solvent interactions, and then interrogate their vibrational spectroscopy using infrared multiple photon dissociation (IRMPD). The spectra of cationic coordination complexes having the composition [UO2(X)(ACO)3]+ (X = F, Cl, Br and I; ACO = acetone) were acquired using electrospray for ion formation, and monitoring the ion signal from the photoelimination of ACO ligands. The studies showed that the asymmetric v3 UO2 frequency was insensitive to halide identity as X was varied from Cl to I, suggesting that in these pseudo octahedral complexes, changing the nucleophilicity of the halide did not appreciably alter the binding in the complex. The v3 peak in the spectrum of the F-containing complex was ~ 10 cm-1 lower indicating stronger coordination in this complex. Similarly the ACO carbonyl stretches showed that the C=O frequency was relatively insensitive to the identity of the halide, although a modest shift to the blue was seen for the complexes with the more nucleophilic anions, consistent with the idea that they loosen solvent binding. Surprisingly, the v1 stretch was activated when the softer anions Cl, Br and I were present in the complexes. IR studies of the anionic complexes were conducted by measuring the v3 UO2 frequencies of [UO2X3]-, where X = Cl-, Br- and I-. The trifluoro complex could not be photodissociated. In these negatively charged complexes, the UO2 v3 values decreased with increasing anion nucleophilicity. This observation was consistent with DFT calculations that indicated that dissociation

  3. A label-free aptasensor for highly sensitive detection of ATP and thrombin based on metal-enhanced PicoGreen fluorescence.

    PubMed

    Wang, Kaiyu; Liao, Jian; Yang, Xiangyue; Zhao, Meng; Chen, Min; Yao, Weirong; Tan, Weihong; Lan, Xiaopeng

    2015-01-15

    A label-free fluorescence aptasensor for highly selective and sensitive detection of ATP and thrombin was developed by using PicoGreen (PG) as signal molecule and surface-bound metal-enhanced fluorescence (MEF) substrates (silver island films, SIFs) as signal enhancers. On binding with ATP or thrombin, aptamers undergo structure switching, leading to a reduction of fluorescence intensity of PG. Chang of fluorescence intensity can be magnified by SIFs. The limit of detection for ATP and thrombin is 1.3 nM and 0.073 nM, respectively. The fluorescence quenching efficiency is linear in the logarithmic scale with ATP concentration range from 10 nM to 100 μM (R(2)=0.995) and thrombin concentration range from 0.1 nM to 100 nM (R(2)=0.997). The coefficients of variation of the intra-assay reproducibility and inter-assay reproducibility for ATP (10 μM) assay are 3.8% and 5.2%, respectively. In addition, the aptasensor is stable and can be reliably used for ATP measurement in biological samples. Overall, the aptasensor can be a useful and cost effective tool for the specific detection of ATP, thrombin and potentially other biomolecules in biological samples. PMID:25086329

  4. Enhanced 2-5 μm emission in Ho3+/Yb3+ codoped halide modified transparent tellurite glasses

    NASA Astrophysics Data System (ADS)

    Zhang, Wenjun; Lin, Jian; Jia, Yujie; Zhang, Shuo; Zhao, Junhong; Sun, Guangyao; Ye, Song; Ren, Junjiang; Rong, Liang

    2015-01-01

    Ho3+/Yb3+ codoped TeO2-WO3-ZnO-ZnX2(X = F, Cl) glasses were prepared by melt-quenching method. The absorption spectra, transmittance spectra, X-ray diffraction (XRD) curves, Raman spectra and mid-infrared fluorescence spectra were measured, along with the Judd-Ofelt intensity parameters, stimulated emission and absorption cross-sections were calculated to evaluate the effects of halide amount of the spectroscopic properties. It is shown that the introduction of an appropriate amount of halide can further improve the mid-infrared fluorescence intensity through an enhanced phonon-assisted energy transfer between Ho3+/Yb3+ ions and the energy transfer mechanisms are investigated quantitatively in detail by calculating energy transfer microparameters and phonon contribution ratios. The results indicate that this kind of glasses is a promising material for mid-infrared optical fiber.

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

    PubMed

    Chen, Kun; Tüysüz, Harun

    2015-11-01

    The booming development of organometal halide perovskites in recent years has prompted the exploration of morphology-control strategies to improve their performance in photovoltaic, photonic, and optoelectronic applications. However, the preparation of organometal halide perovskites with high hierarchical architecture is still highly challenging and a general morphology-control method for various organometal halide perovskites has not been achieved. A mild and scalable method to prepare organometal halide perovskites in inverse opal morphology is presented that uses a polystyrene-based artificial opal as hard template. Our method is flexible and compatible with different halides and organic ammonium compositions. Thus, the perovskite inverse opal maintains the advantage of straightforward structure and band gap engineering. Furthermore, optoelectronic investigations reveal that morphology exerted influence on the conducting nature of organometal halide perovskites. PMID:26376773

  6. Flame inhibition by hydrogen halides - Some spectroscopic measurements

    NASA Technical Reports Server (NTRS)

    Lerner, N. R.; Cagliostro, D. E.

    1973-01-01

    The far-ultraviolet absorption spectrum of an air-propane diffusion flame inhibited with hydrogen halides has been studied. Plots of the absorption of light by hydrogen halides as a function of position in the flame and also as a function of the amount of hydrogen halide added to the flame have been obtained. The hydrogen halides are shown to be more stable on the fuel side of the reaction zone than they are on the air side. Thermal diffusion is seen to be important in determining the concentration distribution of the heavier hydrogen halides in diffusion flames. The relationship between the concentration distribution of the hydrogen halides in the flame and the flame inhibition mechanism is discussed.

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

    PubMed

    Chen, Kun; Tüysüz, Harun

    2015-11-01

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

  8. Infrared spectra of FHF - in alkali halides

    NASA Astrophysics Data System (ADS)

    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.

  9. Halide electroadsorption on single crystal surfaces

    SciTech Connect

    Ocko, B.M.; Wandlowski, T.

    1997-07-01

    The structure and phase behavior of halides have been investigated on single crystals of Ag and Au using synchrotron x-ray scattering techniques. The adlayer coverages are potential dependent. For all halides studied the authors found that with increasing potential, at a critical potential, a disordered adlayer transforms into an ordered structure. Often these ordered phases are incommensurate and exhibit potential-dependent lateral separations (electrocompression). The authors have analyzed the electrocompression in terms of a model which includes lateral interactions and partial charge. A continuous compression is not observed for Br on Ag(100). Rather, they find that the adsorption is site-specific (lattice gas) in both the ordered and disordered phases. The coverage increases with increasing potential and at a critical potential the disordered phase transforms to a well-ordered commensurate structure.

  10. Lanthanide-halide based humidity indicators

    DOEpatents

    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.

  11. Analyses of Heavy Metal Contents in the Bulk Atmospheric Aerosols Simultaneously Collected at Okinawa Archipelago, Japan by Using X-ray fluorescence spectrometric method (XRF)

    NASA Astrophysics Data System (ADS)

    Oshiro, Y.; ITOH, A.; Azechi, S.; Somada, Y.; Handa, D.; Miyagi, Y.; Arakaki, T.; Tanahara, A.

    2012-12-01

    We studied heavy metal contents of bulk atmospheric aerosols using an X-ray fluorescence spectrometric method (XRF). The XRF method enables us to analyze heavy metal contents in the bulk aerosols rapidly without any chemical pretreatments. We used an energy dispersive X-ray fluorescence spectrometer that is compact and portable. We prepared several different amounts of standard reference materials (referred to "SRM", NIES No.28 of Japanese National Institute of Environmental Studies) on quartz filters for calibration curves in two different methods; 1) water-insoluble materials were collected after dispersing SRM in pure water and filtered with the quartz filters ("wet method"), and 2) SRM was dispersed in air in the plastic container and the aerosols were collected by using the low-volume air sampler ("dry method"). Good linear relationships between X-ray intensity and amount of aerosols on the filter were seen in the following 9 metals; Al, K, Ti, V, Fe, Ni, Rb, Ba, and Pb (with wet method) and 12 metals; K, Ti, Fe, Ni, Rb, Ba, Pb, Sr, Ca, Mn, Zn, and Cu (with dry method). Furthermore, we evaluated quantitative responses of XRF method by comparing with the metal contents determined by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS) after acid-digestion. We then used XRF method to determine heavy metal contents in authentic atmospheric aerosols collected in Okinawa islands, Japan. We simultaneously collected bulk aerosol samples by using identical high-volume air samplers at 3 islands; Cape Hedo Atmospheric Aerosol Monitoring Station (CHAAMS, Okinawa island), Kume island (ca. 160 km south-west of CHAAMS), and Minami-Daitou island (ca. 320 km south-east of CHAAMS). We report and discuss spatial and temporal distribution of heavy metals determined by the XRF method in the bulk atmospheric aerosols collected at the three islands during June 2008 to June 2010, and for CHAAMS during June 2008 to October 2012.

  12. Inferring the Geometry of Fourth-Period Metallic Elements in Arabidopsis thaliana Seeds using Synchrotron-Based Multi-Angle X-ray Fluorescence Mapping

    PubMed Central

    Young, Lester; Westcott, Neil; Christensen, Colleen; Terry, Jeff; Lydiate, Derek; Reaney, Martin

    2007-01-01

    Background Improving our knowledge of plant metal metabolism is facilitated by the use of analytical techniques to map the distribution of elements in tissues. One such technique is X-ray fluorescence (XRF), which has been used previously to map metal distribution in both two and three dimensions. One of the difficulties of mapping metal distribution in two dimensions is that it can be difficult to normalize for tissue thickness. When mapping metal distribution in three dimensions, the time required to collect the data can become a major constraint. In this article a compromise is suggested between two- and three-dimensional mapping using multi-angle XRF imaging. Methods A synchrotron-based XRF microprobe was used to map the distribution of K, Ca, Mn, Fe, Ni, Cu and Zn in whole Arabidopsis thaliana seeds. Relative concentrations of each element were determined by measuring fluorescence emitted from a 10 µm excitation beam at 13 keV. XRF spectra were collected from an array of points with 25 or 30 µm steps. Maps were recorded at 0 and 90°, or at 0, 60 and 120° for each seed. Using these data, circular or ellipsoidal cross-sections were modelled, and from these an apparent pathlength for the excitation beam was calculated to normalize the data. Elemental distribution was mapped in seeds from ecotype Columbia-4 plants, as well as the metal accumulation mutants manganese accumulator 1 (man1) and nicotianamine synthetase (nasx). Conclusions Multi-angle XRF imaging will be useful for mapping elemental distribution in plant tissues. It offers a compromise between two- and three-dimensional XRF mapping, as far as collection times, image resolution and ease of visualization. It is also complementary to other metal-mapping techniques. Mn, Fe and Cu had tissue-specific accumulation patterns. Metal accumulation patterns were different between seeds of the Col-4, man1 and nasx genotypes. PMID:17881334

  13. Inferring the Geometry of Fourth-Period Metallic Elements in Arabidopsis thaliana Seeds using Synchrotron-Based Multi-Angle X-ray Fluorescence Mapping

    SciTech Connect

    Young, Lester; Westcott, Neil; Christensen, Colleen; Terry, Jeff; Lydiate, Derek; Reaney, Martin

    2008-06-16

    Improving our knowledge of plant metal metabolism is facilitated by the use of analytical techniques to map the distribution of elements in tissues. One such technique is X-ray fluorescence (XRF), which has been used previously to map metal distribution in both two and three dimensions. One of the difficulties of mapping metal distribution in two dimensions is that it can be difficult to normalize for tissue thickness. When mapping metal distribution in three dimensions, the time required to collect the data can become a major constraint. In this article a compromise is suggested between two- and three-dimensional mapping using multi-angle XRF imaging. A synchrotron-based XRF microprobe was used to map the distribution of K, Ca, Mn, Fe, Ni, Cu and Zn in whole Arabidopsis thaliana seeds. Relative concentrations of each element were determined by measuring fluorescence emitted from a 10 {micro}m excitation beam at 13 keV. XRF spectra were collected from an array of points with 25 or 30 {micro}m steps. Maps were recorded at 0 and 90{sup o}, or at 0, 60 and 120{sup o} for each seed. Using these data, circular or ellipsoidal cross-sections were modelled, and from these an apparent pathlength for the excitation beam was calculated to normalize the data. Elemental distribution was mapped in seeds from ecotype Columbia-4 plants, as well as the metal accumulation mutants manganese accumulator 1 (man1) and nicotianamine synthetase (nasx). Multi-angle XRF imaging will be useful for mapping elemental distribution in plant tissues. It offers a compromise between two- and three-dimensional XRF mapping, as far as collection times, image resolution and ease of visualization. It is also complementary to other metal-mapping techniques. Mn, Fe and Cu had tissue-specific accumulation patterns. Metal accumulation patterns were different between seeds of the Col-4, man1 and nasx genotypes.

  14. Solvation at nanoscale: Alkali-halides in water clusters

    SciTech Connect

    Partanen, Leena; Mikkelae, Mikko-Heikki; Huttula, Marko; Tchaplyguine, Maxim; Zhang Chaofan; Andersson, Tomas; Bjoerneholm, Olle

    2013-01-28

    The solvation of alkali-halides in water clusters at nanoscale is studied by photoelectron spectroscopy using synchrotron radiation. The Na 2p, K 3p, Cl 2p, Br 3d, and I 4d core level binding energies have been measured for salt-containing water clusters. The results have been compared to those of alkali halide clusters and the dilute aqueous salt solutions. It is found that the alkali halides dissolve in small water clusters as ions.

  15. Lead halide perovskite nanowire lasers with low lasing thresholds and high quality factors.

    PubMed

    Zhu, Haiming; Fu, Yongping; Meng, Fei; Wu, Xiaoxi; Gong, Zizhou; Ding, Qi; Gustafsson, Martin V; Trinh, M Tuan; Jin, Song; Zhu, X-Y

    2015-06-01

    The remarkable performance of lead halide perovskites in solar cells can be attributed to the long carrier lifetimes and low non-radiative recombination rates, the same physical properties that are ideal for semiconductor lasers. Here, we show room-temperature and wavelength-tunable lasing from single-crystal lead halide perovskite nanowires with very low lasing thresholds (220 nJ cm(-2)) and high quality factors (Q ∼ 3,600). The lasing threshold corresponds to a charge carrier density as low as 1.5 × 10(16) cm(-3). Kinetic analysis based on time-resolved fluorescence reveals little charge carrier trapping in these single-crystal nanowires and gives estimated lasing quantum yields approaching 100%. Such lasing performance, coupled with the facile solution growth of single-crystal nanowires and the broad stoichiometry-dependent tunability of emission colour, makes lead halide perovskites ideal materials for the development of nanophotonics, in parallel with the rapid development in photovoltaics from the same materials.

  16. Lead halide perovskite nanowire lasers with low lasing thresholds and high quality factors

    NASA Astrophysics Data System (ADS)

    Zhu, Haiming; Fu, Yongping; Meng, Fei; Wu, Xiaoxi; Gong, Zizhou; Ding, Qi; Gustafsson, Martin V.; Trinh, M. Tuan; Jin, Song; Zhu, X.-Y.

    2015-06-01

    The remarkable performance of lead halide perovskites in solar cells can be attributed to the long carrier lifetimes and low non-radiative recombination rates, the same physical properties that are ideal for semiconductor lasers. Here, we show room-temperature and wavelength-tunable lasing from single-crystal lead halide perovskite nanowires with very low lasing thresholds (220 nJ cm-2) and high quality factors (Q ~ 3,600). The lasing threshold corresponds to a charge carrier density as low as 1.5 × 1016 cm-3. Kinetic analysis based on time-resolved fluorescence reveals little charge carrier trapping in these single-crystal nanowires and gives estimated lasing quantum yields approaching 100%. Such lasing performance, coupled with the facile solution growth of single-crystal nanowires and the broad stoichiometry-dependent tunability of emission colour, makes lead halide perovskites ideal materials for the development of nanophotonics, in parallel with the rapid development in photovoltaics from the same materials.

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

    PubMed

    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

  18. Rapid and non-destructive analysis of metallic dental restorations using X-ray fluorescence spectra and light-element sampling tools

    NASA Astrophysics Data System (ADS)

    Furuhashi, K.; Uo, M.; Kitagawa, Y.; Watari, F.

    2012-12-01

    IntroductionRecently, allergic diseases caused by dental metals have been increasing. Therefore, rapid and accurate analytical methods for the metal restorations in the oral cavities of patients are required. The purpose of this study was to develop a non-destructive extraction method for dental alloys, along with a subsequent, rapid and accurate elemental analysis. Materials and methodSamples were obtained by polishing the surfaces of metal restorations using a dental rotating tool with disposable buffs and polishing pastes. As materials for the analysis, three dental alloys were used. To compare the sampling and analysis efficiencies, two buffs and seven pastes were used. After polishing the surface of a metal restoration, the buff was analyzed using X-ray scanning analytical microscopy (XSAM). ResultsThe efficiency of the analysis was judged based on the sampling rate achieved and the absence of disturbing elements in the background in fluorescence X-ray spectra. The best results were obtained for the combination of TexMet as a buff with diamond as a paste. This combination produced a good collection efficiency and a plain background in the fluorescence X-ray spectra, resulting in a high precision of the analysis.

  19. Lanthanide doped strontium-barium cesium halide scintillators

    SciTech Connect

    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.

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

    USGS Publications Warehouse

    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.

  1. A sensitive and selective sensor for biothiols based on the turn-on fluorescence of the Fe-MIL-88 metal-organic frameworks-hydrogen peroxide system.

    PubMed

    Sun, Zheng Juan; Jiang, Jun Ze; Li, Yuan Fang

    2015-12-21

    Herein, we present a novel strategy based on a "turn-on" fluorescence system made up of metal-organic frameworks Fe-MIL-88 and H2O2 for detecting biothiols in human serum. The nonfluorescent Fe-MIL-88 gives weak fluorescence in the presence of H2O2. Interestingly, it was found that biothiols such as glutathione (GSH), cysteine (Cys) or homocysteine (Hcy) could induce fluorescence turn-on of the Fe-MIL-88/H2O2 system. Under optimal conditions, the relative fluorescence intensity exhibited a good linear relationship in the range from 50 nM-10 μM for GSH (r = 0.994), 50 nM-10 μM for Cys (r = 0.990), and 50 nM-10 μM (r = 0.992) for Hcy; the detection limits of GSH, Cys and Hcy were 30 nM, 40 nM, and 40 nM respectively. Mechanism investigation reveals that biothiols could associate with Fe-MIL-88 via hydrogen bonding and electrostatic interaction followed by redox reaction between biothiols and Fe(3+) present in the Fe-MIL-88, Fe(3+) was thus reduced to Fe(2+), and then Fe(2+) could efficiently catalyze the decomposition of H2O2 to yield ˙OH radicals through the Fenton reaction. Besides, biothiols were able to reduce H2O2 to produce ˙OH radicals directly. Thus the Fe-MIL-88 as well as biothiols could cooperatively contribute to the activation of H2O2 to generate higher amounts of ˙OH radicals, which in turn oxidize the free ligand terephthalic acid (BDC) outside or within the Fe-MIL-88 structure to strongly fluorescent hydroxylated terephthalic acid (OHBDC), thereby turning on the fluorescence.

  2. A sensitive and selective sensor for biothiols based on the turn-on fluorescence of the Fe-MIL-88 metal-organic frameworks-hydrogen peroxide system.

    PubMed

    Sun, Zheng Juan; Jiang, Jun Ze; Li, Yuan Fang

    2015-12-21

    Herein, we present a novel strategy based on a "turn-on" fluorescence system made up of metal-organic frameworks Fe-MIL-88 and H2O2 for detecting biothiols in human serum. The nonfluorescent Fe-MIL-88 gives weak fluorescence in the presence of H2O2. Interestingly, it was found that biothiols such as glutathione (GSH), cysteine (Cys) or homocysteine (Hcy) could induce fluorescence turn-on of the Fe-MIL-88/H2O2 system. Under optimal conditions, the relative fluorescence intensity exhibited a good linear relationship in the range from 50 nM-10 μM for GSH (r = 0.994), 50 nM-10 μM for Cys (r = 0.990), and 50 nM-10 μM (r = 0.992) for Hcy; the detection limits of GSH, Cys and Hcy were 30 nM, 40 nM, and 40 nM respectively. Mechanism investigation reveals that biothiols could associate with Fe-MIL-88 via hydrogen bonding and electrostatic interaction followed by redox reaction between biothiols and Fe(3+) present in the Fe-MIL-88, Fe(3+) was thus reduced to Fe(2+), and then Fe(2+) could efficiently catalyze the decomposition of H2O2 to yield ˙OH radicals through the Fenton reaction. Besides, biothiols were able to reduce H2O2 to produce ˙OH radicals directly. Thus the Fe-MIL-88 as well as biothiols could cooperatively contribute to the activation of H2O2 to generate higher amounts of ˙OH radicals, which in turn oxidize the free ligand terephthalic acid (BDC) outside or within the Fe-MIL-88 structure to strongly fluorescent hydroxylated terephthalic acid (OHBDC), thereby turning on the fluorescence. PMID:26568205

  3. Conversion of methyl halides to hydrocarbons on basic zeolites. A discovery by in situ NMR

    SciTech Connect

    Murray, D.K.; Chang, J.W.; Haw, J.F. )

    1993-06-02

    It is shown that methyl halides (I, Br, Cl) react to form ethylene and other hydrocarbons on basic, alkali metal-exchanged zeolites at low temperatures. For example, methyl iodide is converted to ethylene on CsX zeolite at ca. 500 K. The order of reactivity of various catalyst/adsorbate combinations is consistent with the predictions of elementary chemical principles. The order of reactivity of the methyl halides follows the expected leaving-group trend. The activity of the catalyst framework correlates with its basicity (or nucleophilicity). All reactions were performed in a batch mode in sealed magic angle spinning (MAS) rotors while the contents were continuously monitored by in situ [sup 13]C NMR. Methyl iodide reacts on CsX below room temperature to form a framework-bound methoxy species in high yield. An analogous ethoxy species readily formed from ethyliodide. These species were characterized in detail. The ethoxy species was quantitatively converted to ethylene below 500 K. [sup 133]Cs MAS NMR was used to characterize the interactions of methyl iodide and other adsorbates with the cation in zeolite CsZSM-5. Solvation of the alkali metal cation was reflected in large, loading-dependent chemical shifts for [sup 133]Cs. Interactions between the cation and adsorbates were also reflected in the [sup 13]C shifts of the alkyl halides and ethylene. The cumulative evidence suggests a mechanism for carbon-carbon bond formation analogous to one proposed by Chang and co-workers for methanol-to-gasoline chemistry on acidic zeolites (J. Chem. Soc., Chem. Commun, 1987, 1320) that involves framework-bound methoxy and ethoxy species. The mechanism for methyl halide conversion is proposed to include roles for the basicity of the zeolite framework as well as the Lewis acidity of the cation. 68 refs., 18 figs., 2 tabs.

  4. [Design and synthesis of imine compound for metal cation logical gates recognition and setup of double-control fluorescent molecule switch].

    PubMed

    Huang, Tao; Zhu, Yu-lian; Dai, Xue-qin; Zhang, Qi; Huang, Yan

    2011-07-01

    The Schiff base's reduced product N,N-bis(4-methoxybenzyl) ethane-1,2-diamine, which was used as a receptor L, was designed and synthesized for the first time in the present article. It was found that Cu2+ and Fe3+ could quench L in fluorescence observably and Zn2+ and Cd2+ could enhance L remarkably. So the two pair metal cation could set up "OR" logical gate relation with the receptor molecule L, then a logical recognition system be formed. The data of resolved ZnL's single crystal indicated that ZnL belonged to monoclinic (CCDC No. 747994). Integrated spectrum instrument was used to characterize the structure of its alike series of complex compound. According to ZnL's excellent fluorescence character and the ability to exchange with contiguous metal cation, ZnZ+/ZnL/Co2+, Zn2+/ZnL/Nit+ fluorescent molecule switch was designed. It is hoped that the work above could be positive for the development of molecule computer, bio-intellectualized inspection technology (therapy) and instrument.

  5. [Design and synthesis of imine compound for metal cation logical gates recognition and setup of double-control fluorescent molecule switch].

    PubMed

    Huang, Tao; Zhu, Yu-lian; Dai, Xue-qin; Zhang, Qi; Huang, Yan

    2011-07-01

    The Schiff base's reduced product N,N-bis(4-methoxybenzyl) ethane-1,2-diamine, which was used as a receptor L, was designed and synthesized for the first time in the present article. It was found that Cu2+ and Fe3+ could quench L in fluorescence observably and Zn2+ and Cd2+ could enhance L remarkably. So the two pair metal cation could set up "OR" logical gate relation with the receptor molecule L, then a logical recognition system be formed. The data of resolved ZnL's single crystal indicated that ZnL belonged to monoclinic (CCDC No. 747994). Integrated spectrum instrument was used to characterize the structure of its alike series of complex compound. According to ZnL's excellent fluorescence character and the ability to exchange with contiguous metal cation, ZnZ+/ZnL/Co2+, Zn2+/ZnL/Nit+ fluorescent molecule switch was designed. It is hoped that the work above could be positive for the development of molecule computer, bio-intellectualized inspection technology (therapy) and instrument. PMID:21942034

  6. Anthropogenic signature of sediment organic matter probed by UV-Visible and fluorescence spectroscopy and the association with heavy metal enrichment.

    PubMed

    He, Wei; Lee, Jong-Hyun; Hur, Jin

    2016-05-01

    Sediment organic matter (SOM) was extracted in an alkaline solution from 43 stream sediments in order to explore the anthropogenic signatures. The SOM spectroscopic characteristics including excitation-emission matrix (EEM)-parallel factor analysis (PARAFAC) were compared for five sampling site groups classified by the anthropogenic variables of land use, population density, the loadings of organics and nutrients, and metal enrichment. The conventional spectroscopic characteristics including specific UV absorbance, absorbance ratio, and humification index did not properly discriminate among the different cluster groups except in the case of metal enrichment. Of the four decomposed PARAFAC components, humic-like and tryptophan-like fluorescence responded negatively and positively, respectively, to increasing degrees of the anthropogenic variables except for land use. The anthropogenic enrichment of heavy metals was positively associated with the abundance of tryptophan-like component. In contrast, humic-like component, known to be mostly responsible for metal binding, exhibited a decreasing trend corresponding with metal enrichment. These conflicting trends can be attributed to the overwhelmed effects of the coupled discharges of heavy metals and organic pollutants into sediments. Our study suggests that the PARAFAC components can be used as functional signatures to probe the anthropogenic influences on sediments.

  7. Anthropogenic signature of sediment organic matter probed by UV-Visible and fluorescence spectroscopy and the association with heavy metal enrichment.

    PubMed

    He, Wei; Lee, Jong-Hyun; Hur, Jin

    2016-05-01

    Sediment organic matter (SOM) was extracted in an alkaline solution from 43 stream sediments in order to explore the anthropogenic signatures. The SOM spectroscopic characteristics including excitation-emission matrix (EEM)-parallel factor analysis (PARAFAC) were compared for five sampling site groups classified by the anthropogenic variables of land use, population density, the loadings of organics and nutrients, and metal enrichment. The conventional spectroscopic characteristics including specific UV absorbance, absorbance ratio, and humification index did not properly discriminate among the different cluster groups except in the case of metal enrichment. Of the four decomposed PARAFAC components, humic-like and tryptophan-like fluorescence responded negatively and positively, respectively, to increasing degrees of the anthropogenic variables except for land use. The anthropogenic enrichment of heavy metals was positively associated with the abundance of tryptophan-like component. In contrast, humic-like component, known to be mostly responsible for metal binding, exhibited a decreasing trend corresponding with metal enrichment. These conflicting trends can be attributed to the overwhelmed effects of the coupled discharges of heavy metals and organic pollutants into sediments. Our study suggests that the PARAFAC components can be used as functional signatures to probe the anthropogenic influences on sediments. PMID:26901475

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

    PubMed Central

    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 with alkyl halides and demonstrate that the selectivity arises from an unusual catalytic cycle that combines both polar and radical steps to form the new C-C bond. PMID:23952217

  9. Application of field portable X-ray fluorescence spectrometry to rapidly measure metal distributions in sediment cores

    NASA Astrophysics Data System (ADS)

    Kenna, T. C.; Nitsche, F. O.; Sands, E.; Bell, R. E.; Ryan, W. B.; Chillrud, S. N.; Ross, J. M.

    2006-12-01

    This paper describes a technique to rapidly assess sediment deposition on split, wet sediment cores shortly after collection and prior to the commencement of further analyses. To identify sediments impacted by twentieth century activities, we use down-core sediment distributions of lead as a proxy to identify sediments deposited within the last ~100 years. Increases in the concentration of lead and other industrial metals have been used in numerous studies to provide constraints on deposition timing. The timing of the majority of industrial activities generally overlaps with the period of the 20th century. As a result, elevated lead concentrations in sediments also allow the identification of sediments that likely contain other anthropogenic particle-reactive contaminants of concern. Our approach entails the measurement of lead and several other elements using an Innov-X Field Portable x- ray fluorescence spectrometer (XRF). Measurements are made at 5-10cm increments on split, wet sediment cores. Using in-situ wet-bulk density estimates obtained from our core logging system, we are able to calculate water content and correct XRF measurements to a dry weight basis. Confirmatory analyses performed on discrete sub-samples using established protocols that employ wet/dry determinations for water content, homogenization by grinding, total-digestion, and determination by ICP-MS indicate good agreement between the two techniques (r2 = 0.9183; n=24; p<0.0001). Based on deposition chronologies provided by excess Pb-210 and Cs-137, we use the presence of lead concentrations in sediments above natural background levels (~20ppm) as a proxy for identifying those sediments impacted by 20th century activities. Results from a sediment core collected in Haverstraw Bay indicate that environmental lead levels began to rise above natural background in the 1930s. Work to evaluate the instrument's suitability with regard to measuring additional elements in both wet and dry sediments and

  10. Bifunctional fluorescent carbon nanodots: green synthesis via soy milk and application as metal-free electrocatalysts for oxygen reduction.

    PubMed

    Zhu, Chengzhou; Zhai, Junfeng; Dong, Shaojun

    2012-09-28

    We demonstrated a facile and green approach to synthesize bifunctional fluorescent carbon nanodots via soy milk, which not only showed favorable photoluminescent properties, but also exhibited good electrocatalytic activity towards oxygen reduction reaction.

  11. Selective and Sensitive Detection of Heavy Metal Ions in 100% Aqueous Solution and Cells with a Fluorescence Chemosensor Based on Peptide Using Aggregation-Induced Emission.

    PubMed

    Neupane, Lok Nath; Oh, Eun-Taex; Park, Heon Joo; Lee, Keun-Hyeung

    2016-03-15

    A fluorescent peptidyl chemosensor for the detection of heavy metal ions in aqueous solution as well as in cells was synthesized on the basis of the peptide receptor for the metal ions using an aggregation-induced emission fluorophore. The peptidyl chemosensor (1) bearing tetraphenylethylene fluorophore showed an exclusively selective turn-on response to Hg(2+) among 16 metal ions in aqueous buffered solution containing NaCl. The peptidyl chemosensor complexed Hg(2+) ions and then aggregated in aqueous buffered solution, resulting in the significant enhancement (OFF-On) of emissions at around 470 nm. The fluorescent sensor showed a highly sensitive response to Hg(2+), and about 1.0 equiv of Hg(2+) was enough for the saturation of the emission intensity change. The detection limit (5.3 nM, R(2) = 0.99) of 1 for Hg(2+) ions was lower than the maximum allowable level of Hg(2+) in drinking water by EPA. Moreover, the peptidyl chemosensor penetrated live cells and detected intracellular Hg(2+) ions by the turn-on response.

  12. Selective and Sensitive Detection of Heavy Metal Ions in 100% Aqueous Solution and Cells with a Fluorescence Chemosensor Based on Peptide Using Aggregation-Induced Emission.

    PubMed

    Neupane, Lok Nath; Oh, Eun-Taex; Park, Heon Joo; Lee, Keun-Hyeung

    2016-03-15

    A fluorescent peptidyl chemosensor for the detection of heavy metal ions in aqueous solution as well as in cells was synthesized on the basis of the peptide receptor for the metal ions using an aggregation-induced emission fluorophore. The peptidyl chemosensor (1) bearing tetraphenylethylene fluorophore showed an exclusively selective turn-on response to Hg(2+) among 16 metal ions in aqueous buffered solution containing NaCl. The peptidyl chemosensor complexed Hg(2+) ions and then aggregated in aqueous buffered solution, resulting in the significant enhancement (OFF-On) of emissions at around 470 nm. The fluorescent sensor showed a highly sensitive response to Hg(2+), and about 1.0 equiv of Hg(2+) was enough for the saturation of the emission intensity change. The detection limit (5.3 nM, R(2) = 0.99) of 1 for Hg(2+) ions was lower than the maximum allowable level of Hg(2+) in drinking water by EPA. Moreover, the peptidyl chemosensor penetrated live cells and detected intracellular Hg(2+) ions by the turn-on response. PMID:26872241

  13. The Oxidation State of Europium in Halide Glasses

    PubMed Central

    Weber, J.K.R.; Vu, M.; Paßlick, C.; Schweizer, S.; Brown, D.E.; Johnson, C.E.; Johnson, J.A.

    2012-01-01

    The luminescent properties of divalent europium ions can be exploited to produce storage phosphors for x-ray imaging applications. The relatively high cost and limited availability of divalent europium halides makes it desirable to synthesize them from the readily available trivalent salts. In this work, samples of pure EuCl3 and fluoride glass melts doped with EuCl3 were processed at 700-800 °C in an inert atmosphere furnace. The Eu oxidation state in the resulting materials was determined using fluorescence and Mössbauer spectroscopy. Heat treatment of pure EuCl3 for 10 minutes at 710 °C resulted in a material comprising approximately equal amounts of Eu2+ and Eu3+. Glasses made using mixtures of EuCl2 and EuCl3 in the starting material contained both oxidation states. This paper describes the sample preparation and analysis and discusses the results in the context of chemical equilibria in the melts. PMID:22101252

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

    PubMed

    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

  15. Electron and bromine transfer reactions between metal carbonyl anions and metal carbonyl bromides. Crystal and molecular structure of dimeric indenyl molybdenum tricarbonyl

    SciTech Connect

    Striejewske, W.S.; See, R.F.; Churchill, M.R.; Atwood, J.D. )

    1993-11-01

    Reactions of metal carbonyl anions with metal carbonyl halides proceed by two separate paths. When the reactant anion is a strong nucleophile, the halogen is transferred, resulting in a new metal carbonyl halide and a new metal carbonyl anion as intermediates. The ultimate products, in this case, are the homobimetallic complexes. In cases where the reactant metal carbonyl anion is a poor nucleophile, a single electron transfer occurs, leading to the two homobimetallic complexes and to the heterobimetallic complex. Halide effects and possible indenyl effects are examined. The complex [Mo(indenyl)(CO)[sub 3

  16. Synthesis, spectral, thermal, fluorescence, antimicrobial, anthelmintic and DNA cleavage studies of mononuclear metal chelates of bi-dentate 2H-chromene-2-one Schiff base.

    PubMed

    Prabhakara, Chetan T; Patil, Sangamesh A; Kulkarni, Ajaykumar D; Naik, Vinod H; Manjunatha, M; Kinnal, Shivshankar M; Badami, Prema S

    2015-07-01

    The Co(II), Ni(II) and Cu(II) complexes have been synthesized with Schiff base (HL), derived from 8-formyl-7-hydroxy-4-methylcoumarin with benzylamine. The Schiff base and its metal complexes were structurally characterized based on IR, (1)H NMR, (13)C NMR, UV-visible, ESR, magnetic, thermal, fluorescence, mass and ESI-MS studies. The complexes are completely soluble in DMF and DMSO. The molar conductance values indicate that, all synthesized metal complexes are non-electrolytic in nature. Elemental analysis reveals [ML2(H2O)2] stoichiometry, here MCo(II), Ni(II) and Cu(II), L=deprotonated ligand. The coordination between metal ion and Schiff base was supported by IR data, through deprotonation of phenolic oxygen of coumarin and azomethine nitrogen atoms. Solution electronic spectral results unveiled that all the synthesized complexes posses six coordinated geometry around metal ion. Thermal studies suggest the presence of coordinated water molecules. The Schiff base and its metal complexes have been screened for their antibacterial (Escherichia coli, Pseudomonas aureginosa, Klebsiella pneumoniae and Staphylococcus aureus) and antifungal (Penicillium chrysogenum and Aspergillus niger), anthelmintic (Pheretima posthuma) and DNA cleavage (Calf Thymus DNA) activities.

  17. How specific halide adsorption varies hydrophobic interactions.

    PubMed

    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.

  18. Fluorescence-suppressed time-resolved Raman spectroscopy of pharmaceuticals using complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector.

    PubMed

    Rojalin, Tatu; Kurki, Lauri; Laaksonen, Timo; Viitala, Tapani; Kostamovaara, Juha; Gordon, Keith C; Galvis, Leonardo; Wachsmann-Hogiu, Sebastian; Strachan, Clare J; Yliperttula, Marjo

    2016-01-01

    In this work, we utilize a short-wavelength, 532-nm picosecond pulsed laser coupled with a time-gated complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector to acquire Raman spectra of several drugs of interest. With this approach, we are able to reveal previously unseen Raman features and suppress the fluorescence background of these drugs. Compared to traditional Raman setups, the present time-resolved technique has two major improvements. First, it is possible to overcome the strong fluorescence background that usually interferes with the much weaker Raman spectra. Second, using the high photon energy excitation light source, we are able to generate a stronger Raman signal compared to traditional instruments. In addition, observations in the time domain can be performed, thus enabling new capabilities in the field of Raman and fluorescence spectroscopy. With this system, we demonstrate for the first time the possibility of recording fluorescence-suppressed Raman spectra of solid, amorphous and crystalline, and non-photoluminescent and photoluminescent drugs such as caffeine, ranitidine hydrochloride, and indomethacin (amorphous and crystalline forms). The raw data acquired by utilizing only the picosecond pulsed laser and a CMOS SPAD detector could be used for identifying the compounds directly without any data processing. Moreover, to validate the accuracy of this time-resolved technique, we present density functional theory (DFT) calculations for a widely used gastric acid inhibitor, ranitidine hydrochloride. The obtained time-resolved Raman peaks were identified based on the calculations and existing literature. Raman spectra using non-time-resolved setups with continuous-wave 785- and 532-nm excitation lasers were used as reference data. Overall, this demonstration of time-resolved Raman and fluorescence measurements with a CMOS SPAD detector shows promise in diverse areas, including fundamental chemical research, the

  19. Fluorescence-suppressed time-resolved Raman spectroscopy of pharmaceuticals using complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector.

    PubMed

    Rojalin, Tatu; Kurki, Lauri; Laaksonen, Timo; Viitala, Tapani; Kostamovaara, Juha; Gordon, Keith C; Galvis, Leonardo; Wachsmann-Hogiu, Sebastian; Strachan, Clare J; Yliperttula, Marjo

    2016-01-01

    In this work, we utilize a short-wavelength, 532-nm picosecond pulsed laser coupled with a time-gated complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector to acquire Raman spectra of several drugs of interest. With this approach, we are able to reveal previously unseen Raman features and suppress the fluorescence background of these drugs. Compared to traditional Raman setups, the present time-resolved technique has two major improvements. First, it is possible to overcome the strong fluorescence background that usually interferes with the much weaker Raman spectra. Second, using the high photon energy excitation light source, we are able to generate a stronger Raman signal compared to traditional instruments. In addition, observations in the time domain can be performed, thus enabling new capabilities in the field of Raman and fluorescence spectroscopy. With this system, we demonstrate for the first time the possibility of recording fluorescence-suppressed Raman spectra of solid, amorphous and crystalline, and non-photoluminescent and photoluminescent drugs such as caffeine, ranitidine hydrochloride, and indomethacin (amorphous and crystalline forms). The raw data acquired by utilizing only the picosecond pulsed laser and a CMOS SPAD detector could be used for identifying the compounds directly without any data processing. Moreover, to validate the accuracy of this time-resolved technique, we present density functional theory (DFT) calculations for a widely used gastric acid inhibitor, ranitidine hydrochloride. The obtained time-resolved Raman peaks were identified based on the calculations and existing literature. Raman spectra using non-time-resolved setups with continuous-wave 785- and 532-nm excitation lasers were used as reference data. Overall, this demonstration of time-resolved Raman and fluorescence measurements with a CMOS SPAD detector shows promise in diverse areas, including fundamental chemical research, the

  20. Research Update: Luminescence in lead halide perovskites

    NASA Astrophysics Data System (ADS)

    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.