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Synthesis and characterization of diphosphine ligand substituted osmium and ruthenium clusters.

Description: The kinetics for the bridge-to-chelate isomerization of the dppe ligand in H4Ru4(CO)10(dppe) have been investigated by UV-vis and NMR spectroscopies over the temperature range of 308-328 K. The isomerization of the ligand-bridged cluster 1,2-H4Ru4(CO)10(dppe) was found to be reversible by 31P NMR spectroscopy, affording a Keq = 15.7 at 323 K in favor of the chelating dppe isomer. The forward (k1) and reverse (k-1) first-order rate constants for the reaction have been measured in different solvents and in the presence of ligand trapping agents (CO and PPh3). On the basis of the activation parameters and reaction rates that are unaffected by added CO and PPh3, a sequence involving the nondissociative migration of a phosphine moiety and two CO groups between basal ruthenium centers is proposed and discussed. The substitution of the MeCN ligands in the activated cluster 1,2-Os3(CO)10(MeCN)2 by the diphosphine ligands dppbz proceeds rapidly at room temperature to furnish a mixture of bridging and chelating Os3(CO)10(dppbz) isomers and the ortho-metalated product HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C4H4]. Thermolysis of the bridging isomer 1,2-Os3(CO)10(dppbz) under mild conditions gives the chelating isomer 1,1-Os3(CO)10(dppbz), molecular structure of both the isomers have been determined by X-ray crystallography. The kinetics for the ligand isomerization has been investigated by UV-vis and 1H NMR spectroscopy in toluene solution over the temperature range of 318-343 K. On the basis of kinetic data conducted in the presence of added CO and the Eyring activation parameters, a non-dissociative phosphine migration across one of the Os-Os bonds is proposed. Ortho metalation of one of the phenyl groups associated with the dppbz ligand is triggered by near-UV photolysis of the chelating cluster 1,1-Os3(CO)10(dppbz). The triosmium cluster 1,2-Os3(CO)10(MeCN)2 reacts with the diphosphine ligand 3,4­bis(diphenylphosphino)-5-methoxy-2(5)H-furanone (bmf) at 25 ºC to give the bmf-bridged cluster 1,2-Os3(CO)10(bmf). Heating 1,2-Os3(CO)10(bmf) leads to an equilibrium with the chelating isomer 1,1-Os3(CO)10(bmf). The molecular ...
Date: August 2007
Creator: Kandala, Srikanth
Partner: UNT Libraries

The Revival of Electrochemistry: Electrochemical Deposition of Metals in Semiconductor Related Research

Description: Adherent Cu films were electrodeposited onto polycrystalline W foils from purged solutions of 0.05 M CuSO4 in H2SO4 supporting electrolyte and 0.025 M CuCO3∙Cu(OH)2 in 0.32 M H3BO3 and corresponding HBF4 supporting electrolyte, both at pH = 1. Films were deposited under constant potential conditions at voltages between -0.6 V and -0.2 V versus Ag/AgCl. All films produced by pulses of 10 s duration were visible to the eye, copper colored, and survived a crude test called "the Scotch tape test", which involves sticking the scotch tape on the sample, then peeling off the tape and observing if the copper film peels off or not. Characterization by scanning electron microscopy (SEM)/energy dispersive X-ray (EDX) and X-ray photon spectroscopy (XPS) confirmed the presence of metallic Cu, with apparent dendritic growth. No sulfur impurity was observable by XPS or EDX. Kinetics measurements indicated that the Cu nucleation process in the sulfuric bath is slower than in the borate bath. In both baths, nucleation kinetics does not correspond to either instantaneous or progressive nucleation. Films deposited from 0.05 M CuSO4/H2SO4 solution at pH > 1 at -0.2 V exhibited poor adhesion and decreased Cu reduction current. In both borate and sulfate baths, small Cu nuclei are observable by SEM upon deposition at higher negative overpotentials, while only large nuclei (~ 1 micron or larger) are observed upon deposition at less negative potentials. Osmium metal has been successfully electrodeposited directly onto p-Si (100) from both Os3+ and Os4+ in both sulfuric and perchloric baths. This electrochemical deposition of osmium metal can provide sufficient amount of osmium which overcome ion beam implantation limitations. The deposited metal can undergo further processing to form osmium silicides, such as Os2Si3, which can be used as optical active materials. The higher osmium concentration results in large deposition currents and ...
Access: This item is restricted to the UNT Community Members at a UNT Libraries Location.
Date: August 2005
Creator: Wang, Chen
Partner: UNT Libraries

Growth and Characterization of β-Iron Disilicide, β-Iron Silicon Germanide, and Osmium Silicides

Description: The semiconducting silicides offer significant potential for use in optoelectronic devices. Full implementation of the materials, however, requires the ability to tailor the energy gap and band structure to permit the synthesis of heterojunctions. One promising approach is to alloy the silicides with Ge. As part of an investigation into the synthesis of semiconducting silicide heterostructures, a series of β-Fe(Si1−xGex)2 epilayer samples, with nominal alloy content in the range 0 < x < 0.15, have been prepared by molecular beam epitaxy on Si(100). I present results of the epitaxial and crystalline quality of the films, as determined by reflection high-energy electron diffraction, Rutherford backscattering spectroscopy, and double crystal x-ray diffraction, and of the band gap dependence on the alloy composition, as determined by Fourier transform infrared spectroscopy. A reduction in band gap was observed with increasing Ge content, in agreement with previous theoretical predictions. However Ge segregation was also observed in β-Fe(Si1−xGex)2 epilayers when x > 0.04. Osmium silicide films have been grown by molecular beam epitaxy on Si(100). The silicides have been grown using e-beam evaporation sources for both Os and Si onto Si(100) substrates at varying growth rates and temperatures ranging from 600-700ºC. The resulting films have been analyzed using reflection high-energy electron diffraction, Raman spectroscopy, reflectivity measurements, in-plane and out of plane X-ray diffraction and temperature dependent magnetotransport. A change in crystalline quality is observed with an increase in Si overpressure. For a lower silicon to osmium flux ration (JSi/JOs=1.5) both OsSi2 and Os2Si3 occur, whereas with a much larger Si overpressure (JSi/JOs>4), crystalline quality is greatly increased and only a single phase, Os2Si3, is present. The out-of-plane X-ray diffraction data show that the film grows along its [4 0 2] direction, with a good crystal quality as evidenced by the small FWHM in the rocking curve. ...
Date: August 2009
Creator: Cottier, Ryan James
Partner: UNT Libraries


Description: The diffraction techniques used at ANL to obtain scattering amplitudes and cross sections for elements and isotopes are briefly described; and some results obtained for Zr, Tc/sup 89/, Os, Os/sup 188/, Os/sup 189/, Os/sup 190/, Os/sup 192/, K, K /sup 39/, Rb, Rb/sup 85/, Ir, and Mg are summarized. (D.C.W.)
Date: October 1, 1963
Creator: Mueller, M H; Sidhu, S S; Heaton, L; Hitterman, R L & Knott, H W
Partner: UNT Libraries Government Documents Department

Kinetic Studies on C‐h Bond Activation in the Reaction of Triosmium Clusters with Diphosphine and Amidine Ligands

Description: The reaction of 1-(diphenylphosphino)-2-(diphenylphosphito)benzene (PP*) and Os3(CO)10(ACN) has been investigated. A combined experimental and computational study on the isomerization of 1,2-Os3(CO)10[μ-1,2-Ph2P(C6H4)P(OPh)2] (A) and 1,1-Os3(CO)10[μ-1,2-Ph2P(C6H4)P(OPh)2] (B) and reversible ortho-metalation exhibited by the triosmium cluster B are reported. The subsequent conversion of cluster B to the hydrido cluster HOs3(CO)9[μ-1,2-PhP(C6H4-η1)C6H4P(OPh)2] (E) and the benzyne-substituted cluster HOs3(CO)8(µ3-C6H4)[μ-1,2-PhP(C6H4)P(OPh)2] (N) has been established. All of these new clusters have been isolated and fully characterized in solution by IR and NMR spectroscopy; in addition, X-ray diffraction analyses have been performed on the clusters A, B, J, and N. The ortho-metalation reaction that gives cluster E is shown to be reversible, and the mechanism has been probed using selectively deuterated PP* isotopomers. Kinetic and thermodynamic isotope data, in conjunction with DFT calculations, are presented that support the existence of an intermediate unsaturated cluster in the ortho-metalation reaction. Due to interest in the coordination chemistry of formamidines, the non-symmetric amidine ligands PhNC(Me)NHPri, PhNC(Et)NHPri, and (2,4,6-Me3C6H2)NC(Me)NHPri, have been synthesized, and their reaction with Os3(CO)10(MeCN)2 has been investigated. Of the twelve new clusters prepared in section, seven have been structurally characterized by X-ray crystallography.
Date: December 2014
Creator: Yang, Li
Partner: UNT Libraries


Description: A method was developed for the determination of osmium by measuring the absorbancy of osmium tetroxide in CHCl/sub 3/. The osmium is first oxidized to the octavalent state and the osmium tetroxide which is formed is extracted selectively with CHCl/sub 3/. The ultraviolet absorption spectrum of OsO/sub 4/ in CHCl/sub 3/ has a series of absorption bands with peak absorbancies at 282, 289. 297, 304, and 312 m mu , and molar absorbancy indices of 1870. 1760, 1640, 1400, and 1000, respectively. For each wavelength the optimum concentration range for the determination of osmium was evaluated by the method of Ringbom. Only chloride and octavalent ruthenium interfere in the determination. By this method, from 0.4 to 3 mg of osmium can be determined with a coefficient of variation of 3%. (auth)
Date: June 1, 1959
Creator: Goldstein, G
Partner: UNT Libraries Government Documents Department

Coulomb excitation of radioactive nuclear beams in inverse kinematics

Description: Techniques for the measurement of B (E2:0{sub 1}{sup +} {r_arrow} 2{sub 1}{sup +}) values by Coulomb excitation of Radioactive Nuclear Beams in inverse kinematics are described. Using a thin, low Z target, the Coulomb excited beam nuclei will decay in flight downstream of the target. For long lifetimes (nanosecond range) these nuclei decay centimeters downstream of the target and for shorter lifetimes (picoseconds or less) they decay near the target. Corresponding to these two lifetime regimes two methods have been developed to measure {gamma} rays from the Coulomb excited nuclei: the lifetime method in which the lifetime of the excited state is deduced from the decay curve and the integral method in which the B(E2) value is extracted from the measured total Coulomb excitation cross section.
Date: 1996-10~
Creator: Zamfir, N. V.; Barton, C. J.; Brenner, D. S.; Casten, R. F.; Gill, R. L. & Zilges, A.
Partner: UNT Libraries Government Documents Department

The cyro-thermochromatographic separator (CTS): A new detectionand separation system for highly volatile osmium and hassium (element108) tetroxides

Description: We implemented a new concept for heavy element chemistry research using an ion separator to separate the desired products from the beam, transfer products and other undesirable by-products prior to chemical studies. First, a Recoil product Transfer Chamber (RTC) was designed and attached to the Berkeley Gas-filled Separator (BGS) to collect and transfer the recoiling products to the chemical separation system. The RTC consists of a wire-grid-supported thin mylar foil ({le}) 200 {micro}g/cm{sup 2} that separates the BGS detector chamber, at 1.3 mbar pressure, from the chemistry system at different pressures ranging from 480 mbar to 2000 mbar. The overall transport efficiency ranged between 30% and 15%, compared to the activity measured in the focal plane detector of the BGS. The CTS was designed as a separation and {alpha}-decay detection system for the highly volatile tetroxides of osmium and hassium, element 108. The CTS, shown in figure 1, consists of two rows of 32-{alpha} detectors arranged along a negative temperature gradient. The tetroxides adsorb on the surface of one of the silicone photodiodes at a certain deposition temperature, and the nuclide is then identified by the {alpha}-decay. To test the CTS with the expected hassium homologue osmium, different {alpha}-active osmium isotopes were produced using the nuclear reactions {sup 118}Sn({sup 56}Fe, 4,5n) {sup 170,169}Os and {sup 120}Sn({sup 56}Fe, 4,5n) {sup 172,171}Os. After preseparation in the BGS, a mixture of 90% helium and 10% oxygen was used to transport the osmium to a quartz tube heated to 1225 K, where OsO{sub 4} was formed. The negative temperature gradient in the CTS ranged from 248 K to 173 K. Using a flow rate of 500 mL/min, most of the osmium activity was adsorbed at a temperature of about 203 K. From the measured {alpha}-activity distribution, an adsorption enthalpy of 40 {+-} 1 kJ/mol ...
Date: March 8, 2002
Creator: Kirbach, U.W.; Folden III, C.M.; Ginter, T.N.; Gregorich, K.E.; Lee, D.M.; Ninov, V. et al.
Partner: UNT Libraries Government Documents Department

Superdeformation and hyperdeformation at high spin

Description: A short review of theoretical and experimental studies of superdeformation and hyperdeformation is presented. Recent results, based on calculations carried out in a four dimensional deformation space, are presented. Very extended nuclear shapes ranging in mass from A=150 to A=200 are discussed.
Date: August 1, 1995
Creator: Chasman, R.R.
Partner: UNT Libraries Government Documents Department

Catalytic applications of mono- and dinuclear complexes containing metal-carbon sigma bonds. Final report, November 1, 1993--October 31, 1996

Description: This report discusses results from several studies involved in the project. Investigations include: vibrational models for surface olefins and alkylidenes; mechanism of the formation and fragmentation of diosmacyclobutanes; reaction of dienes and allenes with diosmacyclobutanes; determination by nematic phase NMR of the structure of mononuclear and dinuclear ethylene complexes of osmium; and generation of ``coordinatively unsaturated`` complexes by protonation of methyl osmium complexes.
Date: December 31, 1996
Creator: Norton, J.R.
Partner: UNT Libraries Government Documents Department

Nuclear excitation by electronic transition (NEET).

Description: We present a report on recent measurements using the Advanced Photon Source at Argonne National Laboratory to explore the phenomenon of Nuclear Excitation by Electronic Transition (NEET) in the {sup 189}Os atomic/nuclear system.
Date: April 28, 1999
Creator: Ahmad, I.; Dunford, R. W.; Esbensen, H.; Gemmell, D. S.; Kanter, E. P.; Kraessig, B. et al.
Partner: UNT Libraries Government Documents Department

Synthetic, Mechanistic, and Structural Studies of Polynuclear Metal Clusters and Hydrazido-Substituted Tantalum(V) Compounds

Description: A combined experimental and computational study on the reversible ortho-metalation exhibited by the triosmium cluster Os3(CO)10(dppm) (dppm = 1,1-bis(diphenylphosphino)methane is reported. The conversion of nonacarbonyl cluster HOs3(CO)9[&#61549;-PhP(C6H4)CH2PPh2] to Os3(CO)10(dppm) is independent of added CO and exhibits a significant inverse equilibrium isotope effect (EIE). Reductive coupling of the C-H bond in HOs3(CO)9[&#61549;-PhP(C6H4)CH2PPh2] leads to the formation of agostic C-H and two distinct aryl-&#960; species prior to the rate-limiting formation of the unsaturated cluster Os3(CO)9(dppm). Heating the unsaturated dimer H2Re2(CO)8 with Cp*Rh(CO)2 (Cp* = 1,2,3,4,5-pentamethylcyclopentadiene) at elevated temperature affords the new trimetallic clusters H2RhRe2Cp*(CO)9 and HRh2ReCp*2(CO)6, and the spiked-triangular cluster HRhRe3Cp*(CO)14. H2Re2(CO)8 reacts with Cp*2Rh2(CO)2 under identical conditions to furnish H2RhRe2Cp*(CO)9 and HRh2ReCp*2(CO)6 as the principal products, in addition to the tetrahedral cluster H2Rh2Re2Cp*2(CO)8. H2RhRe2Cp*(CO)9 undergoes facile fragmentation in the presence of halogenated solvents and the thiols RSH (where R = H, C6H4Me-p) to afford the structurally characterized products Cp*Rh(&#61549;-Cl)3Re(CO)3, S2Rh3Cp*(CO)4, Cp*Rh(&#61549;-Cl)(&#61549;-SC6H4Me-p)2Re(CO)3, and Cp*Rh(&#61549;-SC6H4Me-p)3Re(CO)3. The new hydrazido-substituted compounds TaCl(NMe2)3[N(TMS)NMe2] (TMS = tetramethylsilyl) and Ta(NMe2)4[N(TMS)NMe2] have been synthesized and their structures established by X-ray crystallography. The latter product represents the first structurally characterized octahedral tantalum(V) complex containing a single hydrazido(I) ligand in an all-nitrogen coordinated environment about the metal center. The fluxional properties of the amido and hydrazido ligands in these new compounds have been established by VT 1H NMR spectroscopy (VT = variable temperature). Preliminary data using Ta(NMe2)4[N(TMS)NMe2] as an ALD (ALD = atomic layer deposition) precursor for the preparation of tantalum nitride and tantalum oxide thin films are presented.
Date: December 2010
Creator: Huang, Shih-huang
Partner: UNT Libraries

Investigation of Selected Optically-Active Nanosystems Fashioned using Ion Implantation

Description: Opto-electronic semiconductor technology continues to grow at an accelerated pace, as the industry seeks to perfect devices such as light emitting diodes for purposes of optical processing and communication. A strive for greater efficiency with shrinking device dimensions, continually pushes the technology from both a design and materials aspect. Nanosystems such a quantum dots, also face new material engineering challenges as they enter the realm of quantum mechanics, with each system and material having markedly different electronic properties. Traditionally, the semiconductor industry has focused on materials such Group II-VI and III-V compounds as the basis material for future opto-electronic needs. Unfortunately, these material systems can be expensive and have difficulties integrating into current Si-based technology. The industry is reluctant to leave silicon due in part to silicon's high quality oxide, and the enormous amount of research invested into silicon based circuit fabrication. Although recently materials such as GaN are starting to dominate the electro-optical industry since a Si-based substitute has not been found. The purpose of the dissertation was to examine several promising systems that could be easily integrated into current Si-based technology and also be produced using simple inexpensive fabrication techniques such ion implantation. The development of optically active nano-sized precipitates in silica to form the active layer of an opto-electronic device was achieved with ion implantation and thermal annealing. Three material systems were investigated. These systems consisted of carbon, silicon and metal silicide based nanocrystals. The physical morphology and electronic properties were monitored using a variety of material characterization techniques. Rutherford backscattering/channeling were used to monitor elemental concentrations, photoluminescence was used to monitor the opto-electronic properties and transmission electron microscopy was used to study the intricate morphology of individual precipitates. The electronic properties and the morphology were studied as a function of implant dose, anneal times and anneal ...
Date: May 2006
Creator: Mitchell, Lee
Partner: UNT Libraries

Excited State Processes in Transition Metal Complexes, Redox Splitting in Soluble Polymers

Description: The photochemical and photophysical properties of polypyridyl complexes of Ru, Os, and Re have been investigated by transient absorption, emission, resonance raman and infrared spectroscopies. The latter technique has been especially useful in defining the acceptor ligand in metal-to-ligand charge transfer (MLCT) excited states and probing the details of excited state electronic and molecular structure. Derivatives of these complexes have been attached to soluble polystyrene polymers. In the resulting metal complex polymer composites it has been possible to demonstrate long range energy transfer and the existence of an antenna effect and create a mimic for the active site in the photosynthetic membrane.
Date: August 8, 2002
Creator: Meyer, T.J. & Papanikolas, J.M.
Partner: UNT Libraries Government Documents Department

Analysis of a reported magnetic monopole

Description: It is shown that there are several substantive errors in a previous work on a cosmic ray event which is consistent with the hypothesis that it was caused by a magnetic monopole. It is shown that the data points fit to the hypothesis that the responsible particle is a platinum nucleus fragmenting to osmium and then to tantalum. (JFP)
Date: September 16, 1975
Creator: Alvarez, L.W.
Partner: UNT Libraries Government Documents Department

Energy conversion based on molecular excited states: Redox splitting in soluble polymers. Final report

Description: A general method was developed for preparing complexes of Ru(II) with three different bidentate ligands; it is being extended to monodentate ligands for more synthetic versatility. This method was used to prepare a series of complexes with pre-designed absorption properties, with the goal of ``black absorbers`` for use as antenna chromophores in a light-to-chemical energy conversion array. The energy gap law for nonradiative decay was studied for preparing near-IR luminophores with long excited state lifetimes. The problem of destructive dd excited states in Ru(II) polypyridyl complexes was focused on, with success in preparing an extremely photo-inert complex with monodentate pyridine ligands. Time-resolved resonance Raman and infrared spectroscopy were used to study subtle excited state properties of complexes of Ru(II), Os(II), and Re(I). Success was achieved in controlled immobilization of d{sup 6} chromophores and quenchers on styrenic polymers. Having perfected our synthetic technique, we have begun to optimize the ground and excited state properties such as chromophore density, dipole orientation, and lifetime.
Date: December 31, 1995
Creator: Meyer, T.J.
Partner: UNT Libraries Government Documents Department

Disproportionation and polymerization of plutonium(IV) in dilute aqueous solutions

Description: The rates of polymerization and disproportionation of Pu(IV) have been studied using low concentrations: (1.7 - 10) x 10{sup -}M Pu, (0.8 - 12) x 10{sup -}M HCl and 0.0iM ionic strength. Osmium(II) complexes such as the tris-4,4`-2,2`-bipyridine complex were found to react rapidly with Pu(IV) but very slowly, if at all, with Pu(IV) polymer, Pu(III), or Pu(V). Thus, it is possible to determine unreacted Pu(IV) in the presence of rection products by using Os(II) complexes. Disproportionation reaction products, Pu(III) and Pu(V), were determined using their reactions with Ce(IV) sulfate. We find -d[Pu(IV)]/dt = k`[Pu(IV)]{sup 2} at constant pH. Log k` varies from about 4.25 at pH 3 to about 7.0 at pH 4.1 (units for k` are M{sup -1}min{sup -1}). The [H{sup +}] dependence varies from about -2 to -3 over the pH range studied. The measured rate is the sum of those for polymerization and disproportionation; the latter reaction amounts to about 75% of the total at pH 3 and 20% at pH 4. The second-order rate constants for disproportionation are very much larger than expected on the basis of extrapolation from 0.2 to 1.0M HC10{sub 4} solutions. The products of the reaction do not affect the rate, but U(VI), aged Pu(IV) polymer, and CO{sub 2} increase the rate.
Date: December 31, 1983
Creator: Newton, T.W. & Rundberg, V.L.
Partner: UNT Libraries Government Documents Department


Description: BS>Ruthenium, either as soluble salts, powdered metal, or oxide, catalyzed the oxidation of Cr(III) to Cr(VI) in dilute oxygenated sulfuric acid solutions. Under the same conditions, in the absence of ruthenium, Cr(Vl) was not produced. In a 2 M Al(NO/sub 3/)/sub 3/-1 M HNO/sub 3/ solution at atmospheric boiling point, ruthenium and compounds of ruthenium, platinum, palladium, rhodium, and osmium very markedly increased the rate at which Cr(III) was oxidized to Cr(VI). Very low concentrations of ruthenium were capable of causing the oxidation to proceed at an appreciable rate. In boiling 65% nitric acid, Cr(HI) was oxidized to Cr(VI) if reduced oxides of nitrogen were removed from solution either m the presence or absence of ruthenium; without removal of the oxides of nitrogen, detectable quantities of Cr(VI) were not formed in either case. Cr(VI) was not produced in boiling and aerated uranyl sulfate solutions containing ruthenium. (auth)
Date: May 23, 1960
Creator: Wisdom, N E; Greeley, R S & Griess, J C
Partner: UNT Libraries Government Documents Department

Isotope tracer studies of diffusion in silicates and of geological transport processes in aqueous systems using actinide elements

Description: This research program has moved ahead with success in several areas. The isotopic composition of osmium in seawater and in some rivers was directly determined for the first time. The concentration of osmium was first estimated in both seawater and rivers. A major effort was directed toward the transport of the U,Th series nuclides in a watershed in Sweden. A serious effort was directed at developing a transport model for the U,Th series nuclides in aquifers. A detailed study of {sup 238}U-{sup 230}Th dating of a cave in Israel was carried out collaboratively. The Os-Re fractionation between silicate and sulfide melts were determined in MORB basalts and glasses and the isotopic composition of Os was measured in sulfide samples.
Date: February 1, 1999
Creator: Wasserburg, G.J.
Partner: UNT Libraries Government Documents Department