Application unit for the administration of contrast gases for pulmonary magnetic resonance imaging: optimization of ventilation distribution for (3) He-MRI.

PubMed

Güldner, M; Becker, St; Wolf, U; Düber, C; Friesenecker, A; Gast, K K; Heil, W; Hoffmann, C; Karpuk, S; Otten, E W; Rivoire, J; Salhi, Z; Scholz, A; Schreiber, L M; Terekhov, M

2015-09-01

MRI of lung airspaces using gases with MR-active nuclei ((3) He, (129) Xe, and (19) F) is an important area of research in pulmonary imaging. The volume-controlled administration of gas mixtures is important for obtaining quantitative information from MR images. State-of-the-art gas administration using plastic bags (PBs) does not allow for a precise determination of both the volume and timing of a (3) He bolus. A novel application unit (AU) was built according to the requirements of the German medical devices law. Integrated spirometers enable the monitoring of the inhaled gas flow. The device is particularly suited for hyperpolarized (HP) gases (e.g., storage and administration with minimal HP losses). The setup was tested in a clinical trial (n = 10 healthy volunteers) according to the German medicinal products law using static and dynamic ventilation HP-(3) He MRI. The required specifications for the AU were successfully realized. Compared to PB-administration, better reproducibility of gas intrapulmonary distribution was observed when using the AU for both static and dynamic ventilation imaging. The new AU meets the special requirements for HP gases, which are storage and administration with minimal losses. Our data suggest that gas AU-administration is superior to manual modes for determining the key parameters of dynamic ventilation measurements. © 2014 Wiley Periodicals, Inc.

Geology and sequence stratigraphy of undiscovered oil and gas resources in conventional and continuous petroleum systems in the Upper Cretaceous Eagle Ford Group and related strata, U.S. Gulf Coast Region

USGS Publications Warehouse

Dubiel, Russell F.; Pearson, Ofori N.; Pitman, Janet K.; Pearson, Krystal M.; Kinney, Scott A.

2012-01-01

The U.S. Geological Survey (USGS) recently assessed the technically recoverable undiscovered oil and gas onshore and in State waters of the Gulf Coast region of the United States. The USGS defined three assessment units (AUs) with potential undiscovered conventional and continuous oil and gas resources in Upper Cretaceous (Cenomanian to Turonian) strata of the Eagle Ford Group and correlative rocks. The assessment is based on geologic elements of a total petroleum system, including hydrocarbon source rocks (source rock maturation, hydrocarbon generation and migration), reservoir rocks (sequence stratigraphy and petrophysical properties), and traps (formation, timing, and seals). Conventional oil and gas undiscovered resources are in updip sandstone reservoirs in the Upper Cretaceous Tuscaloosa and Woodbine Formations (or Groups) in Louisiana and Texas, respectively, whereas continuous oil and continuous gas undiscovered resources reside in the middip and downdip Upper Cretaceous Eagle Ford Shale in Texas and the Tuscaloosa marine shale in Louisiana. Conventional resources in the Tuscaloosa and Woodbine are included in the Eagle Ford Updip Sandstone Oil and Gas AU, in an area where the Eagle Ford Shale and Tuscaloosa marine shale display vitrinite reflectance (Ro) values less than 0.6%. The continuous Eagle Ford Shale Oil AU lies generally south of the conventional AU, is primarily updip of the Lower Cretaceous shelf edge, and is defined by thermal maturity values within shales of the Eagle Ford and Tuscaloosa that range from 0.6 to 1.2% Ro. Similarly, the Eagle Ford Shale Gas AU is defined downdip of the shelf edge where source rocks have Ro values greater than 1.2%. For undiscovered oil and gas resources, the USGS assessed means of: 1) 141 million barrels of oil (MMBO), 502 billion cubic feet of natural gas (BCFG), and 4 million barrels of natural gas liquids (MMBNGL) in the Eagle Ford Updip Sandstone Oil and Gas AU; 2) 853 MMBO, 1707 BCFG, and 34 MMBNGL in the Eagle Ford Shale Oil AU; and 3) 50,219 BCFG and 2009 MMBNGL in the Eagle Ford Shale Gas AU.

International Crisis Information Network

DTIC Science & Technology

2006-12-01

AU African Union CA Civil Affairs (Specifically United States Army) CDHAM Center for Disaster and Humanitarian Assistance Medicine CEMAC Economic...Department of Defense DODD Department of Defense Directive ECOWAS Economic Community of West African States EU European Union FR First Responder HA...passion, such as rugby fans on Rugby365.com, or music lovers on MP3.com. These people exchange ideas and thoughts about the given passion.”83 The

Studying the hopping parameters of half-Heusler NaAuS using maximally localized Wannier function

NASA Astrophysics Data System (ADS)

Sihi, Antik; Lal, Sohan; Pandey, Sudhir K.

2018-04-01

Here, the electronic behavior of half-Heusler NaAuS is studied using PBEsol exchange correlation functional by plotting the band structure curve. These bands are reproduced using maximally localized Wannier function using WANNIER90. Tight-binding bands are nicely matched with density functional theory bands. By fitting the tight-binding model, hopping parameter for NaAuS is obtained by including Na 2s, 2p, Au 6s, 5p, 5d and S 3s, 3p orbitals within the energy interval of -5 to 16 eV around the Fermi level. In present study, hopping integrals for NaAuS are computed for the first primitive unit cell atoms as well as the first nearest neighbor primitive unit cell. The most dominating hopping integrals are found for Na (3s) - S (3s), Na (2px) - S (2px), Au (6s) - S (3px), Au (6s) - S (3py) and Au (6s) - S (3pz) orbitals. The hopping integrals for the first nearest neighbor primitive unit cell are also discussed in this manuscript. In future, these hopping integrals are very important to find the topological invariant for NaAuS compound.

Geology and oil and gas assessment of the Mancos-Menefee Composite Total Petroleum System: Chapter 4 in Total petroleum systems and geologic assessment of undiscovered oil and gas resources in the San Juan Basin Province, exclusive of Paleozoic rocks, New Mexico and Colorado

USGS Publications Warehouse

Ridgley, J.L.; Condon, S.M.; Hatch, J.R.

2013-01-01

Eight assessment units were defined in the Mancos-Menefee Composite TPS. Of the eight assessment units, four were assessed as conventional oil or gas accumulations and four as continuous-type accumulations. The conventional assessment units are Dakota-Greenhorn Conventional Oil and Gas Assessment Unit (AU), Gallup Sandstone Conventional Oil and Gas AU, Mancos Sandstones Conventional Oil AU, and the Mesaverde Updip Conventional Oil AU. Continuous-type assessments are Dakota-Greenhorn Continuous Gas AU, Mancos Sandstones Continuous Gas AU, Mesaverde Central-Basin Continuous Gas AU, and Menefee Coalbed Gas AU. The Mesaverde Updip Conventional AU was not quantitatively assessed for undiscovered oil and gas resources, because the producing oil fields were smaller than the 0.5 million barrel cutoff, and the potential of finding fields above this cutoff was considered to be low. Total oil resources that have the potential for additions to reserves in the next 30 years are estimated at a mean of 16.78 million barrels. Most of this resource will come from reservoirs in the Mancos Sandstones Oil AU. Gas resources that have the potential for additions to reserves in the next 30 years are estimated at a mean of 11.11 trillion cubic feet of gas (TCFG). Of this amount, 11.03 TCFG will come from continuous gas accumulations; the remainder will be gas associated with oil in conventional accumulations.Total natural gas liquids (NGL) that have the potential for additions to reserves in the next 30 years are estimated at a mean of 99.86 million barrels. Of this amount, 96.95 million barrels will come from the continuous gas assessment units, and 78.3 percent of this potential resource will come from the Mancos Sandstones Continuous Gas AU.

Triggering nanoparticle surface ligand rearrangement via external stimuli: light-based actuation of biointerfaces

NASA Astrophysics Data System (ADS)

Tang, Zhenghua; Lim, Chang-Keun; Palafox-Hernandez, J. Pablo; Drew, Kurt L. M.; Li, Yue; Swihart, Mark T.; Prasad, Paras N.; Walsh, Tiffany R.; Knecht, Marc R.

2015-08-01

Bio-molecular non-covalent interactions provide a powerful platform for material-specific self-organization in aqueous media. Here, we introduce a strategy that integrates a synthetic optically-responsive motif with a materials-binding peptide to enable remote actuation. Specifically, we linked a photoswitchable azobenzene moiety to either terminus of a Au-binding peptide. We employed these hybrid molecules as capping agents for synthesis of Au nanoparticles. Integrated experiments and molecular simulations showed that the hybrid molecules maintained both of their functions, i.e. binding to Au and optically-triggered reconfiguration. The azobenzene unit was optically switched reversibly between trans and cis states while adsorbed on the particle surface. Upon switching, the conformation of the peptide component of the molecule also changed. This highlights the interplay between the surface adsorption and conformational switching that will be pivotal to the creation of actuatable nanoparticle bio-interfaces, and paves the way toward multifunctional peptide hybrids that can produce stimuli responsive nanoassemblies.Bio-molecular non-covalent interactions provide a powerful platform for material-specific self-organization in aqueous media. Here, we introduce a strategy that integrates a synthetic optically-responsive motif with a materials-binding peptide to enable remote actuation. Specifically, we linked a photoswitchable azobenzene moiety to either terminus of a Au-binding peptide. We employed these hybrid molecules as capping agents for synthesis of Au nanoparticles. Integrated experiments and molecular simulations showed that the hybrid molecules maintained both of their functions, i.e. binding to Au and optically-triggered reconfiguration. The azobenzene unit was optically switched reversibly between trans and cis states while adsorbed on the particle surface. Upon switching, the conformation of the peptide component of the molecule also changed. This highlights the interplay between the surface adsorption and conformational switching that will be pivotal to the creation of actuatable nanoparticle bio-interfaces, and paves the way toward multifunctional peptide hybrids that can produce stimuli responsive nanoassemblies. Electronic supplementary information (ESI) available: Additional modeling analysis, QCM analysis, UV-vis and CD spectroscopy data. See DOI: 10.1039/C5NR02311D

Bonding properties of FCC-like Au 44 (SR) 28 clusters from X-ray absorption spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Rui; Chevrier, Daniel M.; Zeng, Chenjie

Thiolate-protected gold clusters with precisely controlled atomic composition have recently emerged as promising candidates for a variety of applications because of their unique optical, electronic, and catalytic properties. The recent discovery of the Au44(SR)28 total structure is considered as an interesting finding in terms of the face-centered cubic (FCC)-like core structure in small gold-thiolate clusters. Herein, the unique bonding properties of Au44(SR)28 is analyzed using temperature-dependent X-ray absorption spectroscopy (XAS) measurements at the Au L3-edge and compared with other FCC-like clusters such as Au36(SR)24 and Au28(SR)20. A negative thermal expansion was detected for the Au–Au bonds of the metal coremore » (the first Au–Au shell) and was interpreted based on the unique Au core structure consisting of the Au4 units. EXAFS fitting results from Au28(SR)20, Au36(SR)24, and Au44(SR)28 show a size-dependent negative thermal expansion behavior in the first Au–Au shell, further highlighting the importance of the Au4 units in determining the Au core bonding properties and shedding light on the growth mechanism of these FCC-like Au clusters.« less

Cerebral energy metabolism in diving and non-diving birds during hypoxia and apnoeic asphyxia.

PubMed Central

Bryan, R M; Jones, D R

1980-01-01

1. Cerebral energy metabolism during apnoeic asphyxia and steady-state hypoxia was compared in ducks and chickens; ducks tolerate apnoeic asphyxia 3-8 times longer than chickens. 2. Fluctuations in the reduced form of respiratory chain nicotinamide adenine dinucleotide (NADH) were monitored from the left cerebral hemisphere by a noninvasive fluorometric technique and used as an indicator of mitochondrial hypoxia. NADH fluorescence was expressed in aribtrary units (a.u.) where 100 a.u. was defined as the fluorescence change from normoxia to anoxia. Electroencephalogram (e.e.g.) and surface Po2 were recorded from the right hemisphere. 3. After 1 min of asphyxia NADH fluorescence increased by 37 a.u.+/-3.60 S.E. of mean (n=54) in paralysed chickens and 8 a.u.+/-1.41 (n=55) in aralysed ducks. After 2 min the fluorescence increased by only 15 a.u.+/-1.95 in ducks. 4. Both species showed an isoelectric e.e.g. when fluorescence increased by approximately 35 a.u., indicating that anaerobic ATP production in ducks did not maintain brain function (e.e.g.) for a greater accumulation of respiratory chain NADH. 5. At a given decrease in tissue Po2 ducks and chickens showed the same level of NADH increase, indicating that both species are equally dependent on tissue Po2 for the maintenance of redox state. 6. We conclude that biochemical adjustment which enhance anaerobic ATP production and/or prolong oxidative phosphorylation during progressive hypoxia are not responsible for increased cerebral tolerance to apnoeic asphyxia in the duck. PMID:7381772

Reported exposure to E-cigarette advertising and promotion in different regulatory environments: Findings from the International Tobacco Control Four Country (ITC-4C) Survey.

PubMed

Wadsworth, E; McNeill, A; Li, L; Hammond, D; Thrasher, J F; Yong, H-H; Cummings, K M; Fong, G T; Hitchman, S C

2018-07-01

Electronic cigarette (e-cigarette) advertising regulations differ across countries. This study examines how differences in e-cigarette advertising regulations influence exposure to e-cigarette advertising, and perceptions about what participants had seen and read about e-cigarettes. Data come from the ITC Four Country Survey (Canada [CA], United States [US], Australia [AU] and United Kingdom [UK]) carried out between August 2013 and March 2015 (n = 3460). In 2014, AU and CA had laws prohibiting the retail sale of e-cigarettes containing nicotine while the US and UK had no restrictions, although a voluntary agreement restricting advertising in the UK was introduced during fieldwork. Smokers and ex-smokers were asked whether in the last six months they had noticed e-cigarettes advertisements and received free samples/special offers (promotion), and about their perceptions (positive or otherwise) of what they had seen or read about e-cigarettes. Data were analyzed in 2017. US and UK participants were more likely to report that they had noticed e-cigarette advertisements and received promotions compared to CA or AU participants. For TV and radio advertisements, reported exposure was higher in US compared to UK. For all types of advertisements, reported exposure was higher in CA than AU. Overall, nearly half of AU (44.0%) and UK (47.8%) participants perceived everything they had seen and read about e-cigarettes to be positive, with no significant differences between AU and UK. Participants in countries with permissive e-cigarette advertising restrictions and less restrictive e-cigarette regulations were more likely to notice advertisements than participants in countries with more restrictive e-cigarette regulations. Copyright © 2018 Elsevier Inc. All rights reserved.

Geologic assessment of undiscovered hydrocarbon resources of the Western Oregon and Washington Province

USGS Publications Warehouse

,; Brownfield, Michael E.; Charpentier, Ronald R.; Cook, Troy A.; Klett, Timothy R.; Pollastro, Richard M.; Schenk, Christopher J.; Le, P.A.; ,

2011-01-01

The purpose of the U.S. Geological Survey (USGS) National Oil and Gas Assessment is to develop geology-based hypotheses regarding the potential for additions to oil and gas reserves in priority areas of the United States, focusing on the distribution, quantity, and availability of oil and natural gas resources. The USGS has completed an assessment of the undiscovered, technically recoverable oil and gas resources in western Oregon and Washington (USGS Western Oregon and Washington Province 5004). The province includes all of Oregon and Washington north of the Klamath Mountains and west of the crest of the Cascade Range, and extends offshore to the 3-mi limit of State waters on the west and to the International Boundary in the Straits of Juan de Fuca and Canada on the north. It measures about 450 mi north-south and 50 to 160 mi east-west, encompassing more than 51,000 mi2. The assessment of the Western Oregon and Washington Province is geology based and used the total petroleum system (TPS) concept. The geologic elements of a TPS include hydrocarbon source rocks (source rock maturation and hydrocarbon generation and migration), reservoir rocks (quality and distribution), and traps for hydrocarbon accumulation. Using these geologic criteria, two conventional and one unconventional (continuous) total petroleum systems were defined, with one assessment unit (AU) in each TPS: (1) the Cretaceous-Tertiary Composite TPS and the Western Oregon and Washington Conventional Gas AU, (2) the Tertiary Marine TPS and the Tertiary-Marine Gas AU, and (3) the Tertiary Coalbed Gas TPS and the Eocene Coalbed Gas AU, in which a cell-based methodology was used to estimate coalbed-gas resources.

Structural evolution of atomically precise thiolated bimetallic [Au(12+n)Cu₃₂(SR)(30+n)]⁴⁻ (n = 0, 2, 4, 6) nanoclusters.

PubMed

Yang, Huayan; Wang, Yu; Yan, Juanzhu; Chen, Xi; Zhang, Xin; Häkkinen, Hannu; Zheng, Nanfeng

2014-05-21

A series of all-thiol stabilized bimetallic Au-Cu nanoclusters, [Au(12+n)Cu32(SR)(30+n)](4-) (n = 0, 2, 4, 6 and SR = SPhCF3), are successfully synthesized and characterized by X-ray single-crystal analysis and density functional theory (DFT) calculations. Each cluster consists of a Keplerate two-shell Au12@Cu20 core protected by (6 - n) units of Cu2(SR)5 and n units of Cu2Au(SR)6 (n = 0, 2, 4, 6) motifs on its surface. The size and structural evolution of the clusters is atomically controlled by the Au precursors and countercations used in the syntheses. The clusters exhibit similar optical absorption properties that are not dependent on the number of surface Cu2Au(SR)6 units. Although DFT suggests an electronic structure with an 18-electron superatom shell closure, the clusters display different thermal stabilities. [Au(12+n)Cu32(SR)(30+n)](4-) clusters with n = 0 and 2 are more stable than those with n = 4 and 6. Moreover, an oxidation product of the clusters, [Au13Cu12(SR)20](4-), is structurally identified to gain insight into how the clusters are oxidized.

High-Pressure Study of the Ground- and Superconducting-State Properties of CeAu2Si2

NASA Astrophysics Data System (ADS)

Scheerer, Gernot W.; Giriat, Gaétan; Ren, Zhi; Lapertot, Gérard; Jaccard, Didier

2017-06-01

The pressure-temperature phase diagram of the new heavy-fermion superconductor CeAu2Si2 is markedly different from those studied previously. Indeed, superconductivity emerges not on the verge but deep inside the magnetic phase, and mysteriously Tc increases with the strengthening of magnetism. In this context, we have carried out ac calorimetry, resistivity, and thermoelectric power measurements on a CeAu2Si2 single crystal under high pressure. We uncover a strong link between the enhancement of superconductivity and quantum-critical-like features in the normal-state resistivity. Non-Fermi-liquid behavior is observed around the maximum of superconductivity and enhanced scattering rates are observed close to both the emergence and the maximum of superconductivity. Furthermore we observe signatures of pressure- and temperature-driven modifications of the magnetic structure inside the antiferromagnetic phase. A comparison of the features of CeAu2Si2 and its parent compounds CeCu2Si2 and CeCu2Ge2 plotted as function of the unit-cell volume leads us to propose that critical fluctuations of a valence crossover play a crucial role in the superconducting pairing mechanism. Our study illustrates the complex interplay between magnetism, valence fluctuations, and superconductivity.

Vapochromic Behaviour of M[Au(CN)2]2-Based Coordination Polymers (M = Co, Ni)

PubMed Central

Lefebvre, Julie; Korčok, Jasmine L.; Katz, Michael J.; Leznoff, Daniel B.

2012-01-01

A series of M[Au(CN)2]2(analyte)x coordination polymers (M = Co, Ni; analyte = dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), pyridine; x = 2 or 4) was prepared and characterized. Addition of analyte vapours to solid M(μ-OH2)[Au(CN)2]2 yielded visible vapochromic responses for M = Co but not M = Ni; the IR νCN spectral region changed in every case. A single crystal structure of Zn[Au(CN)2]2(DMSO)2 revealed a corrugated 2-D layer structure with cis-DMSO units. Reacting a Ni(II) salt and K[Au(CN)2] in DMSO yielded the isostructural Ni[Au(CN)2]2(DMSO)2 product. Co[Au(CN)2]2(DMSO)2 and M[Au(CN)2]2(DMF)2 (M = Co, Ni) complexes have flat 2-D square-grid layer structures with trans-bound DMSO or DMF units; they are formed via vapour absorption by solid M(μ-OH2)[Au(CN)2]2 and from DMSO or DMF solution synthesis. Co[Au(CN)2]2(pyridine)4 is generated via vapour absorption by Co(μ-OH2)[Au(CN)2]2; the analogous Ni complex is synthesized by immersion of Ni(μ-OH2)[Au(CN)2]2 in 4% aqueous pyridine. Similar immersion of Co(μ-OH2)[Au(CN)2]2 yielded Co[Au(CN)2]2(pyridine)2, which has a flat 2-D square-grid structure with trans-pyridine units. Absorption of pyridine vapour by solid Ni(μ-OH2)[Au(CN)2]2 was incomplete, generating a mixture of pyridine-bound complexes. Analyte-free Co[Au(CN)2]2 was prepared by dehydration of Co(μ-OH2)[Au(CN)2]2 at 145 °C; it has a 3-D diamondoid-type structure and absorbs DMSO, DMF and pyridine to give the same materials as by vapour absorption from the hydrate. PMID:22737031

Protection in Space: A Self-Defense Acquisition Priority for U.S. Satellites

DTIC Science & Technology

2008-05-01

Advisory Board (Washington, D.C.: United States State Department, 27 April 2007), 4. 27 Barry R . Posen, “Command of the Commons: The Military...space flight has been inexorably tied with the all-too-human 10 28 Barry R . McCaffrey...After Action Report—General Barry R McCaffrey USA (Ret) Visit Nellis and Scott AFB 14-17 August 2007,” 15 October 2007 http://www.maxwell.af.mil/au

Progressive biogeochemical transformation of placer gold particles drives compositional changes in associated biofilm communities.

PubMed

Rea, Maria Angelica; Standish, Christopher D; Shuster, Jeremiah; Bissett, Andrew; Reith, Frank

2018-05-03

Biofilms on placer gold (Au)-particle surfaces drive Au solubilization and re-concentration thereby progressively transforming the particles. Gold solubilization induces Au-toxicity; however, Au-detoxifying community members ameliorates Au-toxicity by precipitating soluble Au to metallic Au. We hypothesize that Au-dissolution and re-concentration (precipitation) places selective pressures on associated microbial communities, leading to compositional changes and subsequent Au-particle transformation. We analyzed Au-particles from eight United Kingdom sites using next generation sequencing, electron microscopy and micro-analyses. Gold particles contained biofilms composed of prokaryotic cells and extracellular polymeric substances intermixed with (bio)minerals. Across all sites communities were dominated by Proteobacteria (689, 97% Operational Taxonomic Units, 59.3% of total reads), with β-Proteobacteria being the most abundant. A wide range of Au-morphotypes including nanoparticles, micro-crystals, sheet-like Au and secondary rims, indicated that dissolution and re-precipitation occurred, and from this transformation indices were calculated. Multivariate statistical analyses showed a significant relationship between the extent of Au-particle transformation and biofilm community composition, with putative metal-resistant Au-cycling taxa linked to progressive Au transformation. These included the genera Pseudomonas, Leptothrix and Acinetobacter. Additionally, putative exoelectrogenic genera Rhodoferax and Geobacter were highly abundant. In conclusion, biogeochemical Au-cycling and Au-particle transformation occurred at all sites and exerted a strong influence on biofilm community composition.

Undiscovered hydrocarbon resources in the U.S. Gulf Coast Jurassic Norphlet and Smackover Formations

USGS Publications Warehouse

Pearson, Ofori N.

2011-01-01

The U.S. Geological Survey has completed assessments of undiscovered technically recoverable oil and gas resources in the Jurassic Norphlet and Smackover formations of the onshore coastal plain and State waters of the U.S. Gulf Coast. The Norphlet Formation consists of sandstones and interbedded shales and siltstones deposited during a marine transgression. Along its northeast margin, deposition of the Norphlet was in alluvial fans, fluvial systems, and dune and clastic sabkha environments. Mudstones of the underlying Smackover Formation act as source rocks for Norphlet reservoirs. The Norphlet was divided into the following three assessment units (AUs): the Norphlet Salt Basins and Updip AU, the Norphlet Mobile Bay Deep Gas AU, and the Norphlet South Texas Gas AU. The lower part of the Smackover consists primarily of dark carbonate mudstone and argillaceous limestone deposited in low-energy environments, and is one of the Gulf of Mexico Basin’s major source rocks. The upper part of the Smackover is comprised primarily of grain-supported carbonates deposited in high-energy environments. The Smackover was divided into the following four AUs: the Smackover Updip and Peripheral Fault Zone AU, the Smackover Salt Basin AU, the Smackover South Texas AU, and the Smackover Downdip Continuous Gas AU. Although the Norphlet and Smackover formations have been the focus of extensive exploration and production, they probably still contain significant undiscovered oil and gas resources.

Au-induced deep groove nanowire structure on the Ge(001) surface: DFT calculations

NASA Astrophysics Data System (ADS)

Tsay, Shiow-Fon

2016-09-01

The atomic geometry, stability, and electronic properties of self-organized Au induced nanowires on the Ge(001) surface are investigated based on the density-functional theory in GGA and the stoichiometry of Au. A giant Ge zigzag chain structure is suggested for 0.75 ML Au coverage, which displays c(8 × 2) deep groove zigzag nanowire structure simulated STM images. The top layer Ge and Au atomic disorder introduces the chevron units into the zigzag nanowire structure STM image as per the experimental observations. The zigzag Ge nanowire exhibits a semi-metallic characteristic, and the electric transport occurs in between the Ge zigzag nanowire and the subsurface. The system exhibits obvious electronic correlations among the Ge nanowire, the nano-facet Au trimers and the deeper layer Ge atoms, that play an important role in the electronic structure. At surface Brillouin zone boundaries, an anisotropic two-dimensional upward parabolic surface-state band is consistent with the ARPES spectra reported by Nakatsuji et al. [Phys. Rev. B 80, 081406(R) (2009); Phys. Rev. B 84, 115411 (2011)]; this electronic structure is different from the quasi-one-dimensional energy trough reported by Schäfer et al. [Phys. Rev. Lett. 101, 236802 (2008); Phys. Rev. B 83, 121411(R) (2011)].

Efficient reverse saturable absorption of sol-gel hybrid plasmonic glasses

NASA Astrophysics Data System (ADS)

Lundén, H.; Lopes, C.; Lindgren, M.; Liotta, A.; Chateau, D.; Lerouge, F.; Chaput, F.; Désert, A.; Parola, S.

2017-07-01

Monolithic silica sol-gel glasses doped with platinum(II) acetylide complexes possessing respectively four or six phenylacetylene units (PE2-CH2OH and PE3-CH2OH) in combination with various concentrations of spherical and bipyramidal gold nanoparticles (AuNPs) known to enhance non-linear optical absorption, were prepared and polished to high optical quality. The non-linear absorption of the glasses was measured and compared to glasses doped solely with AuNPs, a platinum(II) acetylide with shorter delocalized structure, or combinations of both. At 532 nm excitation wavelength the chromophore inhibited the non-linear scattering previously found for glasses only doped with AuNPs. The measured non-linear absorption was attributed to reverse saturable absorption from the chromophore, as previously reported for PE2-CH2OH/AuNP glasses. At 600 nm strong nonlinear absorption was observed for the PE3-CH2OH/AuNPs glasses, also attributed to reverse saturable absorption. But contrary to previous findings for PE2-CH2OH/AuNPs, no distinct enhancement of the non-linear absorption for PE3-CH2OH/AuNPs was observed. A numerical population model for PE3-CH2OH was used to give a qualitative explanation of this difference. A stronger linear absorption in PE3-CH2OH would cause the highly absorbing triplet state to populate quicker during the leading edge of the laser pulse and this would in turn reduce the influence from two-photon absorption enhancement from AuNPs.

Gold(I)-assisted catalysis - a comprehensive view on the [3,3]-sigmatropic rearrangement of allyl acetate

NASA Astrophysics Data System (ADS)

Freindorf, Marek; Cremer, Dieter; Kraka, Elfi

2018-03-01

The unified reaction valley approach (URVA) combined with the local mode, ring puckering and electron density analysis is applied to elucidate the mechanistic differences of the non-catalysed and the Au[I]-N-heterocyclic carbene (NHC)-catalysed [3,3]-sigmatropic rearrangement of allyl acetate. Using a dual-level approach (DFT and DLPNO-CCSD(T)), the influence of solvation, counter-ions, bulky and electron withdrawing/donating substituents as well as the exchange of the Au[I]-NHC with a Au[I]-phosphine catalyst is investigated. The catalyst breaks up the rearrangement into two steps by switching between Au[I]-π and Au[I]-σ complexation, thus avoiding the energy-consuming CO cleavage in the first step. Based on local stretching force constants ka(C=C), we derive for the first time a quantitative measure of the π-acidity of the Au[I] catalyst; in all catalysed reactions, the bond order n(C=C) drops from 2 to 1.65. The ring puckering analysis clarifies that all reactions start and end via a six-membered ring with a boat form. All Au[I]-σ-complex intermediates show a considerable admixture of the chair form. The non-catalysed [3,3]-sigmatropic rearrangement goes through a maximum of charge separation between the allyl and acetate units at the transition state, while all catalysed reactions proceed via a minimum of charge separation reached in the region of the Au[I]-σ-complex.

Joint Patch and Multi-label Learning for Facial Action Unit Detection

PubMed Central

Zhao, Kaili; Chu, Wen-Sheng; De la Torre, Fernando; Cohn, Jeffrey F.; Zhang, Honggang

2016-01-01

The face is one of the most powerful channel of nonverbal communication. The most commonly used taxonomy to describe facial behaviour is the Facial Action Coding System (FACS). FACS segments the visible effects of facial muscle activation into 30+ action units (AUs). AUs, which may occur alone and in thousands of combinations, can describe nearly all-possible facial expressions. Most existing methods for automatic AU detection treat the problem using one-vs-all classifiers and fail to exploit dependencies among AU and facial features. We introduce joint-patch and multi-label learning (JPML) to address these issues. JPML leverages group sparsity by selecting a sparse subset of facial patches while learning a multi-label classifier. In four of five comparisons on three diverse datasets, CK+, GFT, and BP4D, JPML produced the highest average F1 scores in comparison with state-of-the art. PMID:27382243

Ferromagnetic Coupling of Mononuclear Fe Centers in a Self-Assembled Metal-Organic Network on Au(111)

NASA Astrophysics Data System (ADS)

Umbach, T. R.; Bernien, M.; Hermanns, C. F.; Krüger, A.; Sessi, V.; Fernandez-Torrente, I.; Stoll, P.; Pascual, J. I.; Franke, K. J.; Kuch, W.

2012-12-01

The magnetic state and magnetic coupling of individual atoms in nanoscale structures relies on a delicate balance between different interactions with the atomic-scale surroundings. Using scanning tunneling microscopy, we resolve the self-assembled formation of highly ordered bilayer structures of Fe atoms and organic linker molecules (T4PT) when deposited on a Au(111) surface. The Fe atoms are encaged in a three-dimensional coordination motif by three T4PT molecules in the surface plane and an additional T4PT unit on top. Within this crystal field, the Fe atoms retain a magnetic ground state with easy-axis anisotropy, as evidenced by x-ray absorption spectroscopy and x-ray magnetic circular dichroism. The magnetization curves reveal the existence of ferromagnetic coupling between the Fe centers.

Second Language Learners' Attitudes towards English Varieties

ERIC Educational Resources Information Center

Zhang, Weimin; Hu, Guiling

2008-01-01

This pilot project investigates second language (L2) learners' attitudes towards three varieties of English: American (AmE), British (BrE) and Australian (AuE). A 69-word passage spoken by a female speaker of each variety was used. Participants were 30 Chinese students pursuing Masters or Doctoral degrees in the United States, who listened to each…

Le Point sur L'immersion au Canada (The Argument for...Immersion in Canada).

ERIC Educational Resources Information Center

Rebuffot, Jacques

A discussion of French immersion education in Canada begins with a general examination of language immersion, including the historical context and social climate from which the immersion approach has grown in Canada, its beginnings in Quebec and spread throughout Canada, and the status of the approach in the United States, a number of European…

An Icosahedral Quasicrystal and Its 1/0 Crystalline Approximant in the Ca–Au–Al System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pham, Joyce; Kreyssig, Andreas; Goldman, Alan I.

2016-10-17

A new icosahedral quasicrystalline phase, CaAu4.5–xAl1.5+x [0.11 ≤ x ≤ 0.40(6); CaAu4.4Al1.6, aQC = 5.383(4) Å, and Pm35], and its lowest-order 1/0 cubic crystalline approximant phase, CaAu3+xAl1–x [0 ≤ x ≤ 0.31(1); a = 9.0766(5)–9.1261(8) Å, Pa3(No. 205), and Pearson symbol cP40], have been discovered in the Ca-poor region of the Ca–Au–Al system. In the crystalline approximant, eight [Au3–xAl1+x] tetrahedra fill the unit cell, and each tetrahedron is surrounded by four Ca atoms, thus forming a three-dimensional network of {Ca4/4[Au3–xAl1+x]} tetrahedral stars. A computational study of Au and Al site preferences concurs with the experimental results, which indicate a preferencemore » for near-neighbor Au–Al interactions over Au–Au and Al–Al interactions. Analysis of the electronic density of states and the associated crystal orbital Hamilton population curves was used to rationalize the descriptions of CaAu4.5–xAl1.5+x [0.11 ≤ x ≤ 0.46(6)] and CaAu3+xAl1–x [0 ≤ x ≤ 0.31(1)] as polar intermetallic species, whereby Ca atoms engage in polar covalent bonding with the electronegative, electron-deficient [Au3–xAl1+x] tetrahedral clusters and the observed phase width of the crystalline approximant.« less

Oxidation of atomic gold ions: thermochemistry for the activation of O(2) and N(2)O BY Au(+) ((1)S(0) and (3)D).

PubMed

Li, Feng-Xia; Gorham, Katrine; Armentrout, P B

2010-10-28

Reaction of Au(+) ((1)S(0) and (3)D) with O(2) and N(2)O is studied as a function of kinetic energy using guided ion beam tandem mass spectrometry. A flow tube ion source produces Au(+) primarily in its (1)S(0) (5d(10)) electronic ground state level but with some (3)D and perhaps higher lying excited states. The distribution of states can be altered by adding N(2)O, which completely quenches the excited states, or CH(4) to the flow gases. Cross sections as a function of kinetic energy are measured for both neutral reagents and both ground and excited states of Au(+). Formation of AuO(+) is common to both systems with the N(2)O system also exhibiting AuN(2)(+) and AuNO(+) formation. All reactions of Au(+) ((1)S(0)) are observed to be endothermic, whereas the excitation energy available to the (3)D state allows some reactions to be exothermic. Because of the closed shell character of ground state Au(+) ((1)S(0), 5d(10)), the reactivity of these systems is low and has cross sections with onsets and peaks at higher energies than expected from the known thermochemistry but lower than energies expected from impulsive processes. Analyses of the endothermic reaction cross sections yield the 0 K bond dissociation energy (BDE) in eV of D(0)(Au(+)-O) = 1.12 ± 0.08, D(0)(Au(+)-N(2)) ≥ 0.30 ± 0.04, and D(0)(Au(+)-NO) = 0.89 ± 0.17, values that are all speculative because of the unusual experimental behavior. Combining the AuO(+) BDE measured here with literature data also yields the ionization energy of AuO as 10.38 ± 0.23 eV. Quantum chemical calculations show reasonable agreement with the experimental bond energies and provide the electronic structures of these species.

Is there a stable B2Π state for the CNO molecule?

NASA Astrophysics Data System (ADS)

Marian, Christel; Hess, Bernd A.; Schöttke, Sigrid; Buenker, Robert J.

1987-07-01

We report MRD-CI calculations on the ground state X2Π and the excited states A2Σ + and B2Π of the CNO molecule in linear geometry. The surfaces for oxygen and carbon extraction are calculated using a limited CI expansion of 47 configuration state functions; in the vicinity of the minima obtained with this procedure large-scale CI calculations are carried out including deter-mination of the spin-orbit splitting of the 2Π states of the minima. We find that the B2Π state will be difficult to detect spectroscopically due to an avoided crossing just at the equilibrium geometry of the ground state at RCN = 2.25 a.u., RNO = 2.30 a.u. Accordingly we find two shallow minima for B2Π at RCN = 2.33 a.u., RNO = 2.91 a.u. and RCN = 2.78 a.u., RNO = 2.28 a.u., respectively.

DOE Office of Scientific and Technical Information (OSTI.GOV)

León, Iker; ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels; Ruipérez, Fernando

We report a joint photoelectron spectroscopy and theoretical study on AuC{sub 4}{sup −}, AuC{sub 6}{sup −}, and AuC{sub n}H{sup −} (n = 2, 4, and 6) using high-resolution photoelectron imaging and ab initio calculations. The ground state of AuC{sub 2}H{sup −}, AuC{sub 4}H{sup −}, and AuC{sub 6}H{sup −} is found to be linear, while that of AuC{sub 4}{sup −} and AuC{sub 6}{sup −} is bent. All the species are found to be linear in their neutral ground states. The electron affinities (EAs) are measured to be 3.366(1) and 3.593(1) eV for AuC{sub 4} and AuC{sub 6}, respectively. Both bending andmore » stretching frequencies are resolved in the spectra of AuC{sub 4}{sup −} and AuC{sub 6}{sup −}. High-resolution data of AuC{sub n}H{sup −} reveal major vibrational progressions in the Au—C stretching and bending modes. AuC{sub 2}H{sup −} has a ground state stretching frequency of 445(10) cm{sup −1} and a bending frequency of 260(10) cm{sup −1}; AuC{sub 4}H{sup −} has a ground state stretching frequency of 340(10) cm{sup −1}; AuC{sub 6}H{sup −} has a ground state stretching frequency of 260(10) cm{sup −1} and a bending frequency of 55(10) cm{sup −1}. The EAs are measured to be 1.475(1), 1.778(1), and 1.962(1) eV for AuC{sub 2}H, AuC{sub 4}H, and AuC{sub 6}H, respectively. The strength of the Au—C bond decreases as the number of carbon atoms increases. The current study provides a wealth of electronic structure information about AuC{sub 4}{sup −}, AuC{sub 6}{sup −}, and AuC{sub n}H{sup −} (n = 2, 4, and 6) and their corresponding neutrals.« less

A theoretical study of the decomposition of gold (I) complexes

NASA Astrophysics Data System (ADS)

Tossell, J. A.

1998-04-01

Structures, energetics and excitation energies are calculated for the gold (I) complexes CH 3Au, (CH 3) 2Au -, CH 3AuOH 2, CH 3AuPH 3 and PH 3AuCl at the Hartree-Fock and MP2 levels of theory, and for CH 3AuP(CH 3) 3, CH 3AuP(OH) 3 and Au 3Cl 3 at the HF level. The lowest-energy neutral triplet state of each 2-coordinate compound dissociates into either two or three radical species (always including the CH 3 radical), with the exception of (CH 3) 2Au - which shows only slight Au-C bond elongation. In contrast, the doublet anion states dissociate neutral ligands, like PH 3, but do not dissociate CH 3. These results indicate that gold (I) chemical vapor deposition processes must involve excited states of the neutrals rather than their anions.

Evolution from the plasmon to exciton state in ligand-protected atomically precise gold nanoparticles

DOE PAGES

Zhou, Meng; Zeng, Chenjie; Chen, Yuxiang; ...

2016-10-24

The evolution from the metallic (or plasmonic) to molecular state in metal nanoparticles constitutes a central question in nanoscience research because of its importance in revealing the origin of metallic bonding and offering fundamental insights into the birth of surface plasmon resonance. Previous research has not been able to probe the transition due to the unavailability of atomically precise nanoparticles in the 1–3 nm size regime. Herein, we investigate the transition by performing ultrafast spectroscopic studies on atomically precise thiolate-protected Au 25, Au 38, Au 144, Au 333, Au ~520 and Au ~940 nanoparticles. Our results clearly map out threemore » distinct states: metallic (size larger than Au333, that is, larger than 2.3 nm), transition regime (between Au 333 and Au 144, that is, 2.3–1.7 nm) and non-metallic or excitonic state (smaller than Au 144, that is, smaller than 1.7 nm). As a result, the transition also impacts the catalytic properties as demonstrated in both carbon monoxide oxidation and electrocatalytic oxidation of alcohol.« less

Time-dependent density functional theory study of the luminescence properties of gold phosphine thiolate complexes.

PubMed

Guidez, Emilie B; Aikens, Christine M

2015-04-09

The origin of the emission of the gold phosphine thiolate complex (TPA)AuSCH(CH3)2 (TPA = 1,3,5-triaza-7-phosphaadamantanetriylphosphine) is investigated using time-dependent density functional theory (TDDFT). This system absorbs light at 3.6 eV, which corresponds mostly to a ligand-to-metal transition with some interligand character. The P-Au-S angle decreases upon relaxation in the S1 and T1 states. Our calculations show that these two states are strongly spin-orbit coupled at the ground state geometry. Ligand effects on the optical properties of this complex are also discussed by looking at the simple AuP(CH3)3SCH3 complex. The excitation energies differ by several tenths of an electronvolt. Excited state optimizations show that the excited singlet and triplet of the (TPA)AuSCH(CH3)2 complex are bent. On the other hand, the Au-S bond breaks in the excited state for the simple complex, and TDDFT is no longer an adequate method. The excited state energy landscape of gold phosphine thiolate systems is very complex, with several state crossings. This study also shows that the formation of the [(TPA)AuSCH(CH3)2]2 dimer is favorable in the ground state. The inclusion of dispersion interactions in the calculations affects the optimized geometries of both ground and excited states. Upon excitation, the formation of a Au-Au bond occurs, which results in an increase in energy of the low energy excited states in comparison to the monomer. The experimentally observed emission of the (TPA)AuSCH(CH3)2 complex at 1.86 eV cannot be unambiguously assigned and may originate from several excited states.

Coprecipitation of gold(III) complex ions with manganese(II) hydroxide and their stoichiometric reduction to atomic gold (Au(0)): analysis by Mössbauer spectroscopy and XPS.

PubMed

Yamashita, Mamiko; Ohashi, Hironori; Kobayashi, Yasuhiro; Okaue, Yoshihiro; Kurisaki, Tsutomu; Wakita, Hisanobu; Yokoyama, Takushi

2008-03-01

To elucidate the formation process of precursor of gold-supported manganese dioxide (MnO2), the coprecipitation behavior of [AuCl4-n(OH)n](-) (n=0-4) (Au(III)) complex ions with manganese(II) hydroxide (Mn(OH)2 and the change in their chemical state were examined. The Au(III) complex ions were rapidly and effectively coprecipitated with Mn(OH)(2) at pH 9. According to the Mössbauer spectra for gold (Au) coprecipitated with Mn(OH)2, below an Au content of 60 wt% in the coprecipitates, all of the coprecipitated Au existed in the atomic state (Au(0)), while, above an Au content of 65 wt%, part of the gold existed in the Au(III) state, and the proportion increased with increasing coprecipitated Au content. Based on the results of X-ray photoelectron spectroscopy, Mn(II) in Mn(OH)2 converted to Mn(IV) in conjunction with coprecipitation of Au(III) complex ions. These results indicate that the rapid stoichiometric reduction of Au(III) to Au(0) is caused by electron transfer from Mn(II) in Mn(OH)2 to the Au(III) complex ion through an Mn-O-Au bond.

Charge-transfer state and large first hyperpolarizability constant in a highly electronically coupled zinc and gold porphyrin dyad.

PubMed

Fortage, Jérôme; Scarpaci, Annabelle; Viau, Lydie; Pellegrin, Yann; Blart, Errol; Falkenström, Magnus; Hammarström, Leif; Asselberghs, Inge; Kellens, Ruben; Libaers, Wim; Clays, Koen; Eng, Mattias P; Odobel, Fabrice

2009-09-14

We report the synthesis and the characterizations of a novel dyad composed of a zinc porphyrin (ZnP) linked to a gold porphyrin (AuP) through an ethynyl spacer. The UV/Vis absorption spectrum and the electrochemical properties clearly reveal that this dyad exhibits a strong electronic coupling in the ground state as evidenced by shifted redox potentials and the appearance of an intense charge-transfer band localized at lambda = 739 nm in dichloromethane. A spectroelectrochemical study of the dyad along with the parent homometallic system (i.e., ZnP-ZnP and AuP-AuP) was undertaken to determine the spectra of the reduced and oxidized porphyrin units. Femtosecond transient absorption spectroscopic analysis showed that the photoexcitation of the heterometallic dyad leads to an ultrafast formation of a charge-separated state ((+)ZnP-AuP(*)) that displays a particularly long lifetime (tau = 4 ns in toluene) for such a short separation distance. The molecular orbitals of the dyad were determined by DFT quantum-chemical calculations. This theoretical study confirms that the observed intense band at lambda = 739 nm corresponds to an interporphyrin charge-transfer transition from the HOMO orbital localized on the zinc porphyrin to LUMO orbitals localized on the gold porphyrin. Finally, a Hyper-Rayleigh scattering study shows that the dyad possesses a large first molecular hyperpolarizability coefficient (beta = 2100x10(-30) esu at lambda = 1064 nm), thus highlighting the valuable nonlinear optical properties of this new type of push-pull porphyrin system.

In-depth evolution of chemical states and sub-10-nm-resolution crystal orientation mapping of nanograins in Ti(5 nm)/Au(20 nm)/Cr(3 nm) tri-layer thin films

NASA Astrophysics Data System (ADS)

Zhu, Xiaoli; Todeschini, Matteo; Bastos da Silva Fanta, Alice; Liu, Lintao; Jensen, Flemming; Hübner, Jörg; Jansen, Henri; Han, Anpan; Shi, Peixiong; Ming, Anjie; Xie, Changqing

2018-09-01

The applications of Au thin films and their adhesion layers often suffer from a lack of sufficient information about the chemical states of adhesion layers and about the high-lateral-resolution crystallographic morphology of Au nanograins. Here, we demonstrate the in-depth evolution of the chemical states of adhesive layers at the interfaces and the crystal orientation mapping of gold nanograins with a lateral resolution of less than 10 nm in a Ti/Au/Cr tri-layer thin film system. Using transmission electron microscopy, the variation in the interdiffusion at Cr/Au and Ti/Au interfaces was confirmed. From X-ray photoelectron spectroscopy (XPS) depth profiling, the chemical states of Cr, Au and Ti were characterized layer by layer, suggesting the insufficient oxidation of the adhesive layers. At the interfaces the Au 4f peaks shift to higher binding energies and this behavior can be described by a proposed model based on electron reorganization and substrate-induced final-state neutralization in small Au clusters supported by the partially oxidized Ti layer. Utilizing transmission Kikuchi diffraction (TKD) in a scanning electron microscope, the crystal orientation of Au nanograins between two adhesion layers was non-destructively characterized with sub-10 nm spatial resolution. The results provide nanoscale insights into the Ti/Au/Cr thin film system and contribute to our understanding of its behavior in nano-optic and nano-electronic devices.

Covellite CuS as a matrix for "invisible" gold: X-ray spectroscopic study of the chemical state of Cu and Au in synthetic minerals

NASA Astrophysics Data System (ADS)

Tagirov, Boris R.; Trigub, Alexander L.; Kvashnina, Kristina O.; Shiryaev, Andrey A.; Chareev, Dmitriy A.; Nickolsky, Maximilian S.; Abramova, Vera D.; Kovalchuk, Elena V.

2016-10-01

Geological processes leading to formation of sulfide ores often result in precipitation of gold-bearing sulfides which can contain high concentrations of this metal in ;invisible; (or ;refractory;) state. Covellite (CuS) is ubiquitous mineral in many types of the ore deposits, and numerous studies of the natural ores show that covellite can contain high concentrations of Au. At the same time, Au-bearing covellite withstands cooling in contrast to other minerals of the Cu-Fe-S system (chalcocite, bornite, chalcopyrite), where Au exsolves at low temperatures. This makes covellite a convenient model system for investigation of the chemical state (local environment and valence) of the ;invisible; Au in copper-sulfide ores (copper-porphyry, epithermal, volcanogenic massive sulfide, SEDEX deposits). Therefore, it is necessary to determine the location of Au in the covellite matrix as it will have important implications for the methods employed by mineral processing industry to extract Au from sulfide ores. Here we investigate the chemical state of Cu and Au in synthetic covellite containing up to 0.3 wt.% of Au in the ;invisible; state. The covellite crystals were synthesized by hydrothermal and salt flux methods. Formation of the chemically bound Au is indicated by strong dependence of the concentration of Au in covellite on the sulfur fugacity in the experimental system (d(log C(Au))/d(log f(S2)) ∼ 0.65). The Au concentration of covellite grows with increasing temperature from 400 to 450 °C, whereas further temperature increase to 500 °C has only minor effect. The synthesized minerals were studied using X-ray absorption fine structure spectroscopy (XAFS) in high energy resolution fluorescence detection (HERFD) mode. Ab initio simulations of Cu K edge XANES spectra show that the Cu oxidation state in two structural positions in covellite (tetrahedral and triangular coordination with S atoms) is identical: the total loss of electronic charge for the 3d shell is ∼0.3 for both positions of Cu. This result is confirmed by theoretical analysis of electron density performed using quantum theory of atoms in molecules (QTAIM). Modeling of the Au L3 edge EXAFS/XANES spectra showed that Au in covellite exists in the form of the isomorphous solid solution formed by substitution for Cu atoms in triangular coordination with the Me-S distance in the first coordination shell increased by 0.18 Å relative to the pure CuS structure. The ;formal; oxidation state of Au in covellite is +1. The Bader partial atomic charge for Au in covellite is lower than the charge of Cu (+0.2 e vs. +0.5 e) indicating that the degree of covalency for the Au-bearing covellite is higher than that of pure CuS. The analysis of electronic density of states shows that this structural position of Au results in strong interactions between hybridized Au s,p,d, S p, and Cu p,d orbitals. Such chemical bonding of Au to S and Cu can result in the formation of Au-bearing solid solution with other minerals in the Cu-Fe-S system.

Single cytidine units-templated syntheses of multi-colored water-soluble Au nanoclusters.

PubMed

Jiang, Hui; Zhang, Yuanyuan; Wang, Xuemei

2014-09-07

Ultra-small metallic nanoparticles, or so-called "nanoclusters" (NCs), have attracted considerable interest due to their unique optical properties that are different from both larger nanoparticles and single atoms. To prepare high-quality NCs, the stabilizing agent plays an essential role. In this work, we have revealed and validated that cytidine and its nucleotides (cytidine 5'-monophosphate or cytidine 5'-triphosphate) can act as efficient stabilizers for syntheses of multicolored Au NCs. Interestingly, Au NCs with blue, green and yellow fluorescence emissions are simultaneously obtained using various pH environments or reaction times. The transmission electron microscopy verifies that the size of Au NCs ranges from 1.5 to 3 nm. The X-ray photoelectron spectroscopy confirms that only Au (0) species are present in NCs. Generally, the facile preparation of multicolored Au NCs that are stabilized by cytidine units provides access to promising candidates for multiple biolabeling applications.

AFSO 21: Identifying Potential Failure Points in Sustaining Continuous Process Improvement Across the Air Force

DTIC Science & Technology

2007-04-01

Michael W. Wynne, and the Air Force Chief of Staff, General T. Michael Moseley, “our strategy will be a comprehensive effort to improve our work processes...5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7...property of the United States government. ii AU/ACSC/2307/AY07 Preface I have always been a proponent of working smarter and not harder. I

The use of plants in prospecting for gold: A brief overview with a selected bibliography and topic index

USGS Publications Warehouse

Erdman, J.A.; Olson, J.C.

1985-01-01

The focal point of this report is a bibliography of 133 references and an associated topic index - both of which could be useful to geochemists attempting to locate new Au deposits. Fifty of these references originated in the Soviet Union, where most of the initial work on biogeochemical exploration for Au had been done. The 15 topics in the index range from agriculture (Au in crop plants) to silver. As an introduction to the bibliography, we have briefly described some examples of applications and difficulties in using plants. These examples are drawn from the literature and from field experience. Because of the generally low Au concentrations found in plants, the analysis of plant tissue is critical to the successful application of the biogeochemical method of prospecting. Neuron activation analysis is the most widely used method to detect Au in plants, due largely to its sensitivity; levels in the parts per billion range are easily attained. Two general types of sampling media are used in prospecting for Au: humus and living plants. Humus has been widely used in Canada, but the sampling of plants has increased there and elsewhere in recent years. Our use of douglas-fir (Pseudotsuga menziesii) at a Au-bearing stockwork in Idaho is a prime example. A maximum Au concentration of 14 ??g/g (ppm) was detected in the wood ash of this coniferous tree, well above the normal concentration of ??? 0.15 ??g/g. Among shrubs that might be useful in Au prospecting, we recommend sagebrush or wormwood (genus Artemisia), because it is extremely responsive to concealed mineralization. It has been used extensively in the Soviet Union and could be used in areas of the western United States where disseminated Au occurrences might be located. Among the problems one may encounter in using plants for Au prospecting are: (1) physiological barriers, by which many plant species simply do not absorb Au at detectable levels; (2) misconceptions of soil-plant correlations; (3) localization of Au in plant tissue; and (4) the variation of Au concentrations due to season. Despite these limitations, biogeochemical techniques can complement or replace other geochemical methods currently used. ?? 1985.

A Comparative Study of Gold Bonding via Electronic Spectroscopy

NASA Astrophysics Data System (ADS)

Zhang, Ruohan

The bonding and electrostatic properties of gold containing molecules are highly influenced by relativistic effects. To understand this facet on bonding, a series of simple diatomic AuX (X=F, Cl, O and S) molecules, where upon bond formation the Au atom donates or accepts electrons, was investigated and discussed in this thesis. First, the optical field-free, Stark, and Zeeman spectroscopic studies have been performed on AuF and AuCl. The simple polar bonds between Au and typical halogens (i.e. F and Cl) can be well characterized by the electronic structure studies and the permanent electric dipole moments, mu el. The spectroscopic parameters have been precisely determined for the [17.7]1, [17.8]0+ and X1Sigma + states of AuF, and the [17.07]1, [17.20]0+ and X1Sigma+ states of AuCl. The mu el have been determined for ground and excited states of AuF and AuCl. The results from the hyperfine analysis and Stark measurement support the assignments that the [17.7]1 and [17.8]0+ states of AuF are the components of a 3pi state. Similarly, the analysis demonstrated the [19.07]1 and [19.20]0+ states are the components of the 3pi state of AuCl. Second, my study focused on AuO and AuS because the bonding between gold and sulfur/oxygen is a key component to numerous established and emerging technologies that have applications as far ranging as medical imaging, catalysis, electronics, and material science. The high-resolution spectra were record and analyzed to obtain the geometric and electronic structural data for the ground and excited states. The electric dipole moment, muel , and the magnetic dipole moment, mum, has been the precisely measured by applying external static electric and magnetic fields. muel and mum are used to give insight into the unusual complex bonding in these molecules. In addition to direct studies on the gold-containing molecules, other studies of related molecules are included here as well. These works contain the pure rotation measurement of PtC, the hyperfine and Stark spectroscopic studies of PtF, and the Stark and Zeeman spectroscopic studies of MgH and MgD. Finally, a perspective discussion and conclusion will summarize the results of AuF, AuCl, AuO, and AuS from this work (bond lengths, dipole moment, etc.). The highly quantitative information derived from this work is the foundation of a chemical description of matter and essential for kinetic energy manipulation via Stark and Zeeman interactions. This data set also establishes a synergism with computation chemists who are developing new methodologies for treating relativistic effects and electron correlation.

Chapter 4: The Cretaceous-Lower Tertiary Composite Total Petroleum System, Wind River Basin, Wyoming

USGS Publications Warehouse

Johnson, R.C.; Finn, Thomas M.; Kirschbaum, Mark A.; Roberts, Stephen B.; Roberts, Laura N.R.; Cook, Troy; Taylor, David J.

2007-01-01

The Cretaceous-Lower Tertiary Composite Total Petroleum System (TPS) of the Wind River Basin Province includes all strata from the base of the Lower Cretaceous Cloverly Formation to the base of the Waltman Shale Member of the Paleocene age Fort Union Formation and, where the Waltman is absent, includes strata as young as the Eocene Wind River Formation. Locally, Cretaceous-sourced gas migrated into strata as old as the Mississippian Madison Limestone, and in these areas the TPS extends stratigraphically downward to include these reservoirs. The extensive vertical migration of gases in highly fractured areas of the Wind River Basin led to the commingling of gases from several Upper Cretaceous and lower Tertiary sources, thus only two petroleum systems are recognized in these rocks, the Cretaceous-Lower Tertiary Composite TPS, the subject of this report, and the Waltman Shale TPS described by Roberts and others (Chapter 5, this CD-ROM). The Cretaceous-lower Tertiary Composite TPS was subdivided into (1) seven continuous gas assessment units (AU): (a) Frontier-Muddy Continuous Gas AU, (b) Cody Sandstone Continuous Gas AU, (c) Mesaverde--Meeteetse Sandstone Gas AU, (d) Lance-Fort Union Sandstone Gas AU, (e) Mesaverde Coalbed Gas AU, (f) Meeteetse Coalbed Gas AU, and (g) Fort Union Coalbed Gas AU; (2) one continuous oil assessement unit--- Cody Fractured Shale Continuous Oil AU; and (3) one conventional assessment Unit--- Cretaceous-Tertiary Conventional Oil and Gas AU. Estimates of undiscovered resources having the potential for additions to reserves were made for all but the Cody Fractured Shale Continuous Oil AU, which is considered hypothetical and was not quantitively assessed. The mean estimate of the total oil is 41.99 million barrels, mean estimate of gas is 2.39 trillion cubic feet, and mean estimate of natural gas liquids is 20.55 million barrels. For gas, 480.66 billion cubic feet (BCFG) is estimated for the Frontier-Muddy Continuous Gas AU, 115.34 BCFG for the Cody Sandstone Continuous Gas AU, 383.16 BCFG for the Mesaverde-Meeteetse Sandstone Continuous Gas AU, 711.30 BCFG for the Lance-Fort Union Sandstone Gas AU, 107.18 BCFG for the Mesaverde Coalbed Gas AU, 21.29 BCFG for the Meeteetse Coalbed Gas AU, and 118.08 BCFG for the Fort Union Coalbed Gas AU. All the undiscovered oil and 98.94 BCFG of undiscovered gas is in the Cretaceous-Tertiary Conventional Oil and Gas AU.

Evidence of final-state suppression of high-p{_ T} hadrons in Au + Au collisions using d + Au measurements at RHIC

NASA Astrophysics Data System (ADS)

Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Becker, B.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Busza, W.; Carroll, A.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Harrington, A. S.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Hołyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Khan, N.; Kulinich, P.; Kuo, C. M.; Lee, J. W.; Lin, W. T.; Manly, S.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Roland, C.; Roland, G.; Sagerer, J.; Sarin, P.; Sedykh, I.; Skulski, W.; Smith, C. E.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Veres, G. I.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wysłouch, B.; Zhang, J.

Transverse momentum spectra of charged hadrons with pT < 6 GeV/c have been measured near mid-rapidity (0.2 < ɛ < 1.4) by the PHOBOS experiment at RHIC in Au + Au and d + Au collisions at {√ {s{NN}} = {200 GeV}}. The spectra for different collision centralities are compared to {p + ¯ {p}} collisions at the same energy. The resulting nuclear modification factor for central Au + Au collisions shows evidence of strong suppression of charged hadrons in the high-pT region (>2 GeV/c). In contrast, the d + Au nuclear modification factor exhibits no suppression of the high-pT yields. These measurements suggest a large energy loss of the high-pT particles in the highly interacting medium created in the central Au + Au collisions. The lack of suppression in d + Au collisions suggests that it is unlikely that initial state effects can explain the suppression in the central Au + Au collisions. PACS: 25.75.-q

Impact of American Cinema on Nuclear Geopolitical Identity

DTIC Science & Technology

2014-04-01

AU/ACSC/AY14 AIR COMMAND AND STAFF COLLEGE AIR UNIVERSITY IMPACT OF AMERICAN CINEMA ON NUCLEAR GEOPOLITICAL IDENTITY by Major Michael...26 ABSTRACT American cinema has shaped and reinforced nuclear ideological geopolitics in the United States since the beginning of...policymakers and the public. When US nuclear strategy appeared to shift away from deterrence later in the Cold War, American cinema pushed back by

Long-lived, charge-shift states in heterometallic, porphyrin-based dendrimers formed via click chemistry.

PubMed

Le Pleux, Loïc; Pellegrin, Yann; Blart, Errol; Odobel, Fabrice; Harriman, Anthony

2011-05-26

A series of multiporphyrin clusters has been synthesized and characterized in which there exists a logical gradient for either energy or electron transfer between the porphyrins. A central free-base porphyrin (FbP), for example, is equipped with peripheral zinc(II) porphyrins (ZnP) which act as ancillary light harvesters and transfer excitation energy to the FbP under visible light illumination. Additional energy-transfer steps occur at the triplet level, and the series is expanded by including magnesium(II) porphyrins and/or tin(IV) porphyrins as chromophores. Light-induced electron transfer is made possible by incorporating a gold(III) porphyrin (AuP(+)) into the array. Although interesting by themselves, these clusters serve as control compounds by which to understand the photophysical processes occurring within a three-stage dendrimer comprising an AuP(+) core, a second layer formed from four FbP units, and an outer layer containing 12 ZnP residues. Here, illumination into a peripheral ZnP leads to highly efficient electronic energy transfer to FbP, followed by charge transfer to the central AuP(+). Charge recombination within the resultant charge-shift state is intercepted by secondary hole transfer to the ZnP, which occurs with a quantum yield of around 20%. The final charge-shift state survives for some microseconds in fluid solution at room temperature.

Bright Two-Photon Emission and Ultra-Fast Relaxation Dynamics in a DNA-Templated Nanocluster Investigated by Ultra-Fast Spectroscopy

DTIC Science & Technology

2012-01-01

Michigan 3003 S. State St Ann Arbor, MI 48109 -1274 REPORT DOCUMENTATION PAGE b . ABSTRACT UU c. THIS PAGE UU 2. REPORT TYPE New Reprint 17. LIMITATION OF...Figure 1: Steady state absorption for Au25 Au55, Au140, Au2406 and Mie theory calculation using parameter similar to Au25.7 B . Emission Mechanism of...short-lived (hundreds of fs), and it is most likely to be associated with the metal core (State B ).7,17 The near-infrared emission is related to the

Formation and stability of dense arrays of Au nanoclusters on hexagonal boron nitride/Rh(111)

NASA Astrophysics Data System (ADS)

Patterson, Matthew C.; Habenicht, Bradley F.; Kurtz, Richard L.; Liu, Li; Xu, Ye; Sprunger, Phillip T.

2014-05-01

We have studied the nucleation and growth of Au clusters at submonolayer and greater coverages on the h-BN nanomesh grown on Rh(111) by means of scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). STM reveals that submonolayer Au deposited at 115 K nucleates within the nanomesh pores and remains confined to the pores even after warming to room temperature. Whereas there is a propensity of monoatomic high islands at low temperature, upon annealing, bi- and multilayer Au clusters emerge. Deposition of higher coverages of Au similarly results in Au clusters primarily confined to the nanomesh pores at room temperature. XPS analysis of core-level electronic states in the deposited Au shows strong final-state effects induced by restricted particle size dominating for low Au coverage, with indications that larger Au clusters are negatively charged by interaction through the h-BN monolayer. DFT calculations suggest that the structure of the Au clusters transitions from monolayer to bilayer at a size between 30 and 37 atoms per cluster, in line with our experiment. Bader charge analysis supports the negative charge state of deposited Au.

Gold in the layered structures of R 3Au 7Sn 3: From relativity to versatility

DOE PAGES

Provino, Alessia; Steinberg, Simon Alexander; Smetana, Volodymyr; ...

2016-07-11

A new isotypic series of ternary rare earth element-gold-tetrel intermetallic compounds has been synthesized and their structures and properties have been characterized. R 3Au 7Sn 3 (R = Y, La-Nd, Sm, Gd-Tm, Lu) crystallize with the hexagonal Gd 3Au 7Sn 3 prototype (Pearson symbol hP26; P6 3/m, a = 8.110-8.372 Å, c = 9.351-9.609 Å, V cell = 532.7-583.3 Å3, Z = 2), an ordered variant of the Cu 10Sn 3-type. Their structure is built up by GdPt 2Sn-type layers, which feature edge-sharing Sn@Au 6 trigonal antiprisms connected by trigonal R3 groups. Additional insertion of gold atoms leads to themore » formation of new homoatomic Au clusters, Au@Au 6; alternatively, the structure can be considered as a superstructural polyhedral packing of the ZrBeSi-type. The magnetization, heat ca-pacity and electrical resistivity have been measured for R 3Au 7Sn 3 (R = Ce, Pr, Nd and Tb). All four compounds order antiferromagnetically with the highest T N of 13 K for Tb 3Au 7Sn 3. In Ce 3Au 7Sn 3, which has a T N of 2.9 K, the heat capacity and electrical resistivity data in zero and applied fields indicate the presence of Kondo interactions. The coefficient of the linear term in the electronic heat capacity, γ, derived from the heat capacity data below 0.5 K is 211 mJ/Ce mol K 2 suggesting strong electronic correlations due to the Kondo interaction. The electronic structure calculations based on the projector augmented wave method for particular representatives of the series suggest different tendencies of the localized R-4f AOs to hybridize with the valence states. LMTO-based bonding analysis on the non-magnetic La 3Au 7Sn 3 indicates that the integrated crystal orbital Hamilton popu-lations (COHPs) are dominated by the heteroatomic Au–Sn contacts; however, contributions from La–Au and La–Sn separations are significant, both together exceeding 40 % in the overall bonding. Furthermore, homoatomic Au–Au interactions are evident for the Au@Au 6 units but, despite of the high atomic concentration of Au in the compound, they do not dominate the entire bonding picture.« less

Gold in the layered structures of R 3Au 7Sn 3: From relativity to versatility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Provino, Alessia; Steinberg, Simon Alexander; Smetana, Volodymyr

A new isotypic series of ternary rare earth element-gold-tetrel intermetallic compounds has been synthesized and their structures and properties have been characterized. R 3Au 7Sn 3 (R = Y, La-Nd, Sm, Gd-Tm, Lu) crystallize with the hexagonal Gd 3Au 7Sn 3 prototype (Pearson symbol hP26; P6 3/m, a = 8.110-8.372 Å, c = 9.351-9.609 Å, V cell = 532.7-583.3 Å3, Z = 2), an ordered variant of the Cu 10Sn 3-type. Their structure is built up by GdPt 2Sn-type layers, which feature edge-sharing Sn@Au 6 trigonal antiprisms connected by trigonal R3 groups. Additional insertion of gold atoms leads to themore » formation of new homoatomic Au clusters, Au@Au 6; alternatively, the structure can be considered as a superstructural polyhedral packing of the ZrBeSi-type. The magnetization, heat ca-pacity and electrical resistivity have been measured for R 3Au 7Sn 3 (R = Ce, Pr, Nd and Tb). All four compounds order antiferromagnetically with the highest T N of 13 K for Tb 3Au 7Sn 3. In Ce 3Au 7Sn 3, which has a T N of 2.9 K, the heat capacity and electrical resistivity data in zero and applied fields indicate the presence of Kondo interactions. The coefficient of the linear term in the electronic heat capacity, γ, derived from the heat capacity data below 0.5 K is 211 mJ/Ce mol K 2 suggesting strong electronic correlations due to the Kondo interaction. The electronic structure calculations based on the projector augmented wave method for particular representatives of the series suggest different tendencies of the localized R-4f AOs to hybridize with the valence states. LMTO-based bonding analysis on the non-magnetic La 3Au 7Sn 3 indicates that the integrated crystal orbital Hamilton popu-lations (COHPs) are dominated by the heteroatomic Au–Sn contacts; however, contributions from La–Au and La–Sn separations are significant, both together exceeding 40 % in the overall bonding. Furthermore, homoatomic Au–Au interactions are evident for the Au@Au 6 units but, despite of the high atomic concentration of Au in the compound, they do not dominate the entire bonding picture.« less

Pickup protons and pressure-balanced structures: Voyager 2 observations in merged interaction regions near 35 AU

NASA Astrophysics Data System (ADS)

Burlaga, L. F.; Ness, N. F.; Belcher, J. W.; Szabo, A.; Isenberg, P. A.; Lee, M. A.

1994-11-01

Five pressure-balanced structures, each with a scale of the order of a few hundredths of an astonomical unit (AU), were identified in two merged interaction regions (MIRs) near 35 AU in the Voyager 2 plasma and magnetic field data. They include a tangential discontinuity, simple and complex magnetic holes, slow correlated variations among the plasma and magnetic field parameters, and complex uncorrelated variations among the parameters. The changes in the magnetic pressure in these events are balanced by changes in the pressure of interstellar pickup protons. Thus the pickup protons probably play a major role in the dynamics of the MIRs. The solar wind proton and electron pressures are relatively unimportant in the MIRs at 35 AU and beyond. The region near 35 AU is transition region: the Sun is the source of the magnetic field, but the interstellar medium in source of pickups protons. Relative to the solar wind proton guyroadius, the thicknesses of the discontinuities and simple magnetic holes observed near 35 AU are at least an order of magnitude greater than those observed at 1 AU. However, the thicknesses of the tangential discontinuity and simple magnetic holes observed near 35 AU (in units of the pickup proton Larmor radius) are comparable to those observed at 1 AU (in units of the solar wind proton gyroradius). Thus the gyroradius of interstellar pickup protons controls the thickness of current sheets near 35 AU. We determine the interstellar pickup proton pressure in the PBSs. Using a model for the pickup proton temperature, we estimate that the average interstellar pickup proton pressure, temperature, and density in the MIRs at 35 AU are (0.53 +/- 0.14) x 10-12 erg/cu cm, (5.8 +/- 0.4) x 106 K and (7 +/- 2) x 10-4/cu cm.

Single cytidine units-templated syntheses of multi-colored water-soluble Au nanoclusters

NASA Astrophysics Data System (ADS)

Jiang, Hui; Zhang, Yuanyuan; Wang, Xuemei

2014-08-01

Ultra-small metallic nanoparticles, or so-called ``nanoclusters'' (NCs), have attracted considerable interest due to their unique optical properties that are different from both larger nanoparticles and single atoms. To prepare high-quality NCs, the stabilizing agent plays an essential role. In this work, we have revealed and validated that cytidine and its nucleotides (cytidine 5'-monophosphate or cytidine 5'-triphosphate) can act as efficient stabilizers for syntheses of multicolored Au NCs. Interestingly, Au NCs with blue, green and yellow fluorescence emissions are simultaneously obtained using various pH environments or reaction times. The transmission electron microscopy verifies that the size of Au NCs ranges from 1.5 to 3 nm. The X-ray photoelectron spectroscopy confirms that only Au (0) species are present in NCs. Generally, the facile preparation of multicolored Au NCs that are stabilized by cytidine units provides access to promising candidates for multiple biolabeling applications.Ultra-small metallic nanoparticles, or so-called ``nanoclusters'' (NCs), have attracted considerable interest due to their unique optical properties that are different from both larger nanoparticles and single atoms. To prepare high-quality NCs, the stabilizing agent plays an essential role. In this work, we have revealed and validated that cytidine and its nucleotides (cytidine 5'-monophosphate or cytidine 5'-triphosphate) can act as efficient stabilizers for syntheses of multicolored Au NCs. Interestingly, Au NCs with blue, green and yellow fluorescence emissions are simultaneously obtained using various pH environments or reaction times. The transmission electron microscopy verifies that the size of Au NCs ranges from 1.5 to 3 nm. The X-ray photoelectron spectroscopy confirms that only Au (0) species are present in NCs. Generally, the facile preparation of multicolored Au NCs that are stabilized by cytidine units provides access to promising candidates for multiple biolabeling applications. Electronic supplementary information (ESI) available: The feed amount for preparation of Au NCs, photophysical properties of Au NCs, the FL spectra under different pH and reaction time, and XPS results are included. See DOI: 10.1039/c4nr02180k

Electronic and mechanical properties of 5d transition metal mononitrides via first principles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao Erjun; Graduate School, Chinese Academy of Sciences, Beijing 100049; Wu Zhijian

2008-10-15

The electronic and mechanical properties of 5d transition metal mononitrides from LaN to AuN are systematically investigated by use of the density-functional theory. For each nitride, six structures are considered, i.e., rocksalt, zinc blende, CsCl, wurtzite, NiAs and WC structures. Among the considered structures, rocksalt structure is the most stable for LaN, HfN and AuN, WC structure for TaN, NiAs structure for WN, wurtzite structure for ReN, OsN, IrN and PtN. The most stable structure for each nitride is mechanically stable. The formation enthalpy increases from LaN to AuN. For LaN, HfN and TaN, the formation enthalpy is negative formore » all the considered structures, while from WN to AuN, except wurtzite structure in ReN, the formation enthalpy is positive. The calculated density of states shows that they are all metallic. ReN in NiAs structure has the largest bulk modulus, 418 GPa. The largest shear modulus 261 GPa is from TaN in WC structure. Trends are discussed. - Graphical abstract: Formation enthalpy per formula unit {delta}H (eV) for all the considered structures of 5d transition metal mononitrides MN (M=La-Au). It was shown that the formation enthalpy increases from LaN to AuN. The nitrides with negative values indicate that they can be synthesized experimentally at ambient conditions.« less

Organogold oligomers: Exploiting iClick and aurophilic cluster formation to prepare solution stable Au 4 repeating units

DOE PAGES

Yang, Xi; Wang, Shanshan; Ghiviriga, Ion; ...

2015-05-19

A novel synthetic method to create gold based metallo–oligomers/polymers via the combination of inorganic click (iClick) with intermolecular aurophilic interactions is demonstrated. Complexes [PEt 3Au] 4(μ-N 3C 2C 6H 5) (1) and [PPhMe 2Au] 43C 2C 6H 5) (2) and {[PEt 3Au] 4[(μ-N 3C 2) 2-9,9-dihexyl-9H-fluorene]} n (8) have been synthesized via iClick. The tetranuclear structures of 1 and 2, induced by aurophilic bonding, are confirmed in the solid state through single crystal X-ray diffraction experiments and in solution via variable temperature NMR spectroscopy. The extended 1D structure of 8 is constructed by aurophilic induced self-assembly. 1H DOSY NMR analysismore » reveals that the aurophilic bonds in 1, 2, and 8 are retained in the solution phase. The degree of polymerization within complex 8 is temperature and concentration dependent, as determined by 1H DOSY NMR. The complex 8 is a rare example of a solution stable higher ordered structure linked by aurophilic interactions.« less

Geographic distribution of blood collections in Haiti before and after the 2010 earthquake.

PubMed

Bjork, A; Jean Baptiste, A E; Noel, E; Jean Charles, N P D; Polo, E; Pitman, J P

2017-05-01

The January 2010 Haiti earthquake destroyed the National Blood Transfusion Center and reduced monthly national blood collections by > 46%. Efforts to rapidly scale-up blood collections outside of the earthquake-affected region were investigated. Blood collection data for 2004-2014 from Haiti's 10 administrative departments were grouped into four regions: Northern, Central, Port-au-Prince and Southern. Analyses compared regional collection totals during the study period. Collections in Port-au-Prince accounted for 52% of Haiti's blood supply in 2009, but fell 96% in February 2010. Haiti subsequently increased blood collections in the North, Central and Southern regions to compensate. By May 2010, national blood collections were only 10·9% lower than in May 2009, with 70% of collections coming from outside of Port-au-Prince. By 2013 national collections (27 478 units) had surpassed 2009 levels by 30%, and Port-au-Prince collections had recovered (from 11 074 units in 2009 to 11 670 units in 2013). Haiti's National Blood Safety Program managed a rapid expansion of collections outside of Port-au-Prince following the earthquake. Annual collections exceeded pre-earthquake levels by 2012 and continued rising annually. Increased regional collections provided a greater share of the national blood supply, reducing dependence on Port-au-Prince for collections.

Au279(SR)84: The Smallest Gold Thiolate Nanocrystal That Is Metallic and the Birth of Plasmon.

PubMed

Sakthivel, Naga Arjun; Stener, Mauro; Sementa, Luca; Fortunelli, Alessandro; Ramakrishna, Guda; Dass, Amala

2018-03-15

We report a detailed study on the optical properties of Au 279 (SR) 84 using steady-state and transient absorption measurements to probe its metallic nature, time-dependent density functional theory (TDDFT) studies to correlate the optical spectra, and density of states (DOS) to reveal the factors governing the origin of the collective surface plasmon resonance (SPR) oscillation. Au 279 is the smallest identified gold nanocrystal to exhibit SPR. Its optical absorption exhibits SPR at 510 nm. Power-dependent bleach recovery kinetics of Au 279 suggests that electron dynamics dominates its relaxation and it can support plasmon oscillations. Interestingly, TDDFT and DOS studies with different tail group residues (-CH 3 and -Ph) revealed the important role played by the tail groups of ligands in collective oscillation. Also, steady-state and time-resolved absorption for Au 36 , Au 44 , and Au 133 were studied to reveal the molecule-to-metal evolution of aromatic AuNMs. The optical gap and transient decay lifetimes decrease as the size increases.

Evolution of Excited-State Dynamics in Periodic Au 28, Au 36, Au 44, and Au 52 Nanoclusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Meng; Zeng, Chenjie; Sfeir, Matthew Y.

An understanding of the correlation between the atomic structure and optical properties of gold nanoclusters is essential for exploration of their functionalities and applications involving light harvesting and electron transfer. We report the femto-nanosecond excited state dynamics of a periodic series of face-centered cubic (FCC) gold nanoclusters (including Au 28, Au 36, Au 44, and Au 52), which exhibit a set of unique features compared with other similar sized clusters. Molecular-like ultrafast S n → S 1 internal conversions (i.e., radiationless electronic transitions) are observed in the relaxation dynamics of FCC periodic series. Excited-state dynamics with near-HOMO–LUMO gap excitation lacksmore » ultrafast decay component, and only the structural relaxation dominates in the dynamical process, which proves the absence of core–shell relaxation. Interestingly, both the relaxation of the hot carriers and the band-edge carrier recombination become slower as the size increases. The evolution in excited-state properties of this FCC series offers new insight into the structure-dependent properties of metal nanoclusters, which will benefit their optical energy harvesting and photocatalytic applications.« less

Evolution of Excited-State Dynamics in Periodic Au 28, Au 36, Au 44, and Au 52 Nanoclusters

DOE PAGES

Zhou, Meng; Zeng, Chenjie; Sfeir, Matthew Y.; ...

2017-08-10

An understanding of the correlation between the atomic structure and optical properties of gold nanoclusters is essential for exploration of their functionalities and applications involving light harvesting and electron transfer. We report the femto-nanosecond excited state dynamics of a periodic series of face-centered cubic (FCC) gold nanoclusters (including Au 28, Au 36, Au 44, and Au 52), which exhibit a set of unique features compared with other similar sized clusters. Molecular-like ultrafast S n → S 1 internal conversions (i.e., radiationless electronic transitions) are observed in the relaxation dynamics of FCC periodic series. Excited-state dynamics with near-HOMO–LUMO gap excitation lacksmore » ultrafast decay component, and only the structural relaxation dominates in the dynamical process, which proves the absence of core–shell relaxation. Interestingly, both the relaxation of the hot carriers and the band-edge carrier recombination become slower as the size increases. The evolution in excited-state properties of this FCC series offers new insight into the structure-dependent properties of metal nanoclusters, which will benefit their optical energy harvesting and photocatalytic applications.« less

Topological Insulators in Ternary Compounds with a Honeycomb Lattice

NASA Astrophysics Data System (ADS)

Zhang, Hai-Jun; Chadov, Stanislav; Muchler, Lukas; Yan, Binghai; Qi, Xiao-Liang; Kübler, Jürgen; Zhang, Shou-Cheng; Felser, Claudia

2011-03-01

One of the most exciting subjects in solid state physics is a single layer of graphite which exhibits a variety of unconventional novel properties. The key feature of its electronic structure are linear dispersive bands which cross in a single point at the Fermi energy. This is so-called Dirac cone. The ternary compounds, such as LiAuSe and KHgSb with a honeycomb structure of their Au-Se and Hg-Sb layers feature band inversion very similar to HgTe which is a strong precondition for existence of the topological surface states. These materials exhibit the surface states formed by only a single Dirac cone at the G point together with the small direct band gap opened by a strong spin-orbit coupling (SOC) in the bulk. These materials are centro-symmetric, therefore, it is possible to determine the parity of their wave functions, and hence, their topological character. The work was supported by the supercomputing center at Stanford Institute Materials and Energy Science. The financial support of the DFG/ASPIMATT project (unit 1.2-A) is gratefully acknowledged.

Comment on “the ground-state structures of Au10-, Au8Ni and Au9Ni clusters”

NASA Astrophysics Data System (ADS)

Zheng, Ben-Xia; Die, Dong; Li, Qian-Qian; Dai, Ming-Liang; Li, Zhi-Qin; Yang, Ji-Xian

2017-09-01

The lowest energy structures of Aun+1- and AunNi (n = 2-9) clusters have been researched using the CALYPSO structure searching method in conjunction with the density functional theory. It is found that the most stable structures of Au10-, Au8Ni and Au9Ni clusters reported by Tang et al. [C. M. Tang, X. X. Chen and X. D. Yang, Int. J. Mod. Phys. B 28, 1450138 (2014)] are low-lying isomers. The correct ground states and vibrational spectra are given in this paper.

The solubility of Pd and Au in hydrous intermediate silicate melts: The effect of oxygen fugacity and the addition of Cl and S

NASA Astrophysics Data System (ADS)

Sullivan, Neal A.; Zajacz, Zoltan; Brenan, James M.

2018-06-01

The solubilities of Pd and Au in a hydrous trachyandesitic melt were experimentally determined at 1000 °C and 200 MPa at oxygen fugacity (ƒO2) from 0.45 log units below to 6.55 log units above the Ni-NiO buffer (NNO). The effect of adding metal-binding ligands (i.e. Cl and S) to the silicate melt was also studied. The solubility of Au increases from 0.15 ± 0.1 to 3.85 ± 1.48 ppm in Cl- and S-free melts with ƒO2 increasing from NNO-0.45 to NNO+6.55 with a slope that suggests that it is present in 1+ oxidation state over the entire studied ƒO2 range. On the other hand, Pd solubility, shows a more moderate increase with ƒO2, especially in the lower half of the studied range, increasing from 2.66 ± 0.25 ppm at NNO-0.45 to only 3.62 ± 0.38 ppm at NNO+1.72 in Cl- and S-free melts. Overall, the variation in Pd solubility as a function of ƒO2 indicates Pd being dissolved in the silicate melt in both zero and 1+ oxidation state, with the former being dominant below NNO+4.5. At NNO-0.45 to +3.48, the addition of 3170-4060 ppm Cl to the silicate melt increased the solubility of Au by an average factor of 1.5, in comparison to Cl-free melts. However, at NNO+6.55, Au solubility increased by a factor of 2.5. The addition of Cl had a negligible effect on the solubility of Pd except for a large increase (factor of 2.4) at NNO+6.55. At reducing conditions (NNO-0.45), the addition of 170 ppm S to the silicate melt increased the solubility of Au by a factor of ∼4 but did not change the solubility of Pd in comparison to S-free melts. The observation that Pd is dominantly present as Pd0 at NNO < +4.5 may explain the lack of complexation with potential reduced sulfur-bearing and chloride ligands. As one may expect similar behavior in fluids degassing from magmas at depth, the lack of oxidized Pd species could be an important factor behind the scarcity of economically viable Pd-rich magmatic-hydrothermal deposits observed in nature.

The Foreign Disclosure and Technical Information System (FORDTIS) User Manual

DTIC Science & Technology

1985-07-01

INDIA 10 BRITISH INDIAN OCEAN TERRITORY IP CLIPPERTON ISLAND IQ UNITED STATES MISCELLANEOUS PACIFIC ISLANDS (obsolete) IR , IRAN IS ISRAEL IT...CARTIER ISLANDS AU AUSTRIA AV ANGUILLA AY ANTARCTICA BA BAHRAIN BB BARBADOS ’ - ’ BC BOTSWANA BD BERMUDA BE BELGIUM BP...BAHAMAS, THE BG BANGLADESH BH BELIZE BL BOLIVIA BM BURMA BN BENIN (formerly DM) BP SOLOMON ISLANDS BQ NAVASSA ISLAND BR BRAZIL BS BASSAS DA INDIA

Diagnostic System for Decomposition Studies of Energetic Materials

DTIC Science & Technology

2017-10-03

transition states and reaction pathways are sought. The overall objective for these combined experimental studies and quantum mechanics investigations...peak-to-peak 1 min: 50,000:1 ( 8.6×10-6 AU noise) peak-to-peak Interferometer UltraScan linear air bearing scanner with True -Alignment Aperture... True 24 bit dynamic range for all scan velocities, dual channel data acquisition Validation Internal validation unit, 6 positions, certified

Supramolecular Control over the Interparticle Distance in Gold Nanoparticle Arrays by Cyclodextrin Polyrotaxanes

PubMed Central

Paulo Coelho, Joao; Osío Barcina, José; Aicart, Emilio; Tardajos, Gloria; Cruz-Gil, Pablo; Salgado, Cástor; Díaz-Núñez, Pablo

2018-01-01

Amphiphilic nonionic ligands, synthesized with a fixed hydrophobic moiety formed by a thiolated alkyl chain and an aromatic ring, and with a hydrophilic tail composed of a variable number of oxyethylene units, were used to functionalize spherical gold nanoparticles (AuNPs) in water. Steady-state and time-resolved fluorescence measurements of the AuNPs in the presence of α-cyclodextrin (α-CD) revealed the formation of supramolecular complexes between the ligand and macrocycle at the surface of the nanocrystals. The addition of α-CD induced the formation of inclusion complexes with a high apparent binding constant that decreased with the increasing oxyethylene chain length. The formation of polyrotaxanes at the surface of AuNPs, in which many α-CDs are trapped as hosts on the long and linear ligands, was demonstrated by the formation of large and homogeneous arrays of self-assembled AuNPs with hexagonal close packing, where the interparticle distance increased with the length of the oxyethylene chain. The estimated number of α-CDs per polyrotaxane suggests a high rigidization of the ligand upon complexation, allowing for nearly perfect control of the interparticle distance in the arrays. This degree of supramolecular control was extended to arrays formed by AuNPs stabilized with polyethylene glycol and even to binary arrays. Electromagnetic simulations showed that the enhancement and distribution of the electric field can be finely controlled in these plasmonic arrays. PMID:29547539

Structural, (197)Au Mössbauer and solid state (31)P CP/MAS NMR studies on bis (cis-bis(diphenylphosphino)ethylene) gold(I) complexes [Au(dppey)(2)]X for X = PF(6), I.

PubMed

Healy, Peter C; Loughrey, Bradley T; Bowmaker, Graham A; Hanna, John V

2008-07-28

(197)Au Mössbauer spectra for the d(10) gold(i) phosphine complexes, [Au(dppey)(2)]X (X = PF(6), I; dppey = (cis-bis(diphenylphosphino)ethylene), and the single crystal X-ray structure and solid state (31)P CPMAS NMR spectrum of [Au(dppey)(2)]I are reported here. In [Au(dppey)(2)]I the AuP(4) coordination geometry is distorted from the approximately D(2) symmetry observed for the PF(6)(-) complex with Au-P bond lengths 2.380(2)-2.426(2) A and inter-ligand P-Au-P angles 110.63(5)-137.71(8) degrees . Quadrupole splitting parameters derived from the Mössbauer spectra are consistent with the increased distortion of the AuP(4) coordination sphere with values of 1.22 and 1.46 mm s(-1) for the PF(6)(-) and I(-) complexes respectively. In the solid state (31)P CP MAS NMR spectrum of [Au(dppey)(2)]I, signals for each of the four crystallographically independent phosphorus nuclei are observed, with the magnitude of the (197)Au quadrupole coupling being sufficiently large to produce a collapse of (1)J(Au-P) splitting from quartets to doublets. The results highlight the important role played by the counter anion in the determination of the structural and spectroscopic properties of these sterically crowded d(10) complexes.

Ohmic contacts to semiconducting diamond

NASA Astrophysics Data System (ADS)

Zeidler, James R.; Taylor, M. J.; Zeisse, Carl R.; Hewett, C. A.; Delahoussaye, Paul R.

1990-10-01

Work was carried out to improve the electron beam evaporation system in order to achieve better deposited films. The basic system is an ion pumped vacuum chamber, with a three-hearth, single-gun e-beam evaporator. Four improvements were made to the system. The system was thoroughly cleaned and new ion pump elements, an e-gun beam adjust unit, and a more accurate crystal monitor were installed. The system now has a base pressure of 3 X 10(exp -9) Torr, and can easily deposit high-melting-temperature metals such as Ta with an accurately controlled thickness. Improved shadow masks were also fabricated for better alignment and control of corner contacts for electrical transport measurements. Appendices include: A Thermally Activated Solid State Reaction Process for Fabricating Ohmic Contacts to Semiconducting Diamond; Tantalum Ohmic Contacts to Diamond by a Solid State Reaction Process; Metallization of Semiconducting Diamond: Mo, Mo/Au, and Mo/Ni/Au; Specific Contact Resistance Measurements of Ohmic Contracts to Diamond; and Electrical Activation of Boron Implanted into Diamond.

Geologic assessment of undiscovered oil and gas resources: Oligocene Frio and Anahuac Formations, United States Gulf of Mexico coastal plain and State waters

USGS Publications Warehouse

Swanson, Sharon M.; Karlsen, Alexander W.; Valentine, Brett J.

2013-01-01

The Oligocene Frio and Anahuac Formations were assessed as part of the 2007 U.S. Geological Survey (USGS) assessment of Tertiary strata of the U.S. Gulf of Mexico Basin onshore and State waters. The Frio Formation, which consists of sand-rich fluvio-deltaic systems, has been one of the largest hydrocarbon producers from the Paleogene in the Gulf of Mexico. The Anahuac Formation, an extensive transgressive marine shale overlying the Frio Formation, contains deltaic and slope sandstones in Louisiana and Texas and carbonate rocks in the eastern Gulf of Mexico. In downdip areas of the Frio and Anahuac Formations, traps associated with faulted, rollover anticlines are common. Structural traps commonly occur in combination with stratigraphic traps. Faulted salt domes in the Frio and Anahuac Formations are present in the Houston embayment of Texas and in south Louisiana. In the Frio Formation, stratigraphic traps are found in fluvial, deltaic, barrier-bar, shelf, and strandplain systems. The USGS Tertiary Assessment Team defined a single, Upper Jurassic-Cretaceous-Tertiary Composite Total Petroleum System (TPS) for the Gulf Coast basin, based on previous studies and geochemical analysis of oils in the Gulf Coast basin. The primary source rocks for oil and gas within Cenozoic petroleum systems, including Frio Formation reservoirs, in the northern, onshore Gulf Coastal region consist of coal and shale rich in organic matter within the Wilcox Group (Paleocene–Eocene), with some contributions from the Sparta Sand of the Claiborne Group (Eocene). The Jurassic Smackover Formation and Cretaceous Eagle Ford Formation also may have contributed substantial petroleum to Cenozoic reservoirs. Modeling studies of thermal maturity by the USGS Tertiary Assessment Team indicate that downdip portions of the basal Wilcox Group reached sufficient thermal maturity to generate hydrocarbons by early Eocene; this early maturation is the result of rapid sediment accumulation in the early Tertiary, combined with the reaction kinetic parameters used in the models. A number of studies indicate that the migration of oil and gas in the Cenozoic Gulf of Mexico basin is primarily vertical, occurring along abundant growth faults associated with sediment deposition or along faults associated with salt domes. The USGS Tertiary assessment team developed a geologic model based on recurring regional-scale structural and depositional features in Paleogene strata to define assessment units (AUs). Three general areas, as described in the model, are found in each of the Paleogene stratigraphic intervals assessed: “Stable Shelf,” “Expanded Fault,” and “Slope and Basin Floor” zones. On the basis of this model, three AUs for the Frio Formation were defined: (1) the Frio Stable Shelf Oil and Gas AU, containing reservoirs with a mean depth of about 4,800 feet in normally pressured intervals; (2) the Frio Expanded Fault Zone Oil and Gas AU, containing reservoirs with a mean depth of about 9,000 feet in primarily overpressured intervals; and (3) the Frio Slope and Basin Floor Gas AU, which currently has no production but has potential for deep gas resources (>15,000 feet). AUs also were defined for the Hackberry trend, which consists of a slope facies stratigraphically in the middle part of the Frio Formation, and the Anahuac Formation. The Frio Basin Margin AU, an assessment unit extending to the outcrop of the Frio (or basal Miocene), was not quantitatively assessed because of its low potential for production. Two proprietary, commercially available databases containing field and well production information were used in the assessment. Estimates of undiscovered resources for the five AUs were based on a total of 1,734 reservoirs and 586,500 wells producing from the Frio and Anahuac Formations. Estimated total mean values of technically recoverable, undiscovered resources are 172 million barrels of oil (MMBO), 9.4 trillion cubic feet of natural gas (TCFG), and 542 million barrels of natural gas liquids for all of the Frio and Anahuac AUs. Of the five units assessed, the Frio Slope and Basin Floor Gas AU has the greatest potential for undiscovered gas resources, having an estimated mean of 5.6 TCFG. The Hackberry Oil and Gas AU shows the second highest potential for gas of the five units assessed, having an estimated mean of 1.8 TCFG. The largest undiscovered, conventional crude oil resource was estimated for the Frio Slope and Basin Floor Gas AU; the estimated mean for oil in this AU is 110 MMBO.

Two-color two-laser fabrication of gold nanoparticles in a PVA film

NASA Astrophysics Data System (ADS)

Sakamoto, Masanori; Tachikawa, Takashi; Fujitsuka, Mamoru; Majima, Tetsuro

2006-03-01

We developed a new method for the fabrication of gold nanoparticles (AuNps) in a poly(vinyl alcohol) film using a two-color two-laser irradiation. The benzophenone ketyl radical (BPH rad ) in the excited state (BPH rad (D 1)) was used as a reducing agent. Although BPH rad in the ground state also reduced AuCl4- to produce AuNps, the formation of AuNp was significantly enhanced by the BPH rad (D 1) generated by the two-color two-laser irradiation. Because the electron transfer from the BPH rad (D 1) to AuCl4- enhanced the formation of AuNps.

Interaction of CO with an Au monatomic chain at different strains: Electronic structure and ballistic transport

NASA Astrophysics Data System (ADS)

Sclauzero, Gabriele; Dal Corso, Andrea; Smogunov, Alexander

2012-04-01

We study the energetics, the electronic structure, and the ballistic transport of an infinite Au monatomic chain with an adsorbed CO molecule. We find that the bridge adsorption site is energetically favored with respect to the atop site, both at the equilibrium Au-Au spacing of the chain and at larger spacings. Instead, a substitutional configuration requires a very elongated Au-Au bond, well above the rupture distance of the pristine Au chain. The electronic structure properties can be described by the Blyholder model, which involves the formation of bonding/antibonding pairs of 5σ and 2π states through the hybridization between molecular levels of CO and metallic states of the chain. In the atop geometry, we find an almost vanishing conductance due to the 5σ antibonding states giving rise to a Fano-like destructive interference close to the Fermi energy. In the bridge geometry, instead, the same states are shifted to higher energies and the conductance reduction with respect to pristine Au chain is much smaller. We also examine the effects of strain on the ballistic transport, finding opposite behaviors for the atop and bridge conductances. Only the bridge geometry shows a strain dependence compatible with the experimental conductance traces.

Sharp Transition from Nonmetallic Au246 to Metallic Au279 with Nascent Surface Plasmon Resonance.

PubMed

Higaki, Tatsuya; Zhou, Meng; Lambright, Kelly J; Kirschbaum, Kristin; Sfeir, Matthew Y; Jin, Rongchao

2018-05-02

The optical properties of metal nanoparticles have attracted wide interest. Recent progress in controlling nanoparticles with atomic precision (often called nanoclusters) provide new opportunities for investigating many fundamental questions, such as the transition from excitonic to plasmonic state, which is a central question in metal nanoparticle research because it provides insights into the origin of surface plasmon resonance (SPR) as well as the formation of metallic bond. However, this question still remains elusive because of the extreme difficulty in preparing atomically precise nanoparticles larger than 2 nm. Here we report the synthesis and optical properties of an atomically precise Au 279 (SR) 84 nanocluster. Femtosecond transient absorption spectroscopic analysis reveals that the Au 279 nanocluster shows a laser power dependence in its excited state lifetime, indicating metallic state of the particle, in contrast with the nonmetallic electronic structure of the Au 246 (SR) 80 nanocluster. Steady-state absorption spectra reveal that the nascent plasmon band of Au 279 at 506 nm shows no peak shift even down to 60 K, consistent with plasmon behavior. The sharp transition from nonmetallic Au 246 to metallic Au 279 is surprising and will stimulate future theoretical work on the transition and many other relevant issues.

Evidence from d+Au measurements for final-state suppression of high-p(T) hadrons in Au+Au collisions at RHIC.

PubMed

Adams, J; Adler, C; Aggarwal, M M; Ahammed, Z; Amonett, J; Anderson, B D; Anderson, M; Arkhipkin, D; Averichev, G S; Badyal, S K; Balewski, J; Barannikova, O; Barnby, L S; Baudot, J; Bekele, S; Belaga, V V; Bellwied, R; Berger, J; Bezverkhny, B I; Bhardwaj, S; Bhaskar, P; Bhati, A K; Bichsel, H; Billmeier, A; Bland, L C; Blyth, C O; Bonner, B E; Botje, M; Boucham, A; Brandin, A; Bravar, A; Cadman, R V; Cai, X Z; Caines, H; Calderón de la Barca Sánchez, M; Carroll, J; Castillo, J; Castro, M; Cebra, D; Chaloupka, P; Chattopadhyay, S; Chen, H F; Chen, Y; Chernenko, S P; Cherney, M; Chikanian, A; Choi, B; Christie, W; Coffin, J P; Cormier, T M; Cramer, J G; Crawford, H J; Das, D; Das, S; Derevschikov, A A; Didenko, L; Dietel, T; Dong, X; Draper, J E; Du, F; Dubey, A K; Dunin, V B; Dunlop, J C; Dutta Majumdar, M R; Eckardt, V; Efimov, L G; Emelianov, V; Engelage, J; Eppley, G; Erazmus, B; Fachini, P; Faine, V; Faivre, J; Fatemi, R; Filimonov, K; Filip, P; Finch, E; Fisyak, Y; Flierl, D; Foley, K J; Fu, J; Gagliardi, C A; Ganti, M S; Gagunashvili, N; Gans, J; Gaudichet, L; Germain, M; Geurts, F; Ghazikhanian, V; Ghosh, P; Gonzalez, J E; Grachov, O; Grigoriev, V; Gronstal, S; Grosnick, D; Guedon, M; Guertin, S M; Gupta, A; Gushin, E; Gutierrez, T D; Hallman, T J; Hardtke, D; Harris, J W; Heinz, M; Henry, T W; Heppelmann, S; Herston, T; Hippolyte, B; Hirsch, A; Hjort, E; Hoffmann, G W; Horsley, M; Huang, H Z; Huang, S L; Humanic, T J; Igo, G; Ishihara, A; Jacobs, P; Jacobs, W W; Janik, M; Johnson, I; Jones, P G; Judd, E G; Kabana, S; Kaneta, M; Kaplan, M; Keane, D; Kiryluk, J; Kisiel, A; Klay, J; Klein, S R; Klyachko, A; Koetke, D D; Kollegger, T; Konstantinov, A S; Kopytine, M; Kotchenda, L; Kovalenko, A D; Kramer, M; Kravtsov, P; Krueger, K; Kuhn, C; Kulikov, A I; Kumar, A; Kunde, G J; Kunz, C L; Kutuev, R Kh; Kuznetsov, A A; Lamont, M A C; Landgraf, J M; Lange, S; Lansdell, C P; Lasiuk, B; Laue, F; Lauret, J; Lebedev, A; Lednický, R; Leontiev, V M; LeVine, M J; Li, C; Li, Q; Lindenbaum, S J; Lisa, M A; Liu, F; Liu, L; Liu, Z; Liu, Q J; Ljubicic, T; Llope, W J; Long, H; Longacre, R S; Lopez-Noriega, M; Love, W A; Ludlam, T; Lynn, D; Ma, J; Ma, Y G; Magestro, D; Mahajan, S; Mangotra, L K; Mahapatra, D P; Majka, R; Manweiler, R; Margetis, S; Markert, C; Martin, L; Marx, J; Matis, H S; Matulenko, Yu A; McShane, T S; Meissner, F; Melnick, Yu; Meschanin, A; Messer, M; Miller, M L; Milosevich, Z; Minaev, N G; Mironov, C; Mishra, D; Mitchell, J; Mohanty, B; Molnar, L; Moore, C F; Mora-Corral, M J; Morozov, V; de Moura, M M; Munhoz, M G; Nandi, B K; Nayak, S K; Nayak, T K; Nelson, J M; Nevski, P; Nikitin, V A; Nogach, L V; Norman, B; Nurushev, S B; Odyniec, G; Ogawa, A; Okorokov, V; Oldenburg, M; Olson, D; Paic, G; Pandey, S U; Pal, S K; Panebratsev, Y; Panitkin, S Y; Pavlinov, A I; Pawlak, T; Perevoztchikov, V; Peryt, W; Petrov, V A; Phatak, S C; Picha, R; Planinic, M; Pluta, J; Porile, N; Porter, J; Poskanzer, A M; Potekhin, M; Potrebenikova, E; Potukuchi, B V K S; Prindle, D; Pruneau, C; Putschke, J; Rai, G; Rakness, G; Raniwala, R; Raniwala, S; Ravel, O; Ray, R L; Razin, S V; Reichhold, D; Reid, J G; Renault, G; Retiere, F; Ridiger, A; Ritter, H G; Roberts, J B; Rogachevski, O V; Romero, J L; Rose, A; Roy, C; Ruan, L J; Rykov, V; Sahoo, R; Sakrejda, I; Salur, S; Sandweiss, J; Savin, I; Schambach, J; Scharenberg, R P; Schmitz, N; Schroeder, L S; Schweda, K; Seger, J; Seliverstov, D; Seyboth, P; Shahaliev, E; Shao, M; Sharma, M; Shestermanov, K E; Shimanskii, S S; Singaraju, R N; Simon, F; Skoro, G; Smirnov, N; Snellings, R; Sood, G; Sorensen, P; Sowinski, J; Spinka, H M; Srivastava, B; Stanislaus, S; Stock, R; Stolpovsky, A; Strikhanov, M; Stringfellow, B; Struck, C; Suaide, A A P; Sugarbaker, E; Suire, C; Sumbera, M; Surrow, B; Symons, T J M; Szanto de Toledo, A; Szarwas, P; Tai, A; Takahashi, J; Tang, A H; Thein, D; Thomas, J H; Tikhomirov, V; Tokarev, M; Tonjes, M B; Trainor, T A; Trentalange, S; Tribble, R E; Trivedi, M D; Trofimov, V; Tsai, O; Ullrich, T; Underwood, D G; Van Buren, G; VanderMolen, A M; Vasiliev, A N; Vasiliev, M; Vigdor, S E; Viyogi, Y P; Voloshin, S A; Waggoner, W; Wang, F; Wang, G; Wang, X L; Wang, Z M; Ward, H; Watson, J W; Wells, R; Westfall, G D; Whitten, C; Wieman, H; Willson, R; Wissink, S W; Witt, R; Wood, J; Wu, J; Xu, N; Xu, Z; Xu, Z Z; Yakutin, A E; Yamamoto, E; Yang, J; Yepes, P; Yurevich, V I; Zanevski, Y V; Zborovský, I; Zhang, H; Zhang, H Y; Zhang, W M; Zhang, Z P; Zołnierczuk, P A; Zoulkarneev, R; Zoulkarneeva, J; Zubarev, A N

2003-08-15

We report measurements of single-particle inclusive spectra and two-particle azimuthal distributions of charged hadrons at high transverse momentum (high p(T)) in minimum bias and central d+Au collisions at sqrt[s(NN)]=200 GeV. The inclusive yield is enhanced in d+Au collisions relative to binary-scaled p+p collisions, while the two-particle azimuthal distributions are very similar to those observed in p+p collisions. These results demonstrate that the strong suppression of the inclusive yield and back-to-back correlations at high p(T) previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions.

Atomic and electronic structures of Si(1 1 1)-(√3 x √3)R30°-Au and (6 × 6)-Au surfaces.

PubMed

Patterson, C H

2015-12-02

Si(1 1 1)-Au surfaces with around one monolayer of Au exhibit many ordered structures and structures containing disordered domain walls. Hybrid density functional theory (DFT) calculations presented here reveal the origin of these complex structures and tendency to form domain walls. The conjugate honeycomb chain trimer (CHCT) structure of the [Formula: see text]-Au phase contains Si atoms with non-bonding surface states which can bind Au atoms in pairs in interstices of the CHCT structure and make this surface metallic. Si adatoms adsorbed on the [Formula: see text]-Au surface induce a gapped surface through interaction with the non-bonding states. Adsorption of extra Au atoms in interstitial sites of the [Formula: see text]-Au surface is stabilized by interaction with the non-bonding orbitals and leads to higher coverage ordered structures including the [Formula: see text]-Au phase. Extra Au atoms bound in interstitial sites of the [Formula: see text]-Au surface result in top layer Si atoms with an SiAu4 butterfly wing configuration. The structure of a [Formula: see text]-Au phase, whose in-plane top atomic layer positions were previously determined by an electron holography technique (Grozea et al 1998 Surf. Sci. 418 32), is calculated using total energy minimization. The Patterson function for this structure is calculated and is in good agreement with data from an in-plane x-ray diffraction study (Dornisch et al 1991 Phys. Rev. B 44 11221). Filled and empty state scanning tunneling microscopy (STM) images are calculated for domain walls and the [Formula: see text]-Au structure. The [Formula: see text]-Au phase is 2D chiral and this is evident in computed and actual STM images. [Formula: see text]-Au and domain wall structures contain the SiAu4 motif with a butterfly wing shape. Chemical bonding within the Si-Au top layers of the [Formula: see text]-Au and [Formula: see text]-Au surfaces is analyzed and an explanation for the SiAu4 motif structure is given.

The electric dipole moments in the ground states of gold oxide, AuO, and gold sulfide, AuS.

PubMed

Zhang, Ruohan; Yu, Yuanqin; Steimle, Timothy C; Cheng, Lan

2017-02-14

The B 2 Σ - - X 2 Π 3/2 (0,0) bands of a cold molecular beam sample of gold monoxide, AuO, and gold monosulfide, AuS, have been recorded at high resolution both field free and in the presence of a static electric field. The observed electric field induced splittings and shifts were analyzed to produce permanent electric dipole moments, μ→ el , of 2.94±0.06 D and 2.22±0.05 D for the X 2 Π 3/2 (v = 0) states of AuO and AuS, respectively. A molecular orbital correlation diagram is used to rationalize the trend in ground state μ→ el values for AuX (X = F, Cl, O, and S) molecules. The experimentally determined μ→ el are compared to those computed at the coupled-cluster singles and doubles (CCSD) level augmented with a perturbative inclusion of triple excitations (CCSD(T)) level of theory.

Na8Au9.8(4)Ga7.2 and Na17Au5.87(2)Ga46.63: The diversity of pseudo 5-fold symmetries in the Na-Au-Ga system

NASA Astrophysics Data System (ADS)

Smetana, Volodymyr; Corbett, John D.; Miller, Gordon J.

2013-11-01

The Na-rich part (~30% Na) of the Na-Au-Ga system between NaAu2, NaGa4, and Na22Ga39 has been found to contain the ternary phases Na8Au9.8(4)Ga7.2 (I) and Na17Au5.87(2)Ga46.63 (II), according to the results of single crystal X-ray diffraction measurements. I is orthorhombic, Cmcm, a=5.3040(1), b=24.519(5), c=14.573(3) Å, and contains a network of clusters with local 5-fold symmetry along the a-axis. Such clusters are frequent building units in decagonal quasicrystals and their approximants. II is rhombohedral, R3¯m, a=16.325(2), c=35.242(7) Å, and contains building blocks that are structurally identical to the Bergman-type clusters as well as fused icosahedral units known with active metals, triels and late transition elements. II also contains a polycationic network with elements of the clathrate V type structure. Tight-binding electronic structure calculations using linear muffin-tin-orbital (LMTO) methods on idealized models of I and II indicate that both compounds are metallic with evident pseudogaps at the corresponding Fermi levels. The overall Hamilton bond populations are generally dominated by Au-Ga and Au-Au bonds in I and by Ga-Ga bonds in II; moreover, the Na-Au and Na-Ga contributions in I are unexpectedly large, ~20% of the total. A similar involvement of sodium in covalent bonding has also been found in the electron-richer i-Na13Au12Ga15 quasicrystal approximant.

Single-step electron transfer on the nanometer scale: ultra-fast charge shift in strongly coupled zinc porphyrin-gold porphyrin dyads.

PubMed

Fortage, Jérôme; Boixel, Julien; Blart, Errol; Hammarström, Leif; Becker, Hans Christian; Odobel, Fabrice

2008-01-01

The synthesis, electrochemical properties, and photoinduced electron transfer processes of a series of three novel zinc(II)-gold(III) bisporphyrin dyads (ZnP--S--AuP(+)) are described. The systems studied consist of two trisaryl porphyrins connected directly in the meso position via an alkyne unit to tert-(phenylenethynylene) or penta(phenylenethynylene) spacers. In these dyads, the estimated center to center interporphyrin separation distance varies from 32 to 45 A. The absorption, emission, and electrochemical data indicate that there are strong electronic interactions between the linked elements, thanks to the direct attachment of the spacer on the porphyrin ring through the alkyne unit. At room temperature in toluene, light excitation of the zinc porphyrin results in almost quantitative formation of the charge shifted state (.+)ZnP--S--AuP(.), whose lifetime is in the order of hundreds of picoseconds. In this solvent, the charge-separated state decays to the ground state through the intermediate population of the zinc porphyrin triplet excited state. Excitation of the gold porphyrin leads instead to rapid energy transfer to the triplet ZnP. In dichloromethane the charge shift reactions are even faster, with time constants down to 2 ps, and may be induced also by excitation of the gold porphyrin. In this latter solvent, the longest charge-shifted lifetime (tau=2.3 ns) was obtained with the penta-(phenylenethynylene) spacer. The charge shift reactions are discussed in terms of bridge-mediated super-exchange mechanisms as electron or hole transfer. These new bis-porphyrin arrays, with strong electronic coupling, represent interesting molecular systems in which extremely fast and efficient long-range photoinduced charge shift occurs over a long distance. The rate constants are two to three orders of magnitude larger than for corresponding ZnP--AuP(+) dyads linked via meso-phenyl groups to oligo-phenyleneethynylene spacers. This study demonstrates the critical impact of the attachment position of the spacer on the porphyrin on the electron transfer rate, and this strategy can represent a useful approach to develop molecular photonic devices for long-range charge separations.

Input-form data for the U.S. Geological Survey assessment of the Mississippian Barnett Shale of the Bend Arch–Fort Worth Basin Province, 2015

USGS Publications Warehouse

Marra, Kristen R.; Charpentier, Ronald R.; Schenk, Christopher J.; Lewan, Michael D.; Leathers-Miller, Heidi M.; Klett, Timothy R.; Gaswirth, Stephanie B.; Le, Phuong A.; Mercier, Tracey J.; Pitman, Janet K.; Tennyson, Marilyn E.

2016-07-15

In 2015, the U.S. Geological Survey (USGS) released an updated assessment of undiscovered, technically recoverable shale gas and shale oil resources of the Mississippian Barnett Shale in north-central Texas (Marra and others, 2015). The Barnett Shale was assessed using the standard continuous (unconventional) methodology established by the USGS for two assessment units (AUs): (1) Barnett Continuous Gas AU, and (2) Barnett Mixed Continuous Gas and Oil AU. A third assessment unit, the Western Barnett Continuous Oil AU, was also defined but was not quantitatively assessed because of limited data within the extent of the AU. The purpose of this report is to provide supplemental documentation of the quantitative input parameters applied in the Barnett Shale assessment.

Solid-state dewetting of single- and bilayer Au-W thin films: Unraveling the role of individual layer thickness, stacking sequence and oxidation on morphology evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herz, A., E-mail: andreas.herz@tu-ilmenau.de, E-mail: dong.wang@tu-ilmenau.de; Franz, A.; Theska, F.

2016-03-15

Self-assembly of ultrathin Au, W, and Au-W bilayer thin films is investigated using a rapid thermal annealing technique in an inert ambient. The solid-state dewetting of Au films is briefly revisited in order to emphasize the role of initial film thickness. W films deposited onto SiO{sub 2} evolve into needle-like nanocrystals rather than forming particle-like agglomerates upon annealing at elevated temperatures. Transmission electron microscopy reveals that such nanocrystals actually consist of tungsten (VI) oxide (WO{sub 3}) which is related to an anisotropic oxide crystal growth out of the thin film. The evolution of W films is highly sensitive to themore » presence of any residual oxygen. Combination of both the dewetting of Au and the oxide crystal growth of WO{sub 3} is realized by using various bilayer film configurations of the immiscible Au and W. At low temperature, Au dewetting is initiated while oxide crystal growth is still suppressed. Depending on the stacking sequence of the Au-W bilayer thin film, W acts either as a substrate or as a passivation layer for the dewetting of Au. Being the ground layer, W changes the wettability of Au which clearly modifies its initial state for the dewetting. Being the top layer, W prevents Au from dewetting regardless of Au film thickness. Moreover, regular pattern formation of Au-WO{sub 3} nanoparticles is observed at high temperature demonstrating how bilayer thin film dewetting can create unique nanostructure arrangements.« less

Multi-layered nanocomposite dielectrics for high density organic memory devices

NASA Astrophysics Data System (ADS)

Kang, Moonyeong; Chung, Kyungwha; Baeg, Kang-Jun; Kim, Dong Ha; Kim, Choongik

2015-01-01

We fabricated organic memory devices with metal-pentacene-insulator-silicon structure which contain double dielectric layers comprising 3D pattern of Au nanoparticles (Au NPs) and block copolymer (PS-b-P2VP). The role of Au NPs is to charge/discharge carriers upon applied voltage, while block copolymer helps to form highly ordered Au NP patterns in the dielectric layer. Double-layered nanocomposite dielectrics enhanced the charge trap density (i.e., trapped charge per unit area) by Au NPs, resulting in increase of the memory window (ΔVth).

U.S. Geological Survey 2013 assessment of undiscovered resources in the Bakken and Three Forks Formations of the U.S. Williston Basin Province

USGS Publications Warehouse

Gaswirth, Stephanie B.; Marra, Kristen R.

2014-01-01

The Upper Devonian Three Forks and Upper Devonian to Lower Mississippian Bakken Formations comprise a major United States continuous oil resource. Current exploitation of oil is from horizontal drilling and hydraulic fracturing of the Middle Member of the Bakken and upper Three Forks, with ongoing exploration of the lower Three Forks, and the Upper, Lower, and Pronghorn Members of the Bakken Formation. In 2008, the U.S. Geological Survey (USGS) estimated a mean of 3.65 billion bbl of undiscovered, technically recoverable oil resource within the Bakken Formation. The USGS recently reassessed the Bakken Formation, which included an assessment of the underlying Three Forks Formation. The Pronghorn Member of the Bakken Formation, where present, was included as part of the Three Forks assessment due to probable fluid communication between reservoirs. For the Bakken Formation, five continuous and one conventional assessment units (AUs) were defined. These AUs are modified from the 2008 AU boundaries to incorporate expanded geologic and production information. The Three Forks Formation was defined with one continuous and one conventional AU. Within the continuous AUs, optimal regions of hydrocarbon recovery, or “sweet spots,” were delineated and estimated ultimate recoveries were calculated for each continuous AU. Resulting undiscovered, technically recoverable resource estimates were 3.65 billion bbl for the five Bakken continuous oil AUs and 3.73 billion bbl for the Three Forks Continuous Oil AU, generating a total mean resource estimate of 7.38 billion bbl. The two conventional AUs are hypothetical and represent a negligible component of the total estimated resource (8 million barrels of oil).

Economic evaluation of a primary care trial to reduce weight gain in overweight/obese children: the LEAP trial.

PubMed

Wake, Melissa; Gold, Lisa; McCallum, Zoë; Gerner, Bibi; Waters, Elizabeth

2008-01-01

A common policy response to the childhood obesity epidemic is to recommend that primary care physicians screen for and offer counseling to the overweight/obese. As the literature suggests, this approach may be ineffective; it is important to document the opportunity costs incurred by brief primary care obesity interventions that ultimately may not alter body mass index (BMI) trajectory. Live, Eat and Play (LEAP) was a randomized controlled trial of a brief secondary prevention intervention delivered by family physicians in 2002-2003 that targeted overweight/mildly obese children aged 5 to 9 years. Primary care utilization was prospectively audited via medical records, and parents reported family resource use by written questionnaire. Outcome measures were BMI (primary) and parent-reported physical activity and dietary habits (secondary) in intervention compared with control children. The cost of LEAP per intervention family was AU $4094 greater than for control families, mainly due to increased family resources devoted to child physical activity. Total health sector costs were AU $873 per intervention family and AU $64 per control, a difference of AU $809 (P < .001). At 15 months, intervention children did not differ significantly in adjusted BMI or daily physical activity scores compared with the control group, but dietary habits had improved. This brief intervention resulted in higher costs to families and the health care sector, which could have been devoted to other uses that do create benefits to health and/or family well-being. This has implications for countries such as the United States, the United Kingdom, and Australia, whose current guidelines recommend routine surveillance and counseling for high child BMI in the primary care sector.

Near-thermal reactions of Au(+)(1S,3D) with CH3X (X = F,Cl).

PubMed

Taylor, William S; Matthews, Cullen C; Hicks, Ashley J; Fancher, Kendall G; Chen, Li Chen

2012-01-26

Reactions of Au(+)((1)S) and Au(+)((3)D) with CH(3)F and CH(3)Cl have been carried out in a drift cell in He at a pressure of 3.5 Torr at both room temperature and reduced temperatures in order to explore the influence of the electronic state of the metal on reaction outcomes. State-specific product channels and overall two-body rate constants were identified using electronic state chromatography. These results indicate that Au(+)((1)S) reacts to yield an association product in addition to AuCH(2)(+) in parallel steps with both neutrals. Product distributions for association vs HX elimination were determined to be 79% association/21% HX elimination for X = F and 50% association/50% HX elimination when X = Cl. Reaction of Au(+)((3)D) with CH(3)F also results in HF elimination, which in this case is thought to produce (3)AuCH(2)(+). With CH(3)Cl, Au(+)((3)D) reacts to form AuCH(3)(+) and CH(3)Cl(+) in parallel steps. An additional product channel initiated by Au(+)((3)D) is also observed with both methyl halides, which yields CH(2)X(+) as a higher-order product. Kinetic measurements indicate that the reaction efficiency for both Au(+) states is significantly greater with CH(3)Cl than with CH(3)F. The observed two-body rate constant for depletion of Au(+)((1)S) by CH(3)F represents less than 5% of the limiting rate constant predicted by the average dipole orientation model (ADO) at room temperature and 226 K, whereas CH(3)Cl reacts with Au(+)((1)S) at the ADO limit at both room temperature and 218 K. Rate constants for depletion of Au(+)((3)D) by CH(3)F and CH(3)Cl were measured at 226 and 218 K respectively, and indicate that Au(+)((3)D) is consumed at approximately 2% of the ADO limit by CH(3)F and 69% of the ADO limit by CH(3)Cl. Product formation and overall efficiency for all four reactions are consistent with previous experimental results and available theoretical models.

Studies on plasmon characteristics and the local density of states of Au and Ag based nanoparticles

NASA Astrophysics Data System (ADS)

Vinod, M.; Biju, V.; Gopchandran, K. G.

2016-01-01

Knowledge about the conductive properties and the local density of states of chemically pure Au, Ag, Ag@Au core-shell and Au-Ag bimetallic nanoparticles is technologically important. Herein, the I-V characteristics and the density of states derived from scanning tunneling microscopy measurements made under atmospheric conditions is reported. The nanoparticles in thin film form used in this study were prepared by laser ablation in water followed by drop and evaporation. The morphology of the surface of the nanostructures was observed from optimizing tunneling current in each case. The monometallic Au and Ag particles shows almost similar current characteristics as well as discrete energy states but the slope of I-V characteristics was different for bimetallic structures. An attempt has also been made to compare the current measurements done in the nanoscale with the surface plasmon characteristics.

Comment on 'Origin of light-induced states in intense laser fields and their observability in photoelectron spectra'

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stroe, Marius; Boca, Malina

2005-01-01

We report discrepancies between the results presented in Fig. 1 of a recent paper of Yasuike and Someda [Phys. Rev. A 66, 053410 (2002)] and our independent calculation. At the frequency {omega}=0.55 a.u., we find that the state of the one-dimensional modified Poeschl-Teller potential, described by the authors as light induced and originating from a shadow of the field-free ground state, is in fact physical for {alpha}{sub 0}<10 a.u. and its origin is the zero-energy antibound state of the bare potential. For {omega}=0.45 a.u., we also find differences in one of the presented quasienergy trajectories in the low {alpha}{sub 0}more » region ({alpha}{sub 0}<0.4 a.u.), but we confirm the starting point at E=-0.5 a.u. for both quasienergies, as found by Yasuike and Someda.« less

Preparation, Spectroscopic Characterization, and Frontier MO Study of the Heteronuclear Luminescent [Pt(2)Au(2)(dmb)(2)(PPh(3))(4)](PF(6))(2) Cluster (dmb = 1,8-Diisocyano-p-menthane). A Cluster with a Formal Au(0)-Au(0) Bond Encapsulated inside a "Pt(2)(dmb)(2)(2+) " Fragment.

PubMed

Zhang, Tianle; Drouin, Marc; Harvey, Pierre D.

1999-11-01

The title compound is prepared from the direct reaction of Pt(2)(dba)(3) (dba = dibenzylideneacetone) and [Au(PPh(3))(2)](PF(6)) in the presence of 1,8-diisocyano-p-methane (dmb), with Pt(2)(dmb)(2)Cl(2), [Pt(4)(dmb)(4)(PPh(3))(2)](PF(6))(2), and (PPh(3))AuCl being formed as parallel products. X-ray crystallography reveals the presence of a quasi-linear PPh(3)Au-AuPPh(3) fragment encapsulated inside a "Pt(2)(dmb)(2)(2+)" ring which is axially coordinated with two PPh(3) ligands. The d(AuAu) is 2.5977(6) Å and is indicative of a strong Au-Au single bond. The IR nu(CN) data reveal that the Pt oxidation state is I, which places the Au oxidation state at 0. The PtAu distances are 2.8422(5) and 2.8082(5) Å. The Raman-active nu(Au(2)), nu(PtAu) (b(2g) + a(g)), nu(PtP), nu(AuP), and nu(PtC) are found at 121.2, approximately 100, 85.5, 162.1, 183.1, and 457.2, and 440.9 cm(-)(1), respectively. The PtAu (0.67 mdyn Å(-)(1)) and Au(2) (1.21 mdyn Å(-)(1)) force constants (F) confirm the presence of medium PtAu and strong Au(2) bonding interactions. The absorption spectra are characterized by strong bands at lambda(max) (epsilon, M(-1) cm(-1)) at 316 (32 300), 366 (37 800), and 418 nm (21 500) and lower intensity features at 516 (2860) and 655 nm (834). The cluster is luminescent at low temperatures (solid and frozen glasses), and in the solid state at room temperature, and exhibits an emission band at approximately 875 nm, and an emission lifetime, tau(e), of 4.4 +/- 0.4 ns (solvent = butyronitrile, T = 77 K).

Near-edge study of gold-substituted YBa2Cu3O(7-delta)

NASA Technical Reports Server (NTRS)

Ruckman, Mark W.; Hepp, Aloysius F.

1991-01-01

The valence of Cu and Au in YBa2Au0.3Cu2.7O7-delta was investigated using X-ray absorption near edge structure (XANES). X-ray and neutron diffraction studies indicate that Au goes on the Cu(1) site and Cu K-edge XANES shows that this has little effect on the oxidation state of the remaining copper. The Au L3 edge develops a white line feature whose position lies between that of trivalent gold oxide and monovalent potassium gold cyanide, and whose height relative to the edge step is smaller than in the two reference compounds. The appearance of the Au L3 edge suggests that fewer Au 3d states are involved in forming the Au-O bond in YBa2Au0.3Cu2.7O7-delta than in trivalent gold oxide.

Near-edge study of gold-substituted YBa2Cu3O(7-delta)

NASA Technical Reports Server (NTRS)

Ruckman, Mark W.; Hepp, Aloysius F.

1991-01-01

The valence of Cu and Au in YBa2Au0.3Cu2.7O7-delta was investigated using x-ray absorption near edge structure (XANES). X-ray and neutron diffraction studies indicate that Au goes on the Cu(1) site and Cu K-edge XANES shows that this has little effect on the oxidation state of the remaining copper. The Au L3 edge develops a white line feature whose position lies between that of trivalent gold oxide and monovalent potassium gold cyanide, and whose height relative to the edge step is smaller than in the two reference compounds. The appearance of the Au L3 edge suggests that fewer Au 3d states are involved in forming the Au-O bond in YBa2Au0.3Cu2.7O7-delta than in trivalent gold oxide.

Theoretical study on the photocatalytic properties of graphene oxide with single Au atom adsorption

NASA Astrophysics Data System (ADS)

Ju, Lin; Dai, Ying; Wei, Wei; Li, Mengmeng; Jin, Cui; Huang, Baibiao

2018-03-01

The photocatalytic properties of graphene oxide (GO) with single Au atom adsorption are studied via the first-principles calculations based on the density functional theory. The present study addresses the origin of enhancement in photocatalytic efficiency of GO derived from single Au atom depositing. Compared with the clean one, the work function of the single Au atom adsorbed GO is lowered due to the charge transfer from Au to GO, indicating enhanced surface activity. The Au atom plays as an electron trapping center and a mediating role in charge transfer from photon excited GO to target species. The photogenerated electron-hole pairs can be separated effectively. For the GO configuration with atomic Au dispersion, there are some states introduced in the band gap, which are predominantly composed of Au 6s states. Through the in-gap state, the photo-generated electron transfer from the valence band of clean GO to the conductive band more easily. In addition, the reduction of the gap in the system is also presented in the current work, which indicates that the single Au atom adsorption improves light absorption for the GO based photocatalyst. These theoretical results are valuable for the future applications of GO materials as photocatalyst for water splitting.

First-principles study of electronic structure modulations in graphene on Ru(0001) by Au intercalation

NASA Astrophysics Data System (ADS)

Nishidate, Kazume; Tanibayashi, Satoru; Yoshimoto, Noriyuki; Hasegawa, Masayuki

2018-03-01

First-principles calculations based on density functional theory are used to explore the electronic-structure modulations in graphene on Ru(0001) by Au intercalation. We first use a lattice-matched model to demonstrate that a substantial band gap is induced in graphene by sufficiently strong A-B sublattice symmetry breaking. This band gap opening occurs even in the absence of hybridization between graphene π states and Au states, and a strong sublattice asymmetry is established for a small separation (d ) between the graphene and Au layer, typically, d <3.0 Å , which can actually be achieved for a low Au coverage. In realistic situations, which are mimicked using lattice-mismatched models, graphene π states near the Dirac point easily hybridize with nearby (in energy) Au states even for a van der Waals distance, d ˜3.4 Å , and this hybridization usually dictates a band gap opening in graphene. In that case, the top parts of the intact Dirac cones survive the hybridization and are isolated to form midgap states within the hybridization gap, denying that the band gap is induced by sublattice symmetry breaking. This feature of a band gap opening is similar to that found for the so-called "first" graphene layer on silicon carbide (SiC) and the predicted band gap and doping level are in good agreement with the experiments for graphene/Au/Ru(0001).

The structure of 193Au within the Interacting Boson Fermion Model

NASA Astrophysics Data System (ADS)

Thomas, T.; Bernards, C.; Régis, J.-M.; Albers, M.; Fransen, C.; Jolie, J.; Heinze, S.; Radeck, D.; Warr, N.; Zell, K.-O.

2014-02-01

A γγ angular correlation experiment investigating the nucleus 193Au is presented. In this work the level scheme of 193Au is extended by new level information on spins, multipolarities and newly observed states. The new results are compared with theoretical predictions from a general Interacting Boson Fermion Model (IBFM) calculation for the positive-parity states. The experimental data is in good agreement with an IBFM calculation using all proton orbitals between the shell closures at Z=50 and Z=126. As a dominant contribution of the d orbital to the wave function of the lowest excited states is observed, a truncated model of the IBFM using a Bose-Fermi symmetry is applied to the describe 193Au. Using the parameters of a fit performed for 193Au, the level scheme of 192Pt, the supersymmetric partner of 193Au, is predicted but shows a too small boson seniority splitting. We obtained a common fit by including states observed in 192Pt. With the new parameters a supersymmetric description of both nuclei is established.

CuPc/Au(1 1 0): Determination of the azimuthal alignment by a combination of angle-resolved photoemission and density functional theory

PubMed Central

Lüftner, Daniel; Milko, Matus; Huppmann, Sophia; Scholz, Markus; Ngyuen, Nam; Wießner, Michael; Schöll, Achim; Reinert, Friedrich; Puschnig, Peter

2014-01-01

Here we report on a combined experimental and theoretical study on the structural and electronic properties of a monolayer of Copper-Phthalocyanine (CuPc) on the Au(1 1 0) surface. Low-energy electron diffraction reveals a commensurate overlayer unit cell containing one adsorbate species. The azimuthal alignment of the CuPc molecule is revealed by comparing experimental constant binding energy (kxky)-maps using angle-resolved photoelectron spectroscopy with theoretical momentum maps of the free molecule's highest occupied molecular orbital (HOMO). This structural information is confirmed by total energy calculations within the framework of van-der-Waals corrected density functional theory. The electronic structure is further analyzed by computing the molecule-projected density of states, using both a semi-local and a hybrid exchange-correlation functional. In agreement with experiment, the HOMO is located about 1.2 eV below the Fermi-level, while there is no significant charge transfer into the molecule and the CuPc LUMO remains unoccupied on the Au(1 1 0) surface. PMID:25284953

CO2 storage resources, reserves, and reserve growth: Toward a methodology for integrated assessment of the storage capacity of oil and gas reservoirs and saline formations

USGS Publications Warehouse

Burruss, Robert

2009-01-01

Geologically based methodologies to assess the possible volumes of subsurface CO2 storage must apply clear and uniform definitions of resource and reserve concepts to each assessment unit (AU). Application of the current state of knowledge of geologic, hydrologic, geochemical, and geophysical parameters (contingencies) that control storage volume and injectivity allows definition of the contingent resource (CR) of storage. The parameters known with the greatest certainty are based on observations on known traps (KTs) within the AU that produced oil, gas, and water. The aggregate volume of KTs within an AU defines the most conservation volume of contingent resource. Application of the concept of reserve growth to CR volume provides a logical path for subsequent reevaluation of the total resource as knowledge of CO2 storage processes increases during implementation of storage projects. Increased knowledge of storage performance over time will probably allow the volume of the contingent resource of storage to grow over time, although negative growth is possible.

CO2 storage resources, reserves, and reserve growth: Toward a methodology for integrated assessment of the storage capacity of oil and gas reservoirs and saline formations

USGS Publications Warehouse

Burruss, R.C.

2009-01-01

Geologically based methodologies to assess the possible volumes of subsurface CO2 storage must apply clear and uniform definitions of resource and reserve concepts to each assessment unit (AU). Application of the current state of knowledge of geologic, hydrologic, geochemical, and geophysical parameters (contingencies) that control storage volume and injectivity allows definition of the contingent resource (CR) of storage. The parameters known with the greatest certainty are based on observations on known traps (KTs) within the AU that produced oil, gas, and water. The aggregate volume of KTs within an AU defines the most conservation volume of contingent resource. Application of the concept of reserve growth to CR volume provides a logical path for subsequent reevaluation of the total resource as knowledge of CO2 storage processes increases during implementation of storage projects. Increased knowledge of storage performance over time will probably allow the volume of the contingent resource of storage to grow over time, although negative growth is possible. ?? 2009 Elsevier Ltd. All rights reserved.

CO oxidation on Alsbnd Au nano-composite systems

NASA Astrophysics Data System (ADS)

Rajesh, C.; Majumder, C.

2018-03-01

Using first principles method we report the CO oxidation behaviour of Alsbnd Au nano-composites in three different size ranges: Al6Au8, Al13Au42 and a periodic slab of Alsbnd Au(1 1 1) surface. The clusters prefer enclosed structures with alternating arrangement of Al and Au atoms, maximising Auδ-sbnd Alδ+ bonds. Charge distribution analysis suggests the charge transfer from Al to Au atoms, corroborated by the red shift in the density of states spectrum. Further, CO oxidation on these nano-composite systems was investigated through both Eley - Rideal and Langmuir Hinshelwood mechanism. While, these clusters interact with O2 non-dissociatively with an elongation of the Osbnd O bond, further interaction with CO led to formation of CO2 spontaneously. On contrary, the CO2 evolution by co-adsorption of O2 and CO molecules has a transition state barrier. On the basis of the results it is inferred that nano-composite material of Alsbnd Au shows significant promise toward effective oxidative catalysis.

Atomic and electronic structures of Si(1 1 1)-\\left(\\sqrt{\\mathbf{3}}\\times\\sqrt{\\mathbf{3}}\\right)\\text{R}\\mathbf{3}{{\\mathbf{0}}^{\\circ}} -Au and (6 × 6)-Au surfaces

NASA Astrophysics Data System (ADS)

Patterson, C. H.

2015-12-01

Si(1 1 1)-Au surfaces with around one monolayer of Au exhibit many ordered structures and structures containing disordered domain walls. Hybrid density functional theory (DFT) calculations presented here reveal the origin of these complex structures and tendency to form domain walls. The conjugate honeycomb chain trimer (CHCT) structure of the \\sqrt{3} -Au phase contains Si atoms with non-bonding surface states which can bind Au atoms in pairs in interstices of the CHCT structure and make this surface metallic. Si adatoms adsorbed on the \\sqrt{3} -Au surface induce a gapped surface through interaction with the non-bonding states. Adsorption of extra Au atoms in interstitial sites of the \\sqrt{3} -Au surface is stabilized by interaction with the non-bonding orbitals and leads to higher coverage ordered structures including the ≤ft(6× 6\\right) -Au phase. Extra Au atoms bound in interstitial sites of the \\sqrt{3} -Au surface result in top layer Si atoms with an SiAu4 butterfly wing configuration. The structure of a ≤ft(6× 6\\right) -Au phase, whose in-plane top atomic layer positions were previously determined by an electron holography technique (Grozea et al 1998 Surf. Sci. 418 32), is calculated using total energy minimization. The Patterson function for this structure is calculated and is in good agreement with data from an in-plane x-ray diffraction study (Dornisch et al 1991 Phys. Rev. B 44 11221). Filled and empty state scanning tunneling microscopy (STM) images are calculated for domain walls and the ≤ft(6× 6\\right) -Au structure. The ≤ft(6× 6\\right) -Au phase is 2D chiral and this is evident in computed and actual STM images. ≤ft(6× 6\\right) -Au and domain wall structures contain the SiAu4 motif with a butterfly wing shape. Chemical bonding within the Si-Au top layers of the \\sqrt{3} -Au and ≤ft(6× 6\\right) -Au surfaces is analyzed and an explanation for the SiAu4 motif structure is given.

R 14 (Au, M) 51 (R = Y, La–Nd, Sm–Tb, Ho, Er, Yb, Lu; M = Al, Ga, Ge, In, Sn, Sb, Bi): Stability Ranges and Site Preference in the Gd 14Ag 51 Structure Type

DOE PAGES

Celania, Chris; Smetana, Volodymyr; Provino, Alessia; ...

2017-12-19

Twenty new ternary representatives of the Gd 14Ag 51 structure type have been synthesized within the R-Au-M family (R = Y, La–Nd, Sm–Tb, Ho, Er, Yb, Lu; M = Al, Ga, Ge, In, Sn, Sb, Bi) using solid state synthesis techniques. The list of post transition metals (M) involved in the formation of this type of structure could be augmented by five new representatives. All compounds crystallize in the hexagonal space group P6/m (#175) with the unit cell ranges of a = 12.3136(2)–12.918(1) Å and c = 8.9967(3)–9.385(1) Å, and incorporate different degrees of Au/M mixing. The involvement of themore » post transition element in the structure varies from one to another compound both qualitatively and quantitatively. A rather significant phase width can be expected for the majority of compounds, however, not without exclusions. The distribution of the post transition metals within the structure has been analyzed via single crystal X-ray diffraction. While the positional disorder of one near-origin Au position is expectable for all compounds due to steric reasons, two specimens show an obvious deviation from the others including another Au position split along the c axis. Lastly, possible factors affecting this behavior are discussed.« less

R 14 (Au, M) 51 (R = Y, La–Nd, Sm–Tb, Ho, Er, Yb, Lu; M = Al, Ga, Ge, In, Sn, Sb, Bi): Stability Ranges and Site Preference in the Gd 14Ag 51 Structure Type

DOE Office of Scientific and Technical Information (OSTI.GOV)

Celania, Chris; Smetana, Volodymyr; Provino, Alessia

Twenty new ternary representatives of the Gd 14Ag 51 structure type have been synthesized within the R-Au-M family (R = Y, La–Nd, Sm–Tb, Ho, Er, Yb, Lu; M = Al, Ga, Ge, In, Sn, Sb, Bi) using solid state synthesis techniques. The list of post transition metals (M) involved in the formation of this type of structure could be augmented by five new representatives. All compounds crystallize in the hexagonal space group P6/m (#175) with the unit cell ranges of a = 12.3136(2)–12.918(1) Å and c = 8.9967(3)–9.385(1) Å, and incorporate different degrees of Au/M mixing. The involvement of themore » post transition element in the structure varies from one to another compound both qualitatively and quantitatively. A rather significant phase width can be expected for the majority of compounds, however, not without exclusions. The distribution of the post transition metals within the structure has been analyzed via single crystal X-ray diffraction. While the positional disorder of one near-origin Au position is expectable for all compounds due to steric reasons, two specimens show an obvious deviation from the others including another Au position split along the c axis. Lastly, possible factors affecting this behavior are discussed.« less

Near-Earth Objects. Chapter 27

NASA Technical Reports Server (NTRS)

Harris, Alan W.; Drube, Line; McFadden, Lucy A.; Binzel, Richard P.

2014-01-01

A near-Earth object (NEO) is an asteroid or comet orbiting the Sun with a perihelion distance of less than 1.3 Astronomical Units (AU) (1 AU, an astronomical unit, is the mean distance between the Earth and the Sun, around 150 million kilometers). If the orbit of an NEO can bring it to within 0.05 AU of the Earth's orbit, and it is larger than about 120 meters, it is termed a potentially hazardous object (PHO); an object of this size is likely to survive passage through the atmosphere and cause extensive damage on impact. (The acronyms NEA and PHO are used when referring specifically to asteroids.)

First-principles study of Au-decorated carbon nanotubes

NASA Astrophysics Data System (ADS)

Ju, Weiwei; Li, Tongwei; Zhou, Qingxiao; Li, Haisheng; Li, Xiaohong

2018-07-01

The electronic structures and spin-orbit (SO) coupling of carbon nanotubes with adsorbed Au atoms are investigated based on density functional theory. Three kinds of zigzag single-walled CNT (8,0), (10,0) and (12,0) are selected. The Au atoms prefer to adsorb on the top of C atoms. The adsorption of Au atoms can introduce impurity states in the band gap, modifying the electronic properties of systems. Furthermore, the influence of SO coupling on these impurity states is also explored. Considerable SO splitting (∼130 meV) can be obtained. We find that the SO splitting decreases with the increase of the concentration of Au atoms, which can be ascribed to the interaction between Au atoms, suppressing the SO splitting. Our work provides imperative understanding on the electronic properties and SO coupling effect in Au-decorated CNTs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zou, Lianfeng; Li, Jonathan; Zakharov, Dmitri

Using in situ transmission electron microscopy that spatially and temporally resolves the evolution of the atomic structure in the surface and subsurface regions, we Find that the surface segregation of Au atoms in a Cu(Au) solid solution results in the nucleation and growth of a (2 × 1) missing-row reconstructed, half-unit-cell thick L1 2 Cu 3Au(110) surface alloy. Our in situ electron microscopy observations and atomistic simulations demonstrate that the (2 × 1) reconstruction of the Cu 3Au(110) surface alloy remains as a stable surface structure as a result of the favored Cu-Au diatom configuration.

Creating Strategic Visions

DTIC Science & Technology

1990-10-15

3010 o, AuTOVON 242-3010. - =n~m~m i ma ll lil~ m mm m i mii FOREWORD This futures study presents an analysis and discussion of a program used at the U.S...Operations Research Society, and The Planning Forum . iv CREATING STRATEGIC VISIONS 1 Introduction. The United States Army War College (USAWC) prepares its...consideration and time must be given to a program that attempts to help these potential leaders learn how to create strategic visions. In this paper

The Case For Space: A Legislative Framework For An Independent United States Space Force

DTIC Science & Technology

2018-04-01

However, this proposal has merit, and is the subject of extensive studies . AU/ACSC/Neil, M/Grant, D/AY18 10 One primary purpose of such...issues with DOD space acquisition, yet even within this one confined area of study noted problems that appear to be systemic. The GAO report...recommendations drawn from these studies seem to have fallen on deaf ears, and whatever changes these various studies prompted failed to adequately address

NATO Independent Cost Estimating and the Role of Life Cycle Cost Analysis in Managing the Defence Enterprise (Estimation independante des couts de l’OTAN et role de l’analyse des couts globaux de possesssion au sen de l’OTAN)

DTIC Science & Technology

2012-08-01

Command NBCD Nuclear, Biological, and Chemical Defence NCCA U.S. Naval Center for Cost Analysis NGISSI Northrop Grumman Integrated Systems...analysis (CPA) in the United States which investigated how costs, capabilities, and risks could be examined together in an attempt to engen - der more

How Accurately do Leading and Lagging Indictors Predict F-16 Aircraft Availability (AA)

DTIC Science & Technology

2016-08-01

Predictions AU/ACSC/2016 vi PREFACE As the F-16 fleet continues to age, and budgets continue to shrink , United States Air Force (USAF... shrinking budgets, it is imperative for maintenance leaders to use all tools available to them to improve the amount of aircraft available for operations...remarkable considering the overall F-16 fleet shrinking at a steady pace (see table 2 for information). AA is one of the most critical factors that

Extrasolar giant magnetospheric response to steady-state stellar wind pressure at 10, 5, 1, and 0.2 AU

NASA Astrophysics Data System (ADS)

Tilley, Matt; Harnett, Erika; Winglee, Robert

2016-10-01

A three-dimensional, multifluid simulation of a giant planet's magnetospheric interaction with steady-state stellar wind from a Sun-like star was performed for four different orbital semi-major axes - 10, 5, 1 and 0.2 AU. We simulate the effect of the increasing, steady-state stellar wind pressure related to the planetary orbital semi-major axis on the global magnetospheric dynamics for a Saturn-like planet, including an Enceladus-like plasma torus. Mass loss processes are shown to vary with orbital distance, with the centrifugal interchange instability displayed only in the 10 AU and 5 AU cases which reach a state of mass loss equilibrium more slowly than the 1 AU or 0.2 AU cases. The compression of the magnetosphere in the 1 AU and 0.2 AU cases contributes to the quenching of the interchange process by increasing the ratio of total plasma thermal energy to corotational energy. The strength of field-aligned currents (FAC), associated with auroral radio emissions, are shown to increase in magnitude and latitudinal coverage with a corresponding shift equatorward from increased dynamic ram pressure experienced in the hotter orbits. Similar to observed hot Jovian planets, the warm exo-Saturn simulated in the current work shows enhanced ion density in the magnetosheath and magnetopause regions, as well as the plasma torus which could contribute to altered transit signals, suggesting that for planets in warmer (> 0.1 AU) orbits, planetary magnetic field strengths and possibly exomoons - via the plasma torus - could be observable with future missions.

Corrigendum to “Suppression of Υ production in d+Au and Au+Au collisions at √ SNN = 200 GeV" [Phys. Lett. B 735 (2014) 127-137

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamczyk, L.

We report measurements of Υ meson production in p + p, d + Au, and Au+Au collisions using the STAR detector at RHIC. We compare the Υ yield to the measured cross section in p + p collisions in order to quantify any modifications of the yield in cold nuclear matter using d + Au data and in hot nuclear matter using Au+Au data separated into three centrality classes. Our p + p measurement is based on three times the statistics of our previous result. We obtain a nuclear modification factor for Upsilon (1S + 2S + 3S) in themore » rapidity range |y| < 1 in d + Au collisions of R dAu = 0.79 ± 0.24(stat.) ± 0.03(syst.) ± 0.10(p + p syst.). A comparison with models including shadowing and initial state parton energy loss indicates the presence of additional cold-nuclear matter suppression. Similarly, in the top 10% most-central Au + Au collisions, we measure a nuclear modification factor of R AA = 0.49 ±0.1(stat.) ±0.02(syst.) ±0.06(p + p syst.), which is a larger suppression factor than that seen in cold nuclear matter. Our results are consistent with complete suppression of excited-state Upsilon mesons in Au + Au collisions. The additional suppression in Au + Au is consistent with the level expected in model calculations that include the presence of a hot, deconfined Quark–Gluon Plasma. However, understanding the suppression seen in d + Au is still needed before any definitive statements about the nature of the suppression in Au + Au can be made.« less

Suppression of Υ production in d + Au + and Au + Au collisions at √ sNN =200 GeV

DOE PAGES

None

2014-07-01

We report measurements of Upsilon meson production in p + p, d +Au, and Au+Au collisions using the STAR detector at RHIC. We compare the Upsilon yield to the measured cross section in p + p collisions in order to quantify any modifications of the yield in cold nuclear matter using d +Au data and in hot nuclear matter using Au+Au data separated into three centrality classes. Our p +p measurement is based on three times the statistics of our previous result. We obtain a nuclear modification factor for Upsilon (1S + 2S + 3S) in the rapidity range |y|more » < 1 in d + Au collisions of R dAu = 0.79 ± 0.24(stat.) ± 0.03(syst.) ± 0.10(p + p syst.). A comparison with models including shadowing and initial state part on energy loss indicates the presence of additional cold-nuclear matter suppression. Similarly, in the top 10% most-central Au + Au collisions, we measure a nuclear modification factor of R AA = 0.49 ±0.1(stat.) ±0.02(syst.) ±0.06(p + p syst.), which is a larger suppression factor than that seen in cold nuclear matter. Our results are consistent with complete suppression of excited-state Upsilon mesons in Au + Au collisions. The additional suppression in Au + Au is consistent with the level expected in model calculations that include the presence of a hot, deconfined Quark–Gluon Plasma. However, understanding the suppression seen in d + Au is still needed before any definitive statements about the nature of the suppression in Au + Au can be made.« less

Corrigendum to “Suppression of Υ production in d+Au and Au+Au collisions at √ SNN = 200 GeV" [Phys. Lett. B 735 (2014) 127-137

DOE PAGES

Adamczyk, L.

2015-04-01

We report measurements of Υ meson production in p + p, d + Au, and Au+Au collisions using the STAR detector at RHIC. We compare the Υ yield to the measured cross section in p + p collisions in order to quantify any modifications of the yield in cold nuclear matter using d + Au data and in hot nuclear matter using Au+Au data separated into three centrality classes. Our p + p measurement is based on three times the statistics of our previous result. We obtain a nuclear modification factor for Upsilon (1S + 2S + 3S) in themore » rapidity range |y| < 1 in d + Au collisions of R dAu = 0.79 ± 0.24(stat.) ± 0.03(syst.) ± 0.10(p + p syst.). A comparison with models including shadowing and initial state parton energy loss indicates the presence of additional cold-nuclear matter suppression. Similarly, in the top 10% most-central Au + Au collisions, we measure a nuclear modification factor of R AA = 0.49 ±0.1(stat.) ±0.02(syst.) ±0.06(p + p syst.), which is a larger suppression factor than that seen in cold nuclear matter. Our results are consistent with complete suppression of excited-state Upsilon mesons in Au + Au collisions. The additional suppression in Au + Au is consistent with the level expected in model calculations that include the presence of a hot, deconfined Quark–Gluon Plasma. However, understanding the suppression seen in d + Au is still needed before any definitive statements about the nature of the suppression in Au + Au can be made.« less

Tuning the Rectification Ratio by Changing the Electronic Nature (Open-Shell and Closed-Shell) in Donor-Acceptor Self-Assembled Monolayers.

PubMed

Souto, Manuel; Yuan, Li; Morales, Dayana C; Jiang, Li; Ratera, Imma; Nijhuis, Christian A; Veciana, Jaume

2017-03-29

This Communication describes the mechanism of charge transport across self-assembled monolayers (SAMs) of two donor-acceptor systems consisting of a polychlorotriphenylmethyl (PTM) electron-acceptor moiety linked to an electron-donor ferrocene (Fc) unit supported by ultraflat template-stripped Au and contacted by a eutectic alloy of gallium and indium top contacts. The electronic and supramolecular structures of these SAMs were well characterized. The PTM unit can be switched between the nonradical and radical forms, which influences the rectification behavior of the junction. Junctions with nonradical units rectify currents via the highest occupied molecular orbital (HOMO) with a rectification ratio R = 99, but junctions with radical units have a new accessible state, a single-unoccupied molecular orbital (SUMO), which turns rectification off and drops R to 6.

Geologic assessment of undiscovered oil and gas resources in Aptian carbonates, onshore northern Gulf of Mexico Basin, United States

USGS Publications Warehouse

Hackley, Paul C.; Karlsen, Alexander W.

2014-01-01

Carbonate lithofacies of the Lower Cretaceous Sligo Formation and James Limestone were regionally evaluated using established U.S. Geological Survey (USGS) assessment methodology for undiscovered conventional hydrocarbon resources. The assessed area is within the Upper Jurassic–Cretaceous–Tertiary Composite total petroleum system, which was defined for the assessment. Hydrocarbons reservoired in carbonate platform Sligo-James oil and gas accumulations are interpreted to originate primarily from the Jurassic Smackover Formation. Emplacement of hydrocarbons occurred via vertical migration along fault systems; long-range lateral migration also may have occurred in some locations. Primary reservoir facies include porous patch reefs developed over paleostructural salt highs, carbonate shoals, and stacked linear reefs at the carbonate shelf margin. Hydrocarbon traps dominantly are combination structural-stratigraphic. Sealing lithologies include micrite, calcareous shale, and argillaceous lime mudstone. A geologic model, supported by discovery history analysis of petroleum geology data, was used to define a single regional assessment unit (AU) for conventional reservoirs in carbonate facies of the Sligo Formation and James Limestone. The AU is formally entitled Sligo-James Carbonate Platform Oil and Gas (50490121). A fully risked mean undiscovered technically recoverable resource in the AU of 50 million barrels of oil (MMBO), 791 billion cubic feet of natural gas (BCFG), and 26 million barrels of natural gas liquids was estimated. Substantial new development through horizontal drilling has occurred since the time of this assessment (2010), resulting in cumulative production of >200 BCFG and >1 MMBO.

A facile method to prepare "green" nano-phosphors with a large Stokes-shift and solid-state enhanced photophysical properties based on surface-modified gold nanoclusters.

PubMed

Cheng, C H; Huang, H Y; Talite, M J; Chou, W C; Yeh, J M; Yuan, C T

2017-12-15

Colloidal nano-materials, such as quantum dots (QDs) have been applied to light-conversion nano-phosphors due to their unique tunable emission. However, most of the QDs involve toxic elements and are synthesized in a hazardous solvent. In addition, conventional QD nano-phosphors with a small Stokes shift suffered from reabsorption losses and aggregation-induced quenching in the solid state. Here, we demonstrate a facile, matrix-free method to prepare eco-friendly nano-phosphors with a large Stokes shift based on aqueous thiolate-stabilized gold nanoclusters (GSH-AuNCs) with simple surface modifications. Our method is just to drop GSH-AuNCs solution on the aluminum foil and then surface-modified AuNCs (Al-GSH-AuNCs) can be spontaneously precipitated out of the aqueous solution. Compared with pristine GSH-AuNCs in solution, the Al-GSH-AuNCs exhibit enhanced solid-state PL quantum yields, lengthened PL lifetime, and spectral blue shift, which can be attributed to the aggregation-induced emission enhancement facilitated by surface modifications. Such surface-treatment induced aggregation of AuNCs can restrict the surface-ligand motion, leading to the enhancement of PL properties in the solid state. In addition, the Al-GSH-AuNCs nano-phosphors with a large Stokes shift can mitigate the aggregation-induced PL quenching and reabsorption losses, which would be potential candidates for "green" nano-phosphors. Copyright © 2017 Elsevier Inc. All rights reserved.

Ligand-protected gold clusters: the structure, synthesis and applications

NASA Astrophysics Data System (ADS)

Pichugina, D. A.; Kuz'menko, N. E.; Shestakov, A. F.

2015-11-01

Modern concepts of the structure and properties of atomic gold clusters protected by thiolate, selenolate, phosphine and phenylacetylene ligands are analyzed. Within the framework of the superatom theory, the 'divide and protect' approach and the structure rule, the stability and composition of a cluster are determined by the structure of the cluster core, the type of ligands and the total number of valence electrons. Methods of selective synthesis of gold clusters in solution and on the surface of inorganic composites based, in particular, on the reaction of Aun with RS, RSe, PhC≡C, Hal ligands or functional groups of proteins, on stabilization of clusters in cavities of the α-, β and γ-cyclodextrin molecules (Au15 and Au25) and on anchorage to a support surface (Au25/SiO2, Au20/C, Au10/FeOx) are reviewed. Problems in this field are also discussed. Among the methods for cluster structure prediction, particular attention is given to the theoretical approaches based on the density functional theory (DFT). The structures of a number of synthesized clusters are described using the results obtained by X-ray diffraction analysis and DFT calculations. A possible mechanism of formation of the SR(AuSR)n 'staple' units in the cluster shell is proposed. The structure and properties of bimetallic clusters MxAunLm (M=Pd, Pt, Ag, Cu) are discussed. The Pd or Pt atom is located at the centre of the cluster, whereas Ag and Cu atoms form bimetallic compounds in which the heteroatom is located on the surface of the cluster core or in the 'staple' units. The optical properties, fluorescence and luminescence of ligand-protected gold clusters originate from the quantum effects of the Au atoms in the cluster core and in the oligomeric SR(AuSR)x units in the cluster shell. Homogeneous and heterogeneous reactions catalyzed by atomic gold clusters are discussed in the context of the reaction mechanism and the nature of the active sites. The bibliography includes 345 references.

An assessment of nitrogen-based manure application rates on 39 U.S. swine operations.

PubMed

Lory, John A; Massey, Raymond E; Zulovich, Joseph M; Hoehne, John A; Schmidt, Amy M; Carlson, Marcia S; Fulhage, Charles D

2004-01-01

Water quality concerns and revised regulations are changing how confined animal feeding operations manage manure. Devising acceptable and feasible changes in manure practices requires a full understanding of the forces shaping current manure management decisions. Previous theoretical models have shown that a wide range of factors influence the lowest cost solution for manure management. We used a mechanistic model to characterize the manure management practices on 39 swine operations (20 unagitated lagoon and 19 slurry operations) in five states (Iowa, Missouri, North Carolina, Oklahoma, and Pennsylvania). Information was collected from each operation about animal numbers, feed and water use, manure handling and storage characteristics, field locations, crop rotation, fertilizer need, and equipment inventory and usage. Collected data were used as input and to validate results from a mechanistic model that determined acres required for manure application, manure application rate, time required for manure application, value of manure, and costs of manure management. The 39 farms had a mean of 984 animal units (AU) per operation, 18.2 AU ha(-1) (7.4 AU acre(-1)), and manure application costs of dollar 10.49 AU(-1) yr(-1). Significant factors affecting manure management included operation size, manure handling system, state, and ownership structure. Larger operations had lower manure management costs (r2 = 0.32). Manure value potentially exceeded manure application costs on 58% of slurry and 15% of lagoon operations. But 38% of slurry operations needed to apply manure off the farm whereas all lagoon operations had sufficient land for N-based manure management. Manure management was a higher percentage of gross income on contract operations compared with independents (P < 0.01). This research emphasized the importance of site-specific factors affecting manure management decisions and the economics of U.S. swine operations.

Internal-Modified Dithiol DNA-Directed Au Nanoassemblies: Geometrically Controlled Self-Assembly and Quantitative Surface-Enhanced Raman Scattering Properties

NASA Astrophysics Data System (ADS)

Yan, Yuan; Shan, Hangyong; Li, Min; Chen, Shu; Liu, Jianyu; Cheng, Yanfang; Ye, Cui; Yang, Zhilin; Lai, Xuandi; Hu, Jianqiang

2015-11-01

In this work, a hierarchical DNA-directed self-assembly strategy to construct structure-controlled Au nanoassemblies (NAs) has been demonstrated by conjugating Au nanoparticles (NPs) with internal-modified dithiol single-strand DNA (ssDNA) (Au-B-A or A-B-Au-B-A). It is found that the dithiol-ssDNA-modified Au NPs and molecule quantity of thiol-modified ssDNA grafted to Au NPs play critical roles in the assembly of geometrically controlled Au NAs. Through matching Au-DNA self-assembly units, geometrical structures of the Au NAs can be tailored from one-dimensional (1D) to quasi-2D and 2D. Au-B-A conjugates readily give 1D and quasi-2D Au NAs while 2D Au NAs can be formed by A-B-Au-B-A building blocks. Surface-enhanced Raman scattering (SERS) measurements and 3D finite-difference time domain (3D-FDTD) calculation results indicate that the geometrically controllable Au NAs have regular and linearly “hot spots”-number-depended SERS properties. For a certain number of NPs, the number of “hot spots” and accordingly enhancement factor of Au NAs can be quantitatively evaluated, which open a new avenue for quantitative analysis based on SERS technique.

Manipulating molecular quantum states with classical metal atom inputs: demonstration of a single molecule NOR logic gate.

PubMed

Soe, We-Hyo; Manzano, Carlos; Renaud, Nicolas; de Mendoza, Paula; De Sarkar, Abir; Ample, Francisco; Hliwa, Mohamed; Echavarren, Antonio M; Chandrasekhar, Natarajan; Joachim, Christian

2011-02-22

Quantum states of a trinaphthylene molecule were manipulated by putting its naphthyl branches in contact with single Au atoms. One Au atom carries 1-bit of classical information input that is converted into quantum information throughout the molecule. The Au-trinaphthylene electronic interactions give rise to measurable energy shifts of the molecular electronic states demonstrating a NOR logic gate functionality. The NOR truth table of the single molecule logic gate was characterized by means of scanning tunnelling spectroscopy.

Atomically Visualizing Elemental Segregation-Induced Surface Alloying and Restructuring

DOE PAGES

Zou, Lianfeng; Li, Jonathan; Zakharov, Dmitri; ...

2017-12-01

Using in situ transmission electron microscopy that spatially and temporally resolves the evolution of the atomic structure in the surface and subsurface regions, we Find that the surface segregation of Au atoms in a Cu(Au) solid solution results in the nucleation and growth of a (2 × 1) missing-row reconstructed, half-unit-cell thick L1 2 Cu 3Au(110) surface alloy. Our in situ electron microscopy observations and atomistic simulations demonstrate that the (2 × 1) reconstruction of the Cu 3Au(110) surface alloy remains as a stable surface structure as a result of the favored Cu-Au diatom configuration.

Chapter 5. Assessment of undiscovered conventional oil and gas resources-Lower Cretaceous Travis Peak and Hosston formations, Jurassic Smackover interior salt basins total petroleum system, in the East Texas basin and Louisiana-Mississippi salt basins provinces.

USGS Publications Warehouse

Dyman, T.S.; Condon, S.M.

2006-01-01

The petroleum assessment of the Travis Peak and Hosston Formations was conducted by using a total petroleum system model. A total petroleum system includes all of the important elements of a hydrocarbon fluid system needed to develop oil and gas accumulations, including source and reservoir rocks, hydrocarbon generation, migration, traps and seals, and undiscovered accumulations. A total petroleum system is mappable and may include one or more assessment units. For each assessment unit, reservoir rocks contain similar geology, exploration characteristics, and risk. The Jurassic Smackover Interior Salt Basins Total Petroleum System is defined for this assessment to include (1) Upper Jurassic Smackover carbonates and calcareous shales and organic-rich shales of the Upper Jurassic Bossier Shale of the Cotton Valley Group and (2) Lower Cretaceous Travis Peak and Hosston Formations. The Jurassic Smackover Interior Salt Basins Total Petroleum System includes three conventional Travis Peak-Hosston assessment units: Travis Peak-Hosston Gas and Oil (AU 50490205), Travis Peak-Hosston Updip Oil (AU 50490206), and Travis Peak-Hosston Hypothetical Updip Oil (AU 50490207). A fourth assessment unit, the Hosston Hypothetical Slope-Basin Gas Assessment Unit, was named and numbered (AU 50490208) but not geologically defined or quantitatively assessed owing to a lack of data. Together, assessment units 50490205 to 50490207 are estimated to contain a mean undiscovered conventional resource of 29 million barrels of oil, 1,136 billion cubic feet of gas, and 22 million barrels of natural gas liquids.

Solid-state dewetting of magnetic binary multilayer thin films

NASA Astrophysics Data System (ADS)

Esterina, Ria; Liu, X. M.; Adeyeye, A. O.; Ross, C. A.; Choi, W. K.

2015-10-01

We examined solid-state dewetting behavior of magnetic multilayer thin film in both miscible (CoPd) and immiscible (CoAu) systems and found that CoPd and CoAu dewetting stages follow that of elemental materials. We established that CoPd alloy morphology and dewetting rate lie in between that of the elemental materials. Johnson-Mehl-Avrami analysis was utilized to extract the dewetting activation energy of CoPd. For CoAu, Au-rich particles and Co-rich particles are distinguishable and we are able to predict the interparticle spacings and particle densities for the particles that agree well with the experimental results. We also characterized the magnetic properties of CoPd and CoAu nanoparticles.

Environmental Policy Issues Affecting the United States Army in Its Overseas Activities

DTIC Science & Technology

1989-01-01

1988 Containing Reform: The UK Stance en the European Community environmental impact assessment Directive. Policy and Impact Assessment fi (3, 4): 95...protect the en - ’duainau respect et:::l protection de 1’nviron- in adopting Article 130 R of the Single European Act, adoptant P’article 130 R de l’Acte...struments are not always enforced at national level: mentsjuridiques ratifids ne soient pas toujours mis en application au niveau national: 10

The United States Army Medical Department Journal, April - June 2011. Prehospital combat casualty care; The starting point of battlefield survival

DTIC Science & Technology

2011-04-01

74-78. 30. Cotton BA, Guy JS, Morris JA Jr, Abumrad NN. The cellular, metabolic, and systemic consequences of aggressive fluid resuscitation...civilian trauma patients. Ann Surg. 2008;248:447-458. 55. Gunter OL Jr, Au BK, Isbell JM, Mowery NT, Young PP, Cotton BA. Optimizing outcomes in...AFB is composed of a thick layer of absorbent cotton wrapped in layers of gauze and attached to 2 long straps for wrapping around the wound. It

Optical and electrical properties of colloidal (spherical Au)-(spinel ferrite nanorod) heterostructures

NASA Astrophysics Data System (ADS)

George, Chandramohan; Genovese, Alessandro; Qiao, Fen; Korobchevskaya, Kseniya; Comin, Alberto; Falqui, Andrea; Marras, Sergio; Roig, Anna; Zhang, Yang; Krahne, Roman; Manna, Liberato

2011-11-01

We report here a simple synthetic route to Au-FexOy heterostructures in which spinel ferrite (FexOy) grows as a nanorod on a spherical gold (Au) seed. The large red shift in the plasmon resonance in the heterostructures could be explained by a dielectric effect (although we could not entirely exclude a contribution due to electron transfer from Au to defect states at the Au-FexOy interface), while the magnetic properties of the Au-FexOy heterostructures were basically the same as those of the corresponding nanocrystals after Au leaching. In films of Au-FexOy heterostructures the electrical conductivity appeared to be mediated by the Au domains.We report here a simple synthetic route to Au-FexOy heterostructures in which spinel ferrite (FexOy) grows as a nanorod on a spherical gold (Au) seed. The large red shift in the plasmon resonance in the heterostructures could be explained by a dielectric effect (although we could not entirely exclude a contribution due to electron transfer from Au to defect states at the Au-FexOy interface), while the magnetic properties of the Au-FexOy heterostructures were basically the same as those of the corresponding nanocrystals after Au leaching. In films of Au-FexOy heterostructures the electrical conductivity appeared to be mediated by the Au domains. Electronic supplementary information (ESI) available: TEM/HRTEM images of (i) aliquots at the earliest stages of the growth of Au-FexOy HSs; (ii) Au-FexOy HSs synthesized at low DDAB concentrations; (iii) spherical iron oxide nanocrystals synthesized under the same conditions as the HSs, but in the absence of Au seeds; (iv) Au-FexOy urchin like nanostructures, also after attempts to leach out Au; (v) Au-FexOy HSs after treatment with hydrazine; (vi) FexOy HSs after Au leaching from Au-FexOy HSs; additional optical absorption spectra; additional I-V curves, also from films made of Au-FexOy dumbbells; and additional SEM images; vii) X-ray diffraction (XRD) pattern of a sample of Au-FexOy HSs. See DOI: 10.1039/c1nr10768b

Nanometer-thick gold on silicon as a proxy for single-crystal gold for the electrodeposition of epitaxial cuprous oxide thin films

DOE PAGES

Switzer, Jay A.; Hill, James C.; Mahenderkar, Naveen K.; ...

2016-05-27

Here, single-crystal Au is an excellent substrate for electrochemical epitaxial growth due to its chemical inertness, but the high cost of bulk Au single crystals prohibits their use in practical applications. Here, we show that ultrathin epitaxial films of Au electrodeposited onto Si(111), Si(100), and Si(110) wafers can serve as an inexpensive proxy for bulk single-crystal Au for the deposition of epitaxial films of cuprous oxide (Cu 2O). The Au films range in thickness from 7.7 nm for a film deposited for 5 min to 28.3 nm for a film deposited for 30 min. The film thicknesses are measured bymore » low-angle X-ray reflectivity and X-ray Laue oscillations. High-resolution TEM shows that there is not an interfacial SiO x layer between the Si and Au. The Au films deposited on the Si(111) substrates are smoother and have lower mosaic spread than those deposited onto Si(100) and Si(110). The mosaic spread of the Au(111) layer on Si(111) is only 0.15° for a 28.3 nm thick film. Au films deposited onto degenerate Si(111) exhibit ohmic behavior, whereas Au films deposited onto n-type Si(111) with a resistivity of 1.15 Ω·cm are rectifying with a barrier height of 0.85 eV. The Au and the Cu 2O follow the out-of-plane and in-plane orientations of the Si substrates, as determined by X-ray pole figures. The Au and Cu 2O films deposited on Si(100) and Si(110) are both twinned. The films grown on Si(100) have twins with a [221] orientation, and the films grown on Si(110) have twins with a [411] orientation. An interface model is proposed for all Si orientations, in which the –24.9% mismatch for the Au/Si system is reduced to only +0.13% by a coincident site lattice in which 4 unit meshes of Au coincide with 3 unit meshes of Si. Although this study only considers the deposition of epitaxial Cu 2O films on electrodeposited Au/Si, the thin Au films should serve as high-quality substrates for the deposition of a wide variety of epitaxial materials.« less

Toward a modular multi-material nanoparticle synthesis and assembly strategy via bionanocombinatorics: bifunctional peptides for linking Au and Ag nanomaterials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Briggs, Beverly D.; Palafox-Hernandez, J. Pablo; Li, Yue

Materials-binding peptides represent a unique avenue towards controlling the shape and size of nanoparticles (NPs) grown under aqueous conditions. Here, employing a bionanocombinatorics approach, two such materials-binding peptides were linked at either end of a photoswitchable spacer, forming a multi-domain materials-binding molecule to control the in situ synthesis and organization of Ag and Au NPs under ambient conditions. These multi-domain molecules retained the peptides’ ability to nucleate, grow, and stabilize Ag and Au NPs in aqueous media. Disordered co-assemblies of the two nanomaterials were observed by TEM imaging of dried samples after sequential growth of the two metals, and showedmore » a clustering behavior that was not observed without both metals and the linker molecules. While TEM evidence indicated the formation of AuNP/AgNP assemblies upon drying, SAXS analysis indicated that no extended assemblies existed in solution, suggesting that sample drying plays an important role in facilitating NP clustering. Molecular simulations and experimental data revealed tunable materials-binding based upon the isomerization state of the photoswitchable unit and metal employed. This work is a first step in generating externally actuated biomolecules with specific material-binding properties that could be used as the building blocks to achieve multi-material switchable NP assemblies.« less

The Au modified Ge(1 1 0) surface

NASA Astrophysics Data System (ADS)

Zhang, L.; Kabanov, N. S.; Bampoulis, P.; Saletsky, A. M.; Zandvliet, H. J. W.; Klavsyuk, A. L.

2018-05-01

The pristine Ge(1 1 0) surface is composed of Ge pentagons, which are arranged in relatively large (16 × 2) and c(8 × 10) unit cells. The deposition of sub-monolayer amounts of Au and mild annealing results into de-reconstructed Ge(1 1 0) regions completely free of Ge pentagons and regions composed of nanowires that are aligned along the high symmetry [ 1 1 bar 0 ] direction of the Ge(1 1 0) surface. The de-reconstructed Ge(1 1 0) regions consist of atomic rows that are aligned along the [ 1 1 bar 0 ] direction. A substantial fraction of these substrate rows are straight and resemble the atom rows of the unreconstructed, i.e. bulk terminated, Ge(1 1 0) surface, whereas the other substrate rows have a meandering appearance. These meandering atom rows are comprised of two types of atoms, one type that appears dim, whereas the other type appears bright in filled-state scanning tunneling microscopy images. Using density functional theory calculations, we have tested more than 20 different atomic models for the meandering atom rows. The density functional theory calculations reveal that it is energetically favorable for the deposited Au atoms to exchange position with Ge atoms in the first layer. Based on these findings we conclude that the bright atoms are Ge atoms, whereas the dim atoms are Au atoms.

Bendable solid-state supercapacitors with Au nanoparticle-embedded graphene hydrogel films

PubMed Central

Yang, Kyungwhan; Cho, Kyoungah; Yoon, Dae Sung; Kim, Sangsig

2017-01-01

In this study, we fabricate bendable solid-state supercapacitors with Au nanoparticle (NP)-embedded graphene hydrogel (GH) electrodes and investigate the influence of the Au NP embedment on the internal resistance and capacitive performance. Embedding the Au NPs into the GH electrodes results in a decrease of the internal resistance from 35 to 21 Ω, and a threefold reduction of the IR drop at a current density of 5 A/g when compared with GH electrodes without Au NPs. The Au NP-embedded GH supercapacitors (NP-GH SCs) exhibit excellent capacitive performances, with large specific capacitance (135 F/g) and high energy density (15.2 W·h/kg). Moreover, the NP-GH SCs exhibit comparable areal capacitance (168 mF/cm2) and operate under tensile/compressive bending. PMID:28074865

Structures and magnetic properties of Fe and Ni monoatomic chains encapsulated by an Au nanotube

NASA Astrophysics Data System (ADS)

Han, Zhi-Dong; Li, Xiu-Yan; Yang, Zhi; Liu, Rui-Ping; Liu, Shao-Ding; Zhang, Ying

2012-11-01

Structures and magnetic properties of transition metal (TM) Fe or Ni monoatomic chains (MACs) encapsulated by a Au (5, 5) nanotube (Fe@Au and Ni@Au) are investigated using the density functional theory (DFT). The calculated results show that both Fe@Au and Ni@Au prefer to adopt ferromagnetic (FM) orders as ground states. In particular, the Fe@Au keeps the magnetic properties of free-standing Fe MAC, indicating that this system may be viewed as a new candidate in electromagnetic devices.

The Gemini/NICI Planet-Finding Campaign: The Frequency of Planets around Young Moving Group Stars

NASA Astrophysics Data System (ADS)

Biller, Beth A.; Liu, Michael C.; Wahhaj, Zahed; Nielsen, Eric L.; Hayward, Thomas L.; Males, Jared R.; Skemer, Andrew; Close, Laird M.; Chun, Mark; Ftaclas, Christ; Clarke, Fraser; Thatte, Niranjan; Shkolnik, Evgenya L.; Reid, I. Neill; Hartung, Markus; Boss, Alan; Lin, Douglas; Alencar, Silvia H. P.; de Gouveia Dal Pino, Elisabete; Gregorio-Hetem, Jane; Toomey, Douglas

2013-11-01

We report results of a direct imaging survey for giant planets around 80 members of the β Pic, TW Hya, Tucana-Horologium, AB Dor, and Hercules-Lyra moving groups, observed as part of the Gemini/NICI Planet-Finding Campaign. For this sample, we obtained median contrasts of ΔH = 13.9 mag at 1'' in combined CH4 narrowband ADI+SDI mode and median contrasts of ΔH = 15.1 mag at 2'' in H-band ADI mode. We found numerous (>70) candidate companions in our survey images. Some of these candidates were rejected as common-proper motion companions using archival data; we reobserved with Near-Infrared Coronagraphic Imager (NICI) all other candidates that lay within 400 AU of the star and were not in dense stellar fields. The vast majority of candidate companions were confirmed as background objects from archival observations and/or dedicated NICI Campaign followup. Four co-moving companions of brown dwarf or stellar mass were discovered in this moving group sample: PZ Tel B (36 ± 6 M Jup, 16.4 ± 1.0 AU), CD-35 2722B (31 ± 8 M Jup, 67 ± 4 AU), HD 12894B (0.46 ± 0.08 M ⊙, 15.7 ± 1.0 AU), and BD+07 1919C (0.20 ± 0.03 M ⊙, 12.5 ± 1.4 AU). From a Bayesian analysis of the achieved H band ADI and ASDI contrasts, using power-law models of planet distributions and hot-start evolutionary models, we restrict the frequency of 1-20 M Jup companions at semi-major axes from 10-150 AU to <18% at a 95.4% confidence level using DUSTY models and to <6% at a 95.4% using COND models. Our results strongly constrain the frequency of planets within semi-major axes of 50 AU as well. We restrict the frequency of 1-20 M Jup companions at semi-major axes from 10-50 AU to <21% at a 95.4% confidence level using DUSTY models and to <7% at a 95.4% using COND models. This survey is the deepest search to date for giant planets around young moving group stars. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

Technical Note: A simulation study on the feasibility of radiotherapy dose enhancement with calcium tungstate and hafnium oxide nano- and microparticles.

PubMed

Sherck, Nicholas J; Won, You-Yeon

2017-12-01

To assess the radiotherapy dose enhancement (RDE) potential of calcium tungstate (CaWO 4 ) and hafnium oxide (HfO 2 ) nano- and microparticles (NPs). A Monte Carlo simulation study was conducted to gauge their respective RDE potentials relative to that of the broadly studied gold (Au) NP. The study was warranted due to the promising clinical and preclinical studies involving both CaWO 4 and HfO 2 NPs as RDE agents in the treatment of various types of cancers. The study provides a baseline RDE to which future experimental RDE trends can be compared to. All three materials were investigated in silico with the software Penetration and Energy Loss of Positrons and Electrons (PENELOPE 2014) developed by Francesc Salvat and distributed in the United States by the Radiation Safety Information Computational Center (RSICC) at Oak Ridge National Laboratory. The work utilizes the extensively studied Au NP as the "gold standard" for a baseline. The key metric used in the evaluation of the materials was the local dose enhancement factor (DEF loc ). An additional metric used, termed the relative enhancement ratio (RER), evaluates material performance at the same mass concentrations. The results of the study indicate that Au has the strongest RDE potential using the DEF loc metric. HfO 2 and CaWO 4 both underperformed relative to Au with lower DEF loc of 2-3 × and 4-100 ×, respectively. The computational investigation predicts the RDE performance ranking to be: Au > HfO 2 > CaWO 4 . © 2017 American Association of Physicists in Medicine.

Nanoparticle Stabilized Liposomes for Acne Therapy

NASA Astrophysics Data System (ADS)

Fu, Victoria

Acne vulgaris is a common skin disease that affects over 40 million people in the United States alone. The main cause of acne vulgaris is Propionibacterium acnes (P. acnes), resides deep in the pores and follicles of the skin in order to feed on oil produced by the sebaceous glands. The liposome is a lipid based nanoparticle with numerous advantages over free drug molecules as an acne treatment alternative. Bare liposomes loaded with lauric acid (LipoLA) were found to show strong antimicrobial activity against P. acnes while generating minimal toxicity. However, the platform is limited by the spontaneous tendency of liposomes to fuse with each other. Attaching nanoparticles to the surface of liposomes can overcome this challenge by providing steric repulsion and reduce surface tension. Thus, carboxyl-functionalized gold nanoparticles (AuC) were attached to the surface of liposomes (AuC-liposomes) loaded with doxycycline, a general tetracycline antibiotic. These particles were found to have a diameter of 120 nm and a zeta potential of 20.0 mV. Both fluorescent and antimicrobial studies demonstrated that based on electrostatic interaction, negatively charged AuC attached to the liposome's positively charged surface and stabilized liposomes in a neutral pH environment (pH = 7.4). Upon entering the skin's acidic environment (pH = 4), AuC detached from the liposome's surface and liposomes could fuse with P. acnes residing in the pores. Furthermore, toxicity studies showed that AuC-liposomes did not induce any significant toxicity, while two of the leading over-the-counter therapies, benzoyl peroxide and salicylic acid, generated substantial skin irritation.

Reversible Self-Assembly of Water-Soluble Gold(I) Complexes.

PubMed

Aguiló, Elisabet; Moro, Artur J; Gavara, Raquel; Alfonso, Ignacio; Pérez, Yolanda; Zaccaria, Francesco; Guerra, Célia Fonseca; Malfois, Marc; Baucells, Clara; Ferrer, Montserrat; Lima, João Carlos; Rodríguez, Laura

2018-02-05

The reaction of the gold polymers containing bipyridyl and terpyridyl units, [Au(C≡CC 15 H 10 N 3 )] n and [Au(C≡CC 10 H 7 N 2 )] n , with the water-soluble phosphines 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane gives rise to the formation of four gold(I) alkynyl complexes that self-assemble in water (H 2 O) and dimethyl sulfoxide (DMSO), through different intermolecular interactions, with an impact on the observed luminescence displayed by the supramolecular assemblies. A detailed analysis carried out by NMR studies performed in different DMSO/deuterated H 2 O mixtures indicates the presence of two different assembly modes in the aggregates: (i) chain assemblies, which are based mainly on aurophilic interactions, and (ii) stacked assemblies, which are based on Au···π and π···π interactions. These different supramolecular environments can also be detected by their intrinsic optical properties (differences in absorption and emission spectra) and are predicted by the changes in the relative binding energy from density functional theory calculations carried out in DMSO and H 2 O. Small-angle X-ray scattering (SAXS) experiments performed in the same mixture of solvents are in agreement with the formation of aggregates in all cases. The aromatic units chosen, bipyridine and terpyridine, allow the use of external stimuli to reversibly change the aggregation state of the supramolecular assemblies. Interaction with the Zn 2+ cation is observed to disassemble the aggregates, while encapsulating agents competing for Zn 2+ complexation revert the process to the aggregation stage, as verified by SAXS and NMR. The adaptive nature of the supramolecular assemblies to the metal-ion content is accompanied by significant changes in the absorption and emission spectra, signaling the aggregation state and also the content on Zn 2+ .

Study of Omega-proton correlations in heavy-ion collisions

NASA Astrophysics Data System (ADS)

Han, Yifei; STAR Collaboration

2015-10-01

Recently the STAR experiment at RHIC measured Lambda-Lambda correlations from Au+Au collisions at √{sNN} = 200 GeV to search for the H particle (uuddss). The correlation strength indicated that the Lambda-Lambda interaction is weak and is unlikely to be attractive enough to form a bound state. A recent lattice QCD calculation predicted a possible di-baryon bound state with Omega-nucleon. Thus, we will extend the correlation measurements to Omega-proton, which could potentially be a sensitive approach to search for such a state. We will present the Omega-proton correlations based on data collected by STAR in Au+Au collisions at √{sNN} =200 GeV, and discuss the physics implications. for the STAR collaboration.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pei, Dr. Yong; Shao, Nan; Li, Prof. Hui

Using ab initio methods, we investigate the structural evolution of a family of gold-sulfide cluster anions (Au{sub m}S{sub n}{sup -}). We show that this family of clusters exhibits simple size-evolution rules and novel hollow polyhedron structures. The highly stable Au{sub m}S{sub n}{sup -} species such as Au{sub 6}S{sub 4}{sup -}, Au{sub 9}S{sub 5}{sup -}, Au{sub 9}S{sub 6}{sup -}, Au{sub 10}S{sub 6}{sup -}, Au{sub 11}S{sub 6}{sup -}, Au{sub 12}S{sub 8}{sup -}, and Au{sub 13}S{sub 8}{sup -} detected in the recent ion mobility mass spectrometry experiment of Au{sub 25}(SCH{sub 2}CH{sub 2}Ph){sub 18} (Angel et al. ACS Nano2010, 4, 4691) are found tomore » possess either quasi-tetrahedron, pyramidal, quasi-triangular prism, or quasi-cuboctahedron structures. The formation of these polyhedron structures are attributed to the high stability of the S-Au-S structural unit. A unique 'edge-to-face' growth mechanism is proposed to understand the structural evolution of the small Au{sub m}S{sub n}{sup -} cluster. A 3:2 ratio rule of Au/S is suggested for the formation of a hollow polyhedron structure among small-sized Au{sub m}S{sub m} clusters.« less

Near-unity thermally activated delayed fluorescence efficiency in three- and four-coordinate Au(i) complexes with diphosphine ligands.

PubMed

Osawa, Masahisa; Aino, Masa-Aki; Nagakura, Takaki; Hoshino, Mikio; Tanaka, Yuya; Akita, Munetaka

2018-05-14

The synthesis and photoluminescence properties of three-coordinate Au(i) complexes with rigid diphosphine ligands LMe {1,2-bis[bis(2-methylphenyl)phosphino]benzene}, LEt {1,2-bis[bis(2-ethylphenyl)phosphino]benzene}, and LiPr {1,2-bis[bis(2-isopropylphenyl)phosphino]benzene} are investigated. The LMe and LEt ligands afford two types of complexes: dinuclear complexes [μ-LMe(AuCl)2] (1d) and [μ-LEt(AuCl)2] (2d) with an Au(i)-Au(i) bond and mononuclear three-coordinate Au(i) complexes LMeAuCl (1) and LEtAuCl (2). On the other hand, the bulkiest ligand, LiPr, affords three-coordinate Au(i) complexes, LiPrAuCl (3) and LiPrAuI (4), but no dinuclear complexes. X-ray analysis suggests that both 3 and 4 possess a highly distorted trigonal planar geometry. Moreover, luminescence data reveal that at room temperature, 3 and 4 exhibit yellow-green thermally activated delayed fluorescence in the crystalline state with maximum emission wavelengths at 558 and 549 nm, respectively. The emission yields are close to unity. Quantum chemical calculations suggest that the emission of 4 originates from the (σ + X) → π* excited state that possesses strong intraligand charge-transfer character. The luminescent properties of four-coordinate Au(i) complex (5) possessing a tetrahedral geometry are discussed on the basis of the emission spectra and decay times measured in a temperature range of 309-77 K.

Electronic Structure of a Self-Assembled Monolayer with Two Surface Anchors: 6-Mercaptopurine on Au(111).

PubMed

Fernández, Cynthia C; Pensa, Evangelina; Carro, Pilar; Salvarezza, Roberto; Williams, Federico J

2018-05-22

The electronic structure of aromatic and aliphatic thiols on Au(111) has been extensively studied in relation to possible applications in molecular electronics. In this work, the effect on the electronic structure of an additional anchor to the S-Au bond using 6-mercaptopurine as a model system has been investigated. Results from X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and density functional theory (DFT) confirm that this molecule adsorbs on Au(111) with S-Au and iminic N-Au bonds. Combined ultraviolet photoelectron spectroscopy and DFT data reveal that formation of the 6MP self-assembled monolayer generates a molecular dipole perpendicular to the surface, with negative charges residing at the metal/monolayer interface and positive charges at the monolayer/vacuum interface, which lowers the substrate work function. Scanning tunneling microscopy shows two surface molecular domains: a well-ordered rectangular lattice where molecules are tilted on average 30° with respect to the substrate and aligned 6MP islands where molecules are standing upright. Finally, we found a new electronic state located at -1.7 eV with respect to the Fermi level that corresponds to a localized π molecular state, while the state corresponding to the N-Au bond is hybridized with Au d electrons and stabilized at much lower energies (-3 eV).

Gold-induced nanowires on the Ge(100) surface yield a 2D and not a 1D electronic structure

NASA Astrophysics Data System (ADS)

de Jong, N.; Heimbuch, R.; Eliëns, S.; Smit, S.; Frantzeskakis, E.; Caux, J.-S.; Zandvliet, H. J. W.; Golden, M. S.

2016-06-01

Atomic nanowires on semiconductor surfaces induced by the adsorption of metallic atoms have attracted a lot of attention as possible hosts of the elusive, one-dimensional Tomonaga-Luttinger liquid. The Au/Ge(100) system in particular is the subject of controversy as to whether the Au-induced nanowires do indeed host exotic, 1D (one-dimensional) metallic states. In light of this debate, we report here a thorough study of the electronic properties of high quality nanowires formed at the Au/Ge(100) surface. The high-resolution ARPES data show the low-lying Au-induced electronic states to possess a dispersion relation that depends on two orthogonal directions in k space. Comparison of the E (kx,ky) surface measured using high-resolution ARPES to tight-binding calculations yields hopping parameters in the two different directions that differ by approximately factor of two. Additionally, by pinpointing the Au-induced surface states in the first, second, and third surface Brillouin zones and analyzing their periodicity in k||, the nanowire propagation direction seen clearly in STM can be imported into the ARPES data. We find that the larger of the two hopping parameters corresponds, in fact, to the direction perpendicular to the nanowires (tperp). This proves that the Au-induced electron pockets possess a two-dimensional, closed Fermi surface, and this firmly places the Au/Ge(100) nanowire system outside potential hosts of a Tomonaga-Luttinger liquid. We combine these ARPES data with scanning tunneling spectroscopic measurements of the spatially resolved electronic structure and find that the spatially straight—wirelike—conduction channels observed up to energies of order one electron volt below the Fermi level do not originate from the Au-induced states seen in the ARPES data. The former are rather more likely to be associated with bulk Ge states that are localized to the subsurface region. Despite our proof of the 2D (two-dimentional) nature of the Au-induced nanowire and subsurface Ge-related states, an anomalous suppression of the density of states at the Fermi level is observed in both the STS and ARPES data, and this phenomenon is discussed in the light of the effects of disorder.

Structural and dynamical properties of liquid Al-Au alloys

NASA Astrophysics Data System (ADS)

Peng, H. L.; Voigtmann, Th.; Kolland, G.; Kobatake, H.; Brillo, J.

2015-11-01

We investigate temperature- and composition-dependent structural and dynamical properties of Al-Au melts. Experiments are performed to obtain accurate density and viscosity data. The system shows a strong negative excess volume, similar to other Al-based binary alloys. We develop a molecular-dynamics (MD) model of the melt based on the embedded-atom method (EAM), gauged against the available experimental liquid-state data. A rescaling of previous EAM potentials for solid-state Au and Al improves the quantitative agreement with experimental data in the melt. In the MD simulation, the admixture of Au to Al can be interpreted as causing a local compression of the less dense Al system, driven by less soft Au-Au interactions. This local compression provides a microscopic mechanism explaining the strong negative excess volume of the melt. We further discuss the concentration dependence of self- and interdiffusion and viscosity in the MD model. Al atoms are more mobile than Au, and their increased mobility is linked to a lower viscosity of the melt.

Structure of the Si(111)-(5×2)-Au Surface

NASA Astrophysics Data System (ADS)

Abukawa, Tadashi; Nishigaya, Yoshiki

2013-01-01

The structure of the Si(111)-(5×2)-Au surface, one of the long-standing problems in surface science, has been solved by means of Weissenberg reflection high-energy electron diffraction. The arrangement of the Au atoms and their positions with respect to the substrate were determined from a three-dimensional Patterson function with a lateral resolution of 0.3 Å based on a large amount of diffraction data. The new structural model consists of six Au atoms in a 5×2 unit, which agrees with the recently confirmed Au coverage of 0.6 ML [I. Barke , Phys. Rev. B 79, 155301 (2009).PRBMDO1098-0121]. The model has a distinct ×2 periodicity, and includes a Au dimer. The model is also compatible with previously obtained STM images.

Structural evolution and properties of small-size thiol-protected gold nanoclusters

NASA Astrophysics Data System (ADS)

Ma, Miaomiao; Liu, Liren; Zhu, Hengjiang; Lu, Junzhe; Tan, Guiping

2018-07-01

Ligand-protected gold clusters are widely used in biosensors and catalysis. Understanding the structural evolution of these kinds of nanoclusters is important for experimental synthesis. Herein, based on the particle swarm optimisation algorithm and density functional theory method, we use [Au1(SH)2]n, [Au2(SH)3]n, [Au3(SH)4]n (n = 1-3) as basic units to research the structural evolution relationships from building blocks to the final whole structures. Results show that there is a 'line-ring-core' structural evolution pattern in the growth process of the nanoclusters. The core structures of the ligand-protected gold clusters consist of Au3, Au4, Au6 and Au7 atoms. The electronics and optics analysis reflects that stability and optical properties gradually enhance with increase in size. These results can be used to understand the initial growth stage and design new ligand-protected nanoclusters.

Prediction of weak and strong topological insulators in layered semiconductors.

NASA Astrophysics Data System (ADS)

Felser, Claudia

2013-03-01

We investigate a new class of ternary materials such as LiAuSe and KHgSb with a honeycomb structure in Au-Se and Hg-Sb layers. We demonstrate the band inversion in these materials similar to HgTe, which is a strong precondition for existence of the topological surface states. In contrast with graphene, these materials exhibit strong spin-orbit coupling and a small direct band gap at the point. Since these materials are centrosymmetric, it is straightforward to determine the parity of their wave functions, and hence their topological character. Surprisingly, the compound with strong spin-orbit coupling (KHgSb) is trivial, whereas LiAuSe is found to be a topological insulator. However KHgSb is a weak topological insulators in case of an odd number of layers in the primitive unit cell. Here, the single-layered KHgSb shows a large bulk energy gap of 0.24 eV. Its side surface hosts metallic surface states, forming two anisotropic Dirac cones. Although the stacking of even-layered structures leads to trivial insulators, the structures can host a quantum spin Hall layer with a large bulk gap, if an additional single layer exists as a stacking fault in the crystal. The reported honeycomb compounds can serve as prototypes to aid in the finding of new weak topological insulators in layered small-gap semiconductors. In collaboration with Binghai Yan, Lukas Müchler, Hai-Jun Zhang, Shou-Cheng Zhang and Jürgen Kübler.

Controlled assembly and single electron charging of monolayer protected Au144 clusters: an electrochemistry and scanning tunneling spectroscopy study

NASA Astrophysics Data System (ADS)

Bodappa, Nataraju; Fluch, Ulrike; Fu, Yongchun; Mayor, Marcel; Moreno-García, Pavel; Siegenthaler, Hans; Wandlowski, Thomas

2014-11-01

Single gold particles may serve as room temperature single electron memory units because of their size dependent electronic level spacing. Here, we present a proof-of-concept study by electrochemically controlled scanning probe experiments performed on tailor-made Au particles of narrow dispersity. In particular, the charge transport characteristics through chemically synthesized hexane-1-thiol and 4-pyridylbenzene-1-thiol mixed monolayer protected Au144 clusters (MPCs) by differential pulse voltammetry (DPV) and electrochemical scanning tunneling spectroscopy (EC-STS) are reported. The pyridyl groups exposed by the Au-MPCs enable their immobilization on Pt(111) substrates. By varying the humidity during their deposition, samples coated by stacks of compact monolayers of Au-MPCs or decorated with individual, laterally separated Au-MPCs are obtained. DPV experiments with stacked monolayers of Au144-MPCs and EC-STS experiments with laterally separated individual Au144-MPCs are performed both in aqueous and ionic liquid electrolytes. Lower capacitance values were observed for individual clusters compared to ensemble clusters. This trend remains the same irrespective of the composition of the electrolyte surrounding the Au144-MPC. However, the resolution of the energy level spacing of the single clusters is strongly affected by the proximity of neighboring particles.Single gold particles may serve as room temperature single electron memory units because of their size dependent electronic level spacing. Here, we present a proof-of-concept study by electrochemically controlled scanning probe experiments performed on tailor-made Au particles of narrow dispersity. In particular, the charge transport characteristics through chemically synthesized hexane-1-thiol and 4-pyridylbenzene-1-thiol mixed monolayer protected Au144 clusters (MPCs) by differential pulse voltammetry (DPV) and electrochemical scanning tunneling spectroscopy (EC-STS) are reported. The pyridyl groups exposed by the Au-MPCs enable their immobilization on Pt(111) substrates. By varying the humidity during their deposition, samples coated by stacks of compact monolayers of Au-MPCs or decorated with individual, laterally separated Au-MPCs are obtained. DPV experiments with stacked monolayers of Au144-MPCs and EC-STS experiments with laterally separated individual Au144-MPCs are performed both in aqueous and ionic liquid electrolytes. Lower capacitance values were observed for individual clusters compared to ensemble clusters. This trend remains the same irrespective of the composition of the electrolyte surrounding the Au144-MPC. However, the resolution of the energy level spacing of the single clusters is strongly affected by the proximity of neighboring particles. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03793f

Calix[4]arene-Functionalised Silver Nanoparticles as Hosts for Pyridinium-Loaded Gold Nanoparticles as Guests.

PubMed

Vita, Francesco; Boccia, Alice; Marrani, Andrea G; Zanoni, Robertino; Rossi, Francesca; Arduini, Arturo; Secchi, Andrea

2015-10-19

A series of lipophilic gold nanoparticles (AuNPs) circa 5 nm in diameter and having a mixed organic layer consisting of 1-dodecanethiol and 1-(11-mercaptoundecyl) pyridinium bromide was synthesised by reacting tetraoctylammonium bromide stabilised AuNPs in toluene with different mixtures of the two thiolate ligands. A bidentate ω-alkylthiolate calix[4]arene derivative was instead used as a functional protecting layer on AgNPs of approximately 3 nm. The functionalised nanoparticles were characterised by transmission electron microscopy (TEM), and by UV/Vis and X-ray photoelectron spectroscopy (XPS). Recognition of the pyridinium moieties loaded on the AuNPs by the calix[4]arene units immobilised on the AgNPs was demonstrated in solution of weakly polar solvents by UV/Vis titrations and DLS measurements. The extent of Au-AgNPs aggregation, shown through the low-energy shift of their surface plasmon bands (SPB), was strongly dependent on the loading of the pyridinium moieties present in the organic layer of the AuNPs. Extensive aggregation between dodecanethiol-capped AuNPs and the Ag calix[4]arene-functionalised NPs was also promoted by the action of a simple N-octyl pyridinium difunctional supramolecular linker. This linker can interdigitate through its long fatty tail in the organic layer of the dodecanethiol-capped AuNPs, and simultaneously interact through its pyridinium moiety with the calix[4]arene units at the surface of the modified AgNPs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

ELSA 2016 Cohort: Alcohol, Tobacco, and Marijuana Use and Their Association with Age of Drug Use Onset, Risk Perception, and Social Norms in Argentinean College Freshmen

PubMed Central

Pilatti, Angelina; Read, Jennifer P.; Pautassi, Ricardo M.

2017-01-01

The transition from high school to college is a high-risk stage for the initiation and escalation of substance use. Substance use and its associated risk factors have been thoroughly described in developed countries, such as the United States, but largely neglected in Argentina, a South American country with patterns of a collectivist culture. The present cross-sectional study describes the occurrence of alcohol, tobacco, and marijuana use and the association between these behaviors and the age of onset of substance use and cognitive (i.e., risk perception) and social (i.e., prescriptive) variables in a large sample of Argentinean college freshmen (n = 4083, 40.1% men; mean age = 19.39 ± 2.18 years). The response rate across courses was ≥90% and was similarly distributed across sex. Participants completed a survey that measured substance use (alcohol [with a focus on heavy drinking and binge drinking behaviors], tobacco, and marijuana), age of onset of the use of each substance, perceived risk associated with various substance use behaviors, prescriptive norms associated with substance use, and descriptive norms for alcohol use (AU). The results indicated that AU is nearly normative (90.4 and 80.3% with last year and last month use, respectively) in this population, and heavy drinking is highly prevalent (68.6 and 54.9% with heavy episodic and binge drinking, respectively), especially among those with an early drinking onset (97.8 and 93.6% with last year and last month use and 87.8 and 76.3% with heavy episodic and binge drinking, respectively). The last-year occurrence of tobacco and marijuana use was 36 and 28%, respectively. Early substance use was associated with the greater use of that specific substance. The students overestimated their same-sex friend’s AU, and women overestimated the level of AU of their best male friend. At the multivariate level, all of the predictors, with the exception of the parents’ prescriptive norms, significantly explained the frequency of marijuana and tobacco use and frequency of hazardous drinking. Overall, despite important cultural and contextual differences between Argentina and the United States, our findings suggest that certain vulnerability factors have a similar influence across these cultural contexts. PMID:28890707

Theoretical Insights into the Origin of Photoluminescence of Au 25(SR) 18 – Nanoparticles

DOE PAGES

Weerawardene, K. L. Dimuthu M.; Aikens, Christine M.

2016-08-15

Understanding fundamental behavior of luminescent nanomaterials upon photoexcitation is necessary to expand photocatalytic and biological imaging applications. Despite the significant amount of experimental work into the luminescence of Au 25(SR) 18 – clusters, the origin of photoluminescence in these clusters still remains unclear. In this study, the geometric and electronic structural changes of the Au 25(SR) 18 – (R = H, CH 3, CH 2CH 3, CH 2CH 2CH 3) nanoclusters upon photoexcitation are discussed using time-dependent density functional theory (TD-DFT) methods. Geometric relaxations in the optimized excited states of up to 0.33 Å impart remarkable effects on the energymore » levels of the frontier orbitals of Au 25(SR) 18 – nanoclusters. This gives rise to a Stokes shift of 0.49 eV for Au 25(SH) 18 – in agreement with experiments. Even larger Stokes shifts are predicted for longer ligands. Vibrational frequencies in the 75–80 cm –1 range are calculated for the nuclear motion involved in the excited-state nuclear relaxation; this value is in excellent agreement with vibrational beating observed in time-resolved spectroscopy experiments. Several excited states around 0.8, 1.15, and 1.25 eV are calculated for the Au 25(SH) 18 – nanocluster. Considering the typical underestimation of DFT excitation energies, these states are likely responsible for the emission observed experimentally in the 1.15–1.55 eV range. In conclusion, all excited states arise from core-based orbitals; charge-transfer states or other “semi-ring” or ligand-based states are not implicated.« less

Theoretical Insights into the Origin of Photoluminescence of Au 25(SR) 18 – Nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weerawardene, K. L. Dimuthu M.; Aikens, Christine M.

Understanding fundamental behavior of luminescent nanomaterials upon photoexcitation is necessary to expand photocatalytic and biological imaging applications. Despite the significant amount of experimental work into the luminescence of Au 25(SR) 18 – clusters, the origin of photoluminescence in these clusters still remains unclear. In this study, the geometric and electronic structural changes of the Au 25(SR) 18 – (R = H, CH 3, CH 2CH 3, CH 2CH 2CH 3) nanoclusters upon photoexcitation are discussed using time-dependent density functional theory (TD-DFT) methods. Geometric relaxations in the optimized excited states of up to 0.33 Å impart remarkable effects on the energymore » levels of the frontier orbitals of Au 25(SR) 18 – nanoclusters. This gives rise to a Stokes shift of 0.49 eV for Au 25(SH) 18 – in agreement with experiments. Even larger Stokes shifts are predicted for longer ligands. Vibrational frequencies in the 75–80 cm –1 range are calculated for the nuclear motion involved in the excited-state nuclear relaxation; this value is in excellent agreement with vibrational beating observed in time-resolved spectroscopy experiments. Several excited states around 0.8, 1.15, and 1.25 eV are calculated for the Au 25(SH) 18 – nanocluster. Considering the typical underestimation of DFT excitation energies, these states are likely responsible for the emission observed experimentally in the 1.15–1.55 eV range. In conclusion, all excited states arise from core-based orbitals; charge-transfer states or other “semi-ring” or ligand-based states are not implicated.« less

Remarkable Second-Order Optical Nonlinearity of Nano-Sized Au Cluster: A TDDFT Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Kechen; Li, Jun; Lin, Chensheng

2004-04-21

The dipole polarizability, static first hyperpolarizability, and UV-vis spectrum of the recently identified nano-sized tetrahedral cluster of Au have been investigated by using time-dependent density functional response theory. We have discovered that the Au cluster possesses remarkably large molecular second-order optical nonlinearity with the first hyperpolarizabilty (xyz) calculated to be 14.3 x 10 electrostatic unit (esu). The analysis of the low-energy absorption band suggests that the charge transfer from the edged gold atoms to the vertex ones plays the key role in nonlinear optical (NLO) response of Au.

Assessment of undiscovered continuous oil and gas resources in the Monterey Formation, San Joaquin Basin Province, California, 2015

USGS Publications Warehouse

Tennyson, Marilyn E.; Charpentier, Ronald R.; Klett, Timothy R.; Brownfield, Michael E.; Pitman, Janet K.; Gaswirth, Stephanie B.; Hawkins, Sarah J.; Lillis, Paul G.; Marra, Kristen R.; Mercier, Tracey J.; Leathers, Heidi M.; Schenk, Christopher J.; Whidden, Katherine J.

2015-10-06

Using a geology-based assessment methodology, the U.S. Geological Survey assessed mean volumes of 21 million barrels of oil (MMBO), 27 billion cubic feet of gas, and 1 million barrels of natural gas liquids in two assessment units (AUs) that may contain continuous oil resources. Mean volumes of oil for the individual assessment units are 14 MMBO in the Monterey Buttonwillow AU and 7 MMBO in the Monterey Maricopa AU.

Comparison of the space-time extent of the emission source in d +Au and Au + Au collisions at √{sNN} = 200 GeV

NASA Astrophysics Data System (ADS)

Ajitanand, N. N.; Phenix Collaboration

2014-11-01

Two-pion interferometry measurements in d +Au and Au + Au collisions at √{sNN} = 200 GeV are used to extract and compare the Gaussian source radii Rout, Rside and Rlong, which characterize the space-time extent of the emission sources. The comparisons, which are performed as a function of collision centrality and the mean transverse momentum for pion pairs, indicate strikingly similar patterns for the d +Au and Au + Au systems. They also indicate a linear dependence of Rside on the initial transverse geometric size R bar , as well as a smaller freeze-out size for the d +Au system. These patterns point to the important role of final-state re-scattering effects in the reaction dynamics of d +Au collisions.

Neogene Gas Total Petroleum System -- Neogene Nonassociated Gas Assessment Unit of the San Joaquin Basin Province: Chapter 22 in Petroleum systems and geologic assessment of oil and gas in the San Joaquin Basin Province, California

USGS Publications Warehouse

Hosford Scheirer, Allegra; Magoon, Leslie B.

2009-01-01

The Neogene Nonassociated Gas Assessment Unit (AU) of the Neogene Total Petroleum System consists of nonassociated gas accumulations in Pliocene marine and brackish-water sandstone located in the south and central San Joaquin Basin Province (Rudkin, 1968). Traps consist mainly of stratigraphic lenses in low-relief, elongate domes that trend northwest-southeast. Reservoir rocks typically occur as sands that pinch out at shallow depths (1,000 to 7,500 feet) within the Etchegoin and San Joaquin Formations. Map boundaries of the assessment unit are shown in figures 22.1 and 22.2; this assessment unit replaces the Pliocene Nonassociated Gas play 1001 (shown by purple line in fig. 22.1) considered by the U.S. Geological Survey (USGS) in its 1995 National Assessment (Beyer, 1996). The AU is drawn to include all existing fields containing nonassociated gas accumulations in the Pliocene to Pleistocene section, as was done in the 1995 assessment, but it was greatly expanded to include adjacent areas believed to contain similar source and reservoir rock relationships. Stratigraphically, the AU extends from the topographic surface to the base of the Etchegoin Formation (figs. 22.3 and 22.4). The boundaries of the AU explicitly exclude gas accumulations in Neogene rocks on the severely deformed west side of the basin and gas accumulations in underlying Miocene rocks; these resources, which primarily consist of a mixture of mostly thermogenic and some biogenic gas, are included in two other assessment units. Lillis and others (this volume, chapter 10) discuss the geochemical characteristics of biogenic gas in the San Joaquin Basin Province. Primary fields in the assessment unit are defined as those containing hydrocarbon resources greater than the USGS minimum threshold for assessment—3 billion cubic feet (BCF) of gas; secondary fields contain smaller volumes of gas but constitute a significant show of hydrocarbons. Although 12 fields meet the 3 BCF criterion for inclusion in the AU, only 5 fields were considered at the time of assessment.

H2S adsorption on chromium, chromia, and gold/chromia surfaces: Photoemission studies

NASA Astrophysics Data System (ADS)

Rodriguez, J. A.; Chaturvedi, S.; Kuhn, M.; van Ek, J.; Diebold, U.; Robbert, P. S.; Geisler, H.; Ventrice, C. A., Jr.

1997-12-01

The reaction of H2S with chromium, chromia, and Au/chromia films grown on a Pt(111) crystal has been investigated using synchrotron-based high-resolution photoemission spectroscopy. At 300 K, H2S completely decomposes on polycrystalline chromium producing a chemisorbed layer of S that attenuates the Cr 3d valence features. No evidence was found for the formation of CrSx species. The dissociation of H2S on Cr3O4 and Cr2O3 films at room temperature produces a decrease of 0.3-0.8 eV in the work function of the surface and significant binding-energy shifts (0.2-0.6 eV) in the Cr 3p core levels and Cr 3d features in the valence region. The rate of dissociation of H2S increases following the sequence: Cr2O3

A duplex DNA-gold nanoparticle probe composed as a colorimetric biosensor for sequence-specific DNA-binding proteins.

PubMed

Ahn, Junho; Choi, Yeonweon; Lee, Ae-Ree; Lee, Joon-Hwa; Jung, Jong Hwa

2016-03-21

Using duplex DNA-AuNP aggregates, a sequence-specific DNA-binding protein, SQUAMOSA Promoter-binding-Like protein 12 (SPL-12), was directly determined by SPL-12-duplex DNA interaction-based colorimetric actions of DNA-Au assemblies. In order to prepare duplex DNA-Au aggregates, thiol-modified DNA 1 and DNA 2 were attached onto the surface of AuNPs, respectively, by the salt-aging method and then the DNA-attached AuNPs were mixed. Duplex-DNA-Au aggregates having the average size of 160 nm diameter and the maximum absorption at 529 nm were able to recognize SPL-12 and reached the equivalent state by the addition of ∼30 equivalents of SPL-12 accompanying a color change from red to blue with a red shift of the maximum absorption at 570 nm. As a result, the aggregation size grew to about 247 nm. Also, at higher temperatures of the mixture of duplex-DNA-Au aggregate solution and SPL-12, the equivalent state was reached rapidly. On the contrary, in the control experiment using Bovine Serum Albumin (BSA), no absorption band shift of duplex-DNA-Au aggregates was observed.

Mixing of MnPc electronic states at the MnPc/Au(110) interface

NASA Astrophysics Data System (ADS)

Gargiani, Pierluigi; Lisi, Simone; Avvisati, Giulia; Mondelli, Pierluigi; Fatale, Sara; Betti, Maria Grazia

2017-10-01

Manganese-phthalocyanines form assembled chains with a variety of ordered super-structures, flat lying along the Au(110) reconstructed channels. The chains first give rise to a ×5 symmetry reconstruction, while further deposition of MnPc leads to a ×7 periodicity at the completion of the first single layer. A net polarization with the formation of an interface dipole is mainly due to the molecular π-states located on the macrocycles pyrrole rings, while the central metal ion induces a reduction in the polarization, whose amount is related to the Mn-Au interaction. The adsorption-induced interface polarization is compared to other 3d-metal phthalocyanines, to unravel the role of the central metal atom configuration in the interaction process of the d-states. The MnPc adsorption on Au(110) induces the re-hybridization of the electronic states localized on the central metal atom, promoting a charge redistribution of the molecular orbitals of the MnPc molecules. The molecule-substrate interaction is controlled by a symmetry-determined mixing between the electronic states, involving also the molecular empty orbitals with d character hybridized with the nitrogen atoms of the pyrrole ring, as deduced by photoemission and X-ray absorption spectroscopy exploiting light polarization. The symmetry-determined mixing between the electronic states of the Mn metal center and of the Au substrate induces a density of states close to the Fermi level for the ×5 phase.

Formation of Surface and Quantum-Well States in Ultra Thin Pt Films on the Au(111) Surface

PubMed Central

Silkin, Igor V.; Koroteev, Yury M.; Echenique, Pedro M.; Chulkov, Evgueni V.

2017-01-01

The electronic structure of the Pt/Au(111) heterostructures with a number of Pt monolayers n ranging from one to three is studied in the density-functional-theory framework. The calculations demonstrate that the deposition of the Pt atomic thin films on gold substrate results in strong modifications of the electronic structure at the surface. In particular, the Au(111) s-p-type Shockley surface state becomes completely unoccupied at deposition of any number of Pt monolayers. The Pt adlayer generates numerous quantum-well states in various energy gaps of Au(111) with strong spatial confinement at the surface. As a result, strong enhancement in the local density of state at the surface Pt atomic layer in comparison with clean Pt surface is obtained. The excess in the density of states has maximal magnitude in the case of one monolayer Pt adlayer and gradually reduces with increasing number of Pt atomic layers. The spin–orbit coupling produces strong modification of the energy dispersion of the electronic states generated by the Pt adlayer and gives rise to certain quantum states with a characteristic Dirac-cone shape. PMID:29232833

X-ray Absorption Spectroscopy Combined with Time-Dependent Density Functional Theory Elucidates Differential Substitution Pathways of Au(I) and Au(III) with Zinc Fingers.

PubMed

Abbehausen, Camilla; de Paiva, Raphael Enoque Ferraz; Bjornsson, Ragnar; Gomes, Saulo Quintana; Du, Zhifeng; Corbi, Pedro Paulo; Lima, Frederico Alves; Farrell, Nicholas

2018-01-02

A combination of two elements' (Au, Zn) X-ray absorption spectroscopy (XAS) and time-dependent density functional theory (TD-DFT) allowed the elucidation of differential substitution pathways of Au(I) and Au(III) compounds reacting with biologically relevant zinc fingers (ZnFs). Gold L 3 -edge XAS probed the interaction of gold and the C-terminal Cys 2 HisCys finger of the HIV-1 nucleocapsid protein NCp7, and the Cys 2 His 2 human transcription factor Sp1. The use of model compounds helped assign oxidation states and the identity of the gold-bound ligands. The computational studies accurately reproduced the experimental XAS spectra and allowed the proposition of structural models for the interaction products at early time points. The direct electrophilic attack on the ZnF by the highly thiophilic Au(I) resulted in a linear P-Au-Cys coordination sphere after zinc ejection whereas for the Sp1, loss of PEt 3 results in linear Cys-Au-Cys or Cys-Au-His arrangements. Reactions with Au(III) compounds, on the other hand, showed multiple binding modes. Prompt reaction between [AuCl(dien)] 2+ and [Au(dien)(DMAP)] 3+ with Sp1 showed a partially reduced Au center and a final linear His-Au-His coordination. Differently, in the presence of NCp7, [AuCl(dien)] 2+ readily reduces to Au(I) and changes from square-planar to linear geometry with Cys-Au-His coordination, while [Au(dien)(DMAP)] 3+ initially maintains its Au(III) oxidation state and square-planar geometry and the same first coordination sphere. The latter is the first observation of a "noncovalent" interaction of a Au(III) complex with a zinc finger and confirms early hypotheses that stabilization of Au(III) occurs with N-donor ligands. Modification of the zinc coordination sphere, suggesting full or partial zinc ejection, is observed in all cases, and for [Au(dien)(DMAP)] 3+ this represents a novel mechanism for nucleocapsid inactivation. The combination of XAS and TD-DFT presents the first direct experimental observation that not only compound reactivity, but also ZnF core specificity, can be modulated on the basis of the coordination sphere of Au(III) compounds.

An ICT Primer: Information and Communication Technologies for Civil-Military Coordination in Disaster Relief and Stabilization and Reconstruction

DTIC Science & Technology

2006-07-01

Affected Nation DPK O MCD U UN Business Community Civilian M ilitary M ul tinational Inter ag en cy Player s OS CE ICRCIFRC EU AU OA S AS EAN Contractors...the countries of Europe, Canada, and the United States as well as certain countries in Central Asia . NGOs are of many different types and sizes...area includes Europe; North, Central, and parts of southern Africa; the Middle East; Central and South Asia , plus oceans in these regions

Repeated holdout Cross-Validation of Model to Estimate Risk of Lyme Disease by Landscape Attributes

EPA Science Inventory

We previously modeled Lyme disease (LD) risk at the landscape scale; here we evaluate the model's overall goodness-of-fit using holdout validation. Landscapes were characterized within road-bounded analysis units (AU). Observed LD cases (obsLD) were ascertained per AU. Data were ...

Internal-Modified Dithiol DNA–Directed Au Nanoassemblies: Geometrically Controlled Self–Assembly and Quantitative Surface–Enhanced Raman Scattering Properties

PubMed Central

Yan, Yuan; Shan, Hangyong; Li, Min; Chen, Shu; Liu, Jianyu; Cheng, Yanfang; Ye, Cui; Yang, Zhilin; Lai, Xuandi; Hu, Jianqiang

2015-01-01

In this work, a hierarchical DNA–directed self–assembly strategy to construct structure–controlled Au nanoassemblies (NAs) has been demonstrated by conjugating Au nanoparticles (NPs) with internal–modified dithiol single-strand DNA (ssDNA) (Au–B–A or A–B–Au–B–A). It is found that the dithiol–ssDNA–modified Au NPs and molecule quantity of thiol–modified ssDNA grafted to Au NPs play critical roles in the assembly of geometrically controlled Au NAs. Through matching Au–DNA self–assembly units, geometrical structures of the Au NAs can be tailored from one–dimensional (1D) to quasi–2D and 2D. Au–B–A conjugates readily give 1D and quasi–2D Au NAs while 2D Au NAs can be formed by A–B–Au–B–A building blocks. Surface-enhanced Raman scattering (SERS) measurements and 3D finite–difference time domain (3D-FDTD) calculation results indicate that the geometrically controllable Au NAs have regular and linearly “hot spots”–number–depended SERS properties. For a certain number of NPs, the number of “hot spots” and accordingly enhancement factor of Au NAs can be quantitatively evaluated, which open a new avenue for quantitative analysis based on SERS technique. PMID:26581251

Microstructural and electrical properties of Al/n-type Si Schottky diodes with Au-CuPc nanocomposite films as interlayer

NASA Astrophysics Data System (ADS)

Reddy, P. R. Sekhar; Janardhanam, V.; Jyothi, I.; Chang, Han-Soo; Lee, Sung-Nam; Lee, Myung Sun; Reddy, V. Rajagopal; Choi, Chel-Jong

2017-11-01

Au-CuPc nanocomposite films were prepared by simultaneous evaporation of Au and CuPc with various Au and CuPc concentrations. Microstructural analysis of Au-CuPc films revealed elongated Au cluster formation from isolated Au nanoclusters with increasing Au concentration associated with coalescence of Au clusters. Au-CuPc films with different compositions were employed as interlayer in Al/n-Si Schottky diode. Barrier height and series resistance of the Al/n-Si Schottky diode with Au-CuPc interlayer decreased with increasing Au concentration. This could be associated with the enhancement of electron tunneling between neighboring clusters due to decrease in spacing of Au clusters and formation of conducting paths through the composite material. Interface state density of the Al/n-Si Schottky diode with Au-CuPc interlayer increased with increasing Au concentration. This might be because the inclusion of metal decreases the crystallinity and crystal size of the polymer matrix accompanied by the formation of local defect sites at the places of metal nucleation.

A comparative DFT study of interactions of Au and small gold clusters Aun (n = 2-4) with CH3S and CH2 radicals

NASA Astrophysics Data System (ADS)

Blaško, Martin; Rajský, Tomáš; Urban, Miroslav

2017-03-01

We compare DFT binding energies (BEs) of Au and small gold clusters interacting with CH3S and CH2 ligands (Aun-L complexes, n = 1-4). The spin state and the binding mechanism in Aun-L varies with the participation of singly occupied non-bonding orbitals or doubly occupied lone-pair orbitals of a ligand and on the number of atoms (even or odd) of Aun. The highest BE, 354 kJ/mol, exhibits the Au3-CH2 complex with the covalent bond in which participate two singly occupied orbitals of the triplet state of CH2. With CH3S the highest BE (277 kJ/mol) is calculated for Au3-SCH3 with the single Au-S bond.

Initial state nuclear effects for jet production measured in s=200GeV d+Au collisions by STAR

NASA Astrophysics Data System (ADS)

STAR Collaboration; Kapitán, Jan; STAR Collaboration

2009-11-01

Full jet reconstruction in heavy-ion collisions is a promising tool for quantitative study of properties of the dense medium produced at RHIC. Measurements of d+Au collisions are important to disentangle initial state nuclear effects from medium-induced k broadening and jet quenching. We report measurements of mid-rapidity (|η|<0.4|) di-jet correlations in d+Au using high-statistics run 8 RHIC data at s=200GeV.

A hexanuclear gold carbonyl cluster† †Dedicated to Prof. Dr Pablo Espinet on the occasion of his 65th birthday. Abbreviations are defined prior to the Acknowledgements section. As defined in ref. 1, “clusters are molecular units which may contain small or large numbers of similar atoms where there are several short internuclear distances between atom pairs.” This definition is fully compatible with that originally given by F. A. Cotton (ref. 2). ‡ ‡Electronic supplementary information (ESI) available: Experimental procedures, comments on the X-ray structure determinations and 3D Hirschfeld surfaces for the ions constituting the crystal of 4. CCDC 1049919–1049921. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc01578b Click here for additional data file. Click here for additional data file.

PubMed Central

Martínez-Salvador, Sonia; Falvello, Larry R.; Martín, Antonio

2015-01-01

The hexanuclear gold carbonyl cluster [PPh4]2[Au6(CF3)6Br2(CO)2] (4) has been obtained by spontaneous self-assembly of the following independent units: CF3AuCO (1) and [PPh4][Br(AuCF3)2] (3). The cyclo-Au6 aggregate 4, in which the components are held together by unassisted, fairly strong aurophilic interactions (Au···Au ∼310 pm), exhibits a cyclohexane-like arrangement with chair conformation. These aurophilic interactions also result in significant ν(CO) lowering: from 2194 cm–1 in the separate component 1 to 2171 cm–1 in the mixed aggregate 4. Procedures to prepare the single-bridged dinuclear component 3 as well as the mononuclear derivative [PPh4][CF3AuBr] (2) are also reported. PMID:28717445

Measurement of Υ (1 S +2 S +3 S ) production in p +p and Au + Au collisions at √{sNN}=200 GeV

NASA Astrophysics Data System (ADS)

Adare, A.; Afanasiev, S.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Akimoto, R.; Al-Bataineh, H.; Al-Ta'Ani, H.; Alexander, J.; Angerami, A.; Aoki, K.; Apadula, N.; Aphecetche, L.; Aramaki, Y.; Asai, J.; Asano, H.; Aschenauer, E. C.; Atomssa, E. T.; Averbeck, R.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Baksay, G.; Baksay, L.; Baldisseri, A.; Bannier, B.; Barish, K. N.; Barnes, P. D.; Bassalleck, B.; Basye, A. T.; Bathe, S.; Batsouli, S.; Baublis, V.; Baumann, C.; Baumgart, S.; Bazilevsky, A.; Belikov, S.; Belmont, R.; Bennett, R.; Berdnikov, A.; Berdnikov, Y.; Bickley, A. A.; Bing, X.; Blau, D. S.; Boissevain, J. G.; Bok, J. S.; Borel, H.; Boyle, K.; Brooks, M. L.; Buesching, H.; Bumazhnov, V.; Bunce, G.; Butsyk, S.; Camacho, C. M.; Campbell, S.; Castera, P.; Chang, B. S.; Chang, W. C.; Charvet, J.-L.; Chen, C.-H.; Chernichenko, S.; Chi, C. Y.; Chiu, M.; Choi, I. J.; Choi, J. B.; Choi, S.; Choudhury, R. K.; Christiansen, P.; Chujo, T.; Chung, P.; Churyn, A.; Chvala, O.; Cianciolo, V.; Citron, Z.; Cole, B. A.; Connors, M.; Constantin, P.; Csanád, M.; Csörgő, T.; Dahms, T.; Dairaku, S.; Das, K.; Datta, A.; Daugherity, M. S.; David, G.; Denisov, A.; D'Enterria, D.; Deshpande, A.; Desmond, E. J.; Dharmawardane, K. V.; Dietzsch, O.; Ding, L.; Dion, A.; Donadelli, M.; Drapier, O.; Drees, A.; Drees, K. A.; Dubey, A. K.; Durham, J. M.; Durum, A.; Dutta, D.; Dzhordzhadze, V.; D'Orazio, L.; Edwards, S.; Efremenko, Y. V.; Ellinghaus, F.; Engelmore, T.; Enokizono, A.; En'yo, H.; Esumi, S.; Eyser, K. O.; Fadem, B.; Fields, D. E.; Finger, M.; Finger, M.; Fleuret, F.; Fokin, S. L.; Fraenkel, Z.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Fujiwara, K.; Fukao, Y.; Fusayasu, T.; Gainey, K.; Gal, C.; Garishvili, A.; Garishvili, I.; Glenn, A.; Gong, H.; Gong, X.; Gonin, M.; Gosset, J.; Goto, Y.; Granier de Cassagnac, R.; Grau, N.; Greene, S. V.; Grosse Perdekamp, M.; Gunji, T.; Guo, L.; Gustafsson, H.-Å.; Hachiya, T.; Hadj Henni, A.; Haggerty, J. S.; Hahn, K. I.; Hamagaki, H.; Han, R.; Hanks, J.; Hartouni, E. P.; Haruna, K.; Hashimoto, K.; Haslum, E.; Hayano, R.; He, X.; Heffner, M.; Hemmick, T. K.; Hester, T.; Hill, J. C.; Hohlmann, M.; Hollis, R. S.; Holzmann, W.; Homma, K.; Hong, B.; Horaguchi, T.; Hori, Y.; Hornback, D.; Huang, S.; Ichihara, T.; Ichimiya, R.; Iinuma, H.; Ikeda, Y.; Imai, K.; Imrek, J.; Inaba, M.; Iordanova, A.; Isenhower, D.; Ishihara, M.; Isobe, T.; Issah, M.; Isupov, A.; Ivanischev, D.; Ivanishchev, D.; Jacak, B. V.; Javani, M.; Jia, J.; Jiang, X.; Jin, J.; Johnson, B. M.; Joo, K. S.; Jouan, D.; Jumper, D. S.; Kajihara, F.; Kametani, S.; Kamihara, N.; Kamin, J.; Kaneti, S.; Kang, B. H.; Kang, J. H.; Kang, J. S.; Kapustinsky, J.; Karatsu, K.; Kasai, M.; Kawall, D.; Kazantsev, A. V.; Kempel, T.; Khanzadeev, A.; Kijima, K. M.; Kikuchi, J.; Kim, B. I.; Kim, C.; Kim, D. H.; Kim, D. J.; Kim, E.; Kim, E.-J.; Kim, H. J.; Kim, K.-B.; Kim, S. H.; Kim, Y.-J.; Kim, Y. K.; Kinney, E.; Kiriluk, K.; Kiss, Á.; Kistenev, E.; Klatsky, J.; Klay, J.; Klein-Boesing, C.; Kleinjan, D.; Kline, P.; Kochenda, L.; Komatsu, Y.; Komkov, B.; Konno, M.; Koster, J.; Kotchetkov, D.; Kotov, D.; Kozlov, A.; Král, A.; Kravitz, A.; Krizek, F.; Kunde, G. J.; Kurita, K.; Kurosawa, M.; Kweon, M. J.; Kwon, Y.; Kyle, G. S.; Lacey, R.; Lai, Y. S.; Lajoie, J. G.; Layton, D.; Lebedev, A.; Lee, B.; Lee, D. M.; Lee, J.; Lee, K. B.; Lee, K. S.; Lee, S. H.; Lee, S. R.; Lee, T.; Leitch, M. J.; Leite, M. A. L.; Leitgab, M.; Lenzi, B.; Lewis, B.; Li, X.; Liebing, P.; Lim, S. H.; Linden Levy, L. A.; Liška, T.; Litvinenko, A.; Liu, H.; Liu, M. X.; Love, B.; Lynch, D.; Maguire, C. F.; Makdisi, Y. I.; Makek, M.; Malakhov, A.; Malik, M. D.; Manion, A.; Manko, V. I.; Mannel, E.; Mao, Y.; Mašek, L.; Masui, H.; Masumoto, S.; Matathias, F.; McCumber, M.; McGaughey, P. L.; McGlinchey, D.; McKinney, C.; Means, N.; Mendoza, M.; Meredith, B.; Miake, Y.; Mibe, T.; Mignerey, A. C.; Mikeš, P.; Miki, K.; Milov, A.; Mishra, D. K.; Mishra, M.; Mitchell, J. T.; Miyachi, Y.; Miyasaka, S.; Mohanty, A. K.; Moon, H. J.; Morino, Y.; Morreale, A.; Morrison, D. P.; Motschwiller, S.; Moukhanova, T. V.; Mukhopadhyay, D.; Murakami, T.; Murata, J.; Nagae, T.; Nagamiya, S.; Nagle, J. L.; Naglis, M.; Nagy, M. I.; Nakagawa, I.; Nakamiya, Y.; Nakamura, K. R.; Nakamura, T.; Nakano, K.; Nattrass, C.; Nederlof, A.; Newby, J.; Nguyen, M.; Nihashi, M.; Niida, T.; Nouicer, R.; Novitzky, N.; Nyanin, A. S.; O'Brien, E.; Oda, S. X.; Ogilvie, C. A.; Oka, M.; Okada, K.; Onuki, Y.; Oskarsson, A.; Ouchida, M.; Ozawa, K.; Pak, R.; Palounek, A. P. T.; Pantuev, V.; Papavassiliou, V.; Park, B. H.; Park, I. H.; Park, J.; Park, S. K.; Park, W. J.; Pate, S. F.; Patel, L.; Pei, H.; Peng, J.-C.; Pereira, H.; Peresedov, V.; Peressounko, D. Yu.; Petti, R.; Pinkenburg, C.; Pisani, R. P.; Proissl, M.; Purschke, M. L.; Purwar, A. K.; Qu, H.; Rak, J.; Rakotozafindrabe, A.; Ravinovich, I.; Read, K. F.; Rembeczki, S.; Reygers, K.; Reynolds, D.; Riabov, V.; Riabov, Y.; Richardson, E.; Riveli, N.; Roach, D.; Roche, G.; Rolnick, S. D.; Rosati, M.; Rosendahl, S. S. E.; Rosnet, P.; Rukoyatkin, P.; Ružička, P.; Rykov, V. L.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Sakai, S.; Sakashita, K.; Samsonov, V.; Sano, M.; Sarsour, M.; Sato, T.; Sawada, S.; Sedgwick, K.; Seele, J.; Seidl, R.; Semenov, A. Yu.; Semenov, V.; Sen, A.; Seto, R.; Sharma, D.; Shein, I.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shoji, K.; Shukla, P.; Sickles, A.; Silva, C. L.; Silvermyr, D.; Silvestre, C.; Sim, K. S.; Singh, B. K.; Singh, C. P.; Singh, V.; Slunečka, M.; Soldatov, A.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Soumya, M.; Sourikova, I. V.; Staley, F.; Stankus, P. W.; Stenlund, E.; Stepanov, M.; Ster, A.; Stoll, S. P.; Sugitate, T.; Suire, C.; Sukhanov, A.; Sun, J.; Sziklai, J.; Takagui, E. M.; Takahara, A.; Taketani, A.; Tanabe, R.; Tanaka, Y.; Taneja, S.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tarján, P.; Tennant, E.; Themann, H.; Thomas, T. L.; Todoroki, T.; Togawa, M.; Toia, A.; Tomášek, L.; Tomášek, M.; Tomita, Y.; Torii, H.; Towell, R. S.; Tram, V.-N.; Tserruya, I.; Tsuchimoto, Y.; Tsuji, T.; Vale, C.; Valle, H.; van Hecke, H. W.; Vargyas, M.; Vazquez-Zambrano, E.; Veicht, A.; Velkovska, J.; Vértesi, R.; Vinogradov, A. A.; Virius, M.; Vossen, A.; Vrba, V.; Vznuzdaev, E.; Wang, X. R.; Watanabe, D.; Watanabe, K.; Watanabe, Y.; Watanabe, Y. S.; Wei, F.; Wei, R.; Wessels, J.; Whitaker, S.; White, S. N.; Winter, D.; Wolin, S.; Woody, C. L.; Wysocki, M.; Xie, W.; Yamaguchi, Y. L.; Yamaura, K.; Yang, R.; Yanovich, A.; Ying, J.; Yokkaichi, S.; You, Z.; Young, G. R.; Younus, I.; Yushmanov, I. E.; Zajc, W. A.; Zaudtke, O.; Zelenski, A.; Zhang, C.; Zhou, S.; Zolin, L.; Phenix Collaboration

2015-02-01

Measurements of bottomonium production in heavy-ion and p +p collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three Υ states, Υ (1 S +2 S +3 S ) , was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au +Au and p +p collisions at √{sNN}=200 GeV. The Υ (1 S +2 S +3 S ) →e+e- differential cross section at midrapidity was found to be Beed σ /d y =108 ±38 (stat) ±15 (syst) ±11 (luminosity) pb in p +p collisions. The nuclear modification factor in the 30% most central Au +Au collisions indicates a suppression of the total Υ state yield relative to the extrapolation from p +p collision data. The suppression is consistent with measurements made by STAR at RHIC and at higher energies by the CMS experiment at the Large Hadron Collider.

Measurement of Υ(1S + 2S +3S) production in p + p and Au + Au collisions at \\(\\sqrt{s_{\\mathrm{NN}}}=200\\) GeV

DOE PAGES

Adare, A.; Afanasiev, S.; Aidala, C.; ...

2015-02-24

Measurements of bottomonium production in heavy-ion and p+p collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three Υ states, Υ(1S + 2S + 3S), was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au+Au and p+p collisions at \\(\\sqrt{s_{\\mathrm{NN}}}=200\\) GeV. The Υ(1S + 2S + 3S) → e⁺e⁻ differential cross section at midrapidity was found to be B eedσ/dy = 108 ± 38 (stat) ± 15 (syst) ± 11 (luminosity) pb in p+p collisions. The nuclear modification factor in the 30% most central Au+Au collisions indicates a suppression ofmore » the total Υ state yield relative to the extrapolation from p+p collision data. Thus, the suppression is consistent with measurements at higher energies by the CMS experiment at the Large Hadron Collider.« less

Jahn-Teller distortion in the phosphorescent excited state of three-coordinate Au(I) phosphine complexes.

PubMed

Barakat, Khaldoon A; Cundari, Thomas R; Omary, Mohammad A

2003-11-26

DFT calculations were used to optimize the phosphorescent excited state of three-coordinate [Au(PR3)3]+ complexes. The results indicate that the complexes rearrange from their singlet ground-state trigonal planar geometry to a T-shape in the lowest triplet luminescent excited state. The optimized structure of the exciton contradicts the structure predicted based on the AuP bonding properties of the ground-state HOMO and LUMO. The rearrangement to T-shape is a Jahn-Teller distortion because an electron is taken from the degenerate e' (5dxy, 5dx2-y2) orbital upon photoexcitation of the ground-state D3h complex. The calculated UV absorption and visible emission energies are consistent with the experimental data and explain the large Stokes' shifts while such correlations are not possible in optimized models that constrained the exciton to the ground-state trigonal geometry.

Colloidal Random Terpolymers: Controlling Reactivity Ratios of Colloidal Comonomers via Metal Tipping

DOE PAGES

Pavlopoulos, Nicholas G.; Dubose, Jeffrey T.; Hartnett, Erin D.; ...

2016-07-26

We report on a versatile synthetic m-shell nanoparticles (NPs) in the backbone, along with semiconductor CdSe@CdS nanorod (NR), or tetrapod (TP) side chain groups. A seven-step colloidal total synthesis enabled the synthesis of well-defined colloidal comonomers composed of a dipolar Au@CoNP attached to a single CdSe@CdS NR, or TP, where magnetic dipolar associations between Au@CoNP units promoted the formation of colloidal co- or terpolymers. The key step in this synthesis was the ability to photodeposit a single AuNP tip onto CdSe@CdS NR or TP that enables selective seeding of a dipolar CoNP onto the AuNP seed. In conclusion, we showmore » that the variation of the AuNP size directly controlled the size and dipolar character of the CoNP tip, where the size modulation of the Au and Au@CoNP tips is analogous to control of comonomer reactivity ratios in classical copolymerization processes.« less

Undiscovered petroleum resources for the Woodford Shale and Thirteen Finger Limestone-Atoka Shale assessment units, Anadarko Basin

USGS Publications Warehouse

Higley, Debra K.

2011-01-01

In 2010 the U.S. Geological Survey assessed undiscovered oil and gas resources for the Anadarko Basin Province of Colorado, Kansas, Oklahoma, and Texas. The assessment included three continuous (unconventional) assessment units (AU). Mean undiscovered resources for the (1) Devonian Woodford Shale Gas AU are about 16 trillion cubic feet of gas (TCFG) and 192 million barrels of natural gas liquids (MMBNGL), (2) Woodford Shale Oil AU are 393 million barrels of oil (MMBO), 2 TCFG, and 59 MMBNGL, and (3) Pennsylvanian Thirteen Finger Limestone-Atoka Shale Gas AU are 6.8 TCFG and 82 MMBNGL. The continuous gas AUs are mature for gas generation within the deep basin of Oklahoma and Texas. Gas generation from the Woodford Shale source rock started about 335 Ma, and from the Thirteen Finger Limestone-Atoka Shale AU about 300 Ma. Maturation results are based on vitrinite reflectance data, and on 1D and 4D petroleum system models that calculated vitrinite reflectance (Ro), and Rock-Eval and hydrous pyrolysis transformation (HP) ratios through time for petroleum source rocks. The Woodford Shale Gas AU boundary and sweet spot were defined mainly on (1) isopach thickness from well-log analysis and published sources; (2) estimated ultimate recoverable production from existing, mainly horizontal, wells; and (3) levels of thermal maturation. Measured and modeled Ro ranges from about 1.2% to 5% in the AU, which represents marginally mature to overmature for gas generation. The sweet spot included most of the Woodford that was deposited within eroded channels in the unconformably underlying Hunton Group. The Thirteen Finger Limestone-Atoka Shale Gas AU has no known production in the deep basin. This AU boundary is based primarily on the gas generation window, and on thickness and distribution of organic-rich facies from these mainly thin shale and limestone beds. Estimates of organic richness were based on well-log signatures and published data.

An efficient synthetic method for organometallic radicals: structures and properties of gold(i)-(nitronyl nitroxide)-2-ide complexes.

PubMed

Suzuki, Shuichi; Kira, Sayaka; Kozaki, Masatoshi; Yamamura, Masaki; Hasegawa, Toru; Nabeshima, Tatsuya; Okada, Keiji

2017-02-21

One-pot synthesis of (nitronyl nitroxide)-gold(i)-phosphine (NN-Au-P) complexes has been developed using chloro(tetrahydrothiophene)gold(i), phosphine ligands, nitronyl nitroxide radicals, and sodium hydroxide. The NN-Au-P complexes can be easily handled because they were quite stable under aerated conditions in both solution and crystalline states. They showed weak absorption bands with vibrational structures in the 450-650 nm region. The oxidation potentials assigned to the NN moieties of NN-Au-P complexes with aromatic phosphines were observed around -0.1 V vs. Fc/Fc + (-0.11 V for NN-Au-1, -0.08 V for NN-Au-2, -0.13 V for NN-Au-5, and -0.07 V for NN-Au-6), somewhat lower than that of NN-Au-P complexes with aliphatic phosphines (-0.25 V for NN-Au-3 and -0.17 V for NN-Au-4).

Lateral spreading of Au contacts on InP

NASA Technical Reports Server (NTRS)

Fatemi, Navid S.; Weizer, Victor G.

1990-01-01

The contact spreading phenomenon observed when small area Au contacts on InP are annealed at temperatures above about 400 C was investigated. It was found that the rapid lateral expansion of the contact metallization which consumes large quantities of InP during growth is closely related to the third stage in the series of solid state reactions that occur between InP and Au, i.e., to the Au3In-to-Au9In4 transition. Detailed descriptions are presented of both the spreading process and the Au3In-to-Au9In4 transition along with arguments that the two processes are manifestations of the same basic phenomenon.

On the nature of L1{sub 0} ordering in equiatomic AuNi and AuCu thin films grown on Au(001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dynna, M.; Marty, A.; Gilles, B.

1997-01-01

The L1{sub 0} ordering of thin epitaxial films having a (001) surface normal subject to elastic constraints imposed by a similarly oriented substrate has been investigated both experimentally and theoretically. Thin AuNi films grown by MBE at room temperature on Au(001) by means of the alternating deposition of Au and Ni are found to possess a L1{sub 0} structure free of periodic antiphase boundaries when growth is controlled in such a way as to ensure that the quantity of Au or Ni deposited is almost exactly equal to one monolayer. If such control is not exercised during growth, a structuremore » having periodic antiphase boundaries is formed. This behavior stands in contrast to that of AuCu during room temperature MBE growth on Au(001), where a strongly ordered L2{sub 0} structure free of antiphase boundaries is formed even on the codeposition of Au and Cu. The effect of elastic constraints on the state of order in an alloy film which undergoes an L2{sub 0} order-disorder transition is examined as a function of temperature, lattice mismatch, and film thickness within the context of a model which allows for the introduction of dislocations in order to relieve misfit strain. Calculations are performed in detail for the case of AuCu, where particular attention is paid to the coupling between film thickness, the number of misfit dislocations present at equilibrium, and the state of order.« less

Azimuthal Angle Dependence of HBT Radii in Au+Au Collisions at RHIC-PHENIX

NASA Astrophysics Data System (ADS)

Niida, Takafumi

Measurement of Hanbury-Brown and Twiss (HBT) interferometry with respect to the event plane have been performed in Au+Au collisions at √{sNN} = 200 GeV at PHENIX, which is a unique tool to study the spatial extent of the created matter at final state in heavy ion collisions and the detailed picture of the space-time evolution from the initial state to the final state. The Gaussian source radii was measured for charged pions and kaons with respect to 2nd-order event plane. There was a difference in final eccentricity between both species, which may imply the different freeze-out mechanism by the particle species. The pion source radii was also measured relative to 3rd-order event plane, and the azimuthal angle dependence of the radii was observed, which qualitatively agrees with the recent hydrodynamic calculation and the oscillation may be driven from the triangular flow.

From isosuperatoms to isosupermolecules: new concepts in cluster science

NASA Astrophysics Data System (ADS)

Liu, Liren; Li, Pai; Yuan, Lan-Feng; Cheng, Longjiu; Yang, Jinlong

2016-06-01

As an extension of the superatom concept, a new concept ``isosuperatom'' is proposed, reflecting the physical phenomenon that a superatom cluster can take multiple geometrical structures with their electronic structures topologically invariant. The icosahedral and cuboctahedral Au135+ units in the Au25(SCH2CH2Ph)18-, Au23(SC6H11)16- and Au24(SAdm)16 nanoclusters are found to be examples of this concept. Furthermore, two isosuperatoms can combine to form a supermolecule. For example, the structure of the {Ag32(DPPE)5(SC6H4CF3)24}2- nanocluster can be understood well in terms of a Ag2212+ supermolecule formed by two Ag138+ isosuperatoms. On the next level of complexity, various combinations of isosuperatoms can lead to supermolecules with different geometrical structures but similar electronic structures, i.e., ``isosupermolecules''. We take two synthesized nanoclusters Au20(PPhpy2)10Cl42+ and Au30S(StBu)18 to illustrate two Au206+ isosupermolecules. The proposed concepts of isosuperatom and isosupermolecule significantly enrich the superatom concept, give a new framework for understanding a wide range of nanoclusters, and open a new door for designing assembled materials.As an extension of the superatom concept, a new concept ``isosuperatom'' is proposed, reflecting the physical phenomenon that a superatom cluster can take multiple geometrical structures with their electronic structures topologically invariant. The icosahedral and cuboctahedral Au135+ units in the Au25(SCH2CH2Ph)18-, Au23(SC6H11)16- and Au24(SAdm)16 nanoclusters are found to be examples of this concept. Furthermore, two isosuperatoms can combine to form a supermolecule. For example, the structure of the {Ag32(DPPE)5(SC6H4CF3)24}2- nanocluster can be understood well in terms of a Ag2212+ supermolecule formed by two Ag138+ isosuperatoms. On the next level of complexity, various combinations of isosuperatoms can lead to supermolecules with different geometrical structures but similar electronic structures, i.e., ``isosupermolecules''. We take two synthesized nanoclusters Au20(PPhpy2)10Cl42+ and Au30S(StBu)18 to illustrate two Au206+ isosupermolecules. The proposed concepts of isosuperatom and isosupermolecule significantly enrich the superatom concept, give a new framework for understanding a wide range of nanoclusters, and open a new door for designing assembled materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01998f

Cluster-to-cluster transformation among Au6, Au8 and Au11 nanoclusters.

PubMed

Ren, Xiuqing; Fu, Junhong; Lin, Xinzhang; Fu, Xuemei; Yan, Jinghui; Wu, Ren'an; Liu, Chao; Huang, Jiahui

2018-05-22

We present the cluster-to-cluster transformations among three gold nanoclusters, [Au6(dppp)4]2+ (Au6), [Au8(dppp)4Cl2]2+ (Au8) and [Au11(dppp)5]3+ (Au11). The conversion process follows a rule that states that the transformation of a small cluster to a large cluster is achieved through an oxidation process with an oxidizing agent (H2O2) or with heating, while the conversion of a large cluster to a small one occurs through a reduction process with a reducing agent (NaBH4). All the reactions were monitored using UV-Vis spectroscopy and ESI-MS. This work may provide an alternative approach to the synthesis of novel gold nanoclusters and a further understanding of the structural transformation relationship of gold nanoclusters.

Pressure-induced stiffness of Au nanoparticles to 71 GPa under quasi-hydrostatic loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Xinguo; Duffy, Thomas S.; Ehm, Lars

2015-11-16

The compressibility of nanocrystalline gold (n-Au, 20 nm) has been studied by x-ray total scattering using high-energy monochromatic x-rays in the diamond anvil cell under quasi-hydrostatic conditions up to 71 GPa. The bulk modulus, K 0, of the n-Au obtained from fitting to a Vinet equation of state is ~196(3) GPa, which is about 17% higher than for the corresponding bulk materials (K 0: 167 GPa). At low pressures (<7 GPa), the compression behavior of n-Au shows little difference from that of bulk Au. With increasing pressure, the compressive behavior of n-Au gradually deviates from the equation of state (EOS)more » of bulk gold. Analysis of the pair distribution function, peak broadening and Rietveld refinement reveals that the microstructure of n-Au is nearly a single-grain/domain at ambient conditions, but undergoes substantial pressure-induced reduction in grain size until 10 GPa. The results indicate that the nature of the internal microstructure in n-Au is associated with the observed EOS difference from bulk Au at high pressure. Full-pattern analysis confirms that significant changes in grain size, stacking faults, grain orientation and texture occur in n-Au at high pressure. We have observed direct experimental evidence of a transition in compressional mechanism for n-Au at ~20 GPa, i.e. from a deformation dominated by nucleation and motion of lattice dislocations (dislocation-mediated) to a prominent grain boundary mediated response to external pressure. In conclusion, the internal microstructure inside the nanoparticle (nanocrystallinity) plays a critical role for the macro-mechanical properties of nano-Au.« less

Pressure-induced stiffness of Au nanoparticles to 71 GPa under quasi-hydrostatic loading.

PubMed

Hong, Xinguo; Duffy, Thomas S; Ehm, Lars; Weidner, Donald J

2015-12-09

The compressibility of nanocrystalline gold (n-Au, 20 nm) has been studied by x-ray total scattering using high-energy monochromatic x-rays in the diamond anvil cell under quasi-hydrostatic conditions up to 71 GPa. The bulk modulus, K0, of the n-Au obtained from fitting to a Vinet equation of state is ~196(3) GPa, which is about 17% higher than for the corresponding bulk materials (K0: 167 GPa). At low pressures (<7 GPa), the compression behavior of n-Au shows little difference from that of bulk Au. With increasing pressure, the compressive behavior of n-Au gradually deviates from the equation of state (EOS) of bulk gold. Analysis of the pair distribution function, peak broadening and Rietveld refinement reveals that the microstructure of n-Au is nearly a single-grain/domain at ambient conditions, but undergoes substantial pressure-induced reduction in grain size until 10 GPa. The results indicate that the nature of the internal microstructure in n-Au is associated with the observed EOS difference from bulk Au at high pressure. Full-pattern analysis confirms that significant changes in grain size, stacking faults, grain orientation and texture occur in n-Au at high pressure. We have observed direct experimental evidence of a transition in compressional mechanism for n-Au at ~20 GPa, i.e. from a deformation dominated by nucleation and motion of lattice dislocations (dislocation-mediated) to a prominent grain boundary mediated response to external pressure. The internal microstructure inside the nanoparticle (nanocrystallinity) plays a critical role for the macro-mechanical properties of nano-Au.

Synthesis, structure, and bonding in K12Au21Sn4. A polar intermetallic compound with dense Au20 and open AuSn4 layers.

PubMed

Li, Bin; Kim, Sung-Jin; Miller, Gordon J; Corbett, John D

2009-12-07

The new phase K(12)Au(21)Sn(4) has been synthesized by direct reaction of the elements at elevated temperatures. Single crystal X-ray diffraction established its orthorhombic structure, space group Pmmn (No. 59), a = 12.162(2); b = 18.058(4); c = 8.657(2) A, V = 1901.3(7) A(3), and Z = 2. The structure consists of infinite puckered sheets of vertex-sharing gold tetrahedra (Au(20)) that are tied together by thin layers of alternating four-bonded-Sn and -Au atoms (AuSn(4)). Remarkably, the dense but electron-poorer blocks of Au tetrahedra coexist with more open and saturated Au-Sn layers, which are fragments of a zinc blende type structure that maximize tetrahedral heteroatomic bonding outside of the network of gold tetrahedra. LMTO band structure calculations reveal metallic properties and a pseudogap at 256 valence electrons per formula unit, only three electrons fewer than in the title compound and at a point at which strong Au-Sn bonding is optimized. Additionally, the tight coordination of the Au framework atoms by K plays an important bonding role: each Au tetrahedra has 10 K neighbors and each K atom has 8-12 Au contacts. The appreciably different role of the p element Sn in this structure from that in the triel members in K(3)Au(5)In and Rb(2)Au(3)Tl appears to arise from its higher electron count which leads to better p-bonding (valence electron concentrations = 1.32 versus 1.22).

Geology and assessment of undiscovered oil and gas resources of the Chukchi Borderland Province, 2008

USGS Publications Warehouse

Bird, Kenneth J.; Houseknecht, David W.; Moore, Thomas E.; Gautier, Donald L.

2017-12-22

The Chukchi Borderland is both a stand-alone petroleum province and assessment unit (AU) that lies north of the Chukchi Sea. It is a bathymetrically high-standing block of continental crust that was probably rifted from the Canadian continental margin. The sum of our knowledge of this province is based upon geophysical data (seismic, gravity, and magnetic) and a limited number of seafloor core and dredge samples. As expected from the limited data set, the basin’s petroleum potential is poorly known. A single assessment unit, the Chukchi Borderland AU, was defined and assigned an overall probability of about a 5 percent chance of at least one petroleum accumulation >50 million barrels of oil equivalent (MMBOE). No quantitative assessment of sizes and numbers of petroleum accumulations was conducted for this AU.

Single-layer ZnS supported on Au(111): A combined XPS, LEED, STM and DFT study

DOE PAGES

Deng, Xingyi; Sorescu, Dan C.; Lee, Junseok

2016-12-31

Single-layer of ZnS, consisting of one atomic layer of ZnS(111) plane, has been grown on Au(111) and characterized using X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). While the LEED measurement indicates a coincidence structure of ZnS-(3×3)/Au(111)-(4×4), high resolution STM images reveal hexagonal unit cells of 6.7×6.7 Å 2 and 11.6×11.6 Å 2, corresponding to √3 and 3 times the unit cell of the ideal zincblende ZnS-(1×1), respectively, depending on the tunneling conditions. Calculations based on density functional theory (DFT) indicate a significantly reconstructed non-planar structure of ZnS single-layer on Au(111) with 2/3 ofmore » the S anions being located nearly in the plane of the Zn cations and the rest 1/3 of the S anions protruding above the Zn plane. In conclusion, the calculated STM image shows similar characteristics to those of the experimental STM image. Additionally, the DFT calculations reveal the different bonding nature of the S anions in ZnS single-layer supported on Au(111).« less

Assay of enterocin AS-48 for inhibition of foodborne pathogens in desserts.

PubMed

Martinez Viedma, Pilar; Abriouel, Hikmate; Ben Omar, Nabil; Lucas López, Rosario; Valdivia, Eva; Gálvez, Antonio

2009-08-01

Enterocin AS-48 was tested against Staphylococcus aureus, Bacillus cereus, and Listeria monocytogenes in different kinds of desserts. The highest activity against S. aureus was detected in baker cream. However, in yogurt-type soy-based desserts and in gelatin pudding, AS-48 (175 arbitrary units [AU]/g) reduced viable cell counts of S. aureus by only 1.5 to 1.8 log units at most. The efficacy of AS-48 in puddings greatly depended on inoculum size, and viable S. aureus counts decreased below detection levels within 24 h for inocula lower than 4 to 5.5 log CFU/g. For L. monocytogenes, bacteriocin concentrations of 52.5 to 87.5 AU/g reduced viable counts below detection levels and avoided regrowth of survivors. The lowest activity was detected in yogurt-type desserts. For B. cereus, viable cell counts were reduced below detection levels for bacteriocin concentrations of 52.5 AU/g in instant pudding without soy or by 175 AU/g in the soy pudding. In gelatin pudding, AS-48 (175 AU/g) reduced viable cell counts of B. cereus below detection levels after 8 h at 10 degrees C or after 48 h at 22 degrees C. Bacteriocin addition also inhibited gelatin liquefaction caused by the proteolytic activity of B. cereus.

Tunable energy transfer from d 10 heterobimetallic dicyanide(I) donor ions to terbium(III) acceptor ions in luminescent Tb[Ag xAu 1- x(CN) 2] 3 ( x = 0 → 1)

NASA Astrophysics Data System (ADS)

Lu, Haiyan; Yson, Renante; Ford, James; Tracy, Henry J.; Carrier, Alora B.; Keller, Aaron; Mullin, Jerome L.; Poissan, Michelle J.; Sawan, Samuel; Patterson, Howard H.

2007-07-01

We report on the heterobimetallic system, Tb[Ag xAu 1- x(CN) 2] 3 ( x = 0 → 1), in which sensitization of terbium luminescence occurs by energy transfer from [Ag xAu 1- x(CN) 2] - donor excited states. The donor states have energies which are tunable and dependent on the Ag/Au stoichiometric ratio. We report on their use as donor systems with Tb(III) ions as acceptor ions in energy transfer studies. Luminescence results show that the mixed metal dicyanides with the higher silver loading have a better energy transfer efficiency than the pure Ag(CN)2- and Au(CN)2- donors. The better energy transfer efficiency is due to the greater overlap between the donor emission and acceptor excitation.

Enhancing photothermal cancer therapy by clustering gold nanoparticles into spherical polymeric nanoconstructs

NASA Astrophysics Data System (ADS)

Iodice, Carmen; Cervadoro, Antonio; Palange, AnnaLisa; Key, Jaehong; Aryal, Santosh; Ramirez, Maricela R.; Mattu, Clara; Ciardelli, Gianluca; O'Neill, Brian E.; Decuzzi, Paolo

2016-01-01

Gold nanoparticles (AuNPs) have been proposed as agents for enhancing photothermal therapy in cancer and cardiovascular diseases. Different geometrical configurations have been used, ranging from spheres to rods and more complex star shapes, to modulate optical and ablating properties. In this work, multiple, ultra-small 6 nm AuNPs are encapsulated into larger spherical polymeric nanoconstructs (SPNs), made out of a poly(lactic acid-co-glycol acid) (PLGA) core stabilized by a superficial lipid-PEG monolayer. The optical and photothermal properties of the resulting nanoconstructs (Au-SPNs) are modulated by varying the initial loading input of AuNPs, ranging between 25 and 150 μgAu. Au-SPNs exhibit a hydrodynamic diameter varying from ~100 to 180 nm, growing with the gold content, and manifest up to 2-fold increase in thermal energy production per unit mass of gold for an initial input of 100 μgAu. Au-SPNs are stable under physiological conditions up to 7 days and have direct cytotoxic effect on tumor cells. The superior photothermal performance of Au-SPNs is assessed in vitro on monolayers of breast cancer cells (SUM-159) and tumor spheroids of glioblastoma multiforme cells (U87-MG). The encapsulation of small AuNPs into larger spherical nanoconstructs enhances photothermal ablation and could favor tumor accumulation.

Chapter 19: Geology and petroleum potential of the east Barents Sea Basins and Admiralty Arch

USGS Publications Warehouse

Klett, T.R.; Pitman, Janet K.

2011-01-01

The US Geological Survey (USGS) recently assessed the potential for undiscovered oil and gas resources of the East Barents Basins and Novaya Zemlya Basins and Admiralty Arch Provinces as part of the USGS Circum-Arctic Resource Appraisal. These two provinces are located NE of Scandinavia and the northwestern Russian Federation, on the Barents Sea Shelf between Novaya Zemlya to the east and the Barents Platform to the west. Three assessment units (AUs) were defined in the East Barents Basins for this study - Kolguyev Terrace Assessment Unit (AU), South Barents Basin and Ludlov Saddle AU, and North Barents Basin AU. A fourth, defined as Novaya Zemlya Basins and Admiralty Arch AU, is coincident with the Novaya Zemlya basins and Admiralty Arch Province. These AUs, all lying north of the Arctic Circle, were assessed for undiscovered, technically recoverable resources resulting in total estimated mean volumes of approximately 7.4 billion barrels of crude oil, 318 trillion cubic feet of natural gas and 1.4 billion barrels of natural gas liquids. ?? 2011 The Geological Society of London.

Assessment of Coalbed Gas Resources in Cretaceous and Tertiary Rocks on the North Slope, Alaska, 2006

USGS Publications Warehouse

Roberts, Steve; Barker, Charles E.; Bird, Kenneth J.; Charpentier, Ronald R.; Cook, Troy; Houseknecht, David W.; Klett, Timothy R.; Pollastro, Richard M.; Schenk, Christopher J.

2006-01-01

The North Slope of Alaska is a vast area of land north of the Brooks Range, extending from the Chukchi Sea eastward to the Canadian border. This Arctic region is known to contain extensive coal deposits; hypothetical coal resource estimates indicate that nearly 4 trillion short tons of coal are in Cretaceous and Tertiary rocks. Because of the large volume of coal, other studies have indicated that this region might also have potential for significant coalbed gas resources. The present study represents the first detailed assessment of undiscovered coalbed gas resources beneath the North Slope by the USGS. The assessment is based on the total petroleum system (TPS) concept. Geologic elements within a TPS relate to hydrocarbon source rocks (maturity, hydrocarbon generation, migration), the characteristics of reservoir rocks, and trap and seal formation. In the case of coalbed gas, the coal beds serve as both source rock and reservoir. The Brookian Coalbed Gas Composite TPS includes coal-bearing rocks in Cretaceous and Tertiary strata underlying the North Slope and adjacent Alaska State waters. Assessment units (AUs) within the TPS (from oldest to youngest) include the Nanushuk Formation Coalbed Gas AU, the Prince Creek and Tuluvak Formations Coalbed Gas AU, and the Sagavanirktok Formation Coalbed Gas AU.

Electron Transfer Mechanism in Gold Surface Modified with Self-Assembly Monolayers from First Principles

NASA Astrophysics Data System (ADS)

Lima, Filipe C. D. A.; Iost, Rodrigo M.; Crespilho, Frank N.; Caldas, Marília J.; Calzolari, Arrigo; Petrilli, Helena M.

2013-03-01

We report the investigation of electron tunneling mechanism of peptide ferrocenyl-glycylcystamine self-assembled monolayers (SAMs) onto Au (111) electrode surfaces. Recent experimental investigations showed that electron transfer in peptides can occur across long distances by separating the donor from the acceptor. This mechanism can be further fostered by the presence of electron donor terminations of Fc terminal units on SAMs but the charge transfer mechanism is still not clear. We study the interaction of the peptide ferrocenyl-glycylcystamine on the Au (111) from first principles calculations to evaluate the electron transfer mechanism. For this purpose, we used the Kohn Sham (KS) scheme for the Density Functional Theory (DFT) as implemented in the Quantum-ESPRESSO suit of codes, using Vandebilt ultrasoft pseudopotentials and GGA-PBE exchange correlation functional to evaluate the ground-state atomic and electronic structure of the system. The analysis of KS orbital at the Fermi Energy showed high electronic density localized in Fc molecules and the observation of a minor contribution from the solvent and counter ion. Based on the results, we infer evidences of electron tunneling mechanism from the molecule to the Au(111). We acknowledge FAPESP for grant support. Also, LCCA/USP, RICE and CENAPAD for computational resources.

Geologic assessment of undiscovered oil and gas resources in the Albian Clastic and Updip Albian Clastic Assessment Units, U.S. Gulf Coast Region

USGS Publications Warehouse

Merrill, Matthew D.

2016-03-11

U.S. Geological Survey National Oil and Gas Assessments (NOGA) of Albian aged clastic reservoirs in the U.S. Gulf Coast region indicate a relatively low prospectivity for undiscovered hydrocarbon resources due to high levels of past production and exploration. Evaluation of two assessment units (AUs), (1) the Albian Clastic AU 50490125, and (2) the Updip Albian Clastic AU 50490126, were based on a geologic model incorporating consideration of source rock, thermal maturity, migration, events timing, depositional environments, reservoir rock characteristics, and production analyses built on well and field-level production histories. The Albian Clastic AU is a mature conventional hydrocarbon prospect with undiscovered accumulations probably restricted to small faulted and salt-associated structural traps that could be revealed using high resolution subsurface imaging and from targeting structures at increased drilling depths that were unproductive at shallower intervals. Mean undiscovered accumulation volumes from the probabilistic assessment are 37 million barrels of oil (MMBO), 152 billion cubic feet of gas (BCFG), and 4 million barrels of natural gas liquids (MMBNGL). Limited exploration of the Updip Albian Clastic AU reflects a paucity of hydrocarbon discoveries updip of the periphery fault zones in the northern Gulf Coastal region. Restricted migration across fault zones is a major factor behind the small discovered fields and estimation of undiscovered resources in the AU. Mean undiscovered accumulation volumes from the probabilistic assessment are 1 MMBO and 5 BCFG for the Updip Albian Clastic AU.

Nanoporous Au structures by dealloying Au/Ag thermal- or laser-dewetted bilayers on surfaces

NASA Astrophysics Data System (ADS)

Ruffino, F.; Torrisi, V.; Grillo, R.; Cacciato, G.; Zimbone, M.; Piccitto, G.; Grimaldi, M. G.

2017-03-01

Nanoporous Au attracts great technological interest and it is a promising candidate for optical and electrochemical sensors. In addition to nanoporous Au leafs and films, recently, interest was focused on nanoporous Au micro- and nano-structures on surfaces. In this work we report on the study of the characteristics of nanoporous Au structures produced on surfaces. We developed the following procedures to fabricate the nanoporous Au structures: we deposited thin Au/Ag bilayers on SiO2 or FTO (fluorine-doped tin oxide) substrates with thickness xAu and xAg of the Au and Ag layers; we induced the alloying and dewetting processes of the bilayers by furnace annealing processes of the bilayers deposited on SiO2 and by laser irradiations of the bilayers deposited on FTO; the alloying and dewetting processes result in the formation of AuxAgy alloy sub-micron particles being x and y tunable by xAu and xAg. These particles are dealloyed in HNO3 solution to remove the Ag atoms. We obtain, so, nanoporous sub-micron Au particles on the substrates. Analyzing the characteristics of these particles we find that: a) the size and shape of the particles depend on the nature of the dewetting process (solid-state dewetting on SiO2, molten-state dewetting on FTO); b) the porosity fraction of the particles depends on how the alloying process is reached: about 32% of porosity for the particles fabricated by the furnace annealing at 900 °C, about 45% of porosity for the particles fabricated by the laser irradiation at 0.5 J/cm2, in both cases independently on the Ag concentration in the alloy; c) After the dealloying process the mean volume of the Au particles shrinks of about 39%; d) After an annealing at 400 °C the nanoporous Au particles reprise their initial volume while the porosity fraction is reduced. Arguments to justify these behaviors are presented.

Synthesis and redox activity of "clicked" triazolylbiferrocenyl polymers, network encapsulation of gold and silver nanoparticles and anion sensing.

PubMed

Rapakousiou, Amalia; Deraedt, Christophe; Irigoyen, Joseba; Wang, Yanlan; Pinaud, Noël; Salmon, Lionel; Ruiz, Jaime; Moya, Sergio; Astruc, Didier

2015-03-02

The design of redox-robust polymers is called for in view of interactions with nanoparticles and surfaces toward applications in nanonetwork design, sensing, and catalysis. Redox-robust triazolylbiferrocenyl (trzBiFc) polymers have been synthesized with the organometallic group in the side chain by ring-opening metathesis polymerization using Grubbs-III catalyst or radical polymerization and with the organometallic group in the main chain by Cu(I) azide alkyne cycloaddition (CuAAC) catalyzed by [Cu(I)(hexabenzyltren)]Br. Oxidation of the trzBiFc polymers with ferricenium hexafluorophosphate yields the stable 35-electron class-II mixed-valent biferrocenium polymer. Oxidation of these polymers with Au(III) or Ag(I) gives nanosnake-shaped networks (observed by transmission electron microscopy and atomic force microscopy) of this mixed-valent Fe(II)Fe(III) polymer with encapsulated metal nanoparticles (NPs) when the organoiron group is located on the side chain. The factors that are suggested to be synergistically responsible for the NP stabilization and network formation are the polymer bulk, the trz coordination, the nearby cationic charge of trzBiFc, and the inter-BiFc distance. For instance, reduction of such an oxidized trzBiFc-AuNP polymer to the neutral trzBiFc-AuNP polymer with NaBH4 destroys the network, and the product flocculates. The polymers easily provide modified electrodes that sense, via the oxidized Fe(II)Fe(III) and Fe(III)Fe(III) polymer states, respectively, ATP(2-) via the outer ferrocenyl units of the polymer and Pd(II) via the inner Fc units; this recognition works well in dichloromethane, but also to a lesser extent in water with NaCl as the electrolyte.

Surface diffusion of a carbon-adatom on Au(110) surfaces

NASA Astrophysics Data System (ADS)

Kim, E.; Safavi-Naini, A.; Hite, D. A.; McKay, K. S.; Pappas, D. P.; Weck, P. F.; Sadeghpour, H. R.

We have investigated the surface diffusion of carbon-adatom on gold surfaces using density functional theory and detailed scanning probe microscopy. The decoherence of trapped-ion quantum gates due to heating of their motional modes is a fundamental science and engineering problem. In an effort to understand heating at the trap-electrode surfaces, we investigate the possible source of noise by focusing on the diffusion of carbon-containing adsorbates onto the Au(110) surface. In this study, we show how the diffusive motion of carbon adatom on gold surface significantly affects the energy landscape and adatom dipole moment variation. A simple model for the diffusion noise, which varies quadratically with the variation of the dipole moment, qualitatively reproduces the measured noise spectrum, and the estimate of the noise spectral density is in accord with measured values. Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the United States Department of Energy's NNSA under Contract DE-AC04-94AL85000.

On-Chip Supercapacitor Electrode Based On Polypyrrole Deposited Into Nanoporous Au Scaffold

NASA Astrophysics Data System (ADS)

Lu, P.; Ohlckers, P.; Chen, X. Y.

2016-11-01

On-chip supercapacitors hold the potential promise for serving as the energy storage units in integrated circuit system, due to their much higher energy density in comparison with conventional dielectric capacitors, high power density and long-term cycling stability. In this study, nanoporous Au (NP-Au) film on-chip was employed as the electrode scaffold to help increase the electrolyte-accessible area for active material. Pseudo-capacitive polypyrrole (PPY) with high theoretical capacitance was deposited into the NP-Au scaffold, to construct the tailored NP-Au/PPY hybrid on-chip electrode with improved areal capacitance. Half cell test in three- electrode system revealed the improved capacitor performance of nanoporous Au supported PPY electrode, compared to the densely packed PPY nanowire film electrode on planer Au substrate (Au/PPY). The areal capacitance of 37 mF/cm2∼10 mV/s, 32 mF/cm2∼50 mV/s, 28 mF/cm2∼100 mV/s, 16 mF/cm2∼500 mV/s, were offered by NP-Au/PPY. Also, the cycling performance was enhanced via using NP-Au scaffold. The developed NP-Au/PPY on-chip electrode demonstrated herein paves a feasible pathway to employ dealloying derived porous metal as the scaffold for improving both the energy density and cycling performance for supercapacitor electrodes.

New PHOBOS results on event-by-event fluctuations

NASA Astrophysics Data System (ADS)

Alver, B.; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Chai, Z.; Chetluru, V.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Heintzelman, G. A.; Henderson, C.; Harnarine, I.; Hofman, D. J.; Hollis, R. S.; Hołyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Li, W.; Lin, W. T.; Loizides, C.; Manly, S.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Reed, C.; Remsberg, L. P.; Reuter, M.; Richardson, E.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Sedykh, I.; Skulski, W.; Smith, C. E.; Stankiewicz, M. A.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Szostak, A.; Tang, J.-L.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Vaurynovich, S. S.; Verdier, R.; Veres, G. I.; Walters, P.; Wenger, E.; Willhelm, D.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wuosmaa, A. H.; Wyngaardt, S.; Wysłouch, B.

2006-04-01

We present new results from the PHOBOS experiment at RHIC on event-by-event fluctuations of particle multiplicities and angular distributions in nucleus-nucleus collisions at RHIC. Our data for Au+Au collisions at √sNN = 200 GeV show that at a level of 10-4 or less, no rare, large-amplitude fluctuations in the total multiplicity distributions or the shape of the pseudorapidity distributions are observed. We however find significant short-range multiplicity correlations in these data, that can be described as particle production in clusters. In Cu+Cu collisions, we observe large final-state azimuthal anisotropies ν2. A common scaling behavior for Cu+Cu and Au+Au for these anisotropies emerges when fluctuations in the initial state geometry are taken into account.

Striking Confinement Effect: AuCl[subscript 4][superscript -] Binding to Amines in a Nanocage Cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henao, Juan D.; Suh, Young-Woong; Lee, Jeong-Kyu

2009-02-23

Binding of AuCl{sub 4}{sup -} to amine groups tethered to the interior of a 2 nm siloxane nanocage was determined in solutions containing various concentrations of acid. The mode of binding was inferred from EXAFS and UV-vis spectra to be by ligand exchange of amine for chloride, which implies that the amines remain unprotonated. Cyclic voltammetry confirmed that the Au complexes bind to the nanocage interior and established a 1:1 relationship between bound Au complex and amine groups. The results suggested a 5-7 pH unit shift in the protonation constant of the interior amines relative to free amines in solution.

XANES and EXAFS study of Au-substituted YBa2Cu3O(7-delta)

NASA Technical Reports Server (NTRS)

Ruckman, Mark W.; Hepp, Aloysius F.

1990-01-01

The near-edge structure (XANES) of the Au L3 and Cu K edges of YBa2Au(0.3)Cu(2.7)O(7-delta) was studied. X ray diffraction suggests that Au goes on the Cu(1) site and XANES shows that this has little effect on the oxidation state of the remaining copper. The gold L3 edge develops a white line feature whose position lies between that of trivalent gold oxide (Au2O3) and monovalent potassium gold cyanide (KAu(CN)2) and whose intensity relative to the edge step is smaller than in the two reference compounds. The L3 EXAFS for Au in the superconductor resembles that of Au2O3. However, differences in the envelope of the Fourier filtered component for the first shell suggest that the local structure of the Au in the superconductor is not equivalent to Au2O3.

Effects of single atom doping on the ultrafast electron dynamics of M1Au24(SR)18 (M = Pd, Pt) nanoclusters

NASA Astrophysics Data System (ADS)

Zhou, Meng; Qian, Huifeng; Sfeir, Matthew Y.; Nobusada, Katsuyuki; Jin, Rongchao

2016-03-01

Atomically precise, doped metal clusters are receiving wide research interest due to their synergistic properties dependent on the metal composition. To understand the electronic properties of doped clusters, it is highly desirable to probe the excited state behavior. Here, we report the ultrafast relaxation dynamics of doped M1@Au24(SR)18 (M = Pd, Pt; R = CH2CH2Ph) clusters using femtosecond visible and near infrared transient absorption spectroscopy. Three relaxation components are identified for both mono-doped clusters: (1) sub-picosecond relaxation within the M1Au12 core states; (2) core to shell relaxation in a few picoseconds; and (3) relaxation back to the ground state in more than one nanosecond. Despite similar relaxation pathways for the two doped nanoclusters, the coupling between the metal core and surface ligands is accelerated by over 30% in the case of the Pt dopant compared with the Pd dopant. Compared to Pd doping, the case of Pt doping leads to much more drastic changes in the steady state and transient absorption of the clusters, which indicates that the 5d orbitals of the Pt atom are more strongly mixed with Au 5d and 6s orbitals than the 4d orbitals of the Pd dopant. These results demonstrate that a single foreign atom can lead to entirely different excited state spectral features of the whole cluster compared to the parent Au25(SR)18 cluster. The detailed excited state dynamics of atomically precise Pd/Pt doped gold clusters help further understand their properties and benefit the development of energy-related applications.Atomically precise, doped metal clusters are receiving wide research interest due to their synergistic properties dependent on the metal composition. To understand the electronic properties of doped clusters, it is highly desirable to probe the excited state behavior. Here, we report the ultrafast relaxation dynamics of doped M1@Au24(SR)18 (M = Pd, Pt; R = CH2CH2Ph) clusters using femtosecond visible and near infrared transient absorption spectroscopy. Three relaxation components are identified for both mono-doped clusters: (1) sub-picosecond relaxation within the M1Au12 core states; (2) core to shell relaxation in a few picoseconds; and (3) relaxation back to the ground state in more than one nanosecond. Despite similar relaxation pathways for the two doped nanoclusters, the coupling between the metal core and surface ligands is accelerated by over 30% in the case of the Pt dopant compared with the Pd dopant. Compared to Pd doping, the case of Pt doping leads to much more drastic changes in the steady state and transient absorption of the clusters, which indicates that the 5d orbitals of the Pt atom are more strongly mixed with Au 5d and 6s orbitals than the 4d orbitals of the Pd dopant. These results demonstrate that a single foreign atom can lead to entirely different excited state spectral features of the whole cluster compared to the parent Au25(SR)18 cluster. The detailed excited state dynamics of atomically precise Pd/Pt doped gold clusters help further understand their properties and benefit the development of energy-related applications. Electronic supplementary information (ESI) available: The pump dependent transient absorption spectra and the corresponding global analysis results. See DOI: 10.1039/c6nr01008c

Spectroscopic determination of surface geometry: Ti(0001)-H(1×1)

NASA Astrophysics Data System (ADS)

Feibelman, Peter J.; Hamann, D. R.

1980-02-01

The electronic structure of a Ti(0001) film covered by a monolayer of H is shown to depend strongly on the location of the H atom in the surface unit cell. Best agreement with experiment is found with the H's in three-fold sites, 0.8 a.u. outside the outer Ti layer. In this geometry the H atoms "heal" the surface-the clean Ti(0001) surface state near the Fermi level is removed and the outer layer d-like local density of states (LDOS) is quite similar to that of the interior. Additionally, the calculated work function is 4.0 eV and an H-derived peak in the calculated LDOS appears 5 eV below EF, in agreement with photoemission measurements.

Gold Ultrathin Nanorods with Controlled Aspect Ratios and Surface Modifications: Formation Mechanism and Localized Surface Plasmon Resonance.

PubMed

Takahata, Ryo; Yamazoe, Seiji; Koyasu, Kiichirou; Imura, Kohei; Tsukuda, Tatsuya

2018-05-30

We synthesized gold ultrathin nanorods (AuUNRs) by slow reductions of gold(I) in the presence of oleylamine (OA) as a surfactant. Transmission electron microscopy revealed that the lengths of AuUNRs were tuned in the range of 5-20 nm while keeping the diameter constant (∼2 nm) by changing the relative concentration of OA and Au(I). It is proposed on the basis of time-resolved optical spectroscopy that AuUNRs are formed via the formation of small (<2 nm) Au spherical clusters followed by their one-dimensional attachment in OA micelles. The surfactant OA on AuUNRs was successfully replaced with glutathionate or dodecanethiolate by the ligand exchange approach. Optical extinction spectroscopy on a series of AuUNRs with different aspect ratios (ARs) revealed a single intense extinction band in the near-IR (NIR) region due to the longitudinal localized surface plasmon resonance (LSPR), the peak position of which is red-shifted with the AR. The NIR bands of AuUNRs with AR < 5 were blue-shifted upon the ligand exchange from OA to thiolates, in sharp contrast to the red shift observed in the conventional Au nanorods and nanospheres (diameter >10 nm). This behavior suggests that the NIR bands of thiolate-protected AuUNRs with AR < 5 are not plasmonic in nature, but are associated with a single-electron excitation between quantized states. The LSPR band was attenuated by thiolate passivation that can be explained by the direct decay of plasmons into an interfacial charge transfer state (chemical interface damping). The LSPR wavelengths of AuUNRs are remarkably longer than those of the conventional AuNRs with the same AR, demonstrating that the miniaturization of the diameter to below ∼2 nm significantly affects the optical response. The red shift of the LSPR band can be ascribed to the increase in the effective mass of electrons in AuUNRs.

Relativistic Effects and Gold Site Distributions: Synthesis, Structure, and Bonding in a Polar Intermetallic Na6Cd16Au7

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samal, Saroj L.; Corbett, John D.

Na{sub 6}Cd{sub 16}Au{sub 7} has been synthesized via typical high-temperature reactions, and its structure refined by single crystal X-ray diffraction as cubic, Fm{bar 3}m, a = 13.589(1) {angstrom}, Z = 4. The structure consists of Cd{sub 8} tetrahedral star (TS) building blocks that are face capped by six shared gold (Au2) vertexes and further diagonally bridged via Au1 to generate an orthogonal, three-dimensional framework [Cd{sub 8}(Au2){sub 6/2}(Au1){sub 4/8}], an ordered ternary derivative of Mn{sub 6}Th{sub 23}. Linear muffin-tin-orbital (LMTO)-atomic sphere approximation (ASA) electronic structure calculations indicate that Na{sub 6}Cd{sub 16}Au{sub 7} is metallic and that {approx}76% of the total crystalmore » orbital Hamilton populations (-ICOHP) originate from polar Cd-Au bonding with 18% more from fewer Cd-Cd contacts. Na{sub 6}Cd{sub 16}Au{sub 7} (45 valence electron count (vec)) is isotypic with the older electron-richer Mg{sub 6}Cu{sub 16}Si{sub 7} (56 vec) in which the atom types are switched and bonding characteristics among the network elements are altered considerably (Si for Au, Cu for Cd, Mg for Na). The earlier and more electronegative element Au now occupies the Si site, in accord with the larger relativistic bonding contributions from polar Cd-Au versus Cu-Si bonds with the neighboring Cd in the former Cu positions. Substantial electronic differences in partial densities-of-states (PDOS) and COHP data for all atoms emphasize these. Strong contributions of nearby Au 5d{sup 10} to bonding states without altering the formal vec are the likely origin of these effects.« less

Magnetic spiral induced by strong correlations in MnAu2

NASA Astrophysics Data System (ADS)

Glasbrenner, J. K.; Bussmann, K. M.; Mazin, I. I.

2014-10-01

The compound MnAu2 is one of the oldest known spin-spiral materials, yet the nature of the spiral state is still not clear. The spiral cannot be explained via relativistic effects due to the short pitch of the spiral and the weakness of the spin-orbit interaction in Mn, and another common mechanism, nesting, is ruled out as direct calculations show no features at the relevant wave vector. We propose that the spiral state is induced by a competition between the short-range antiferromagnetic exchange and a long-range interaction induced by the polarization of Au bands, similar to double exchange. We find that, contrary to earlier reports, the ground state in standard density functional theory is ferromagnetic, i.e., the latter interaction dominates. However, an accounting for Coulomb correlations via a Hubbard U suppresses the Schrieffer-Wolff-type s-d magnetic interaction between Mn and Au faster than the superexchange interaction, favoring a spin-spiral state. For realistic values of U, the resulting spiral wave vector is in close agreement with experiment.

Eco-friendly luminescent solar concentrators with low reabsorption losses and resistance to concentration quenching based on aqueous-solution-processed thiolate-gold nanoclusters

NASA Astrophysics Data System (ADS)

Huang, H. Y.; Cai, K. B.; Chang, L. Y.; Chen, P. W.; Lin, T. N.; Lin, C. A. J.; Shen, J. L.; Talite, M. J.; Chou, W. C.; Yuan, C. T.

2017-09-01

Heavy-metal-containing quantum dots (QDs) with engineered electronic states have been served as luminophores in luminescent solar concentrators (LSCs) with impressive optical efficiency. Unfortunately, those QDs involve toxic elements and need to be synthesized in a hazardous solvent. Recently, biocompatible, eco-friendly gold nanoclusters (AuNCs), which can be directly synthesized in an aqueous solution, have gained much attention for promising applications in ‘green photonics’. Here, we explored the solid-state photophysical properties of aqueous-solution-processed, glutathione-stabilized gold nanoclusters (GSH-AuNCs) with a ligand-to-metal charge-transfer (LMCT) state for developing ‘green’ LSCs. We found that such GSH-AuNCs exhibit a large Stokes shift with almost no spectral overlap between the optical absorption and PL emission due to the LMCT states, thus, suppressing reabsorption losses. Compared with GSH-AuNCs in solution, the photoluminescence quantum yields (PL-QYs) of the LSCs can be enhanced, accompanied with a lengthened PL lifetime owing to the suppression of non-radiative recombination rates. In addition, the LSCs do not suffer from severe concentration-induced PL quenching, which is a common weakness for conventional luminophores. As a result, a common trade-off between light-harvesting efficiency and solid-state PL-QYs can be bypassed due to nearly-zero spectral overlap integral between the optical absorption and PL emission. We expect that GSH-AuNCs hold great promise for serving as luminophores for ‘green’ LSCs by further enhancing solid-state PL-QYs.

Eco-friendly luminescent solar concentrators with low reabsorption losses and resistance to concentration quenching based on aqueous-solution-processed thiolate-gold nanoclusters.

PubMed

Huang, H Y; Cai, K B; Chang, L Y; Chen, P W; Lin, T N; Lin, C A J; Shen, J L; Talite, M J; Chou, W C; Yuan, C T

2017-09-15

Heavy-metal-containing quantum dots (QDs) with engineered electronic states have been served as luminophores in luminescent solar concentrators (LSCs) with impressive optical efficiency. Unfortunately, those QDs involve toxic elements and need to be synthesized in a hazardous solvent. Recently, biocompatible, eco-friendly gold nanoclusters (AuNCs), which can be directly synthesized in an aqueous solution, have gained much attention for promising applications in 'green photonics'. Here, we explored the solid-state photophysical properties of aqueous-solution-processed, glutathione-stabilized gold nanoclusters (GSH-AuNCs) with a ligand-to-metal charge-transfer (LMCT) state for developing 'green' LSCs. We found that such GSH-AuNCs exhibit a large Stokes shift with almost no spectral overlap between the optical absorption and PL emission due to the LMCT states, thus, suppressing reabsorption losses. Compared with GSH-AuNCs in solution, the photoluminescence quantum yields (PL-QYs) of the LSCs can be enhanced, accompanied with a lengthened PL lifetime owing to the suppression of non-radiative recombination rates. In addition, the LSCs do not suffer from severe concentration-induced PL quenching, which is a common weakness for conventional luminophores. As a result, a common trade-off between light-harvesting efficiency and solid-state PL-QYs can be bypassed due to nearly-zero spectral overlap integral between the optical absorption and PL emission. We expect that GSH-AuNCs hold great promise for serving as luminophores for 'green' LSCs by further enhancing solid-state PL-QYs.

Geochemistry of shale and sedimentary pyrite as a proxy for gold fertility in the Selwyn basin area, Yukon

NASA Astrophysics Data System (ADS)

Sack, Patrick J.; Large, Ross R.; Gregory, Daniel D.

2018-01-01

Selwyn basin area strata contain sedimentary pyrite with Au above background levels when analyzed by laser ablation-inductively coupled mass spectrometry. Hyland Group rocks contain framboidal pyrite contents of 670 ppb Au, 1223 ppm As, and 5.3 ppm Te; the mean of all types of sedimentary pyrite in the Hyland Group is 391 ppb Au, 1489 ppm As, and 3.8 ppm Te. These levels are similar to sedimentary pyrite in host lithologies from major orogenic gold districts in New Zealand and Australia. Comparison of whole rock and pyrite data show that rocks deposited in continental slope settings with significant terrigenous input contain pyrite that is consistently enriched in Au, As, Te, Co, and Cu. Although data are limited, whole rock samples of stratigraphic units containing Au-rich pyrite also contain high Au, indicating that most of the Au is within sedimentary pyrite. Based on geologic characteristics and comparison of pyrite chemistry data with whole rock chemistry, Selwyn basin area strata have the necessary ingredients to form orogenic gold deposits: Au-enriched source rocks, metamorphic conditions permissive of forming a metamorphic ore fluid, and abundant structural preparation for channeling fluids and depositing ore.

Extrasolar Giant Magnetospheric Response to Steady-state Stellar Wind Pressure at 10, 5, 1, and 0.2 au

NASA Astrophysics Data System (ADS)

Tilley, Matt A.; Harnett, Erika M.; Winglee, Robert M.

2016-08-01

A three-dimensional, multifluid simulation of a giant planet’s magnetospheric interaction with steady-state stellar wind from a Sun-like star was performed for four different orbital semimajor axes—10, 5, 1, and 0.2 au. We simulate the effect of the increasing, steady-state stellar wind pressure related to the planetary orbital semimajor axis on the global magnetospheric dynamics for a Saturn-like planet, including an Enceladus-like plasma torus. Mass-loss processes are shown to vary with orbital distance, with the centrifugal interchange instability displayed only in the 10 and 5 au cases, which reach a state of mass-loss equilibrium more slowly than the 1 or 0.2 au cases. The compression of the magnetosphere in the 1 and 0.2 au cases contributes to the quenching of the interchange process by increasing the ratio of total plasma thermal energy to corotational energy. The strength of field-aligned currents, associated with auroral radio emissions, is shown to increase in magnitude and latitudinal coverage with a corresponding shift equatorward from increased dynamic ram pressure experienced in the hotter orbits. Similar to observed hot Jovian planets, the warm exo-Saturn simulated in the current work shows enhanced ion density in the magnetosheath and magnetopause regions, as well as the plasma torus, which could contribute to altered transit signals, suggesting that for planets in warmer (>0.1 au) orbits, planetary magnetic field strengths and possibly exomoons—via the plasma torus—could be observable with future missions.

Synthesis, crystal structure and antimicrobial activities of two isomeric gold(I) complexes with nitrogen-containing heterocycle and triphenylphosphine ligands, [Au(L)(PPh3)] (HL = pyrazole and imidazole).

PubMed

Nomiya, K; Noguchi, R; Ohsawa, K; Tsuda, K; Oda, M

2000-03-01

Two isomeric gold(I)-triphenylphosphine complexes with nitrogen-containing heterocycles, [Au(L)(PPh3) (HL = pyrazole (1), imidazole (2)) were isolated as colorless cubic crystals for 1 and colorless plate crystals for 2, respectively. The crystal structures of 1 and 2 were determined by single-crystal X-ray diffraction. These complexes were also fully characterized by complete elemental analyses, thermogravimetric/differential thermal analyses (TG/DTA) and FT-IR in the solid state and by solution NMR (31P, 1H and 13C) spectroscopy and molecular weight measurements in acetone solution. These complexes consisted of a monomeric 2-coordinate AuNP core both in the solid state and in solution. The molecular structures of 1 and 2 were compared with those of related gold(I) complexes, [Au(1,2,3-triz)(PPh3)] (3, Htriz = triazole), [Au(1,2,4-triz)(PPh3)]2 (4) as a dimer through a gold(I)-gold(I) bond in the solid state, and [Au(tetz)(PPh3)] (5, Htetz = tetrazole). Selective and effective antimicrobial activities against two gram-positive bacteria (B. subtilis, S. aureus) and modest activities against one yeast (C. albicans) found in these gold(I) complexes 1-4 are noteworthy, in contrast to poor activities observed in the corresponding silver(I) complexes.

25 CFR 161.1 - What definitions do I need to know?

Code of Federal Regulations, 2013 CFR

2013-04-01

... number of animal units authorized in each grazing permit. Animal Unit (AU) means one adult cow and her 6...: Housing permits, farm leases, governmental facilities, rights-of-way, schools, parks, business leases, etc. Stocking rate means the maximum number of sheep units, or animal units authorized to graze on a particular...

FlowCal: A user-friendly, open source software tool for automatically converting flow cytometry data from arbitrary to calibrated units

PubMed Central

Castillo-Hair, Sebastian M.; Sexton, John T.; Landry, Brian P.; Olson, Evan J.; Igoshin, Oleg A.; Tabor, Jeffrey J.

2017-01-01

Flow cytometry is widely used to measure gene expression and other molecular biological processes with single cell resolution via fluorescent probes. Flow cytometers output data in arbitrary units (a.u.) that vary with the probe, instrument, and settings. Arbitrary units can be converted to the calibrated unit molecules of equivalent fluorophore (MEF) using commercially available calibration particles. However, there is no convenient, non-proprietary tool available to perform this calibration. Consequently, most researchers report data in a.u., limiting interpretation. Here, we report a software tool named FlowCal to overcome current limitations. FlowCal can be run using an intuitive Microsoft Excel interface, or customizable Python scripts. The software accepts Flow Cytometry Standard (FCS) files as inputs and is compatible with different calibration particles, fluorescent probes, and cell types. Additionally, FlowCal automatically gates data, calculates common statistics, and produces publication quality plots. We validate FlowCal by calibrating a.u. measurements of E. coli expressing superfolder GFP (sfGFP) collected at 10 different detector sensitivity (gain) settings to a single MEF value. Additionally, we reduce day-to-day variability in replicate E. coli sfGFP expression measurements due to instrument drift by 33%, and calibrate S. cerevisiae mVenus expression data to MEF units. Finally, we demonstrate a simple method for using FlowCal to calibrate fluorescence units across different cytometers. FlowCal should ease the quantitative analysis of flow cytometry data within and across laboratories and facilitate the adoption of standard fluorescence units in synthetic biology and beyond. PMID:27110723

An Atomically Precise Au10 Ag2 Nanocluster with Red-Near-IR Dual Emission.

PubMed

Lei, Zhen; Guan, Zong-Jie; Pei, Xiao-Li; Yuan, Shang-Fu; Wan, Xian-Kai; Zhang, Jin-Yuan; Wang, Quan-Ming

2016-08-01

A red-near-IR dual-emissive nanocluster with the composition [Au10 Ag2 (2-py-C≡C)3 (dppy)6 ](BF4 )5 (1; 2-py-C≡C is 2-pyridylethynyl, dppy=2-pyridyldiphenylphosphine) has been synthesized. Single-crystal X-ray structural analysis reveals that 1 has a trigonal bipyramidal Au10 Ag2 core that contains a planar Au4 (2-py-C≡C)3 unit sandwiched by two Au3 Ag(dppy)3 motifs. Cluster 1 shows intense red-NIR dual emission in solution. The visible emission originates from metal-to-ligand charge transfer (MLCT) from silver atoms to phosphine ligands in the Au3 Ag(dppy)3 motifs, and the intense NIR emission is associated with the participation of 2-pyridylethynyl in the frontier orbitals of the cluster, which is confirmed by a time-dependent density functional theory (TD-DFT) calculation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quasi-Dual-Packed-Kerneled Au49 (2,4-DMBT)27 Nanoclusters and the Influence of Kernel Packing on the Electrochemical Gap.

PubMed

Liao, Lingwen; Zhuang, Shengli; Wang, Pu; Xu, Yanan; Yan, Nan; Dong, Hongwei; Wang, Chengming; Zhao, Yan; Xia, Nan; Li, Jin; Deng, Haiteng; Pei, Yong; Tian, Shi-Kai; Wu, Zhikun

2017-10-02

Although face-centered cubic (fcc), body-centered cubic (bcc), hexagonal close-packed (hcp), and other structured gold nanoclusters have been reported, it was unclear whether gold nanoclusters with mix-packed (fcc and non-fcc) kernels exist, and the correlation between kernel packing and the properties of gold nanoclusters is unknown. A Au 49 (2,4-DMBT) 27 nanocluster with a shell electron count of 22 has now been been synthesized and structurally resolved by single-crystal X-ray crystallography, which revealed that Au 49 (2,4-DMBT) 27 contains a unique Au 34 kernel consisting of one quasi-fcc-structured Au 21 and one non-fcc-structured Au 13 unit (where 2,4-DMBTH=2,4-dimethylbenzenethiol). Further experiments revealed that the kernel packing greatly influences the electrochemical gap (EG) and the fcc structure has a larger EG than the investigated non-fcc structure. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Communique: Special Issue on the International Network for Cooperation in Northern Science Created at a Meeting held in Edmonton, Alberta (October 12-15, 1982). Summary of Discussions and Agreements Reached = Numero special sur le Reseau Scientifique Internationale pour le Nord cree a la reunion tenue a Edmonton, Alberta (du 12 au 15 octobre 1982). Resume des discussions et accords conclus.

ERIC Educational Resources Information Center

Communique, 1983

1983-01-01

Delegations from Canada, Finland, Greenland, Norway, Sweden, and the United States agreed to the establishment of a network for cooperation among individuals engaged in problems peculiar to the circumpolar North. The Northern Science Network, established within the Unesco Man and the Biosphere Program, consists of three themes: studies on the…

(Tl, Au)/Si(1 1 1){\\sqrt7 \\times \\sqrt7} 2D compound: an ordered array of identical Au clusters embedded in Tl matrix

NASA Astrophysics Data System (ADS)

Mihalyuk, A. N.; Hsing, C. R.; Wei, C. M.; Eremeev, S. V.; Bondarenko, L. V.; Tupchaya, A. Y.; Gruznev, D. V.; Zotov, A. V.; Saranin, A. A.

2018-01-01

Formation of the highly-ordered \\sqrt7 × \\sqrt7 -periodicity 2D compound has been detected in the (Tl, Au)/Si(1 1 1) system as a result of Au deposition onto the Tl/Si(1 1 1) surface, its composition, structure and electronic properties have been characterized using scanning tunneling microscopy, angle-resolved photoelectron spectroscopy and density-functional-theory calculations. On the basis of these data, the structural model of the Tl-Au compound has been proposed, which adopts 12 Tl atoms and 10 Au atoms (in total, 22 atoms) per \\sqrt7 × \\sqrt7 unit cell, i.e.  ˜1.71 ML of Tl and  ˜1.43 ML of Au (in total, ˜3.14 ML). Qualitatively, the model can be visualized as consisting of truncated-pyramid-like Au clusters with a Tl atom on top, while the other Tl atoms form a double layer around the Au clusters. The (Tl, Au)/Si(1 1 1)\\sqrt7 × \\sqrt7 compound has been found to exhibit pronounced metallic properties at least down to temperatures as low as  ˜25 K, which makes it a promising object for studying electrical transport phenomena in the 2D metallic systems.

Low-symmetry structures of Au32Z (Z = +1, 0, -1) clusters.

PubMed

Jalbout, Abraham F; Contreras-Torres, Flavio F; Pérez, Luis A; Garzón, Ignacio L

2008-01-24

In this work, we have explored new stable structures of the Au32Z (Z = +1, 0, -1) clusters. Theoretical calculations using density functional theory within the generalized-gradient approximation were performed. Our results show that, in the anion state (Au32-), low-symmetry (disordered) structures are preferred over the caged fullerene-like isomer. In addition, the cationic cluster (Au32+) also exhibits a disordered low-symmetry structure as its lowest energy configuration, but it is much closer in energy to the fullerene-like isomer. These results, obtained at T = 0 K, indicate that disordered structures for the Au32- and Au32+ clusters may be detected not only at room temperature, as was experimentally verified for the Au32- one, but also at much lower temperatures.

Electron localization in rod-shaped triicosahedral gold nanocluster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Meng; Jin, Renxi; Sfeir, Matthew Y.

Atomically precise gold nanocluster based on linear assembly of repeating icosahedrons (clusters of clusters) is a unique type of linear nanostructure, which exhibits strong near-infrared absorption as their free electrons are confined in a one-dimensional quantum box. There is little known about the carrier dynamics in these nanoclusters, which limit their energy-related applications. We reported the observation of exciton localization in triicosahedral Au37 nanoclusters (0.5 nm in diameter and 1.6 nm in length) by measuring femtosecond and nanosecond carrier dynamics. Upon photoexcitation to S1 electronic state, electrons in Au37 undergo ~100-ps localization from the two vertexes of three icosahedrons tomore » one vertex, forming a long-lived S1* state. Such phenomenon is not observed in Au25 (dimer) and Au13 (monomer) consisting of two and one icosahedrons, respectively. We have further observed temperature dependence on the localization process, which proves it is thermally driven. Two excited-state vibration modes with frequencies of 20 and 70 cm -1 observed in the kinetic traces are assigned to the axial and radial breathing modes, respectively. The electron localization is ascribed to the structural distortion of Au37 in the excited state induced by the strong coherent vibrations. The electron localization phenomenon we observed provides unique physical insight into one-dimensional gold nanoclusters and other nanostructures, which will advance their applications in solar-energy storage and conversion.« less

Electron localization in rod-shaped triicosahedral gold nanocluster

DOE PAGES

Zhou, Meng; Jin, Renxi; Sfeir, Matthew Y.; ...

2017-05-30

Atomically precise gold nanocluster based on linear assembly of repeating icosahedrons (clusters of clusters) is a unique type of linear nanostructure, which exhibits strong near-infrared absorption as their free electrons are confined in a one-dimensional quantum box. There is little known about the carrier dynamics in these nanoclusters, which limit their energy-related applications. We reported the observation of exciton localization in triicosahedral Au37 nanoclusters (0.5 nm in diameter and 1.6 nm in length) by measuring femtosecond and nanosecond carrier dynamics. Upon photoexcitation to S1 electronic state, electrons in Au37 undergo ~100-ps localization from the two vertexes of three icosahedrons tomore » one vertex, forming a long-lived S1* state. Such phenomenon is not observed in Au25 (dimer) and Au13 (monomer) consisting of two and one icosahedrons, respectively. We have further observed temperature dependence on the localization process, which proves it is thermally driven. Two excited-state vibration modes with frequencies of 20 and 70 cm -1 observed in the kinetic traces are assigned to the axial and radial breathing modes, respectively. The electron localization is ascribed to the structural distortion of Au37 in the excited state induced by the strong coherent vibrations. The electron localization phenomenon we observed provides unique physical insight into one-dimensional gold nanoclusters and other nanostructures, which will advance their applications in solar-energy storage and conversion.« less

Solid-state, ambient-operation thermally activated delayed fluorescence from flexible, non-toxic gold-nanocluster thin films: towards the development of biocompatible light-emitting devices

NASA Astrophysics Data System (ADS)

Talite, M. J. A.; Lin, H. T.; Jiang, Z. C.; Lin, T. N.; Huang, H. Y.; Heredia, E.; Flores, A.; Chao, Y. C.; Shen, J. L.; Lin, C. A. J.; Yuan, C. T.

2016-08-01

Luminescent gold nanoclusters (AuNCs) with good biocompatibility have gained much attention in bio-photonics. In addition, they also exhibit a unique photo-physical property, namely thermally activated delayed fluorescence (TADF), by which both singlet and triplet excitons can be harvested. The combination of their non-toxic material property and unique TADF behavior makes AuNCs biocompatible nano-emitters for bio-related light-emitting devices. Unfortunately, the TADF emission is quenched when colloidal AuNCs are transferred to solid states under ambient environment. Here, a facile, low-cost and effective method was used to generate efficient and stable TADF emissions from solid AuNCs under ambient environment using polyvinyl alcohol as a solid matrix. To unravel the underlying mechanism, temperature-dependent static and transient photoluminescence measurements were performed and we found that two factors are crucial for solid TADF emission: small energy splitting between singlet and triplet states and the stabilization of the triplet states. Solid TADF films were also deposited on the flexible plastic substrate with patterned structures, thus mitigating the waveguide-mode losses. In addition, we also demonstrated that warm white light can be generated based on a co-doped single emissive layer, consisting of non-toxic, solution-processed TADF AuNCs and fluorescent carbon dots under UV excitation.

Uncommon and Emissive {[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2} Mixed Au+ and Au3+ Pseudotetranuclear Crystalline Compound: Synthesis, Structural Characterization, and Optical Properties.

PubMed

Langaro, Ana P; Souza, Ana K R; Morassuti, Claudio Y; Lima, Sandro M; Casagrande, Gleison A; Deflon, Victor M; Nunes, Luiz A O; Da Cunha Andrade, Luis H

2016-11-23

An uncommon emissive pseudotetranuclear compound, {[Au 2 (C 3 H 6 NS 2 ) 2 ][Au(C 3 H 6 NS 2 ) 2 ] 2 (PF 6 ) 2 }, was synthesized and characterized in terms of its structure and optical properties. The synthesis produced a crystalline compound composed of four gold atoms with two different oxidation states (Au + and Au 3+ ) in the same crystalline structure. The title complex belonged to a triclinic crystalline system involving the centrosymmetric P1̅ space group. X-ray diffractometry and vibrational spectroscopy (infrared, Raman, and SERS) were used for structural characterization of the new crystal. The vibrational spectroscopy techniques supported the X-ray diffraction results and confirmed the presence of bonds including Au-Au and Au-S. Optical characterization performed using UV-vis spectroscopy showed that under ultraviolet excitation, the emissive crystalline complex presented characteristic broad luminescent bands centered at 420 and 670 nm.

Dipole moment and solvatochromism of benzoic acid liquid crystals: Tuning the dipole moment and molecular orbital energies by substituted Au under external electric field

NASA Astrophysics Data System (ADS)

Sıdır, Yadigar Gülseven; Sıdır, İsa; Demiray, Ferhat

2017-06-01

The optical absorption and steady-state fluorescence spectra of 4-heptyloxybenzoic acid (4hoba), 4-octyloxybenzoic acid (4ooba) and 4-nonyloxybenzoic acid (4noba) liquid crystals have been measured in a series of different polarity organic solvents. The ground state (μg) and excited state (μe) dipole moments of the monomeric and dimeric 4-alkyloxybenzoic acid liquid crystals have been obtained by means of different solvatochromic shift methods. HOMO-LUMO gaps (HLG) and dipole moments have been tuned by applying external electric (EF) field on monomer, dimer and Au substituted monomer and dimer liquid crystal structures. By applying external electric field, Au substituted monomer liquid crystals display semiconductor character, while Au substituted dimer liquid crystals gain metallic character under E = 0.04 V/Å. Eventuated specific and non-specific interactions between solvent and solute in solvent medium have been expounded by using LSER (Linear Solvation Energy Relationships).

Phosphide oxides RE2AuP2O (RE = La, Ce, Pr, Nd): synthesis, structure, chemical bonding, magnetism, and 31P and 139La solid state NMR.

PubMed

Bartsch, Timo; Wiegand, Thomas; Ren, Jinjun; Eckert, Hellmut; Johrendt, Dirk; Niehaus, Oliver; Eul, Matthias; Pöttgen, Rainer

2013-02-18

Polycrystalline samples of the phosphide oxides RE(2)AuP(2)O (RE = La, Ce, Pr, Nd) were obtained from mixtures of the rare earth elements, binary rare earth oxides, gold powder, and red phosphorus in sealed silica tubes. Small single crystals were grown in NaCl/KCl fluxes. The samples were studied by powder X-ray diffraction, and the structures were refined from single crystal diffractometer data: La(2)AuP(2)O type, space group C2/m, a = 1515.2(4), b = 424.63(8), c = 999.2(2) pm, β = 130.90(2)°, wR2 = 0.0410, 1050 F(2) values for Ce(2)AuP(2)O, and a = 1503.6(4), b = 422.77(8), c = 993.0(2) pm, β = 130.88(2)°, wR2 = 0.0401, 1037 F(2) values for Pr(2)AuP(2)O, and a = 1501.87(5), b = 420.85(5), c = 990.3(3) pm, β = 131.12(1)°, wR2 = 0.0944, 1143 F(2) values for Nd(2)AuP(2)O with 38 variables per refinement. The structures are composed of [RE(2)O](4+) polycationic chains of cis-edge-sharing ORE(4/2) tetrahedra and polyanionic strands [AuP(2)](4-), which contain gold in almost trigonal-planar phosphorus coordination by P(3-) and P(2)(4-) entities. The isolated phosphorus atoms and the P(2) pairs in La(2)AuP(2)O could clearly be distinguished by (31)P solid state NMR spectroscopy and assigned on the basis of a double quantum NMR technique. Also, the two crystallographically inequivalent La sites could be distinguished by static (139)La NMR in conjunction with theoretical electric field gradient calculations. Temperature-dependent magnetic susceptibility measurements show diamagnetic behavior for La(2)AuP(2)O. Ce(2)AuP(2)O and Pr(2)AuP(2)O are Curie-Weiss paramagnets with experimental magnetic moments of 2.35 and 3.48 μ(B) per rare earth atom, respectively. Their solid state (31)P MAS NMR spectra are strongly influenced by paramagnetic interactions. Ce(2)AuP(2)O orders antiferromagnetically at 13.1(5) K and shows a metamagnetic transition at 11.5 kOe. Pr(2)AuP(2)O orders ferromagnetically at 7.0 K.

Hierarchical Flowerlike Gold Nanoparticles Labeled Immunochromatography Test Strip for Highly Sensitive Detection of Escherichia coli O157:H7.

PubMed

Zhang, Lei; Huang, Youju; Wang, Jingyun; Rong, Yun; Lai, Weihua; Zhang, Jiawei; Chen, Tao

2015-05-19

Gold nanoparticles (AuNPs) labeled lateral-flow test strip immunoassay (LFTS) has been widely used in biomedical, feed/food, and environmental analysis fields. Conventional ILFS assay usually uses spherical AuNPs as labeled probes and shows low detection sensitivity, which further limits its widespread practical application. Unlike spherical AuNP used as labeled probe in conventional ILFS, in our present study, a hierarchical flowerlike AuNP specific probe was designed for LFTS and further used to detect Escherichia coli O157:H7 (E. coli O157:H7). Three types of hierarchical flowerlike AuNPs, such as tipped flowerlike, popcornlike, and large-sized flowerlike AuNPs were synthesized in a one-step method. Compared with other two kinds of Au particles, tipped flowerlike AuNPs probes for LFTS particularly exhibited highly sensitive detection of E. coli O157:H7. The remarkable improvement of detection sensitivity of tipped flowerlike AuNPs probes can be achieved even as low as 10(3) colony-forming units (CFU)/mL by taking advantages of its appropriate size and hierarchical structures, which is superior over the detection performance of conventional LFTS. Using this novel tipped flower AuNPs probes, quantitative detection of E. coli O157:H7 can be obtained partially in a wide concentration range with good repeatability. This hierarchical tipped flower-shaped AuNPs probe for LFTS is promising for the practical applications in widespread analysis fields.

Periodicity, Electronic Structures, and Bonding of Gold Tetrahalides [AuX4](-) (X = F, CI, Br, I, At, Uus)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Wan-Lu; Li, Yong; Xu, Congqiao

2015-12-07

Systematic theoretical and experimental investigations have been performed to understand the periodicity and electronic structures of trivalent-gold halides using gold tetrahalides [AuX4]⁻ anions (X = F, Cl, Br, I, At, Uus). The [AuX4]⁻ (X = Cl, Br, I) anions were produced in gas phase and their negative-ion photoelectron spectra were obtained, which exhibited rich and well-resolved spectral peaks. We calculated the adiabatic as well as vertical electron detachment energies using density functional methods with scalar and spin-orbit coupling relativistic effects. The simulated photoelectron spectra based on these calculations are in good agreement with the experimental spectra. Our results show thatmore » the trivalent Au(III) oxidation state becomes progressively less stable while Au(I) is preferred when the halides become heavier along the Period Table. This trend reveals that the oxidation state of metals in complexes can be manipulated through ligand design« less

Structure and Stability of GeAu{sub n}, n = 1-10 clusters: A Density Functional Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Priyanka,; Dharamvir, Keya; Sharma, Hitesh

2011-12-12

The structures of Germanium doped gold clusters GeAu{sub n} (n = 1-10) have been investigated using ab initio calculations based on density functional theory (DFT). We have obtained ground state geometries of GeAu{sub n} clusters and have it compared with Silicon doped gold clusters and pure gold clusters. The ground state geometries of the GeAu{sub n} clusters show patterns similar to silicon doped gold clusters except for n = 5, 6 and 9. The introduction of germanium atom increases the binding energy of gold clusters. The binding energy per atom of germanium doped cluster is smaller than the corresponding siliconmore » doped gold cluster. The HUMO-LOMO gap for Au{sub n}Ge clusters have been found to vary between 0.46 eV-2.09 eV. The mullikan charge analysis indicates that charge of order of 0.1e always transfers from germanium atom to gold atom.« less

[INVITED] Design of turn around point long period fiber grating sensor with Au-nanoparticle self monolayer

NASA Astrophysics Data System (ADS)

Bandyopadhyay, Sankhyabrata; Basumallick, Nandini; Bysakh, Sandip; Dey, Tanoy Kumar; Biswas, Palas; Bandyopadhyay, Somnath

2018-06-01

In this paper studies on the design and fabrication of a long period fiber grating (LPFG) with a self mono layer of gold nanoparticle (AuNP) has been presented. Refractive index (RI) sensitivity of a dispersed cladding mode (DCM) near turn around point (TAP) of its phase matching curve (PMC) has been investigated with and also without AuNP coated LPFG. The typical role played by the intermediate layer of AuNP on the effective index and thus on the sensitivity of the cladding mode to the surrounding RI has also been explored by carrying out coupled mode analysis of the requisite multilayer waveguide. Deposition of AuNP enhanced the sensitivity by more than a factor of 2. Measured sensitivity was found to be ∼3928 nm/refractive index unit (RIU) in the range of 1.3333-1.3428.

Flow in Au+Au collisions at RHIC

NASA Astrophysics Data System (ADS)

Belt Tonjes, Marguerite; the PHOBOS Collaboration; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Decowski, M. P.; García, E.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Hołyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Lin, W. T.; Manly, S.; McLeod, D.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Reuter, M.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Skulski, W.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Tang, J.-L.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Wolfs, F. L. H.; Wosiek, B.; Wozniak, K.; Wuosmaa, A. H.; Wysłouch, B.

2004-08-01

The study of flow can provide information on the initial state dynamics and the degree of equilibration attained in heavy-ion collisions. This contribution presents results for both elliptic and directed flow as determined from data recorded by the PHOBOS experiment in Au+Au runs at RHIC at \\sqrt{sNN} = 19.6, 130 and 200 GeV. The PHOBOS detector provides a unique coverage in pseudorapidity for measuring flow at RHIC. The systematic dependence of flow on pseudorapidity, transverse momentum, centrality and energy is discussed.

Flow in Au+Au collisions at RHIC

NASA Astrophysics Data System (ADS)

Belt Tonjes, Marguerite; PHOBOS Collaboration; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Decowski, M. P.; García, E.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holynski, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Lin, W. T.; Manly, S.; McLeod, D.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Reuter, M.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Skulski, W.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Tang, J.-L.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Wolfs, F. L. H.; Wosiek, B.; Wozniak, K.; Wuosmaa, A. H.; Wyslouch, B.

2004-08-01

The study of flow can provide information on the initial state dynamics and the degree of equilibration attained in heavy-ion collisions. This contribution presents results for both elliptic and directed flow as determined from data recorded by the PHOBOS experiment in Au+Au runs at RHIC at \\sqrt{s_{{\\rm NN}}} = 19.6, 130 and 200 GeV. The PHOBOS detector provides a unique coverage in pseudorapidity for measuring flow at RHIC. The systematic dependence of flow on pseudorapidity, transverse momentum, centrality and energy is discussed.

The Gemini Planet-finding Campaign: The Frequency Of Giant Planets around Debris Disk Stars

NASA Astrophysics Data System (ADS)

Wahhaj, Zahed; Liu, Michael C.; Nielsen, Eric L.; Biller, Beth A.; Hayward, Thomas L.; Close, Laird M.; Males, Jared R.; Skemer, Andrew; Ftaclas, Christ; Chun, Mark; Thatte, Niranjan; Tecza, Matthias; Shkolnik, Evgenya L.; Kuchner, Marc; Reid, I. Neill; de Gouveia Dal Pino, Elisabete M.; Alencar, Silvia H. P.; Gregorio-Hetem, Jane; Boss, Alan; Lin, Douglas N. C.; Toomey, Douglas W.

2013-08-01

We have completed a high-contrast direct imaging survey for giant planets around 57 debris disk stars as part of the Gemini NICI Planet-Finding Campaign. We achieved median H-band contrasts of 12.4 mag at 0.''5 and 14.1 mag at 1'' separation. Follow-up observations of the 66 candidates with projected separation <500 AU show that all of them are background objects. To establish statistical constraints on the underlying giant planet population based on our imaging data, we have developed a new Bayesian formalism that incorporates (1) non-detections, (2) single-epoch candidates, (3) astrometric and (4) photometric information, and (5) the possibility of multiple planets per star to constrain the planet population. Our formalism allows us to include in our analysis the previously known β Pictoris and the HR 8799 planets. Our results show at 95% confidence that <13% of debris disk stars have a >=5 M Jup planet beyond 80 AU, and <21% of debris disk stars have a >=3 M Jup planet outside of 40 AU, based on hot-start evolutionary models. We model the population of directly imaged planets as d 2 N/dMdavpropm α a β, where m is planet mass and a is orbital semi-major axis (with a maximum value of a max). We find that β < -0.8 and/or α > 1.7. Likewise, we find that β < -0.8 and/or a max < 200 AU. For the case where the planet frequency rises sharply with mass (α > 1.7), this occurs because all the planets detected to date have masses above 5 M Jup, but planets of lower mass could easily have been detected by our search. If we ignore the β Pic and HR 8799 planets (should they belong to a rare and distinct group), we find that <20% of debris disk stars have a >=3 M Jup planet beyond 10 AU, and β < -0.8 and/or α < -1.5. Likewise, β < -0.8 and/or a max < 125 AU. Our Bayesian constraints are not strong enough to reveal any dependence of the planet frequency on stellar host mass. Studies of transition disks have suggested that about 20% of stars are undergoing planet formation; our non-detections at large separations show that planets with orbital separation >40 AU and planet masses >3 M Jup do not carve the central holes in these disks. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

Atomistic simulations of highly conductive molecular transport junctions under realistic conditions

NASA Astrophysics Data System (ADS)

French, William R.; Iacovella, Christopher R.; Rungger, Ivan; Souza, Amaury Melo; Sanvito, Stefano; Cummings, Peter T.

2013-04-01

We report state-of-the-art atomistic simulations combined with high-fidelity conductance calculations to probe structure-conductance relationships in Au-benzenedithiolate (BDT)-Au junctions under elongation. Our results demonstrate that large increases in conductance are associated with the formation of monatomic chains (MACs) of Au atoms directly connected to BDT. An analysis of the electronic structure of the simulated junctions reveals that enhancement in the s-like states in Au MACs causes the increases in conductance. Other structures also result in increased conductance but are too short-lived to be detected in experiment, while MACs remain stable for long simulation times. Examinations of thermally evolved junctions with and without MACs show negligible overlap between conductance histograms, indicating that the increase in conductance is related to this unique structural change and not thermal fluctuation. These results, which provide an excellent explanation for a recently observed anomalous experimental result [Bruot et al., Nat. Nanotechnol., 2012, 7, 35-40], should aid in the development of mechanically responsive molecular electronic devices.We report state-of-the-art atomistic simulations combined with high-fidelity conductance calculations to probe structure-conductance relationships in Au-benzenedithiolate (BDT)-Au junctions under elongation. Our results demonstrate that large increases in conductance are associated with the formation of monatomic chains (MACs) of Au atoms directly connected to BDT. An analysis of the electronic structure of the simulated junctions reveals that enhancement in the s-like states in Au MACs causes the increases in conductance. Other structures also result in increased conductance but are too short-lived to be detected in experiment, while MACs remain stable for long simulation times. Examinations of thermally evolved junctions with and without MACs show negligible overlap between conductance histograms, indicating that the increase in conductance is related to this unique structural change and not thermal fluctuation. These results, which provide an excellent explanation for a recently observed anomalous experimental result [Bruot et al., Nat. Nanotechnol., 2012, 7, 35-40], should aid in the development of mechanically responsive molecular electronic devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00459g

Educational Expenditure in France, Japan and the United Kingdom. Les Depenses d'enseignement en France, au Japon et au Royaume-Uni.

ERIC Educational Resources Information Center

Levy-Garboua, Louis; And Others

This study is intended to improve analyses of the cost of education at both the national level and in international comparisons. Hitherto, international comparisons of educational costs have been hindered by the fact that governmental education budgets often include many noninstructional costs while excluding adult education costs and private…

Understanding the microcrystal tests of three related phenethylamines: the ortho-metallated (±)-amphetamine formed with gold(III) chloride, and the tetrachloridoaurate(III) salts of (+)-methamphetamine and (±)-ephedrine.

PubMed

Wood, Matthew R; Lalancette, Roger A

2013-04-01

The ortho-metallation product of the reaction of (±)-amphetamine with gold(III) chloride, [D,L-2-(2-aminopropyl)phenyl-κ(2)N,C(1)]dichloridogold(III), [Au(C9H12N)Cl2], and the two salts resulting from crystallization of (+)-methamphetamine with gold(III) chloride, D-methyl(1-phenylpropan-2-yl)azanium tetrachloridoaurate(III), (C10H16N)[AuCl4], and of (±)-ephedrine with gold(III) chloride, D,L-(1-hydroxy-1-phenylpropan-2-yl)(methyl)azanium tetrachloridoaurate(III), (C10H16NO)[AuCl4], have different structures. The first makes a bidentate complex directly with a dichloridogold(III) group, forming a six-membered ring structure; the second and third each form a salt with [AuCl4](-) (each has two formula units in the asymmetric unit). The organic components are all members of the same class of stimulants that are prevalent in illicit drug use. These structures are important contributions to the understanding of the microcrystal tests for these drugs that have been employed for well over 100 years.

Gold deposits of the Carolina Slate Belt, southeastern United States--Age and origin of the major gold producers

USGS Publications Warehouse

Foley, Nora K.; Ayuso, Robert A.

2012-01-01

Gold- and iron sulfide-bearing deposits of the southeastern United States have distinctive mineralogical and geochemical features that provide a basis for constructing models of ore genesis for exploration and assessment of gold resources. The largest (historic) deposits, in approximate million ounces of gold (Moz Au), include those in the Haile (~ 4.2 Moz Au), Ridgeway (~1.5 Moz Au), Brewer (~0.25 Moz Au), and Barite Hill (0.6 Moz Au) mines. Host rocks are Late Proterozoic to early Paleozoic (~553 million years old) metaigneous and metasedimentary rocks of the Carolina Slate Belt that share a geologic affinity with the classic Avalonian tectonic zone. The inferred syngenetic and epithermal-subvolcanic quartz-porphyry settings occur stratigraphically between sequences of metavolcanic rocks of the Persimmon Fork and Uwharrie Formations and overlying volcanic and epiclastic rocks of the Tillery and Richtex Formations (and regional equivalents). The Carolina Slate Belt is highly prospective for many types of gold ore hosted within quartz-sericite-pyrite altered volcanic rocks, juvenile metasedimentary rocks, and in associated shear zones. For example, sheared and deformed auriferous volcanogenic massive sulfide deposits at Barite Hill, South Carolina, and in the Gold Hill trend, North Carolina, are hosted primarily by laminated mudstone and felsic volcanic to volcaniclastic rocks. The high-sulfidation epithermal style of gold mineralization at Brewer and low-sulfidation gold ores of the Champion pit at Haile occur in breccias associated with subvolcanic quartz porphyry and within crystal-rich tuffs, ash flows, and subvolcanic rhyolite. The Ridgeway and Haile deposits are primarily epithermal replacements and feeder zones within (now) metamorphosed crystal-rich tuffs, volcaniclastic sediments, and siltstones originally deposited in a marine volcanic-arc basinal setting. Recent discoveries in the region include (1) extensions of known deposits, such as at Haile where drilling has identified an extensive gold-rich feeder system; and (2) newly discovered prospects like the porphyry-style gold-copper-molybdenum occurrence reported at Deep River, N.C. Gold ores at Ridgeway and Haile represent the low-sulfidation, disseminated, shallow subaqueous tuffaceous equivalents of intrusion-related high-sulfidation ores such as those at Brewer. Haile also has mineralogical features that support a stockwork disseminated model of pyrite-gold-sericite mineralization in which a significant amount of ore was deposited in sediments at or near the surface. The potential is high for gold-rich ore at depth in the funnel-shaped feeder zones that likely underlie such surface variants of high sulfidation–low sulfidation epithermal systems and for new discoveries of similar deposits in areas undercover. Exploration strategies for large-scale gold-mineralizing systems applied to rocks of the Carolina Slate Belt, and by extension, the Carolinian-Avalonian tectonic zone of North America, benefit from applying subvolcanic and basinal epithermal models for gold mineralization.

Effects of single atom doping on the ultrafast electron dynamics of M1Au24(SR)18 (M = Pd, Pt) nanoclusters.

PubMed

Zhou, Meng; Qian, Huifeng; Sfeir, Matthew Y; Nobusada, Katsuyuki; Jin, Rongchao

2016-04-07

Atomically precise, doped metal clusters are receiving wide research interest due to their synergistic properties dependent on the metal composition. To understand the electronic properties of doped clusters, it is highly desirable to probe the excited state behavior. Here, we report the ultrafast relaxation dynamics of doped M1@Au24(SR)18 (M = Pd, Pt; R = CH2CH2Ph) clusters using femtosecond visible and near infrared transient absorption spectroscopy. Three relaxation components are identified for both mono-doped clusters: (1) sub-picosecond relaxation within the M1Au12 core states; (2) core to shell relaxation in a few picoseconds; and (3) relaxation back to the ground state in more than one nanosecond. Despite similar relaxation pathways for the two doped nanoclusters, the coupling between the metal core and surface ligands is accelerated by over 30% in the case of the Pt dopant compared with the Pd dopant. Compared to Pd doping, the case of Pt doping leads to much more drastic changes in the steady state and transient absorption of the clusters, which indicates that the 5d orbitals of the Pt atom are more strongly mixed with Au 5d and 6s orbitals than the 4d orbitals of the Pd dopant. These results demonstrate that a single foreign atom can lead to entirely different excited state spectral features of the whole cluster compared to the parent Au25(SR)18 cluster. The detailed excited state dynamics of atomically precise Pd/Pt doped gold clusters help further understand their properties and benefit the development of energy-related applications.

Effects of single atom doping on the ultrafast electron dynamics of M 1Au 24(SR) 18 (M = Pd, Pt) nanoclusters

DOE PAGES

Zhou, Meng; Qian, Huifeng; Sfeir, Matthew Y.; ...

2016-02-29

Atomically precise, doped metal clusters are receiving wide research interest due to their synergistic properties dependent on the metal composition. To understand the electronic properties of doped clusters, it is highly desirable to probe the excited state behavior. Here, we report the ultrafast relaxation dynamics of doped M 1@Au 24(SR) 18 (M = Pd, Pt; R = CH 2CH 2Ph) clusters using femtosecond visible and near infrared transient absorption spectroscopy. Three relaxation components are identified for both mono-doped clusters: (1) sub-picosecond relaxation within the M 1Au 12 core states; (2) core to shell relaxation in a few picoseconds; and (3)more » relaxation back to the ground state in more than one nanosecond. Despite similar relaxation pathways for the two doped nanoclusters, the coupling between the metal core and surface ligands is accelerated by over 30% in the case of the Pt dopant compared with the Pd dopant. Compared to Pd doping, the case of Pt doping leads to much more drastic changes in the steady state and transient absorption of the clusters, which indicates that the 5d orbitals of the Pt atom are more strongly mixed with Au 5d and 6s orbitals than the 4d orbitals of the Pd dopant. These results demonstrate that a single foreign atom can lead to entirely different excited state spectral features of the whole cluster compared to the parent Au 25(SR) 18 cluster. As a result, the detailed excited state dynamics of atomically precise Pd/Pt doped gold clusters help further understand their properties and benefit the development of energy-related applications.« less

Synthesis of a colloid solution of silica-coated gold nanoparticles for X-ray imaging applications

NASA Astrophysics Data System (ADS)

Kobayashi, Yoshio; Nagasu, Ryoko; Shibuya, Kyosuke; Nakagawa, Tomohiko; Kubota, Yohsuke; Gonda, Kohsuke; Ohuchi, Noriaki

2014-08-01

This work proposes a method for fabricating silica-coated gold (Au) nanoparticles, surface modified with poly(ethylene glycol) (PEG) (Au/SiO2/PEG), with a particle size of 54.8 nm. X-ray imaging of a mouse is performed with the colloid solution. A colloid solution of 17.9 nm Au nanoparticles was prepared by reducing Au ions (III) with sodium citrate in water at 80 °C. The method used for silica-coating the Au nanoparticles was composed of surface-modification of the Au nanoparticles with (3-aminopropyl)-trimethoxysilane (APMS) and a sol-gel process. The sol-gel process was performed in the presence of the surface-modified Au nanoparticles using tetraethylorthosilicate, APMS, water, and sodium hydroxide, in which the formation of silica shells and the introduction of amino groups to the silica-coated particles took place simultaneously (Au/SiO2-NH2). Surface modification of the Au/SiO2-NH2 particles with PEG, or PEGylation of the particle surface, was performed by adding PEG with a functional group that reacted with an amino group in the Au/SiO2-NH2 particle colloid solution. A computed tomography (CT) value of the aqueous colloid solution of Au/SiO2/PEG particles with an actual Au concentration of 0.112 M was as high as 922 ± 12 Hounsfield units, which was higher than that of a commercial X-ray contrast agent with the same iodine concentration. Injecting the aqueous colloid solution of Au/SiO2/PEG particles into a mouse increased the light contrast of tissues. A CT value of the heart rose immediately after the injection, and this rise was confirmed for up to 6 h.

Transverse-momentum and collision-energy dependence of high-pT hadron suppression in Au+Au collisions at ultrarelativistic energies.

PubMed

Adams, J; Adler, C; Aggarwal, M M; Ahammed, Z; Amonett, J; Anderson, B D; Anderson, M; Arkhipkin, D; Averichev, G S; Badyal, S K; Balewski, J; Barannikova, O; Barnby, L S; Baudot, J; Bekele, S; Belaga, V V; Bellwied, R; Berger, J; Bezverkhny, B I; Bhardwaj, S; Bhaskar, P; Bhati, A K; Bichsel, H; Billmeier, A; Bland, L C; Blyth, C O; Bonner, B E; Botje, M; Boucham, A; Brandin, A; Bravar, A; Cadman, R V; Cai, X Z; Caines, H; Calderón de la Barca Sánchez, M; Carroll, J; Castillo, J; Castro, M; Cebra, D; Chaloupka, P; Chattopadhyay, S; Chen, H F; Chen, Y; Chernenko, S P; Cherney, M; Chikanian, A; Choi, B; Christie, W; Coffin, J P; Cormier, T M; Cramer, J G; Crawford, H J; Das, D; Das, S; Derevschikov, A A; Didenko, L; Dietel, T; Dong, X; Draper, J E; Drees, K A; Du, F; Dubey, A K; Dunin, V B; Dunlop, J C; Dutta Majumdar, M R; Eckardt, V; Efimov, L G; Emelianov, V; Engelage, J; Eppley, G; Erazmus, B; Fachini, P; Faine, V; Faivre, J; Fatemi, R; Filimonov, K; Filip, P; Finch, E; Fisyak, Y; Flierl, D; Foley, K J; Fu, J; Gagliardi, C A; Ganti, M S; Gagunashvili, N; Gans, J; Gaudichet, L; Germain, M; Geurts, F; Ghazikhanian, V; Ghosh, P; Gonzalez, J E; Grachov, O; Grigoriev, V; Gronstal, S; Grosnick, D; Guedon, M; Guertin, S M; Gupta, A; Gushin, E; Gutierrez, T D; Hallman, T J; Hardtke, D; Harris, J W; Heinz, M; Henry, T W; Heppelmann, S; Herston, T; Hippolyte, B; Hirsch, A; Hjort, E; Hoffmann, G W; Horsley, M; Huang, H Z; Huang, S L; Humanic, T J; Igo, G; Ishihara, A; Jacobs, P; Jacobs, W W; Janik, M; Johnson, I; Jones, P G; Judd, E G; Kabana, S; Kaneta, M; Kaplan, M; Keane, D; Kiryluk, J; Kisiel, A; Klay, J; Klein, S R; Klyachko, A; Kollegger, T; Konstantinov, A S; Kopytine, M; Kotchenda, L; Kovalenko, A D; Kramer, M; Kravtsov, P; Krueger, K; Kuhn, C; Kulikov, A I; Kumar, A; Kunde, G J; Kunz, C L; Kutuev, R Kh; Kuznetsov, A A; Lamont, M A C; Landgraf, J M; Lange, S; Lansdell, C P; Lasiuk, B; Laue, F; Lauret, J; Lebedev, A; Lednický, R; Leontiev, V M; LeVine, M J; Li, C; Li, Q; Lindenbaum, S J; Lisa, M A; Liu, F; Liu, L; Liu, Z; Liu, Q J; Ljubicic, T; Llope, W J; Long, H; Longacre, R S; Lopez-Noriega, M; Love, W A; Ludlam, T; Lynn, D; Ma, J; Ma, Y G; Magestro, D; Mahajan, S; Mangotra, L K; Mahapatra, D P; Majka, R; Manweiler, R; Margetis, S; Markert, C; Martin, L; Marx, J; Matis, H S; Matulenko, Yu A; McShane, T S; Meissner, F; Melnick, Yu; Meschanin, A; Messer, M; Miller, M L; Milosevich, Z; Minaev, N G; Mironov, C; Mishra, D; Mitchell, J; Mohanty, B; Molnar, L; Moore, C F; Mora-Corral, M J; Morozov, V; de Moura, M M; Munhoz, M G; Nandi, B K; Nayak, S K; Nayak, T K; Nelson, J M; Nevski, P; Nikitin, V A; Nogach, L V; Norman, B; Nurushev, S B; Odyniec, G; Ogawa, A; Okorokov, V; Oldenburg, M; Olson, D; Paic, G; Pandey, S U; Pal, S K; Panebratsev, Y; Panitkin, S Y; Pavlinov, A I; Pawlak, T; Perevoztchikov, V; Peryt, W; Petrov, V A; Phatak, S C; Picha, R; Planinic, M; Pluta, J; Porile, N; Porter, J; Poskanzer, A M; Potekhin, M; Potrebenikova, E; Potukuchi, B V K S; Prindle, D; Pruneau, C; Putschke, J; Rai, G; Rakness, G; Raniwala, R; Raniwala, S; Ravel, O; Ray, R L; Razin, S V; Reichhold, D; Reid, J G; Renault, G; Retiere, F; Ridiger, A; Ritter, H G; Roberts, J B; Rogachevski, O V; Romero, J L; Rose, A; Roy, C; Ruan, L J; Rykov, V; Sahoo, R; Sakrejda, I; Salur, S; Sandweiss, J; Savin, I; Schambach, J; Scharenberg, R P; Schmitz, N; Schroeder, L S; Schweda, K; Seger, J; Seliverstov, D; Seyboth, P; Shahaliev, E; Shao, M; Sharma, M; Shestermanov, K E; Shimanskii, S S; Singaraju, R N; Simon, F; Skoro, G; Smirnov, N; Snellings, R; Sood, G; Sorensen, P; Sowinski, J; Spinka, H M; Srivastava, B; Stanislaus, S; Stock, R; Stolpovsky, A; Strikhanov, M; Stringfellow, B; Struck, C; Suaide, A A P; Sugarbaker, E; Suire, C; Sumbera, M; Surrow, B; Symons, T J M; Szanto de Toledo, A; Szarwas, P; Tai, A; Takahashi, J; Tang, A H; Thein, D; Thomas, J H; Tikhomirov, V; Tokarev, M; Tonjes, M B; Trainor, T A; Trentalange, S; Tribble, R E; Trivedi, M D; Trofimov, V; Tsai, O; Ullrich, T; Underwood, D G; Van Buren, G; VanderMolen, A M; Vasiliev, A N; Vasiliev, M; Vigdor, S E; Viyogi, Y P; Voloshin, S A; Waggoner, W; Wang, F; Wang, G; Wang, X L; Wang, Z M; Ward, H; Watson, J W; Wells, R; Westfall, G D; Whitten, C; Wieman, H; Willson, R; Wissink, S W; Witt, R; Wood, J; Wu, J; Xu, N; Xu, Z; Xu, Z Z; Yakutin, A E; Yamamoto, E; Yang, J; Yepes, P; Yurevich, V I; Zanevski, Y V; Zborovský, I; Zhang, H; Zhang, H Y; Zhang, W M; Zhang, Z P; Zołnierczuk, P A; Zoulkarneev, R; Zoulkarneeva, J; Zubarev, A N

2003-10-24

We report high statistics measurements of inclusive charged hadron production in Au+Au and p+p collisions at sqrt[s(NN)]=200 GeV. A large, approximately constant hadron suppression is observed in central Au+Au collisions for 5

Facet-controlled phase separation in supersaturated Au-Ni nanoparticles upon shape equilibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herz, A., E-mail: andreas.herz@tu-ilmenau.de, E-mail: dong.wang@tu-ilmenau.de; Rossberg, D.; Hentschel, M.

2015-08-17

Solid-state dewetting is used to fabricate supersaturated, submicron-sized Au-Ni solid solution particles out of thin Au/Ni bilayers by means of a rapid thermal annealing technique. Phase separation in such particles is studied with respect to their equilibrium crystal (or Wulff) shape by subsequent annealing at elevated temperature. It is found that (100) faceting planes of the equilibrated particles are enriched with Ni and (111) faces with Au. Both phases are considered by quantum-mechanical calculations in combination with an error-reduction scheme that was developed to compensate for a missing exchange-correlation potential that would reliably describe both Au and Ni. The observedmore » phase configuration is then related to the minimization of strongly anisotropic elastic energies of Au- and Ni-rich phases and results in a rather unique nanoparticle composite state that is characterized by nearly uniform value of elastic response to epitaxial strains all over the faceted surface. The same conclusion is yielded also by evaluating bi-axial elastic moduli when employing interpolated experimental elastic constants. This work demonstrates a useful route for studying features of physical metallurgy at the mesoscale.« less

Time-resolved X-ray Absorption Spectroscopy for Electron Transport Study in Warm Dense Gold

NASA Astrophysics Data System (ADS)

Lee, Jong-Won; Bae, Leejin; Engelhorn, Kyle; Heimann, Philip; Ping, Yuan; Barbrel, Ben; Fernandez, Amalia; Beckwith, Martha Anne; Cho, Byoung-Ick; GIST Team; IBS Team; LBNL Collaboration; SLAC Collaboration; LLNL Collaboration

2015-11-01

The warm dense Matter represents states of which the temperature is comparable to Fermi energy and ions are strongly coupled. One of the experimental techniques to create such state in the laboratory condition is the isochoric heating of thin metal foil with femtosecond laser pulses. This concept largely relies on the ballistic transport of electrons near the Fermi-level, which were mainly studied for the metals in ambient conditions. However, they were barely investigated in warm dense conditions. We present a time-resolved x-ray absorption spectroscopy measured for the Au/Cu dual layered sample. The front Au layer was isochorically heated with a femtosecond laser pulse, and the x-ray absorption changes around L-edge of Cu, which was attached on the backside of Au, was measured with a picosecond resolution. Time delays between the heating of the `front surface' of Au layer and the alternation of x-ray spectrum of Cu attached on the `rear surface' of Au indicate the energetic electron transport mechanism through Au in the warm dense conditions. IBS (IBS-R012-D1) and the NRF (No. 2013R1A1A1007084) of Korea.

Gold as hydrogen: Structural and electronic properties and chemical bonding in Si3Au3+/0/- and comparisons to Si3H3+/0/-

NASA Astrophysics Data System (ADS)

Kiran, Boggavarapu; Li, Xi; Zhai, Hua-Jin; Wang, Lai-Sheng

2006-10-01

A single Au atom has been shown to behave like H in its bonding to Si in several mono- and disilicon gold clusters. In the current work, we investigate the Au /H analogy in trisilicon gold clusters, Si3Au3+/0/-. Photoelectron spectroscopy and density functional calculations are combined to examine the geometric and electronic structure of Si3Au3-. We find that there are three isomers competing for the ground state of Si3Au3- as is the case for Si3H3-. Extensive structural searches show that the potential energy surfaces of the trisilicon gold clusters (Si3Au3-, Si3Au3, and Si3Au3+) are similar to those of the corresponding silicon hydrides. The lowest energy isomers for Si3Au3- and Si3Au3 are structurally similar to a Si3Au four-membered ring serving as a common structural motif. For Si3Au3+, the 2π aromatic cyclotrisilenylium auride ion, analogous to the aromatic cyclotrisilenylium ion (Si3H3+), is the most stable species. Comparison of the structures and chemical bonding between Si3Au3+/0/- and the corresponding silicon hydrides further extends the isolobal analogy between Au and H.

Active control of methanol carbonylation selectivity over Au/carbon anode by electrochemical potential.

PubMed

Funakawa, Akiyasu; Yamanaka, Ichiro; Otsuka, Kiyoshi

2005-05-12

Electrochemical oxidative carbonylation of methanol was studied over Au supported carbon anode in CO. The major carbonylation products were dimethyl oxalate (DMO) and dimethyl carbonate (DMC). The minor oxidation products were dimethoxy methane (DMM) and methyl formate (MF) from methanol and CO(2). Influences of various reaction conditions were studied on carbonylation activities and selectivities. The selectivities to DMO and DMC can be controlled by the electrochemical potential. Electrocatalysis of Au/carbon anode was studied by cyclic voltammetry (CV), stoichiometric reactions among Au(3+), methanol, and CO, and UV-vis spectra. The Au/carbon anode was characterized by XRD, SEM, and BE images before and after the carbonylation. These experimental facts strongly suggest that transition of oxidation states of Au affects changing of the carbonylation selectivities to DMO and DMC. Au(0) is the active species for the selective DMO formation by direct electrochemical carbonylation at low potentials (<+1.2 V (Ag/AgCl)). On the other hand, Au(3+) is the active spices for the selective DMC formation by indirect electrochemical carbonylation through Au(3+)/Au(+) redox at high potentials (>+1.3 V).

A study of growth and thermal dewetting behavior of ultra-thin gold films using transmission electron microscopy

NASA Astrophysics Data System (ADS)

Sudheer, Mondal, Puspen; Rai, V. N.; Srivastava, A. K.

2017-07-01

The growth and solid-state dewetting behavior of Au thin films (0.7 to 8.4 nm) deposited on the formvar film (substrate) by sputtering technique have been studied using transmission electron microscopy. The size and number density of the Au nanoparticles (NPs) change with an increase in the film thickness (0.7 to 2.8 nm). Nearly spherical Au NPs are obtained for <3 nm thickness films whereas percolated nanostructures are observed for ≥3 nm thickness films as a consequence of the interfacial interaction of Au and formvar film. The covered area fraction (CAF) increases from ˜13 to 75 % with the change in film thickness from 0.7 to 8.4 nm. In-situ annealing of ≤3 nm film produces comparatively bigger size and better sphericity Au NPs along with their narrow distributions, whereas just percolated film produces broad distribution in size having spherical as well as elongated Au NPs. The films with thickness ≤3 nm show excellent thermal stability. The films having thickness >6 nm show capability to be used as an irreversible temperature sensor with a sensitivity of ˜0.1 CAF/°C. It is observed that annealing affects the crystallinity of the Au grains in the films. The electron diffraction measurement also shows annealing induced morphological evolution in the percolated Au thin films (≥3 nm) during solid-state dewetting and recrystallization of the grains.

Au-rich filamentary behavior and associated subband gap optical absorption in hyperdoped Si

NASA Astrophysics Data System (ADS)

Yang, W.; Akey, A. J.; Smillie, L. A.; Mailoa, J. P.; Johnson, B. C.; McCallum, J. C.; Macdonald, D.; Buonassisi, T.; Aziz, M. J.; Williams, J. S.

2017-12-01

Au-hyperdoped Si, synthesized by ion implantation and pulsed laser melting, is known to exhibit a strong sub-band gap photoresponse that scales monotonically with the Au concentration. However, there is thought to be a limit to this behavior since ultrahigh Au concentrations (>1 ×1020c m-3 ) are expected to induce cellular breakdown during the rapid resolidification of Si, a process that is associated with significant lateral impurity precipitation. This work shows that the cellular morphology observed in Au-hyperdoped Si differs from that in conventional, steady-state cellular breakdown. In particular, Rutherford backscattering spectrometry combined with channeling and transmission electron microscopy revealed an inhomogeneous Au distribution and a subsurface network of Au-rich filaments, within which the Au impurities largely reside on substitutional positions in the crystalline Si lattice, at concentrations as high as ˜3 at. %. The measured substitutional Au dose, regardless of the presence of Au-rich filaments, correlates strongly with the sub-band gap optical absorptance. Upon subsequent thermal treatment, the supersaturated Au forms precipitates, while the Au substitutionality and the sub-band gap optical absorption both decrease. These results offer insight into a metastable filamentary regime in Au-hyperdoped Si that has important implications for Si-based infrared optoelectronics.

Controlling Au Nanorod Dispersion in Thin Film Polymer Blends

NASA Astrophysics Data System (ADS)

Hore, Michael J. A.; Composto, Russell J.

2012-02-01

Dispersion of Au nanorods (Au NRs) in polymer thin films is studied using a combination of experimental and theoretical techniques. Here, we incorporate small volume fractions of polystyrene-functionalized Au NRs (φrod 0.05) into polystyrene (PS) thin films. By controlling the ratio of the brush length (N) to that of the matrix polymers (P), we can selectively obtain dispersed or aggregated Au NR structures in the PS-Au(N):PS(P) films. A dispersion map of these structures allows one to choose N and P to obtain either uniformly dispersed Au NRs or aggregates of closely packed, side-by-side aligned Au NRs. Furthermore, by blending poly(2,6-dimethyl-p-phenylene oxide) (PPO) into the PS films, we demonstrate that the Au nanorod morphology can be further tuned by reducing depletion-attraction forces and promoting miscibility of the Au NRs. These predictable structures ultimately give rise to tunable optical absorption in the films resulting from surface plasmon resonance coupling between the Au NRs. Finally, self-consistent field theoretic (SCFT) calculations for both the PS-Au(N):PS(P) and PS-Au(N):PS(P):PPO systems provide insight into the PS brush structure, and allow us to interpret morphology and optical property results in terms of wet and dry PS brush states.

Effect of disorder on the pressure-induced superconducting state of CeAu 2Si 2

NASA Astrophysics Data System (ADS)

Ren, Z.; Giriat, G.; Scheerer, G. W.; Lapertot, G.; Jaccard, D.

2015-03-01

CeAu2Si2 is a newly discovered pressure-induced heavy fermion superconductor, which shows very unusual interplay between superconductivity and magnetism under pressure. Here we compare the results of high-pressure measurements on single-crystalline CeAu2Si2 samples with different levels of disorder. It is found that while the magnetic properties are essentially sample independent, superconductivity is rapidly suppressed when the residual resistivity of the sample increases. We show that the depression of bulk Tc can be well understood in terms of pair breaking by nonmagnetic disorder, which strongly suggests an unconventional pairing state in pressurized CeAu2Si2 . Furthermore, increasing the level of disorder leads to the emergence of another phase transition at T* within the magnetic phase, which might be in competition with superconductivity.

Computational insights into the concomitant changes of hollow interior evolution in [SbnAunSbn]m (n=3, 4, 5, 6; m= -3, -2, -1, -2) complex

NASA Astrophysics Data System (ADS)

Zhu, Tingting; Ning, Ping; Tang, Lihong; Li, Kai; Bao, Shuangyou; Jin, Xu; Song, Xin; Zhang, Xiuying; Han, Shuang

2017-02-01

A series of novel all-metal sandwich species, [SbnAunSbn]m (n= 3, 4, 5, 6; m= -3, -2, -1, -2), are carefully designed and are systematically investigated in term of structure, bonding nature, stability, and potential application. These results show that [SbnAunSbn]m (n=3, 4, 5, 6; m= -3, -2, -1, -2), have local minimum values on their potential energy surfaces. For the Sb-Sb and Sb-Au bond, they are obviously covalent features, while in Au-Au, there is a typical aurophilic interaction. Furthermore, these species present expected stability owing to the positive dissociation energy, great Egap, ionization potential (IP), aromaticity and perfected mechanical stability. Interestingly, [Sb5Au5Sb5]- and [Sb6Au6Sb6]2- are aromatic, while both [Sb3Au3Sb3]3- and [Sb4Au4Sb4]2- possess conflicting aromaticity. And all the title species hold tube aromaticty and δ aromaticty. prediction The application suggests that the Sb site is favorable for absorbing CO in the units, and [Sb3Au3Sb3]3- is more suitable than others; CO is absorbed by the p-p interaction between the C and Sb atoms.

Hexanuclear gold(I) phosphide complexes as platforms for multiple redox-active ferrocenyl units.

PubMed

Lee, Terence Kwok-Ming; Cheng, Eddie Chung-Chin; Zhu, Nianyong; Yam, Vivian Wing-Wah

2014-01-03

The synthesis, X-ray crystal structures, electrochemical, and spectroscopic studies of a series of hexanuclear gold(I) μ(3)-ferrocenylmethylphosphido complexes stabilized by bridging phosphine ligands, [Au(6)(P-P)(n)(Fc-CH(2)-P)(2)][PF(6)](2) (n=3, P-P=dppm (bis(diphenylphosphino)methane) (1), dppe (1,2-bis(diphenylphosphino)ethane) (2), dppp (1,3-bis(diphenylphosphino)propane) (3), Ph(2)PN(C(3)H(7))-PPh(2) (4), Ph(2)PN(Ph-CH(3)-p)PPh(2) (5), dppf (1,1′-bis(diphenylphosphino)ferrocene) (6); n=2, P-P=dpepp (bis(2-diphenylphosphinoethyl)phenylphosphine) (7)), as platforms for multiple redox-active ferrocenyl units, are reported. The investigation of the structural changes of the clusters has been probed by introducing different bridging phosphine ligands. This class of gold(I) μ(3)-ferrocenylmethylphosphido complexes has been found to exhibit one reversible oxidation couple, suggestive of the absence of electronic communication between the ferrocene units through the Au(6)P(2) cluster core, providing an understanding of the electronic properties of the hexanuclear Au(I) cluster linkage. The present complexes also serve as an ideal system for the design of multi-electron reservoir and molecular battery systems.

Supramolecular Assembly of Gold Nanoparticles in PS-b-P2VP Diblock Copolymers via Hydrogen Bonding

NASA Astrophysics Data System (ADS)

Jang, Se Gyu; Hawker, Craig J.; Kramer, Edward J.

2011-03-01

We report a simple route to control the spatial distribution of Au nanoparticles (Au-NPs) in PS- b -P2VP diblock copolymers using hydrogen bonding between P2VP and the hydroxyl-containing (PI-OH) units in PS- b -PIOH thiol-terminated ligands on Au-NP. End-functional thiol ligands of poly(styrene- b -1,2&3,4-isoprene-SH) are synthesized by anionic polymerization. After synthesis of Au-NPs, the inner PI block is hydroxylated by hydroboration and the resulting micelle-like Au-NPs consist of a hydrophobic PS outer brush and a hydrophilic inner PI-OH block. The influence of the hydroxyl groups is significant with strong segregation being observed to the PS/P2VP interface and then to the P2VP domain of lamellar-forming PS-b-P2VP diblock copolymers as the length of the PI-OH block is increased. The strong hydrogen bonding between nanoparticle block copolymer ligands and the P2VP block allows the Au-NPs to be incorporated within the P2VP domain to high Au--NP volume fractions ϕp without macrophase separation, driving transitions from lamellar to bicontinuous morphologies as ϕp increases.

Spin-split silicon states at step edges of Si(553)-Au

NASA Astrophysics Data System (ADS)

Biedermann, K.; Regensburger, S.; Fauster, Th.; Himpsel, F. J.; Erwin, S. C.

2012-06-01

The quasi-one-dimensional Si(553)-Au surface is investigated with time-resolved two-photon photoemission and laser-based photoemission. Several occupied and unoccupied states inside and outside the bulk band gap of silicon were found near the center of the surface Brillouin zone. A nondispersing unoccupied state 0.62 eV above the Fermi level with a lifetime of 125 fs matches the spin-split silicon step-edge state predicted by density functional theory calculations. Two occupied bands can be associated with the bands calculated for nonpolarized step-edge atoms.

Time-resolved electronic and optical properties of a thiolate-protected Au38 nanocluster

NASA Astrophysics Data System (ADS)

Meng, Qingguo; May, Stanley P.; Berry, Mary T.; Kilin, Dmitri S.

2015-02-01

Density functional theory and density matrix theory are employed to investigate the time-dependent optical and electronic properties of an Au14 nanocluster protected by six cyclic thiolate ligands, Au4(SCH3)4. The Au14[Au4(SCH3)4]6 nanocluster, i.e. Au38(SCH3)24, is equivalent to a truncated-octahedral face-centred cubic Au38 core coated by a monolayer of 24 methylthiol molecules. The electronic and optical properties, such as density of states, linear absorption spectra, nonradiative nonadiabatic dissipative electronic dynamics and radiative emission spectra were calculated and compared for the core Au14 and thiolate-protected Au38(SCH3)24 nanocluster. The main observation from computed photoluminescence for both models is a mechanism of radiative emission. Specifically, a strong contribution to light emission intensity originates from intraband transitions inside the conduction band (CB) in addition to interband LUMO → HOMO transition (HOMO: highest occupied molecular orbital and LUMO: lowest unoccupied molecular orbital). Such comparison clarifies the contributions from Au core and methylthiol ligands to the electronic and optical properties of the Au38(SCH3)24 nanocluster.

Atomic scale origins of sub-band gap optical absorption in gold-hyperdoped silicon

NASA Astrophysics Data System (ADS)

Ferdous, Naheed; Ertekin, Elif

2018-05-01

Gold hyperdoped silicon exhibits room temperature sub band gap optical absorption, with potential applications as infrared absorbers/detectors and impurity band photovoltaics. We use first-principles density functional theory to establish the origins of the sub band gap response. Substitutional gold AuSi and substitutional dimers AuSi - AuSi are found to be the energetically preferred defect configurations, and AuSi gives rise to partially filled mid-gap defect bands well offset from the band edges. AuSi is predicted to offer substantial sub-band gap absorption, exceeding that measured in prior experiments by two orders of magnitude for similar Au concentration. This suggests that in experimentally realized systems, in addition to AuSi, the implanted gold is accommodated by the lattice in other ways, including other defect complexes and gold precipitates. We further identify that it is energetically favorable for isolated AuSi to form AuSi - AuSi, which by contrast do not exhibit mid-gap states. The formation of dimers and other complexes could serve as nuclei in the earliest stages of Au precipitation, which may be responsible for the observed rapid deactivation of sub-band gap response upon annealing.

A gold nanocluster-based fluorescent probe for simultaneous pH and temperature sensing and its application to cellular imaging and logic gates

NASA Astrophysics Data System (ADS)

Wu, Yun-Tse; Shanmugam, Chandirasekar; Tseng, Wei-Bin; Hiseh, Ming-Mu; Tseng, Wei-Lung

2016-05-01

Metal nanocluster-based nanomaterials for the simultaneous determination of temperature and pH variations in micro-environments are still a challenge. In this study, we develop a dual-emission fluorescent probe consisting of bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) and fluorescein-5-isothiocyanate (FITC) as temperature- and pH-responsive fluorescence signals. Under single wavelength excitation the FITC/BSA-AuNCs exhibited well-separated dual emission bands at 525 and 670 nm. When FITC was used as a reference fluorophore, FITC/BSA-AuNCs showed a good linear response over the temperature range 1-71 °C and offered temperature-independent spectral shifts, temperature accuracy, activation energy, and reusability. The possible mechanism for high temperature-induced fluorescence quenching of FITC/BSA-AuNCs could be attributed to a weakening of the Au-S bond, thereby lowering the charge transfer from BSA to AuNCs. Additionally, the pH- and temperature-responsive properties of FITC/BSA-AuNCs allow simultaneous temperature sensing from 21 to 41 °C (at intervals of 5 °C) and pH from 6.0 to 8.0 (at intervals of 0.5 pH unit), facilitating the construction of two-input AND logic gates. Three-input AND logic gates were also designed using temperature, pH, and trypsin as inputs. The practicality of using FITC/BSA-AuNCs to determine the temperature and pH changes in HeLa cells is also validated.Metal nanocluster-based nanomaterials for the simultaneous determination of temperature and pH variations in micro-environments are still a challenge. In this study, we develop a dual-emission fluorescent probe consisting of bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) and fluorescein-5-isothiocyanate (FITC) as temperature- and pH-responsive fluorescence signals. Under single wavelength excitation the FITC/BSA-AuNCs exhibited well-separated dual emission bands at 525 and 670 nm. When FITC was used as a reference fluorophore, FITC/BSA-AuNCs showed a good linear response over the temperature range 1-71 °C and offered temperature-independent spectral shifts, temperature accuracy, activation energy, and reusability. The possible mechanism for high temperature-induced fluorescence quenching of FITC/BSA-AuNCs could be attributed to a weakening of the Au-S bond, thereby lowering the charge transfer from BSA to AuNCs. Additionally, the pH- and temperature-responsive properties of FITC/BSA-AuNCs allow simultaneous temperature sensing from 21 to 41 °C (at intervals of 5 °C) and pH from 6.0 to 8.0 (at intervals of 0.5 pH unit), facilitating the construction of two-input AND logic gates. Three-input AND logic gates were also designed using temperature, pH, and trypsin as inputs. The practicality of using FITC/BSA-AuNCs to determine the temperature and pH changes in HeLa cells is also validated. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02341j

Cascade synthesis of a gold nanoparticle-network polymer composite

DOE PAGES

Grubjesic, Simonida; Ringstrand, Bryan Scott; Jungjohann, Katherine L.; ...

2015-11-02

In this paper, the multi-step, cascade synthesis of a self-supporting, hierarchically-structured gold nanoparticle hydrogel composite is described. The composite is spontaneously prepared from a non-covalent, lamellar lyotropic mesophase composed of amphiphiles that support the reactive constituents, a mixture of hydroxyl- and acrylate-end-derivatized PEO 117-PPO 47-PEO 117 and [AuCl 4] -. The reaction sequence begins with the auto-reduction of aqueous [AuCl 4] - by PEO 117-PPO 47-PEO 117 which leads to both the production of Au NPs and the free radical initiated polymerization and crosslinking of the acrylate endderivatized PEO 117-PPO 47-PEO 117 to yield a network polymer. Optical spectroscopy andmore » TEM monitored the reduction of [AuCl 4] -, formation of large aggregated Au NPs and oxidative etching into a final state of dispersed, spherical Au NPs. ATR/FT-IR spectroscopy and thermal analysis confirms acrylate crosslinking to yield the polymer network. X-ray scattering (SAXS and WAXS) monitored the evolution of the multilamellar structured mesophase and revealed the presence of semi-crystalline PEO confined within the water layers. The hydrogel could be reversibly swollen without loss of the well-entrained Au NPs with full recovery of composite structure. Finally, optical spectroscopy shows a notable red shift (Δλ~ 45 nm) in the surface plasmon resonance between swollen and contracted states, demonstrating solvent-mediated modulation of the internal NP packing arrangement.« less

Colorimetric Detection with Aptamer-Gold Nanoparticle Conjugates: Effect of Aptamer Length on Response

DTIC Science & Technology

2012-11-01

random bases to its 5’ end and the response of these Apt-AuNPs was evaluated. These extra bases were designed to avoid interactions with the RBA...its 5’ end and the response of these Apt-AuNPs was evaluated. These extra bases were designed to avoid interactions with the RBA binding site. We...produces a purple-blue color.4.5 AuNP-based sensing strategies are designed by promoting a change in the AuNPs stability and aggregation state as a result

Geologic Assessment of Undiscovered Oil and Gas Resources of the West Greenland-East Canada Province

USGS Publications Warehouse

Schenk, Christopher J.

2010-01-01

The U.S. Geological Survey (USGS) recently assessed the potential for undiscovered oil and gas resources of the West Greenland-East Canada Province as part of the USGS Circum-Arctic Resource Appraisal program. The province lies in the offshore area between western Greenland and eastern Canada and includes Baffin Bay, Davis Strait, Lancaster Sound, and Nares Strait west of and including part of Kane Basin. A series of major tectonic events led to the formation of several distinct structural domains that are the geologic basis for defining five assessment units (AU) in the province, all of which are within the Mesozoic-Cenozoic Composite Total Petroleum System (TPS). Potential petroleum source rocks within the TPS include strata of Ordovician, Early and Late Cretaceous, and Paleogene ages. The five AUs defined for this study-the Eurekan Structures AU, Northwest Greenland Rifted Margin AU, Northeast Canada Rifted Margin AU, Baffin Bay Basin AU, and the Greater Ungava Fault Zone AU-encompass the entire province and were assessed for undiscovered, technically recoverable resources.

Chapter 1: Executive Summary - 2003 Assessment of Undiscovered Oil and Gas Resources in the Upper Cretaceous Navarro and Taylor Groups, Western Gulf Province, Gulf Coast Region, Texas

USGS Publications Warehouse

,

2006-01-01

The U.S. Geological Survey (USGS) recently completed an assessment of the undiscovered oil and gas potential of the Upper Cretaceous Navarro and Taylor Groups in the Western Gulf Province of the Gulf Coast region (fig. 1) as part of a national oil and gas assessment effort (USGS Navarro and Taylor Groups Assessment Team, 2004). The assessment of the petroleum potential of the Navarro and Taylor Groups was based on the general geologic elements used to define a total petroleum system (TPS), including hydrocarbon source rocks (source rock maturation, hydrocarbon generation and migration), reservoir rocks (sequence stratigraphy and petrophysical properties), and hydrocarbon traps (trap formation and timing). Using this geologic framework, the USGS defined five assessment units (AU) in the Navarro and Taylor Groups as parts of a single TPS, the Smackover-Austin-Eagle Ford Composite TPS: Travis Volcanic Mounds Oil AU, Uvalde Volcanic Mounds Gas and Oil AU, Navarro-Taylor Updip Oil and Gas AU, Navarro-Taylor Downdip Gas and Oil AU, and Navarro-Taylor Slope-Basin Gas AU (table 1).

Structural and optical properties of the naked and passivated Al{sub 5}Au{sub 5} bimetallic nanoclusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grande-Aztatzi, Rafael; Formoso, Elena; Matxain, Jon M.

The structural and optical properties of both the naked and passivated bimetallic Al{sub 5}Au{sub 5} nanoclusters have been analyzed based on data obtained from ab initio density functional theory and quantum molecular dynamics simulations. It has been found that the Al{sub 5}Au{sub 5} nanocluster possesses a hollow shaped minimum energy structure with segregated Al and Au layered domains, the former representing the electrophilic domain and the latter the nucleophilic domain. In particular, it has been shown that alkali metal cations attach in the nucleophilic domain and hop from one Au site to the next one in the picoseconds time scale,more » while anions are bound tightly to the Al atoms of the electrophilic domain. Simulating annealing studies are very suggestive of the proneness of the nanocluster towards coalescence into large cluster units, when the cluster is left unprotected by appropriate ligands. Further passivation studies with NaF salt suggest, nonetheless, the possibility of the isolation of the Al{sub 5}Au{sub 5} cluster in molten salts or ionic liquids.« less

A novel alcohol dehydrogenase biosensor based on solid-state electrogenerated chemiluminescence by assembling dehydrogenase to Ru(bpy)(3)2+-Au nanoparticles aggregates.

PubMed

Zhang, Lihua; Xu, Zhiai; Sun, Xuping; Dong, Shaojun

2007-01-15

Based on electrogenerated chemiluminescence (ECL), a novel method for fabrication of alcohol dehydrogenase (ADH) biosensor by self-assembling ADH to Ru(bpy)(3)(2+)-AuNPs aggregates (Ru-AuNPs) on indium tin oxide (ITO) electrode surface has been developed. Positively charged Ru(bpy)(3)(2+) could be immobilized stably on the electrode surface with negatively charged AuNPs in the form of aggregate via electrostatic interaction. On the other hand, AuNPs are favourable candidates for the immobilization of enzymes because amine groups and cysteine residues in the enzymes are known to bind strongly with AuNPs. Moreover, AuNPs can act as tiny conduction centers to facilitate the transfer of electrons. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate, and it displayed wide linear range, high sensitivity and good stability.

The effect of copper and silver on the properties of Au-ZnO catalyst and its activity in glycerol oxidation

NASA Astrophysics Data System (ADS)

Kaskow, Iveta; Decyk, Piotr; Sobczak, Izabela

2018-06-01

The goal of this work was to use ZnO as a support for gold and copper (Au-Cu system) or gold and silver (Au-Ag system) and comparison of the effect of copper and silver on the properties of gold and its activity in glycerol oxidation with oxygen in the liquid phase. The samples prepared were fully characterized by XRD, TEM techniques and UV-vis, XPS, ESR spectroscopic methods. It was found that the introduction of copper and silver changed the electronic state of gold loaded on ZnO by the electron transfer between metals. Three different metallic gold species were identified in calcined catalysts: (Au°)δ- (Au-ZnO), (Au°)η- (AuCu-ZnO) and (Au°)γ- (AuAg-ZnO), where δ-,η-,γ- indicate a different partial negative charge on metallic gold and γ > δ > η. The results showed that (Au°)η- centers (metallic gold with the lowest negative charge) formed on AuCu-ZnO were the most active in glycerol oxidation. The increase in the negative charge on metallic gold loaded on AuAg-ZnO reduced the gold activity in silver containing sample. The glyceric acid adsorption and desorption rate influenced the selectivity of the catalysts.

Estimation of spin contamination error in dissociative adsorption of Au2 onto MgO(0 0 1) surface: First application of approximate spin projection (AP) method to plane wave basis

NASA Astrophysics Data System (ADS)

Tada, Kohei; Koga, Hiroaki; Okumura, Mitsutaka; Tanaka, Shingo

2018-06-01

Spin contamination error in the total energy of the Au2/MgO system was estimated using the density functional theory/plane-wave scheme and approximate spin projection methods. This is the first investigation in which the errors in chemical phenomena on a periodic surface are estimated. The spin contamination error of the system was 0.06 eV. This value is smaller than that of the dissociation of Au2 in the gas phase (0.10 eV). This is because of the destabilization of the singlet spin state due to the weakening of the Au-Au interaction caused by the Au-MgO interaction.

Controlled Vectorial Electron Transfer and Photoelectrochemical Applications of Layered Relay/Photosensitizer-Imprinted Au Nanoparticle Architectures on Electrodes.

PubMed

Metzger, Tzuriel S; Tel-Vered, Ran; Willner, Itamar

2016-03-23

Two configurations of molecularly imprinted bis-aniline-bridged Au nanoparticles (NPs) for the specific binding of the electron acceptor N,N'-dimethyl-4,4'-bipyridinium (MV(2+) ) and for the photosensitizer Zn(II)-protoporphyrin IX (Zn(II)-PP-IX) are assembled on electrodes, and the photoelectrochemical features of the two configurations are discussed. Configuration I includes the MV(2+) -imprinted Au NPs matrix as a base layer, on which the Zn(II)-PP-IX-imprinted Au NPs layer is deposited, while configuration II consists of a bilayer corresponding to the reversed imprinting order. Irradiation of the two electrodes in the presence of a benzoquinone/benzohydroquinone redox probe yields photocurrents of unique features: (i) Whereas configuration I yields an anodic photocurrent, the photocurrent generated by configuration II is cathodic. (ii) The photocurrents obtained upon irradiation of the imprinted electrodes are substantially higher as compared to the nonimprinted surfaces. The high photocurrents generated by the imprinted Au NPs-modified electrodes are attributed to the effective loading of the imprinted matrices with the MV(2+) and Zn(II)-PP-IX units and to the effective charge separation proceeding in the systems. The directional anodic/cathodic photocurrents are rationalized in terms of vectorial electron transfer processes dictated by the imprinting order and by the redox potentials of the photosensitizer/electron acceptor units associated with the imprinted sites in the two configurations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gold complexes with the selenolate ligand [2-(Me2NCH2)C6H4Se]-.

PubMed

Crespo, Olga; Gimeno, M Concepción; Laguna, Antonio; Kulcsar, Monika; Silvestru, Cristian

2009-05-04

The reaction of [2-(Me(2)NCH(2))C(6)H(4)Se]M (M = Li, K) with the gold(phosphine) complexes [AuCl(PR(3))] gives the mononuclear gold-selenolate species [Au{SeC(6)H(4)(CH(2)NMe(2))-2}(PPh(3))] (1) or [Au{SeC(6)H(4)(CH(2)NMe(2))-2}(PPh(2)py)] (2), respectively. The treatment of the [2-(Me(2)NCH(2))C(6)H(4)Se]M with [Au(2)Cl(2)(mu-P-P)] [P-P = bis(diphenylphosphino)methane (dppm), bis(diphenylphosphino)ethane (dppe), 1,1'-bis(diphenylphosphino)ferrocene (dppf)] derivatives gives complexes with stoichiometry [Au(2){SeC(6)H(4)(CH(2)NMe(2))-2}(2)(mu-P-P)] [P-P = dppm (3), dppe (4), or dppf (5)]. These complexes exhibit a different structural framework, that is, 4 crystallizes as a chain polymer with intermolecular aurophilic bonding, while 5 shows an intramolecular Au(I)...Au(I) interaction. The gold(III) derivative Bu(4)N[Au(C(6)F(5))(3){SeC(6)H(4)(CH(2)NMe(2))-2}] (6) is obtained by reaction of [2-(Me(2)NCH(2))C(6)H(4)Se]K and Bu(4)N[AuBr(C(6)F(5))(3)], in a 1:1 molar ratio. These species exhibit luminescence which probably arises from a mixed (3)LMMCT and (3)MC excited state. The emission properties in these complexes seem to be useful for structural predictions and lead to the proposal of intermolecular aggregation in the solid state and frozen solution for complexes 1, 2, 3, whose crystal structures have not been elucidated.

A3-Coupling catalyzed by robust Au nanoparticles covalently bonded to HS-functionalized cellulose nanocrystalline films

PubMed Central

Huang, Jian-Lin

2013-01-01

Summary We decorated HS-functionalized cellulose nanocrystallite (CNC) films with monodisperse Au nanoparticles (AuNPs) to form a novel nanocomposite catalyst AuNPs@HS-CNC. The uniform, fine AuNPs were made by the reduction of HAuCl4 solution with thiol (HS-) group-functionalized CNC films. The AuNPs@HS-CNC nanocomposites were examined by X-ray photoelectron spectroscopy (XPS), TEM, ATR-IR and solid-state NMR. Characterizations suggested that the size of the AuNPs was about 2–3 nm and they were evenly distributed onto the surface of CNC films. Furthermore, the unique nanocomposite Au@HS-CNC catalyst displayed high catalytic efficiency in promoting three-component coupling of an aldehyde, an alkyne, and an amine (A3-coupling) either in water or without solvent. Most importantly, the catalyst could be used repetitively more than 11 times without significant deactivation. Our strategy also promotes the use of naturally renewable cellulose to prepare reusable nanocomposite catalysts for organic synthesis. PMID:23946833

Controllable synthesis of Au@SnO2 core-shell nanohybrids with enhanced photocatalytic activities

NASA Astrophysics Data System (ADS)

Zhang, Shaofeng; Hao, Jinggang; Ren, Feng; Wu, Wei; Xiao, Xiangheng

2017-05-01

Combination of semiconductors with plasmonic nanostructures is an effective route to promote the solar light harvesting as well as the efficiency of photocatalysis. In the present work, the Au@SnO2 hybrid nanostructures with Au nanorods as the cores and highly crystallized SnO2 nanoparticles as the shells were fabricated by a facile hydrothermal method. A critical factor, which influences the coating state of the SnO2 shells over Au NRs, was found to be the concentration of CTAB agent in the system and the corresponding mechanism was also proposed. The photocatalytic activities of the Au@SnO2 nanohybrids were examined by degradation of rhodamine B (RhB) dyes at room temperature. The Au@SnO2 nanohybrids exhibited much higher catalytic activities than that of the commercial SnO2 NPs, which could be attributed to the localized electric field enhancement effect of Au nanorods plasmon and charges transfer between the Au nanorods and SnO2.

Extension of the charge separated-state lifetime by supramolecular association of a tetrathiafulvalene electron donor to a zinc/gold bisporphyrin.

PubMed

Boixel, Julien; Fortage, Jérôme; Blart, Errol; Pellegrin, Yann; Hammarström, Leif; Becker, Hans-Christian; Odobel, Fabrice

2010-02-14

Supramolecular triads were prepared by self-assembly of 4'-pyridyl-2-tetrathiafulvalene axially bound on ZnP-spacer-AuP(+) dyads; the lifetime of the charge separated state ((+)TTF-ZnP-Spacer-AuP ) formed upon light excitation of the triad is greatly increased with respect to that found in the parent dyad.

Adsorption of squaraine molecules to Au(111) and Ag(001) surfaces

NASA Astrophysics Data System (ADS)

Luft, Maike; Groß, Boris; Schulz, Matthias; Lützen, Arne; Schiek, Manuela; Nilius, Niklas

2018-02-01

The adsorption of anilino squaraines, an important chromophore for the use in organic solar cells, to Ag(001) and Au(111) has been studied with scanning tunneling microscopy. Self-assembly into square building blocks with eight molecules per unit cell is revealed on the Ag surface, while no ordering effects occur on gold. The squaraine-silver interaction is mediated by the carbonyl and hydroxyl oxygens located in the center of the molecule. The intermolecular coupling, on the other hand, is governed by hydrogen bonds formed between the terminal isobutyl groups and oxygen species of adjacent molecules. The latter gets maximized by rotating the molecules by a few degrees against a perfect square alignment. A similar molecular pattern does not form on Au(111) due to symmetry mismatch. Moreover, the high electronegativity of gold reduces the directing effect of oxygen-metal bonds that trigger the ordering process on silver. As a consequence, only frustrated three-fold symmetric units that do not expand into an ordered molecular network are present on the gold surface.

Variability of oil and gas well productivities for continuous (unconventional) petroleum accumulations

USGS Publications Warehouse

Charpentier, Ronald R.; Cook, Troy A.

2013-01-01

Over the last decade, oil and gas well productivities were estimated using decline-curve analysis for thousands of wells as part of U.S. Geological Survey (USGS) studies of continuous (unconventional) oil and gas resources in the United States. The estimated ultimate recoveries (EURs) of these wells show great variability that was analyzed at three scales: within an assessment unit (AU), among AUs of similar reservoir type, and among groups of AUs with different reservoir types. Within a particular oil or gas AU (such as the Barnett Shale), EURs vary by about two orders of magnitude between the most productive wells and the least productive ones (excluding those that are dry and abandoned). The distributions of EURs are highly skewed, with most of the wells in the lower part of the range. Continuous AUs were divided into four categories based on reservoir type and major commodity (oil or gas): coalbed gas, shale gas, other low-permeability gas AUs (such as tight sands), and low-permeability oil AUs. Within each of these categories, there is great variability from AU to AU, as shown by plots of multiple EUR distributions. Comparing the means of each distribution within a category shows that the means themselves have a skewed distribution, with a range of approximately one to two orders of magnitude. A comparison of the three gas categories (coalbed gas, shale gas, and other low-permeability gas AUs) shows large overlap in the ranges of EUR distributions. Generally, coalbed gas AUs have lower EUR distributions, shale gas AUs have intermediate sizes, and the other low-permeability gas AUs have higher EUR distributions. The plot of EUR distributions for each category shows the range of variation among developed AUs in an appropriate context for viewing the historical development within a particular AU. The Barnett Shale is used as an example to demonstrate that dividing wells into groups by time allows one to see the changes in EUR distribution. Subdivision into groups can also be done by vertical versus horizontal wells, by length of horizontal completion, by distance to closest previously drilled well, by thickness of reservoir interval, or by any other variable for which one has or can calculate values for each well. The resulting plots show how one can subdivide the total range of productivity in shale-gas wells into smaller subsets that are more appropriate for use as analogs.

Synthesis of Au microwires by selective oxidation of Au–W thin-film composition spreads

PubMed Central

Hamann, Sven; Brunken, Hayo; Salomon, Steffen; Meyer, Robert; Savan, Alan; Ludwig, Alfred

2013-01-01

We report on the stress-induced growth of Au microwires out of a surrounding Au–W matrix by selective oxidation, in view of a possible application as ‘micro-Velcro’. The Au wires are extruded due to the high compressive stress in the tungsten oxide formed by oxidation of elemental W. The samples were fabricated as a thin-film materials library using combinatorial sputter deposition followed by thermal oxidation. Sizes and shapes of the Au microwires were investigated as a function of the W to Au ratio. The coherence length and stress state of the Au microwires were related to their shape and plastic deformation. Depending on the composition of the Au–W precursor, the oxidized samples showed regions with differently shaped Au microwires. The Au48W52 composition yielded wires with the maximum length to diameter ratio due to the high compressive stress in the tungsten oxide matrix. The values of wire length (35 μm) and diameter (2 μm) achieved at the Au48W52 composition are suitable for micro-Velcro applications. PMID:27877561

Gold surfaces and nanoparticles are protected by Au(0)-thiyl species and are destroyed when Au(I)-thiolates form.

PubMed

Reimers, Jeffrey R; Ford, Michael J; Halder, Arnab; Ulstrup, Jens; Hush, Noel S

2016-03-15

The synthetic chemistry and spectroscopy of sulfur-protected gold surfaces and nanoparticles is analyzed, indicating that the electronic structure of the interface is Au(0)-thiyl, with Au(I)-thiolates identified as high-energy excited surface states. Density-functional theory indicates that it is the noble character of gold and nanoparticle surfaces that destabilizes Au(I)-thiolates. Bonding results from large van der Waals forces, influenced by covalent bonding induced through s-d hybridization and charge polarization effects that perturbatively mix in some Au(I)-thiolate character. A simple method for quantifying these contributions is presented, revealing that a driving force for nanoparticle growth is nobleization, minimizing Au(I)-thiolate involvement. Predictions that Brust-Schiffrin reactions involve thiolate anion intermediates are verified spectroscopically, establishing a key feature needed to understand nanoparticle growth. Mixing of preprepared Au(I) and thiolate reactants always produces Au(I)-thiolate thin films or compounds rather than monolayers. Smooth links to O, Se, Te, C, and N linker chemistry are established.

Gold surfaces and nanoparticles are protected by Au(0)–thiyl species and are destroyed when Au(I)–thiolates form

PubMed Central

Reimers, Jeffrey R.; Ford, Michael J.; Halder, Arnab; Ulstrup, Jens; Hush, Noel S.

2016-01-01

The synthetic chemistry and spectroscopy of sulfur-protected gold surfaces and nanoparticles is analyzed, indicating that the electronic structure of the interface is Au(0)–thiyl, with Au(I)–thiolates identified as high-energy excited surface states. Density-functional theory indicates that it is the noble character of gold and nanoparticle surfaces that destabilizes Au(I)–thiolates. Bonding results from large van der Waals forces, influenced by covalent bonding induced through s–d hybridization and charge polarization effects that perturbatively mix in some Au(I)–thiolate character. A simple method for quantifying these contributions is presented, revealing that a driving force for nanoparticle growth is nobleization, minimizing Au(I)–thiolate involvement. Predictions that Brust–Schiffrin reactions involve thiolate anion intermediates are verified spectroscopically, establishing a key feature needed to understand nanoparticle growth. Mixing of preprepared Au(I) and thiolate reactants always produces Au(I)–thiolate thin films or compounds rather than monolayers. Smooth links to O, Se, Te, C, and N linker chemistry are established. PMID:26929334

Simulation of STM technique for electron transport through boron-nitride nanotubes

NASA Astrophysics Data System (ADS)

Ganji, M. D.; Mohammadi-nejad, A.

2008-06-01

We report first-principles calculations on the electrical transport properties of boron-nitrid nanotubes (BNNTs). We consider a single walled (5,0) boron-nitrid nanotube sandwiched between an Au(1 0 0) substrate and a monatomic Au scanning tunneling microscope (STM) tip. Lateral motion of the tip over the nanotube wall cause it to change from one conformation class to the others and to switch between a strongly and a weakly conducting state. Thus, surprisingly, despite their apparent simplicity these Au/BNNT/Au nanowires are shown to be a convenient switch. Experiments with a conventional STM are proposed to test these predictions. The projection of the density of states (PDOS) and the transmission coefficients T(E) of the two-probe systems at zero bias are analyzed, and it suggests that the variation of the coupling between the wire and the electrodes leads to switching behaviour.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adare, A.; Afanasiev, S.; Aidala, C.

Measurements of bottomonium production in heavy-ion and p+p collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three Υ states, Υ(1S + 2S + 3S), was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au+Au and p+p collisions at \\(\\sqrt{s_{\\mathrm{NN}}}=200\\) GeV. The Υ(1S + 2S + 3S) → e⁺e⁻ differential cross section at midrapidity was found to be B eedσ/dy = 108 ± 38 (stat) ± 15 (syst) ± 11 (luminosity) pb in p+p collisions. The nuclear modification factor in the 30% most central Au+Au collisions indicates a suppression ofmore » the total Υ state yield relative to the extrapolation from p+p collision data. Thus, the suppression is consistent with measurements at higher energies by the CMS experiment at the Large Hadron Collider.« less

The structure and binding mode of citrate in the stabilization of gold nanoparticles

NASA Astrophysics Data System (ADS)

Al-Johani, Hind; Abou-Hamad, Edy; Jedidi, Abdesslem; Widdifield, Cory M.; Viger-Gravel, Jasmine; Sangaru, Shiv Shankar; Gajan, David; Anjum, Dalaver H.; Ould-Chikh, Samy; Hedhili, Mohamed Nejib; Gurinov, Andrei; Kelly, Michael J.; El Eter, Mohamad; Cavallo, Luigi; Emsley, Lyndon; Basset, Jean-Marie

2017-09-01

Elucidating the binding mode of carboxylate-containing ligands to gold nanoparticles (AuNPs) is crucial to understand their stabilizing role. A detailed picture of the three-dimensional structure and coordination modes of citrate, acetate, succinate and glutarate to AuNPs is obtained by 13C and 23Na solid-state NMR in combination with computational modelling and electron microscopy. The binding between the carboxylates and the AuNP surface is found to occur in three different modes. These three modes are simultaneously present at low citrate to gold ratios, while a monocarboxylate monodentate (1κO1) mode is favoured at high citrate:gold ratios. The surface AuNP atoms are found to be predominantly in the zero oxidation state after citrate coordination, although trace amounts of Auδ+ are observed. 23Na NMR experiments show that Na+ ions are present near the gold surface, indicating that carboxylate binding occurs as a 2e- L-type interaction for each oxygen atom involved. This approach has broad potential to probe the binding of a variety of ligands to metal nanoparticles.

Solid-state diffusion-controlled growth of the phases in the Au-Sn system

NASA Astrophysics Data System (ADS)

Baheti, Varun A.; Kashyap, Sanjay; Kumar, Praveen; Chattopadhyay, Kamanio; Paul, Aloke

2018-01-01

The solid state diffusion-controlled growth of the phases is studied for the Au-Sn system in the range of room temperature to 200 °C using bulk and electroplated diffusion couples. The number of product phases in the interdiffusion zone decreases with the decrease in annealing temperature. These phases grow with significantly high rates even at the room temperature. The growth rate of the AuSn4 phase is observed to be higher in the case of electroplated diffusion couple because of the relatively small grains and hence high contribution of the grain boundary diffusion when compared to the bulk diffusion couple. The diffraction pattern analysis indicates the same equilibrium crystal structure of the phases in these two types of diffusion couples. The analysis in the AuSn4 phase relating the estimated tracer diffusion coefficients with grain size, crystal structure, the homologous temperature of experiments and the concept of the sublattice diffusion mechanism in the intermetallic compounds indicate that Au diffuses mainly via the grain boundaries, whereas Sn diffuses via both the grain boundaries and the lattice.

Midportion achilles tendon microcirculation after intermittent combined cryotherapy and compression compared with cryotherapy alone: a randomized trial.

PubMed

Knobloch, Karsten; Grasemann, Ruth; Spies, Marcus; Vogt, Peter M

2008-11-01

The effect of combined cryotherapy/compression versus cryotherapy alone on the Achilles tendon is undetermined. Standardized combined cryotherapy/compression changes in midportion Achilles tendon microcirculation are superior to those with cryotherapy during intermittent application. Controlled laboratory study. Sixty volunteers were randomized for either combined cryotherapy/compression (Cryo/Cuff, DJO Inc, Vista, California: n = 30; 32 +/- 11 years) or cryotherapy alone (KoldBlue, TLP Industries, Kent, United Kingdom: n = 30; 33 +/- 12 years) with intermittent 3 x 10-minute application. Midportion Achilles tendon microcirculation was determined (O2C, LEA Medizintechnik, Giessen, Germany). Both Cryo/Cuff and KoldBlue significantly reduced superficial and deep capillary tendon blood flow within the first minute of application (43 +/- 46 arbitrary units [AU] vs 10 +/- 19 AU and 42 +/- 46 AU vs 12 +/- 10 AU; P = .0001) without a significant difference throughout all 3 applications. However, during recovery, superficial and deep capillary blood flow was reestablished significantly faster using Cryo/Cuff (P = .023). Tendon oxygen saturation was reduced in both groups significantly (3 minutes Cryo/Cuff: 36% +/- 20% vs 16% +/- 15%; KoldBlue: 42% +/- 19% vs 28% +/- 20%; P < .05) with significantly stronger effects using Cryo/Cuff (P = .014). Cryo/Cuff led to significantly higher tendon oxygenation (Cryo/Cuff: 62% +/- 28% vs baseline 36% +/- 20%; P = .0001) in superficial and deep tissue (Cryo/Cuff: 73% +/- 14% vs baseline 65% +/- 17%; P = .0001) compared with KoldBlue during all recoveries. Postcapillary venous filling pressures were significantly reduced in both groups during application; however, Cryo/Cuff led to significantly, but marginally, lower pressures (Cryo/Cuff: 41 +/- 7 AU vs baseline 51 +/- 13 AU; P = .0001 and KoldBlue: 46 +/- 7 AU vs baseline 56 +/- 11 AU; P = .026 for Cryo/Cuff vs KoldBlue). Increased tendon oxygenation is achieved as tendon preconditioning by combined cryotherapy and compression with significantly increased tendon oxygen saturation during recovery in contrast to cryotherapy alone. Both regimens lead to a significant amelioration of tendinous venous outflow. Combined cryotherapy and compression is superior to cryotherapy alone regarding the Achilles tendon microcirculation. Further studies in tendinopathy and tendon rehabilitation are warranted to elucidate its value regarding functional issues.

Amplified photoacoustic performance and enhanced photothermal stability of reduced graphene oxide coated gold nanorods for sensitive photoacoustic imaging.

PubMed

Moon, Hyungwon; Kumar, Dinesh; Kim, Haemin; Sim, Changbeom; Chang, Jin-Ho; Kim, Jung-Mu; Kim, Hyuncheol; Lim, Dong-Kwon

2015-03-24

We report a strongly amplified photoacoustic (PA) performance of the new functional hybrid material composed of reduced graphene oxide and gold nanorods. Due to the excellent NIR light absorption properties of the reduced graphene oxide coated gold nanorods (r-GO-AuNRs) and highly efficient heat transfer process through the reduced graphene oxide layer, r-GO-AuNRs exhibit excellent photothermal stability and significantly higher photoacoustic amplitudes than those of bare-AuNRs, nonreduced graphene oxide coated AuNRs (GO-AuNRs), or silica-coated AuNR, as demonstrated in both in vitro and in vivo systems. The linear response of PA amplitude from reduced state controlled GO on AuNR indicates the critical role of GO for a strong photothermal effect of r-GO-AuNRs. Theoretical studies with finite-element-method lab-based simulation reveal that a 4 times higher magnitude of the enhanced electromagnetic field around r-GO-AuNRs can be generated compared with bare AuNRs or GO-AuNRs. Furthermore, the r-GO-AuNRs are expected to be a promising deep-tissue imaging probe because of extraordinarily high PA amplitudes in the 4-11 MHz operating frequency of an ultrasound transducer. Therefore, the r-GO-AuNRs can be a useful imaging probe for highly sensitive photoacoustic images and NIR sensitive therapeutics based on a strong photothermal effect.

The formation age of ores from the Pebble Cu-Au-Mo giant deposit (Alaska, United States)

NASA Astrophysics Data System (ADS)

Kremenetskii, A. A.; Popov, V. S.; Gromalova, N. A.

2012-02-01

Zircons from the porphyry-like quartz-diorite boss of the Pebble Cu-Au-Mo deposit (southwest Alaska) have been examined. By their appearance and internal structure (cathode luminescence and electron probing), the zircons have been subdivided into four genetic groups: (1) xenogenic detrital (mainly rounded); (2) magmatogene (protolith crystal in the center and growth zone at the edge); (3) hydrothermally altered (with new-formed regeneration edges in growth zones); (4) metamict-altered (unconsolidated center of the crystal and sectoring in growth zones). Based on SHRIMP U-Pb dating for the principal heterogeneous elements in every group, the following stages of ore formation have been identified for the Pebble deposit: (a) crystallization of quartz diorite-porphyry bosses (95-92 Ma, the concordant age is 94.7 ± 1.5 Ma); (b) late magmatic metasomatic alterations with copper-molybdenum mineralization (92-85 Ma, the concordant age is 90.15 ± 0.78 Ma); (c) postmagmatic argillization with epithermal gold-sulfide mineralization (82-80 Ma, the concordant age is 82.9 ± 2.7 Ma).

Bottom-up substitution assembly of AuF4-n0,-+nPO3 (n = 1-4): a theoretical study of novel oxyfluoride hyperhalogen molecules and anions AuF4-n(PO3)n0,-

NASA Astrophysics Data System (ADS)

Yang, Yi-fan; Cui, Zhong-hua; Ding, Yi-hong

2014-06-01

Compounds with high electron affinity, i.e. superhalogens, have continued to attract chemists' attention, due to their potential importance in fundamental chemistry and materials science. It has now proven very effective to build up novel superhalogens with multi-positively charged centres, which are usually called 'hyperhalogens'. Herein, using AuF4- and PO3 as the model building blocks, we made the first attempt to design the Au,P-based hyperhalogen anions AuF4-n(PO3)n- (n = 1-4) at the B3LYP/6-311+G(d)&SDD and CCSD(T)/6-311+G(d)&SDD (single-point) levels (6-311+G(d) for O, F, P and SDD for Au). Notably, for all the considered Au,P systems, the ground state bears a dioxo-bonded structure with n ≤ 3, which is significantly more stable than the usually presumed mono-oxo-bonded one. Moreover, the clustering of the -PO3 moieties becomes energetically favoured for n ≥ 3. The ground states of AuP4O120,- are the first reported cage-like oxide hyperhalogens. Thus, the -PO3 moiety cannot be retained during the 'bottom-up' assembly. The vertical detachment energy (VDE) value of the most stable AuF4-n(PO3)n- (n = 1-4) ranges from 7.16 to 8.20 eV, higher than the VDE values of the corresponding building blocks AuF4- (7.08 eV) and PO3- (4.69 eV). The adiabatic detachment energy values of these four hyperhalogens exceed 6.00 eV. Possible generation routes for AuF4-n(PO3)n- (n = 1-4) were discussed. The presently designed oxyfluorides not only enriches the family of hyperhalogens, but also demonstrates the great importance of considering the structural transformation during the superhalogen → hyperhalogen design such as for the present Au-P based systems.

Eocene Total Petroleum System -- North and East of the Eocene West Side Fold Belt Assessment Unit of the San Joaquin Basin Province: Chapter 19 in Petroleum systems and geologic assessment of oil and gas in the San Joaquin Basin Province, California

USGS Publications Warehouse

Gautier, Donald L.; Hosford Scheirer, Allegra

2009-01-01

The North and East of Eocene West Side Fold Belt Assessment Unit (AU) of the Eocene Total Petroleum System of the San Joaquin Basin Province comprises all hydrocarbon accumulations within the geographic and stratigraphic limits of this confirmed AU. Oil and associated gas accumulations occur in Paleocene through early middle Miocene marine to nonmarine sandstones found on the comparatively stable northeast shelf of the basin. The assessment unit is located north and east of the thickest accumulation of Neogene sediments and the west side fold belt. The area enclosed by the AU has been affected by only mild deformation since Eocene time. Traps containing known accumulations are mostly low-relief domes, anticlines, and up-dip basin margin traps with faulting and stratigraphic components. Map boundaries of the assessment unit are shown in figures 19.1 and 19.2; this assessment unit replaces the Northeast Shelf of Neogene Basin play 1006, the East Central Basin and Slope North of Bakersfield Arch play 1010, and part of the West Side Fold Belt Sourced by Pre-middle Miocene Rocks play 1005 considered by the U.S. Geological Survey (USGS) in their 1995 National Assessment (Beyer, 1996). Stratigraphically, the AU includes rocks from the uppermost crystalline basement to the topographic surface. In the region of overlap with the Central Basin Monterey Diagenetic Traps Assessment Unit, the North and East of Eocene West Side Fold Belt AU extends from basement rocks to the top of the Temblor Formation (figs. 19.3 and 19.4). In map view, the northern boundary of the assessment unit corresponds to the northernmost extent of Eocene-age Kreyenhagen Formation. The northeast boundary is the eastern limit of possible oil reservoir rocks near the eastern edge of the basin. The southeast boundary corresponds to the pinch-out of Stevens sand of Eckis (1940) to the south, which approximately coincides with the northern flank of the Bakersfield Arch (fig. 19.1). The AU is bounded on the southwest by the limit of major west side structural deformation and to the northwest by the San Andreas Fault and the limit of hydrocarbon-prospective strata in the Coast Ranges. As described by Gautier and others (this volume, chapter 2), existing oil fields in the San Joaquin Basin Province were assigned to assessment units based on the identified petroleum system and reservoir rocks in each field. Vallecitos oil field in the extreme northwest corner of the basin was assigned to the Eocene Total Petroleum System, because oil analyses conducted for this San Joaquin Basin assessment indicate that Eocene oil charged the reservoir rocks (Lillis and Magoon, this volume, chapter 9). Some literature classifies the Vallecitos oil field as part of the northernmost fold of the basin’s west side fold belt (see, for example, Rentschler, 1985; Bartow, 1991), but because of the oil field’s spatial separation and differing trend from the west side fold belt, Vallecitos field was considered here to be within the North and East of Eocene West Side Fold Belt Assessment Unit rather than in the other assessment unit in the Eocene Total Petroleum System, the Eocene West Side Fold Belt. Primary fields in the assessment unit are defined as those containing hydrocarbon resources greater than the USGS minimum threshold for assessment (0.5 million barrels of oil); secondary fields contain smaller volumes of oil but constitute a significant show of hydrocarbons.

USGS World Petroleum Assessment 2000: New Conventional Provinces

USGS Publications Warehouse

Ahlbrandt, T.S.; Klett, T.R.

2000-01-01

The USGS has completed a new assessment of the undiscovered oil and gas resources of the world. One hundred and five geologic provinces were analyzed for assessment. Assessment units (AU) that comprise Total Petroleum Systems (TPS) were identified and described for each of these provinces. The AU served as the basis for assessing undiscovered petroleum within these provinces, 157 TPS and 270 AU were assessed. Some of data included in the assessment include the cumulative percent of world known petroleum volume by ranked oil and gas provinces; undiscovered NGL; reserve growth of the worlds largest oil and gas fields; and world potential reserve growth for oil/gas/NGL.

Periodic Assembly of Nanospecies on Repetitive DNA Sequences Generated on Gold Nanoparticles by Rolling Circle Amplification

NASA Astrophysics Data System (ADS)

Zhao, Weian; Brook, Michael A.; Li, Yingfu

Periodical assembly of nanospecies is desirable for the construction of nanodevices. We provide a protocol for the preparation of a gold nanoparticle (AuNP)/DNA scaffold on which nanospecies can be assembled in a periodical manner. AuNP/DNA scaffold is prepared by growing long single-stranded DNA (ssDNA) molecules (typically hundreds of nanometers to a few microns in length) on AuNPs via rolling circle amplification (RCA). Since these long ssDNA molecules contain many repetitive sequence units, complementary DNA-attached nanospecies can be assembled through specific hybridization in a controllable and periodical manner.

Nuclear modification factor RCP for φ meson production in d+Au collisions at √SNN=200 GeV measured by the PHENIX experiment at RHIC

NASA Astrophysics Data System (ADS)

Guo, Lei

2009-10-01

In d+Au collisions, vector mesons produced in hard scattering are sensitive to various nuclear effects such as parton shadowing/saturation in the small x region (forward rapidity) leading to suppression, and antishadowing (large x region, backward rapidity) or the Cronin effect which both can produce enhancement. Since approaches such as the Color Glass Condensate (CGC) and pQCD-based Glauber-Eikonal models do not agree on the nature of these nuclear effects on particle production at large rapidity, it is essential that they be tested with experimental data in this kinematic regime. Knowledge of the difference between the forward and backward rapidity regions, in d+Au collisions, could also be used to separate the initial-state nuclear wave function modifications and final state in-medium effects in Au+Au collisions. In addition, the relative ratio for the production of ρ, φ and φ can provide information on the production mechanisms of light vector mesons. The PHENIX collaboration at RHIC has recently collected data in d+Au collisions at √s=200 GeV during the 2008 run. The latest work on the RCP measurements of φ, through the di-muon decays at forward and backward rapidities (1.2<η<2.2), will be discussed.

Construction of an all-solid-state artificial Z-scheme system consisting of Bi2WO6/Au/CdS nanostructure for photocatalytic CO2 reduction into renewable hydrocarbon fuel.

PubMed

Wang, Meng; Han, Qiutong; Li, Liang; Tang, Lanqin; Li, Haijin; Zhou, Yong; Zou, Zhigang

2017-07-07

An all-solid-state Bi 2 WO 6 /Au/CdS Z-scheme system was constructed for the photocatalytic reduction of CO 2 into methane in the presence of water vapor. This Z-scheme consists of ultrathin Bi 2 WO 6 nanoplates and CdS nanoparticles as photocatalysts, and a Au nanoparticle as a solid electron mediator offering a high speed charge transfer channel and leading to more efficient spatial separation of electron-hole pairs. The photo-generated electrons from the conduction band (CB) of Bi 2 WO 6 transfer to the Au, and then release to the valence band (VB) of CdS to recombine with the holes of CdS. It allows the electrons remaining in the CB of CdS and holes in the VB of Bi 2 WO 6 to possess strong reduction and oxidation powers, respectively, leading the Bi 2 WO 6 /Au/CdS to exhibit high photocatalytic reduction of CO 2 , relative to bare Bi 2 WO 6 , Bi 2 WO 6 /Au, and Bi 2 WO 6 /CdS. The depressed hole density on CdS also enhances the stability of the CdS against photocorrosion.

Study on surface-enhanced Raman scattering efficiency of Ag core-Au shell bimetallic nanoparticles

NASA Astrophysics Data System (ADS)

Dong, Xiao; Gu, Huaimin; Kang, Jian; Yuan, Xiaojuan

2009-08-01

In this article, the relationship between the states of Ag core-Au shell (core-shell) nanoparticles (NP) and the intensity of Raman scattering of analytes dissolved in the water and adsorbed on the NP was studied. The core-shell NP were synthesised by coating Au layers over Ag seeds by the method of "seed-growth". To highlight the advantage of the core-shell NP, Ag colloid and Au colloid were chosen for contrasting. The analyte that were chosen for this testing were methylene blue (MB) for the reason that MB has very strong signal in surface-enhanced Raman scattering (SERS). The SERS activity of optimalizing states of Ag and Au colloids were compared with that of core-shell NP when MB was used as analyte. In this study, sodium chloride, sodium sulfate and sodium nitrate were used as aggregating agents for Ag, Au colloids and core-shell NP, because anions have a strong influence on the SERS efficiency and the stability of colloids. The results indicate that core-shell NP can obviously enhance the SERS of MB. The aim of this study is to prove that compared with the metal colloid, the core-shell NP is a high efficiency SERS active substrate.

Multilevel resistance switching effect in Au/La2/3Ba1/3MnO3/Pt heterostructure manipulated by external fields

NASA Astrophysics Data System (ADS)

Wen, Jiahong; Zhao, Xiaoyu; Li, Qian; Zhang, Sheng; Wang, Dunhui; Du, Youwei

2018-04-01

Multilevel resistance switching (RS) effect has attracted more and more attention due to its promising potential for the increase of storage density in memory devices. In this work, the transport properties are investigated in an Au/La2/3Ba1/3MnO3 (LBMO)/Pt heterostructure. Taking advantage of the strong interplay among the spin, charge, orbital and lattice of LBMO, the Au/LBMO/Pt device can exhibit bipolar RS effect and magnetoresistance effect simultaneously. Under the coaction of electric field and magnetic field, four different resistance states are achieved in this device. These resistance states show excellent repeatability and retentivity and can be switched between any two states, which suggest the potential applications in the multilevel RS memory devices with enhanced storage density.

Sensor Arrays from Multicomponent Micropatterned Nanoparticles and Graphene

DTIC Science & Technology

2013-10-10

UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Case Western Reserve University,Case School of Engineering,Cleveland, OH ,44106 8...treatment, followed by region-selective substrate-enhanced electroless deposition of Au nanoparticles and solution alkalization of ferrous chloride...tetrahydrate in the presence of ammonia into Fe3O4 nanoparticles. The resultant Fe3O4/ Au multicomponent micropatterned-graphene films were found to be highly

Coverage Dependent Charge Reduction of Cationic Gold Clusters on Surfaces Prepared Using Soft Landing of Mass-selected Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Grant E.; Priest, Thomas A.; Laskin, Julia

2012-11-29

The ionic charge state of monodisperse cationic gold clusters on surfaces may be controlled by selecting the coverage of mass-selected ions soft landed onto a substrate. Polydisperse diphosphine-capped gold clusters were synthesized in solution by reduction of chloro(triphenylphosphine)gold(I) with borane tert-butylamine in the presence of 1,3-bis(diphenylphosphino)propane. The polydisperse gold clusters were introduced into the gas phase by electrospray ionization and mass selection was employed to select a multiply charged cationic cluster species (Au11L53+, m/z = 1409, L = 1,3-bis(diphenylphosphino)propane) which was delivered to the surfaces of four different self-assembled monolayers on gold (SAMs) at coverages of 1011 and 1012 clusters/mm2.more » Employing the spatial profiling capabilities of in-situ time-of-flight secondary ion mass spectrometry (TOF-SIMS) it is shown that, in addition to the chemical functionality of the monolayer (as demonstrated previously: ACS Nano, 2012, 6, 573) the coverage of cationic gold clusters on the surface may be used to control the distribution of ionic charge states of the soft-landed multiply charged clusters. In the case of a 1H,1H,2H,2H-perfluorodecanethiol SAM (FSAM) almost complete retention of charge by the deposited Au11L53+ clusters was observed at a lower coverage of 1011 clusters/mm2. In contrast, at a higher coverage of 1012 clusters/mm2, pronounced reduction of charge to Au11L52+ and Au11L5+ was observed on the FSAM. When soft landed onto 16- and 11-mercaptohexadecanoic acid surfaces on gold (16,11-COOH-SAMs), the mass-selected Au11L53+ clusters exhibited partial reduction of charge to Au11L52+ at lower coverage and additional reduction of charge to both Au11L52+ and Au11L5+ at higher coverage. The reduction of charge was found to be more pronounced on the surface of the shorter (thinner) C11 than the longer (thicker) C16-COOH-SAM. On the surface of the 1-dodecanethiol (HSAM) monolayer, the most abundant charge state was found to be Au11L52+ at lower coverage and Au11L5+ at higher coverage, respectively. A coverage-dependent electron tunneling mechanism is proposed to account for the observed reduction of charge of mass-selected multiply charged gold clusters soft landed on SAMs. The results demonstrate that one of the critical parameters that influence the chemical and physical properties of supported metal clusters, ionic charge state, may be controlled by selecting the coverage of charged species soft landed onto surfaces.« less

Gold-plasmon enhanced photocatalytic performance of anatase titania nanotubes under visible-light irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Bingyang; He, Dawei, E-mail: dwhe@bjtu.edu.cn; Wang, Wenshuo

2016-02-15

Highlights: • APTMS/(TNTs-Au) was synthesized using a deposition-precipitation process. • APTMS/(TNTs-Au) showed superior visible light activity for the degradation of methylene blue. • The electromagnetic field distribution at the interface between TNTs and Au NPs were estimated by the 3D finite-difference time domain simulation. • The working mechanism of the photocatalytic activity of APTMS/(TNTs-Au) was illustrated. - Abstract: [3-Aminopropyl]trimethoxysilane-modified titania nanotubes decorated with Au nanoparticles (APTMS/(TNTs-Au)) nanocomposites were synthesized using a deposition-precipitation process. The results showed that Au nanoparticles (NPs) in the metallic state were firmly adhered to the surface of the anatase TNTs. APTMS/(TNTs-Au) exhibited great photocatalytic activities whichmore » were evaluated from the degradation rate of methylene blue aqueous solution under visible light irradiation. 3D finite-difference time domain simulation was performed to estimate the electromagnetic field distribution at the interface between TNTs and Au NPs. The visible photocatalytic activity of APTMS/(TNTs-Au) was largely attributed to the surface plasmon absorption of metallic Au NPs, which generated and transferred hot electrons to the CB of TNTs. In addition, the hot electrons on the surface of TNTs also suppressed the radiative electron–hole recombination and consequently enhanced the photocatalytic activity.« less

Photoassisted photoluminescence fine-tuning of gold nanodots through free radical-mediated ligand-assembly

NASA Astrophysics Data System (ADS)

Tseng, Yu-Ting; Cherng, Rochelle; Harroun, Scott G.; Yuan, Zhiqin; Lin, Tai-Yuan; Wu, Chien-Wei; Chang, Huan-Tsung; Huang, Chih-Ching

2016-05-01

In this study, we have developed a simple photoassisted ligand assembly to fine-tune the photoluminescence (PL) of (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide-capped gold nanodots (11-MUTAB-Au NDs). The 11-MUTAB-Au NDs (size: ca. 1.8 nm), obtained from the reaction of gold nanoparticles (ca. 3 nm) and 11-MUTAB, exhibited weak, near-infrared (NIR) PL at 700 nm with a quantum yield (QY) of 0.37% upon excitation at 365 nm. The PL QY of the Au NDs increased to 11.43% after reaction with 11-mercaptoundecanoic acid (11-MUA) for 30 min under ultraviolet (UV) light, which was accompanied by a PL wavelength shift to the green region (~520 nm). UV-light irradiation accelerates 11-MUA assembly on the 11-MUTABAu NDs (11-MUA/11-MUTAB-Au NDs) through a radical-mediated reaction. Furthermore, the PL wavelength of the 11-MUA/11-MUTAB-Au NDs can be switched to 640 nm via cysteamine under UV-light irradiation. We propose that the PL of the Au NDs with NIR and visible emissions was originally from the surface thiol-Au complexes and the Au core, respectively. These dramatically different optical properties of the Au NDs were due to variation in the surface ligands, as well as the densities and surface oxidant states of the surface Au atoms/ions. These effects can be controlled by assembling surface thiol ligands and accelerated by UV irradiation.In this study, we have developed a simple photoassisted ligand assembly to fine-tune the photoluminescence (PL) of (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide-capped gold nanodots (11-MUTAB-Au NDs). The 11-MUTAB-Au NDs (size: ca. 1.8 nm), obtained from the reaction of gold nanoparticles (ca. 3 nm) and 11-MUTAB, exhibited weak, near-infrared (NIR) PL at 700 nm with a quantum yield (QY) of 0.37% upon excitation at 365 nm. The PL QY of the Au NDs increased to 11.43% after reaction with 11-mercaptoundecanoic acid (11-MUA) for 30 min under ultraviolet (UV) light, which was accompanied by a PL wavelength shift to the green region (~520 nm). UV-light irradiation accelerates 11-MUA assembly on the 11-MUTABAu NDs (11-MUA/11-MUTAB-Au NDs) through a radical-mediated reaction. Furthermore, the PL wavelength of the 11-MUA/11-MUTAB-Au NDs can be switched to 640 nm via cysteamine under UV-light irradiation. We propose that the PL of the Au NDs with NIR and visible emissions was originally from the surface thiol-Au complexes and the Au core, respectively. These dramatically different optical properties of the Au NDs were due to variation in the surface ligands, as well as the densities and surface oxidant states of the surface Au atoms/ions. These effects can be controlled by assembling surface thiol ligands and accelerated by UV irradiation. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00795c

Winters-Domengine Total Petroleum System—Northern Nonassociated Gas Assessment Unit of the San Joaquin Basin Province: Chapter 21 in Petroleum systems and geologic assessment of oil and gas in the San Joaquin Basin Province, California

USGS Publications Warehouse

Hosford Scheirer, Allegra; Magoon, Leslie B.

2008-01-01

The Northern Nonassociated Gas Assessment Unit (AU) of the Winters-Domengine Total Petroleum System of the San Joaquin Basin Province consists of all nonassociated gas accumulations in Cretaceous, Eocene, and Miocene sandstones located north of township 15 South in the San Joaquin Valley. The northern San Joaquin Valley forms a northwest-southeast trending asymmetrical trough. It is filled with an alternating sequence of Cretaceous-aged sands and shales deposited on Franciscan Complex, ophiolitic, and Sierran basement. Eocene-aged strata unconformably overlie the thick Cretaceous section, and in turn are overlain unconformably by nonmarine Pliocene-Miocene sediments. Nonassociated gas accumulations have been discovered in the sands of the Panoche, Moreno, Kreyenhagen, andDomengine Formations and in the nonmarine Zilch formation of Loken (1959) (hereafter referred to as Zilch formation). Most hydrocarbon accumulations occur in low-relief, northwest-southeast trending anticlines formed chiefly by differential compaction of sediment and by northeast southwest directed compression during the Paleogene (Bartow, 1991) and in stratigraphic traps formed by pinch out of submarine fan sands against slope shales. To date, 176 billion cubic feet (BCF) of nonassociated recoverable gas has been found in fields within the assessment unit (table 21.1). A small amount of biogenic gas forms near the surface of the AU. Map boundaries of the assessment unit are shown in figures 21.1 and 21.2; in plan view, this assessment unit is identical to the Northern Area Nonassociated Gas play 1007 considered by the U.S. Geological Survey (USGS) in its 1995 National Assessment (Beyer, 1996). The AU is bounded on the east by the mapped limits of Cretaceous sandstone reservoir rocks and on the west by the east flank of the Diablo Range. The southern limit of the AU is the southernmost occurrence of nonassociated thermogenic-gas accumulations. The northern limit of the AU corresponds to the Stanislaus-San Joaquin county line, which also defines the northern boundary of the San Joaquin Basin Province. In the vertical dimension, the AU extends from the uppermost crystalline basement to the topographic surface (fig. 21.3), to allow for the possibility of down-section charge across fault surfaces and up-dip migration. The gas in this AU may be sourced from the Winters- Domengine(?) petroleum system, located in the Sacramento Valley north of the San Joaquin Valley, as defined by Magoon and others (1994a,b) (question mark notation derives from convention of Magoon and Dow, 1994, and indicates speculative genetic relationship between hydrocarbons and source rock). The Winters-Domengine Total Petroleum System defined for this assessment contains about 7.2 trillion cubic feet (TCF) of known, recoverable gas and includes the Rio Vista gas field, which alone accounts for 4 TCF of recoverable gas through 2002 (CDOGGR, 2003). Alternatively, the northern nonassociated gas may be sourced from the Moreno Formation within the San Joaquin Valley itself.

Gold-nanoparticle-mediated jigsaw-puzzle-like assembly of supersized plasmonic DNA origami.

PubMed

Yao, Guangbao; Li, Jiang; Chao, Jie; Pei, Hao; Liu, Huajie; Zhao, Yun; Shi, Jiye; Huang, Qing; Wang, Lianhui; Huang, Wei; Fan, Chunhai

2015-03-02

DNA origami has rapidly emerged as a powerful and programmable method to construct functional nanostructures. However, the size limitation of approximately 100 nm in classic DNA origami hampers its plasmonic applications. Herein, we report a jigsaw-puzzle-like assembly strategy mediated by gold nanoparticles (AuNPs) to break the size limitation of DNA origami. We demonstrated that oligonucleotide-functionalized AuNPs function as universal joint units for the one-pot assembly of parent DNA origami of triangular shape to form sub-microscale super-origami nanostructures. AuNPs anchored at predefined positions of the super-origami exhibited strong interparticle plasmonic coupling. This AuNP-mediated strategy offers new opportunities to drive macroscopic self-assembly and to fabricate well-defined nanophotonic materials and devices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Manipulation of electronic phases in Au-nanodots-decorated manganite films by laser illumination

NASA Astrophysics Data System (ADS)

Li, Hui; Zhang, Kaixuan; Wang, Dongli; Xu, Han; Zhou, Haibiao; Fan, Xiaodong; Cheng, Guanghui; Cheng, Long; Lu, Qingyou; Li, Lin; Zeng, Changgan

2018-06-01

Precise manipulation of the electronic phases in strongly correlated oxides offers an avenue to control the macroscopic functionalities, thereby sparking enormous research interests in condensed matter physics. In the present paper, phase-separated La0.33Pr0.34Ca0.33MnO3 (LPCMO) thin films with a fraction of the ferromagnetic metallic phase close to the percolation threshold are successfully prepared, in which the nonvolatile and erasable switching between different electronic states is realized through cooperative effects of Au-nanodots capping and laser illumination. The deposition of Au nanodots on LPCMO thin films leads to the occurrence of a thermally inaccessible nonpercolating state at low temperatures, manifested as the absence of insulator-metal transition as temperature decreases. Such a nonpercolating state can be substantially tuned back to a percolating state by laser illumination in a nonvolatile and erasable way, accompanied by gigantic resistance drops in a wide temperature range. The formation of local oxygen vacancies near Au nanodots and thereby the modulation of mesoscopic electronic texture should be the key factor for the realization of flexible modulation of global transport properties in LPCMO thin films. Our findings pave a way toward the manipulation of physical properties of the electronically phase-separated systems and the design of optically controlled electronic devices.

A general and high-yield galvanic displacement approach to Au-M (M = Au, Pd, and Pt) core-shell nanostructures with porous shells and enhanced electrocatalytic performances.

PubMed

Kuai, Long; Geng, Baoyou; Wang, Shaozhen; Sang, Yan

2012-07-23

In this work, we utilize the galvanic displacement synthesis and make it a general and efficient method for the preparation of Au-M (M = Au, Pd, and Pt) core-shell nanostructures with porous shells, which consist of multilayer nanoparticles. The method is generally applicable to the preparation of Au-Au, Au-Pd, and Au-Pt core-shell nanostructures with typical porous shells. Moreover, the Au-Au isomeric core-shell nanostructure is reported for the first time. The lower oxidation states of Au(I), Pd(II), and Pt(II) are supposed to contribute to the formation of porous core-shell nanostructures instead of yolk-shell nanostructures. The electrocatalytic ethanol oxidation and oxygen reduction reaction (ORR) performance of porous Au-Pd core-shell nanostructures are assessed as a typical example for the investigation of the advantages of the obtained core-shell nanostructures. As expected, the Au-Pd core-shell nanostructure indeed exhibits a significantly reduced overpotential (the peak potential is shifted in the positive direction by 44 mV and 32 mV), a much improved CO tolerance (I(f)/I(b) is 3.6 and 1.63 times higher), and an enhanced catalytic stability in comparison with Pd nanoparticles and Pt/C catalysts. Thus, porous Au-M (M = Au, Pd, and Pt) core-shell nanostructures may provide many opportunities in the fields of organic catalysis, direct alcohol fuel cells, surface-enhanced Raman scattering, and so forth. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cation-Poor Complex Metallic Alloys in Ba(Eu)-Au-Al(Ga) Systems: Identifying the Keys that Control Structural Arrangements and Atom Distributions at the Atomic Level.

PubMed

Smetana, Volodymyr; Steinberg, Simon; Mudryk, Yaroslav; Pecharsky, Vitalij; Miller, Gordon J; Mudring, Anja-Verena

2015-11-02

Four complex intermetallic compounds BaAu(6±x)Ga(6±y) (x = 1, y = 0.9) (I), BaAu(6±x)Al(6±y) (x = 0.9, y = 0.6) (II), EuAu6.2Ga5.8 (III), and EuAu6.1Al5.9 (IV) have been synthesized, and their structures and homogeneity ranges have been determined by single crystal and powder X-ray diffraction. Whereas I and II originate from the NaZn13-type structure (cF104-112, Fm3̅c), III (tP52, P4/nbm) is derived from the tetragonal Ce2Ni17Si9-type, and IV (oP104, Pbcm) crystallizes in a new orthorhombic structure type. Both I and II feature formally anionic networks with completely mixed site occupation by Au and triel (Tr = Al, Ga) atoms, while a successive decrease of local symmetry from the parental structures of I and II to III and, ultimately, to IV correlates with increasing separation of Au and Tr on individual crystallographic sites. Density functional theory-based calculations were employed to determine the crystallographic site preferences of Au and the respective triel element to elucidate reasons for the atom distribution ("coloring scheme"). Chemical bonding analyses for two different "EuAu6Tr6" models reveal maximization of the number of heteroatomic Au-Tr bonds as the driving force for atom organization. The Fermi levels fall in broad pseudogaps for both models allowing some electronic flexibility. Spin-polarized band structure calculations on the "EuAu6Tr6" models hint to singlet ground states for europium and long-range magnetic coupling for both EuAu6.2Ga5.8 (III) and EuAu6.1Al5.9 (IV). This is substantiated by experimental evidence because both compounds show nearly identical magnetic behavior with ferromagnetic transitions at TC = 6 K and net magnetic moments of 7.35 μB/f.u. at 2 K. The effective moments of 8.3 μB/f.u., determined from Curie-Weiss fits, point to divalent oxidation states for europium in both III and IV.

Quarkonium measurements in heavy-ion collisions with the STAR experiment

NASA Astrophysics Data System (ADS)

Huang, Xinjie

2018-02-01

In these proceedings, we present the latest measurements of J/ψ and ϒ by the STAR experiment. The J/ψ and ϒ production measured in p+p collisions provide new baselines for similar measurements in Au+Au collisions, while the measurements in p+Au collisions can help quantify the cold nuclear matter effects. The J/ψ υ2 is measured in both U+U and Au+Au collisions to place constraints on the amount of J/ψ arising from recombination of deconfined charm and anti-charm pairs. Furthermore, the nuclear modification factors for ground and excited ϒ states as a function of transverse momentum and centrality are presented, and compared to those measured at the LHC as well as to theoretical calculations.

X-ray spectroscopy study of electronic structure of laser-irradiated Au nanoparticles in a silica film

NASA Astrophysics Data System (ADS)

Jonnard, P.; Bercegol, H.; Lamaignère, L.; Morreeuw, J.-P.; Rullier, J.-L.; Cottancin, E.; Pellarin, M.

2005-03-01

The electronic structure of gold nanoparticles embedded in a silica film is studied, both before and after irradiation at 355nm by a laser. The Au 5d occupied valence states are observed by x-ray emission spectroscopy. They show that before irradiation the gold atoms are in metallic states within the nanoparticles. After irradiation with a fluence of 0.5J/cm2, it is found that gold valence states are close to those of a metal-poor gold silicide; thanks to a comparison of the experimental Au 5d states with the calculated ones for gold silicides using the density-functional theory. The formation of such a compound is driven by the diffusion of the gold atoms into the silica film upon the laser irradiation. At higher fluence, 1J/cm2, we find a higher percentage of metallic gold that could be attributed to annealing in the silica matrix.

Effect of molecular conformations on the electronic transport in oxygen-substituted alkanethiol molecular junctions

NASA Astrophysics Data System (ADS)

Wang, Minglang; Wang, Hao; Zhang, Guangping; Wang, Yongfeng; Sanvito, Stefano; Hou, Shimin

2018-05-01

The relationship between the molecular structure and the electronic transport properties of molecular junctions based on thiol-terminated oligoethers, which are obtained by replacing every third methylene unit in the corresponding alkanethiols with an oxygen atom, is investigated by employing the non-equilibrium Green's function formalism combined with density functional theory. Our calculations show that the low-bias conductance depends strongly on the conformation of the oligoethers in the junction. Specifically, in the cases of trans-extended conformation, the oxygen-dominated transmission peaks are very sharp and well below the Fermi energy, EF, thus hardly affect the transmission around EF; the Au-S interface hybrid states couple with σ-bonds in the molecular backbone forming the conduction channel at EF, resulting in a conductance decay against the molecular length close to that for alkanethiols. By contrast, for junctions with oligoethers in helical conformations, some π-type oxygen orbitals coupling with the Au-S interface hybrid states contribute to the transmission around EF. The molecule-electrode electronic coupling is also enhanced at the non-thiol side due to the specific spatial orientation introduced by the twist of the molecular backbone. This leads to a much smaller conductance decay constant. Our findings highlight the important role of the molecular conformation of oligoethers in their electronic transport properties and are also helpful for the design of molecular wires with heteroatom-substituted alkanethiols.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koryazhkina, M. N., E-mail: mahavenok@mail.ru; Tikhov, S. V.; Gorshkov, O. N.

It is shown that the formation of Au nanoparticles at the insulator–silicon interface in structures with a high density of surface states results in a shift of the Fermi-level pinning energy at this interface towards the valence-band ceiling in silicon and in increasing the surface-state density at energies close to the Fermi level. In this case, a band with a peak at 0.85 eV arises on the photosensivity curves of the capacitor photovoltage, which is explained by the photoemission of electrons from the formed Au-nanoparticle electron states near the valence-band ceiling in silicon.

Electronic Absorption and MCD Spectra for Pd(AuPPh(3))(8)(2+), Pt(AuPPh(3))(8)(2+), and Related Platinum-Centered Gold Cluster Complexes.

PubMed

Adrowski, Michael J.; Mason, W. Roy

1997-03-26

Electronic absorption and 7.0 T magnetic circular dichroism (MCD) spectra in the UV-vis region, 1.6 to approximately 4.0 &mgr;m(-)(1) (1 &mgr;m(-)(1) = 10(4) cm(-)(1)) are reported for [Pd(AuPPh(3))(8)](NO(3))(2) and [Pt(AuPPh(3))(8)](NO(3))(2) in acetonitrile solutions at room temperature. The MCD spectra are better resolved than the absorption spectra and consist of both A and B terms. The spectra are interpreted in terms of D(4)(d)() skeletal geometry and MO's that are approximated by 5s and 6s orbitals for Pd and Pt/Au atoms, respectively. The lowest energy excited configurations and states are attributed to intraframework (IF) Au(8)(2+) transitions. Evidence is also presented for Pt 5d --> Au 6s transitions in the MCD spectra for Pt(AuPPh(3))(8)(2+). Acetonitrile solution absorption and MCD spectra for the related Pt-centered cluster complexes [Pt(CO)(AuPPh(3))(8)](NO(3))(2), [Pt(AuP(p-tolyl)(3))(8)](NO(3))(2), [Pt(CuCl)(AuPPh(3))(8)](NO(3))(2), [Pt(AgNO(3))(AuPPh(3))(8)](NO(3))(2), [Pt(Hg)(2)(AuPPh(3))(8)](NO(3))(2), [Pt(HgCl)(2)(AuPPh(3))(8)](BF(4))(2), and [Pt(HgNO(3))(2)(AuPPh(3))(8)](BF(4))(2) are also reported and interpreted within the context of the model developed for the M(AuPPh(3))(8)(2+) complexes.

Maintenance dosing for sublingual immunotherapy by prominent European allergen manufacturers expressed in bioequivalent allergy units.

PubMed

Larenas-Linnemann, Désirée; Esch, Robert; Plunkett, Greg; Brown, Shannon; Maddox, Daniel; Barnes, Charles; Constable, Derek

2011-11-01

Sublingual immunotherapy (SLIT) has become established in Europe, and its efficacy is being evaluated in the United States. The doses used for SLIT in Europe today are difficult to evaluate, because each manufacturer expresses the potency of its extracts differently. To compare in vitro European SLIT maintenance solutions against US licensed standardized allergenic extract concentrates and to determine the monthly SLIT doses delivered expressed in bioequivalent allergy units ([B]AU). We studied Dermatophagoides pteronyssinus, timothy grass pollen, cat (hair) and short ragweed pollen allergen extracts. The SLIT maintenance solutions of 4 leading European manufacturers and standardized concentrate extracts of 3 US manufacturers were analyzed with the following assays: protein content, relative potency (immunoglobulin E [IgE]-binding enzyme-linked immunosorbent assay [ELISA] inhibition) and major allergen content. The relative monthly allergen dose in (B)AU was calculated for each recommended SLIT schedule. Relative potency was approximately 10 times higher for US concentrate standardized extracts-which are meant to be diluted-than for European SLIT maintenance solutions of D pteronyssinus and timothy grass pollen. For cat (hair) and short ragweed pollen, the difference was less. Measurements of relative potency and major allergen content correlated well. In our assays, European mite extracts contain a very low quantity of Der p 2 compared with US mites. Recommended SLIT doses in Europe vary widely among the manufacturers, but are consistently lower (Eur1) or higher (Eur4) over all four allergens tested. SLIT efficacy probably depends on additional factors apart from the exact dose. SLIT dose finding studies should be done for each product. Copyright © 2011 American College of Allergy. Published by Elsevier Inc. All rights reserved.

Gold nanoparticles cellular toxicity and recovery: adipose Derived Stromal cells.

PubMed

Mironava, Tatsiana; Hadjiargyrou, Michael; Simon, Marcia; Rafailovich, Miriam H

2014-03-01

Gold nanoparticles (AuNPs) are currently used in numerous medical applications. Herein, we describe their in vitro impact on human adipose-derived stromal cells (ADSCs) using 13 nm and 45 nm citrate-coated AuNPs. In their non-differentiated state, ADSCs were penetrated by the AuNPs and stored in vacuoles. The presence of the AuNPs in ADSCs resulted in increased population doubling times, decreased cell motility and cell-mediated collagen contraction. The degree to which the cells were impacted was a function of particle concentration, where the smaller particles required a sevenfold higher concentration to have the same effect as the larger ones. Furthermore, AuNPs reduced adipogenesis as measured by lipid droplet accumulation and adiponectin secretion. These effects correlated with transient increases in DLK1 and with relative reductions in fibronectin. Upon removal of exogenous AuNPs, cellular NP levels decreased and normal ADSC functions were restored. As adiponectin helps regulate energy metabolism, local fluctuations triggered by AuNPs can lead to systemic changes. Hence, careful choice of size, concentration and clinical application duration of AuNPs is warranted.

Energy levels, wavelengths, and transition rates of multipole transitions (E1, E2, M1, M2) in Au{sup 67+} and Au{sup 66+} ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamasha, Safeia, E-mail: safeia@hu.edu.jo

2013-11-15

The fully relativistic configuration interaction method of the FAC code is used to calculate atomic data for multipole transitions in Mg-like Au (Au{sup 67+}) and Al-like Au (Au{sup 66+}) ions. Generated atomic data are important in the modeling of M-shell spectra for heavy Au ions and Au plasma diagnostics. Energy levels, oscillator strengths and transition rates are calculated for electric-dipole (E1), electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole (M2) for transitions between excited and ground states 3l−nl{sup ′}, such that n=4,5,6,7. The local central potential is derived using the Dirac–Fock–Slater method. Correlation effects to all orders are consideredmore » by the configuration interaction expansion. All relativistic effects are included in the calculations. Calculated energy levels are compared against published values that were calculated using the multi-reference many body perturbation theory, which includes higher order QED effects. Favorable agreement was observed, with less than 0.15% difference.« less

Theranostic potential of gold nanoparticle-protein agglomerates

NASA Astrophysics Data System (ADS)

Sanpui, Pallab; Paul, Anumita; Chattopadhyay, Arun

2015-11-01

Owing to the ever-increasing applications, glittered with astonishing success of gold nanoparticles (Au NPs) in biomedical research as diagnostic and therapeutic agents, the study of Au NP-protein interaction seems critical for maximizing their theranostic efficiency, and thus demands comprehensive understanding. The mutual interaction of Au NPs and proteins at physiological conditions may result in the aggregation of protein, which can ultimately lead to the formation of Au NP-protein agglomerates. In the present article, we try to appreciate the plausible steps involved in the Au NP-induced aggregation of proteins and also the importance of the proteins' three-dimensional structures in the process. The Au NP-protein agglomerates can potentially be exploited for efficient loading and subsequent release of various therapeutically important molecules, including anticancer drugs, with the unique opportunity of incorporating hydrophilic as well as hydrophobic drugs in the same nanocarrier system. Moreover, the Au NP-protein agglomerates can act as `self-diagnostic' systems, allowing investigation of the conformational state of the associated protein(s) as well as the protein-protein or protein-Au NP interaction within the agglomerates. Furthermore, the potential of these Au NP-protein agglomerates as a novel platform for multifunctional theranostic application along with exciting future-possibilities is highlighted here.

Density-functional theory study of the geometries, stabilities, and electronic properties of Au n Rb (n = 1-10) clusters: comparison with pure gold clusters

NASA Astrophysics Data System (ADS)

Hu, Yan-Fei; Jiang, Gang; Meng, Da-Qiao

2012-01-01

The density functional method with the relativistic effective core potential has been employed to investigate systematically the geometric structures, relative stabilities, growth-pattern behavior, and electronic properties of small bimetallic Au n Rb (n = 1-10) and pure gold Au n (n ≤ 11) clusters. For the geometric structures of the Au n Rb (n = 1-10) clusters, the dominant growth pattern is for a Rb-substituted Au n +1 cluster or one Au atom capped on a Au n -1Rb cluster, and the turnover point from a two-dimensional to a three-dimensional structure occurs at n = 4. Moreover, the stability of the ground-state structures of these clusters has been examined via an analysis of the average atomic binding energies, fragmentation energies, and the second-order difference of energies as a function of cluster size. The results exhibit a pronounced even-odd alternation phenomenon. The same pronounced even-odd alternations are found for the HOMO-LUMO gap, VIPs, VEAs, and the chemical hardness. In addition, about one electron charge transfers from the Au n host to the Rb atom in each corresponding Au n Rb cluster.

The role of tephra studies in African paleoanthropology as exemplified by the Sidi Hakoma Tuff

NASA Astrophysics Data System (ADS)

WoldeGabriel, Giday; Endale, Tamrat; White, Tim D.; Thouveny, Nicolas; Hart, William K.; Renne, Paul R.; Asfaw, Berhane

2013-01-01

Beginning in the 1960s, geological and paleoanthropological exploration of the Ethiopian rift system's basins have led to the discovery and assembly of the most comprehensive record of human biological and technological change during the last 6 million years. The hominid fossils, including partial skeletons, were primarily discovered in the Afar Rift, the Main Ethiopian Rift, and in the Omo Basin of the broadly rifted zone of SW Ethiopia. The paleoanthropological research areas within the SW Afar Rift that have yielded many diverse hominid species and the oldest stone tools are, from north to south, Woranso-Mille (aff. Ardipithecus and Au. afarensis), Hadar (Au. afarensis, Homo sp.), Dikika (Au. afarensis), Gona (Ar. kadabba, Ar. ramidus, H. erectus, and oldest stone tools), Middle Awash (Ar. kadabba, Ar. ramidus, Au. anamensis, Au. afarensis, Au. garhi, H. erectus, H. rhodesiensis, H. sapiens idaltu, and the oldest paleo-butchery locality), and Galili (Au. afarensis). Additional hominid remains were discovered at Melka Kunture on the banks of the Awash River near its source along the western margin of the central part of the Main Ethiopian Rift (H. erectus), at Konso (H. erectus and A. boisei), and at the southern end of the MER, and in the Omo Basin (Au. anamensis, Au. afarensis, Au. aethiopicus, Au. boisei, H. habilis, and H. erectus). Distal and sometimes proximal tephra units interbedded within fossilifeous sedimentary deposits have become key elements in this work by providing chronological and correlative control and depositional contexts. Several regional tephra markers have been identified within the northern half of the eastern African rift valley in Ethiopia and Kenya, and in marine sediments of the Gulf of Aden Rift and the NW Indian Ocean. Out of the many regional tephra stratigraphic markers that range in age from the early Pliocene (3.97 Ma) to the late Pleistocene (0.16 Ma), the Sidi Hakoma Tuff (SHT) has been more widely identified and thoroughly characterized than any of the others. An age of 3.446 ± 0.041 Ma was determined on the SHT according to the most recent calibration, and it is the only regional stratigraphic marker whose source has been traced to a buried caldera in the central sector of the Main Ethiopian Rift. This paper describes new SHT occurrences and presents chemical and chronological results in the context of a broader review of the importance of this key marker. Moreover, the geographic distributions, probable dispersal mechanisms, and importance of regional tephra units in determining the tectonic and sedimentological processes in the different rift basins of the eastern African rift valleys are considered.

Voice-coil technology for the E-ELT M4 Adaptive Unit

NASA Astrophysics Data System (ADS)

Gallieni, D.; Tintori, M.; Mantegazza, M.; Anaclerio, E.; Crimella, L.; Acerboni, M.; Biasi, R.; Angerer, G.; Andrigettoni, M.; Merler, A.; Veronese, D.; Carel, J.-L.; Marque, G.; Molinari, E.; Tresoldi, D.; Toso, G.; Spanó, P.; Riva, M.; Mazzoleni, R.; Riccardi, A.; Mantegazza, P.; Manetti, M.; Morandini, M.; Vernet, E.; Hubin, N.; Jochum, L.; Madec, P.; Dimmler, M.; Koch, F.

We present our design of the E-ELT M4 Adaptive Unit based on voice-coil driven deformable mirror technology. This technology was developed by INAF-Arcetri, Microgate and ADS team in the past 15 years and it has been adopted by a number of large ground based telescopes as the MMT, LBT, Magellan and lastly the VLT in the frame of the Adaptive Telescope Facility project. Our design is based on contactless force actuators made by permanent magnets glued on the back of the deformable mirror and coils mounted on a stiff reference structure. We use capacitive sensors to close a position loop co-located with each actuator. Dedicated high performance parallel processors are used to implement the local de-centralized control at actuator level and a centralized feed-forward computation of all the actuators forces. This allowed achieving in our previous systems dynamic performances well in line with the requirements of the M4 Adaptive Unit (M4AU) case. The actuator density of our design is in the order of 30-mm spacing for a figure of about 6000 actuators on the M4AU and it allows fulfilling the fitting error and corrections requirements of the E-ELT high order DM. Moreover, our contact-less technology makes the Deformable Mirror tolerant to up 5% actuators failures without spoiling system capability to reach its specified performances, besides allowing large mechanical tolerances between the reference structure and the deformable mirror. Finally, we present the Demonstration Prototype we are building in the frame of the M4AU Phase B study to measure the optical dynamical performances predicted by our design. Such a prototype will be fully representative of the M4AU features, in particular it will address the controllability of two adjacent segments of the 2-mm thick mirror and implement the actuators "brick" modular concept that has been adopted to dramatically improve the maintainability of the final unit.

Geology and assessment of the undiscovered, technically recoverable petroleum resources of Armenia, 2013

USGS Publications Warehouse

Klett, T.R.

2016-02-23

The U.S. Geological Survey (USGS) assessed the undiscovered, technically recoverable oil and gas resources of Armenia in 2013. A Paleozoic and a Cenozoic total petroleum system (TPS) were identified within the country of Armenia. The postulated petroleum system elements are uncertain, resulting in low geologic probabilities for significant oil an gas resources. Two assessment units (AU) were delineated in each TPS—a Paleozoic-Sourced Conventional Reservoirs AU and a Permian Shale Gas AU in the Paleozoic Composite TPS and a Paleogene-Sourced Conventional Reservoirs AU and a Cenozoic Coalbed Gas AU in the Cenozoic Composite TPS. The TPS elements are largely uncertain and risked, and so only the Paleogene-Sourced Conventional Reservoirs AU was quantitatively assessed because the geologic probability is more than the threshold of 10 percent (that is, the probability of at least one conventional oil or gas accumulation of 5 million barrels of oil equivalent or greater based on postulated petroleum-system elements). The USGS estimated fully risked mean volumes of about 1 million barrels of oil (MMBO), about 6 billion cubic feet of natural gas (BCFG), and less than 1 million barrels of natural gas liquids (MMBNGL).

Exploring the Angstrom Excursion of Au Nanoparticles Excited away from a Metal Surface by an Impulsive Acoustic Perturbation.

PubMed

Kim, Ji-Wan; Kovalenko, Oleksandr; Liu, Yu; Bigot, Jean-Yves

2016-12-27

We report the anharmonic angstrom dynamics of self-assembled Au nanoparticles (Au:NPs) away from a nickel surface on top of which they are coupled by their near-field interaction. The deformation and the oscillatory excursion away from the surface are induced by picosecond acoustic pulses and probed at the surface plasmon resonance with femtosecond laser pulses. The overall dynamics are due to an efficient transfer of translational momentum from the Ni surface to the Au:NPs, therefore avoiding usual thermal effects and energy redistribution among the electronic states. Two modes are clearly revealed by the oscillatory shift of the Au:NPs surface plasmon resonance-the quadrupole deformation mode due to the transient ellipsoid shape and the excursion mode when the Au:NPs bounce away from the surface. We find that, contrary to the quadrupole mode, the excursion mode is sensitive to the distance between Au:NPs and Ni. Importantly, the excursion dynamics display a nonsinusoidal motion that cannot be explained by a standard harmonic potential model. A detailed modeling of the dynamics using a Hamaker-type Lennard-Jones potential between two media is performed, showing that each Au:NPs coherently evolves in a nearly one-dimensional anharmonic potential with a total excursion of ∼1 Å. This excursion induces a shift of the surface plasmon resonance detectable because of the strong near-field interaction. This general method of observing the spatiotemporal dynamics with angstrom and picosecond resolutions can be directly transposed to many nanostructures or biosystems to reveal the interaction and contact mechanism with their surrounding medium while remaining in their fundamental electronic states.

Approximate treatment of semicore states in GW calculations with application to Au clusters.

PubMed

Xian, Jiawei; Baroni, Stefano; Umari, P

2014-03-28

We address the treatment of transition metal atoms in GW electronic-structure calculations within the plane-wave pseudo-potential formalism. The contributions of s and p semi-core electrons to the self-energy, which are essential to grant an acceptable accuracy, are dealt with using a recently proposed scheme whereby the exchange components are treated exactly at the G0W0 level, whereas a suitable approximation to the correlation components is devised. This scheme is benchmarked for small gold nano-clusters, resulting in ionization potentials, electron affinities, and density of states in very good agreement with those obtained from calculations where s and p semicore states are treated as valence orbitals, and allowing us to apply this same scheme to clusters of intermediate size, Au20 and Au32, that would be otherwise very difficult to deal with.

Crystallization-induced emission enhancement: A novel fluorescent Au-Ag bimetallic nanocluster with precise atomic structure

PubMed Central

Chen, Tao; Yang, Sha; Chai, Jinsong; Song, Yongbo; Fan, Jiqiang; Rao, Bo; Sheng, Hongting; Yu, Haizhu; Zhu, Manzhou

2017-01-01

We report the first noble metal nanocluster with a formula of Au4Ag13(DPPM)3(SR)9 exhibiting crystallization-induced emission enhancement (CIEE), where DPPM denotes bis(diphenylphosphino)methane and HSR denotes 2,5-dimethylbenzenethiol. The precise atomic structure is determined by x-ray crystallography. The crystalline state of Au4Ag13 shows strong luminescence at 695 nm, in striking contrast to the weak emission of the amorphous state and hardly any emission in solution phase. The structural analysis and the density functional theory calculations imply that the compact C–H⋯π interactions significantly restrict the intramolecular rotations and vibrations and thus considerably enhance the radiative transitions in the crystalline state. Because the noncovalent interactions can be easily modulated via varying the chemical environments, the CIEE phenomenon might represent a general strategy to amplify the fluorescence from weakly (or even non-) emissive nanoclusters. PMID:28835926

Local 3d Electronic Structures of Co-Based Complexes with Medicinal Molecules Probed by Soft X-ray Absorption

NASA Astrophysics Data System (ADS)

Yamagami, Kohei; Fujiwara, Hidenori; Imada, Shin; Kadono, Toshiharu; Yamanaka, Keisuke; Muro, Takayuki; Tanaka, Arata; Itai, Takuma; Yoshinari, Nobuto; Konno, Takumi; Sekiyama, Akira

2017-07-01

We have examined the local 3d electronic structures of Co-Au multinuclear complexes with the medicinal molecules d-penicillaminate (d-pen) [Co{Au(PPh3)(d-pen)}2]ClO4 and [Co3{Au3(tdme)(d-pen)3}2] by Co L2,3-edge soft X-ray absorption (XAS) spectroscopy, where PPh3 denotes triphenylphosphine and tdme stands for 1,1,1-tris[(diphenylphosphino)methyl]ethane. The Co L2,3-edge XAS spectra indicate the localized ionic 3d electronic states in both materials. The experimental spectra are well explained by spectral simulation for a localized Co ion under ligand fields with the full multiplet theory, which verifies that the ions are in the low-spin Co3+ state in the former compound and in the high-spin Co2+ state in the latter.

New State of Nuclear Matter: Nearly Perfect Fluid of Quarks and Gluons in Heavy Ion Collisions at RHIC Energies From Charged Particle Density to Jet Quenching

DOE PAGES

Nouicer, R.

2016-03-28

This article reviews several important results from RHIC experiments and discusses their implications. They were obtained in a unique environment for studying QCD matter at temperatures and densities that exceed the limits wherein hadrons can exist as individual entities and raises to prominence the quark-gluon degrees of freedom. These findings are supported by major experimental observations via measuring of the bulk properties of particle production, particle ratios and chemical freeze-out conditions, and elliptic ow; followed by hard probe measurements: high-pT hadron suppression, dijet fragment azimuthal correlations, and heavy favor probes. These measurements are presented for particles of different species asmore » a function of system sizes, collision centrality, and energy carried out in RHIC experiments. The results reveal that a dense, strongly-interacting medium is created in central Au + Au collisions at p sNN = 200 GeV at RHIC. This revelation of a new state of nuclear matter has also been observed in measurements at the LHC. Further, the IP-Glasma model coupled with viscous hydrodynamic models, which assumes the formation of a QGP, reproduces well the experimental ow results from Au + Au at p sNN = 200 GeV. This implies that the fluctuations in the initial geometry state are important and the created medium behaves as a nearly perfect liquid of nuclear matter because it has an extraordinarily low ratio of shear viscosity to entropy density, =s 0.12. However, these discoveries are far from being fully understood. Furthermore, recent experimental results from RHIC and LHC in small p + A, d + Au and 3He+Au collision systems provide brand new insight into the role of initial and final state effects. These have proven to be interesting and more surprising than originally anticipated; and could conceivably shed new light in our understanding of collective behavior in heavy-ion physics. Accordingly, the focus of the experiments at both facilities RHIC and the LHC is on detailed exploration of the properties of this new state of nuclear matter, the QGP.« less

New state of nuclear matter: Nearly perfect fluid of quarks and gluons in heavy-ion collisions at RHIC energies. From charged particle density to jet quenching

NASA Astrophysics Data System (ADS)

Nouicer, R.

2016-03-01

This article reviews several important results from RHIC experiments and discusses their implications. They were obtained in a unique environment for studying QCD matter at temperatures and densities that exceed the limits wherein hadrons can exist as individual entities and raises to prominence the quark-gluon degrees of freedom. These findings are supported by major experimental observations via measuring of the bulk properties of particle production, particle ratios and chemical freeze-out conditions, and elliptic flow; followed by hard probe measurements: high- pT hadron suppression, dijet fragment azimuthal correlations, and heavy-flavor probes. These measurements are presented for particles of different species as a function of system sizes, collision centrality, and energy carried out in RHIC experiments. The results reveal that a dense, strongly interacting medium is created in central Au+Au collisions at sqrt{s_{NN}} = 200 GeV at RHIC. This revelation of a new state of nuclear matter has also been observed in measurements at the LHC. Further, the IP-Glasma model coupled with viscous hydrodynamic models, which assumes the formation of a QGP, reproduces well the experimental flow results from Au+Au at sqrt{s_{NN}} = 200 GeV. This implies that the fluctuations in the initial geometry state are important and the created medium behaves as a nearly perfect liquid of nuclear matter because it has an extraordinarily low ratio of shear viscosity to entropy density, η/s≈ 0.12. However, these discoveries are far from being fully understood. Furthermore, recent experimental results from RHIC and LHC in small p+A, d+ Au and 3He+Au collision systems provide brand new insight into the role of initial and final state effects. These have proven to be interesting and more surprising than originally anticipated; and could conceivably shed new light in our understanding of collective behavior in heavy-ion physics. Accordingly, the focus of the experiments at both facilities RHIC and the LHC is on detailed exploration of the properties of this new state of nuclear matter, the QGP.

New State of Nuclear Matter: Nearly Perfect Fluid of Quarks and Gluons in Heavy Ion Collisions at RHIC Energies From Charged Particle Density to Jet Quenching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nouicer, R.

This article reviews several important results from RHIC experiments and discusses their implications. They were obtained in a unique environment for studying QCD matter at temperatures and densities that exceed the limits wherein hadrons can exist as individual entities and raises to prominence the quark-gluon degrees of freedom. These findings are supported by major experimental observations via measuring of the bulk properties of particle production, particle ratios and chemical freeze-out conditions, and elliptic ow; followed by hard probe measurements: high-pT hadron suppression, dijet fragment azimuthal correlations, and heavy favor probes. These measurements are presented for particles of different species asmore » a function of system sizes, collision centrality, and energy carried out in RHIC experiments. The results reveal that a dense, strongly-interacting medium is created in central Au + Au collisions at p sNN = 200 GeV at RHIC. This revelation of a new state of nuclear matter has also been observed in measurements at the LHC. Further, the IP-Glasma model coupled with viscous hydrodynamic models, which assumes the formation of a QGP, reproduces well the experimental ow results from Au + Au at p sNN = 200 GeV. This implies that the fluctuations in the initial geometry state are important and the created medium behaves as a nearly perfect liquid of nuclear matter because it has an extraordinarily low ratio of shear viscosity to entropy density, =s 0.12. However, these discoveries are far from being fully understood. Furthermore, recent experimental results from RHIC and LHC in small p + A, d + Au and 3He+Au collision systems provide brand new insight into the role of initial and final state effects. These have proven to be interesting and more surprising than originally anticipated; and could conceivably shed new light in our understanding of collective behavior in heavy-ion physics. Accordingly, the focus of the experiments at both facilities RHIC and the LHC is on detailed exploration of the properties of this new state of nuclear matter, the QGP.« less

The Influence of Interstitial Ga and Interfacial Au (sub 2)P (sub 3) on the Electrical and Metallurgical Behavior of Au-Contacted III-V Semiconductors

NASA Technical Reports Server (NTRS)

Weizer, Victor G.; Fatemi, Navid S.

1991-01-01

The introduction of a very small amount of Ga into Au contact metallization on InP is shown to have a significant effect on both the metallurgical and electrical behavior of that contact system. Ga atoms in the interstices of the Au lattice are shown to be effective in preventing the solid state reactions that normally take place between Au and InP during contact sintering. In addition to suppressing the metallurgical interaction, the presence of small amounts of Ga is shown to cause an order of magnitude reduction in the specific contact resistivity. Evidence is presented that the reactions of GaP and GaAs with Au contacts are also drastically affected by the presence of Ga. The sintering behavior of the Au-GaP and the Au-GaAs systems (as contrasted with that of the Au-InP system) is explained as due to the presence of interstitial Ga in the contact metallization. Finally the large, two-to-three order of magnitude drop in the contact resistance that occurs in the Au-InP system upon sintering at 400 degrees Centigrade is shown to be a result of the formation of an Au (sub 2) P (sub 3) layer at the metal-semiconductor interface. Contact resistivities in the 10 (sup -6) ohm square centimeter range are obtained for as-deposited Au on InP when a thin (20 Angstrom) layer of Au (sub 2) P (sub 3) is introduced between the InP and the Au contacts.

MICROWAVE-ASSISTED SYNTHESIS OF NOBLE NANOSTRUCTURES USING BIODEGRADABLE POLYMER CARBOXYMETHYL CELLULOSE

EPA Science Inventory

Microwave-assisted (MW) synthesis of noble metals such as Au, Pt and Pd is reported using biodegradable polymer carboxymethyl cellulose (CMC) at 100°C within few seconds. The possible reduction entails the coupling of polar hydroxyl units in beta-glucopyranose units with micr...

Solid-state voltammetry-based electrochemical immunosensor for Escherichia coli using graphene oxide-Ag nanoparticle composites as labels.

PubMed

Jiang, Xiaochun; Chen, Kun; Wang, Jing; Shao, Kang; Fu, Tao; Shao, Feng; Lu, Donglian; Liang, Jiangong; Foda, M Frahat; Han, Heyou

2013-06-21

A new electrochemical immunosensor based on solid-state voltammetry was fabricated for the detection of Escherichia coli (E. coli) by using graphene oxide-Ag nanoparticle composites (P-GO-Ag) as labels. To construct the platform, Au nanoparticles (AuNPs) were first self-assembled on an Au electrode surface through cysteamine and served as an effective matrix for antibody (Ab) attachment. Under a sandwich-type immunoassay format, the analyte and the probe (P-GO-Ag-Ab) were successively captured onto the immunosensor. Finally, the bonded AgNPs were detected through a solid-state redox process in 0.2 M of KCl solution. Combining the advantages of the high-loading capability of graphene oxide with promoted electron-transfer rate of AuNPs, this immunosensor produced a 26.92-fold signal enhancement compared with the unamplified protocol. Under the optimal conditions, the immunosensor exhibited a wide linear dependence on the logarithm of the concentration of E. coli ranging from 50 to 1.0 × 10(6) cfu mL(-1) with a detection limit of 10 cfu mL(-1). Moreover, as a practical application, the proposed immunosensor was used to monitor E. coli in lake water with satisfactory results.

Multi-center evaluation of analytical performance of the Beckman Coulter AU5822 chemistry analyzer.

PubMed

Zimmerman, M K; Friesen, L R; Nice, A; Vollmer, P A; Dockery, E A; Rankin, J D; Zmuda, K; Wong, S H

2015-09-01

Our three academic institutions, Indiana University, Northwestern Memorial Hospital, and Wake Forest, were among the first in the United States to implement the Beckman Coulter AU5822 series chemistry analyzers. We undertook this post-hoc multi-center study by merging our data to determine performance characteristics and the impact of methodology changes on analyte measurement. We independently completed performance validation studies including precision, linearity/analytical measurement range, method comparison, and reference range verification. Complete data sets were available from at least one institution for 66 analytes with the following groups: 51 from all three institutions, and 15 from 1 or 2 institutions for a total sample size of 12,064. Precision was similar among institutions. Coefficients of variation (CV) were <10% for 97%. Analytes with CVs >10% included direct bilirubin and digoxin. All analytes exhibited linearity over the analytical measurement range. Method comparison data showed slopes between 0.900-1.100 for 87.9% of the analytes. Slopes for amylase, tobramycin and urine amylase were <0.8; the slope for lipase was >1.5, due to known methodology or standardization differences. Consequently, reference ranges of amylase, urine amylase and lipase required only minor or no modification. The four AU5822 analyzers independently evaluated at three sites showed consistent precision, linearity, and correlation results. Since installations, the test results had been well received by clinicians from all three institutions. Copyright © 2015. Published by Elsevier Inc.

The effects of high-energy uranium ion irradiation on Au/n-GaN Schottky diodes

NASA Astrophysics Data System (ADS)

Gou, J.; Zhang, C. H.; Zhang, L. Q.; Song, Y.; Wang, L. X.; Li, J. J.; Meng, Y. C.; Li, H. X.; Yang, Y. T.; Lu, Z. W.

2014-11-01

The I-V and C-V characteristics of Au/n-GaN Schottky diodes irradiated with 290-MeV 238U32+ ions are presented. The U ions can penetrate the n-type GaN epi-layer with a thickness about 3 μm grown on the c-plane of a sapphire substrate using the MOCVD technique, leaving a purely electronic energy deposition. The Au/n-GaN Schottky diodes were irradiated to successively increasing fluences from 1 × 109 to 5 × 1011 ions cm-2. The measured I-V curves show that the height of the Schottky barrier decreases after irradiation and that the Schottky barrier almost disappears when the ion fluence reaches 5 × 1010 ions cm-2. Meanwhile, the irradiation increases the series resistance. The C-V curves show that the capacitance drops sharply when the ion fluence reaches 5 × 1010 ions cm-2. The dielectric constant also decreases following the irradiation. The changes of the electrical properties are ascribed to the neutralization of the donor-like surface state and the acceptor-like surface state due to the migration of Au atoms at the interface of Au/n-GaN under energetic U ions irradiations.

Effects of crystalline electronic field and onsite interorbital interaction in Yb-based quasicrystal and approximant crystal.

PubMed

Watanabe, Shinji; Miyake, Kazumasa

2018-05-10

To get an insight into a new type of quantum critical phenomena recently discovered in the quasicrystal Yb 15 Al 34 Au 51 and approximant crystal (AC) Yb 14 Al 35 Au 51 under pressure, we discuss the property of the crystalline electronic field (CEF) at Yb in the AC and show that uneven CEF levels at each Yb site can appear because of the Al/Au mixed sites. Then we construct the minimal model for the electronic state on the AC by introducing the onsite Coulomb repulsion between the 4f and 5d orbitals at Yb. Numerical calculations for the ground state shows that the lattice constant dependence of the Yb valence well explains the recent measurement done by systematic substitution of elements of Al and Au in the quasicrystal and AC, where the quasicrystal Yb 15 Al 34 Au 51 is just located at the point from where the Yb-valence starts to change drastically. Our calculation convincingly demonstrates that this is indeed the evidence that this material is just located at the quantum critical point of the Yb-valence transition.

Effects of crystalline electronic field and onsite interorbital interaction in Yb-based quasicrystal and approximant crystal

NASA Astrophysics Data System (ADS)

Watanabe, Shinji; Miyake, Kazumasa

2018-05-01

To get an insight into a new type of quantum critical phenomena recently discovered in the quasicrystal Yb15Al34Au51 and approximant crystal (AC) Yb14Al35Au51 under pressure, we discuss the property of the crystalline electronic field (CEF) at Yb in the AC and show that uneven CEF levels at each Yb site can appear because of the Al/Au mixed sites. Then we construct the minimal model for the electronic state on the AC by introducing the onsite Coulomb repulsion between the 4f and 5d orbitals at Yb. Numerical calculations for the ground state shows that the lattice constant dependence of the Yb valence well explains the recent measurement done by systematic substitution of elements of Al and Au in the quasicrystal and AC, where the quasicrystal Yb15Al34Au51 is just located at the point from where the Yb-valence starts to change drastically. Our calculation convincingly demonstrates that this is indeed the evidence that this material is just located at the quantum critical point of the Yb-valence transition.

Geochemistry and statistical analyses of porphyry system and epithermal veins at Hizehjan in northwestern Iran

NASA Astrophysics Data System (ADS)

Radmard, Kaikhosrov; Zamanian, Hassan; Hosseinzadeh, Mohamad Reza; Khalaji, Ahmad Ahmadi

2017-12-01

Situated about 130 km northeast of Tabriz (northwest Iran), the Mazra'eh Shadi deposit is in the Arasbaran metallogenic belt (AAB). Intrusion of subvolcanic rocks, such as quartz monzodiorite-diorite porphyry, into Eocene volcanic and volcano-sedimentary units led to mineralisation and alteration. Mineralisation can be subdivided into a porphyry system and Au-bearing quartz veins within andesite and trachyandesite which is controlled by fault distribution. Rock samples from quartz veins show maximum values of Au (17100 ppb), Pb (21100 ppm), Ag (9.43ppm), Cu (611ppm) and Zn (333 ppm). Au is strongly correlated with Ag, Zn and Pb. In the Au-bearing quartz veins, factor group 1 indicates a strong correlation between Au, Pb, Ag, Zn and W. Factor group 2 indicates a correlation between Cu, Te, Sb and Zn, while factor group 3 comprises Mo and As. Based on Spearman correlation coefficients, Sb and Te can be very good indicator minerals for Au, Ag and Pb epithermal mineralisation in the study area. The zoning pattern shows clearly that base metals, such as Cu, Pb, Zn and Mo, occur at the deepest levels, whereas Au and Ag are found at higher elevations than base metals in boreholes in northern Mazra'eh Shadi. This observation contrasts with the typical zoning pattern caused by boiling in epithermal veins. At Mazra'eh Shadi, quartz veins containing co-existing liquid-rich and vapour-rich inclusions, as strong evidence of boiling during hydrothermal evolution, have relatively high Au grades (up to 813 ppb). In the quartz veins, Au is strongly correlated with Ag, and these elements are in the same group with Fe and S. Mineralisation of Au and Ag is a result of pyrite precipitation, boiling of hydrothermal fluids and a pH decrease.

Enhanced selective photocatalytic reduction of CO2 to CH4 over plasmonic Au modified g-C3N4 photocatalyst under UV-vis light irradiation

NASA Astrophysics Data System (ADS)

Li, Hailong; Gao, Yan; Xiong, Zhuo; Liao, Chen; Shih, Kaimin

2018-05-01

A series of Au-g-C3N4 (Au-CN) catalysts were prepared through a NaBH4-reduction method using g-C3N4 (CN) from pyrolysis of urea as precursor. The catalysts' surface area, crystal structure, surface morphology, chemical state, functional group composition and optical properties were characterized by X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, ultraviolet visible (UV-vis) diffuse reflectance spectra, fourier transform infrared, photoluminescence and transient photocurrent analysis. The carbon dioxide (CO2) photoreduction activities under ultraviolet visible (UV-vis) light irradiation were significantly enhanced when gold (Au) was loaded on the surface of CN. 2Au-CN catalyst with Au to CN mole ratio of 2% showed the best catalytic activity. After 2 h UV-vis light irradiation, the methane (CH4) yield over the 2Au-CN catalyst was 9.1 times higher than that over the pure CN. The CH4 selectivity also greatly improved for the 2Au-CN compared to the CN. The deposited Au nanoparticles facilitated the separation of electron-hole pairs on the CN surface. Moreover, the surface plasmon resonance effect of Au further promoted the generation of hot electrons and visible light absorption. Therefore, Au loading significantly improved CO2 photoreduction performance of CN under UV-vis light irradiation.

Ab initio study of gold-doped zigzag graphene nanoribbons

NASA Astrophysics Data System (ADS)

Srivastava, Pankaj; Dhar, Subhra; Jaiswal, Neeraj K.

2014-12-01

The electronic transport properties of zigzag graphene nanoribbons (ZGNRs) through covalent functionalization of gold (Au) atoms is investigated by using non-equilibrium Green's function combined with density functional theory. It is revealed that the electronic properties of Au-doped ZGNRs vary significantly due to spin and its non-inclusion. We find that the DOS profiles of Au-adsorbed ZGNR due to spin reveal very less number of states available for conduction, whereas non-inclusion of spin results in higher DOS across the Fermi level. Edge Au-doped ribbons exhibit stable structure and are energetically more favorable than the center Au-doped ZGNRs. Though the chemical interaction at the ZGNR-Au interface modifies the Fermi level, Au-adsorbed ZGNR reveals semimetallic properties. A prominent qualitative change of the I-V curve from linear to nonlinear is observed as the Au atom shifts from center toward the edges of the ribbon. Number of peaks present near the Fermi level ensures conductance channels available for charge transport in case of Au-center-substituted ZGNR. We predict semimetallic nature of the Au-adsorbed ZGNR with a high DOS peak distributed over a narrow energy region at the Fermi level and fewer conductance channels. Our calculations for the magnetic properties predict that Au functionalization leads to semiconducting nature with different band gaps for spin up and spin down. The outcomes are compared with the experimental and theoretical results available for other materials.

Geology and oil and gas assessment of the Fruitland Total Petroleum System, San Juan Basin, New Mexico and Colorado: Chapter 6 in Geology and Oil and Gas Assessment of the Fruitland Total Petroleum System, San Juan Basin, New Mexico and Colorado

USGS Publications Warehouse

Ridgley, J.L.; Condon, S.M.; Hatch, J.R.

2013-01-01

Four assessment units (AU) were defined in the Fruitland TPS. Of the four AUs, one consists of conventional gas accumulations and the other three are continuous-type gas accumulations: Tertiary Conventional Gas AU, Pictured Cliffs Continuous Gas AU, Basin Fruitland Coalbed Gas (CBG) AU, and Fruitland Fairway CBG AU. No oil resources that have the potential for additions to reserves in the next 30 years were estimated for this TPS. Gas resources that have the potential for additions to reserves in the next 30 years are estimated at a mean of 29.3 trillion cubic feet of gas (TCFG). Of this amount, 23.58 TCFG will come from coal-bed gas accumulations and 83.1 percent of this total is estimated to come from the Basin Fruitland CBG AU. The remaining 5.72 TCFG is allocated to continuous-type gas accumulations (5.64 TCFG) and conventional gas accumulations (0.08 TCFG). Although the Fruitland Fairway CBG AU has produced the most significant amount of coal-bed gas to date, the area of the AU is limited. New potentially productive wells will come from infill drilling, and the number of these wells will be limited by effective drainage area. Total natural gas liquids (NGL) that have the potential for additions to reserves in the next 30 years are estimated at a mean of 17.76 million barrels. Of this amount, 16.92 million barrels will come from the Pictured Cliffs Continuous Gas AU and the remainder from the Tertiary Conventional Gas AU.

Solubility of gold in oxidized, sulfur-bearing fluids at 500-850 °C and 200-230 MPa: A synthetic fluid inclusion study

NASA Astrophysics Data System (ADS)

Guo, Haihao; Audétat, Andreas; Dolejš, David

2018-02-01

Although Au solubility in magmatic-hydrothermal fluids has been investigated by numerous previous studies, there is a dearth of data on oxidized (log fO2 > FMQ+2.5; FMQ - fayalite-magnetite-quartz buffer), sulfur-bearing fluids such as those that formed porphyry Cu-Au (-Mo) deposits. We performed experiments to constrain the effects of fluid salinity, HCl content, sulfur content, fO2 and temperature on Au solubility in such oxidized, sulfur-bearing fluids. For this purpose, small aliquots of fluids equilibrated with Au metal were trapped at high pressure and temperature in the form of synthetic fluid inclusions in quartz and were subsequently analyzed by LA-ICP-MS. Additionally, Raman spectra were collected from quartz-hosted fluid inclusions at up to 600 °C to help to identify the nature of dissolved gold and sulfur species. Gold solubility was found to be affected most strongly by the HCl content of the fluid, followed by fO2, fluid salinity and temperature. Compared to these factors the sulfur content of the fluid has relatively little influence. At 600 °C and 100 MPa, fluids with geologically realistic HCl contents (∼1.1 wt%) and salinities (7-50 wt% NaClequiv) dissolve ∼1000-3000 ppm Au at oxygen fugacities controlled by the magnetite-hematite buffer. At even more oxidized conditions (three log units above the hematite-magnetite fO2 buffer), HCl-, NaCl- and H2SO4-rich fluids can dissolve up to 5 wt% Au at 800 °C and 200 MPa. The observed Au solubility trends are controlled by HCl0 species in the Na-H-Cl-SO4 fluid and are quantitatively reproduced by existing thermodynamic data for Au-Cl complexes. In all experiments, AuCl0 and AuCl2- species are predicted to occur in comparable although variable concentrations, and account for more than 95% of Au solutes. Natural, high-temperature (>500 °C) brine inclusions from porphyry Cu-Au (-Mo) deposits contain significantly less Au than gold-saturated brines that were synthesized experimentally, implying that the natural brines were Au-undersaturated. Consequently, gold grades in Au-rich porphyries were not controlled by the precipitation of native Au, but rather by factors that caused the precipitation of Au-bearing hydrothermal sulfides such as bornite.

Multitechnique characterization of oligo(ethylene glycol) functionalized gold nanoparticles.

PubMed

Rafati, Ali; Shard, Alexander G; Castner, David G

2016-11-09

Gold nanoparticles (AuNPs) with average diameters of ∼14 and ∼40 nm, as well as flat gold coated silicon wafers, were functionalized with oligo ethylene glycol (OEG) terminated 1-undecanethiol (HS-CH 2 ) 11 self-assembled monolayers (SAMs). Both hydroxyl [(OEG) 4 OH] and methoxy [(OEG) 4 OMe] terminated SAMs were prepared. The AuNPs were characterized with transmission electron microscopy (TEM), time of flight secondary ion mass spectrometry (ToF-SIMS), x-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier infrared spectroscopy (ATR-FTIR), and low-energy ion scattering (LEIS). These studies provided quantitative information about the OEG functionalized AuNPs. TEM showed the 14 nm AuNPs were more spherical and had a narrower size distribution than the 40 nm AuNPs. ToF-SIMS clearly differentiated between the two OEG SAMs based on the C 3 H 7 O + peak attributed to the methoxy group in the OMe terminated SAMs as well as the different masses of the [Au + M] - ion (M = mass of the thiol molecule) from each type of SAM. Overlayer/substrate ratios quantitatively determined with XPS show a greater proportion of OEG units at the surface of 40 nm AuNPs compared to the 14 nm AuNPs. ATR-FTIR suggested the C11 backbone of the two SAMs on both AuNPs are similar and crystalline, but the OEG head groups are more crystalline on the 40 nm AuNPs compared to the 14 nm AuNPs. This indicated a better ordered SAM present at the surface of the larger, more irregular particles due to greater ordering of the OEG groups. This was consistent with the XPS and LEIS results, which showed a 30% thicker SAM was formed on the 40 nm AuNPs compared to the 14 nm AuNPs. The OH or OMe functionality did not have a significant effect on the ordering and thickness of the OEG SAMs.

Relative humidity sensor based on surface plasmon resonance of D-shaped fiber with polyvinyl alcohol embedding Au grating

NASA Astrophysics Data System (ADS)

Yan, Haitao; Han, Daofu; Li, Ming; Lin, Bo

2017-01-01

This paper presents the design, fabrication, and characterization of a D-shaped fiber coated with polyvinyl alcohol (PVA) embedding an Au grating-based relative humidity (RH) sensor. The Au grating is fabricated on a D-shaped fiber to match the wave-vector and excite the surface plasmon, and the PVA is embedded in the Au grating as a sensitive cladding film. The refractive index of PVA changes with the ambient humidity. Measurements in a controlled environment show that the RH sensor can achieve a sensitivity of 5.4 nm per relative humidity unit in the RH range from 0% to 70% RH. Moreover, the surface plasmon resonance can be realized and used for RH sensing at the C band of optical fiber communication instead of the visible light band due to the metallic grating microstructure on the D-shaped fiber.

Exoplanet detection. A terrestrial planet in a ~1-AU orbit around one member of a ~15-AU binary.

PubMed

Gould, A; Udalski, A; Shin, I-G; Porritt, I; Skowron, J; Han, C; Yee, J C; Kozłowski, S; Choi, J-Y; Poleski, R; Wyrzykowski, Ł; Ulaczyk, K; Pietrukowicz, P; Mróz, P; Szymański, M K; Kubiak, M; Soszyński, I; Pietrzyński, G; Gaudi, B S; Christie, G W; Drummond, J; McCormick, J; Natusch, T; Ngan, H; Tan, T-G; Albrow, M; DePoy, D L; Hwang, K-H; Jung, Y K; Lee, C-U; Park, H; Pogge, R W; Abe, F; Bennett, D P; Bond, I A; Botzler, C S; Freeman, M; Fukui, A; Fukunaga, D; Itow, Y; Koshimoto, N; Larsen, P; Ling, C H; Masuda, K; Matsubara, Y; Muraki, Y; Namba, S; Ohnishi, K; Philpott, L; Rattenbury, N J; Saito, To; Sullivan, D J; Sumi, T; Suzuki, D; Tristram, P J; Tsurumi, N; Wada, K; Yamai, N; Yock, P C M; Yonehara, A; Shvartzvald, Y; Maoz, D; Kaspi, S; Friedmann, M

2014-07-04

Using gravitational microlensing, we detected a cold terrestrial planet orbiting one member of a binary star system. The planet has low mass (twice Earth's) and lies projected at ~0.8 astronomical units (AU) from its host star, about the distance between Earth and the Sun. However, the planet's temperature is much lower, <60 Kelvin, because the host star is only 0.10 to 0.15 solar masses and therefore more than 400 times less luminous than the Sun. The host itself orbits a slightly more massive companion with projected separation of 10 to 15 AU. This detection is consistent with such systems being very common. Straightforward modification of current microlensing search strategies could increase sensitivity to planets in binary systems. With more detections, such binary-star planetary systems could constrain models of planet formation and evolution. Copyright © 2014, American Association for the Advancement of Science.

Geology and assessment of undiscovered oil and gas resources of the Laptev Sea Shelf Province, 2008

USGS Publications Warehouse

Klett, Timothy; Pitman, Janet K.; Moore, Thomas E.; Gautier, Donald L.

2017-12-21

The U.S. Geological Survey (USGS) recently assessed the potential for undiscovered oil and gas resources of the Laptev Sea Shelf Province as part of the 2008 Circum-Arctic Resource Appraisal (CARA) program. The province is situated in the Russian Federation and is located between the Taimyr Peninsula and the Novosibirsk (New Siberian) Islands. Three assessment units (AUs) were defined for this study: the West Laptev Grabens AU, the East Laptev Horsts AU, and the Anisin-Novosibirsk AU, two of which were assessed for undiscovered, technically recoverable resources. The East Laptev Horsts AU was not quantitatively assessed. The estimated mean volumes of undiscovered oil and gas for the Laptev Sea Shelf Province are approximately 3 billion barrels of crude oil, 32 trillion cubic feet of natural gas, and <1 billion barrels of natural gas liquids, all north of the Arctic Circle.

Porous silicon-based direct hydrogen sulphide fuel cells.

PubMed

Dzhafarov, T D; Yuksel, S Aydin

2011-10-01

In this paper, the use of Au/porous silicon/Silicon Schottky type structure, as a direct hydrogen sulphide fuel cell is demonstrated. The porous silicon filled with hydrochlorid acid was developed as a proton conduction membrane. The Au/Porous Silicon/Silicon cells were fabricated by first creating the porous silicon layer in single-crystalline Si using the anodic etching under illumination and then deposition Au catalyst layer onto the porous silicon. Using 80 mM H2S solution as fuel the open circuit voltage of 0.4 V was obtained and maximum power density of 30 W/m2 at room temperature was achieved. These results demonstrate that the Au/Porous Silicon/Silicon direct hydrogen sulphide fuel cell which uses H2S:dH2O solution as fuel and operates at room temperature can be considered as the most promising type of low cost fuel cell for small power-supply units.

A facile approach for reducing the working voltage of Au/TiO2/Au nanostructured memristors by enhancing the local electric field

NASA Astrophysics Data System (ADS)

Arab Bafrani, Hamidreza; Ebrahimi, Mahdi; Bagheri Shouraki, Saeed; Moshfegh, Alireza Z.

2018-01-01

Memristor devices have attracted tremendous interest due to different applications ranging from nonvolatile data storage to neuromorphic computing units. Exploring the role of surface roughness of the bottom electrode (BE)/active layer interface provides useful guidelines for the optimization of the memristor switching performance. This study focuses on the effect of surface roughness of the BE electrode on the switching characteristics of Au/TiO2/Au three-layer memristor devices. An optimized wet-etching treatment condition was found to modify the surface roughness of the Au BE where the measurement results indicate that the roughness of the Au BE is affected by both duration time and solution concentrations of the wet-etching process. Then we fabricated arrays of TiO2-based nanostructured memristors sandwiched between two sets of cross-bar Au electrode lines (junction area 900 μm2). The results revealed a reduction in the working voltages in current-voltage characteristic of the device performance when increasing the surface roughness at the Au(BE)/TiO2 active layer interface. The set voltage of the device (Vset) significantly decreased from 2.26-1.93 V when we increased the interface roughness from 4.2-13.1 nm. The present work provides information for better understanding the switching mechanism of titanium-dioxide-based devices, and it can be inferred that enhancing the roughness of the Au BE/TiO2 active layer interface leads to a localized non-uniform electric field distribution that plays a vital role in reducing the energy consumption of the device.

Synthesis and energetics of gold nanoclusters tailored by interfacial bonding structure

NASA Astrophysics Data System (ADS)

Tang, Zhenghua

In addition to the well known quantum confinement effects resulted from size and shape, interfacial bond structure is another factor, affecting the properties of the nanomaterial that is rarely studied. Inspired by the "Au-S-Au" staple motif discovered from the crystal structure of monothiol protected Au102 nanocluster (Science, 2007, 318, 430), dithiol molecules (e.g. 1, 2-dithiol, 1, 4-dithiol, etc.) with molecular structural constraint have been employed to create dithiolate protected clusters or mixed monothiolate and dithiolate protected clusters. The structure and properties of the Au clusters are expected to change due to two effects: The entropy gain of dithiol over monothiol protection and the constraint to the formation of the thiol bridging motif. DMPS (1, 2-dithiol molecule) stabilized clusters with characteristic absorption bands have been obtained, and characterized by multiple techniques. Monolayer reaction on gold core surface between the monothiol tiopronin and dithiol DMPS has been performed, and the mechanism has been probed. Mixed phenylethanethiolate and durene-dithiolate (1, 4-dithiol molecule) protected Au130 clusters with rich electrochemical features have been created, and the optical and electrochemical energetics have been successfully correlated based on core and core-ligand energy states. Furthermore, the impact of 1, 4-dithiolate-Au bonding on the near infrared luminescence has been studied. INDEX WORDS: Au MPCs, Staple motif, DMPS, Au DTCs, Au4, Tiopronin, Monolayer reaction, Durene-DT, Au MTCs, Au130, Optical energetic, Electrochemistry, Near infrared luminescence, 1, 4-Dithiolate-Au bonding.

First Results on High-spin States in ^179Au

NASA Astrophysics Data System (ADS)

Mueller, W. F.; Bingham, C. R.; Reviol, W.; Riedinger, L. L.; Smith, B. H.; Wauters, J.; Ahmad, I.; Amro, H. A.; Blumenthal, D. J.; Carpenter, M. P.; Davids, C. N.; Fischer, S. M.; Hackman, G.; Henderson, D. J.; Janssens, R. V. F.; Khoo, T. L.; Lauritsen, T.; Lister, C. J.; Nisius, D. T.; Seweryniak, D.; Ma, W. C.

1996-05-01

High-spin states in ^179Au were studied for the first time in two experiments at the Argonne uc(atlas) facility. The ^144Sm(^40Ar,p4n)^179Au reaction at 207 MeV was used for the first experiment and ^124Te(^58Ni,p2n)^179Au at 255 MeV in the second. The setup in the first experiment consisted of the Fragment Mass Analyzer (uc(fma)) plus Parallel Plate Avalanche Counter (uc(ppac)) system and 10 Compton-suppressed Ge detectors (CSG's). From this run, several transitions from the yrast bands were established. The latter experiment utilized the uc(fma) + uc(ppac) system in conjunction with the uc(aye-ball) array of 19 Ge detectors (eight >70% efficient CSG's, nine 25% efficient CSG's, and two LEPS; one with Compton suppression) and a double sided silicon strip detector (uc(dssd).) The results from these experiments, including a level scheme, will be presented and discussed.

The electronic structure of Au25 clusters: between discrete and continuous

NASA Astrophysics Data System (ADS)

Katsiev, Khabiboulakh; Lozova, Nataliya; Wang, Lu; Sai Krishna, Katla; Li, Ruipeng; Mei, Wai-Ning; Skrabalak, Sara E.; Kumar, Challa S. S. R.; Losovyj, Yaroslav

2016-08-01

Here, an approach based on synchrotron resonant photoemission is employed to explore the transition between quantization and hybridization of the electronic structure in atomically precise ligand-stabilized nanoparticles. While the presence of ligands maintains quantization in Au25 clusters, their removal renders increased hybridization of the electronic states in the vicinity of the Fermi level. These observations are supported by DFT studies.Here, an approach based on synchrotron resonant photoemission is employed to explore the transition between quantization and hybridization of the electronic structure in atomically precise ligand-stabilized nanoparticles. While the presence of ligands maintains quantization in Au25 clusters, their removal renders increased hybridization of the electronic states in the vicinity of the Fermi level. These observations are supported by DFT studies. Electronic supplementary information (ESI) available: Experimental details including chemicals, sample preparation, and characterization methods. Computation techniques, SV-AUC, GIWAXS, XPS, UPS, MALDI-TOF, ESI data of Au25 clusters. See DOI: 10.1039/c6nr02374f

Charging and exciton-mediated decharging of metal nanoparticles in organic semiconductor matrices

NASA Astrophysics Data System (ADS)

Ligorio, Giovanni; Vittorio Nardi, Marco; Christodoulou, Christos; Florea, Ileana; Monteiro, Nicolas-Crespo; Ersen, Ovidiu; Brinkmann, Martin; Koch, Norbert

2014-04-01

Gold nanoparticles (Au-NPs) were deposited on the surface of n- and p-type organic semiconductors to form defined model systems for charge storage based electrically addressable memory elements. We used ultraviolet photoelectron spectroscopy to study the electronic properties and found that the Au-NPs become positively charged because of photoelectron emission, evidenced by spectral shifts to higher binding energy. Upon illumination with light that can be absorbed by the organic semiconductors, dynamic charge neutrality of the Au-NPs could be re-established through electron transfer from excitons. The light-controlled charge state of the Au-NPs could add optical addressability to memory elements.

A gold nanocluster-based fluorescent probe for simultaneous pH and temperature sensing and its application to cellular imaging and logic gates.

PubMed

Wu, Yun-Tse; Shanmugam, Chandirasekar; Tseng, Wei-Bin; Hiseh, Ming-Mu; Tseng, Wei-Lung

2016-06-07

Metal nanocluster-based nanomaterials for the simultaneous determination of temperature and pH variations in micro-environments are still a challenge. In this study, we develop a dual-emission fluorescent probe consisting of bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) and fluorescein-5-isothiocyanate (FITC) as temperature- and pH-responsive fluorescence signals. Under single wavelength excitation the FITC/BSA-AuNCs exhibited well-separated dual emission bands at 525 and 670 nm. When FITC was used as a reference fluorophore, FITC/BSA-AuNCs showed a good linear response over the temperature range 1-71 °C and offered temperature-independent spectral shifts, temperature accuracy, activation energy, and reusability. The possible mechanism for high temperature-induced fluorescence quenching of FITC/BSA-AuNCs could be attributed to a weakening of the Au-S bond, thereby lowering the charge transfer from BSA to AuNCs. Additionally, the pH- and temperature-responsive properties of FITC/BSA-AuNCs allow simultaneous temperature sensing from 21 to 41 °C (at intervals of 5 °C) and pH from 6.0 to 8.0 (at intervals of 0.5 pH unit), facilitating the construction of two-input AND logic gates. Three-input AND logic gates were also designed using temperature, pH, and trypsin as inputs. The practicality of using FITC/BSA-AuNCs to determine the temperature and pH changes in HeLa cells is also validated.

Evaluation of lactic acid bacterium fermentation products and food-grade chemicals to control Listeria monocytogenes in blue crab (Callinectes sapidus) meat.

PubMed Central

Degnan, A J; Kaspar, C W; Otwell, W S; Tamplin, M L; Luchansky, J B

1994-01-01

Fresh blue crab (Callinectes sapidus) meat was obtained from retail markets in Florida and sampled for viable Listeria monocytogenes. The pathogen was found in crabmeat in three of four different lots tested by enrichment and at levels of 75 CFU/g in one of the same four lots by direct plating. Next, crabmeat was steam sterilized, inoculated with a three-strain mixture of L. monocytogenes (ca. 5.5 log10 CFU/g), washed with various lactic acid bacterium fermentation products (2,000 to 20,000 arbitrary units [AU]/ml of wash) or food-grade chemicals (0.25 to 4 M), and stored at 4 degrees C. Counts of the pathogen remained relatively constant in control samples during storage for 6 days, whereas in crabmeat washed with Perlac 1911 or MicroGard (10,000 to 20,000 AU), numbers initially decreased (0.5 to 1.0 log10 unit/g) but recovered to original levels within 6 days. Numbers of L. monocytogenes cells decreased 1.5 to 2.7 log10 units/g of crabmeat within 0.04 day when washed with 10,000 to 20,000 AU of Alta 2341, enterocin 1083, or Nisin per ml. Thereafter, counts increased 0.5 to 1.6 log10 units within 6 days. After washing with food-grade chemicals, modest reductions (0.4 to 0.8 log10 unit/g) were observed with sodium acetate (4 M), sodium diacetate (0.5 or 1 M), sodium lactate (1 M), or sodium nitrite (1.5 M). However, Listeria counts in crabmeat washed with 2 M sodium diacetate decreased 2.6 log10 units/g within 6 days. In addition, trisodium phosphate reduced L. monocytogenes counts from 1.7 (0.25 M) to > 4.6 (1 M) log10 units/g within 6 days.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7944362

Metal adsorption on monolayer blue phosphorene: A first principles study

NASA Astrophysics Data System (ADS)

Khan, Imran; Son, Jicheol; Hong, Jisang

2018-01-01

We investigated the electronic structure, adsorption energies, magnetic properties, dipole moment and work function of metal adatoms (Mg, Cr, Mo, Pd, Pt, and Au) adsorption on a blue phosphorene monolayer. For Mg, Pt and Au metals, the most stable state was found in hollow site while for Cr, Mo and Pd metals we found an adsorption in valley site. We suggest that the Pd and Pt atoms prefer 2D growth mode while the Mg, Cr, Mo and Au atoms prefer 3D island growth mode on monolayer phosphorene. The electronic band structures and magnetic properties were dependent on the doping site and dopant materials. For instance, the semiconducting features were preserved in Mg, Pd, Pt, and Au doped systems. However, the Cr and Mo doped systems displayed half-metallic band structures. The total magnetic moment of 4.05, 2.0 and 0.77 μB /impurity atom were obtained in Cr, Mo and Au doped systems whereas the Mg, Pd and Pt doped systems remained nonmagnetic. We also investigated the magnetic interaction between two transition metal impurities. We observed ferromagnetic coupling between two transition metal impurities in Cr and Mo doped systems while the Au doped system displayed almost degenerated magnetic state. For Mg, Cr, and Mo adsorptions, we found relatively large values of dipole moments compared to those in the Pd, Pt and Au adsorptions. This resulted in a significant suppression of the work function in Mg, Cr and Mo adsorptions. Overall, adsorption can tune the physical and magnetic properties of phosphorene monolayer.

Irradiation response and stability of nanoporous materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Engang; Wang, Yongqiang; Serrano De Caro, Magdalena

2012-08-28

Nanoporous materials consist of a regular organic or inorganic framework supporting a regular, porous structure. Pores are by definition roughly in the nanometre range, that is between 0.2 nm and 100 nm. Nanoporous materials can be subdivided into 3 categories (IUPAC): (1) Microporous materials - 0.2-2 nm; (2) Mesoporous materials - 2-50 nm; and (3) Macroporous materials - 50-1000 nm. np-Au foams were successfully synthesized by de-alloying process. np-Au foams remain porous structure after Ne ion irradiation to 1 dpa. Stacking Fault Tetrahedra (SFTs) were observed in RT irradiated np-Au foams under the highest and intermediate fluxes, but not undermore » the lowest flux. SFTs were not observed in LNT irradiated np-Au foams under all fluxes. The vacancy diffusivity in Au at RT is high enough so that the vacancies have enough time to agglomerate and then collapse to form SFTs. The high ion flux creates more damage per unit time; vacancies don't have enough time to diffuse or recombine. As a result, SFTs were formed at high ion fluxes.« less

Geology and Assessment of Undiscovered Oil and Gas Resources of the East Barents Basins Province and the Novaya Zemlya Basins and Admiralty Arch Province, 2008

USGS Publications Warehouse

Klett, Timothy R.; Moore, Thomas E.; Gautier, D.L.

2017-11-15

The U.S. Geological Survey (USGS) recently assessed the potential for undiscovered petroleum resources of the East Barents Basins Province and the Novaya Zemlya Basins and Admiralty Arch Province as part of its Circum-Arctic Resource Appraisal. These two provinces are situated northeast of Scandinavia and the northwestern Russian Federation, on the Barents Sea Shelf between Novaya Zemlya to the east and the Barents Platform to the west. Three assessment units (AUs) were defined in the East Barents Basins Province for this study: the Kolguyev Terrace AU, the South Barents and Ludlov Saddle AU, and the North Barents Basin AU. A fourth AU, defined as the Novaya Zemlya Basins and Admiralty Arch AU, coincides with the Novaya Zemlya Basins and Admiralty Arch Province. These four AUs, all lying north of the Arctic Circle, were assessed for undiscovered, technically recoverable resources, resulting in total estimated mean volumes of ~7.4 billion barrels of crude oil, 318 trillion cubic feet (TCF) of natural gas, and 1.4 billion barrels of natural-gas liquids.

Assessment of Appalachian basin oil and gas resources: Utica-Lower Paleozoic Total Petroleum System: Chapter G.10 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

USGS Publications Warehouse

Ryder, Robert T.; Ruppert, Leslie F.; Ryder, Robert T.

2014-01-01

Both conventional oil and gas resources and continuous (unconventional) gas resources are present in the UticaLower Paleozoic TPS. Conventional oil and gas resources in the Utica-Lower Paleozoic TPS were assessed by the U.S. Geological Survey (USGS) in 2002 in the following assessment units (AU): (1) the Lower Paleozoic Carbonates in Thrust Belt AU, (2) the Knox Unconformity AU, (3) the Black River-Trenton Hydrothermal Dolomite AU, and (4) the Lockport Dolomite AU. The total estimated undiscovered oil and gas resources for these four AUs, at a mean value, was about 46 million barrels of oil (MMBO) and about 3 trillion cubic feet of gas (TCFG), respectively. In contrast, continuous (unconventional) gas resources in the TPS were assessed by the USGS in 2002 in four AUs associated with the “Clinton” sandstone, Medina sandstone, Medina Group sandstones, Tuscarora Sandstone, and sandstones in the Queenston Shale. The total estimated undiscovered gas for these four AUs, at a mean value, was about 26.8 TCFG. A hypothetical Utica Shale AU for oil(?) and continuous gas is identified in this report. In 2012, the Utica Shale was recognized by the USGS as a continuous AU and was assessed by Kirschbaum and others (2012).

The role of charge transfer in the oxidation state change of Ce atoms in the TM13-CeO2(111) systems (TM = Pd, Ag, Pt, Au): a DFT + U investigation.

PubMed

Tereshchuk, Polina; Freire, Rafael L H; Ungureanu, Crina G; Seminovski, Yohanna; Kiejna, Adam; Da Silva, Juarez L F

2015-05-28

Despite extensive studies of transition metal (TM) clusters supported on ceria (CeO2), fundamental issues such as the role of the TM atoms in the change in the oxidation state of Ce atoms are still not well understood. In this work, we report a theoretical investigation based on static and ab initio molecular dynamics density functional theory calculations of the interaction of 13-atom TM clusters (TM = Pd, Ag, Pt, Au) with the unreduced CeO2(111) surface represented by a large surface unit cell and employing Hubbard corrections for the strong on-site Coulomb correlation in the Ce f-electrons. We found that the TM13 clusters form pyramidal-like structures on CeO2(111) in the lowest energy configurations with the following stacking sequence, TM/TM4/TM8/CeO2(111), while TM13 adopts two-dimensional structures at high energy structures. TM13 induces a change in the oxidation state of few Ce atoms (3 of 16) located in the topmost Ce layer from Ce(IV) (itinerant Ce f-states) to Ce(III) (localized Ce f-states). There is a charge flow from the TM atoms to the CeO2(111) surface, which can be explained by the electronegativity difference between the TM (Pd, Ag, Pt, Au) and O atoms, however, the charge is not uniformly distributed on the topmost O layer due to the pressure induced by the TM13 clusters on the underlying O ions, which yields a decrease in the ionic charge of the O ions located below the cluster and an increase in the remaining O ions. Due to the charge flow mainly from the TM8-layer to the topmost O-layer, the charge cannot flow from the Ce(IV) atoms to the O atoms with the same magnitude as in the clean CeO2(111) surface. Consequently, the effective cationic charge decreases mainly for the Ce atoms that have a bond with the O atoms not located below the cluster, and hence, those Ce atoms change their oxidation state from IV to III. This increases the size of the Ce(III) compared with the Ce(IV) cations, which builds-in a strain within the topmost Ce layer, and hence, also affecting the location of the Ce(III) cations and the structure of the TM13 clusters.

An experimental study of Au removal from solution by non-metabolizing bacterial cells and their exudates

NASA Astrophysics Data System (ADS)

Kenney, Janice P. L.; Song, Zhen; Bunker, Bruce A.; Fein, Jeremy B.

2012-06-01

In this study, we examine the initial interactions between aqueous Au(III)-hydroxide-chloride aqueous complexes and bacteria by measuring the effects of non-metabolizing cells on the speciation and distribution of Au. We conducted batch Au(III) removal experiments, measuring the kinetics and pH dependence of Au removal, and tracking valence state transformations and binding environments using XANES spectroscopy. These experiments were conducted using non-metabolizing cells of Bacillus subtilis or Pseudomonas putida suspended in a 5 ppm Au(III)-(hydroxide)-chloride starting solution of 0.1 M NaClO4 to buffer ionic strength. Both bacterial species removed greater than 85% of the Au from solution after 2 h of exposure time below approximately pH 5. Above pH 5, the extent of Au removed from solution decreased with increasing pH, with less than approximately 10% removal of Au from solution above pH 7.5. Kinetics experiments indicated that the Au removal with both bacterial species was rapid at pH 3, and slowed with increasing pH. Reversibility experiments demonstrated that (1) once the Au was removed from solution, adjusting 35 the pH alone did not remobilize the Au into solution and (2) the presence of cysteine in solution in the reversibility experiments caused Au to desorb, suggesting that the Au was not internalized within the bacterial cells. Our results suggest that Au removal occurs as a two-step pH-dependent adsorption reduction process. The speciation of the aqueous Au and the bacterial surface appears to control the rate of Au removal from solution. Under low pH conditions, the cell walls are only weakly negatively charged and aqueous Au complexes adsorb readily and rapidly. With increasing pH, the cell wall becomes more negatively charged, slowing adsorption significantly. The XANES data demonstrate that the reduction of Au(III) by bacterial exudates is slower and less extensive than the reduction observed in the bacteria-bearing systems, and we conclude that Au reduction occurs most rapidly and extensively upon interaction with cell wall functional groups.

Turning the ECOWAS Standby Force in a More Proactive Force: An Analysis of Past Interventions to Assess Key Deployment Hindrances

DTIC Science & Technology

2015-06-12

collective security mechanisms, almost from nothing, in less than 20 years. Since 2003, the AU has deployed missions to Burundi (AMIB), Sudan/ Darfur (AMIS...deployment of AU missions in Somalia, Darfur and in the CAR. ECOWAS, despite the absence of a formalized MOU between its member states, is...proven somewhat effective in eastern Africa where the AU deployed a mission first in Darfur and then in Somalia, which the UN later undertook. However

Cross-sectional characterization of the dewetting of a Au/Ni bilayer film.

PubMed

Cen, Xi; Thron, Andrew M; Zhang, Xinming; van Benthem, Klaus

2017-07-01

The solid state dewetting of Au/Ni bilayer films was investigated by cross-sectional transmission electron microscopy techniques, including energy-dispersive X-ray spectroscopy, electron energy-loss spectroscopy and precession electron diffraction. After annealing under high vacuum conditions the early stage of film agglomeration revealed significant changes in film morphology and chemical distribution. Both Au and Ni showed texturing. Despite the initial deposition sequence of the as-deposited Au/Ni/SiO 2 /Si interface structure, the majority of the metal/SiO 2 interface was Au/SiO 2 after annealing at 675°C for 1h. Void nucleation was predominantly observed at Au/Ni/SiO 2 triple junctions, rather than grain boundary grooving at free surface of the metal film. Detailed cross-sectional characterization reveals that the Au/Ni interface in addition to small amounts of metal alloying strongly affects film break-up and agglomeration kinetics. The formation of Au/SiO 2 interface sections is found to be energetically preferred over Ni/SiO 2 due to compressive stress in the as-deposited Ni layer. Void nucleation is observed at the film/substrate interface, while the formation of voids at Ni/Au phase boundaries inside the metal film is caused by the Kirkendall effect. Copyright © 2016 Elsevier B.V. All rights reserved.

Dewetting process of Au films on SiO2 nanowires: Activation energy evaluation

NASA Astrophysics Data System (ADS)

Ruffino, F.; Grimaldi, M. G.

2015-05-01

SiO2 nanowires gain scientific and technological interest in application fields ranging from nano-electronics, optics and photonics to bio-sensing. Furthermore, the SiO2 nanowires chemical and physical properties, and so their performances in devices, can be enhanced if decorated by metal nanoparticles (such Au) due to local plasmonic effects. In the present paper, we propose a simple, low-cost and high-throughput three-steps methodology for the mass-production of Au nanoparticles coated SiO2 nanowires. It is based on (1) production of the SiO2 nanowires on Si surface by solid state reaction of an Au film with the Si substrate at high temperature; (2) sputtering deposition of Au on the SiO2 nanowires to obtain the nanowires coated by an Au film; and (3) furnace annealing processes to induce the Au film dewetting on the SiO2 nanowires surface. Using scanning electron microscopy analyses, we followed the change of the Au nanoparticles mean versus the annealing time extracting values for the characteristic activation energy of the dewetting process of the Au film on the SiO2 nanowires surface. Such a study can allow the tuning of the nanowires/nanoparticles sizes for desired technological applications.

Probing the Behaviors of Gold Nanorods in Metastatic Breast Cancer Cells Based on UV-vis-NIR Absorption Spectroscopy

PubMed Central

Zhang, Weiqi; Ji, Yinglu; Meng, Jie; Wu, Xiaochun; Xu, Haiyan

2012-01-01

In this work, behaviors of positively-charged AuNRs in a highly metastatic tumor cell line MDA-MB-231 are examined based on UV-vis-NIR absorption spectroscopy in combination with inductively coupled plasma mass spectrometry (ICP-MS), transmission electron microscopy (TEM) and dark-field microscopic observation. It is found that characteristic surface plasmon resonance (SPR) peaks of AuNRs can be detected using spectroscopic method within living cells that have taken up AuNRs. The peak area of transverse SPR band is shown to be proportionally related to the amount of AuNRs in the cells determined with ICP-MS, which suggests a facile and real time quantification method for AuNRs in living cells. The shape of longitudinal SPR band in UV-vis-NIR spectrum reflects the aggregation state of AuNRs in the cells during the incubation period, which is proved by TEM and microscopic observations. Experimental results reveal that AuNRs are internalized by the cells rapidly; the accumulation, distribution and aggregation of AuNRs in the cells compartments are time and dose dependent. The established spectroscopic analysis method can not only monitor the behaviors of AuNRs in living cells but may also be helpful in choosing the optimum laser stimulation wavelength for anti-tumor thermotherapy. PMID:22384113

Enhanced Catalytic Reduction of 4-Nitrophenol Driven by Fe3O4-Au Magnetic Nanocomposite Interface Engineering: From Facile Preparation to Recyclable Application

PubMed Central

Chen, Yue; Zhang, Yuanyuan; Kou, Qiangwei; Liu, Yang; Han, Donglai; Wang, Dandan; Sun, Yantao; Zhang, Yongjun; Wang, Yaxin; Lu, Ziyang; Chen, Lei; Yang, Jinghai; Xing, Scott Guozhong

2018-01-01

In this work, we report the enhanced catalytic reduction of 4-nitrophenol driven by Fe3O4-Au magnetic nanocomposite interface engineering. A facile solvothermal method is employed for Fe3O4 hollow microspheres and Fe3O4-Au magnetic nanocomposite synthesis via a seed deposition process. Complementary structural, chemical composition and valence state studies validate that the as-obtained samples are formed in a pure magnetite phase. A series of characterizations including conventional scanning/transmission electron microscopy (SEM/TEM), Mössbauer spectroscopy, magnetic testing and elemental mapping is conducted to unveil the structural and physical characteristics of the developed Fe3O4-Au magnetic nanocomposites. By adjusting the quantity of Au seeds coating on the polyethyleneimine-dithiocarbamates (PEI-DTC)-modified surfaces of Fe3O4 hollow microspheres, the correlation between the amount of Au seeds and the catalytic ability of Fe3O4-Au magnetic nanocomposites for 4-nitrophenol (4-NP) is investigated systematically. Importantly, bearing remarkable recyclable features, our developed Fe3O4-Au magnetic nanocomposites can be readily separated with a magnet. Such Fe3O4-Au magnetic nanocomposites shine the light on highly efficient catalysts for 4-NP reduction at the mass production level. PMID:29789457

Fabrication of quantum dot/silica core-shell particles immobilizing Au nanoparticles and their dual imaging functions

NASA Astrophysics Data System (ADS)

Kobayashi, Yoshio; Matsudo, Hiromu; Li, Ting-ting; Shibuya, Kyosuke; Kubota, Yohsuke; Oikawa, Takahiro; Nakagawa, Tomohiko; Gonda, Kohsuke

2016-03-01

The present work proposes preparation methods for quantum dot/silica (QD/SiO2) core-shell particles that immobilize Au nanoparticles (QD/SiO2/Au). A colloid solution of QD/SiO2 core-shell particles with an average size of 47.0 ± 6.1 nm was prepared by a sol-gel reaction of tetraethyl orthosilicate in the presence of the QDs with an average size of 10.3 ± 2.1 nm. A colloid solution of Au nanoparticles with an average size of 17.9 ± 1.3 nm was prepared by reducing Au3+ ions with sodium citrate in water at 80 °C. Introduction of amino groups to QD/SiO2 particle surfaces was performed using (3-aminopropyl)-triethoxysilane (QD/SiO2-NH2). The QD/SiO2/Au particles were fabricated by mixing the Au particle colloid solution and the QD/SiO2-NH2 particle colloid solution. Values of radiant efficiency and computed tomography for the QD/SiO2/Au particle colloid solution were 2.23 × 107 (p/s/cm2/sr)/(μW/cm2) at a QD concentration of 8 × 10-7 M and 1180 ± 314 Hounsfield units and an Au concentration of 5.4 × 10-2 M. The QD/SiO2/Au particle colloid solution was injected into a mouse chest wall. Fluorescence emitted from the colloid solution could be detected on the skin covering the chest wall. The colloid solution could also be X-ray-imaged in the chest wall. Consequently, the QD/SiO2/Au particle colloid solution was found to have dual functions, i.e., fluorescence emission and X-ray absorption in vivo, which makes the colloid solution suitable to function as a contrast agent for dual imaging processes.

Ultrafast Relaxation Dynamics of Au 38 (SC 2 H 4 Ph) 24 Nanoclusters and Effects of Structural Isomerism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Meng; Tian, Shubo; Zeng, Chenjie

Structural isomerism in nanoparticles has recently emerged as a new topic and stimulated research interest because the atomic structures of ultrasmall nanoparticles may have great impact on their fundamental properties and applications. We report the correlation between ultrafast relaxation dynamics and atomic structures of two isomers of thiolate-protected Au 38(SC 2H 4Ph) 24. The bi-icosahedral Au 38 (denoted as Au 38Q) with a Au 23 inner core in its atomic structure shows rapid decay (1.5 ps) followed by nanosecond relaxation to the ground state, whereas its structural isomer (Au 38T) exhibits similar relaxation processes, but the rapid decay is acceleratedmore » by ~50% (1.0 ps). The picosecond relaxations in both cases can be assigned to core–shell charge transfer or electronic rearrangement within the metal core. The acceleration of the fast decay in Au38T is ascribed to its unique core structure, which is made up of a mono-icosahedral Au 13 capped by a Au 12 tri-tetrahedron by sharing two atoms. Interestingly, coherent phonon emissions (25 cm –1 for Au 38Q, 27 and 60 cm –1 for Au 38T) are observed in both isomers with pumping in the NIR region. These results illustrate for the first time the importance of atomic structures in the photophysics of same sized gold nanoclusters.« less

Potential of Chilopsis Linearis for Gold Phytomining: Using XAS to Determine Gold Reduction And Nanoparticle Formation Within Plant Tissues

DOE Office of Scientific and Technical Information (OSTI.GOV)

E, Rodriguez; Parsons, J.G.; Peralta-Videa, J.R.

This study reports on the capability of the desert plant Chilopsis linearis (Cav.) Sweet (desert willow) to uptake gold (Au) from gold-enriched media at different plant-growth stages. Plants were exposed to 20, 40, 80, 160, and 320 mg Au L{sup -1} in agar-based growing media for 13, 18, 23, and 35 d. The Au content and oxidation state of Au in the plants were determined using an inductively coupled plasma/optical emission spectrometer (ICP/OES) and X-ray absorption spectroscopy (XAS), respectively. Gold concentrations ranging from 20 to 80 mg Au L{sup -1} did not significantly affect Chilopsis linearis plant growth. The concentrationmore » of gold in the plants increased as the age of the plant increased. The Au concentrations in leaves for the 20, 40, 80, and 160 mg Au L{sup -1} treatments were 32, 60, 62, and 179 mg Au kg{sup -1} dry weight mass, respectively, demonstrating the gold uptake capability of desert willow. The XAS data indicated that desert willow produced gold nanoparticles within plant tissues. Plants exposed to 160 mg Au L{sup -1} formed nanoparticles that averaged approximately 8, 35, and 18 in root, stem, and leaves, respectively. It was observed that the average size of the Au nanoparticles formed by the plants is related to the total Au concentration in tissues and their location in the plant.« less

Ultrafast Relaxation Dynamics of Au 38 (SC 2 H 4 Ph) 24 Nanoclusters and Effects of Structural Isomerism

DOE PAGES

Zhou, Meng; Tian, Shubo; Zeng, Chenjie; ...

2016-12-22

Structural isomerism in nanoparticles has recently emerged as a new topic and stimulated research interest because the atomic structures of ultrasmall nanoparticles may have great impact on their fundamental properties and applications. We report the correlation between ultrafast relaxation dynamics and atomic structures of two isomers of thiolate-protected Au 38(SC 2H 4Ph) 24. The bi-icosahedral Au 38 (denoted as Au 38Q) with a Au 23 inner core in its atomic structure shows rapid decay (1.5 ps) followed by nanosecond relaxation to the ground state, whereas its structural isomer (Au 38T) exhibits similar relaxation processes, but the rapid decay is acceleratedmore » by ~50% (1.0 ps). The picosecond relaxations in both cases can be assigned to core–shell charge transfer or electronic rearrangement within the metal core. The acceleration of the fast decay in Au38T is ascribed to its unique core structure, which is made up of a mono-icosahedral Au 13 capped by a Au 12 tri-tetrahedron by sharing two atoms. Interestingly, coherent phonon emissions (25 cm –1 for Au 38Q, 27 and 60 cm –1 for Au 38T) are observed in both isomers with pumping in the NIR region. These results illustrate for the first time the importance of atomic structures in the photophysics of same sized gold nanoclusters.« less

Communication Dependent Control of Multi-Vehicle Formations

DTIC Science & Technology

2016-05-11

On Maximizing the Second Smallest Eigen- value of a State-Dependent Graph Laplacian,” IEEE Transactions on Au- tomatic Control, vol. 51, no. 1, pp...Collective Motion With Limited Communication,” IEEE Transactions on Au- tomatic Control, vol. 53, no. 3, pp. 706–719, 2008. [Online]. Available: http

Fabrication and surface enhanced Raman scattering effect of centimeter level AgCuAu composite nanowires

NASA Astrophysics Data System (ADS)

Xu, Dapeng; Zhang, Song; Yang, Wei; Chen, Jian

2017-10-01

Centimeter level AgCuAu composite nanowires were prepared by a solid-state ionics method under a direct current electric field (DCEF) using fast ionic conductor RbAg4I5 films and vacuum thermal evaporation method. The surface morphology and chemical composition of the AuAgCu composite nanowires were characterized by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), respectively. Raman enhancement performance of the AgCuAu composite nanowires substrates was detected by Rhodamine 6G (R6G) aqueous solutions as probe molecules. Long-range order and short-range order AgCuAu composite nanowires with the length of 1 cm were prepared. The nanowires were bamboo-shaped with high surface roughness and the diameters of nanowires ranged from 60 to 100 nm. The molar ratio of Ag:Cu:Au in composite nanowires is 15:2:1. The intrinsic Raman peaks of 10-16 mol/L R6G at 612, 773, 1125, 1182, 1307, 1361, 1418, 1506, 1545, 1575, 1597, 1650 cm-1 are all present when AgCuAu composite nanowires were used as the SERS substrates.

Study of Doubly Charged Delta Baryons in Collisions of Copper Nuclei at the Relativistic Heavy Ion Collider

DTIC Science & Technology

2017-05-22

previous studies from proton on proton colli- sions and deuteron on gold nucleus collisions, as well as with model calculations, may provide deeper insight...designed to achieve target energies. Machines are also designed for different collision systems, such as Cu+Cu or Au+Au. This is one way to study ...charge states of delta baryons are minus one , zero, plus one , and plus two. For this project, we are studying the plus two charge state, commonly referred

Direct determination of oxidation state of gold deposits in metal-reducing bacterium Shewanella algae using X-ray absorption near-edge structure spectroscopy (XANES).

PubMed

Konishi, Yasuhiro; Tsukiyama, Takeshi; Saitoh, Norizoh; Nomura, Toshiyuki; Nagamine, Shinsuke; Takahashi, Yoshio; Uruga, Tomoya

2007-06-01

X-ray absorption near-edge structure spectroscopy (XANES) was successfully employed to determine the gold valence in the metal-reducing bacterium Shewanella algae after exposure to a 1 mM aqueous HAuCl4 solution for 10-120 min. XANES spectra revealed the oxidation state of gold in the bacterial cells to be Au(0) without any contribution from Au(III), demonstrating that S. algae cells can reduce AuCl4- ions to elemental gold. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis confirmed that gold nanoparticles 5-15 nm in size were deposited in the periplasmic space of the bacterial cells; a preferable, cell surface location for the easy recovery of biogenic nanoparticles.

The structural, electronic and optical properties of Au-ZnO interface structure from the first-principles calculation

NASA Astrophysics Data System (ADS)

Huo, Jin-Rong; Li, Lu; Cheng, Hai-Xia; Wang, Xiao-Xu; Zhang, Guo-Hua; Qian, Ping

2018-03-01

The interface structure, electronic and optical properties of Au-ZnO are studied using the first-principles calculation based on density functional theory (DFT). Given the interfacial distance, bonding configurations and terminated surface, we built the optimal interface structure and calculated the electronic and optical properties of the interface. The total density of states, partial electronic density of states, electric charge density and atomic populations (Mulliken) are also displayed. The results show that the electrons converge at O atoms at the interface, leading to a stronger binding of interfaces and thereby affecting the optical properties of interface structures. In addition, we present the binding energies of different interface structures. When the interface structure of Au-ZnO gets changed, furthermore, varying optical properties are exhibited.

Ligand-Enhanced Optical Response of Gold Nanomolecules and Its Fragment Projection Analysis: The Case of Au 30 (SR) 18

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sementa, Luca; Barcaro, Giovanni; Baseggio, Oscar

We investigate via first-principles simulations the optical absorption spectra of three different Au 30(SR) 18 monolayer-protected clusters (MPC): Au 30(StBu) 18, Au 30(SPh) 18, and Au 30(SPh-pNO 2) 18. Au 30(StBu) 18 is known in the literature, and its crystal structure is available. In contrast, Au 30(SPh) 18 and Au 30(SPh-pNO 2) 18 are two species that have been designed by replacing the tert-butyl organic residues of Au 30(StBu) 18 with aromatic ones so as to investigate the effects of ligand replacement on the optical response of Au nanomolecules. By analogy to a previously studied Au 23(SR)16– anionic species, despitemore » distinct differences in charge and chemical composition, a substantial ligand enhancement of the absorption intensity in the optical region is also obtained for the Au 30(SPh-pNO 2) 18 MPC. Furthermore, the use of conjugated aromatic ligands with properly chosen electron-withdrawing substituents and exhibiting steric hindrance so as to also achieve charge decompression at the surface is therefore demonstrated as a general approach to enhancing the MPC photoabsorption intensity in the optical region. In addition, we here subject the ligand-enhancement phenomenon to a detailed analysis based on the fragment projection of electronic excited states and on induced transition densities, leading to a better understanding of the physical origin of this phenomenon, thus opening avenues to its more precise control and exploitation.« less

Ligand-Enhanced Optical Response of Gold Nanomolecules and Its Fragment Projection Analysis: The Case of Au 30 (SR) 18

DOE PAGES

Sementa, Luca; Barcaro, Giovanni; Baseggio, Oscar; ...

2017-01-24

We investigate via first-principles simulations the optical absorption spectra of three different Au 30(SR) 18 monolayer-protected clusters (MPC): Au 30(StBu) 18, Au 30(SPh) 18, and Au 30(SPh-pNO 2) 18. Au 30(StBu) 18 is known in the literature, and its crystal structure is available. In contrast, Au 30(SPh) 18 and Au 30(SPh-pNO 2) 18 are two species that have been designed by replacing the tert-butyl organic residues of Au 30(StBu) 18 with aromatic ones so as to investigate the effects of ligand replacement on the optical response of Au nanomolecules. By analogy to a previously studied Au 23(SR)16– anionic species, despitemore » distinct differences in charge and chemical composition, a substantial ligand enhancement of the absorption intensity in the optical region is also obtained for the Au 30(SPh-pNO 2) 18 MPC. Furthermore, the use of conjugated aromatic ligands with properly chosen electron-withdrawing substituents and exhibiting steric hindrance so as to also achieve charge decompression at the surface is therefore demonstrated as a general approach to enhancing the MPC photoabsorption intensity in the optical region. In addition, we here subject the ligand-enhancement phenomenon to a detailed analysis based on the fragment projection of electronic excited states and on induced transition densities, leading to a better understanding of the physical origin of this phenomenon, thus opening avenues to its more precise control and exploitation.« less

A study on the imaging characteristics of Gold nanoparticles as a contrast agent in X-ray computed tomography

NASA Astrophysics Data System (ADS)

Mesbahi, Asghar; Famouri, Fatemeh; Ahar, Mohammad Johari; Ghaffari, Maryam Olade; Ghavami, Seyed Mostafa

2017-03-01

Aim: In the current study, some imaging characteristics of AuNPs were quantitatively analyzed and compared with two conventional contrast media (CM) including Iodine and Gadolinium by using of a cylindrical phantom. Methods: AuNPs were synthesized with the mean diameter of 16 nm and were equalized to the concentration of 0.5, 1, 2 and 4 mg/mL in the same volumes. A cylindrical phantom resembling the head and neck was fabricated and drilled to contain small tubes filled with Iodine, Gadolinium, and AuNPs as contrast media. The phantom was scanned in different exposure techniques and CT numbers of three studied contrast media inside test tubes were measured in terms of Hounsfield Unit (HU). The imaging parameters of the noise and contrast to noise ratios (CNR) were calculated for all studied CMs. Results: AuNPs showed 128% and 166% higher CT number in comparison with Iodine and Gadolinium respectively. Also, Iodine had a greater CT number than Gadolinium for the same exposure techniques and concentration. The maximum CT number for AuNPs and studied contrast materials was obtained at the highest mAs and the lowest tube potential. The maximum CT number were 1033±11 (HU) for AuNP, 565±10 (HU) for Iodine, 458±11 for Gadolinium. Moreover, the maximum CNRs of 433±117, 203±53, 145±37 were found for AuNPs, Iodine and Gadolinium respectively. Conclusion: The contrast agent based on AuNPs showed higher imaging quality in terms of contrast and noise relative to other iodine and gadolinium based contrast media in X-ray computed tomography. Application of the AuNPs as a contrast medium in x-ray CT is recommended.

Development of a High Performance Acousto-ultrasonic Scan System

NASA Technical Reports Server (NTRS)

Roth, D. J.; Martin, R. E.; Harmon, L. M.; Gyekenyesi, A. L.; Kautz, H. E.

2002-01-01

Acousto-ultrasonic (AU) interrogation is a single-sided nondestructive evaluation (NDE) technique employing separated sending and receiving transducers. It is used for assessing the microstructural condition/distributed damage state of the material between the transducers. AU is complementary to more traditional NDE methods such as ultrasonic c-scan, x-ray radiography, and thermographic inspection that tend to be used primarily for discrete flaw detection. Through its history, AU has been used to inspect polymer matrix composite, metal matrix composite, ceramic matrix composite, and even monolithic metallic materials. The development of a high-performance automated AU scan system for characterizing within-sample microstructural and property homogeneity is currently in a prototype stage at NASA. In this paper, a review of essential AU technology is given. Additionally, the basic hardware and software configuration, and preliminary results with the system, are described.

An intermetallic Au24Ag20 superatom nanocluster stabilized by labile ligands.

PubMed

Wang, Yu; Su, Haifeng; Xu, Chaofa; Li, Gang; Gell, Lars; Lin, Shuichao; Tang, Zichao; Häkkinen, Hannu; Zheng, Nanfeng

2015-04-08

An intermetallic nanocluster containing 44 metal atoms, Au24Ag20(2-SPy)4(PhC≡C)20Cl2, was successfully synthesized and structurally characterized by single-crystal analysis and density funtional theory computations. The 44 metal atoms in the cluster are arranged as a concentric three-shell Au12@Ag20@Au12 Keplerate structure having a high symmetry. For the first time, the co-presence of three different types of anionic ligands (i.e., phenylalkynyl, 2-pyridylthiolate, and chloride) was revealed on the surface of metal nanoclusters. Similar to thiolates, alkynyls bind linearly to surface Au atoms using their σ-bonds, leading to the formation of two types of surface staple units (PhC≡C-Au-L, L = PhC≡C(-) or 2-pyridylthiolate) on the cluster. The co-presence of three different surface ligands allows the site-specific surface and functional modification of the cluster. The lability of PhC≡C(-) ligands on the cluster was demonstrated, making it possible to keep the metal core intact while removing partial surface capping. Moreover, it was found that ligand exchange on the cluster occurs easily to offer various derivatives with the same metal core but different surface functionality and thus different solubility.

Cation-poor complex metallic alloys in Ba(Eu)–Au–Al(Ga) systems: Identifying the keys that control structural arrangements and atom distributions at the atomic level

DOE PAGES

Smetana, Volodymyr; Steinberg, Simon; Mudryk, Yaroslav; ...

2015-10-19

Four complex intermetallic compounds BaAu 6±xGa 6±y (x = 1, y = 0.9) (I), BaAu 6±xAl 6±y (x = 0.9, y = 0.6) (II), EuAu 6.2Ga 5.8 (III), and EuAu 6.1Al 5.9 (IV) have been synthesized, and their structures and homogeneity ranges have been determined by single crystal and powder X-ray diffraction. Whereas I and II originate from the NaZn 13-type structure (cF104–112, Fm3C), III (tP52, P4/nbm) is derived from the tetragonal Ce 2Ni 17Si 9-type, and IV (oP104, Pbcm) crystallizes in a new orthorhombic structure type. Both I and II feature formally anionic networks with completely mixed site occupationmore » by Au and triel (Tr = Al, Ga) atoms, while a successive decrease of local symmetry from the parental structures of I and II to III and, ultimately, to IV correlates with increasing separation of Au and Tr on individual crystallographic sites. Density functional theory-based calculations were employed to determine the crystallographic site preferences of Au and the respective triel element to elucidate reasons for the atom distribution (“coloring scheme”). Chemical bonding analyses for two different “EuAu 6Tr 6” models reveal maximization of the number of heteroatomic Au–Tr bonds as the driving force for atom organization. The Fermi levels fall in broad pseudogaps for both models allowing some electronic flexibility. Spin-polarized band structure calculations on the “EuAu 6Tr 6” models hint to singlet ground states for europium and long-range magnetic coupling for both EuAu 6.2Ga 5.8 (III) and EuAu 6.1Al 5.9 (IV). This is substantiated by experimental evidence because both compounds show nearly identical magnetic behavior with ferromagnetic transitions at T C = 6 K and net magnetic moments of 7.35 μB/f.u. at 2 K. As a result, the effective moments of 8.3 μB/f.u., determined from Curie–Weiss fits, point to divalent oxidation states for europium in both III and IV.« less

Evolution in the charge injection efficiency of evaporated Au contacts on a molecularly doped polymer

NASA Astrophysics Data System (ADS)

Ioannidis, Andronique; Facci, John S.; Abkowitz, Martin A.

1998-08-01

Injection efficiency from evaporated Au contacts on a molecularly doped polymer (MDP) system has been previously observed to evolve from blocking to ohmic over time. In the present article this contact forming phenomenon is analyzed in detail. The initially blocking nature of the Au contact is in contrast with that expected from the relative workfunctions of Au and of the polymer which suggest Au should inject holes efficiently. It is also in apparent contrast to a differently prepared interface of the same materials. The phenomenon is not unique to this interface, having been confirmed also for evaporated Ag and mechanically made liquid Hg contacts on the same MDP. The MDP is a disordered solid state solution of electroactive triarylamine hole transporting TPD molecules in a polycarbonate matrix. The trap-free hole-transport MDP provides a model system for the study of metal/polymer interfaces by enabling the use of a recently developed technique that gives a quantitative measure of contact injection efficiency. The technique combines field-dependent steady state injection current measurements at a contact under test with time-of-flight (TOF) mobility measurements made on the same sample. In the present case, MDP films were prepared with two top vapor-deposited contacts, one of Au (test contact) and one of Al (for TOF), and a bottom carbon-loaded polymer electrode which is known to be ohmic for hole injection. The samples were aged at various temperatures below the glass transition of the MDP (85 °C) and the evolution of current versus field and capacitance versus frequency behaviors are followed in detail over time and analyzed. Control measurements ensure that the evolution of the electrical properties is due to the Au/polymer interface behavior and not the bulk. All evaporated Au contacts eventually achieved ohmic injection. The evaporated Au/MDP interface was also investigated by transmission electron microscopy as a function of time and showed no evidence of Au interdiffusion in the MDP layer, remaining abrupt to within ˜10 Å over the course of the evolution in injection efficiency. Mechanisms related to Au penetration into the MDP are therefore unlikely. Rapid sequence data acquisition enabled the detection of two main processes in the injection evolution. The evolving injection efficiency is very well fit by two exponentials, enabling the characterization of time and temperature dependence of the evolution processes.

A nebula of gases from Io surrounding Jupiter.

PubMed

Krimigis, Stamatios M; Mitchell, Donald G; Hamilton, Douglas C; Dandouras, Jannis; Armstrong, Thomas P; Bolton, Scott J; Cheng, Andrew F; Gloeckler, George; Hsieh, K C; Keath, Edwin P; Krupp, Norbert; Lagg, Andreas; Lanzerotti, Louis J; Livi, Stefano; Mauk, Barry H; McEntire, Richard W; Roelof, Edmond C; Wilken, Berend; Williams, Donald J

2002-02-28

Several planetary missions have reported the presence of substantial numbers of energetic ions and electrons surrounding Jupiter; relativistic electrons are observable up to several astronomical units (au) from the planet. A population of energetic (>30[?]keV) neutral particles also has been reported, but the instrumentation was not able to determine the mass or charge state of the particles, which were subsequently labelled energetic neutral atoms. Although images showing the presence of the trace element sodium were obtained, the source and identity of the neutral atoms---and their overall significance relative to the loss of charged particles from Jupiter's magnetosphere---were unknown. Here we report the discovery by the Cassini spacecraft of a fast (>103[?]km[?]s-1) and hot magnetospheric neutral wind extending more than 0.5[?]au from Jupiter, and the presence of energetic neutral atoms (both hot and cold) that have been accelerated by the electric field in the solar wind. We suggest that these atoms originate in volcanic gases from Io, undergo significant evolution through various electromagnetic interactions, escape Jupiter's magnetosphere and then populate the environment around the planet. Thus a 'nebula' is created that extends outwards over hundreds of jovian radii.

25 CFR 700.711 - Grazing permits.

Code of Federal Regulations, 2010 CFR

2010-04-01

... OFFICE OF NAVAJO AND HOPI INDIAN RELOCATION COMMISSION OPERATIONS AND RELOCATION PROCEDURES New Lands... residency on the New Lands Range Unit of permit issue, and (4) Own livestock which graze on the range unit of permit issue. (c) Permits will be issued for a base of 80 SUYL (20 AU) and may not be divided or...

Real time acousto-ultrasonic NDE technique for monitoring damage in ceramic composites under dynamic loads

NASA Technical Reports Server (NTRS)

Tiwari, Anil

1995-01-01

Research effort was directed towards developing a near real-time, acousto-ultrasonic (AU), nondestructive evaluation (NDE) tool to study the failure mechanisms of ceramic composites. Progression of damage is monitored in real-time by observing the changes in the received AU signal during the actual test. During the real-time AU test, the AU signals are generated and received by the AU transducers attached to the specimen while it is being subjected to increasing quasi-static loads or cyclic loads (10 Hz, R = 1.0). The received AU signals for 64 successive pulses were gated in the time domain (T = 40.96 micro sec) and then averaged every second over ten load cycles and stored in a computer file during fatigue tests. These averaged gated signals are representative of the damage state of the specimen at that point of its fatigue life. This is also the first major attempt in the development and application of real-time AU for continuously monitoring damage accumulation during fatigue without interrupting the test. The present work has verified the capability of the AU technique to assess the damage state in silicon carbide/calcium aluminosilicate (SiC/CAS) and silicon carbide/ magnesium aluminosilicate (SiC/MAS) ceramic composites. Continuous monitoring of damage initiation and progression under quasi-static ramp loading in tension to failure of unidirectional and cross-ply SiC/CAS and quasi-isotropic SiC/MAS ceramic composite specimens at room temperature was accomplished using near real-time AU parameters. The AU technique was shown to be able to detect the stress levels for the onset and saturation of matrix cracks, respectively. The critical cracking stress level is used as a design stress for brittle matrix composites operating at elevated temperatures. The AU technique has found that the critical cracking stress level is 10-15% below the level presently obtained for design purposes from analytical models. An acousto-ultrasonic stress-strain response (AUSSR) model for unidirectional and cross-ply ceramic composites was formulated. The AUSSR model predicts the strain response to increasing stress levels using real-time AU data and classical laminated plate theory. The Weibull parameters of the AUSSR model are used to calculate the design stress for thermo-structural applications. Real-time AU together with the AUSSR model was used to study the failure mechanisms of SiC/CAS ceramic composites under static and fatigue loading. An S-N curve was generated for a cross-ply SiC/CAS ceramic composite material. The AU results are corroborated and complemented by other NDE techniques, namely, in-situ optical microscope video recordings and edge replication.

Υ production in U + U collisions at √{sN N}=193 GeV measured with the STAR experiment

NASA Astrophysics Data System (ADS)

Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Anderson, D. M.; Aoyama, R.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Ashraf, M. U.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chatterjee, A.; Chattopadhyay, S.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Eppley, G.; Esha, R.; Esumi, S.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Hamad, A. I.; Hamed, A.; Haque, R.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Horvat, S.; Huang, H. Z.; Huang, B.; Huang, T.; Huang, X.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jentsch, A.; Jia, J.; Jiang, K.; Jowzaee, S.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z.; Kikoła, D. P.; Kisel, I.; Kisiel, A.; Kochenda, L.; Koetke, D. D.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kumar, L.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, Y.; Li, C.; Li, X.; Li, W.; Li, X.; Lin, T.; Lisa, M. A.; Liu, F.; Liu, Y.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Luo, S.; Ma, G. L.; Ma, R.; Ma, L.; Ma, Y. G.; Magdy, N.; Majka, R.; Manion, A.; Margetis, S.; Markert, C.; Matis, H. S.; McDonald, D.; McKinzie, S.; Meehan, K.; Mei, J. C.; Miller, Z. W.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nandi, B. K.; Nasim, Md.; Nayak, T. K.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Nonaka, T.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Pruthi, N. K.; Przybycien, M.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Ray, R. L.; Reed, R.; Rehbein, M. J.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Roth, J. D.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, M. K.; Sharma, A.; Sharma, B.; Shen, W. Q.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, D.; Smirnov, N.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stepanov, M.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sugiura, T.; Sumbera, M.; Summa, B.; Sun, Y.; Sun, Z.; Sun, X. M.; Surrow, B.; Svirida, D. N.; Tang, Z.; Tang, A. H.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Varma, R.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, G.; Wang, J. S.; Wang, F.; Wang, Y.; Wang, Y.; Webb, J. C.; Webb, G.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, G.; Xie, W.; Xin, K.; Xu, Z.; Xu, H.; Xu, N.; Xu, J.; Xu, Y. F.; Xu, Q. H.; Yang, Y.; Yang, Y.; Yang, S.; Yang, Q.; Yang, Y.; Yang, C.; Ye, Z.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, J.; Zhang, Z.; Zhang, J.; Zhang, S.; Zhang, X. P.; Zhang, J. B.; Zhang, Y.; Zhang, S.; Zhao, J.; Zhong, C.; Zhou, L.; Zhu, X.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

2016-12-01

We present a measurement of the inclusive production of Υ mesons in U+U collisions at √{sN N}=193 GeV at midrapidity (|y |<1 ). Previous studies in central Au+Au collisions at √{sN N}=200 GeV show a suppression of Υ (1S+2S+3S) production relative to expectations from the Υ yield in p+p collisions scaled by the number of binary nucleon-nucleon collisions (Ncoll), with an indication that the Υ (1S) state is also suppressed. The present measurement extends the number of participant nucleons in the collision (Npart) by 20% compared to Au+Au collisions, and allows us to study a system with higher energy density. We observe a suppression in both the Υ (1 S +2 S +3 S ) and Υ (1 S ) yields in central U+U data, which consolidates and extends the previously observed suppression trend in Au+Au collisions.

Metal-Metal Interactions in Heterobimetallic Complexes with Dinucleating Redox-Active Ligands.

PubMed

Broere, Daniël L J; Modder, Dieuwertje K; Blokker, Eva; Siegler, Maxime A; van der Vlugt, Jarl Ivar

2016-02-12

The tuning of metal-metal interactions in multinuclear assemblies is a challenge. Selective P coordination of a redox-active PNO ligand to Au(I) followed by homoleptic metalation of the NO pocket with Ni(II) affords a unique trinuclear Au-Ni-Au complex. This species features two antiferromagnetically coupled ligand-centered radicals and a double intramolecular d(8)-d(10) interaction, as supported by spectroscopic, single-crystal X-ray diffraction, and computational data. A corresponding cationic dinuclear Au-Ni analogue with a stronger d(8)-d(10) interaction is also reported. Although both heterobimetallic structures display rich electrochemistry, only the trinuclear Au-Ni-Au complex facilitates electrocatalytic C-X bond activation of alkyl halides in its doubly reduced state. Hence, the presence of a redox-active ligand framework, an available coordination site at gold, and the nature of the nickel-gold interaction appear to be essential for this reactivity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Υ production in U + U collisions at s N N = 193 GeV measured with the STAR experiment

DOE PAGES

Adamczyk, L.

2016-12-15

We present a measurement of the inclusive production of ¡ mesons in U+U collisions at √sNN = 193 GeV at mid-rapidity (|y| < 1). Previous studies in central Au+Au collisions at √sNN = 200 GeV show a suppression of ¡(1S+2S+3S) production relative to expectations from the ¡ yield in p+p collisions scaled by the number of binary nucleon-nucleon collisions (N coll), with an indication that the ¡(1S) state is also suppressed. The present measurement extends the number of participant nucleons in the collision (N part) by 20% compared to Au+Au collisions, and allows us to study a system with highermore » energy density. We observe a suppression in both the ¡(1S+2S+3S) and ¡(1S) yields in central U+U data, which consolidates and extends the previously observed suppression trend in Au+Au collisions.« less

Gas Sensitivity and Sensing Mechanism Studies on Au-Doped TiO2 Nanotube Arrays for Detecting SF6 Decomposed Components

PubMed Central

Zhang, Xiaoxing; Yu, Lei; Tie, Jing; Dong, Xingchen

2014-01-01

The analysis to SF6 decomposed component gases is an efficient diagnostic approach to detect the partial discharge in gas-insulated switchgear (GIS) for the purpose of accessing the operating state of power equipment. This paper applied the Au-doped TiO2 nanotube array sensor (Au-TiO2 NTAs) to detect SF6 decomposed components. The electrochemical constant potential method was adopted in the Au-TiO2 NTAs' fabrication, and a series of experiments were conducted to test the characteristic SF6 decomposed gases for a thorough investigation of sensing performances. The sensing characteristic curves of intrinsic and Au-doped TiO2 NTAs were compared to study the mechanism of the gas sensing response. The results indicated that the doped Au could change the TiO2 nanotube arrays' performances of gas sensing selectivity in SF6 decomposed components, as well as reducing the working temperature of TiO2 NTAs. PMID:25330053

Multispectroscopic and bioimaging approach for the interaction of rhodamine 6G capped gold nanoparticles with bovine serum albumin.

PubMed

Manjubaashini, N; Kesavan, Mookkandi Palsamy; Rajesh, Jegathalaprathaban; Daniel Thangadurai, T

2018-06-01

Binding interaction of Bovine Serum Albumin (BSA) with newly prepared rhodamine 6G-capped gold nanoparticles (Rh6G-Au NPs) under physiological conditions (pH 7.2) was investigated by a wide range of photophysical techniques. Rh6G-Au NPs caused the static quenching of the intrinsic fluorescence of BSA that resulted from the formation of ground-state complex between BSA and Rh6G-Au NPs. The binding constant from fluorescence quenching method (K a  = 1.04 × 10 4  L mol -1 ; LoD = 14.0 μM) is in accordance with apparent association constant (K app  = 1.14 × 10 1  M -1 ), which is obtained from absorption spectral studies. Förster resonance energy transfer (FRET) efficiency between the tryptophan (Trp) residue of BSA and fluorophore of Rh6G-Au NPs during the interaction was calculated to be 90%. The free energy change (ΔG = -23.07 kJ/mol) of BSA-Rh6G-Au NPs complex was calculated based on modified Stern-Volmer Plot. The time-resolved fluorescence analysis confirmed that quenching of BSA follows static mechanism through the formation of ground state complex. Furthermore, synchronous and three-dimensional fluorescence measurement, Raman spectral analysis and Circular Dichroism spectrum results corroborate the strong binding between Rh6G-Au NPs and BSA, which causes the conformational changes on BSA molecule. In addition, fluorescence imaging experiments of BSA in living human breast cancer (HeLa) cells was successfully demonstrated, which articulated the value of Rh6G-Au NPs practical applications in biological systems. Copyright © 2018. Published by Elsevier B.V.

Optical properties and electronic energy relaxation of metallic Au144(SR)60 nanoclusters.

PubMed

Yi, Chongyue; Tofanelli, Marcus A; Ackerson, Christopher J; Knappenberger, Kenneth L

2013-12-04

Electronic energy relaxation of Au144(SR)60(q) ligand-protected nanoclusters, where SR = SC6H13 and q = -1, 0, +1, and +2, was examined using femtosecond time-resolved transient absorption spectroscopy. The observed differential transient spectra contained three distinct components: (1) transient bleaches at 525 and 600 nm, (2) broad visible excited-state absorption (ESA), and (3) stimulated emission (SE) at 670 nm. The bleach recovery kinetics depended upon the excitation pulse energy and were thus attributed to electron-phonon coupling typical of metallic nanostructures. The prominent bleach at 525 nm was assigned to a core-localized plasmon resonance (CLPR). ESA decay kinetics were oxidation-state dependent and could be described using a metal-sphere charging model. The dynamics, emission energy, and intensity of the SE peak exhibited dielectric-dependent responses indicative of Superatom charge transfer states. On the basis of these data, the Au144(SR)60 system is the smallest-known nanocluster to exhibit quantifiable electron dynamics and optical properties characteristic of metals.

Leakage current transport mechanism under reverse bias in Au/Ni/GaN Schottky barrier diode

NASA Astrophysics Data System (ADS)

Peta, Koteswara Rao; Kim, Moon Deock

2018-01-01

The leakage current transport mechanism under reverse bias of Au/Ni/GaN Schottky diode is studied using temperature dependent current-voltage (I-V-T) and capacitance-voltage (C-V) characteristics. I-V measurement in this study is in the range of 140 K-420 K in steps of 10 K. A reduction in voltage dependent barrier height and a strong internal electric field in depletion region under reverse bias suggested electric field enhanced thermionic emission in carrier transport via defect states in Au/Ni/GaN SBD. A detailed analysis of reverse leakage current revealed two different predominant transport mechanisms namely variable-range hopping (VRH) and Poole-Frenkel (PF) emission conduction at low (<260 K) and high (>260 K) temperatures respectively. The estimated thermal activation energies (0.20-0.39 eV) from Arrhenius plot indicates a trap assisted tunneling of thermally activated electrons from a deep trap state into a continuum of states associated with each conductive threading dislocation.

Le domaine Tariquide (arc de Gibraltar, Espagne et Maroc) : succession sédimentaire et événements structuraux au Lias et au Dogger

NASA Astrophysics Data System (ADS)

Durand-Delga, Michel; Gardin, Silvia; Esteras, Manuel; Paquet, Hélène

2005-06-01

The Lias-Dogger successions of the Tariquide units in the Gibraltar Arc differ from the series of tectonically adjacent units, the Penibetic (Iberia margin) and the Limestone 'Dorsale' (Alboran Domain). Lower Lias limestones are eroded and covered by the Domerian, which starts by deposits of open sea, continuous up to the Dogger (J. Musa-type successions), and elsewhere (Los Pastores-type successions) by a thin series (Upper Lias to Upper Dogger), starting by a manganesiferous episode (Ras Leona) and including marls deposited into three episodes, dated by calcareous nannofossils. Faulting events occurred before the Domerian and during the Late Toarcian (Los Pastores). To cite this article: M. Durand-Delga et al., C. R. Geoscience 337 (2005).

High-Performance Acousto-Ultrasonic Scan System Being Developed

NASA Technical Reports Server (NTRS)

Roth, Don J.; Martin, Richard E.; Cosgriff, Laura M.; Gyekenyesi, Andrew L.; Kautz, Harold E.

2003-01-01

Acousto-ultrasonic (AU) interrogation is a single-sided nondestructive evaluation (NDE) technique employing separated sending and receiving transducers. It is used for assessing the microstructural condition and distributed damage state of the material between the transducers. AU is complementary to more traditional NDE methods, such as ultrasonic cscan, x-ray radiography, and thermographic inspection, which tend to be used primarily for discrete flaw detection. Throughout its history, AU has been used to inspect polymer matrix composites, metal matrix composites, ceramic matrix composites, and even monolithic metallic materials. The development of a high-performance automated AU scan system for characterizing within-sample microstructural and property homogeneity is currently in a prototype stage at NASA. This year, essential AU technology was reviewed. In addition, the basic hardware and software configuration for the scanner was developed, and preliminary results with the system were described. Mechanical and environmental loads applied to composite materials can cause distributed damage (as well as discrete defects) that plays a significant role in the degradation of physical properties. Such damage includes fiber/matrix debonding (interface failure), matrix microcracking, and fiber fracture and buckling. Investigations at the NASA Glenn Research Center have shown that traditional NDE scan inspection methods such as ultrasonic c-scan, x-ray imaging, and thermographic imaging tend to be more suited to discrete defect detection rather than the characterization of accumulated distributed micro-damage in composites. Since AU is focused on assessing the distributed micro-damage state of the material in between the sending and receiving transducers, it has proven to be quite suitable for assessing the relative composite material state. One major success story at Glenn with AU measurements has been the correlation between the ultrasonic decay rate obtained during AU inspection and the mechanical modulus (stiffness) seen during fatigue experiments with silicon carbide/silicon carbide (SiC/SiC) ceramic matrix composite samples. As shown in the figure, ultrasonic decay increased as the modulus decreased for the ceramic matrix composite tensile fatigue samples. The likely microstructural reason for the decrease in modulus (and increase in ultrasonic decay) is the matrix microcracking that commonly occurs during fatigue testing of these materials. Ultrasonic decay has shown the capability to track the pattern of transverse cracking and fiber breakage in these composites.

High-Performance Acousto-Ultrasonic Scan System Being Developed

NASA Technical Reports Server (NTRS)

Roth, Don J.; Martin, Richard E.; Cosgriff, Laura M.; Gyekenyesi, Andrew L.; Kautz, Harold E.

2003-01-01

Acousto-ultrasonic (AU) interrogation is a single-sided nondestructive evaluation (NDE) technique employing separated sending and receiving transducers. It is used for assessing the microstructural condition and distributed damage state of the material between the transducers. AU is complementary to more traditional NDE methods, such as ultrasonic cscan, x-ray radiography, and thermographic inspection, which tend to be used primarily for discrete flaw detection. Throughout its history, AU has been used to inspect polymer matrix composites, metal matrix composites, ceramic matrix composites, and even monolithic metallic materials. The development of a high-performance automated AU scan system for characterizing within-sample microstructural and property homogeneity is currently in a prototype stage at NASA. This year, essential AU technology was reviewed. In addition, the basic hardware and software configuration for the scanner was developed, and preliminary results with the system were described. Mechanical and environmental loads applied to composite materials can cause distributed damage (as well as discrete defects) that plays a significant role in the degradation of physical properties. Such damage includes fiber/matrix debonding (interface failure), matrix microcracking, and fiber fracture and buckling. Investigations at the NASA Glenn Research Center have shown that traditional NDE scan inspection methods such as ultrasonic c-scan, x-ray imaging, and thermographic imaging tend to be more suited to discrete defect detection rather than the characterization of accumulated distributed microdamage in composites. Since AU is focused on assessing the distributed microdamage state of the material in between the sending and receiving transducers, it has proven to be quite suitable for assessing the relative composite material state. One major success story at Glenn with AU measurements has been the correlation between the ultrasonic decay rate obtained during AU inspection and the mechanical modulus (stiffness) seen during fatigue experiments with silicon carbide/silicon carbide (SiC/SiC) ceramic matrix composite samples. As shown in the figure, ultrasonic decay increased as the modulus decreased for the ceramic matrix composite tensile fatigue samples. The likely microstructural reason for the decrease in modulus (and increase in ultrasonic decay) is the matrix microcracking that commonly occurs during fatigue testing of these materials. Ultrasonic decay has shown the capability to track the pattern of transverse cracking and fiber breakage in these composites.

Vibrational energy transfer near a dissociative adsorption transition state: State-to-state study of HCl collisions at Au(111).

PubMed

Geweke, Jan; Shirhatti, Pranav R; Rahinov, Igor; Bartels, Christof; Wodtke, Alec M

2016-08-07

In this work we seek to examine the nature of collisional energy transfer between HCl and Au(111) for nonreactive scattering events that sample geometries near the transition state for dissociative adsorption by varying both the vibrational and translational energy of the incident HCl molecules in the range near the dissociation barrier. Specifically, we report absolute vibrational excitation probabilities for HCl(v = 0 → 1) and HCl(v = 1 → 2) scattering from clean Au(111) as a function of surface temperature and incidence translational energy. The HCl(v = 2 → 3) channel could not be observed-presumably due to the onset of dissociation. The excitation probabilities can be decomposed into adiabatic and nonadiabatic contributions. We find that both contributions strongly increase with incidence vibrational state by a factor of 24 and 9, respectively. This suggests that V-T as well as V-EHP coupling can be enhanced near the transition state for dissociative adsorption at a metal surface. We also show that previously reported HCl(v = 0 → 1) excitation probabilities [Q. Ran et al., Phys. Rev. Lett. 98, 237601 (2007)]-50 times smaller than those reported here-were influenced by erroneous assignment of spectroscopic lines used in the data analysis.

The orbital distribution of Near-Earth Objects inside Earth's orbit

NASA Astrophysics Data System (ADS)

Greenstreet, Sarah; Ngo, Henry; Gladman, Brett

2012-01-01

Canada's Near-Earth Object Surveillance Satellite (NEOSSat), set to launch in early 2012, will search for and track Near-Earth Objects (NEOs), tuning its search to best detect objects with a < 1.0 AU. In order to construct an optimal pointing strategy for NEOSSat, we needed more detailed information in the a < 1.0 AU region than the best current model (Bottke, W.F., Morbidelli, A., Jedicke, R., Petit, J.M., Levison, H.F., Michel, P., Metcalfe, T.S. [2002]. Icarus 156, 399-433) provides. We present here the NEOSSat-1.0 NEO orbital distribution model with larger statistics that permit finer resolution and less uncertainty, especially in the a < 1.0 AU region. We find that Amors = 30.1 ± 0.8%, Apollos = 63.3 ± 0.4%, Atens = 5.0 ± 0.3%, Atiras (0.718 < Q < 0.983 AU) = 1.38 ± 0.04%, and Vatiras (0.307 < Q < 0.718 AU) = 0.22 ± 0.03% of the steady-state NEO population. Vatiras are a previously undiscussed NEO population clearly defined in our integrations, whose orbits lie completely interior to that of Venus. Our integrations also uncovered the unexpected production of retrograde orbits from main-belt asteroid sources; this retrograde NEA population makes up ≃0.1% of the steady-state NEO population. The relative NEO impact rate onto Mercury, Venus, and Earth, as well as the normalized distribution of impact speeds, was calculated from the NEOSSat-1.0 orbital model under the assumption of a steady-state. The new model predicts a slightly higher Mercury impact flux.

Luminescent Copper(I) Halide Butterfly Dimers Coordinated to [Au(CH3imCH2py)2]BF4 and [Au(CH3imCH2quin)2]BF4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Catalano, V.; Moore, A; Shearer, J

2009-01-01

The coordination chemistry of copper(I) halides to the homoleptic, N-heterocyclic carbene Au(I) complexes [Au(CH{sub 3}imCH{sub 2}quin){sub 2}]BF{sub 4} and [Au(CH{sub 3}imCH{sub 2}py){sub 2}]BF{sub 4} was explored. The reaction of CuX (X = Cl, Br, I) with either [Au(CH{sub 3}imCH{sub 2}quin){sub 2}]BF{sub 4} or [Au(CH{sub 3}imCH{sub 2}py){sub 2}]BF{sub 4} produces trimetallic complexes containing Cu{sub 2}X{sub 2}-butterfly copper clusters coordinated to the two imine moieties. The triangular arrangement of the metals places the gold(I) center in close proximity ({approx}2.5-2.6 {angstrom}) to the centroid of the Cu-Cu vector. The Cu-Cu separations vary as a function of bridging halide with the shortest Cu-Cu separationsmore » of {approx}2.5 {angstrom} found in the iodo-complexes and the longest separations of 2.9 {angstrom} found in the bridging chloride complexes. In all six complexes the Au-Cu separations range from {approx}2.8 to 3.0 {angstrom}. In the absence of halides, the dimetallic complex [AuCu(CH{sub 3}imCH{sub 2}py){sub 2}(NCCH{sub 3}){sub 2}](BF{sub 4}){sub 2}, containing a long Au-Cu distance of {approx}4.72 {angstrom} is formed. Additionally, as the byproduct of the reaction of CuBr with [Au(CH{sub 3}imCH{sub 2}quin){sub 2}]BF{sub 4} the deep-red, dimetallic compound, AuCuBr{sub 2}(CH{sub 3}imCH{sub 2}quin){sub 2}, was isolated in very low yield. All of these complexes were studied by NMR spectroscopy, mass spectrometry, and the copper containing species were additionally characterized by X-ray crystallography. In solution the copper centers dissociate from the gold complexes, but as shown by XANES and EXAFS spectroscopy, at low temperature the Cu-Cu linkage is broken, and the individual copper(I) halides reposition themselves to opposite sides of the gold complex while remaining coordinated to one imine moiety. In the solid state all of the complexes are photoluminescent, though the nature of the excited state was not determined.« less

Chapter 2: 2003 Geologic Assessment of Undiscovered Conventional Oil and Gas Resources in the Upper Cretaceous Navarro and Taylor Groups, Western Gulf Province, Texas

USGS Publications Warehouse

Condon, S.M.; Dyman, T.S.

2006-01-01

The Upper Cretaceous Navarro and Taylor Groups in the western part of the Western Gulf Province were assessed for undiscovered oil and gas resources in 2003. The area is part of the Smackover-Austin-Eagle Ford Composite Total Petroleum System. The rocks consist of, from youngest to oldest, the Escondido and Olmos Formations of the Navarro Group and the San Miguel Formation and the Anacacho Limestone of the Taylor Group (as well as the undivided Navarro Group and Taylor Group). Some units of the underlying Austin Group, including the 'Dale Limestone' (a term of local usage that describes a subsurface unit), were also part of the assessment in some areas. Within the total petroleum system, the primary source rocks comprise laminated carbonate mudstones and marine shales of the Upper Jurassic Smackover Formation, mixed carbonate and bioclastic deposits of the Upper Cretaceous Eagle Ford Group, and shelf carbonates of the Upper Cretaceous Austin Group. Possible secondary source rocks comprise the Upper Jurassic Bossier Shale and overlying shales within the Upper Jurassic to Lower Cretaceous Cotton Valley Group, Lower Cretaceous marine rocks, and the Upper Cretaceous Taylor Group. Oil and gas were generated in the total petroleum system at different times because of variations in depth of burial, geothermal gradient, lithology, and organic-matter composition. A burial-history reconstruction, based on data from one well in the eastern part of the study area (Jasper County, Tex.), indicated that (1) the Smackover generated oil from about 117 to 103 million years ago (Ma) and generated gas from about 52 to 41 Ma and (2) the Austin and Eagle Ford Groups generated oil from about 42 to 28 Ma and generated gas from about 14 Ma to the present. From the source rocks, oil and gas migrated upsection and updip along a pervasive system of faults and fractures as well as along bedding planes and within sandstone units. Types of traps include stratigraphic pinchouts, folds, faulted folds, and combinations of these. Seals consist of interbedded shales and mudstones and diagenetic cementation. The area assessed is divided into five assessment units (AUs): (1) Travis Volcanic Mounds Oil (AU 50470201), (2) Uvalde Volcanic Mounds Gas and Oil (AU 50470202), (3) Navarro-Taylor Updip Oil and Gas (AU 50470203), (4) Navarro-Taylor Downdip Gas and Oil (AU 50470204), and (5) Navarro-Taylor Slope-Basin Gas (AU 50470205). Total estimated mean undiscovered conventional resources in the five assessment units combined are 33.22 million barrels of oil, 1,682.80 billion cubic feet of natural gas, and 34.26 million barrels of natural gas liquids.

Systematic parameter study of hadron spectra and elliptic flow from viscous hydrodynamic simulations of Au+Au collisions at sNN=200 GeV

NASA Astrophysics Data System (ADS)

Shen, Chun; Heinz, Ulrich; Huovinen, Pasi; Song, Huichao

2010-11-01

Using the (2+1)-dimensional viscous hydrodynamic code vish2+1 [H. Song and U. Heinz, Phys. Lett. BPYLBAJ0370-269310.1016/j.physletb.2007.11.019 658, 279 (2008); H. Song and U. Heinz, Phys. Rev. CPRVCAN0556-281310.1103/PhysRevC.77.064901 77, 064901 (2008); H. Song, Ph. D. thesis, The Ohio State University, 2009], we present systematic studies of the dependence of pion and proton transverse-momentum spectra and their elliptic flow in 200A GeV Au+Au collisions on the parameters of the hydrodynamic model (thermalization time, initial entropy density distribution, decoupling temperature, equation of state, and specific shear viscosity η/s). We identify a tension between the slope of the proton spectra, which (within hydrodynamic simulations that assume a constant shear viscosity to entropy density ratio) prefer larger η/s values, and the slope of the pT dependence of charged hadron elliptic flow, which prefers smaller values of η/s. Changing other model parameters does not appear to permit dissolution of this tension.

Noncentrosymmetric superconductor BeAu

NASA Astrophysics Data System (ADS)

Amon, A.; Svanidze, E.; Cardoso-Gil, R.; Wilson, M. N.; Rosner, H.; Bobnar, M.; Schnelle, W.; Lynn, J. W.; Gumeniuk, R.; Hennig, C.; Luke, G. M.; Borrmann, H.; Leithe-Jasper, A.; Grin, Yu.

2018-01-01

Mixed spin-singlet and spin-triplet pairing can occur in noncentrosymmetric superconductors. In this respect, a comprehensive characterization of the noncentrosymmetric superconductor BeAu was carried out. It was established that BeAu undergoes a structural phase transition from a low-temperature noncentrosymmetric FeSi structure type to a high-temperature centrosymmetric structure in the CsCl type at Ts=860 K. The low-temperature modification exhibits a superconducting transition below Tc=3.3 K. The values of lower (Hc1=32 Oe) and upper (Hc2=335 Oe) critical fields are rather small, confirming that this type-II (κG-L=2.3 ) weakly coupled (λe-p=0.5 ,Δ Ce/γnTc≈1.26 ) superconductor can be well understood within the Bardeen-Cooper-Schrieffer theory. The muon spin relaxation analysis indicates that the time-reversal symmetry is preserved when the superconducting state is entered, supporting conventional superconductivity in BeAu. From the density functional band structure calculations, a considerable contribution of the Be electrons to the superconducting state was established. On average, a rather small mass renormalization was found, consistent with the experimental data.

Systematic parameter study of hadron spectra and elliptic flow from viscous hydrodynamic simulations of Au+Au collisions at {radical}(s{sub NN})=200 GeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen Chun; Heinz, Ulrich; Huovinen, Pasi

2010-11-15

Using the (2+1)-dimensional viscous hydrodynamic code vish2+1[H. Song and U. Heinz, Phys. Lett. B 658, 279 (2008); H. Song and U. Heinz, Phys. Rev. C 77, 064901 (2008); H. Song, Ph. D. thesis, The Ohio State University, 2009], we present systematic studies of the dependence of pion and proton transverse-momentum spectra and their elliptic flow in 200A GeV Au+Au collisions on the parameters of the hydrodynamic model (thermalization time, initial entropy density distribution, decoupling temperature, equation of state, and specific shear viscosity {eta}/s). We identify a tension between the slope of the proton spectra, which (within hydrodynamic simulations that assumemore » a constant shear viscosity to entropy density ratio) prefer larger {eta}/s values, and the slope of the p{sub T} dependence of charged hadron elliptic flow, which prefers smaller values of {eta}/s. Changing other model parameters does not appear to permit dissolution of this tension.« less

Solid-state dewetting of thin Au films studied with real-time, in situ spectroscopic ellipsometry

NASA Astrophysics Data System (ADS)

Magnozzi, M.; Bisio, F.; Canepa, M.

2017-11-01

We report the design and testing of a small, high vacuum chamber that allows real-time, in situ spectroscopic ellipsometry (SE) measurements; the chamber was designed to be easily inserted within the arms of a commercial ellipsometer. As a test application, we investigated the temperature-induced solid-state dewetting of thin (20 to 8 nm) Au layers on Si wafers. In situ SE measurements acquired in real time during the heating of the samples reveal features that can be related to the birth of a localized surface plasmon resonance (LSPR), and demonstrate the presence of a temperature threshold for the solid-state dewetting.

Extracellular Saccharide-Mediated Reduction of Au3+ to Gold Nanoparticles: New Insights for Heavy Metals Biomineralization on Microbial Surfaces.

PubMed

Kang, Fuxing; Qu, Xiaolei; Alvarez, Pedro J J; Zhu, Dongqiang

2017-03-07

Biomineralization is a critical process controlling the biogeochemical cycling, fate, and potential environmental impacts of heavy metals. Despite the indispensability of extracellular polymeric substances (EPS) to microbial life and their ubiquity in soil and aquatic environments, the role played by EPS in the transformation and biomineralization of heavy metals is not well understood. Here, we used gold ion (Au 3+ ) as a model heavy metal ion to quantitatively assess the role of EPS in biomineralization and discern the responsible functional groups. Integrated spectroscopic analyses showed that Au 3+ was readily reduced to zerovalent gold nanoparticles (AuNPs, 2-15 nm in size) in aqueous suspension of Escherichia coli or dissolved EPS extracted from microbes. The majority of AuNPs (95.2%) was formed outside Escherichia coli cells, and the removal of EPS attached to cells pronouncedly suppressed Au 3+ reduction, reflecting the predominance of the extracellular matrix in Au 3+ reduction. XPS, UV-vis, and FTIR analyses corroborated that Au 3+ reduction was mediated by the hemiacetal groups (aldehyde equivalents) of reducing saccharides of EPS. Consistently, the kinetics of AuNP formation obeyed pseudo-second-order reaction kinetics with respect to the concentrations of Au 3+ and the hemiacetal groups in EPS, with minimal dependency on the source of microbial EPS. Our findings indicate a previously overlooked, universally significant contribution of EPS to the reduction, mineralization, and potential detoxification of metal species with high oxidation state.

Electronic structures and nonlinear optical properties of trinuclear transition metal clusters M-(mu-S)-M' (M = Mo, W; M' = Cu, Ag, Au).

PubMed

Chen, Xihua; Wu, Kechen; Snijders, Jaap G; Lin, Chensheng

2003-01-27

A series of trinuclear metal clusters MS4(M'PPh3)2(M'PPh3) (M = Mo, W; M' = Cu, Ag, Au) have been studied using the density functional theory (DFT) method. The static polarizabilities and hyperpolarizabilities of the model clusters have been calculated using the finite-field (F-F) method. The model clusters, divided into two groups, are alike in the structure of two fragments of rhombic units M-(mu-S)2-M' (M = Mo, W; M' = Cu, Ag, Au), perpendicular to each other, which are joined by sharing the bridge metal M. It is the charge transfer from one of these moieties to the other in these characteristic sulfido-transitional metal cores that is responsible for the polarizabilities and hyperpolarizabilities. This kind of electronic delocalization, different from that of the planar pi-system, is interesting and warrants further investigation. The structural effects on properties are important. In these models, considerable third-order nonlinearities are exhibited. The element substitution effect of Mo and W is weak, while that of Cu and Ag is relatively substantial. An overall order is gamma xxxx(Mo-Ag) > gamma xxxx(W-Ag) > gamma xxxx(Mo-Au) > gamma xxxx(W-Au) > gamma xxxx (Mo-Cu) > gamma xxxx(W-Cu) and gamma av(Mo-Ag) approximately gamma av(W-Ag) > gamma av(Mo-Au) approximately gamma av(W-Au) approximately gamma av (Mo-Cu) approximately gamma av(W-Cu).

Bombesin functionalized gold nanoparticles show in vitro and in vivo cancer receptor specificity.

PubMed

Chanda, Nripen; Kattumuri, Vijaya; Shukla, Ravi; Zambre, Ajit; Katti, Kavita; Upendran, Anandhi; Kulkarni, Rajesh R; Kan, Para; Fent, Genevieve M; Casteel, Stan W; Smith, C Jeffrey; Boote, Evan; Robertson, J David; Cutler, Cathy; Lever, John R; Katti, Kattesh V; Kannan, Raghuraman

2010-05-11

Development of cancer receptor-specific gold nanoparticles will allow efficient targeting/optimum retention of engineered gold nanoparticles within tumors and thus provide synergistic advantages in oncology as it relates to molecular imaging and therapy. Bombesin (BBN) peptides have demonstrated high affinity toward gastrin-releasing peptide (GRP) receptors in vivo that are overexpressed in prostate, breast, and small-cell lung carcinoma. We have synthesized a library of GRP receptor-avid nanoplatforms by conjugating gold nanoparticles (AuNPs) with BBN peptides. Cellular interactions and binding affinities (IC(50)) of AuNP-BBN conjugates toward GRP receptors on human prostate cancer cells have been investigated in detail. In vivo studies using AuNP-BBN and its radiolabeled surrogate (198)AuNP-BBN, exhibiting high binding affinity (IC(50) in microgram ranges), provide unequivocal evidence that AuNP-BBN constructs are GRP-receptor-specific showing accumulation with high selectivity in GRP-receptor-rich pancreatic acne in normal mice and also in tumors in prostate-tumor-bearing, severe combined immunodeficient mice. The i.p. mode of delivery has been found to be efficient as AuNP-BBN conjugates showed reduced RES organ uptake with concomitant increase in uptake at tumor targets. The selective uptake of this new generation of GRP-receptor-specific AuNP-BBN peptide analogs has demonstrated realistic clinical potential in molecular imaging via x-ray computed tomography techniques as the contrast numbers in prostate tumor sites are severalfold higher as compared to the pretreatment group (Hounsfield unit = 150).

Mixed-charge nanoparticles for long circulation, low reticuloendothelial system clearance, and high tumor accumulation.

PubMed

Liu, Xiangsheng; Li, Huan; Chen, Yangjun; Jin, Qiao; Ren, Kefeng; Ji, Jian

2014-09-01

Mixed-charge zwitterionic surface modification shows great potential as a simple strategy to fabricate nanoparticle (NP) surfaces that are nonfouling. Here, the in vivo fate of 16 nm mixed-charge gold nanoparticles (AuNPs) is investigated, coated with mixed quaternary ammonium and sulfonic groups. The results show that mixed-charge AuNPs have a much longer blood half-life (≈30.6 h) than do poly(ethylene glycol) (PEG, M¯w = 2000) -coated AuNPs (≈6.65 h) and they accumulate in the liver and spleen far less than do the PEGylated AuNPs. Using transmission electron microscopy, it is further confirmed that the mixed-charge AuNPs have much lower uptake and different existing states in liver Kupffer cells and spleen macrophages one month after injection compared with the PEGylated AuNPs. Moreover, these mixed-charge AuNPs do not cause appreciable toxicity at this tested dose to mice in a period of 1 month as evidenced by histological examinations. Importantly, the mixed-charge AuNPs have higher accumulation and slower clearance in tumors than do PEGylated AuNPs for times of 24-72 h. Results from this work show promise for effectively designing tumor-targeting NPs that can minimize reticuloendothelial system clearance and circulate for long periods by using a simple mixed-charge strategy. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of the Metal-MoS2 interface on MoS2 Transistor Performance

NASA Astrophysics Data System (ADS)

Yuan, Hui; Cheng, Guangjun; Hight Walker, Angela; You, Lin; Kopanski, Joseph J.; Li, Qiliang; Richter, Curt A.

2015-03-01

We compare the electrical characteristics of MoS2 field-effect transistors (FETS) with Ag source/drain contacts with transistors with Ti contacts, and we demonstrate that the metal-MoS2 interface is crucial to the final device performance. The topography of 5nm Au/5nm Ag (contact layer) and 5nm Au/5nm Ti metal films deposited onto mono- and few-layer MoS2 was characterized by using scanning electron microscopy and atomic force microscopy. The surface morphology of the Au/Ti films on MoS2 shows a rough, dewetting pattern while Au/Ag forms smooth, dense films. These smoother and denser Au/Ag contacts lead to improved carrier transport efficiency. FETs with Ag contacts show more than 60 times higher on-state current and a steeper subthreshold slope. Raman spectroscopy of MoS2 covered with Au/Ag or Au/Ti films revealed that the contact layer is Ag or Ti, respectively. In addition, there is a dramatic difference in the heat transfer between the MoS2 and the two metals: while laser heating is observed in Au/Ti covered MoS2, no heating effects are seen in Au/Ag covered MoS2. It is reasonable to conclude that the smoother and denser Ag contact leads to higher carrier transport efficiency and contributes to the improved thermal properties.

Nano-jewellery: C5Au12--a gold-plated diamond at molecular level.

PubMed

Naumkin, F

2006-06-07

A mixed carbon-metal cluster is designed by combining the tetrahedral C(5) radical (with a central atom-the skeleton of the C(5)H(12) molecule) and the spherical Au(12) layer (the external atomic shell of the Au(13) cluster). The C(5)Au(12) cluster and its negative and positive ionic derivatives, C(5)Au(12)(+/-), are investigated ab initio (DFT) in terms of optimized structures and relative energies of a few spin-states, for the icosahedral-like and octahedral-like isomers. The cluster is predicted to be generally more stable in its octahedral shape (similar to C(5)H(12)) which prevails for the negative ion and may compete with the icosahedral shape for the neutral system and positive ion. Adiabatic ionization energies (AIE) and electron affinities (AEA) of C(5)Au(12), vertical electron-detachment (VDE) energies of C(5)Au(12)(-), and vertical ionization and electron-attachment energies (VIE, VEA) of C(5)Au(12) are calculated as well, and compared with those for the corresponding isomers of the Au(13) cluster. The AIE and VIE values are found to be close for the two systems, while the AEA and VDE values are significantly reduced for the radical-based species. A simple fragment-based model is proposed for the decomposition of the total interaction into carbon-gold and gold-gold components.

Pt L3,2-edge whiteline anomaly and its implications for the chemical behaviour of Pt 5d5/2 and 5d3/2 electronic states - a study of Pt-Au nanowires and nanoparticles

NASA Astrophysics Data System (ADS)

Sham, T. K.; Ward, M. J.; Murphy, M. W.; Liu, L. J.; Han, W. Q.

2013-04-01

We report the L3,2-edge whiteline anomaly observed in PtAu nanowire, PtAu and Pt nanoparticles deposited on Si nanowire, and their comparison with that of Pt metal. It is found that charge redistribution upon the formation of these materials can indeed be tracked with the L3,2 whiteline intensity. The implications of these findings are discussed.

Prostate-Specific Membrane Antigen Targeted Gold Nanoparticles for Theranostics of Prostate Cancer.

PubMed

Mangadlao, Joey Dacula; Wang, Xinning; McCleese, Christopher; Escamilla, Maria; Ramamurthy, Gopalakrishnan; Wang, Ziying; Govande, Mukul; Basilion, James P; Burda, Clemens

2018-04-24

Prostate cancer is one of the most common cancers and among the leading causes of cancer deaths in the United States. Men diagnosed with the disease typically undergo radical prostatectomy, which often results in incontinence and impotence. Recurrence of the disease is often experienced by most patients with incomplete prostatectomy during surgery. Hence, the development of a technique that will enable surgeons to achieve a more precise prostatectomy remains an open challenge. In this contribution, we report a theranostic agent (AuNP-5kPEG-PSMA-1-Pc4) based on prostate-specific membrane antigen (PSMA-1)-targeted gold nanoparticles (AuNPs) loaded with a fluorescent photodynamic therapy (PDT) drug, Pc4. The fabricated nanoparticles are well-characterized by spectroscopic and imaging techniques and are found to be stable over a wide range of solvents, buffers, and media. In vitro cellular uptake experiments demonstrated significantly higher nanoparticle uptake in PSMA-positive PC3pip cells than in PSMA-negative PC3flu cells. Further, more complete cell killing was observed in Pc3pip than in PC3flu cells upon exposure to light at different doses, demonstrating active targeting followed by Pc4 delivery. Likewise, in vivo studies showed remission on PSMA-expressing tumors 14 days post-PDT. Atomic absorption spectroscopy revealed that targeted AuNPs accumulate 4-fold higher in PC3pip than in PC3flu tumors. The nanoparticle system described herein is envisioned to provide surgical guidance for prostate tumor resection and therapeutic intervention when surgery is insufficient.

Solid-State Synthesized Nanostructured Au Dendritic Aggregates Towards Surface-Enhanced Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Gentile, A.; Ruffino, F.; D'Andrea, C.; Gucciardi, P. G.; Reitano, R.; Grimaldi, M. G.

2016-06-01

Micrometric Au structures, presenting a dendritic nano-structure, have been fabricated on a Si-based substrate. The fabrication method involves the deposition of a thin Au film on the substrate and a high-temperature annealing (1100°C) using fast heating and cooling ramps. The thermal process produces the growth, from the substrate, of Si micro-pillars whose top surfaces, covered by a crystalline Au layer, present a nanodendritic morphology. In addition to the micro-pillars, the sample surface presents a complex structural and chemical composition including Si3N4 regions due to the silicon-nitrogen intermixing during the heating stage. By studying the kinetic processes at the Au-Si interface during the thermal treatment, we describe the stages involved in the micro-pillars growth, in the dendritic morphology development, and in the Au atoms entrapment at the top of the dendritic surfaces. Finally, we present the analyses of the optical and surface enhanced Raman scattering properties of the Au dendritic aggregates. We show, in particular, that: (1) the Au dendrites aggregates act as effective scattering elements for the electromagnetic radiation in the infrared spectral region; and (2) the higher surface area due to the branched dendritic structure is responsible for the improvement in the sensitivity of the surface enhanced Raman scattering activity.

Bose-Fermi symmetry in the odd-even gold isotopes

NASA Astrophysics Data System (ADS)

Thomas, T.; Régis, J.-M.; Jolie, J.; Heinze, S.; Albers, M.; Bernards, C.; Fransen, C.; Radeck, D.

2014-05-01

In this work the results of an in-beam experiment on 195Au are presented, yielding new spins, multipole mixing ratios, and new low-lying states essential for the understanding of this nucleus. The positive-parity states from this work together with compiled data from the available literature for 185-199Au are compared to Interacting Boson Fermion Model calculations employing the Spin(6) Bose-Fermi symmetry. The evolution of the parameters for the τ splitting and the J splitting reveals a smooth behavior. Thereby, a common description based on the Bose-Fermi symmetry is found for 189-199Au. Furthermore, the calculated E2 transition strengths are compared to experimental values with fixed effective boson and fermion charges for all odd-even gold isotopes, emphasizing that the Spin(6) Bose-Fermi symmetry is valid for the gold isotopes.

Electronically Transparent Au-N Bonds for Molecular Junctions.

PubMed

Zang, Yaping; Pinkard, Andrew; Liu, Zhen-Fei; Neaton, Jeffrey B; Steigerwald, Michael L; Roy, Xavier; Venkataraman, Latha

2017-10-25

We report a series of single-molecule transport measurements carried out in an ionic environment with oligophenylenediamine wires. These molecules exhibit three discrete conducting states accessed by electrochemically modifying the contacts. Transport in these junctions is defined by the oligophenylene backbone, but the conductance is increased by factors of ∼20 and ∼400 when compared to traditional dative junctions. We propose that the higher-conducting states arise from in situ electrochemical conversion of the dative Au←N bond into a new type of Au-N contact. Density functional theory-based transport calculations establish that the new contacts dramatically increase the electronic coupling of the oligophenylene backbone to the Au electrodes, consistent with experimental transport data. The resulting contact resistance is the lowest reported to date; more generally, our work demonstrates a facile method for creating electronically transparent metal-organic interfaces.

Three reversible states controlled on a gold monoatomic contact by the electrochemical potential

NASA Astrophysics Data System (ADS)

Kiguchi, Manabu; Konishi, Tatsuya; Hasegawa, Kouta; Shidara, Satoshi; Murakoshi, Kei

2008-06-01

Conductance of a Au monoatomic contact was investigated under the electrochemical potential control. The Au contact showed three different behaviors depending on the potential: 1G0 (G0=2e2/h) , 0.5G0 , and not-well-defined values below 1G0 were shown when the potential of the contact was kept at -0.6V (double layer potential), -1.0V (hydrogen evolution potential), and 0.8 V (oxide formation potential) versus Ag/AgCl in 0.1M Na2SO4 solution, respectively. These three reversible states and their respective conductances could be fully controlled by the electrochemical potential. These changes in the conductance values are discussed based on the proposed structure models of hydrogen adsorbed and oxygen incorporated on a Au monoatomic contact.

Excited-state dynamics of acetylene excited to individual rotational level of the V04K01 subband

NASA Astrophysics Data System (ADS)

Makarov, Vladimir I.; Kochubei, Sergei A.; Khmelinskii, Igor V.

2006-01-01

Dynamics of the IR emission induced by excitation of the acetylene molecule using the (32Ka0,1,2,ÃAu1←41la1,X˜Σg+1) transition was investigated. The observed IR emission was assigned to transitions between the ground-state vibrational levels. Acetylene fluorescence quenching induced by external electric and magnetic fields acting upon the system prepared using the (34Ka1,ÃAu1←00la0,X˜Σg+1) excitation was also studied. External electric field creates an additional radiationless pathway to the ground-state levels, coupling levels of the ÃAu1 excited state to the quasiresonant levels of the X˜Σg+1 ground state. The level density of the ground state in the vicinity of the excited state is very high, thus the electric-field-induced transition is irreversible, with the rate constant described by the Fermi rule. Magnetic field alters the decay profile without changing the fluorescence quantum yield in collisionless conditions. IR emission from the CCH transient was detected, and was also affected by the external electric and magnetic fields. Acetylene predissociation was demonstrated to proceed by the direct S1→S0 mechanism. The results were explained using the previously developed theoretical approach, yielding values of the relevant model parameters.

Electronic behaviour of Au-Pt alloys and the 4f binding energy shift anomaly in Au bimetallics- X-ray spectroscopy studies

NASA Astrophysics Data System (ADS)

Wang, Dongniu; Cui, Xiaoyu; Xiao, Qunfeng; Hu, Yongfeng; Wang, Zhiqiang; Yiu, Y. M.; Sham, T. K.

2018-06-01

The electronic structure and charge redistribution of 6s conduction charge and 5d charge in Au and Pt alloys, Au9Pt and AuPt9 have been investigated using a charge compensation model. It is found that, both the Au and Pt 4f binding energy (BE) exhibits a negative shift in the alloys relatively to the pure metal in apparent disagreement with electroneutrality considerations (Au is the most electronegative metallic element); more interestingly, the negative Au 4f BE shift in Au-Pt alloy is in contrast to previous observations for a large number of Au bimetallic systems with more electropositive hosts in which the more electropositive the host„ the more positive the Au 4f BE shift. This anomaly is counter intuitive to electronegativity considerations. This dilemma was resolved by the charge compensation model in which both electronegativity and charge neutrality can be satisfied and the overall charge flow δ, onto Au is small and positive and δ arises from charge flow of 6s conduction charge, Δnc onto Au site, which is partially compensated by the depletion of 6d charge Δnd at the Au site (δ = Δnc+ Δnd ˜0.1 >0). The much larger Coulomb interaction between 4f and 5d than that between 4f and 6s results in positive 4f BE shifts. The Au 4f BE shift in Au-Pt alloys together with 193Au Mössbauer data were used in the charge compensation model analysis which shows that the model is still valid in that the Au 4f shift in Au-Pt alloy arises from mainly conduction charge gain with little depletion of d charge at the Au site. The model also works for Pt. The Au and Pt 5d character in the alloys have been examined with valence band spectra which show both maintain their d characteristic in dilute alloys with Pt d piling up at the Fermi level, and the top of the Au valence band being pushed toward the Fermi level; this is confirmed with DFT densities of state calculations. When Pt is diluted in Au, it gains d charge as evident from the reduction in whiteline intensity at the Pt L3-edge XANES. What emerges from this work is a picture in which the s-d charge compensation in Au bimetallic alloys is triggered by electronegativity difference between Au and the host. For Au-Pt and Au-Pd systems, the difference in electronegativity is very small, conduction charge transfer dominates, and the Au 4f shift is negative whereas in most Au bimetallics, the larger the electronegativity difference, the larger the compensation and the larger the Au 4f shifts.

CO adsorption on small Au{sub n} (n = 1–4) structures supported on hematite. II. Adsorption on the O-rich termination of α-Fe{sub 2}O{sub 3}(0001) surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pabisiak, Tomasz; Kiejna, Adam, E-mail: kiejna@ifd.uni.wroc.pl; Winiarski, Maciej J.

2016-01-28

The adsorption of small Au{sub n} (n = 1–4) nanostructures on oxygen terminated α-Fe{sub 2}O{sub 3}(0001) surface was investigated using density functional theory in the generalized gradient approximation of Perdew-Burke-Ernzerhof (PBE) form with Hubbard correction U, accounting for strong electron correlations (PBE+U). The structural, energetic, and electronic properties were examined for two classes of the adsorbed Au{sub n} nanostructures with vertical and flattened configurations. Similarly to the Fe-terminated α-Fe{sub 2}O{sub 3}(0001) surface considered in Part I, the flattened configurations were found energetically more favored than vertical ones. The binding of Au{sub n} to the O-terminated surface is much stronger thanmore » to the Fe-termination. The adsorption bonding energy of Au{sub n} and the work function of the Au{sub n}/α-Fe{sub 2}O{sub 3}(0001) systems decrease with the increased number of Au atoms in a structure. All of the adsorbed Au{sub n} structures are positively charged. The bonding of CO molecules to the Au{sub n} structures is distinctly stronger than on the Fe-terminated surface; however, it is weaker than the binding to the bare O-terminated surface. The CO molecule binds to the Au{sub n}/α-Fe{sub 2}O{sub 3}(0001) system through a peripheral Au atom partly detached from the Au{sub n} structure. The results of this work indicate that the most energetically favored sites for adsorption of a CO molecule on the Au{sub n}/α-Fe{sub 2}O{sub 3}(0001) systems are atoms in the Au{sup 0.5+} oxidation state.« less

The abundance of Galactic planets from OGLE-III 2002 microlensing data

NASA Astrophysics Data System (ADS)

Snodgrass, Colin; Horne, Keith; Tsapras, Yiannis

2004-07-01

From the 389 OGLE-III 2002 observations of Galactic bulge microlensing events, we select 321 that are well described by a point-source point-lens light-curve model. From this sample we identify one event, 2002-BLG-055, that we regard as a strong planetary lensing candidate, and another, 2002-BLG-140, that is a possible candidate. If each of the 321 lens stars has one planet with a mass ratio q = m/M = 10-3 and orbit radius a = RE, the Einstein ring radius, analysis of detection efficiencies indicates that 14 planets should have been detectable with Δχ2 > 25. Assuming our candidate is due to planetary lensing, then the abundance of planets with q = 10-3 and a = RE is np ~ n/14 = 7 per cent. Conversion to physical units (Jupiter masses, MJup, and astronomical units, au) gives the abundance of `cool Jupiters' (m ~ MJup, a ~ 4 au) per lens star as np ~ n/5.5 = 18 per cent. The detection probability scales roughly with q and (Δχ2)-1/2, and drops off from a peak at a ~ 4 au like a Gaussian with a dispersion of 0.4 dex.

Electron transport in doped fullerene molecular junctions

NASA Astrophysics Data System (ADS)

Kaur, Milanpreet; Sawhney, Ravinder Singh; Engles, Derick

The effect of doping on the electron transport of molecular junctions is analyzed in this paper. The doped fullerene molecules are stringed to two semi-infinite gold electrodes and analyzed at equilibrium and nonequilibrium conditions of these device configurations. The contemplation is done using nonequilibrium Green’s function (NEGF)-density functional theory (DFT) to evaluate its density of states (DOS), transmission coefficient, molecular orbitals, electron density, charge transfer, current, and conductance. We conclude from the elucidated results that Au-C16Li4-Au and Au-C16Ne4-Au devices behave as an ordinary p-n junction diode and a Zener diode, respectively. Moreover, these doped fullerene molecules do not lose their metallic nature when sandwiched between the pair of gold electrodes.

Influence of indium supply on Au-catalyzed InGaAs nanowire growth studied by in situ X-ray diffraction

NASA Astrophysics Data System (ADS)

Sasaki, Takuo; Takahasi, Masamitu

2017-06-01

In this study, we analyzed the influence of indium supply on the growth dynamics of gold-catalyzed InGaAs nanowires by in situ synchrotron X-ray diffraction. A high In/Ga supply ratio results in strong size inhomogeneity of Au particles and interrupts the nanowire growth at a certain point of time. Based on the experimental results, we discussed the state of Au catalysts with high indium content during the nanowire growth. We found that a growth temperature below the eutectic temperature is essential to avoid the growth interruption and maintain the nanowire growth. The high In/Ga ratio necessitates accurate size control of Au particles before growth for further improvement of the nanowire growth.

Self-assembling Gold Nanoparticle Monolayers in a Three-phase System - Overcoming Ligand Size Limitations

NASA Astrophysics Data System (ADS)

Yang, Guang; Nanda, Jagjit; Wang, Boya; Chen, Gang; Hallinan, Daniel T., Jr.

An effective self-assembly technique was developed to prepare centimeter-scale monolayer gold nanoparticle (Au NP) films of long-range order with hydrophobic ligands. Aqueous Au NPs were entrapped in the organic/aqueous interface where the Au NP surface was in situ modified with different types of amine ligands, including amine-terminated polystyrene. The Au NPs then spontaneously relocated to the air/water interface to form an NP monolayer. The spontaneous formation of an Au NP film at the organic/water interface was due to the minimization of the system Helmholtz free energy. Self-assembled Au NP films has a hexagonal close packed structure. The interparticle spacing was dictated by the amine ligand length. Thus-assembled Au NP monolayers exhibit tunable surface plasma resonance and excellent spacial homogeneity of surface-enhanced Raman-scattering. The ``air/water/oil'' self-assembly method developed in this study not only benefits the fundamental understanding of NP ligand conformations, but is also promising to scale up the manufacture of plasmonic nanoparticle devices with precisely designed optical properties. This study was financially supported by start-up funding supplied by the Florida State University and the FAMU-FSU College of Engineering.

First-principles simulations on suspended coinage-metal nanotubes composed of different atomic species.

PubMed

Fa, Wei; Zhou, Jian; Dong, Jinming

2013-04-07

Substitutional doping of gold and copper atoms in a (4, 4) silver single-wall nanotube has been investigated using first-principles simulations. It is found that the Au- and Cu-substitutional doping of the tip-suspended (4, 4) Ag tube can maintain the hollow tubular structure at different alloy compositions due to the existence of a local minimum in the string tension variation with their unit cell lengths. The bonding energy differences between the mono-elements and hetero-elements and string tension may play important roles in suppressing the "self-purification" effects so that the nanoalloy tubes can be formed. Analysis of the band structure suggests that the number of conduction channels of the Ag-Au alloy tubes may lie between the pure (4, 4) Ag and Au tubes.

Measurement of Elliptic Llow in p+Au Collisions at √SNN = 200 GeV Using the PHENIX Detector at RHIC

NASA Astrophysics Data System (ADS)

Koblesky, Theodore E.

The Quark Gluon Plasma (QGP), a hot and dense state of matter in which quarks are not confined inside hadrons, is thought to be the same as the matter comprising the entire universe approximately one microsecond after the Big Bang. In Au+Au collisions at √SNN = 200 GeV at the Relativistic Heavy Ion Collider (RHIC) and Pb+Pb collisions at √ SNN = 2.76 TeV at the Large Hadron Collider (LHC), QGP has been discovered to have unique properties, such as its opacity to color charges and the fact that it behaves like a near-perfect fluid. Collective behavior in the form of a substantial elliptical azimuthal anisotropy ( v2) in the momentum distribution of final state particles has been observed, indicating a strongly-coupled, hydrodynamically flowing medium. Recently, features of collectivity have been detected in high-multiplicity, small collision systems thought to be too small to produce the QGP, such as 3He+Au and d+Au at √SNN = 200 GeV, p+Pb at √SNN = 5 TeV, and in p+p = 13 TeV events. In order to constrain models seeking to describe this phenomena, collision systems with distinct initial collision geometries were run at RHIC: 3He+Au for triangular geometry, d+Au for elliptical geometry, and p+Au for circular geometry. Together with coauthors, in a theory paper published in 2014, we proposed the suite of measurements at RHIC of the three collision systems. This thesis is the completion of that set of three measurements, by measuring v2 in the p+Au system. This thesis gives details on the analysis techniques used to make the measurement including the quality assurance of the data, the optimization of the midrapidity charged hadron cuts, and the event plane angle calibration. Special attention is given to correcting the systematic effects produced by the beam alignment unique to the p+Au dataset in order to make the v2 measurement with sufficient precision. Comparisons of v2 in the three collision systems and various theoretical models are made and it appears to be consistent with a QGP being formed. I am a coauthor on the experimental paper with these thesis results which has been published in Physical Review C.

The end states of long-period comets and the origin of Halley-type comets

NASA Astrophysics Data System (ADS)

Fernández, Julio A.; Gallardo, Tabaré; Young, Juan D.

2016-09-01

We analyse a sample of 73 old long-period comets (LPCs) (orbital periods 200 < P < 1000 yr) with perihelion distances q < 2.5 au, discovered in the period 1850-2014. We cloned the observed comets and also added fictitious LPCs with perihelia in the Jupiter's zone. We consider both a purely dynamical evolution and a physico-dynamical one with different physical lifetimes. We can fit the computed energy distribution of comets with q < 1.3 au to the observed one only within the energy range 0.01 < x < 0.04 au-1 (or periods 125 < P < 1000 yr), where the `energy' is taken as the inverse of the semimajor axis a, namely x ≡ 1/a. The best results are obtained for physical lifetimes of about 200-300 revolutions (for a comet with a standard q = 1 au). We find that neither a purely dynamical evolution, nor a physico-dynamical one can reproduce the long tail of larger binding energies (x ≳ 0.04 au-1) that correspond to most Halley-type comets (HTCs) and Jupiter-family comets. We conclude that most HTCs are not the end states of the evolution of LPCs, but come from a different source, a flattened one that we identify with the Centaurs that are scattered to the inner planetary region from the trans-Neptunian belt. These results also show that the boundary between LPCs and HTCs should be located at an energy x ˜ 0.04 au-1 (P ˜ 125 yr), rather than the conventional classical boundary at P = 200 yr.

Kinetic Investigation of Homogeneous H(2)-D(2) Equilibration Catalyzed by Pt-Au Cluster Compounds. Characterization of the Cluster [(H)Pt(AuPPh(3))(9)](NO(3))(2).

PubMed

Rubinstein, Leon I.; Pignolet, Louis H.

1996-11-06

The new Pt-Au hydrido cluster compound [(H)Pt(AuPPh(3))(9)](NO(3))(2) (3) has been synthesized and characterized by NMR, FABMS, and single-crystal X-ray diffraction [triclinic, P&onemacr;, a = 17.0452(1) Å, b = 17.4045(2) Å, c = 55.2353(1) Å, alpha = 89.891(1) degrees, beta = 85.287(1) degrees, gamma = 75.173(1) degrees, V = 15784.0(2) Å(3), Z = 4 (two molecules in asymmetric unit), residual R = 0.089 for 45 929 observed reflections and 3367 variables, Mo Kalpha radiation]. The Pt(AuP)(9) core geometry is a distorted icosahedron with three vertices vacant. The Pt-Au, Au-Au, and Au-P distances are within the normal ranges observed in other Pt-Au clusters. This cluster is a catalyst for H(2)-D(2) equilibration in homogeneous solution phase and has been used in a general mechanistic study of this reaction catalyzed by Pt-Au clusters. We previously proposed that a key step in the mechanism for catalytic H(2)-D(2) equilibration is the dissociation of a PPh(3) ligand to give a cluster with an open Au site for bonding of H(2) or D(2). This was based on qualitative observations that PPh(3) inhibited the rate of HD production with [Pt(AuPPh(3))(8)](NO(3))(2) (1) as catalyst. In order to test this hypothesis, phosphine inhibition (on the rate of HD production) and phosphine ligand exchange kinetic experiments were carried out with [(H)(PPh(3))Pt(AuPPh(3))(7)](NO(3))(2) (2) and 3. In this paper we show that the rate constant for phosphine dissociation determined from the PPh(3) inhibition rate study of H(2)-D(2) equilibration with cluster 2 is nearly identical to the rate constant for dissociative phosphine ligand exchange. The slower rate for H(2)-D(2) equilibration observed with 3 compared with 2 (5.5 x 10(-3) vs 7.7 x 10(-2) turnover s(-1)) is explained by its smaller rate constant for phosphine dissociation (2.8 x 10(-5) vs 2.9 x 10(-4) s(-1)). The fact that clusters 2 and 3 show similar kinetic behaviors suggests that the PPh(3) dissociation step in the catalytic H(2)-D(2) equilibration is general for 18-electron hydrido Pt-AuPPh(3) clusters.

Structural and electronic properties of Aun-xPtx (n = 2-14; x ⩽ n) clusters: The density functional theory investigation

NASA Astrophysics Data System (ADS)

Yuan, H. K.; Kuang, A. L.; Tian, C. L.; Chen, H.

2014-03-01

The structural evolutions and electronic properties of bimetallic Aun-xPtx (n = 2-14; x ⩽ n) clusters are investigated by using the density functional theory (DFT) with the generalized gradient approximation (GGA). The monatomic doping Aun-1Pt clusters are emphasized and compared with the corresponding pristine Aun clusters. The results reveal that the planar configurations are favored for both Aun-1Pt and Aun clusters with size up to n = 13, and the former often employ the substitution patterns based on the structures of the latter. The most stable clusters are Au6 and Au6Pt, which adopt regular planar triangle (D3h) and hexagon-ring (D6h) structures and can be regarded as the preferential building units in designing large clusters. For Pt-rich bimetallic clusters, their structures can be obtained from the substitution of Pt atoms by Au atoms from the Ptn structures, where Pt atoms assemble together and occupy the center yet Au atoms prefer the apex positions showing a segregation effect. With respect to pristine Au clusters, AunPt clusters exhibit somewhat weaker and less pronounced odd-even oscillations in the highest occupied and lowest unoccupied molecular-orbital gaps (HOMO-LUMO gap), electron affinity (EA), and ionization potential (IP) due to the partially released electron pairing effect. The analyses of electronic structure indicate that Pt atoms in AuPt clusters would delocalize their one 6s and one 5d electrons to contribute the electronic shell closure. The sp-d hybridizations as well as the d-d interactions between the host Au and dopant Pt atoms result in the enhanced stabilities of AuPt clusters.

Estimating the long-term costs of ischemic and hemorrhagic stroke for Australia: new evidence derived from the North East Melbourne Stroke Incidence Study (NEMESIS).

PubMed

Cadilhac, Dominique A; Carter, Rob; Thrift, Amanda G; Dewey, Helen M

2009-03-01

Stroke is associated with considerable societal costs. Cost-of-illness studies have been undertaken to estimate lifetime costs; most incorporating data up to 12 months after stroke. Costs of stroke, incorporating data collected up to 12 months, have previously been reported from the North East Melbourne Stroke Incidence Study (NEMESIS). NEMESIS now has patient-level resource use data for 5 years. We aimed to recalculate the long-term resource utilization of first-ever stroke patients and compare these to previous estimates obtained using data collected to 12 months. Population structure, life expectancy, and unit prices within the original cost-of-illness models were updated from 1997 to 2004. New Australian stroke survival and recurrence data up to 10 years were incorporated, as well as cross-sectional resource utilization data at 3, 4, and 5 years from NEMESIS. To enable comparisons, 1997 costs were inflated to 2004 prices and discounting was standardized. In 2004, 27 291 ischemic stroke (IS) and 4291 intracerebral hemorrhagic stroke (ICH) first-ever events were estimated. Average annual resource use after 12 months was AU$6022 for IS and AU$3977 for ICH. This is greater than the 1997 estimates for IS (AU$4848) and less than those for ICH (previously AU$10 692). The recalculated average lifetime costs per first-ever case differed for IS (AU$57 106 versus AU$52 855 [1997]), but differed more for ICH (AU$49 995 versus AU$92 308 [1997]). Basing lifetime cost estimates on short-term data overestimated the costs for ICH and underestimated those for IS. Patterns of resource use varied by stroke subtype and, overall, the societal cost impact was large.

Geology and assessment of undiscovered oil and gas resources of the Yukon Flats Basin Province, 2008

USGS Publications Warehouse

Bird, Kenneth J.; Stanley, Richard G.; Moore, Thomas E.; Gautier, Donald L.

2017-12-22

The hydrocarbon potential of the Yukon Flats Basin Province in Central Alaska was assessed in 2004 as part of an update to the National Oil and Gas Assessment. Three assessment units (AUs) were identified and assessed using a methodology somewhat different than that of the 2008 Circum-Arctic Resource Appraisal (CARA). An important difference in the methodology of the two assessments is that the 2004 assessment specified a minimum accumulation size of 0.5 million barrels of oil equivalent (MMBOE), whereas the 2008 CARA assessment specified a minimum size of 50 MMBOE. The 2004 assessment concluded that >95 percent of the estimated mean undiscovered oil and gas resources occur in a single AU, the Tertiary Sandstone AU. This is also the only AU of the three that extends north of the Arctic Circle.For the CARA project, the number of oil and gas accumulations in the 2004 assessment of the Tertiary Sandstone AU was re-evaluated in terms of the >50-MMBOE minimum accumulation size. By this analysis, and assuming the resource to be evenly distributed across the AU, 0.23 oil fields and 1.20 gas fields larger than 50 MMBOE are expected in the part of the AU north of the Arctic Circle. The geology suggests, however, that the area north of the Arctic Circle has a lower potential for oil and gas accumulations than the area to the south where the sedimentary section is thicker, larger volumes of hydrocarbons may have been generated, and potential structural traps are probably more abundant. Because of the low potential implied for the area of the AU north of the Arctic Circle, the Yukon Flats Tertiary Sandstone AU was not quantitatively assessed for the 2008 CARA.

Petroleum Systems and Geologic Assessment of Oil and Gas Resources in the Wind River Basin Province, Wyoming

USGS Publications Warehouse

,

2007-01-01

The purpose of the U.S. Geological Survey's (USGS) National Oil and Gas Assessment is to develop geologically based hypotheses regarding the potential for additions to oil and gas reserves in priority areas of the United States. The U.S. Geological Survey (USGS) recently completed an assessment of the undiscovered oil and gas potential of the Wind River Basin Province which encompasses about 4.7 million acres in central Wyoming. The assessment is based on the geologic elements of each total petroleum system (TPS) defined in the province, including hydrocarbon source rocks (source-rock maturation, hydrocarbon generation, and migration), reservoir rocks (sequence stratigraphy and petrophysical properties), and hydrocarbon traps (trap formation and timing). Using this geologic framework, the USGS defined three TPSs: (1) Phosphoria TPS, (2) Cretaceous-Tertiary TPS, and (3) Waltman TPS. Within these systems, 12 Assessment Units (AU) were defined and undiscovered oil and gas resources were quantitatively estimated within 10 of the 12 AUs.

Interface state density distribution in Au/n-ZnO nanorods Schottky diodes

NASA Astrophysics Data System (ADS)

Faraz, S. M.; Willander, M.; Wahab, Q.

2012-04-01

Interface states density (NSS) distribution is extracted in Au/ ZnO Schottky diodes. Nanorods of ZnO are grown on silver (Ag) using aqueous chemical growth (ACG) technique. Well aligned hexagonal-shaped vertical nanorods of a mean diameter of 300 - 450 nm and 1.3 -1.9 μm high are revealed in SEM. Gold (Au) Schottky contacts of thickness 60 nm and 1.5mm diameter were evaporated. For electrical characterization of Schottky diodes current-voltage (I-V) and capacitance-Voltage (C-V) measurements are performed. The diodes exhibited a typical non-linear rectifying behavior with a barrier height of 0.62eV and ideality factor of 4.3. Possible reasons for low barrier height and high ideality factor have been addressed. Series resistance (RS) has been calculated from forward I-V characteristics using Chueng's function. The density of interfacial states (NSS) below the conduction band (EC-ESS) is extracted using I-V and C-V measured values. A decrease in interface states density (NSS) is observed from 3.74 × 1011 - 7.98 × 1010 eV-1 cm-2 from 0.30eV - 0.61eV below the conduction band edge.

The chemistry of the superheavy elements. II. The stability of high oxidation states in group 11 elements: Relativistic coupled cluster calculations for the di-, tetra- and hexafluoro metallates of Cu, Ag, Au, and element 111

NASA Astrophysics Data System (ADS)

Seth, Michael; Cooke, Fiona; Schwerdtfeger, Peter; Heully, Jean-Louis; Pelissier, Michel

1998-09-01

The stability of the high oxidation states +3 and +5 in Group 11 fluorides is studied by relativistic Møller-Plesset (MP) and coupled cluster methods. Higher metal oxidation states are stabilized by relativistic effects. As a result, the hexafluoro complex of the Group 11 element with nuclear charge 111 and oxidation state +5 is the most stable compared to the other congeners. The results also suggest that AgF6- is thermodynamically stable and, therefore, it might be feasable to synthesize this compound. For the copper fluorides we observe very large oscillations in the Møller-Plesset series up to the fourth order. Nonrelativistic calculations lead to the expected trend in the metal-fluorine bond distances for the MF2- compounds, CuF2-

Solid state dewetting of thin plasmonic films under focused cw-laser irradiation

DOE PAGES

Abbott, William M.; Corbett, Simon; Cunningham, Graeme; ...

2017-12-21

Elevated temperatures and large thermal gradients are a significant source of component failure in microelectronics, and is the limiting factor in heat-assisted magnetic recording (HAMR). Here, we have investigated the effect of solid-state dewetting in Au thin films, as a function of local temperature, film thickness, and substrate adhesion. In this work, a localised temperature rise is induced in thin (≤ 50 nm) polycrystalline Au films on SiO 2 substrates via focused continuous-wave laser irradiation at 488 nm. The magnitude and distribution of the total temperature rise is measured using CCD-based thermoreflectance. This also allows a sensitive measurement of themore » temperature at which dewetting occurs, showing that for thin (≤ 50 nm) Au films without adhesion layers, rapid dewetting can occur at temperatures as low as 50° C. The time decay of the reflected light from the illuminating laser is used to monitor locally the dynamics of solid state dewetting. TEM diffraction analysis shows significant changes in the microstructure and crystallographic texture of the films as far as 10 µm away from the illuminated area. The use of a thin metallic adhesion layer (such as Ti or Cr) is shown to significantly improve the adhesion of the Au to the substrate and reduce the tendency towards dewetting, but does not entirely protect it from changes to the crystallographic texture.« less

Solid state dewetting of thin plasmonic films under focused cw-laser irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abbott, William M.; Corbett, Simon; Cunningham, Graeme

Elevated temperatures and large thermal gradients are a significant source of component failure in microelectronics, and is the limiting factor in heat-assisted magnetic recording (HAMR). Here, we have investigated the effect of solid-state dewetting in Au thin films, as a function of local temperature, film thickness, and substrate adhesion. In this work, a localised temperature rise is induced in thin (≤ 50 nm) polycrystalline Au films on SiO 2 substrates via focused continuous-wave laser irradiation at 488 nm. The magnitude and distribution of the total temperature rise is measured using CCD-based thermoreflectance. This also allows a sensitive measurement of themore » temperature at which dewetting occurs, showing that for thin (≤ 50 nm) Au films without adhesion layers, rapid dewetting can occur at temperatures as low as 50° C. The time decay of the reflected light from the illuminating laser is used to monitor locally the dynamics of solid state dewetting. TEM diffraction analysis shows significant changes in the microstructure and crystallographic texture of the films as far as 10 µm away from the illuminated area. The use of a thin metallic adhesion layer (such as Ti or Cr) is shown to significantly improve the adhesion of the Au to the substrate and reduce the tendency towards dewetting, but does not entirely protect it from changes to the crystallographic texture.« less

The Enrichment of Smoler’s Model of Land Combat.

DTIC Science & Technology

1980-09-01

of land Combat RupIe ICSO ( -. AU TWORVS) 4. CONTRACT OR GRANT NIANG9WO) Glenn M. Mills 9, 09m0000000 0RGANIZATION "NME AU AGGRS Is. :00OGRAN £LMEN61T...each unit prior to the initiation of the battle. This realization, A is determined by using a random Uniform(O,1) number and the above formula. A new...move to an alternate position the user has selected. The duration of the move is also a user input. He simply specifies the number of 10 second time

Caliste 64: detection unit of a spectro imager array for a hard x-ray space telescope

NASA Astrophysics Data System (ADS)

Limousin, O.; Meuris, A.; Lugiez, F.; Gevin, Olivier; Pinsard, F.; Blondel, C.; Le Mer, I.; Delagnes, E.; Vassal, M. C.; Soufflet, F.; Bocage, R.; Penquer, A.; Billot, M.

2017-11-01

In the frame of the hard X-ray Simbol-X observatory, a joint CNES-ASI space mission to be flown in 2014, a prototype of miniature Cd(Zn)Te camera equipped with 64 pixels has been designed. The device, called Caliste 64, is a spectro-imager with high resolution event timetagging capability. Caliste 64 integrates a Cd(Zn)Te semiconductor detector with segmented electrode and its front-end electronics made of 64 independent analog readout channels. This 1 × 1 × 2 cm3 camera, able to detect photons in the range from 2 keV up to 250 keV, is an elementary detection unit juxtaposable on its four sides. Consequently, large detector array can be made assembling a mosaic of Caliste 64 units. Electronics readout module is achieved by stacking four IDeF-X V1.1 ASICs, perpendicular to the detection plane. We achieved good noise performances, with a mean Equivalent Noise Charge of 65 electrons rms over the 64 channels. For the first prototypes, we chose Pt//CdTe//Al/Ti/Au Schottky detectors because of their very low dark current and excellent spectroscopic performances. Recently a Caliste 64 prototype has been also equipped with a 2 mm thick Au//CdZnTe//Au detector. This paper presents the performances of these four prototypes and demonstrates spectral performances better than 1 keV fwhm at 59.54 keV when the samples are moderately cooled down to -10°C.

Coinage metal coordination chemistry of stable primary, secondary and tertiary ferrocenylethyl-based phosphines.

PubMed

Azizpoor Fard, M; Rabiee Kenaree, A; Boyle, P D; Ragogna, P J; Gilroy, J B; Corrigan, J F

2016-02-21

Ferrocene-based phosphines constitute an important auxiliary ligand in inorganic chemistry. Utilizing the (ferrocenylethyl)phosphines (FcCH2CH2)3-nHnP (Fc = ferrocenyl; n = 2, 1; n = 1, 2; n = 0, 3) the synthesis of a series of coordination complexes [(FcCH2CH2)3-nHnPCuCl]4 (n = 2, 1-CuCl; n = 0, 3-CuCl), [(FcCH2CH2)2HPCuCl] (2-CuCl), {[(FcCH2CH2)H2P]2AgCl}2 (1-AgCl), [(FcCH2CH2)2HPAgCl] (2-AgCl), [(FcCH2CH2)3PAgCl]4 (3-AgCl), [(FcCH2CH2)3PM(OAc)]4 (M = Cu, 3-CuOAc M = Ag, 3-AgOAc), [(FcCH2CH2)3-nHnPAuCl] (n = 1, 2-AuCl; n = 0, 3-AuCl), via the reaction between the free phosphine and MX (M = Cu, Ag and Au; X = Cl, OAc), is described. The reaction between the respective phosphine with a suspension of metal-chloride or -acetate in a 1 : 1 ratio in THF at ambient temperature affords coordinated phosphine-coinage metal complexes. Varying structural motifs are observed in the solid state, as determined via single crystal X-ray analysis of 1-CuCl, 3-CuCl, 1-AgCl, 3-AgCl, 3-CuOAc, 3-AgOAc, 2-AuCl and 3-AuCl. Complexes 1-CuCl and 3-CuCl are tetrameric Cu(i) cubane-like structures with a Cu4Cl4 core, whereas silver complexes with primary and tertiary phosphine reveal two different structural types. The structure of 1-AgCl, unlike the rest, displays the coordination of two phosphines to each silver atom and shows a quadrangle defined by two Ag and two Cl atoms. In contrast, 3-AgCl is distorted from a cubane structure via elongation of one of the ClAg distances. 3-CuOAc and 3-AgOAc are isostructural with step-like cores, while complexes 2-AuCl and 3-AuCl reveal a linear geometry of a phosphine gold(i) chloride devoid of any aurophilic interactions. All of the complexes were characterized in solution by multinuclear (1)H, (13)C{(1)H} and (31)P NMR spectroscopic techniques; the redox chemistry of the series of complexes was examined using cyclic voltammetry. This class of complexes has been found to exhibit one reversible Fe(ii)/Fe(iii) oxidation couple, suggesting the absence of electronic communication between the ferrocenyl units on individual phosphine ligands as well as between different phosphines on the polymetallic cores.

Gold nanoclusters-Cu(2+) ensemble-based fluorescence turn-on and real-time assay for acetylcholinesterase activity and inhibitor screening.

PubMed

Sun, Jian; Yang, Xiurong

2015-12-15

Based on the specific binding of Cu(2+) ions to the 11-mercaptoundecanoic acid (11-MUA)-protected AuNCs with intense orange-red emission, we have proposed and constructed a novel fluorescent nanomaterials-metal ions ensemble at a nonfluorescence off-state. Subsequently, an AuNCs@11-MUA-Cu(2+) ensemble-based fluorescent chemosensor, which is amenable to convenient, sensitive, selective, turn-on and real-time assay of acetylcholinesterase (AChE), could be developed by using acetylthiocholine (ATCh) as the substrate. Herein, the sensing ensemble solution exhibits a marvelous fluorescent enhancement in the presence of AChE and ATCh, where AChE hydrolyzes its active substrate ATCh into thiocholine (TCh), and then TCh captures Cu(2+) from the ensemble, accompanied by the conversion from fluorescence off-state to on-state of the AuNCs. The AChE activity could be detected less than 0.05 mU/mL within a good linear range from 0.05 to 2.5 mU/mL. Our proposed fluorescence assay can be utilized to evaluate the AChE activity quantitatively in real biological sample, and furthermore to screen the inhibitor of AChE. As far as we know, the present study has reported the first analytical proposal for sensing AChE activity in real time by using a fluorescent nanomaterials-Cu(2+) ensemble or focusing on the Cu(2+)-triggered fluorescence quenching/recovery. This strategy paves a new avenue for exploring the biosensing applications of fluorescent AuNCs, and presents the prospect of AuNCs@11-MUA-Cu(2+) ensemble as versatile enzyme activity assay platforms by means of other appropriate substrates/analytes. Copyright © 2015 Elsevier B.V. All rights reserved.

Local structure of molten AuGa 2 under pressure: Evidence for coordination change and planetary implications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalkan, Bora; Godwal, Budhiram; Raju, Selva Vennila

In situ x-ray diffraction measurements and inverse Monte Carlo simulations of pair distribution functions were used to characterize the local structure of molten AuGa 2 up to 16 GPa and 940 K. Our results document systematic changes in liquid structure due to a combination of bond compression and coordination increase. Empirical potential structure refinement shows the first-neighbor coordination of Ga around Au and of Au around Ga to increase from about 8 to 10 and 4 to 5, respectively between 0 and 16 GPa, and the inferred changes in liquid structure can explain the observed melting-point depression of AuGa2 upmore » to 5 GPa. As intermetallic AuGa 2 is an analogue for metallic SiO 2 at much higher pressures, our results imply that structural changes documented for non-metallic silicate melts below 100 GPa are followed by additional coordination changes in the metallic state at pressures in the 0.2–1 TPa range achieved inside large planets.« less

Local structure of molten AuGa 2 under pressure: Evidence for coordination change and planetary implications

DOE PAGES

Kalkan, Bora; Godwal, Budhiram; Raju, Selva Vennila; ...

2018-05-01

In situ x-ray diffraction measurements and inverse Monte Carlo simulations of pair distribution functions were used to characterize the local structure of molten AuGa 2 up to 16 GPa and 940 K. Our results document systematic changes in liquid structure due to a combination of bond compression and coordination increase. Empirical potential structure refinement shows the first-neighbor coordination of Ga around Au and of Au around Ga to increase from about 8 to 10 and 4 to 5, respectively between 0 and 16 GPa, and the inferred changes in liquid structure can explain the observed melting-point depression of AuGa2 upmore » to 5 GPa. As intermetallic AuGa 2 is an analogue for metallic SiO 2 at much higher pressures, our results imply that structural changes documented for non-metallic silicate melts below 100 GPa are followed by additional coordination changes in the metallic state at pressures in the 0.2–1 TPa range achieved inside large planets.« less

Characterization of opto-electrical enhancement of tandem photoelectrochemical cells by using photoconductive-AFM

NASA Astrophysics Data System (ADS)

Park, Sun-Young; Elbersen, Rick; Huskens, Jurriaan; Gardeniers, Han; Lee, Joo-Yul; Mul, Guido; Heo, Jinhee

2017-07-01

Solar-to-hydrogen conversion by water splitting in photoelectrochemical cells (PECs) is a promising approach to alleviate problems associated with intermittency in solar energy supply and demand. Several interfacial resistances in photoelectrodes limit the performance of such cells, while the properties of interfaces are not easy to analyze in situ. We applied photoconductive-AFM to analyze the performance of WO3/p+n Si photoanodes, containing an ultra-thin metal interface of either Au or Pt. The Au interface consisted of Au nanoparticles with well-ordered interspacing, while Pt was present in the form of a continuous film. Photoconductive-AFM data show that upon illumination significantly larger currents are measured for the WO3/p+n Si anode equipped with the Au interface, as compared to the WO3/p+n Si anode with the Pt interface, in agreement with the better performance of the former electrode in a photoelectrochemical cell. The remarkable performance of the Au-containing electrode is proposed to be the result of favorable electron-hole recombination rates induced by the Au nanoparticles in a plasmon resonance excited state.

Ultrathin Au film on polymer surface for surface plasmon polariton waveguide application

NASA Astrophysics Data System (ADS)

Liu, Tong; Ji, Lanting; He, Guobing; Sun, Xiaoqiang; Wang, Fei; Zhang, Daming

2017-11-01

Formation of laterally continuous ultrathin gold films on polymer substrates is a technological challenge. In this work, the vacuum thermal evaporation method is adopted to form continuous Au films in the thickness range of 7-17 nm on polymers of Poly(methyl-methacrylate-glycidly-methacrylate) and SU-8 film surface without using the adhesion or metallic seeding layers. Absorption spectrum, scanning electron microscope and atomic force microscope images are used to characterize the Au film thickness, roughness and optical loss. The result shows that molecular-scale structure, surface energy and electronegativity have impacts on the Au film morphology on polymers. Wet chemical etching is used to fabricate 7-nm thick Au stripes embedded in polymer claddings. These long-range surface plasmon polariton waveguides demonstrate the favorable morphological configurations and cross-sectional states. Through the end-fire excitation method, propagation losses of 6-μm wide Au stripes are compared to theoretical values and analyzed from practical film status. The smooth, patternable gold films on polymer provide potential applications to plasmonic waveguides, biosensing, metamaterials and optical antennas.

Gamma radiation mediated green synthesis of gold nanoparticles using fermented soybean-garlic aqueous extract and their antimicrobial activity.

PubMed

El-Batal, Ahmed Ibrahim; Hashem, Abd-Algawad M; Abdelbaky, Noha M

2013-12-01

Aspergillus oryzae was used to enhance the mobilization of antioxidants of soybean matrix along with garlic as a co-substrate by modulating polyphenolic substances during solid-state fermentation. Mobilized polyphenols were used as a green tool for synthesis and stabilization of gold nanoparticles (AuNPs). The radiation-induced AuNPs synthesis is a simple, clean and inexpensive process which involves radiolysis of aqueous solution that provides an efficient method to reduce metal ions. Gamma irradiated aqueous extract of fermented soybean and garlic was used for rapid preparation of AuNPs combining both effects of radiolytic reactions by radiation and stabilization by bioactive components of fermented extract. The synthesized AuNPs were confirmed by UV-Visible spectrophotometry, dynamic light scattering (DLS), Fourier Transform infra red (FT-IR) spectrophotometry, and transmission electron microscope (TEM) analysis which revealed morphology of spherical AuNPs with size ranging from 7-12 nm. The synthesized AuNPs exhibited antimicrobial activity against both Gram positive and Gram negative bacteria, as measured by well diffusion assay.

Direct Deposition of Gas Phase Generated Aerosol Gold Nanoparticles into Biological Fluids - Corona Formation and Particle Size Shifts

PubMed Central

Svensson, Christian R.; Messing, Maria E.; Lundqvist, Martin; Schollin, Alexander; Deppert, Knut; Pagels, Joakim H.; Rissler, Jenny; Cedervall, Tommy

2013-01-01

An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the risks associated with nanoparticle inhalation has led to the emergence of Air-Liquid interface toxicology. As a step in this process, this study explores the evolution of particle characteristics as they move from the airborne state into physiological solution. Airborne gold nanoparticles (AuNP) are generated using an evaporation-condensation technique. Spherical and agglomerate AuNPs are deposited into physiological solutions of increasing biological complexity. The AuNP size is characterized in air as mobility diameter and in liquid as hydrodynamic diameter. AuNP:Protein aggregation in physiological solutions is determined using dynamic light scattering, particle tracking analysis, and UV absorption spectroscopy. AuNPs deposited into homocysteine buffer form large gold-aggregates. Spherical AuNPs deposited in solutions of albumin were trapped at the Air-Liquid interface but was readily suspended in the solutions with a size close to that of the airborne particles, indicating that AuNP:Protein complex formation is promoted. Deposition into serum and lung fluid resulted in larger complexes, reflecting the formation of a more complex protein corona. UV absorption spectroscopy indicated no further aggregation of the AuNPs after deposition in solution. The corona of the deposited AuNPs shows differences compared to AuNPs generated in suspension. Deposition of AuNPs from the aerosol phase into biological fluids offers a method to study the protein corona formed, upon inhalation and deposition in the lungs in a more realistic way compared to particle liquid suspensions. This is important since the protein corona together with key particle properties (e.g. size, shape and surface reactivity) to a large extent may determine the nanoparticle effects and possible translocation to other organs. PMID:24086363

Density functional theory study on the metal-support interaction between a Au9 cluster and an anatase TiO2(001) surface.

PubMed

Jiang, Zong-You; Zhao, Zong-Yan

2017-08-23

Noble metals supported on TiO 2 surfaces have shown extraordinary photocatalytic properties in many important processes such as hydrogenation, water splitting, degradation of hazards, and so on. Using density functional theory calculations, this work has systematically investigated the microstructure and electronic structure of three different Au 9 isomers loaded on anatase TiO 2 (001) surface. The calculated results show that the interaction between the Au 9 cluster and the TiO 2 support is closely related to the adsorption site and the stability of the Au 9 cluster in the gas phase. The adsorption energy of the 2D configuration is larger than that of the 3D configuration of the Au 9 cluster, owing to the stronger interactions between more adsorption sites. The stable adsorption site for Au 9 clusters deposited on the anatase TiO 2 (001) surface tends to be the O 2c -O 2c hollow site. The presentation of the MIGS of the Au 9 cluster, the disappearance of surface states of the TiO 2 (001) surface, and the shifting of the Fermi level from the top of the valence band to the bottom of the conduction band suggest strong interactions between the Au 9 clusters and the TiO 2 (001) surface. Importantly, the electron transfer from the Au 9 clusters to the TiO 2 support occurs mainly through Au-O 2c interactions, which are mainly localized at the contact layer of the Au 9 clusters. These conclusions are useful to understand various physical and chemical properties of noble metal clusters loaded onto an oxide surface, and helpful to design novel metal/semiconductor functional composite materials and devices.

Gold Nanoparticles Stabilized with MPEG-Grafted Poly(l-lysine): in Vitro and in Vivo Evaluation of a Potential Theranostic Agent

PubMed Central

2015-01-01

As the number of diagnostic and therapeutic applications utilizing gold nanoparticles (AuNPs) increases, so does the need for AuNPs that are stable in vivo, biocompatible, and suitable for bioconjugation. We investigated a strategy for AuNP stabilization that uses methoxypolyethylene glycol-graft-poly(l-lysine) copolymer (MPEG-gPLL) bearing free amino groups as a stabilizing molecule. MPEG-gPLL injected into water solutions of HAuCl4 with or without trisodium citrate resulted in spherical (Zav = 36 nm), monodisperse (PDI = 0.27), weakly positively charged nanoparticles (AuNP3) with electron-dense cores (diameter: 10.4 ± 2.5 nm) and surface amino groups that were amenable to covalent modification. The AuNP3 were stable against aggregation in the presence of phosphate and serum proteins and remained dispersed after their uptake into endosomes. MPEG-gPLL-stabilized AuNP3 exhibited high uptake and very low toxicity in human endothelial cells, but showed a high dose-dependent toxicity in epithelioid cancer cells. Highly stable radioactive labeling of AuNP3 with 99mTc allowed imaging of AuNP3 biodistribution and revealed dose-dependent long circulation in the blood. The minor fraction of AuGNP3 was found in major organs and at sites of experimentally induced inflammation. Gold analysis showed evidence of a partial degradation of the MPEG-gPLL layer in AuNP3 particles accumulated in major organs. Radiofrequency-mediated heating of AuNP3 solutions showed that AuNP3 exhibited heating behavior consistent with 10 nm core nanoparticles. We conclude that PEG-pPLL coating of AuNPs confers “stealth” properties that enable these particles to exist in vivo in a nonaggregating, biocompatible state making them suitable for potential use in biomedical applications such as noninvasive radiofrequency cancer therapy. PMID:25496453

Physicochemical and catalytic properties of Au nanorods micro-assembled in solvents of varying dipole moment and refractive index

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaur, Rupinder; Pal, Bonamali, E-mail: bpal@thapar.edu

2015-02-15

Highlights: • Physicochemical activities of Au nanorods in water largely differ from organic solvents. • Au nanorods agglomeration increased with dipole moments of different polar solvents. • Refractive indexes of Au nanorods dispersion in various polar solvents are enhanced. • Electrokinetics significantly altered depending on agglomerated size of Au nanorods. • Catalysis or co-catalysis activity is varied as per the extent of Au nanorods coagulation. - Abstract: This paper deals with the impact of dipole moment (1.66–3.96 D) and refractive index (1.333–1.422) of the dispersion solvent on the plasmon absorption, surface charge, zeta potential, and adsorption properties of Au nanorodsmore » (AuNRs). AuNRs (length ≈ 53 nm and width ≈ 20 nm) undergo agglomeration (size 50–180 nm) with increase in the dipole moment of solvent (iPrOH < MeOH < DMF < DMSO). Whereas, no such coagulation occurs in H{sub 2}O and CCl{sub 4} suspension as confirmed by DLS and TEM size distribution. The electrostatic interaction of AuNRs with its surface adsorbed solvent dipoles leads to alteration of the their ionic state, absolute electronic charge and zeta potential (+49.79 mV in H{sub 2}O, +8.99 mV in DMF and −4.65 mV in MeOH dispersion) to a greater extent. This interaction distinctly modifies the adsorption behavior of polar molecules like p-nitrophenol and salicylic acid on AuNRs surface, as evidenced by the measured changes in their electro-kinetic parameters. As a result, we observe a substantial difference in catalytic and co-catalytic activities of AuNRs dispersed in various solvents as mentioned above because the catalytic properties of AuNRs are strongly dependent on the type of solvent in which they are dispersed.« less

The Role of Work Function and Band Gap in Resistive Switching Behaviour of ZnTe Thin Films

NASA Astrophysics Data System (ADS)

Rowtu, Srinu; Sangani, L. D. Varma; Krishna, M. Ghanashyam

2018-02-01

Resistive switching behavior by engineering the electrode work function and band gap of ZnTe thin films is demonstrated. The device structures Au/ZnTe/Au, Au/ZnTe/Ag, Al/ZnTe/Ag and Pt/ZnTe/Ag were fabricated. ZnTe was deposited by thermal evaporation and the stoichiometry and band gap were controlled by varying the source-substrate distance. Band gap could be varied between 1.0 eV to approximately 4.0 eV with the larger band gap being attributed to the partial oxidation of ZnTe. The transport characteristics reveal that the low-resistance state is ohmic in nature which makes a transition to Poole-Frenkel defect-mediated conductivity in the high-resistance states. The highest R off-to- R on ratio achieved is 109. Interestingly, depending on stoichiometry, both unipolar and bipolar switching can be realized.

Characteristics of hardron-nucleus interactions at 100 GeV/c

NASA Astrophysics Data System (ADS)

Toothacker, W. S.; Whitmore, J.; Elcombe, P. A.; Hill, J. C.; Neale, W. W.; Kowald, W.; Walker, W. D.; Lucas, P.; Voyvodic, L.; Ammar, R.; Coppage, D.; Davis, R.; Gress, J.; Kanekal, S.; Kwak, N.; Bishop, J. M.; Biswas, N. N.; Cason, N. M.; Kenney, V. P.; Mattingly, M. C. K.; Ruchti, R. C.; Shepard, W. D.; Ting, S. J. Y.

1988-11-01

We report on 100 GeV/c interactions of p and p¯ with Ag and Au targets. This is a subset of the data from Fermilab experiment E597 and was performed with the 30-inch bubble chamber and Downstream Particle Identifier. Final state protons with laboratory momentum less than 1.4 GeV/c have been identified by their ionization in the bubble chamber. Final state protons/antiprotons with laboratory momentum greater than 10 GeV/c have been identified using CRISIS, an ionization sampling drift chamber. The cross section and mean transverse momentum squared of the leading baryon from the reactions p+(Ag,Au)→p+X and p¯+(Ag,Au)→p¯+X are presented as a function of the rapidity loss of the leading baryon. The laboratory rapidity and transverse momentum squared of the associated pions are also presented.

Approximate treatment of semicore states in GW calculations with application to Au clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xian, Jiawei; Baroni, Stefano; CNR-IOM Democritos, Theory-Elettra group, Trieste

We address the treatment of transition metal atoms in GW electronic-structure calculations within the plane-wave pseudo-potential formalism. The contributions of s and p semi-core electrons to the self-energy, which are essential to grant an acceptable accuracy, are dealt with using a recently proposed scheme whereby the exchange components are treated exactly at the G{sub 0}W{sub 0} level, whereas a suitable approximation to the correlation components is devised. This scheme is benchmarked for small gold nano-clusters, resulting in ionization potentials, electron affinities, and density of states in very good agreement with those obtained from calculations where s and p semicore statesmore » are treated as valence orbitals, and allowing us to apply this same scheme to clusters of intermediate size, Au{sub 20} and Au{sub 32}, that would be otherwise very difficult to deal with.« less

Laser generation of Au ions with charge states above 50+

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laska, L.; Jungwirth, K.; Krasa, J.

2008-02-15

Results of recent studies on highly charged Au ion generation, using the intense long pulses of the PALS high power iodine laser ({lambda}=1.315 {mu}m, E{sub L}=800 J/400 ps), operating under variable experimental conditions (1{omega}, 3{omega}, varying target thickness and changing focus positions), are presented. Both the ion collectors and the ion electrostatic analyzers were applied for the identification of ions in a large distance from the target. The time-of-flight collector signals were treated by a means of peak deconvolution assuming a shifted Maxwell-Boltzmann form of the constituent ion current peaks. Attention was paid to the influence of pulse precursor, whichmore » becomes evident, especially, if using thinner targets and 1{omega}. The results for 3{omega} point to the presence of several groups of ions with the highest recorded charge state Au{sup 53+}.« less

Improved two-temperature model including electron density of states effects for Au during femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Fang, Ranran; Wei, Hua; Li, Zhihua; Zhang, Duanming

2012-01-01

The electron temperature dependences of the electron-phonon coupling factor and electron heat capacity based on the electron density of states are investigated for precious metal Au under femtosecond laser irradiation. The thermal excitation of d band electrons is found to result in large deviations from the commonly used approximations of linear temperature dependence of the electron heat capacity, and the constant electron-phonon coupling factor. Results of the simulations performed with the two-temperature model demonstrate that the electron-phonon relaxation time becomes short for high fluence laser for Au. The satisfactory agreement between our numerical results and experimental data of threshold fluence indicates that the electron temperature dependence of the thermophysical parameters accounting for the thermal excitation of d band electrons should not be neglected under the condition that electron temperature is higher than 10 4 K.

Rhenium-phthalocyanine molecular nanojunction with high magnetic anisotropy and high spin filtering efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J.; Institute of Nanomaterial and Nanostructure, Changsha University of Science and Technology, Changsha 410114; Hu, J.

2015-07-20

Using the density functional and non-equilibrium Green's function approaches, we studied the magnetic anisotropy and spin-filtering properties of various transition metal-Phthalocyanine molecular junctions across two Au electrodes. Our important finding is that the Au-RePc-Au junction has both large spin filtering efficiency (>80%) and large magnetic anisotropy energy, which makes it suitable for device applications. To provide insights for the further experimental work, we discussed the correlation between the transport property, magnetic anisotropy, and wave function features of the RePc molecule, and we also illustrated the possibility of controlling its magnetic state.

William Wales and the 1769 Transit of Venus: Puzzle Solving and the Determination of the Astronomical Unit

ERIC Educational Resources Information Center

Metz, Don

2009-01-01

According to Thomas Kuhn, a significant part of "normal science" is the fact gathering, empirical work which is intended to illustrate an existing paradigm. Some of this effort focuses on the determination of physical constants such as the astronomical unit (AU). For Kuhn, normal science is also what prepares students for membership in a…

SURFACE PHONONS IN THE ORDERED c(2 × 2) PHASE OF Pd ON Au(100)

NASA Astrophysics Data System (ADS)

Chadli, R.; Khater, A.; Tigrine, R.

2013-03-01

The vibrational properties of the Au(100)-c(2 × 2)-Pd ordered phase, which is a stable system in the temperature range of 500 K to 600 K, are presented. This surface alloy is formed by depositing Pd atoms onto the Au(100) surface, and annealing at higher temperatures. The equilibrium structural characteristics, phonon dispersions as well as the local density of phonon states are calculated using the matching theory associated with Green's function formalism evaluated in the harmonic approximation. New surface modes have been found on the ordered metallic surface alloy along the three directions of high symmetry /line{Γ X}, /line{XM}, and /line{MΓ }, in comparison with the clean surface Au(100). Three of them are observed above the bulk bands spectrum.

Event-by-Event Fluctuations of Azimuthal Particle Anisotropy in Au+Au Collisions at sNN=200GeV

NASA Astrophysics Data System (ADS)

Alver, B.; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Busza, W.; Carroll, A.; Chai, Z.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Halliwell, C.; Hamblen, J.; Hauer, M.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Hołyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Khan, N.; Kulinich, P.; Kuo, C. M.; Li, W.; Lin, W. T.; Loizides, C.; Manly, S.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Reed, C.; Roland, C.; Roland, G.; Sagerer, J.; Seals, H.; Sedykh, I.; Smith, C. E.; Stankiewicz, M. A.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Vaurynovich, S. S.; Verdier, R.; Veres, G. I.; Walters, P.; Wenger, E.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wysłouch, B.

2010-04-01

This Letter presents the first measurement of event-by-event fluctuations of the elliptic flow parameter v2 in Au+Au collisions at sNN=200GeV as a function of collision centrality. The relative nonstatistical fluctuations of the v2 parameter are found to be approximately 40%. The results, including contributions from event-by-event elliptic flow fluctuations and from azimuthal correlations that are unrelated to the reaction plane (nonflow correlations), establish an upper limit on the magnitude of underlying elliptic flow fluctuations. This limit is consistent with predictions based on spatial fluctuations of the participating nucleons in the initial nuclear overlap region. These results provide important constraints on models of the initial state and hydrodynamic evolution of relativistic heavy ion collisions.

Modeling of two-particle femtoscopic correlations at top RHIC energy

NASA Astrophysics Data System (ADS)

Ermakov, N.; Nigmatkulov, G.

2017-01-01

The spatial and temporal characteristics of particle emitting source produced in particle and/or nuclear collisions can be measured by using two-particle femtoscopic correlations. These correlations arise due to quantum statistics, Coulomb and strong final state interactions. In this paper we report on the calculations of like-sign pion femtoscopic correlations produced in p+p, p+Au, d+Au, Au+Au at top RHIC energy using Ultra Relativistic Quantum Molecular Dynamics Model (UrQMD). Three-dimensional correlation functions are constructed using the Bertsch-Pratt parametrization of the two-particle relative momentum. The correlation functions are studied in several transverse mass ranges. The emitting source radii of charged pions, Rout, Rside, Rlong , are obtained from Gaussian fit to the correlation functions and compared to data from the STAR and PHENIX experiments.

Inhibition of Zero Drift in Perovskite-Based Photodetector Devices via [6,6]-Phenyl-C61-butyric Acid Methyl Ester Doping.

PubMed

Liu, Yintao; Jia, Renxu; Wang, Yucheng; Hu, Ziyang; Zhang, Yuming; Pang, Tiqiang; Zhu, Yuejin; Luan, Suzhen

2017-05-10

Zero drift can severely deteriorate the stability of the light-dark current ratio, detectivity, and responsivity of photodetectors. In this paper, the effects of a [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)-doped perovskite-based photodetector device on the inhibition of zero drift under dark state are discussed. Two kinds of photodetectors (Au/CH 3 NH 3 PbI x Cl 3-x /Au and Au/CH 3 NH 3 PbI x Cl 3-x :PCBM/Au) were prepared, and the materials and photodetector devices were measured by scanning electron microscopy, X-ray diffraction, photoluminescence, ultraviolet absorption spectra, and current-voltage and current-time measurements. It was found that similar merit parameters, including light-dark current ratio (∼10 2 ), detectivity (∼10 11 Jones), and responsivity were obtained for these two kinds of photodetectors. However, the drift of Au/CH 3 NH 3 PbI x Cl 3-x :PCBM/Au devices is negligible, while a drift of ∼0.2 V exists in Au/CH 3 NH 3 PbI x Cl 3-x /Au devices. A new model is proposed based on the hindering theory of ion (vacancy) migration, and it is believed that the dopant PCBM can hinder the ion (vacancy) migration of perovskite materials to suppress the phenomenon of zero drift in perovskite-based photodetectors.

Molecular dynamics simulations of the formation of 1D spin-valves from stretched Au-Co and Pt-Co nanowires

NASA Astrophysics Data System (ADS)

Cortes-Huerto, R.; Sondon, T.; Saúl, A.

2014-11-01

We have performed molecular dynamics (MD) simulations of stretched Aux-Co1 - x and Ptx-Co1 - x nanowires to investigate the formation of bimetallic monoatomic wires between two electrodes. We have considered nanowires with two concentrations x = 0.2 and 0.8, aspect ratio of 13, a cross section of 1 nm2 and a wide range of temperatures (from 10 to 400 K). For the MD simulations we have used a semi-empirical interatomic potential based on the second moment approximation (SMA) of the density of states to the tight-binding Hamiltonian. For Au-Co alloys, Au atoms tends to migrate towards the narrowed region to form almost pure Au wires. In the PtCo case the formed chains usually consist of Pt enriched alternating structures. The most striking result is probably the Au0.2-Co0.8 alloy where pure monoatomic Au chains form between two Co electrodes constituting a potential 1D spin valve. Despite the known ease with which the 5d metals (Pt, Ir, and Au) form monoatomic chains (MACS), our results show that in the presence of Co (x = 0.2), the percentage of chain formation is higher than in the Pt and Au rich cases (x = 0.8).

Dispersed-nanoparticle loading synthesis for monodisperse Au-titania composite particles and their crystallization for highly active UV and visible photocatalysts.

PubMed

Sakamoto, Takeshi; Nagao, Daisuke; Noba, Masahiro; Ishii, Haruyuki; Konno, Mikio

2014-06-24

Submicrometer-sized amorphous titania spheres incorporating Au nanoparticles (NPs) were prepared in a one-pot synthesis consisting of a sol-gel reaction of titanium(IV) isopropoxide in the presence of chloroauric acid and a successive reduction with sodium borohydride in a mixed solvent of ethanol/acetonitrile. The synthesis was allowed to prepare monodisperse titania spheres that homogeneously incorporated Au NPs with sizes of ca. 7 nm. The Au NP-loaded titania spheres underwent different crystallization processes, including 500 °C calcination in air, high-temperature hydrothermal treatment (HHT), and/or low-temperature hydrothermal treatment (LHT). Photocatalytic experiments were conducted with the Au NP-loaded crystalline titania spheres under irradiation of UV and visible light. A combined process of LHT at 80 °C followed by calcination at 500 °C could effectively crystallize titania spheres maintaining the dispersion state of Au NPs, which led to photocatalytic activity higher than that of commercial P25 under UV irradiation. Under visible light irradiation, the Au NP-titania spheres prepared with a crystallization process of LHT at 80 °C for 6 h showed photocatalytic activity much higher than a commercial product of visible light photocatalyst. Structure analysis of the visible light photocatalysts indicates the importance of prevention of the Au NPs aggregation in the crystallization processes for enhancement of photocatalytic activity.

Ligand-Enhanced Optical Response of Gold Nanomolecules and Its Fragment Projection Analysis: The Case of Au 30 (SR) 18

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sementa, Luca; Barcaro, Giovanni; Baseggio, Oscar

Here we investigate via first-principles simulations the optical absorption spectra of three different Au30(SR)18 monolayer-protected clusters (MPC): Au30(StBu)18, which is known in the literature and whose crystal structure is available, and two species – Au30(SPh)18 and Au30(SPh-pNO2)18 – which have been designed by replacing the tert-butyl organic residues with aromatic ones so as to investigate the effects of ligand replacement on the optical response of Au nanomolecules. In analogy with previously studied but rather different Au23(SR)16- anionic species, a substantial ligand-enhancement of the absorption intensity in the optical region is obtained for the Au30(SPhpNO2)18 neutral MPC. This demonstrates that usingmore » conjugated aromatic ligands with properly chosen electron withdrawal substituents and exhibiting steric hindrance so as to also achieve charge decompression at the surface is a general approach to enhance MPC photo-absorption intensity in the optical region. Moreover, the ligand-enhancement phenomenon is subjected to a detailed analysis based on fragment projection of electronic excited states and on induced transition densities, leading to a better understanding of its physical origin, thus opening avenues to its more precise control and exploitation.« less

Jahn-Teller effects in transition-metal compounds with small charge-transfer energy

NASA Astrophysics Data System (ADS)

Mizokawa, Takashi

2013-04-01

We have studied Jahn-Teller effects in Cs2Au2Br6, ACu3Co4O12(A=Ca or Y), and IrTe2 in which the ligand p-to-transition-metal d charge-transfer energy is small or negative. The Au+/Au3+ charge disproportionation of Cs2Au2Br6 manifests in Au 4f photoemission spectra. In Cs2Au2Br6 with negative Δ and intermediate U, the charge disproportionation can be described using effective d orbitals constructed from the Au 5d and Br 4p orbitals and is stabilized by the Jahn-Teller distortion of the Au3+ site with low-spin d8 configuration. In ACu3Co4O12, Δs for Cu3+ and Co4+ are negative and Us are very large. The Zhang-Rice picture is valid to describe the electronic state, and the valence change from Cu2+/Co4+ to Cu3+/Co3+ can be viewed as the O 2p hole transfer from Co to Cu or d9 + d6L → d9L + d6. In IrTe2, both Δ and U are small and the Ir 5d and Te 5p electrons are itinerant to form the multi-band Fermi surfaces. The ideas of band Jahn-Teller transition and Peierls transition are useful to describe the structural instabilities.

The Scales of Time, Length, Mass, Energy, and Other Fundamental Physical Quantities in the Atomic World and the Use of Atomic Units in Quantum Mechanical Calculations

ERIC Educational Resources Information Center

Teo, Boon K.; Li, Wai-Kee

2011-01-01

This article is divided into two parts. In the first part, the atomic unit (au) system is introduced and the scales of time, space (length), and speed, as well as those of mass and energy, in the atomic world are discussed. In the second part, the utility of atomic units in quantum mechanical and spectroscopic calculations is illustrated with…

Direct visualization of quasi-ordered oxygen chain structures on Au(110)-(1 × 2)

NASA Astrophysics Data System (ADS)

Hiebel, F.; Montemore, M. M.; Kaxiras, E.; Friend, C. M.

2016-08-01

The Au(110) surface offers unique advantages for atomically-resolved model studies of catalytic oxidation processes on gold. We investigate the adsorption of oxygen on Au(110) using a combination of scanning tunneling microscopy (STM) and density functional theory (DFT) methods. We identify the typical (empty-states) STM contrast resulting from adsorbed oxygen as atomic-sized dark features of electronic origin. DFT-based image simulations confirm that chemisorbed oxygen is generally detected indirectly, from the binding-induced electronic structure modification of gold. STM images show that adsorption occurs without affecting the general structure of the pristine Au(110) missing-row reconstruction. The tendency to form one-dimensional structures is observed already at low coverage (< 0.05 ML), with oxygen adsorbing on alternate sides of the reconstruction ridges. Consistently, calculations yield preferred adsorption on the (111) facets of the reconstruction, on a 3-fold coordination site, with increased stability when adsorbed in chains. Gold atoms with two oxygen neighbors exhibit enhanced electronic hybridization with the O states. Finally, the species observed are reactive to CO oxidation at 200 K and desorption of CO2 leaves a clean and ordered gold surface.

Redox driven conductance changes for resistive memory

NASA Astrophysics Data System (ADS)

Shoute, Lian C. T.; Pekas, Nikola; Wu, Yiliang; McCreery, Richard L.

2011-03-01

The relationship between bias-induced redox reactions and resistance switching is considered for memory devices containing TiO2 or a conducting polymer in "molecular heterojunctions" consisting of thin (2-25 nm) films of covalently bonded molecules, polymers, and oxides. Raman spectroscopy was used to monitor changes in the oxidation state of polythiophene in Au/P3HT/SiO2/Au devices, and it was possible to directly determine the formation and stability of the conducting polaron state of P3HT by applied bias pulses [P3HT = poly(3-hexyl thiophene)]. Polaron formation was strongly dependent on junction composition, particularly on the interfaces between the polymer, oxide, and electrodes. In all cases, trace water was required for polaron formation, leading to the proposal that water reduction acts as a redox counter-reaction to polymer oxidation. Polaron stability was longest for the case of a direct contact between Au and SiO2, implying that catalytic water reduction at the Au surface generated hydroxide ions which stabilized the cationic polaron. The spectroscopic information about the dependence of polaron stability on device composition will be useful for designing and monitoring resistive switching memory based on conducting polymers, with or without TiO2 present.

Exotic species with explicit noble metal-noble gas-noble metal linkages.

PubMed

Moreno, Norberto; Restrepo, Albeiro; Hadad, C Z

2018-02-14

We present a study of the isoelectronic Pt 2 Ng 2 F 4 and [Au 2 Ng 2 F 4 ] 2+ species with noble gas atoms (Ng = Kr, Xe, Rn) acting as links bridging the two noble metal atoms. The stability of the species is investigated using several thermodynamic, kinetic and reactivity indicators. The results are compared against [AuXe 4 ] 2+ , which is thermodynamically unstable in the gas phase but is stabilized in the solid state to the point that it has been experimentally detected as [AuXe 4 ](Sb 2 F 11 ) 2 (S. Seidel and K. Seppelt, Science, 2000, 290, 117-118). Our results indicate that improving upon [AuXe 4 ] 2+ , these exotic combinations between the a priori non-reactive noble metals and noble gases lead to metastable species, and, therefore, they have the possibility of existing in the solid state under adequate conditions. Our calculations include accurate energies and geometries at both the CCSD/SDDALL and MP2/SDDALL levels. We offer a detailed description of the nature of the bonding interactions using orbital and density-based analyses. The computational evidence suggests partially covalent and ionic interactions as the stabilization factors.

Geology and assessment of undiscovered oil and gas resources of the North Kara Basins and Platforms Province, 2008

USGS Publications Warehouse

Klett, Timothy R.; Pitman, Janet K.; Moore, Thomas E.; Gautier, D.L.

2017-11-15

The U.S. Geological Survey (USGS) recently assessed the potential for undiscovered oil and gas resources of the North Kara Basins and Platforms Province as part of the its Circum-Arctic Resource Appraisal. This geologic province is north of western Siberia, Russian Federation, in the North Kara Sea between Novaya Zemlya to the west and Severnaya Zemlya to the east. One assessment unit (AU) was defined, the North Kara Basins and Platforms AU, which coincides with the geologic province. This AU was assessed for undiscovered, technically recoverable resources. The total estimated mean volumes of undiscovered petroleum resources in the province are ~1.8 billion barrels of crude oil, ~15.0 trillion cubic feet of natural gas, and ~0.4 billion barrels of natural-gas liquids, all north of the Arctic Circle.

Mixed Valence Perovskite Cs2 Au2 I6 : A Potential Material for Thin-Film Pb-Free Photovoltaic Cells with Ultrahigh Efficiency.

PubMed

Debbichi, Lamjed; Lee, Songju; Cho, Hyunyoung; Rappe, Andrew M; Hong, Ki-Ha; Jang, Min Seok; Kim, Hyungjun

2018-03-01

New light is shed on the previously known perovskite material, Cs 2 Au 2 I 6 , as a potential active material for high-efficiency thin-film Pb-free photovoltaic cells. First-principles calculations demonstrate that Cs 2 Au 2 I 6 has an optimal band gap that is close to the Shockley-Queisser value. The band gap size is governed by intermediate band formation. Charge disproportionation on Au makes Cs 2 Au 2 I 6 a double-perovskite material, although it is stoichiometrically a single perovskite. In contrast to most previously discussed double perovskites, Cs 2 Au 2 I 6 has a direct-band-gap feature, and optical simulation predicts that a very thin layer of active material is sufficient to achieve a high photoconversion efficiency using a polycrystalline film layer. The already confirmed synthesizability of this material, coupled with the state-of-the-art multiscale simulations connecting from the material to the device, strongly suggests that Cs 2 Au 2 I 6 will serve as the active material in highly efficient, nontoxic, and thin-film perovskite solar cells in the very near future. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ferric hydroxide supported gold subnano clusters or quantum dots: enhanced catalytic performance in chemoselective hydrogenation.

PubMed

Liu, Lequan; Qiao, Botao; Ma, Yubo; Zhang, Juan; Deng, Youquan

2008-05-21

An attempt to prepare ferric hydroxide supported Au subnano clusters via modified co-precipitation without any calcination was made. High resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been employed to study the structure and chemical states of these catalysts. No Au species could be observed in the HRTEM image nor from the XRD pattern, suggesting that the sizes of the Au species in and on the ferric hydroxide support were less than or around 1 nm. Chemoselective hydrogenation of aromatic nitro compounds and alpha,beta-unsaturated aldehydes was selected as a probe reaction to examine the catalytic properties of this catalyst. Under the same reaction conditions, such as 100 degrees C and 1 MPa H2 in the hydrogenation of aromatic nitro compounds, a 96-99% conversion (except for 4-nitrobenzonitrile) with 99% selectivity was obtained over the ferric hydroxide supported Au catalyst, and the TOF values were 2-6 times higher than that of the corresponding ferric oxide supported catalyst with 3-5 nm size Au particles. For further evaluation of this Au catalyst in the hydrogenation of citral and cinnamaldehyde, selectivity towards unsaturated alcohols was 2-20 times higher than that of the corresponding ferric oxide Au catalyst.

Synthesis of Ti3AuC2, Ti3Au2C2 and Ti3IrC2 by noble metal substitution reaction in Ti3SiC2 for high-temperature-stable Ohmic contacts to SiC

NASA Astrophysics Data System (ADS)

Fashandi, Hossein; Dahlqvist, Martin; Lu, Jun; Palisaitis, Justinas; Simak, Sergei I.; Abrikosov, Igor A.; Rosen, Johanna; Hultman, Lars; Andersson, Mike; Lloyd Spetz, Anita; Eklund, Per

2017-08-01

The large class of layered ceramics encompasses both van der Waals (vdW) and non-vdW solids. While intercalation of noble metals in vdW solids is known, formation of compounds by incorporation of noble-metal layers in non-vdW layered solids is largely unexplored. Here, we show formation of Ti3AuC2 and Ti3Au2C2 phases with up to 31% lattice swelling by a substitutional solid-state reaction of Au into Ti3SiC2 single-crystal thin films with simultaneous out-diffusion of Si. Ti3IrC2 is subsequently produced by a substitution reaction of Ir for Au in Ti3Au2C2. These phases form Ohmic electrical contacts to SiC and remain stable after 1,000 h of ageing at 600 °C in air. The present results, by combined analytical electron microscopy and ab initio calculations, open avenues for processing of noble-metal-containing layered ceramics that have not been synthesized from elemental sources, along with tunable properties such as stable electrical contacts for high-temperature power electronics or gas sensors.

Microstructural, electrical and frequency-dependent properties of Au/p-Cu2ZnSnS4/n-GaN heterojunction.

PubMed

Rajagopal Reddy, V; Janardhanam, V; Won, Jonghan; Choi, Chel-Jong

2017-08-01

An Au/Cu 2 ZnSnS 4 (CZTS)/n-GaN heterojunction (HJ) is fabricated with a CZTS interlayer and probed its chemical states, structural, electrical and frequency-dependent characteristics by XPS, TEM, I-V and C-V measurements. XPS and TEM results confirmed that the CZTS films are formed on the n-GaN surface. The band gap of deposited CZTS film is found to be 1.55eV. The electrical properties of HJ correlated with the Au/n-GaN Schottky junction (SJ). The Au/CZTS/n-GaN HJ reveals a good rectification nature with high barrier height (0.82eV) compared to the Au/n-GaN SJ (0.69eV), which suggests the barrier height is influenced by the CZTS interlayer. The barrier height values assessed by I-V, Cheung's and Norde functions are closely matched with one other, thus the methods used here are reliable and valid. The extracted interface state density (N SS ) of Au/CZTS/n-GaN HJ is lower compared to the Au/n-GaN SJ that suggests the CZTS interlayer plays an important role in the reduction of N SS . Moreover, the capacitance-frequency (C-f) and conductance-frequency (G-f) characteristics of SJ and HJ are measured in the range of 1kHz-1MHz, and found that the capacitance and conductance strappingly dependent on frequency. It is found that the N SS estimated from C-f and G-f characteristics is lower compared to those estimated from I-V characteristics. Analysis confirmed that Poole-Frenkel emission dominates the reverse leakage current in both SJ and HJ, probably related to the structural defects and trap levels in the CZTS interlayer. Copyright © 2017 Elsevier Inc. All rights reserved.

Aluminum and gold deposition on cleaved single crystals of Bi2CaSr2Cu2O8 superconductor

NASA Astrophysics Data System (ADS)

Wells, B. O.; Lindberg, P. A. P.; Shen, Z.-X.; Dessau, D. S.; Lindau, I.; Spicer, W. E.; Mitzi, D. B.; Kapitulnik, A.

1989-02-01

We have used photoelectron spectroscopy to study the changes in the electronic structure of cleaved, single crystal Bi2CaSr2Cu2O8 caused by deposition of aluminum and gold. Al reacts strongly with the superconductor surface. Even the lowest coverages of Al reduces the valency of Cu in the superconductor, draws oxygen out of the bulk, and strongly modifies the electronic states in the valence band. The Au shows little reaction with the superconductor surface. Underneath Au, the Cu valency is unchanged and the core peaks show no chemically shifted components. Au appears to passivate the surface of the superconductor and thus may aid in the processing of the Bi-Ca-Sr-Cu-O material. These results are consistent with earlier studies of Al and Au interfaces with other, polycrystalline oxide superconductors. Comparing with our own previous results, we conclude that Au is superior to Ag in passivating the Bi-Ca-Sr-Cu-O surface.

In situ formation of the active sites in Pd-Au bimetallic nanocatalysts for CO oxidation: NAP (near ambient pressure) XPS and MS study.

PubMed

Bukhtiyarov, A V; Prosvirin, I P; Saraev, A A; Klyushin, A Yu; Knop-Gericke, A; Bukhtiyarov, V I

2018-06-07

Model bimetallic Pd-Au/HOPG catalysts have been investigated in the CO oxidation reaction using a combination of NAP XPS and MS techniques. The samples have shown catalytic activity at temperatures above 150 °C. The redistribution of Au and Pd on the surface depending on the reaction conditions has been demonstrated using NAP XPS. The Pd enrichment of the bimetallic particles' surface under reaction gas mixture has been shown. Apparently, CO adsorption induces Pd segregation on the surface. Heating the sample under reaction conditions above 150 °C decomposes the Pd-CO state due to CO desorption and reaction and simultaneous Pd-Au alloy formation on the surface takes place. Cooling back down to RT results in reversible Pd segregation due to Pd-CO formation and the sample becomes inactive. It has been shown that in situ studies are necessary for investigation of the active sites in Pd-Au bimetallic systems.

Spin resolved electronic transport through N@C20 fullerene molecule between Au electrodes: A first principles study

NASA Astrophysics Data System (ADS)

Caliskan, Serkan

2018-05-01

Using first principles study, through Density Functional Theory combined with Non Equilibrium Green's Function Formalism, electronic properties of endohedral N@C20 fullerene molecule joining Au electrodes (Au-N@C20) was addressed in the presence of spin property. The electronic transport behavior across the Au-N@C20 molecular junction was investigated by spin resolved transmission, density of states, molecular orbitals, differential conductance and current-voltage (I-V) characteristics. Spin asymmetric variation was clearly observed in the results due to single N atom encapsulated in the C20 fullerene cage, where the N atom played an essential role in the electronic behavior of Au-N@C20. This N@C20 based molecular bridge, exhibiting a spin dependent I-V variation, revealed a metallic behavior within the bias range from -1 V to 1 V. The induced magnetic moment, spin polarization and other relevant quantities associated with the spin resolved transport were elucidated.

Cross section of the 197Au(n,2n)196Au reaction

NASA Astrophysics Data System (ADS)

Kalamara, A.; Vlastou, R.; Kokkoris, M.; Diakaki, M.; Serris, M.; Patronis, N.; Axiotis, M.; Lagoyannis, A.

2017-09-01

The 197Au(n,2n)196Au reaction cross section has been measured at two energies, namely at 17.1 MeV and 20.9 MeV, by means of the activation technique, relative to the 27Al(n,α)24Na reference reaction cross section. Quasi-monoenergetic neutron beams were produced at the 5.5 MV Tandem T11/25 accelerator laboratory of NCSR "Demokritos", by means of the 3H(d,n)4He reaction, implementing a new Ti-tritiated target of ˜ 400 GBq activity. The induced γ-ray activity at the targets and reference foils has been measured with HPGe detectors. The cross section for the population of the second isomeric (12-) state m2 of 196Au was independently determined. Auxiliary Monte Carlo simulations were performed using the MCNP code. The present results are in agreement with previous experimental data and with theoretical calculations of the measured reaction cross sections, which were carried out with the use of the EMPIRE code.

Three-Dimensional CdS/Au Butterfly Wing Scales with Hierarchical Rib Structures for Plasmon-Enhanced Photocatalytic Hydrogen Production.

PubMed

Fang, Jing; Gu, Jiajun; Liu, Qinglei; Zhang, Wang; Su, Huilan; Zhang, Di

2018-06-13

Localized surface plasmon resonance (LSPR) of plasmonic metals (e.g., Au) can help semiconductors improve their photocatalytic hydrogen (H 2 ) production performance. However, an artificial synthesis of hierarchical plasmonic structures down to nanoscales is usually difficult. Here, we adopt the butterfly wing scales from Morpho didius to fabricate three-dimensional (3D) CdS/Au butterfly wing scales for plasmonic photocatalysis. The as-prepared materials well-inherit the pristine hierarchical biostructures. The 3D CdS/Au butterfly wing scales exhibit a high H 2 production rate (221.8 μmol·h -1 within 420-780 nm), showing a 241-fold increase over the CdS butterfly wing scales. This is attributed to the effective potentiation effect of LSPR introduced by multilayer metallic rib structures and a good interface bonding state between Au and CdS nanoparticles. Thus, our study provides a relatively simple method to learn from nature and inspiration for preparing highly efficient plasmonic photocatalysts.

Collective effects in light-heavy ion collisions

NASA Astrophysics Data System (ADS)

Schenke, Björn; Venugopalan, Raju

2014-11-01

We present results for the azimuthal anisotropy of charged hadron distributions in A+A, p+A, d+A, and 3He+A collisions within the IP-Glasma+MUSIC model. Obtained anisotropies are due to the fluid dynamic response of the system to the fluctuating initial geometry of the interaction region. While the elliptic and triangular anisotropies in peripheral Pb+Pb collisions at √{ s} = 2.76 TeV are well described by the model, the same quantities in √{ s} = 5.02 TeV p+Pb collisions underestimate the experimental data. This disagreement can be due to neglected initial state correlations or the lack of a detailed description of the fluctuating spatial structure of the proton, or both. We further present predictions for azimuthal anisotropies in p+Au, d+Au, and 3He+Au collisions at √{ s} = 200 GeV. For d+Au and 3He+Au collisions we expect the detailed substructure of the nucleon to become less important.

Logical regulation of the enzyme-like activity of gold nanoparticles by using heavy metal ions.

PubMed

Lien, Chia-Wen; Chen, Ying-Chieh; Chang, Huan-Tsung; Huang, Chih-Ching

2013-09-07

In this study we employed self-deposition and competitive or synergistic interactions between metal ions and gold nanoparticles (Au NPs) to develop OR, AND, INHIBIT, and XOR logic gates through regulation of the enzyme-like activity of Au NPs. In the presence of various metal ions (Ag(+), Bi(3+), Pb(2+), Pt(4+), and Hg(2+)), we found that Au NPs (13 nm) exhibited peroxidase-, oxidase-, or catalase-like activity. After Ag(+), Bi(3+), or Pb(2+) ions had been deposited on the Au NPs, the particles displayed strong peroxidase-like activity; on the other hand, they exhibited strong oxidase- and catalase-like activities after reactions with Ag(+)/Hg(2+) and Hg(2+)/Bi(3+) ions, respectively. The catalytic activities of these Au NPs arose mainly from the various oxidation states of the surface metal atoms/ions. Taking advantage of this behavior, we constructed multiplex logic operations-OR, AND, INHIBIT, and XOR logic gates-through regulation of the enzyme-like activity after the introduction of metal ions into the Au NP solution. When we deposited Hg(2+) and/or Bi(3+) ions onto the Au NPs, the catalase-like activities of the Au NPs were strongly enhanced (>100-fold). Therefore, we could construct an OR logic gate by using Hg(2+)/Bi(3+) as inputs and the catalase-like activity of the Au NPs as the output. Likewise, we constructed an AND logic gate by using Pt(4+) and Hg(2+) as inputs and the oxidase-like activity of the Au NPs as the output; the co-deposition of Pt and Hg atoms/ions on the Au NPs was responsible for this oxidase-like activity. Competition between Pb(2+) and Hg(2+) ions for the Au NPs allowed us to develop an INHIBIT logic gate-using Pb(2+) and Hg(2+) as inputs and the peroxidase-like activity of the Au NPs as the output. Finally, regulation of the peroxidase-like activity of the Au NPs through the two inputs Ag(+) and Bi(3+) enabled us to construct an XOR logic gate.

Density functional theory study on Herzberg-Teller contribution in Raman scattering from 4-aminothiophenol-metal complex and metal-4-aminothiophenol-metal junction

NASA Astrophysics Data System (ADS)

Liu, Shasha; Zhao, Xiuming; Li, Yuanzuo; Zhao, Xiaohong; Chen, Maodu

2009-06-01

Density functional theory (DFT) and time-dependent DFT calculations have been performed to investigate the Raman scattering spectra of metal-molecule complex and metal-molecule-metal junction architectures interconnected with 4-aminothiophenol (PATP) molecule. The simulated profiles of normal Raman scattering (NRS) spectra for the two complexes (Ag2-PATP and PATP-Au2) and the two junctions (Ag2-PATP-Au2 and Au2-PATP-Ag2) are similar to each other, but exhibit obviously different Raman intensities. Due to the lager static polarizabilities of the two junctions, which directly influence the ground state chemical enhancement in NRS spectra, the calculated normal Raman intensities of them are stronger than those of two complexes by the factor of 102. We calculate preresonance Raman scattering (RRS) spectra with incident light at 1064 nm, which is much lower than the S1 electronic transition energy of complexes and junctions. Ag2-PATP-Au2 and Au2-PATP-Ag2 junctions yield higher Raman intensities than those of Ag2-PATP and PATP-Au2 complexes, especially for b2 modes. This effect is mainly attributed to charge transfer (CT) between the metal gap and the PAPT molecule which results in the occurrence of CT resonance enhancement. The calculated pre-RRS spectra strongly depend on the electronic transition state produced by new structures. With excitation at 514.5 nm, the calculated pre-RRS spectra of two complexes and two junctions are stronger than those of with excitation at 1064 nm. A charge difference densities methodology has been used to visually describe chemical enhancement mechanism of RRS spectrum. This methodology aims at visualizing intermolecular CT which provides direct evidence of the Herzberg-Teller mechanism.

Heavy-quark production and elliptic flow in Au+Au collisions at √s NN=62.4 GeV

DOE PAGES

Adare, A.

2015-04-28

In this study, we present measurements of electrons and positrons from the semileptonic decays of heavy-flavor hadrons at midrapidity (|y|< 0.35) in Au+Au collisions at √s NN = 62.4 GeV. The data were collected in 2010 by the PHENIX experiment that included the new hadron-blind detector. The invariant yield of electrons from heavy-flavor decays is measured as a function of transverse momentum in the range 1 < p e T < 5 GeV/c. The invariant yield per binary collision is slightly enhanced above the p+p reference in Au+Au 0%–20%, 20%–40%, and 40%–60% centralities at a comparable level. At this lowmore » beam energy this may be a result of the interplay between initial-state Cronin effects, final-state flow, and energy loss in medium. The v₂ of electrons from heavy-flavor decays is nonzero when averaged between 1.3 < p e T < 2.5 GeV/c for 0%–40% centrality collisions at √s NN = 62.4 GeV. For 20%–40% centrality collisions, the v₂ at √s NN = 62.4 GeV is smaller than that for heavy-flavor decays at √s NN = 200 GeV. The v₂ of the electrons from heavy-flavor decay at the lower beam energy is also smaller than v₂ for pions. Both results indicate that the heavy-quarks interact with the medium formed in these collisions, but they may not be at the same level of thermalization with the medium as observed at √s NN = 200 GeV.« less

Heavy-quark production and elliptic flow in Au + Au collisions at √{sN N}=62.4 GeV

NASA Astrophysics Data System (ADS)

Adare, A.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Akimoto, R.; Al-Ta'Ani, H.; Alexander, J.; Angerami, A.; Aoki, K.; Apadula, N.; Aramaki, Y.; Asano, H.; Aschenauer, E. C.; Atomssa, E. T.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Bannier, B.; Barish, K. N.; Bassalleck, B.; Bathe, S.; Baublis, V.; Baumgart, S.; Bazilevsky, A.; Belmont, R.; Berdnikov, A.; Berdnikov, Y.; Bing, X.; Blau, D. S.; Bok, J. S.; Boyle, K.; Brooks, M. L.; Buesching, H.; Bumazhnov, V.; Butsyk, S.; Campbell, S.; Castera, P.; Chen, C.-H.; Chi, C. Y.; Chiu, M.; Choi, I. J.; Choi, J. B.; Choi, S.; Choudhury, R. K.; Christiansen, P.; Chujo, T.; Chvala, O.; Cianciolo, V.; Citron, Z.; Cole, B. A.; Connors, M.; Csanád, M.; Csörgő, T.; Dairaku, S.; Datta, A.; Daugherity, M. S.; David, G.; Denisov, A.; Deshpande, A.; Desmond, E. J.; Dharmawardane, K. V.; Dietzsch, O.; Ding, L.; Dion, A.; Donadelli, M.; Drapier, O.; Drees, A.; Drees, K. A.; Durham, J. M.; Durum, A.; D'Orazio, L.; Edwards, S.; Efremenko, Y. V.; Engelmore, T.; Enokizono, A.; Esumi, S.; Eyser, K. O.; Fadem, B.; Fields, D. E.; Finger, M.; Finger, M.; Fleuret, F.; Fokin, S. L.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Fukao, Y.; Fusayasu, T.; Gainey, K.; Gal, C.; Garishvili, A.; Garishvili, I.; Glenn, A.; Gong, X.; Gonin, M.; Goto, Y.; Granier de Cassagnac, R.; Grau, N.; Greene, S. V.; Grosse Perdekamp, M.; Gunji, T.; Guo, L.; Gustafsson, H.-Å.; Hachiya, T.; Haggerty, J. S.; Hahn, K. I.; Hamagaki, H.; Hanks, J.; Hashimoto, K.; Haslum, E.; Hayano, R.; He, X.; Hemmick, T. K.; Hester, T.; Hill, J. C.; Hollis, R. S.; Homma, K.; Hong, B.; Horaguchi, T.; Hori, Y.; Huang, S.; Ichihara, T.; Iinuma, H.; Ikeda, Y.; Imrek, J.; Inaba, M.; Iordanova, A.; Isenhower, D.; Issah, M.; Ivanishchev, D.; Jacak, B. V.; Javani, M.; Jia, J.; Jiang, X.; Johnson, B. M.; Joo, K. S.; Jouan, D.; Jumper, D. S.; Kamin, J.; Kaneti, S.; Kang, B. H.; Kang, J. H.; Kang, J. S.; Kapustinsky, J.; Karatsu, K.; Kasai, M.; Kawall, D.; Kazantsev, A. V.; Kempel, T.; Khanzadeev, A.; Kijima, K. M.; Kim, B. I.; Kim, C.; Kim, D. J.; Kim, E.-J.; Kim, H. J.; Kim, K.-B.; Kim, Y.-J.; Kim, Y. K.; Kinney, E.; Kiss, Á.; Kistenev, E.; Klatsky, J.; Kleinjan, D.; Kline, P.; Komatsu, Y.; Komkov, B.; Koster, J.; Kotchetkov, D.; Kotov, D.; Král, A.; Krizek, F.; Kunde, G. J.; Kurita, K.; Kurosawa, M.; Kwon, Y.; Kyle, G. S.; Lacey, R.; Lai, Y. S.; Lajoie, J. G.; Lebedev, A.; Lee, B.; Lee, D. M.; Lee, J.; Lee, K. B.; Lee, K. S.; Lee, S. H.; Lee, S. R.; Leitch, M. J.; Leite, M. A. L.; Leitgab, M.; Lewis, B.; Lim, S. H.; Linden Levy, L. A.; Liu, M. X.; Love, B.; Maguire, C. F.; Makdisi, Y. I.; Makek, M.; Manion, A.; Manko, V. I.; Mannel, E.; Masumoto, S.; McCumber, M.; McGaughey, P. L.; McGlinchey, D.; McKinney, C.; Mendoza, M.; Meredith, B.; Miake, Y.; Mibe, T.; Mignerey, A. C.; Milov, A.; Mishra, D. K.; Mitchell, J. T.; Miyachi, Y.; Miyasaka, S.; Mohanty, A. K.; Moon, H. J.; Morrison, D. P.; Motschwiller, S.; Moukhanova, T. V.; Murakami, T.; Murata, J.; Nagae, T.; Nagamiya, S.; Nagle, J. L.; Nagy, M. I.; Nakagawa, I.; Nakamiya, Y.; Nakamura, K. R.; Nakamura, T.; Nakano, K.; Nattrass, C.; Nederlof, A.; Nihashi, M.; Nouicer, R.; Novitzky, N.; Nyanin, A. S.; O'Brien, E.; Ogilvie, C. A.; Okada, K.; Oskarsson, A.; Ouchida, M.; Ozawa, K.; Pak, R.; Pantuev, V.; Papavassiliou, V.; Park, B. H.; Park, I. H.; Park, S. K.; Pate, S. F.; Patel, L.; Pei, H.; Peng, J.-C.; Pereira, H.; Peressounko, D. Yu.; Petti, R.; Pinkenburg, C.; Pisani, R. P.; Proissl, M.; Purschke, M. L.; Qu, H.; Rak, J.; Ravinovich, I.; Read, K. F.; Reynolds, D.; Riabov, V.; Riabov, Y.; Richardson, E.; Riveli, N.; Roach, D.; Roche, G.; Rolnick, S. D.; Rosati, M.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Samsonov, V.; Sano, M.; Sarsour, M.; Sawada, S.; Sedgwick, K.; Seidl, R.; Sen, A.; Seto, R.; Sharma, D.; Shein, I.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shoji, K.; Shukla, P.; Sickles, A.; Silva, C. L.; Silvermyr, D.; Sim, K. S.; Singh, B. K.; Singh, C. P.; Singh, V.; Slunečka, M.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Soumya, M.; Sourikova, I. V.; Stankus, P. W.; Stenlund, E.; Stepanov, M.; Ster, A.; Stoll, S. P.; Sugitate, T.; Sukhanov, A.; Sun, J.; Sziklai, J.; Takagui, E. M.; Takahara, A.; Taketani, A.; Tanaka, Y.; Taneja, S.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tennant, E.; Themann, H.; Todoroki, T.; Tomášek, L.; Tomášek, M.; Torii, H.; Towell, R. S.; Tserruya, I.; Tsuchimoto, Y.; Tsuji, T.; Vale, C.; van Hecke, H. W.; Vargyas, M.; Vazquez-Zambrano, E.; Veicht, A.; Velkovska, J.; Vértesi, R.; Virius, M.; Vossen, A.; Vrba, V.; Vznuzdaev, E.; Wang, X. R.; Watanabe, D.; Watanabe, K.; Watanabe, Y.; Watanabe, Y. S.; Wei, F.; Wei, R.; Whitaker, S.; White, S. N.; Winter, D.; Wolin, S.; Woody, C. L.; Wysocki, M.; Yamaguchi, Y. L.; Yang, R.; Yanovich, A.; Ying, J.; Yokkaichi, S.; You, Z.; Younus, I.; Yushmanov, I. E.; Zajc, W. A.; Zelenski, A.; Phenix Collaboration

2015-04-01

We present measurements of electrons and positrons from the semileptonic decays of heavy-flavor hadrons at midrapidity (|y |< 0.35) in Au +Au collisions at √{sN N}=62.4 GeV. The data were collected in 2010 by the PHENIX experiment that included the new hadron-blind detector. The invariant yield of electrons from heavy-flavor decays is measured as a function of transverse momentum in the range 1

Metastability of the atomic structures of size-selected gold nanoparticles

NASA Astrophysics Data System (ADS)

Wells, Dawn M.; Rossi, Giulia; Ferrando, Riccardo; Palmer, Richard E.

2015-04-01

All nanostructures are metastable - but some are more metastable than others. Here we employ aberration-corrected electron microscopy and atomistic computer simulations to demonstrate the hierarchy of metastability in deposited, size-selected gold nanoparticles (clusters), an archetypal class of nanomaterials well known for the catalytic activity which only appears on the nanometer-scale. We show that the atomic structures presented by ``magic number'' Au561, Au742 and Au923 clusters are ``locked''. They are in fact determined by the solidification which occurs from the liquid state early in their growth (by assembly from atoms in the gas phase) followed by template growth. It is quite likely that transitions from a locked, metastable configuration to a more stable (but still metastable) structure, as observed here under the electron beam, will occur during catalytic reactions, for example.All nanostructures are metastable - but some are more metastable than others. Here we employ aberration-corrected electron microscopy and atomistic computer simulations to demonstrate the hierarchy of metastability in deposited, size-selected gold nanoparticles (clusters), an archetypal class of nanomaterials well known for the catalytic activity which only appears on the nanometer-scale. We show that the atomic structures presented by ``magic number'' Au561, Au742 and Au923 clusters are ``locked''. They are in fact determined by the solidification which occurs from the liquid state early in their growth (by assembly from atoms in the gas phase) followed by template growth. It is quite likely that transitions from a locked, metastable configuration to a more stable (but still metastable) structure, as observed here under the electron beam, will occur during catalytic reactions, for example. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05811a

Liquid Crystal Mediated Nano-assembled Gold Micro-shells

NASA Astrophysics Data System (ADS)

Quint, Makiko; Sarang, Som; Quint, David; Huang, Kerwyn; Gopinathan, Ajay; Hirst, Linda; Ghosh, Sayantani

We have created 3D nano-assenbled micro-shell by using thermotropic liquid crystal (LC), 4-Cyano-4'-pentylbiphenyl (5CB), doped with mesogen-functionalized gold nanoparticles (AuNPs). The assembly process is driven by the isotropic-nematic phase transition dynamics. We uniformly disperse the functionalized AuNPs into isotropic liquid crystal matrix and the mixture is cooled from the isotropic to the nematic phase. During the phase transition, the separation of LC-AuNP rich isotropic and ordered 5CB rich domains cause the functionalized AuNPs to move into the shrinking isotropic regions. The mesogenic ligands are locally crystalized during this process, which leads to the formation of a spherical shell with a densely packed wall of AuNPs. These micro-shells are capable of encapsulating fluorescence dye without visible leakages for several months. Additionally, they demonstrate strong localized surface plasmon resonance, which leads to localized heating on optical excitation. This photothermal effect disrupts the structure, releasing contents within seconds. Our results exhibiting the capture and optically regulated release of encapsulated substances is a novel platform that combines drug-delivery and photothermal therapy in one versatile and multifunctional unit. This work is supported by the NSF Grants No. DMR-1056860, ECC-1227034, and a University of California Merced Faculty Mentor Fellowship.

Interactions between the antifungal drug myclobutanil and gold and silver nanoparticles in Penicillium digitatum investigated by surface-enhanced Raman scattering.

PubMed

Cho, Eun-Min; Singh, Dheeraj K; Ganbold, Erdene-Ochir; Dembereldorj, Uuriintuya; Jang, Seok-Won; Kim, Doseok; Choo, Jaebum; Kim, Sehun; Lee, Cheol Min; Yang, Sung Ik; Joo, Sang-Woo

2014-01-01

Surface-enhanced Raman scattering (SERS) of an antifungal reagent, myclobutanil (MCB), was performed on Au and Ag nanoparticles (NPs) to estimate the drug-release behaviors in fungal cells. A density functional theory (DFT) calculation was introduced to predict a favorable binding site of MCB to either the Ag or Au atom. Myclobutanil was presumed to bind more strongly to Au than to Ag in their most stable, optimized geometries of the N4 atom in its 1,2,4-triazole unit binding to the metal atom. Strong intensities were observed in the Ag SERS spectra only at acidic pH values, whereas the most prominent peaks in the Au SERS spectra of MCB matched quite well with those of 1,2,4-triazole regardless of pH conditions. The Raman spectral intensities of the MCB-assembled Ag and Au NPs decreased after treatment with either potato dextrose agar (PDA) or glutathione (GSH). Darkfield microscopy and confocal SERS were performed to analyze the MCB-assembled metal NPs inside Penicillium digitatum fungal cells. The results suggested that MCB was released from the metal NPs in the intracellular GSH in the fungi because we observed only fungal cell peaks.

Habitable Planetary Systems (un)like our own: Which of the Known Extra-Solar Systems Could Harbor Earth-like Planets?

NASA Astrophysics Data System (ADS)

Raymond, Sean; Mandell, A.; Sigurdsson, S.

2006-12-01

Gas giant planets are far easier than terrestrial planets to detect around other stars, and are thought to form much more quickly than terrestrial planets. Thus, in systems with giant planets, the final stages of terrestrial planet formation are strongly affected by the giant planets' dynamical presence. Observations of giant planet orbits may therefore constrain the systems that can harbor potentially habitable, Earth-like planets. We combine two recent studies (1,2) and establish rough inner and outer limits for the giant planet orbits that allow terrestrial planets of at least 0.3 Earth masses to form in the habitable zone (HZ). For a star like the Sun, potentially habitable planets can form in systems with relatively low-eccentricity giant planets inside 0.5 Astronomical Units (AU) or outside 2.5 AU. More than one third of the currently known giant planet systems could have formed and now harbor a habitable planet. We thank NASA Astrobiology Institute for funding, through the Penn State, NASA Goddard, Virtual Planetary Laboratory, and University of Colorado lead teams. (1. Raymond, S.N., 2006, ApJ, 643, L131.; 2. Raymond, S.N., Mandell, A.M., Sigurdsson, S. 2006, Science, 313, 1413).

A dynamic appearance descriptor approach to facial actions temporal modeling.

PubMed

Jiang, Bihan; Valstar, Michel; Martinez, Brais; Pantic, Maja

2014-02-01

Both the configuration and the dynamics of facial expressions are crucial for the interpretation of human facial behavior. Yet to date, the vast majority of reported efforts in the field either do not take the dynamics of facial expressions into account, or focus only on prototypic facial expressions of six basic emotions. Facial dynamics can be explicitly analyzed by detecting the constituent temporal segments in Facial Action Coding System (FACS) Action Units (AUs)-onset, apex, and offset. In this paper, we present a novel approach to explicit analysis of temporal dynamics of facial actions using the dynamic appearance descriptor Local Phase Quantization from Three Orthogonal Planes (LPQ-TOP). Temporal segments are detected by combining a discriminative classifier for detecting the temporal segments on a frame-by-frame basis with Markov Models that enforce temporal consistency over the whole episode. The system is evaluated in detail over the MMI facial expression database, the UNBC-McMaster pain database, the SAL database, the GEMEP-FERA dataset in database-dependent experiments, in cross-database experiments using the Cohn-Kanade, and the SEMAINE databases. The comparison with other state-of-the-art methods shows that the proposed LPQ-TOP method outperforms the other approaches for the problem of AU temporal segment detection, and that overall AU activation detection benefits from dynamic appearance information.

Control and monitoring of oxygen fugacity in piston cylinder experiments

NASA Astrophysics Data System (ADS)

Matjuschkin, Vladimir; Brooker, Richard A.; Tattitch, Brian; Blundy, Jon D.; Stamper, Charlotte C.

2015-01-01

We present a newly developed capsule design that resolves some common problems associated with the monitoring and control of oxygen fugacity ( fO2) in high-pressure piston cylinder experiments. The new fO2 control assembly consists of an AuPd outer capsule enclosing two inner capsules: one of AuPd capsule containing the experimental charge (including some water), and the other of Pt containing a solid oxygen buffer plus water. The inner capsules are separated by crushable alumina. The outer capsule is surrounded by a Pyrex sleeve to simultaneously minimise hydrogen loss from the cell and carbon infiltration from the graphite furnace. Controlled fO2 experiments using this cell design were carried out at 1.0 GPa and 1,000 °C. We used NiPd, CoPd and (Ni, Mg)O fO2 sensors, whose pressure sensitivity is well calibrated, to monitor the redox states achieved in experiments buffered by Re-ReO2, Ni-NiO and Co-CoO, respectively. Results for the fO2 sensors are in good agreement with the intended fO2 established by the buffer, demonstrating excellent control for durations of 24-48 h, with uncertainties less than ± 0.3 log bar units of fO2.

Adsorption and diffusion of Au atoms on the (001) surface of Ti, Zr, Hf, V, Nb, Ta, and Mo carbides.

PubMed

Florez, Elizabeth; Viñes, Francesc; Rodriguez, Jose A; Illas, Francesc

2009-06-28

The adsorption of atomic Au on the (001) surface of TiC, ZrC, HfC, VC, NbC, TaC, and delta-MoC and the mechanism of diffusion of this adatom through the surface have been studied in terms of a periodic density functional theory based approach. In all the cases, the Au adsorption energies are in the range of 1.90-2.35 eV. The moderately large adsorption energies allow the Au diffusion before desorption could take place. For TiC(001), ZrC(001), and HfC(001), atomic Au is adsorbed directly on top of C atoms and diffusion takes place along the diagonal of the squares formed by M-C-M-C atoms with the transition state located above the hollow sites. For the rest of transition metal carbides the situation is less simple with the appearance of more than one stable adsorption site, as for NbC and TaC, of a small energy barrier for diffusion around the most stable adsorption site and of a more complex diffusion pathway. The small energy barrier for diffusion around the most stable site will result in a highly mobile Au species which could be observed in scanning tunnel microscope experiments. After depositing Au on metal-carbide surfaces, there is a noticeable charge transfer from the substrate to the adsorbed Au atom. The electronic perturbations on Au increase when going from TiC to ZrC or TaC. Our results indicate that metal carbides should be better supports for the chemical activation of Au than metal oxides.

Coincidence studies of He ionized by C{sup 6+}, Au{sup 24+}, and Au{sup 53+}

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGovern, M.; Walters, H. R. J.; Assafrao, D.

2010-04-15

A recently developed [Phys. Rev. A 79, 042707 (2009)] impact parameter coupled pseudostate approximation (CP) is applied to calculate triple differential cross sections for single ionization of He by C{sup 6+}, Au{sup 24+}, and Au{sup 53+} projectiles at impact energies of 100 and 2 MeV/amu for C{sup 6+} and 3.6 MeV/amu for Au{sup 24+} and Au{sup 53+}. For C{sup 6+}, satisfactory, but not perfect, agreement is found with experimental measurements in coplanar geometry, but there is substantial disagreement with data taken in a perpendicular plane geometry. The CP calculations firmly contradict a projectile-nucleus interaction model which has been used tomore » support the perpendicular plane measurements. For Au{sup 24+} and Au{sup 53+}, there is a complete lack of accord with the available experiments. However, for Au{sup 24+} the theoretical position appears to be quite firm with clear indications of convergence in the CP approximation and very good agreement between CP and the completely different three-distorted-waves eikonal-initial-state (3DW-EIS) approximation. The situation for Au{sup 53+} is different. At the momentum transfers at which the measurements were made, there are doubts about the convergence of the CP approximation and a factor of 2 difference between the CP and 3DW-EIS predictions. The discord between theory and experiment is even greater with the experiment giving cross sections a factor of 10 larger than the theory. A study of the convergence of the CP approximation shows that it improves rapidly with reducing momentum transfer. As a consequence, lower-order cross sections than the triple are quite well converged and present an opportunity for a more reliable test of the experiment.« less

Controlling the stereochemistry and regularity of butanethiol self-assembled monolayers on au(111).

PubMed

Yan, Jiawei; Ouyang, Runhai; Jensen, Palle S; Ascic, Erhad; Tanner, David; Mao, Bingwei; Zhang, Jingdong; Tang, Chunguang; Hush, Noel S; Ulstrup, Jens; Reimers, Jeffrey R

2014-12-10

The rich stereochemistry of the self-assembled monolayers (SAMs) of four butanethiols on Au(111) is described, the SAMs containing up to 12 individual C, S, or Au chiral centers per surface unit cell. This is facilitated by synthesis of enantiomerically pure 2-butanethiol (the smallest unsubstituted chiral alkanethiol), followed by in situ scanning tunneling microscopy (STM) imaging combined with density functional theory molecular dynamics STM image simulations. Even though butanethiol SAMs manifest strong headgroup interactions, steric interactions are shown to dominate SAM structure and chirality. Indeed, steric interactions are shown to dictate the nature of the headgroup itself, whether it takes on the adatom-bound motif RS(•)Au(0)S(•)R or involves direct binding of RS(•) to face-centered-cubic or hexagonal-close-packed sites. Binding as RS(•) produces large, organizationally chiral domains even when R is achiral, while adatom binding leads to rectangular plane groups that suppress long-range expression of chirality. Binding as RS(•) also inhibits the pitting intrinsically associated with adatom binding, desirably producing more regularly structured SAMs.

Novel Gold Intermetallics with Unique Properties and Bonding Patterns

NASA Astrophysics Data System (ADS)

Celania, Christopher Ranger

Gold has drawn the fascination of society through its brilliant color, malleability, and chemical resistance (hence its chemical nobility) since its discovery in ancient times. Today, this material is still highly coveted by consumers, but also for research within the scientific realm. The inclusion of gold in intermetallics often leads to notably unique structural and bonding features due to the pronounced relativistic effects on its 5d and 6s orbitals. Examples include quasicrystals and their approximants, unique gold clusters such as isolated Au7 clusters in A4Au7X2 (A = K, Rb, Cs; X = Ge, Sn), one dimensional columns such as Au zig-zag chains through Ca3Au3In, two dimensional slabs, such as in K2 Au3, as well as three dimensional gold networks as observed in the interconnected trigonal bipyramids in KAu5, hexagonal diamond-like frameworks of Au tetrahedra in Au-rich Sr-Au-Al systems; and combinations of tetrahedral and fourfold planar Au atoms in Rb3Au7. In recent years, compounds in the gold-rich region of the R-Au- M system (R = rare earth, M = groups 13-15) have come under increased study. Many compounds within this system produce varied electronic and magnetic properties such as Pauli paramagnetism, superconductivity, thermoelectricity, etc. The shielded 4f electrons of the added rare earth elements provide the unpaired spins that lead to the wealth of interesting magnetic properties in their compounds. Metals and metalloids from groups 13-15 may then be used as a bank of available options useful in tuning the valence electron count of the R-Au system toward the formation of stable compounds. Exploration of the Gd-Au-Sb system by utilizing common solid state synthesis techniques frequently used for the production of intermetallics (such as arc melting and high-temperature furnaces for self-flux reactions with low melting components) has yielded rich outcomes. These results include the discovery of a new R3Au9Pn series of compounds (R = Y, Gd-Ho; Pn = Sb, Bi), which undergo interesting metamagnetic transitions, varied coloring schemes for Sb substitutions in the known R14Au51 compound forming R 14(Au, M)51 (R = Y, La-Nd, Sm-Tb, Ho, Er, Yb, Lu; M = Al, Ga, Ge, In, Sn, Sb, Bi), and a complex tetragonal Gd-Au-Sb structure with significant Sb site mixing and positional disorder, as well as preliminary structure results of several other previously unreported compounds within the R-Au- M family.

Anisotropic expansion and amorphization of Ga2O3 irradiated with 946 MeV Au ions

NASA Astrophysics Data System (ADS)

Tracy, Cameron L.; Lang, Maik; Severin, Daniel; Bender, Markus; Trautmann, Christina; Ewing, Rodney C.

2016-05-01

The structural response of β-Ga2O3 to irradiation-induced electronic excitation was investigated. A polycrystalline pellet of this material was irradiated with 946 MeV Au ions and the resulting structural modifications were characterized using in situ X-ray diffraction analysis at various ion fluences, up to 1 × 1013 cm-2. Amorphization was induced, with the accumulation of the amorphous phase following a single-impact mechanism in which each ion produces an amorphous ion track along its path. Concurrent with this phase transformation, an increase in the unit cell volume of the material was observed and quantified using Rietveld refinement. This unit cell expansion increased as a function of ion fluence before saturating at 1.8%. This effect is attributed to the generation of defects in an ion track shell region surrounding the amorphous track cores. The unit cell parameter increase was highly anisotropic, with no observed expansion in the [0 1 0] direction. This may be due to the structure of β-Ga2O3, which exhibits empty channels of connected interstitial sites oriented in this direction.

Chapter 41: Geology and petroleum potential of the West Greenland-East Canada Province

USGS Publications Warehouse

Schenk, C.J.

2011-01-01

The US Geological Survey (USGS) assessed the potential for undiscovered oil and gas resources of the West Greenland-East Canada Province as part of the USGS Circum-Arctic Resource Appraisal programme. The province lies in the offshore area between western Greenland and eastern Canada and includes Baffin Bay, Davis Strait, Lancaster Sound and Nares Strait west of and including part of Kane Basin. A series of major tectonic events led to the formation of several distinct structural domains that are the geological basis for defining five assessment units (AU) in the province, all of which are within the Mesozoic-Cenozoic Composite Petroleum System. Potential petroleum source rocks include strata of Ordovician, Lower and Upper Cretaceous, and Palaeogene ages. The five AUs defined for this study - the Eurekan Structures AU, NW Greenland Rifted Margin AU, NE Canada Rifted Margin AU, Baffin Bay Basin AU and the Greater Ungava Fault Zone AU - encompass the entire province and were assessed for undiscovered technically recoverable resources. The mean volumes of undiscovered resources for the West Greenland-East Canada Province are 10.7 ?? 109 barrels of oil, 75 ?? 1012 cubic feet of gas, and 1.7 ?? 109 barrels of natural gas liquids. For the part of the province that is north of the Arctic Circle, the estimated mean volumes of these undiscovered resources are 7.3 ?? 109 barrels of oil, 52 ?? 1012 cubic feet of natural gas, and 1.1 ?? 109 barrels of natural gas liquids. ?? 2011 The Geological Society of London.

An Electrochemical Genosensing Assay Based on Magnetic Beads and Gold Nanoparticle-Loaded Latex Microspheres for Vibrio cholerae Detection.

PubMed

Low, Kim-Fatt; Rijiravanich, Patsamon; Singh, Kirnpal Kaur Banga; Surareungchai, Werasak; Yean, Chan Yean

2015-04-01

An ultrasensitive electrochemical genosensing assay was developed for the sequence-specific detection of Vibrio cholerae DNA using magnetic beads as the biorecognition surface and gold nanoparticle-loaded latex microspheres (latex-AuNPs) as a signal-amplified hybridization tag. This biorecognition surface was prepared by immobilizing specific biotinylated capturing probes onto the streptavidin-coupled magnetic beads. Fabricating a hybridization tag capable of amplifying the electrochemical signal involved loading multiple AuNPs onto polyelectrolyte multilayer film-coated poly(styrene-co-acrylic acid) latex microspheres as carrier particles. The detection targets, single-stranded 224-bp asymmetric PCR amplicons of the V. cholerae lolB gene, were sandwich-hybridized to magnetic bead-functionalized capturing probes and fluorescein-labeled detection probes and tagged with latex-AuNPs. The subsequent electrochemical stripping analysis of chemically dissolved AuNPs loaded onto the latex microspheres allowed for the quantification of the target amplicons. The high-loading capacity of the AuNPs on the latex microspheres for sandwich-type dual-hybridization genosensing provided eminent signal amplification. The genosensing variables were optimized, and the assay specificity was demonstrated. The clinical applicability of the assay was evaluated using spiked stool specimens. The current signal responded linearly to the different V. cholerae concentrations spiked into stool specimens with a detection limit of 2 colony-forming units (CFU)/ml. The proposed latex-AuNP-based magnetogenosensing platform is promising, exhibits an effective amplification performance, and offers new opportunities for the ultrasensitive detection of other microbial pathogens.

Feasibility and costs of phosphorus application limits on 39 U.S. swine operations.

PubMed

Lory, John A; Massey, Raymond E; Zulovich, Joseph M; Hoehne, John A; Schmidt, Amy M; Carlson, Marcia S; Fulhage, Charles D

2004-01-01

Concerns about manure P and water quality have prompted new regulations imposing P limits on land application of manure. Previous research established that P limits increase land needs for animal feeding operations. We evaluated the effect of N, annual P, and rotation P limits on the feasibility of manure management. A mechanistic model characterized manure management practices on 39 swine operations (20 unagitated lagoon and 19 slurry operations) in five states (Iowa, Missouri, North Carolina, Oklahoma, and Pennsylvania). Extensive information collected from each operation was used to determine effects of manure storage type, ownership structure, and application limits on attributes of manure management. Phosphorus limits had substantially greater effect on slurry operations, increasing land needs 250% (0.3 hectares per animal unit [AU]) and time for manure application 24% (2.5 min AU(-1)) for rotation P limits and 41% (4.4 min AU(-1)) for annual P limits. Annual P limits were infeasible for current land application equipment on two operations and had the greatest effect on time and costs because they required all but three slurry operations to reduce discharge rate. We recommend implementing rotation P limits (not to exceed crop N need) to minimize time effects, allow most farmers to use their current manure application methods, and allow manure to fulfill crop N and P needs in the year of application. Phosphorus limits increased potential manure value but would require slurry operations to recover at least 61% of manure value through manure sales. Phosphorus limits are likely to shape the U.S. swine industry through differential effects on the various sectors of the swine industry.

Rotating Disk Slurry Au Electrodeposition at Unsupported Carbon Vulcan XC-72 and Ce 3+ Impregnation for Ethanol Oxidation in Alkaline Media

DOE PAGES

Betancourt, Luis E.; Guzman-Blas, Rolando; Luo, Si; ...

2016-11-19

A robust electrodeposition method consisting of the rotating disk slurry electrode (RoDSE) technique to obtain Au nanoparticles highly dispersed on a conductive carbonaceous support, i.e., Vulcan XC-72R, for ethanol electrooxidation reaction in alkaline media was developed. Ceria was used as a cocatalyst using a Ce(III)-EDTA impregnation method in order to enhance the catalytic activity and improve the catalyst’s overall stability. Furthermore, the RoDSE method used to obtain highly dispersed Au nanoparticles does not require the use of a reducing agent or stabilizing agent, and the noble-metal loading was controlled by the addition and tuning of the metal precursor concentration. Inductivelymore » coupled plasma and thermogravimetric analysis indicated that the Au loading in the catalyst was 9 %. We determined the particle size and characteristic Au fcc crystal facets by X-ray diffraction. The morphology of the catalyst was also investigated using electron microscopy techniques. In addition, X-ray absorption spectroscopy was used to corroborate the presence and identify the oxidation state of Ce in the system and to observe if there are any electronic interactions within the 8 % Au/CeO x/C system. Cyclic voltammetry of electrodeposited 9 % Au/C and Ce-promoted 8 % Au/C showed a higher catalytic current density for ethanol oxidation when compared with commercially available catalysts (20 % Au/C) of a higher precious metal loading. Additionally, we report a higher stability toward the ethanol electrooxidation process, which was corroborated by 1 mV/s linear sweep voltammetry and chronoamperometric studies.« less

Electrical and carrier transport properties of the Au/Y2O3/n-GaN metal-insulator-semiconductor (MIS) diode with rare-earth oxide interlayer

NASA Astrophysics Data System (ADS)

Venkata Prasad, C.; Rajagopal Reddy, V.; Choi, Chel-Jong

2017-04-01

The electrical and transport properties of rare-earth Y2O3 on n-type GaN with Au electrode have been investigated by current-voltage and capacitance-voltage techniques at room temperature. The Au/Y2O3/n-GaN metal-insulator-semiconductor (MIS) diode shows a good rectification behavior compared to the Au/n-GaN metal-semiconductor (MS) diode. Statistical analysis showed that a mean barrier height (BH) and ideality factor are 0.78 eV and 1.93, and 0.96 eV and 2.09 for the Au/n-GaN MS and Au/Y2O3/n-GaN MIS diodes, respectively. Results indicate that the high BH is obtained for the MIS diode compared to the MS diode. The BH, ideality factor and series resistance are also estimated by Cheung's function and Norde method. From the forward current-voltage data, the interface state density ( N SS) is estimated for both the MS and MIS Schottky diodes, and found that the estimated N SS is lower for the MIS diode compared to the MS diode. The results reveal that the introduction of Y2O3 interlayer facilitated the reduction of N SS of the Au/n-GaN interface. Experimental results suggest that the Poole-Frenkel emission is a dominant conduction mechanism in the reverse bias region of both Au/n-GaN MS and Au/Y2O3/n-GaN MIS diodes.

Preliminary scientific rationale for a voyage to a thousand astronomical units

NASA Technical Reports Server (NTRS)

Etchegaray, M. I. (Compiler)

1987-01-01

A proposed mission to 1000 astronomical units (TAU) is under study by the Jet Propulsion Laboratory. Launch date for a TAU mission is likely to be well into the first decade of the 21st century. Study of TAU has focused on the technologies required to carry out this ambitious mission and the identification of preliminary scientific rationale for such a deep space flight. A 1-MW nuclear-powered electric propulsion (NEP) system forms the baseline method for achieving the high velocities required. A solar system escape velocity of 106 km/s is needed to propel the TAU vehicle to 1000 AU in 50 years. The NEP system must accelerate the vehicle for about ten years before this velocity is attained because of the extremely low thrust nature of the xenon-fueled ion engines. At the end of the thrusting phase the NEP system is jettisoned to allow the TAU spacecraft and science experiments to coast out to 1000 AU. Another important technology for TAU is advanced optical communication systems, which are envisioned for transmitting science data to Earth. A 1-m optical telescope combined with a 10-W laser transponder can transmit 20 kbps to a 10-m Earth-orbit-based telescope from 1000 AU.

William Wales and the 1769 transit of Venus: puzzle solving and the determination of the astronomical unit

NASA Astrophysics Data System (ADS)

Metz, Don

2009-05-01

According to Thomas Kuhn, a significant part of “normal science” is the fact gathering, empirical work which is intended to illustrate an existing paradigm. Some of this effort focuses on the determination of physical constants such as the astronomical unit (AU). For Kuhn, normal science is also what prepares students for membership in a particular scientific community and is embodied in some form in our science textbooks. However, neither Kuhn nor the textbook says much about the individuals who practice normal science, especially those who had been relegated to the “hack” duties of long and arduous measurement and calculation. In this paper, to provide a context for students of astronomy, I will outline the story of the determination of the AU and in particular the contribution of William Wales, an obscure British astronomer. Wales, toiling in the shadow of Halley (of Halley’s comet fame), Mason and Dixon (of Mason and Dixon line fame) and the infamous Captain Cook endured a brutal winter in northern Canada for a brief glimpse of the 1769 transit of Venus. In the end, Wales supplied one small piece of the puzzle in the determination of the AU and he exemplified the human spirit and persistence of a Kuhnian “puzzle solver”.

An efficient enzyme-powered micromotor device fabricated by cyclic alternate hybridization assembly for DNA detection.

PubMed

Fu, Shizhe; Zhang, Xueqing; Xie, Yuzhe; Wu, Jie; Ju, Huangxian

2017-07-06

An efficient enzyme-powered micromotor device was fabricated by assembling multiple layers of catalase on the inner surface of a poly(3,4-ethylenedioxythiophene and sodium 4-styrenesulfonate)/Au microtube (PEDOT-PSS/Au). The catalase assembly was achieved by programmed DNA hybridization, which was performed by immobilizing a designed sandwich DNA structure as the sensing unit on the PEDOT-PSS/Au, and then alternately hybridizing with two assisting DNA to bind the enzyme for efficient motor motion. The micromotor device showed unique features of good reproducibility, stability and motion performance. Under optimal conditions, it showed a speed of 420 μm s -1 in 2% H 2 O 2 and even 51 μm s -1 in 0.25% H 2 O 2 . In the presence of target DNA, the sensing unit hybridized with target DNA to release the multi-layer DNA as well as the multi-catalase, resulting in a decrease of the motion speed. By using the speed as a signal, the micromotor device could detect DNA from 10 nM to 1 μM. The proposed micromotor device along with the cyclic alternate DNA hybridization assembly technique provided a new path to fabricate efficient and versatile micromotors, which would be an exceptional tool for rapid and simple detection of biomolecules.

Microwave-assisted synthesis of water-soluble, fluorescent gold nanoclusters capped with small organic molecules and a revealing fluorescence and X-ray absorption study

NASA Astrophysics Data System (ADS)

Helmbrecht, C.; Lützenkirchen-Hecht, D.; Frank, W.

2015-03-01

Colourless solutions of blue light-emitting, water-soluble gold nanoclusters (AuNC) were synthesized from gold colloids under microwave irradiation using small organic molecules as ligands. Stabilized by 1,3,5-triaza-7-phosphaadamantane (TPA) or l-glutamine (GLU), fluorescence quantum yields up to 5% were obtained. AuNC are considered to be very promising for biological labelling, optoelectronic devices and light-emitting materials but the structure-property relationships have still not been fully clarified. To expand the knowledge about the AuNC apart from their fluorescent properties they were studied by X-ray absorption spectroscopy elucidating the oxidation state of the nanoclusters' gold atoms. Based on curve fitting of the XANES spectra in comparison to several gold references, optically transparent fluorescent AuNC are predicted to be ligand-stabilized Au5+ species. Additionally, their near edge structure compared with analogous results of polynuclear clusters known from the literature discloses an increasing intensity of the feature close to the absorption edge with decreasing cluster size. As a result, a linear relationship between the cluster size and the X-ray absorption coefficient can be established for the first time.Colourless solutions of blue light-emitting, water-soluble gold nanoclusters (AuNC) were synthesized from gold colloids under microwave irradiation using small organic molecules as ligands. Stabilized by 1,3,5-triaza-7-phosphaadamantane (TPA) or l-glutamine (GLU), fluorescence quantum yields up to 5% were obtained. AuNC are considered to be very promising for biological labelling, optoelectronic devices and light-emitting materials but the structure-property relationships have still not been fully clarified. To expand the knowledge about the AuNC apart from their fluorescent properties they were studied by X-ray absorption spectroscopy elucidating the oxidation state of the nanoclusters' gold atoms. Based on curve fitting of the XANES spectra in comparison to several gold references, optically transparent fluorescent AuNC are predicted to be ligand-stabilized Au5+ species. Additionally, their near edge structure compared with analogous results of polynuclear clusters known from the literature discloses an increasing intensity of the feature close to the absorption edge with decreasing cluster size. As a result, a linear relationship between the cluster size and the X-ray absorption coefficient can be established for the first time. Electronic supplementary information (ESI) available: The deconvoluted reference spectra are given in ESI Fig. 1-9. See DOI: 10.1039/c4nr07051h

Inter-molecule interaction for magnetic property of vanadyl tetrakis(thiadiazole) porphyrazine film on Au(1 1 1)

NASA Astrophysics Data System (ADS)

Hou, Jie; Wang, Yu; Eguchi, Keitaro; Nanjo, Chihiro; Takaoka, Tsuyoshi; Sainoo, Yasuyuki; Awaga, Kunio; Komeda, Tadahiro

2018-05-01

We report scanning tunneling microscope (STM) observation of vanadyl tetrakis(thiadiazole) porphyrazine (VOTTDPz) molecules, which is a family molecule of phthalocyanine (Pc) but without Csbnd H termination in the perimeter, deposited on Au(1 1 1) surface. Well-ordered film corresponding to 4 × 4 superstructure with respect to Au(1 1 1) surface is formed, in which the centers of the molecules are separated by 1.12 nm, which is much smaller than that observed for a VOPc molecule on Au(1 1 1), due to the absence of Csbnd H termination. At the same time, the azimuthal angles of neighboring molecules rotate with each other by 30°. A contrast variation of bright and dark molecules is observed, which are interpreted as O-up and O-down molecules, respectively, based on the density functional theory simulation. Spin-polarized local density of states calculation shows spin-polarized V 3d state, which is delocalized over the ring. Spin detection is executed by measuring Kondo resonance in the tunneling spectroscopy near the Fermi level, which is caused by the interaction of an isolated spin and conduction electron of the substrate. We detected asymmetric and weak Kondo peak for out-of-plane outer magnetic field of 0 T, which becomes strong and symmetric peak at 5 T, which is understood by the shift of the spin center of the Kondo resonance from V 3d to delocalized π state in ring with the magnetic field.

Candidate Elastic Quantum Critical Point in LaCu 6 - x Au x

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poudel, Lekh; May, Andrew F.; Koehler, Michael R.

2016-11-30

In this paper, the structural properties of LaCu 6-xAu x are studied using neutron diffraction, x-ray diffraction, and heat capacity measurements. The continuous orthorhombic-monoclinic structural phase transition in LaCu 6 is suppressed linearly with Au substitution until a complete suppression of the structural phase transition occurs at the critical composition x c=0.3. Heat capacity measurements at low temperatures indicate residual structural instability at x c. The instability is ferroelastic in nature, with density functional theory calculations showing negligible coupling to electronic states near the Fermi level. Finally, the data and calculations presented here are consistent with the zero temperature terminationmore » of a continuous structural phase transition suggesting that the LaCu 6-xAu x series hosts an elastic quantum critical point.« less

Beam-Energy Dependence of Directed Flow of Λ , Λ ¯, K±, Ks0, and ϕ in Au +Au Collisions

NASA Astrophysics Data System (ADS)

Adamczyk, L.; Adams, J. R.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Ajitanand, N. N.; Alekseev, I.; Anderson, D. M.; Aoyama, R.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Ashraf, M. U.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Barish, K.; Behera, A.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Brown, D.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chankova-Bunzarova, N.; Chatterjee, A.; Chattopadhyay, S.; Chen, X.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Elsey, N.; Engelage, J.; Eppley, G.; Esha, R.; Esumi, S.; Evdokimov, O.; Ewigleben, J.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Federicova, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C. E.; Fujita, J.; Fulek, L.; Gagliardi, C. A.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Hamad, A. I.; Hamed, A.; Harlenderova, A.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Horvat, S.; Huang, X.; Huang, B.; Huang, T.; Huang, H. Z.; Humanic, T. J.; Huo, P.; Igo, G.; Jacobs, W. W.; Jentsch, A.; Jia, J.; Jiang, K.; Jowzaee, S.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kapukchyan, D.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z.; Kikoła, D. P.; Kim, C.; Kisel, I.; Kisiel, A.; Kochenda, L.; Kocmanek, M.; Kollegger, T.; Kosarzewski, L. K.; Kraishan, A. F.; Krauth, L.; Kravtsov, P.; Krueger, K.; Kulathunga, N.; Kumar, L.; Kvapil, J.; Kwasizur, J. H.; Lacey, R.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, C.; Li, X.; Li, Y.; Li, W.; Lidrych, J.; Lin, T.; Lisa, M. A.; Liu, P.; Liu, H.; Liu, Y.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, S.; Luo, X.; Ma, Y. G.; Ma, L.; Ma, R.; Ma, G. L.; Magdy, N.; Majka, R.; Mallick, D.; Margetis, S.; Markert, C.; Matis, H. S.; Meehan, K.; Mei, J. C.; Miller, Z. W.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mizuno, S.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nie, M.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Nonaka, T.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Pruthi, N. K.; Przybycien, M.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Ray, R. L.; Reed, R.; Rehbein, M. J.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Roth, J. D.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Salur, S.; Sandweiss, J.; Saur, M.; Schambach, J.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Schweid, B. R.; Seger, J.; Sergeeva, M.; Seto, R.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, A.; Sharma, M. K.; Shen, W. Q.; Shi, S. S.; Shi, Z.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Strikhanov, M.; Stringfellow, B.; Suaide, A. A. P.; Sugiura, T.; Sumbera, M.; Summa, B.; Sun, Y.; Sun, X. M.; Sun, X.; Surrow, B.; Svirida, D. N.; Tang, Z.; Tang, A. H.; Taranenko, A.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Trzeciak, B. A.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vasiliev, A. N.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, G.; Wang, Y.; Wang, F.; Wang, Y.; Webb, J. C.; Webb, G.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, G.; Xie, W.; Xu, J.; Xu, Z.; Xu, Q. H.; Xu, Y. F.; Xu, N.; Yang, S.; Yang, Y.; Yang, C.; Yang, Q.; Ye, Z.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, Z.; Zhang, J. B.; Zhang, J.; Zhang, S.; Zhang, Y.; Zhang, X. P.; Zhang, J.; Zhang, S.; Zhao, J.; Zhong, C.; Zhou, C.; Zhou, L.; Zhu, X.; Zhu, Z.; Zyzak, M.; STAR Collaboration

2018-02-01

Rapidity-odd directed-flow measurements at midrapidity are presented for Λ , Λ ¯, K±, Ks0, and ϕ at √{sN N }=7.7 , 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV in Au +Au collisions recorded by the Solenoidal Tracker detector at the Relativistic Heavy Ion Collider. These measurements greatly expand the scope of data available to constrain models with differing prescriptions for the equation of state of quantum chromodynamics. Results show good sensitivity for testing a picture where flow is assumed to be imposed before hadron formation and the observed particles are assumed to form via coalescence of constituent quarks. The pattern of departure from a coalescence-inspired sum rule can be a valuable new tool for probing the collision dynamics.

Interfacial surfactant competition and its impact on poly(ethylene oxide)/Au and poly(ethylene oxide)/Ag nanocomposite properties

PubMed Central

Seyhan, Merve; Kucharczyk, William; Yarar, U Ecem; Rickard, Katherine; Rende, Deniz; Baysal, Nihat; Bucak, Seyda; Ozisik, Rahmi

2017-01-01

The structure and properties of nanocomposites of poly(ethylene oxide), with Ag and Au nanoparticles, surface modified with a 1:1 (by volume) oleylamine/oleic acid mixture, were investigated via transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), infrared spectroscopy, dynamic mechanical analysis, and static mechanical testing. Results indicated that there was more oleylamine on Ag nanoparticles but more oleic acid on Au nanoparticles. This difference in surfactant populations on each nanoparticle led to different interfacial interactions with poly(ethylene oxide) and drastically influenced the glass transition temperature of these two nanocomposite systems. Almost all other properties were found to correlate strongly with dispersion and distribution state of Au and Ag nanoparticles, such that the property in question changed direction at the onset of agglomeration. PMID:28461744

Time Resolved Spectroscopic Studies on a Novel Synthesized Photo-Switchable Organic Dyad and Its Nanocomposite Form in Order to Develop Light Energy Conversion Devices.

PubMed

Dutta Pal, Gopa; Paul, Abhijit; Yadav, Somnath; Bardhan, Munmun; De, Asish; Chowdhury, Joydeep; Jana, Aindrila; Ganguly, Tapan

2015-08-01

UV-vis absorption, steady state and time resolved spectroscopic investigations in pico and nanosecond time domain were made in the different environments on a novel synthesized dyad, 3-(2-methoxynaphthalen-1-yl)-1-(4-methoxyphenyl)prop-2-en-1-one (MNTMA) in its pristine form and when combined with gold (Au) nanoparticles i.e., in its nanocomposite structure. Both steady state and time resolved measurements coupled with the DFT calculations performed by using Gaussian 03 suit of software operated in the linux operating system show that though the dyad exhibits mainly the folded conformation in the ground state but on photoexcitation the nanocomposite form of dyad prefers to be in elongated structure in the excited state indicating its photoswitchable nature. Due to the predominancy of elongated isomeric form of the dyad in the excited state in presence of Au Nps, it appears that the dyad MNTMA may behave as a good light energy converter specially in its nanocomposite form. As larger charge separation rate (kcs ~ 4 x 10(8) s-1) is found relative to the rate associated with the energy wasting charge recombination processes (kcR ~ 3 x 10(5) s-1) in the nanocomposite form of the dyad, it demonstrates the suitability of constructing the efficient light energy conversion devices with Au-dyad hybrid nanomaterials.

Energy transfer from InGaN quantum wells to Au nanoclusters via optical waveguiding.

PubMed

Shu, G W; Lin, C C; Lin, H T; Lin, T N; Shen, J L; Chiu, C H; Li, Z Y; Kuo, H C; Lin, C C; Wang, S C; Lin, C A J; Chang, W H

2011-03-14

We present the first observation of resonance energy transfer from InGaN quantum wells to Au nanoclusters via optical waveguiding. Steady-state and time-resolved photoluminescence measurements provide conclusive evidence of resonance energy transfer and obtain an optimum transfer efficiency of ~72%. A set of rate equations is successfully used to model the kinetics of resonance energy transfer.

The electronic structure of Au25 clusters: between discrete and continuous.

PubMed

Katsiev, Khabiboulakh; Lozova, Nataliya; Wang, Lu; Sai Krishna, Katla; Li, Ruipeng; Mei, Wai-Ning; Skrabalak, Sara E; Kumar, Challa S S R; Losovyj, Yaroslav

2016-08-21

Here, an approach based on synchrotron resonant photoemission is employed to explore the transition between quantization and hybridization of the electronic structure in atomically precise ligand-stabilized nanoparticles. While the presence of ligands maintains quantization in Au25 clusters, their removal renders increased hybridization of the electronic states in the vicinity of the Fermi level. These observations are supported by DFT studies.

Effects of plasmonic field due to gold nanoparticles and magnetic field on photocurrents of zinc porphyrin-viologen linked compound-gold nanoparticle composite films

NASA Astrophysics Data System (ADS)

Yonemura, Hiroaki; Niimi, Tomoki; Yamada, Sunao

2016-03-01

Composite films of zinc-porphyrin-viologen (ZnP-V2+) linked compound containing six methylene group [ZnP(6)V]-gold nanoparticles (AuNP) were fabricated by combining electrostatic layer-by-layer adsorption and the Langmuir-Blodgett method. The anodic photocurrents of the ZnP(6)V-AuNP composite films are higher than those of the ZnP(6)V films. The large photocurrents in ZnP(6)V-AuNP composite films are most likely attributable to the combination of localized surface plasmon resonance due to AuNP and photoinduced intramolecular electron transfer from excited state of ZnP to V2+. The photocurrents of the ZnP(6)V-AuNP composite films increase in the presence of magnetic field. The photocurrents increase with low magnetic fields (B ≤ 150 mT) and are almost constant under high magnetic fields (B ≥ 150 mT). Magnetic field effects (MFEs) were clearly observed for both ZnP(6)V-AuNP composite films and ZnP(6)V films. The MFEs can be explained by a radical pair mechanism.

Magnetism and 155Gd Mössbauer spectroscopy of GdAuMg

NASA Astrophysics Data System (ADS)

Łątka, Kazimierz; Kmieć, Roman; Pacyna, Andrzej W.; Fickenscher, Thomas; Hoffmann, Rolf-Dieter; Pöttgen, Rainer

2004-03-01

GdAuMg was synthesized by reaction of the elements in a sealed tantalum ampule in a high-frequency furnace. The structure was investigated by X-ray diffraction on both powders and single crystals: ZrNiAl type, P 6¯2m , a=756.3(1), c=412.71(7) pm, wR2=0.0285 for 308 F2 values, 14 variables. Geometrical motifs of the GdAuMg structure are gold centered tricapped trigonal prisms [Au1Mg 3Gd 6] and [Au2Mg 6Gd 3]. Together the gold and magnesium atoms form a three-dimensional [AuMg] network in which the gadolinium atoms fill distorted hexagonal channels. Bulk magnetic properties have been investigated by means of AC and DC magnetic susceptibility measurements and 155Gd Mössbauer spectroscopy was used to monitor the local electronic and magnetic structure. Two magnetic phase transitions were found. One transition, at T1= TN=81.1(1) K, is from a paramagnetic to an antiferromagnetic state of collinear character and the other at T2=19.0(1) from the antiferromagnetic to a kind of canted magnetic ordering characterized by a very narrow hysteresis loop.

Ultrafast and Efficient Transport of Hot Plasmonic Electrons by Graphene for Pt Free, Highly Efficient Visible-Light Responsive Photocatalyst.

PubMed

Kumar, Dinesh; Lee, Ahreum; Lee, Taegon; Lim, Manho; Lim, Dong-Kwon

2016-03-09

We report that reduced graphene-coated gold nanoparticles (r-GO-AuNPs) are excellent visible-light-responsive photocatalysts for the photoconversion of CO2 into formic acid (HCOOH). The wavelength-dependent quantum and chemical yields of HCOOH shows a significant contribution of plasmon-induced hot electrons for CO2 photoconversion. Furthermore, the presence and reduced state of the graphene layers are critical parameters for the efficient CO2 photoconversion because of the electron mobility of graphene. With an excellent selectivity toward HCOOH (>90%), the quantum yield of HCOOH using r-GO-AuNPs is 1.52%, superior to that of Pt-coated AuNPs (quantum yield: 1.14%). This indicates that r-GO is a viable alternative to platinum metal. The excellent colloidal stability and photocatalytic stability of r-GO-AuNPs enables CO2 photoconversion under more desirable reaction conditions. These results highlight the role of reduced graphene layers as highly efficient electron acceptors and transporters to facilitate the use of hot electrons for plasmonic photocatalysts. The femtosecond transient spectroscopic analysis also shows 8.7 times higher transport efficiency of hot plasmonic electrons in r-GO-AuNPs compared with AuNPs.