Chamomile flower extract-directed CuO nanoparticle formation for its antioxidant and DNA cleavage properties.

PubMed

Duman, Fatih; Ocsoy, Ismail; Kup, Fatma Ozturk

2016-03-01

In this study, we report the synthesis of copper oxide nanoparticles (CuO NPs) using a medicinal plant (Matricaria chamomilla) flower extract as both reducing and capping agent and investigate their antioxidant activity and interaction with plasmid DNA (pBR322).The CuO NPs were characterized using Uv-Vis spectroscopy, FT-IR (Fourier transform infrared spectroscopy), DLS (dynamic light scattering), XRD (X-ray diffraction), EDX (energy-dispersive X-ray) spectroscopy and SEM (scanning electron microscopy). The CuO NPs exhibited nearly mono-distributed and spherical shapes with diameters of 140 nm size. UV-Vis absorption spectrum of CuO NPs gave a broad peak around 285 and 320 nm. The existence of functional groups on the surface of CuO NPs was characterized with FT-IR analysis. XRD pattern showed that the NPs are in the form of a face-centered cubic crystal. Zeta potential value was measured as -20 mV due to the presence of negatively charged functional groups in plant extract. Additionally, we demonstrated concentration-dependent antioxidant activity of CuO NPs and their interaction with plasmid DNA. We assumed that the CuO NPs both cleave and break DNA double helix structure. Copyright © 2015 Elsevier B.V. All rights reserved.

Temperature dependence of positron annihilation parameters in Tl-Ba-Ca-Cu-O superconductors

NASA Astrophysics Data System (ADS)

Sundar, C. S.; Bharathi, A.; Ching, W. Y.; Jean, Y. C.; Hor, P. H.; Meng, R. L.; Huang, Z. J.; Chu, C. W.

1990-08-01

The results of positron lifetime and Doppler broadened line-shape parameter measurements as a function of temperature, across Tc, in the Tl-Ba-Ca-Cu-O superconductors are presented. The bulk lifetime in the normal state is found to decrease with the increase in the number of CuO2 layers. Different temperature dependencies of the annihilation parameters are observed in the various Tl systems containing different numbers of CuO2 layers. In the Tl2Ba2Ca2Cu3O10 system, an increase in lifetime is observed below Tc, whereas in Tl2Ba2CaCu2O8, a decrease in lifetime is seen below Tc. In the Tl2Ba2CuO6 system, the lifetime is observed to be temperature independent. The different temperature variations of positron annihilation parameters are discussed in the light of the positron density distribution, obtained with use of the results of the self-consistent orthogonalized linear combination of atomic orbitals band-structure calculations. It is argued that the different temperature dependencies of the annihilation parameters is related to the positron density distribution within the unit cell and arise due to local charge transfer in the vicinity of the CuO2 layer in the superconducting state.

Nucleon shadowing effects in Cu + Cu and Au + Au collisions at RHIC within the HIJING code

NASA Astrophysics Data System (ADS)

Abdel-Waged, Khaled; Felemban, Nuha

2018-02-01

The centrality dependence of pseudorapidity density of charged particles ({{{d}}{N}}{{ch}}/{{d}}η ) in Cu + Cu (Au + Au) collisions at Relativistic Heavy Ion Collider energy of \\sqrt{{s}{{NN}}}=22.4, 62.4 and 200 (19.6, 62.4 and 200) GeV, is investigated within an improved HIJING code. The standard HIJING model is enhanced by a prescription for collective nucleon-nucleon (NN) interactions and more modern parton distribution functions. The collective NN-interactions are used to induce both cascade and nucleon shadowing effects. We find collective cascade broadens the pseudorapidity distributions in the tails (at | η | > {y}{beam}) above 25%-30% collision centrality to be consistent with the {{{d}}{N}}{{ch}}/{{d}}η data at \\sqrt{{s}{{NN}}} =19.6,22.4,62.4 {GeV}. The overall contribution of nucleon shadowing is shown to depress the whole shape of {{{d}}{N}}{{ch}}/{{d}}η in the primary interaction region (at | η | < {y}{beam}) for semiperipheral (20%-25%) and peripheral (≥slant 35 % {--}40 % ) Cu + Cu (Au + Au) interactions at \\sqrt{{s}{{NN}}}=200 {GeV}, in accordance with the PHOBOS data.

Revisiting Cu 63 NMR evidence for charge order in superconducting La 1.885 Sr 0.115 CuO 4

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

Imai, T.; Takahashi, S. K.; Arsenault, A.

Here, the presence of charge and spin stripe order in the La 2CuO 4-based family of superconductors continues to lead to new insight on the unusual ground-state properties of high- T c cuprates. Soon after the discovery of charge stripe order at T charge≃65 K in Nd 3+ co-doped La 1.48Nd 0.4Sr 0.12CuO 4( Tc≃6 K), Hunt et al. demonstrated that La 1.48Nd 0.4Sr 0.12CuO 4 and superconducting La 2–xSr xCuO 4 with x~1/8( Tc≃30 K) share nearly identical NMR anomalies near Tcharge of the former. Their inevitable conclusion that La 1.885Sr 0.115CuO 4 also undergoes charge order at amore » comparable temperature became controversial, because diffraction measurements at the time were unable to detect Bragg peaks associated with charge order. Recent advances in x-ray diffraction techniques finally led to definitive confirmations of the charge order Bragg peaks in La 1.885Sr 0.115CuO 4 with an onset at as high as Tcharge≃80 K. Meanwhile, improved instrumental technology has enabled routine NMR measurements that were not feasible two decades ago. Motivated by these new developments, we revisit the charge order transition of a La 1.885Sr 0.115CuO 4 single crystal based on 63Cu NMR techniques. We demonstrate that 63Cu NMR properties of the nuclear spin I z=–1/2 to +1/2 central transition below Tcharge exhibit unprecedentedly strong dependence on the measurement time scale set by the separation time τ between the 90° and 180° radio-frequency pulses; a new kind of anomalous, very broad winglike 63Cu NMR signals gradually emerge below Tcharge only for extremely short τ≲4μs, while the spectral weight I Normal of the normal NMR signals is progressively wiped out. The NMR linewidth and relaxation rates depend strongly on τ below Tcharge, and their enhancement in the charge ordered state indicates that charge order turns on strong but inhomogeneous growth of Cu spin-spin correlations.« less

Revisiting Cu 63 NMR evidence for charge order in superconducting La 1.885 Sr 0.115 CuO 4

DOE PAGES

Imai, T.; Takahashi, S. K.; Arsenault, A.; ...

2017-12-26

Here, the presence of charge and spin stripe order in the La 2CuO 4-based family of superconductors continues to lead to new insight on the unusual ground-state properties of high- T c cuprates. Soon after the discovery of charge stripe order at T charge≃65 K in Nd 3+ co-doped La 1.48Nd 0.4Sr 0.12CuO 4( Tc≃6 K), Hunt et al. demonstrated that La 1.48Nd 0.4Sr 0.12CuO 4 and superconducting La 2–xSr xCuO 4 with x~1/8( Tc≃30 K) share nearly identical NMR anomalies near Tcharge of the former. Their inevitable conclusion that La 1.885Sr 0.115CuO 4 also undergoes charge order at amore » comparable temperature became controversial, because diffraction measurements at the time were unable to detect Bragg peaks associated with charge order. Recent advances in x-ray diffraction techniques finally led to definitive confirmations of the charge order Bragg peaks in La 1.885Sr 0.115CuO 4 with an onset at as high as Tcharge≃80 K. Meanwhile, improved instrumental technology has enabled routine NMR measurements that were not feasible two decades ago. Motivated by these new developments, we revisit the charge order transition of a La 1.885Sr 0.115CuO 4 single crystal based on 63Cu NMR techniques. We demonstrate that 63Cu NMR properties of the nuclear spin I z=–1/2 to +1/2 central transition below Tcharge exhibit unprecedentedly strong dependence on the measurement time scale set by the separation time τ between the 90° and 180° radio-frequency pulses; a new kind of anomalous, very broad winglike 63Cu NMR signals gradually emerge below Tcharge only for extremely short τ≲4μs, while the spectral weight I Normal of the normal NMR signals is progressively wiped out. The NMR linewidth and relaxation rates depend strongly on τ below Tcharge, and their enhancement in the charge ordered state indicates that charge order turns on strong but inhomogeneous growth of Cu spin-spin correlations.« less

Revisiting 63Cu NMR evidence for charge order in superconducting La1.885Sr0.115CuO4

NASA Astrophysics Data System (ADS)

Imai, T.; Takahashi, S. K.; Arsenault, A.; Acton, A. W.; Lee, D.; He, W.; Lee, Y. S.; Fujita, M.

2017-12-01

The presence of charge and spin stripe order in the La2CuO4 -based family of superconductors continues to lead to new insight on the unusual ground-state properties of high-Tc cuprates. Soon after the discovery of charge stripe order at Tcharge≃65 K in Nd3 + co-doped La1.48Nd0.4Sr0.12CuO4 (Tc≃6 K) [Tranquada et al., Nature (London) 375, 561 (1995), 10.1038/375561a0], Hunt et al. demonstrated that La1.48Nd0.4Sr0.12CuO4 and superconducting La2 -xSrxCuO4 with x ˜1 /8 (Tc≃30 K) share nearly identical NMR anomalies near Tcharge of the former [Phys. Rev. Lett. 82, 4300 (1999), 10.1103/PhysRevLett.82.4300]. Their inevitable conclusion that La1.885Sr0.115CuO4 also undergoes charge order at a comparable temperature became controversial, because diffraction measurements at the time were unable to detect Bragg peaks associated with charge order. Recent advances in x-ray diffraction techniques finally led to definitive confirmations of the charge order Bragg peaks in La1.885Sr0.115CuO4 with an onset at as high as Tcharge≃80 K. Meanwhile, improved instrumental technology has enabled routine NMR measurements that were not feasible two decades ago. Motivated by these new developments, we revisit the charge order transition of a La1.885Sr0.115CuO4 single crystal based on 63Cu NMR techniques. We demonstrate that 63Cu NMR properties of the nuclear spin Iz=-1/2 to +1/2 central transition below Tcharge exhibit unprecedentedly strong dependence on the measurement time scale set by the separation time τ between the 90∘ and 180∘ radio-frequency pulses; a new kind of anomalous, very broad winglike 63Cu NMR signals gradually emerge below Tcharge only for extremely short τ ≲4 μ s , while the spectral weight INormal of the normal NMR signals is progressively wiped out. The NMR linewidth and relaxation rates depend strongly on τ below Tcharge, and their enhancement in the charge ordered state indicates that charge order turns on strong but inhomogeneous growth of Cu spin-spin correlations.

Photoelectrodes based on 2D opals assembled from Cu-delafossite double-shelled microspheres for an enhanced photoelectrochemical response.

PubMed

Oh, Yunjung; Yang, Wooseok; Tan, Jeiwan; Lee, Hyungsoo; Park, Jaemin; Moon, Jooho

2018-02-22

Although a unique light-harvesting property was recently demonstrated in a photocathode based on 2-dimensional (2D) opals of CuFeO 2 -shelled SiO 2 microspheres, the performance of a monolayer of ultra-thin CuFeO 2 -shelled microspheres is limited by ineffective charge separation. Herein, we propose an innovative design rule, in which an inner CuFeO 2 /outer CuAlO 2 double-shelled heterojunction is formed on each partially etched microsphere to obtain a hexagonally assembled 2D opal photoelectrode. Our Cu-delafossite double-shelled photocathode shows a dramatically improved charge separation capability, with a 9-fold increase in the photocurrent compared to that of the single-shelled counterpart. Electrochemical impedance spectroscopy clearly confirms the reduced charge transport/transfer resistance associated with the Cu-delafossite double-shelled photocathode, while surface photovoltage spectra reveal enhanced polarization of the photogenerated carrier, indicating improved charge separation capability with the aid of the heterojunction. Our finding sheds light on the importance of heterojunction interfaces in achieving optimal charge separation in opal architectures as well as the inner-shell/electrolyte interface to expedite charge separation/transport.

Unconventional charge order in a co-doped high-Tc superconductor

PubMed Central

Pelc, D.; Vučković, M.; Grafe, H. -J.; Baek, S. -H.; Požek, M.

2016-01-01

Charge-stripe order has recently been established as an important aspect of cuprate high-Tc superconductors. However, owing to the complex interplay between competing phases and the influence of disorder, it is unclear how it emerges from the parent high-temperature state. Here we report on the discovery of an unconventional ordered phase between charge-stripe order and (pseudogapped) metal in the cuprate La1.8−xEu0.2SrxCuO4. We use three complementary experiments—nuclear quadrupole resonance, nonlinear conductivity and specific heat—to demonstrate that the order appears through a sharp phase transition and exists in a dome-shaped region of the phase diagram. Our results imply that the new phase is a state, which preserves translational symmetry: a charge nematic. We thus resolve the process of charge-stripe development in cuprates, show that this nematic phase is distinct from high-temperature pseudogap and establish a link with other strongly correlated electronic materials with prominent nematic order. PMID:27605152

Gradient Self-Doped CuBi2O4 with Highly Improved Charge Separation Efficiency.

PubMed

Wang, Fuxian; Septina, Wilman; Chemseddine, Abdelkrim; Abdi, Fatwa F; Friedrich, Dennis; Bogdanoff, Peter; van de Krol, Roel; Tilley, S David; Berglund, Sean P

2017-10-25

A new strategy of using forward gradient self-doping to improve the charge separation efficiency in metal oxide photoelectrodes is proposed. Gradient self-doped CuBi 2 O 4 photocathodes are prepared with forward and reverse gradients in copper vacancies using a two-step, diffusion-assisted spray pyrolysis process. Decreasing the Cu/Bi ratio of the CuBi 2 O 4 photocathodes introduces Cu vacancies that increase the carrier (hole) concentration and lowers the Fermi level, as evidenced by a shift in the flat band toward more positive potentials. Thus, a gradient in Cu vacancies leads to an internal electric field within CuBi 2 O 4 , which can facilitate charge separation. Compared to homogeneous CuBi 2 O 4 photocathodes, CuBi 2 O 4 photocathodes with a forward gradient show highly improved charge separation efficiency and enhanced photoelectrochemical performance for reduction reactions, while CuBi 2 O 4 photocathodes with a reverse gradient show significantly reduced charge separation efficiency and photoelectrochemical performance. The CuBi 2 O 4 photocathodes with a forward gradient produce record AM 1.5 photocurrent densities for CuBi 2 O 4 up to -2.5 mA/cm 2 at 0.6 V vs RHE with H 2 O 2 as an electron scavenger, and they show a charge separation efficiency of 34% for 550 nm light. The gradient self-doping accomplishes this without the introduction of external dopants, and therefore the tetragonal crystal structure and carrier mobility of CuBi 2 O 4 are maintained. Lastly, forward gradient self-doped CuBi 2 O 4 photocathodes are protected with a CdS/TiO 2 heterojunction and coated with Pt as an electrocatalyst. These photocathodes demonstrate photocurrent densities on the order of -1.0 mA/cm 2 at 0.0 V vs RHE and evolve hydrogen with a faradaic efficiency of ∼91%.

CHARGED PARTICLE MULTIPLICITIES IN ULTRA-RELATIVISTIC AU+AU AND CU+CU COLLISIONS

NASA Astrophysics Data System (ADS)

Back, B. B.; 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.; Chetluru, V.; Decowski, M. P.; Garcia, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Halliwell, C.; Hamblen, J.; Harnarine, I.; Hauer, M.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holynski, 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.; Richardson, E.; Roland, C.; Roland, G.; Sagerer, J.; Seals, H.; Sedykh, I.; Smith, C. E.; Stankiewicz, M. A.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Szostak, A.; Tonjes, M. B.; Trzupek, A.; Vale, C.; Vannieuwenhuizen, G. J.; Vaurynovich, S. S.; Verdier, R.; Veres, G. I.; Walters, P.; Wenger, E.; Willhelm, D.; Wolfs, F. L. H.; Wosiek, B.; Wozniak, K.; Wyngaardt, S.; Wyslouch, B.

The PHOBOS collaboration has carried out a systematic study of charged particle multiplicities in Cu+Cu and Au+Au collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory. A unique feature of the PHOBOS detector is its ability to measure charged particles over a very wide angular range from 0.5° to 179.5° corresponding to |η| <5.4. The general features of the charged particle multiplicity distributions as a function of pseudo-rapidity, collision energy and centrality, as well as system size, are discussed.

Cu nuclear magnetic resonance study of charge and spin stripe order in La 1.875 Ba 0.125 CuO 4

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

Pelc, D.; Grafe, H. -J.; Gu, G. D.

In this paper, we present a Cu nuclear magnetic/quadrupole resonance study of the charge stripe ordered phase of LBCO, with detection of previously unobserved (“wiped-out”) signal. We show that spin-spin and spin-lattice relaxation rates are strongly enhanced in the charge ordered phase, explaining the apparent signal decrease in earlier investigations. The enhancement is caused by magnetic, rather than charge fluctuations, conclusively confirming the long-suspected assumption that spin fluctuations are responsible for the wipeout effect. Observation of the full Cu signal enables insight into the spin and charge dynamics of the stripe-ordered phase, and measurements in external magnetic fields provide informationmore » on the nature and suppression of spin fluctuations associated with charge order. Lastly, we find glassy spin dynamics, in agreement with previous work, and incommensurate static charge order with charge modulation amplitude similar to other cuprate compounds, suggesting that the amplitude of charge stripes is universal in the cuprates.« less

Cu nuclear magnetic resonance study of charge and spin stripe order in La 1.875 Ba 0.125 CuO 4

DOE PAGES

Pelc, D.; Grafe, H. -J.; Gu, G. D.; ...

2017-02-15

In this paper, we present a Cu nuclear magnetic/quadrupole resonance study of the charge stripe ordered phase of LBCO, with detection of previously unobserved (“wiped-out”) signal. We show that spin-spin and spin-lattice relaxation rates are strongly enhanced in the charge ordered phase, explaining the apparent signal decrease in earlier investigations. The enhancement is caused by magnetic, rather than charge fluctuations, conclusively confirming the long-suspected assumption that spin fluctuations are responsible for the wipeout effect. Observation of the full Cu signal enables insight into the spin and charge dynamics of the stripe-ordered phase, and measurements in external magnetic fields provide informationmore » on the nature and suppression of spin fluctuations associated with charge order. Lastly, we find glassy spin dynamics, in agreement with previous work, and incommensurate static charge order with charge modulation amplitude similar to other cuprate compounds, suggesting that the amplitude of charge stripes is universal in the cuprates.« less

Electrostatic occlusion and quaternary structural ion pairing are key determinants of Cu(I)-mediated allostery in the copper-sensing operon repressor (CsoR).

PubMed

Chang, Feng-Ming James; Martin, Julia E; Giedroc, David P

2015-04-21

The copper-sensing operon repressor (CsoR) is an all-α-helical disc-shaped D2-symmetric homotetramer that forms a 2:1 tetramer/DNA operator complex and represses the expression of copper-resistance genes in a number of bacteria. A previous bioinformatics analysis of CsoR-family repressors distributes Cu(I)-sensing CsoRs in four of seven distinct clades on the basis of global sequence similarity. In this work, we define energetically important determinants of DNA binding in the apo-state (ΔΔGbind), and for allosteric negative coupling of Cu(I) binding to DNA binding (ΔΔGc) in a model clade IV CsoR from Geobacillus thermodenitrificans (Gt) of known structure, by selectively targeting for mutagenesis those charged residues uniquely conserved in clade IV CsoRs. These include a folded N-terminal "tail" and a number of Cu(I)-sensor and clade-specific residues that when mapped onto a model of Cu(I)-bound Gt CsoR define a path across one face of the tetramer. We find that Cu(I)-binding prevents formation of the 2:1 "sandwich" complex rather than DNA binding altogether. Folding of the N-terminal tail (residues R18, E22, R74) upon Cu-binding to the periphery of the tetramer inhibits assembly of the 2:1 apoprotein-DNA complex. In contrast, Ala substitution of residues that surround the central "hole" (R65, K101) in the tetramer, as well R48, impact DNA binding. We also identify a quaternary structural ion-pair, E73-K101″, that crosses the tetramer interface, charge-reversal of which restores DNA binding activity, allosteric regulation by Cu(I), and transcriptional derepression by Cu(I) in cells. These findings suggest an "electrostatic occlusion" model, in which basic residues important for DNA binding and/or allostery become sequestered via ion-pairing specifically in the Cu(I)-bound state, and this aids in copper-dependent disassembly of a repression complex.

Ligand-hole localization in oxides with unusual valence Fe

PubMed Central

Chen, Wei-Tin; Saito, Takashi; Hayashi, Naoaki; Takano, Mikio; Shimakawa, Yuichi

2012-01-01

Unusual high-valence states of iron are stabilized in a few oxides. A-site-ordered perovskite-structure oxides contain such iron cations and exhibit distinct electronic behaviors at low temperatures, e.g. charge disproportionation (4Fe4+ → 2Fe3+ + 2Fe5+) in CaCu3Fe4O12 and intersite charge transfer (3Cu2+ + 4Fe3.75+ → 3Cu3+ + 4Fe3+) in LaCu3Fe4O12. Here we report the synthesis of solid solutions of CaCu3Fe4O12 and LaCu3Fe4O12 and explain how the instabilities of their unusual valence states of iron are relieved. Although these behaviors look completely different from each other in simple ionic models, they can both be explained by the localization of ligand holes, which are produced by the strong hybridization of iron d and oxygen p orbitals in oxides. The localization behavior in the charge disproportionation of CaCu3Fe4O12 is regarded as charge ordering of the ligand holes, and that in the intersite charge transfer of LaCu3Fe4O12 is regarded as a Mott transition of the ligand holes. PMID:22690318

Hierarchical, porous CuS microspheres integrated with carbon nanotubes for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Lu, Yang; Liu, Xianming; Wang, Weixiao; Cheng, Jinbing; Yan, Hailong; Tang, Chengchun; Kim, Jang-Kyo; Luo, Yongsong

2015-11-01

Carbon nanotubes (CNTs) incorporated porous 3-dimensional (3D) CuS microspheres have been successfully synthesized via a simple refluxing method assisted by PVP. The composites are composed of flower-shaped CuS secondary microspheres, which in turn are assembled with primary nanosheets of 15-30 nm in thickness and fully integrated with CNT. The composites possess a large specific surface area of 189.6 m2 g-1 and a high conductivity of 0.471 S cm-1. As electrode materials for supercapacitors, the nanocomposites show excellent cyclability and rate capability and deliver an average reversible capacitance as high as 1960 F g-1 at a current density of 10 mA cm-2 over 10000 cycles. The high electrochemical performance can be attributed to the synergistic effect of CNTs and the unique microstructure of CuS. The CNTs serve as not only a conductive agent to accelerate the transfer of electrons in the composites, but also as a buffer matrix to restrain the volume change and stabilize the electrode structure during the charge/discharge process. The porous structure of CuS also helps to stabilize the electrode structure and facilitates the transport for electrons.

Hierarchical, porous CuS microspheres integrated with carbon nanotubes for high-performance supercapacitors.

PubMed

Lu, Yang; Liu, Xianming; Wang, Weixiao; Cheng, Jinbing; Yan, Hailong; Tang, Chengchun; Kim, Jang-Kyo; Luo, Yongsong

2015-11-16

Carbon nanotubes (CNTs) incorporated porous 3-dimensional (3D) CuS microspheres have been successfully synthesized via a simple refluxing method assisted by PVP. The composites are composed of flower-shaped CuS secondary microspheres, which in turn are assembled with primary nanosheets of 15-30 nm in thickness and fully integrated with CNT. The composites possess a large specific surface area of 189.6 m(2) g(-1) and a high conductivity of 0.471 S cm(-1). As electrode materials for supercapacitors, the nanocomposites show excellent cyclability and rate capability and deliver an average reversible capacitance as high as 1960 F g(-1) at a current density of 10 mA cm(-2) over 10000 cycles. The high electrochemical performance can be attributed to the synergistic effect of CNTs and the unique microstructure of CuS. The CNTs serve as not only a conductive agent to accelerate the transfer of electrons in the composites, but also as a buffer matrix to restrain the volume change and stabilize the electrode structure during the charge/discharge process. The porous structure of CuS also helps to stabilize the electrode structure and facilitates the transport for electrons.

Charge carrier dynamics investigation of CuInS2 quantum dots films using injected charge extraction by linearly increasing voltage (i-CELIV): the role of ZnS Shell

NASA Astrophysics Data System (ADS)

Bi, Ke; Sui, Ning; Zhang, Liquan; Wang, Yinghui; Liu, Qinghui; Tan, Mingrui; Zhou, Qiang; Zhang, Hanzhuang

2016-12-01

The role of ZnS shell on the photo-physical properties within CuInS2/ZnS quantum dots (QDs) is carefully studied in optoelectronic devices. Linearly increasing voltage technique has been employed to investigate the charge carrier dynamics of both CuInS2 and CuInS2/ZnS QDs films. This study shows that charge carriers follow a similar behavior of monomolecular recombination in this film, with their charge transfer rate correlates to the increase of applied voltage. It turns out that the ZnS shell could affect the carrier diffusion process through depressing the trapping states and would build up a potential barrier.

Structural, dynamical & electronic properties of CaCuO{sub 2}

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

Agrawal, B.K.; Agrawal, S.

1994-12-31

The scalar relativistic version of an accurate first principles full potential self- consistent linearized muffin tin orbital (LMTO) method has been employed for describing the physical properties of the parent system of the high-Tc oxide superconductors, i.e., CaCuO2. The presently employed modified version of the LMTO method is quite fast and goes beyond the usual LMTO-ASA method in the sense that it permits a completely general shape of the potential and the charge density. Also, in contrast to LMTO-ASA, the present method is also capable of treating distorted lattice structures accurately. The calculated values of the lattice parameters of puremore » CaCuO2 lie within 3% of the experimentally measured values for the Sr-doped system Ca(.86)Sr(.14)CuO(2). The computed electronic structures and the density of states is quite similar to those of the other oxide superconductors, except of their three- dimensional character because of the presence of strong coupling between the closely spaced CuO2 layers. The van Hove singularity peak appears slightly below the Fermi level and a small concentration of oxygenation /or/ substitutional doping may pin it as the Fermi level. The calculated frequencies for some symmetric frozen phonons for undoped CaCuO2 are quite near to the measured data for the Sr-doped CaCuO2.« less

Structural, dynamical and electronic properties of CaCuO2

NASA Technical Reports Server (NTRS)

Agrawal, Bal K.; Agrawal, Savitri

1995-01-01

The scalar relativistic version of an accurate first principles full potential self-consistent linearized muffin tin orbital (LMTO) method has been employed for describing the physical properties of the parent system of the high-T(sub c) oxide superconductors, i.e., CaCuO2. The presently employed modified version of the LMTO method is quite fast and goes beyond the usual LMTO ASA method in the sense that it permits a completely general shape of the potential and the charge density. Also, in contrast to LMTO ASA, the present method is also capable of treating distorted lattice structures accurately. The calculated values of the lattice parameters of pure CaCuO2 lie within 3% of the experimentally measured values for the Sr-doped system Ca(0.86)Sr(0.14)CuO(2). The computed electronic structures and the density of states is quite similar to those of the other oxide superconductors, except of their three- dimensional character because of the presence of strong coupling between the closely spaced CuO2 layers. The van Hove singularity peak appears slightly below the Fermi level and a small concentration of oxygenation /or/ substitutional doping may pin it at the Fermi level. The calculated frequencies for some symmetric frozen phonons for undoped CaCuO2 are quite near to the measured data for the Sr-doped CaCuO2.

Electroactive Shape Memory Property of a Cu-decorated CNT Dispersed PLA/ESO Nanocomposite

PubMed Central

Alam, Javed; Khan, Aslam; Alam, Manawwer; Mohan, Raja

2015-01-01

Shape memory polymer (SMP) nanocomposites with a fast electro-actuation speed were prepared by dispersing Cu-decorated carbon nanotubes (CNTs) (Cu-CNTs, 1 wt %, 2 wt %, and 3 wt %) in a polylactic acid (PLA)/epoxidized soybean oil (ESO) blend matrix. The shape memory effect (SME) induced by an electrical current was investigated by a fold-deploy “U”-shape bending test. In addition, the Cu-CNT dispersed PLA/ESO nanocomposite was characterized by atomic force microscopy (AFM), dynamic mechanical analysis (DMA) and tensile and electrical measurements. The results demonstrated that the SME was dependent on the Cu-CNT content in the nanocomposites. When comparing the SMEs of the nanocomposite specimens with different Cu-CNT contents, the 2 wt % Cu-CNT dispersed system exhibited a shape recovery as high as 98% within 35 s due to its higher electrical conductivity that results from uniform Cu-CNT dispersion. However, the nanocomposites that contained 1 wt % and 3 wt % Cu-CNTs required 75 s and 63 s, respectively, to reach a maximum recovery level. In addition, the specimens exhibited better mechanical properties after the addition of Cu-CNTs. PMID:28793570

Delayed Triplet-State Formation through Hybrid Charge Transfer Exciton at Copper Phthalocyanine/GaAs Heterojunction.

PubMed

Lim, Heeseon; Kwon, Hyuksang; Kim, Sang Kyu; Kim, Jeong Won

2017-10-05

Light absorption in organic molecules on an inorganic substrate and subsequent electron transfer to the substrate create so-called hybrid charge transfer exciton (HCTE). The relaxation process of the HCTE states largely determines charge separation efficiency or optoelectronic device performance. Here, the study on energy and time-dispersive behavior of photoelectrons at the hybrid interface of copper phthalocyanine (CuPc)/p-GaAs(001) upon light excitation of GaAs reveals a clear pathway for HCTE relaxation and delayed triplet-state formation. According to the ground-state energy level alignment at the interface, CuPc/p-GaAs(001) shows initially fast hole injection from GaAs to CuPc. Thus, the electrons in GaAs and holes in CuPc form an unusual HCTE state manifold. Subsequent electron transfer from GaAs to CuPc generates the formation of the triplet state in CuPc with a few picoseconds delay. Such two-step charge transfer causes delayed triplet-state formation without singlet excitation and subsequent intersystem crossing within the CuPc molecules.

The study of changes in structural properties of Cu films under ionizing radiation

NASA Astrophysics Data System (ADS)

Kaliekperov, M.; Kozlovskiy, A.; Shlimas, D.; Kenzhina, I.; Ivanov, I.; Kozin, S.; Aleksandrenko, V.; Kurakhmedov, A.; Sambaev, E.; Seitbaev, A.; Zdorovets, M.; Kadyrzhanov, K.

2018-05-01

In this paper, we present the results of studies of the irradiation effect with low-energy He+2 ions with an energy of 30 keV (15 keV per charge) on the structural properties of Cu films. Using SEM, EDS, and x-ray diffraction analysis, the surface morphology and structural properties of samples before and after irradiation were studied. As a result of irradiation of initial samples with He+2 ions with a dose of 1·1016 ion cm‑2, a change in the Cu surface morphology of films is observed, and the formation of nanoscale inclusions of hexagonal shape is observed. An increase in the irradiation dose to 1·1017 ion cm‑2 and higher leads to the formation of cracks and amorphous oxide inclusions on the sample surface. It is established that an increase in the irradiation dose leads to a decrease in the degree of crystallinity and a change in the basic crystallographic characteristics. The effect of irradiation on the strength characteristics was estimated.

Biokinetics of different-shaped copper oxide nanoparticles in the freshwater gastropod, Potamopyrgus antipodarum

USGS Publications Warehouse

Ramskov, Tina; Croteau, Marie-Noele; Forbes, Valery E.; Selck, Henriette

2015-01-01

Sediment is recognized as a major environmental sink for contaminants, including engineered nanoparticles (NPs). Consequently, sediment-living organisms are likely to be exposed to NPs. There is evidence that both accumulation and toxicity of metal NPs to sediment-dwellers increase with decreasing particle size, although NP size does not always predict effects. In contrast, not much is known about the influence of particle shape on bioaccumulation and toxicity. Here, we examined the influence of copper oxide (CuO) NP shape (rods, spheres, and platelets) on their bioaccumulation kinetics and toxicity to the sediment-dwelling gastropod, Potamopyrgus antipodarum. The influence of Cu added as CuCl2 (i.e., aqueous Cu treatment) was also examined. Exposure to sediment mixed with aqueous Cu or with different-shaped CuO NPs at an average measured exposure concentration of 207 μg Cu per g dry weight sediment for 14 days did not significantly affect snail mortality. However, growth decreased for snails exposed to sediment amended with CuO NP spheres and platelets. P. antipodarum accumulated Cu from all Cu forms/shapes in significant amounts compared to control snails. In addition, once accumulated, Cu was efficiently retained (i.e., elimination rate constants were generally not significantly different from zero). Consequently, snails are likely to concentrate Cu over time, from both aqueous and NP sources, resulting in a high potential for toxicity.

Charge and orbital orders and structural instability in high-pressure quadruple perovskite CeCuMn6O12

NASA Astrophysics Data System (ADS)

Zhang, Lei; Matsushita, Yoshitaka; Katsuya, Yoshio; Tanaka, Masahiko; Yamaura, Kazunari; Belik, Alexei A.

2018-02-01

We prepared a quadruple perovskite CeCuMn6O12 under high-pressure and high-temperature conditions at 6 GPa and about 1670 K and investigated its structural, magnetic and transport properties. CeCuMn6O12 crystallizes in space group Im-3 above T CO  =  297 K below this temperature, it adopts space group R-3 with the 1:3 (Mn4+:Mn3+) charge and orbital orders. Unusual compressed Mn3+O6 octahedra are realized in CeCuMn6O12 similar to CaMn7O12 with the  -Q 3 Jahn-Teller distortion mode. Below about 90 K, structural instability takes place with phase separation and the appearance of competing phases; and below 70 K, two R-3 phases coexist. CeCuMn6O12 exhibits a ferromagnetic-like transition below T C  =  140 K, and it is a semiconductor with the magnetoresistance reaching about  -40% at 140 K and 70 kOe. We argued that the valence of Ce is  +3 in CeCuMn6O12 with the Ce3+(C{{u}2+}Mn23+ )(Mn33+M{{n}4+} )O12 charge distribution in the charge-ordered R-3 phase and Ce3+(C{{u}2+}Mn23+ )(Mn43.25+ )O12 in the charge-disordered Im-3 phase.

Charged-particle multiplicity and pseudorapidity distributions measured with the PHOBOS detector in Au+Au, Cu+Cu, d+Au, and p+p collisions at ultrarelativistic energies

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.; Hofman, D. J.; Hollis, R. S.; Hołyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kotuła, J.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Li, W.; Lin, W. T.; Loizides, C.; Manly, S.; McLeod, D.; Michałowski, J.; 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.; Sedykh, I.; Skulski, W.; Smith, C. E.; Steadman, S. G.; Steinberg, P.; Stephans, G. S. F.; Stodulski, M.; Sukhanov, A.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Vaurynovich, S. S.; Verdier, R.; Veres, G. I.; Wadsworth, B.; Walters, P.; Wenger, E.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wuosmaa, A. H.; Wysłouch, B.

2011-02-01

Pseudorapidity distributions of charged particles emitted in Au+Au, Cu+Cu, d+Au, and p+p collisions over a wide energy range have been measured using the PHOBOS detector at the BNL Relativistic Heavy-Ion Collider (RHIC). The centrality dependence of both the charged particle distributions and the multiplicity at midrapidity were measured. Pseudorapidity distributions of charged particles emitted with |η|<5.4, which account for between 95% and 99% of the total charged-particle emission associated with collision participants, are presented for different collision centralities. Both the midrapidity density dNch/dη and the total charged-particle multiplicity Nch are found to factorize into a product of independent functions of collision energy, sNN, and centrality given in terms of the number of nucleons participating in the collision, Npart. The total charged particle multiplicity, observed in these experiments and those at lower energies, assumes a linear dependence of (lnsNN)2 over the full range of collision energy of sNN=2.7-200 GeV.

High field charge order across the phase diagram of YBa2Cu3Oy

NASA Astrophysics Data System (ADS)

Laliberté, Francis; Frachet, Mehdi; Benhabib, Siham; Borgnic, Benjamin; Loew, Toshinao; Porras, Juan; Le Tacon, Mathieu; Keimer, Bernhard; Wiedmann, Steffen; Proust, Cyril; LeBoeuf, David

2018-03-01

In hole-doped cuprates there is now compelling evidence that inside the pseudogap phase, charge order breaks translational symmetry. In YBa2Cu3Oy charge order emerges in two steps: a 2D order found at zero field and at high temperature inside the pseudogap phase, and a 3D order that is superimposed below the superconducting transition Tc when superconductivity is weakened by a magnetic field. Several issues still need to be addressed such as the effect of disorder, the relationship between those charge orders and their respective impact on the Fermi surface. Here, we report high magnetic field sound velocity measurements of the 3D charge order in underdoped YBa2Cu3Oy in a large doping range. We found that the 3D charge order exists over the same doping range as its 2D counterpart, indicating an intimate connection between the two distinct orders. Moreover, our data suggest that 3D charge order has only a limited impact on low-lying electronic states of YBa2Cu3Oy.

Fragile charge order in the nonsuperconducting ground state of the underdoped high-temperature superconductors.

PubMed

Tan, B S; Harrison, N; Zhu, Z; Balakirev, F; Ramshaw, B J; Srivastava, A; Sabok-Sayr, S A; Sabok, S A; Dabrowski, B; Lonzarich, G G; Sebastian, Suchitra E

2015-08-04

The normal state in the hole underdoped copper oxide superconductors has proven to be a source of mystery for decades. The measurement of a small Fermi surface by quantum oscillations on suppression of superconductivity by high applied magnetic fields, together with complementary spectroscopic measurements in the hole underdoped copper oxide superconductors, point to a nodal electron pocket from charge order in YBa2Cu3(6+δ). Here, we report quantum oscillation measurements in the closely related stoichiometric material YBa2Cu4O8, which reveals similar Fermi surface properties to YBa2Cu3(6+δ), despite the nonobservation of charge order signatures in the same spectroscopic techniques, such as X-ray diffraction, that revealed signatures of charge order in YBa2Cu3(6+δ). Fermi surface reconstruction in YBa2Cu4O8 is suggested to occur from magnetic field enhancement of charge order that is rendered fragile in zero magnetic fields because of its potential unconventional nature and/or its occurrence as a subsidiary to more robust underlying electronic correlations.

Rotary engine research

NASA Astrophysics Data System (ADS)

1992-06-01

A development history is presented for NASA's 1983-1991 Rotary Engine Enablement Program, emphasizing the CFD approaches to various problems that were instituted from 1987 to the end of the program. In phase I, a test rig was built to intensively clarify and characterize the stratified-charge rotary engine concept. In phase II, a high pressure, electronically controlled fuel injection system was tested. In phase III, the testing of improved fuel injectors led to the achievement of the stipulated 5 hp/cu inch specific power goal. CFD-aided design of advanced rotor-pocket shapes led to additional performance improvements.

Electrical Study of Trapped Charges in Copper-Doped Zinc Oxide Films by Scanning Probe Microscopy for Nonvolatile Memory Applications

PubMed Central

Su, Ting; Zhang, Haifeng

2017-01-01

Charge trapping properties of electrons and holes in copper-doped zinc oxide (ZnO:Cu) films have been studied by scanning probe microscopy. We investigated the surface potential dependence on the voltage and duration applied to the copper-doped ZnO films by Kelvin probe force microscopy. It is found that the Fermi Level of the 8 at.% Cu-doped ZnO films shifted by 0.53 eV comparing to undoped ZnO films. This shift indicates significant change in the electronic structure and energy balance in Cu-doped ZnO films. The Fermi Level (work function) of zinc oxide films can be tuned by Cu doping, which are important for developing this functional material. In addition, Kelvin probe force microscopy measurements demonstrate that the nature of contact at Pt-coated tip/ZnO:Cu interface is changed from Schottky contact to Ohmic contact by increasing sufficient amount of Cu ions. The charge trapping property of the ZnO films enhance greatly by Cu doping (~10 at.%). The improved stable bipolar charge trapping properties indicate that copper-doped ZnO films are promising for nonvolatile memory applications. PMID:28135335

Copper Electrodeposition on a Magnesium Alloy (AZ80) with a U-Shaped Surface

PubMed Central

Huang, Ching An; Yeh, Yu Hu; Lin, Che Kuan; Hsieh, Chen Yun

2014-01-01

Cu electrodeposition was performed on a cylindrical AZ80 substrate with a U-shaped surface. A uniform deposition of Cu was achieved on an AZ80 electrode via galvanostatic etching, followed by Cu electrodeposition in an eco-friendly alkaline Cu plating bath. Improper wetting and lower rotational speeds of the AZ80 electrode resulted in an uneven Cu deposition at the inner upper site of the U-shaped surface during the Cu electroplating process. This wetting effect could be deduced from the variation in the anodic potential during the galvanostatic etching. The corrosion resistance of the Cu-deposited AZ80 electrode can be considerably improved after Ni electroplating. PMID:28788252

Hierarchical, porous CuS microspheres integrated with carbon nanotubes for high-performance supercapacitors

PubMed Central

Lu, Yang; Liu, Xianming; Wang, Weixiao; Cheng, Jinbing; Yan, Hailong; Tang, Chengchun; Kim, Jang-Kyo; Luo, Yongsong

2015-01-01

Carbon nanotubes (CNTs) incorporated porous 3-dimensional (3D) CuS microspheres have been successfully synthesized via a simple refluxing method assisted by PVP. The composites are composed of flower-shaped CuS secondary microspheres, which in turn are assembled with primary nanosheets of 15–30 nm in thickness and fully integrated with CNT. The composites possess a large specific surface area of 189.6 m2 g−1 and a high conductivity of 0.471 S cm−1. As electrode materials for supercapacitors, the nanocomposites show excellent cyclability and rate capability and deliver an average reversible capacitance as high as 1960 F g−1 at a current density of 10 mA cm−2 over 10000 cycles. The high electrochemical performance can be attributed to the synergistic effect of CNTs and the unique microstructure of CuS. The CNTs serve as not only a conductive agent to accelerate the transfer of electrons in the composites, but also as a buffer matrix to restrain the volume change and stabilize the electrode structure during the charge/discharge process. The porous structure of CuS also helps to stabilize the electrode structure and facilitates the transport for electrons. PMID:26568518

Elucidating doping driven microstructure evolution and optical properties of lead sulfide thin films grown from a chemical bath

NASA Astrophysics Data System (ADS)

Mohanty, Bhaskar Chandra; Bector, Keerti; Laha, Ranjit

2018-03-01

Doping driven remarkable microstructural evolution of PbS thin films grown by a single-step chemical bath deposition process at 60 °C is reported. The undoped films were discontinuous with octahedral-shaped crystallites after 30 min of deposition, whereas Cu doping led to a distinctly different surface microstructure characterized by densely packed elongated crystallites. A mechanism, based on the time sequence study of microstructural evolution of the films, and detailed XRD and Raman measurements, has been proposed to explain the contrasting microstructure of the doped films. The incorporation of Cu forms an interface layer, which is devoid of Pb. The excess Cu ions in this interface layer at the initial stages of film growth strongly interact and selectively stabilize the charged {111} faces containing either Pb or S compared to the uncharged {100} faces that contain both Pb and S. This interaction interferes with the natural growth habit resulting in the observed surface features of the doped films. Concurrently, the Cu-doping potentially changed the optical properties of the films: A significant widening of the bandgap from 1.52 eV to 1.74 eV for increase in Cu concentration from 0 to 20% was observed, making it a highly potential absorber layer in thin film solar cells.

Charge-state dependence of binary-encounter-electron cross sections and peak energies

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

Hidmi, H.I.; Richard, P.; Sanders, J.M.

The charge-state dependence of the binary-encounter-electron (BEE) double-differential cross section (DDCS) at 0[degree] with respect to the beam direction resulting from collisions of 1 MeV/amu H[sup +], C[sup [ital q]+], N[sup [ital q]+], O[sup [ital q]+], F[sup [ital q]+], Si[sup [ital q]+], and Cl[sup [ital q]+], and 0.5 MeV/amu Cu[sup [ital q]+] with H[sub 2] is reported. The data show an enhancement in the BEE DDCS as the charge state of the projectile is decreased, in agreement with the data reported by Richard [ital et] [ital al]. [J. Phys. B 23, L213 (1990)]. The DDCS enhancement ratios observed for themore » three-electron isoelectronic sequence C[sup 3+]:C[sup 6+], N[sup 4+]:N[sup 7+], O[sup 5+]:O[sup 8+], and F[sup 6+]:F[sup 9+] are about 1.35, whereas a DDCS enhancement of 3.5 was observed for Cu[sup 4+]. The BEE enhancement with increasing electrons on the projectile has been shown by several authors to be due to the non-Coulomb static potential of the projectile and additionally to the [ital e]-[ital e] exchange interaction. An impulse-approximation (IA) model fits the shape of the BEE DDCS and predicts a [ital Z][sub [ital p

Excellent photocatalytic hydrogen production over CdS nanorods via using noble metal-free copper molybdenum sulfide (Cu2MoS4) nanosheets as co-catalysts

NASA Astrophysics Data System (ADS)

Hong, Sangyeob; Kumar, D. Praveen; Reddy, D. Amaranatha; Choi, Jiha; Kim, Tae Kyu

2017-02-01

Charge carrier recombination and durability issues are major problems in photocatalytic hydrogen (H2) evolution processes. Thus, there is a very important necessitate to extend an efficient photocatalyst to control charge-carrier dynamics in the photocatalytic system. We have developed copper molybdenum sulfide (Cu2MoS4) nanosheets as co-catalysts with CdS nanorods for controlling charge carriers without recombination for use in photocatalytic H2 evolution under simulated solar light irradiation. Effective control and utilization of charge carriers are possible by loading Cu2MoS4 nanosheets onto the CdS nanorods. The loading compensates for the restrictions of CdS, and stimulated synergistic effects, such as efficient photoexcited charge separation, lead to an improvement in photostability because of the layered structure of the Cu2MoS4nanosheets. These layered Cu2MoS4 nanosheets have emerged as novel and active replacements for precious noble metal co-catalysts in photocatalytic H2 production by water splitting. We have obtained superior H2 production rates by using Cu2MoS4 loaded CdS nanorods. The physicochemical properties of the composites are analyzed by diverse characterization techniques.

Adding high time resolution to charge-state-specific ion energy measurements for pulsed copper vacuum arc plasmas

NASA Astrophysics Data System (ADS)

Tanaka, Koichi; Han, Liang; Zhou, Xue; Anders, André

2015-08-01

Charge-state-resolved ion energy-time distributions of pulsed Cu arc plasma were obtained by using direct (time-dependent) acquisition of the ion detection signal from a commercial ion mass-per-charge and energy-per-charge analyzer. We find a shift of energies of Cu2+, Cu3+ and Cu4+ ions to lower values during the first few hundred microseconds after arc ignition, which is evidence for particle collisions in the plasma. The generation of Cu+ ions in the later part of the pulse, measured by the increase of Cu+ signal intensity and an associated slight reduction of the mean charge state, points to charge exchange reactions between ions and neutrals. At the very beginning of the pulse, when the plasma expands into vacuum and the plasma potential strongly fluctuates, ions with much higher energy (over 200 eV) are observed. Early in the pulse, the ion energies observed are approximately proportional to the ion charge state, and we conclude that the acceleration mechanism is primarily based on acceleration in an electric field. This field is directed away from the cathode, indicative of a potential hump. Measurements by a floating probe suggest that potential structures travel, and ions moving in the traveling field can gain high energies up to a few hundred electron-volts. Later in the pulse, the approximate proportionality is lost, which is related to increased smearing out of different energies due to collisions with neutrals, and/or to a change of the acceleration character from electrostatic to ‘gas-dynamic’, i.e. dominated by pressure gradient.

Charge-screening role of c -axis atomic displacements in YBa 2 Cu 3 O 6 + x and related superconductors

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

Božin, E. S.; Huq, A.; Shen, Bing

2016-02-01

The importance of charge reservoir layers for supplying holes to the CuO 2 planes of cuprate superconductors has long been recognized. Less attention has been paid to the screening of the charge transfer by the intervening ionic layers. We address this issue in the case of YBa 2 Cu 3 O 6 + x , where CuO chains supply the holes for the planes. We present a simple dielectric-screening model that gives a linear correlation between the relative displacements of ions along the c axis, determined by neutron powder diffraction, and the hole density of the planes. Applying this modelmore » to the temperature-dependent shifts of ions along the c axis, we infer a charge transfer of 5–10% of the hole density from the planes to the chains on warming from the superconducting transition to room temperature. Given the significant coupling of c -axis displacements to the average charge density, we point out the relevance of local displacements for screening charge modulations and note recent evidence for dynamic screening of in-plane quasiparticles. This line of argument leads us to a simple model for atomic displacements and charge modulation that is consistent with images from scanning-tunneling microscopy for underdoped Bi 2 Sr 2 CaCu 2 O 8 + δ .« less

Charge-screening role of c -axis atomic displacements in YBa 2 Cu 3 O 6 + x and related superconductors

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

Božin, E. S.; Huq, A.; Shen, Bing

2016-02-01

The importance of charge reservoir layers for supplying holes to the CuO2 planes of cuprate superconductors has long been recognized. Less attention has been paid to the screening of the charge transfer by the intervening ionic layers.We address this issue in the case of YBa2Cu3O6+x , where CuO chains supply the holes for the planes. We present a simple dielectric-screening model that gives a linear correlation between the relative displacements of ions along the c axis, determined by neutron powder diffraction, and the hole density of the planes. Applying this model to the temperature-dependent shifts of ions along the cmore » axis, we infer a charge transfer of 5–10% of the hole density from the planes to the chains on warming from the superconducting transition to room temperature. Given the significant coupling of c-axis displacements to the average charge density, we point out the relevance of local displacements for screening charge modulations and note recent evidence for dynamic screening of in-plane quasiparticles. This line of argument leads us to a simple model for atomic displacements and charge modulation that is consistent with images from scanning-tunneling microscopy for underdoped Bi2Sr2CaCu2O8+δ .« less

Charge-screening role of c-axis atomic displacements in YBa 2Cu 3O 6+x and related superconductors

DOE PAGES

E. S. Bozin; Huq, A.; Shen, Bing; ...

2016-02-29

The importance of charge reservoir layers for supplying holes to the CuO 2 planes of cuprate superconductors has long been recognized. Less attention has been paid to the screening of the charge transfer by the intervening ionic layers. We address this issue in the case of YBa 2Cu 3O 6+x, where CuO chains supply the holes for the planes. We present a simple dielectric-screening model that gives a linear correlation between the relative displacements of ions along the c axis, determined by neutron powder diffraction, and the hole density of the planes. Applying this model to the temperature-dependent shifts ofmore » ions along the c axis, we infer a charge transfer of 5-10% of the hole density from the planes to the chains on warming from the superconducting transition to room temperature. Given the significant coupling of c-axis displacements to the average charge density, we point out the relevance of local displacements for screening charge modulations and note recent evidence for dynamic screening of in-plane quasiparticles. Furthermore, this line of argument leads us to a simple model for atomic displacements and charge modulation that is consistent with images from scanning-tunneling microscopy for underdoped Bi 2Sr 2CaCu 2O 8+δ.« less

Structural and electronic snapshots during the transition from a Cu(II) to Cu(I) metal center of a lytic polysaccharide monooxygenase by X-ray photoreduction.

PubMed

Gudmundsson, Mikael; Kim, Seonah; Wu, Miao; Ishida, Takuya; Momeni, Majid Hadadd; Vaaje-Kolstad, Gustav; Lundberg, Daniel; Royant, Antoine; Ståhlberg, Jerry; Eijsink, Vincent G H; Beckham, Gregg T; Sandgren, Mats

2014-07-04

Lytic polysaccharide monooxygenases (LPMOs) are a recently discovered class of enzymes that employ a copper-mediated, oxidative mechanism to cleave glycosidic bonds. The LPMO catalytic mechanism likely requires that molecular oxygen first binds to Cu(I), but the oxidation state in many reported LPMO structures is ambiguous, and the changes in the LPMO active site required to accommodate both oxidation states of copper have not been fully elucidated. Here, a diffraction data collection strategy minimizing the deposited x-ray dose was used to solve the crystal structure of a chitin-specific LPMO from Enterococcus faecalis (EfaCBM33A) in the Cu(II)-bound form. Subsequently, the crystalline protein was photoreduced in the x-ray beam, which revealed structural changes associated with the conversion from the initial Cu(II)-oxidized form with two coordinated water molecules, which adopts a trigonal bipyramidal geometry, to a reduced Cu(I) form in a T-shaped geometry with no coordinated water molecules. A comprehensive survey of Cu(II) and Cu(I) structures in the Cambridge Structural Database unambiguously shows that the geometries observed in the least and most reduced structures reflect binding of Cu(II) and Cu(I), respectively. Quantum mechanical calculations of the oxidized and reduced active sites reveal little change in the electronic structure of the active site measured by the active site partial charges. Together with a previous theoretical investigation of a fungal LPMO, this suggests significant functional plasticity in LPMO active sites. Overall, this study provides molecular snapshots along the reduction process to activate the LPMO catalytic machinery and provides a general method for solving LPMO structures in both copper oxidation states. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

La 139 NMR investigation of the charge and spin order in a La 1.885 Sr 0.115 CuO 4 single crystal

DOE PAGES

Arsenault, A.; Takahashi, S. K.; Imai, T.; ...

2018-02-14

139La NMR is suited for investigations into magnetic properties of La 2CuO 4 -based cuprates in the vicinity of their magnetic instabilities, owing to the modest hyperfine interactions between 139La nuclear spins and Cu electron spins. We report comprehensive 139La NMR measurements on a single-crystal sample of high-T c superconductor La 1.885 Sr 0.115 CuO 4 in a broad temperature range across the charge and spin order transitions (T charge ≃ 80 K, T neutron spin ≃ T c = 30 K). From the high-precision measurements of the linewidth for the nuclear spin I z = + 1 / 2 to -1/2 central transition, we show that paramagnetic line broadening sets in precisely at T charge due to enhanced spin correlations within the CuO 2 planes. Additional paramagnetic line broadening ensues below ~35 K, signaling that Cu spins in some segments of CuO 2 planes are on the verge of three-dimensional magnetic order. A static hyperfine magnetic field arising from ordered Cu moments along the ab plane, however, begins to develop only below Tmore » $$μSR\\atop{spin}$$ = 15 – 20 K, where earlier muon spin rotation measurements detected Larmor precession for a small volume fraction (~20 % ) of the sample. Based on the measurement of 139 La nuclear-spin-lattice relaxation rate 1/T 1, we also show that charge order triggers enhancement of low-frequency Cu spin fluctuations inhomogeneously; a growing fraction of 139 La sites is affected by enhanced low-frequency spin fluctuations toward the eventual magnetic order, whereas a diminishing fraction continues to exhibit a behavior analogous to the optimally superconducting phase even below T charge. In conclusion, these 139La NMR results corroborate our recent 63Cu NMR observation that a very broad, anomalous winglike signal gradually emerges below T charge, whereas the normally behaving, narrower main peak is gradually wiped out [T. Imai et al., Phys. Rev. B 96, 224508 (2017)]. Furthermore, we show that the enhancement of low-energy spin excitations in the low-temperature regime below Tneutron spin (≃ Tc) depends strongly on the magnitude and orientation of the applied magnetic field.« less

La 139 NMR investigation of the charge and spin order in a La 1.885 Sr 0.115 CuO 4 single crystal

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

Arsenault, A.; Takahashi, S. K.; Imai, T.

139La NMR is suited for investigations into magnetic properties of La 2CuO 4 -based cuprates in the vicinity of their magnetic instabilities, owing to the modest hyperfine interactions between 139La nuclear spins and Cu electron spins. We report comprehensive 139La NMR measurements on a single-crystal sample of high-T c superconductor La 1.885 Sr 0.115 CuO 4 in a broad temperature range across the charge and spin order transitions (T charge ≃ 80 K, T neutron spin ≃ T c = 30 K). From the high-precision measurements of the linewidth for the nuclear spin I z = + 1 / 2 to -1/2 central transition, we show that paramagnetic line broadening sets in precisely at T charge due to enhanced spin correlations within the CuO 2 planes. Additional paramagnetic line broadening ensues below ~35 K, signaling that Cu spins in some segments of CuO 2 planes are on the verge of three-dimensional magnetic order. A static hyperfine magnetic field arising from ordered Cu moments along the ab plane, however, begins to develop only below Tmore » $$μSR\\atop{spin}$$ = 15 – 20 K, where earlier muon spin rotation measurements detected Larmor precession for a small volume fraction (~20 % ) of the sample. Based on the measurement of 139 La nuclear-spin-lattice relaxation rate 1/T 1, we also show that charge order triggers enhancement of low-frequency Cu spin fluctuations inhomogeneously; a growing fraction of 139 La sites is affected by enhanced low-frequency spin fluctuations toward the eventual magnetic order, whereas a diminishing fraction continues to exhibit a behavior analogous to the optimally superconducting phase even below T charge. In conclusion, these 139La NMR results corroborate our recent 63Cu NMR observation that a very broad, anomalous winglike signal gradually emerges below T charge, whereas the normally behaving, narrower main peak is gradually wiped out [T. Imai et al., Phys. Rev. B 96, 224508 (2017)]. Furthermore, we show that the enhancement of low-energy spin excitations in the low-temperature regime below Tneutron spin (≃ Tc) depends strongly on the magnitude and orientation of the applied magnetic field.« less

Design and development of novel antibacterial Ti-Ni-Cu shape memory alloys for biomedical application.

PubMed

Li, H F; Qiu, K J; Zhou, F Y; Li, L; Zheng, Y F

2016-11-29

In the case of medical implants, foreign materials are preferential sites for bacterial adhesion and microbial contamination, which can lead to the development of prosthetic infections. Commercially biomedical TiNi shape memory alloys are the most commonly used materials for permanent implants in contact with bone and dental, and the prevention of infections of TiNi biomedical shape memory alloys in clinical cases is therefore a crucial challenge for orthopaedic and dental surgeons. In the present study, copper has been chosen as the alloying element for design and development novel ternary biomedical Ti‒Ni‒Cu shape memory alloys with antibacterial properties. The effects of copper alloying element on the microstructure, mechanical properties, corrosion behaviors, cytocompatibility and antibacterial properties of biomedical Ti‒Ni‒Cu shape memory alloys have been systematically investigated. The results demonstrated that Ti‒Ni‒Cu alloys have good mechanical properties, and remain the excellent shape memory effects after adding copper alloying element. The corrosion behaviors of Ti‒Ni‒Cu alloys are better than the commercial biomedical Ti‒50.8Ni alloys. The Ti‒Ni‒Cu alloys exhibit excellent antibacterial properties while maintaining the good cytocompatibility, which would further guarantee the potential application of Ti‒Ni‒Cu alloys as future biomedical implants and devices without inducing bacterial infections.

Design and development of novel antibacterial Ti-Ni-Cu shape memory alloys for biomedical application

NASA Astrophysics Data System (ADS)

Li, H. F.; Qiu, K. J.; Zhou, F. Y.; Li, L.; Zheng, Y. F.

2016-11-01

In the case of medical implants, foreign materials are preferential sites for bacterial adhesion and microbial contamination, which can lead to the development of prosthetic infections. Commercially biomedical TiNi shape memory alloys are the most commonly used materials for permanent implants in contact with bone and dental, and the prevention of infections of TiNi biomedical shape memory alloys in clinical cases is therefore a crucial challenge for orthopaedic and dental surgeons. In the present study, copper has been chosen as the alloying element for design and development novel ternary biomedical Ti‒Ni‒Cu shape memory alloys with antibacterial properties. The effects of copper alloying element on the microstructure, mechanical properties, corrosion behaviors, cytocompatibility and antibacterial properties of biomedical Ti‒Ni‒Cu shape memory alloys have been systematically investigated. The results demonstrated that Ti‒Ni‒Cu alloys have good mechanical properties, and remain the excellent shape memory effects after adding copper alloying element. The corrosion behaviors of Ti‒Ni‒Cu alloys are better than the commercial biomedical Ti‒50.8Ni alloys. The Ti‒Ni‒Cu alloys exhibit excellent antibacterial properties while maintaining the good cytocompatibility, which would further guarantee the potential application of Ti‒Ni‒Cu alloys as future biomedical implants and devices without inducing bacterial infections.

Enhanced Visible-Light Photocatalytic H2 Evolution in Cu2O/Cu2Se Multilayer Heterostructure Nanowires Having {111} Facets and Physical Mechanism.

PubMed

Liu, Bin; Ning, Lichao; Zhang, Congjie; Zheng, Hairong; Liu, Shengzhong Frank; Yang, Heqing

2018-06-21

It is rather challenging to develop photocatalysts based on narrow-band-gap semiconductors for water splitting under solar irradiation. Herein, we synthesized the Cu 2 O/Cu 2 Se multilayer heterostructure nanowires exposing {111} crystal facets by a hydrothermal reaction of Se with Cu and KBH 4 in ethanol amine aqueous solution and subsequent annealing in air. The photocatalytic H 2 production activity of Cu 2 O/Cu 2 Se multilayer heterostructure nanowires is dramatically improved, with an increase on the texture coefficient of Cu 2 O(111) and Cu 2 Se(111) planes, and thus the exposed {111} facets may be the active surfaces for photocatalytic H 2 production. On the basis of the polar structure of Cu 2 O {111} and Cu 2 Se {111} surfaces, we presented a model of charge separation between the Cu-Cu 2 Se(111) and O-Cu 2 O(1̅ 1̅ 1̅) polar surfaces. An internal electric field is created between Cu-Cu 2 Se(111) and O-Cu 2 O(1̅ 1̅ 1̅) polar surfaces, because of spontaneous polarization. As a result, this internal electric field drives the photocreated charge separation. The oxidation and reduction reactions selectively occur at the negative O-Cu 2 O(1̅ 1̅ 1̅) and the positive Cu-Cu 2 Se(111) surfaces. The polar surface-engineering may be a general strategy for enhancing the photocatalytic H 2 -production activity of semiconductor photocatalysts. The charge separation mechanism not only can deepen the understanding of photocatalytic H 2 production mechanism but also provides a novel insight into the design of advanced photocatalysts, other photoelectric devices, and solar cells.

Fabrication of CuO-Pt core-shell nanohooks by in situ reconstructing the Pt-shells.

PubMed

Cao, Fan; Zheng, He; Zhao, Ligong; Huang, Rui; Jia, Shuangfeng; Liu, Huihui; Li, Lei; Wang, Zhao; Hu, Yongming; Gu, Haoshuang; Wang, Jianbo

2018-05-25

The design of various nanostructures with specific compositions and shapes is highly demanded due to the widespread use of micro/nano electro-mechanical systems. In this work, one-dimensional CuO-Pt core-shell nanowires (NWs) are acquired by depositing Pt nanoparticles onto CuO NWs and then mechanically-shaped into nanohooks. Subsequently, the hook-like shape is maintained by the Pt-shell which is reconstructed via Joule heat and re-solidified after cooling down, during which the elastic strain energy is stored in the CuO-core. The results provide a simple strategy to design nanostructures with various compositions and shapes, implying the potential applications in mechanical energy storage and shape memory nanodevices.

Fabrication of CuO–Pt core–shell nanohooks by in situ reconstructing the Pt-shells

NASA Astrophysics Data System (ADS)

Cao, Fan; Zheng, He; Zhao, Ligong; Huang, Rui; Jia, Shuangfeng; Liu, Huihui; Li, Lei; Wang, Zhao; Hu, Yongming; Gu, Haoshuang; Wang, Jianbo

2018-05-01

The design of various nanostructures with specific compositions and shapes is highly demanded due to the widespread use of micro/nano electro-mechanical systems. In this work, one-dimensional CuO–Pt core–shell nanowires (NWs) are acquired by depositing Pt nanoparticles onto CuO NWs and then mechanically-shaped into nanohooks. Subsequently, the hook-like shape is maintained by the Pt-shell which is reconstructed via Joule heat and re-solidified after cooling down, during which the elastic strain energy is stored in the CuO-core. The results provide a simple strategy to design nanostructures with various compositions and shapes, implying the potential applications in mechanical energy storage and shape memory nanodevices.

Bipolar charge storage characteristics in copper and cobalt co-doped zinc oxide (ZnO) thin film.

PubMed

Kumar, Amit; Herng, Tun Seng; Zeng, Kaiyang; Ding, Jun

2012-10-24

The bipolar charge phenomenon in Cu and Co co-doped zinc oxide (ZnO) film samples has been studied using scanning probe microscopy (SPM) techniques. Those ZnO samples are made using a pulsed laser deposition (PLD) technique. It is found that the addition of Cu and Co dopants suppresses the electron density in ZnO and causes a significant change in the work function (Fermi level) value of the ZnO film; this results in the ohmic nature of the contact between the electrode (probe tip) and codoped sample, whereas this contact exhibits a Schottky nature in the undoped and single-element-doped samples. These results are verified by Kelvin probe force microscopy (KPFM) and ultraviolet photoelectron spectroscopy (UPS) measurements. It is also found that the co-doping (Cu and Co) can stabilize the bipolar charge, whereas Cu doping only stabilizes the positive charge in ZnO thin films.

Linear shaped charge

DOEpatents

Peterson, David; Stofleth, Jerome H.; Saul, Venner W.

2017-07-11

Linear shaped charges are described herein. In a general embodiment, the linear shaped charge has an explosive with an elongated arrowhead-shaped profile. The linear shaped charge also has and an elongated v-shaped liner that is inset into a recess of the explosive. Another linear shaped charge includes an explosive that is shaped as a star-shaped prism. Liners are inset into crevices of the explosive, where the explosive acts as a tamper.

Fabrication and charge/energy-transfer study of 4,7-bis(4-triphenylamino)benzo- 2,1,3-thiadiazole/CuPc composite films

NASA Astrophysics Data System (ADS)

Zhu, Yuanyuan; Gu, Shuangxi; Wei, Xiao; Xue, Minzhao; Zhang, Qing; Sheng, Qiaorong; Liu, Yangang

2010-12-01

Composite films of 4,7-bis(4-triphenylamino)benzo-2,1,3-thiadiazole (TBT) and copper phthalocyanine (CuPc) are fabricated via protonation-coelectrophoretic deposition from nitromethane solutions of TBT/CuPc mixture in the presence of trifluoroacetic acid as a protonation reagent. A nanospheres-nanowires interpenetrating network structure is obtained when the molar percentage of TBT is 70%. Furthermore, the existence of TBT makes α-phased CuPc be partly transformed into the β-phase, and simultaneously, CuPc disorganizes the TBT unit cells. The blue shift on the absorption edge of TBT and the significant fluorescence quenching in the composite films indicate energy/charge transfer and donor-acceptor (D-A) heterojunction formation. Then these results are proved from another point of view: the mutual overlap of absorption and emission spectra of TBT and CuPc lead to a bidirectional Förster resonance energy transfer at the interface; the molecular energy levels calculated from the results of cyclic voltammetry theoretically determine that there exist a D-A heterojunction and charge transfer from TBT to CuPc. Finally, from the investigation of the field-induced surface photovoltage spectra, it can be concluded that this charge transfer results in efficient dissociation of the photoinduced excitons in the composite films, followed by the generation of a strong photovoltage response.

Semiconductor bridge, SCB, ignition studies of Al/CuO thermite

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

Bickes, R.W. Jr.; Wackerbarth, D.E.; Mohler, J.H.

1997-04-01

The authors briefly summarize semiconductor bridge operation and review their ignition studies of Al/CuO thermite as a function of the capacitor discharge unit (CDU) firing set capacitance, charge holder material and morphology of the CuO. Ignition thresholds were obtained using a brass charge holder and a non-conducting fiber-glass-epoxy composite material, G10. At - 18 C and a charge voltage of 50V, the capacitance thresholds were 30.1 {mu}F and 2.0 {mu}F respectively. They also present new data on electrostatic discharge (ESD) and radio frequency (RF) vulnerability tests.

Functional Performances of CuZnAl Shape Memory Alloy Open-Cell Foams

NASA Astrophysics Data System (ADS)

Biffi, C. A.; Casati, R.; Bassani, P.; Tuissi, A.

2018-01-01

Shape memory alloys (SMAs) with cellular structure offer a unique mixture of thermo-physical-mechanical properties. These characteristics can be tuned by changing the pore size and make the shape memory metallic foams very attractive for developing new devices for structural and functional applications. In this work, CuZnAl SMA foams were produced through the liquid infiltration of space holder method. In comparison, a conventional CuZn brass alloy was foamed trough the same method. Functional performances were studied on both bulk and foamed SMA specimens. Calorimetric response shows similar martensitic transformation (MT) below 0 °C. Compressive response of CuZnAl revealed that mechanical behavior is strongly affected by sample morphology and that damping capacity of metallic foam is increased above the MT temperatures. The shape memory effect was detected in the CuZnAl foams. The conventional brass shows a compressive response similar to that of the martensitic CuZnAl, in which plastic deformation accumulation occurs up to the cellular structure densification after few thermal cycles.

Plane wave density functional molecular dynamics study of exothermic reactions of Al/CuO thermites

NASA Astrophysics Data System (ADS)

Oloriegbe, Suleiman; Sewell, Thomas; Chen, Zhen; Jiang, Shan; Gan, Yong

2014-03-01

Exothermic reactions between nanosize aluminum (Al) and copper oxide (CuO) structures are of current interest because of their high reaction enthalpy and energy density which exceed those of traditional monomolecular energetic compounds such as TNT, RDX, and HMX. In this work, molecular dynamics simulations with forces obtained from plane wave density functional theory are used to investigate the atomic-scale and electronic processes that occur during the fast thermite reactions between Al and CuO nanostructures under adiabatic conditions. Aluminum surfaces in contact with O-exposed and Cu-exposed CuO surfaces are studied. Starting from initial temperature T = 800 K, we have observed: faster chemical reaction at the oxygen-rich interface during the initial 0.5 ps, linear temperature rise, and fast oxygen diffusion into the Al region with the rate 1.87 X 10-3 cm2/s. The density-derived electrostatic and chemical method is used to evaluate the net atomic charges and charge transfer during the important redox processes. High charge density around the oxygen-exposed interface may be responsible for the faster initial reactions at that interface. The overall reaction rate, determined using the time evolution of Cu-O charge orbital overlap population, is approximately first order.

Molecular charge distribution and dispersion of electronic states in the contact layer between pentacene and Cu(119) and beyond

NASA Astrophysics Data System (ADS)

Annese, E.; Fujii, J.; Baldacchini, C.; Zhou, B.; Viol, C. E.; Vobornik, I.; Betti, M. G.; Rossi, G.

2008-05-01

The interaction of pentacene molecules in contact with the Cu(119) stepped surface has been directly imaged by scanning tunneling microscopy and analyzed by angle resolved photoemission spectroscopy. Interacting molecules, which are in contact with copper, generate dispersive electronic states associated with a perturbed electron charge density distribution of the molecular orbitals. In contrast, the electron charge density of molecules of the pentacene on top of the first layer, which is not in direct contact with the Cu surface, shows an intramolecular structure very similar to that of the free molecule. Our results indicate that the delocalization of the molecular states in the pentacene/Cu system is confined to the very first molecular layer at the interface.

Electrochemical properties of copper-based compounds with polyanion frameworks

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

Mizuno, Yoshifumi; Hata, Shoma; Suzuki, Kota

The copper-based polyanion compounds Li{sub 6}CuB{sub 4}O{sub 10} and Li{sub 2}CuP{sub 2}O{sub 7} were synthesized using a conventional solid-state reaction, and their electrochemical properties were determined. Li{sub 6}CuB{sub 4}O{sub 10} showed reversible capacity of 340 mA g{sup −1} at the first discharge–charge process, while Li{sub 2}CuP{sub 2}O{sub 7} showed large irreversible capacity and thus low charge capacity. Ex situ X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) measurements revealed that the electrochemical Li{sup +} intercalation/deintercalation reaction in Li{sub 6}CuB{sub 4}O{sub 10} occurred via reversible Cu{sup 2+}/Cu{sup +} reduction/oxidation reaction. These differences in their discharge/charge mechanisms are discussed basedmore » on the strength of the Cu–O covalency via their inductive effects. - Graphical abstract: Electrochemical properties for Cu-based polyanion compounds were investigated. The electrochemical reaction mechanisms are strongly affected by their Cu–O covalentcy. - Highlights: • Electrochemical properties of Cu-based polyanion compounds were investigated. • The Li{sup +} intercalation/deintercalation reaction progressed in Li{sub 6}CuB{sub 4}O{sub 10}. • The electrochemical displacement reaction progressed in Li{sub 2}CuP{sub 2}O{sub 7}. • The strength of Cu–O covalency affects the reaction mechanism.« less

Valence charge fluctuations in YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ from core-level spectroscopies

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

Balzarotti, A.; De Crescenzi, M.; Motta, N.

1988-10-01

From x-ray photoemission and Auger measurements of the Cu 2p and O 1s core levels of YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ as a function of the oxygen concentration delta, the average copper charge is determined. Evidence is found of dynamic charge fluctuations on the oxygen sublattice giving rise to a greater concentration of trivalent copper at the Cu(1) sites with respect to that determined by the analysis of neutron-diffraction data. On the basis of our experimental results, we introduce a molecular cluster description for the Cu states. The lowest final-states configurations of Cu/sup 2+/ and Cu/sup 3+/ are c3d/sup 10/Lmore » and c3d/sup 10/L/sup 2/, respectively, where c and L denote core holes on copper and oxygen atoms. Oxygen holes have high mobility and a Hubbard correlation energy less than 2 eV, a signature of their delocalization. The effect of temperature on the spectra is minor. Surface degradation modifies the relative intensity of the structures, particularly those of the O spectrum.« less

Cu2O-tipped ZnO nanorods with enhanced photoelectrochemical performance for CO2 photoreduction

NASA Astrophysics Data System (ADS)

Iqbal, Muzaffar; Wang, Yanjie; Hu, Haifeng; He, Meng; Hassan Shah, Aamir; Lin, Lin; Li, Pan; Shao, Kunjuan; Reda Woldu, Abebe; He, Tao

2018-06-01

The design of Cu2O-tipped ZnO nanorods is proposed here aiming at enhanced photoelectrochemical properties. The tip-selective deposition of Cu2O is confirmed by scanning transmission electron microscopy (STEM). The photoinduced charge behavior like charge generation, separation and transport has been thoroughly studied by UV-vis absorption analysis and different photoelectrochemical characterizations, including transient photocurrent, incident photon-to-current efficiency (IPCE), electrochemical impedance spectroscopy (EIS), intensity-modulated photocurrent spectroscopy (IMPS), and Mott-Schottky measurements. The photoelectrochemical characterizations clearly indicate that ZnO/Cu2O structures exhibit much higher performance than pristine ZnO, due to the formation of p-n junction, as well as the tip selective growth of Cu2O on ZnO. Photocatalytic CO2 reduction in aqueous solution under UV-visible light illumination shows that CO is the main product, and with the increase of the Cu2O content in the heterostructure, the CO yield increases. This work shows that Cu2O-tipped ZnO nanorods possess improved behavior of charge generation, separation and transport, which may work as a potential candidate for photocatalytic CO2 reduction.

A facile strategy to fabricate plasmonic Cu modified TiO{sub 2} nano-flower films for photocatalytic reduction of CO{sub 2} to methanol

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

Liu, Enzhou; Qi, Lulu; Bian, Juanjuan

Graphical abstract: Photoreduction of CO{sub 2} to CH{sub 3}OH over plasmonic Cu/TiO{sub 2} film. - Highlights: • Cu nanoparticles modified TiO{sub 2} nano-flower film was prepared by a facile strategy. • Cu nanoparticles can enhance the light absorption and the Raman scattering of TiO{sub 2}. • Cu nanoparticles can effectively restrain the recombination of the charge carriers. • A synergistic mechanism is proposed for photocatalytic reduction of CO{sub 2} on Cu/TiO{sub 2} film. - Abstract: Cu nanoparticles (NPs) deposited TiO{sub 2} nano-flower films were fabricated using a combination of a hydrothermal method and a microwave-assisted reduction process. The investigations indicatedmore » that Cu NPs and TiO{sub 2} film both exhibit visible light harvesting properties based on localized surface plasmon resonance (LSPR) of Cu NPs and unique nanostructures of TiO{sub 2} film. Fluorescence quenching was observed because the recombination of charge carriers was effectively suppressed by Cu NPs deposition. The experimental results indicate that Cu/TiO{sub 2} films exhibit better activity for the photocatalytic reduction of CO{sub 2} due to the charge transfer property and LSPR effect of Cu NPs. The CH{sub 3}OH production rate reached 1.8 μmol cm{sup −2} h{sup −1} (energy efficiency was 0.8%) over 0.5 Cu/TiO{sub 2} film under UV and visible light irradiation, which was 6.0 times higher than that observed over pure TiO{sub 2} film. In addition, a tentative photocatalytic mechanism is proposed to understand the experimental results over the Cu modified TiO{sub 2} nano-flower films.« less

Charge dynamics of 57Fe probe atoms in La2Li0.5Cu0.5O4

NASA Astrophysics Data System (ADS)

Presniakov, I. A.; Sobolev, A. V.; Rusakov, V. S.; Moskvin, A. S.; Baranov, A. V.

2018-06-01

The objective of this study is to characterize the electronic state and local surrounding of 57Fe Mössbauer probe atoms within iron-doped layered perovskite La2Li0.5Cu0.5O4 containing transition metal in unusual formal oxidation states "+3". An approach based on the qualitative energy diagrams analysis and the calculations within the cluster configuration interaction method have been developed. It was shown that a large amount of charge is transferred via Cu-O bonds from the O: 2p bands to the Cu: 3d orbitals and the ground state is dominated by the d9L configuration ("Cu2+-O-" state). The dominant d9L ground state for the (CuO6) sublattice induces in the environment of the 57Fe probe cations a charge transfer Fe3+ + O-(L) → Fe4+ + O2-, which transforms "Fe3+" into "Fe4+" state. The experimental spectra in the entire temperature range 77-300 K were described with the use of the stochastic two-level model based on the assumption of dynamic equilibrium between two Fe3+↔Fe4+ valence states related to the iron atom in the [Fe(1)O4]4- center. The relaxation frequencies and activation energies of the corresponding charge fluctuations were estimated based on Mössbauer data. The results are discussed assuming a temperature-induced change in the electronic state of the [CuO4]5- clusters in the layered perovskite.

Bonding in d9 complexes derived from EPR: Application to CuCl2-4, CuBr2-4, and CdCl2:Cu2+

NASA Astrophysics Data System (ADS)

Aramburu, J. A.; Moreno, M.

1985-12-01

In this work are reported the theoretical expressions for the [g], hyperfine, and superhyperfine (shf) tensors of a d9 square-planar complex within a molecular orbital (MO) scheme. These expressions include contributions arising from crystal field and charge transfer excitations calculated up to third and second order perturbations, respectively. This makes the present framework more general than those previously used. Through those expressions we have derived from the experimental EPR and optical data the MO coefficients corresponding to the valence b1g(x2-y2), b2g(xy), and eg(xz,yz) levels and also the core polarization contribution K to the hyperfine tensor for the systems CuCl2-4, CuBr2-4, and CdCl2:Cu2+. The 3d charge obtained for CuCl2-4 is equal to 0.61, 0.83, and 0.85 for the antibonding 3b1g, 2b2g, and 2eg levels, respectively. These figures are much closer to the Xα results by Bencini and Gatteschi [J. Am. Chem. Soc. 105, 5535 (1983)] than to those by Desjardins et al. [J. Am. Chem. Soc. 105, 4590 (1983)]. The σ and π covalency for CuBr2-4 are both higher than for CuCl2-4 in accord to the lower electronegativity for bromine. However, only for the antibonding 3b1g level of CuBr2-4 have we obtained an electronic charge lying mainly on ligands. The covalency of CdCl2:Cu2+ is smaller than that found for CuCl2-4, a fact associated to a higher metal-ligand distance for the former. Evidence of this statement are also given from the analysis of crystal-field spectra and isotropic shf constant. The values of K derived for CuCl2-4 (128.1×10-4 cm-1), CuBr2-4 (103.6×10-4 cm-1), and CdCl2:Cu2+ (123.9×10-4 cm-1) point out the dependence of K on the equatorial covalency but also on the existence of axial ligands. The [g] tensor of CuBr2-4 is dominated by the charge transfer contribution while the crystal field one is negative. Finally an analysis of the importance of each one of the involved contributions to the spin-Hamiltonian parameters is reported for the three systems, together with the results obtained through a full diagonalization within crystal field and charge transfer states.

Study of Cu-Al-Ni-Ga as high-temperature shape memory alloys

NASA Astrophysics Data System (ADS)

Zhang, Xin; Wang, Qian; Zhao, Xu; Wang, Fang; Liu, Qingsuo

2018-03-01

The effect of Ga element on the microstructure, mechanical properties and shape memory effect of Cu-13.0Al-4.0Ni- xGa (wt%) high-temperature shape memory alloy was investigated by optical microscopy, SEM, XRD and compression test. The microstructure observation results showed that the Cu-13.0Al-4.0Ni- xGa ( x = 0.5 and 1.0) alloys displayed dual-phase morphology which consisted of 18R martensite and (Al, Ga)Cu phase, and their grain size was about several hundred microns, smaller than that of Cu-13.0Al-4.0Ni alloy. The compression test results proved that the mechanical properties of Cu-13.0Al-4.0Ni- xGa alloys were improved by addition of Ga element owing to the grain refinement and solid solution strengthening, and the compressive fracture strains were 11.5% for x = 0.5 and 14.9% for x = 1.0, respectively. When the pre-strain was 8%, the shape memory effect of 4.2 and 4.6% were obtained for Cu-13.0Al-4.0Ni-0.5 Ga and Cu-13.0Al-4.0Ni-1.0 Ga alloys after being heated to 400 °C for 1 min.

Biopsy applications of Ti50Ni41Cu9 shape memory films for wireless capsule endoscope

NASA Astrophysics Data System (ADS)

Du, Hejun; Fu, Yongqing; Zhang, S.; Luo, Jack K.; Flewitt, Andrew J.; Milne, William I.

2004-02-01

Wireless capsule endoscopy (WCE) is a new technology to evaluate the patient with obscure gastrointestinal bleeding. However, there is still some deficiency existing in the current WCE, for example, lack of ability to biopsy and precisely locate the pathology. This study aimed to prepare and characterize TiNiCu shape memory alloy thin films for developing microgripper for biopsy (tissue sampling and tagging) applications. Ti50Ni41Cu9 thin films were prepared by co-sputtering of TiNi and Cu targets, and their transformation temperatures were slightly above that of human body. Results from differential scanning calorimetry, in-situ X-ray diffraction, curvature and electrical resistance measurement revealed clearly martensitic transformation of the deposited TiNiCu films upon heating and cooling. The biocompatibility of the TiNiCu films in the simulated gastric and intestinal solutions was also studied. Results showed the release of Ni and Cu ions is much less than the toxic level and the film did not lose shape memory effect even after 10-day immersion in the simulated solutions. TiNiCu/Si micro-cantilevers with and without electrodes were fabricated using the conventional micromachining methods and apparent shape memory effect upon heating and cooling was demonstrated.

Morphological Control of Mesoporosity and Nanoparticles within Co3O4-CuO Electrospun Nanofibers: Quantum Confinement and Visible Light Photocatalysis Performance.

PubMed

Pradhan, Amaresh C; Uyar, Tamer

2017-10-18

The one-dimensional (1D) mesoporous and interconnected nanoparticles (NPs) enriched composite Co 3 O 4 -CuO nanofibers (NFs) in the ratio Co:Cu = 1/4 (Co 3 O 4 -CuO NFs) composite have been synthesized by electrospinning and calcination of mixed polymeric template. Not merely the mesoporous composite Co 3 O 4 -CuO NFs but also single mesoporous Co 3 O 4 NFs and CuO NFs have been produced for comparison. The choice of mixed polymer templates such as polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) for electrospinning is responsible for the formation of 1D mesoporous NFs. The HR-TEM result showed evolution of interconnected nanoparticles (NPs) and creation of mesoporosity in all electrospun NFs. The quantum confinement is due to NPs within NFs and has been proved by the surface-enhanced Raman scattering (SERS) study and the UV-vis-NRI diffuse reflectance spectra (DRS). The high intense photoluminescence (PL) spectra showing blue shift of all NFs also confirmed the quantum confinement phenomena. The lowering of PL spectrum after mixing of CuO in Co 3 O 4 nanofibers framework (Co 3 O 4 -CuO NFs) proved CuO as an efficient visible light response low cost cocatalyst/charge separator. The red shifting of the band gap in composite Co 3 O 4 -CuO NFs is due to the internal charge transfer between Co 2+ to Co 3+ and Cu 2+ , proved by UV-vis absorption spectroscopy. Creation of oxygen vacancies by mixing of CuO and Co 3 O 4 also prevents the electron-hole recombination and enhances the photocatalytic activity in composite Co 3 O 4 -CuO NFs. The photocurrent density, Mott-Schottky (MS), and electrochemical impedance spectroscopy (EIS) studies of all NFs favor the high photocatalytic performance. The mesoporous composite Co 3 O 4 -CuO NFs exhibits high photocatalytic activity toward phenolic compounds degradation as compared to the other two NFs (Co 3 O 4 NFs and CuO NFs). The kinetic study of phenolic compounds followed first order rate equation. The high photocatalytic activity of composite Co 3 O 4 -CuO NFs is attributed to the formation of mesoporosity and interconnected NPs within NFs framework, quantum confinement, extended light absorption property, internal charge transfer, and effective photogenerated charge separations.

Effect of Ta Additions on the Microstructure, Damping, and Shape Memory Behaviour of Prealloyed Cu-Al-Ni Shape Memory Alloys.

PubMed

Saud, Safaa N; Hamzah, E; Bakhsheshi-Rad, H R; Abubakar, T

2017-01-01

The influence of Ta additions on the microstructure and properties of Cu-Al-Ni shape memory alloys was investigated in this paper. The addition of Ta significantly affects the green and porosity densities; the minimum percentage of porosity was observed with the modified prealloyed Cu-Al-Ni-2.0 wt.% Ta. The phase transformation temperatures were shifted towards the highest values after Ta was added. Based on the damping capacity results, the alloy of Cu-Al-Ni-3.0 wt.% Ta has very high internal friction with the maximum equivalent internal friction value twice as high as that of the prealloyed Cu-Al-Ni SMA. Moreover, the prealloyed Cu-Al-Ni SMAs with the addition of 2.0 wt.% Ta exhibited the highest shape recovery ratio in the first cycle (i.e., 100% recovery), and when the number of cycles is increased, this ratio tends to decrease. On the other hand, the modified alloys with 1.0 and 3.0 wt.% Ta implied a linear increment in the shape recovery ratio with increasing number of cycles. Polarization tests in NaCl solution showed that the corrosion resistance of Cu-Al-Ni-Ta SMA improved with escalating Ta concentration as shown by lower corrosion current densities, higher corrosion potential, and formation of stable passive film.

Realization of a mixed-symmetry superconducting gap in correlated organic metals

NASA Astrophysics Data System (ADS)

Altmeyer, Michaela; Guterding, Daniel; Jeschke, Harald O.; Diehl, Sandra; Methfessel, Torsten; Tutsch, Ulrich; Schubert, Harald; Lang, Michael; Müller, Jens; Huth, Michael; Jourdan, Martin; Elmers, Hans-Joachim; Valenti, Roser

Recent scanning tunneling spectroscopy measurements on the organic charge tranfer salt κ-(BEDT-TTF)2Cu[N(CN)2]Br show clear evidence of a highly anisotropic gap structure. Based on an ab initio derived model Hamiltonian we employ random phase approximation spin fluctuation theory yielding a composite order parameter of (extended) s+dx2-y2 symmetry. Taking explicitly also the shape of the Fermi surface into account we calculate STS spectra that are in excellent agreement to the experimental observations [1]. Moreover we determine the minimal tight binding model to describe the general lattice structure of these compounds accurately and generate a phase diagram for the gap symmetry by varying the hopping parameters. Based on ab initio derived parameter sets we predict the gap symmetry of other superconducting κ charge transfer salts. This work was supported by Deutsche Forschungsgemeinschaft under Grant No. SFB/TR 49.

Effect of oxide insertion layer on resistance switching properties of copper phthalocyanine

NASA Astrophysics Data System (ADS)

Joshi, Nikhil G.; Pandya, Nirav C.; Joshi, U. S.

2013-02-01

Organic memory device showing resistance switching properties is a next-generation of the electrical memory unit. We have investigated the bistable resistance switching in current-voltage (I-V) characteristics of organic diode based on copper phthalocyanine (CuPc) film sandwiched between aluminum (Al) electrodes. Pronounced hysteresis in the I-V curves revealed a resistance switching with on-off ratio of the order of 85%. In order to control the charge injection in the CuPc, nanoscale indium oxide buffer layer was inserted to form Al/CuPc/In2O3/Al device. Analysis of I-V measurements revealed space charge limited switching conduction at the Al/CuPc interface. The traps in the organic layer and charge blocking by oxide insertion layer have been used to explain the absence of resistance switching in the oxide buffer layered memory device cell. Present study offer potential applications for CuPc organic semiconductor in low power non volatile resistive switching memory and logic circuits.

Soft-template-synthesis of hollow CuO/Co3O4 composites for pseudo-capacitive electrode: A synergetic effect on electrochemical performance

NASA Astrophysics Data System (ADS)

Wang, Kuaibing; Lv, Bo; Wu, Hua; Luo, Xuefei; Xu, Jiangyan; Geng, Zhirong

2016-12-01

Hollow CuO/Co3O4 hybrids, which inherited from its coordination polymer precursor consisting of sheets layer and nanoparticles layer composites, were synthesized and characterized by SEM, EDX, XRD and XPS. To assess its electrochemical capacitive performances, cyclic voltammetry, galvanostatic charging-discharging measurements and A.C. impedance tests were performed successively. The CuO/Co3O4 hybrids had higher capacitance and lower charge transfer resistance than bare Co3O4 nanostructures, revealing that it provided a protection layer and produced a synergistic effect due to the existence of CuO layer. The distinct synergistic effect could be further confirmed by endurance cycling tests. The capacitance of the CuO/Co3O4 hybrids was 111% retained after 500 cycles at a charging rate of 1.0 A g-1 and remained an intense growth trend after 2000 cycles at scan rate of 200 mV s-1.

What is the origin of anomalous dielectric response in 2D organic dimer Mott insulators κ-(BEDT-TTF)2Cu[N(CN)2]Cl and κ-(BEDT-TTF)2Cu2(CN)3

NASA Astrophysics Data System (ADS)

Pinterić, M.; Ivek, T.; Čulo, M.; Milat, O.; Basletić, M.; Korin-Hamzić, B.; Tafra, E.; Hamzić, A.; Dressel, M.; Tomić, S.

2015-03-01

Novel forms of the low-temperature phases in the two-dimensional molecular solids with competing interactions between charges, spins and lattice, in particular those featuring anomalous dielectric relaxation, have been the focus of intense activity in recent years. Open issues concern the nature of collective charge excitations as well as their coupling to applied ac and dc electric fields. The charge response is reasonably well understood by now in the charge-ordered phase with the formation of ferroelectric-like domains below the metal-to-insulator phase transition. Conversely, the dielectric response observed in dimer Mott insulator phases with no complete evidence for charge ordering is rather intriguing. We overview our recent results of anisotropic complex conductivity (dc - MHz) in the magnetic phase of κ-(BEDT - TTF) 2 Cu [ N(CN)2 ] Cl and in the spin-liquid phase of κ-(BEDT - TTF) 2Cu2(CN)3. We discuss possible explanations for the observed dynamics within current theoretical models and compare them with the well-known fingerprints of the spin density wave response to ac electric fields.

Cued American English: A Variety in the Visual Mode

ERIC Educational Resources Information Center

Portolano, Marlana

2008-01-01

Cued American English (CAE) is a visual variety of English derived from a mode of communication called Cued Speech (CS). CS, or cueing, is a system of communication for use with the deaf, which consists of hand shapes, hand placements, and mouth shapes that signify the phonemic information conventionally conveyed through speech in spoken…

X-ray absorption edge spectroscopy and computational studies on LCuO2 species: Superoxide-Cu(II) versus peroxide-Cu(III) bonding.

PubMed

Sarangi, Ritimukta; Aboelella, Nermeen; Fujisawa, Kiyoshi; Tolman, William B; Hedman, Britt; Hodgson, Keith O; Solomon, Edward I

2006-06-28

The geometric and electronic structures of two mononuclear CuO2 complexes, [Cu(O2){HB(3-Ad-5-(i)Prpz)3}] (1) and [Cu(O2)(beta-diketiminate)] (2), have been evaluated using Cu K- and L-edge X-ray absorption spectroscopy (XAS) studies in combination with valence bond configuration interaction (VBCI) simulations and spin-unrestricted broken symmetry density functional theory (DFT) calculations. Cu K- and L-edge XAS data indicate the Cu(II) and Cu(III) nature of 1 and 2, respectively. The total integrated intensity under the L-edges shows that the 's in 1 and 2 contain 20% and 28% Cu character, respectively, indicative of very covalent ground states in both complexes, although more so in 1. Two-state VBCI simulations also indicate that the ground state in 2 has more Cu (/3d8) character. DFT calculations show that the in both complexes is dominated by O2(n-) character, although the O2(n-) character is higher in 1. It is shown that the ligand L plays an important role in modulating Cu-O2 bonding in these LCuO2 systems and tunes the ground states of 1 and 2 to have dominant Cu(II)-superoxide-like and Cu(III)-peroxide-like character, respectively. The contributions of ligand field (LF) and the charge on the absorbing atom in the molecule (Q(mol)M) to L- and K-edge energy shifts are evaluated using DFT and time-dependent DFT calculations. It is found that LF makes a dominant contribution to the edge energy shift, while the effect of Q(mol)M is minor. The charge on the Cu in the Cu(III) complex is found to be similar to that in Cu(II) complexes, which indicates a much stronger interaction with the ligand, leading to extensive charge transfer.

Electronic Interactions of Size-Selected Oxide Clusters on Metallic and Thin Film Oxide Supports

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

Xue, Meng; Nakayama, Miki; Liu, Ping

The interfacial electronic structure of various size-selected metal oxide nanoclusters (M 3O x; M = Mo, Nb, Ti) on Cu(111) and a thin film of Cu 2O supports were investigated in this paper by a combination of experimental methods and density functional theory (DFT). These systems explore electron transfer at the metal–metal oxide interface which can modify surface structure, metal oxidation states, and catalytic activity. Electron transfer was probed by measurements of surface dipoles derived from coverage dependent work function measurements using two-photon photoemission (2PPE) and metal core level binding energy spectra from X-ray photoelectron spectroscopy (XPS). The measured surfacemore » dipoles are negative for all clusters on Cu(111) and Cu 2O/Cu(111), but those on the Cu 2O surface are much larger in magnitude. In addition, sub-stoichiometric or “reduced” clusters exhibit smaller surface dipoles on both the Cu(111) and Cu 2O surfaces. Negative surface dipoles for clusters on Cu(111) suggest Cu → cluster electron transfer, which is generally supported by DFT-calculated Bader charge distributions. For Cu 2O/Cu(111), calculations of the surface electrostatic potentials show that the charge distributions associated with cluster adsorption structures or distortions at the cluster–Cu 2O–Cu(111) interface are largely responsible for the observed negative surface dipoles. Changes observed in the XPS spectra for the Mo 3d, Nb 3d, and Ti 2p core levels of the clusters on Cu(111) and Cu 2O/Cu(111) are interpreted with help from the calculated Bader charges and cluster adsorption structures, the latter providing information about the presence of inequivalent cation sites. Finally, the results presented in this work illustrate how the combined use of different experimental probes along with theoretical calculations can result in a more realistic picture of cluster–support interactions and bonding.« less

Electronic Interactions of Size-Selected Oxide Clusters on Metallic and Thin Film Oxide Supports

DOE PAGES

Xue, Meng; Nakayama, Miki; Liu, Ping; ...

2017-09-13

The interfacial electronic structure of various size-selected metal oxide nanoclusters (M 3O x; M = Mo, Nb, Ti) on Cu(111) and a thin film of Cu 2O supports were investigated in this paper by a combination of experimental methods and density functional theory (DFT). These systems explore electron transfer at the metal–metal oxide interface which can modify surface structure, metal oxidation states, and catalytic activity. Electron transfer was probed by measurements of surface dipoles derived from coverage dependent work function measurements using two-photon photoemission (2PPE) and metal core level binding energy spectra from X-ray photoelectron spectroscopy (XPS). The measured surfacemore » dipoles are negative for all clusters on Cu(111) and Cu 2O/Cu(111), but those on the Cu 2O surface are much larger in magnitude. In addition, sub-stoichiometric or “reduced” clusters exhibit smaller surface dipoles on both the Cu(111) and Cu 2O surfaces. Negative surface dipoles for clusters on Cu(111) suggest Cu → cluster electron transfer, which is generally supported by DFT-calculated Bader charge distributions. For Cu 2O/Cu(111), calculations of the surface electrostatic potentials show that the charge distributions associated with cluster adsorption structures or distortions at the cluster–Cu 2O–Cu(111) interface are largely responsible for the observed negative surface dipoles. Changes observed in the XPS spectra for the Mo 3d, Nb 3d, and Ti 2p core levels of the clusters on Cu(111) and Cu 2O/Cu(111) are interpreted with help from the calculated Bader charges and cluster adsorption structures, the latter providing information about the presence of inequivalent cation sites. Finally, the results presented in this work illustrate how the combined use of different experimental probes along with theoretical calculations can result in a more realistic picture of cluster–support interactions and bonding.« less

New aspects of the structure of human hair on the basis of optical microscopic observations of disassembled hair parts.

PubMed

Yamauchi, Asao; Yamauchi, Kiyoshi

2015-01-01

Infant' and adult' scalp hair fibers were disassembled to various cellular components and blocks by chemical and enzymatic treatments, followed by random scission with rapidly rotating cutters. The hair fibers were also fractured by the use of a vise. The optical microscopic inspection of these specimens led to the discovery of many previously unknown structures in the hair shaft. In particular, a cuticular cell (Cu) was found to take a trowel-like shape consisting of a part with a blade-like shape (CuB) and a part with a handle-like shape (CuH), where CuB overlapped one another and fused partially to build the honeycomb-like structure on a large cuticular thin plate (CuP). Whereas CuH was closely similar to the cortical cell in dimensions and richness of macrofibrils (Mf). It was considered that human hair is stabilized structurally and physicochemically by the presence of the honeycomb-like structure, the CuP and the Mf.

Highly charged swelling mica reduces Cu bioavailability in Cu-contaminated soils.

PubMed

Stuckey, Jason W; Neaman, Alexander; Ravella, Ramesh; Komarneni, Sridhar; Martínez, Carmen Enid

2009-01-01

This is the first test of a highly charged swelling mica's (Na-2-mica) ability to reduce the plant-absorbed Cu in Cu-contaminated soils from Chile. Perennial ryegrass (Lolium perenne L.) was grown in two acid soils (Sector 2: pH 4.2, total Cu = 172 mg Cu kg(-1) and Sector 3: pH 4.2, total Cu = 112 mg Cu kg(-1)) amended with 0.5% and 1% (w/w) mica, and 1% (w/w) montmorillonite. At 10 weeks of growth, both mica treatments decreased the shoot Cu of ryegrass grown in Sector 2 producing shoot Cu concentrations above 21-22 mg Cu kg(-1) (the phytotoxicity threshold for that species), yet the mica treatments did not reduce shoot Cu concentrations when grown in Sector 3, which were at a typical level. The mica treatments improved shoot growth in Sector 3 by reducing free and extractable Cu to low enough levels where other nutrients could compete for plant absorption and translocation. In addition, the mica treatments improved root growth in both soils, and the 1% mica treatment reduced root Cu in both soils. This swelling mica warrants further testing of its ability to assist re-vegetation and reduce Cu bioavailability in Cu-contaminated surface soils.

Thermo-Mechanical Response of Monolithic and NiTi Shape Memory Alloy Fiber Reinforced Sn-3.8Ag-0.7Cu Solder

DTIC Science & Technology

2005-09-01

novel adaptive Tin-Silver-Copper ( SnAgCu ) solder reinforced with NiTi shape-memory alloy (particles or fiber) developed. An experimental...to meet the demands of miniaturization and enhanced performance in severe environments, a novel adaptive Tin-Silver-Copper ( SnAgCu ) solder...4. Crack region of SnAgCu solder after TMF, from reference [1] ............. 5 Figure 5. Phase diagram of 95.5Sn-3.8Ag-0.7Cu solder, from reference

Theoretical Insights into a CO Dimerization Mechanism in CO2 Electroreduction.

PubMed

Montoya, Joseph H; Shi, Chuan; Chan, Karen; Nørskov, Jens K

2015-06-04

In this work, we present DFT simulations that demonstrate the ability of Cu to catalyze CO dimerization in CO2 and CO electroreduction. We describe a previously unreported CO dimer configuration that is uniquely stabilized by a charged water layer on both Cu(111) and Cu(100). Without this charged water layer at the metal surface, the formation of the CO dimer is prohibitively endergonic. Our calculations also demonstrate that dimerization should have a lower activation barrier on Cu(100) than Cu(111), which, along with a more exergonic adsorption energy and a corresponding higher coverage of *CO, is consistent with experimental observations that Cu(100) has a high activity for C-C coupling at low overpotentials. We also demonstrate that this effect is present with cations other than H(+), a finding that is consistent with the experimentally observed pH independence of C2 formation on Cu.

Electronic excitations in electron-doped cuprate superconductors

NASA Astrophysics Data System (ADS)

Unger, P.; Fulde, P.

1995-04-01

We calculate the electronic single-particle spectrum of an electron-doped cuprate superconductor such as Nd2-xCexCuO4-y. The dynamics of holes in the Cu-O planes is described by the extended Hubbard or Emery model. We consider the system at half-filling (one hole per unit cell, nh=1) and in the case of electron doping where the ground state is paramagnetic. The projection technique of Mori and Zwanzig is applied to derive the equations of motion for the Green's functions of Cu and O holes. These equations are solved self-consistently as in a previous calculation, where we considered the case of hole doping. At half-filling the system exhibits a charge-transfer gap bounded by Zhang-Rice singlet states and the upper Hubbard band. Upon electron doping the upper Hubbard band crosses the Fermi level and the system becomes metallic. With increasing electron doping the singlet band loses intensity and finally vanishes for nh=0. The corresponding spectral weight is transferred to the upper Hubbard band, which becomes a usual tight-binding band for zero hole concentration. The shape of the flat band crossing the Fermi level fits well to angle-resolved photoemission spectra of Nd2-xCexCuO4-y for x=0.15 and 0.22. Furthermore, our findings are in excellent agreement with exact diagonalization studies of 2×2 CuO2 cluster with periodic boundary conditions.

Reduced anti-ferromagnetism promoted by Zn 3d 10 substitution at CuO 2 planar sites of Cu 0.5Tl 0.5Ba 2Ca 3Cu 4O 12-δ superconductors

NASA Astrophysics Data System (ADS)

Mumtaz, M.; Khan, Nawazish A.

2009-11-01

The role of charge carriers in ZnO 2/CuO 2 planes of Cu 0.5Tl 0.5Ba 2Ca 3Cu 4-yZn yO 12-δ material in bringing about superconductivity has been explained. Due to suppression of anti-ferromagnetic order with Zn 3d 10 ( S=0) substitution at Cu 3d 9(S={1}/{2}) sites in the inner CuO 2 planes of Cu 0.5Tl 0.5Ba 2Ca 3Cu 4O 12-δ superconductor, the distribution of charge carriers becomes homogeneous and optimum, which is evident from the enhanced superconductivity parameters. The decreased c-axis length with the increase of Zn doping improves interlayer coupling and hence the three dimensional (3D) conductivity in the unit cell is enhanced. Also the softening of phonon modes with the increased Zn doping indicates that the electron-phonon interaction has an essential role in the mechanism of high- Tc superconductivity in these compounds.

A combined model for pseudo-rapidity distributions in Cu-Cu collisions at BNL-RHIC energies

NASA Astrophysics Data System (ADS)

Jiang, Z. J.; Wang, J.; Huang, Y.

2016-04-01

The charged particles produced in nucleus-nucleus collisions come from leading particles and those frozen out from the hot and dense matter created in collisions. The leading particles are conventionally supposed having Gaussian rapidity distributions normalized to the number of participants. The hot and dense matter is assumed to expand according to the unified hydrodynamics, a hydro model which unifies the features of Landau and Hwa-Bjorken model, and freeze out into charged particles from a time-like hypersurface with a proper time of τFO. The rapidity distribution of this part of charged particles can be derived analytically. The combined contribution from both leading particles and unified hydrodynamics is then compared against the experimental data performed by BNL-RHIC-PHOBOS Collaboration in different centrality Cu-Cu collisions at sNN = 200 and 62.4GeV, respectively. The model predictions are consistent with experimental measurements.

Magnetic field effect in stripe-ordered 214 (La1.6 -xNd0.4) SrxCuO4 and La2 -xBaxCuO4 superconducting cuprates studied by resonant soft x-ray scattering

NASA Astrophysics Data System (ADS)

Blanco-Canosa, S.; Schierle, E.; Li, Z. W.; Guo, H.; Adachi, T.; Koike, Y.; Sobolev, O.; Weschke, E.; Komarek, A. C.; Schüßler-Langeheine, C.

2018-05-01

We present a study of the charge order of 214 stripe ordered superconducting cuprates (La1.6 -xNd0.4) SrxCuO4 and La2 -xBaxCuO4 for doping levels 0.11 ≤p ≤0.14 by means of resonant x-ray scattering. Up to 6 T, we find no field dependence on either the integrated intensity or the correlation length of the charge modulations, providing evidence for strong stability of charge order under applied fields. The magnetic field data support a strong pinning scenario induced by the low-temperature tetragonal distortion and static disorder, and they highlight the role of the symmetry of the lattice on the stabilization of electronic periodicities.

Structure and charge transfer correlated with oxygen content for a Y0.8Ca0.2Ba2Cu3Oy (y = 6.84 6.32) system: a positron study

NASA Astrophysics Data System (ADS)

Cao, Shixun; Li, Lingwei; Liu, Fen; Li, Wenfeng; Chi, Changyun; Jing, Chao; Zhang, Jincang

2005-05-01

The structure and charge transfer correlated with oxygen content are studied by measuring the positron lifetime parameters of the Y0.8Ca0.2Ba2Cu3Oy system with a large range of oxygen content (y = 6.84-6.32). The local electron density ne is evaluated from the positron lifetime data. The positron lifetime parameters show a clear change around y = 6.50 where the compounds undergo the orthorhombic-tetragonal phase transition. The effect of ne and oxygen content on the structure, charge transfer and superconductivity are discussed. With the decrease of oxygen content y, O(4) tends to the Cu(1) site, causing carrier localization, and accordingly, the decrease of ne. This would prove that the localized carriers (electrons and holes) in the Cu-O chain region have great influence on the superconductivity by affecting the charge transfer between the reservoir layers and the conducting layers. The positron annihilation mechanism and its relation with superconductivity are also discussed.

Highly stable CuO incorporated TiO(2) catalyst for photo-catalytic hydrogen production from H(2)O.

PubMed

Bandara, J; Udawatta, C P K; Rajapakse, C S K

2005-11-01

A CuO incorporated TiO(2) catalyst was found to be an active photo-catalyst for the reduction of H(2)O under sacrificial conditions. The catalytic activity originates from the photogeneration of excited electrons in the conduction bands of both TiO(2) and CuO resulting in a build-up of excess electrons in the conduction band of CuO. Consequently, the accumulation of excess electrons in CuO causes a negative shift in the Fermi level of CuO. The efficient inter-particle charge transfer leads to a higher catalytic activity and the formation of highly reduced states of TiO(2)/CuO, which are stable even under oxygen saturated condition. Negative shift in the Fermi level of CuO of the catalyst TiO(2)/CuO gains the required over-voltage necessary for efficient water reduction reaction. The function of CuO is to help the charge separation and to act as a water reduction site. The amount of CuO and crystalline structure were found to be crucial for the catalytic activity and the optimum CuO loading was ca. approximately 5-10%(w/w).

Control of interfacial charge-transfer interaction of dye and p-CuI in solid-state dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Moribe, Shinya; Kato, Naohiko; Higuchi, Kazuo; Mizumoto, Katsuyoshi; Toyoda, Tatsuo

2017-04-01

We systematically investigated the photovoltaic and absorption characteristics of solid-state dye-sensitized solar cells with CuI to elucidate the impact of the interaction between the dye and CuI. For the ruthenium complex N719, the incident photon-to-current conversion efficiency (IPCE) on the longer-wavelength side decreased owing to the change of the metal-to-ligand charge transfer (CT) of N719 due to the interaction between the thiocyanate groups of N719 and CuI. In contrast, when D149 — which included rhodanine groups — was used, the interaction with CuI and the resultant CT increased the IPCE. The results provide a new strategy for improving the photovoltaic performance by controlling the interfacial CT between the dye and CuI.

Novel p-n heterojunction copper phosphide/cuprous oxide photocathode for solar hydrogen production.

PubMed

Chen, Ying-Chu; Chen, Zhong-Bo; Hsu, Yu-Kuei

2018-08-01

A Copper phosphide (Cu 3 P) micro-rod (MR) array, with coverage by an n-Cu 2 O thin layer by electrodeposition as a photocathode, has been directly fabricated on copper foil via simple electro-oxidation and phosphidation for photoelectrochemical (PEC) hydrogen production. The morphology, structure, and composition of the Cu 3 P/Cu 2 O heterostructure are systematically analyzed using a scanning electron microscope (SEM), X-ray diffraction and X-ray photoelectron spectra. The PEC measurements corroborate that the p-Cu 3 P/n-Cu 2 O heterostructural photocathode illustrates efficient charge separation and low charge transfer resistance to achieve the highest photocurrent of 430 μA cm -2 that is greater than other transition metal phosphide materials. In addition, a detailed energy diagram of the p-Cu 3 P/n-Cu 2 O heterostructure was investigated using Mott-Schottky analysis. Our study paves the way to explore phosphide-based materials in a new class for solar energy applications. Copyright © 2018 Elsevier Inc. All rights reserved.

Photocatalytic removal of 2,4-dichlorophenoxyacetic acid herbicide on copper oxide/titanium dioxide prepared by co-precipitation method

NASA Astrophysics Data System (ADS)

Lee, Shu Chin; Hasan, Norhasnita; Lintang, Hendrik O.; Shamsuddin, Mustaffa; Yuliati, Leny

2016-02-01

In this work, suppression of the charge recombination on the titanium dioxide (TiO2) was reported by the addition of copper oxide (CuO), which led to a higher activity of TiO2 for removal of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide. A series of CuO/TiO2 with CuO loadings of 0.1-1 wt% was prepared through a co-precipitation method. X-ray diffraction patterns revealed that the presence of CuO could not be detected as the low loading amount of CuO might have good dispersion on the surface of TiO2. Diffuse reflectance UV-visible spectra suggested that low loading amount of CuO did not influence the optical property of TiO2. Fluorescence spectroscopy revealed that TiO2 possessed a dominant emission peak of 407 nm at an excitation wavelength of 218 nm. The increasing loading amount of CuO decreased the emission intensity of TiO2, suggesting the successful reduction of charge recombination. After irradiation under UV light for 1 h, CuO(0.1 wt%)/TiO2 gave the highest percentage removal of the herbicide among the samples. The optimum loading amount of CuOmight improve the charge separation and reduce the electron-hole recombination on TiO2 without blocking the active sites, thus leading to the improved photocatalytic activity. This work showed that CuO/TiO2 is a potential photocatalyst for environmental remediation.

The ionic charge of Copper-64 complexes conjugated to an engineered antibody effects biodistribution

DOE PAGES

Dearling, Jason L. J.; Smith, Suzanne V.; Paterson, Brett M.; ...

2015-04-15

The development of biomolecules as imaging probes requires radiolabeling methods that do not significantly influence their biodistribution. Sarcophagine (Sar) chelators form extremely stable complexes with copper, and are therefore a promising option for labeling proteins with ⁶⁴Cu. However, initial studies using the first-generation sarcophagine bifunctional chelator SarAr to label the engineered antibody fragment ch14.18-ΔC H2 (MW 120 kDa) with ⁶⁴Cu showed high tracer retention in the kidneys,(>38% injected dose per gram (ID/g) 48 h post-injection), presumably because the high local positive charge on the Cu II-SarAr moiety resulted in increased binding of the labeled protein to the negatively charged basalmore » cells of the glomerulus. To test this hypothesis, ch14.18-ΔC H2 was conjugated with a series of Sar derivatives of decreasing positive charge and three commonly used macrocyclic polyaza polycarboxylate (PAC) BFCs. The immunoconjugates were labeled with ⁶⁴Cu and injected into mice, and PET/CT images were obtained at 24 and 48 h post injection (p.i.). At 48 h p.i., ex vivo biodistribution was carried out. In addition, to demonstrate the potential of metastasis detection using ⁶⁴Cu-labeled ch14.18-ΔC H2, a preclinical imaging study of intrahepatic neuroblastoma tumors was performed carried out. Reducing the positive charge on the Sar chelators decreased kidney uptake of Cu-labeled ch14.18-ΔC H2 by more than 6-fold, from >45 ID/g to <6% ID/g, while the uptake in most other tissues, including liver, was relatively unchanged. However, despite this dramatic decrease, the renal uptake of the PAC BFCs was generally lower than that of the Sar derivatives, as was the liver uptake. Uptake of ⁶⁴Cu-labeled ch14.18-ΔC H2 in neuroblastoma hepatic metastases was detected using PET.« less

High-temperature charge density wave correlations in La1.875Ba0.125CuO4 without spin–charge locking

PubMed Central

Lorenzana, J.; Seibold, G.; Peng, Y. Y.; Amorese, A.; Yakhou-Harris, F.; Kummer, K.; Brookes, N. B.; Konik, R. M.; Thampy, V.; Gu, G. D.; Ghiringhelli, G.; Braicovich, L.

2017-01-01

Although all superconducting cuprates display charge-ordering tendencies, their low-temperature properties are distinct, impeding efforts to understand the phenomena within a single conceptual framework. While some systems exhibit stripes of charge and spin, with a locked periodicity, others host charge density waves (CDWs) without any obviously related spin order. Here we use resonant inelastic X-ray scattering to follow the evolution of charge correlations in the canonical stripe-ordered cuprate La1.875Ba0.125CuO4 across its ordering transition. We find that high-temperature charge correlations are unlocked from the wavevector of the spin correlations, signaling analogies to CDW phases in various other cuprates. This indicates that stripe order at low temperatures is stabilized by the coupling of otherwise independent charge and spin density waves, with important implications for the relation between charge and spin correlations in the cuprates. PMID:29114049

Measuring the isoelectric point of the edges of clay mineral particles: the case of montmorillonite.

PubMed

Pecini, Eliana M; Avena, Marcelo J

2013-12-03

The isoelectric point (IEP) of the edge surface of a montmorillonite sample was determined by using electrophoretic mobility measurements. This parameter, which is fundamental for the understanding of the charging behavior of clay mineral surfaces, was never measured so far because of the presence of permanent negative charges within the montmorillonite structure, charges that mask the electrokinetic behavior of the edges. The strategy was to block or neutralize the structural charges with two different cations, methylene blue (MB(+)) and tetraethylenepentaminecopper(II) ([Cu(tetren)](2+)), so that the charging behavior of the particles becomes that of the edge surfaces. Adsorption isotherms of MB(+) and [Cu(tetren)](2+) at different ionic strengths (NaCl) were performed to establish the uptakes that neutralize the cation exchange capacity (CEC, 0.96 meq g(-1)) of the sample. At high adsorptive concentrations, there was a superequivalent adsorption of MB(+) (adsorption exceeding the CEC) and an equivalent adsorption of [Cu(tetren)](2+) (adsorption reaching the CEC). In both cases, structural charges were neutralized at uptakes very close to the CEC. Zeta potential (ζ) vs pH data at different ionic strengths of montmorillonite with adsorbed MB(+) allowed to estimate an upper limit of the edge's IEP, 5.3 ± 0.2. The same kind of data obtained with adsorbed [Cu(tetren)](2+) provided a lower limit of the IEP, 4.0 ± 0.2. These values are in agreement with previously informed IEP and point of zero charge of pyrophyllite, which is structurally analogous to montmorillonite but carries no permanent charges. The importance of knowing the IEP of the edge surface of clay minerals is discussed. This value characterizes the intrinsic reactivity of edges, that is, the protonating capacity of edge groups in absence of any electric field generated by structural charges. It also allows us to correct relative edge charge vs pH curves obtained by potentiometric titrations and to obtain the true edge charge vs pH curves at different electrolyte concentrations.

Cu doped diamond: Effect of charge state and defect aggregation on spin interactions in a 3d transition metal doped wide band-gap semiconductor

NASA Astrophysics Data System (ADS)

Benecha, E. M.; Lombardi, E. B.

2018-05-01

We present a first principles study of Cu in diamond using DFT+U electronic structure methods, by carefully considering the impact of co-doping, charge state, and Fermi level position on its stability, lattice location, spin states, and electronic properties. We show that the energetic stability and spin states of Cu are strongly dependent on the Fermi level position and the type of diamond co-doping, with Cu being energetically more favorable in n-type or p-type co-doped diamond compared to intrinsic diamond. Since Cu has been predicted to order magnetically in a number of other wide band-gap semiconductors, we have also evaluated this possibility for Cu doped diamond. We show that while Cu exhibits strong spin interactions at specific interatomic separations in diamond, a detailed consideration of the impact of Fermi level position and Cu aggregation precludes magnetic ordering, with Cu forming non-magnetic, antiferromagnetic, or paramagnetic clusters. These results have important implications in the understanding of the properties of transition metal dopants in diamond for device applications.

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

Influences of TiO2 phase structures on the structures and photocatalytic hydrogen production of CuOx/TiO2 photocatalysts

NASA Astrophysics Data System (ADS)

Liu, Yuanxu; Wang, Zhonglei; Huang, Weixin

2016-12-01

CuOx/TiO2 photocatalysts employing TiO2 with different phase structures as well as P25 as supports were prepared, and their structures and activity for photocatalytic H2 production in methanol/water solution under simulated solar light were comparatively studied. Structural characterization results demonstrated that the TiO2 phase structure strongly affects the CuOx-TiO2 interaction and copper species in various CuOx/TiO2 photocatalysts. The Cu2O-rutile TiO2 interaction is much stronger than the Cu2O-anatase TiO2 interaction, facilitates the interfacial charge transfer process within the Cu2O-rutile TiO2 heterojunction but disables supported Cu2O to catalyze the hole-participated methanol oxidation. The Cu2O-anatase TiO2 heterojunction with the appropriate Cu2O-anatase TiO2 interaction and thus the balancing efficiencies between the interfacial charge transfer process and hole-participated methanol oxidation is most photocatalytic active, and CuOx/P25 with the largest population of Cu2O-anatase TiO2 heterojunction exhibits the highest photocatalytic H2 production. These results provide novel insights in the applied surface science of CuOx/TiO2 photocatalysts.

Effective charge separation in BiOI/Cu2O composites with enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Xia, Yongmei; He, Zuming; Yang, Wei; Tang, Bin; Lu, Yalin; Hu, Kejun; Su, Jiangbin; Li, Xiaoping

2018-02-01

Novel BiOI/Cu2O composites were designed and synthesized for the first time by coupling reduction method at low temperature. The samples were characterized by XRD, XPS, SEM, EDS, HRTEM, UV-vis (DRS), FTIR and photo-electro-chemical (PEC) analysis. Results showed that the BiOI/Cu2O composites consisted of three-dimensional (3D), hierarchical cauliflower-like structure composed of BiOI nanosheet and Cu2O cubic submicrometer structure, the composite absorption band broadened, and the absorption intensity in the visible region strengthened. And the composites exhibited an excellent photocatalytic performance, which might be attributed to the improvement of the composite absorption and effective charge separation in BiOI/Cu2O composites. In addition, the possible photocatalytic mechanism was proposed.

Preparation of Advanced CuO Nanowires/Functionalized Graphene Composite Anode Material for Lithium Ion Batteries.

PubMed

Zhang, Jin; Wang, Beibei; Zhou, Jiachen; Xia, Ruoyu; Chu, Yingli; Huang, Jia

2017-01-17

The copper oxide (CuO) nanowires/functionalized graphene (f-graphene) composite material was successfully composed by a one-pot synthesis method. The f-graphene synthesized through the Birch reduction chemistry method was modified with functional group "-(CH₂)₅COOH", and the CuO nanowires (NWs) were well dispersed in the f-graphene sheets. When used as anode materials in lithium-ion batteries, the composite exhibited good cyclic stability and decent specific capacity of 677 mA·h·g -1 after 50 cycles. CuO NWs can enhance the lithium-ion storage of the composites while the f-graphene effectively resists the volume expansion of the CuO NWs during the galvanostatic charge/discharge cyclic process, and provide a conductive paths for charge transportation. The good electrochemical performance of the synthesized CuO/f-graphene composite suggests great potential of the composite materials for lithium-ion batteries anodes.

Interstitial copper defect induced reconstruction of a new ;CuO4; quadrilateral in CaCu3Ti4O12: A first-principles study

NASA Astrophysics Data System (ADS)

Xiao, Haibo; Xu, Linfang; Wang, Ruilong; Yang, Changping

2017-09-01

The geometric structure, electronic structure and formation energy of CaCu3Ti4O12 (CCTO) with interstitial copper atom have been studied using the density-functional method within the GGA approximation. Result of structural optimization shows that the interstitial Cu-atom (Cu7) prefers to occupy a special location which is symmetrical with an intrinsic copper atom (Cu13) deviated from the normal site. The mulliken analysis indicates the loss of electrons from interstitial atom (Cu7) and Cu13 are only half more of the losing in other copper atom, which reveals a characteristics of covalent bonding between Cu7/Cu13 and surrounding oxygen atoms respectively. Meanwhile, it is found from electron density difference (EDD) and orbital analysis that the introduction of interstitial Cu atom causes prominent structural reconstruction of a new ;CuO4; quadrilateral. Moreover, the new ;CuO4; planar leads to a corresponding electronic reconstruction in the hybridization between Cu7/Cu13 3d and O 2p at the vicinity of fermi surface, for which a new conductive filament channel comes into being. Besides, the formation energies of the interstitial defects in various charge states are corrected with the value of 2.18, -4.17 and -9.46 eV for charge of 0, 1+ and 2+, respectively.

Time-controlled synthesis mechanism analysis of kesterite-phased Cu2ZnSnS4 nanorods via colloidal route

NASA Astrophysics Data System (ADS)

Jain, Shefali; Singh, Dinesh; Vijayan, N.; Sharma, Shailesh Narain

2018-05-01

In this work, stable Cu2ZnSnS4 (CZTS) nanocrystals (NCs) in pure kesterite phase were synthesized by a facile one-pot rapid injection technique (colloidal route). Time-dependent reaction mechanism for the synthesis of CZTS nanoparticles is explained. When TOP-S (Tri-octyl phosphine-sulphur) was injected in the CuZnSn-complex with TOPO (Tri-octyl phosphine oxide) as capping ligand, orthorhombic phase Cu2-X S nanoparticles of spherical shape were found at nucleation sites. With an advancement in the reaction time, Sn got infused in Cu2-X S to form Cu2SnS3 and its shape got deformed. Further increase in reaction time infuses Zn to form Cu2ZnSnS4 with the gradual vanishing of Cu2-X S and Cu2SnS3 phases and finally, the rod-shaped CZTS Np's were obtained. This factor of reaction time, which influence the morphology and size were studied in detail. The structural and optical properties of the pure kesterite phase CZTS nanorods were also analysed. The band gap of the rod-like CZTS is determined to be around 1.43 eV, which is an optimum value for solar photoelectric conversion.

Piezo-phototronic effect enhanced UV photodetector based on CuI/ZnO double-shell grown on flexible copper microwire.

PubMed

Liu, Jingyu; Zhang, Yang; Liu, Caihong; Peng, Mingzeng; Yu, Aifang; Kou, Jinzong; Liu, Wei; Zhai, Junyi; Liu, Juan

2016-12-01

In this work, we present a facile, low-cost, and effective approach to fabricate the UV photodetector with a CuI/ZnO double-shell nanostructure which was grown on common copper microwire. The enhanced performances of Cu/CuI/ZnO core/double-shell microwire photodetector resulted from the formation of heterojunction. Benefiting from the piezo-phototronic effect, the presentation of piezocharges can lower the barrier height and facilitate the charge transport across heterojunction. The photosensing abilities of the Cu/CuI/ZnO core/double-shell microwire detector are investigated under different UV light densities and strain conditions. We demonstrate the I-V characteristic of the as-prepared core/double-shell device; it is quite sensitive to applied strain, which indicates that the piezo-phototronic effect plays an essential role in facilitating charge carrier transport across the CuI/ZnO heterojunction, then the performance of the device is further boosted under external strain.

Heavy metals alter the electrokinetic properties of bacteria, yeasts, and clay minerals.

PubMed Central

Collins, Y E; Stotzky, G

1992-01-01

The electrokinetic patterns of four bacterial species (Bacillus subtilis, Bacillus megaterium, Pseudomonas aeruginosa, and Agrobacterium radiobacter), two yeasts (Saccharomyces cerevisiae and Candida albicans), and two clay minerals (montmorillonite and kaolinite) in the presence of the chloride salts of the heavy metals, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, and of Na and Mg were determined by microelectrophoresis. The cells and kaolinite were net negatively charged at pH values above their isoelectric points (pI) in the presence of Na, Mg, Hg, and Pb at an ionic strength (mu) of 3 x 10(-4); montmorillonite has no pI and was net negatively charged at all pH values in the presence of these metals. However, the charge of some bacteria, S. cerevisiae, and kaolinite changed to a net positive charge (charge reversal) in the presence of Cd, Cr, Cu, Ni, and Zn at pH values above 5.0 (the pH at which charge reversal occurred differed with the metal) and then, at higher pH values, again became negative. The charge of the bacteria and S. cerevisiae also reversed in solutions of Cu and Ni with a mu of greater than 3 x 10(-4), whereas there was no reversal in solutions with a mu of less than 3 x 10(-4). The clays became net positively charged when the mu of Cu was greater than 3 x 10(-4) and that of Ni was greater than 1.5 x 10(-4). The charge of the cells and clays also reversed in solutions containing both Mg and Ni or both Cu and Ni (except montmorillonite) but not in solutions containing both Mg and Cu (except kaolinite) (mu = 3 x 10(-4)). The pIs of the cells in the presence of the heavy metals were at either higher or lower pH values than in the presence of Na and Mg. Exposure of the cells to the various metals at pH values from 2 to 9 for the short times (ca. 10 min) required to measure the electrophoretic mobility did not affect their viability. The specific adsorption on the cells and clays of the hydrolyzed species of some of the heavy metals that formed at higher pH values was probably responsible for the charge reversal. These results suggest that the toxicity of some heavy metals to microorganisms varies with pH because the hydrolyzed speciation forms of these metals, which occur at higher pH values, bind on the cell surface and alter the net charge of the cell.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1622229

A Single-Step Hydrothermal Route to 3D Hierarchical Cu2 O/CuO/rGO Nanosheets as High-Performance Anode of Lithium-Ion Batteries.

PubMed

Wu, Songhao; Fu, Gaoliang; Lv, Weiqiang; Wei, Jiake; Chen, Wenjin; Yi, Huqiang; Gu, Meng; Bai, Xuedong; Zhu, Liang; Tan, Chao; Liang, Yachun; Zhu, Gaolong; He, Jiarui; Wang, Xinqiang; Zhang, Kelvin H L; Xiong, Jie; He, Weidong

2018-02-01

As anodes of Li-ion batteries, copper oxides (CuO) have a high theoretical specific capacity (674 mA h g -1 ) but own poor cyclic stability owing to the large volume expansion and low conductivity in charges/discharges. Incorporating reduced graphene oxide (rGO) into CuO anodes with conventional methods fails to build robust interaction between rGO and CuO to efficiently improve the overall anode performance. Here, Cu 2 O/CuO/reduced graphene oxides (Cu 2 O/CuO/rGO) with a 3D hierarchical nanostructure are synthesized with a facile, single-step hydrothermal method. The Cu 2 O/CuO/rGO anode exhibits remarkable cyclic and high-rate performances, and particularly the anode with 25 wt% rGO owns the best performance among all samples, delivering a record capacity of 550 mA h g -1 at 0.5 C after 100 cycles. The pronounced performances are attributed to the highly efficient charge transfer in CuO nanosheets encapsulated in rGO network and the mitigated volume expansion of the anode owing to its robust 3D hierarchical nanostructure. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Charge transport mechanism in p-type copper ion containing triazine thiolate metallopolymer thin film devices

NASA Astrophysics Data System (ADS)

K, Deepak; Roy, Amit; Anjaneyulu, P.; Kandaiah, Sakthivel; Pinjare, Sampatrao L.

2017-10-01

The charge transport mechanism in copper ions containing 1,3,5-Triazine-2,4,6-trithiolate (CuTCA) based polymer device in sandwich (Ag/CuTCA/Cu) geometry is studied. The current-voltage (I-V) characteristics of the metallopolymer CuTCA device have shown a transition in the charge transport mechanism from Ohmic to Space-charge limited conduction when temperature and voltage are varied. The carriers in CuTCA devices exhibit hopping transport, in which carriers hop from one site to the other. The hole mobility in this polymer device is found to be dependent on electric field E ( μpα√{E } ) and temperature, which suggests that the polymer has inherent disorder. The electric-field coefficient γ and zero-field mobility μ0 are temperature dependent. The values of mobility and activation energies are estimated from temperature (90-140 K) dependent charge transport studies and found to be in the range of 1 × 10-11-8 × 10-12 m2/(V s) and 16.5 meV, respectively. Temperature dependent electric-field coefficient γ is in the order of 17.8 × 10-4 (m/V)1/2, and the value of zero-field mobility μ0 is in the order of 1.2 × 10-11 m2/(V s) at 140 K. A constant phase element (Q) is used to model the device parameters, which are extracted using the Impedance spectroscopy technique. The bandgap of the polymer is estimated to be 2.6 eV from UV-Vis reflectance spectra.

Effects of targeting moiety, linker, bifunctional chelator, and molecular charge on biological properties of 64Cu-labeled triphenylphosphonium cations.

PubMed

Kim, Young-Seung; Yang, Chang-Tong; Wang, Jianjun; Wang, Lijun; Li, Zi-Bo; Chen, Xiaoyuan; Liu, Shuang

2008-05-22

In this report, we present the synthesis and evaluation of six new 64Cu-labeled triphenylphosphonium (TPP) cations. Biodistribution studies were performed using the athymic nude mice bearing U87MG human glioma xenografts to explore the impact of TPP moieties, linkers, bifunctional chelators (BFCs), and molecular charge on biological properties of 64Cu radiotracers. On the basis of the results from this study, it is concluded that (1) mTPP (tris(4-methoxyphenyl)phosphonium) is a better mitochondrion-targeting molecule than TPP and 3mTPP (tris(2,4,6-trimethoxyphenyl)phosphonium); (2) DO3A (1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid) and DO2A (1,4,7,10-tetraazacyclododecane-4,7-diacetic acid) are suitable BFCs for the 64Cu-labeling of TPP cations; (3) NOTA-Bn ( S-2-(4-thioureidobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid) has a significant adverse effect on the radiotracer tumor uptake and tumor-to-background ratios; and (4) monoanionic BFCs should be avoided to ensure that 64Cu chelate has a neutral or negative charge. Considering the tumor uptake and tumor/liver ratios, 64Cu(DO2A-xy-TPP)+ is the best candidate for more extensive evaluations in different tumor-bearing animal models.

Coherent charge and spin density waves in underdoped HgBa 2CuO 4+δ

DOE PAGES

Lee, Jeongseop A.; Xin, Yizhou; Halperin, W. P.; ...

2017-03-16

Charge order in cuprate superconductors appears to be a universal characteristic, often associated with pseudogap behavior in the normal state. The central question is whether such charge ordering or the pseudogap are required for the existence of high temperature superconductivity and embody its mechanism. An important but phenomenological approach to this question is to examine whether these phenomena extend over various members of the cuprate family. Recent nuclear magnetic resonance (NMR) measurements on oxygen chain-ordered single crystals of YBa 2Cu 3O 6+y (Y123) have demonstrated temperature and magnetic field induced charge ordering that was confirmed in x-ray experiments. In themore » present work on high-quality single crystals of the tetragonal compound, HgBa 2CuO 4+δ, we use 17O NMR to investigate the interplay between charge and spin order deduced from the full quadrupolar-split NMR spectrum over a wide range of temperature and magnetic field. We have found evidence for a coherent modulation of charge and spin order in this compound. Furthermore, neither temperature nor magnetic field induced ordering was observed and we infer that this aspect of high temperature superconductivity is not universal.« less

A thundercloud electric field sounding - Charge distribution and lightning

NASA Technical Reports Server (NTRS)

Weber, M. E.; Few, A. A.; Stewart, M. F.; Christian, H. J.

1982-01-01

An instrumented free balloon measured electric fields and field changes as it rose through a thundercloud above Langmuir Laboratory, New Mexico. The variation of the electric field with altitude implied that the cloud contained negative space charge of density -0.6 to -4 nC/cu m between 5.5 and 8.0 km MSL. The environmental temperature at these levels ranged from -5 to -20 C. The measurements imply that the areal extent of this negative charge center was significantly greater than that of the cloud's intense precipitation shafts. At altitudes greater than 8 km, the instrument ascended past net positive charge. In addition, positive space charge adjacent to the earth's surface (concentration 0.6 nC/cu m and in the lowest portion of the cloud (1.0 nC/cu m) is inferred from the measurements. Electric field changes from intracloud lightning were interpreted by using a simple model for the developing streamer of the initial phase. Thunder source reconstructions provided estimates for the orientation of lightning channels. Seven 'streamers' so analyzed propagated on the average, at 50,000 m/s and carried a current of 390 A. The mean charge dissipated during a flash was 30 C.

Atomic scale real-space mapping of holes in YBa2Cu3O(6+δ).

PubMed

Gauquelin, N; Hawthorn, D G; Sawatzky, G A; Liang, R X; Bonn, D A; Hardy, W N; Botton, G A

2014-07-15

The high-temperature superconductor YBa2Cu3O(6+δ) consists of two main structural units--a bilayer of CuO2 planes that are central to superconductivity and a CuO(2+δ) chain layer. Although the functional role of the planes and chains has long been established, most probes integrate over both, which makes it difficult to distinguish the contribution of each. Here we use electron energy loss spectroscopy to directly resolve the plane and chain contributions to the electronic structure in YBa2Cu3O6 and YBa2Cu3O7. We directly probe the charge transfer of holes from the chains to the planes as a function of oxygen content, and show that the change in orbital occupation of Cu is large in the chain layer but modest in CuO2 planes, with holes in the planes doped primarily into the O 2p states. These results provide direct insight into the local electronic structure and charge transfers in this important high-temperature superconductor.

Electron-lattice interactions strongly renormalize the charge-transfer energy in the spin-chain cuprate Li 2CuO 2

DOE PAGES

Johnston, Steve; Monney, Claude; Bisogni, Valentina; ...

2016-02-17

Strongly correlated insulators are broadly divided into two classes: Mott–Hubbard insulators, where the insulating gap is driven by the Coulomb repulsion U on the transition-metal cation, and charge-transfer insulators, where the gap is driven by the charge-transfer energy Δ between the cation and the ligand anions. The relative magnitudes of U and Δ determine which class a material belongs to, and subsequently the nature of its low-energy excitations. These energy scales are typically understood through the local chemistry of the active ions. Here we show that the situation is more complex in the low-dimensional charge-transfer insulator Li 2CuO 2, wheremore » Δ has a large non-electronic component. Combining resonant inelastic X-ray scattering with detailed modelling, we determine how the elementary lattice, charge, spin and orbital excitations are entangled in this material. This results in a large lattice-driven renormalization of Δ, which significantly reshapes the fundamental electronic properties of Li 2CuO 2.« less

Collective Dynamics and Strong Pinning near the Onset of Charge Order in La1.48Nd0.4Sr0.12CuO4

NASA Astrophysics Data System (ADS)

Baity, P. G.; Sasagawa, T.; Popović, Dragana

2018-04-01

The dynamics of charge-ordered states is one of the key issues in underdoped cuprate high-temperature superconductors, but static short-range charge-order (CO) domains have been detected in almost all cuprates. We probe the dynamics across the CO (and structural) transition in La1.48Nd0.4Sr0.12CuO4 by measuring nonequilibrium charge transport, or resistance R as the system responds to a change in temperature and to an applied magnetic field. We find evidence for metastable states, collective behavior, and criticality. The collective dynamics in the critical regime indicates strong pinning by disorder. Surprisingly, nonequilibrium effects, such as avalanches in R , are revealed only when the critical region is approached from the charge-ordered phase. Our results on La1.48Nd0.4Sr0.12CuO4 provide the long-sought evidence for the fluctuating order across the CO transition, and also set important constraints on theories of dynamic stripes.

Disintegration of the net-shaped grain-boundary phase by multi-directional forging and its influence on the microstructure and properties of Cu-Ni-Si alloy

NASA Astrophysics Data System (ADS)

Zhang, Jinlong; Lu, Zhenlin; Zhao, Yuntao; Jia, Lei; Xie, Hui; Tao, Shiping

2017-09-01

Cu-Ni-Si alloys with 90% Cu content and Ni to Si ratios of 5:1 were fabricated by fusion casting, and severe plastic deformation of the Cu-Ni-Si alloy was carried out by multi-direction forging (MDF). The results showed that the as-cast and homogenized Cu-Ni-Si alloys consisted of three phases, namely the matrix phase α-Cu (Ni, Si), the reticular grain boundary phase Ni31Si12 and the precipitated phase Ni2Si. MDF significantly destroyed the net-shaped grain boundary phase, the Ni31Si12 phase and refined the grain size of the Cu matrix, and also resulted in the dissolving of Ni2Si precipitates into the Cu matrix. The effect of MDF on the conductivity of the solid solution Cu-Ni-Si alloy was very significant, with an average increase of 165.16%, and the hardness of the Cu-Ni-Si alloy also increased obviously.

Significant enhancement in volumetric and gravimetric capacitance of Cu-TiO2/PPY composite for supercapacitor application

NASA Astrophysics Data System (ADS)

Purty, B.; Choudhary, R. B.

2018-04-01

Copper doped titanium dioxide-polypyrrole (Cu-TiO2/PPY) composite was successfully synthesized via chemical oxidative in-situ polymerization process. The structural and morphological properties of Cu-TiO2/PPY composite were investigated using X-ray diffractometer (XRD), field emission electron microscopy (FESEM) and transmission electron microscopy(TEM) techniques. The electrochemical properties of as-synthesized composite were studied using cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopic (EIS) techniques. The novel Cu-TiO2/PPY composite showed enhanced volumetric capacitance ˜714 F cm-1 and gravimetric capacitance ˜674 F g-1 at 1 A g-1. In addition an excellent coulombic efficiency and comparabley low charge transfer resistance than pure PPY suggests improved supercapacitive performance of Cu-TiO2/PPY composite as an electrode material.

Cu-Al-Ni Shape Memory Single Crystal Wires with High Transformation Temperature

NASA Technical Reports Server (NTRS)

Hautcoeur, Alain; Fouché, Florian; Sicre, Jacques

2016-01-01

CN-250X is a new material with higher performance than Nickel-Titanium Shape Memory Alloy (SMA). For space mechanisms, the main disadvantage of Nickel-Titanium Shape Memory Alloy is the limited transformation temperature. The new CN-250X Nimesis alloy is a Cu-Al-Ni single crystal wire available in large quantity because of a new industrial process. The triggering of actuators made with this Cu-Al-Ni single crystal wire can range from ambient temperature to 200 C in cycling and even to 250 C in one-shot mode. Another advantage of CN-250X is a better shape recovery (8 to 10%) than Ni-Ti (6 to 7%). Nimesis is the first company able to produce this type of material with its new special industrial process. A characterization study is presented in this work, including the two main solicitation modes for this material: tensile and torsion. Different tests measure the shape recovery of Cu-Al-Ni single crystals wires during heating from room temperature to a temperature higher than temperature of end of martensitic transformation.

Evolutionary conservativeness of electric field in the Cu,Zn superoxide dismutase active site. Evidence for co-ordinated mutation of charged amino acid residues.

PubMed

Desideri, A; Falconi, M; Polticelli, F; Bolognesi, M; Djinovic, K; Rotilio, G

1992-01-05

Equipotential lines were calculated, using the Poisson-Boltzmann equation, for six Cu,Zn superoxide dismutases with different protein electric charge and various degrees of sequence homology, namely those from ox, pig, sheep, yeast, and the isoenzymes A and B from the amphibian Xenopus laevis. The three-dimensional structures of the porcine and ovine superoxide dismutases were obtained by molecular modelling reconstruction using the structure of the highly homologous bovine enzyme as a template. The three-dimensional structure of the evolutionary distant yeast Cu,Zn superoxide dismutase was recently resolved by us, while computer-modelled structures are available for X. laevis isoenzymes. The six proteins display large differences in the net protein charge and distribution of electrically charged surface residues but the trend of the equipotential lines in the proximity of the active sites was found to be constant in all cases. These results are in line with the very similar catlytic rate constants experimentally measured for the corresponding enzyme activities. This analysis shows that electrostatic guidance for the enzyme-substrate interaction in Cu,Zn superoxide dismutases is related to a spatial distribution of charges, arranged so as to maintain, in the area surrounding the active sites, an identical electrostatic potential distribution, which is conserved in the evolution of this protein family.

High-temperature charge density wave correlations in La 1.875Ba 0.125CuO 4 without spin–charge locking

DOE PAGES

Miao, H.; Lorenzana, J.; Seibold, G.; ...

2017-11-07

Although all superconducting cuprates display charge-ordering tendencies, their low-temperature properties are distinct, impeding efforts to understand the phenomena within a single conceptual framework. While some systems exhibit stripes of charge and spin, with a locked periodicity, others host charge density waves (CDWs) without any obviously related spin order. Here we use resonant inelastic X-ray scattering to follow the evolution of charge correlations in the canonical stripe-ordered cuprate La 1.875Ba 0.125CuO 4 across its ordering transition. We find that high-temperature charge correlations are unlocked from the wavevector of the spin correlations, signaling analogies to CDW phases in various other cuprates. Thismore » indicates that stripe order at low temperatures is stabilized by the coupling of otherwise independent charge and spin density waves, with important implications for the relation between charge and spin correlations in the cuprates.« less

High-temperature charge density wave correlations in La 1.875Ba 0.125CuO 4 without spin–charge locking

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

Miao, H.; Lorenzana, J.; Seibold, G.

Although all superconducting cuprates display charge-ordering tendencies, their low-temperature properties are distinct, impeding efforts to understand the phenomena within a single conceptual framework. While some systems exhibit stripes of charge and spin, with a locked periodicity, others host charge density waves (CDWs) without any obviously related spin order. Here we use resonant inelastic X-ray scattering to follow the evolution of charge correlations in the canonical stripe-ordered cuprate La 1.875Ba 0.125CuO 4 across its ordering transition. We find that high-temperature charge correlations are unlocked from the wavevector of the spin correlations, signaling analogies to CDW phases in various other cuprates. Thismore » indicates that stripe order at low temperatures is stabilized by the coupling of otherwise independent charge and spin density waves, with important implications for the relation between charge and spin correlations in the cuprates.« less

Poly(glycidyl methacrylate)-A soft template for the facile preparation of poly(glycidyl methacrylate) core-copper nanoparticle shell nanocomposite

NASA Astrophysics Data System (ADS)

Mohammed Safiullah, S.; Abdul Wasi, K.; Anver Basha, K.

2015-12-01

Poly(glycidyl methacrylate) core/copper nanoparticle shell nanocomposite (PGMA/Cu nanohybrid) was prepared by simple two step method (i) The synthesis of poly(glycidyl methacrylate) (PGMA) beads by free radical suspension polymerization followed by (ii) direct deposition of copper nanoparticles (CuNPs) on activated PGMA beads. The PGMA beads were used as a soft template to host the CuNPs without surface modification of it. In this method the CuNPs were formed by chemical reduction of copper salts using sodium borohydride in water medium and deposited directly on the activated PGMA. Two different concentrations of copper salts were employed to know the effect of concentration on the shape and size of nanoparticles. The results showed that, the different sizes and shapes of CuNPs were deposited on the PGMA matrix. The X-ray Diffraction study results showed that the CuNPs were embedded on the surface of the PGMA matrix. The scanning electron microscopic images revealed that the fabrication of CuNPs on the PGMA matrix possess different shapes and changes the morphology and nature of PGMA beads significantly. The fluorescent micrograph also confirmed that the CuNPs were doped on the PGMA surface. The thermal studies have demonstrated that the CuNPs deposition on the surface of PGMA beads had a significant effect.

Determination of diffusion coefficient in disordered organic semiconductors

NASA Astrophysics Data System (ADS)

Rani, Varsha; Sharma, Akanksha; Ghosh, Subhasis

2016-05-01

Charge carrier transport in organic semiconductors is dominated by positional and energetic disorder in Gaussian density of states (GDOS) and is characterized by hopping through localized states. Due to the immobilization of charge carriers in these localized states, significant non-uniform carrier distribution exists, resulting diffusive transport. A simple, nevertheless powerful technique to determine diffusion coefficient D in disordered organic semiconductors has been presented. Diffusion coefficients of charge carriers in two technologically important organic molecular semiconductors, Pentacene and copper phthalocyanine (CuPc) have been measured from current-voltage (J-V) characteristics of Al/Pentacene/Au and Al/CuPc/Au based Schottky diodes. Ideality factor g and carrier mobility μ have been calculated from the exponential and space charge limited region respectively of J-V characteristics. Classical Einstein relation is not valid in organic semiconductors due to energetic disorders in DOS. Using generalized Einstein relation, diffusion coefficients have been obtained to be 1.31×10-6 and 1.73×10-7 cm2/s for Pentacene and CuPc respectively.

Using RIXS to uncover elementary charge and spin excitations

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

Jia, Chunjing; Wohlfeld, Krzysztof; Wang, Yao

2016-05-13

Despite significant progress in resonant inelastic x-ray scattering (RIXS) experiments on cuprates at the Cu L-edge, a theoretical understanding of the cross section remains incomplete in terms of elementary excitations and the connection to both charge and spin structure factors. Here, we use state-of-the-art, unbiased numerical calculations to study the low-energy excitations probed by RIXS in the Hubbard model, relevant to the cuprates. The results highlight the importance of scattering geometry, in particular, both the incident and scattered x-ray photon polarization, and they demonstrate that on a qualitative level the RIXS spectral shape in the cross-polarized channel approximates that ofmore » the spin dynamical structure factor. Furthermore, in the parallel-polarized channel, the complexity of the RIXS process beyond a simple two-particle response complicates the analysis and demonstrates that approximations and expansions that attempt to relate RIXS to less complex correlation functions cannot reproduce the full diversity of RIXS spectral features.« less

Surface Structure Spread Single Crystals (S4C): Preparation and characterization

NASA Astrophysics Data System (ADS)

de Alwis, A.; Holsclaw, B.; Pushkarev, V. V.; Reinicker, A.; Lawton, T. J.; Blecher, M. E.; Sykes, E. C. H.; Gellman, A. J.

2013-02-01

A set of six spherically curved Cu single crystals referred to as Surface Structure Spread Single Crystals (S4Cs) has been prepared in such a way that their exposed surfaces collectively span all possible crystallographic surface orientations that can be cleaved from the face centered cubic Cu lattice. The method for preparing these S4Cs and for finding the high symmetry pole point is described. Optical profilometry has been used to determine the true shapes of the S4Cs and show that over the majority of the surface, the shape is extremely close to that of a perfect sphere. The local orientations of the surfaces lie within ± 1° of the orientation expected on the basis of the spherical shape; their orientation is as good as that of many commercially prepared single crystals. STM imaging has been used to characterize the atomic level structure of the Cu(111) ± 11°-S4C. This has shown that the average step densities and the average step orientations match those expected based on the spherical shape. In other words, although there is some distribution of step-step spacing and step orientations, there is no evidence of large scale reconstruction or faceting. The Cu S4Cs have local structures based on the ideal termination of the face centered cubic Cu lattice in the direction of termination. The set of Cu S4Cs will serve as the basis for high throughput investigations of structure sensitive surface chemistry on Cu.

The effect of Ti-B on stabilization of Cu-Zn-Al martensite

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

Stipcich, M.; Romero, R.

1998-10-05

The application of shape memory effect in devices requires, in many cases, stable and reliable transformation temperatures. However, as a consequence of diffusional processes, in Cu-based shape memory alloys, reverse transformation temperature significantly rises after aging at temperatures above room temperature. This generally unwanted behavior is usually referred to as the stabilization of martensite. Numerous investigations have been carried out on this subject as reviewed by Ahlers and Chandrasekaran et al. Within the Cu-based alloys the Cu-Zn-Al are claimed to be more prone to stabilization than Cu-Al-Ni on aging. It has been proposed that in the Cu-Zn-Al the stabilization ismore » due to the interchange of Cu and Zn atoms assisted by vacancies, changing, consequently, the long range order inherited from the {beta} phase. In the present work, the authors investigate the stabilization behavior of polycrystalline samples of stress induced Cu-Zn-Al and Cu-Zn-Al-B martensite.« less

Orienting the Microstructure Evolution of Copper Phthalocyanine as an Anode Interlayer in Inverted Polymer Solar Cells for High Performance.

PubMed

Li, Zhiqi; Liu, Chunyu; Zhang, Xinyuan; Li, Shujun; Zhang, Xulin; Guo, Jiaxin; Guo, Wenbin; Zhang, Liu; Ruan, Shengping

2017-09-20

Recent advances in the interfacial modification of inverted-type polymer solar cells (PSCs) have resulted from controlling the surface energy of the cathode-modified layer (TiO 2 or ZnO) to enhance the short-circuit current (J sc ) or optimizing the contact morphology of the cathode (indium tin oxide or fluorine-doped tin oxide) and active layer to increase the fill factor. Herein, we report that the performance enhancement of PSCs is achieved by incorporating a donor macromolecule copper phthalocyanine (CuPc) as an anode modification layer. Using the approach based on orienting the microstructure evolution, uniformly dispersed island-shaped CuPc spot accumulations are built on the top of PTB7:PC 71 BM blend film, leading to an efficient spectral absorption and photogenerated exciton splitting. The best power conversion efficiency of PSCs is increased up to 9.726%. In addition to the enhanced light absorption, the tailored anode energy level alignment and optimized boundary morphology by incorporating the CuPc interlayer boost charge extraction efficiency and suppress the interfacial molecular recombination. These results demonstrate that surface morphology induction through molecular deposition is an effective method to improve the performance of PSCs, which reveals the potential implications of the interlayer between the organic active layer and the electrode buffer layer.

Highly charged swelling mica reduces free and extractable Cu levels in Cu-contaminated soils.

PubMed

Stuckey, Jason W; Neaman, Alexander; Ravella, Ramesh; Komarneni, Sridhar; Martínez, Carmen Enid

2008-12-15

Smelting of copper (Cu) results in the atmospheric deposition of Cu onto surrounding soils. Excess concentrations of Cu in soils can be absorbed by soil biota to toxic levels or leached into the groundwater, threatening the entire ecosystem. A means to restrict Cu mobility and uptake by plants is to remove it from the aqueous phase by applying an adsorptive material. A synthetic clay (highly charged swelling mica) was tested for its ability to decrease the levels of free and 0.1 M KNO3-extractable Cu in 15 surface soils from three different Cu mining areas in central Chile. The soils contained excessive total Cu levels (112-2790 mg Cu (kg soil)(-1)), while extractable Cu ranged from 0.3 to 22.9 mg Cu L(-1). The mica was applied to each soil at rates of 0.1%, 1%, and 2% (w/w). A 2% sodium-montmorillonite treatment and the nonamended soil served as controls. The order of treatment efficacy in reducing extractable Cu and free Cu2+ for low pH soils ( 1% mica > 2% montmorillonite > 0.1% mica. At 120 days, the 2% mica treatment maintained reductions of up to 93% in the free Cu2+ activity and up to 75% in the extractable Cu concentration upon acidification to the original soil pH value. In addition, Cu retention in mica-treated soils was more resistant to acidification than in lime-treated soils. This mica has promise for the remediation of acidic soils with metal contamination at the surface.

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

Wang, Kuaibing, E-mail: wangkb@njau.edu.cn; State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing University, Nanjing 210093; Lv, Bo

Hollow CuO/Co{sub 3}O{sub 4} hybrids, which inherited from its coordination polymer precursor consisting of sheets layer and nanoparticles layer composites, were synthesized and characterized by SEM, EDX, XRD and XPS. To assess its electrochemical capacitive performances, cyclic voltammetry, galvanostatic charging-discharging measurements and A.C. impedance tests were performed successively. The CuO/Co{sub 3}O{sub 4} hybrids had higher capacitance and lower charge transfer resistance than bare Co{sub 3}O{sub 4} nanostructures, revealing that it provided a protection layer and produced a synergistic effect due to the existence of CuO layer. The distinct synergistic effect could be further confirmed by endurance cycling tests. The capacitancemore » of the CuO/Co{sub 3}O{sub 4} hybrids was 111% retained after 500 cycles at a charging rate of 1.0 A g{sup −1} and remained an intense growth trend after 2000 cycles at scan rate of 200 mV s{sup −1}. - Graphical abstract: Hollow CuO/Co{sub 3}O{sub 4} hybrids are synthesized and display a peculiar synergetic effect on the resulting performances, which can further be evaluated and confirmed by series of electrochemical measurements. - Highlights: • Hollow CuO/Co{sub 3}O{sub 4} hybrids are synthesized from bimetallic-Schiff base polymer precursors. • The capacitance of the CuO/Co{sub 3}O{sub 4} hybrids keeps a growth tendency after 2000 cycles. • A synergetic effect is found for the hybrids in electrochemical energy storage process.« less

2009 Insensitive Munitions and Energetic Materials Technology Symposium

DTIC Science & Technology

2009-05-14

Multilayer Structure 1D STIMULI Flat end rod Round end rod Flat cookie -cutter Spherical fragment Simple shaped charge jet Real shaped charge jet Thin plate... cookie -cutter Spherical fragment Simple shaped charge jet Real shaped charge jet Thin plate Constant Temperature Rising Temperature Multilayer...Propellants  Plasticizer mixed into the Propellant - Dough NO SURFACE COATING Formulation Impetus (J/g) Flame Temp (K) Mw (g/mole) A

Preparation of Advanced CuO Nanowires/Functionalized Graphene Composite Anode Material for Lithium Ion Batteries

PubMed Central

Zhang, Jin; Wang, Beibei; Zhou, Jiachen; Xia, Ruoyu; Chu, Yingli; Huang, Jia

2017-01-01

The copper oxide (CuO) nanowires/functionalized graphene (f-graphene) composite material was successfully composed by a one-pot synthesis method. The f-graphene synthesized through the Birch reduction chemistry method was modified with functional group “–(CH2)5COOH”, and the CuO nanowires (NWs) were well dispersed in the f-graphene sheets. When used as anode materials in lithium-ion batteries, the composite exhibited good cyclic stability and decent specific capacity of 677 mA·h·g−1 after 50 cycles. CuO NWs can enhance the lithium-ion storage of the composites while the f-graphene effectively resists the volume expansion of the CuO NWs during the galvanostatic charge/discharge cyclic process, and provide a conductive paths for charge transportation. The good electrochemical performance of the synthesized CuO/f-graphene composite suggests great potential of the composite materials for lithium-ion batteries anodes. PMID:28772432

Photochemistry of copper(II) complexes with macrocyclic amine ligands

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

Muralidharan, S.; Ferraudi, G.

1981-07-01

The photochemical properties of Cu(dl-Me/sub 6/(14)aneN/sub 4/)/sup 2 +/ and Cu(rac-Me/sub 6/(14)aneN/sub 4/)/sup 2 +/ in the presence and absence of axially coordinated ligands have been investigated by continuous and flash irradiations. Flash photolysis of the complexes in deaerated aqueous solutions revealed the presence of copper-ligand radical complexes with closed- and open-cycle ligands. Flash photolysis of methanolic solutions of the complexes, in the presence of halides and pseudohalides, shows Cu(III) macrocyclic intermediates. The experimental observations can be explained in terms of two primary photoprocesses with origins in distinctive charge transfer to metal states. These states have been assigned as aminomore » to copper(II) charge-transfer state and acido to copper(II) charge-transfer state.« less

Self-doping processes between planes and chains in the metal-to-superconductor transition of YBa2Cu3O6.9.

PubMed

Magnuson, M; Schmitt, T; Strocov, V N; Schlappa, J; Kalabukhov, A S; Duda, L-C

2014-11-12

The interplay between the quasi 1-dimensional CuO-chains and the 2-dimensional CuO2 planes of YBa(2)Cu(3)O(6+x) (YBCO) has been in focus for a long time. Although the CuO-chains are known to be important as charge reservoirs that enable superconductivity for a range of oxygen doping levels in YBCO, the understanding of the dynamics of its temperature-driven metal-superconductor transition (MST) remains a challenge. We present a combined study using x-ray absorption spectroscopy and resonant inelastic x-ray scattering (RIXS) revealing how a reconstruction of the apical O(4)-derived interplanar orbitals during the MST of optimally doped YBCO leads to substantial hole-transfer from the chains into the planes, i.e. self-doping. Our ionic model calculations show that localized divalent charge-transfer configurations are expected to be abundant in the chains of YBCO. While these indeed appear in the RIXS spectra from YBCO in the normal, metallic, state, they are largely suppressed in the superconducting state and, instead, signatures of Cu trivalent charge-transfer configurations in the planes become enhanced. In the quest for understanding the fundamental mechanism for high-Tc-superconductivity (HTSC) in perovskite cuprate materials, the observation of such an interplanar self-doping process in YBCO opens a unique novel channel for studying the dynamics of HTSC.

Equilibrium charge state distributions of Ni, Co, and Cu beams in molybdenum foil at 2 MeV/u

NASA Astrophysics Data System (ADS)

Gastis, Panagiotis; Perdikakis, George; Robertson, Daniel; Bauder, Will; Skulski, Michael; Collon, Phillipe; Anderson, Tyler; Ostdiek, Karen; Aprahamian, Ani; Lu, Wenting; Almus, Robert

2015-10-01

The charge states of heavy-ions are important for the study of nuclear reactions in inverse kinematics when electromagnetic recoil mass spectrometers are used. The passage of recoil products through a material, like the windows of gas cells or charge state boosters, results a charge state distribution (CSD) in the exit. This distribution must be known for the extraction of any cross section since only few charge-state can be transmitted through a magnetic separator separator for a given setting. The calculation of CSDs for heavy ions is challenging. Currently we rely on semi-empirical models with unknown accuracy for ion/target combinations in the Z > 20 region. In the present study were measured the CSDs of the stable 60Ni, 59Co, and 63Cu beams while passing through a 1 μm molybdenum foil. The beam energies were 1.84 MeV/u, 2.09 MeV/u, and 2.11 MeV/u for the 60Ni, 59Co, and 63Cu respectively. The results of this study mainly check the accuracy of the semi-empirical models used by the program LISE++, on calculating CSDs for ion/target combinations of Z > 20. In addition, other empirical models on calculating mean charge states were compared and checked.

Production of Spin Polarized 58Cu and its Magnetic Moment

NASA Astrophysics Data System (ADS)

Mihara, Mototsugu; Ishibashi, Yoko; Abe, Yasushi; Kamisho, Yasuto; Morita, Yusuke; Ohno, Junichi; Tanaka, Masaomi; Shinozaki, Shinichi; Kanbe, Ryosuke; Fukuda, Mitsunori; Matsuta, Kensaku; Ozawa, Akira; Nagae, Daisuke; Inaba, Seiki; Okada, Shunsuke; Saito, Yuta; Ueno, Hideki; Yamada, Kazunari; Izumikawa, Takuji; Ohtsubo, Takashi; Momota, Sadao; Nishimura, Daiki; Suzuki, Takeshi; Yamaguchi, Takayuki; Kobayashi, Yoshio; Imamura, Kei; Yang, Xiaofei; Nagatomo, Takashi; Minamisono, Tadanori; Takechi, Maya; Ogura, Masako; Matsukawa, Kazuhito; Shirai, Koun; Fujimura, Takumi

Spin polarization of short-lived β emitter 58Cu was generated through the charge exchange reaction of 58Ni on a Be target at 63 MeV/u and the β-NQR spectrum of 58Cu in Si was measured at 15 K. As a result, the 58Cu magnetic dipole moment μ [58Cu] was determined to be | μ [{}58Cu] | = (0.58 ± 0.01)μ N, which is in agreement with the recent result using collinear laser spectroscopy.

Apport de la microscopie a effet tunnel a la caracterisation d'interfaces molecule-metal a fort transfert de charge

NASA Astrophysics Data System (ADS)

Bedwani, Stephane

To assess the importance of charge-transfer on the interface properties, we studied the interaction of the tetracyanoethylene (TCNE) molecule with various copper surfaces. TCNE, a highly electrophilic molecule, appears as an ideal candidate to study the influence of high charge-transfer on the electronic and structural properties of molecule-surface interfaces. Indeed, various TCNE-transition metal complexes exhibit magnetism at room temperature, which is in agreement with a very significant change of the residual charge on the TCNE molecule. The adsorption of TCNE molecules on Cu(100) and Cu(111) surfaces was studied by scanning tunneling microscopy (STM) and by density functional theory (DFT) calculations with a local density approximation (LDA). DFT-LDA calculations were performed to determine the geometric and electronic structure of the studied interfaces. Mulliken analysis was used to evaluate the partial net charge on the adsorbed species. The density of states (DOS) diagrams provided informations on the nature of the frontier orbitals involved in the charge-transfer at molecule-metal interfaces. To validate the theoretical observations, a comparative study was conducted between our simulated STM images and experimental STM images provided by our collaborators. The theoretical STM images were obtained with the SPAGS-STM software using the Landauer-Buttiker formalism with a semi-empirical Hamiltonian based on the extended Huckel theory (EHT) and parameterized using DFT calculations. During the development of the SPAGS-STM software, we have created a discretization module allowing rapid generation of STM images. This module is based on an adaptive Delaunay meshing scheme to minimize the amount of tunneling current to be computed. The general idea consists into refining the mesh, and therefore the calculations, near large contrast zones rather than over the entire image. The adapted mesh provides an STM image resolution equivalent to that obtained with a conventional Cartesian grid but with a significantly smaller number of calculated pixels. This module is independent of the solver used to compute the tunneling current and can be transposed to different imaging techniques. Our work on the adsorption of TCNE molecules on Cu(100) surfaces revealed that the molecules assemble into a 1D chain, thereby buckling excessively a few Cu atoms from the surface. The large deformations observed at the molecule-metal interface show that the Cu atoms close to the TCNE nitrile groups assist the molecular assembly and show a distinct behavior compared with other Cu atoms. A strong charge-transfer is observed at the interface leading to an almost complete occupation of the state ascribed to the lowest unoccupied molecular orbital (LUMO) of TCNE in gas phase. In addition, a back-donation of charge from the molecule to the metal via the states associated with the highest occupied molecular orbitals (HOMO) of TCNE in gas phase may be seen. The magnitude of the charge-transfer between a TCNE molecule and Cu atoms is of the same order on the Cu(111) surface but causes much less buckling than that on the Cu(100) surface. However, experimental STM images of single TCNE molecules adsorbed on Cu(111) surfaces reveal a surprising electronic multistability. In addition, scanning tunneling spectroscopy (STS) reveals that one of these states has a magnetic nature and shows a Kondo resonance. STM simulations identified the source of two non-magnetic states. DFT-LDA calculations were able to ascribe the magnetic state to the partial occupation of a state corresponding to the LUMO+2 of TCNE. Moreover, the calculations showed that additional molecular deformations to those of TCNE in adsorbed phase, such the elongation of the C=C central bond and the bend of nitrile groups toward the surface, favor this charge-transfer to the LUMO+2. This suggested the presence of a Kondo state through the vibrational excitation of the stretching mode of the C=C central bond. The main results of this thesis led to the conclusion that strong charge-transfer between adsorbed molecules on a metallic surface may induce significant buckling of the surface. This surface reconstruction mechanism that involves a bidirectional charge-transfer between the species results into a partial net charge over the molecule. This mechanism is involved in the supramolecular self-assembly process that appears similar to a coordination network. Moreover, the adsorbed molecule presents some important geometric distortions that alter its electronic structure. Additional distortions on the adsorbed molecule induced by some molecular vibration modes seem to explain a stable magnetic state that can be switch on or off by an electrical impulse. (Abstract shortened by UMI.)

Nonintrinsic origin of the colossal dielectric constants in Ca Cu3 Ti4 O12

NASA Astrophysics Data System (ADS)

Lunkenheimer, P.; Fichtl, R.; Ebbinghaus, S. G.; Loidl, A.

2004-11-01

The dielectric properties of CaCu3Ti4O12 , a material showing colossal values of the dielectric constant, were investigated over a broad temperature and frequency range extending up to 1.3GHz . A detailed equivalent-circuit analysis of the results and two crucial experiments, employing different types of contacts and varying the sample thickness were performed. The results provide clear evidence that the apparently high values of the dielectric constant in CaCu3Ti4O12 are nonintrinsic and due to electrode polarization effects. The intrinsic properties of CaCu3Ti4O12 are characterized by charge transport via hopping of localized charge carriers and a relatively high dielectric constant of the order of 100.

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

Dearling, Jason L. J.; Smith, Suzanne V.; Paterson, Brett M.

The development of biomolecules as imaging probes requires radiolabeling methods that do not significantly influence their biodistribution. Sarcophagine (Sar) chelators form extremely stable complexes with copper, and are therefore a promising option for labeling proteins with ⁶⁴Cu. However, initial studies using the first-generation sarcophagine bifunctional chelator SarAr to label the engineered antibody fragment ch14.18-ΔC H2 (MW 120 kDa) with ⁶⁴Cu showed high tracer retention in the kidneys,(>38% injected dose per gram (ID/g) 48 h post-injection), presumably because the high local positive charge on the Cu II-SarAr moiety resulted in increased binding of the labeled protein to the negatively charged basalmore » cells of the glomerulus. To test this hypothesis, ch14.18-ΔC H2 was conjugated with a series of Sar derivatives of decreasing positive charge and three commonly used macrocyclic polyaza polycarboxylate (PAC) BFCs. The immunoconjugates were labeled with ⁶⁴Cu and injected into mice, and PET/CT images were obtained at 24 and 48 h post injection (p.i.). At 48 h p.i., ex vivo biodistribution was carried out. In addition, to demonstrate the potential of metastasis detection using ⁶⁴Cu-labeled ch14.18-ΔC H2, a preclinical imaging study of intrahepatic neuroblastoma tumors was performed carried out. Reducing the positive charge on the Sar chelators decreased kidney uptake of Cu-labeled ch14.18-ΔC H2 by more than 6-fold, from >45 ID/g to <6% ID/g, while the uptake in most other tissues, including liver, was relatively unchanged. However, despite this dramatic decrease, the renal uptake of the PAC BFCs was generally lower than that of the Sar derivatives, as was the liver uptake. Uptake of ⁶⁴Cu-labeled ch14.18-ΔC H2 in neuroblastoma hepatic metastases was detected using PET.« less

Modification of structural disorder by hydrostatic pressure in the superconducting cuprate YBa 2 Cu 3 O 6.73

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

Huang, H.; Jang, H.; Fujita, M.

Here, compelling efforts to improve the critical temperature (T c) of superconductors have been made through high-pressure application. Understanding the underlying mechanism behind such improvements is critically important; however, much remains unclear. Here we studied ortho-III YBa 2Cu 3O 6.73 (YBCO) using x-ray scattering under hydrostatic pressure (HP) up to ~6.0GPa. We found the reinforced oxygen order of YBCO under HP, revealing an oxygen rearrangement in the Cu-O layer, which evidently shows the charge-transfer phenomenon between the CuO 2 plane and Cu-O layer. Concurrently, we also observed no disorder-pinned charge-density-wave signature in CuO 2 plane under HP. This indicates thatmore » the oxygen rearrangement modifies the quenched disorder state in the CuO 2 plane. Using these results, we appropriately explain why pressure condition can achieve higher T c compared with the optimal T c under ambient pressure in YBa 2Cu 3O 6+x. As an implication of these results, finally we have discussed that the change in disorder could make it easier for YBa 2Cu 3O 6+x to undergo a transition to the nematic order under an external magnetic field.« less

Modification of structural disorder by hydrostatic pressure in the superconducting cuprate YBa2Cu3O6.73

NASA Astrophysics Data System (ADS)

Huang, H.; Jang, H.; Fujita, M.; Nishizaki, T.; Lin, Y.; Wang, J.; Ying, J.; Smith, J. S.; Kenney-Benson, C.; Shen, G.; Mao, W. L.; Kao, C.-C.; Liu, Y.-J.; Lee, J.-S.

2018-05-01

Compelling efforts to improve the critical temperature (Tc) of superconductors have been made through high-pressure application. Understanding the underlying mechanism behind such improvements is critically important; however, much remains unclear. Here we studied ortho-III YBa2Cu3O6.73 (YBCO) using x-ray scattering under hydrostatic pressure (HP) up to ˜6.0 GPa . We found the reinforced oxygen order of YBCO under HP, revealing an oxygen rearrangement in the Cu-O layer, which evidently shows the charge-transfer phenomenon between the Cu O2 plane and Cu-O layer. Concurrently, we also observed no disorder-pinned charge-density-wave signature in Cu O2 plane under HP. This indicates that the oxygen rearrangement modifies the quenched disorder state in the Cu O2 plane. Using these results, we appropriately explain why pressure condition can achieve higher Tc compared with the optimal Tc under ambient pressure in YBa2Cu3O6 +x . As an implication of these results, finally we have discussed that the change in disorder could make it easier for YBa2Cu3O6 +x to undergo a transition to the nematic order under an external magnetic field.

Modification of structural disorder by hydrostatic pressure in the superconducting cuprate YBa 2 Cu 3 O 6.73

DOE PAGES

Huang, H.; Jang, H.; Fujita, M.; ...

2018-05-09

Here, compelling efforts to improve the critical temperature (T c) of superconductors have been made through high-pressure application. Understanding the underlying mechanism behind such improvements is critically important; however, much remains unclear. Here we studied ortho-III YBa 2Cu 3O 6.73 (YBCO) using x-ray scattering under hydrostatic pressure (HP) up to ~6.0GPa. We found the reinforced oxygen order of YBCO under HP, revealing an oxygen rearrangement in the Cu-O layer, which evidently shows the charge-transfer phenomenon between the CuO 2 plane and Cu-O layer. Concurrently, we also observed no disorder-pinned charge-density-wave signature in CuO 2 plane under HP. This indicates thatmore » the oxygen rearrangement modifies the quenched disorder state in the CuO 2 plane. Using these results, we appropriately explain why pressure condition can achieve higher T c compared with the optimal T c under ambient pressure in YBa 2Cu 3O 6+x. As an implication of these results, finally we have discussed that the change in disorder could make it easier for YBa 2Cu 3O 6+x to undergo a transition to the nematic order under an external magnetic field.« less

Copper(ii) oxide nanoparticles penetrate into HepG2 cells, exert cytotoxicity via oxidative stress and induce pro-inflammatory response

NASA Astrophysics Data System (ADS)

Piret, Jean-Pascal; Jacques, Diane; Audinot, Jean-Nicolas; Mejia, Jorge; Boilan, Emmanuelle; Noël, Florence; Fransolet, Maude; Demazy, Catherine; Lucas, Stéphane; Saout, Christelle; Toussaint, Olivier

2012-10-01

The potential toxic effects of two types of copper(ii) oxide (CuO) nanoparticles (NPs) with different specific surface areas, different shapes (rod or spheric), different sizes as raw materials and similar hydrodynamic diameter in suspension were studied on human hepatocarcinoma HepG2 cells. Both CuO NPs were shown to be able to enter into HepG2 cells and induce cellular toxicity by generating reactive oxygen species. CuO NPs increased the abundance of several transcripts coding for pro-inflammatory interleukins and chemokines. Transcriptomic data, siRNA knockdown and DNA binding activities suggested that Nrf2, NF-κB and AP-1 were implicated in the response of HepG2 cells to CuO NPs. CuO NP incubation also induced activation of MAPK pathways, ERKs and JNK/SAPK, playing a major role in the activation of AP-1. In addition, cytotoxicity, inflammatory and antioxidative responses and activation of intracellular transduction pathways induced by rod-shaped CuO NPs were more important than spherical CuO NPs. Measurement of Cu2+ released in cell culture medium suggested that Cu2+ cations released from CuO NPs were involved only to a small extent in the toxicity induced by these NPs on HepG2 cells.The potential toxic effects of two types of copper(ii) oxide (CuO) nanoparticles (NPs) with different specific surface areas, different shapes (rod or spheric), different sizes as raw materials and similar hydrodynamic diameter in suspension were studied on human hepatocarcinoma HepG2 cells. Both CuO NPs were shown to be able to enter into HepG2 cells and induce cellular toxicity by generating reactive oxygen species. CuO NPs increased the abundance of several transcripts coding for pro-inflammatory interleukins and chemokines. Transcriptomic data, siRNA knockdown and DNA binding activities suggested that Nrf2, NF-κB and AP-1 were implicated in the response of HepG2 cells to CuO NPs. CuO NP incubation also induced activation of MAPK pathways, ERKs and JNK/SAPK, playing a major role in the activation of AP-1. In addition, cytotoxicity, inflammatory and antioxidative responses and activation of intracellular transduction pathways induced by rod-shaped CuO NPs were more important than spherical CuO NPs. Measurement of Cu2+ released in cell culture medium suggested that Cu2+ cations released from CuO NPs were involved only to a small extent in the toxicity induced by these NPs on HepG2 cells. Electronic supplementary information (ESI) available: Additional tables and figures supporting the information presented in the manuscript. See DOI: 10.1039/c2nr31785k

Copper-catalyzed azide alkyne cycloaddition polymer networks

NASA Astrophysics Data System (ADS)

Alzahrani, Abeer Ahmed

The click reaction concept, introduced in 2001, has since spurred the rapid development and reexamination of efficient, high yield reactions which proceed rapidly under mild conditions. Prior to the discovery of facile copper catalysis in 2002, the thermally activated azide-alkyne or Huisgen cycloaddition reaction was largely ignored following its discovery in large part due to its slow kinetics, requirement for elevated temperature and limited selectivity. Now, arguably, the most prolific and capable of the click reactions, the copper-catalyzed azide alkyne cycloaddition (CuAAC) reaction is extremely efficient and affords exquisite control of the reaction. The orthogonally and chemoselectivity of this reaction enable its wide utility across varied scientific fields. Despite numerous inherent advantages and widespread use for small molecule synthesis and solution-based polymer chemistry, it has only recently and rarely been utilized to form polymer networks. This work focuses on the synthesis, mechanisms, and unique attributes of the CuAAC reaction for the fabrication of functional polymer networks. The photo-reduction of a series of copper(II)/amine complexes via ligand metal charge transfer was examined to determine their relative efficiency and selectivity in catalyzing the CuAAC reaction. The aliphatic amine ligands were used as an electron transfer species to reduce Cu(II) upon irradiation with 365 nm light while also functioning as an accelerating agent and as protecting ligands for the Cu(I) that was formed. Among the aliphatic amines studied, tertiary amines such as triethylamine (TEA), tetramethyldiamine (TMDA), N,N,N',N",N"-pentamethyldiethylenetriamine (PMDTA), and hexamethylenetetramine (HMTETA) were found to be the most effective. The reaction kinetics were accelerated by increasing the PMDETA : Cu(II) ratio with a ratio of ligand to Cu(II) of 4:1 yielding the maximum conversion in the shortest time. The sequential and orthogonal nature of the photo-CuAAC reaction and a chain-growth acrylate homopolymerization were demonstrated and used to form branched polymer structures. A bulk, organic soluble initiation system consisting of a Cu(II) salt and a primary amine was also examined in both model reactions and in bulk polymerizations. The system was shown to be highly efficient, leading to nearly complete CuAAC polymerization at ambient temperature. Increasing the ratio of amine to copper from 1 to 4 increases the CuAAC reaction rate significantly from 4 mM/min for 1:1 ratio of Cu(II):hexyalmine to 14mM/min for 1:4 ratio. The concentration dependence of the amine on the reaction rate enables the polymerization rate to be controlled simply by manipulating the hexylamine concentration. Sequential thiol--acrylate and photo-CuAAC click reactions were utilized to form two-stage reactive polymer networks capable of generating wrinkles in a facile manner. The click thiol-Michael addition reaction was utilized to form a cross-linked polymer with residual, reactive alkyne sites that remained tethered throughout the network. The latent, unreacted alkyne sites are subsequently reacted with diazide monomers via a photoinduced Cu(I)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction to increase the cross-link density. Increased cross-linking raised the modulus and glass transition temperature from 1.6 MPa and 2 °C after the thiol-acrylate reaction to 4.4 MPa and 22 °C after the CuAAC reaction, respectively. The double click reaction approach led to micro-wrinkles with well-controlled wavelength and amplitude of 8.50 +/- 1.6 and 1.4 μm, respectively, for a polymer with a 1280 μm total film thickness. Additionally, this approach further enables spatial selectivity of wrinkle formation by photo-patterning. The CuAAC-based polymerization was also used to design smart, responsive porous materials from well-defined CuAAC networks, which possesses a high glass transition temperature (Tg= 115°C) due to the formation of the triazole linkages. The toughness, recovery, fixity, and shape memory attributes of this material were examined. The unique recovery behavior of the porous CuAAC material is characterized by its ability to recover plastic deformation upon heating. The tough and stiff nature of the glassy CuAAC polymer networks translates into desirable high compressive strain shape memory foams. The CuAAC foam exhibited excellent shape-memory behavior and was able to recover through each of five successive cycles of 80% compression at ambient temperature, presenting a significant volume change and resistance to fracture. In addition, the glassy CuAAC foam was able to withstand more than 10 cycles of compression to 50% strain and subsequent recovery at ambient temperature, indicative of ductile behavior in the glassy state.

Multishelled Si@Cu Microparticles Supported on 3D Cu Current Collectors for Stable and Binder-free Anodes of Lithium-Ion Batteries.

PubMed

Zhang, Zailei; Wang, Zhong Lin; Lu, Xianmao

2018-04-24

Silicon has proved to be a promising anode material of high-specific capacity for the next-generation lithium ion batteries (LIBs). However, during repeated discharge/charge cycles, Si-based electrodes, especially those in microscale size, pulverize and lose electrical contact with the current collectors due to large volume expansion. Here, we introduce a general method to synthesize Cu@M (M = Si, Al, C, SiO 2 , Si 3 N 4 , Ag, Ti, Ta, SnIn 2 O 5 , Au, V, Nb, W, Mg, Fe, Ni, Sn, ZnO, TiN, Al 2 O 3 , HfO 2 , and TiO 2 ) core-shell nanowire arrays on Cu substrates. The resulting Cu@Si nanowire arrays were employed as LIB anodes that can be reused via HCl etching and H 2 -reduction. Multishelled Cu@Si@Cu microparticles supported on 3D Cu current collectors were further prepared as stable and binder-free LIB anodes. This 3D Cu@Si@Cu structure allows the interior conductive Cu network to effectively accommodate the volume expansion of the electrode and facilitates the contact between the Cu@Si@Cu particles and the current collectors during the repeated insertion/extraction of lithium ions. As a result, the 3D Cu@Si@Cu microparticles at a high Si-loading of 1.08 mg/cm 2 showed a capacity retention of 81% after 200 cycles. In addition, charging tests of 3D Cu@Si@Cu-LiFePO 4 full cells by a triboelectric nanogenerator with a pulsed current demonstrated that LIBs with silicon anodes can effectively store energy delivered by mechanical energy harvesters.

Profiling charge complementarity and selectivity for binding at the protein surface.

PubMed

Sulea, Traian; Purisima, Enrico O

2003-05-01

A novel analysis and representation of the protein surface in terms of electrostatic binding complementarity and selectivity is presented. The charge optimization methodology is applied in a probe-based approach that simulates the binding process to the target protein. The molecular surface is color coded according to calculated optimal charge or according to charge selectivity, i.e., the binding cost of deviating from the optimal charge. The optimal charge profile depends on both the protein shape and charge distribution whereas the charge selectivity profile depends only on protein shape. High selectivity is concentrated in well-shaped concave pockets, whereas solvent-exposed convex regions are not charge selective. This suggests the synergy of charge and shape selectivity hot spots toward molecular selection and recognition, as well as the asymmetry of charge selectivity at the binding interface of biomolecular systems. The charge complementarity and selectivity profiles map relevant electrostatic properties in a readily interpretable way and encode information that is quite different from that visualized in the standard electrostatic potential map of unbound proteins.

Relationship between morphologies and orientations of Cu{sub 6}Sn{sub 5} grains in Sn3.0Ag0.5Cu solder joints on different Cu pads

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

Tian, Yanhong, E-mail: tianyh@hit.edu.cn; Zhang, Rui; Hang, Chunjin

2014-02-15

The morphologies and orientations of Cu{sub 6}Sn{sub 5} intermetallic compounds in the Sn3.0Ag0.5Cu solder joints both on polycrystalline and single crystal Cu pads under different peak reflow temperatures and times above liquids were investigated. The relationship between Cu{sub 6}Sn{sub 5} grain orientations and morphologies was clarified. At the interface of Sn3.0Ag0.5Cu/polycrystalline Cu pad, scalloped Cu{sub 6}Sn{sub 5} intermetallic compounds formed at 250 °C and roof shape Cu{sub 6}Sn{sub 5} formed at 300 °C. Both scalloped Cu{sub 6}Sn{sub 5} and roof shape Cu{sub 6}Sn{sub 5} had a preferred orientation of (0001) plane being parallel to polycrystalline Cu pad surface. Besides, themore » percentage of large angle grain boundaries increased as the peak reflow temperature rose. At the interface of Sn3.0Ag0.5Cu/(111) single crystal Cu pad, the Cu{sub 6}Sn{sub 5} intermetallic compounds were mainly scallop-type at 250 °C and were prism type at 300 °C. The prismatic Cu{sub 6}Sn{sub 5} grains grew along the three preferred directions with the inter-angles of 60° on (111) single crystal Cu pad while along two perpendicular directions on (100) single crystal Cu pad. The orientation relationship between Cu{sub 6}Sn{sub 5} grains and the single crystal Cu pads was investigated by electron backscatter diffraction technology. In addition, two types of hollowed Cu{sub 6}Sn{sub 5} intermetallic compounds were found inside the joints of polycrystalline Cu pads. The long hexagonal Cu{sub 6}Sn{sub 5} strips were observed in the joints reflowing at 250 °C while the hollowed Cu{sub 6}Sn{sub 5} strips with the ‘▪’ shape cross-sections appeared at 300 °C, which was attributed to the different grain growth rates of different Cu{sub 6}Sn{sub 5} crystal faces. - Highlights: • The orientation of interfacial Cu{sub 6}Sn{sub 5} grains was obtained by EBSD technology. • Two types of hollowed Cu{sub 6}Sn{sub 5} strips were found at different temperatures. • The formation mechanism of hollowed Cu{sub 6}Sn{sub 5} was elaborated based on Bravais law. • The relationship between Cu{sub 6}Sn{sub 5} grain orientations and morphologies was clarified.« less

New Three-Dimensional Porous Electrode Concept: Vertically-Aligned Carbon Nanotubes Directly Grown on Embroidered Copper Structures.

PubMed

Aguiló-Aguayo, Noemí; Amade, Roger; Hussain, Shahzad; Bertran, Enric; Bechtold, Thomas

2017-12-11

New three-dimensional (3D) porous electrode concepts are required to overcome limitations in Li-ion batteries in terms of morphology (e.g., shapes, dimensions), mechanical stability (e.g., flexibility, high electroactive mass loadings), and electrochemical performance (e.g., low volumetric energy densities and rate capabilities). Here a new electrode concept is introduced based on the direct growth of vertically-aligned carbon nanotubes (VA-CNTs) on embroidered Cu current collectors. The direct growth of VA-CNTs was achieved by plasma-enhanced chemical vapor deposition (PECVD), and there was no application of any post-treatment or cleaning procedure. The electrochemical behavior of the as-grown VA-CNTs was analyzed by charge/discharge cycles at different specific currents and with electrochemical impedance spectroscopy (EIS) measurements. The results were compared with values found in the literature. The as-grown VA-CNTs exhibit higher specific capacities than graphite and pristine VA-CNTs found in the literature. This together with the possibilities that the Cu embroidered structures offer in terms of specific surface area, total surface area, and designs provide a breakthrough in new 3D electrode concepts.

Homogeneous (Cu, Ni)6Sn5 intermetallic compound joints rapidly formed in asymmetrical Ni/Sn/Cu system using ultrasound-induced transient liquid phase soldering process.

PubMed

Li, Z L; Dong, H J; Song, X G; Zhao, H Y; Tian, H; Liu, J H; Feng, J C; Yan, J C

2018-04-01

Homogeneous (Cu, Ni) 6 Sn 5 intermetallic compound (IMC) joints were rapidly formed in asymmetrical Ni/Sn/Cu system by an ultrasound-induced transient liquid phase (TLP) soldering process. In the traditional TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system consisted of major (Cu, Ni) 6 Sn 5 and minor Cu 3 Sn IMCs, and the grain morphology of (Cu, Ni) 6 Sn 5 IMCs subsequently exhibited fine rounded, needlelike and coarse rounded shapes from the Ni side to the Cu side, which was highly in accordance with the Ni concentration gradient across the joints. However, in the ultrasound-induced TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system only consisted of the (Cu, Ni) 6 Sn 5 IMCs which exhibited an uniform grain morphology of rounded shape with a remarkably narrowed Ni concentration gradient. The ultrasound-induced homogeneous intermetallic joints exhibited higher shear strength (61.6 MPa) than the traditional heterogeneous intermetallic joints (49.8 MPa). Copyright © 2017 Elsevier B.V. All rights reserved.

Charge-transfer mechanisms for high-T/sub c/ superconductivity

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

Jarrell, M.; Krishnamurthy, H.R.; Cox, D.L.

1988-09-01

We report results from a Bardeen-Cooper-Schrieffer (BCS) analysis of the Weber d-d exciton model of the high-temperature superconductors. The pairing between oxygen holes is mediated by localized intrasite charge-transfer excitations between the d/sub x//sub <2/-y/sup =/ and the d/sub 3//sub z//sub <2/-r/sup =/ Cu orbitals. For reasonable oxygen on-site Coulomb energies, we find s-wave superconductivity for low filling fraction (<0.44), and d-wave superconductivity for larger filling. The same symmetry analysis applies to a localized version of the intersite Cu-O charge-transfer model of Varma, Schmitt-Rink, and Abrahams. We explore the limitations imposed by the Weber model symmetry, and interpret optical datamore » based upon the d-d exciton picture. We briefly discuss the suppression of antiferromagnetism of the Cu moments by the Ruderman-Kittel-Kasuya-Yoshida interaction in the metallic limit.« less

A low-ignition energy, SCB, thermite igniter

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

Bickes, R.W. Jr.; Grubelich, M.C.; Wackerbarth, D.E.

1996-06-01

The authors describe threshold ignition studies for semiconductor bridge, SCB, ignition of aluminum/copper oxide (Al/CuO) thermite as a function of the capacitor discharge unit (CDU) firing set discharge capacitance, the charge holder material and the morphology of the CuO. All of the tests were carried out with the devices cooled to 0 F ({minus}18 C). They compared ignition thresholds using a brass charge holder and a G10 charge holder; G10 is a non-conducting, fiber-glass-epoxy composite material. They determined that at 50 V on the discharge capacitor, the thresholds were 30.1 {micro}F and 2.0 {micro}F respectively. The tests revealed that differentmore » CuO morphologies affected the function time (interval between start of the firing set current and the output of the thermite device) but did not significantly affect the threshold sensitivity.« less

Lexan Linear Shaped Charge Holder with Magnets and Backing Plate

NASA Technical Reports Server (NTRS)

Maples, Matthew W.; Dutton, Maureen L.; Hacker, Scott C.; Dean, Richard J.; Kidd, Nicholas; Long, Chris; Hicks, Robert C.

2013-01-01

A method was developed for cutting a fabric structural member in an inflatable module, without damaging the internal structure of the module, using linear shaped charge. Lexan and magnets are used in a charge holder to precisely position the linear shaped charge over the desired cut area. Two types of charge holders have been designed, each with its own backing plate. One holder cuts fabric straps in the vertical configuration, and the other charge holder cuts fabric straps in the horizontal configuration.

Superconductivity, phase separation, and charge-transfer instability in the U = infinity limit of the three-band model of the CuO sub 2 planes

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

Grilli, M.; Raimondi, R.; Castellani, C.

1991-07-08

The {ital U}={infinity} limit of the three-band Hubbard model with nearest-neighbor repulsion {ital V} is studied using the slave-boson approach and the large-{ital N} expansion technique to order 1/{ital N}. A charge-transfer instability is found as in weak-coupling theory. The charge-transfer instability is always associated with a diverging compressibility leading to a phase separation. Near the phase-separation, charge-transfer-instability region we find superconducting instabilities in the {ital s}- and {ital d}-wave channel. The requirement for superconductivity is that {ital V} be on the scale of the Cu-O hopping as suggested by Varma, Schmitt-Rink, and Abrahams.

Charge-Dependent Directed Flow in Cu +Au Collisions at √{sN N } =200 GeV

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, X.; Chen, J. H.; 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.; di Ruzza, B.; 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, S.; Gupta, A.; 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, B.; Huang, X.; Huang, H. Z.; Huang, T.; 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. H.; 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, W.; Li, X.; Li, X.; Lin, T.; Lisa, M. A.; Liu, Y.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Luo, S.; Ma, G. L.; Ma, R.; Ma, Y. G.; Ma, L.; 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, A.; Sharma, M. K.; Sharma, B.; Shen, W. Q.; Shi, S. S.; Shi, Z.; 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, Z.; Sun, Y.; Sun, X. M.; Surrow, B.; Svirida, D. N.; Tang, A. H.; Tang, Z.; 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, F.; Wang, J. S.; Wang, Y.; Wang, H.; 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, W.; Xie, G.; Xin, K.; Xu, Q. H.; Xu, Y. F.; Xu, H.; Xu, Z.; Xu, N.; Xu, J.; Yang, C.; Yang, Y.; Yang, S.; Yang, Y.; Yang, Q.; Yang, Y.; Ye, Z.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, J.; Zhang, X. P.; Zhang, S.; Zhang, Y.; Zhang, J. B.; Zhang, Z.; Zhang, S.; Zhang, J.; Zhao, J.; Zhong, C.; Zhou, L.; Zhu, X.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

2017-01-01

We present the first measurement of charge-dependent directed flow in Cu +Au collisions at √{sN N }=200 GeV . The results are presented as a function of the particle transverse momentum and pseudorapidity for different centralities. A finite difference between the directed flow of positive and negative charged particles is observed that qualitatively agrees with the expectations from the effects of the initial strong electric field between two colliding ions with different nuclear charges. The measured difference in directed flow is much smaller than that obtained from the parton-hadron-string-dynamics model, which suggests that most of the electric charges, i.e., quarks and antiquarks, have not yet been created during the lifetime of the strong electric field, which is of the order of, or less than, 1 fm /c .

Cu2O/CuO Bilayered Composite as a High-Efficiency Photocathode for Photoelectrochemical Hydrogen Evolution Reaction

NASA Astrophysics Data System (ADS)

Yang, Yang; Xu, Di; Wu, Qingyong; Diao, Peng

2016-10-01

Solar powered hydrogen evolution reaction (HER) is one of the key reactions in solar-to-chemical energy conversion. It is desirable to develop photocathodic materials that exhibit high activity toward photoelectrochemical (PEC) HER at more positive potentials because a higher potential means a lower overpotential for HER. In this work, the Cu2O/CuO bilayered composites were prepared by a facile method that involved an electrodeposition and a subsequent thermal oxidation. The resulting Cu2O/CuO bilayered composites exhibited a surprisingly high activity and good stability toward PEC HER, expecially at high potentials in alkaline solution. The photocurrent density for HER was 3.15 mA·cm-2 at the potential of 0.40 V vs. RHE, which was one of the two highest reported at the same potential on copper-oxide-based photocathode. The high photoactivity of the bilayered composite was ascribed to the following three advantages of the Cu2O/CuO heterojunction: (1) the broadened light absorption band that made more efficient use of solar energy, (2) the large space-charge-region potential that enabled a high efficiency for electron-hole separation, and (3) the high majority carrier density that ensured a faster charge transportation rate. This work reveals the potential of the Cu2O/CuO bilayered composite as a promising photocathodic material for solar water splitting.

Theory of dynamic spin susceptibility in terms of the t-J-V model: Comparison with neutron scattering data for Pr0.88LaCe0.12CuO4 - x and La2 - x Sr x CuO4

NASA Astrophysics Data System (ADS)

Andreev, A. I.; Eremin, I. M.; Eremin, M. V.

2009-01-01

A formula for the dynamic spin susceptibility is derived in terms of the t-J-V model. This formula makes it possible to explain the main features of recent experiments on neutron scattering in the electron-doped superconductor Pr0.88LaCe0.12CuO4 - x . In particular, the proposed theory reproduces well a V-shaped relief in the frequency behavior of the imaginary part χ″( Q, ω) of the susceptibility of the Pr0.88LaCe0.12CuO4 - x compound in the vicinity of the wave vector Q = (π,π) and the scaling behavior of the position of the maxima in the dependence of the function χ″( Q, ω) T on the quantity ω/ T. The magnetism of the high-temperature superconductors is dual. These materials contain charge carriers, on the one hand, and localized spins in the copper ion sublattice, on the other hand. Both these systems are strongly coupled to each other. The mode of collective oscillations is common. The magnetism of localized spins “freezes” with the appearance of the superconducting gap. The recently revealed double-peak structure of the imaginary part χ″( Q, ω) of the susceptibility in superconductors of the La1.84Sr0.16CuO4 type is explained. The low-frequency absorption peak is located within the superconducting gap and interpreted as a manifestation of the branch of spin excitons, and the high-frequency absorption peak predominantly corresponds to renormalized collective oscillations of localized spins.

Precision Blasting Techniques For Avalanche Control

NASA Astrophysics Data System (ADS)

Powell, Kevin M.

Experimental firings sponsored by the Center For Snow Science at Alta, Utah have demonstrated the potential of a unique prototype shaped charge device designed to stimulate snow pack and ice. These studies, conducted against stable snow pack, demonstrated a fourfold increase in crater volume yield and introduced a novel application of Shock Tube technology to facilitate position control, detonation and dud recovery of manually deployed charges. The extraordinary penetration capability of the shaped charge mechanism has been exploited in many non-military applications to meet a wide range of rapidpiercing and/or cutting requirements. The broader exploitation of the potential of the shaped charge mechanism has nevertheless remained confined to defence based applications. In the studies reported in this paper, the inimitable ability of the shaped charge mechanism to project shock energy, or a liner material, into a highly focussed energetic stream has been applied uniquely to the stimulation of snow pack. Recent research and development work, conducted within the UK, has resulted in the integration of shaped charge technology into a common Avalauncher and hand charge device. The potential of the common charge configuration and spooled Shock Tube fire and control system to improve the safety and cost effectiveness of explosives used in avalanche control operations was successfully demonstrated at Alta in March 2001. Future programmes of study will include focussed shock/blast mechanisms for suspended wire traverse techniques, application of the shaped charge mechanism to helibombing, and the desig n and development of non-fragmenting shaped charge ammunition formilitary artillery gun systems.

Shelf life extension for the lot AAE nozzle severance LSCs

NASA Technical Reports Server (NTRS)

Cook, M.

1990-01-01

Shelf life extension tests for the remaining lot AAE linear shaped charges for redesigned solid rocket motor nozzle aft exit cone severance were completed in the small motor conditioning and firing bay, T-11. Five linear shaped charge test articles were thermally conditioned and detonated, demonstrating proper end-to-end charge propagation. Penetration depth requirements were exceeded. Results indicate that there was no degradation in performance due to aging or the linear shaped charge curving process. It is recommended that the shelf life of the lot AAE nozzle severance linear shaped charges be extended through January 1992.

Photoinduced charge transfer from vacuum-deposited molecules to single-layer transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Osada, Kazuki; Tanaka, Masatoshi; Ohno, Shinya; Suzuki, Takanori

2016-06-01

Variations of photoluminescence (PL) and Raman spectra of single-layer MoS2, MoSe2, WS2, and WSe2 due to the vacuum deposition of C60 or copper phthalocyanine (CuPc) molecules have been investigated. PL spectra are decomposed into two competitive components, an exciton and a charged exciton (trion), depending on carrier density. The variation of PL spectra is interpreted in terms of charge transfer across the interfaces between transition metal dichalcogenides (TMDs) and dopant molecules. We find that deposited C60 molecules inject photoexcited electrons into MoS2, MoSe2, and WS2 or holes into WSe2. CuPc molecules also inject electrons into MoS2, MoSe2, and WS2, while holes are depleted from WSe2 to CuPc. We then propose a band alignment between TMDs and dopant molecules. Peak shifts of Raman spectra and doped carrier density estimated using a three-level model also support the band alignment. We thus demonstrate photoinduced charge transfer from dopant molecules to single-layer TMDs.

AGGREGATION PATHWAYS OF THE AMYLOID β(1–42) PEPTIDE DEPEND ON ITS COLLOIDAL STABILITY AND ORDERED β-SHEET STACKING

PubMed Central

Jiang, Dianlu; Rauda, Iris; Han, Shubo; Chen, Shu; Zhou, Feimeng

2012-01-01

Amyloid β (Aβ) fibrils are present as a major component in senile plaques, the hallmark of Alzheimer’s disease (AD). Diffuse plaques (non-fibrous, loosely packed Aβ aggregates) containing amorphous Aβ aggregates are also formed in brain. This work examines the influence of Cu2+ complexation by Aβ on the aggregation process in the context of charge and structural variations. Changes in the surface charges of Aβ molecules due to Cu2+ binding, measured with a zeta potential measurement device, were correlated with the aggregate morphologies examined by atomic force microscopy. As a result of the charge variation, the “colloid-like” stability of the aggregation intermediates, which is essential to the fibrillation process, is affected. Consequently Cu2+ enhances the amorphous aggregate formation. By monitoring variations in the secondary structures with circular dichroism spectroscopy, a direct transformation from the unstructured conformation to the β-sheet structure was observed for all types of aggregates observed (oligomers, fibrils, and/or amorphous aggregates). Compared to the Aβ aggregation pathway in the absence of Cu2+ and taking other factors affecting Aβ aggregation (i.e., pH and temperature) into account, our investigation indicates that formations of amorphous and fibrous aggregates diverge from the same β-sheet-containing partially folded intermediate. This study suggests that the hydrophilic domain of Aβ also plays a role in the Aβ aggregation process. A kinetic model was proposed to account for the effects of the Cu2+ binding on these two aggregation pathways in terms of charge and structural variations. PMID:22870885

Distinct charge orders in the planes and chains of ortho-III-ordered YBa2Cu3O(6+δ) superconductors identified by resonant elastic x-ray scattering.

PubMed

Achkar, A J; Sutarto, R; Mao, X; He, F; Frano, A; Blanco-Canosa, S; Le Tacon, M; Ghiringhelli, G; Braicovich, L; Minola, M; Sala, M Moretti; Mazzoli, C; Liang, Ruixing; Bonn, D A; Hardy, W N; Keimer, B; Sawatzky, G A; Hawthorn, D G

2012-10-19

Recently, charge density wave (CDW) order in the CuO(2) planes of underdoped YBa(2)Cu(3)O(6+δ) was detected using resonant soft x-ray scattering. An important question remains: is the chain layer responsible for this charge ordering? Here, we explore the energy and polarization dependence of the resonant scattering intensity in a detwinned sample of YBa(2)Cu(3)O(6.75) with ortho-III oxygen ordering in the chain layer. We show that the ortho-III CDW order in the chains is distinct from the CDW order in the planes. The ortho-III structure gives rise to a commensurate superlattice reflection at Q=[0.33 0 L] whose energy and polarization dependence agrees with expectations for oxygen ordering and a spatial modulation of the Cu valence in the chains. Incommensurate peaks at [0.30 0 L] and [0 0.30 L] from the CDW order in the planes are shown to be distinct in Q as well as their temperature, energy, and polarization dependence, and are thus unrelated to the structure of the chain layer. Moreover, the energy dependence of the CDW order in the planes is shown to result from a spatial modulation of energies of the Cu 2p to 3d(x(2)-y(2)) transition, similar to stripe-ordered 214 cuprates.

Ab initio molecular dynamics study of thermite reaction at Al and CuO nano-interfaces at different temperatures

NASA Astrophysics Data System (ADS)

Tang, Cui-Ming; Chen, Xiao-Xu; Cheng, Xin-Lu; Zhang, Chao-Yang; Lu, Zhi-Peng

2018-05-01

The thermite reaction at Al/CuO nano-interfaces is investigated with ab initio molecular dynamics calculations in canonical ensemble at 500 K, 800 K, 1200 K and 1500 K, respectively. The reaction process and reaction products are analyzed in terms of chemical bonds, average charge, time constants and total potential energy. The activity of the reactants enhances with increasing temperature, which induces a faster thermite reaction. The alloy reaction obviously expands outward at Cu-rich interface of Al/CuO system, and the reaction between Al and O atoms obviously expands outward at O-rich interface as temperature increases. Different reaction products are found at the outermost layer of different interfaces in the Al/CuO system. In generally, the average charge of the outer layer aluminum atoms (i.e., Al1, Al2, Al5 and Al6) increases with temperature. The potential energy of Al/CuO system decreases significantly, which indicates that drastic exothermic reaction occurs at the Al/CuO system. This research enhances fundamental understanding in temperature effect on the thermite reaction at atomic level, which can potentially open new possibilities for its industrial application.

Thermodynamic stability and structure of cuprous chloride surfaces: a DFT investigation.

PubMed

Suleiman, Ibrahim A; Radny, Marian W; Gladys, Michael J; Smith, Phillip V; Mackie, John C; Kennedy, Eric M; Dlugogorski, Bogdan Z

2015-03-14

Density functional theory together with ab initio atomistic thermodynamics has been utilized to study the structures and stabilities of the low index CuCl surfaces. It is shown that the Cl-terminated structures are more stable than the Cu-terminated configurations, and that the defective CuCl(110)-Cu structure is more stable than the stoichiometric CuCl(110) surface. The equilibrium shape of a cuprous chloride nanostructure terminated by low-index CuCl surfaces has also been predicted using a Wulff construction. It was found that the (110) facets dominate at low chlorine concentration. As the chlorine concentration is increased, however, the contributions of the (100) and (111) facets to the Wulff construction also increase giving the crystal a semi-prism shape. At high chlorine concentration, and close to the rich limit, the (111) facets were found to be the only contributors to the Wulff construction, resulting in prismatic nanocrystals.

Large single domain 123 material produced by seeding with single crystal rare earth barium copper oxide single crystals

DOEpatents

Todt, V.; Miller, D.J.; Shi, D.; Sengupta, S.

1998-07-07

A method of fabricating bulk YBa{sub 2}Cu{sub 3}O{sub x} where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa{sub 2}Cu{sub 3}O{sub x} are heated in the presence of a Nd{sub 1+x}Ba{sub 2{minus}x}Cu{sub 3}O{sub y} seed crystal to a temperature sufficient to form a liquid phase in the YBa{sub 2}Cu{sub 3}O{sub x} while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa{sub 2}Cu{sub 3}O{sub x} material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material. 7 figs.

Large single domain 123 material produced by seeding with single crystal rare earth barium copper oxide single crystals

DOEpatents

Todt, Volker; Miller, Dean J.; Shi, Donglu; Sengupta, Suvankar

1998-01-01

A method of fabricating bulk YBa.sub.2 Cu.sub.3 O.sub.x where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa.sub.2 Cu.sub.3 O.sub.x are heated in the presence of a Nd.sub.1+x Ba.sub.2-x Cu.sub.3 O.sub.y seed crystal to a temperature sufficient to form a liquid phase in the YBa.sub.2 Cu.sub.3 O.sub.x while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa.sub.2 Cu.sub.3 O.sub.x material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material.

Ideal band shape in the potential thermoelectric material CuAlO2: Comparison to NaxCoO2

NASA Astrophysics Data System (ADS)

Mori, Kouta; Sakakibara, Hirofumi; Usui, Hidetomo; Kuroki, Kazuhiko

2013-08-01

A potential thermoelectric material CuAlO2 is theoretically studied. We first construct a model Hamiltonian of CuAlO2 based on the first principles band calculation, and calculate the Seebeck coefficient. Then, we compare the model with that of a well-known thermoelectric material NaxCoO2, and discuss the similarities and the differences. It is found that the two materials are similar from an electronic structure viewpoint in that they have a peculiar pudding-mold type band shape, which is advantageous for thermoelectric materials. There are, however, some differences, and we analyze the origin of the difference from a microscopic viewpoint. The band shape (a very flat band top but with an overall wide bandwidth) of CuAlO2 is found to be even more ideal than that of NaxCoO2, and we predict that once a significant amount of holes is doped in CuAlO2, thermoelectric properties (especially the power factor) even better than those of NaxCoO2 can be expected.

Prediction of precipitate evolution and martensite transformation in Ti-Ni-Cu shape memory alloys by computational thermodynamics

NASA Astrophysics Data System (ADS)

Povoden-Karadeniz, A.; Cirstea, D. C.; Kozeschnik, E.

2016-04-01

Ti-50Ni to Ti-55Ni (at.%) can be termed as the pioneer of shape memory alloys (SMA). Intermetallic precipitates play an important role for strengthening. Their influence on the start temperature of the martensitic transformation is a crucial property for the shape memory effect. Efforts for increasing the martensite start temperature include replacement of a part of Ni atoms by Cu. The influence of Cu-addition to Ti-Ni SMA on T0- temperatures and the character of the austenite-martensite transformation is evaluated using a new thermodynamic database for the Ti-Ni-system extended by Cu. Trends of precipitation of intermetallic phases are simulated by combining the assessed thermodynamics of the Ti-Ni-Cu system with assessed diffusion mobility data and kinetic models, as implemented in the solid-state transformation software MatCalc and are presented in the form of time-temperature-precipitation diagrams. Thermodynamic equilibrium considerations, complemented by predictive thermo-kinetic precipitation simulation, facilitates SMA alloy design and definition of optimized aging conditions.

Facile synthesis and shape evolution of oleic acid decorated Cu2O microcrystals

NASA Astrophysics Data System (ADS)

Xu, Bin; Cao, Xiaohai; Zhu, Bingchun; Lou, Baiyang; Ma, Xiaocun; Li, Xiao; Wang, Yuguang

2015-11-01

A facile synthetic method of oleic acid decorated Cu2O microcrystals has been developed by thermal decomposition of copper formate-octylamine complexes in paraffin using oleic acid as dispersing agent. This new method showed many advantages, which include free-reducing agent, enhancing antioxidant properties of Cu2O and good dispersity in paraffin, etc. The phase structure and morphology were investigated by means of XRD, SEM and TEM. It is found that the reaction time and temperature play the important roles in the crystallite morphology. With the increase of the reaction time, the Cu2O rhombic dodecahedron is gradually transformed into the spherical particle by intraparticle ripening. The shape evolution of Cu2O microcrystals can be accelerated with the increase of temperature.

Visible light responsive Cu2MoS4 nanosheets incorporated reduced graphene oxide for efficient degradation of organic pollutant

NASA Astrophysics Data System (ADS)

Rameshbabu, R.; Vinoth, R.; Navaneethan, M.; Harish, S.; Hayakawa, Y.; Neppolian, B.

2017-10-01

Visible light active copper molybdenum sulfide (Cu2MoS4) nanosheets were successfully anchored on reduced graphene oxide (rGO) using facile hydrothermal method. During the hydrothermal reaction, reduction of graphene oxide into rGO and the formation of Cu2MoS4 nanosheets were successfully obtained. The charge transfer interaction between the rGO sheets and Cu2MoS4 nanosheets extended the absorption to visible region in comparison with bare Cu2MoS4 nanosheets i.e without rGO sheets. Furthermore, the notable photoluminescence quenching observed for Cu2MoS4/rGO nanocomposite revealed the effective role of rGO towards the significant inhibition of electron-hole pair recombination. The photocatalytic efficiencies of bare Cu2MoS4 and Cu2MoS4/rGO nanocomposite was evaluated for the degradation of methyl orange dye under visible irradiation (λ > 420 nm). A maximum photodegradation efficiency of 99% was achieved for Cu2MoS4/rGO nanocomposite, while only 64% photodegradation was noted for bare Cu2MoS4. The enhanced optical absorption in visible region, high surface area, and low charge carrier recombination in the presence of rGO sheets were the main reasons for the enhancement in photodegardation of MO dye. In addition, the resultant Cu2MoS4/rGO nanocomposite was found to be reusable for five successive cycles without significant loss in its photocatalytic performance.

Copper(II) adsorption on the kaolinite(001) surface: Insights from first-principles calculations and molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Kong, Xiang-Ping; Wang, Juan

2016-12-01

The adsorption behavior of Cu(II) on the basal hydroxylated kaolinite(001) surface in aqueous environment was investigated by first-principles calculations and molecular dynamics simulations. Structures of possible monodentate and bidentate inner-sphere adsorption complexes of Cu(II) were examined, and the charge transfer and bonding mechanism were analyzed. Combining the binding energy of complex, the radial distribution function of Cu(II) with oxygen and the extended X-ray absorption fine structure data, monodentate complex on site of surface oxygen with ;upright; hydrogen and bidentate complex on site of two oxygens (one with ;upright; hydrogen and one with ;lying; hydrogen) of single Al center have been found to be the major adsorption species of Cu(II). Both adsorption species are four-coordinated with a square planar geometry. The distribution of surface hydroxyls with ;lying; hydrogen around Cu(II) plays a key role in the structure and stability of adsorption complex. Upon the Mulliken population analysis and partial density of states, charge transfer occurs with Cu(II) accepting some electrons from both surface oxygens and aqua oxygens, and the bonding Cu 3d-O 2p state filling is primarily responsible for the strong covalent interaction of Cu(II) with surface oxygen.

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.

Enhanced Charge Separation in Ternary P3HT/PCBM/CuInS2 Nanocrystals Hybrid Solar Cells

PubMed Central

Lefrançois, Aurélie; Luszczynska, Beata; Pepin-Donat, Brigitte; Lombard, Christian; Bouthinon, Benjamin; Verilhac, Jean-Marie; Gromova, Marina; Faure-Vincent, Jérôme; Pouget, Stéphanie; Chandezon, Frédéric; Sadki, Saïd; Reiss, Peter

2015-01-01

Geminate recombination of bound polaron pairs at the donor/acceptor interface is one of the major loss mechanisms in organic bulk heterojunction solar cells. One way to overcome Coulomb attraction between opposite charge carriers and to achieve their full dissociation is the introduction of high dielectric permittivity materials such as nanoparticles of narrow band gap semiconductors. We selected CuInS2 nanocrystals of 7.4 nm size, which present intermediate energy levels with respect to poly(3-hexylthiophene) (P3HT) and Phenyl-C61-butyric acid methyl ester (PCBM). Efficient charge transfer from P3HT to nanocrystals takes place as evidenced by light-induced electron spin resonance. Charge transfer between nanocrystals and PCBM only occurs after replacing bulky dodecanethiol (DDT) surface ligands with shorter 1,2-ethylhexanethiol (EHT) ligands. Solar cells containing in the active layer a ternary blend of P3HT:PCBM:CuInS2-EHT nanocrystals in 1:1:0.5 mass ratio show strongly improved short circuit current density and a higher fill factor with respect to the P3HT:PCBM reference device. Complementary measurements of the absorption properties, external quantum efficiency and charge carrier mobility indicate that enhanced charge separation in the ternary blend is at the origin of the observed behavior. The same trend is observed for blends using the glassy polymer poly(triarylamine) (PTAA). PMID:25588811

Hydrogen isotope trapping in Al-Cu binary alloys

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

Chao, Paul; Karnesky, Richard A.

In this study, the trapping mechanisms for hydrogen isotopes in Al–X Cu (0.0 at. % < X < 3.5 at. %) alloys were investigated using thermal desorption spectroscopy (TDS), electrical conductivity, and differential scanning calorimetry. Constant heating rate TDS was used to determine microstructural trap energies and occupancies. In addition to the trapping states in pure Al reported in the literature (interstitial lattice sites, dislocations, and vacancies), a trap site due to Al–Cu intermetallic precipitates is observed. The binding energy of this precipitate trap is (18 ± 3) kJ•mol –1 (0.19 ± 0.03 eV). Typical occupancy of this trap ismore » high; for Al–2.6 at. % Cu (a Cu composition comparable to that in AA2219) charged at 200 °C with 130 MPa D 2 for 68 days, there is ca. there is 3.15×10 –7 mol D bound to the precipitate trap per mol of Al, accounting for a third of the D in the charged sample.« less

Hydrogen isotope trapping in Al-Cu binary alloys

DOE PAGES

Chao, Paul; Karnesky, Richard A.

2016-01-01

In this study, the trapping mechanisms for hydrogen isotopes in Al–X Cu (0.0 at. % < X < 3.5 at. %) alloys were investigated using thermal desorption spectroscopy (TDS), electrical conductivity, and differential scanning calorimetry. Constant heating rate TDS was used to determine microstructural trap energies and occupancies. In addition to the trapping states in pure Al reported in the literature (interstitial lattice sites, dislocations, and vacancies), a trap site due to Al–Cu intermetallic precipitates is observed. The binding energy of this precipitate trap is (18 ± 3) kJ•mol –1 (0.19 ± 0.03 eV). Typical occupancy of this trap ismore » high; for Al–2.6 at. % Cu (a Cu composition comparable to that in AA2219) charged at 200 °C with 130 MPa D 2 for 68 days, there is ca. there is 3.15×10 –7 mol D bound to the precipitate trap per mol of Al, accounting for a third of the D in the charged sample.« less

Measurements of directed, elliptic, and triangular flow in Cu + Au collisions at √{sNN}=200 GeV

NASA Astrophysics Data System (ADS)

Adare, A.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Akimoto, R.; Alexander, J.; Alfred, M.; Aoki, K.; Apadula, N.; Asano, H.; Atomssa, E. T.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Bai, X.; Bandara, N. S.; Bannier, B.; Barish, K. N.; Bathe, S.; Baublis, V.; Baumann, C.; Baumgart, S.; Bazilevsky, A.; Beaumier, M.; Beckman, S.; Belmont, R.; Berdnikov, A.; Berdnikov, Y.; Black, D.; Blau, D. S.; Bok, J. S.; Boyle, K.; Brooks, M. L.; Bryslawskyj, J.; Buesching, H.; Bumazhnov, V.; Butsyk, S.; Campbell, S.; Chen, C.-H.; Chi, C. Y.; Chiu, M.; Choi, I. J.; Choi, J. B.; Choi, S.; Christiansen, P.; Chujo, T.; Cianciolo, V.; Citron, Z.; Cole, B. A.; Cronin, N.; Crossette, N.; Csanád, M.; Csörgő, T.; Danley, T. W.; Datta, A.; Daugherity, M. S.; David, G.; Deblasio, K.; Dehmelt, K.; Denisov, A.; Deshpande, A.; Desmond, E. J.; Ding, L.; Dion, A.; Diss, P. B.; Do, J. H.; D'Orazio, L.; Drapier, O.; Drees, A.; Drees, K. A.; Durham, J. M.; Durum, A.; Engelmore, T.; Enokizono, A.; Esumi, S.; Eyser, K. O.; Fadem, B.; Feege, N.; 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.; Gallus, P.; Garg, P.; Garishvili, A.; Garishvili, I.; Ge, H.; Giordano, F.; Glenn, A.; Gong, X.; Gonin, M.; Goto, Y.; Granier de Cassagnac, R.; Grau, N.; Greene, S. V.; Grosse Perdekamp, M.; Gu, Y.; Gunji, T.; Guragain, H.; Hachiya, T.; Haggerty, J. S.; Hahn, K. I.; Hamagaki, H.; Hamilton, H. F.; Han, S. Y.; Hanks, J.; Hasegawa, S.; Haseler, T. O. S.; Hashimoto, K.; Hayano, R.; He, X.; Hemmick, T. K.; Hester, T.; Hill, J. C.; Hollis, R. S.; Homma, K.; Hong, B.; Hoshino, T.; Hotvedt, N.; Huang, J.; Huang, S.; Ichihara, T.; Ikeda, Y.; Imai, K.; Imazu, Y.; Inaba, M.; Iordanova, A.; Isenhower, D.; Isinhue, A.; Ivanishchev, D.; Jacak, B. V.; Jeon, S. J.; Jezghani, M.; Jia, J.; Jiang, X.; Johnson, B. M.; Joo, K. S.; Jouan, D.; Jumper, D. S.; Kamin, J.; Kanda, S.; Kang, B. H.; Kang, J. H.; Kang, J. S.; Kapustinsky, J.; Kawall, D.; Kazantsev, A. V.; Key, J. A.; Khachatryan, V.; Khandai, P. K.; Khanzadeev, A.; Kijima, K. M.; Kim, C.; Kim, D. J.; Kim, E.-J.; Kim, G. W.; Kim, M.; Kim, Y.-J.; Kim, Y. K.; Kimelman, B.; Kistenev, E.; Kitamura, R.; Klatsky, J.; Kleinjan, D.; Kline, P.; Koblesky, T.; Kofarago, M.; Komkov, B.; Koster, J.; Kotchetkov, D.; Kotov, D.; Krizek, F.; Kurita, K.; Kurosawa, M.; Kwon, Y.; Lacey, R.; Lai, Y. S.; Lajoie, J. G.; Lebedev, A.; Lee, D. M.; Lee, G. H.; Lee, J.; Lee, K. B.; Lee, K. S.; Lee, S.; Lee, S. H.; Leitch, M. J.; Leitgab, M.; Lewis, B.; Li, X.; Lim, S. H.; Liu, M. X.; Lynch, D.; Maguire, C. F.; Makdisi, Y. I.; Makek, M.; Manion, A.; Manko, V. I.; Mannel, E.; Maruyama, T.; McCumber, M.; McGaughey, P. L.; McGlinchey, D.; McKinney, C.; Meles, A.; Mendoza, M.; Meredith, B.; Miake, Y.; Mibe, T.; Mignerey, A. C.; Milov, A.; Mishra, D. K.; Mitchell, J. T.; Miyasaka, S.; Mizuno, S.; Mohanty, A. K.; Mohapatra, S.; Montuenga, P.; Moon, T.; Morrison, D. P.; Moskowitz, M.; Moukhanova, T. V.; Murakami, T.; Murata, J.; Mwai, A.; Nagae, T.; Nagamiya, S.; Nagashima, K.; Nagle, J. L.; Nagy, M. I.; Nakagawa, I.; Nakagomi, H.; Nakamiya, Y.; Nakamura, K. R.; Nakamura, T.; Nakano, K.; Nattrass, C.; Netrakanti, P. K.; Nihashi, M.; Niida, T.; Nishimura, S.; Nouicer, R.; Novák, T.; Novitzky, N.; Nyanin, A. S.; O'Brien, E.; Ogilvie, C. A.; Oide, H.; Okada, K.; Orjuela Koop, J. D.; Osborn, J. D.; Oskarsson, A.; Ozawa, K.; Pak, R.; Pantuev, V.; Papavassiliou, V.; Park, I. H.; Park, J. S.; Park, S.; Park, S. K.; Pate, S. F.; Patel, L.; Patel, M.; Peng, J.-C.; Perepelitsa, D. V.; Perera, G. D. N.; Peressounko, D. Yu.; Perry, J.; Petti, R.; Pinkenburg, C.; Pinson, R.; Pisani, R. P.; Purschke, M. L.; Qu, H.; Rak, J.; Ramson, B. J.; Ravinovich, I.; Read, K. F.; Reynolds, D.; Riabov, V.; Riabov, Y.; Richardson, E.; Rinn, T.; Riveli, N.; Roach, D.; Rolnick, S. D.; Rosati, M.; Rowan, Z.; Rubin, J. G.; Ryu, M. S.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Sako, H.; Samsonov, V.; Sarsour, M.; Sato, S.; Sawada, S.; Schaefer, B.; Schmoll, B. K.; Sedgwick, K.; Seele, J.; Seidl, R.; Sekiguchi, Y.; Sen, A.; Seto, R.; Sett, P.; Sexton, A.; Sharma, D.; Shaver, A.; Shein, I.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shoji, K.; Shukla, P.; Sickles, A.; Silva, C. L.; Silvermyr, D.; Singh, B. K.; Singh, C. P.; Singh, V.; Skolnik, M.; Slunečka, M.; Snowball, M.; Solano, S.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Sourikova, I. V.; Stankus, P. W.; Steinberg, P.; Stenlund, E.; Stepanov, M.; Ster, A.; Stoll, S. P.; Stone, M. R.; Sugitate, T.; Sukhanov, A.; Sumita, T.; Sun, J.; Sziklai, J.; Takahara, A.; Taketani, A.; Tanaka, Y.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tennant, E.; Tieulent, R.; Timilsina, A.; Todoroki, T.; Tomášek, M.; Torii, H.; Towell, C. L.; Towell, R.; Towell, R. S.; Tserruya, I.; van Hecke, H. W.; Vargyas, M.; Vazquez-Zambrano, E.; Veicht, A.; Velkovska, J.; Vértesi, R.; Virius, M.; Vrba, V.; Vznuzdaev, E.; Wang, X. R.; Watanabe, D.; Watanabe, K.; Watanabe, Y.; Watanabe, Y. S.; Wei, F.; Whitaker, S.; White, A. S.; Wolin, S.; Woody, C. L.; Wysocki, M.; Xia, B.; Xue, L.; Yalcin, S.; Yamaguchi, Y. L.; Yanovich, A.; Yokkaichi, S.; Yoo, J. H.; Yoon, I.; You, Z.; Younus, I.; Yu, H.; Yushmanov, I. E.; Zajc, W. A.; Zelenski, A.; Zhou, S.; Zou, L.; Phenix Collaboration

2016-11-01

Measurements of anisotropic flow Fourier coefficients (vn) for inclusive charged particles and identified hadrons π±, K±, p , and p ¯ produced at midrapidity in Cu +Au collisions at √{s NN}=200 GeV are presented. The data were collected in 2012 by the PHENIX experiment at the Relativistic Heavy-Ion Collider (RHIC). The particle azimuthal distributions with respect to different-order symmetry planes Ψn, for n =1 , 2, and 3 are studied as a function of transverse momentum pT over a broad range of collision centralities. Mass ordering, as expected from hydrodynamic flow, is observed for all three harmonics. The charged-particle results are compared with hydrodynamical and transport model calculations. We also compare these Cu +Au results with those in Cu +Cu and Au +Au collisions at the same √{sNN} and find that the v2 and v3, as a function of transverse momentum, follow a common scaling with 1 /(ɛnNpart1 /3) .

Optical spectra of La2-xSrxCuO4: Effect of carrier doping on the electronic structure of the CuO2 plane

NASA Astrophysics Data System (ADS)

Uchida, S.; Ido, T.; Takagi, H.; Arima, T.; Tokura, Y.; Tajima, S.

1991-04-01

Optical reflectivity spectra are studied for single crystals of the prototypical high-Tc system La2-xSrxCuO4 over a wide compositional range 0<=x<=0.34, which covers insulating, superconducting, and normal metallic phases. The measurements are made at room temperature over an energy range from 0.004 to 35 eV for the polarization parallel to the CuO2 planes. They are also extended to the perpendicular polarization to study anisotropy and to discriminate the contribution from the CuO2 plane. The present study focuses on the x dependence of the optical spectrum, which makes it possible to sort out the features of the excitations in the CuO2 plane and thus to characterize the electronic structure of the CuO2 plane in the respective phase. Upon doping into the parent insulator La2CuO4 with a charge-transfer energy gap of about 2 eV the spectral weight is rapidly transferred from the charge-transfer excitation to low-energy excitations below 1.5 eV. The low-energy spectrum is apparently composed of two contributions; a Drude-type one peaked at ω=0 and a broad continuum centered in the midinfrared range. The high-Tc superconductivity is realized as doping proceeds and when the transfer of the spectrum weight is saturated. The resulting spectrum in the high-Tc regime is suggestive of a strongly itinerant character of the state in the moderately doped CuO2 plane while appreciable weight remains in the charge-transfer energy region. The spectrum exhibits a second drastic change for heavy doping (x~0.25) corresponding to the superconductor-to-normal-metal transition and becomes close to that of a Fermi liquid. The results are universal for all the known cuprate superconductors including the electron-doped compounds, and they reconcile the dc transport properties with the high-energy spectroscopic results.

Profiling Charge Complementarity and Selectivity for Binding at the Protein Surface

PubMed Central

Sulea, Traian; Purisima, Enrico O.

2003-01-01

A novel analysis and representation of the protein surface in terms of electrostatic binding complementarity and selectivity is presented. The charge optimization methodology is applied in a probe-based approach that simulates the binding process to the target protein. The molecular surface is color coded according to calculated optimal charge or according to charge selectivity, i.e., the binding cost of deviating from the optimal charge. The optimal charge profile depends on both the protein shape and charge distribution whereas the charge selectivity profile depends only on protein shape. High selectivity is concentrated in well-shaped concave pockets, whereas solvent-exposed convex regions are not charge selective. This suggests the synergy of charge and shape selectivity hot spots toward molecular selection and recognition, as well as the asymmetry of charge selectivity at the binding interface of biomolecular systems. The charge complementarity and selectivity profiles map relevant electrostatic properties in a readily interpretable way and encode information that is quite different from that visualized in the standard electrostatic potential map of unbound proteins. PMID:12719221

Shape transitions in strained islands: kinetics versus energetics

NASA Astrophysics Data System (ADS)

Shim, Yunsic; Kryukov, Yevgen; Amar, Jacques

2011-03-01

Recently, it has been argued that the shape transition from compact to ramified islands observed experimentally in submonolayer Cu/Ni(100) growth is not due to kinetics but can be understood in terms of energetic arguments. In order to determine the responsible mechanisms we have carried out temperature-accelerated dynamics (TAD) simulations as well as energetics calculations. Surprisingly, our results indicate that the strain-energy contribution to the dependence of island-energy on shape is relatively weak. In contrast, our TAD simulations indicate that unexpected concerted motions occurring at step edges may be responsible. The energy barriers for these concerted motions are significantly lower than for Cu/Cu(100) and Ni/Ni(100), decrease with increasing island size, and appear to saturate for islands larger than 300 - 400 atoms. These results suggest that the shape transition is of kinetic origin but is strongly mediated by strain. Supported by NSF-DMR 0907399.

Temperature evolution of the charge and spin transport in Cu/Nb interface

NASA Astrophysics Data System (ADS)

Ishitaki, Masayuki; Ohnishi, Kohei; Kimura, Takashi

2018-06-01

The transport properties for the charge and spin currents in a normal-metal/superconductor interface have been investigated by using a nano-pillar based lateral spin valve. Owing to the efficient reduction of the Joule heating, we were able to observe the temperature and bias-current dependences of the spin transport in the Cu/Nb bilayer system. From the temperature dependence of the spin signal, the superconducting gap of the Nb in contact with Cu was found to open gradually with decreasing the temperature. We also found that the inhomogeneous superconducting property produces the significant temperature and field dependences of the background signal in the nonlocal measurement around the transition temperature.

STM/STS study of graphene directly grown on h-BN films on Cu foils

NASA Astrophysics Data System (ADS)

Jang, Won-Jun; Wang, Min; Jang, Seong-Gyu; Kim, Minwoo; Park, Seong-Yong; Kim, Sang-Woo; Kahng, Se-Jong; Choi, Jae-Young; Song, Young; Lee, Sungjoo; Sanit Collaboration; Department Of Physics, Korea University Collaboration; Graphene Research Center, Samsung Advanced Institute Of Technology Collaboration

2013-03-01

Graphene-based devices on standard SiO2 substrate commonly exhibit inferior characteristics relative to the expected intrinsic properties of graphene, due to the disorder existing at graphene-SiO2 interface. Recently, it has been shown that exfoliated and chemical vapor deposition (CVD) graphene transferred onto hexagonal boron nitride (h-BN) possesses significantly reduced charge inhomogeneity, and yields improved device performance. Here we report the scanning tunneling microscopy (STM) and spectroscopy (STS) results obtained from a graphene layer directly grown on h-BN insulating films on Cu foils. STS measurements illustrate that graphene/h-BN film is charge neutral without electronic perturbation from h-BN/Cu substrate. Corresponding Author

Fully recoverable rigid shape memory foam based on copper-catalyzed azide-alkyne cycloaddition (CuAAC) using a salt leaching technique.

PubMed

Alzahrani, Abeer A; Saed, Mohand; Yakacki, Christopher M; Song, Han Byul; Sowan, Nancy; Walston, Joshua J; Shah, Parag K; McBride, Matthew K; Stansbury, Jeffrey W; Bowman, Christopher N

2018-01-07

This study is the first to employ the use of the copper-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization to form a tough and stiff, porous material from a well-defined network possessing a high glass transition temperature. The effect of the network linkages formed as a product of the CuAAC reaction, i.e., the triazoles, on the mechanical behavior at high strain was evaluated by comparing the CuAAC foam to an epoxy-amine-based foam, which consisted of monomers with similar backbone structures and mechanical properties (i.e., T g of 115 °C and a rubbery modulus of 1.0 MPa for the CuAAC foam, T g of 125 °C and a rubbery modulus of 1.2 MPa for the epoxy-amine foam). When each foam was compressed uniformly to 80% strain at ambient temperature, the epoxy-amine foam was severely damaged after only reaching 70% strain in the first compression cycle with a toughness of 300 MJ/m 3 . In contrast, the CuAAC foam exhibited pronounced ductile behavior in the glassy state with three times higher toughness of 850 MJ/m 3 after the first cycle of compression to 80% strain. Additionally, when the CuAAC foam was heated above T g after each of five compression cycles to 80% strain at ambient temperature, the foam completely recovered its original shape while exhibiting a gradual decrease in mechanical performance over the multiple compression cycles. The foam demonstrated almost complete shape fixity and recovery ratios even through five successive cycles, indicative of "reversible plasticity", making it highly desirable as a glassy shape memory foams.

Observation of a Charge Density Wave Incommensuration Near the Superconducting Dome in Cu x TiSe 2

DOE PAGES

Kogar, A.; de la Pena, G. A.; Lee, Sangjun; ...

2017-01-11

X-ray diffraction was employed to study the evolution of the charge density wave (CDW) in Cu xTiSe 2 as a function of copper intercalation in order to clarify the relationship between the CDW and superconductivity. In this paper, the results show a CDW incommensuration arising at an intercalation value coincident with the onset of superconductivity at around x = 0.055(5) . Additionally, it was found that the charge density wave persists to higher intercalant concentrations than previously assumed, demonstrating that the CDW does not terminate inside the superconducting dome. A charge density wave peak was observed in samples up tomore » x = 0.091(6) , the highest copper concentration examined in this study. Lastly, the phase diagram established in this work suggests that charge density wave incommensuration may play a role in the formation of the superconducting state.« less

Charge-Dependent Directed Flow in Cu + Au Collisions at s N N = 200 GeV

DOE PAGES

Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; ...

2017-01-05

Here we present the first measurement of charge-dependent directed flow in Cu + Au collisions atmore » $$\\sqrt{s}$$$_ {NN}$$ = 200 GeV . The results are presented as a function of the particle transverse momentum and pseudorapidity for different centralities. A finite difference between the directed flow of positive and negative charged particles is observed that qualitatively agrees with the expectations from the effects of the initial strong electric field between two colliding ions with different nuclear charges. The measured difference in directed flow is much smaller than that obtained from the parton-hadron-string-dynamics model, which suggests that most of the electric charges, i.e., quarks and antiquarks, have not yet been created during the lifetime of the strong electric field, which is of the order of, or less than, 1fm / c .« less

Elastocaloric effect in CuAlZn and CuAlMn shape memory alloys under compression

PubMed Central

Qian, Suxin; Wang, Yi; Pillsbury, Thomas E.; Hada, Yoshiharu; Yamaguchi, Yuki; Fujimoto, Kenjiro; Hwang, Yunho; Radermacher, Reinhard; Cui, Jun; Yuki, Yoji; Toyotake, Koutaro; Takeuchi, Ichiro

2016-01-01

This paper reports the elastocaloric effect of two Cu-based shape memory alloys: Cu68Al16Zn16 (CuAlZn) and Cu73Al15Mn12 (CuAlMn), under compression at ambient temperature. The compression tests were conducted at two different rates to approach isothermal and adiabatic conditions. Upon unloading at a strain rate of 0.1 s−1 (adiabatic condition) from 4% strain, the highest adiabatic temperature changes (ΔTad) of 4.0 K for CuAlZn and 3.9 K for CuAlMn were obtained. The maximum stress and hysteresis at each strain were compared. The stress at the maximum recoverable strain of 4.0% for CuAlMn was 120 MPa, which is 70% smaller than that of CuAlZn. A smaller hysteresis for the CuAlMn alloy was also obtained, about 70% less compared with the CuAlZn alloy. The latent heat, determined by differential scanning calorimetry, was 4.3 J g−1 for the CuAlZn alloy and 5.0 J g−1 for the CuAlMn alloy. Potential coefficients of performance (COPmat) for these two alloys were calculated based on their physical properties of measured latent heat and hysteresis, and a COPmat of approximately 13.3 for CuAlMn was obtained. This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’. PMID:27402936

Sensitization of TiO₂ nanosheets with Cu-biphenylamine frame work to enhance photocatalytic degradation performance of toxic organic contaminants: Synthesis, mechanism and kinetic studies.

PubMed

Khan, Muhammad Asim; Mutahir, Sadaf; Wang, Fengyun; Lei, Wu; Xia, Mingzhu

2018-06-25

TNS/Cu(X) composite materials were firstly synthesized via simple overnight stirring of TNS in the methanolic solution of Cu complexes. The developed TNS/Cu(X) composites having a well-designed nanostructure, in which TNS and Cu complexes were closely bounded with each other. Biphenylamine complexes fixed on TNS surface in form of Nano-capsules, which were confirmed by TEM and SEM, thus improving the surface area and subsequently charge separation. Innovatively merged photocatalysts of Cu complexes with TNS were successfully verified for photocatalytic mineralization of colored and colorless organic contaminants under the visible light degradation. As compared to original TNS, TNS/Cu(BA) showed prominent improvement in the catalytic actions. Kinetics i.e. t1/2 (half-life times period), Kapp, and R2 (linear regression co-efficient) were also studied. The amended materials created charge separation, by means of electrons gathering at the higher CB, and holes gathering at lower level VB of Cu complex, therefore improving mineralization efficiency of electrons and holes. TNS/Cu(BA) degrade 99% to 99.6% of MO & RhB dyes in 120 min, and 160 min, respectively, and 68 % of phenol and 53% of TCP were destroyed in 180 min. The resilient holes can directly destroy MO, RhB, phenol, and TCP. © 2018 IOP Publishing Ltd.

Glutathione-stabilized Cu nanoclusters as fluorescent probes for sensing pH and vitamin B1.

PubMed

Luo, Yawen; Miao, Hong; Yang, Xiaoming

2015-11-01

Glutathione (GSH), playing roles as both a reducing reagent and protecting ligand, has been successfully employed for synthesizing Cu nanoclusters (CuNCs@GSH) on the basis of a simple and facile approach. The as-prepared CuNCs exhibited a fluorescence emission at 600nm with a quantum yield (QY) of approximately 3.6%. Subsequently, the CuNCs described here was employed as a broad-range pH sensor by virtue of the fluorescence intensity of CuNCs responding sensitively to pH fluctuating in a linear range of 4.0-12.0. Meanwhile, these prepared CuNCs were applied for detections of vitamin B1 (VB1) on the basis of positively charged VB1 neutralizing the negative surface charge of CuNCs, thus leading to the instability and aggregations of CuNCs, and further facilitating to quench their fluorescence. In addition, the proposed analytical method permitted detecting VB1 with a linear range of 2.0×10(-8)-1.0×10(-4) mol L(-1) as well as a detection limit of 4.6×10(-9) mol L(-1). Eventually, the practicability of this sensing approach was validated by assaying VB1 in human urine samples and pharmaceutical tablets, confirming its potential to broaden avenues for assaying VB1. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of inorganic electrolyte anions on enrichment of Cu(II) ions with aminated Fe3O4/graphene oxide: Cu(II) speciation prediction and surface charge measurement.

PubMed

Hu, Xin-jiang; Liu, Yun-guo; Zeng, Guang-ming; Wang, Hui; You, Shao-hong; Hu, Xi; Tan, Xiao-fei; Chen, An-wei; Guo, Fang-ying

2015-05-01

The present work evaluated the effects of six inorganic electrolyte anions on Cu(II) removal using aminated Fe3O4/graphene oxide (AMGO) in single- and multi-ion systems. A 2(6-2) fractional factorial design (FFD) was employed for assessing the effects of multiple anions on the adsorption process. The results indicated that the Cu(II) adsorption was strongly dependent on pH and could be significantly affected by inorganic electrolyte anions due to the changes in Cu(II) speciation and surface charge of AMGO. In the single-ion systems, the presence of monovalent anions (Cl(-), ClO4(-), and NO3(-)) slightly increased the Cu(II) adsorption onto AMGO at low pH, while the Cu(II) adsorption was largely enhanced by the presence of SO4(2-), CO3(2-), and HPO4(2-). Based on the estimates of major effects and interactions from FFD, the factorial effects of the six selected species on Cu(II) adsorption in multi-ion system were in the following sequence: HPO4(2-)>CO3(2-)>Cl(-)>SO4(2-)>NO3(-)=ClO4(-), and the combined factors of AD (Cl(-)×SO4(2-)) and EF (Cl(-)×SO4(2-)) had significant effects on Cu(II) removal. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

Crăciunescu, Corneliu M., E-mail: corneliu.craciunescu@upt.ro; Mitelea, Ion, E-mail: corneliu.craciunescu@upt.ro; Budău, Victor, E-mail: corneliu.craciunescu@upt.ro

Shape memory alloy films belonging to the NiTi-based systems were deposited on heated and unheated substrates, by magnetron sputtering in a custom made system, and their structure and composition was analyzed using electron microscopy. Several substrates were used for the depositions: glass, Cu-Zn-Al, Cu-Al-Ni and Ti-NiCu shape memory alloy ribbons and kapton. The composition of the Ti-Ni-Cu films showed limited differences, compared to the one of the target and the microstructure for the DC magnetron sputtering revealed crystallized structure with features determined on peel off samples from a Si wafer. Both inter and transcrystalline fractures were observed and related tomore » the interfacial stress developed on cooling from deposition temperature.« less

Fast photocatalytic degradation of sulforhodamine B using ZnO:Cu nanorods

NASA Astrophysics Data System (ADS)

Raji, R.; Gopchandran, K. G.

2018-02-01

In this work, ZnO:Cu nanorods with tunable Cu content were successfully synthesized via co-precipitation method and investigations were made on the use of these nanorods as photocatalyst by observing the photodegradation of a representative dye pollutant of sulforhodamine B (SRB) under sunlight. The X-ray diffraction analysis and high resolution transmission electron microscopy showed that ZnO:Cu nanorods possess wurtzite phase with preferential growth along (101) plane. The formation of additional defect levels in these nanorods on doping with Cu and its dependence on the concentration of Cu were studied using photoluminescence and X-ray photoelectron spectroscopy. ZnO:Cu nanorods results in faster degradation of dye as compared to the undoped ZnO and is found that Cu doping enhances the photodegradation activity significantly and is highly sensitive to Cu doping level. The fast photocatalytic degradation is attributed to the fact that Cu ions promote the interfacial charge transfer and favors the effective charge separation of photogenerated electrons and holes generated during sunlight irradiation, increasing the rate of production of reactive oxygen species needed for the degradation of the dye. The chemical oxygen demand analysis of the dye solution after sunlight irradiation indicates that rate of mineralization is slower than the decoloration. The possible mechanism for degradation of dye under sunlight irradiation is described with a schematic. Additionally, the photostability of the ZnO:Cu nanorods was also tested through three repetitive cycles. This work suggest that the prepared ZnO:Cu nanorods are suitable for cost-effective water purification.

A combined experimental and computational study of water-gas shift reaction over rod-shaped Ce 0.75 M 0.25O 2 (M=Ti, Zr, and Mn) supported Cu catalysts

DOE PAGES

Ren, Zhibo; Peng, Fei; Chen, Biaohua; ...

2017-11-02

Water-gas shift (WGS) reaction over a series of ceria-based mixed oxides supported Cu catalysts was investigated using a combined experimental and theoretical method. The mixed rod-shaped Ce 0.75M 0.25O 2 (M = Ti 4+, Zr 4+, Mn 4+) solid solutions, which majorly expose the (110) and (100) facets, are synthesized by hydrothermal method and used to prepare supported Cu catalysts. We found that the Cu/Ce0.75Ti 0.25O 2 (Cu-CT) exhibits the highest CO conversion in the temperature range of 150-250 °C among all supported Cu catalysts. This is mainly attributed to (i) good dispersion of Cu; (ii) largest amount of moderatemore » copper oxide; and (iii) strongest Cu-support interaction of Cu-CT. And compared to other mixed metals, periodic density functional theory calculations performed, this work further suggest that the introduction of Ti into CeO 2 not only promotes oxygen vacancy formation and CO adsorption, but also facilitates the carboxyl (COOH) formation at the interface of the Cu cluster and the support, which leads to the enhanced catalytic activity of the Cu-CT toward WGS reaction.« less

Restoring interlayer Josephson coupling in La 1.885 Ba 0.115 CuO 4 by charge transfer melting of stripe order

DOE PAGES

Khanna, V.; Mankowsky, R.; Petrich, M.; ...

2016-06-30

Here, we show that disruption of charge-density-wave (stripe) order by charge transfer excitation, enhances the superconducting phase rigidity in La 1.885Ba 0.115CuO 4. Time-resolved resonant soft x-ray diffraction demonstrates that charge order melting is prompt following near-infrared photoexcitation whereas the crystal structure remains intact for moderate fluences. THz time-domain spectroscopy reveals that, for the first 2 ps following photoexcitation, a new Josephson plasma resonance edge, at higher frequency with respect to the equilibrium edge, is induced indicating enhanced superconducting interlayer coupling. Furthermore, the fluence dependence of the charge-order melting and the enhanced superconducting interlayer coupling are correlated with a saturationmore » limit of ~0.5mJ/cm 2. When using a combination of x-ray and optical spectroscopies we establish a hierarchy of timescales between enhanced superconductivity, melting of charge order, and rearrangement of the crystal structure.« less

Restoring interlayer Josephson coupling in La 1.885 Ba 0.115 CuO 4 by charge transfer melting of stripe order

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

Khanna, V.; Mankowsky, R.; Petrich, M.

Here, we show that disruption of charge-density-wave (stripe) order by charge transfer excitation, enhances the superconducting phase rigidity in La 1.885Ba 0.115CuO 4. Time-resolved resonant soft x-ray diffraction demonstrates that charge order melting is prompt following near-infrared photoexcitation whereas the crystal structure remains intact for moderate fluences. THz time-domain spectroscopy reveals that, for the first 2 ps following photoexcitation, a new Josephson plasma resonance edge, at higher frequency with respect to the equilibrium edge, is induced indicating enhanced superconducting interlayer coupling. Furthermore, the fluence dependence of the charge-order melting and the enhanced superconducting interlayer coupling are correlated with a saturationmore » limit of ~0.5mJ/cm 2. When using a combination of x-ray and optical spectroscopies we establish a hierarchy of timescales between enhanced superconductivity, melting of charge order, and rearrangement of the crystal structure.« less

AIE active multianalyte fluorescent probe for the detection of Cu2+, Ni2+ and Hg2+ ions.

PubMed

Pannipara, Mehboobali; Al-Sehemi, Abdullah G; Irfan, Ahmad; Assiri, Mohammed; Kalam, Abul; Al-Ammari, Yahya S

2018-08-05

A novel pyrazolyl chromene derivative (Probe 1) displaying aggregation induced emission (AIE) properties that capable of sensing of multiple metal ions has been designed and synthesized. The multi analyte probe exhibits selective sensing for Cu 2+ and Ni 2+ ions via fluorescence turn-off mechanism and ratiometric selectivity for Hg 2+ ions in aqueous media. The extent of binding of the probe with sensitive metal ions has been demonstrated. The experimental results were further investigated by computational means by optimizing the ground state geometries of Probe 1 and its various metal complexes for Probe 1-Ni, Probe 1-Hg and Probe 1-Cu using density functional theory (DFT) at B3LYP/6-31+g(d,p) (LANL2DZ) level. On the basis of binding energies, the stability of metal complexes has been studied. In Probe 1-Ni and Probe 1-Cu complexes, charge transfer has been observed from Probe 1 to metal ions revealing ligand to metal charge transfer (LMCT) while in Probe1-Hg complex LMCT as well as intra-molecular charge tranfer (ICT) within Probe 1. Copyright © 2018 Elsevier B.V. All rights reserved.

Cu2O/CuO Bilayered Composite as a High-Efficiency Photocathode for Photoelectrochemical Hydrogen Evolution Reaction

PubMed Central

Yang, Yang; Xu, Di; Wu, Qingyong; Diao, Peng

2016-01-01

Solar powered hydrogen evolution reaction (HER) is one of the key reactions in solar-to-chemical energy conversion. It is desirable to develop photocathodic materials that exhibit high activity toward photoelectrochemical (PEC) HER at more positive potentials because a higher potential means a lower overpotential for HER. In this work, the Cu2O/CuO bilayered composites were prepared by a facile method that involved an electrodeposition and a subsequent thermal oxidation. The resulting Cu2O/CuO bilayered composites exhibited a surprisingly high activity and good stability toward PEC HER, expecially at high potentials in alkaline solution. The photocurrent density for HER was 3.15 mA·cm−2 at the potential of 0.40 V vs. RHE, which was one of the two highest reported at the same potential on copper-oxide-based photocathode. The high photoactivity of the bilayered composite was ascribed to the following three advantages of the Cu2O/CuO heterojunction: (1) the broadened light absorption band that made more efficient use of solar energy, (2) the large space-charge-region potential that enabled a high efficiency for electron-hole separation, and (3) the high majority carrier density that ensured a faster charge transportation rate. This work reveals the potential of the Cu2O/CuO bilayered composite as a promising photocathodic material for solar water splitting. PMID:27748380

ESR, SIMS and TEMF of an Y-Ba-Cu-O superconductor

NASA Technical Reports Server (NTRS)

Kirschner, I.; Giber, J.; Halasz, I.

1995-01-01

Superconducting transition comes into being between 92 K and 82 K in the samples having a Meissner's state value of 68 vol. percent. The main material content has an orthorhombic unit cell of Y1Ba2Cu408 accompanied by low quantity CuO and a sporadic phase. A proof of anisotropic superconductivity, an unusually high Cu ion concentration and a temperature dependent transition of charge carriers have been observed.

Junction formation of Cu3BiS3 investigated by Kelvin probe force microscopy and surface photovoltage measurements

PubMed Central

Mesa, Fredy; Chamorro, William; Vallejo, William; Baier, Robert; Dittrich, Thomas; Grimm, Alexander; Lux-Steiner, Martha C

2012-01-01

Summary Recently, the compound semiconductor Cu3BiS3 has been demonstrated to have a band gap of ~1.4 eV, well suited for photovoltaic energy harvesting. The preparation of polycrystalline thin films was successfully realized and now the junction formation to the n-type window needs to be developed. We present an investigation of the Cu3BiS3 absorber layer and the junction formation with CdS, ZnS and In2S3 buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20–100 nm, and a considerably smaller work-function distribution for In2S3 compared to that of CdS and ZnS. For In2S3 and CdS buffer layers the KPFM experiments indicate negatively charged Cu3BiS3 grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate the influence of defect states below the band gap on charge separation and a surface-defect passivation by the In2S3 buffer layer. Our findings indicate that Cu3BiS3 may become an interesting absorber material for thin-film solar cells; however, for photovoltaic application the band bending at the charge-selective contact has to be increased. PMID:22497001

Junction formation of Cu(3)BiS(3) investigated by Kelvin probe force microscopy and surface photovoltage measurements.

PubMed

Mesa, Fredy; Chamorro, William; Vallejo, William; Baier, Robert; Dittrich, Thomas; Grimm, Alexander; Lux-Steiner, Martha C; Sadewasser, Sascha

2012-01-01

Recently, the compound semiconductor Cu(3)BiS(3) has been demonstrated to have a band gap of ~1.4 eV, well suited for photovoltaic energy harvesting. The preparation of polycrystalline thin films was successfully realized and now the junction formation to the n-type window needs to be developed. We present an investigation of the Cu(3)BiS(3) absorber layer and the junction formation with CdS, ZnS and In(2)S(3) buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20-100 nm, and a considerably smaller work-function distribution for In(2)S(3) compared to that of CdS and ZnS. For In(2)S(3) and CdS buffer layers the KPFM experiments indicate negatively charged Cu(3)BiS(3) grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate the influence of defect states below the band gap on charge separation and a surface-defect passivation by the In(2)S(3) buffer layer. Our findings indicate that Cu(3)BiS(3) may become an interesting absorber material for thin-film solar cells; however, for photovoltaic application the band bending at the charge-selective contact has to be increased.

Two superconducting transitions in single-crystal La 2 - x Ba x CuO 4

DOE PAGES

Tee, X. Y.; Ito, T.; Ushiyama, T.; ...

2017-02-27

Here, we use spatially-resolved transport techniques to investigate the superconducting properties of single crystals La 2-xBa xCuO 4. We also found a superconducting transition temperature T cs associated with the ab-plane surface region which is considerably higher than the bulk T c. This effect is pronounced in the region of charge carrier doping x with strong spin-charge stripe correlations, reaching T cs = 36 K or 1.64T c.

Macroscopic shape change of melt-processed YBa{sub 2}Cu{sub 3}O{sub x-}Y{sub 2}BaCuO{sub 5} bulk superconductors.

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

Diko, P.; Goretta, K. C.; Energy Technology

A macroscopic change in the shape of five-domain melt-processed YBa{sub 2}Cu{sub 3}O{sub x}/Y{sub 2}BaCuO{sub 5} bulk superconductors is reported and explained. The change, a distortion from circular cross-section, is attributed to liquid transport from a slower growth front in an a-axis direction to a faster growth front in a c-axis direction at the edge between the a- and c-growth fronts, a phenomenon that we call the edge melt distribution (EMD) effect. Formation of bands of higher Y{sub 2}BaCuO{sub 5} particle density along the a/c growth boundaries, which nearly coincide with {l_brace}110{r_brace}-type planes, is explained by the EMD effect.

Spin-isospin excitations from the ground-state of 64Ni

NASA Astrophysics Data System (ADS)

Popescu, L.; Adachi, T.; Bäumer, C.; Berg, G. P. A.; van den Berg, A. M.; von Brentano, P.; Frekers, D.; de Frenne, D.; Fujita, K.; Fujita, Y.; Grewe, E. W.; Haefner, P.; Hatanaka, K.; Hunyadi, M.; de Huu, M.; Jacobs, E.; Johansson, H.; Korff, A.; Negret, A.; Nakanishi, K.; von Neumann-Cosel, P.; Rakers, S.; Ryezayeva, N.; Sakemi, Y.; Shevchenko, A.; Shimbara, Y.; Shimizu, Y.; Simon, H.; Tameshige, Y.; Tamii, A.; Uchida, M.; Wörtche, H. J.; Yosoi, M.

2006-03-01

Spin-isospin (Gamow-Teller) excitations in 64Cu and 64Co have been studied using (3He,t) and (d,2He) charge-exchange reactions on 64Ni. As the isospin of the 64Ni ground-state is T0=4, states with T=3, 4 and 5 in 64Cu are excited via the (3He,t) reaction and states with T=5 in 64Co via (d,2He). If we assume that the nuclear interaction is charge symmetric, the T=5 states in 64Cu should appear at corresponding excitation energies (if corrected for the Coulomb displacement) and with similar strengths as the T=5 states in 64Co. As in the 64Cu spectrum the T=5 states are very weakly excited, only by combining the results of the two complementary experiments one can estimate the Gamow-Teller strength starting from 64Ni in a consistent way.

Spin-isospin excitations from the ground-state of 64Ni

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

Popescu, L.; Frenne, D. de; Jacobs, E.

2006-03-13

Spin-isospin (Gamow-Teller) excitations in 64Cu and 64Co have been studied using (3He,t) and (d,2He) charge-exchange reactions on 64Ni. As the isospin of the 64Ni ground-state is T0=4, states with T=3, 4 and 5 in 64Cu are excited via the (3He,t) reaction and states with T=5 in 64Co via (d,2He). If we assume that the nuclear interaction is charge symmetric, the T=5 states in 64Cu should appear at corresponding excitation energies (if corrected for the Coulomb displacement) and with similar strengths as the T=5 states in 64Co. As in the 64Cu spectrum the T=5 states are very weakly excited, only bymore » combining the results of the two complementary experiments one can estimate the Gamow-Teller strength starting from 64Ni in a consistent way.« less

Tunable Core-Shell Single-Walled Carbon Nanotube-Cu2S Networked Nanocomposites as High-Performance Cathodes for Lithium-ion Batteries

DOE PAGES

Meng, Xiangbo; Riha, Shannon C.; Libera, Joseph A.; ...

2015-01-24

In this study, nanoscale copper(I) sulfide (n-Cu2S) was deposited over networks of single-walled carbon nanotubes (SWCNTs) by atomic layer deposition (ALD). This synthetic route provides a high degree of control for tuning the materials properties. The resulting core shell SWCNT-n-Cu2S composite structure ensures an intimate contact between the two components while maintaining a high porosity for efficient transport of charges. Indeed, electrochemical testing demonstrates that these nanocomposites are promising as cathodes in lithium-ion batteries (LIBs), exhibiting excellent stability over 200 discharge-charge cycles with a sustainable, high capacity of 260 mAh g(-1) (92% of the theoretical value in terms of Cu2S)more » and >99% Coulombic efficiency. This work establishes a general strategy for developing high-performance nanoscale electrode materials.« less

Systematic Introduction of Aromatic Rings to Diphosphine Ligands for Emission Color Tuning of Dinuclear Copper(I) Iodide Complexes.

PubMed

Okano, Yuka; Ohara, Hiroki; Kobayashi, Atsushi; Yoshida, Masaki; Kato, Masako

2016-06-06

We have newly synthesized two solution-stable luminescent dinuclear copper(I) complexes, [Cu2(μ-I)2(dpppy)2] (Cu-py) and [Cu2(μ-I)2(dpppyz)2] (Cu-pyz), where dpppy = 2,3-bis(diphenylphosphino)pyridine and dpppyz = 2,3-bis(diphenylphosphino)pyrazine, using chelating diphosphine ligands composed of N-heteroaromatic rings. X-ray analysis clearly indicates that the molecular structures of Cu-py and Cu-pyz are almost identical with that of the parent complex, [Cu2(μ-I)2(dppb)2] [Cu-bz; dppb = 2,3-bis(diphenylphosphino)benzene]. Complexes Cu-py and Cu-pyz exhibit luminescence [emission quantum yield (Φem) = 0.48 and 0.02, respectively] in the solid state at 298 K. A wide emission color tuning, from 497 to 638 nm (energy = 0.55 eV, with an emission color ranging from green to reddish-orange), was achieved in the solid state by the introduction of pyridinic N atoms into the bridging phenyl group between the two diphenylphosphine groups. Density functional theory calculations suggest that the emission could originate from the effective combination of the metal-to-ligand charge-transfer excited state with the halide-to-ligand charge-transfer excited state. Thus, the emission color change is due to stabilization of the π* levels of the central aryl group in the diphosphine ligand. Furthermore, these copper(I) complexes exhibit thermally activated delayed fluorescence at 298 K because of the small singlet-triplet energy difference (ΔE = 523 and 564 cm(-1) for Cu-py and Cu-pyz, respectively). The stability of these complexes in chloroform, due to the rigid bonds between the diphosphine ligands and the Cu(I) ions, enables the preparation of emissive poly(methyl methacrylate) films by the solution-doping technique.

Effect of magnetic ion Ni doping for Cu in the CuO 2 plane on electronic structure and superconductivity on Y123 cuprate

NASA Astrophysics Data System (ADS)

Cao, Shixun; Li, Pinglin; Cao, Guixin; Zhang, Jincang

2003-05-01

The YBa2Cu3-xNixO7-δ with x=0-0.4 have been studied using positron annihilation technique. The changes of positron annihilation parameters with the Ni substitution concentration x are given. From the change of electronic density ne and Tc, it would prove that the localized carriers (electron and hole) in Cu-O chain and CuO2 planes have enormous influence on superconductivity by affecting charge transfer between the reservoir layer and CuO2 planes.

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

Li, Yue Ru; Poyraz, Altug S.; Hu, Xiaobing

Birnessite type layered manganese dioxides (δ-MnO 2) have attracted considerable attention in recent years as 2D intercalation cathodes for rechargeable Li +, Na +, and Mg 2+ batteries due to fast ion diffusion through their negatively charged δ-MnO 2 sheets separated by interlayer cations and a stable Mn 3+/4+ redox couple. Here we report the preparation and electrochemistry of zero and divalent copper co-intercalated birnessite type manganese dioxide (Cu 0 0.03Cu 2+ 0.21Na 0.12MnO 2·0.9H 2O). The copper intercalated birnessite materials were fully characterized utilizing powder X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), transmission electron microscopy (TEM).more » The mixed valent nature of intercalated Cu 0 and Cu 2+ was confirmed by X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS). Electrochemical evaluation results show that zero valent copper intercalated birnessite exhibits higher discharge capability, improved cyclability, and lower impedance compared to the Cu 2+ only intercalated (Cu 0.26MnO 2·1.0H 2O) and Cu free Na birnessite (Na 0.40MnO 2·1.0H 2O) materials. Remarkably, zero valent copper birnessite shows almost no fade after 10 cycles at 0.1 mV/s. Electrochemical impedance spectroscopy results suggest that charge transfer resistivity of Cu 0 modified samples was much lower than that of Cu 2+ and Cu free birnessite, indicating that the presence of a small amount of Cu 0 improves the conductivity of birnessite and results in better electrochemical cyclability, rate capability, and lower impedance.« less

Magnetic field induced anisotropy of 139La spin-lattice relaxation rates in stripe ordered La 1.875Ba 0.125CuO 4

DOE PAGES

S. -H. Baek; Gu, G. D.; Utz, Y.; ...

2015-10-26

We report 139La nuclear magnetic resonance studies performed on a La 1.875Ba 0.125CuO 4 single crystal. The data show that the structural phase transitions (high-temperature tetragonal → low-temperature orthorhombic → low-temperature tetragonal phase) are of the displacive type in this material. The 139La spin-lattice relaxation rate T –1 1 sharply upturns at the charge-ordering temperature T CO = 54 K, indicating that charge order triggers the slowing down of spin fluctuations. Detailed temperature and field dependencies of the T –1 1 below the spin-ordering temperature T SO=40 K reveal the development of enhanced spin fluctuations in the spin-ordered state formore » H ∥ [001], which are completely suppressed for large fields along the CuO 2 planes. Lastly, our results shed light on the unusual spin fluctuations in the charge and spin stripe ordered lanthanum cuprates.« less

Magnetic field induced anisotropy of 139La spin-lattice relaxation rates in stripe ordered La 1.875Ba 0.125CuO 4

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

S. -H. Baek; Gu, G. D.; Utz, Y.

We report 139La nuclear magnetic resonance studies performed on a La 1.875Ba 0.125CuO 4 single crystal. The data show that the structural phase transitions (high-temperature tetragonal → low-temperature orthorhombic → low-temperature tetragonal phase) are of the displacive type in this material. The 139La spin-lattice relaxation rate T –1 1 sharply upturns at the charge-ordering temperature T CO = 54 K, indicating that charge order triggers the slowing down of spin fluctuations. Detailed temperature and field dependencies of the T –1 1 below the spin-ordering temperature T SO=40 K reveal the development of enhanced spin fluctuations in the spin-ordered state formore » H ∥ [001], which are completely suppressed for large fields along the CuO 2 planes. Lastly, our results shed light on the unusual spin fluctuations in the charge and spin stripe ordered lanthanum cuprates.« less

Development of Techniques for Investigating Energy Contributions to Target Deformation and Penetration During Reactive Projectile Hypervelocity Impact

DTIC Science & Technology

2011-07-01

a reactive and a non reactive shaped charge liner is in the energy release of the combustion ... reactive shaped charge jets the reaction is explained and the possible energy release of the metal combustion is estimated. Addition- ally the...Charges In a shaped charge a -in most cases- conical cavity in the explosive is covered with a liner. If the explosive detonates , a small portion

Influence of oxygen vacancy on the electronic structure of CaCu3Ti4O12 and its deep-level vacancy trap states by first-principle calculation

NASA Astrophysics Data System (ADS)

Xiao, H. B.; Yang, C. P.; Huang, C.; Xu, L. F.; Shi, D. W.; Marchenkov, V. V.; Medvedeva, I. V.; Bärner, K.

2012-03-01

The electronic structure, formation energy, and transition energy levels of intrinsic defects have been studied using the density-functional method within the generalized gradient approximation for neutral and charged oxygen vacancy in CaCu3Ti4O12 (CCTO). It is found that oxygen vacancies with different charge states can be formed in CCTO under both oxygen-rich and poor conditions for nonequilibrium and higher-energy sintering processes; especially, a lower formation energy is obtained for poor oxygen environment. The charge transition level (0/1+) of the oxygen vacancy in CCTO is located at 0.53 eV below the conduction-band edge. The (1+/2+) transition occurs at 1.06 eV below the conduction-band edge. Oxygen vacancies of Vo1+ and Vo2+ are positive stable charge states in most gap regions and can act as a moderately deep donor for Vo1+ and a borderline deep for Vo2+, respectively. The polarization and dielectric constant are considerably enhanced by oxygen vacancy dipoles, due to the off-center Ti and Cu ions in CCTO.

Self-consistent calculations for the electronic structure of a vacancy in copper. A solution of the embedding problem

NASA Astrophysics Data System (ADS)

Zeller, R.; Braspenning, P. J.

1982-06-01

The charge density and the local density of states for a vacancy in Cu and for the first shell of Cu neighbours are calculated by the KKR-Green's function technique. The muffin-tin potentials for the vacancy and the neighbour shell atoms are determined self-consistently in the local density approximation of density functional theory. By the use of the proper host Green's function the embedding of this cluster of 13 perturbed muffin-tins into the infinite array of bulk Cu muffin-tin potentials is described rigorously, thus representing a solution of the embedding problem. The calculations demonstrate a rather large charge transfer of 1.1 electrons from the first neighbour shell to the vacancy.

Electrochemically deposited Cu2O cubic particles on boron doped diamond substrate as efficient photocathode for solar hydrogen generation

NASA Astrophysics Data System (ADS)

Mavrokefalos, Christos K.; Hasan, Maksudul; Rohan, James F.; Compton, Richard G.; Foord, John S.

2017-06-01

Herein, we report a novel photocathode for the water splitting reaction. The electrochemical deposition of Cu2O particles on boron doped diamond (BDD) electrodes and the subsequent decoration with NiO nanoparticles by a dip coating method to act as co-catalyst for hydrogen evolution reaction is described. The morphology analysis by scanning electron microscope (SEM) revealed that Cu2O particles are cubic and decorated sporadically with NiO nanoparticles. X-ray photoelectron spectroscopy (XPS) confirmed the electronic interaction at the interface between Cu2O and NiO through a binding energy shift of the main Cu 2p peak. The photoelectrochemical (PEC) performance of NiO-Cu2O/BDD showed a much higher current density (-0.33 mA/cm2) and photoconversion efficiency (0.28%) compared to the unmodified Cu2O/BDD electrode, which are only -0.12 mA/cm2 and 0.06%, respectively. The enhancement in PEC performance is attributable to the synergy of NiO as an electron conduction mediator leading to the enhanced charge separation and transfer to the reaction interface for hydrogen evolution as evidenced by electrochemical impedance spectroscopy (EIS) and charge carrier density calculation. Stability tests showed that the NiO nanoparticles loading content on Cu2O surface is a crucial parameter in this regard.

Controlled Synthesis of CuS/TiO2 Heterostructured Nanocomposites for Enhanced Photocatalytic Hydrogen Generation through Water Splitting.

PubMed

Chandra, Moumita; Bhunia, Kousik; Pradhan, Debabrata

2018-04-16

Photocatalytic hydrogen (H 2 ) generation through water splitting has attracted substantial attention as a clean and renewable energy generation process that has enormous potential in converting solar-to-chemical energy using suitable photocatalysts. The major bottleneck in the development of semiconductor-based photocatalysts lies in poor light absorption and fast recombination of photogenerated electron-hole pairs. Herein we report the synthesis of CuS/TiO 2 heterostructured nanocomposites with varied TiO 2 contents via simple hydrothermal and solution-based process. The morphology, crystal structure, composition, and optical properties of the as-synthesized CuS/TiO 2 hybrids are evaluated in detail. Controlling the CuS/TiO 2 ratio to an optimum value leads to the highest photocatalytic H 2 production rate of 1262 μmol h -1 g -1 , which is 9.7 and 9.3 times higher than that of pristine TiO 2 nanospindles and CuS nanoflakes under irradiation, respectively. The enhancement in the H 2 evolution rate is attributed to increased light absorption and efficient charge separation with an optimum CuS coverage on TiO 2 . The photoluminescence and photoelectrochemical measurements further confirm the efficient separation of charge carriers in the CuS/TiO 2 hybrid. The mechanism and synergistic role of CuS and TiO 2 semiconductors for enhanced photoactivity is further delineated.

Fabrication of nano copper oxide evenly patched on cubic sodium tantalate for oriented photocatalytic reduction of carbon dioxide.

PubMed

Xiang, Tianyu; Xin, Feng; Zhao, Can; Lou, Shuo; Qu, Wenxiu; Wang, Yong; Song, Yuexiao; Zhang, Shuangfang; Yin, Xiaohong

2018-05-15

A synthetic process was exploited to fabricate patchy CuO evenly planted on cubic NaTaO 3 for photocatalytically reducing CO 2 in isopropanol. The nano patches of CuO with about 15 nm in size were uniformly distributed on the surface of NaTaO 3 via a phase-transfer protocol and solvothermal synthesis. The crystal phase, morphology, composition, optical absorption and charge separation of as-prepared CuO-NaTaO 3 were characterized by XRD, SEM, TEM, EDX, XPS, UV-Vis and PL. The results of photocatalytic reduction of CO 2 confirmed that the CuO patched NaTaO 3 possessed better ability to separate charge carriers and selectively reduce CO 2 to methanol than CuO directly loaded NaTaO 3 using the traditional liquid phase reduction procedure after comparing the methanol yields. Furthermore, 5 wt% CuO patched NaTaO 3 led to the highest methanol yield of 1302.22 μmol g -1 h -1 . A redox mechanism was proposed and illustrated in a schematic diagram. Copyright © 2018 Elsevier Inc. All rights reserved.

Theoretical study of hydrated copper(II) interactions with guanine: a computational density functional theory study.

PubMed

Pavelka, Matej; Shukla, Manoj K; Leszczynski, Jerzy; Burda, Jaroslav V

2008-01-17

Optimization of the hydrated Cu(II)(N7-guanine) structures revealed a number of minima on the potential energy surface. For selected structures, energy decompositions together with the determination of electronic properties (partial charges and electron spin densities) were performed. In the complexes of guanine with the bare copper cation and that with the monoaqua ligated cation, an electron transfer from guanine to Cu(II) was observed, resulting in a Cu(I)-guanine(+) type of complex. Conformers with two aqua ligands are borderline systems characterized by a Cu partial charge of +0.7e and a similar value of the spin density (0.6e) localized on guanine. When tetracoordination of copper was achieved, only then the prevailing electron spin density is unambiguously localized on copper. The energetic preference of diaqua-Cu-(N7,O6-guanine) over triaqua-Cu-(N7-guanine) was found for the four-coordinate structures. However, the energy difference between these two conformations decreases with the number of water molecules present in the systems, and in complexes with five water molecules this preference is preserved only at DeltaG level where thermal and entropy terms are included.

Synthesis of Stable Interfaces on SnO2 Surfaces for Charge-Transfer Applications

NASA Astrophysics Data System (ADS)

Benson, Michelle C.

The commercial market for solar harvesting devices as an alternative energy source requires them to be both low-cost and efficient to replace or reduce the dependence on fossil fuel burning. Over the last few decades there has been promising efforts towards improving solar devices by using abundant and non-toxic metal oxide nanomaterials. One particular metal oxide of interest has been SnO2 due to its high electron mobility, wide-band gap, and aqueous stability. However SnO2 based solar cells have yet to reach efficiency values of other metal oxides, like TiO2. The advancement of SnO2 based devices is dependent on many factors, including improved methods of surface functionalization that can yield stable interfaces. This work explores the use of a versatile functionalization method through the use of the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The CuAAC reaction is capable of producing electrochemically, photochemically, and electrocatalytically active surfaces on a variety of SnO2 materials. The resulting charge-transfer characteristics were investigated as well as an emphasis on understanding the stability of the resulting molecular linkage. We determined the CuAAC reaction is able to proceed through both azide-modified and alkyne-modified surfaces. The resulting charge-transfer properties showed that the molecular tether was capable of supporting charge separation at the interface. We also investigated the enhancement of electron injection upon the introduction of an ultra-thin ZrO2 coating on SnO2. Several complexes were used to fully understand the charge-transfer capabilities, including model systems of ferrocene and a ruthenium coordination complex, a ruthenium mononuclear water oxidation catalyst, and a commercial ruthenium based dye.

Analysis of spectra of 3s-3p and 3p-3d transitions of highly-charged copper ions

NASA Astrophysics Data System (ADS)

Su, M. G.; Min, Q.; He, S. Q.; Wu, L.; Sun, R.; Ding, X. B.; Sun, D. X.

2017-08-01

Beam-foil excited spectra in the range of 160-360 Å from highly charged copper ions were identified with the aid of the National Institute of Standards and Technology Atomic Spectra Database and theoretical calculations with Cowan and Flexible Atomic Code (FAC) calculations. Spectra arising from 3s-3p and 3p-3d transitions of Cu13+-Cu22+ ions were considered. The ion fraction at an ion beam energy of 110 MeV was estimated from the equilibrium charge distribution of the fast ion beams after passing through the solid. The corresponding simulated spectra were in good agreement with the experimental result. Our Cowan and FAC calculation results should be useful for further spectral identification and lifetime measurements of highly charged copper ions.

A comparative study on charge carrier recombination across the junction region of Cu{sub 2}ZnSn(S,Se){sub 4} and Cu(In,Ga)Se{sub 2} thin film solar cells

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

Halim, Mohammad Abdul, E-mail: halimtsukuba2012@gmail.com; Islam, Muhammad Monirul; Luo, Xianjia

A comparative study with focusing on carrier recombination properties in Cu{sub 2}ZnSn(S,Se){sub 4} (CZTSSe) and the CuInGaSe{sub 2} (CIGS) solar cells has been carried out. For this purpose, electroluminescence (EL) and also bias-dependent time resolved photoluminescence (TRPL) using femtosecond (fs) laser source were performed. For the similar forward current density, the EL-intensity of the CZTSSe sample was obtained significantly lower than that of the CIGS sample. Primarily, it can be attributed to the existence of excess amount of non-radiative recombination center in the CZTSSe, and/or CZTSSe/CdS interface comparing to that of CIGS sample. In case of CIGS sample, TRPL decaymore » time was found to increase with the application of forward-bias. This can be attributed to the reduced charge separation rate resulting from the reduced electric-field at the junction. However, in CZTSSe sample, TRPL decay time has been found almost independent under the forward and reverse-bias conditions. This phenomenon indicates that the charge recombination rate strongly dominates over the charge separation rate across the junction of the CZTSSe sample. Finally, temperature dependent V{sub OC} suggests that interface related recombination in the CZTSSe solar cell structure might be one of the major factors that affect EL-intensity and also, TRPL decay curves.« less

Improving the efficiency of quantum-dot-sensitized solar cells by optimizing the growth time of the CuS counter electrode

NASA Astrophysics Data System (ADS)

Sunesh, Chozhidakath Damodharan; Gopi, Chandu V. V. M.; Muthalif, Mohammed Panthakkal Abdul; Kim, Hee-Je; Choe, Youngson

2017-09-01

CuS counter electrodes (CEs) were prepared to fabricate efficient quantum-dot-sensitized solar cells (QDSSCs) based on a CdS/CdSe photo sensitizer. The CEs were prepared on a fluorine-doped tin oxide (FTO) glass substrate by a facile chemical bath deposition (CBD) method by dissolving CuSO4·5H2O and CH3CSNH2 in water, followed by adding 0.25 mM polyvinylpyrrolidone (PVP). The CBD was performed at 60 °C for 1 h, 2 h, and 3 h, and the samples were labeled as CuS 1 h, CuS 2 h, and CuS 3 h, respectively. The QDSSCs were assembled using prepared CuS CEs and a TiO2/CdS/CdSe/ZnS photoanode, and the effect of the growth time of CuS CEs on the QDSSC performance was investigated. As the CuS growth time increases, the short-circuit current density (Jsc), fill factor (FF), and open-circuit voltage (Voc) of the QDSSCs gradually increases, leading to an enhanced power conversion efficiency (η). QDSSCs that use the CuS 2 h CE exhibit a high Jsc of 14.31 mA cm-2, Voc of 0.603 V, and FF of 0.49, which are higher than that using conventional Pt electrodes as well as CuS 1 h and CuS 3 h electrodes. The electrochemical impedance spectroscopy results show that the CuS 2 h CE exhibits an inferior charge transfer resistance of only 2.93 Ω, which is 33 times lesser than that of the Pt CE. The enhanced device performance of CuS 2 h is ascribed to the high catalytic activity and low charge transfer resistance of the CuS CE in the reduction process of oxidized polysulfide. Consequently, a superior power conversion efficiency of 4.27% is achieved for QDSSCs utilizing CuS 2 h.

In situ oxidation studies on /001/ copper-nickel alloy thin films

NASA Technical Reports Server (NTRS)

Heinemann, K.; Rao, D. B.; Douglass, D. L.

1977-01-01

High-resolution transmission electron microscopy studies are reported of (001)-oriented single crystalline thin films of Cu-3%Ni, Cu-4.6%Ni, and Cu-50%Ni alloy which were prepared by vapor deposition onto (001) NaCl substrates and subsequently annealed at around 1100 K and oxidized at 725 K at low oxygen partial pressure. At all alloy concentrations, Cu2O and NiO nucleated and grew independently without the formation of mixed oxides. The shape and growth rates of Cu2O nuclei were similar to rates found earlier. For low-nickel alloy concentrations, the NiO nuclei were larger and the number density of NiO was less than that of Cu-50%Ni films for which the shape and growth rates of NiO were identical to those for pure nickel films. Phenomena involving a reduced induction period, surface precipitation, and through-thickness growth are also described. The results are consistent with previously established oxidation mechanisms for pure copper and pure nickel films.

A first-principles model of copper-boron interactions in Si: implications for the light-induced degradation of solar Si

NASA Astrophysics Data System (ADS)

Wright, E.; Coutinho, J.; Öberg, S.; Torres, V. J. B.

2017-02-01

The recent discovery that Cu contamination of Si combined with light exposure has a significant detrimental impact on carrier life-time has drawn much concern within the solar-Si community. The effect, known as the copper-related light-induced degradation (Cu-LID) of Si solar cells, has been connected to the release of Cu interstitials within the bulk (2016 Sol. Energy Mater. Sol. Cells 147 115-26). In this paper, we describe a comprehensive analysis of the formation/dissociation process of the CuB pair in Si by means of first-principles modelling, as well as the interaction of CuB defects with photo-excited minority carriers. We confirm that the long-range interaction between the \\text{Cu}\\text{i}+ cation and the \\text{B}\\text{s}- anion has a Coulomb-like behaviour, in line with the trapping-limited diffusivity of Cu observed by transient ion drift measurements. On the other hand, the short-range interaction between the d-electrons of Cu and the excess of negative charge on \\text{B}\\text{s}- produces a repulsive effect, thereby decreasing the binding energy of the pair when compared to the ideal point-charge Coulomb model. We also find that metastable CuB pairs produce acceptor states just below the conduction band minimum, which arise from the Cu level emptied by the B acceptor. Based on these results, we argue that photo-generated minority carriers trapped by the metastable pairs can switch off the Coulomb interaction that holds the pairs together, enhancing the release of Cu interstitials, and acting as a catalyst for Cu-LID.

Longitudinal bunch shaping of picosecond high-charge MeV electron beams

DOE PAGES

Beaudoin, B. L.; Thangaraj, J. C. T.; Edstrom, Jr., D.; ...

2016-10-20

With ever increasing demands for intensities in modern accelerators, the understanding of space-charge effects becomes crucial. Herein are presented measurements of optically shaped picosecond-long electron beams in a superconducting L-band linac over a wide range of charges, from 0.2 nC to 3.4 nC. At low charges, the shape of the electron beam is preserved, while at higher charge densities, modulations on the beam convert to energy modulations. Here, energy profile measurements using a spectrometer and time profile measurements using a streak camera reveal the dynamics of longitudinal space-charge on MeV-scale electron beams.

Double-shell CuS nanocages as advanced supercapacitor electrode materials

NASA Astrophysics Data System (ADS)

Guo, Jinxue; Zhang, Xinqun; Sun, Yanfang; Zhang, Xiaohong; Tang, Lin; Zhang, Xiao

2017-07-01

Metal sulfides hollow structures are advanced materials for energy storage applications of lithium-ion batteries and supercapacitors. However, constructing hollow metal sulfides with specific features, such as multi-shell and non-spherical shape, still remains great challenge. In this work, we firstly demonstrate the synthesis of CuS double-shell hollow nanocages using Cu2O nanocubes as precursors. The synthesis processes involve the repeated anion exchange reaction with Na2S and the controllable etching using hydrochloric acid. The whole synthesis processes are well revealed and the obtained double-shell CuS is tested as pseudocapacitive electrode material for supercapacitors. As expected, the CuS double-shell hollow nanocages deliver high specific capacitance, good rate performance and excellent cycling stability due to their unique nano-architecture. The present work contributes greatly to the exploration of hollow metal sulfides with complex architecture and non-spherical shape, as well as their promising application in high-performance electrochemical supercapacitors.

Controlled Synthesis of Nanomaterials at the Undergraduate Laboratory: Cu(OH)[subscript 2] and CuO Nanowires

ERIC Educational Resources Information Center

da Silva, Anderson G. M.; Rodrigues, Thenner S.; Parussulo, Andre´ L. A.; Candido, Eduardo G.; Geonmonond, Rafael S.; Brito, Hermi F.; Toma, Henrique E.; Camargo, Pedro H. C.

2017-01-01

Undergraduate-level laboratory experiments that involve the synthesis of nanomaterials with well-defined/controlled shapes are very attractive under the umbrella of nanotechnology education. Herein we describe a low-cost and facile experiment for the synthesis of Cu(OH)[subscript 2] and CuO nanowires comprising three main parts: (i) synthesis of…

Temperature and depth dependence of positron annihilation parameters in YBa2Cu3O7-x and La1.85Sr0.15CuO4

NASA Astrophysics Data System (ADS)

Lynn, K. G.; Usmar, S. G.; Nielsen, B.; van der Kolk, G. J.; Kanazawa, I.; Sferlazzo, P.; Moodenbaugh, A. R.

1988-02-01

The temperature dependence of the positron annihilation parameters for YBa2Cu3O7-x x=0.7, 0.4 and 0.0 and La1.85Sr0.15CuO4 were measured. The depth dependence of the YBa2Cu3O7 was studied using a variable-energy positron beam showing a strong depth dependence in the Doppler line-shape extending up to an average depth of ˜5.0 μm. It was found that a transition in the Doppler line-shape parameter, ``S'', was associated with the superconducting transition temperature (Tc) in YBa2Cu3O7-x x=0.4 and 0.0 while no transition was observed in the nonsuperconducting YBa2Cu3O6.3. Positron lifetime parameters in YBa2Cu3O7 were found to be consistent with positrons localized at open volume regions (probably unoccupied crystallographic sites) in this material with a lifetime of 210 psec at 300 K. These results indicate that the electron density at these unoccupied sites increases, using a free electron model, approximately 9% between 100 and 12 K.

Fluorescence turn-on detection of alkaline phosphatase activity based on controlled release of PEI-capped Cu nanoclusters from MnO2 nanosheets.

PubMed

Zhang, Yunyi; Li, Yongxin; Zhang, Cuiyun; Zhang, Qingfeng; Huang, Xinan; Yang, Meiding; Shahzad, Sohail Anjum; Lo, Kenneth Kam-Wing; Yu, Cong; Jiang, Shichun

2017-08-01

A fluorescence turn-on assay for alkaline phosphatase (ALP) activity is developed through the controlled release of polyethyleneimine-capped copper nanoclusters (PEI-capped CuNCs) from the MnO 2 nanosheets. In an aqueous solution, the positively charged PEI-capped CuNCs could be adsorbed onto the surface of the negatively charged MnO 2 nanosheets. Such adsorption through favorable electrostatic interactions could efficiently quench the nanocluster fluorescence emission via resonance energy transfer from the PEI-capped CuNCs to the MnO 2 nanosheets. 2-Phospho-L-ascorbic acid (AAP) could be hydrolyzed to L-ascorbic acid (AA) in the presence of ALP. AA could reduce MnO 2 into Mn 2+ and trigger the disintegration of the MnO 2 nanosheets. As a result, the CuNCs were released and the quenched fluorescence was recovered efficiently. The detection strategy is simple, inexpensive, sensitive, selective, with low toxicity, and has better biocompatibility. The newly fabricated biosensor for ALP activity will potentially make it a robust candidate for numerous biological and biomedical applications.

The computation of lipophilicities of ⁶⁴Cu PET systems based on a novel approach for fluctuating charges.

PubMed

Comba, Peter; Martin, Bodo; Sanyal, Avik; Stephan, Holger

2013-08-21

A QSPR scheme for the computation of lipophilicities of ⁶⁴Cu complexes was developed with a training set of 24 tetraazamacrocylic and bispidine-based Cu(II) compounds and their experimentally available 1-octanol-water distribution coefficients. A minimum number of physically meaningful parameters were used in the scheme, and these are primarily based on data available from molecular mechanics calculations, using an established force field for Cu(II) complexes and a recently developed scheme for the calculation of fluctuating atomic charges. The developed model was also applied to an independent validation set and was found to accurately predict distribution coefficients of potential ⁶⁴Cu PET (positron emission tomography) systems. A possible next step would be the development of a QSAR-based biodistribution model to track the uptake of imaging agents in different organs and tissues of the body. It is expected that such simple, empirical models of lipophilicity and biodistribution will be very useful in the design and virtual screening of positron emission tomography (PET) imaging agents.

Measurements of directed, elliptic, and triangular flow in Cu + Au collisions at s NN = 200 GeV

DOE PAGES

Adare, A.; Aidala, C.; Ajitanand, N. N.; ...

2016-11-28

In this paper, measurements of anisotropic flow Fourier coefficients (v n) for inclusive charged particles and identified hadrons π ± ,K ±, p, andmore » $$\\overline{p}$$ produced at midrapidity in Cu + Au collisions at √sNN = 200 GeV are presented. The data were collected in 2012 by the PHENIX experiment at the Relativistic Heavy-Ion Collider (RHIC). The particle azimuthal distributions with respect to different-order symmetry planes Ψ n ,for n = 1, 2, and 3 are studied as a function of transverse momentum p T over a broad range of collision centralities. Mass ordering, as expected from hydrodynamic flow, is observed for all three harmonics. The charged-particle results are compared with hydrodynamical and transport model calculations. In addition, we also compare these Cu + Au results with those in Cu + Cu and Au + Au collisions at the same √sNN and find that the v 2 and v 3, as a function of transverse momentum, follow a common scaling with 1/(ε nN 1/3 part).« less

The microscopic structure of charge density waves in underdoped YBa 2Cu 3O 6.54 revealed by x-ray diffraction

DOE PAGES

E. M. Forgan; Huecker, M.; Blackburn, E.; ...

2015-12-09

Charge density wave (CDW) order appears throughout the underdoped high-temperature cuprate superconductors, but the underlying symmetry breaking and the origin of the CDW remain unclear. We use X-ray diffraction to determine the microscopic structure of the CDWs in an archetypical cuprate YBa 2Cu 3O 6.54 at its superconducting transition temperature ~60 K. We find that the CDWs in this material break the mirror symmetry of the CuO 2 bilayers. The ionic displacements in the CDWs have two components, which are perpendicular and parallel to the CuO 2 planes, and are out of phase with each other. The planar oxygen atomsmore » have the largest displacements, perpendicular to the CuO 2 planes. Our results allow many electronic properties of the underdoped cuprates to be understood. For example, the CDWs will lead to local variations in the electronic structure, giving an explicit explanation of density-wave states with broken symmetry observed in scanning tunnelling microscopy and soft X-ray measurements.« less

The microscopic structure of charge density waves in underdoped YBa2Cu3O6.54 revealed by X-ray diffraction

NASA Astrophysics Data System (ADS)

Forgan, E. M.; Blackburn, E.; Holmes, A. T.; Briffa, A. K. R.; Chang, J.; Bouchenoire, L.; Brown, S. D.; Liang, Ruixing; Bonn, D.; Hardy, W. N.; Christensen, N. B.; Zimmermann, M. V.; Hücker, M.; Hayden, S. M.

2015-12-01

Charge density wave (CDW) order appears throughout the underdoped high-temperature cuprate superconductors, but the underlying symmetry breaking and the origin of the CDW remain unclear. We use X-ray diffraction to determine the microscopic structure of the CDWs in an archetypical cuprate YBa2Cu3O6.54 at its superconducting transition temperature ~60 K. We find that the CDWs in this material break the mirror symmetry of the CuO2 bilayers. The ionic displacements in the CDWs have two components, which are perpendicular and parallel to the CuO2 planes, and are out of phase with each other. The planar oxygen atoms have the largest displacements, perpendicular to the CuO2 planes. Our results allow many electronic properties of the underdoped cuprates to be understood. For instance, the CDWs will lead to local variations in the electronic structure, giving an explicit explanation of density-wave states with broken symmetry observed in scanning tunnelling microscopy and soft X-ray measurements.

Cu substituted CeCo 5 : New optimal permanent magnetic material with reduced criticality

DOE PAGES

Chouhan, Rajiv K.; Paudyal, D.

2017-06-26

A comprehensive theoretical prediction using a mechanism of site substitution confirms the crucial role of Cu in enhancing the capabilities of CeCo 5 as a competitive magnet with its known high coercivity. A remarkable enhancement of magnetic anisotropy energy (MAE) of 3.09 meV/f.u. and 2.94 meV/f.u. without significant decrease of magnetic moment is found for 10% and 5% Cu substitution at 2c sites of the hexagonal lattice. Our calculations predict the increment of coercivity and magnetocrystalline anisotropy (1.6 times) compared to pristine CeCo 5. Furthermore, the exceptional enhancement in MAE is due to the formation of asymmetric charge hybridization amongmore » the Cu (2c) and Co (both 2c and 3g) sites along the uniaxial direction. Because of this asymmetric charge distribution environment, the intrinsic behavior of Ce adjacent to Cu changes abruptly making them more uniaxial and magnetically enhanced creating mixed valence states. For our calculations, we have employed the full-potential augmented plane wave method in conjunction with spin orbit coupling.« less

PMMA interlayer-modulated memory effects by space charge polarization in resistive switching based on CuSCN-nanopyramids/ZnO-nanorods p-n heterojunction

PubMed Central

Cheng, Baochang; Zhao, Jie; Xiao, Li; Cai, Qiangsheng; Guo, Rui; Xiao, Yanhe; Lei, Shuijin

2015-01-01

Resistive switching (RS) devices are commonly believed as a promising candidate for next generation nonvolatile resistance random access memory. Here, polymethylmethacrylate (PMMA) interlayer was introduced at the heterointerface of p-CuSCN hollow nanopyramid arrays and n-ZnO nanorod arrays, resulting in a typical bipolar RS behavior. We propose the mechanism of nanostructure trap-induced space charge polarization modulated by PMMA interlayer. At low reverse bias, PMMA insulator can block charges through the heterointerface, and and trapped states are respectively created on both sides of PMMA, resulting in a high resistance state (HRS) due to wider depletion region. At high reverse bias, however, electrons and holes can cross PMMA interlayer by Fowler-Nordeim tunneling due to a massive tilt of energy band, and then inject into the traps of ZnO and CuSCN, respectively. and trapped states are created, resulting in the formation of degenerate semiconductors on both sides of PMMA. Therefore, quantum tunneling and space charge polarization lead to a low resistance state (LRS). At relatively high forward bias, subsequently, the trapped states of and are recreated due to the opposite injection of charges, resulting in a recovery of HRS. The introduction of insulating interlayer at heterointerface, point a way to develop next-generation nonvolatile memories. PMID:26648249

High T c superconductivity in YBa2Cu3O7- x studied by PAC and PAS

NASA Astrophysics Data System (ADS)

Zhu, Shengyun; Li, Anli; Zheng, Shengnan; Huang, Hanchen; Li, Donghong; Din, Honglin; Du, Hongshan; Sun, Hancheng

1993-03-01

High T c superconductivity has been investigated in YBaCuO by both perturbed angular correlation and positron annihilation spectroscopy techniques as a function of temperature from 77 to 300 K. An abrupt change has been observed in the positron lifetime and Doppler broadening and the electric field gradient and its asymmetry parameter across T c, indicating a transition of two- to one-dimensional Cu-O-Cu chain structure and a charge transfer from CuO layers to CuO chains. An anomaly of the normal state has been demonstrated around 125 K, which is attributed to the structural instability.

[Co(NH3)6]3[Cu4(OH)(CO3)8].2H2O--a new carbonato-copper(II) anion stabilized by extensive hydrogen bonding.

PubMed

Abrahams, Brendan F; Haywood, Marissa G; Robson, Richard

2004-04-21

Addition of Co(NH3)6(3+) to aqueous solutions of Cu(II) in excess carbonate promotes the assembly of a new highly charged carbonato-copper(II) anion, [Cu4(OH)(CO3)8](9-), which contains an unusual mu4 hydroxo-bridged square Cu4 arrangement, stabilised in the crystal by no less than forty hydrogen bonds (< 3 Angstrom) to hexammine cations.

Copper-tuned magnetic order and excitations in iron-based superconductors Fe1+yTe1-xSex

NASA Astrophysics Data System (ADS)

Wen, Jinsheng; Xu, Zhijun; Xu, Guangyong; Lumsden, Mark; Matsuda, Masaaki; Valdivia, Patrick; Bourret, Edith; Lee, Dunghai; Gu, Genda; Tranquada, John; Birgeneau, Robert

2012-02-01

We report neutron scattering results on the Cu-substitution effects in the iron-based superconductors, Fe1+yTe1-xSex. In the parent compound, it is found that Cu drives the low-temperature magnetic ground state from long-range commensurate antiferromagnetic order in Fe1.06TeCu0.04 to short-range incommensurate order in FeTeCu0.1. In the former sample, the structural and magnetic ordering temperature is 40 K; in FeTeCu0.1, the structural phase transition is not obvious and a transition to the spin-glass state is found at 22 K. Cu suppresses superconductivity in FeTe0.5Se0.5---Tc is reduced to 7 K with a 2% Cu doping, and no superconductivity is found in the 10% Cu-doped sample. In the meantime, the intensity and energy of the resonance mode are suppressed in the 2% Cu-doped sample, while there is no resonance in the non-superconducting sample. Besides, the low-temperature magnetic excitation spectra are distinct for these two samples, with the superconducting one having an ``hour-glass" shape and the other one having a ``waterfall" shape. Our results provide further insights on the interplay between magnetism and superconductivity in the iron-based superconductors.

Controlling the orbital sequence in individual Cu-phthalocyanine molecules.

PubMed

Uhlmann, C; Swart, I; Repp, J

2013-02-13

We report on the controlled change of the energetic ordering of molecular orbitals. Negatively charged copper(II)phthalocyanine on NaCl/Cu(100) undergoes a Jahn-Teller distortion that lifts the degeneracy of two frontier orbitals. The energetic order of the levels can be controlled by Au and Ag atoms in the vicinity of the molecule. As only one of the states is occupied, the control of the energetic order is accompanied by bistable changes of the charge distribution inside the molecule, rendering it a bistable switch.

New Three-Dimensional Porous Electrode Concept: Vertically-Aligned Carbon Nanotubes Directly Grown on Embroidered Copper Structures

PubMed Central

Amade, Roger; Hussain, Shahzad; Bertran, Enric; Bechtold, Thomas

2017-01-01

New three-dimensional (3D) porous electrode concepts are required to overcome limitations in Li-ion batteries in terms of morphology (e.g., shapes, dimensions), mechanical stability (e.g., flexibility, high electroactive mass loadings), and electrochemical performance (e.g., low volumetric energy densities and rate capabilities). Here a new electrode concept is introduced based on the direct growth of vertically-aligned carbon nanotubes (VA-CNTs) on embroidered Cu current collectors. The direct growth of VA-CNTs was achieved by plasma-enhanced chemical vapor deposition (PECVD), and there was no application of any post-treatment or cleaning procedure. The electrochemical behavior of the as-grown VA-CNTs was analyzed by charge/discharge cycles at different specific currents and with electrochemical impedance spectroscopy (EIS) measurements. The results were compared with values found in the literature. The as-grown VA-CNTs exhibit higher specific capacities than graphite and pristine VA-CNTs found in the literature. This together with the possibilities that the Cu embroidered structures offer in terms of specific surface area, total surface area, and designs provide a breakthrough in new 3D electrode concepts. PMID:29232892

Resonant Two-Magnon Raman Scattering in Cuprate Antiferromagnetic Insulators and Superconductors.

NASA Astrophysics Data System (ADS)

Blumberg, G.; Abbamonte, P.; Klein, M. V.

1996-03-01

We present results of low-temperature two-magnon resonance Raman excitation profile measurements for single layer Sr_2CuO_2Cl2 and bilayer YBa_2Cu_3O6 + δ antiferromagnets over the excitation region from 1.65 to 3.05 eV. These data reveal composite structure of the B_1g two-magnon line shape peaked at ~ 2.7J and ~ 4J and strong nonmonotonic dependence of the scattering intensity on excitation energy. Resonant magnetic scattering contributes also to A_1g and B_2g channels. We analyze these data using the triple resonance theory of Chubukov and Frenkel(A. Chubukov and D. Frenkel, Phys. Rev. Lett.74), 3057 (1995). and deduce information about magnetic interaction (J and J_⊥) and band parameters (NN hopping t and charge transfer gap 2Δ) in these antiferromagnets.(G. Blumberg et. al.), Preprint cond-mat/9511080. The ~ 3J spin superexchange excitation persists upon hole doping and is present in superconductors, proving the universality of the short wavelength magnetic excitations in the cuprate superconducting metals and the parent antiferromagnetic insulators.(G. Blumberg et. al.), Phys. Rev. B 49, 13 295 (1994).

Generation of multicomponent ion beams by a vacuum arc ion source with compound cathode.

PubMed

Savkin, K P; Yushkov, Yu G; Nikolaev, A G; Oks, E M; Yushkov, G Yu

2010-02-01

This paper presents the results of time-of-flight mass spectrometry studies of the elemental and mass-to-charge state compositions of metal ion beams produced by a vacuum arc ion source with compound cathode (WC-Co(0.5), Cu-Cr(0.25), Ti-Cu(0.1)). We found that the ion beam composition agrees well with the stoichiometric composition of the cathode material from which the beam is derived, and the maximum ion charge state of the different plasma components is determined by the ionization capability of electrons within the cathode spot plasma, which is common to all components. The beam mass-to-charge state spectrum from a compound cathode features a greater fraction of multiply charged ions for those materials with lower electron temperature in the vacuum arc cathode spot, and a smaller fraction for those with higher electron temperature within the spot. We propose a potential diagram method for determination of attainable ion charge states for all components of the compound cathodes.

Edge-shape barrier irreversibility and decomposition of vortices in Bi 2Sr 2CaCu 2O 8

NASA Astrophysics Data System (ADS)

Indenbom, M. V.; D'Anna, G.; André, M.-O.; Kabanov, V. V.; Benoit, W.

1994-12-01

Magnetic flux dynamics is studied in Bi 2Sr 2CaCu 2O 8 single crystals by means of magneto-optical technique. It is clearly demonstrated that the magnetic irreversibility of these crystals in a magnetic field perpendicular to the basal plane at temperatures higher than approximately 35 K is governed by an edge-shape barrier and its disappearance determines the high temperature part of the magnetic irreversibility line which is commonly associated in the literature with vortex lattice melting. We argue that this barrier exists because of the non ellipsoidal shape of the samples and can disappear only when the flux lines lose their rigidity decomposing into pancakes, which is the only true magnetic phase transition on the B-T diagram for Bi 2Sr 2CaCu 2O 8.

Spin susceptibility of charge-ordered YBa2Cu3Oy across the upper critical field

NASA Astrophysics Data System (ADS)

Zhou, Rui; Hirata, Michihiro; Wu, Tao; Vinograd, Igor; Mayaffre, Hadrien; Krämer, Steffen; Reyes, Arneil P.; Kuhns, Philip L.; Liang, Ruixing; Hardy, W. N.; Bonn, D. A.; Julien, Marc-Henri

2017-12-01

The value of the upper critical field Hc2, a fundamental characteristic of the superconducting state, has been subject to strong controversy in high-Tc copper oxides. Since the issue has been tackled almost exclusively by macroscopic techniques so far, there is a clear need for local-probe measurements. Here, we use 17O NMR to measure the spin susceptibility χspin of the CuO2 planes at low temperature in charge-ordered YBa2Cu3Oy. We find that χspin increases (most likely linearly) with magnetic field H and saturates above field values ranging from 20 T to 40 T. This result is consistent with the lowest Hc2 values claimed previously and with the interpretation that the charge density wave (CDW) reduces Hc2 in underdoped YBa2Cu3Oy. Furthermore, the absence of marked deviation in χspin(H) at the onset of long-range CDW order indicates that this Hc2 reduction and the Fermi-surface reconstruction are primarily rooted in the short-range CDW order already present in zero field, not in the field-induced long-range CDW order. Above Hc2, the relatively low values of T= 2 K show that the pseudogap is a ground-state property, independent of the superconducting gap.

Zerovalent Copper Intercalated Birnessite as a Cathode for Lithium Ion Batteries: Extending Cycle Life

DOE PAGES

Li, Yue Ru; Poyraz, Altug S.; Hu, Xiaobing; ...

2017-01-01

Birnessite type layered manganese dioxides (δ-MnO 2) have attracted considerable attention in recent years as 2D intercalation cathodes for rechargeable Li +, Na +, and Mg 2+ batteries due to fast ion diffusion through their negatively charged δ-MnO 2 sheets separated by interlayer cations and a stable Mn 3+/4+ redox couple. Here we report the preparation and electrochemistry of zero and divalent copper co-intercalated birnessite type manganese dioxide (Cu 0 0.03Cu 2+ 0.21Na 0.12MnO 2·0.9H 2O). The copper intercalated birnessite materials were fully characterized utilizing powder X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), transmission electron microscopy (TEM).more » The mixed valent nature of intercalated Cu 0 and Cu 2+ was confirmed by X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS). Electrochemical evaluation results show that zero valent copper intercalated birnessite exhibits higher discharge capability, improved cyclability, and lower impedance compared to the Cu 2+ only intercalated (Cu 0.26MnO 2·1.0H 2O) and Cu free Na birnessite (Na 0.40MnO 2·1.0H 2O) materials. Remarkably, zero valent copper birnessite shows almost no fade after 10 cycles at 0.1 mV/s. Electrochemical impedance spectroscopy results suggest that charge transfer resistivity of Cu 0 modified samples was much lower than that of Cu 2+ and Cu free birnessite, indicating that the presence of a small amount of Cu 0 improves the conductivity of birnessite and results in better electrochemical cyclability, rate capability, and lower impedance.« less

Energetics and crystal chemistry of Ruddlesden-Popper type structures in high T(sub c) ceramic superconductors

NASA Technical Reports Server (NTRS)

Dwivedi, Anurag; Cormack, A. N.

1990-01-01

The formation of Ruddlesden-Popper type layers (alternating slabs of rocksalt and perovskite structures) is seen in these oxides which is similar in many respects to what is seen in the system Sr-Ti-O. However, it was observed that there are some significant differences, for example the rocksalt and perovskite blocks in new superconducting compounds are not necessarily electrically, unlike in Sr-Ti-O systems. This will certainly render an additional coulombic bonding energy between two different types of blocks and may well lead to significant differences in their structural chemistry. In the higher order members of the various homologous series, additional Cu-O planes are inserted in the perovskite blocks. In order for the unit cell to electrically neutral the net positive charge on rocksalt block (which remains constant throughout the homologous series) should be balanced by an equal negative charge on perovskite block. It, thus becomes necessary to create oxygen vacancies in the basic perovskite structure, when width of the perovskite slab changes on addition of extra Cu-O planes. Results of atomistic simulations suggest that these missing oxygen ions allow the Cu-O planes to buckle in these compounds. This is also supported by the absence of buckling in the first member of Bi-containing compounds in which there are no missing oxygen ions and the Sr-Ti-O series of compounds. Additional results are presented on the phase stability of polytypoid structures in these crystal chemically complex systems. The studies will focus on the determination of the location of Cu(3+) in the structures of higher order members of the La-Cu-O system and whether Cu(3+) ions or oxygen vacancies are energetically more favorable charge compensating mechanism.

Convergent Synthesis and Photoinduced Processes in Multi-Chromophoric Rotaxanes1

PubMed Central

Megiatto, Jackson D.; Li, Ke; Schuster, David I.; Palkar, Amit; Herranz, M. Ángeles; Echegoyen, Luis; Abwandner, Silke; de Miguel, Gustavo; Guldi, Dirk M.

2010-01-01

A series of [2]rotaxane materials, in which [60]fullerene is linked to a macrocycle and ferrocene (Fc) moieties are placed at the termini of a thread, both of which possess a central Cu(I)-1,10-phenanthroline [Cu(phen)2]+ complex, were synthesized by self-assembly using Sauvage metal template methodology. Two types of threads were constructed, one with terminal ester linkages, and a second with terminal 1,2,3-triazole linkages derived from Cu(I)-catalyzed “click” 1,3-cycloaddition reactions. Model compounds lacking the fullerene moiety were prepared in an analogous manner. The ability of the interlocked Fc-[Cu(phen)2]+-C60 hybrids to undergo electron transfer upon photoexcitation was investigated by means of time-resolved fluorescence and transient absorption spectroscopy, using excitation wavelengths directed at the fullerene and [Cu(phen)2]+ subunits. The energies of the electronic excited states and charge separated (CS) states that might be formed upon photoexcitation were determined from spectroscopic and electrochemical data. These studies showed that MLCT excited states of the copper complex in the fullerenerotaxanes were quenched by electron transfer to the fullerene, resulting in charge separated states with oxidized copper and reduced fullerene moieties, (Fc)2-[Cu(phen)2]2+-C60•−. Even though electron transfer from Fc to the oxidized copper complex is predicted to be exergonic by 0.18 eV, no unequivocal evidence in support of such a process was obtained. The conclusion that Fc plays no role in the photoinduced processes in our systems rests on the lack of enhancement of the lifetime of the charge separated state as measured by decay of C60•− at ~ 1000 nm, since one-electron oxidized Fc is very difficult to detect spectroscopically in the 500–800 nm spectral region. PMID:20518479

Size, shape, and compositional effects on the order-disorder phase transitions in Au-Cu and Pt-M (M = Fe, Co, and Ni) nanocluster alloys.

PubMed

Kaatz, Forrest H; Bultheel, Adhemar

2018-08-24

Au-Cu and Pt-M (M = Fe, Co, and Ni) nanocluster alloys are currently being investigated world-wide by many researchers for their interesting catalytic and nanophase properties. The low temperature behavior of the phase diagrams is not well understood for alloys with nanometer sizes and shapes. We consider two models for low temperature ordering in the phase diagrams of Au-Cu and Pt-M nanocluster alloys. These models are valid for sizes ∼5 nm and approach bulk values for sizes ∼20 nm. We study the phase transitions in nanoclusters with cubic, octahedral, and cuboctahedral shapes, covering the compositions of interest. These models are based on studying the melting temperatures in nanoclusters using the regular solution, mixing model for alloys. From our data, experiments on nanocubes about 5 nm in size, of stoichiometric AuCu and PtM composition, could help differentiate between the models. Dispersion data shows that for the three shapes considered, octahedra have the highest percentage of surface atoms for the same relative diameter. We summarize the effects of structural ordering on the catalytic activity and suggest a method to avoid sintering during annealing of Pt-M alloys.

Heavy fragment production cross sections from 1.05 GeV/nucleon 56Fe in C, Al, Cu, Pb, and CH2 targets

NASA Technical Reports Server (NTRS)

Zeitlin, C.; Heilbronn, L.; Miller, J.; Rademacher, S. E.; Borak, T.; Carter, T. R.; Frankel, K. A.; Schimmerling, W.; Stronach, C. E.; Chatterjee, A. (Principal Investigator)

1997-01-01

We have obtained charge-changing cross sections and partial cross sections for fragmentation of 1.05 GeV/nucleon Fe projectiles incident on H, C, Al, Cu, and Pb nuclei. The energy region covered by this experiment is critical for an understanding of galactic cosmic ray propagation and space radiation biophysics. Surviving primary beam particles and fragments with charges from 12 to 25 produced within a forward cone of half-angle 61 mrad were detected using a silicon detector telescope to identify their charge and the cross sections were calculated after correction of the measured yields for finite target thickness effects. The cross sections are compared to model calculations and to previous measurements. Cross sections for the production of fragments with even-numbered nuclear charges are seen to be enhanced in almost all cases.

Secondary ion emission from Ti, V, Cu, Ag and Au surfaces under KeV Cs + irradiation

NASA Astrophysics Data System (ADS)

van der Heide, P. A. W.

2005-02-01

Low energy mono-atomic singly charged secondary ion emissions from Ti, V, Cu, Ag and Au substrates during the initial stages of sputtering with Cs + primary ions have been studied. With the exception of the Ag - secondary ions, all exhibited exponential like correlations with the Cs induced work function changes. This, along with the lack of variations in the valence band structure around the Fermi edge, is consistent with resonance charge transfer to/from states located at the Fermi edge. The insensitivity of Ag - to work function appears to stem from the dominance of a separate ion formation process, namely charge transfer into vacant 4d states in the sputtered population, which themselves appear to be produced through collective oscillations. A similar excitation-mediated process involving different levels also appears to be active in the formation of other negatively charged transition metal ions, albeit to a much lesser degree.

Static charge-density-wave order in the superconducting state of La 2 - x Ba x CuO 4

DOE PAGES

Thampy, V.; Chen, X. M.; Cao, Y.; ...

2017-06-15

Charge-density-wave (CDW) correlations feature prominently in the phase diagram of the cuprates, motivating competing theories of whether fluctuating CDW correlations aid superconductivity or whether static CDW order coexists with superconductivity in inhomogeneous or spatially modulated states. Here we report Cu L-edge resonant x-ray photon correlation spectroscopy measurements of CDW correlations in superconducting La 2–xBa xCuO 4, x = 0.11. Static CDW order is shown to exist in the superconducting state at low temperatures and to persist up to at least 85% of the CDW transition temperature. As a result, we discuss the implications of our observations for how nominally competingmore » order parameters can coexist in the cuprates.« less

ESR studies on the spin-liquid candidate κ-(BEDT-TTF)2Cu2(CN)3: Anomalous response below T=8 K

NASA Astrophysics Data System (ADS)

Padmalekha, K. G.; Blankenhorn, M.; Ivek, T.; Bogani, L.; Schlueter, J. A.; Dressel, M.

2015-03-01

The organic conductor κ-(BEDT-TTF)2Cu2(CN)3 seems to form a quantum spin liquid, although at low temperatures unusual properties are seen in the charge, spin and lattice degrees of freedom. Here we report results of X-band ESR studies of κ-(BEDT-TTF)2Cu2(CN)3 single crystals as a function of temperature and angle. We find indications of two anisotropic relaxation mechanisms at low temperatures and compare them to the spin-liquid behavior observed in other strongly correlated systems. In addition, we can recognize charge inhomogeneities in the copper ions of the anion layer. This disorder might be linked to the dielectric response measured in this compound.

Charged drop dynamics experiment using an electrostatic-acoustic hybrid system

NASA Technical Reports Server (NTRS)

Rhim, W. K.; Chung, S. K.; Trinh, E. H.; Elleman, D. D.

1987-01-01

The design and the performance of an electrostatic-acoustic hybrid system and its application to a charge drop rotation experiment are presented. This system can levitate a charged drop electrostatically and induce drop rotation or oscillation by imposing an acoustic torque or an oscillating acoustic pressure. Using this system, the equilibrium shapes and stability of a rotating charged drop were experimentally investigated. A 3 mm size water drop was rotated as a rigid body and its gyrostatic equilibrium shapes were observed. Families of axisymmetric shapes, two-lobed shapes, and eventual fissioning have been observed. With the assumption of 'effective surface tension' in which the surface charge simply modified the surface tension of neutral liquid, the results agree exceptionally well with the Brown and Scriven's (1980) prediction for uncharged drops.

Engineering nonspherical hollow structures with complex interiors by template-engaged redox etching.

PubMed

Wang, Zhiyu; Luan, Deyan; Li, Chang Ming; Su, Fabing; Madhavi, Srinivasan; Boey, Freddy Yin Chiang; Lou, Xiong Wen

2010-11-17

Despite the significant advancement in making hollow structures, one unsolved challenge in the field is how to engineer hollow structures with specific shapes, tunable compositions, and desirable interior structures. In particular, top-down engineering the interiors inside preformed hollow structures is still a daunting task. In this work, we demonstrate a facile approach for the preparation of a variety of uniform hollow structures, including Cu(2)O@Fe(OH)(x) nanorattles and Fe(OH)(x) cages with various shapes and dimensions by template-engaged redox etching of shape-controlled Cu(2)O crystals. The composition can be readily modulated at different structural levels to generate other interesting structures such as Cu(2)O@Fe(2)O(3) and Cu@Fe(3)O(4) rattles, as well as Fe(2)O(3) and Fe(3)O(4) cages. More remarkably, this strategy enables top-down engineering the interiors of hollow structures as demonstrated by the fabrication of double-walled nanorattles and nanoboxes, and even box-in-box structures. In addition, this approach is also applied to form Au and MnO(x) based hollow structures.

Morphology transition of the primary silicon particles in a hypereutectic A390 alloy in high pressure die casting.

PubMed

Wang, J; Guo, Z; Song, J L; Hu, W X; Li, J C; Xiong, S M

2017-11-03

The microstructure of a high-pressure die-cast hypereutectic A390 alloy, including PSPs, pores, α-Al grains and Cu-rich phases, was characterized using synchrotron X-ray tomography, together with SEM, TEM and EBSD. The Cu-rich phases exhibited a net morphology and distributed at the boundaries of the α-Al grains, which in turn surrounded the PSPs. Statistical analysis of the reconstructed 1000 PSPs showed that both equivalent diameter and shape factor of the PSPs exhibited a unimodal distribution with peaks corresponding to 25 μm and 0.78, respectively.) PSPs morphology with multiple twinning were observed and morphological or growth transition of the PSPs from regular octahedral shape (with a shape factor of 0.85 was mainly caused by the constraint of the Cu-rich phases. In particular, the presence of the Cu-rich phases restricted the growth of the α-Al grains, inducing stress on the internal silicon particles, which caused multiple twinning occurrence with higher growth potential and consequently led to growth transitions of the PSPs.

Relationship between microstructure, cytotoxicity and corrosion properties of a Cu-Al-Ni shape memory alloy.

PubMed

Colić, Miodrag; Rudolf, Rebeka; Stamenković, Dragoslav; Anzel, Ivan; Vucević, Dragana; Jenko, Monika; Lazić, Vojkan; Lojen, Gorazd

2010-01-01

Cu-Al-Ni shape memory alloys (SMAs) have been investigated as materials for medical devices, but their biomedical application is still limited. The aim of this work was to compare the microstructure, corrosion and cytotoxicity in vitro of a Cu-Al-Ni SMA. Rapidly solidified (RS) thin ribbons, manufactured via melt spinning, were used for the tests. The control alloy was a permanent mould casting of the same composition, but without shape memory effect. The results show that RS ribbons are significantly more resistant to corrosion compared with the control alloy, as judged by the lesser release of Cu and Ni into the conditioning medium. These results correlate with the finding that RS ribbons were not cytotoxic to L929 mouse fibroblasts and rat thymocytes. In addition, the RS ribbon conditioning medium inhibited cellular proliferation and IL-2 production by activated rat splenocytes to a much lesser extent. The inhibitory effects were almost completely abolished by conditioning the RS ribbons in culture medium for 4 weeks. Microstructural analysis showed that RS ribbons are martensitic, with boron particles as a minor phase. In contrast, the control Cu-Al-Ni alloy had a complex multiphase microstructure. Examination of the alloy surfaces after conditioning by energy dispersive X-ray and Auger electron spectroscopy showed the formation of Cu and Al oxide layers and confirmed that the metals in RS ribbons are less susceptible to oxidation and corrosion compared with the control alloy. In conclusion, these results suggest that rapid solidification significantly improves the corrosion stability and biocompatibility in vitro of Cu-Al-Ni SMA ribbons.

Neutron scattering study of spin ordering and stripe pinning in superconducting La 1.93 Sr 0.07 CuO 4

DOE PAGES

Jacobsen, H.; Zaliznyak, I. A.; Savici, A. T.; ...

2015-11-20

Tmore » he relationships among charge order, spin fluctuations, and superconductivity in underdoped cuprates remain controversial. We use neutron scattering techniques to study these phenomena in La 1.93 Sr 0.07 CuO 4 a superconductor with a transition temperature of c = 20 K. At << c, we find incommensurate spin fluctuations with a quasielastic energy spectrum and no sign of a gap within the energy range from 0.2 to 15 meV. A weak elastic magnetic component grows below ~ 10 K, consistent with results from local probes. Regarding the atomic lattice, we have discovered unexpectedly strong fluctuations of the CuO 6 octahedra about Cu-O bonds, which are associated with inequivalent O sites within the CuO 2 planes. Moreover, we observed a weak elastic (3 ⁻30) superlattice peak that implies a reduced lattice symmetry. he presence of inequivalent O sites rationalizes various pieces of evidence for charge stripe order in underdoped La 2-xSr xCuO 4. he coexistence of superconductivity with quasi-static spin-stripe order suggests the presence of intertwined orders; however, the rotation of the stripe orientation away from the Cu-O bonds might be connected with evidence for a finite gap at the nodal points of the superconducting gap function.« less

Neutron scattering study of spin ordering and stripe pinning in superconducting La 1.93 Sr 0.07 CuO 4

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

Jacobsen, H.; Zaliznyak, I. A.; Savici, A. T.

Tmore » he relationships among charge order, spin fluctuations, and superconductivity in underdoped cuprates remain controversial. We use neutron scattering techniques to study these phenomena in La 1.93 Sr 0.07 CuO 4 a superconductor with a transition temperature of c = 20 K. At << c, we find incommensurate spin fluctuations with a quasielastic energy spectrum and no sign of a gap within the energy range from 0.2 to 15 meV. A weak elastic magnetic component grows below ~ 10 K, consistent with results from local probes. Regarding the atomic lattice, we have discovered unexpectedly strong fluctuations of the CuO 6 octahedra about Cu-O bonds, which are associated with inequivalent O sites within the CuO 2 planes. Moreover, we observed a weak elastic (3 ⁻30) superlattice peak that implies a reduced lattice symmetry. he presence of inequivalent O sites rationalizes various pieces of evidence for charge stripe order in underdoped La 2-xSr xCuO 4. he coexistence of superconductivity with quasi-static spin-stripe order suggests the presence of intertwined orders; however, the rotation of the stripe orientation away from the Cu-O bonds might be connected with evidence for a finite gap at the nodal points of the superconducting gap function.« less

Rebounding of a shaped-charge jet

NASA Astrophysics Data System (ADS)

Proskuryakov, E. V.; Sorokin, M. V.; Fomin, V. M.

2007-09-01

The phenomenon of rebounding of a shaped-charge jet from the armour surface with small angles between the jet axis and the target surface is considered. Rebounding angles as a function of jet velocity are obtained in experiments for a copper shaped-charge jet. An engineering calculation technique is developed. The results calculated with the use of this technique are in reasonable agreement with experimental data.

Cluster studies of La[sub 2]CuO[sub 4]: A mapping onto the Pariser--Parr--Pople (PPP) model

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

Martin, R.L.

1993-06-01

The techniques of [ital ab] [ital initio] electronic structure theory are used to study Cu[sub 2]O[sub 7] and Cu[sub 2]O[sub 11] cluster models of La[sub 2]CuO[sub 4]. Fair agreement is obtained with the experimentally determined spin exchange constant [ital J] (90 meV calculated vs 125 meV measured) at the expense of quite large configuration interactions (CI) expansions. Results for various charge states of the cluster are well described by a single-band'' Pariser--Parr--Pople (PPP) model. As in earlier local-density-functional (LDF) based parameter determinations, the present work suggests these materials fall in the strong coupling regime. However, a significant intersite Coulomb repulsionmore » is found in the present research. It is of sufficient strength [ital V][similar to][ital U]/5 to indicate that charge fluctuations may be more important in these materials than generally believed.« less

Orbital symmetry of charge-density-wave order in La 1.875Ba 0.125CuO 4 and YBa 2Cu 3O 6.67

DOE PAGES

A. J. Achkar; He, F.; Sutarto, R.; ...

2016-02-15

Recent theories of charge density wave (CDW) order in high temperature superconductors have predicted a primarily d CDW orbital symmetry. Here, we report on the orbital symmetry of CDW order in the canonical cuprate superconductors La 1.875Ba 0.125CuO 4 (LBCO) and YBa 2Cu 3O 6.67 (YBCO), using resonant soft x-ray scattering and a model mapped to the CDW orbital symmetry. From measurements sensitive to the O sublattice, we conclude that LBCO has predominantly s0 CDW orbital symmetry, in contrast to the d orbital symmetry recently reported in other cuprates. Additionally, we show for YBCO that the CDW orbital symmetry differsmore » along the a and b crystal axes and that these both differ from LBCO. This work highlights CDW orbital symmetry as an additional key property that distinguishes the di erent cuprate families.« less

EPR probes with well-defined, long distances between two or three unpaired electrons

PubMed

Godt; Franzen; Veit; Enkelmann; Pannier; Jeschke

2000-11-03

The synthesis of rod- and star-shaped compounds carrying two or three spin labels as end groups is described. The unpaired electrons are 2.8-5.1 nm apart from each other. The shape-persistent scaffolds were obtained through Pd-Cu-catalyzed alkynyl-aryl coupling and Pd-Cu-catalyzed alkyne dimerization in the presence of oxygen using p-phenyleneethynylene as the basic shape-persistent building block. The spin label 1-oxyl-2,2,5,5-tetramethylpyrroline-3-carboxylic acid (4) was attached through esterification of the terminal phenolic OH groups of the scaffold.

The response of macrophages to a Cu-Al-Ni shape memory alloy.

PubMed

Colić, Miodrag; Tomić, Sergej; Rudolf, Rebeka; Anzel, Ivan; Lojen, Gorazd

2010-09-01

Cu-Al-Ni shape memory alloys (SMAs) have been investigated as materials for medical devices, but little is known about their biocompatibility. The aim of this work was to study the response of rat peritoneal macrophages (PMØ) to a Cu-Al-Ni SMA in vitro, by measuring the functional activity of mitochondria, necrosis, apoptosis, and production of proinflammatory cytokines. Rapidly solidified (RS) thin ribbons were used for the tests. The control alloy was a permanent mold casting of the same composition, but without the shape memory effect. Our results showed that the control alloy was severely cytotoxic, whereas RS ribbons induced neither necrosis nor apoptosis of PMØ. These findings correlated with the data that RS ribbons are significantly more resistant to corrosion compared to the control alloy, as judged by the lesser release of Cu and Ni in the conditioning medium. However, the ribbons generated intracellular reactive oxygen species and upregulated the production of IL-6 by PMØ. These effects were almost completely abolished by conditioning the RS ribbons for 5 weeks. In conclusion, RS significantly improves the corrosion stability and biocompatibility of Cu-Al-Ni SMA. The biocompatibility of this functional material could be additionally enhanced by conditioning the ribbons in cell culture medium.

Facile synthesis of core-shell Cu2O@ ZnO structure with enhanced photocatalytic H2 production

NASA Astrophysics Data System (ADS)

Zhang, Yong-Hui; Jiu, Bei-Bei; Gong, Fei-Long; Lu, Kuan; Jiang, Nan; Zhang, Hao-Li; Chen, Jun-Li

2018-05-01

Core-shell Cu2O@ZnO composites were synthesized successfully based on a one-pot hydrothermal method in the presence of dioctyl sulfosuccinate sodium salt (AOT) surfactant. The Cu2O can be converted to rough core-shell Cu2O@ZnO structure by adjusting the amount of zinc powder added. The as-synthesized Cu2O@ZnO composites exhibited excellent photocatalytic activity and the amount of H2 generated using these composites was 4.5-fold more than that produced with Cu2O cubes. A possible photocatalytic mechanism for the Cu2O@ZnO composites with enhanced photocatalytic activity could be the separation by ZnO of the effective charge carriers.

Fabrication and electrical properties of p-CuAlO2/(n-, p-)Si heterojunctions

NASA Astrophysics Data System (ADS)

Suzhen, Wu; Zanhong, Deng; Weiwei, Dong; Jingzhen, Shao; Xiaodong, Fang

2014-04-01

CuAlO2 thin films have been prepared by the chemical solution deposition method on both n-Si and p-Si substrates. X-ray diffraction analysis indicates that the obtained CuAlO2 films have a single delafossite structure. The current transport properties of the resultant p-CuAlO2/n-Si and p-CuAlO2/p-Si heterojunctions are investigated by current-voltage measurements. The p-CuAlO2/n-Si has a rectifying ratio of ~35 within the applied voltages of -3.0 to +3.0 V, while the p-CuAlO2/p-Si shows Schottky diode-like characteristics, dominated in forward bias by the flow of space-charge-limited current.

Enhanced charge density wave order in La2-xSrxCuO4 at high magnetic field.

NASA Astrophysics Data System (ADS)

He, Wei; Wen, Jiajia; Jang, Hoyoung; Nojiri, Hiroyuki; Matsuzawa, Satoshi; Song, Sanghoon; Chollet, Matthieu; Zhu, Diling; Fujita, Masaki; Rotundu, Costel R.; Sheckelton, John P.; Jiang, Mingde; Kao, Chi-Chang; Lee, Jun-Sik; Lee, Young S.

There has been much recent interest in the charge density wave (CDW) order in the cuprate superconductors. An intriguing form of the density wave occurs in the La2CuO4-based family where both the charge and spin form ``stripes'' near 1/8 doping. Charge order has been reported in La2-xSrxCuO4 (LSCO) in zero magnetic field near 1/8 doping that was enhanced in moderate DC fields (up to 10 T). In this talk, I will discuss our recent experiment which combines a pulsed magnet with the x-rays from a free electron laser to characterize the CDW in LSCO with x =0.115 in fields up to 24 Tesla. In contrast to the YBCO family, which shows field-induced 3D CDW order, the field-enhanced CDW order in LSCO remains two-dimensional up to 24 T. Further results regarding the field-dependence and zero-field behavior of the CDW will be discussed. Our study provides important information on the interplay between CDW order and high-Tc superconductivity. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under contract DE-AC02-76SF00515.

Dispersive charge density wave excitations in Bi 2Sr 2CaCu 2O 8+δ [Dispersive charge density wave excitations and temperature dependent commensuration in Bi 2Sr 2CaCu 2O 8+δ

DOE PAGES

Chaix, L.; Ghiringhelli, G.; Peng, Y. Y.; ...

2017-06-12

Experimental evidence on high-T c cuprates reveals ubiquitous charge density wave (CDW) modulations, which coexist with superconductivity. Although the CDW had been predicted by theory, important questions remain about the extent to which the CDW influences lattice and charge degrees of freedom and its characteristics as functions of doping and temperature. These questions are intimately connected to the origin of the CDW and its relation to the mysterious cuprate pseudogap. We use ultrahigh-resolution resonant inelastic X-ray scattering to reveal new CDW character in underdoped Bi 2.2Sr 1.8Ca 0.8Dy 0.2Cu 2O 8+δ. At low temperature, we observe dispersive excitations from anmore » incommensurate CDW that induces anomalously enhanced phonon intensity, unseen using other techniques. Furthermore, near the pseudogap temperature T*, the CDW persists, but the associated excitations significantly weaken with an indication of CDW wavevector shift. The dispersive CDW excitations, phonon anomaly, and analysis of the CDW wavevector provide a comprehensive momentum-space picture of complex CDW behaviour and point to a closer relationship with the pseudogap state.« less

Surface complexation modeling of Cu(II) adsorption on mixtures of hydrous ferric oxide and kaolinite

PubMed Central

Lund, Tracy J; Koretsky, Carla M; Landry, Christopher J; Schaller, Melinda S; Das, Soumya

2008-01-01

Background The application of surface complexation models (SCMs) to natural sediments and soils is hindered by a lack of consistent models and data for large suites of metals and minerals of interest. Furthermore, the surface complexation approach has mostly been developed and tested for single solid systems. Few studies have extended the SCM approach to systems containing multiple solids. Results Cu adsorption was measured on pure hydrous ferric oxide (HFO), pure kaolinite (from two sources) and in systems containing mixtures of HFO and kaolinite over a wide range of pH, ionic strength, sorbate/sorbent ratios and, for the mixed solid systems, using a range of kaolinite/HFO ratios. Cu adsorption data measured for the HFO and kaolinite systems was used to derive diffuse layer surface complexation models (DLMs) describing Cu adsorption. Cu adsorption on HFO is reasonably well described using a 1-site or 2-site DLM. Adsorption of Cu on kaolinite could be described using a simple 1-site DLM with formation of a monodentate Cu complex on a variable charge surface site. However, for consistency with models derived for weaker sorbing cations, a 2-site DLM with a variable charge and a permanent charge site was also developed. Conclusion Component additivity predictions of speciation in mixed mineral systems based on DLM parameters derived for the pure mineral systems were in good agreement with measured data. Discrepancies between the model predictions and measured data were similar to those observed for the calibrated pure mineral systems. The results suggest that quantifying specific interactions between HFO and kaolinite in speciation models may not be necessary. However, before the component additivity approach can be applied to natural sediments and soils, the effects of aging must be further studied and methods must be developed to estimate reactive surface areas of solid constituents in natural samples. PMID:18783619

Photo-induced CO2 reduction by CH4/H2O to fuels over Cu-modified g-C3N4 nanorods under simulated solar energy

NASA Astrophysics Data System (ADS)

Tahir, Beenish; Tahir, Muhammad; Amin, Nor Aishah Saidina

2017-10-01

Copper modified polymeric graphitic carbon nitride (Cu/g-C3N4) nanorods for photo-induced CO2 conversion with methane (CH4) and water (H2O) as reducing system under simulated solar energy has been investigated. The nanocatalysts, synthesized by pyrolysis and sonication, were characterized by XRD, FTIR, Raman analysis, XPS, SEM, N2 adsorption-desorption and PL spectroscopy. The presence of Cu2+ ions over the g-C3N4 structure inhibited charge carriers recombination process. The results indicated that photo-activity and selectivity of Cu/g-C3N4 photo-catalyst for CO2 reduction greatly dependent on the type of CO2-reduction system. CO2 was efficiently converted to CH4 and CH3OH with traces of C2H4 and C2H6 hydrocarbons in the CO2-water system. The yield of the main product, CH4 over 3 wt.% Cu/g-C3N4 was 109 μmole g-cata.-1 h-1 under visible light irradiation, significantly higher than the pure g-C3N4 catalyst (60 μmole/g.cat). In photo-induced CO2-CH4 reaction, CO and H2 were detected as the main products with smaller amount of hydrocarbons. The highest efficiency was detected over 3 wt.%Cu-loading of g-C3N4 and at optimal CH4/CO2 feed ratio of 1.0. The maximum yield of CO and H2 detected were 142 and 76 μmole g-catal.-1 h-1, respectively at selectivity 66.6% and 32.5%, respectively. Significantly enhanced CO2/CH4 reduction over Cu/g-C3N4 was attributed to its polymeric structure with efficient charge transfer property and inhibited charges recombination rate. A proposed photo-induced reaction mechanism, corroborated with the experimental data, was also deliberated.

Synthesis of nanoporous CuO/TiO2/Pd-NiO composite catalysts by chemical dealloying and their performance for methanol and ethanol electro-oxidation

NASA Astrophysics Data System (ADS)

Niu, Mengying; Xu, Wence; Zhu, Shengli; Liang, Yanqin; Cui, Zhenduo; Yang, Xianjin; Inoue, Akihisa

2017-09-01

Nanoporous CuO/TiO2/Pd-NiO-x (x = 0, 1, 3, 5, 7 at%) catalysts have been synthesized by dealloying Cu-Ti-Pd-Ni alloy ribbons in acid solution. The nanoporous structure and chemical composition of the catalysts distribute uniformly. Based on the electrochemical active area (EASA), electrocatalytic activity and stability, the np-CuO/TiO2/Pd-NiO-3 catalyst possesses the best performance for methanol and ethanol electro-oxidation. For methanol and ethanol electro-oxidation, the anodic current densities in forward scan of the np-CuO/TiO2/Pd-NiO-3 catalyst are about 5.6 times and 2.1 times larger than that of the np-CuO/TiO2/Pd catalyst, respectively. The introduction of NiO provides more electrochemical active sites due to the improved geometrical and bifunctional mechanism. NiO promotes the adsorption of oxygen-containing species (OHads) on the catalyst surface, and electron effect between Pd and Ni is favorable for charge transfer. This accelerates the removal of intermediate products during the oxidation process. The electrocatalytic processes of methanol and ethanol oxidation in alkaline solution are controlled by both charge transfer and diffusion.

Electrochemical immunoassay for carcinoembryonic antigen based on signal amplification strategy of nanotubular mesoporous PdCu alloy.

PubMed

Cai, Yanyan; Li, He; Li, Yuyang; Zhao, Yanfang; Ma, Hongmin; Zhu, Baocun; Xu, Caixia; Wei, Qin; Wu, Dan; Du, Bin

2012-01-01

Interests in using nanoporous metals for biosensing applications have been increasing. Herein, nanotubular mesoporous PdCu (NM-PdCu) alloy is used to fabricate a novel label-free electrochemical immunosensor for cancer biomarker carcinoembryonic antigen (CEA). It operates through physisorption of anti-CEA on NM-PdCu and the mixture of sulfonated graphene sheets (HSO(3)-GS) and thionine (TH) functionalized glassy carbon electrode interface as the detection platform. In this study, chitosan (CS)-PdCu is bound very strongly to carcinoembryonic antibody (anti-CEA), because of the good electron conductivity, high surface area, and good biocompatibility. CS-PdCu is immobilized on electrodes by electrostatic interactions between the negatively charged sulfo group of HSO(3)-GS and the abundant positively charged amino groups of chitosan. TH acts as the redox probe. Under the optimized conditions, the electrochemical immunosensor exhibits a wide working range from 0.01 to 12 ng/mL with a low detection limit of 4.86 pg/mL. The accuracy, reproducibility, and stability of the immunosensor are acceptable. The assay is evaluated for real serum samples, receiving satisfactory results. The nanoporous metal materials-based immunoassay provides a promising approach in clinical application and thus represents a versatile detection method. Copyright © 2012 Elsevier B.V. All rights reserved.

Non-noble metal Cu-loaded TiO2 for enhanced photocatalytic H2 production.

PubMed

Foo, Wei Jian; Zhang, Chun; Ho, Ghim Wei

2013-01-21

Here we have demonstrated the preparation of high-quality, monodispersed and tunable phases of Cu nanoparticles. Structural and chemical composition studies depict the evolution of Cu-Cu(2)O-CuO nanoparticles at various process stages. The loading of Cu and Cu oxide nanoparticles on TiO(2) catalyst has enhanced the photocatalytic H(2) production. Comparatively, H(2) treatment produces well-dispersed Cu nanoparticles with thin oxide shells that show the highest H(2) production amongst the samples. The relatively higher photocatalytic performance is deemed to result from reduced structural defects, higher surface area and dispersivity as well as favorable charge transfer, which inhibits recombination. The Cu nanoparticles are shown to be a promising alternative to noble metal-loaded TiO(2) catalyst systems due to their low cost and high performance in photocatalytic applications.

Artificial twin-layer configurations of Zn(O,S) films by radio frequency sputtering in all dry processed eco-friendly Cu(In,Ga)Se2 solar cells

NASA Astrophysics Data System (ADS)

Liu, Wei; Fan, Yu; Li, Xiaodong; Lin, Shuping; Liu, Yang; Shi, Sihan; Wang, He; Zhou, Zhiqiang; Zhang, Yi; Sun, Yun

2018-03-01

Cu(In,Ga)Se2 thin film solar cells are of great interest for research and industrial applications with their high conversion efficiencies, long-term stability and significant lifetimes. Such a solar cell of a p-n junction consists of p-type Cu(In,Ga)Se2 films as a light absorber and n-type CdS as a buffer layer, which often emerges with intrinsic ZnO. Aimed at eco-friendly fabrication protocols, a large number of strategies have been investigated to fabricate a Cd-free n-type buffer layer such as Zn(O,S) in Cu(In,Ga)Se2 solar cells. Also, if the Zn(O,S) films are prepared by coevaporation or sputtering, it will offer high compatibility with the preferred mass production. Here, we propose and optimize a dry method for Zn(O,S) deposition in a radio frequency sputtering. In particular, the strategy for the twin-layer configurations of Zn(O,S) films not only greatly improve their electrical conductance and suppress charge carrier recombination, but also avoid degradation of the Zn(O,S)/Cu(In,Ga)Se2 interfaces. Indeed, the high quality of such twin Zn(O,S) layers have been reflected in the similar conversion efficiencies of the complete solar cells as well as the large short-circuit current density, which exceeds the CdS reference device. In addition, Zn(O,S) twin layers have reduced the production time and materials by replacing the CdS/i-ZnO layers, which removes two fabrication steps in the multilayered thin film solar cells. Furthermore, the device physics for such improvements have been fully unveiled with both experimental current-voltage and capacitance-voltage spectroscopies and device simulations via wxAMPS program. Finally, the proposed twin-layer Zn(O,S)/Cu(In,Ga)Se2 interfaces account for the broadening of the depletion region of photogenerated charge carriers, which greatly suppress the carrier recombination at the space charge region, and eventually lead to the more efficient collection of charge carriers at both electrodes.

Studies Of Oxidation And Thermal Reduction Of The Cu(100) Surface Using Positron Annihilation Induced Auger Electron Spectroscopy

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Nadesalingam, M. P.; Maddox, W.; Weiss, A. H.

2011-06-01

Positron annihilation induced Auger electron spectroscopy (PAES) measurements from the surface of an oxidized Cu(100) single crystal show a large increase in the intensity of the annihilation induced Cu M2,3VV Auger peak as the sample is subjected to a series of isochronal anneals in vacuum up to annealing temperature 300 °C. The PAES intensity then decreases monotonically as the annealing temperature is increased to ˜550 °C. Experimental positron annihilation probabilities with Cu 3p and O 1s core electrons are estimated from the measured intensities of the positron annihilation induced Cu M2,3VV and O KLL Auger transitions. PAES results are analyzed by performing calculations of positron surface states and annihilation probabilities of the surface-trapped positrons with relevant core electrons taking into account the charge redistribution at the surface and various surface structures associated with low and high oxygen coverages. The variations in atomic structure and chemical composition of the topmost layers of the oxidized Cu(100) surface are found to affect localization and spatial extent of the positron surface state wave function. The computed positron binding energy and annihilation characteristics reveal their sensitivity to charge transfer effects, atomic structure and chemical composition of the topmost layers of the oxidized Cu(100) surface. Theoretical positron annihilation probabilities with Cu 3p and O 1s core electrons computed for the oxidized Cu(100) surface are compared with experimental ones. The obtained results provide a demonstration of thermal reduction of the copper oxide surface after annealing at 300 °C followed by re-oxidation of the Cu(100) surface at higher annealing temperatures presumably due to diffusion of subsurface oxygen to the surface.

Structural Transformations in High-Capacity Li 2 Cu 0.5 Ni 0.5 O 2 Cathodes

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

Ruther, Rose E.; Samuthira Pandian, Amaresh; Yan, Pengfei

2017-03-21

Cathode materials that can cycle > 1 Li+ per transition metal are of substantial interest to increase the overall energy density of lithium-ion batteries. Li2Cu0.5Ni0.5O2 has a very high theoretical capacity of ~ 500 mAh/g assuming both Li+ are cycled reversibly. The Cu2+/3+ and Ni2+/3+/4+ redox couples are also at high voltage, which could further boost the energy density of this system. Despite such promise, Li2Cu0.5Ni0.5O2 undergoes irreversible phase changes during charge (delithiation) that result in large first-cycle irreversible loss and poor long-term cycling stability. Oxygen is evolved before the Cu2+/3+ or Ni3+/4+ transitions are accessed. In this contribution, XRD,more » TEM, and TXM-XANES are used to follow the chemical and structural changes that occur in Li2Cu0.5Ni0.5O2 during electrochemical cycling. Li2Cu0.5Ni0.5O2 is a solid solution of orthorhombic Li2CuO2 and Li2NiO2, but the structural changes more closely mimic the Li2NiO2 endmember. Li2Cu0.5Ni0.5O2 loses long-range order during charge, but TEM analysis provides clear evidence for particle exfoliation and the transformation from orthorhombic to a partially layered structure. Linear combination fitting and principal component analysis of TXM-XANES are used to map the different phases that emerge during cycling ex situ and in situ. Significant changes in the XANES at the Cu and Ni K-edges correlate with the onset of oxygen evolution.« less

Studies Of Oxidation And Thermal Reduction Of The Cu(100) Surface Using Positron Annihilation Induced Auger Electron Spectroscopy

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

Fazleev, N. G.; Department of Physics, Kazan State University, Kazan 420008; Nadesalingam, M. P.

2011-06-01

Positron annihilation induced Auger electron spectroscopy (PAES) measurements from the surface of an oxidized Cu(100) single crystal show a large increase in the intensity of the annihilation induced Cu M2,3VV Auger peak as the sample is subjected to a series of isochronal anneals in vacuum up to annealing temperature 300 deg. C. The PAES intensity then decreases monotonically as the annealing temperature is increased to {approx}550 deg. C. Experimental positron annihilation probabilities with Cu 3p and O 1s core electrons are estimated from the measured intensities of the positron annihilation induced Cu M{sub 2,3}VV and O KLL Auger transitions. PAESmore » results are analyzed by performing calculations of positron surface states and annihilation probabilities of the surface-trapped positrons with relevant core electrons taking into account the charge redistribution at the surface and various surface structures associated with low and high oxygen coverages. The variations in atomic structure and chemical composition of the topmost layers of the oxidized Cu(100) surface are found to affect localization and spatial extent of the positron surface state wave function. The computed positron binding energy and annihilation characteristics reveal their sensitivity to charge transfer effects, atomic structure and chemical composition of the topmost layers of the oxidized Cu(100) surface. Theoretical positron annihilation probabilities with Cu 3p and O 1s core electrons computed for the oxidized Cu(100) surface are compared with experimental ones. The obtained results provide a demonstration of thermal reduction of the copper oxide surface after annealing at 300 deg. C followed by re-oxidation of the Cu(100) surface at higher annealing temperatures presumably due to diffusion of subsurface oxygen to the surface.« less

Frenkel-Charge-Transfer exciton intermixing theory for molecular crystals with two isolated Frenkel exciton states.

NASA Astrophysics Data System (ADS)

Bondarev, Igor; Popescu, Adrian

We develop an analytical theory for the intra-intermolecular exciton intermixing in periodic 1D chains of planar organic molecules with two isolated low-lying Frenkel exciton states, typical of copper phthalocyanine (CuPc) and other transition metal phthalocyanine molecules. We formulate the Hamiltonian and use the exact Bogoliubov diagonalization procedure to derive the eigen energy spectrum for the two lowest intramolecular Frenkel excitons coupled to the intermolecular charge transfer (CT) exciton state. By comparing our theoretical spectrum with available experimental CuPc absorption data, we obtain the parameters of the Frenkel-CT exciton intermixing in CuPc thin films. The two Frenkel exciton states here are spaced apart by 0.26 eV, and the charge transfer exciton state is 50 meV above the lowest Frenkel exciton. Both Frenkel excitons are strongly mixed with the CT exciton, showing the coupling constant 0.17 eV in agreement with earlier electron transport experiments. Our results can be used for the proper interpretation of the physical properties of crystalline phthalocyanines. DOE-DE-SC0007117 (I.B.), UNC-GA ROI Grant (A.P.).

Influence of lattice orientation on growth and structure of graphene on Cu(001)

DOE PAGES

Wofford, Joseph M.; Nie, Shu; Thürmer, Konrad; ...

2015-03-31

We have used low-energy electron microscopy (LEEM) and diffraction (LEED) to examine the significance of lattice orientation in graphene growth on Cu(0 0 1). Individual graphene domains undergo anisotropic growth on the Cu surface, and develop into lens shapes with their long axes roughly aligned with Cu <1 0 0> in-plane directions. Furthermore, the long axis of a lens-shaped domain is only rarely oriented along a C <1 1> direction, suggesting that carbon attachment at “zigzag” graphene island edges is unfavorable. A kink-mediated adatom attachment process is consistent with the behavior observed here and reported in the literature. Likewise, themore » details of the ridged moiré pattern formed by the superposition of the graphene lattice on the (0 0 1) Cu surface also evolve with the graphene lattice orientation, and are predicted well by a simple geometric model. Managing the kink-mediated growth mode of graphene on Cu(0 0 1) will be necessary for the continued improvement of this graphene synthesis technique.« less

Testing Shaped Charges in Unfrozen and Frozen Silt in Alaska

DTIC Science & Technology

1982-03-01

AwTrRACT Cte sm reveg N emeagay -id d*ify by block number) SBorehole blasting tests using 15- and 40-lb charges were conducted in silt at Fort Wainwright...Table 3-5 of the manual, performance data on the blasting of boreholes with shaped charges are presented. Of particular interest in that table a-e the...Commander of the 47th Engineers at Fort Wainwright asked if I could verify his findings that the M2A4 (15-1b) shaped charge cannot produce a borehole in

Interfacial Engineering and Charge Carrier Dynamics in Extremely Thin Absorber Solar Cells

NASA Astrophysics Data System (ADS)

Edley, Michael

Photovoltaic energy is a clean and renewable source of electricity; however, it faces resistance to widespread use due to cost. Nanostructuring decouples constraints related to light absorption and charge separation, potentially reducing cost by allowing a wider variety of processing techniques and materials to be used. However, the large interfacial areas also cause an increased dark current which negatively affects cell efficiency. This work focuses on extremely thin absorber (ETA) solar cells that used a ZnO nanowire array as a scaffold for an extremely thin CdSe absorber layer. Photoexcited electrons generated in the CdSe absorber are transferred to the ZnO layer, while photogenerated holes are transferred to the liquid electrolyte. The transfer of photoexcited carriers to their transport layer competes with bulk recombination in the absorber layer. After charge separation, transport of charge carriers to their respective contacts must occur faster than interfacial recombination for efficient collection. Charge separation and collection depend sensitively on the dimensions of the materials as well as their interfaces. We demonstrated that an optimal absorber thickness can balance light absorption and charge separation. By treating the ZnO/CdSe interface with a CdS buffer layer, we were able to improve the Voc and fill factor, increasing the ETA cell's efficiency from 0.53% to 1.34%, which is higher than that achievable using planar films of the same material. We have gained additional insight into designing ETA cells through the use of dynamic measurements. Ultrafast transient absorption spectroscopy revealed that characteristic times for electron injection from CdSe to ZnO are less than 1 ps. Electron injection is rapid compared to the 2 ns bulk lifetime in CdSe. Optoelectronic measurements such as transient photocurrent/photovoltage and electrochemical impedance spectroscopy were applied to study the processes of charge transport and interfacial recombination. With these techniques, the extension of the depletion layer from CdSe into ZnO was determined to be vital to suppression of interfacial recombination. However, depletion of the ZnO also restricted the effective diffusion core for electrons and slowed their transport. Thus, materials and geometries should be chosen to allow for a depletion layer that suppresses interfacial recombination without impeding electron transport to the point that it is detrimental to cell performance. Thin film solar cells are another promising technology that can reduce costs by relaxing material processing requirements. CuInxGa (1-x)Se (CIGS) is a well studied thin film solar cell material that has achieved good efficiencies of 22.6%. However, use of rare elements raise concerns over the use of CIGS for global power production. CuSbS2 shares chemistry with CuInSe2 and also presents desirable properties for thin film absorbers such as optimal band gap (1.5 eV), high absorption coefficient, and Earth-abundant and non-toxic elements. Despite the promise of CuSbS2, direct characterization of the material for solar cell application is scarce in the literature. CuSbS2 nanoplates were synthesized by a colloidal hot-injection method at 220 °C in oleylamine. The CuSbS2 platelets synthesized for 30 minutes had dimensions of 300 nm by 400 nm with a thickness of 50 nm and were capped with the insulating oleylamine synthesis ligand. The oleylamine synthesis ligand provides control over nanocrystal growth but is detrimental to intercrystal charge transport that is necessary for optoelectronic device applications. Solid-state and solution phase ligand exchange of oleylamine with S2- were used to fabricate mesoporous films of CuSbS2 nanoplates for application in solar cells. Exchange of the synthesis ligand with S2- resulted in a two order of magnitude increase in 4-point probe conductivity. Photoexcited carrier lifetimes of 1.4 ns were measured by time-resolved terahertz spectroscopy, indicating potential for CuSbS2 as a solar cell absorber material.

Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part II. Intermetallic Coarsening Behavior of Rapidly Solidified Solders After Multiple Reflows

NASA Astrophysics Data System (ADS)

Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.; Handwerker, Carol A.

2016-12-01

Controlling the size, dispersion, and stability of intermetallic compounds in lead-free solder alloys is vital to creating reliable solder joints regardless of how many times the solder joints are melted and resolidified (reflowed) during circuit board assembly. In this article, the coarsening behavior of Cu x Al y and Cu6Sn5 in two Sn-Cu-Al alloys, a Sn-2.59Cu-0.43Al at. pct alloy produced via drip atomization and a Sn-5.39Cu-1.69Al at. pct alloy produced via melt spinning at a 5-m/s wheel speed, was characterized after multiple (1-5) reflow cycles via differential scanning calorimetry between the temperatures of 293 K and 523 K (20 °C and 250 °C). Little-to-no coarsening of the Cu x Al y particles was observed for either composition; however, clustering of Cu x Al y particles was observed. For Cu6Sn5 particle growth, a bimodal size distribution was observed for the drip atomized alloy, with large, faceted growth of Cu6Sn5 observed, while in the melt spun alloy, Cu6Sn5 particles displayed no significant increase in the average particle size, with irregularly shaped, nonfaceted Cu6Sn5 particles observed after reflow, which is consistent with shapes observed in the as-solidified alloys. The link between original alloy composition, reflow undercooling, and subsequent intermetallic coarsening behavior was discussed by using calculated solidification paths. The reflowed microstructures suggested that the heteroepitaxial relationship previously observed between the Cu x Al y and the Cu6Sn5 was maintained for both alloys.

Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part II. Intermetallic Coarsening Behavior of Rapidly Solidified Solders After Multiple Reflows

DOE PAGES

Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.; ...

2016-10-06

Controlling the size, dispersion, and stability of intermetallic compounds in lead-free solder alloys is vital to creating reliable solder joints regardless of how many times the solder joints are melted and resolidified (reflowed) during circuit board assembly. In this article, the coarsening behavior of Cu x Al y and Cu 6Sn 5 in two Sn-Cu-Al alloys, a Sn-2.59Cu-0.43Al at. pct alloy produced via drip atomization and a Sn-5.39Cu-1.69Al at. pct alloy produced via melt spinning at a 5-m/s wheel speed, was characterized after multiple (1-5) reflow cycles via differential scanning calorimetry between the temperatures of 293 K and 523 Kmore » (20 °C and 250 °C). Little-to-no coarsening of the Cu x Al y particles was observed for either composition; however, clustering of Cu x Al y particles was observed. For Cu 6Sn 5 particle growth, a bimodal size distribution was observed for the drip atomized alloy, with large, faceted growth of Cu 6Sn 5 observed, while in the melt spun alloy, Cu 6Sn 5 particles displayed no significant increase in the average particle size, with irregularly shaped, nonfaceted Cu 6Sn 5 particles observed after reflow, which is consistent with shapes observed in the as-solidified alloys. The link between original alloy composition, reflow undercooling, and subsequent intermetallic coarsening behavior was discussed by using calculated solidification paths. As a result, the reflowed microstructures suggested that the heteroepitaxial relationship previously observed between the Cu x Al y and the Cu 6Sn 5 was maintained for both alloys.« less

Deployment of Shaped Charges by a Semi-Autonomous Ground Vehicle

DTIC Science & Technology

2007-06-01

lives on a daily basis. BigFoot seeks to replace the local human component by deploying and remotely detonating shaped charges to destroy IEDs...robotic arm to deploy and remotely detonate shaped charges. BigFoot incorporates improved communication range over previous Autonomous Ground Vehicles...and an updated user interface that includes controls for the arm and camera by interfacing multiple microprocessors. BigFoot is capable of avoiding

Shaped Charge Liner Materials: Resources, Processes, Properties, Costs, and Applications

DTIC Science & Technology

1991-02-01

SUBTITLE 5. FUNDING NUMBERS Shaped Charge Liner Materials: Resources, Processes, Properties, Costs, and Applications 2 6. AUTHOC Steven M. Buc 7...summaries of the mineral availability, Cq prmarymetal refinement processeb, material costs in raw form and as finished shaped charge liners , relevant... liner materials. 94-11479 gI 14, SUBJECT TERMS iSt NUMBER OF PAGIS 13chrg wrhad :xplosively formed penetrators material R. PRCE COEV" processing

Active experiments using rocket-borne shaped charge barium releases. [solar-terrestrial magnetospheric physics

NASA Technical Reports Server (NTRS)

Wescott, E. M.; Davis, T. N.

1980-01-01

A reliable payload system and scaled down shaped charges were developed for carrying out experiments in solar-terrestrial magnetospheric physics. Four Nike-Tomahawk flights with apogees near 450 km were conducted to investigate magnetospheric electric fields, and two Taurus-Tomahawk rockets were flown in experiments on the auroral acceleration process in discrete auroras. In addition, a radial shaped charge was designed for plasma perturbation experiments.

Longitudinally Controlled Modification of Cylindrical and Conical Track-Etched Poly(ethylene terephthalate) Pores Using an Electrochemically Assisted Click Reaction

DOE PAGES

Coceancigh, Herman; Tran-Ba, Khanh-Hoa; Siepser, Natasha; ...

2017-09-27

Here in this study, the longitudinally controlled modification of the inner surfaces of poly(ethylene terephthalate) (PET) track-etched pores was explored using an electrochemically assisted Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) click reaction. Cylindrical or conical PET track-etched pores were first decorated with ethynyl groups via the amidation of surface -COOH groups, filled with a solution containing Cu(II) and azide-tagged fluorescent dye, and then sandwiched between comb-shaped and planar gold electrodes. Cu(I) was produced at the comb-shaped working electrode by the reduction of Cu(II); it diffused along the pores toward the other electrode and catalyzed CuAAC between an azide-tagged fluorescent dye and amore » pore-tethered ethynyl group. The modification efficiency of cylindrical pores (ca. 1 μm in diameter) was assessed from planar and cross-sectional fluorescence microscope images of modified membranes. Planar images showed that pore modification took place only above the teeth of the comb-shaped electrode with a higher reaction yield for longer Cu(II) reduction times. Cross-sectional images revealed micrometer-scale gradient modification along the pore axis, which reflected a Cu(I) concentration profile within the pores, as supported by finite-element computer simulations. The reported approach was applicable to the asymmetric modification of cylindrical pores with two different fluorescent dyes in the opposite directions and also for the selective visualization of the tip and base openings of conical pores (ca. 3.5 μm in base diameter and ca. 1 μm in tip diameter). Lastly, the method based on electrochemically assisted CuAAC provides a controlled means to fabricate asymmetrically modified nanoporous membranes and, in the future, will be applicable for chemical separations and the development of sequential catalytic reactors.« less

Longitudinally Controlled Modification of Cylindrical and Conical Track-Etched Poly(ethylene terephthalate) Pores Using an Electrochemically Assisted Click Reaction

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

Coceancigh, Herman; Tran-Ba, Khanh-Hoa; Siepser, Natasha

Here in this study, the longitudinally controlled modification of the inner surfaces of poly(ethylene terephthalate) (PET) track-etched pores was explored using an electrochemically assisted Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) click reaction. Cylindrical or conical PET track-etched pores were first decorated with ethynyl groups via the amidation of surface -COOH groups, filled with a solution containing Cu(II) and azide-tagged fluorescent dye, and then sandwiched between comb-shaped and planar gold electrodes. Cu(I) was produced at the comb-shaped working electrode by the reduction of Cu(II); it diffused along the pores toward the other electrode and catalyzed CuAAC between an azide-tagged fluorescent dye and amore » pore-tethered ethynyl group. The modification efficiency of cylindrical pores (ca. 1 μm in diameter) was assessed from planar and cross-sectional fluorescence microscope images of modified membranes. Planar images showed that pore modification took place only above the teeth of the comb-shaped electrode with a higher reaction yield for longer Cu(II) reduction times. Cross-sectional images revealed micrometer-scale gradient modification along the pore axis, which reflected a Cu(I) concentration profile within the pores, as supported by finite-element computer simulations. The reported approach was applicable to the asymmetric modification of cylindrical pores with two different fluorescent dyes in the opposite directions and also for the selective visualization of the tip and base openings of conical pores (ca. 3.5 μm in base diameter and ca. 1 μm in tip diameter). Lastly, the method based on electrochemically assisted CuAAC provides a controlled means to fabricate asymmetrically modified nanoporous membranes and, in the future, will be applicable for chemical separations and the development of sequential catalytic reactors.« less

Thin Cu film resistivity using four probe techniques: Effect of film thickness and geometrical shapes

NASA Astrophysics Data System (ADS)

Choudhary, Sumita; Narula, Rahul; Gangopadhyay, Subhashis

2018-05-01

Precise measurement of electrical sheet resistance and resistivity of metallic thin Cu films may play a significant role in temperature sensing by means of resistivity changes which can further act as a safety measure of various electronic devices during their operation. Four point probes resistivity measurement is a useful approach as it successfully excludes the contact resistance between the probes and film surface of the sample. Although, the resistivity of bulk samples at a particular temperature mostly depends on its materialistic property, however, it may significantly differ in the case of thin films, where the shape and thickness of the sample can significantly influence on it. Depending on the ratio of the film thickness to probe spacing, samples are usually classified in two segments such as (i) thick films or (ii) thin films. Accordingly, the geometric correction factors G can be related to the sample resistivity r, which has been calculated here for thin Cu films of thickness up to few 100 nm. In this study, various rectangular shapes of thin Cu films have been used to determine the shape induced geometric correction factors G. An expressions for G have been obtained as a function of film thickness t versus the probe spacing s. Using these expressions, the correction factors have been plotted separately for each cases as a function of (a) film thickness for fixed linear probe spacing and (b) probe distance from the edge of the film surface for particular thickness. Finally, we compare the experimental results of thin Cu films of various rectangular geometries with the theoretical reported results.

Covalent Electron Transfer Theory of Superconductivity

DTIC Science & Technology

1992-06-19

carriers. This situation is analogous to a vacuum diode without space charge, where each electron emitted from the cathode arrives at the anode before...Generic MO energy level diagram for a do cation in an oxygen octahedral complex. 89 53 Band model approximation of the MO states of a Cu perovskite ...C2) CuO4 complex. 94 57 p-type 3d 2,2-2p a Cu2+-O-Cu3+ covalent transfer in I 80-deg perovskite bond 95 geometry for d9 - d8(low-spin). xi LIST OF

An experimental investigation of localised surface plasmon resonance (LSPR) for Cu nanoparticles depending as a function of laser pulse number in Pulsed Laser Deposition

NASA Astrophysics Data System (ADS)

Gezgin, Serap Yiǧit; Kepceoǧlu, Abdullah; Kılıç, Hamdi Şükür

2017-02-01

Copper is a low cost metal and its nanoparticles have a unique optical properties such as LSPR. The location of LSPR wavelength can be tuned by controlling nanoparticles sizes and size distributions of nanoparticles, shapes and interparticle distances. This morphological changes are provided by controlling system parameters in PLD. For this work, 48000 and 36000 laser pulses from Nd:YAG laser were applied to produce Cu nanoparticle thin films. These thin films were characterised by performing UV-VIS absorption spectroscopy, Atomic Force Microscopy (AFM) analysis. When the number of laser pulse decreases, the size of Cu nanoparticles and the number of nanoparticles arriving on the substrate are reduced, and LSPR peak of thin films are red shifted depending on the geometrical shapes of the Cu nanoparticles. We have driven a conclusion in this work that LSPR properties of Cu nanoparticles can be tuned by proposed method.

Interface Superconductivity in Cuprates Defies Fermi-Liquid Description

DOE PAGES

Radović, Zoran; Vanević, Mihajlo; Wu, Jie; ...

2016-07-26

La 2-xSr xCuO 4/La 2CuO 4 bilayers show interface superconductivity that originates from accumulation and depletion of mobile charge carriers across the interface. Surprisingly, the doping level can be varied broadly (within the interval 0.15 < x < 0.47) without affecting the transition temperature, which stays essentially constant and equal to that in optimally doped material, T c ≈ 40 K. Here we argue that this finding implies that doping up to the optimum level does not shift the chemical potential, unlike in ordinary Fermi liquids. Lastly, we discuss possible physical scenarios that can give doping-independent chemical potential in themore » pseudogap regime: electronic phase separation, formation of charge-density waves, strong Coulomb interactions, or self-trapping of mobile charge carriers.« less

Composition dependence of the in-plane Cu-O bond-stretching LO phonon mode in YBa2Cu3O6+x

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

Stercil, F.; Egami, T.; Mook Jr, Herbert A

An inelastic pulsed neutron scattering study was performed on the dependence of the dispersion and spectral intensity of the in-plane Cu-O bond-stretching LO phonon mode on doped charge density. The measurements were made in the time-of-flight mode with the multiangle position sensitive spectrometer of the ISIS facility on single crystals of YBa{sub 2}Cu{sub 3}O{sub 6+x} (x=0.15, 0.35, 0.6, 0.7, and 0.95). The focus of the study is the in-plane Cu-O bond-stretching LO phonon mode, which is known for strong electron-phonon coupling and unusual dependence on composition and temperature. It is shown that the dispersions for the samples with x=0.35, 0.6,more » and 0.7 are similar to the superposition of those for x=0.15 and 0.95 samples, and cannot be explained in terms of the structural anisotropy. It is suggested that the results are consistent with the model of nanoscale electronic phase separation, with the fraction of the phases being dependent on the doped charge density.« less

Production of .sup.64 Cu and other radionuclides using a charged-particle accelerator

DOEpatents

Welch, Michael J.; McCarthy, Deborah W.; Shefer, Ruth E.; Klinkowstein, Robert E.

2000-01-01

Radionuclides are produced according to the present invention at commercially significant yields and at specific activities which are suitable for use in radiodiagnostic agents such as PET imaging agents and radiotherapeutic agents and/or compositions. In the method and system of the present invention, a solid target having an isotopically enriched target layer electroplated on an inert substrate is positioned in a specially designed target holder and irradiated with a charged-particle beam. The beam is preferably generated using an accelerator such as a biomedical cyclotron at energies ranging from about 5 MeV to about 25 MeV. The target is preferably directly irradiated, without an intervening attenuating foil, and with the charged particle beam impinging an area which substantially matches the target area. The irradiated target is remotely and automatically transferred from the target holder, preferably without transferring any target holder subassemblies, to a conveyance system which is preferably a pneumatic or hydraulic conveyance system, and then further transferred to an automated separation system. The system is effective for processing a single target or a plurality of targets. After separation, the unreacted target material can be recycled for preparation of other targets. In a preferred application of the invention, a biomedical cyclotron has been used to produce over 500 mCi of .sup.64 Cu having a specific activity of over 300 mCi/.mu.g Cu according to the reaction .sup.64 Ni(p,n).sup.64 Cu. These results indicate that accelerator-produced .sup.64 Cu is suitable for radiopharmaceutical diagnostic and therapeutic applications.

Evaluation of Cu(i) binding to the E2 domain of the amyloid precursor protein - a lesson in quantification of metal binding to proteins via ligand competition.

PubMed

Young, Tessa R; Wedd, Anthony G; Xiao, Zhiguang

2018-01-24

The extracellular domain E2 of the amyloid precursor protein (APP) features a His-rich metal-binding site (denoted as the M1 site). In conjunction with surrounding basic residues, the site participates in interactions with components of the extracellular matrix including heparins, a class of negatively charged polysaccharide molecules of varying length. This work studied the chemistry of Cu(i) binding to APP E2 with the probe ligands Bcs, Bca, Fz and Fs. APP E2 forms a stable Cu(i)-mediated ternary complex with each of these anionic ligands. The complex with Bca was selected for isolation and characterization and was demonstrated, by native ESI-MS analysis, to have the stoichiometry E2 : Cu(i) : Bca = 1 : 1 : 1. Formation of these ternary complexes is specific for the APP E2 domain and requires Cu(i) coordination to the M1 site. Mutation of the M1 site was consistent with the His ligands being part of the E2 ligand set. It is likely that interactions between the negatively charged probe ligands and a positively charged patch on the surface of APP E2 are one aspect of the generation of the stable ternary complexes. Their formation prevented meaningful quantification of the affinity of Cu(i) binding to the M1 site with these probe ligands. However, the ternary complexes are disrupted by heparin, allowing reliable determination of a picomolar Cu(i) affinity for the E2/heparin complex with the Fz or Bca probe ligands. This is the first documented example of the formation of stable ternary complexes between a Cu(i) binding protein and a probe ligand. The ready disruption of the complexes by heparin identified clear 'tell-tale' signs for diagnosis of ternary complex formation and allowed a systematic review of conditions and criteria for reliable determination of affinities for metal binding via ligand competition. This study also provides new insights into a potential correlation of APP functions regulated by copper binding and heparin interaction.

The role of support morphology on the performance of Cu/ZnO-catalyst for hydrogenation of CO{sub 2} to methanol

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

Tasfy, Sara Faiz Hanna, E-mail: miss25208@gmail.com; Zabidi, Noor Asmawati Mohd, E-mail: noorasmawati-mzabidi@petronas.com.my; Shaharun, Maizatul Shima, E-mail: maizats@petronas.com.my

The effects of SBA-15 support morphology on the activity of Cu/ZnO catalyst in the hydrogenation of CO{sub 2} to methanol was investigated. In the hydrogenation of CO{sub 2} to methanol at 210°C, 2.25 MPa, H{sub 2}/CO{sub 2} ratio of three remarkable difference was obtained using Cu/ZnO catalyst supported on SBA-15 with different morphology. The catalysts were characterized using N{sub 2}-adsorption, field emission scanning microscopy (FESEM/EDX), transmission electron microscopy (HRTEM), and temperature-programmed reduction (TPR). Characterization of the catalyst showed that support morphology, surface area, metals dispersion, and reducibility influenced the catalytic performance. On the fiber-shaped SBA-15, copper dispersion was 29 % whereasmore » on the spherical-shaped SBA-15, the dispersion was 20 %. The experimental results showed that the catalyst supported over fiber-shaped SBA-15 exhibit higher CO{sub 2} conversion (13.96 %) and methanol selectivity (91.32 %) compare to catalyst supported over spherical-shaped SBA-15.« less

Assembling non-ferromagnetic materials to ferromagnetic architectures using metal-semiconductor interfaces

PubMed Central

Ma, Ji; Liu, Chunting; Chen, Kezheng

2016-01-01

In this work, a facile and versatile solution route was used to fabricate room-temperature ferromagnetic fish bone-like, pteridophyte-like, poplar flower-like, cotton-like Cu@Cu2O architectures and golfball-like Cu@ZnO architecture. The ferromagnetic origins in these architectures were found to be around metal-semiconductor interfaces and defects, and the root cause for their ferromagnetism lay in charge transfer processes from metal Cu to semiconductors Cu2O and ZnO. Owing to different metallization at their interfaces, these architectures exhibited different ferromagnetic behaviors, including coercivity, saturation magnetization as well as magnetic interactions. PMID:27680286

Free form hemispherical shaped charge

DOEpatents

Haselman, L.C. Jr.

1996-06-04

A hemispherical shaped charge has been modified such that one side of the hemisphere is spherical and the other is aspherical allowing a wall thickness variation in the liner. A further modification is to use an elongated hemispherical shape. The liner has a thick wall at its pole and a thin wall at the equator with a continually decreasing wall thickness from the pole to the equator. The ratio of the wall thickness from the pole to the equator varies depending on liner material and HE shape. Hemispherical shaped charges have previously been limited to spherical shapes with no variations in wall thicknesses. By redesign of the basic liner thicknesses, the jet properties of coherence, stability, and mass distribution have been significantly improved. 8 figs.

Free form hemispherical shaped charge

DOEpatents

Haselman, Jr., Leonard C.

1996-01-01

A hemispherical shaped charge has been modified such that one side of the hemisphere is spherical and the other is aspherical allowing a wall thickness variation in the liner. A further modification is to use an elongated hemispherical shape. The liner has a thick wall at its pole and a thin wall at the equator with a continually decreasing wall thickness from the pole to the equator. The ratio of the wall thickness from the pole to the equator varies depending on liner material and HE shape. Hemispherical shaped charges have previously been limited to spherical shapes with no variations in wall thicknesses. By redesign of the basic liner thicknesses, the jet properties of coherence, stability, and mass distribution have been significantly improved.

Spin susceptibility of charge-ordered YBa2Cu3Oy across the upper critical field

PubMed Central

Zhou, Rui; Hirata, Michihiro; Wu, Tao; Vinograd, Igor; Mayaffre, Hadrien; Krämer, Steffen; Reyes, Arneil P.; Kuhns, Philip L.; Liang, Ruixing; Hardy, W. N.; Bonn, D. A.; Julien, Marc-Henri

2017-01-01

The value of the upper critical field Hc2, a fundamental characteristic of the superconducting state, has been subject to strong controversy in high-Tc copper oxides. Since the issue has been tackled almost exclusively by macroscopic techniques so far, there is a clear need for local-probe measurements. Here, we use 17O NMR to measure the spin susceptibility χspin of the CuO2 planes at low temperature in charge-ordered YBa2Cu3Oy. We find that χspin increases (most likely linearly) with magnetic field H and saturates above field values ranging from 20 T to 40 T. This result is consistent with the lowest Hc2 values claimed previously and with the interpretation that the charge density wave (CDW) reduces Hc2 in underdoped YBa2Cu3Oy. Furthermore, the absence of marked deviation in χspin(H) at the onset of long-range CDW order indicates that this Hc2 reduction and the Fermi-surface reconstruction are primarily rooted in the short-range CDW order already present in zero field, not in the field-induced long-range CDW order. Above Hc2, the relatively low values of χspin at T= 2 K show that the pseudogap is a ground-state property, independent of the superconducting gap. PMID:29183974

Shape memory effect in nanosized Ti2NiCu alloy-based composites

NASA Astrophysics Data System (ADS)

Irzhak, A. V.; Lega, P. V.; Zhikharev, A. M.; Koledov, V. V.; Orlov, A. P.; Kuchin, D. S.; Tabachkova, N. Yu.; Dikan, V. A.; Shelyakov, A. V.; Beresin, M. Yu.; Pushin, V. G.; von Gratowski, S. V.; Pokrovskiy, V. Ya.; Zybtsev, S. G.; Shavrov, V. G.

2017-01-01

The shape memory effect (SME) in alloys with a thermoelastic martensite transition opens unique opportunities for the creation of miniature mechanical devices. The SME has been studied in layered composite microstructures consisting of a Ti2NiCu alloy and platinum. It occurs upon a decrease in the active layer thickness at least to 80 nm. Some physical and technological restrictions on the minimum size of a material with SME are discussed.

Positron annihilation study of Y 1- xPr xBa 2Cu 3O 7

NASA Astrophysics Data System (ADS)

Zhao, Y. G.; Cao, B. S.; Yu, W. Z.; Du, Z. H.; Wang, Y. J.; Luo, C. Y.; Hu, H.; Wang, S.; Yang, J. H.; He, A. S.; Gu, B. L.

1995-02-01

A positron annihilation study of Y 1- xPr xBa 2Cu 3O 7 was performed. The results showed that charge transfer between the CuO 2 planes and 1D CuO chains upon Pr doping, as proposed in the literature, did not occur. Pr doping suppressed the anomaly of positron annihilation lifetime near and below Tc which has been observed in YBa 2Cu 3O 7. The perfection of the 1D CuO chains was reduced by Pr doping and this may be partly responsible for the increase of resistivity with Pr doping, and finally the semiconducting behaviour of DC resistivity in Y 1- xPr xBa 2Cu 3O 7 with x > 0.6.

Periodic table of 3d-metal dimers and their ions.

PubMed

Gutsev, G L; Mochena, M D; Jena, P; Bauschlicher, C W; Partridge, H

2004-10-08

The ground states of the mixed 3d-metal dimers TiV, TiCr, TiMn, TiFe, TiCo, TiNi, TiCu, TiZn, VCr, VMn, VFe, VCo, VNi, VCu, VZn, CrMn, CrFe, CrCo, CrNi, CrCu, CrZn, MnFe, MnCo, MnNi, MnCu, MnZn, FeCo, FeNi, FeCu, FeZn, CoNi, CoCu, CoZn, NiCu, NiZn, and CuZn along with their singly negatively and positively charged ions are assigned based on the results of computations using density functional theory with generalized gradient approximation for the exchange-correlation functional. Except for TiCo and CrMn, our assignment agrees with experiment. Computed spectroscopic constants (r(e),omega(e),D(o)) are in fair agreement with experiment. The ground-state spin multiplicities of all the ions are found to differ from the spin multiplicities of the corresponding neutral parents by +/-1. Except for TiV, MnFe, and MnCu, the number of unpaired electrons, N, in a neutral ground-state dimer is either N(1)+N(2) or mid R:N(1)-N(2)mid R:, where N(1) and N(2) are the numbers of unpaired 3d electrons in the 3d(n)4s(1) occupation of the constituent atoms. Combining the present and previous results obtained at the same level of theory for homonuclear 3d-metal and ScX (X=Ti-Zn) dimers allows one to construct "periodic" tables of all 3d-metal dimers along with their singly charged ions.

Copper(I) Complexes of N-(2-{[(2E)-2-(4-Nitrobenzylidenyl)Hydrazinyl]Carbonyl}Phenyl)Benzamide and Triphenylphosphine: Synthesis, Characterization and Luminescence Properties.

PubMed

Chavan, S S; Pawal, S B; More, M S; Willis, A C

2016-11-01

Copper(I) complexes of the formula [Cu(L)(PPh 3 ) 2 ]X (1-4) (X = Cl(1), ClO 4 (2), BF 4 (3) and PF 6 (4)) [where L = N-(2-{[(2E)-2-(4-nitrobenzylidenyl)hydrazinyl]carbonyl}phenyl)benzamide; PPh 3  = triphenylphosphine] have been prepared by the condensation of N-[2-(hydrazinocarbonyl)phenyl]benzamide with 4-nitrobenzaldehyde followed by the reaction with CuCl, [Cu(MeCN) 4 ]ClO 4 , [Cu(MeCN) 4 ]BF 4 and [Cu(MeCN) 4 ]PF 6 in presence of triphenylphosphine as a coligand. Complexes 1-4 were then characterized by elemental analyses, FTIR, UV-visible and 1 H NMR spectroscopy. Mononuclear copper(I) complexes 1-4 were formed with L in its keto form by involvement of azomethine nitrogen and the carbonyl oxygen along with two PPh 3 groups. A single crystal X-ray diffraction study of the representative complex [(Cu(L)(PPh 3 ) 2 ]CIO 4 (2) reveals a distorted tetrahedral geometry around Cu(I). Crystal data of (2): space group = C2/c, a = 42.8596 (9) Å, b = 14.6207 (3) Å, c = 36.4643 (7) Å, V = 20,653.7 (7) Å 3 , Z = 16. Complexes 1-4 exhibit quasireversible redox behaviour corresponding to a Cu(I)/Cu(II) couple. All complexes show blue-green emission as a result of fluorescence from an intra-ligand charge transition (ILCT), ligand to ligand charge transfer transition (LLCT) or mixture of both. Significant increase in size of the counter anion shows marked effect on quantum efficiency and lifetime of the complexes in solution.

Simultaneous determination of built-in voltage and charge carrier mobility in organic diodes from light intensity dependent current-voltage characteristics

NASA Astrophysics Data System (ADS)

Huang, Fobao; Peng, Yingquan; Xu, Kun; Lv, Wenli; Xu, Sunan; Wang, Ying; Tang, Ying; Wei, Yi; Yang, Yuhuan; Liu, Guohan

2017-05-01

Built-in voltage (V bi) and charge carrier mobility are essential parameters of organic diodes, such as organic photodiodes, organic light-emitting diodes and organic solar cells. The existing methods for charge carrier mobility measurement require either expensive equipment, or stringent sample preparation. We demonstrate a method that simultaneously determines the V bi and charge carrier mobility in organic photodiodes and solar cells from incident light intensity dependent current-voltage characteristics. The V bi is determined from the saturation open-circuit voltage, while the charge carrier mobility from the space-charge limited photocurrent. The V bi for organic diodes, ‘ITO/copper phthalocyanine (CuPc)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/Al’, ‘ITO/ lead phthalocyanine (PbPc)/BCP/Al’, ‘ITO/CuPc/C60/BCP/Al’, and ‘ITO/PbPc/C60/BCP/Al’, were measured to be 0.583  ±  0.019, 0.458  ±  0.002, 0.605  ±  0.009 and 0.538  ±  0.004 V, respectively; the hole mobility of CuPc and PbPc thin films were measured to be (1.383  ±  0.367)  ×  10-6 cm2 V-1 s-1 and (3.675  ±  0.887)  ×  10-6 cm2 V-1 s-1, respectively. The measured values for V bi and carrier mobility coincide with related experimental results reported in other literature.

Redox chemistry of a binary transition metal oxide (AB 2 O 4 ): a study of the Cu 2+ /Cu 0 and Fe 3+ /Fe 0 interconversions observed upon lithiation in a CuFe 2 O 4 battery using X-ray absorption spectroscopy

DOE PAGES

Cama, Christina A.; Pelliccione, Christopher J.; Brady, Alexander B.; ...

2016-06-06

Copper ferrite, CuFe 2 O 4, is a promising candidate for application as a high energy electrode material in lithium based batteries. Mechanistic insight on the electrochemical reduction and oxidation processes was gained through the first X-ray absorption spectroscopic study of lithiation and delithiation of CuFe 2 O 4. A phase pure tetragonal CuFe 2 O 4 material was prepared and characterized using laboratory and synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. We used ex situ X-ray absorption spectroscopy (XAS) measurements to study the battery redox processes at the Fe and Cu K-edges, using X-ray absorption near-edge structuremore » (XANES), extended X-ray absorption fine structure (EXAFS), and transmission X-ray microscopy (TXM) spectroscopies. EXAFS analysis showed upon discharge, an initial conversion of 50% of the copper(II) to copper metal positioned outside of the spinel structure, followed by a migration of tetrahedral iron(III) cations to octahedral positions previously occupied by copper(II). Then, upon charging to 3.5 V, the copper metal remained in the metallic state, while iron metal oxidation to iron(III) was achieved. Our results provide new mechanistic insight regarding the evolution of the local coordination environments at the iron and copper centers upon discharging and charging.« less

Redox chemistry of a binary transition metal oxide (AB2O4): a study of the Cu(2+)/Cu(0) and Fe(3+)/Fe(0) interconversions observed upon lithiation in a CuFe2O4 battery using X-ray absorption spectroscopy.

PubMed

Cama, Christina A; Pelliccione, Christopher J; Brady, Alexander B; Li, Jing; Stach, Eric A; Wang, Jiajun; Wang, Jun; Takeuchi, Esther S; Takeuchi, Kenneth J; Marschilok, Amy C

2016-06-22

Copper ferrite, CuFe2O4, is a promising candidate for application as a high energy electrode material in lithium based batteries. Mechanistic insight on the electrochemical reduction and oxidation processes was gained through the first X-ray absorption spectroscopic study of lithiation and delithiation of CuFe2O4. A phase pure tetragonal CuFe2O4 material was prepared and characterized using laboratory and synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. Ex situ X-ray absorption spectroscopy (XAS) measurements were used to study the battery redox processes at the Fe and Cu K-edges, using X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and transmission X-ray microscopy (TXM) spectroscopies. EXAFS analysis showed upon discharge, an initial conversion of 50% of the copper(ii) to copper metal positioned outside of the spinel structure, followed by a migration of tetrahedral iron(iii) cations to octahedral positions previously occupied by copper(ii). Upon charging to 3.5 V, the copper metal remained in the metallic state, while iron metal oxidation to iron(iii) was achieved. The results provide new mechanistic insight regarding the evolution of the local coordination environments at the iron and copper centers upon discharging and charging.

Self-Assembled Cu-Sn-S Nanotubes with High (De)Lithiation Performance.

PubMed

Lin, Jie; Lim, Jin-Myoung; Youn, Duck Hyun; Kawashima, Kenta; Kim, Jun-Hyuk; Liu, Yang; Guo, Hang; Henkelman, Graeme; Heller, Adam; Mullins, Charles Buddie

2017-10-24

Through a gelation-solvothermal method without heteroadditives, Cu-Sn-S composites self-assemble to form nanotubes, sub-nanotubes, and nanoparticles. The nanotubes with a Cu 3-4 SnS 4 core and Cu 2 SnS 3 shell can tolerate long cycles of expansion/contraction upon lithiation/delithiation, retaining a charge capacity of 774 mAh g -1 after 200 cycles with a high initial Coulombic efficiency of 82.5%. The importance of the Cu component for mitigation of the volume expansion and structural evolution upon lithiation is informed by density functional theory calculations. The self-generated template and calculated results can inspire the design of analogous Cu-M-S (M = metal) nanotubes for lithium batteries or other energy storage systems.

Facile synthesis of highly active reduced graphene oxide-CuI catalyst through a simple combustion method for photocatalytic reduction of CO2 to methanol

NASA Astrophysics Data System (ADS)

Zhang, Wenjun; Li, Yingjie; Zhang, Xiaoxiong; Li, Cuiluo

2017-09-01

We report a facile combustion method synthesis of reduced graphene oxide/CuI composites as a photocatalyst, in which CuI nanoparticles were homogeneously distributed on the surface of reduced graphene oxide (rGO), showing a good visible light response. The rGO-supported and unsupported CuI hybrids were tested over the photocatalytic reduction of CO2 for methanol evolution in visible light. In the current study rGO-CuI composites have shown excellent yields (19.91 μmol g-cat-1). rGO provides a light-weight, charge complementary and two-dimensional material that interacts effectively with the CuI nanoparticles.

CHARACTERISTICS OF THERMOLUMINESCENCE LiF:Mg,Cu,Ag NANOPHOSPHOR.

PubMed

Yahyaabadi, A; Torkzadeh, F; Rezaei-Ochbelagh, D

2018-04-23

A nanophosphor of LiF:Mg,Cu,Ag was prepared by planetary ball milling for the first time in the laboratory. The size and shape of the nanophosphor were confirmed by XRD and SEM, which showed that it was cubic in shape and ~53 nm in size. The thermoluminescence (TL) characteristics of this nanophosphor were then investigated. It was found that the optimum annealing condition was 250°C for 10 min. The TL sensitivity of the prepared nanopowder was less than that of its micropowder counterpart and the TL glow curve structure exhibited several peaks. The LiF:Mg,Cu,Ag nanophosphor exhibited a linear response over a range of doses from 1 Gy to ~10 kGy. From this study, it appears that LiF:Mg,Cu,Ag nanophosphor is a good candidate for dosimetry because of its linearity over a range of doses, low tendency to fade, good repeatability and simple glow curve structure.

Microstructure and Shape Memory Characteristics of Powder-Metallurgical-Processed Ti-Ni-Cu Alloys

NASA Astrophysics Data System (ADS)

Kim, Yeon-Wook; Chung, Young-Soo; Choi, Eunsoo; Nam, Tae-Hyun

2012-08-01

Even though Ti-Ni-Cu alloys have attracted a lot of attention because of their high performance in shape memory effect and decrease in thermal and stress hysteresis compared with Ti-Ni binary alloys, their poor workability restrains the practical applications of Ti-Ni-Cu shape memory alloys. Consolidation of Ti-Ni-Cu alloy powders is useful for the fabrication of bulk near-net-shape shape memory alloy. Ti50Ni30Cu20 shape memory alloy powders were prepared by gas atomization, and the sieved powders with the specific size range of 25 to 150 μm were chosen for this study. The evaluation of powder microstructures was based on a scanning electron microscope (SEM) examination of the surface and the polished and etched powder cross sections. The typical images showed cellular/dendrite morphology and high population of small shrinkage cavities at intercellular regions. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis showed that a B2-B19 one-step martensitic transformation occurred in the as-atomized powders. The martensitic transformation start temperature (Ms) of powders ranging between 25 and 50 μm was 304.5 K (31.5 °C). The Ms increased with increasing powder size. However, the difference of Ms in the as-atomized powders ranging between 25 and 150 μm was only 274 K (1 °C). A dense cylindrical specimen of 10 mm diameter and 15 mm length were fabricated by spark plasma sintering (SPS) at 1073 K (800 °C) and 10 MPa for 20 minutes. Then, this bulk specimen was heat treated for 60 minutes at 1123 K (850 °C) and quenched in ice water. The Ms of the SPS specimen was 310.5 K (37.5 °C) whereas the Ms of conventionally cast ingot is found to be as high as 352.7 K (79.7 °C). It is considered that the depression of the Ms in rapidly solidified powders is ascribed to the density of dislocations and the stored energy produced by rapid solidification.

Kinetics and Equilibrium of Age-Induced Precipitation in Cu-4 At. Pct Ti Binary Alloy

NASA Astrophysics Data System (ADS)

Semboshi, Satoshi; Amano, Shintaro; Fu, Jie; Iwase, Akihiro; Takasugi, Takayuki

2017-03-01

Transformation kinetics and phase equilibrium of metastable and stable precipitates in age-hardenable Cu-4 at. pct Ti binary alloy have been investigated by monitoring the microstructural evolution during isothermal aging at temperatures between 693 K (420 °C) and 973 K (700 °C). The microstructure of the supersaturated solid solution evolves in four stages: compositional modulation due to spinodal decomposition, continuous precipitation of the needle-shaped metastable β'-Cu4Ti with a tetragonal structure, discontinuous precipitation of cellular components containing stable β-Cu4Ti lamellae with an orthorhombic structure, and eventually precipitation saturation at equilibrium. In specimens aged below 923 K (650 °C), the stable β-Cu4Ti phase is produced only due to the cellular reaction, whereas it can be also directly obtained from the intergranular needle-shaped β'-Cu4Ti precipitates in specimens aged at 973 K (700 °C). The precipitation kinetics and phase equilibrium observed for the specimens aged between 693 K (420 °C) and 973 K (700 °C) were characterized in accordance with a time-temperature-transformation (TTT) diagram and a Cu-Ti partial phase diagram, which were utilized to determine the alloy microstructure, strength, and electrical conductivity.

Tension-controlled single-crystallization of copper foils for roll-to-roll synthesis of high-quality graphene films

NASA Astrophysics Data System (ADS)

Jo, Insu; Park, Subeom; Kim, Dongjin; San Moon, Jin; Park, Won Bae; Kim, Tae Hyeong; Hyoun Kang, Jin; Lee, Wonbae; Kim, Youngsoo; Lee, Dong Nyung; Cho, Sung-Pyo; Choi, Hyunchul; Kang, Inbyeong; Park, Jong Hyun; Lee, Jeong Soo; Hong, Byung Hee

2018-04-01

It has been known that the crystalline orientation of Cu substrates plays a crucial role in chemical vapor deposition (CVD) synthesis of high-quality graphene. In particular, Cu (1 1 1) surface showing the minimum lattice mismatch with graphene is expected to provide an ideal catalytic reactivity that can minimize the formation of defects, which also induces larger single-crystalline domain sizes of graphene. Usually, the Cu (1 1 1) substrates can be epitaxially grown on single-crystalline inorganic substrates or can be recrystallized by annealing for more than 12 h, which limits the cost and time-effective synthesis of graphene. Here, we demonstrate a new method to optimize the crystalline orientations of vertically suspended Cu foils by tension control during graphene growth, resulting in large-area recrystallization into Cu (1 1 1) surface as the applied tension activates the grain boundary energy of Cu and promotes its abnormal grain growth to single crystals. In addition, we found a clue that the formation of graphene cooperatively assists the recrystallization into Cu (1 1 1) by minimizing the surface energy of Cu. The domain sizes and charge carrier mobility of graphene grown on the single-crystalline Cu (1 1 1) are 5 times and ~50% increased, respectively, in comparison with those of graphene from Cu (1 0 0), indicating that the less lattice mismatch and the lower interaction energy between Cu (1 1 1) and graphene allows the growth of larger single-crystalline graphene with higher charge carrier mobility. Thus, we believe that our finding provides a crucial idea to design a roll-to-roll (R2R) graphene synthesis system where the tension control is inevitably involved, which would be of great importance for the continuous production of high-quality graphene in the future.

Design of Copper and Titanium Dioxide Nanoparticles Doped with Reduced Graphene Oxide for Hydrogen Evolution by Water Splitting

NASA Astrophysics Data System (ADS)

Yang, Yuhao; Huang, Wenhuan

2018-05-01

TiO2-graphene (P25-GR, PG) nanocomposite was fabricated from P25 titania and graphite oxide by hydrothermal method, and then Cu nanoparticles (Cu NPs) were assembled in P25-GR composite (Cu- P25-GR, CPG) under microwave-assisted chemical reduction. The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV-Vis absorption (UV-Vis) and Raman spectroscopies. Cu NPs were well dispersed on the surface of PG and are in metallic state. The ternary Cu-P25-GR (CPG) nanocomposites show an extended light absorption range and more efficient charge separation properties compared to binary P25-GR (PG) composite. Methylene blue photodegradation experiment proved that surface plasmon resonance (SPR) phenomenon had an effect on photoreaction efficiency. The corresponding hydrogen evolution rate for CPG prepared using 0.002 M Cu(NO3)2 solution was 10 times higher than with pure P25, and 2.3 times higher than with PG in the same test conditions. The improved photocatalytic performance can be attributed to the presence of GR in the prepared composite and to the SPR effect, leading to the longer lifetime of photogenerated electronhole pairs and faster interfacial charge transfer rate. We expect that our work would be useful for the further exploration of GR-based nanocomposites.

Improved visible-light photocatalytic activity of TiO2 co-doped with copper and iodine

NASA Astrophysics Data System (ADS)

Dorraj, Masoumeh; Goh, Boon Tong; Sairi, Nor Asrina; Woi, Pei Meng; Basirun, Wan Jefrey

2018-05-01

Cu-I-co-doped TiO2 photocatalysts active to visible light absorption were prepared by hydrothermal method and calcined at various temperatures (350 °C, 450 °C, and 550 °C). The co-doped powders at 350 °C displayed the highest experimental Brunauer-Emmett-Teller surface area and lowest photoluminescence intensity, which demonstrated that a decrease in electron-hole recombination process. The synthesis of co-doped TiO2 was performed at this optimized temperature. In the co-doped sample, the Cu2+ doped TiO2 lattice created a major "red-shift" in the absorption edge due to the presence of the 3d Cu states, whereas the amount of red-shift from the I5+ doping in the TiO2 lattice was minor. Interestingly, the presence of Cu2+ species also boosted the reduction of I5+ ions to the lower multi-valance state I- in the TiO2 lattice by trapping the photogenerated electrons, which resulted in effective separation of the photogenerated charges. The Cu-I-co-doped TiO2 was able to degrade methyl orange dye under visible-light irradiation with improved photocatalytic activity compared with the single metal-doped TiO2 and pure TiO2 because of the strong visible light absorption and effective separation of photogenerated charges caused by the synergistic effects of Cu and I co-dopants.

Efficiency Analysis of Waveform Shape for Electrical Excitation of Nerve Fibers

PubMed Central

Wongsarnpigoon, Amorn; Woock, John P.; Grill, Warren M.

2011-01-01

Stimulation efficiency is an important consideration in the stimulation parameters of implantable neural stimulators. The objective of this study was to analyze the effects of waveform shape and duration on the charge, power, and energy efficiency of neural stimulation. Using a population model of mammalian axons and in vivo experiments on cat sciatic nerve, we analyzed the stimulation efficiency of four waveform shapes: square, rising exponential, decaying exponential, and rising ramp. No waveform was simultaneously energy-, charge-, and power-optimal, and differences in efficiency among waveform shapes varied with pulse width (PW) For short PWs (≤ 0.1 ms), square waveforms were no less energy-efficient than exponential waveforms, and the most charge-efficient shape was the ramp. For long PWs (≥0.5 ms), the square was the least energy-efficient and charge-efficient shape, but across most PWs, the square was the most power-efficient shape. Rising exponentials provided no practical gains in efficiency over the other shapes, and our results refute previous claims that the rising exponential is the energy-optimal shape. An improved understanding of how stimulation parameters affect stimulation efficiency will help improve the design and programming of implantable stimulators to minimize tissue damage and extend battery life. PMID:20388602

Investigation of the martensitic transformation of (Cu-Zn-Ni) shape memory alloys

NASA Astrophysics Data System (ADS)

Naat, N. A.; Mohammed, M. A.

2017-02-01

(Cu-Zn-Ni) shape memory alloy with different percent have been prepared by using high frequency induction furnace under argon atmosphere. All of the specimens obtained from this alloys were heated in furnace for (15 minutes at 865°C) for homogenization and quenched in iced-water. Comparisons has been made with data obtained via differential scanning calorimetry (DSC) and energy-dispersive X-ray spectroscopy (EDS). The metallographic analyses were carried out by using optical microscopy (OM).

Two types of nematicity in the phase diagram of the cuprate superconductor YBa2Cu3Oy

NASA Astrophysics Data System (ADS)

Cyr-Choinière, O.; Grissonnanche, G.; Badoux, S.; Day, J.; Bonn, D. A.; Hardy, W. N.; Liang, R.; Doiron-Leyraud, N.; Taillefer, Louis

2015-12-01

Nematicity has emerged as a key feature of cuprate superconductors, but its link to other fundamental properties such as superconductivity, charge order, and the pseudogap remains unclear. Here we use measurements of transport anisotropy in YBa2Cu3Oy to distinguish two types of nematicity. The first is associated with short-range charge-density-wave modulations in a doping region near p =0.12 . It is detected in the Nernst coefficient, but not in the resistivity. The second type prevails at lower doping, where there are spin modulations but no charge modulations. In this case, the onset of in-plane anisotropy—detected in both the Nernst coefficient and the resistivity—follows a line in the temperature-doping phase diagram that tracks the pseudogap energy. We discuss two possible scenarios for the latter nematicity.

Towards a thermally regenerative all-copper redox flow battery.

PubMed

Peljo, Pekka; Lloyd, David; Doan, Nguyet; Majaneva, Marko; Kontturi, Kyösti

2014-02-21

An all-copper redox flow battery based on strong complexation of Cu(+) with acetonitrile is demonstrated, exhibiting reasonable battery performance. More interestingly, the battery can be charged by heat sources of 100 °C, by distilling off the acetonitrile. This destabilizes the Cu(+) complex, leading to recovery of the starting materials.

Shape-Controlled Synthesis of High-Quality Cu7 S4 Nanocrystals for Efficient Light-Induced Water Evaporation.

PubMed

Zhang, Changbo; Yan, Cong; Xue, Zhenjie; Yu, Wei; Xie, Yinde; Wang, Tie

2016-10-01

Copper sulfides (Cu 2-x S), are a novel kind of photothermal material exhibiting significant photothermal conversion efficiency, making them very attractive in various energy conversion related devices. Preparing high quality uniform Cu 2-x S nanocrystals (NCs) is a top priority for further energy-and sustainability relevant nanodevices. Here, a shape-controlled high quality Cu 7 S 4 NCs synthesis strategy is reported using sulfur in 1-octadecene as precursor by varying the heating temperature, as well as its forming mechanism. The performance of the Cu 7 S 4 NCs is further explored for light-driven water evaporation without the need of heating the bulk liquid to the boiling point, and the results suggest that as-synthesized highly monodisperse NCs perform higher evaporation rate than polydisperse NCs under the identical morphology. Furthermore, disk-like NCs exhibit higher water evaporation rate than spherical NCs. The water evaporation rate can be further enhanced by assembling the organic phase Cu 7 S 4 NCs into a dense film on the aqueous solution surface. The maximum photothermal conversion efficiency is as high as 77.1%. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure and electronic properties of Cu nanoclusters supported on Mo 2C(001) and MoC(001) surfaces

DOE PAGES

Posada-Pérez, Sergio; Viñes, Francesc; Rodríguez, José A.; ...

2015-09-15

In this study, the atomic structure and electronic properties of Cu n nanoclusters (n = 4, 6, 7, and 10) supported on cubic nonpolar δ-MoC(001) and orthorhombic C- or Mo-terminated polar β-Mo 2C(001) surfaces have been investigated by means of periodic density functional theory based calculations. The electronic properties have been analyzed by means of the density of states, Bader charges, and electron localization function plots. The Cu nanoparticles supported on β-Mo 2C(001), either Mo- or C-terminated, tend to present a two-dimensional structure whereas a three-dimensional geometry is preferred when supported on δ-MoC(001), indicating that the Mo:C ratio and themore » surface polarity play a key role determining the structure of supported clusters. Nevertheless, calculations also reveal important differences between the C- and Mo-terminated β-Mo 2C(001) supports to the point that supported Cu particles exhibit different charge states, which opens a way to control the reactivity of these potential catalysts.« less

Bi1−xLaxCuSeO as New Tunable Full Solar Light Active Photocatalysts

PubMed Central

Wang, Huanchun; Li, Shun; Liu, Yaochun; Ding, Jinxuan; Lin, Yuan-Hua; Xu, Haomin; Xu, Ben; Nan, Ce-Wen

2016-01-01

Photocatalysis is attracting enormous interest driven by the great promise of addressing current energy and environmental crises by converting solar light directly into chemical energy. However, efficiently harvesting solar energy for photocatalysis remains a pressing challenge, and the charge kinetics and mechanism of the photocatalytic process is far from being well understood. Here we report a new full solar spectrum driven photocatalyst in the system of a layered oxyselenide BiCuSeO with good photocatalytic activity for degradation of organic pollutants and chemical stability under light irradiation, and the photocatalytic performance of BiCuSeO can be further improved by band gap engineering with introduction of La. Our measurements and density-functional-theory calculations reveal that the effective mass and mobility of the carriers in BiCuSeO can be tuned by the La-doping, which are responsible for the tunable photocatalytic activity. Our findings may offer new perspectives for understanding the mechanism of photocatalysis through modulating the charge mobility and the effective mass of carriers and provide a guidance for designing efficient photocatalyts. PMID:27095046

Doping effect on the thermoelectric properties of chalcopyrite CuGaTe2

NASA Astrophysics Data System (ADS)

Sharma, Sonu; Singh, Birender; Kumar, Pradeep

2018-05-01

In the present work, we have investigated the thermoelectric properties of CuGaTe2 by combining the first principle calculations with Boltzmann transport theory. CuGaTe2 is found to be a potential thermoelectric material with Seebeck coefficient 275µVK-1 at 200K. The thermoelectric properties of the compound can be further improved by doping it with p as well as n-type charge carriers. The heavily p-doped and lightly n-doped, CuGaTe2 provides power factor comparable to that of state-of-art Bi2Te3.

An aqueous friendly chemosensor derived from vitamin B6 cofactor for colorimetric sensing of Cu2 + and fluorescent turn-off sensing of Fe3 +

NASA Astrophysics Data System (ADS)

Sharma, Darshna; Kuba, Aman; Thomas, Rini; Kumar, Rajender; Choi, Heung-Jin; Sahoo, Suban K.

2016-01-01

Chemosensor L derived from vitamin B6 cofactor pyridoxal-5-phosphate was investigated for the selective detection of Cu2 + and Fe3 + in aqueous medium. Sensor L formed a 1:1 complex with Cu2 + and displays a perceptible color change from colorless to yellow brown with the appearance of a new charge transfer band at 450 nm. In contrast, the fluorescence of L was quenched selectively in the presence of Fe3 + without any interference from other metal ions including Cu2 +.

SR90, strontium shaped-charge critical ionization velocity experiment

NASA Technical Reports Server (NTRS)

Wescott, Eugene M.; Stenbaek-Nielsen, Hans; Swift, Daniel W.; Valenzuela, Arnoldo; Rees, David

1990-01-01

In May 1986 an experiment was performed to test Alfven's critical ionization velocity (CIV) effect in free space, using the first high explosive shaped charge with a conical liner of strontium metal. The release, made at 540 km altitude at dawn twilight, was aimed at 48 deg to B. The background electron density was 1.5 x 10(exp 4) cu cm. A faint field-aligned Sr(+) ion streak with tip velocity of 2.6 km/s was observed from two optical sites. Using two calibration methods, it was calculated that between 4.5 x 10(exp 20) and 2 x 10(exp 21) ions were visible. An ionization time constant of 1920 s was calculated for Sr from the solar UV spectrum and ionization cross section which combined with a computer simulation of the injection predicts 1.7 x 10(exp 21) solar UV ions in the low-velocity part of the ion streak. Thus all the observed ions are from solar UV ionization of the slow (less than critical) velocity portion of the neutral jet. The observed neutral Sr velocity distribution and computer simulations indicate that 2 x 10(exp 21) solar UV ions would have been created from the fast (greater than critical) part of the jet. They would have been more diffuse, and were not observed. Using this fact it was estimated that any CIV ions created were less than 10(exp 21). It was concluded that future Sr CIV free space experiments should be conducted below the UV shadow height and in much larger background plasma density.

Effects of charge inhomogeneities on elementary excitations in La 2-xSr xCuO₄

DOE PAGES

Park, S. R.; Hamann, A.; Pintschovius, L.; ...

2011-12-12

Purely local experimental probes of many copper oxide superconductors show that their electronic states are inhomogeneous in real space. For example, scanning tunneling spectroscopic imaging shows strong variations in real space, and according to nuclear quadrupole resonance (NQR) studies, the charge distribution in the bulk varies on the nanoscale. However, the analysis of the experimental results utilizing spatially averaged probes often ignores this fact. We have performed a detailed investigation of the doping dependence of the energy and linewidth of the zone-boundary Cu-O bond-stretching vibration in La 2-xSr xCuO₄ by inelastic neutron scattering. Both our results as well as previouslymore » reported angle-dependent momentum widths of the electronic spectral function detected by angle-resolved photoemission can be reproduced by including the same distribution of local environments extracted from the NQR analysis.« less

Remarkable Stability of Charge Density Wave Order in La 1.875Ba 0.125CuO 4

DOE PAGES

Chen, X. M.; Thampy, V.; Mazzoli, C.; ...

2016-10-11

The occurrence of charge-density-wave (CDW) order in underdoped cuprates is now well established, although the precise nature of the CDW and its relationship with superconductivity is not. Theoretical proposals include contrasting ideas such as that pairing may be driven by CDW uctuations or that static CDWs may intertwine with a spatially-modulated superconducting wave function. We test the dynamics of CDW order in La 1.875Ba 0.125CuO 4 by using x-ray photon correlation spectroscopy (XPCS) at the CDW wave vector, detected resonantly at the Cu L 3-edge. We nd that the CDW domains are strikingly static, with no evidence of signi cantmore » uctuations up to 2 3/4 hours. We discuss the implications of these results for some of the competing theories.« less

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

Iyer, Abishek K.; Rudyk, Brent W.; Lin, Xinsong

The quaternary rare-earth chalcogenides RE{sub 3}CuGaS{sub 7} and RE{sub 3}CuGaSe{sub 7} (RE=La–Nd) have been prepared by reactions of the elements at 1050 °C and 900 °C, respectively. They crystallize in the noncentrosymmetric La{sub 3}CuSiS{sub 7}-type structure (hexagonal, space group P6{sub 3}, Z=2) in which the a-parameter is largely controlled by the RE component (a=10.0–10.3 Å for the sulfides and 10.3–10.6 Å for the selenides) whereas the c-parameter is essentially fixed by the choice of Ga and chalcogen atoms within tetrahedral units (c=6.1 Å for the sulfides and 6.4 Å for the selenides). They extend the series RE{sub 3}MGaCh{sub 7}, previouslymore » known for divalent metal atoms (M=Mn–Ni), differing in that the Cu atoms in RE{sub 3}CuGaCh{sub 7} occupy trigonal planar sites instead of octahedral sites. Among quaternary chalcogenides RE{sub 3}MM′Ch{sub 7}, the combination of monovalent (M=Cu) and trivalent (M′=Ga) metals is unusual because it appears to violate the condition of charge balance satisfied by most La{sub 3}CuSiS{sub 7}-type compounds. The possibility of divalent Cu atoms was ruled out by bond valence sum analysis, magnetic measurements, and X-ray photoelectron spectroscopy. The electron deficiency in RE{sub 3}CuGaCh{sub 7} is accommodated through S-based holes at the top of the valence band, as shown by band structure calculations on La{sub 3}CuGaS{sub 7}. An optical band gap of about 2.0 eV was found for La{sub 3}CuGaSe{sub 7}. - Graphical abstract: The chalcogenides RE{sub 3}CuGaCh{sub 7} contain monovalent Cu in trigonal planes and trivalent Ga in tetrahedra; they are electron-deficient representatives of La{sub 3}CuSiS{sub 7}-type compounds, which normally satisfy charge balance. - Highlights: • Quaternary chalcogenides RE{sub 3}CuGaCh{sub 7} (RE=La–Nd; Ch=S, Se) were prepared. • Bond valence sums, magnetism, and XPS data give evidence for monovalent Cu. • Crystal structures reveal high anisotropy of Cu displacement. • Electron deficiency is accommodated by S-based holes in valence band.« less

Hierarchical Cu2O foam/g-C3N4 photocathode for photoelectrochemical hydrogen production

NASA Astrophysics Data System (ADS)

Ma, Xinzhou; Zhang, Jingtao; Wang, Biao; Li, Qiuguo; Chu, Sheng

2018-01-01

Solar photoelectrochemical (PEC) hydrogen production is a promising way for solving energy and environment problems. Earth-abundant Cu2O is a potential light absorber for PEC hydrogen production. In this article, hierarchical porous Cu2O foams are prepared by thermal oxidation of the electrochemically deposited Cu foams. PEC performances of the Cu2O foams are systematically studied and discussed. Benefiting from their higher light harvesting and more efficient charge separation, the Cu2O foams demonstrate significantly enhanced photocurrents and photostability compared to their film counterparts. Moreover, by integrating g-C3N4, hierarchical Cu2O foam/g-C3N4 composites are prepared with further improved photocurrent and photostability, appearing to be potential photocathodes for solar PEC hydrogen production. This study may provide a new and useful insight for the development of Cu2O-based photocathodes for PEC hydrogen production.

Facile synthesis of polyaniline-modified CuS with enhanced adsorbtion and photocatalytic activity

NASA Astrophysics Data System (ADS)

Wang, Xiufang; Chen, Shaohua; Shuai, Ying

2016-10-01

Novel hierarchical polyaniline-modified CuS (PANI-CuS) has been synthesized by simple assembling PANI on the surface of flower-like CuS spheres. The PANI modification enhances the adsorption properties of flower-like CuS. The prepared PANI-CuS composites exhibit higher visible-light-driven photocatalytic activities in degradation of rhodamine B (RhB) than that of neat CuS. The unusual photocatalytic activity could be attributed to the great adsorptivity of dyes, the extended photoresponse range, and the high migration efficiency of photoinduced electrons, which may effectively suppress the charge recombination. This work not only provides a simple strategy for fabricating highly efficient and stable CuS-based composites, but also proves that these unique structures are excellent platforms for significantly improving their visible- light-driven photoactivities, holding great promise for their applications in the field of purifying polluted water resources.

Symmetry and novelty in the electronic and geometric structure of nanoalloys:. the case of Ag27Cu7

NASA Astrophysics Data System (ADS)

Ortigoza, M. Alcántara; Rahman, T. S.

2008-04-01

Nanoparticles of bimetallic alloys have been shown to possess composition dependent characteristics which distinguish themselves from the corresponding bulk alloys. Taking the 34-atom nanoalloy of Ag and Cu (Ag27Cu7), we show using first principles electronic structure calculations that this core-shell alloy indeed has perfect D5h symmetry and consists of only 6 non-equivalent (2 Cu and 4 Ag) atoms. Analysis of the interatomic bond lengths and detailed electronic structure further reveal that the Cu atoms play a major role in controlling the characteristics of the nanoalloy. The higher cohesive energy, together with shorter bond length for Cu, compared to Ag, conspire to produce a hierarchy in the relative strengths of the Ag - Cu, Ag - Ag, and Cu - Cu bonds and corresponding interatomic bond lengths, point to the uniqueness in the characteristics of this nanoalloy. Charge density plots of Ag27Cu7 provide further insights into the relative strengths of the various interatomic bonds.

Pyrotechnic shock: A literature survey of the Linear Shaped Charge (LSC)

NASA Technical Reports Server (NTRS)

Smith, J. L.

1984-01-01

Linear shaped charge (LSC) literature for the past 20 years is reviewed. The following topics are discussed: (1) LSC configuration; (2) LSC usage; (3) LSC induced pyroshock; (4) simulated pyrotechnic testing; (5) actual pyrotechnic testing; (6) data collection methods; (7) data analysis techniques; (8) shock reduction methods; and (9) design criteria. Although no new discoveries have been made in LSC research, charge shapes are improved to allow better cutting performance, testing instrumentation is refined, and some new explosives, for use in LSC, are formulated.

Improving the accuracy of ultrafast ligand-based screening: incorporating lipophilicity into ElectroShape as an extra dimension.

PubMed

Armstrong, M Stuart; Finn, Paul W; Morris, Garrett M; Richards, W Graham

2011-08-01

In a previous paper, we presented the ElectroShape method, which we used to achieve successful ligand-based virtual screening. It extended classical shape-based methods by applying them to the four-dimensional shape of the molecule where partial charge was used as the fourth dimension to capture electrostatic information. This paper extends the approach by using atomic lipophilicity (alogP) as an additional molecular property and validates it using the improved release 2 of the Directory of Useful Decoys (DUD). When alogP replaced partial charge, the enrichment results were slightly below those of ElectroShape, though still far better than purely shape-based methods. However, when alogP was added as a complement to partial charge, the resulting five-dimensional enrichments shows a clear improvement in performance. This demonstrates the utility of extending the ElectroShape virtual screening method by adding other atom-based descriptors.

Single cyanide-bridged Mo(W)/S/Cu cluster-based coordination polymers: Reactant- and stoichiometry-dependent syntheses, effective photocatalytic properties

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

Zhang, Jinfang, E-mail: zjf260@jiangnan.edu.cn; Wang, Chao; Wang, Yinlin

2015-11-15

The systematic study on the reaction variables affecting single cyanide-bridged Mo(W)/S/Cu cluster-based coordination polymers (CPs) is firstly demonstrated. Five anionic single cyanide-bridged Mo(W)/S/Cu cluster-based CPs {[Pr_4N][WS_4Cu_3(CN)_2]}{sub n} (1), {[Pr_4N][WS_4Cu_4(CN)_3]}{sub n} (2), {[Pr_4N][WOS_3Cu_3(CN)_2]}{sub n} (3), {[Bu_4N][WOS_3Cu_3(CN)_2]}{sub n} (4) and {[Bu_4N][MoOS_3Cu_3(CN)_2]}{sub n} (5) were prepared by varying the molar ratios of the starting materials, and the specific cations, cluster building blocks and central metal atoms in the cluster building blocks. 1 possesses an anionic 3D diamondoid framework constructed from 4-connected T-shaped clusters [WS{sub 4}Cu{sub 3}]{sup +} and single CN{sup −} bridges. 2 is fabricated from 6-connected planar ‘open’ clusters [WS{sub 4}Cu{sub 4}]{supmore » 2+} and single CN{sup −} bridges, forming an anionic 3D architecture with an “ACS” topology. 3 and 4 exhibit novel anionic 2-D double-layer networks, both constructed from nest-shaped clusters [WOS{sub 3}Cu{sub 3}]{sup +} linked by single CN{sup −} bridges, but containing the different cations [Pr{sub 4}N]{sup +} and [Bu{sub 4}N]{sup +}, respectively. 5 is constructed from nest-shaped clusters [MoOS{sub 3}Cu{sub 3}]{sup +} and single CN{sup −} bridges, with an anionic 3D diamondoid framework. The anionic frameworks of 1-5, all sustained by single CN{sup −} bridges, are non-interpenetrating and exhibit huge potential void volumes. Employing differing molar ratios of the reactants and varying the cluster building blocks resulted in differing single cyanide-bridged Mo(W)/S/Cu cluster-based CPs, while replacing the cation ([Pr{sub 4}N]{sup +} vs. [Bu{sub 4}N]{sup +}) was found to have negligible impact on the nature of the architecture. Unexpectedly, replacement of the central metal atom (W vs. Mo) in the cluster building blocks had a pronounced effect on the framework. Furthermore, the photocatalytic activities of heterothiometallic cluster-based CPs were firstly explored by monitoring the photodegradation of methylene blue (MB) under visible light irradiation, which reveals that 2 exhibits effective photocatalytic properties. - Highlights: • Reaction variables affecting Mo(W)/S/Cu cluster-based CPs is firstly explored. • Replacing central metal atom had a pronounced effect on W/S/Cu cluster-based CPs. • Photocatalytic activities of Mo(W)/S/Cu cluster-based CPs are firstly investigated.« less

Structural and electronic properties of chiral single-wall copper nanotubes

NASA Astrophysics Data System (ADS)

Duan, YingNi; Zhang, JianMin; Xu, KeWei

2014-04-01

The structural, energetic and electronic properties of chiral ( n, m) (3⩽ n⩽6, n/2⩽ m⩽ n) single-wall copper nanotubes (CuNTs) have been investigated by using projector-augmented wave method based on density-functional theory. The (4, 3) CuNT is energetically stable and should be observed experimentally in both free-standing and tip-suspended conditions, whereas the (5, 5) and (6, 4) CuNTs should be observed in free-standing and tip-suspended conditions, respectively. The number of conductance channels in the CuNTs does not always correspond to the number of atomic strands comprising the nanotube. Charge density contours show that there is an enhanced interatomic interaction in CuNTs compared with Cu bulk. Current transporting states display different periods and chirality, the combined effects of which lead to weaker chiral currents on CuNTs.

The Shaped Charge Concept. Part 2. The History of Shaped Charges

DTIC Science & Technology

1990-09-01

research of Evans. Ubbel•ode. LAmurd-Jones, Devonihire, and An&ew. 1hW U.K. Mufied cadmium liners (which probably produce molten jets) msd steel liners...34 Mathematical Jet Theory of Lined Hollow Charges." BRL Report No. 370, U.S. Army Ballistic Research Laboratory. Aberdeen Proving Ground, MD, 18 June

Controlling molecular condensation/diffusion of copper phthalocyanine by local electric field induced with scanning tunneling microscope tip

NASA Astrophysics Data System (ADS)

Nagaoka, Katsumi; Yaginuma, Shin; Nakayama, Tomonobu

2018-02-01

We have discovered the condensation/diffusion phenomena of copper phthalocyanine (CuPc) molecules controlled with a pulsed electric field induced by the scanning tunneling microscope tip. This behavior is not explained by the conventional induced dipole model. In order to understand the mechanism, we have measured the electronic structure of the molecule by tunneling spectroscopy and also performed theoretical calculations on molecular orbitals. These data clearly indicate that the molecule is positively charged owing to charge transfer to the substrate, and that hydrogen bonding exists between CuPc molecules, which makes the molecular island stable.

Momentum Dependence of Charge Excitations in YBa2Cu3O7-δ and Nd2-xCexCuO4

NASA Astrophysics Data System (ADS)

Ishii, Kenji

2006-03-01

Resonant inelastic x-ray scattering (RIXS) studies at Cu K-edge on high-Tc superconducting cuprates, YBa2Cu3O7-δ and Nd2-xCexCuO4 are presented. The superconductivity occurs in the vicinity of the Mott insulating state and it is important to clarify the nature of the Mott gap and its doping dependence. Because RIXS has an advantage that we can measure charge excitation in a wide energy-momentum space, it gives a unique opportunity to study the electronic structure of materials. We apply this technique to high-Tc superconducting cuprates. In particular the electronic structure of strongly correlated metals is in the focus of our RIXS study. The experiments were performed at BL11XU of SPring-8, Japan, where a specially designed spectrometer for inelastic x-ray scattering is installed. In optimally doped YBa2Cu3O7-δ, anisotropic spectra are observed in the ab plane of a twin-free crystal. The Mott gap excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the chain direction, while the excitation from the CuO2 plane is broad at 1.5-4 eV and almost independent of momentum. Theoretical calculation based on the one-dimensional and two-dimensional Hubbard model reproduces the observed features in the RIXS spectra when smaller values of the on-site Coulomb energy of the chain than that of the plane are assumed. This means that the charge transfer gap of the chain is smaller than that of the plane. On the other hand, both interband excitation across the Mott gap and intraband excitation in the upper Hubbard band are observed in the electron-doped Nd2-xCexCuO4. The intensity of the interband excitation is concentrated at ˜ 2 eV near the zone boundary while a dispersion relation with a momentum-dependent width emerges in the intraband excitation. The author would like to acknowledge to his collaborators, K. Tsutsui, Y. Endoh, T. Tohyama, K. Kuzushita, T. Inami, K. Ohwada, M. Hoesch, M. Tsubota, Y. Murakami, J. Mizuki, S. Maekawa, T. Masui, S. Tajima, and K. Yamada. The crystal growth of YBa2Cu3O7-δ was supported by the New Energy and Industrial Technology Development Organization (NEDO) as the Collaborative Research and Development of Fundamental Technologies for Superconductivity Applications.

Convergent synthesis and photoinduced processes in multi-chromophoric rotaxanes.

PubMed

Megiatto, Jackson D; Li, Ke; Schuster, David I; Palkar, Amit; Herranz, M Ángeles; Echegoyen, Luis; Abwandner, Silke; de Miguel, Gustavo; Guldi, Dirk M

2010-11-18

A series of [2]rotaxane materials, in which [60]fullerene is linked to a macrocycle and ferrocene (Fc) moieties are placed at the termini of a thread, both of which possess a central Cu(I)-1,10-phenanthroline [Cu(phen)(2)](+) complex, were synthesized by self-assembly using Sauvage metal template methodology. Two types of threads were constructed, one with terminal ester linkages, and a second with terminal 1,2,3-triazole linkages derived from Cu(I)-catalyzed "click" 1,3-cycloaddition reactions. Model compounds lacking the fullerene moiety were prepared in an analogous manner. The ability of the interlocked Fc-[Cu(phen)(2)](+)-C(60) hybrids to undergo electron transfer upon photoexcitation in benzonitrile, dichloromethane, and ortho-dichlorobenzene was investigated by means of time-resolved fluorescence and transient absorption spectroscopy, using excitation wavelengths directed at the fullerene and [Cu(phen)(2)](+) subunits. The energies of the electronic excited states and charge separated (CS) states that might be formed upon photoexcitation were determined from spectroscopic and electrochemical data. These studies showed that MLCT excited states of the copper complex in the fullerenerotaxanes were quenched by electron transfer to the fullerene in benzonitrile, resulting in charge separated states with oxidized copper and reduced fullerene moieties, (Fc)(2)-[Cu(phen)(2)](2+)-C(60)(•-). Even though electron transfer from Fc to the oxidized copper complex is predicted to be exergonic by 0.16 to 0.20 eV, no unequivocal evidence in support of such a process was obtained. The conclusion that Fc plays no role in the photoinduced processes in our systems rests on the lack of enhancement of the lifetime of the charge separated state, as measured by decay of C(60)(•-) at ∼1000 nm, since one-electron oxidized Fc is very difficult to detect spectroscopically in the 500-800 nm spectral region.

Solution-processed all-oxide bulk heterojunction solar cells based on CuO nanaorod array and TiO2 nanocrystals.

PubMed

Wu, Fan; Qiao, Qiquan; Bahrami, Behzad; Chen, Ke; Pathak, Rajesh; Tong, Yanhua; Li, Xiaoyi; Zhang, Tiansheng; Jian, Ronghua

2018-05-25

We present a method to synthesize CuO nanorod array/TiO 2 nanocrystals bulk heterojunction (BHJ) on fluorine-tin-oxide (FTO) glass, in which single-crystalline p-type semiconductor of the CuO nanorod array is grown on the FTO glass by hydrothermal reaction and the n-type semiconductor of the TiO 2 precursor is filled into the CuO nanorods to form well-organized nano-interpenetrating BHJ after air annealing. The interface charge transfer in CuO nanorod array/TiO 2 heterojunction is studied by Kelvin probe force microscopy (KPFM). KPFM results demonstrate that the CuO nanorod array/TiO 2 heterojunction can realize the transfer of photo-generated electrons from the CuO nanorod array to TiO 2 . In this work, a solar cell with the structure FTO/CuO nanoarray/TiO 2 /Al is successfully fabricated, which exhibits an open-circuit voltage (V oc ) of 0.20 V and short-circuit current density (J sc ) of 0.026 mA cm -2 under AM 1.5 illumination. KPFM studies indicate that the very low performance is caused by an undesirable interface charge transfer. The interfacial surface potential (SP) shows that the electron concentration in the CuO nanorod array changes considerably after illumination due to increased photo-generated electrons, but the change in the electron concentration in TiO 2 is much less than in CuO, which indicates that the injection efficiency of the photo-generated electrons from CuO to TiO 2 is not satisfactory, resulting in an undesirable J sc in the solar cell. The interface photovoltage from the KPFM measurement shows that the low V oc results from the small interfacial SP difference between CuO and TiO 2 because the low injected electron concentration cannot raise the Fermi level significantly in TiO 2 . This conclusion agrees with the measured work function results under illumination. Hence, improvement of the interfacial electron injection is primary for the CuO nanorod array/TiO 2 heterojunction solar cells.

Solution-processed all-oxide bulk heterojunction solar cells based on CuO nanaorod array and TiO2 nanocrystals

NASA Astrophysics Data System (ADS)

Wu, Fan; Qiao, Qiquan; Bahrami, Behzad; Chen, Ke; Pathak, Rajesh; Tong, Yanhua; Li, Xiaoyi; Zhang, Tiansheng; Jian, Ronghua

2018-05-01

We present a method to synthesize CuO nanorod array/TiO2 nanocrystals bulk heterojunction (BHJ) on fluorine-tin-oxide (FTO) glass, in which single-crystalline p-type semiconductor of the CuO nanorod array is grown on the FTO glass by hydrothermal reaction and the n-type semiconductor of the TiO2 precursor is filled into the CuO nanorods to form well-organized nano-interpenetrating BHJ after air annealing. The interface charge transfer in CuO nanorod array/TiO2 heterojunction is studied by Kelvin probe force microscopy (KPFM). KPFM results demonstrate that the CuO nanorod array/TiO2 heterojunction can realize the transfer of photo-generated electrons from the CuO nanorod array to TiO2. In this work, a solar cell with the structure FTO/CuO nanoarray/TiO2/Al is successfully fabricated, which exhibits an open-circuit voltage (V oc) of 0.20 V and short-circuit current density (J sc) of 0.026 mA cm‑2 under AM 1.5 illumination. KPFM studies indicate that the very low performance is caused by an undesirable interface charge transfer. The interfacial surface potential (SP) shows that the electron concentration in the CuO nanorod array changes considerably after illumination due to increased photo-generated electrons, but the change in the electron concentration in TiO2 is much less than in CuO, which indicates that the injection efficiency of the photo-generated electrons from CuO to TiO2 is not satisfactory, resulting in an undesirable J sc in the solar cell. The interface photovoltage from the KPFM measurement shows that the low V oc results from the small interfacial SP difference between CuO and TiO2 because the low injected electron concentration cannot raise the Fermi level significantly in TiO2. This conclusion agrees with the measured work function results under illumination. Hence, improvement of the interfacial electron injection is primary for the CuO nanorod array/TiO2 heterojunction solar cells.

Effect of surface charge convection and shape deformation on the dielectrophoretic motion of a liquid drop

NASA Astrophysics Data System (ADS)

Mandal, Shubhadeep; Bandopadhyay, Aditya; Chakraborty, Suman

2016-04-01

The dielectrophoretic motion and shape deformation of a Newtonian liquid drop in an otherwise quiescent Newtonian liquid medium in the presence of an axisymmetric nonuniform dc electric field consisting of uniform and quadrupole components is investigated. The theory put forward by Feng [J. Q. Feng, Phys. Rev. E 54, 4438 (1996), 10.1103/PhysRevE.54.4438] is generalized by incorporating the following two nonlinear effects—surface charge convection and shape deformation—towards determining the drop velocity. This two-way coupled moving boundary problem is solved analytically by considering small values of electric Reynolds number (ratio of charge relaxation time scale to the convection time scale) and electric capillary number (ratio of electrical stress to the surface tension) under the framework of the leaky dielectric model. We focus on investigating the effects of charge convection and shape deformation for different drop-medium combinations. A perfectly conducting drop suspended in a leaky (or perfectly) dielectric medium always deforms to a prolate shape and this kind of shape deformation always augments the dielectrophoretic drop velocity. For a perfectly dielectric drop suspended in a perfectly dielectric medium, the shape deformation leads to either increase (for prolate shape) or decrease (for oblate shape) in the dielectrophoretic drop velocity. Both surface charge convection and shape deformation affect the drop motion for leaky dielectric drops. The combined effect of these can significantly increase or decrease the dielectrophoretic drop velocity depending on the electrohydrodynamic properties of both the liquids and the relative strength of the electric Reynolds number and electric capillary number. Finally, comparison with the existing experiments reveals better agreement with the present theory.

Kinetic parameters and structural variations in Cu-Al-Mn and Cu-Al-Mn-Mg shape memory alloys

NASA Astrophysics Data System (ADS)

Canbay, Canan Aksu

2017-02-01

In this work polycrystalline Cu-Al-Mn and Cu-Al-Mn-Mg SMAs were fabricated by arc melting. The thermal analysis was made to determine the characteristic transformation temperatures of the samples and kinetic parameters. Also the effect of Mg on transformation temperatures and kinetic parameters detected. The structural analysis was made to designate the diffraction planes of martensite phase at room temperature and this was supported by optical measurement observations.

The effects of CuO particle size on microstructure evolution of AgCuO compo-sites in plastic deformation process: finite element simulation and experimental study

NASA Astrophysics Data System (ADS)

Li, Zhiguo; Cao, Hanxing; Zhou, Xiaolong; Zhou, Zhaobo; Cao, Jianchun

2018-04-01

The effects of CuO with different particle sizes on the microstructure evolution of AgCuO composite material during plastic deformation process were investigated by finite element (FE) analysis and experiment. The results are as follows: with the decrease of CuO particle size, the degree of radial compression and axial elongation of CuO particle cluster increase gradually, as well as the dispersion of CuO also increase. Meanwhile, the shape of CuO particles is constantly transformed from polygonal to fibrous, which makes the number of linear fibrous CuO increase continuously while bent fibrous CuO reduce gradually. By comparing the simulation and experiment results we find that there are four different typical microstructure regions, which caused by the interaction between monoclinic and cubic CuO during the extrusion process.

3D coordination polymers with nitrilotriacetic and 4,4'-bipyridyl mixed ligands: structural variation based on dinuclear or tetranuclear subunits assisted by Na-O and/or O-H...O interactions.

PubMed

Lü, Xing-Qiang; Jiang, Ji-Jun; Chen, Chun-Long; Kang, Bei-Sheng; Su, Cheng-Yong

2005-06-27

The reactions of Cu(II) with the mixed nitrilotriacetic acid (H3NTA) and 4,4'-bipyridyl (4,4'-bpy) ligands in different metal-to-ligand ratios in the presence of NaOH and NaClO4 afforded two complexes, Na3[Cu2(NTA)2(4,4'-bpy)]ClO4 x 5H2O (1) and [Cu2(NTA) (4,4'-bpy)2]ClO4 x 4H2O (2). The two complexes have been characterized by elemental analysis, IR, XRD, and single-crystal X-ray diffraction. 1 contains a basic doubly negatively charged [Cu2(NTA)2(4,4'-bpy)]2- dinuclear unit which was further assembled via multiple Na-O and O-H...O interactions into a three-dimensional (3D) pillared-layer structure. 2 features a two-dimensional (2D) undulated brick-wall architecture containing a basic doubly positively charged [Cu4(NTA)2(4,4'-bpy)2]2+ tetranuclear unit. The 2D network possesses large cavities hosting guest molecules and was further assembled via O-H...O hydrogen bonds into a 3D structure with several channels running in different directions.

Understanding the doping effects on the structural and electrical properties of ultrathin carbon nanotube networks

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

Zhou, Ying, E-mail: y-shuu@aist.go.jp; Shimada, Satoru; Azumi, Reiko

Similar to other semiconductor technology, doping of carbon nanotube (CNT) thin film is of great significance for performance improvement or modification. However, it still remains a challenge to seek a stable and effective dopant. In this paper, we unitize several spectroscopic techniques and electrical characterizations under various conditions to investigate the effects of typical dopants and related methods. Nitric acid (HNO{sub 3}) solution, I{sub 2} vapor, and CuI nanoparticles are used to modify a series of ultrathin CNT networks. Although efficient charge transfer is achieved initially after doping, HNO{sub 3} is not applicable because it suffers from severe reliability problemsmore » in structural and electrical properties, and it also causes a number of undesired structural defects. I{sub 2} vapor doping at 150 °C can form some stable C-I bonding structures, resulting in relatively more stable but less efficient electrical performances. CuI nanoparticles seem to be an ideal dopant. Photonic curing enables the manipulation of CuI, which not only results in the construction of novel CNT-CuI hybrid structures but also encourages the deepest level of charge transfer doping. The excellent reliability as well as processing feasibility identify the bright perspective of CNT-CuI hybrid film for practical applications.« less

Preparation and characterization of copper oxide nanoparticles decorated carbon nanoparticles using laser ablation in liquid

NASA Astrophysics Data System (ADS)

Khashan, K. S.; Jabir, M. S.; Abdulameer, F. A.

2018-05-01

Carbon nanoparticles CNPs ecorated by copper oxide nano-sized particles would be successfully equipped using technique named pulsed laser ablation in liquid. The XRD pattern proved the presence of phases assigned to carbon and different phases of copper oxide. The chemical structure of the as-prepared nanoparticles samples was decided by Energy Dispersive Spectrum (EDS) measurement. EDS analysis results show the contents of Carbon, Oxygen and Copper in the final product. These nanoparticles were spherical shaped with a size distribution 10 to 80 nm or carbon nanoparticles and 5 to 50 nm for carbon decorated copper oxide nanoparticles, according to Transmission Electron Microscopy (TEM) images and particle-size distribution histogram. It was found that after doping with copper oxide, nanoparticles become smaller and more regular in shape. Optical absorption spectra of prepared nanoparticles were measured using UV–VIS spectroscopy. The absorption spectrum of carbon nanoparticles without doping indicates absorption peak at about 228 nm. After doping with copper oxide, absorption shows appearance of new absorption peak at about (254-264) nm, which is referred to the movement of the charge between 2p and 4s band of Cu2+ ions.

A Diarylethene Derived Chemosensor for Colorimetric Sensing of Cu2+

NASA Astrophysics Data System (ADS)

Pu, Shouzhi; Sun, Qi; Zheng, Chunhong

2017-07-01

A diarylethene bearing a 8-hydroxyquinoline-linked salicylhydrazide Schift base unit has been synthesized. In CH3CN, the conpound displayed a highly selective and sensitive response to Cu2+ via perceptible color and UV-vis absorbance changes among the other tested metal ions. In the presence of Cu2+, the peak at 341 nm disappeared and concomitantly a new charge transfer absorption band emerged at 381 and 450 nm. Moreover, the compound formed host-guest complexe in 1:1 stoichiometry.

System Size, Energy, Pseudorapidity, and Centrality Dependence of Elliptic Flow

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.; Chetluru, V.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Halliwell, C.; Hamblen, J.; Harnarine, I.; 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.; Richardson, E.; Roland, C.; Roland, G.; Sagerer, J.; Seals, H.; Sedykh, I.; Smith, C. E.; Stankiewicz, M. A.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Szostak, A.; 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.; Wyngaardt, S.; Wysłouch, B.

2007-06-01

This Letter presents measurements of the elliptic flow of charged particles as a function of pseudorapidity and centrality from Cu-Cu collisions at 62.4 and 200 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider. The elliptic flow in Cu-Cu collisions is found to be significant even for the most central events. For comparison with the Au-Au results, it is found that the detailed way in which the collision geometry (eccentricity) is estimated is of critical importance when scaling out system-size effects. A new form of eccentricity, called the participant eccentricity, is introduced which yields a scaled elliptic flow in the Cu-Cu system that has the same relative magnitude and qualitative features as that in the Au-Au system.

Graphene-oxide-supported CuAl and CoAl layered double hydroxides as enhanced catalysts for carbon-carbon coupling via Ullmann reaction

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

Ahmed, Nesreen S.; Surface Chemistry and Catalytic Studies Group, King Abdulaziz University; Menzel, Robert

Two efficient catalyst based on CuAl and CoAl layered double hydroxides (LDHs) supported on graphene oxide (GO) for the carbon-carbon coupling (Classic Ullmann Homocoupling Reaction) are reported. The pure and hybrid materials were synthesised by direct precipitation of the LDH nanoparticles onto GO, followed by a chemical, structural and physical characterisation by electron microscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), surface area measurements and X-ray photoelectron spectroscopy (XPS). The GO-supported and unsupported CuAl-LDH and CoAl-LDH hybrids were tested over the Classic Ullman Homocoupling Reaction of iodobenzene. In the current study CuAl- and CoAl-LDHs have shown excellent yields (91% and 98%,more » respectively) at very short reaction times (25 min). GO provides a light-weight, charge complementary and two-dimensional material that interacts effectively with the 2D LDHs, in turn enhancing the stability of LDH. After 5 re-use cycles, the catalytic activity of the LDH/GO hybrid is up to 2 times higher than for the unsupported LDH. - Graphical abstract: CuAl- and CoAl-LDHs have shown excellent yields (91% and 98%, respectively) at very short reaction times (25 min). GO provides a light-weight, charge complementary, two-dimensional material that interacts effectively with the 2D LDHs, in turn enhancing the stability of LDH. - Highlights: • CuAl LDH/GO and CoAl LDH/GO hybrid materials with different LDH compositions were prepared. • Hybrids were fully characterised and their catalytic efficiency over the Classic Ullman Reaction was studied. • CuAl- and CoAl-LDHs have shown excellent yields (91% and 98%, respectively) in 25 min reaction times. • GO provides a light-weight, charge complementary, two-dimensional material that interacts effectively with the 2D LDHs. • After 5 re-use cycles, the catalytic activity of the LDH/GO hybrid is up to 2 times higher than for the unsupported LDH.« less

Accumulative Roll Bonding and Post-Deformation Annealing of Cu-Al-Mn Shape Memory Alloy

NASA Astrophysics Data System (ADS)

Moghaddam, Ahmad Ostovari; Ketabchi, Mostafa; Afrasiabi, Yaser

2014-12-01

Accumulative roll bonding is a severe plastic deformation process used for Cu-Al-Mn shape memory alloy. The main purpose of this study is to investigate the possibility of grain refinement of Cu-9.5Al-8.2Mn (in wt.%) shape memory alloy using accumulative roll bonding and post-deformation annealing. The alloy was successfully subjected to 5 passes of accumulative roll bonding at 600 °C. The microstructure, properties as well as post-deformation annealing of this alloy were investigated by optical microscopy, scanning electron microscopy, x-ray diffraction, differential scanning calorimeter, and bend and tensile testing. The results showed that after 5 passes of ARB at 600 °C, specimens possessed α + β microstructure with the refined grains, but martensite phases and consequently shape memory effect completely disappeared. Post-deformation annealing was carried out at 700 °C, and the martensite phase with the smallest grain size (less than 40 μm) was obtained after 150 s of annealing at 700 °C. It was found that after 5 passes of ARB and post-deformation annealing, the stability of SME during thermal cycling improved. Also, tensile properties of alloys significantly improved after post-deformation annealing.

Quantitative ESD Guidelines for Charged Spacecraft Derived from the Physics of Discharges

NASA Technical Reports Server (NTRS)

Frederickson, A. R.

1992-01-01

Quantitative guidelines are proposed for Electrostatic Discharge (ESD) pulse shape on charged spacecraft. The guidelines are based on existing ground test data, and on a physical description of the pulsed discharge process. The guidelines are designed to predict pulse shape for surface charging and internal charging on a wide variety of spacecraft structures. The pulses depend on the area of the sample, its capacitance to ground, and the strength of the electric field in the vacuum adjacent to the charged surface. By knowing the pulse shape, current vs. time, one can determine if nearby circuits are threatened by the pulse. The quantitative guidelines might be used to estimate the level of threat to an existing spacecraft, or to redesign a spacecraft to reduce its pulses to a known safe level. The experiments which provide the data and the physics that allow one to interpret the data will be discussed, culminating in examples of how to predict pulse shape/size. This method has been used, but not confirmed, on several spacecraft.

Inverse correlation between quasiparticle mass and T c in a cuprate high-T c superconductor.

PubMed

Putzke, Carsten; Malone, Liam; Badoux, Sven; Vignolle, Baptiste; Vignolles, David; Tabis, Wojciech; Walmsley, Philip; Bird, Matthew; Hussey, Nigel E; Proust, Cyril; Carrington, Antony

2016-03-01

Close to a zero-temperature transition between ordered and disordered electronic phases, quantum fluctuations can lead to a strong enhancement of electron mass and to the emergence of competing phases such as superconductivity. A correlation between the existence of such a quantum phase transition and superconductivity is quite well established in some heavy fermion and iron-based superconductors, and there have been suggestions that high-temperature superconductivity in copper-oxide materials (cuprates) may also be driven by the same mechanism. Close to optimal doping, where the superconducting transition temperature T c is maximal in cuprates, two different phases are known to compete with superconductivity: a poorly understood pseudogap phase and a charge-ordered phase. Recent experiments have shown a strong increase in quasiparticle mass m* in the cuprate YBa2Cu3O7-δ as optimal doping is approached, suggesting that quantum fluctuations of the charge-ordered phase may be responsible for the high-T c superconductivity. We have tested the robustness of this correlation between m* and T c by performing quantum oscillation studies on the stoichiometric compound YBa2Cu4O8 under hydrostatic pressure. In contrast to the results for YBa2Cu3O7-δ, we find that in YBa2Cu4O8, the mass decreases as T c increases under pressure. This inverse correlation between m* and T c suggests that quantum fluctuations of the charge order enhance m* but do not enhance T c.

Selective CO2 adsorption by a new metal-organic framework: synergy between open metal sites and a charged imidazolinium backbone.

PubMed

Kochetygov, Ilia; Bulut, Safak; Asgari, Mehrdad; Queen, Wendy L

2018-05-30

Metal-organic frameworks (MOFs) are porous, tunable crystalline materials that are attracting widespread scientific attention for their potential use in post-combustion CO2 capture. In this work, we report the synthesis of a new ligand, 1,3-bis(4-carboxyphenyl)-4,5-dihydro-1H-imidazol-3-ium tetrafluoroborate, H2Sp5-BF4, that is subsequently used for the construction of a novel MOF, Cu-Sp5-EtOH. This highly crystalline material has a charged framework that is expected to give rise to high CO2/N2 selectivity. However, the pores of the parent structure could not be accessed due to the presence of strongly coordinated ethanol molecules. After solvent exchange with methanol and subsequently heating Cu-Sp5-MeOH under vacuum, we are able to liberate the solvent providing other small molecules like CO2 access to the inside of the now porous structure, Cu-Sp5. The combination of open metal sites and framework charge leads to an exceptionally high CO2/N2 selectivity, as determined by Ideal Adsorbed Solution Theory (IAST) calculations performed on single-component adsorption isotherms. The CO2/N2 selectivity of Cu-Sp5 reaches a value of over 200 at pressures typically found in post-combustion flue gas (0.15 bar CO2/0.85 bar N2), a value that is among the highest reported to date.

Inverse correlation between quasiparticle mass and Tc in a cuprate high-Tc superconductor

PubMed Central

Putzke, Carsten; Malone, Liam; Badoux, Sven; Vignolle, Baptiste; Vignolles, David; Tabis, Wojciech; Walmsley, Philip; Bird, Matthew; Hussey, Nigel E.; Proust, Cyril; Carrington, Antony

2016-01-01

Close to a zero-temperature transition between ordered and disordered electronic phases, quantum fluctuations can lead to a strong enhancement of electron mass and to the emergence of competing phases such as superconductivity. A correlation between the existence of such a quantum phase transition and superconductivity is quite well established in some heavy fermion and iron-based superconductors, and there have been suggestions that high-temperature superconductivity in copper-oxide materials (cuprates) may also be driven by the same mechanism. Close to optimal doping, where the superconducting transition temperature Tc is maximal in cuprates, two different phases are known to compete with superconductivity: a poorly understood pseudogap phase and a charge-ordered phase. Recent experiments have shown a strong increase in quasiparticle mass m* in the cuprate YBa2Cu3O7-δ as optimal doping is approached, suggesting that quantum fluctuations of the charge-ordered phase may be responsible for the high-Tc superconductivity. We have tested the robustness of this correlation between m* and Tc by performing quantum oscillation studies on the stoichiometric compound YBa2Cu4O8 under hydrostatic pressure. In contrast to the results for YBa2Cu3O7-δ, we find that in YBa2Cu4O8, the mass decreases as Tc increases under pressure. This inverse correlation between m* and Tc suggests that quantum fluctuations of the charge order enhance m* but do not enhance Tc. PMID:27034989

Is Performance in Task-Cuing Experiments Mediated by Task Set Selection or Associative Compound Retrieval?

ERIC Educational Resources Information Center

Forrest, Charlotte L. D.; Monsell, Stephen; McLaren, Ian P. L.

2014-01-01

Task-cuing experiments are usually intended to explore control of task set. But when small stimulus sets are used, they plausibly afford learning of the response associated with a combination of cue and stimulus, without reference to tasks. In 3 experiments we presented the typical trials of a task-cuing experiment: a cue (colored shape) followed,…

Intermixing behaviors of PCBM with CuPc on Au(1 1 1) surface

NASA Astrophysics Data System (ADS)

Masui, Akane; Sakaue, Hiroyuki; Takahagi, Takayuki; Suzuki, Hitoshi

2016-09-01

The behavior of phenyl-C61-butyric acid methyl ester (PCBM) and copper-phthalocyanine (CuPc) on a Au(1 1 1) surface was investigated using scanning tunneling microscopy (STM). When CuPc was deposited in addition to PCBM it entered and disturbed the regularly spaced double row superstructure of the PCBM molecules. PCBM intermixed with CuPc to form a new square shaped superstructure that consisted of six to eight PCBM molecules with a CuPc molecule in its center. The intermixing of these materials that was observed indicated that they possessed an attractive interaction.

Synthesis of high efficient Cu/TiO2 photocatalysts by grinding and their size-dependent photocatalytic hydrogen production

NASA Astrophysics Data System (ADS)

Ni, Dawei; Shen, Haiyan; Li, Huiqiao; Ma, Ying; Zhai, Tianyou

2017-07-01

Recently, copper species have been extensively investigated to replace Pt as efficient co-catalysts for the evolution of H2 due to their low cost and relatively high activity. Cu nanoparticles less than 5 nm are successfully decorated on TiO2 surface in this work by an easy and mild milling process. These Cu nanoparticles are highly dispersed on TiO2 when the loading amount of Cu is no more than 10 wt%. The sizes of Cu nanoparticles can be controlled by changing the milling environment and decrease in the order of Cu-ethanol > Cu-water > Cu nanoparticles obtained through drying milling. The highest and stable hydrogen generation can be realized on Cu/TiO2 with 2.0 wt% Cu and sizes of Cu nanoparticles ranging from 2 to 4 nm, in which high and stable photocurrent confirms promoted photogenerated charge separation. Smaller Cu clusters are demonstrated to be detrimental to hydrogen evolution at same Cu content. High loading of Cu nanoparticles of 2-4 nm will benefit photogenerated electron-hole recombination and thus decrease the activity of Cu/TiO2. The results here demonstrate the key roles of Cu cluster size in addition to Cu coverage on photocatalytic activity of Cu/TiO2 composite photocatalysts.

Synthesis and characterization of Cu2O/TiO2 photocatalysts for H2 evolution from aqueous solution with different scavengers

NASA Astrophysics Data System (ADS)

Li, Yanping; Wang, Baowei; Liu, Sihan; Duan, Xiaofei; Hu, Zongyuan

2015-01-01

A series of Cu2O/TiO2 photocatalysts with different molar fraction of Cu2O were prepared by a facile modified ethanol-induced approach followed by a calcination process. The chemical state of copper compound was proved to be cuprous oxide by the characterization of X-ray photoelectron spectra (XPS). Furthermore, these composite oxides were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption desorption and UV-vis techniques to study the morphologies, structures, and optical properties of the as-prepared samples. The results indicated that the photocatalytic activity of n-type TiO2 was significantly enhanced by combined with p-type Cu2O, due to the efficient p-n heterojunction. The p-n heterojunction between Cu2O and TiO2 can enhance visible-light adsorption, efficiently suppress charge recombination, improve interfacial charge transfer, and especially provide plentiful reaction active sites on the surface of photocatalyst. As a consequence, the prepared 2.5-Cu2O/TiO2 photocatalyst exhibited the highest photocatalytic activity for H2 evolution rate and reached 2048.25 μmol/(g h), which is 14.48 times larger than that of pure P25. The apparent quantum yield (AQY) of the 2.5-Cu2O/TiO2 sample at 365 nm was estimated to be 4.32%. In addition, the influence of different scavengers, namely methanol, anhydrous ethanol, ethylene glycol and glycerol, on the photocatalytic activity for H2 evolution rate was discussed.

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.

Directed flow in asymmetric nucleus-nucleus collisions and the inverse Landau-Pomeranchuk-Migdal effect

NASA Astrophysics Data System (ADS)

Toneev, V. D.; Voronyuk, V.; Kolomeitsev, E. E.; Cassing, W.

2017-03-01

It is proposed to identify a strong electric field—created during relativistic collisions of asymmetric nuclei—via the observation of pseudorapidity and transverse momentum distributions of hadrons with the same mass but opposite charge. The results of detailed calculations within the parton-hadron string dynamics (PHSD) approach for the charge-dependent directed flow v1 are presented for semicentral Cu+Au collision at √{sN N}=200 GeV incorporating the inverse Landau-Pomeranchuk-Migdal (iLPM) effect, which accounts for a delay in the electromagnetic interaction with the charged degrees of freedom. By including the iLPM effect, we achieve a reasonable agreement of the PHSD results for the charge splitting in v1(pT) in line with the recent measurements by the STAR Collaboration for Cu+Au collisions at √{sN N}=200 GeV while an instant appearance and coupling of electric charges at the hard collision vertex overestimates the splitting by about a factor of 10. We predict that the iLPM effect should practically disappear at energies of √{sN N}≈ 9 GeV, which should lead to a significantly larger charge splitting of v1 at the future FAIR/NICA facilities.

Microstructural change in electroformed copper liners of shaped charges upon plastic deformation at ultra-high strain rate

NASA Astrophysics Data System (ADS)

Tian, W. H.; Hu, S. L.; Fan, A. L.; Wang, Z.

2002-01-01

Transmission electron microscopy (TEM) observations were carried out for examining the as-formed and post-deformed microstructures in a variety of electroformed copper liners of shaped charges. The deformation was carried out at an ultra-high strain rate. Specifically, the electron backscattering Kikuchi pattern (EBSP) technique was utilized to examine the micro-texture of these materials. TEM observations revealed that these electroformed copper liners of shaped charges have a grain size of about 1-3 mum, EBSP analysis demonstrated that the as-grown copper liners of shaped charges exhibit a l 10) fiber micro-texture which is parallel to the normal direction of the surface of the liners of shaped charges. Having undergone plastic deformation at ultra-high strain rate (10(7) s(-1)), the specimens which were recovered from the copper slugs were found to have grain size of the same order as that before deformation. EBSP analysis revealed that the (110) fiber texture existed in the as-formed copper liners disappears in the course of deformation. TEM examination results indicate that dynamic recovery and recrystallization play a significant role in this deformation process.

Native hole trap in bulk GaAs and its association with the double-charge state of the arsenic antisite defect

NASA Technical Reports Server (NTRS)

Lagowski, J.; Lin, D. G.; Chen, T.-P.; Skowronski, M.; Gatos, H. C.

1985-01-01

A dominant hole trap has been identified in p-type bulk GaAs employing deep level transient and photocapacitance spectroscopies. The trap is present at a concentration up to about 4 x 10 to the 16th per cu cm, and it has two charge states with energies 0.54 + or - 0.02 and 0.77 + or - 0.02 eV above the top of the valence band (at 77 K). From the upper level the trap can be photoexcited to a persistent metastable state just as the dominant midgap level, EL2. Impurity analysis and the photoionization characteristics rule out association of the trap with impurities Fe, Cu, or Mn. Taking into consideration theoretical results, it appears most likely that the two charge states of the trap are the single and double donor levels of the arsenic antisite As(Ga) defect.

Reversible structure manipulation by tuning carrier concentration in metastable Cu2S

PubMed Central

Tao, Jing; Chen, Jingyi; Li, Jun; Mathurin, Leanne; Zheng, Jin-Cheng; Li, Yan; Lu, Deyu; Cao, Yue; Wu, Lijun; Cava, Robert Joseph; Zhu, Yimei

2017-01-01

The optimal functionalities of materials often appear at phase transitions involving simultaneous changes in the electronic structure and the symmetry of the underlying lattice. It is experimentally challenging to disentangle which of the two effects––electronic or structural––is the driving force for the phase transition and to use the mechanism to control material properties. Here we report the concurrent pumping and probing of Cu2S nanoplates using an electron beam to directly manipulate the transition between two phases with distinctly different crystal symmetries and charge-carrier concentrations, and show that the transition is the result of charge generation for one phase and charge depletion for the other. We demonstrate that this manipulation is fully reversible and nonthermal in nature. Our observations reveal a phase-transition pathway in materials, where electron-induced changes in the electronic structure can lead to a macroscopic reconstruction of the crystal structure. PMID:28855335

Magnetic anisotropy and magnetization reversal in Co/Cu multilayers nanowires

NASA Astrophysics Data System (ADS)

Ahmad, Naeem; Chen, J. Y.; Shi, D. W.; Iqbal, Javed; Han, Xiufeng

2012-04-01

The Co/Cu multilayer nanowires fabricated in an array using anodized aluminum oxide (AAO) template by electrodeposition method, have been investigated. It has been observed that the magnetization reversal mode and magnetic anisotropy depend upon the Co and Cu layer thicknesses. Magnetization reversal occurs by curling mode at around Co = 400 nm and Cu = 10 nm, while for Co = 30 nm and Cu = 60 nm, magnetization reversal occurs by nucleation mode. A change of magnetic anisotropy from out of plane to in plane is observed when thickness of Cu layer tCu = 60 nm and that of Co tCo = 30 nm. Magnetic anisotropy is lost when thickness of the Co layer tCo = 400 nm and that of Cu tCu= 10 nm. Magnetic properties have been explained by the competition among shape anisotropy, magnetostatic interactions and magnetocrystalline anisotropy. Magnetic properties can be tuned accordingly depending upon the thickness of the Co and Cu nanodisks.

Electronic structure calculations on multiply charged anions containing M bond S bonds (M = Cr, Mo, W) and their heterobimetallic cluster complexes

NASA Astrophysics Data System (ADS)

Gili, Pedro; Tsipis, Athanassios C.

Molecular and electronic structures of multiply charged mononuclear [CrS4]2-/3-, [MoOxS4-x]2-/3- (x = 0-4) and [WS4]2-/3- anionic species, and their heterobimetallic dinuclear and trinuclear clusters formulated as [MoOS3(CuCl)]2-, [WOS3(CuCl)]2-, [MoS4{Cu(CN)}]2-, [(CN)Cu(?-CrS4)Cu(CN)]2-, [(CN)Cu(?-MoS4)Cu(CN)]2-, [ClCu(?-MoS4)CuCl]2-, [Cl2Fe(?-MoS4)CuCl2]2-, and [(CN)Cu(?-WS4)Cu(CN)]2- have been investigated using electronic structure calculation (HF, MP4SDQ and DFT) methods. For the discrete mononuclear anions HF/lanl2dz(M)?6-31+G*(S,O) method provided the best description of their molecular structures, while for the heterobimetallic dinuclear and trinuclear clusters the B3LYP/lanl2dz(M)?6-31+G* method gave equilibrium geometries closely resembling the experimental ones. Electronic and spectroscopic (IR, UV-Vis) properties of the thiometalates are discussed in relation to their structures, while the bonding mechanism was analyzed in the framework of the natural bond orbital (NBO) approach. The nature of the highest occupied molecular orbitals (HOMOs) of all thiometalates indicated their ability to act as ligands coordinated with metal centers and forming clusters of higher nuclearity. The lowest-lying vertical one-electron detachment processes from the ground state of the [CrS4]2/3-, [MoOxS4-x]2/3- (x = 0-4) and [WS4]2/3- anions have been calculated using the outer valence Green's function (OVGF) method. Interestingly, in the heterobimetallic dinuclear and trinuclear clusters intemetallic M?M? interactions exist corresponding to d10 ? d0 dative bonding. Finally, the complete energetic and geometric profile of the successive acid-catalyzed formation reactions:and the reverse hydrolysis reactions have been delineated and details of the mechanism have been furnished.

Copper Salts Mediated Morphological Transformation of Cu2O from Cubes to Hierarchical Flower-like or Microspheres and Their Supercapacitors Performances

PubMed Central

Chen, Liang; Zhang, Yu; Zhu, Pengli; Zhou, Fengrui; Zeng, Wenjin; Lu, Daoqiang Daniel; Sun, Rong; Wong, Chingping

2015-01-01

Monodisperse Cu2O of different microstructures, such as cubes, flower-like, and microspheres, have been extensively synthesized by a simple polyol reduction method using different copper salts, i.e. (Cu(acac)2, Cu(OH)2, and Cu(Ac)2·H2O). The effects of copper salts on the morphology of Cu2O were investigated in details through various characterization methods, including X-ray diffraction, transmission electron microscopy, scanning electron microscopy and UV-Vis absorption spectra. The effects of morphology on the electrochemical properties were further studied. Among the different structures, Cu2O with the microspheric morphology shows the highest specific capacitance and the best cycling stability compared with those of the other two structures, thus bear larger volume charge during the electrochemical reaction due to the microspheres of small nanoparticles. PMID:25857362

A comprehensive energy approach to predict fatigue life in CuAlBe shape memory alloy

NASA Astrophysics Data System (ADS)

Sameallah, S.; Legrand, V.; Saint-Sulpice, L.; Kadkhodaei, M.; Arbab Chirani, S.

2015-02-01

Stabilized dissipated energy is an effective parameter on the fatigue life of shape memory alloys (SMAs). In this study, a formula is proposed to directly evaluate the stabilized dissipated energy for different values of the maximum and minimum applied stresses, as well as the loading frequency, under cyclic tensile loadings. To this aim, a one-dimensional fully coupled thermomechanical constitutive model and a cycle-dependent phase diagram are employed to predict the uniaxial stress-strain response of an SMA in a specified cycle, including the stabilized one, with no need of obtaining the responses of the previous cycles. An enhanced phase diagram in which different slopes are defined for the start and finish of a backward transformation strip is also proposed to enable the capture of gradual transformations in a CuAlBe shape memory alloy. It is shown that the present approach is capable of reproducing the experimental responses of CuAlBe specimens under cyclic tensile loadings. An explicit formula is further presented to predict the fatigue life of CuAlBe as a function of the maximum and minimum applied stresses as well as the loading frequency. Fatigue tests are also carried out, and this formula is verified against the empirically predicted number of cycles for failure.

Novel calix[4]pyrrole assembly: Punctilious recognition of F- and Cu+2 ions

NASA Astrophysics Data System (ADS)

Bhatt, Keyur D.; Shah, Hemangini; Modi, Krunal M.; Kongor, Anita; Panchal, Manthan; Jain, Vinod K.

2017-12-01

A new tetra hydroxyl methoxy substituted calix[4]pyrrole (HMCP) has been synthesized and found to form stable complex with F- ions and Cu+2 ions. The red-shift in absorption band of HMCP was observed due to the presence of both cation (Cu+2) and anion (F-). These results displayed that formation of the complex is mainly attributed to the charge-transfer interactions between HMCP with electron deficient pyrrole rings and the electron-rich guest ions. Molecular dynamics simulation predicts intermolecular H-bonds and van der Waals types of interaction for the complex formation of HMCP-Cu+2 and HMCP-F-.

Surface states and annihilation characteristics of positrons trapped at the oxidized Cu(100) surface

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Weiss, A. H.

2013-06-01

In this work we present the results of theoretical studies of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. Oxidation of the Cu(100) surface has been studied by performing an ab-initio investigation of the stability and electronic structure of the Cu(100) missing row reconstructed surface at various on-surface and subsurface oxygen coverages ranging from 0.5 to 1.5 monolayers using density functional theory (DFT). All studied structures have been found to be energetically more favorable as compared to structures formed by purely on-surface oxygen adsorption. The observed decrease in the positron work function when oxygen atoms occupy on-surface and subsurface sites has been attributed to a significant charge redistribution within the first two layers, buckling effects within each layer and an interlayer expansion. The computed positron binding energy, positron surface state wave function, and annihilation probabilities of the surface trapped positrons with relevant core electrons demonstrate their sensitivity to oxygen coverage, atomic structure of the topmost layers of surfaces, and charge transfer effects. Theoretical results are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy (PAES). The results presented provide an explanation for the changes observed in the probability of annihilation of surface trapped positrons with Cu 3p core-level electrons as a function of annealing temperature.

The role of surface/interfacial Cu{sup 2+} sites in the photocatalytic activity of coupled CuO-TiO{sub 2} nanocomposites.

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

Li, G.; Dimitrijevic, N. M.; Chen, L.

Coupled CuO-TiO{sub 2} nanocomposite photocatalysts were prepared by a deposition precipitation method and were characterized with a variety of techniques. Electron paramagnetic resonance (EPR) spectroscopy was employed to study the local structures of surface/interfacial Cu{sup 2+}+ sites using Cu{sup 2+} as a sensitive paramagnetic probe. The addition of bulk CuO to TiO{sub 2} led to decreased photocatalytic efficiency in the degradation of methylene blue. However, doping with a very small amount of CuO (0.1 wt % copper loading) significantly enhanced the photocatalytic activity of TiO{sub 2}. EPR study of the TiO{sub 2} surface revealed the presence of both highly dispersedmore » CuO clusters and substitutional Cu{sup 2+} sites (Ti-O-Cu linkages) at 0.1 wt % copper loading. The data suggest that the Ti-O-Cu linkages contributed to the improved photooxidative activity of the 0.1% CuO-TiO{sub 2} nanocomposite. In contrast, at higher loadings the bulk form of CuO created charge recombination centers lowering the photoactivity of the composites.« less

Quantification of strain and charge co-mediated magnetoelectric coupling on ultra-thin Permalloy/PMN-PT interface.

PubMed

Nan, Tianxiang; Zhou, Ziyao; Liu, Ming; Yang, Xi; Gao, Yuan; Assaf, Badih A; Lin, Hwaider; Velu, Siddharth; Wang, Xinjun; Luo, Haosu; Chen, Jimmy; Akhtar, Saad; Hu, Edward; Rajiv, Rohit; Krishnan, Kavin; Sreedhar, Shalini; Heiman, Don; Howe, Brandon M; Brown, Gail J; Sun, Nian X

2014-01-14

Strain and charge co-mediated magnetoelectric coupling are expected in ultra-thin ferromagnetic/ferroelectric multiferroic heterostructures, which could lead to significantly enhanced magnetoelectric coupling. It is however challenging to observe the combined strain charge mediated magnetoelectric coupling, and difficult in quantitatively distinguish these two magnetoelectric coupling mechanisms. We demonstrated in this work, the quantification of the coexistence of strain and surface charge mediated magnetoelectric coupling on ultra-thin Ni0.79Fe0.21/PMN-PT interface by using a Ni0.79Fe0.21/Cu/PMN-PT heterostructure with only strain-mediated magnetoelectric coupling as a control. The NiFe/PMN-PT heterostructure exhibited a high voltage induced effective magnetic field change of 375 Oe enhanced by the surface charge at the PMN-PT interface. Without the enhancement of the charge-mediated magnetoelectric effect by inserting a Cu layer at the PMN-PT interface, the electric field modification of effective magnetic field was 202 Oe. By distinguishing the magnetoelectric coupling mechanisms, a pure surface charge modification of magnetism shows a strong correlation to polarization of PMN-PT. A non-volatile effective magnetic field change of 104 Oe was observed at zero electric field originates from the different remnant polarization state of PMN-PT. The strain and charge co-mediated magnetoelectric coupling in ultra-thin magnetic/ferroelectric heterostructures could lead to power efficient and non-volatile magnetoelectric devices with enhanced magnetoelectric coupling.

Uncovering the Key Role of the Fermi Level of the Electron Mediator in a Z-Scheme Photocatalyst by Detecting the Charge Transfer Process of WO3-metal-gC3N4 (Metal = Cu, Ag, Au).

PubMed

Li, Houfen; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhang, Yaobin

2016-01-27

Z-scheme photocatalytic system shows superiority in degradation of refractory pollutants and water splitting due to the high redox capacities caused by its unique charge transfer behaviors. As a key component of Z-scheme system, the electron mediator plays an important role in charge carrier migration. According to the energy band theory, we believe the interfacial energy band bendings facilitate the electron transfer via Z-scheme mechanism when the Fermi level of electron mediator is between the Fermi levels of Photosystem II (PS II) and Photosystem I (PS I), whereas charge transfer is inhibited in other cases as energy band barriers would form at the semiconductor-metal interfaces. Here, this inference was verified by the increased hydroxyl radical generation and improved photocurrent on WO3-Cu-gC3N4 (with the desired Fermi level structure), which were not observed on either WO3-Ag-gC3N4 or WO3-Au-gC3N4. Finally, photocatalytic degradation rate of 4-nonylphenol on WO3-Cu-gC3N4 was proved to be as high as 11.6 times than that of WO3-gC3N4, further demonstrating the necessity of a suitable electron mediator in Z-scheme system. This study provides scientific basis for rational construction of Z-scheme photocatalytic system.

A Stable Plasmonic Cu@Cu2 O/ZnO Heterojunction for Enhanced Photocatalytic Hydrogen Generation.

PubMed

Lou, Yongbing; Zhang, Yake; Cheng, Lin; Chen, Jinxi; Zhao, Yixin

2018-05-09

The localized surface plasmon resonance (LSPR) effect has been widely utilized in photocatalysis, but most reported LSPR materials are based on noble metals of gold or silver with high chemical stability. Plasmonic copper nanoparticles that exhibit an LSPR absorbance at 600 nm are promising for many applications, such as photocatalysis. Unfortunately, plasmonic copper nanoparticles are affected by serious surface oxidation in air. Herein, a novel lollipop-shaped Cu@Cu 2 O/ZnO heterojunction nanostructure was designed, for the first time, to stabilize the plasmonic Cu core by decorating Cu@Cu 2 O core-shell structures with ZnO nanorods. This Cu@Cu 2 O/ZnO nanostructure exhibited significantly enhanced stability than that of regular Cu@Cu 2 O, which accounted for the remarkably enhanced photocatalytic H 2 evolution rate through water splitting, relative to pristine ZnO nanorods, over an extended wavelength range due to the plasmonic Cu core. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solution processed molecular floating gate for flexible flash memories

NASA Astrophysics Data System (ADS)

Zhou, Ye; Han, Su-Ting; Yan, Yan; Huang, Long-Biao; Zhou, Li; Huang, Jing; Roy, V. A. L.

2013-10-01

Solution processed fullerene (C60) molecular floating gate layer has been employed in low voltage nonvolatile memory device on flexible substrates. We systematically studied the charge trapping mechanism of the fullerene floating gate for both p-type pentacene and n-type copper hexadecafluorophthalocyanine (F16CuPc) semiconductor in a transistor based flash memory architecture. The devices based on pentacene as semiconductor exhibited both hole and electron trapping ability, whereas devices with F16CuPc trapped electrons alone due to abundant electron density. All the devices exhibited large memory window, long charge retention time, good endurance property and excellent flexibility. The obtained results have great potential for application in large area flexible electronic devices.

Solution processed molecular floating gate for flexible flash memories

PubMed Central

Zhou, Ye; Han, Su-Ting; Yan, Yan; Huang, Long-Biao; Zhou, Li; Huang, Jing; Roy, V. A. L.

2013-01-01

Solution processed fullerene (C60) molecular floating gate layer has been employed in low voltage nonvolatile memory device on flexible substrates. We systematically studied the charge trapping mechanism of the fullerene floating gate for both p-type pentacene and n-type copper hexadecafluorophthalocyanine (F16CuPc) semiconductor in a transistor based flash memory architecture. The devices based on pentacene as semiconductor exhibited both hole and electron trapping ability, whereas devices with F16CuPc trapped electrons alone due to abundant electron density. All the devices exhibited large memory window, long charge retention time, good endurance property and excellent flexibility. The obtained results have great potential for application in large area flexible electronic devices. PMID:24172758

X-ray Spectroscopy Uncovering the Effects of Cu Based Nanoparticle Concentration and Structure on Phaseolus vulgaris Germination and Seedling Development.

PubMed

Duran, Nádia M; Savassa, Susilaine M; Lima, Rafael Giovanini de; de Almeida, Eduardo; Linhares, Francisco S; van Gestel, Cornelis A M; Pereira de Carvalho, Hudson W

2017-09-13

Nanoparticles properties such as solubility, tunable surface charges, and singular reactivity might be explored to improve the performance of fertilizers. Nevertheless, these unique properties may also bring risks to the environment since the fate of nanoparticles is poorly understood. This study investigated the impact of a range of CuO nanoparticles sizes and concentrations on the germination and seedling development of Phaseolus vulgaris L. Nanoparticles did not affect seed germination, but seedling weight gain was promoted by 100 mg Cu L -1 and inhibited by 1 000 mg Cu L -1 of 25 nm CuO and CuSO 4 . Most of the Cu taken up remained in the seed coat with Cu hotspots in the hilum. X-ray absorption spectroscopy unraveled that most of the Cu remained in its pristine form. The higher surface reactivity of the 25 nm CuO nanoparticles might be responsible for its deleterious effects. The present study therefore highlights the importance of the nanoparticle structure for its physiological impacts.

The preparation, surface structure, zeta potential, surface charge density and photocatalytic activity of TiO2 nanostructures of different shapes

NASA Astrophysics Data System (ADS)

Grover, Inderpreet Singh; Singh, Satnam; Pal, Bonamali

2013-09-01

Titania based nanocatalysts such as sodium titanates of different morphology having superior surface properties are getting wide importance in photocatalysis research. Despite having sodium (Na) contents and its high temperature synthesis (that generally deteriorate the photoreactivity), these Na-titanates often exhibit better photoactivity than P25-TiO2 catalyst. Hence, this work demonstrated the influence of crystal structure, BET surface area, surface charge, zeta potential (ζ) and metal loading on the photocatalytic activity of as-prepared sodium titanate nanotube (TNT) and titania nanorod (TNR). Straw like hollow orthorhombic-TNT (Na2Ti2O5·H2O) particles (W = 9-12 nm and L = 82-115 nm) and rice like pure anatase-TNR particles (W = 8-13 nm and L = 81-134 nm) are obtained by the hydrothermal treatment of P25-TiO2 with NaOH, which in fact, altered the net surface charge of TNT and TNR particles. The observed ζ = -2.82 (P25-TiO2), -13.5 (TNT) and -22.5 mV (TNR) are significantly altered by the Ag and Cu deposition. It has been found here that TNT displayed best photocatalytic activity for the imidacloprid insecticide (C9H10ClN5O2) degradation to CO2 formation under UV irradiation because of its largest surface area 176 m2 g-1 among the catalysts studied.

Ultralow-fatigue shape memory alloy films

NASA Astrophysics Data System (ADS)

Chluba, Christoph; Ge, Wenwei; Lima de Miranda, Rodrigo; Strobel, Julian; Kienle, Lorenz; Quandt, Eckhard; Wuttig, Manfred

2015-05-01

Functional shape memory alloys need to operate reversibly and repeatedly. Quantitative measures of reversibility include the relative volume change of the participating phases and compatibility matrices for twinning. But no similar argument is known for repeatability. This is especially crucial for many future applications, such as artificial heart valves or elastocaloric cooling, in which more than 10 million transformation cycles will be required. We report on the discovery of an ultralow-fatigue shape memory alloy film system based on TiNiCu that allows at least 10 million transformation cycles. We found that these films contain Ti2Cu precipitates embedded in the base alloy that serve as sentinels to ensure complete and reproducible transformation in the course of each memory cycle.

Facile synthesis of CuFe2O4-Fe2O3 composite for high-performance supercapacitor electrode applications

NASA Astrophysics Data System (ADS)

Khan, Rashid; Habib, Muhammad; Gondal, Mohammed A.; Khalil, Adnan; Rehman, Zia Ur; Muhammad, Zahir; Haleem, Yasir A.; Wang, Changda; Wu, Chuan Qiang; Song, Li

2017-10-01

We report the synthesis of CuFe2O4-Fe2O3 composite material for efficient and highly stable supercapacitor electrode by using eco-friendly low-temperature co-precipitation method. The CuFe2O4-Fe2O3 composite demonstrated the highest specific capacitance of 638.24 F g-1 and excellent stability up to 2000 charge/discharge cycles. The achieved capacitance value is 16 times higher than that of pure CuFe2O4. The results revealed the extraordinary performance of CuFe2O4-Fe2O3 composite as supercapacitor electrode with excellent retention in comparison to CuFe2O4. The enhanced electrochemical activity of CuFe2O4-Fe2O3 composite is attributed to the synergistic effect which is responsible for redox coupling between Cu2+ and Fe3+ that has never been achieved by single component before.

Oxygen-deficient photostable Cu2O for enhanced visible light photocatalytic activity.

PubMed

Singh, Mandeep; Jampaiah, Deshetti; Kandjani, Ahmad E; Sabri, Ylias M; Della Gaspera, Enrico; Reineck, Philipp; Judd, Martyna; Langley, Julien; Cox, Nicholas; van Embden, Joel; Mayes, Edwin L H; Gibson, Brant C; Bhargava, Suresh K; Ramanathan, Rajesh; Bansal, Vipul

2018-03-29

Oxygen vacancies in inorganic semiconductors play an important role in reducing electron-hole recombination, which may have important implications in photocatalysis. Cuprous oxide (Cu2O), a visible light active p-type semiconductor, is a promising photocatalyst. However, the synthesis of photostable Cu2O enriched with oxygen defects remains a challenge. We report a simple method for the gram-scale synthesis of highly photostable Cu2O nanoparticles by the hydrolysis of a Cu(i)-triethylamine [Cu(i)-TEA] complex at low temperature. The oxygen vacancies in these Cu2O nanoparticles led to a significant increase in the lifetimes of photogenerated charge carriers upon excitation with visible light. This, in combination with a suitable energy band structure, allowed Cu2O nanoparticles to exhibit outstanding photoactivity in visible light through the generation of electron-mediated hydroxyl (OH˙) radicals. This study highlights the significance of oxygen defects in enhancing the photocatalytic performance of promising semiconductor photocatalysts.

Investigation the electroplating behavior of self formed CuMn barrier.

PubMed

Wu, Chia-Yang; Lee, Wen-Hsi; Chang, Shih-Chieh; Wang, Ying-Lang

2013-08-01

The electrical and material properties of Copper (Cu) mixed with [0-10 atomic% manganese (Mn)] and pure Cu films deposited on silicon oxide (SiO2)/silicon (Si) are explored. Cu electroplating on self formed CuMn barrier was investigated with different Mn content. The electrochemical deposition of the Cu thin film onto the electrode using CuMn barrier was investigated. Scanning electron microscopic (SEM) micrographs of copper electroplating on CuMn films were examined, and the copper nucleation behaviors changed with the Mn content. Since the electrochemical impedance spectroscopy (EIS) is widely recognized as a powerful tool for the investigation of electrochemical behaviors, the tool was also used to verify the phenomena during plating. It was found that the charge-trasfer impedance decrease with the rise in the Mn content below 5%, but increase with the rise in the Mn content higher than 5%. The result was corresponded to the surface energy, the surface morphology, the corrosion and the oxidation of the substrate.

Electronic Structure of TlBa2CaCu2O(7-Delta)

NASA Technical Reports Server (NTRS)

Vasquez, R. P.; Novikov, D. L.; Freeman, A. J.; Siegal, M. P.

1997-01-01

The core levels of TlBa2CaCu2O(7-delta) (Tl-1212) epitaxial films have been measured with X-ray photoelectron spectroscopy (XPS). The valence electronic structure has been determined using the full-potential linear muffin-tin-orbital band-structure method and measured with XPS. The calculations show that a van Hove singularity (VHS) lies above the Fermi level (E(sub F)) for the stoichiometric compound (delta = 0.5), while for 50% oxygen vacancies in the Tl-O layer (delta = 0.5) E(sub F) is in close proximity to the VHS. Samples annealed in nitrogen (to reduce the hole overdoping by the removal of oxygen) exhibit higher core-level binding energies and a higher T(sub c), consistent with a shift of E(sub F) closer to the VHS. Comparisons are made to the core levels and valence bands of Tl2Ba2CaCu2O(8 + delta)(Tl-2212) and HgBa2CaCu2O)6 + delta) (Hg- 1212). The similarity of the Cu 2p(sub 3/2) spectra for Tl-1212 and Tl-2212 indicates that the number of Tl-O layers has little effect on the Cu-O bonding. However, the Tl-1212 and Hg-1212 Cu 2p(sub 3/2) signals exhibit differences which suggest that the replacement of T(sup 3+) with Hg(sup 2+) results in a decrease in the O 2p right arrow Cu 3d charge-transfer energy and differences in the probabilities of planar vs apical oxygen charge transfer and/or Zhang-Rice singlet-state formation. Differences between the Tl-1212 and the Tl-2212 and Hg-1212 measured valence bands are consistent with the calculated Cu 3d and (Tl,Hg) 6s/5d partial densities of states.

Structural transformations in high-capacity Li 2Cu 0.5Ni 0.5O 2 cathodes

DOE PAGES

Ruther, Rose E.; Pandian, Amaresh Samuthira; Yan, Pengfei; ...

2017-03-09

Cathode materials that can cycle >1 Li + per transition metal are of substantial interest for increasing the overall energy density of lithium-ion batteries. Li 2Cu 0.5Ni 0.5O 2 has a very high theoretical capacity of ~500 mAh/g assuming both Li+ ions are cycled reversibly. The Cu 2+/3+ and Ni 2+/3+/4+ redox couples are also at high voltage, which could further boost the energy density of this system. Despite such promise, Li 2Cu 0.5Ni 0.5O 2 undergoes irreversible phase changes during charge (delithiation) that result in large first-cycle irreversible loss and poor long-term cycling stability. Oxygen evolves before the Cumore » 2+/3+ or Ni 3+/4+ transitions are accessed. In this contribution, X-ray diffraction, transmission electron microscopy (TEM), and transmission X-ray microscopy combined with X-ray absorption near edge structure (TXM–XANES) are used to follow the chemical and structural changes that occur in Li 2Cu 0.5Ni 0.5O 2 during electrochemical cycling. Li 2Cu 0.5Ni 0.5O 2 is a solid solution of orthorhombic Li2CuO2 and Li2NiO2, but the structural changes more closely mimic the changes that the Li 2NiO 2 endmember undergoes. Li 2Cu 0.5Ni 0.5O 2 loses long-range order during charge, but TEM analysis provides clear evidence of particle exfoliation and the transformation from orthorhombic to a partially layered structure. Linear combination fitting and principal component analysis of TXM–XANES are used to map the different phases that emerge during cycling ex situ and in situ. Lastly, significant changes in the XANES at the Cu and Ni K-edges correlate with the onset of oxygen evolution.« less

Characteristics of dielectric properties and conduction mechanism of TlInS2:Cu single crystals

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Ali, H. A. M.; El-Zaidia, E. F. M.

2013-12-01

Single crystals of TlInS2:Cu were grown by the modified Bridgman method. The dielectric behavior of TlInS2:Cu was investigated using the impedance spectroscopy technique. The real (ε1), imaginary (ε2) parts of complex dielectric permittivity and ac conductivity were measured in the frequency range (42-2×105) Hz with a variation of temperature in the range from 291 K to 483 K. The impedance data were presented in Nyquist diagrams for different temperatures. The frequency dependence of σtot (ω) follows the Jonscher's universal dynamic law with the relation σtot (ω)=σdc+Aωs, (where s is the frequency exponent). The mechanism of the ac charge transport across the layers of TlInS2:Cu single crystals was referred to the hopping over localized states near the Fermi level. The examined system exhibits temperature dependence of σac (ω), which showed a linear increase with the increase in temperature at different frequencies. Some parameters were calculated as: the density of localized states near the Fermi level, NF, the average time of charge carrier hopping between localized states, τ, and the average hopping distance, R.

Observation of a three-dimensional quasi-long-range electronic supermodulation in YBa 2Cu 3O 7-x/La 0.7Ca 0.3MnO 3 heterostructures

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

He, Junfeng; Shafer, Padraic; Mion, Thomas R.

Recent developments in high-temperature superconductivity highlight a generic tendency of the cuprates to develop competing electronic (charge) supermodulations. While coupled with the lattice and showing different characteristics in different materials, these supermodulations themselves are generally conceived to be quasi-two-dimensional, residing mainly in individual CuO 2 planes, and poorly correlated along the c axis. Here we observed with resonant elastic X-ray scattering a distinct type of electronic supermodulation in YBa 2Cu 3O 7–x (YBCO) thin films grown epitaxially on La 0.7Ca 0.3MnO 3 (LCMO). This supermodulation has a periodicity nearly commensurate with four lattice constants in-plane, eight out of plane, withmore » long correlation lengths in three dimensions. It sets in far above the superconducting transition temperature and competes with superconductivity below this temperature for electronic states predominantly in the CuO 2 plane. Our finding sheds light on the nature of charge ordering in cuprates as well as a reported long-range proximity effect between superconductivity and ferromagnetism in YBCO/LCMO heterostructures.« less

Copper(II) complex with 6-methylpyridine-2-carboxyclic acid: Experimental and computational study on the XRD, FT-IR and UV-Vis spectra, refractive index, band gap and NLO parameters

NASA Astrophysics Data System (ADS)

Altürk, Sümeyye; Avcı, Davut; Başoğlu, Adil; Tamer, Ömer; Atalay, Yusuf; Dege, Necmi

2018-02-01

Crystal structure of the synthesized copper(II) complex with 6-methylpyridine-2-carboxylic acid, [Cu(6-Mepic)2·H2O]·H2O, was determined by XRD, FT-IR and UV-Vis spectroscopic techniques. Furthermore, the geometry optimization, harmonic vibration frequencies for the Cu(II) complex were carried out by using Density Functional Theory calculations with HSEh1PBE/6-311G(d,p)/LanL2DZ level. Electronic absorption wavelengths were obtained by using TD-DFT/HSEh1PBE/6-311G(d,p)/LanL2DZ level with CPCM model and major contributions were determined via Swizard/Chemissian program. Additionally, the refractive index, linear optical (LO) and non-nonlinear optical (NLO) parameters of the Cu(II) complex were calculated at HSEh1PBE/6-311G(d,p) level. The experimental and computed small energy gap shows the charge transfer in the Cu(II) complex. Finally, the hyperconjugative interactions and intramolecular charge transfer (ICT) were studied by performing of natural bond orbital (NBO) analysis.

Copper(II) complex with 6-methylpyridine-2-carboxyclic acid: Experimental and computational study on the XRD, FT-IR and UV-Vis spectra, refractive index, band gap and NLO parameters.

PubMed

Altürk, Sümeyye; Avcı, Davut; Başoğlu, Adil; Tamer, Ömer; Atalay, Yusuf; Dege, Necmi

2018-02-05

Crystal structure of the synthesized copper(II) complex with 6-methylpyridine-2-carboxylic acid, [Cu(6-Mepic) 2 ·H 2 O]·H 2 O, was determined by XRD, FT-IR and UV-Vis spectroscopic techniques. Furthermore, the geometry optimization, harmonic vibration frequencies for the Cu(II) complex were carried out by using Density Functional Theory calculations with HSEh1PBE/6-311G(d,p)/LanL2DZ level. Electronic absorption wavelengths were obtained by using TD-DFT/HSEh1PBE/6-311G(d,p)/LanL2DZ level with CPCM model and major contributions were determined via Swizard/Chemissian program. Additionally, the refractive index, linear optical (LO) and non-nonlinear optical (NLO) parameters of the Cu(II) complex were calculated at HSEh1PBE/6-311G(d,p) level. The experimental and computed small energy gap shows the charge transfer in the Cu(II) complex. Finally, the hyperconjugative interactions and intramolecular charge transfer (ICT) were studied by performing of natural bond orbital (NBO) analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

Observation of a three-dimensional quasi-long-range electronic supermodulation in YBa 2Cu 3O 7-x/La 0.7Ca 0.3MnO 3 heterostructures

DOE PAGES

He, Junfeng; Shafer, Padraic; Mion, Thomas R.; ...

2016-03-01

Recent developments in high-temperature superconductivity highlight a generic tendency of the cuprates to develop competing electronic (charge) supermodulations. While coupled with the lattice and showing different characteristics in different materials, these supermodulations themselves are generally conceived to be quasi-two-dimensional, residing mainly in individual CuO 2 planes, and poorly correlated along the c axis. Here we observed with resonant elastic X-ray scattering a distinct type of electronic supermodulation in YBa 2Cu 3O 7–x (YBCO) thin films grown epitaxially on La 0.7Ca 0.3MnO 3 (LCMO). This supermodulation has a periodicity nearly commensurate with four lattice constants in-plane, eight out of plane, withmore » long correlation lengths in three dimensions. It sets in far above the superconducting transition temperature and competes with superconductivity below this temperature for electronic states predominantly in the CuO 2 plane. Our finding sheds light on the nature of charge ordering in cuprates as well as a reported long-range proximity effect between superconductivity and ferromagnetism in YBCO/LCMO heterostructures.« less

Magnetic Ordering under Strain and Spin-Peierls Dimerization in GeCuO3

NASA Astrophysics Data System (ADS)

Filippetti, Alessio; Fiorentini, Vincenzo

2007-05-01

Studying from first principles the competition between ferromagnetic (FM) and antiferromagnetic (AF) interactions in the charge-transfer-insulator GeCuO3, we predict that a small external pressure should switch the uniform AF ground state to FM, and estimate (using exchange parameters computed as a function of strain) the competing AF couplings and the transition temperature to the dimerized spin-Peierls state. Although idealized as a one-dimensional Heisenberg antiferromagnet, GeCuO3 is found to be influenced by nonideal geometry and side groups.

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.

The footprints of visual attention in the Posner cueing paradigm revealed by classification images

NASA Technical Reports Server (NTRS)

Eckstein, Miguel P.; Shimozaki, Steven S.; Abbey, Craig K.

2002-01-01

In the Posner cueing paradigm, observers' performance in detecting a target is typically better in trials in which the target is present at the cued location than in trials in which the target appears at the uncued location. This effect can be explained in terms of a Bayesian observer where visual attention simply weights the information differently at the cued (attended) and uncued (unattended) locations without a change in the quality of processing at each location. Alternatively, it could also be explained in terms of visual attention changing the shape of the perceptual filter at the cued location. In this study, we use the classification image technique to compare the human perceptual filters at the cued and uncued locations in a contrast discrimination task. We did not find statistically significant differences between the shapes of the inferred perceptual filters across the two locations, nor did the observed differences account for the measured cueing effects in human observers. Instead, we found a difference in the magnitude of the classification images, supporting the idea that visual attention changes the weighting of information at the cued and uncued location, but does not change the quality of processing at each individual location.

Photoinduced Br Desorption from CsBr Thin Films Grown on Cu(100)

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

Halliday, Matthew T.; Joly, Alan G.; Hess, Wayne P.

2015-10-22

Thin films of CsBr deposited onto metals such as copper are potential photocathode materials for light sources and other applications. We investigate desorption dynamics of Br atoms from CsBr films grown on insulator (KBr, LiF) and metal (Cu) substrates induced by sub-bandgap 6.4 eV laser pulses. The experimental results demonstrate that the peak kinetic energy of Br atoms desorbed from CsBr/Cu films is much lower than that for the hyperthermal desorption from CsBr/LiF films. Kelvin probe measurements indicate negative charge at the surface following Br desorption from CsBr/Cu films. Our ab initio calculations of excitons at CsBr surfaces demonstrate thatmore » this behavior can be explained by an exciton model of desorption including electron trapping at the CsBr surface. Trapped negative charges reduce the energy of surface excitons available for Br desorption. We examine the electron-trapping characteristics of low-coordinated sites at the surface, in particular, divacancies and kink sites. We also provide a model of cation desorption caused by Franck-Hertz excitation of F centers at the surface in the course of irradiation of CsBr/Cu films. These results provide new insights into the mechanisms of photoinduced structural evolution of alkali halide films on metal substrates and activation of metal photocathodes coated with CsBr.« less

Phototherapeutic spectrum expansion through synergistic effect of mesoporous silica trio-nanohybrids against antibiotic-resistant gram-negative bacterium.

PubMed

Kuthati, Yaswanth; Kankala, Ranjith Kumar; Busa, Prabhakar; Lin, Shi-Xiang; Deng, Jin-Pei; Mou, Chung-Yuan; Lee, Chia-Hung

2017-04-01

The extensive impact of antibiotic resistance has led to the exploration of new anti-bacterial modalities. We designed copper impregnated mesoporous silica nanoparticles (Cu-MSN) with immobilizing silver nanoparticles (SNPs) to apply photodynamic inactivation (PDI) of antibiotic-resistant E. coli. SNPs were decorated over the Cu-MSN surfaces by coordination of silver ions on diamine-functionalized Cu-MSN and further reduced to silver nanoparticles with formalin. We demonstrate that silver is capable of sensitizing the gram-negative bacteria E. coli to a gram-positive specific phototherapeutic agent in vitro; thereby expanding curcumin's phototherapeutic spectrum. The mesoporous structure of Cu-MSN remains intact after the exterior decoration with silver nanoparticles and subsequent curcumin loading through an enhanced effect from copper metal-curcumin affinity interaction. The synthesis, as well as successful assembly of the functional nanomaterials, was confirmed by various physical characterization techniques. Curcumin is capable of producing high amounts of reactive oxygen species (ROS) under light irradiation, which can further improve the silver ion release kinetics for antibacterial activity. In addition, the positive charged modified surfaces of Cu-MSN facilitate antimicrobial response through electrostatic attractions towards negatively charged bacterial cell membranes. The antibacterial action of the synthesized nanocomposites can be activated through a synergistic mechanism of energy transfer of the absorbed light from SNP to curcumin. Copyright © 2017 Elsevier B.V. All rights reserved.

Low-frequency Electronic Transport Noise in La2-xBaxCuO4 Nanowires

NASA Astrophysics Data System (ADS)

Weis, Adam; Xin, Yizhou; van Harlingen, Dale

2013-03-01

In the pseudogap regime, high temperature superconductors often exhibit electronic structure, such as charge stripes. Charge stripes pinned to disorder have been predicted to contribute to low-frequency resistance fluctuations when sample dimensions are comparable to the size of stripe domains (Carlson, 2006). We are extending our previous studies of resistance fluctuations in YBa2Cu3O7-δ (Bonetti, 2004; Caplan, 2010) to thin films of La-based cuprates expected to have a more stable stripe phase, particularly in the regime near 1/8-filling. We present measurements of the low-frequency electronic transport in La2-xBaxCuO4 nanowires fabricated by pulsed laser deposition and lithographic techniques. We discuss temperature dependence of the power spectral density and its relevance to correlated electron phases above Tc. This research was supported by the DOE-DMS under grant DE-FG02-07ER46453, through the Frederick Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign.

Exploring Charge Transport in Guest Molecule Infiltrated Cu 3(BTC) 2 Metal Organic Framework

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

Leonard, Francois Leonard; Stavila, Vitalie; Allendorf, Mark D.

2014-09-01

The goal of this Exploratory Express project was to expand the understanding of the physical properties of our recently discovered class of materials consisting of metal-organic frameworks with electroactive ‘guest’ molecules that together form an electrically conducting charge-transfer complex (molecule@MOF). Thin films of Cu 3(BTC) 2 were grown on fused silica using solution step-by-step growth and were infiltrated with the molecule tetracyanoquinodimethane (TCNQ). The infiltrated MOF films were extensively characterized using optical microscopy, scanning electron microscopy, Raman spectroscopy, electrical conductivity, and thermoelectric properties. Thermopower measurements on TCNQ@Cu 3(BTC) 2 revealed a positive Seebeck coefficient of ~400 μV/k, indicating that holesmore » are the primary carriers in this material. The high value of the Seebeck coefficient and the expected low thermal conductivity suggest that molecule@MOF materials may be attractive for thermoelectric power conversion applications requiring low cost, solution-processable, and non-toxic active materials.« less

Electron capture by U(91+) and U(92+) and ionization of U(90+) and U(91+)

NASA Technical Reports Server (NTRS)

Gould, H.; Greiner, D.; Lindstrom, P.; Symons, T. J. M.; Crawford, H.

1984-01-01

U(92+)/U(91+) and U(91+)/U(90+) electron-capture and ionization cross sections and equilibrium charge-state distributions are measured experimentally in mylar, Cu and Ta of varying thickness. Relativistic U(68+) ions at 437 or 962 MeV/nucleon are produced by a heavy-ion linear accelerator and synchrotron in tandem and passed through the target material into a magnetic specrometer and position-sensitive proportional counter for evaluation of charge states. The results are presented graphically and discussed. At 962 MeV/nucleon, beams containing 85 percent bare U(92+) nuclei are obtained using 150-mg/sq cm Cu or 85-mg/sq cm Ta; at 437 MeV/nucleon, 50 percent bare U(92+) nuclei are obtained with 90-mg/sq cm Cu. The techniques decribed can be applied to produce beams of bare U nuclei for acceleration to ultrarelativistic speeds or beams of few-electron U for atomic-physics experiments on quantum electrodynamics.

Synthesis of three-dimensional mesoporous Cu-Al layered double hydroxide/g-C3N4 nanocomposites on Ni-foam for enhanced supercapacitors with excellent long-term cycling stability.

PubMed

Adhikari, Surya Prasad; Awasthi, Ganesh Prasad; Kim, Kyung-Suk; Park, Chan Hee; Kim, Cheol Sang

2018-03-26

In this study, a novel composite of Cu-Al layered double hydroxide (LDH) nanosheets and g-C3N4-covered Ni-foam was fabricated via a simple and facile two-step process. First, g-C3N4 sheets were deposited on Ni-foam by via electrodeposition method on a three-electrode system (Ni-foam@g-C3N4) and then, Cu-Al LDH nanosheets were grown on the Ni-foam via in situ redox reaction using a hydrothermal process (Ni-foam@Cu-Al LDH/g-C3N4). The FE-SEM image confirmed that the Cu-Al LDH nanosheets arose vertically and were anchored on the surface of electrodeposited g-C3N4 sheets, thus generating unique 3D porous interconnected networks. The electrochemical capacitive performances of the as-prepared samples were evaluated by cyclic volatammetry (CV), galvanostatic charge/discharge tests, and electrochemical impedance spectra (EIS) Nyquist plots. The specific capacitances of the Ni-foam@Cu-Al LDH/g-C3N4 nanocomposite measured from the CV curve (770.98 F g-1 at 50 mV s-1) and the galvanostatic charge/discharge curve (831.871 at 0.4 A g-1) were significantly higher than the others. Moreover, the Ni-foam@Cu-Al LDH/g-C3N4 nanocomposite revealed a remarkable high-current capacitive behavior and the capacitance retention could be maintained at 92.71% even after 5000 cycles of CV. Thus, the obtained results demonstrated that the as-prepared nanocomposite has great potential to be used as a novel supercapacitor electrode.

Pressure enhanced penetration with shaped charge perforators

DOEpatents

Glenn, Lewis A.

2001-01-01

A downhole tool, adapted to retain a shaped charge surrounded by a superatmospherically pressurized light gas, is employed in a method for perforating a casing and penetrating reservoir rock around a wellbore. Penetration of a shaped charge jet can be enhanced by at least 40% by imploding a liner in the high pressure, light gas atmosphere. The gas pressure helps confine the jet on the axis of penetration in the latter stages of formation. The light gas, such as helium or hydrogen, is employed to keep the gas density low enough so as not to inhibit liner collapse.

Explosive shaped charge penetration into tuff rock

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

Vigil, M.G.

1988-10-01

Analysis and data for the use of Explosive Shaped Charges (ESC) to generate holes in tuff rock formation is presented. The ESCs evaluated include Conical Shaped Charges (CSC) and Explosive Formed Projectiles (EFP). The CSCs vary in size from 0.158 to 9.1 inches inside cone diameter. The EFPs were 5.0 inches in diameter. Data for projectile impact angles of 30 and 90 degrees are presented. Analytically predicted depth of penetration data generally compared favorably with experimental data. Predicted depth of penetration versus ESC standoff data and hole profile dimensions in tuff are also presented. 24 refs., 45 figs., 6 tabs.

Variation of stresses ahead of the internal cracks in ReNi{sub 5} powders during hydrogen charging and discharging cycles

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

Biner, S.B.

1998-07-01

In this study, the evolution of the stress-states ahead of the penny shaped internal cracks in both spherical and disk shaped ReNi{sub 5} particles during hydrogen charging and discharging cycles were investigated using coupled diffusion/deformation FEM analyses. The results indicate that large tensile stresses, on the order of 20--50% of the modulus of elasticity, develop in the particles. The disk shaped particles, in addition to having faster charging/discharging cycles, may offer better resistance to fracture than the spherical particles.

Lead-Sulfide-Selenide Quantum Dots and Gold-Copper Alloy Nanoparticles Augment the Light-Harvesting Ability of Solar Cells.

PubMed

Das, Aparajita; Deepa, Melepurath; Ghosal, Partha

2017-04-05

Lead-sulfide-selenide (PbSSe) quantum dots (QDs) and gold-copper (AuCu) alloy nanoparticles (NPs) were incorporated into a cadmium sulfide (CdS)/titanium oxide (TiO 2 ) photoanode for the first time to achieve enhanced conversion of solar energy into electricity. PbSSe QDs with a band gap of 1.02 eV extend the light-harvesting range of the photoanode from the visible region to the near-infrared region. The conduction band (CB) edge of the PbSSe QDs is wedged between the CBs of TiO 2 and CdS; this additional level coupled with the good electrical conductivity of the dots facilitate charge transport and collection, and a high power conversion efficiency (PCE) of 4.44 % is achieved for the champion cell with the TiO 2 /PbSSe/CdS electrode. Upon including AuCu alloy NPs in the QD-sensitized electrodes, light absorption is enhance by plasmonic and light-scattering effects and also by the injection of hot electrons to the CBs of the QDs. Comparison of the incident photon-to-current conversion efficiency enhancement factors in addition to fluorescence decay and impedance studies reveal that the PbSSe QDs and AuCu alloy NPs promote charge injection to the current collector and increase the photogenerated charges produced, which thus enables the TiO 2 /PbSSe/CdS/AuCu cell to deliver the highest PCE of 5.26 % among all the various photoanode compositions used. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modeling the adsorption of metal ions (Cu 2+, Ni 2+, Pb 2+) onto ACCs using surface complexation models

NASA Astrophysics Data System (ADS)

Faur-Brasquet, Catherine; Reddad, Zacaria; Kadirvelu, Krishna; Le Cloirec, Pierre

2002-08-01

Activated carbon cloths (ACCs), whose efficiency has been demonstrated for microorganics adsorption from water, were here studied in the removal of metal ions from aqueous solution. Two ACCs are investigated, they are characterized in terms of porosity parameters (BET specific surface area, percentage of microporosity) and chemical characteristics (acidic surface groups, acidity constants, point of zero charge). A first part consists in the experimental study of three metal ions removal (Cu 2+, Ni 2+ and Pb 2+) in a batch reactor. Isotherms modeling by Freundlich and Brunauer-Emmett-Teller (BET) equations enables the following adsorption order: Cu 2+>Ni 2+>Pb 2+ to be determined for adsorption capacities on a molar basis. It may be related to adsorbates characteristics in terms of electronegativity and ionic radius. The influence of adsorbent's microporosity is also shown. Adsorption experiments carried out for pH values ranging from 2 to 10 demonstrate: (i) an adsorption occurring below the precipitation pH; (ii) the strong influence of pH, with a decrease of electrostatic repulsion due to the formation of less charged hydrolyzed species coupled with a decrease of activated carbon surface charge as pH increases. The second part focuses on the modeling of adsorption versus the pH experimental data by the diffuse layer model (DLM) using Fiteql software. The model is efficient to describe the system behavior in the pH range considered. Regarding complexation constants, they show the following affinity for ACC: Pb 2+>Cu 2+>Ni 2+. They are related to initial concentrations used for the three metal ions.

A novel method combining additive manufacturing and alloy infiltration for NdFeB bonded magnet fabrication

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

Li, Ling; Tirado, Angelica; Conner, Benjamin S.

In this paper, binder jetting additive manufacturing technique is employed to fabricate NdFeB isotropic bonded magnets, followed by an infiltration process with low-melting point eutectic alloys [i.e., Nd 3Cu 0.25Co 0.75 (NdCuCo) and Pr 3Cu 0.25Co 0.75 (PrCuCo)]. Densification and mechanical strength improvement are achieved for the as-printed porous part. Meanwhile, the intrinsic coercivity H ci is enhanced from 732 to 1345 kA/m and 1233 kA/m after diffusion of NdCuCo and PrCuCo, respectively. This study presents a novel method for fabricating complex-shaped bonded magnets with promising mechanical and magnetic properties.

Development of High-Speed Copper Chemical Mechanical Polishing Slurry for Through Silicon Via Application Based on Friction Analysis Using Atomic Force Microscope

NASA Astrophysics Data System (ADS)

Amanokura, Jin; Ono, Hiroshi; Hombo, Kyoko

2011-05-01

In order to obtain a high-speed copper chemical mechanical polishing (CMP) process for through silicon vias (TSV) application, we developed a new Cu CMP slurry through friction analysis of Cu reaction layer by an atomic force microscope (AFM) technique. A lateral modulation friction force microscope (LM-FFM) is able to measure the friction value properly giving a vibration to the layer. We evaluated the torsional displacement between the probe of the LM-FFM and the Cu reaction layer under a 5 nm vibration to cancel the shape effect of the Cu reaction layer. The developed Cu CMP slurry forms a frictionally easy-removable Cu reaction layer.

A novel method combining additive manufacturing and alloy infiltration for NdFeB bonded magnet fabrication

DOE PAGES

Li, Ling; Tirado, Angelica; Conner, Benjamin S.; ...

2017-04-27

In this paper, binder jetting additive manufacturing technique is employed to fabricate NdFeB isotropic bonded magnets, followed by an infiltration process with low-melting point eutectic alloys [i.e., Nd 3Cu 0.25Co 0.75 (NdCuCo) and Pr 3Cu 0.25Co 0.75 (PrCuCo)]. Densification and mechanical strength improvement are achieved for the as-printed porous part. Meanwhile, the intrinsic coercivity H ci is enhanced from 732 to 1345 kA/m and 1233 kA/m after diffusion of NdCuCo and PrCuCo, respectively. This study presents a novel method for fabricating complex-shaped bonded magnets with promising mechanical and magnetic properties.

Adsorption and desorption of Cu2+ on paddy soil aggregates pretreated with different levels of phosphate.

PubMed

Dai, Jun; Wang, Wenqin; Wu, Wenchen; Gao, Jianbo; Dong, Changxun

2017-05-01

Interactions between anions and cations are important for understanding the behaviors of chemical pollutants and their potential risks in the environment. Here we prepared soil aggregates of a yellow paddy soil from the Taihu Lake region, and investigated the effects of phosphate (P) pretreatment on adsorption-desorption of Cu 2+ of soil aggregates, free iron oxyhydrates-removed soil aggregates, goethite, and kaolinite with batch adsorption method. The results showed that Cu 2+ adsorption was reduced on the aggregates pretreated with low concentrations of P, and promoted with high concentrations of P, showing a V-shaped change. Compared with the untreated aggregates, the adsorption capacity of Cu 2+ was reduced when P application rates were lower than 260, 220, 130 and 110mg/kg for coarse, clay, silt and fine sand fractions, respectively. On the contrary, the adsorption capacity of Cu 2+ was higher on P-pretreated soil aggregates than on the control ones when P application rates were greater than those values. However, the desorption of Cu 2+ was enhanced at low levels of P, but suppressed at high levels of P, displaying an inverted V-shaped change over P adsorption. The Cu 2+ adsorption by the aggregate particles with and without P pretreatments was well described by the Freundlich equation. Similar results were obtained on P-pretreated goethite. However, such P effects on Cu 2+ adsorption-desorption were not observed on kaolinite and free iron oxyhydrates-removed soil aggregates. The present results indicate that goethite is one of the main soil substances responsible for the P-induced promotion and inhibition of Cu 2+ adsorption. Copyright © 2016. Published by Elsevier B.V.

Enhanced catalyst activity by decorating of Au on Ag@Cu2O nanoshell

NASA Astrophysics Data System (ADS)

Chen, Lei; Liu, Maomao; Zhao, Yue; Kou, Qiangwei; Wang, Yaxin; Liu, Yang; Zhang, Yongjun; Yang, Jinghai; Jung, Young Mee

2018-03-01

We successfully synthesized Au-decorated Ag@Cu2O heterostructures via a simple galvanic replacement method. As the Au precursor concentration increased, the density of the Au nanoparticles (NPs) on the Ag@Cu2O surface increased, which changed the catalytic activity of the Ag@Cu2O-Au structure. The combination of Au, Ag, and Cu2O exhibited excellent catalytic properties, which can further effect on the catalyst activity of the Ag@Cu2O-Au structure. In addition, the proposed Ag@Cu2O-Au nanocomposite was used to transform the organic, toxic pollutant, 4-nitrophenol (4-NP), into its nontoxic and medicinally important amino derivative via a catalytic reduction to optimize the material performance. The proposed Au-decorated Ag@Cu2O exhibited excellent catalytic activity, and the catalytic reduction time greatly decreased (5 min). Thus, three novel properties of Ag@Cu2O-Au, i.e., charge redistribution and transfer, adsorption, and catalytic reduction of organic pollutants, were ascertained for water remediation. The proposed catalytic properties have potential applications for photocatalysis and localized surface plasmon resonance (LSPR)- and peroxidase-like catalysis.

Surface complexation model for multisite adsorption of copper(II) onto kaolinite

NASA Astrophysics Data System (ADS)

Peacock, Caroline L.; Sherman, David M.

2005-08-01

We measured the adsorption of Cu(II) onto kaolinite from pH 3-7 at constant ionic strength. EXAFS spectra show that Cu(II) adsorbs as (CuO 4H n) n-6 and binuclear (Cu 2O 6H n) n-8 inner-sphere complexes on variable-charge ≡AlOH sites and as Cu 2+ on ion exchangeable ≡X-H + sites. Sorption isotherms and EXAFS spectra show that surface precipitates have not formed at least up to pH 6.5. Inner-sphere complexes are bound to the kaolinite surface by corner-sharing with two or three edge-sharing Al(O,OH) 6 polyhedra. Our interpretation of the EXAFS data are supported by ab initio (density functional theory) geometries of analog clusters simulating Cu complexes on the {110} and {010} crystal edges and at the ditrigonal cavity sites on the {001}. Having identified the bidentate (≡AlOH) 2Cu(OH) 20, tridentate (≡Al 3O(OH) 2)Cu 2(OH) 30 and ≡X-Cu 2+ surface complexes, the experimental copper(II) adsorption data can be fit to the reactions

In situ spectroscopic monitoring of CO2 reduction at copper oxide electrode.

PubMed

Wang, Liying; Gupta, Kalyani; Goodall, Josephine B M; Darr, Jawwad A; Holt, Katherine B

2017-04-28

Copper oxide modified electrodes were investigated as a function of applied electrode potential using in situ infrared spectroscopy and ex situ Raman and X-ray photoelectron spectroscopy. In deoxygenated KHCO 3 electrolyte bicarbonate and carbonate species were found to adsorb to the electrode during reduction and the CuO was reduced to Cu(i) or Cu(0) species. Carbonate was incorporated into the structure and the CuO starting material was not regenerated on cycling to positive potentials. In contrast, in CO 2 saturated KHCO 3 solution, surface adsorption of bicarbonate and carbonate was not observed and adsorption of a carbonato-species was observed with in situ infrared spectroscopy. This species is believed to be activated, bent CO 2 . On cycling to negative potentials, larger reduction currents were observed in the presence of CO 2 ; however, less of the charge could be attributed to the reduction of CuO. In the presence of CO 2 CuO underwent reduction to Cu 2 O and potentially Cu, with no incorporation of carbonate. Under these conditions the CuO starting material could be regenerated by cycling to positive potentials.

A novel single-stranded DNA detection method based on organic semiconductor heterojunction

NASA Astrophysics Data System (ADS)

Gu, Wen; Liu, Hongbo; Zhang, Xia; Zhang, Hao; Chen, Xiong; Wang, Jun

2016-12-01

We demonstrate a novel DNA detection method with low-cost and disposable advantages by utilizing F16CuPc/CuPc planar organic heterojunction device. Single-stranded DNA (ssDNA) molecules have been well immobilized on the surface of CuPc film observed by atomic force microscopy, producing an obvious electrical response of the device. The conductivity of the organic heterojunction film was significantly increased by ssDNA immobilization because ssDNA molecules brought additional positive charges at heterojunction interface. Furthermore, the thickness dependence of CuPc upper layer on the electrical response was studied to optimize the sensitivity. This study will be helpful for the development of organic heterojunction based biosensors.

A new bimetallic plasmonic photocatalyst consisting of gold(core)-copper(shell) nanoparticle and titanium(IV) oxide support

NASA Astrophysics Data System (ADS)

Sato, Yuichi; Naya, Shin-ichi; Tada, Hiroaki

2015-10-01

Ultrathin Cu layers (˜2 atomic layers) have been selectively formed on the Au surfaces of Au nanoparticle-loaded rutile TiO2 (Au@Cu/TiO2) by a deposition precipitation-photodeposition technique. Cyclic voltammetry and photochronopotentiometry measurements indicate that the reaction proceeds via the underpotential deposition. The ultrathin Cu shell drastically increases the activity of Au/TiO2 for the selective oxidation of amines to the corresponding aldehydes under visible-light irradiation (λ > 430 nm). Photochronoamperometry measurements strongly suggest that the striking Cu shell effect stems from the enhancement of the charge separation in the localized surface plasmon resonance-excited Au/TiO2.

Fabrication and chemical composition of RF magnetron sputtered Tl-Ca-Ba-Cu-O high Tc superconducting thin films

NASA Technical Reports Server (NTRS)

Subramanyam, G.; Radpour, F.; Kapoor, V. J.; Lemon, G. H.

1990-01-01

The preparation of TlCaBaCuO superconducting thin films on (100) SrTiO3 substrates is described, and the results of their characterization are presented. Sintering and annealing the thin films in a Tl-rich ambient yielded superconductivity with a Tc of 107 K. The results of an XPS study support two possible mechanisms for the creation of holes in the TlCaBaCuO compound: (1) partial substitution of Ca(2+) for Tl(3+), resulting in hole creation, and (2) charge transfer from Tl(3+) to the CuO layers, resulting in a Tl valence between +3 and +1.

Facile and quantitative electrochemical detection of yeast cell apoptosis

NASA Astrophysics Data System (ADS)

Yue, Qiulin; Xiong, Shiquan; Cai, Dongqing; Wu, Zhengyan; Zhang, Xin

2014-03-01

An electrochemical method based on square wave anodic stripping voltammetry (SWASV) was developed to detect the apoptosis of yeast cells conveniently and quantitatively through the high affinity between Cu2+ and phosphatidylserine (PS) translocated from the inner to the outer plasma membrane of the apoptotic cells. The combination of negatively charged PS and Cu2+ could decrease the electrochemical response of Cu2+ on the electrode. The results showed that the apoptotic rates of cells could be detected quantitatively through the variations of peak currents of Cu2+ by SWASV, and agreed well with those obtained through traditional flow cytometry detection. This work thus may provide a novel, simple, immediate and accurate detection method for cell apoptosis.

Study of photoirradiation for YBa 2Cu 3O 6+ x compounds and the electron structure by positron experiment

NASA Astrophysics Data System (ADS)

Guosheng, Cheng; Jiaxiang, Shang; Xigui, Li; xianqi, Dai; Xizhong, Wang; Jincang, Zhang

1997-08-01

We present positron lifetime data of YBa 2Cu 3O 6+ x (x=0.92, 0.43) compounds for different photo-irradiation time. It is given that change of the local electron density and vacancy concentration with photoirradiation time. It is found that there is transform at the electronic structure of CuO chains. We also have discussed the effect of photoirradiations time on the electronic structure of YBa 2Cu 3O 6+ x systems and their charge reservoir layer and CuO 2 plane conduction.layer. The positron experimental results support the model of photoinduced oxygen-diffusion mechanism.

Magnetic properties of quadruple perovskite solid solutions Ca{sub 1–x}Y{sub x}Cu{sub 3}Fe{sub 4}O{sub 12} and Y{sub 1–y}Ce{sub x}Cu{sub 3}Fe{sub 4}O{sub 12}

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

Murakami, Makoto; Mori, Shigeo; Yamada, Ikuya, E-mail: i-yamada@21c.osakafu-u.ac.jp

Magnetic properties of the quadruple perovskite solid solutions Ca{sub 1–x}Y{sub x}Cu{sub 3}Fe{sub 4}O{sub 12} and Y{sub 1–y}Ce{sub y}Cu{sub 3}Fe{sub 4}O{sub 12} are investigated. Ca{sub 1–x}Y{sub x}Cu{sub 3}Fe{sub 4}O{sub 12} shows continuous increase in the ferromagnetic transition temperature as x increases. Y{sub 1–y}Ce{sub y}Cu{sub 3}Fe{sub 4}O{sub 12} exhibits a ferromagnetic-antiferromagnetic transition in the vicinity of y = 0.5. These observations demonstrate the electron doping effect on magnetic properties of charge-disproportionated ACu{sub 3}Fe{sub 4}O{sub 12} phases.

Photochemical redox reactions of copper(II)-alanine complexes in aqueous solutions.

PubMed

Lin, Chen-Jui; Hsu, Chao-Sheng; Wang, Po-Yen; Lin, Yi-Liang; Lo, Yu-Shiu; Wu, Chien-Hou

2014-05-19

The photochemical redox reactions of Cu(II)/alanine complexes have been studied in deaerated solutions over an extensive range of pH, Cu(II) concentration, and alanine concentration. Under irradiation, the ligand-to-metal charge transfer results in the reduction of Cu(II) to Cu(I) and the concomitant oxidation of alanine, which produces ammonia and acetaldehyde. Molar absorptivities and quantum yields of photoproducts for Cu(II)/alanine complexes at 313 nm are characterized mainly with the equilibrium Cu(II) speciation where the presence of simultaneously existing Cu(II) species is taken into account. By applying regression analysis, individual Cu(I) quantum yields are determined to be 0.094 ± 0.014 for the 1:1 complex (CuL) and 0.064 ± 0.012 for the 1:2 complex (CuL2). Individual quantum yields of ammonia are 0.055 ± 0.007 for CuL and 0.036 ± 0.005 for CuL2. Individual quantum yields of acetaldehyde are 0.030 ± 0.007 for CuL and 0.024 ± 0.007 for CuL2. CuL always has larger quantum yields than CuL2, which can be attributed to the Cu(II) stabilizing effect of the second ligand. For both CuL and CuL2, the individual quantum yields of Cu(I), ammonia, and acetaldehyde are in the ratio of 1.8:1:0.7. A reaction mechanism for the formation of the observed photoproducts is proposed.

Elliptical flux vortices in YBa2Cu3O7

NASA Technical Reports Server (NTRS)

Hickman, H.; Dekker, A. J.; Chen, T. M.

1991-01-01

The most energetically favorable vortex in YBa2Cu3O7 forms perpendicular to an anisotropic plane. This vortex is elliptical in shape and is distinguished by an effective interchange of London penetration depths from one axis of the ellipse to another. By generalizing qualitatively from the isotropic to the anisotropic case, we suggest that the flux flow resistivity for the vortex that forms perpendicular to an anistropic plane should have a preferred direction. Similar reasoning indicates that the Kosterlitz-Thouless transition temperature for a vortex mediated transition should be lower if the vortex is elliptical in shape.

Precipitation Hardenable High Temperature Shape Memory Alloy

NASA Technical Reports Server (NTRS)

Noebe, Ronald Dean (Inventor); Draper, Susan L. (Inventor); Nathal, Michael V. (Inventor); Crombie, Edwin A. (Inventor)

2010-01-01

A composition of the invention is a high temperature shape memory alloy having high work output, and is made from (Ni+Pt+Y),Ti(100-x) wherein x is present in a total amount of 49-55 atomic % Pt is present in a total amount of 10-30 atomic %, Y is one or more of Au, Pd. and Cu and is present in a total amount of 0 to 10 atomic %. The alloy has a matrix phase wherein the total concentration of Ni, Pt, and the one or more of Pd. Au, and Cu is greater than 50 atomic %.

CuO nanowire/microflower/nanowire modified Cu electrode with enhanced electrochemical performance for non-enzymatic glucose sensing.

PubMed

Li, Changli; Yamahara, Hiroyasu; Lee, Yaerim; Tabata, Hitoshi; Delaunay, Jean-Jacques

2015-07-31

CuO nanowire/microflower structure on Cu foil is synthesized by annealing a Cu(OH)2 nanowire/CuO microflower structure at 250 °C in air. The nanowire/microflower structure with its large surface area leads to an efficient catalysis and charge transfer in glucose detection, achieving a high sensitivity of 1943 μA mM(-1) cm(-2), a wide linear range up to 4 mM and a low detection limit of 4 μM for amperometric glucose sensing in alkaline solution. With a second consecutive growth of CuO nanowires on the microflowers, the sensitivity of the obtained CuO nanowire/microflower/nanowire structure further increases to 2424 μA mM(-1) cm(-2), benefiting from an increased number of electrochemically active sites. The enhanced electrocatalytic performance of the CuO nanowire/microflower/nanowire electrode compared to the CuO nanowire/microflower electrode, CuO nanowire electrode and CuxO film electrode provides evidence for the significant role of available surface area for electrocatalysis. The rational combination of CuO nanowire and microflower nanostructures into a nanowire supporting microflower branching nanowires structure makes it a promising composite nanostructure for use in CuO based electrochemical sensors with promising analytical properties.

Single-phase and well-dispersed Cu1.75S nanocrystals by ambient pressure diethylene glycol solution synthesis

NASA Astrophysics Data System (ADS)

Zheng, Xuerong; Jin, Zhengguo; Liu, Hui; Wang, Yueqiu; Wang, Xin; Du, Haiyan

2013-02-01

Single-phase, well-dispersed Cu1.75S nanocrystals were synthesized by an ambient pressure, hydrazine hydrate and ethylenediamine co-assisted diethylene glycol based solution chemical process using copper chloride and thioacetamide as precursors at the temperature range from 180 to 210 °C. Influence of hydrazine hydrate and ethylenediamine adding amounts, synthetic temperature on crystal growth, size distribution and optical properties of the synthesized Cu1.75S nanocrystals were investigated by XRD, TEM, HRTEM, EDX and UV-vis measurements. The synthetic reaction at above 200 °C grew flaky-shaped nanocrystals with relatively narrow size distribution. The formation of single-phase Cu1.75S nanocrystals in the diethylene glycol based solution process might be involved in the presence of intermediate [Cu(en)n]1+ and [Cu(NH3)4]2+ complexes in reaction solution, providing a stable Cu(I) and Cu(II) valent-mixed precursor.

Polarizable molecular mechanics studies of Cu(I)/Zn(II) superoxide dismutase: bimetallic binding site and structured waters.

PubMed

Gresh, Nohad; El Hage, Krystel; Perahia, David; Piquemal, Jean-Philip; Berthomieu, Catherine; Berthomieu, Dorothée

2014-11-05

The existence of a network of structured waters in the vicinity of the bimetallic site of Cu/Zn-superoxide dismutase (SOD) has been inferred from high-resolution X-ray crystallography. Long-duration molecular dynamics (MD) simulations could enable to quantify the lifetimes and possible interchanges of these waters between themselves as well as with a ligand diffusing toward the bimetallic site. The presence of several charged or polar ligands makes it necessary to resort to second-generation polarizable potentials. As a first step toward such simulations, we benchmark in this article the accuracy of one such potential, sum of interactions between fragments Ab initio computed (SIBFA), by comparisons with quantum mechanics (QM) computations. We first consider the bimetallic binding site of a Cu/Zn-SOD, in which three histidines and a water molecule are bound to Cu(I) and three histidines and one aspartate are bound to Zn(II). The comparisons are made for different His6 complexes with either one or both cations, and either with or without Asp and water. The total net charges vary from zero to three. We subsequently perform preliminary short-duration MD simulations of 296 waters solvating Cu/Zn-SOD. Six representative geometries are selected and energy-minimized. Single-point SIBFA and QM computations are then performed in parallel on model binding sites extracted from these six structures, each of which totals 301 atoms including the closest 28 waters from the Cu metal site. The ranking of their relative stabilities as given by SIBFA is identical to the QM one, and the relative energy differences by both approaches are fully consistent. In addition, the lowest-energy structure, from SIBFA and QM, has a close overlap with the crystallographic one. The SIBFA calculations enable to quantify the impact of polarization and charge transfer in the ranking of the six structures. Five structural waters, which connect Arg141 and Glu131, are endowed with very high dipole moments (2.7-3.0 Debye), equal and larger than the one computed by SIBFA in ice-like arrangements (2.7 D). Copyright © 2014 Wiley Periodicals, Inc.

Jet Formation and Penetration Study of Double-Layer Shaped Charge

NASA Astrophysics Data System (ADS)

Wang, Zhe; Jiang, Jian-Wei; Wang, Shu-You; Liu, Han

2018-04-01

A theoretical analysis on detonation wave propagation in a double-layer shaped charge (DLSC) is performed. Numerical simulations using the AUTODYN software are carried out to compare the distinctions between jet formations in DLSC and ordinary shaped charge (OSC), in particular, the OSC made using a higher detonation velocity explosive, which is treated as the outer layer charge in the DLSC. The results show that the improved detonation velocity ratio and radial charge percentage of outer-to-inner layer charge are conducive to the formation of a convergent detonation wave, which contributes to enhancement of jet tip velocity in DLSC. The thickness and mass percentages of liner flowing into jet in DLSC closely follow the exponential distribution along the radial direction, but the percentages in DLSC and the mass of effective jet, which have significant influence on the penetration depth, are lower than those in OSC with the outer layer charge. This implies that the total charge energy is the major factor controlling the effective jet formation, which is confirmed by the verification tests using flash X-ray system and following penetration tests. The numerical simulation and test results compare well, while penetration test results indicate that the performance of DLSC is not better than that of OSC with the outer layer charge, due to the differences in jet formation.

X-ray photoemission studies of Zn doped Cu 1- xTl xBa 2Ca 2Cu 3- yZn yO 10- δ ( y = 0, 2.65) superconductors

NASA Astrophysics Data System (ADS)

Khan, Nawazish A.; Mumtaz, M.; Ahadian, M. M.; Iraji-zad, Azam

2007-03-01

The X-ray photoemission (XPS) measurements of Cu 1- xTl xBa 2Ca 2Cu 3- yZn yO 10- δ ( y = 0, 2.65) superconductors have been performed and compared. These studies revealed that the charge state of thallium in the Cu 0.5Tl 0.5Ba 2O 4- δ charge reservoir layer in Zn doped samples is Tl 1+, while it is a mix of Tl 1+ and Tl 2+ in Zn free samples. The binding energy of Ba atoms in the Zn doped samples is shifted to higher energy, which when considered along with the presence of Tl 1+ suggested that it more efficiently directed the carriers to ZnO 2 and CuO 2 planes. The evidence of improved inter-plane coupling witnessed in X-ray diffraction is also confirmed by XPS measurements of Ca atoms in the Zn doped samples. The shift of the valance band spectrum in these Zn doped samples to higher energies suggested that the electrons at the top edge of the valance band were tied to a higher binding energy (relative to samples without Zn doping), which most likely resulted in a much lower energy state of the system in the superconducting state. The stronger superconducting state arising out of these effects is witnessed in the form of increased Tc( R = 0), Jc and the extent of diamagnetism in the final compound.

Effect of Cu Doping on the Structural and Electrochemical Performance of LiNi1/3Co1/3Mn1/3O2 Cathode Materials

NASA Astrophysics Data System (ADS)

Yang, Li; Ren, Fengzhagn; Feng, Qigao; Xu, Guangri; Li, Xiaobo; Li, Yuanchao; Zhao, Erqing; Ma, Jignjign; Fan, Shumin

2018-04-01

The structural and electrochemical performance of Cu-doped, Li[Ni1/3-xCo1/3 Mn1/3Cux]O2 (x = 0-0.1) cathode materials obtained by means of the sol-gel method are discussed; we used critic acid as gels and spent mixed batteries as the raw materials. The effects of the sintering time, sintering temperature, and Cu doping ratio on the phase structure, morphology, and element composition and the behavior in a galvanostatical charge/discharge test have been systemically studied. The results show that the Cu-doped material exhibits better galvanostatic charge/discharge cycling performance. At 0.2 C, its original discharge specific capacity is 180.4 mAh g-1 and its Coulomb efficiency is 90.3%. The Cu-doped material demonstrate an outstanding specific capacity at 0.2 C, 0.5 C, and 2.0 C. In comparison with the original capacities of 178 mAh g-1, 159.5 mAh g-1, and 119.4 mAh g-1, the discharge capacity after 50 cycles is 160.8 mAh g-1, 143.4 mAh g-1, and 90.1 mAh g-1, respectively. This obvious improvement relative to bare Li[Ni1/3Co1/3Mn1/3]O2 cathode materials arises from an enlarged Li layer spacing and a reduced degree of cation mixing. Therefore, Cu-doped cathode materials have obvious advantages in the field of lithium-ion batteries and their applications.

Effect of Cu Doping on the Structural and Electrochemical Performance of LiNi1/3Co1/3Mn1/3O2 Cathode Materials

NASA Astrophysics Data System (ADS)

Yang, Li; Ren, Fengzhagn; Feng, Qigao; Xu, Guangri; Li, Xiaobo; Li, Yuanchao; Zhao, Erqing; Ma, Jignjign; Fan, Shumin

2018-07-01

The structural and electrochemical performance of Cu-doped, Li[Ni1/3-xCo1/3 Mn1/3Cux]O2 ( x = 0-0.1) cathode materials obtained by means of the sol-gel method are discussed; we used critic acid as gels and spent mixed batteries as the raw materials. The effects of the sintering time, sintering temperature, and Cu doping ratio on the phase structure, morphology, and element composition and the behavior in a galvanostatical charge/discharge test have been systemically studied. The results show that the Cu-doped material exhibits better galvanostatic charge/discharge cycling performance. At 0.2 C, its original discharge specific capacity is 180.4 mAh g-1 and its Coulomb efficiency is 90.3%. The Cu-doped material demonstrate an outstanding specific capacity at 0.2 C, 0.5 C, and 2.0 C. In comparison with the original capacities of 178 mAh g-1, 159.5 mAh g-1, and 119.4 mAh g-1, the discharge capacity after 50 cycles is 160.8 mAh g-1, 143.4 mAh g-1, and 90.1 mAh g-1, respectively. This obvious improvement relative to bare Li[Ni1/3Co1/3Mn1/3]O2 cathode materials arises from an enlarged Li layer spacing and a reduced degree of cation mixing. Therefore, Cu-doped cathode materials have obvious advantages in the field of lithium-ion batteries and their applications.

Production of superconductor/carbon bicomponent fibers

NASA Technical Reports Server (NTRS)

Wise, S. A.; Fain, C. C.; Leigh, H. D.

1991-01-01

Certain materials are unable to be drawn or spun into fiber form due to their improper melting characteristics or brittleness. However, fibrous samples of such materials are often necessary for the fabrication of intricate shapes and composites. In response to this problem, a unique process, referred to as the piggyback process, was developed to prepare fibrous samples of a variety of nonspinnable ceramics. In this technique, specially produced C shaped carbon fibers serve as micromolds to hold the desired materials prior to sintering. Depending on the sintering atmosphere used, bicomponent or single component fibers result. While much has been shown worldwide concerning the YBa2Cu3O(7-x) superconductor, fabrication into unique forms has proven quite difficult. However, a variety of intricate shapes are necessary for rapid commercialization of the superconducting materials. The potential for producing fibrous samples of the YBa2Cu3O(7-x) compound by the piggyback process is being studied. Various organic and acrylic materials were studied to determine suspending ability, reactivity with the YBa2Cu3O(7-x) compound during long term storage, and burn out characteristics. While many questions were answered with respect to the interfacial reactions between YBa2Cu3O(7-x) and carbon, much work is still necessary to improve the quality of the sintered material if the fibers produced are to be incorporated into useful composite or cables.

Properties of Cu-Based Shape-Memory Alloys Prepared by Selective Laser Melting

NASA Astrophysics Data System (ADS)

Gustmann, T.; dos Santos, J. M.; Gargarella, P.; Kühn, U.; Van Humbeeck, J.; Pauly, S.

2017-03-01

Two shape-memory alloys with the nominal compositions (in wt.%) Cu-11.85Al-3.2Ni-3Mn and Cu-11.35Al-3.2Ni-3Mn-0.5Zr were prepared by selective laser melting (SLM). The parameters were optimised to identify the process window, in which almost fully dense samples can be obtained. Their microstructures were analysed and correlated with the shape-memory behaviour as well as the mechanical properties. Suction-cast specimens were also produced for comparison. Mainly, β 1' martensite forms in all samples, but 0.5 wt.% of Zr stabilises the Y phase (Cu2AlZr), and its morphology depends on the thermal history and cooling rate. After annealing, the Y phase is primarily found at the grain boundaries hampering grain coarsening. Due to the relative high cooling rates applied here, Zr is mostly dissolved in the martensite in the as-prepared samples and it has a grain-refining effect only up to a critical cooling rate. The Zr-containing samples have increased transformation temperatures, and the Y phase seems to be responsible for the jerky martensite-to-austenite transformation. All the samples are relatively ductile because they mostly fracture in a transgranular manner, exhibiting the typical double yielding. Selective laser melting allows the adjustment of the transformation temperatures and the mechanical properties already during processing without the need of a subsequent heat treatment.

The competition between magnetocrystalline and shape anisotropy on the magnetic and magneto-transport properties of crystallographically aligned CuCr2Se4 thin films

NASA Astrophysics Data System (ADS)

Edelman, I.; Esters, M.; Johnson, D. C.; Yurkin, G.; Tarasov, A.; Rautsky, M.; Volochaev, M.; Lyashchenko, S.; Ivantsov, R.; Petrov, D.; Solovyov, L. A.

2017-12-01

Crystallographically aligned nanocrystalline films of the ferromagnetic spinel CuCr2Se4 were successfully synthesized and their structure and alignment were confirmed by X-ray diffraction and high-resolution transmission electron microscopy. The average size of the crystallites is about 200-250 nm, and their (1 1 1) crystal planes are parallel to the film plane. A good match of the film's electronic structure to that of bulk CuCr2Se4 is confirmed by transverse Kerr effect measurements. Four easy 〈1 1 1〉 axes are present in the films. One of these axes is oriented perpendicular and three others are oriented at an angle of 19.5° relative to the film plane. The magnetic properties of the films are determined by a competition between the out-of-plane magnetocrystalline anisotropy and the in-plane shape anisotropy. Magnetic measurements show that the dominating type of anisotropy switches from shape to magnetocrystalline anisotropy near 160 K, which leads to a switch of the effective easy axis from inside the film plane at room temperature to perpendicular to the film plane as the temperature decreases. At last, a moderately large, negative value of the low-temperature magnetoresistance was observed for the first time in CuCr2Se4 films.

Tunable Porosities and Shapes of Fullerene-Like Spheres

PubMed Central

Dielmann, Fabian; Fleischmann, Matthias; Heindl, Claudia; Peresypkina, Eugenia V; Virovets, Alexander V; Gschwind, Ruth M; Scheer, Manfred

2015-01-01

The formation of reversible switchable nanostructures monitored by solution and solid-state methods is still a challenge in supramolecular chemistry. By a comprehensive solid state and solution study we demonstrate the potential of the fivefold symmetrical building block of pentaphosphaferrocene in combination with CuI halides to switch between spheres of different porosity and shape. With increasing amount of CuX, the structures of the formed supramolecules change from incomplete to complete spherically shaped fullerene-like assemblies possessing an Ih-C80 topology at one side and to a tetrahedral-structured aggregate at the other. In the solid state, the formed nano-sized aggregates reach an outer diameter of 3.14 and 3.56 nm, respectively. This feature is used to reversibly encapsulate and release guest molecules in solution. PMID:25759976

Application of CaCu3Ti4O12 based quadruple perovskites as a promising candidate for optoelectronic devices

NASA Astrophysics Data System (ADS)

Pal, Kamalesh; Jana, Rajkumar; Dey, Arka; Ray, Partha P.; Seikh, Md Motin; Gayen, Arup

2018-05-01

We report the synthesis of nanosized (40-50 nm) CaCu3-xMnxTi4-xMnxO12 (x = 0, 0.5 and 1) quadruple perovskite (QP) semiconductor via a modified combustion method for use as Schottky barrier diode (SBD) at the Al/QP junction. The fabricated SBD is analysed on the basis of thermionic emission theory to observe its quality and some important diode parameters. For insight analysis of charge transport mechanism through metal-semiconductor junction, theory of space charge limited currents is applied and discussed in the light of parameters like carrier concentration, mobility-lifetime product and diffusion length. The Mn-doped exhibit better device performance compared to parent material.

Hydrodynamic description for the pseudorapidity distributions of the charged particles produced in nucleus+nucleus collisions at high energy

NASA Astrophysics Data System (ADS)

Zhang, Haili; Jiang, Zhijin; Li, Qingguang; Jiang, Guanxiang

2014-02-01

By using the revised Landau hydrodynamic model and taking into account the effect of leading particles, we discuss the pseudorapidity distributions of the charged particles produced in high-energy heavy-ion collisions. The leading particles are assumed to have the rapidity distributions with Gaussian forms with the normalization constant being equal to the number of participants, which can be figured out in theory. The results from the revised Landau hydrodynamic model, together with the contributions from leading particles, were found to be consistent with the experimental data obtained by the PHOBOS Collaboration on RHIC (Relativistic Heavy Ion Collider) at BNL (Brookhaven National Laboratory) in different centrality Cu+Cu and Au+Au collisions at high energies.

Effect of samarium in corrosion and microstructure of Al-5Zn-0.5Cu as low driving voltage sacrificial anode

NASA Astrophysics Data System (ADS)

Pratesa, Yudha; Ferdian, Deni; Ramadhan, Fajar Yusya; Maulana, Bramuda

2018-05-01

Sacrificial Anode Low voltage is the latest generation of the sacrificial anode that can prevent the occurrence of Hydrogen Cracking (HIC) due to overprotection. The Al-5n-0.5Cu alloy showed the potential to be developed as the new sacrificial anode. However, the main problem is copper made Al2Cu intermetallic in grain boundary. Samarium is added to modify the shape of the intermetallic to make it finer and make the corrosion uniform. Several characterizations were conducted to analyze the effect of Samarium. Scanning electron microscope (SEM) and Energy dispersive spectroscopy was used to analyzed the microstructure of the alloy. Metallography preparation was prepared for SEM analysis. Corrosion behavior was characterized by cyclic polarization in 3.5% NaCl solution. The results show samarium can change the shape of intermetallic and refine the grains. In addition, samarium makes better pitting resistance and exhibits a tendency for uniform corrosion. It is indicated by the loop reduction (ΔEpit-prot). Current density increased as an effect of samarium addition from 6x10-5 Ampere (Al-5Zn-0.5Cu) to 2.5x10-4 Ampere (Al-5Zn-0.5Cu-0.5Sm). Steel potential protection increased after addition of samarium which is an indication the possibility of Al-Zn-Cu-Sm to be used as low voltage sacrificial anode.

Morphology-controlled electrodeposition of Cu{sub 2}O microcrystalline particle films for application in photocatalysis under sunlight

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

Wu, Guodong; Zhai, Wei; Sun, Fengqiang, E-mail: fqsun@scnu.edu.cn

2012-12-15

Graphical abstract: Display Omitted Highlights: ► PEG was used to electro-deposit Cu{sub 2}O microcrystalline particle films. ► Morphologies of Cu{sub 2}O microcrystals could be controlled by the amount of PEG. ► The films showed regularly varied photocatalytic activities under sunlight. ► The films could be recycled and showed stable activities. -- Abstract: Morphology-controlled Cu{sub 2}O microcrystalline particle films had been successfully electrodeposited on tin-doped indium oxide glass substrates in CuSO{sub 4} solutions containing different amounts of polyethylene glycol (PEG) additives. With an increase of PEG, microcrystals gradually changed from irregular shapes to cubes, octahedrons, and spherical shapes. Sizes increasingly becamemore » smaller with an increase of PEG under the same deposition time. These films had been first used as recyclable photocatalysts and showed excellent and photocatalytic activities in photodegradation of methylene blue (MB) under sunlight. Activities were regularly varied relative to the morphologies of films controlled by the amount of PEG and could be further enhanced by adding a little amount of hydrogen peroxide in the MB solution. The method for controllable preparation of Cu{sub 2}O microcrystals with photocatalytic activities was simple and inexpensive. The as-prepared particle films could also be used in photodegradation of many other pollutants under sunlight.« less

Rapid Photodegradation of Methyl Orange (MO) Assisted with Cu(II) and Tartaric Acid

PubMed Central

Guo, Jing; Chen, Xue; Shi, Ying; Lan, Yeqing; Qin, Chao

2015-01-01

Cu(II) and organic carboxylic acids, existing extensively in soil and aquatic environments, can form complexes that may play an important role in the photodegradation of organic contaminants. In this paper, the catalytic role of Cu(II) in the removal of methyl orange (MO) in the presence of tartaric acid with light was investigated through batch experiments. The results demonstrate that the introduction of Cu(II) could markedly enhance the photodegradation of MO. In addition, high initial concentrations of Cu(II) and tartaric acid benefited the decomposition of MO. The most rapid removal of MO assisted by Cu(II) was achieved at pH 3. The formation of Cu(II)-tartaric acid complexes was assumed to be the key factor, generating hydroxyl radicals (•OH) and other oxidizing free radicals under irradiation through a ligand-to-metal charge-transfer pathway that was responsible for the efficient degradation of MO. Some intermediates in the reaction system were also detected to support this reaction mechanism. PMID:26241043

One-Dimensional Cu2- xSe Nanorods as the Cathode Material for High-Performance Aluminum-Ion Battery.

PubMed

Jiang, Jiali; Li, He; Fu, Tao; Hwang, Bing-Joe; Li, Xue; Zhao, Jinbao

2018-05-30

In this work, nonstoichiometric Cu 2- x Se fabricated by a facile water evaporation process is used as high-performance Al-ion battery cathode materials. Cu 2- x Se electrodes show high reversible capacity and excellent cycling stability, even at a high current density of 200 mA g -1 , the specific charge capacity in the initial cycle is 241 mA h g -1 and maintains 100 mA h g -1 after 100 cycles with a Coulombic efficiency of 96.1%, showing good capacity retention. The prominent kinetics of Cu 2- x Se electrodes is also revealed by the GITT, which is attributed to the ultrahigh electronic conductivity of the Cu 2- x Se material. Most importantly, an extensive research is dedicated to investigating the detailed intercalation and de-intercalation of relatively large chloroaluminate anions into the cubic Cu 2- x Se, which is conducive to better understand the reaction mechanism of the Al/Cu 2- x Se battery.

Isotopically modified nanoparticles for enhanced detection in bioaccumulation studies

USGS Publications Warehouse

Misra, S.K.; Dybowska, A.; Berhanu, D.; Croteau, M.-N.; Luoma, S.N.; Boccaccini, A.R.; Valsami-Jones, E.

2012-01-01

This work presents results on synthesis of isotopically enriched (99% 65Cu) copper oxide nanoparticles and its application in ecotoxicological studies. 65CuO nanoparticles were synthesized as spheres (7 nm) and rods (7 ?? 40 nm). Significant differences were observed between the reactivity and dissolution of spherical and rod shaped nanoparticles. The extreme sensitivity of the stable isotope tracing technique developed in this study allowed determining Cu uptake at exposure concentrations equivalent to background Cu concentrations in freshwater systems (0.2-30 ??g/L). Without a tracer, detection of newly accumulated Cu was impossible, even at exposure concentrations surpassing some of the most contaminated water systems (>1 mg/L). ?? 2011 American Chemical Society.

Simulation Study on Jet Formability and Damage Characteristics of a Low-Density Material Liner

PubMed Central

Tang, Wenhui; Ran, Xianwen

2018-01-01

The shaped charge tandem warhead is an effective weapon against the ERA (explosive reactive armor). Whether the pre-warhead can reliably initiate the ERA directly determines the entire performance of the tandem warhead. The existing shaped charge pre-warhead mostly adopts a metal shaped jet, which effectively initiates the ERA, but interferes the main shaped jet. This article, on the other hand, explores the possibility of producing a pre-warhead using a low-density material as the liner. The nonlinear dynamic analysis software Autodyn-2D is used to simulate and compare three kinds of low-density shaped jets, including floatglass, Lucite, and Plexiglas, to the copper shaped jet in the effectiveness of impacting ERA. Based on the integrative criteria (including u-d initiation criterion, explosive reactive degree, explosive pressure, and particle velocity of the panels), it can be determined whether the low-density shaped jet can reliably initiate the sandwich charge. The results show that the three kinds of low-density shaped jets can not only initiate the reaction armor, but are also superior to the existing copper shaped jet in ductility, jet tip velocity, jet tip diameter, and the mass; namely, it is feasible to use the low-density material shaped jet to destroy the ERA. PMID:29300351

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.

TCNQ molecular semiconductor of the Cu(II)TAAB macrocycle: Optical and electrical properties.

PubMed

Sánchez Vergara, M E; Salcedo, R; Molina, Bertha; Carrera-Téllez, R; Álvarez-Bada, J R; Hernández-García, A; Gómez-Vidales, V

2018-07-05

The present study reports the doping of a semiconducting molecular material through the formation of hydrogen bonds between the macrocycle Cu(II)(TAAB) and the electronic acceptor TCNQ. According to density functional theory (DFT) calculations and electron paramagnetic resonance (EPR) analysis, the doped compound has the shape of a distorted square pyramid, with four nitrogen atoms in the equatorial position and the apical oxygen atom from the water ligands. These water molecules can generate strong hydrogen bonds with TCNQ and the TAAB metallic complex. Thin films of copper molecular material were obtained through high vacuum evaporation and were structurally characterized by IR spectroscopy, EPR and scanning electron microscopy (SEM). Additionally, the absorption coefficient (α) and photon energy (hν) were calculated from UV-vis spectroscopy and used to determine the optical activation energy in each film, from which its semiconducting behavior was established. An important aspect to consider is that the presence of hydrogen bonds is essential to establish the semiconducting nature of these species; this chemical behavior, as well as the resulting electronic mobility, have been studied by DFT theoretical calculations, which reinforce the experimental conclusion of a relationship between Cu(II)TAAB and TCNQ moieties generated by a weak bond. Finally, I-V characteristics have been obtained from a glass/ITO/doped molecular semiconductor/Ag device using Ag and ITO electrodes. Results for the copper-based device show that, at low voltages, the conduction process is of an ohmic nature while, at higher voltages, space-charge-limited current (SCLC) is found. It is highly probable that the doping effect in TCNQ favors electronic transport due to the formation of conduction channels caused by dopant-favored anisotropy. Copyright © 2018 Elsevier B.V. All rights reserved.

Chemical synthesis of flower-like hybrid Cu(OH)2/CuO electrode: Application of polyvinyl alcohol and triton X-100 to enhance supercapacitor performance.

PubMed

Shinde, S K; Fulari, V J; Kim, D-Y; Maile, N C; Koli, R R; Dhaygude, H D; Ghodake, G S

2017-08-01

In this research article, we report hybrid nanomaterials of copper hydroxide/copper oxide (Cu(OH) 2 /CuO). A thin films were prepared by using a facile and cost-effective successive ionic layer adsorption and reaction (SILAR) method. As-synthesized and hybrid Cu(OH) 2 /CuO with two different surfactants polyvinyl alcohol (PVA) and triton-X 100 (TRX-100) was prepared having distinct morphological, structural, and supercapacitor properties. The surface of the thin film samples were examined by scanning electron microscopy (SEM). A nanoflower-like morphology of the Cu(OH) 2 /CuO nanostructures arranged vertically was evidenced on the stainless steel substrate. The surface was well covered by nanoflake-like morphology and formed a uniform Cu(OH) 2 /CuO nanostructures after treating with surfactants. X-ray diffraction patterns were used to confirm the hybrid phase of Cu(OH) 2 /CuO materials. The electrochemical properties of the pristine Cu(OH) 2 /CuO, PVA:Cu(OH) 2 /CuO, TRX-100:Cu(OH) 2 /CuO films were observed by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy technique. The electrochemical examination reveals that the Cu(OH) 2 /CuO electrode has excellent specific capacitance, 292, 533, and 443Fg -1 with pristine, PVA, and TRX-100, respectively in 1M Na 2 SO 4 electrolyte solution. The cyclic voltammograms (CV) of Cu(OH) 2 /CuO electrode shows positive role of the PVA and TRX-100 to enhance supercapacitor performance. Copyright © 2017 Elsevier B.V. All rights reserved.

Optimization of photoelectrochemical performance in Pt-modified p-Cu2O/n-Cu2O nanocomposite

NASA Astrophysics Data System (ADS)

Wang, Yichen; Lou, Zirui; Niu, Wenzhe; Ye, Zhizhen; Zhu, Liping

2018-04-01

As it is expected to be one of the most promising materials for utilizing solar energy, Cu2O has attracted considerable attention with respect to the achievement of solar energy conversion. Until now, the photocurrent densities of all planar structure of the Cu2O photocathode have not even come close to the theoretical value of -14.7 mA cm-2 due to the incompatible light absorption and charge carrier diffusion lengths. Here, we have fabricated p-n Cu2O homojunction nanocomposite by multiple steps of electrochemical deposition processing with the optimization of deposition periods. The p-Cu2O/n-Cu2O nanocomposite fabricated by optimized pH (4.9) and deposition time (4 min) exhibited double the photocurrent density of that of the bare p-Cu2O photocathode. And the highest photocurrent density of nanostructured p-n Cu2O nanorod homojunction photocathode with a p-Cu2O blocking layer reached -10.0 mA cm-2 at 0 V versus the reversible hydrogen electrode under simulated AM 1.5G illumination (100 mW cm-2).

Electronic structures of C u 2 O , C u 4 O 3 , and CuO: A joint experimental and theoretical study

DOE PAGES

Wang, Y.; Lany, S.; Ghanbaja, J.; ...

2016-12-14

We present a joint experimental and theoretical study for the electronic structures of copper oxides including Cu 2O, CuO, and the metastable mixed-valence oxide Cu 4O 3. The optical band gap is determined by experimental optical absorption coefficient, and the electronic structure in valence and conduction bands is probed by photoemission and electron energy loss spectroscopies, respectively. Furthermore, we compare our experimental results with many-body GW calculations utilizing an additional on-site potential for d-orbital energies that facilitates tractable and predictive computations. The side-by-side comparison between the three oxides, including a band insulator (Cu2O) and two Mott/charge-transfer insulators (CuO, Cu 4Omore » 3) leads to a consistent picture for the optical and band-structure properties of the Cu oxides, strongly supporting indirect band gaps of about 1.2 and 0.8 eV in CuO and Cu 4O 3, respectively. This comparison also points towards surface oxidation and reduction effects that can complicate the interpretation of the photoemission spectra.« less

Variation of stresses ahead of the internal cracks in ReNi{sub 5} powders during hydrogen charging and discharging cycles

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

Biner, S.B.

1997-12-31

In this study, the evolution of the stress-states ahead of the penny shaped internal cracks in both spherical and disk shaped ReNi{sub 5} particles where Re denotes the rare earths La, Ce, and Misch-metals during hydrogen charging and discharging cycles were investigated using coupled diffusion/deformation FEM analyses. The results indicate that large tensile stresses, on the order of 20--30% of the modulus of elasticity, develop in the particles. The disk shaped particles, in addition to having faster charging/discharging cycles, may offer better resistance to fracture than the spherical particles.

CuMnOS Nanoflowers with Different Cu+/Cu2+ Ratios for the CO2-to-CH3OH and the CH3OH-to-H2 Redox Reactions

PubMed Central

Chen, Xiaoyun; Abdullah, Hairus; Kuo, Dong-Hau

2017-01-01

A conservative CO2-Methanol (CH3OH) regeneration cycle, to capture and reutilize the greenhouse gas of CO2 by aqueous hydrogenation for industry-useful CH3OH and to convert aqueous CH3OH solution by dehydrogenation for the clean energy of hydrogen (H2), is demonstrated at normal temperature and pressure (NTP) with two kinds of CuMnOS nanoflower catalysts. The [Cu+]-high CuMnOS led to a CH3OH yield of 21.1 mmol·g−1catal.·h−1 in the CuMnOS-CO2-H2O system and the other [Cu+]-low one had a H2 yield of 7.65 mmol·g−1catal.·h−1 in the CuMnOS-CH3OH-H2O system. The successful redox reactions at NTP rely on active lattice oxygen of CuMnOS catalysts and its charge (hole or electron) transfer ability between Cu+ and Cu2+. The CO2-hydrogenated CH3OH in aqueous solution is not only a fuel but also an ideal liquid hydrogen storage system for transportation application. PMID:28117456

CuMnOS Nanoflowers with Different Cu+/Cu2+ Ratios for the CO2-to-CH3OH and the CH3OH-to-H2 Redox Reactions

NASA Astrophysics Data System (ADS)

Chen, Xiaoyun; Abdullah, Hairus; Kuo, Dong-Hau

2017-01-01

A conservative CO2-Methanol (CH3OH) regeneration cycle, to capture and reutilize the greenhouse gas of CO2 by aqueous hydrogenation for industry-useful CH3OH and to convert aqueous CH3OH solution by dehydrogenation for the clean energy of hydrogen (H2), is demonstrated at normal temperature and pressure (NTP) with two kinds of CuMnOS nanoflower catalysts. The [Cu+]-high CuMnOS led to a CH3OH yield of 21.1 mmol·g-1catal.·h-1 in the CuMnOS-CO2-H2O system and the other [Cu+]-low one had a H2 yield of 7.65 mmol·g-1catal.·h-1 in the CuMnOS-CH3OH-H2O system. The successful redox reactions at NTP rely on active lattice oxygen of CuMnOS catalysts and its charge (hole or electron) transfer ability between Cu+ and Cu2+. The CO2-hydrogenated CH3OH in aqueous solution is not only a fuel but also an ideal liquid hydrogen storage system for transportation application.

CuMnOS Nanoflowers with Different Cu+/Cu2+ Ratios for the CO2-to-CH3OH and the CH3OH-to-H2 Redox Reactions.

PubMed

Chen, Xiaoyun; Abdullah, Hairus; Kuo, Dong-Hau

2017-01-24

A conservative CO 2 -Methanol (CH 3 OH) regeneration cycle, to capture and reutilize the greenhouse gas of CO 2 by aqueous hydrogenation for industry-useful CH 3 OH and to convert aqueous CH 3 OH solution by dehydrogenation for the clean energy of hydrogen (H 2 ), is demonstrated at normal temperature and pressure (NTP) with two kinds of CuMnOS nanoflower catalysts. The [Cu + ]-high CuMnOS led to a CH 3 OH yield of 21.1 mmol·g -1 catal.·h -1 in the CuMnOS-CO 2 -H 2 O system and the other [Cu + ]-low one had a H 2 yield of 7.65 mmol·g -1 catal.·h -1 in the CuMnOS-CH 3 OH-H 2 O system. The successful redox reactions at NTP rely on active lattice oxygen of CuMnOS catalysts and its charge (hole or electron) transfer ability between Cu + and Cu 2+ . The CO 2 -hydrogenated CH 3 OH in aqueous solution is not only a fuel but also an ideal liquid hydrogen storage system for transportation application.

In situ measurements and radar observations of a severe storm - Electricity, kinematics, and precipitation

NASA Technical Reports Server (NTRS)

Byrne, G. J.; Few, A. A.; Stewart, M. F.; Conrad, A. C.; Torczon, R. L.

1987-01-01

Electric field measurements made inside a multicell severe storm in Oklahoma in 1983 with a balloon-borne instrument are presented. The properties of the electric charge regions, such as altitude, thickness, and charge concentrations, are studied. These measurements are analzyed with meteorological measurements of temperature and humidity, and balloon tracking and radar observations. The relation between the electric charge structure and the precipitation and kinematic features of the storm is examined. The data reveal that the cell exhibits a bipolar charge structure with negative charge below positive charge. The average charge concentrations of the two regions are estimated as -1.2 and 0.15 nC/cu m, respectively; the upper positive charge is about 6 km in vertical extent, and the lower negative charge is less than 1 km in vertical extent.

Charge Order and Superconductivity in Underdoped YBa2 Cu3 O7 -δ under Pressure

NASA Astrophysics Data System (ADS)

Putzke, Carsten; Ayres, Jake; Buhot, Jonathan; Licciardello, Salvatore; Hussey, Nigel E.; Friedemann, Sven; Carrington, Antony

2018-03-01

In underdoped cuprates, an incommensurate charge density wave (CDW) order is known to coexist with superconductivity. A dip in Tc at the hole doping level where the CDW is strongest (np≃0.12 ) suggests that CDW order may suppress superconductivity. We investigate the interplay of charge order with superconductivity in underdoped YBa2 Cu3 O7 -δ by measuring the temperature dependence of the Hall coefficient RH(T ) at high magnetic field and at high hydrostatic pressure. We find that, although pressure increases Tc by up to 10 K at 2.6 GPa, it has very little effect on RH(T ). This suggests that pressure, at these levels, only weakly affects the CDW and that the increase in Tc with pressure cannot be attributed to a suppression of the CDW. We argue, therefore, that the dip in Tc at np≃0.12 at ambient pressure is probably not caused by the CDW formation.

Energy transfer through a multi-layer liner for shaped charges

DOEpatents

Skolnick, Saul; Goodman, Albert

1985-01-01

This invention relates to the determination of parameters for selecting materials for use as liners in shaped charges to transfer the greatest amount of energy to the explosive jet. Multi-layer liners constructed of metal in shaped charges for oil well perforators or other applications are selected in accordance with the invention to maximize the penetrating effect of the explosive jet by reference to four parameters: (1) Adjusting the explosive charge to liner mass ratio to achieve a balance between the amount of explosive used in a shaped charge and the areal density of the liner material; (2) Adjusting the ductility of each layer of a multi-layer liner to enhance the formation of a longer energy jet; (3) Buffering the intermediate layers of a multi-layer liner by varying the properties of each layer, e.g., composition, thickness, ductility, acoustic impedance and areal density, to protect the final inside layer of high density material from shattering upon impact of the explosive force and, instead, flow smoothly into a jet; and (4) Adjusting the impedance of the layers in a liner to enhance the transmission and reduce the reflection of explosive energy across the interface between layers.

Effect of different Zr contents on properties and microstructure of Cu-Cr-Zr alloys

NASA Astrophysics Data System (ADS)

Jinshui, Chen; Bin, Yang; Junfeng, Wang; Xiangpeng, Xiao; Huiming, Chen; Hang, Wang

2018-02-01

The crystallography and morphology of precipitate particles of Cu-Cr-Zr alloys with varying Zr contents were studied by transmission electron microscopy (TEM) after solution treatments at 950 °C for 1 h and aging treatments at 500 °C for different times ranged from 0.5 h to 24 h. The microhardness and electrical conductivity of Cu-Cr-Zr alloys after various aging process were tested. The results show that the microhardness and electrical conductivity rapidly increased at first, then the microhardness decreased slowly after reaching the peak, while the conductivity continues to increase. Nano-scaled precipitates exhibit two kinds of morphology (coffee bean and ellipse shaped). With increasing Zr content, the Zr-containing precipitation sequence of Cu-Cr-Zr alloys at peak-ageing is Heusler CrCu2Zr → Cu5Zr → Cu4Zr. The Heusler CrCu2Zr phase decomposed into fine and homogeneous Cr and Cu4Zr, resulting in improved alloy properties.

Effect of Na presence during CuInSe{sub 2} growth on stacking fault annihilation and electronic properties

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

Stange, H., E-mail: helena.stange@helmholtz-berlin.de; Brunken, S.; Hempel, H.

While presence of Na is essential for the performance of high-efficiency Cu(In,Ga)Se{sub 2} thin film solar cells, the reasons why addition of Na by post-deposition treatment is superior to pre-deposition Na supply—particularly at low growth temperatures—are not yet fully understood. Here, we show by X-ray diffraction and electron microscopy that Na impedes annihilation of stacking faults during the Cu-poor/Cu-rich transition of low temperature 3-stage co-evaporation and prevents Cu homogeneity on a microscopic level. Lower charge carrier mobilities are found by optical pump terahertz probe spectroscopy for samples with remaining high stacking fault density, indicating a detrimental effect on electronic propertiesmore » if Na is present during growth.« less

Improved performance of CdSe/CdS co-sensitized solar cells adopting efficient CuS counter electrode modified by PbS film using SILAR method

NASA Astrophysics Data System (ADS)

Zhang, Xiaolong; Lin, Yu; Wu, Jihuai; Fang, Biaopeng; Zeng, Jiali

2018-04-01

In this paper, CuS film was deposited onto fluorine-doped tin oxide (FTO) substrate using a facile chemical bath deposition method, and then modified by PbS using simple successive ionic layer absorption and reaction (SILAR) method with different cycles. These CuS/PbS films were utilized as counter electrodes (CEs) for CdSe/CdS co-sensitized solar cells. Field-emission scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer was used to characterize the CuS/PbS films. The results show that CuS/PbS (10 cycles) CE exhibits an improved power conversion efficiency of 5.54% under the illumination of one sun (100 mW cm-2), which is higher than the CuS/PbS (0 cycles), CuS/PbS (5 cycles), and CuS/PbS (15 cycles) CEs. This enhancement is mainly attributed to good catalytic activity and lower charge-transfer and series resistances, which have been proved by electrochemical impedance spectroscopy, and Tafel polarization measurements.

First-principles study of native defects in bulk Sm2CuO4 and its (001) surface structure

NASA Astrophysics Data System (ADS)

Zheng, Fubao; Zhang, Qinfang; Meng, Qiangqiang; Wang, Baolin; Song, Fengqi; Yunoki, Seiji; Wang, Guanghou

2018-04-01

Using the first-principles calculations based on the density functional theory, we have studied the bulk defect formation and surface structures of Sm2CuO4. To ensure the accuracy of calculations, the spin order of Cu atoms is rechecked and it is the well-known nearest-neighbor antiferromagnetic ground state, which can be attributed to the hole-mediated superexchange through the strong pdσ hybridization interaction between Cu dx2-y2 electron and the neighboring oxygen px (or py) electron. Under each present experimental condition, the Sm vacancy has a very high formation energy and is unlikely to be stable. The Cu vacancy is a shallow acceptor, which is preferred under O-rich conditions, whereas the O vacancy is a donor and energetically favorable under O-poor conditions. To construct its (001) surface structure, CuOO, CuO, and Cu terminated surfaces are found to be most favorable under different experimental conditions. The stable surface structures are always accompanied by significant surface atomic reconstructions and electron charge redistribution, which are intimately correlated to each other.

Porous HKUST-1 derived CuO/Cu2O shell wrapped Cu(OH)2 derived CuO/Cu2O core nanowire arrays for electrochemical nonenzymatic glucose sensors with ultrahigh sensitivity

NASA Astrophysics Data System (ADS)

Yu, Cuiping; Cui, Jiewu; Wang, Yan; Zheng, Hongmei; Zhang, Jianfang; Shu, Xia; Liu, Jiaqin; Zhang, Yong; Wu, Yucheng

2018-05-01

Self-supported CuO/Cu2O@CuO/Cu2O core-shell nanowire arrays (NWAs) are successfully fabricated by a simple and efficient method in this paper. Anodized Cu(OH)2 NWAs could in-situ convert to HKUST-1 at room temperature easily. Cu(OH)2 NWAs cores and HKUST-1 shells transform into CuO/Cu2O simultaneously after calcinations and form CuO/Cu2O@CuO/Cu2O core-shell NWAs. This smart configuration of the core-shell structure not only avoids the agglomeration of the traditional MOF-derived materials in particle-shape, but also facilitates the ion diffusion and increases the active sites. This novel structure is employed as substrate to construct nonenzymatic glucose sensors. The results indicate that glucose sensor based on CuO/Cu2O@CuO/Cu2O core-shell NWAs presents ultrahigh sensitivity (10,090 μA mM-1 cm-2), low detection limit (0.48 μM) and wide linear range (0.99-1,330 μM). In addition, it also shows excellent anti-interference ability toward uric acid, ascorbic acid and L-Cysteine co-existing with glucose, good reproducibility and superior ability of real sample analysis.

Open apex shaped charge-type explosive device having special disc means with slide surface thereon to influence movement of open apex shaped charge liner during collapse of same during detonation

DOEpatents

Murphy, Michael J.

1993-01-01

An open apex shape charge explosive device is disclosed having an inner liner defining a truncated cone, an explosive charge surrounding the truncated inner liner, a primer charge, and a disc located between the inner liner and the primer charge for directing the detonation of the primer charge around the end edge of the disc means to the explosive materials surrounding the inner liner. The disc comprises a material having one or more of: a higher compressive strength, a higher hardness, and/or a higher density than the material comprising the inner liner, thereby enabling the disc to resist deformation until the liner collapses. The disc has a slide surface thereon on which the end edge of the inner liner slides inwardly toward the vertical axis of the device during detonation of the main explosive surrounding the inner liner, to thereby facilitate the inward collapse of the inner liner. In a preferred embodiment, the geometry of the slide surface is adjusted to further control the collapse or .beta. angle of the inner liner.

Open apex shaped charge-type explosive device having special disc means with slide surface thereon to influence movement of open apex shaped charge liner during collapse of same during detonation

DOEpatents

Murphy, M.J.

1993-10-12

An open apex shape charge explosive device is disclosed having an inner liner defining a truncated cone, an explosive charge surrounding the truncated inner liner, a primer charge, and a disc located between the inner liner and the primer charge for directing the detonation of the primer charge around the end edge of the disc means to the explosive materials surrounding the inner liner. The disc comprises a material having one or more of: a higher compressive strength, a higher hardness, and/or a higher density than the material comprising the inner liner, thereby enabling the disc to resist deformation until the liner collapses. The disc has a slide surface thereon on which the end edge of the inner liner slides inwardly toward the vertical axis of the device during detonation of the main explosive surrounding the inner liner, to thereby facilitate the inward collapse of the inner liner. In a preferred embodiment, the geometry of the slide surface is adjusted to further control the collapse or [beta] angle of the inner liner. 12 figures.

Increasing light coupling in a photovoltaic film by tuning nanoparticle shape with substrate surface energy

NASA Astrophysics Data System (ADS)

Kataria, Devika; Krishnamoorthy, Kothandam; Iyer, S. Sundar Kumar

2017-08-01

Tuning metal nanoparticle (MNP) contact angle on the surface it is formed can help maximise the useful optical coupling in photovoltaic films by localized surface plasmon (LSP) resonance—opening up the possibility of building improved photovoltaic cells. In this work experimental demonstration of optical absorption increase in copper phthalocyanine (CuPc) films by tuning silver MNP shape by changing its contact angles with substrate has been reported. Thin films of poly3,4 ethylenedioxythiophene: sodium dodecycl sulphate (PEDOT:SDS) with different surface energies were formed on indium tin oxide (ITO) coated glass by electro-deposition. Silver MNPs thermally evaporated directly on ozonised ITO as well as on the PEDOT:SDS films showed contact angles ranging from 60° to 125°. The CuPc layer was deposited on top of the MNPs. For the samples studied, best optical absorption in the CuPc layer was for a contact angle of 110°.

Commensurate antiferromagnetic excitations as a signature of the pseudogap in the tetragonal high-T c cuprate HgBa 2CuO 4+δ

DOE PAGES

Chan, M. K.; Dorow, C. J.; Mangin-Thro, L.; ...

2016-03-04

We report that antiferromagnetic correlations have been argued to be the cause of the d-wave superconductivity and the pseudogap phenomena exhibited by the cuprates. Although the antiferromagnetic response in the pseudogap state has been reported for a number of compounds, there exists no information for structurally simple HgBa 2CuO 4+δ. We report neutron-scattering results for HgBa 2CuO 4+δ (superconducting transition temperature T c≈71 K, pseudogap temperature T*≈305 K) that demonstrate the absence of the two most prominent features of the magnetic excitation spectrum of the cuprates: the X-shaped ‘hourglass’ response and the resonance mode in the superconducting state. Instead, themore » response is Y-shaped, gapped and significantly enhanced below T*, and hence a prominent signature of the pseudogap state.« less

Charge transfer and symmetry reduction at the CuPc/Ag(110) interface studied by photoemission tomography

NASA Astrophysics Data System (ADS)

Schönauer, K.; Weiss, S.; Feyer, V.; Lüftner, D.; Stadtmüller, B.; Schwarz, D.; Sueyoshi, T.; Kumpf, C.; Puschnig, P.; Ramsey, M. G.; Tautz, F. S.; Soubatch, S.

2016-11-01

On the Ag(110) surface copper phthalocyanine (CuPc) orders in two structurally similar superstructures, as revealed by low-energy electron diffraction. Scanning tunneling microscopy (STM) shows that in both superstructures the molecular planes are oriented parallel to the surface and the long molecular axes, defined as diagonals of the square molecule, are rotated by ≃±32∘ away from the high-symmetry directions [1 1 ¯0 ] and [001] of the silver surface. Similarly to many other adsorbed metal phthalocyanines, the CuPc molecules on Ag(110) appear in STM as crosslike features with twofold symmetry. Photoemission tomography based on angle-resolved photoemission spectroscopy reveals a charge transfer from the substrate into the molecule. A symmetry analysis of experimental and theoretical constant binding energy maps of the photoemission intensity in the kx,ky -plane points to a preferential occupation of one of the two initially degenerate lowest unoccupied molecular orbitals (LUMOs) of eg symmetry. The occupied eg orbital is rotated by 32∘ against the [001] direction of the substrate. The lifting of the degeneracy of the LUMOs and the related reduction of the symmetry of the adsorbed CuPc molecule are attributed to an anisotropy in the chemical reactivity of the Ag(110) surface.

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

Xing, Yingjie, E-mail: xingyj@pku.edu.cn; Li, Shuai; Wang, Guiwei

The donor/acceptor heterojunction plays an important role in organic solar cells. An investigation of band bending in the donor/acceptor heterojunction is helpful in analysis of the charge transport behavior and for the improvement of the device performance. In this work, we report an approach for detection of band bending in a donor/acceptor heterojunction that has been prepared on a small and sharp tungsten tip. In situ field emission measurements are performed after the deposition process, and a linear Fowler-Nordheim plot is obtained from the fresh organic film surface. The thickness-dependent work function is then measured in the layer-by-layer deposited heterojunction.more » Several different types of heterojunction (zinc phthalocyanine (ZnPc)/C60, copper phthalocyanine (CuPc)/3,4,9,10-perylenetetracarboxylic bisbenzimidazole, and CuPc/C60) are fabricated and analyzed. The different charge transfer directions in the heterojunctions are distinguished by field emission measurements. The calculation method used to determine the band bending is then discussed in detail. A triple layer heterojunction (C60/ZnPc/CuPc) is also analyzed using this method. A small amount of band bending is measured in the outer CuPc layer. This method provides an independent reference method for determination of the band bending in an organic heterojunction that will complement photoemission spectroscopy and current-voltage measurement methods.« less

Efficient Carbon-Based CsPbBr3 Inorganic Perovskite Solar Cells by Using Cu-Phthalocyanine as Hole Transport Material

NASA Astrophysics Data System (ADS)

Liu, Zhiyong; Sun, Bo; Liu, Xingyue; Han, Jinghui; Ye, Haibo; Shi, Tielin; Tang, Zirong; Liao, Guanglan

2018-06-01

Metal halide perovskite solar cells (PSCs) have attracted extensive research interest for next-generation solution-processed photovoltaic devices because of their high solar-to-electric power conversion efficiency (PCE) and low fabrication cost. Although the world's best PSC successfully achieves a considerable PCE of over 20% within a very limited timeframe after intensive efforts, the stability, high cost, and up-scaling of PSCs still remain issues. Recently, inorganic perovskite material, CsPbBr3, is emerging as a promising photo-sensitizer with excellent durability and thermal stability, but the efficiency is still embarrassing. In this work, we intend to address these issues by exploiting CsPbBr3 as light absorber, accompanied by using Cu-phthalocyanine (CuPc) as hole transport material (HTM) and carbon as counter electrode. The optimal device acquires a decent PCE of 6.21%, over 60% higher than those of the HTM-free devices. The systematic characterization and analysis reveal a more effective charge transfer process and a suppressed charge recombination in PSCs after introducing CuPc as hole transfer layer. More importantly, our devices exhibit an outstanding durability and a promising thermal stability, making it rather meaningful in future fabrication and application of PSCs.[Figure not available: see fulltext.

Molecular adsorption and multilayer growth of pentacene on Cu(100):Layer structure and energetics

NASA Astrophysics Data System (ADS)

Satta, M.; Iacobucci, S.; Larciprete, R.

2007-04-01

We used the partial charge tight binding method to perform a full structure optimization to determine equilibrium adsorption geometries, energetics, and local charge redistribution for molecular adsorption and multilayer growth of pentacene on Cu(100). We found that single molecule adsorption induces only a localized perturbation of the metal lattice which is limited to the topmost layers. At saturation coverage four stable topologies (Brick, Wave, Lines and Zigzag) were identified, all based on pentacene molecules lying flat on the metal surface and with the central phenyl ring adsorbed in top position. Only two (Brick and Wave) out of the four structures are able to sustain multilayer growth. In both cases, assembling beyond the second layer corresponds to a transition from the flat to a tilted geometry, in which the pentacenes adopt a face-plane-face arrangement leading to a herringbone structure. The energetics of the different structure are reported as a function of the molecular number density of the pentacene multilayer by calculating cohesive, stress, and electrostatic energies. The dominant tilted molecular orientation in the pentacene multilayer is in agreement with the average tilt angle of 65° between the molecular plane and the Cu surface derived by near edge x-ray absorption spectroscopy of a four monolayer pentacene film deposited on Cu(100).

Room-temperature preparation of trisilver-copper-sulfide/polymer based heterojunction thin film for solar cell application

NASA Astrophysics Data System (ADS)

Lei, Yan; Yang, Xiaogang; Gu, Longyan; Jia, Huimin; Ge, Suxiang; Xiao, Pin; Fan, Xiaoli; Zheng, Zhi

2015-04-01

Solar cells devices based on inorganic/polymer heterojunction can be a possible solution to harvest solar energy and convert to electric energy with high efficiency through a cost-effective fabrication. The solution-process method can be easily used to produce large area devices. Moreover, due to the intrinsic different charge separation, diffusion or recombination in various semiconductors, the interfaces between each component may strongly influence the inorganic/polymer heterojunction performance. Here we prepared a n-type Ag3CuS2 (Eg = 1.25 eV) nanostructured film through a room-temperature element reaction process, which was confirmed as direct bandgap semiconductor through density function theory simulation. This Ag3CuS2 film was spin-coated with an organic semiconducting poly(3-hexythiophene) (P3HT) or polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) film, which formed an inorganic/polymer heterojunction. After constructing it to a solar cell device, the power conversion efficiencies of 0.79% and 0.31% were achieved with simulated solar illumination on Ag3CuS2/P3HT and Ag3CuS2/PTB7, respectively. A possible mechanism was discussed and we showed the charge separation at interface of inorganic and polymer semiconductors played an important role.

Organic heterojunctions: Contact-induced molecular reorientation, interface states, and charge re-distribution

PubMed Central

Opitz, Andreas; Wilke, Andreas; Amsalem, Patrick; Oehzelt, Martin; Blum, Ralf-Peter; Rabe, Jürgen P.; Mizokuro, Toshiko; Hörmann, Ulrich; Hansson, Rickard; Moons, Ellen; Koch, Norbert

2016-01-01

We reveal the rather complex interplay of contact-induced re-orientation and interfacial electronic structure – in the presence of Fermi-level pinning – at prototypical molecular heterojunctions comprising copper phthalocyanine (H16CuPc) and its perfluorinated analogue (F16CuPc), by employing ultraviolet photoelectron and X-ray absorption spectroscopy. For both layer sequences, we find that Fermi-level (EF) pinning of the first layer on the conductive polymer substrate modifies the work function encountered by the second layer such that it also becomes EF-pinned, however, at the interface towards the first molecular layer. This results in a charge transfer accompanied by a sheet charge density at the organic/organic interface. While molecules in the bulk of the films exhibit upright orientation, contact formation at the heterojunction results in an interfacial bilayer with lying and co-facial orientation. This interfacial layer is not EF-pinned, but provides for an additional density of states at the interface that is not present in the bulk. With reliable knowledge of the organic heterojunction’s electronic structure we can explain the poor performance of these in photovoltaic cells as well as their valuable function as charge generation layer in electronic devices. PMID:26887445

Fabrication of bimetallic Cu/Au nanotubes and their sensitive, selective, reproducible and reusable electrochemical sensing of glucose

NASA Astrophysics Data System (ADS)

Tee, Si Yin; Ye, Enyi; Pan, Pei Hua; Lee, Coryl Jing Jun; Hui, Hui Kim; Zhang, Shuang-Yuan; Koh, Leng Duei; Dong, Zhili; Han, Ming-Yong

2015-06-01

Herein, we report a facile two-step approach to produce gold-incorporated copper (Cu/Au) nanostructures through controlled disproportionation of the Cu+-oleylamine complex at 220 °C to form copper nanowires and the subsequent reaction with Au3+ at different temperatures of 140, 220 and 300 °C. In comparison with copper nanowires, these bimetallic Cu/Au nanostructures exhibit their synergistic effect to greatly enhance glucose oxidation. Among them, the shape-controlled Cu/Au nanotubes prepared at 140 °C show the highest electrocatalytic activity for non-enzymatic glucose sensing in alkaline solution. In addition to high sensitivity and fast response, the Cu/Au nanotubes possess high selectivity against interferences from other potential interfering species and excellent reproducibility with long-term stability. By introducing gold into copper nanostructures at a low level of 3, 1 and 0.1 mol% relative to the initial copper precursor, a significant electrocatalytic enhancement of the resulting bimetallic Cu/Au nanostructures starts to occur at 1 mol%. Overall, the present fabrication of stable Cu/Au nanostructures offers a promising low-cost platform for sensitive, selective, reproducible and reusable electrochemical sensing of glucose.Herein, we report a facile two-step approach to produce gold-incorporated copper (Cu/Au) nanostructures through controlled disproportionation of the Cu+-oleylamine complex at 220 °C to form copper nanowires and the subsequent reaction with Au3+ at different temperatures of 140, 220 and 300 °C. In comparison with copper nanowires, these bimetallic Cu/Au nanostructures exhibit their synergistic effect to greatly enhance glucose oxidation. Among them, the shape-controlled Cu/Au nanotubes prepared at 140 °C show the highest electrocatalytic activity for non-enzymatic glucose sensing in alkaline solution. In addition to high sensitivity and fast response, the Cu/Au nanotubes possess high selectivity against interferences from other potential interfering species and excellent reproducibility with long-term stability. By introducing gold into copper nanostructures at a low level of 3, 1 and 0.1 mol% relative to the initial copper precursor, a significant electrocatalytic enhancement of the resulting bimetallic Cu/Au nanostructures starts to occur at 1 mol%. Overall, the present fabrication of stable Cu/Au nanostructures offers a promising low-cost platform for sensitive, selective, reproducible and reusable electrochemical sensing of glucose. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02399h

Atomistic Simulations of Grain Boundary Pinning in CuFe Alloys

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

Zepeda-Ruiz, L A; Gilmer, G H; Sadigh, B

2005-05-22

The authors apply a hybrid Monte Carlo-molecular dynamics code to the study of grain boundary motion upon annealing of pure Cu and Cu with low concentrations of Fe. The hybrid simulations account for segregation and precipitation of the low solubility Fe, together with curvature driven grain boundary motion. Grain boundaries in two different systems, a {Sigma}7+U-shaped half-loop grain and a nanocrystalline sample, were found to be pinned in the presence of Fe concentrations exceeding 3%.

Gravitational effects on the weld pool shape and microstructural evolution during gas tungsten arc and laser beam welding of 304 stainless steel and Al-4 wt% Cu alloy.

PubMed

Kang, Namhyun; Singh, Jogender; Kulkarni, Anil K

2004-11-01

Effects of gravitational acceleration were investigated on the weld pool shape and microstructural evolution for 304 stainless steel and Al-4wt% Cu alloy. Effects of welding heat source were investigated by using laser beam welding (LBW) and gas tungsten arc welding (GTAW). As the gravitational level was increased from low gravity (LG approximately 1.2 g) to high gravity (HG approximately 1.8 g) using a NASA KC-135 aircraft, the weld pool shape for 304 stainless steel was influenced considerably during GTAW. However, insignificant change in the microstructure and solute distribution was observed at gravitational levels between LG and HG. The GTAW on Al-4 wt% Cu alloy was used to investigate the effect of gravitational orientation on the weld solidification behavior. Gravitational orientation was manipulated by varying the welding direction with respect to gravity vector; that is, by welding upward opposing gravity ( ||-U) and downward with gravity ( ||-D) on a vertical weld piece and welding perpendicular to gravity (perpendicular) on a horizontal weld piece. Under the same welding conditions, a larger primary dendrite spacing in the ||-U weld was observed near the weld pool surface and the fusion boundary than in the case of perpendicular or ||-D welds. The ||-D weld exhibited different solidification morphology and abnormal S shape of solidification rate curve during its growth. For 304 stainless steel GTAW, significant effects of gravitational orientation were observed on the weld pool shape that was associated with weld surface morphology and convection flow. However, the weld pool shape for LBW was mostly constant with respect to the gravitational orientation.

Influence of Co and W powders on viscosity of composite solders during soldering of specially shaped diamond-abrasive tools

NASA Astrophysics Data System (ADS)

Sokolov, E. G.; Aref’eva, S. A.; Svistun, L. I.

2018-03-01

The influence of Co and W powders on the structure and the viscosity of composite solders Sn-Cu-Co-W used for the manufacture of the specially shaped diamond tools has been studied. The solders were obtained by mixing the metallic powders with an organic binder. The mixtures with and without diamonds were applied to steel rollers and shaped substrates. The sintering was carried out in a vacuum at 820 ° C with time-exposure of 40 minutes. The influence of Co and W powders on the viscosity solders was evaluated on the basis of the study of structures and according to the results of sintering specially shaped diamond tools. It was found that to provide the necessary viscosity and to obtain the uniform diamond-containing layers on the complex shaped surfaces, Sn-Cu-Co-W solder should contain 27–35 vol % of solid phase. This is achieved with a total solder content of 24–32 wt % of cobalt powder and 7 wt % of tungsten powder.

2007 Insensitive Munitions and Energetic Materials Technology Symposium

DTIC Science & Technology

2007-10-18

Flat end rod Round end rod Flat cookie -cutter Spherical fragment Simple shaped charge jet Real shaped charge jet Thin plate Constant Temperature...while the press is running • No one allowed in the facility before dough -up • Maximum pressures, torque and temperatures set. • First warnings and

Double-Sided Transparent TiO2 Nanotube/ITO Electrodes for Efficient CdS/CuInS2 Quantum Dot-Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Chen, Chong; Ling, Lanyu; Li, Fumin

2017-01-01

In this paper, to improve the power conversion efficiencies (PCEs) of quantum dot-sensitized solar cells (QDSSCs) based on CdS-sensitized TiO2 nanotube (TNT) electrodes, two methods are employed on the basis of our previous work. First, by replacing the traditional single-sided working electrodes, double-sided transparent TNT/ITO (DTTO) electrodes are prepared to increase the loading amount of quantum dots (QDs) on the working electrodes. Second, to increase the light absorption of the CdS-sensitized DTTO electrodes and improve the efficiency of charge separation in CdS-sensitized QDSSCs, copper indium disulfide (CuInS2) is selected to cosensitize the DTTO electrodes with CdS, which has a complementary property of light absorption with CdS. The PCEs of QDSSCs based on these prepared QD-sensitized DTTO electrodes are measured. Our experimental results show that compared to those based on the CdS/DTTO electrodes without CuInS2, the PCEs of the QDSSCs based on CdS/CuInS2-sensitized DTTO electrode are significantly improved, which is mainly attributed to the increased light absorption and reduced charge recombination. Under simulated one-sun illumination, the best PCE of 1.42% is achieved for the QDSSCs based on CdS(10)/CuInS2/DTTO electrode, which is much higher than that (0.56%) of the QDSSCs based on CdS(10)/DTTO electrode.

Synchrotron x-ray scattering study of charge-density-wave order in HgBa2CuO4 +δ

NASA Astrophysics Data System (ADS)

Tabis, W.; Yu, B.; Bialo, I.; Bluschke, M.; Kolodziej, T.; Kozlowski, A.; Blackburn, E.; Sen, K.; Forgan, E. M.; Zimmermann, M. v.; Tang, Y.; Weschke, E.; Vignolle, B.; Hepting, M.; Gretarsson, H.; Sutarto, R.; He, F.; Le Tacon, M.; Barišić, N.; Yu, G.; Greven, M.

2017-10-01

We present a detailed synchrotron x-ray scattering study of the charge-density-wave (CDW) order in simple tetragonal HgBa2CuO4 +δ (Hg1201). Resonant soft x-ray scattering measurements reveal that short-range order appears at a temperature that is distinctly lower than the pseudogap temperature and in excellent agreement with a prior transient reflectivity result. Despite considerable structural differences between Hg1201 and YBa2Cu3O6 +δ , the CDW correlations exhibit similar doping dependencies, and we demonstrate a universal relationship between the CDW wave vector and the size of the reconstructed Fermi pocket observed in quantum oscillation experiments. The CDW correlations in Hg1201 vanish already below optimal doping, once the correlation length is comparable to the CDW modulation period, and they appear to be limited by the disorder potential from unit cells hosting two interstitial oxygen atoms. A complementary hard x-ray diffraction measurement, performed on an underdoped Hg1201 sample in magnetic fields along the crystallographic c axis of up to 16 T, provides information on the form factor of the CDW order. As expected from the single-CuO2-layer structure of Hg1201, the CDW correlations vanish at half-integer values of L and appear to be peaked at integer L . We conclude that the atomic displacements associated with the short-range CDW order are mainly planar, within the CuO2 layers.

Mediator- and co-catalyst-free direct Z-scheme composites of Bi2WO6-Cu3P for solar-water splitting.

PubMed

Rauf, Ali; Ma, Ming; Kim, Sungsoon; Sher Shah, Md Selim Arif; Chung, Chan-Hwa; Park, Jong Hyeok; Yoo, Pil J

2018-02-08

Exploring new single, active photocatalysts for solar-water splitting is highly desirable to expedite current research on solar-chemical energy conversion. In particular, Z-scheme-based composites (ZBCs) have attracted extensive attention due to their unique charge transfer pathway, broader redox range, and stronger redox power compared to conventional heterostructures. In the present report, we have for the first time explored Cu 3 P, a new, single photocatalyst for solar-water splitting applications. Moreover, a novel ZBC system composed of Bi 2 WO 6 -Cu 3 P was designed employing a simple method of ball-milling complexation. The synthesized materials were examined and further investigated through various microscopic, spectroscopic, and surface area characterization methods, which have confirmed the successful hybridization between Bi 2 WO 6 and Cu 3 P and the formation of a ZBC system that shows the ideal position of energy levels for solar-water splitting. Notably, the ZBC composed of Bi 2 WO 6 -Cu 3 P is a mediator- and co-catalyst-free photocatalyst system. The improved photocatalytic efficiency obtained with this system compared to other ZBC systems assisted by mediators and co-catalysts establishes the critical importance of interfacial solid-solid contact and the well-balanced position of energy levels for solar-water splitting. The promising solar-water splitting under optimum composition conditions highlighted the relationship between effective charge separation and composition.

Low-temperature solid-state preparation of ternary CdS/g-C3N4/CuS nanocomposites for enhanced visible-light photocatalytic H2-production activity

NASA Astrophysics Data System (ADS)

Cheng, Feiyue; Yin, Hui; Xiang, Quanjun

2017-01-01

Low-temperature solid-state method were gradually demonstrated as a high efficiency, energy saving and environmental protection strategy to fabricate composite semiconductor materials. CdS-based multiple composite photocatalytic materials have attracted increasing concern owning to the heterostructure constituents with tunable band gaps. In this study, the ternary CdS/g-C3N4/CuS composite photocatalysts were prepared by a facile and novel low-temperature solid-state strategy. The optimal ternary CdS/g-C3N4/CuS composite exhibits a high visible-light photocatalytic H2-production rate of 57.56 μmol h-1 with the corresponding apparent quantum efficiency reaches 16.5% at 420 nm with Na2S/Na2SO3 mixed aqueous solution as sacrificial agent. The ternary CdS/g-C3N4/CuS composites show the enhanced visible-light photocatalytic H2-evolution activity comparing with the binary CdS-based composites or simplex CdS. The enhanced photocatalytic activity is ascribed to the heterojunctions and the synergistic effect of CuS and g-C3N4 in promotion of the charge separation and charge mobility. This work shows that the low-temperature solid-state method is efficient and environmentally benign for the preparation of CdS-based multiple composite photocatalytic materials with enhanced visible-light photocatalytic H2-production activity.

Trap and transfer. two-step hole injection across the Sb2S3/CuSCN interface in solid-state solar cells.

PubMed

Christians, Jeffrey A; Kamat, Prashant V

2013-09-24

In solid-state semiconductor-sensitized solar cells, commonly known as extremely thin absorber (ETA) or solid-state quantum-dot-sensitized solar cells (QDSCs), transfer of photogenerated holes from the absorber species to the p-type hole conductor plays a critical role in the charge separation process. Using Sb2S3 (absorber) and CuSCN (hole conductor), we have constructed ETA solar cells exhibiting a power conversion efficiency of 3.3%. The hole transfer from excited Sb2S3 into CuSCN, which limits the overall power conversion efficiency of these solar cells, is now independently studied using transient absorption spectroscopy. In the Sb2S3 absorber layer, photogenerated holes are rapidly localized on the sulfur atoms of the crystal lattice, forming a sulfide radical (S(-•)) species. This trapped hole is transferred from the Sb2S3 absorber to the CuSCN hole conductor with an exponential time constant of 1680 ps. This process was monitored through the spectroscopic signal seen for the S(-•) species in Sb2S3, providing direct evidence for the hole transfer dynamics in ETA solar cells. Elucidation of the hole transfer mechanism from Sb2S3 to CuSCN represents a significant step toward understanding charge separation in Sb2S3 solar cells and provides insight into the design of new architectures for higher efficiency devices.

Treatment of delocalized electron transfer in periodic and embedded cluster DFT calculations: The case of Cu on ZnO (10(1)0).

PubMed

Hellström, Matti; Spångberg, Daniel; Hermansson, Kersti

2015-12-15

We assess the consequences of the interface model-embedded-cluster or periodic-slab model-on the ability of DFT calculations to describe charge transfer (CT) in a particularly challenging case where periodic-slab calculations indicate a delocalized charge-transfer state. Our example is Cu atom adsorption on ZnO(10(1)0), and in fact the periodic slab calculations indicate three types of CT depending on the adsorption site: full CT, partial CT, and no CT. Interestingly, when full CT occurs in the periodic calculations, the calculated Cu atom adsorption energy depends on the underlying ZnO substrate supercell size, since when the electron enters the ZnO it delocalizes over as many atoms as possible. In the embedded-cluster calculations, the electron transferred to the ZnO delocalizes over the entire cluster region, and as a result the calculated Cu atom adsorption energy does not agree with the value obtained using a large periodic supercell, but instead to the adsorption energy obtained for a periodic supercell of roughly the same size as the embedded cluster. Different density functionals (of GGA and hybrid types) and basis sets (local atom-centered and plane-waves) were assessed, and we show that embedded clusters can be used to model Cu adsorption on ZnO(10(1)0), as long as care is taken to account for the effects of CT. © 2015 Wiley Periodicals, Inc.

Phosphorus-doped silicon nanorod anodes for high power lithium-ion batteries.

PubMed

Yan, Chao; Liu, Qianru; Gao, Jianzhi; Yang, Zhibo; He, Deyan

2017-01-01

Heavy-phosphorus-doped silicon anodes were fabricated on CuO nanorods for application in high power lithium-ion batteries. Since the conductivity of lithiated CuO is significantly better than that of CuO, after the first discharge, the voltage cut-off window was then set to the range covering only the discharge-charge range of Si. Thus, the CuO core was in situ lithiated and acts merely as the electronic conductor in the following cycles. The Si anode presented herein exhibited a capacity of 990 mAh/g at the rate of 9 A/g after 100 cycles. The anode also presented a stable rate performance even at a current density as high as 20 A/g.

μSR investigation of a new diluted magnetic semiconductor Li(Zn,Mn,Cu)As with Mn and Cu codoping at the same Zn sites

NASA Astrophysics Data System (ADS)

Guo, S. L.; Zhao, Y.; Man, H. Y.; Ding, C.; Gong, X.; Zhi, G. X.; Fu, L. C.; Gu, Y. L.; Frandsen, B. A.; Liu, L.; Cheung, S. C.; Munsie, T. J.; Wilson, M. N.; Cai, Y. P.; Luke, G. M.; Uemura, Y. J.; Ning, F. L.

2016-09-01

We report the successful synthesis and characterization of a new type I-II-V bulk form diluted magnetic semiconductor (DMS) Li(Zn,Mn,Cu)As, in which charge and spin doping are decoupled via (Cu,Zn) and (Mn,Zn) substitution at the same Zn sites. Ferromagnetic transition temperature up to  ˜33 K has been observed with a coercive field  ˜40 Oe for the 12.5% doping level. μSR measurements confirmed that the magnetic volume fraction reaches nearly 100% at 2 K, and the mechanism responsible for the ferromagnetic interaction in this system is the same as other bulk form DMSs.

Theoretical studies on the possible sensitizers of DSSC: Nanocomposites of graphene quantum dot hybrid phthalocyanine/tetrabenzoporphyrin/tetrabenzotriazaporphyrins/cis-tetrabenzodiazaporphyrins/tetrabenzomonoazaporphyrins and their Cu-metallated macrocycles

NASA Astrophysics Data System (ADS)

Gao, Feng; Yang, Chuan-Lu; Wang, Mei-Shan; Ma, Xiao-Guang; Liu, Wen-Wang

2018-04-01

The feasibility of nanocomposites of cir-coronene graphene quantum dot (GQD) with phthalocyanine, tetrabenzoporphyrin, tetrabenzotriazaporphyrins, cis-tetrabenzodiazaporphyrins, tetrabenzomonoazaporphyrins and their Cu-metallated macrocycles as a sensitizer of dye-sensitized solar cells (DSSC) are investigated. Based on the first principles density functional theory (DFT), the geometrical structures of the separate GQD and 10 macrocycles, and their hybridized nanocomposites are fully optimized. The energy stabilities of the obtained structures are confirmed by harmonic frequency analysis. The optical absorptions of the optimized structures are calculated with time-dependent DFT. The feasibility of the nanocomposites as the sensitizer of DSSC is examined by the charge spatial separation, the electron transfer, the molecular orbital energy levels of the nanocomposites and the electrolyte, and the conduction band minimum of TiO2 electrode. The results demonstrate that all the nanocomposites have enhanced absorptions in the visible light range, and their molecular orbital energies satisfy the requirement of sensitizers. However, only two of the ten considered nanocomposites demonstrate significantly charge spatial separation. The GQD-Cu-TBP is identified as the most favorable candidate sensitizer of DSSC by the most enhanced in optical absorption, obvious charge spatial separation, suitable LUMO energy levels and driving force for electron transfer, and low recombination rate of electron and hole.

geant4 hadronic cascade models analysis of proton and charged pion transverse momentum spectra from p + Cu and Pb collisions at 3, 8, and 15 GeV/c

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

Abdel-Waged, Khaled; Benha University, Faculty of Science, Physics Department; Felemban, Nuha

2011-07-15

We describe how various hadronic cascade models, which are implemented in the geant4 toolkit, describe proton and charged pion transverse momentum spectra from p + Cu and Pb collisions at 3, 8, and 15 GeV/c, recently measured in the hadron production (HARP) experiment at CERN. The Binary, ultrarelativistic quantum molecular dynamics (UrQMD) and modified FRITIOF (FTF) hadronic cascade models are chosen for investigation. The first two models are based on limited (Binary) and branched (UrQMD) binary scattering between cascade particles which can be either a baryon or meson, in the three-dimensional space of the nucleus, while the latter (FTF) considersmore » collective interactions between nucleons only, on the plane of impact parameter. It is found that the slow (p{sub T}{<=}0.3 GeV/c) proton spectra are quite sensitive to the different treatments of cascade pictures, while the fast (p{sub T}>0.3 GeV/c) proton spectra are not strongly affected by the differences between the FTF and UrQMD models. It is also shown that the UrQMD and FTF combined with Binary (FTFB) models could reproduce both proton and charged pion spectra from p + Cu and Pb collisions at 3, 8, and 15 GeV/c with the same accuracy.« less

Density functional theory calculations on transition metal atoms adsorbed on graphene monolayers

NASA Astrophysics Data System (ADS)

Dimakis, Nicholas; Flor, Fernando Antonio; Salgado, Andres; Adjibi, Kolade; Vargas, Sarah; Saenz, Justin

2017-11-01

Transition metal atom adsorption on graphene monolayers has been elucidated using periodic density functional theory under hybrid and generalized gradient approximation functionals. More specifically, we examined the adsorption of Cu, Fe, Zn, Ru, and Os on graphene monolayers by calculating, among others, the electronic density-of-states spectra of the adatom-graphene system and the overlap populations of the adatom with the nearest adsorbing graphene carbon atoms. These calculations reveal that Cu form primarily covalent bonds with graphene atoms via strong hybridization between the adatom orbitals and the sp band of the graphene substrate, whereas the interaction of the Ru and Os with graphene also contain ionic parts. Although the interaction of Fe with graphene atoms is mostly covalent, some charge transfer to graphene is also observed. The interaction of Zn with graphene is weak. Mulliken population analysis and charge contour maps are used to elucidate charge transfers between the adatom and the substrate. The adsorption strength is correlated with the metal adsorption energy and the height of the metal adatom from the graphene plane for the geometrically optimized adatom-graphene system. Our analysis shows that show that metal adsorption strength follows the adatom trend Ru ≈ Os > Fe > Cu > Zn, as verified by corresponding changes in the adsorption energies. The increased metal-carbon orbital overlap for the Ru relative to Os adatom is attributed to hybridization defects.

The stability of copper oxo species in zeolite frameworks

DOE PAGES

Vilella, Laia; Studt, Felix

2016-03-07

Cu-exchanged zeolites are promising heterogeneous catalysts, as they provide a confined environment to carry out highly selective reactions. Furthermore, the knowledge of how the zeolite framework and the location of Al atoms therein affect the adsorption of copper species is still not well understood. In this work, DFT was used to investigate the adsorption of potential Cu oxo active species suggested in the literature [Cu(η 2-O 2), Cu(µ-O)Cu, and Cu 2O 2] into zeolites with different pore sizes and shapes (AFI, CHA, TON, MOR, and MFI). The calculations revealed that both monomeric and dimeric Cu oxo species bind strongly tomore » the O atoms of the lattice. For the monometallic species similar adsorption energies are obtained with the different zeolite frameworks, whereas an optimum Al–Al distance is required for the dimeric species.« less

Ammonia Vapor-Assisted Synthesis of Cu(OH)2 and CuO Nanostructures: Anionic (Cl-, NO3 -, SO4 2-) Influence on the Product Morphology

NASA Astrophysics Data System (ADS)

Mansournia, Mohammadreza; Arbabi, Akram

2017-01-01

Shape control of inorganic nanostructures generally requires using surfactants or ligands to passivate certain crystallographic planes. This paper describes a novel additive-free synthesis of cupric oxide nanostructures with different morphologies from the aqueous solutions of copper(II) with Cl-, NO3 -, and SO4 2- as counter ions. Through a one-step approach, CuO nanoleaves, nanoparticles and flower-like microspheres were directly synthesized at 80°C upon exposure to ammonia vapor using a cupric solution as a single precursor. Furthermore, during a two-step process, Cu(OH)2 nanofibers and nanorods were prepared under an ammonia atmosphere, then converted to CuO nanostructures with morphology preservation by heat treatment in air. The as-prepared Cu(OH)2 and CuO nanostructures are characterized using x-ray diffraction, scanning electron microscopy and Fourier transformation infrared spectroscopy techniques.

Role of Co3O4 Nanoparticles in Dielectric Properties of Cu0.5Tl0.5Ba2Ca2Cu3O10-δ Superconducting Phase

NASA Astrophysics Data System (ADS)

Imran, M.; Mumtaz, M.; Naveed, M.; Khan, M. Nasir

2018-04-01

Cobalt oxide (Co3O4) nanoparticles and Cu0.5Tl0.5Ba2Ca2Cu3O10-δ (CuTl-1223) superconducting phase were prepared by sol-gel and solid-state reaction methods, respectively. Co3O4 nanoparticles were added in CuTl-1223 superconducting matrix to get (Co3O4)x/CuTl-1223, x = 0-2.0 wt.%, nanoparticles-superconductor composites. The unchanged crystal structure of the host CuTl-1223 superconducting phase (i.e. tetragonal) revealed that Co3O4 nanoparticles were settled at the grain boundaries. Superconducting properties of the CuTl-1223 phase were overall suppressed due to hole-charge carriers interaction at the grain boundaries. The dielectric properties of (Co3O4)x/CuTl-1223 composites were investigated by varying the test frequencies from 40 Hz to 100 MHz and operating temperatures from 77 to 298 K. The values of dielectric properties were found maximal at lower frequencies and started to decrease at higher frequencies. So, the dielectric properties of the CuTl-1223 superconducting phase can be tuned by varying the contents of (Co3O4) nanoparticles, test frequencies as well as operating temperatures.

Band-offsets at BaTiO3/Cu2O heterojunction and enhanced photoelectrochemical response: theory and experiment(Conference Presentation)

NASA Astrophysics Data System (ADS)

Sharma, Dipika; Satsangi, Vibha R.; Dass Kaura, Sahab; Shrivastav, Rohit; Waghmare, Umesh V.

2016-10-01

Band-offsets at BaTiO3/Cu2O heterojunction and enhanced photoelectrochemical response: theory and experiment Dipika Sharmaa, Vibha R. Satsangib, Rohit Shrivastava, Umesh V. Waghmarec, Sahab Dassa aDepartment of Chemistry, Dayalbagh Educational Institute, Agra-282 110 (India) bDepartment of Physics and Computer Sciences, Dayalbagh Educational Institute, Agra-282 110 (India) cTheoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore-560 064 (India) * Phone: +91-9219695960. Fax: +91-562-2801226. E-mail: drsahabdas@gmail.com. Study on photoelectrochemical activity of pristine BaTiO3, Cu2O and BaTiO3/Cu2O heterojunction has been carried out using DFT based band offsets and charge carriers effective mass calculations and their experimental verification. The results of DFT calculations show that BaTiO3 and Cu2O have staggered type band alignment after the heterojunction formation and high mobility of electrons in Cu2O as compared to the electrons in BaTiO3. Staggered type band edges alignment and high mobility of electrons and holes improved the separation of photo-generated charge carriers in BaTiO3/Cu2O heterojunction. To validate the theoretical results experiments were carried out on pristine BaTiO3, Cu2O and BaTiO3/Cu2O heterojunction with varying thickness of Cu2O. All samples were characterized by X- Ray Diffractometer, SEM and UV-Vis spectrometry. Nanostructured thin films of pristine BaTiO3, Cu2O and BaTiO3/Cu2O heterojunction were used as photoelectrode in the photoelectrochemical cell for water splitting reaction. Maximum photocurrent density of 1.44 mA/cm2 at 0.90 V/SCE was exhibited by 442 nm thick BaTiO3/Cu2O heterojunction photoelectrode Increased photocurrent density and enhanced photoconversion efficiency, exhibited by the heterojunction may be attributed to improved conductivity and enhanced separation of the photogenerated carriers at the BaTiO3/Cu2O interface. The experimental results and first-principles calculations compare well, thus suggesting that such calculations have the potential to be used in screening various metal oxide heterojunction before performing the experiments thereby saving precious chemicals, time and energy. Keywords: Photoelectrochemical, Water splitting, heterojunction, Cu2O, BaTiO3 References: [1] Surbhi Choudhary, et al. Nanostructured bilayered thin films in photoelectrochemical water splitting - A review: International Journal of Hydrogen Energy, (2012). [2] Dipika Sharma, Anuradha Verma, V.R. Satsangi, Rohit shrivastav, Sahab Dass Nanostructured SrTiO3 thin films sensitized by Cu2O for Photoelectrochemical Hydrogen Generation. International journal of Hydrogen Energy;42:,4230-4241, 2014.

Axially adjustable magnetic properties in arrays of multilayered Ni/Cu nanowires with variable segment sizes

NASA Astrophysics Data System (ADS)

Shirazi Tehrani, A.; Almasi Kashi, M.; Ramazani, A.; Montazer, A. H.

2016-07-01

Arrays of multilayered Ni/Cu nanowires (NWs) with variable segment sizes were fabricated into anodic aluminum oxide templates using a pulsed electrodeposition method in a single bath for designated potential pulse times. Increasing the pulse time between 0.125 and 2 s in the electrodeposition of Ni enabled the formation of segments with thicknesses ranging from 25 to 280 nm and 10-110 nm in 42 and 65 nm diameter NWs, respectively, leading to disk-shaped, rod-shaped and/or near wire-shaped geometries. Using hysteresis loop measurements at room temperature, the axial and perpendicular magnetic properties were investigated. Regardless of the segment geometry, the axial coercivity and squareness significantly increased with increasing Ni segment thickness, in agreement with a decrease in calculated demagnetizing factors along the NW length. On the contrary, the perpendicular magnetic properties were found to be independent of the pulse times, indicating a competition between the intrawire interactions and the shape demagnetizing field.

In vitro release of cupric ion from intrauterine devices: influence of frame, shape, copper surface area and indomethacin.

PubMed

Zhang, Shuangshuang; Li, Ying; Yu, Panpan; Chen, Tong; Zhou, Weisai; Zhang, Wenli; Liu, Jianping

2015-02-01

The release of cupric ion from copper intrauterine device (Cu-IUD) in human uterus is essential for contraception. However, excessive cupric ion will cause cytotoxic effect. In this paper, we investigated the influence of device characteristics (frame, copper surface area, shape, copper type and indomethacin) on copper release for the efficacy and adverse effects vary with IUD types which may correlate to their different release behaviors. Nine types of Cu-IUDs were selected and incubated in simulated uterine fluid. They were paired for comparison based on the device properties and the release of cupric ion was determined by flame atomic absorption spectrometer for about 160 days. The result showed that there was a burst release during the first month and the release rate tends to slow down and become steady afterwards. In addition, the copper release was mainly influenced by frame, indomethacin and copper type (copper wire and copper sleeve) while the shape variation had little effect on copper release throughout the experiment. Moreover, the influence of copper surface area was only noticeable during the first month. These findings were seldom reported before and may provide some useful information for the design of Cu-IUDs.

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

Xiao, Anguo, E-mail: hixiaoanguo@126.com; Zhou, Shibiao; Zuo, Chenggang

Graphical abstract: CuO nanotube array electrodes prepared by electrodeposition method exhibit an excellent lithium ion storage ability as anode of Li-ion battery. - Highlights: • CuO nanotube arrays are synthesized by an electrodeposition method. • CuO nanotube shows a high-rate performance. • CuO nanotube shows an excellent cycling performance. - Abstract: We report a facile strategy to prepared CuO nanotube arrays directly grown on Cu plate through the electrodeposition method. The as-prepared CuO nanotubes show a quasi-cylinder nanostructure with internal diameters of ca. ∼100 nm, external diameters of ca. ∼120 nm, and average length of ∼3 μm. As an anodemore » for lithium ion batteries, the electrochemical properties of the CuO nanotube arrays are investigated by cyclic voltammetry (CV) and galvanostatic charge/discharge tests. Due to the unique nanotube nanostructure, the as-prepared CuO electrodes exhibit good rate performance (550 mAh g{sup −1} at 0.1 C and 464 mAh g{sup −1} at 1 C) and cycling performance (581 mAh g{sup −1} at 0.1 C and 538 mAh g{sup −1} at 0.5 C)« less

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

Utschig, L. M.; Dalosto, S. D.; Thurnauer, M. C.

Metal ion binding to a surface site on photosynthetic reaction centers (RCs) modulates light-induced electron and proton transfer events in the RC. Whereas many studies have elucidated aspects of metal ion modulation events in Rhodobacter sphaeroides RCs, much less is understood about the surface site in Blastochloris viridis (Blc. viridis) RCs. Interestingly, electron paramagnetic resonance studies revealed two spectroscopically distinct Cu{sup 2+} surface site environments in Blc. viridis RCs. Herein, Cu{sup 2+} has been used to spectroscopically probe the structure of these Cu{sup 2+} site(s) in response to freezing conditions, temperature, and charge separation. One Cu{sup 2+} environment in Blc.more » viridis RCs, termed CuA, exhibits temperature-dependent conformational flexibility. Different conformation states of the CuA{sup 2+} site are trapped when the RC is frozen in the dark either by fast-freeze or slow-freeze procedure. The second Cu{sup 2+} environment, termed CuB, is structurally invariant to different freezing conditions and shows resolved hyperfine coupling to three nitrogen atoms. Cu{sup 2+} is most likely binding at the same location on the RC, but in different coordination environments which may reflect two distinct conformational states of the isolated Blc. viridis RC protein.« less

Density functional study of hypophosphite adsorption on Ni (1 1 1) and Cu (1 1 1) surfaces

NASA Astrophysics Data System (ADS)

Zeng, Yue; Liu, Shubin; Ou, Lihui; Yi, Jianlong; Yu, Shanci; Wang, Huixian; Xiao, Xiaoming

2006-02-01

Surface structures and electronic properties of hypophosphite, H 2PO 2-, molecularly adsorbed on Ni(1 1 1) and Cu(1 1 1) surfaces are investigated in this work by density functional theory at B3LYP/6-31++g(d, p) level. We employ a four-metal-atom cluster as the simplified model for the surface and have fully optimized the geometry and orientation of H 2PO 2- on the metal cluster. Six stable orientations have been discovered on both Ni (1 1 1) and Cu (1 1 1) surfaces. The most stable orientation of H 2PO 2- was found to have its two oxygen atoms interact the surface with two P sbnd O bonds pointing downward. Results of the Mulliken population analysis showed that the back donation from 3d orbitals of the transition metal substrate to the unfilled 3d orbital of the phosphorus atom in H 2PO 2- and 4s orbital's acceptance of electron donation from one lone pair of the oxygen atom in H 2PO 2- play very important roles in the H 2PO 2- adsorption on the transition metals. The averaged electron configuration of Ni in Ni 4 cluster is 4s 0.634p 0.023d 9.35 and that of Cu in Cu 4 cluster is 4s 1.004p 0.033d 9.97. Because of this subtle difference of electron configuration, the adsorption energy is larger on the Ni surface than on the Cu surface. The amount of charge transfers due to above two donations is larger from H 2PO 2- to the Ni surface than to the Cu surface, leading to a more positively charged P atom in Ni nH 2PO 2- than in Cu nH 2PO 2-. These results indicate that the phosphorus atom in Ni nH 2PO 2- complex is easier to be attacked by a nucleophile such as OH - and subsequent oxidation of H 2PO 2- can take place more favorably on Ni substrate than on Cu substrate.

Q-switched Yb3+:YAG laser using plasmonic Cu2-xSe quantum dots as saturable absorbers

NASA Astrophysics Data System (ADS)

Wang, Yimeng; Zhan, Yi; Lee, Sooho; Wang, Li; Zhang, Xinping

2018-04-01

Cu2-xSe quantum dots (QDs) were synthesized by organometallic synthesis methods. Due to heavy self-doping, the Cu2-xSe QDs exhibit particle plasmon resonance in the near-infrared. Transient absorption spectroscopic investigation revealed strong nonlinear optical absorption and bleaching performance of the QDs under femtosecond pulse excitation, which enabled the Cu2-xSe QDs to be excellent saturable absorbers and applied in Q-switched or mode-locked lasers. A passively Q-switched Yb3+:YAG solid-state laser at 1.03 μm was achieved by coating Cu2-xSe QDs as saturable absorbers onto one of the output coupler of the V-shaped linear cavity.

Distinct oxygen hole doping in different layers of Sr₂CuO 4-δ/La₂CuO₄ superlattices

DOE PAGES

Smadici, S.; Lee, J. C. T.; Rusydi, A.; ...

2012-03-28

X-ray absorption in Sr₂CuO 4-δ/La₂CuO₄ (SCO/LCO) superlattices shows a variable occupation with doping of a hole state different from holes doped for x≲x optimal in bulk La 2-xSr xCuO₄ and suggests that this hole state is on apical oxygen atoms and polarized in the a-b plane. Considering the surface reflectivity gives a good qualitative description of the line shapes of resonant soft x-ray scattering. The interference between superlattice and surface reflections was used to distinguish between scatterers in the SCO and the LCO layers, with the two hole states maximized in different layers of the superlattice.

High performance fuel electrodes fabricated by electroless plating of copper on BaZr0.8Ce0.1Y0.1O3-δ proton-conducting ceramic

NASA Astrophysics Data System (ADS)

Patki, Neil S.; Way, J. Douglas; Ricote, Sandrine

2017-10-01

The stability of copper at high temperatures in reducing and hydrocarbon-containing atmospheres makes it a good candidate for fabricating fuel electrodes on proton-conducting ceramics, such as BaZr0.9-xCexY0.1O3-δ (BZCY). In this work, the electrochemical performance of Cu-based electrodes fabricated by electroless plating (ELP) on BaZr0.8Ce0.1Y0.1O3-δ is studied with impedance spectroscopy. Three activation catalysts (Pd, Ru, and Cu) are investigated and ELP is compared to a commercial Cu paste (ESL 2312-G) for electrode fabrication. The area specific resistances (ASR) for Pd, Ru, and Cu activations at 700 °C in moist 5% H2 in Ar are 2.1, 3.2, and 13.4 Ω cm2, respectively. That is a 1-2 orders of magnitude improvement over the commercial Cu paste (192 Ω cm2). Furthermore, the ASR has contributions from electrode processes and charge transfer at the electrode/electrolyte interface. Additionally, the morphology of the as-fabricated electrode is unaffected by the activation catalyst. However, heat treatment at 750 °C in H2 for 24 h leads to sintering and large reorganization of the electrode fabricated with Cu activation (micron sized pores seen in the tested sample), while Pd and Ru activations are immune to such reorganization. Thus, Pd and Ru are identified as candidates for future work with improvements to charge transfer required for the former, and better electrode processes required for the latter.

Alternative mechanistic explanation for ligand-dependent selectivities in copper-catalyzed N- and O-arylation reactions.

PubMed

Yu, Hai-Zhu; Jiang, Yuan-Ye; Fu, Yao; Liu, Lei

2010-12-29

The ligand-dependent selectivities in Ullmann-type reactions of amino alcohols with iodobenzene by β-diketone- and 1,10-phenanthroline-ligated Cu(I) complexes were recently explained by the single-electron transfer and iodine atom transfer mechanisms (Jones, G. O., Liu, P., Houk, K. N., and Buchwald, S. L. J. Am. Chem. Soc. 2010, 132, 6205.). The present study shows that an alternative, oxidative addition/reductive elimination mechanism may also explain the selectivities. Calculations indicate that a Cu(I) complex with a negatively charged β-diketone ligand is electronically neutral, so that oxidative addition of ArI to a β-diketone-ligated Cu(I) prefers to occur (and occur readily) in the absence of the amino alcohol. Thus, coordination of the amino alcohol in its neutral form can only occur at the Cu(III) stage where N-coordination is favored over O-coordination. The coordination step is the rate-limiting step and the outcome is that N-arylation is favored with the β-diketone ligand. On the other hand, a Cu(I) complex with a neutral 1,10-phenanthroline ligand is positively charged, so that oxidative addition of ArI to a 1,10-phenanthroline-ligated Cu(I) has to get assistance from a deprotonated amino alcohol substrate. This causes oxidative addition to become the rate-limiting step in the 1,10-phenanthroline-mediated reaction. The immediate product of the oxidative addition step is found to undergo facile reductive elimination to provide the arylation product. Because O-coordination of a deprotonated amino alcohol is favored over N-coordination in the oxidative addition transition state, O-arylation is favored with the 1,10-phenanthroline ligand.

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

Ren, Zhibo; Peng, Fei; Chen, Biaohua

Water-gas shift (WGS) reaction over a series of ceria-based mixed oxides supported Cu catalysts was investigated using a combined experimental and theoretical method. The mixed rod-shaped Ce 0.75M 0.25O 2 (M = Ti 4+, Zr 4+, Mn 4+) solid solutions, which majorly expose the (110) and (100) facets, are synthesized by hydrothermal method and used to prepare supported Cu catalysts. We found that the Cu/Ce0.75Ti 0.25O 2 (Cu-CT) exhibits the highest CO conversion in the temperature range of 150-250 °C among all supported Cu catalysts. This is mainly attributed to (i) good dispersion of Cu; (ii) largest amount of moderatemore » copper oxide; and (iii) strongest Cu-support interaction of Cu-CT. And compared to other mixed metals, periodic density functional theory calculations performed, this work further suggest that the introduction of Ti into CeO 2 not only promotes oxygen vacancy formation and CO adsorption, but also facilitates the carboxyl (COOH) formation at the interface of the Cu cluster and the support, which leads to the enhanced catalytic activity of the Cu-CT toward WGS reaction.« less

CuO/CeO2 catalysts for glycerol selective conversion to lactic acid.

PubMed

Palacio, Ruben; Torres, Sebastian; Royer, Sébastien; Mamede, Anne Sophie; López, Diana; Hernández, Diana

2018-03-26

Ceria supported copper oxide catalysts were produced by a deposition-precipitation method, at a high copper loading (up to >25 wt%). These materials demonstrated excellent properties for glycerol selective conversion to lactic acid, with a conversion reaching up to 87% with a selectivity to lactic acid of 74% (8 h reaction, 220 °C, under N2 pressure). These catalysts also exhibited high stability upon 5 successive reaction cycles. The formation of a crystalline CuO phase was demonstrated in the nanocomposites at a high Cu loading, with elongated shaped particles formed on the cerium oxide surface. Such particles were however, not observed at low Cu loadings. XPS analysis revealed that Cu(ii) was the main Cu species on the fresh catalyst, and that this species was reduced to Cu(i) during the reaction. Complementary characterization over the spent catalyst clearly showed the morphological modifications of the CuO phase, however, did not impact significantly either glycerol conversion or selectivity to lactic acid upon recycling. For instance, apparently, the catalytic activity of CuO largely depends on the Cu(ii) species.

Influence of Cu Content on the Microstructure and Mechanical Properties of Cr-Cu-N Coatings

PubMed Central

Ding, Ji Cheng; Zhang, Teng Fei; Wan, Zhi Xin; Mei, Hai Juan; Kang, Myung Chang

2018-01-01

The Cr-Cu-N coatings with various Cu contents (0–25.18 (±0.17) at.%) were deposited on Si wafer and stainless steel (SUS 304) substrates in reactive Ar+N2 gas mixture by a hybrid coating system combining pulsed DC and RF magnetron sputtering techniques. The influence of Cu content on the coating composition, microstructure, and mechanical properties was investigated. The microstructure of the coatings was significantly altered by the introduction of Cu. The deposited coatings exhibit solid solution structure with different compositions in all of the samples. Addition of Cu is intensively favored for preferred orientation growth along (200) direction by restricting in (111) direction. With increasing Cu content, the surface and cross-sectional morphology of coatings were changed from triangle cone-shaped, columnar feature to broccoli-like and compact glassy microstructure, respectively. The mechanical properties including the residual stress, nanohardness, and toughness of the coatings were explored on the basis of Cu content. The highest hardness was obtained at the Cu content of 1.49 (±0.10) at.%. PMID:29552269