WorldWideScience

Sample records for interfacial electron transfer

  1. Facile Interfacial Electron Transfer of Hemoglobin

    Directory of Open Access Journals (Sweden)

    Chunhai Fan

    2005-12-01

    Full Text Available Abstract: We herein describe a method of depositing hemoglobin (Hb and sulfonated polyaniline (SPAN on GC electrodes that facilitate interfacial protein electron transfer. Well-defined, reproducible, chemically reversible peaks of Hb and SPAN can be obtained in our experiments. We also observed enhanced peroxidase activity of Hb in SPAN films. These results clearly showed that SPAN worked as molecular wires and effectively exchanged electrons between Hb and electrodes.Mediated by Conjugated Polymers

  2. Electron transfer and interfacial behavior of redox proteins

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper reviews the recent progress in the electron transfer and interfacial behavior of redox proteins. Significant achievements in the relevant fields are summarized including the direct electron transfer between proteins and electrodes, the thermodynamic and kinetic properties, catalytic activities and activity regulation of the redox proteins. It has been demonstrated that the electrochemical technique is an effective tool for protein studies, especially for probing into the electron transfer and interfacial behavior of redox proteins.

  3. Adsorption and Interfacial Electron Transfer of Saccharomyces Cerevisiae

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thanulov

    2003-01-01

    We have studied the adsorption and electron-transfer dynamics of Saccharomyces cerevisiae (yeast) iso-l-cytochrome c adsorbed on Au(lll) electrodes in aqueous phosphate buffer media. This cytochrome possesses a thiol group dos e to the protein surface (Cysl02) suitable for linking the protein...... negative ofthe equilibrium potential of YCC, where the protein is electrochemically functional. The MCS data show tensile differential stress signals when YCC is adsorbed on a gold-coate d MCS, with distinguishable adsorption phases in the time range from

  4. Interfacial Electron Transfer and Transient Photoconductivity Studied with Terahertz Spectroscopy

    Science.gov (United States)

    Milot, Rebecca Lee

    Terahertz spectroscopy is distinguished from other far infrared and millimeter wave spectroscopies by its inherent phase sensitivity and sub-picosecond time resolution making it a versatile technique to study a wide range of physical phenomena. As THz spectroscopy is still a relatively new field, many aspects of THz generation mechanisms have not been fully examined. Using terahertz emission spectroscopy (TES), THz emission from ZnTe(110) was analyzed and found to be limited by two-photon absorption and free-carrier generation at high excitation fluences. Due to concerns about the continued use of fossil fuels, solar energy has been widely investigated as a promising source of renewable energy. Dye-sensitized solar cells (DSSCs) have been developed as a low-cost alternative to conventional photovoltaic solar cells. To solve the issues of the intermittency and inefficient transport associated with solar energy, researchers are attempting to adapt DSSCs for water oxidation and chemical fuel production. Both device designs incorporate sensitizer molecules covalently bound to metal oxide nanoparticles. The sensitizer, which is comprised of a chromophore and anchoring group, absorbs light and transfers an electron from its excited state to the conduction band of the metal oxide, producing an electric current. Using time-resolved THz spectroscopy (TRTS), an optical pump/THz probe technique, the efficiency and dynamics of electron injection from sensitizers to metal oxides was evaluated as a function of the chromophore, its anchoring group, and the metal oxide identity. Experiments for studying fully functioning DSSCs and water oxidation devices are also described. Bio-inspired pentafluorophenyl porphyrin chromophores have been designed and synthesized for use in photoelectrochemical water oxidation cells. Influences on the efficiency and dynamics of electron injection from the chromophores into TiO2 and SnO2 nanoparticles due to changes in both the central substituent to

  5. Gold nanoparticle assisted assembly of a heme protein for enhancement of long-range interfacial electron transfer

    DEFF Research Database (Denmark)

    Jensen, Palle Skovhus; Chi, Qijin; Grumsen, Flemming Bjerg;

    2007-01-01

    Interfacial electron transfer (ET) of biological macromolecules such as metalloproteins is the key process in bioelectrochemistry, enzymatic electrocatalysis, artificial ET chains, single-molecule electronic amplification and rectification, and other phenomena associated with the area of bioelect......Interfacial electron transfer (ET) of biological macromolecules such as metalloproteins is the key process in bioelectrochemistry, enzymatic electrocatalysis, artificial ET chains, single-molecule electronic amplification and rectification, and other phenomena associated with the area...

  6. Kinetic pathway for interfacial electron transfer from a semiconductor to a molecule

    Science.gov (United States)

    Hu, Ke; Blair, Amber D.; Piechota, Eric J.; Schauer, Phil A.; Sampaio, Renato N.; Parlane, Fraser G. L.; Meyer, Gerald J.; Berlinguette, Curtis P.

    2016-09-01

    Molecular approaches to solar-energy conversion require a kinetic optimization of light-induced electron-transfer reactions. At molecular-semiconductor interfaces, this optimization has previously been accomplished through control of the distance between the semiconductor donor and the molecular acceptor and/or the free energy that accompanies electron transfer. Here we show that a kinetic pathway for electron transfer from a semiconductor to a molecular acceptor also exists and provides an alternative method for the control of interfacial kinetics. The pathway was identified by the rational design of molecules in which the distance and the driving force were held near parity and only the geometric torsion about a xylyl- or phenylthiophene bridge was varied. Electronic coupling through the phenyl bridge was a factor of ten greater than that through the xylyl bridge. Comparative studies revealed a significant bridge dependence for electron transfer that could not be rationalized by a change in distance or driving force. Instead, the data indicate an interfacial electron-transfer pathway that utilizes the aromatic bridge orbitals.

  7. Interfacial electron transfer dynamics of ru(II)-polypy6ridine sensitized TiO2

    Energy Technology Data Exchange (ETDEWEB)

    Jakubikova, Elena [Los Alamos National Laboratory; Martin, Richard L [Los Alamos National Laboratory; Batista, Enrique R [Los Alamos National Laboratory; Snoeberger, Robert C [YALE UNIV.; Batista, Victor S [YALE UNIV.

    2009-01-01

    Quantum dynamics simulations combined with density functional theory calculations are applied to study interfacial electron transfer (IET) from pyridine-4-phosphonic acid, [Ru(tpy)(tpy(PO{sub 3}H{sub 2}))]{sup 2+} and [Ru(tpy)(bpy)(H{sub 2}O)-Ru(tpy)(tpy(PO{sub 3}H{sub 2}))]{sup 4+} into the (101) surface of anatase TiO{sub 2}. IET rate from pyridine-4-phosphonic acid attached to the nanoparticle in bidentate mode ({tau} {approx} 100 fs) is an order of magnitude faster than the IET rate of the adsorbate attached in the monodentate mode ({tau} {approx} 1 ps). Upon excitation with visible light, [Ru(tpy)(tpy(PO{sub 3}H{sub 2}))]{sup 2+} attached to TiO{sub 2} in bidentate binding mode will undergo IET with the rate of {approx} 1-10 ps, which is competitive with the excited state decay into the ground state. The probability of electron injection from [Ru(tpy)(bpy)(H{sub 2}O)-Ru(tpy)(tpy(PO{sub 3}H{sub 2}))]{sup 4+} is rather low, as the excitation with visible light localizes the excited electron in the tpy-tpy bridge, which does not have favorable coupling with the TiO{sub 2} nanoparticle. The results are relevant to better understanding of the adsorbate features important for promoting efficient interfacial electron transfer into the semiconductor.

  8. Electronic Coupling Dependence of Ultrafast Interfacial Electron Transfer on Nanocrystalline Thin Films and Single Crystal

    Energy Technology Data Exchange (ETDEWEB)

    Lian, Tianquan

    2014-04-22

    The long-term goal of the proposed research is to understand electron transfer dynamics in nanoparticle/liquid interface. This knowledge is essential to many semiconductor nanoparticle based devices, including photocatalytic waste degradation and dye sensitized solar cells.

  9. Dynamics and mechanisms of interfacial photoinduced electron transfer processes of third generation photovoltaics and photocatalysis.

    Science.gov (United States)

    Bauer, Christophe; Teuscher, Joël; Brauer, Jan C; Punzi, Angela; Marchioro, Arianna; Ghadiri, Elham; De Jonghe, Jelissa; Wielopolski, Mateusz; Banerji, Natalie; Moser, Jacques E

    2011-01-01

    Photoinduced electron transfer (PET) across molecular/bulk interfaces has gained attention only recently and is still poorly understood. These interfaces offer an excellent case study, pertinent to a variety of photovoltaic systems, photo- and electrochemistry, molecular electronics, analytical detection, photography, and quantum confinement devices. They play in particular a key role in the emerging fields of third-generation photovoltaic energy converters and artificial photosynthetic systems aimed at the production of solar fuels, creating a need for a better understanding and theoretical treatment of the dynamics and mechanisms of interfacial PET processes. We aim to achieve a fundamental understanding of these phenomena by designing experiments that can be used to test and alter modern theory and computational modeling. One example illustrating recent investigations into the details of the ultrafast processes that form the basis for photoinduced charge separation at a molecular/bulk interface relevant to dye-sensitized solar cells is briefly presented here: Kinetics of interfacial PET and charge recombination processes were measured by fs and ns transient spectroscopy in a heterogeneous donor-bridge-acceptor (D-B-A) system, where D is a Ru(II)(terpyridyl-PO3)(NCS)3 complex, B an oligo-p-phenylene bridge, and A nanocrystalline TiO2. The forward ET reaction was found to be faster than vibrational relaxation of the vibronic excited state of the donor. Instead, the back ET occurred on the micros time scale and involved fully thermalized species. The D-A distance dependence of the electron transfer rate was studied by varying the number of p-phenylene units contained in the bridge moiety. The remarkably low damping factor beta = 0.16 angstroms(-1) observed for the ultrafast charge injection from the dye excited state into the conduction band of TiO2 is attributed to the coupling of electron tunneling with nonequilibrium vibrations redistributed on the bridge

  10. Dynamics and mechanisms of interfacial photoinduced electron transfer processes of third generation photovoltaics and photocatalysis.

    Science.gov (United States)

    Bauer, Christophe; Teuscher, Joël; Brauer, Jan C; Punzi, Angela; Marchioro, Arianna; Ghadiri, Elham; De Jonghe, Jelissa; Wielopolski, Mateusz; Banerji, Natalie; Moser, Jacques E

    2011-01-01

    Photoinduced electron transfer (PET) across molecular/bulk interfaces has gained attention only recently and is still poorly understood. These interfaces offer an excellent case study, pertinent to a variety of photovoltaic systems, photo- and electrochemistry, molecular electronics, analytical detection, photography, and quantum confinement devices. They play in particular a key role in the emerging fields of third-generation photovoltaic energy converters and artificial photosynthetic systems aimed at the production of solar fuels, creating a need for a better understanding and theoretical treatment of the dynamics and mechanisms of interfacial PET processes. We aim to achieve a fundamental understanding of these phenomena by designing experiments that can be used to test and alter modern theory and computational modeling. One example illustrating recent investigations into the details of the ultrafast processes that form the basis for photoinduced charge separation at a molecular/bulk interface relevant to dye-sensitized solar cells is briefly presented here: Kinetics of interfacial PET and charge recombination processes were measured by fs and ns transient spectroscopy in a heterogeneous donor-bridge-acceptor (D-B-A) system, where D is a Ru(II)(terpyridyl-PO3)(NCS)3 complex, B an oligo-p-phenylene bridge, and A nanocrystalline TiO2. The forward ET reaction was found to be faster than vibrational relaxation of the vibronic excited state of the donor. Instead, the back ET occurred on the micros time scale and involved fully thermalized species. The D-A distance dependence of the electron transfer rate was studied by varying the number of p-phenylene units contained in the bridge moiety. The remarkably low damping factor beta = 0.16 angstroms(-1) observed for the ultrafast charge injection from the dye excited state into the conduction band of TiO2 is attributed to the coupling of electron tunneling with nonequilibrium vibrations redistributed on the bridge

  11. Single-molecule interfacial electron transfer in donor-bridge-nanoparticle acceptor complexes.

    Science.gov (United States)

    Jin, Shengye; Snoeberger, Robert C; Issac, Abey; Stockwell, David; Batista, Victor S; Lian, Tianquan

    2010-11-18

    Photoinduced interfacial electron transfer (IET) in sulforhodamine B (SRhB)-aminosilane-Tin oxide (SnO(2)) nanoparticle donor-bridge-acceptor complexes has been studied on a single molecule and ensemble average level. On both SnO(2) and ZrO(2), the sum of single molecule fluorescence decays agree with the ensemble average results, suggesting complete sampling of molecules under single molecule conditions. Shorter fluorescence lifetime on SnO(2) than on ZrO(2) is observed and attributed to IET from SRhB to SnO(2). Single molecule lifetimes fluctuate with time and vary among different molecules, suggesting both static and dynamic IET heterogeneity in this system. Computational modeling of the complexes shows a distribution of molecular conformation, leading to a distribution of electronic coupling strengths and ET rates. It is likely that the conversion between these conformations led to the fluctuation of ET rate and fluorescence lifetime on the single molecule level. PMID:20225886

  12. Interfacial electron transfer of glucose oxidase on poly(glutamic acid)-modified glassy carbon electrode and glucose sensing.

    Science.gov (United States)

    Zhou, Xuechou; Tan, Bingcan; Zheng, Xinyu; Kong, Dexian; Li, Qinglu

    2015-11-15

    The interfacial electron transfer of glucose oxidase (GOx) on a poly(glutamic acid)-modified glassy carbon electrode (PGA/GCE) was investigated. The redox peaks measured for GOx and flavin adenine dinucleotide (FAD) are similar, and the anodic peak of GOx does not increase in the presence of glucose in a mediator-free solution. These indicate that the electroactivity of GOx is not the direct electron transfer (DET) between GOx and PGA/GCE and that the observed electroactivity of GOx is ascribed to free FAD that is released from GOx. However, efficient electron transfer occurred if an appropriate mediator was placed in solution, suggesting that GOx is active. The PGA/GCE-based biosensor showed wide linear response in the range of 0.5-5.5 mM with a low detection limit of 0.12 mM and high sensitivity and selectivity for measuring glucose. PMID:26278169

  13. Beyond vibrationally mediated electron transfer: interfacial charge injection on a sub-10-fs time scale

    Science.gov (United States)

    Huber, Robert; Moser, Jacques E.; Gratzel, Michael; Wachtveitl, Josef L.

    2003-12-01

    The electron transfer (ET) from organic dye molecules to semiconductor-colloidal systems is characterized by a special energetic situation with a charge transfer reaction from a system of discrete donor levels to a continuum of acceptor states. If these systems show a strong electronic coupling they are amongst the fastest known ET systems with transfer times of less than 10 fs. In the first part a detailed discussion of the direct observation of an ET reaction with a time constant of about 6 fs will be given, with an accompanying argumentation concerning possible artifacts or other interfering signal contributions. In a second part we will try to give a simple picture for the scenario of such superfast ET reactions and one main focus will be the discussion of electronic dephasing and its consequences for the ET reaction. The actual ET process can be understood as a kind of dispersion process of the initially located electron into the colloid representing a real motion of charge density from the alizarin to the colloid.

  14. Molecular monolayers and interfacial electron transfer of pseudomonas aeruginosa azurin on Au(111)

    DEFF Research Database (Denmark)

    Chi, Qijin; Zhang, Jingdong; Nielsen, Jens Ulrik;

    2000-01-01

    disulfide group to form a monolayer. The adsorption of this protein on Au(111) via a gold-sulfur binding mode is further supported by XPS measurements. In situ STM images with molecular resolution have been recorded and show a dense monolayer organization of adsorbed azurin molecules. Direct electron......, and long-range electrochemical electron transfer between the electrode and the copper center. Voltammetry, electrochemical impedance spectroscopy (EIS), in situ scanning tunneling microscopy (STM), and X-ray photoelectron spectroscopy (XPS) have been employed to disclose features of these issues. Zn...

  15. Adsorption and interfacial electron transfer of Saccharomyces cerevisiae yeast cytochrome c monolayers on Au(111) electrodes

    DEFF Research Database (Denmark)

    Hansen, Allan Glargaard; Boisen, Anja; Nielsen, Jens Ulrik;

    2003-01-01

    We have studied the adsorption and electron-transfer dynamics of Saccharomyces cerevisiae (yeast) iso-1-cytochrome c adsorbed on Au(111) electrodes in aqueous phosphate buffer media. This cytochrome possesses a thiol group close to the protein surface (Cys102) suitable for linking the protein....... The voltammetric data display a thiol reductive desorption signal corresponding to close to monolayer coverage. Reductive desorption is also reflected in a capacitance peak. Voltammetric signals from the heme group in both native and partially denatured states could also be detected. XPS shows clear Au-S bond...

  16. Interfacial Electron Transfer Barrier at Compact TiO2 /CH3 NH3 PbI3 Heterojunction.

    Science.gov (United States)

    Xing, Guichuan; Wu, Bo; Chen, Shi; Chua, Julianto; Yantara, Natalia; Mhaisalkar, Subodh; Mathews, Nripan; Sum, Tze Chien

    2015-08-01

    Low-temperature solution-processed CH3 NH3 PbI3 interfaced with TiO2 has recently been demonstrated as a highly successful type-II light harvesting heterojunction with ≈20% efficiency. Therefore, an efficient ultrafast photoexcited electron transfer from CH3 NH3 PbI3 to TiO2 is expected. However, by probing the photoexcited charge carrier dynamics in CH3 NH3 PbI3 /quartz, CH3 NH3 PbI3 /TiO2 (compact), and CH3 NH3 PbI3 /PCBM in a comparative study, an electron transfer potential barrier between CH3 NH3 PbI3 and the compact TiO2 (prepared with the spray pyrolysis method) formed by surface states is uncovered. Consequently, the CH3 NH3 PbI3 photoluminescence intensity and lifetime is enhanced when interfaced to compact TiO2 . The electron accumulation within CH3 NH3 PbI3 needed to overcome this interfacial potential barrier results in the undesirable large current-voltage hysteresis observed for CH3 NH3 PbI3 /TiO2 planar heterojunctions. The findings in this study indicate that careful surface engineering to reduce this potential barrier is key to pushing perovskite solar cell efficiencies toward the theoretical limit. PMID:25824264

  17. Interfacial Electrochemical Electron Transfer Processes in Bacterial Biofilm Environments on Au(111)

    DEFF Research Database (Denmark)

    Hu, Yifan; Zhang, Jingdong; Ulstrup, Jens

    2010-01-01

    We have studied Streptococcus mutans (S. mutans) biolilm growth and growth inhibition on Au(111)-surfaces using atomic force microscopy (AFM) and interfacial electrochemistry of a number of redox probe molecules. AFM of the biofilm growth and growth inhibition on both mica and Au(111)-surfaces wa...

  18. Enhanced van der Waals epitaxy via electron transfer-enabled interfacial dative bond formation

    CERN Document Server

    Xie, Weiyu; Wang, Gwo-Ching; Bhat, Ishwara; Zhang, Shengbai

    2016-01-01

    Enhanced van der Waals (vdW) epitaxy of semiconductors on layered vdW substrate is identified as the formation of dative bonds. For example, despite that NbSe2 is a vdW layered material, first-principles calculations reveal that the bond strength at CdTe-NbSe2 interface is five times as large as that of vdW interaction at CdTe-graphene interface. The unconventional chemistry here is enabled by an effective net electron transfer from Cd dangling-bond states at CdTe surface to metallic non-bonding NbSe2 states, which is a necessary condition to activate the Cd for enhanced binding with Se.

  19. Effect of strong coupling on interfacial electron transfer dynamics in dye-sensitized TiO2 semiconductor nanoparticles

    Indian Academy of Sciences (India)

    Hirendra N Ghosh

    2007-03-01

    Dynamics of interfacial electron transfer (ET) in ruthenium polypyridyl complex [{bis-(2,2'-bpy)-(4-[2-(4'-methyl-[2,2']bipyridinyl-4-yl)-vinyl]-benzene-1,2-diol)}ruthenium(II) hexafluorophosphate] (Ru-cat) and 5,10,15-tris phenyl-20-(3,4-dihydroxy benzene) porphyrin (TPP-cat)-sensitized TiO2 nanoparticles have been investigated using femtosecond transient absorption spectroscopic detection in the visible and near-infrared region. We have observed that both Ru-cat and TPP-cat are coupled strongly with the TiO2 nanoparticles through their pendant catechol moieties. We have observed a single exponential and pulse-width limited (< 100 fs) electron injection from nonthermalized-excited states of Ru-complex. Here electron injection competes with the singlet-triplet manifold relaxation due to strong coupling of catecholate binding, which is a unique observation. Optical absorption measurements indicate that the catechol moiety interacts with TiO2 nanoparticles showing the characteristic pure catechol-TiO2 charge-transfer (CT) band in the visible region. Transient absorption studies on TPP-cat/TiO2 system exciting both the Soret band at 400 nm and the Q-band at 800 nm have been carried out to determine excitation wavelength-dependence on ET dynamics. The reaction channel for the electron-injection process has been found to be different for both the excitation wavelengths. Excitation at 800 nm, is found directly populate directly the excited CT state from where diffusion of electrons into the conduction band takes place. On the other hand, excitation at 400 nm light excites both the CT band of cat-TiO2 and also Soret band of TPP-cat.

  20. Amine-terminated ionic liquid functionalized carbon nanotubes for enhanced interfacial electron transfer of Shewanella putrefaciens anode in microbial fuel cells

    Science.gov (United States)

    Wei, Huan; Wu, Xiao-Shuai; Zou, Long; Wen, Guo-Yun; Liu, Ding-Yu; Qiao, Yan

    2016-05-01

    An amine-terminated ionic liquid (IL-NH2) is applied to functionalize carbon nanotubes (CNTs) for improving the interfacial electron transfer of Shewanella putrefaciens (S. putrefaciens) anode in Microbial fuel cells (MFCs). The introduction of thin layer of ILs does not change the morphology of CNTs a lot but increases surface positive charges as well as nitrogen functional groups of the CNTs based anode. The CNT-IL composite not only improves the adhesion of S. putrefaciens cells but also promotes both of the flavin-mediated and the direct electron transfer between the S. putrefaciens cells and the anode. It is interesting that the CNT-IL is more favorable for the mediated electron transfer than for the direct electron transfer. The CNT-IL/carbon cloth anode delivers 3-fold higher power density than that of CNT anode and shows great long-term stability in the batch-mode S. putrefaciens MFCs. This CNT-IL could be a promising anode material for high performance MFCs.

  1. Surface plasmon enhanced interfacial electron transfer and resonance Raman, surface-enhanced resonance Raman studies of cytochrome C mutants

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Junwei

    1999-11-08

    Surface plasmon resonance was utilized to enhance the electron transfer at silver/solution interfaces. Photoelectrochemical reductions of nitrite, nitrate, and CO{sub 2} were studied on electrochemically roughened silver electrode surfaces. The dependence of the photocurrent on photon energy, applied potential and concentration of nitrite demonstrates that the photoelectrochemical reduction proceeds via photoemission process followed by the capture of hydrated electrons. The excitation of plasmon resonances in nanosized metal structures resulted in the enhancement of the photoemission process. In the case of photoelectrocatalytic reduction of CO{sub 2}, large photoelectrocatalytic effect for the reduction of CO{sub 2} was observed in the presence of surface adsorbed methylviologen, which functions as a mediator for the photoexcited electron transfer from silver metal to CO{sub 2} in solution. Photoinduced reduction of microperoxidase-11 adsorbed on roughened silver electrode was also observed and attributed to the direct photoejection of free electrons of silver metal. Surface plasmon assisted electron transfer at nanostructured silver particle surfaces was further determined by EPR method.

  2. Interfacial area and interfacial transfer in two-phase systems. DOE final report

    Energy Technology Data Exchange (ETDEWEB)

    Ishii, Mamoru; Hibiki, T.; Revankar, S.T.; Kim, S.; Le Corre, J.M.

    2002-07-01

    In the two-fluid model, the field equations are expressed by the six conservation equations consisting of mass, momentum and energy equations for each phase. The existence of the interfacial transfer terms is one of the most important characteristics of the two-fluid model formulation. The interfacial transfer terms are strongly related to the interfacial area concentration and to the local transfer mechanisms such as the degree of turbulence near interfaces. This study focuses on the development of a closure relation for the interfacial area concentration. A brief summary of several problems of the current closure relation for the interfacial area concentration and a new concept to overcome the problem are given.

  3. Interfacial structures - Thermodynamical and experimental studies of the interfacial mass transfer

    International Nuclear Information System (INIS)

    In the first section, we put forward hypotheses concerning the structure of the interfacial regions between two immiscible liquid phases. It appears that the longitudinal structure is comparable with that of a crystallized solid and that the transversal structure is nearest of that of a liquid. In the second section, we present a thermodynamical treatment of the irreversible phenomena in the interfacial region. The equation of evolution of a system consisting of two immiscible liquid phases are deduced. The third part allows an experimental verification of the theoretical relations. We also make clear, in certain cases, the appearance of a great 'interfacial resistance' which slows down the interfacial mass transfer. (author)

  4. Interfacial electronic structure and charge transfer of hybrid graphene quantum dot and graphitic carbon nitride nanocomposites: insights into high efficiency for photocatalytic solar water splitting.

    Science.gov (United States)

    Ma, Zuju; Sa, Rongjian; Li, Qiaohong; Wu, Kechen

    2016-01-14

    New metal-free carbon nanodot/carbon nitride (C3N4) nanocomposites have shown to exhibit high efficiency for photocatalytic solar water splitting. (J. Liu, et al., Science, 2015, 347, 970) However, the mechanism underlying the ultrahigh performance of these nanocomposites and consequently the possibilities for further improvements are not at present clear. In this work, we performed hybrid functional calculations and included long-range dispersion corrections to accurately characterize the interfacial electron coupling of the graphene quantum dot-graphitic carbon nitride composites (Gdot/g-C3N4). The results revealed that the band gap of Gdot/g-C3N4 could be engineered by changing the lateral size of Gdots. In particular, the C24H12/g-C3N4 composites present an ideal band gap of 1.92 eV to harvest a large part of solar light. More interestingly, a type-II heterojunction is formed at the interface of the Gdot/g-C3N4 composites, a desirable feature for enhanced photocatalytic activity. The charge redistribution at the interface leads to strong electron depletion above the Gdot sheet and electron accumulation below the g-C3N4 monolayer, potentially facilitating the separation of H2O oxidation and reduction reactions. Furthermore, we suggested that the photocatalytic performance of the Gdot/g-C3N4 nanocomposites can be further improved by decreasing the thickness of Gdots and tuning the size of Gdots.

  5. Electronic structures of TiO2-TCNE, -TCNQ, and -2,6-TCNAQ surface complexes studied by ionization potential measurements and DFT calculations: Mechanism of the shift of interfacial charge-transfer bands

    Science.gov (United States)

    Fujisawa, Jun-ichi; Hanaya, Minoru

    2016-06-01

    Interfacial charge-transfer (ICT) transitions between inorganic semiconductors and π-conjugated molecules allow direct charge separation without loss of energy. This feature is potentially useful for efficient photovoltaic conversions. Charge-transferred complexes of TiO2 nanoparticles with 7,7,8,8-tetracyanoquinodimethane (TCNQ) and its analogues (TCNX) show strong ICT absorption in the visible region. The ICT band was reported to be significantly red-shifted with extension of the π-conjugated system of TCNX. In order to clarify the mechanism of the red-shift, in this work, we systematically study electronic structures of the TiO2-TCNX surface complexes (TCNX; TCNE, TCNQ, 2,6-TCNAQ) by ionization potential measurements and density functional theory (DFT) calculations.

  6. Electron transfer reactions

    CERN Document Server

    Cannon, R D

    2013-01-01

    Electron Transfer Reactions deals with the mechanisms of electron transfer reactions between metal ions in solution, as well as the electron exchange between atoms or molecules in either the gaseous or solid state. The book is divided into three parts. Part 1 covers the electron transfer between atoms and molecules in the gas state. Part 2 tackles the reaction paths of oxidation states and binuclear intermediates, as well as the mechanisms of electron transfer. Part 3 discusses the theories and models of the electron transfer process; theories and experiments involving bridged electron transfe

  7. Investigation and assessment of interfacial area/interfacial heat and mass transfer correlations in SPACE code

    International Nuclear Information System (INIS)

    SPACE, which is a safety analysis code for nuclear power plants, has been developed to analyze the multidimensional, two-component and three-field flow. This code can be applied to safety analysis for approval which is thermal-hydraulic analysis to support the nuclear power station design, establishment of accident ease strategy, development of operating guide line, experiment plan and analysis. To do so, SPACE code has the interfacial area and interfacial heat and mass transfer to predict the physical phenomenon occurring at the interface between two different phases. In this report, the physical correlation models are explained and their performance is assessed against several SET

  8. Reversible Tuning of Interfacial and Intramolecular Charge Transfer in Individual MnPc Molecules.

    Science.gov (United States)

    Zhong, Jian-Qiang; Wang, Zhunzhun; Zhang, Jia Lin; Wright, Christopher A; Yuan, Kaidi; Gu, Chengding; Tadich, Anton; Qi, Dongchen; Li, He Xing; Lai, Min; Wu, Kai; Xu, Guo Qin; Hu, Wenping; Li, Zhenyu; Chen, Wei

    2015-12-01

    The reversible selective hydrogenation and dehydrogenation of individual manganese phthalocyanine (MnPc) molecules has been investigated using photoelectron spectroscopy (PES), low-temperature scanning tunneling microscopy (LT-STM), synchrotron-based near edge X-ray absorption fine structure (NEXAFS) measurements, and supported by density functional theory (DFT) calculations. It is shown conclusively that interfacial and intramolecular charge transfer arises during the hydrogenation process. The electronic energetics upon hydrogenation is identified, enabling a greater understanding of interfacial and intramolecular charge transportation in the field of single-molecule electronics. PMID:26528623

  9. Investigations on interfacial dynamics with ultrafast electron diffraction

    Science.gov (United States)

    Murdick, Ryan A.

    An ultrafast electron diffractive voltammetry (UEDV) technique is introduced, extended from ultrafast electron diffraction, to investigate the ultrafast charge transport dynamics at interfaces and in nanostructures. Rooted in Coulomb-induced refraction, formalisms are presented to quantitatively deduce the transient surface voltages (TSVs), caused by photoinduced charge redistributions at interfaces, and are applied to examine a prototypical Si/SiO2 interface, known to be susceptible to photoinduced interfacial charging The ultrafast time resolution and high sensitivity to surface charges of this electron diffractive approach allows direct elucidation of the transient effects of photoinduced hot electron transport at nanometer (˜2 nm) interfaces. Two distinctive regimes are uncovered, characterized by the time scales associated with charge separation. At the low fluence regime, the charge transfer is described by a thermally-mediated process with linear dependence on the excitation fluence. Theoretical analysis of the transient thermal properties of the carriers show that it is well-described by a direct tunneling of the laser heated electrons through the dielectric oxide layer to surface states. At higher fluences, a coherent multiphoton absorption process is invoked to directly inject electrons into the conduction band of SiO2, leading to a more efficient surface charge accumulation. A quadratic fluence dependence on this coherent, 3-photon lead electron injection is characterized by the rapid dephasing of the intermediately generated hot electrons from 2-photon absorption, limiting the yield of the consecutive 1-photon absorption by free carriers. The TSV formalism is extended beyond the simple slab geometry associated with planar surfaces (Si/SiO2), to interfaces with arbitrary geometrical features, by imposing a corrective scheme to the slab model. The validity of this treatment is demonstrated in an investigation of the charge transfer dynamics at a metal

  10. Pickering emulsion templated interfacial atom transfer radical polymerization for microencapsulation.

    Science.gov (United States)

    Li, Jian; Hitchcock, Adam P; Stöver, Harald D H

    2010-12-01

    This Article describes a new microencapsulation method based on a Pickering emulsion templated interfacial atom transfer radical polymerization (PETI-ATRP). Cationic LUDOX CL nanoparticles were coated electrostatically with an anionic polymeric ATRP initiator, poly(sodium styrene sulfonate-co-2-(2-bromoisobutyryloxy)ethyl methacrylate) (PSB), prepared by radical copolymerization of sodium styrene sulfonate and 2-(2-bromoisobutyryloxy)ethyl methacrylate (BIEM). The resulting PSB-modified CL particles were surface active and could be used to stabilize oil-in-water Pickering emulsions. ATRP of water-soluble cross-linking monomers, confined to the oil-water interface by the surface-bound PSB, then led to nanoparticle/polymer composite shells. This method allowed encapsulation of core solvents (xylene, hexadecane, perfluoroheptane) with different solubility parameters. The microcapsule (MC) wall chemistry could accommodate different monomers, demonstrating the versatility of this method. Double-walled MCs were formed by sequentially carrying out PETI-ATRP and in situ polymerization of encapsulated monomers. The double-walled structure was verified by both transmission electron microscopy (TEM) and scanning transmission X-ray microscopy (STXM).

  11. Pressure transfer functions for interfacial fluid problems

    CERN Document Server

    Chen, Robin Ming; Walsh, Samuel

    2015-01-01

    We make a consistent derivation, from the governing equations, of the pressure transfer function in the small-amplitude Stokes wave regime and the hydrostatic approximation in the small-amplitude solitary water wave regime, in the presence of a background shear flow. The results agree with the well-known formulae in the zero vorticity case,but they incorporate the effects of vorticity through solutions to the Rayleigh equation. We extend the results to permit continuous density stratification and to internal waves between two constant-density fluids. Several examples are discussed.

  12. Electron transfer in peptides.

    Science.gov (United States)

    Shah, Afzal; Adhikari, Bimalendu; Martic, Sanela; Munir, Azeema; Shahzad, Suniya; Ahmad, Khurshid; Kraatz, Heinz-Bernhard

    2015-02-21

    In this review, we discuss the factors that influence electron transfer in peptides. We summarize experimental results from solution and surface studies and highlight the ongoing debate on the mechanistic aspects of this fundamental reaction. Here, we provide a balanced approach that remains unbiased and does not favor one mechanistic view over another. Support for a putative hopping mechanism in which an electron transfers in a stepwise manner is contrasted with experimental results that support electron tunneling or even some form of ballistic transfer or a pathway transfer for an electron between donor and acceptor sites. In some cases, experimental evidence suggests that a change in the electron transfer mechanism occurs as a result of donor-acceptor separation. However, this common understanding of the switch between tunneling and hopping as a function of chain length is not sufficient for explaining electron transfer in peptides. Apart from chain length, several other factors such as the extent of the secondary structure, backbone conformation, dipole orientation, the presence of special amino acids, hydrogen bonding, and the dynamic properties of a peptide also influence the rate and mode of electron transfer in peptides. Electron transfer plays a key role in physical, chemical and biological systems, so its control is a fundamental task in bioelectrochemical systems, the design of peptide based sensors and molecular junctions. Therefore, this topic is at the heart of a number of biological and technological processes and thus remains of vital interest.

  13. Electronic structures of interfacial states formed at polymeric semiconductor heterojunctions

    Science.gov (United States)

    Huang, Ya-Shih; Westenhoff, Sebastian; Avilov, Igor; Sreearunothai, Paiboon; Hodgkiss, Justin M.; Deleener, Caroline; Friend, Richard H.; Beljonne, David

    2008-06-01

    Heterojunctions between organic semiconductors are central to the operation of light-emitting and photovoltaic diodes, providing respectively for electron-hole capture and separation. However, relatively little is known about the character of electronic excitations stable at the heterojunction. We have developed molecular models to study such interfacial excited electronic excitations that form at the heterojunction between model polymer donor and polymer acceptor systems: poly(9,9-dioctylfluorene-co-bis-N,N-(4-butylphenyl)-bis-N,N-phenyl-1,4-phenylenediamine) (PFB) with poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), and poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB) with F8BT. We find that for stable ground-state geometries the excited state has a strong charge-transfer character. Furthermore, when partly covalent, modelled radiative lifetimes (~10-7s) and off-chain axis polarization (30∘) match observed `exciplex' emission. Additionally for the PFB:F8BT blend, geometries with fully ionic character are also found, thus accounting for the low electroluminescence efficiency of this system.

  14. ANALYSIS OF EFFECT OF GAS–LIQUID INTERFACIAL DISTURBANCE ON MASS TRANSFER PERFORMANCE

    OpenAIRE

    HONDA WU; TSAIR-WANG CHUNG

    2006-01-01

    In order to study the mass transfer phenomena for water vapor absorbed by triethylene glycol (TEG) solution and to elucidate effect of interfacial disturbance on absorption performance, the interfacial phenomena for water drop instilling on the surface of TEG solution and mass transfer process were observed and operated in this study. Besides liquid and gas flow rates, the interfacial disturbance can also affect the mass transfer performance in the absorption system with continuous liquid pha...

  15. Electron transfer in proteins

    DEFF Research Database (Denmark)

    Farver, O; Pecht, I

    1991-01-01

    Electron migration between and within proteins is one of the most prevalent forms of biological energy conversion processes. Electron transfer reactions take place between active centers such as transition metal ions or organic cofactors over considerable distances at fast rates and with remarkab...

  16. Study of Interfacial Mass Transfer on Vapor Bubbles in Microgravity

    Directory of Open Access Journals (Sweden)

    Johannes Straub

    2005-03-01

    Full Text Available The knowledge of interfacial heat and mass transfer is important for environmental and technical applications, especially nowadays for numerical simulations of two phase problems. However, the data available up to now are inconsistent, because most experiments performed on earth suffer under buoyancy and convection, and thus the boundary conditions at the evaluation could not clearly be defined. Therefore, we seized the opportunity to investigate interfacial heat and mass transfer in microgravity environment. In these experiments the growth and collapse in the overall superheated and subcooled bubles, respectively, liquid or free vapor bubbles were observed at various liquid temperature and pressure states and over periods of from a few seconds up to 300 seconds. It was for the first time that such very long periods of bubble growth could be observed. The experimental set-up allowed the control of the liquid supersaturation before the bubbles were initiated by a short heat pulse at a miniaturized heater. Therefore it was possible to perform a systematic parametric study. The measured curves for vapor bubble growth are in good agreement with our numerical simulation. Based on this model the kinetic coefficients for the evaporation and condensation according to Hertz-Knudsen have been derived from the experimental data.

  17. A Summary of Interfacial Heat Transfer Models and Correlations

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Sung Won; Cho, Hyung Kyu; Lee, Young Jin; Kim, Hee Chul; Jung, Young Jong; Kim, K. D. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2007-10-15

    A long term project has been launched in October 2006 to develop a plant safety analysis code. 5 organizations are joining together for the harmonious coworking to build up the code. In this project, KAERI takes the charge of the building up the physical models and correlations about the transport phenomena. The momentum and energy transfer terms as well as the mass are surveyed from the RELAP5/MOD3, RELAP5-3D, CATHARE, and TRAC-M does. Also the recent papers are surveyed. Among these resources, most of the CATHARE models are based on their own experiment and test results. Thus, the CATHARE models are only used as the comparison purposes. In this paper, a summary of the models and the correlations about the interfacial heat transfer are represented. These surveyed models and correlations will be tested numerically and one correlation is selected finally.

  18. Interfacial load transfer in polymer/carbon nanotube nanocomposites with a nanohybrid shish kebab modification.

    Science.gov (United States)

    Nie, Min; Kalyon, Dilhan M; Fisher, Frank T

    2014-09-10

    Interfacial properties are known to have a critical effect on the mechanical properties of a nanocomposite material system. Here, the interfacial load transfer in a carbon nanotube (CNT)/nylon-11 composite was studied with a CNT/nylon-11 nanohybrid shish kebab (NHSK) structure modification using Raman spectroscopy. Characterization of the polymer crystal in the NHSK using differential scanning calorimetry (DSC) for the first time indicates that the NHSK structure formed a more perfect crystal structure than the bulk polymer. On the basis of transmission electron microscopy and DSC results, a new growth model for the NHSK crystal is hypothesized, indicating the formation of an initial uniform crystal layer on the CNT prior to the crystallization of the kebabs. Characterization of the nanocomposites using Raman spectroscopy, with the samples heated to introduce interfacial shear stress caused by thermal expansion mismatch, found that the D* band of the CNT in the NHSK/nylon-11 composite displayed a more pronounced shift with an increase in temperature, which is attributed to the NHSK structure being more effective at transferring load from the nylon matrix to the nanotube inclusions. The NHSK structure was also used to fabricate composites with two amorphous polymers, polycarbonate and poly(methyl methacrylate), to investigate the load transfer mechanism. It was found that when the compatibility between the polymer in the NHSK structure and the bulk polymer matrix at the molecular level is sufficiently high, the ensuing mechanical interlocking effect further enhances the interfacial load transfer for polymer nanocomposites. Additional mechanical characterization of polymer nanocomposites with 0.1 wt % NHSK reinforcement demonstrates how the moduli and ultimate tensile strength of the nanocomposites can be improved via this NHSK structure. PMID:25134606

  19. Quantum Oscillations in an Interfacial 2D Electron Gas.

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bingop [Zhejiang Univ., Hangzhou (China); Lu, Ping [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Liu, Henan [Univ. of North Carolina, Charlotte, NC (United States); Lin, Jiao [Zhejiang Univ., Hangzhou (China); Ye, Zhenyu [Zhejiang Univ., Hangzhou (China); Jaime, Marcelo [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab); Balakirev, Fedor F. [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab); Yuan, Huiqiu [Zhejiang Univ., Hangzhou (China); Wu, Huizhen [Zhejiang Univ., Hangzhou (China); Pan, Wei [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Zhang, Yong [Univ. of North Carolina, Charlotte, NC (United States)

    2016-01-01

    Recently, it has been predicted that topological crystalline insulators (TCIs) may exist in SnTe and Pb1-xSnxTe thin films [1]. To date, most studies on TCIs were carried out either in bulk crystals or thin films, and no research activity has been explored in heterostructures. We present here the results on electronic transport properties of the 2D electron gas (2DEG) realized at the interfaces of PbTe/ CdTe (111) heterostructures. Evidence of topological state in this interfacial 2DEG was observed.

  20. Electron transfer in proteins.

    Science.gov (United States)

    Gray, H B; Winkler, J R

    1996-01-01

    Electron-transfer (ET) reactions are key steps in a diverse array of biological transformations ranging from photosynthesis to aerobic respiration. A powerful theoretical formalism has been developed that describes ET rates in terms of two parameters: the nuclear reorganization energy (lambda) and the electronic-coupling strength (HAB). Studies of ET reactions in ruthenium-modified proteins have probed lambda and HAB in several metalloproteins (cytochrome c, myoglobin, azurin). This work has shown that protein reorganization energies are sensitive to the medium surrounding the redox sites and that an aqueous environment, in particular, leads to large reorganization energies. Analyses of electronic-coupling strengths suggest that the efficiency of long-range ET depends on the protein secondary structure: beta sheets appear to mediate coupling more efficiently than alpha-helical structures, and hydrogen bonds play a critical role in both. PMID:8811189

  1. Wetting and Interfacial Characteristics of Mg AZ61 Alloy/Galvanized Steel in Cold Metal Transfer Process

    Science.gov (United States)

    Lin, Qiaoli; Yang, Fan; Cao, Rui; Chen, Jianhong; Guo, Tingbiao

    2015-09-01

    The dynamic sessile drop method was used to study the wetting behavior of galvanized steel by molten Mg AZ61 alloy under cold metal transfer condition. The interfacial microstructures were also analyzed by using scanning electron microscope and energy dispersive spectrometry. The observed results showed that the wetting behavior was directly determined by the wire feed speed (or the heat input). The Al-Fe intermetallic layer and Zn-rich zone were observed both at the interface and at the close of triple line. The formations of these interfacial characteristics satisfy the thermodynamic characteristic of Mg-Al/Fe and Mg-Zn/Fe systems.

  2. Relationship Between Casting Distortion, Mold Filling, and Interfacial Heat Transfer in Sand Molds

    Energy Technology Data Exchange (ETDEWEB)

    J. K. Parker; K. A. Woodbury; T. S. Piwonka; Y. Owusu

    1999-09-30

    This project sought to determine the relationship between casting dimensions and interfacial heat transfer in aluminum alloy sand castings. The program had four parts; measurement of interfacial heat transfer coefficients in resin bonded and green sand molds, the measurement of gap formation in these molds, the analysis of castings made in varying gatings, orientations and thicknesses, and the measurement of residual stresses in castings in the as-cast and gate removed condition. New values for interfacial heat transfer coefficients were measured, a novel method for gap formation was developed, and the variation of casting dimensions with casting method, gating, and casting orientation in the mold was documented.

  3. Advances in electron transfer chemistry

    CERN Document Server

    Mariano, Patrick S

    1993-01-01

    Advances in Electron Transfer Chemistry, Volume 3 presents studies that discuss findings in the various aspects of electron chemistry. The book is comprised of four chapters; each chapter reviews a work that tackles an issue in electron transfer chemistry. Chapter 1 discusses the photoinduced electron transfer in flexible biaryl donor-acceptor molecules. Chapter 2 tackles light-induced electron transfer in inorganic systems in homogeneous and heterogeneous phases. The book also covers internal geometry relaxation effects on electron transfer rates of amino-centered systems. The sequential elec

  4. Defect-driven interfacial electronic structures at an organic/metal-oxide semiconductor heterojunction.

    Science.gov (United States)

    Winget, Paul; Schirra, Laura K; Cornil, David; Li, Hong; Coropceanu, Veaceslav; Ndione, Paul F; Sigdel, Ajaya K; Ginley, David S; Berry, Joseph J; Shim, Jaewon; Kim, Hyungchui; Kippelen, Bernard; Brédas, Jean-Luc; Monti, Oliver L A

    2014-07-16

    The electronic structure of the hybrid interface between ZnO and the prototypical organic semiconductor PTCDI is investigated via a combination of ultraviolet and X-ray photoelectron spectroscopy (UPS/XPS) and density functional theory (DFT) calculations. The interfacial electronic interactions lead to a large interface dipole due to substantial charge transfer from ZnO to 3,4,9,10-perylenetetracarboxylicdiimide (PTCDI), which can be properly described only when accounting for surface defects that confer ZnO its n-type properties. PMID:24830796

  5. The Effect of Interfacial Geometry on Charge-Transfer States in the Phthalocyanine/Fullerene Organic Photovoltaic System.

    Science.gov (United States)

    Lee, Myeong H; Geva, Eitan; Dunietz, Barry D

    2016-05-19

    The dependence of charge-transfer states on interfacial geometry at the phthalocyanine/fullerene organic photovoltaic system is investigated. The effect of deviations from the equilibrium geometry of the donor-donor-acceptor trimer on the energies of and electronic coupling between different types of interfacial electronic excited states is calculated from first-principles. Deviations from the equilibrium geometry are found to destabilize the donor-to-donor charge transfer states and to weaken their coupling to the photoexcited donor-localized states, thereby reducing their ability to serve as charge traps. At the same time, we find that the energies of donor-to-acceptor charge transfer states and their coupling to the donor-localized photoexcited states are either less sensitive to the interfacial geometry or become more favorable due to modifications relative to the equilibrium geometry, thereby enhancing their ability to serve as gateway states for charge separation. Through these findings, we eludicate how interfacial geometry modifications can play a key role in achieving charge separation in this widely studied organic photovoltaic system.

  6. The Effect of Interfacial Geometry on Charge-Transfer States in the Phthalocyanine/Fullerene Organic Photovoltaic System.

    Science.gov (United States)

    Lee, Myeong H; Geva, Eitan; Dunietz, Barry D

    2016-05-19

    The dependence of charge-transfer states on interfacial geometry at the phthalocyanine/fullerene organic photovoltaic system is investigated. The effect of deviations from the equilibrium geometry of the donor-donor-acceptor trimer on the energies of and electronic coupling between different types of interfacial electronic excited states is calculated from first-principles. Deviations from the equilibrium geometry are found to destabilize the donor-to-donor charge transfer states and to weaken their coupling to the photoexcited donor-localized states, thereby reducing their ability to serve as charge traps. At the same time, we find that the energies of donor-to-acceptor charge transfer states and their coupling to the donor-localized photoexcited states are either less sensitive to the interfacial geometry or become more favorable due to modifications relative to the equilibrium geometry, thereby enhancing their ability to serve as gateway states for charge separation. Through these findings, we eludicate how interfacial geometry modifications can play a key role in achieving charge separation in this widely studied organic photovoltaic system. PMID:26237431

  7. Determination of Interfacial Charge-Transfer Rate Constants in Perovskite Solar Cells.

    Science.gov (United States)

    Pydzińska, Katarzyna; Karolczak, Jerzy; Kosta, Ivet; Tena-Zaera, Ramon; Todinova, Anna; Idígoras, Jesus; Anta, Juan A; Ziółek, Marcin

    2016-07-01

    A simple protocol to study the dynamics of charge transfer to selective contacts in perovskite solar cells, based on time-resolved laser spectroscopy studies, in which the effect of bimolecular electron-hole recombination has been eliminated, is proposed. Through the proposed procedure, the interfacial charge-transfer rate constants from methylammonium lead iodide perovskite to different contact materials can be determined. Hole transfer is faster for CuSCN (rate constant 0.20 ns(-1) ) than that for 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (spiro-OMeTAD; 0.06 ns(-1) ), and electron transfer is faster for mesoporous (0.11 ns(-1) ) than that for compact (0.02 ns(-1) ) TiO2 layers. Despite more rapid charge separation, the photovoltaic performance of CuSCN cells is worse than that of spiro-OMeTAD cells; this is explained by faster charge recombination in CuSCN cells, as revealed by impedance spectroscopy. The proposed direction of studies should be one of the key strategies to explore efficient hole-selective contacts as an alternative to spiro-OMeTAD. PMID:27253726

  8. Mass Transfer in Slag Refining of Silicon with Mechanical Stirring: Transient Interfacial Phenomena

    Science.gov (United States)

    White, Jesse F.; Sichen, Du

    2013-12-01

    Experiments have been carried out to study the rates of mass transfer between liquid silicon and CaO-SiO2 slag with impeller stirring at 1823 K (1550 °C). The occurrence of transient interfacial phenomena related to the mass transfer of calcium has been observed; the evidence suggests that the reduction of calcium oxide at the interface leads to a rapid, temporary drop in the apparent interfacial tension. At low apparent interfacial tension, mechanical agitation facilitates the dispersion of metal into the slag phase, which dramatically increases the interfacial area; here, it has been estimated to increase by at least one order of magnitude. As the reaction rate slows down, the apparent interfacial tension increases and the metal recoalesces. The incidental transfer of calcium very likely promotes the transfer of boron by increasing the interfacial area. Mechanical mixing appears to be an extremely effective means to increase the reaction rate of boron extraction and could feasibly be implemented in the industrial slag refining of silicon to improve reaction rates.

  9. The effect of interfacial evaporation on heat and mass transfer of falling liquid film

    Institute of Scientific and Technical Information of China (English)

    WANG; Buxuan; (

    2001-01-01

    [1]Wasden, F.K., Dukler, A.E., Insight into the hydrodynamics of free falling wavy films, AIChE J., 1989, 35(2): 187.[2]Jayanti, S., Hewitt, G.F., Hydrodynamics and heat transfer of wavy thin film flow, Int. J. Heat Mass Transfer, 1997, 40(10): 179.[3]Seban, R.A., Faghri, A., Evaporation and heating with turbulent falling liquid films, ASME J. Heat Transfer, 1976, 98C: 315.[4]Yang, W.M., Evaporation cooling of liquid film in turbulent mixed convection channel flows, Int. J. Heat Mass Transfer, 1998, 41(23): 3719.[5]Wang, B.X., Zhang, J.T., Peng, X.F., Experimental study on the dryout heat flux of falling liquid film, accepted by Int. J. Heat Mass Transfer as HMT# 2507.[6]Udell, K.S., Heat transfer in porous media heated from above with evaporation, condensation, and capillary effects, ASME J. Heat Transfer, 1983, 105: 485.[7]Carey, V.P., Liquid-Vapor Phase-Change Phenomena——An Introduction to the Thermophysics of Vaporization and Conduction Processes in Heat Transfer Equipment, Washington: Hemisphere Publishing Corporation, 1992, 112.[8]Eames, I.W., Marr, N.J., Sabir, H., The evaporation coefficient of water: a review, Int. J. Heat Mass Transfer, 1997, 40(12): 2963.[9]Israelachvili, J.N., Intermolecular and Surface Forces, San Diego: Academic Press, 1990, 16-30.[10]Holman, J.P., Heat Transfer, 5th ed., Tokyo: McGraw-Hill, Inc, 1981.[11]Zhang, J.T., Wang, B.X., Peng, X.F., Falling liquid film thickness measurement by optical-electronic method, Rev. Scientific Instruments, 2000, 71(4): [12]Zhang, J.T., Wang, B.X., Peng, X.F., Investigation on the interfacial evaporation of falling liquid film with wall heating, accepted by J. Tsinghua University.[13]Fujita, T., Ueda, T., Heat transfer to falling liquid films and film breakdown, Int. J. Heat Mass Transfer, 1978, 21: 97.[14]Bohn, M.S., Davis, S.H., Thermocapillary breakdown of falling liquid films at high Reynolds numbers, Int. J. Heat Masss Transfer, 1993, 36

  10. Effect of modification melt treatment on casting/chill interfacial heat transfer and electrical conductivity of Al-13% Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Narayan Prabhu, K.; Ravishankar, B.N

    2003-11-15

    For successful modelling of the solidification process, a reliable heat transfer boundary condition data is required. These boundary conditions are significantly influenced by the casting and mould parameters. In the present work, the effect of sodium modification melt treatment on casting/chill interfacial heat transfer during upward solidification of an Al-13% Si alloy against metallic chills is investigated using thermal analysis and inverse modelling techniques. In the presence of chills, modification melt treatment resulted in an increase in the cooling rate of the solidifying casting near the casting/chill interfacial region. The corresponding interfacial heat flux transients and electrical conductivities are also found to be higher. This is attributed to (i) improvement in the casting/chill interfacial thermal contact condition brought about by the decrease in the surface tension of the liquid metal on addition of sodium and (ii) increase in the electronic heat conduction in the initial solidified shell due to change in the morphology of silicon from a acicular type to a fine fibrous structure and increase in the ratio of the modification rating to the secondary dendrite arm spacing.

  11. A numerical investigation on the influence of liquid properties and interfacial heat transfer during microdroplet deposition onto a glass substrate

    CERN Document Server

    Bhardwaj, Rajneesh; Attinger, Daniel

    2010-01-01

    This work investigates the impingement of a liquid microdroplet onto a glass substrate at different temperatures. A finite-element model is applied to simulate the transient fluid dynamics and heat transfer during the process. Results for impingement under both isothermal and non-isothermal conditions are presented for four liquids: isopropanol, water, dielectric fluid (FC-72) and eutectic tin-lead solder (63Sn-37Pb). The objective of the work is to select liquids for a combined numerical and experimental study involving a high resolution, laser-based interfacial temperature measurement to measure interfacial heat transfer during microdroplet deposition. Applications include spray cooling, micro-manufacturing and coating processes, and electronics packaging. The initial droplet diameter and impact velocity are 80 {\\mu}m and 5 m/s, respectively. For isothermal impact, our simulations with water and isopropanol show very good agreement with experiments. The magnitude and rates of spreading for all four liquids ...

  12. Interfacial stress transfer and property mismatch in discontinuous nanofiber/nanotube composite materials.

    Science.gov (United States)

    Xu, L Roy; Sengupta, Sreeparna

    2005-04-01

    Novel nanotubes/nanofibers with high strength and stiffness did not lead to high failure strengths/strains of nanocomposite materials. Therefore, the interfacial stress transfer and possible stress singularities, arising at the interfacial ends of discontinuous nanofibers embedded in a matrix, subjected to tensile and shear loading, were investigated by finite element analysis. The effects of Young's moduli and volume fractions on interfacial stress distributions were studied. Round-ended nanofibers were proposed to remove the interfacial singular stresses, which were caused by high stiffness mismatch of the nanoscale reinforcement and the matrix. However, the normal stress induced in the nanofiber through interfacial stress transfer was still less than 2 times that in the matrix. This stress value is far below the high strength of the nanofiber. Therefore, the load transfer efficiency of discontinuous nanofibers or nanotube composites is very low. Hence, nanofibers or nanotubes in continuous forms, which also preclude the formation of singular interfacial stress zones, are recommended over discontinuous nanofibers to achieve high strengths in nanocomposite materials. PMID:16004129

  13. Analysis of Effect of Gas-Liquid Interfacial Disturbance on Mass Transfer Performance

    Science.gov (United States)

    Wu, Honda; Chung, Tsair-Wang

    In order to study the mass transfer phenomena for water vapor absorbed by triethylene glycol (TEG) solution and to elucidate effect of interfacial disturbance on absorption performance, the interfacial phenomena for water drop instilling on the surface of TEG solution and mass transfer process were observed and operated in this study. Besides liquid and gas flow rates, the interfacial disturbance can also affect the mass transfer performance in the absorption system with continuous liquid phase, and the advanced mass transfer phenomena must be discussed from the interface of matter. Therefore, the surface tensions of desiccant solutions were measured to analyze the disturbed phenomena of water drop instilling on the surface of TEG solution. Since the Marangoni-Index (MI) means the maximum surface tension difference on the surface of liquid layer, the values of MI were calculated and compared with the mass transfer performance of packed-bed absorber. Generally speaking, the interfacial disturbance, resulted from the surface tension difference, would promote the contacting area of gas and liquid phases. The observation of water drop instilling on surface of TEG solution found that the interfacial disturbance existed between water drop and TEG solution, and the interfacial instability was found in the peripheral region of the water drop. On the other hand, the values of MI were increased by the increased TEG concentrations, and it can be deduced that the surface tension effect should be significant in the higher concentration of TEG solution and the interfacial disturbance would be heavier above 95 wt.% TEG solutions. Finally, the absorption performance for 95 and 96 wt.% TEG solutions were much larger than that of 90 and 88.6 wt.% TEG solutions in the operation of packed-bed absorber.

  14. Mass-Transfer-Controlled Dynamic Interfacial Tension in Microfluidic Emulsification Processes.

    Science.gov (United States)

    Wang, Kai; Zhang, Liming; Zhang, Wanlu; Luo, Guangsheng

    2016-04-01

    Varied interfacial tension caused by the unsaturated adsorption of surfactants on dripping droplet surfaces is experimentally studied. The mass transfer and adsorption of surfactants, as well as the generation of fresh interfaces, are considered the main factors dominating the surfactant adsorption ratio on droplet surfaces. The diffusion and convective mass transfer of the surfactants are first distinguished by comparing the adsorption depth and the mass flux boundary layer thickness. A characterized mass transfer time is then calculated by introducing an effective diffusion coefficient. A time ratio is furthermore defined by dividing the droplet generation time by the characteristic mass transfer time, t/tm, in order to compare the rates of surfactant mass transfer and droplet generation. Different control mechanisms for different surfactants are analyzed based on the range of t/t(m), and a criterion time ratio using a simplified characteristic mass transfer time, t(m)*, is finally proposed for predicting the appearance of dynamic interfacial tension.

  15. Studies on the liquid-liquid interfacial mass transfer process using holographic interferometry

    Institute of Scientific and Technical Information of China (English)

    Chaofan ZHAO; Youguang MA; Chunying ZHU

    2008-01-01

    This paper aims at the interracial phenomena of liquid-liquid mass transfer and its characteristic. By using the real-time holographic technique, the concen-tration distributions on the aqueous side were obtained according to holographic diagrams of mass transfer of ethanol through the interface of oil and water at different initial concentrations. Furthermore, the concentrations near the interface and the mass transfer coefficients were attained. A correlation of concentration near the interface to the concentration of the solute in the oil side was proposed. An approach of interfacial energy with solute concentration was established, and the calculated results are at good agreement with the experimental data. It is indicated that the liquid-liquid mass transfer process is approximately in accordance with two-film theory, the interfacial performance may be changed by the addition of the solute, and the interface of liquid-liquid is non-equilibrium thermodynamically during the mass transfer process.

  16. Study on heat transfer for falling liquid film flow with consideration of interfacial evaporation

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The interfacial evaporative heat transfer was included in the semi-empirical study of the heat transfer for the falling liquid film flow. The investigations showed that, the inclusion of the interfacial evaporative heat transfer in the turbulent model would lower the predicted convective heat transfer coefficient. Predictions of the new model resulted in a prominent deviation from that predictions of the normal model in the case of large mass flow rate and low wall heat flux. This deviation will be decreased with increasing wall heat flux, such that it will be asymptotic zero at very high wall heat flux. Predictions of the new model agreed well with the current experimental measurements. This study has verified that the Reynolds number is not the sole crucial parameter for heat transfer of falling liquid film flow, and wall heat flux will be another important independent parameter. This result is consistent with our previous studies.

  17. Electronic fund transfer & the "unbanked"

    OpenAIRE

    Luxman Nathan

    1998-01-01

    As the Federal Government moves to switch most federal payments from paper check delivery to Direct Deposit by January 2, 1999, the Electronic Fund Transfer Initiative (EFT) attempts to educate consumers and serve the "unbanked."

  18. The Mechanism of Interfacial Mass Transfer in Gas Absorption Process

    Institute of Scientific and Technical Information of China (English)

    马友光; 冯惠生; 徐世昌; 余国琮

    2003-01-01

    Based on the method of molecular thermodynamics ,the mass transfer mechanism at gas-liquid interface is studied theoretically,and a nowe mathematical model is proposed,Using laser holographic interference technique,the hydrodynamics and mass transfer characteristics of CO2 absorption are measured,It is shown that the calculated results are in good agreement with the experimental data.

  19. Advances in electron transfer chemistry

    CERN Document Server

    Mariano, Patrick S

    1995-01-01

    Advances in Electron Transfer Chemistry, Volume 4 presents the reaction mechanisms involving the movement of single electrons. This book discusses the electron transfer reactions in organic, biochemical, organometallic, and excited state systems. Organized into four chapters, this volume begins with an overview of the photochemical behavior of two classes of sulfonium salt derivatives. This text then examines the parameters that control the efficiencies for radical ion pair formation. Other chapters consider the progress in the development of parameters that control the dynamics and reaction p

  20. Characterization of interfacially electronic structures of gold-magnetite heterostructures using X-ray absorption spectroscopy.

    Science.gov (United States)

    Lin, Fang-hsin; Doong, Ruey-an

    2014-03-01

    Gold-magnetite heterostructures are novel nanomaterials which can rapidly catalyze the reduction reaction of nitroaromatics. In this study, the interfacially structural and electronic properties of various morphologies of Au-Fe3O4 heterostructures were systematically investigated using X-ray absorbance spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS). The effect of change in electronic structure and charge transfer on electrochemically catalytic activity of Au-Fe3O4 heterostructures was further evaluated by oxygen reduction reaction (ORR). The shifts in binding energy of Au4f and Fe2p peaks in XPS spectra indicate the charge transfer between the Au and Fe3O4 nanoparticles. The increase in d-hole population of Au seeds after the conjugation with iron oxides follows the order flower-like Au-Fe3O4 (FLNPs)>dumbbell-like Au-Fe3O4 (DBNPs)>Au seeds. In addition, the Fe(2+) valence state increases in Au-Fe3O4 heterostructures, which provides evidence to support the hypothesis of charge transfer between Au and Fe3O4 nanoparticles. The theoretical simulation of Au L3-edge XAS further confirms the production of Au-Fe and Au-O bonds at the interface of Au/Fe3O4 and the epitaxial linkage relationship between Au and Fe3O4 nanoparticles. In addition, the electron deficient of Au seeds increases upon increasing Fe3O4 nanoparticles on a single Au seed, and subsequently decreases the catalytic activity of Au in the Au-Fe3O4 heterostructures. The catalytic activity of Au-Fe3O4 toward ORR follows the order Au seeds>Au-Fe3O4 DBNPs>Au-Fe3O4 FLNPs, which is positively correlated to the extent of electronic deficiency of Au in Au-Fe3O4 heterostructures.

  1. The electronic couplings in electron transfer and excitation energy transfer.

    Science.gov (United States)

    Hsu, Chao-Ping

    2009-04-21

    The transport of charge via electrons and the transport of excitation energy via excitons are two processes of fundamental importance in diverse areas of research. Characterization of electron transfer (ET) and excitation energy transfer (EET) rates are essential for a full understanding of, for instance, biological systems (such as respiration and photosynthesis) and opto-electronic devices (which interconvert electric and light energy). In this Account, we examine one of the parameters, the electronic coupling factor, for which reliable values are critical in determining transfer rates. Although ET and EET are different processes, many strategies for calculating the couplings share common themes. We emphasize the similarities in basic assumptions between the computational methods for the ET and EET couplings, examine the differences, and summarize the properties, advantages, and limits of the different computational methods. The electronic coupling factor is an off-diagonal Hamiltonian matrix element between the initial and final diabatic states in the transport processes. ET coupling is essentially the interaction of the two molecular orbitals (MOs) where the electron occupancy is changed. Singlet excitation energy transfer (SEET), however, contains a Frster dipole-dipole coupling as its most important constituent. Triplet excitation energy transfer (TEET) involves an exchange of two electrons of different spin and energy; thus, it is like an overlap interaction of two pairs of MOs. Strategies for calculating ET and EET couplings can be classified as (1) energy-gap-based approaches, (2) direct calculation of the off-diagonal matrix elements, or (3) use of an additional operator to describe the extent of charge or excitation localization and to calculate the coupling value. Some of the difficulties in calculating the couplings were recently resolved. Methods were developed to remove the nondynamical correlation problem from the highly precise coupled cluster

  2. Raman study of interfacial load transfer in graphene nanocomposites

    Science.gov (United States)

    Srivastava, Iti; Mehta, Rutvik J.; Yu, Zhong-Zhen; Schadler, Linda; Koratkar, Nikhil

    2011-02-01

    We tracked the strain-sensitive characteristic Raman G-band shift of graphene platelets in polydimethyl-siloxane (PDMS) nanocomposites revealing the filler-to-matrix interactions. We obtained large debonding strains of ˜7% for graphene in PDMS, with the peak shift rate with strain being ˜2.4 cm-1/composite strain % in comparison to single-walled carbon nanotube composites, where a relatively low rate of ˜0.1 cm-1/composite strain % was obtained, suggesting enhanced load-transfer effectiveness for graphene. A surprising observation was that for large strains (>1.5%) the graphene fillers went into compression under uniaxial tensile deformation and vice versa. We propose that this effect is related to the high mobility of the PDMS chains at room temperature.

  3. Regularized determination of interfacial heat transfer coefficient during ZL102 solidification process

    Institute of Scientific and Technical Information of China (English)

    SUI Da-shan; CUI Zhen-shan

    2008-01-01

    The interfacial heat transfer coefficient(IHTC) between the casting and the mould is essential to the numerical simulation as one of boundary conditions. A new inverse method was presented according to the Tikhonov regularization theory. A regularized functional was established and the regularization parameter was deduced. The functional was solved to determine the interfacial heat transfer coefficient by using the sensitivity coefficient and Newton-Raphson iteration method. The temperature measurement experiment was done to ZL102 sand mold casting, and the appropriate mathematical model of the IHTC was established. Moreover, the regularization method was used to determinate the IHTC. The results indicate that the regularization method is very efficient in overcoming the ill-posedness of the inverse heat conduction problem(IHCP), and ensuring the accuracy and stability of the solutions.

  4. Near-infrared fluorescent single walled carbon nanotube-chitosan composite: Interfacial strain transfer efficiency assessment

    Science.gov (United States)

    Mol Menamparambath, Mini; Arabale, Girish; Nikolaev, Pavel; Baik, Seunghyun; Arepalli, Sivaram

    2013-04-01

    Effective load transfer at the single walled carbon nanotube (SWCNT)-polymer interface is most desirable for mechanically reinforced polymer composites. Versatile layer-by-layer assembly technique achieved dispersion and uniform distribution of sodium carboxymethylcellulose (CMC)-solubilized SWCNTs within the polymer matrix. Electrostatic interaction between positively charged chitosan and negatively charged CMC facilitates design of an optically active biocompatible nanocomposite. Interfacial strain transfer efficiency of SWCNT-chitosan nanocomposite was assessed via SWCNT Raman and photoluminescence band shifts under uniaxial strain. Photoluminescence peak shift rates of individual semiconducting SWCNTs were investigated and compared with tight binding model calculations.

  5. A layer-by-layer ZnO nanoparticle-PbS quantum dot self-assembly platform for ultrafast interfacial electron injection

    KAUST Repository

    Eita, Mohamed Samir

    2014-08-28

    Absorbent layers of semiconductor quantum dots (QDs) are now used as material platforms for low-cost, high-performance solar cells. The semiconductor metal oxide nanoparticles as an acceptor layer have become an integral part of the next generation solar cell. To achieve sufficient electron transfer and subsequently high conversion efficiency in these solar cells, however, energy-level alignment and interfacial contact between the donor and the acceptor units are needed. Here, the layer-by-layer (LbL) technique is used to assemble ZnO nanoparticles (NPs), providing adequate PbS QD uptake to achieve greater interfacial contact compared with traditional sputtering methods. Electron injection at the PbS QD and ZnO NP interface is investigated using broadband transient absorption spectroscopy with 120 femtosecond temporal resolution. The results indicate that electron injection from photoexcited PbS QDs to ZnO NPs occurs on a time scale of a few hundred femtoseconds. This observation is supported by the interfacial electronic-energy alignment between the donor and acceptor moieties. Finally, due to the combination of large interfacial contact and ultrafast electron injection, this proposed platform of assembled thin films holds promise for a variety of solar cell architectures and other settings that principally rely on interfacial contact, such as photocatalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Studies on the interfacial charge transfer processes of nanocrystalline CdSe thin film electrodes by intensity modulated photocurrent spectroscopy

    Institute of Scientific and Technical Information of China (English)

    张敬波; 林原; 尹峰; 肖绪瑞

    2000-01-01

    Interfacial charge transfer kinetics of the nanocrystalline CdSe thin film electrodes have been studied in sodium polysulfide solutions by intensity modulated photocurrent spectroscopy (IMPS). The interfacial direct and indirect charge transfer and recombination processes were analyzed in terms of the parameters: normalized steady state photocurrents and surface state lifetimes obtained by measuring the IMPS responses under different applied potentials and different solution concentrations. IMPS responses of polycrystalline CdSe thin film electrodes were also presented for comparison.

  7. Large impact of reorganization energy on photovoltaic conversion due to interfacial charge-transfer transitions.

    Science.gov (United States)

    Fujisawa, Jun-ichi

    2015-05-14

    Interfacial charge-transfer (ICT) transitions are expected to be a novel charge-separation mechanism for efficient photovoltaic conversion featuring one-step charge separation without energy loss. Photovoltaic conversion due to ICT transitions has been investigated using several TiO2-organic hybrid materials that show organic-to-inorganic ICT transitions in the visible region. In applications of ICT transitions to photovoltaic conversion, there is a significant problem that rapid carrier recombination is caused by organic-inorganic electronic coupling that is necessary for the ICT transitions. In order to solve this problem, in this work, I have theoretically studied light-to-current conversions due to the ICT transitions on the basis of the Marcus theory with density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. An apparent correlation between the reported incident photon-to-current conversion efficiencies (IPCE) and calculated reorganization energies was clearly found, in which the IPCE increases with decreasing the reorganization energy consistent with the Marcus theory in the inverted region. This activation-energy dependence was systematically explained by the equation formulated by the Marcus theory based on a simple excited-state kinetic scheme. This result indicates that the reduction of the reorganization energy can suppress the carrier recombination and enhance the IPCE. The reorganization energy is predominantly governed by the structural change in the chemical-adsorption moiety between the ground and ICT excited states. This work provides crucial knowledge for efficient photovoltaic conversion due to ICT transitions. PMID:25892453

  8. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume II. Chapters 6-10)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  9. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume III. Chapters 11-14)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  10. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume I. Chapters 1-5)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  11. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume IV. Chapters 15-19)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  12. Nanoantioxidant-driven plasmon enhanced proton-coupled electron transfer

    Science.gov (United States)

    Sotiriou, Georgios A.; Blattmann, Christoph O.; Deligiannakis, Yiannis

    2015-12-01

    Proton-coupled electron transfer (PCET) reactions involve the transfer of a proton and an electron and play an important role in a number of chemical and biological processes. Here, we describe a novel phenomenon, plasmon-enhanced PCET, which is manifested using SiO2-coated Ag nanoparticles functionalized with gallic acid (GA), a natural antioxidant molecule that can perform PCET. These GA-functionalized nanoparticles show enhanced plasmonic response at near-IR wavelengths, due to particle agglomeration caused by the GA molecules. Near-IR laser irradiation induces strong local hot-spots on the SiO2-coated Ag nanoparticles, as evidenced by surface enhanced Raman scattering (SERS). This leads to plasmon energy transfer to the grafted GA molecules that lowers the GA-OH bond dissociation enthalpy by at least 2 kcal mol-1 and therefore facilitates PCET. The nanoparticle-driven plasmon-enhancement of PCET brings together the so far unrelated research domains of nanoplasmonics and electron/proton translocation with significant impact on applications based on interfacial electron/proton transfer.Proton-coupled electron transfer (PCET) reactions involve the transfer of a proton and an electron and play an important role in a number of chemical and biological processes. Here, we describe a novel phenomenon, plasmon-enhanced PCET, which is manifested using SiO2-coated Ag nanoparticles functionalized with gallic acid (GA), a natural antioxidant molecule that can perform PCET. These GA-functionalized nanoparticles show enhanced plasmonic response at near-IR wavelengths, due to particle agglomeration caused by the GA molecules. Near-IR laser irradiation induces strong local hot-spots on the SiO2-coated Ag nanoparticles, as evidenced by surface enhanced Raman scattering (SERS). This leads to plasmon energy transfer to the grafted GA molecules that lowers the GA-OH bond dissociation enthalpy by at least 2 kcal mol-1 and therefore facilitates PCET. The nanoparticle-driven plasmon

  13. Heterostructure Intervalley Transferred Electron Effects

    Institute of Scientific and Technical Information of China (English)

    XUE Fang-Shi

    2001-01-01

    A Gunn active layer is used as an X electron probe to detect the X tunnelling current in the GaAs-AlAs heterostructure, from which a new heterostructure intervalley transferred electron (HITE) device is obtained. In the 8 mm band, the highest pulse output power of these diodes is 2.65 W and the highest conversion efficiency is 18%. The dc and rf performance of the HITE devices was simulated by the band mixing resonant tunnelling theory and Monte Carlo transport simulation. The HITE effect has transformed the transit-time dipole-layer mode in the Gunn diode into a relaxation oscillation mode in the HITE device. From the comparison of simulated results to the measured data, the HITE effect is demonstrated straightforwardly

  14. Direct correlation of charge transfer absorption with molecular donor:acceptor interfacial area via photothermal deflection spectroscopy

    KAUST Repository

    Domingo, Ester

    2015-04-09

    We show that the Charge Transfer (CT) absorption signal in bulk-heterojunction (BHJ) solar cell blends, measured by photothermal deflection spectroscopy (PDS), is directly proportional to the density of molecular donor/acceptor interfaces. Since the optical transitions from ground state to the interfacial CT state are weakly allowed at photon energies below the optical gap of both donor and acceptor, we can exploit the use of this sensitive linear absorption spectroscopy for such quantification. Moreover, we determine the absolute molar extinction coefficient of the CT transition for an archetypical polymer-fullerene interface. The latter is ~100 times lower than the extinction coefficient of the donor chromophore involved, allowing us to experimentally estimate the transition dipole moment (0.3 D) and the electronic coupling between ground state and CT state to be on the order of 30 meV.

  15. Surface chemistry and interfacial charge-transfer mechanisms in photoinduced oxygen exchange at O2-TiO2 interfaces.

    Science.gov (United States)

    Montoya, Juan Felipe; Peral, José; Salvador, Pedro

    2011-04-01

    Experimental results obtained over the last three decades on photoinduced oxygen isotopic exchange (POIE) of TiO₂ oxygen atoms with those of adsorbed water molecules and gaseous O₂ are analyzed in the light of recent information from the literature on the interaction of water and O₂ species with the TiO₂ surface (obtained by application of surface spectroscopy techniques in combination with high-resolution scanning tunnelling microscopy). The analysis emphasizes the singular role that bridging oxygen ions and bridging oxygen vacancies play in TiO₂ surface chemistry and interfacial electron transfer at the gas phase-TiO₂ interface in the absence and presence of water. The observed competition between POIE and the photo-oxidation (PO) of organic compounds is analyzed in terms of the recently developed direct-indirect (D-I) kinetic model for heterogeneous photocatalysis (D. Monllor-Satoca et al., Catal. Today, 2007, 129, 247, and references therein). PMID:21442702

  16. Determination of the interfacial heat transfer coefficient in the hot stamping of AA7075

    OpenAIRE

    Liu Xiaochuan; Ji Kang; Fakir Omer El; Liu Jun; Zhang Qunli; Wang Liliang

    2015-01-01

    The interfacial heat transfer coefficient (IHTC) is a key parameter in hot stamping processes, in which a hot blank is formed and quenched by cold dies simultaneously. The IHTC should therefore be identified and used in FE models to improve the accuracy of simulation results of hot stamping processes. In this work, a hot stamping simulator was designed and assembled in a Gleeble 3800 thermo-mechanical testing system and a FE model was built in PAM-STAMP to determine the IHTC value between a h...

  17. Detrimental effect of interfacial Dzyaloshinskii-Moriya interaction on perpendicular spin-transfer-torque magnetic random access memory

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Peong-Hwa; Lee, Seo-Won, E-mail: swlee-sci@korea.ac.kr, E-mail: kj-lee@korea.ac.kr [Department of Materials Science and Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Song, Kyungmi; Lee, Seung-Jae [KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 136-713 (Korea, Republic of); Lee, Kyung-Jin, E-mail: swlee-sci@korea.ac.kr, E-mail: kj-lee@korea.ac.kr [Department of Materials Science and Engineering, Korea University, Seoul 136-713 (Korea, Republic of); KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 136-713 (Korea, Republic of)

    2015-11-16

    Interfacial Dzyaloshinskii-Moriya interaction in ferromagnet/heavy metal bilayers is recently of considerable interest as it offers an efficient control of domain walls and the stabilization of magnetic skyrmions. However, its effect on the performance of perpendicular spin transfer torque memory has not been explored yet. We show based on numerical studies that the interfacial Dzyaloshinskii-Moriya interaction decreases the thermal energy barrier while increases the switching current. As high thermal energy barrier as well as low switching current is required for the commercialization of spin torque memory, our results suggest that the interfacial Dzyaloshinskii-Moriya interaction should be minimized for spin torque memory applications.

  18. An experimental investigation of the interfacial condensation heat transfer in steam/water countercurrent stratified flow in a horizontal pipe

    Energy Technology Data Exchange (ETDEWEB)

    Chu, In Cheol; Yu, Seon Oh; Chun, Moon Hyun [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of); Kim, Byong Sup; Kim, Yang Seok; Kim, In Hwan; Lee, Sang Won [Korea Electric Power Research Institute, Taejon (Korea, Republic of)

    1998-12-31

    An interfacial condensation heat transfer phenomenon in a steam/water countercurrent stratified flow in a nearly horizontal pipe has been experimentally investigated. The present study has been focused on the measurement of the temperature and velocity distributions within the water layer. In particular, the water layer thickness used in the present work is large enough so that the turbulent mixing is limited and the thermal stratification is established. As a result, the thermal resistance of the water layer to the condensation heat transfer is increased significantly. An empirical correlation of the interfacial condensation heat transfer has been developed. The present correlation agrees with the data within {+-} 15%. 5 refs., 6 figs. (Author)

  19. Interfacial electronic properties of the heterojunctions C{sub 60}/rubrene/Au and rubrene/C{sub 60}/Au

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Chiu-Ping; Chan, Yi-Wei; Hsueh, Chih-Feng [Department of Electrophysics, National Chiayi University, 300 University Road, Chiayi 60004, Taiwan (China); Pi, Tun-Wen [National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China)

    2012-07-15

    Using synchrotron-radiation photoemission, we have studied the electronic structures of rubrene:C{sub 60} heterojunctions on Au substrates. The photoelectron spectra show that the interfacial properties at the C{sub 60}/rubrene/Au and rubrene/C{sub 60}/Au interfaces are asymmetric and do not follow the commutation rule. In the C{sub 60}/rubrene case, a gap state appearing in the initial deposition stage results from negative charges transferred from rubrene to C{sub 60}, while in the inverse deposition process, no strong chemical reaction could be found. A significant shift of the vacuum level induced by alignment of the charge neutrality levels of the two materials was observed in both cases. Furthermore, the charge transfer strongly enhances the dipole potential of the C{sub 60}/rubrene interface. The energy level diagrams show that the C{sub 60}-on-rubrene process has a superior number of advantages in the photovoltaic applications.

  20. Positive electron affinity of interfacial region in Polyethylene-MgO nanocomposite dielectric

    OpenAIRE

    Kubyshkina, Elena; Unge, Mikael; Jonsson, B. L. G.

    2016-01-01

    Polymer-based nanocomposite dielectrics are expected to become essential in future generations of high voltage electrical insulation. However, the physics behind their performance is not yet understood. Here we investigate electronic properties of the interfacial area in magnesium oxide-polyethylene nanocomposite. We use density functional theory to demonstrate positive electron affinity for MgO (100) and hydroxylated MgO (111) interfaces with polyethylene. We evaluate the role of silicon-bas...

  1. Exocellular electron transfer in anaerobic microbial communities

    NARCIS (Netherlands)

    Stams, A.J.M.; Bok, de F.A.M.; Plugge, C.M.; Eekert, van M.H.A.; Dolfing, J.; Schraa, G.

    2006-01-01

    Exocellular electron transfer plays an important role in anaerobic microbial communities that degrade organic matter. Interspecies hydrogen transfer between microorganisms is the driving force for complete biodegradation in methanogenic environments. Many organic compounds are degraded by obligatory

  2. Nanoscale and single-molecule interfacial electron transfer

    DEFF Research Database (Denmark)

    Hansen, Allan Glargaard; Wackerbarth, Hainer; Nielsen, Jens Ulrik;

    2003-01-01

    for comprehensive later theoretical work and data interpretation in many areas of chemistry, electrochemistry, and biology. We discuss here some new areas of theoretical electrochemical ET science, with focus on nanoscale electrochemical and bioelectrochemical sciences. Particular attention is given to in situ...

  3. Interfacial charge-transfer transitions in a TiO2-benzenedithiol complex with Ti-S-C linkages.

    Science.gov (United States)

    Fujisawa, Jun-ichi; Muroga, Ryuki; Hanaya, Minoru

    2015-11-28

    Interfacial charge-transfer (ICT) transitions between organic materials and inorganic semiconductors are a new mechanism for light absorption at organic-semiconductor interfaces. ICT transitions cause one-step interfacial charge separation without loss of energy. This feature is potentially useful to realize efficient organic-inorganic hybrid solar cells. ICT transitions have been examined by employing titanium dioxide (TiO2) nanoparticles chemisorbed with π-conjugated molecules via Ti-O-C linkages. Here, we report ICT transitions in a TiO2 and 1,2-benzenedithiol (BDT) complex with Ti-S-C linkages. BDT adsorbs on TiO2 by the bridging bidentate coordination of the sulfur atoms to surface titanium atoms. The TiO2-BDT complex shows ICT transitions from the BDT moiety to the conduction band of TiO2 in the visible region. The ICT transitions occur by orbital overlaps between the d orbitals of the surface titanium atoms and the π orbitals of the benzene ring. Our density-functional-theory (DFT) analysis reveals that the 3p valence orbitals of the sulfur bridging atoms contribute to more than 50% of the highest occupied molecular orbital (HOMO) and the 3d-3p(sulfur)-π interaction via the Ti-S-C linkage enhances the electronic mixing between the titanium atoms and the benzene moiety as compared to the 3d-2p(oxygen)-πvia the Ti-O-C linkage. This result indicates the important role of the heavier-atom linkers for strong organic-inorganic electronic couplings. PMID:26486297

  4. Hierarchical control of electron-transfer

    DEFF Research Database (Denmark)

    Westerhoff, Hans V.; Jensen, Peter Ruhdal; Egger, Louis;

    1997-01-01

    In this chapter the role of electron transfer in determining the behaviour of the ATP synthesising enzyme in E. coli is analysed. It is concluded that the latter enzyme lacks control because of special properties of the electron transfer components. These properties range from absence of a strong...... back pressure by the protonmotive force on the rate of electron transfer to hierarchical regulation of the expression of the gens that encode the electron transfer proteins as a response to changes in the bioenergetic properties of the cell.The discussion uses Hierarchical Control Analysis...

  5. Interfacial adhesion in metal/polymer systems for electronics

    OpenAIRE

    Ge, Jun

    2003-01-01

    The effects of the different surface modification methods on the adhesion of electroless and sputter-deposited metals to dielectric polymers were investigated. The adhesion of Cu and Cr/Cu metallizations to the epoxies, liquid crystalline polymer and inorganic-organic hybrid polymer was measured with the newly developed pull test method. The microstructure and chemical state of the surfaces were characterized with the help of X-ray photoelectron spectroscopy (XPS), scanning electron microscop...

  6. "Butterfly effect" in CuO/graphene composite nanosheets: a small interfacial adjustment triggers big changes in electronic structure and Li-ion storage performance.

    Science.gov (United States)

    Zhang, Xiaoting; Zhou, Jisheng; Song, Huaihe; Chen, Xiaohong; Fedoseeva, Yu V; Okotrub, A V; Bulusheva, L G

    2014-10-01

    Generally speaking, excellent electrochemical performance of metal oxide/graphene nanosheets (GNSs) composite is attributed to the interfacial interaction (or "synergistic effect") between constituents. However, there are no any direct observations on how the electronic structure is changed and how the properties of Li-ion storage are affected by adjusting the interfacial interaction, despite of limited investigations on the possible nature of binding between GNSs and metal oxide. In this paper, CuO nanosheets/GNSs composites with a little Cu2O (ca. 4 wt %) were utilized as an interesting model to illustrate directly the changes of interfacial nature as well as its deep influence on the electronic structure and Li-ion storage performance of composite. The interfacial adjustment was successfully fulfilled by removal of Cu2O in the composite by NH3·H2O. Formation of Cu-O-C bonds on interfaces both between CuO and GNSs, and Cu2O and GNSs in the original CuO/GNSs composites was detected. The small interfacial alteration by removal of the little Cu2O results in the obvious changes in electronic structure, such as weakening of covalent Cu-O-C interfacial interaction and recovery of π bonds in graphene, and simultaneously leads to variations in electrochemical performance of composites, including a 21% increase of reversible capacity, degradation of cyclic stability and rate-performance, and obvious increase of charge-transfer resistance, which can be called a "butterfly effect" in graphene-based metal oxide composites. These interesting phenomena could be helpful to design not only the high-performance graphene/metal oxide anode materials but also various advanced graphene-based composites used in the other fields such as sensors, catalysis, fuel cells, solar cells, etc. PMID:25226227

  7. Determination of the interfacial heat transfer coefficient in the hot stamping of AA7075

    Directory of Open Access Journals (Sweden)

    Liu Xiaochuan

    2015-01-01

    Full Text Available The interfacial heat transfer coefficient (IHTC is a key parameter in hot stamping processes, in which a hot blank is formed and quenched by cold dies simultaneously. The IHTC should therefore be identified and used in FE models to improve the accuracy of simulation results of hot stamping processes. In this work, a hot stamping simulator was designed and assembled in a Gleeble 3800 thermo-mechanical testing system and a FE model was built in PAM-STAMP to determine the IHTC value between a hot aluminium alloy 7075 blank and cold dies. The IHTC was determined at different contact pressures under both dry and lubricated (Omega-35 conditions. In addition, a model to calculate the IHTC value at different contact pressures and area densities of lubricant was developed for the hot stamping process.

  8. Improvement of Interfacial Heat Transfer Model and Correlations in SPACE Code

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Sung Won; Kim, Kyung Du [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-05-15

    The SPACE code development project has been successfully proceeded since 2006. The first stage of development program has been finished at April 2010. During the first stage, main logic and conceptual structure have been established under the support of Korea Ministry of Knowledge and Economy. In the second stage, it is focused to assess the physical models and correlations of SPACE code by using the well known SET problems. A problem selection process has been performed under the leading of KEPRI. KEPRI has listed suitable SET problems according to the individual assessment purpose. Among the SET problems, the MIT pressurizer test reveals a improper results by using SPACE code. This paper introduce the problem found during the assessment of MIT pressurizer test assessment and the resolving process about the interfacial heat transfer model and correlations in SPACE code

  9. Interfacial electron and phonon scattering processes in high-powered nanoscale applications.

    Energy Technology Data Exchange (ETDEWEB)

    Hopkins, Patrick E.

    2011-10-01

    The overarching goal of this Truman LDRD project was to explore mechanisms of thermal transport at interfaces of nanomaterials, specifically linking the thermal conductivity and thermal boundary conductance to the structures and geometries of interfaces and boundaries. Deposition, fabrication, and post possessing procedures of nanocomposites and devices can give rise to interatomic mixing around interfaces of materials leading to stresses and imperfections that could affect heat transfer. An understanding of the physics of energy carrier scattering processes and their response to interfacial disorder will elucidate the potentials of applying these novel materials to next-generation high powered nanodevices and energy conversion applications. An additional goal of this project was to use the knowledge gained from linking interfacial structure to thermal transport in order to develop avenues to control, or 'tune' the thermal transport in nanosystems.

  10. Engineering interfacial photo-induced charge transfer based on nanobamboo array architecture for efficient solar-to-chemical energy conversion.

    Science.gov (United States)

    Wang, Xiaotian; Liow, Chihao; Bisht, Ankit; Liu, Xinfeng; Sum, Tze Chien; Chen, Xiaodong; Li, Shuzhou

    2015-04-01

    Engineering interfacial photo-induced charge transfer for highly synergistic photocatalysis is successfully realized based on nanobamboo array architecture. Programmable assemblies of various components and heterogeneous interfaces, and, in turn, engineering of the energy band structure along the charge transport pathways, play a critical role in generating excellent synergistic effects of multiple components for promoting photocatalytic efficiency. PMID:25704499

  11. Determination of the metal/die interfacial heat transfer coefficient of high pressure die cast B390 alloy

    Science.gov (United States)

    Cao, Yongyou; Guo, Zhipeng; Xiong, Shoumei

    2012-07-01

    High-pressure die cast B390 alloy was prepared on a 350 ton cold chamber die casting machine. The metal/die interfacial heat transfer coefficient of the alloy was investigated. Considering the filling process, a "finger"-shaped casting was designed for the experiments. This casting consisted of five plates with different thicknesses (0.05 inch or 1.27 mm to 0.25 inch or 6.35 mm) as well as individual ingates and overflows. Experiments under various operation conditions were conducted, and temperatures were measured at various specific locations inside the die. Based on the results, the interfacial heat transfer coefficient and heat flux were determined by solving the inverse heat transfer problem. The influence of the mold-filling sequence, sensor locations, as well as processing parameters including the casting pressure, die temperature, and fast/slow shot speeds on the heat transfer coefficient were discussed.

  12. Relationship between casting distortion, mold filling, and interfacial heat transfer. Annual technical report, September 1997 - September 1998

    Energy Technology Data Exchange (ETDEWEB)

    Woodbury, K.A.; Parker, J.K.; Piwonka, T.S.; Owusu, Y.

    1998-10-22

    In the third year of this program, the final castings necessary to evaluate the effect of casting orientation and gating in silica sand lost foam were poured and measured using a CMM machine. Interfacial heat transfer and gap formation measurements continued. However, significant problems were encountered in making accurate measurements. No consistent evidence of gap formation was found in aluminum sand casting. Initial analysis yields heat transfer values below those previously reported in the literature. The program in continuing.

  13. Optical properties of poly(3-hexylthiophene) and interfacial charge transfer between poly(3-hexylthiophene) and titanium dioxide in composites

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Long; Zhang, Jianling [State Key Laboratory of Polymer Materials Engineering of China, Sichuan University, Polymer Research Institute of Sichuan University, Chengdu 610065 (China); Wang, Weiwei [State Key Laboratory of Polymer Materials Engineering of China, Sichuan University, Polymer Research Institute of Sichuan University, Chengdu 610065 (China); Institut des Matériaux Jean Rouxel, University of Nantes, CNRS, 2 rue de la Houssinière, 44322 Nantes (France); Yang, Haigang [State Key Laboratory of Polymer Materials Engineering of China, Sichuan University, Polymer Research Institute of Sichuan University, Chengdu 610065 (China); Reisdorffer, Frederic [Institut des Matériaux Jean Rouxel, University of Nantes, CNRS, 2 rue de la Houssinière, 44322 Nantes (France); Nguyen, Thien-Phap, E-mail: Thien-Phap.Nguyen@cnrs-imn.fr [Institut des Matériaux Jean Rouxel, University of Nantes, CNRS, 2 rue de la Houssinière, 44322 Nantes (France); Dan, Yi, E-mail: danyi@scu.edu.cn [State Key Laboratory of Polymer Materials Engineering of China, Sichuan University, Polymer Research Institute of Sichuan University, Chengdu 610065 (China)

    2015-03-15

    The optical properties of poly(3-hexylthiophene) (P3HT), in pristine form or with added anatase titanium dioxide (TiO{sub 2}) nanoparticles have been investigated, and the interfacial charge transfer between P3HT and TiO{sub 2} have been studied by steady-state luminescence spectroscopy analysis. The photoluminescence results revealed that incorporation of TiO{sub 2} nanoparticles in concentrations up to 0.3 mM significantly enhanced the luminescence intensity of P3HT when exposing to light of energy higher than TiO{sub 2} bandgap. The observed variation suggested an energy transfer from TiO{sub 2} nanoparticles to P3HT. Meanwhile, when P3HT/TiO{sub 2} composites were exposed to light of energy below TiO{sub 2} bandgap, TiO{sub 2} nanoparticles gradually quench the fluorescence of P3HT, demonstrating the injection of excited electrons from lowest unoccupied molecular orbit of P3HT to the conduction band of TiO{sub 2}. - Highlights: • Optical properties of P3HT, in pristine form or with added TiO{sub 2} were investigated. • Excitation above TiO{sub 2} bandgap produces a remarkable increase in P3HT emission. • The enhancement is attributed to transfer of excitation energy from TiO{sub 2} to P3HT. • TiO{sub 2} quenches P3HT emission when composites are excited below TiO{sub 2} bandgap. • The quench is due to the injection of excitons from LUMO of P3HT to CB of TiO{sub 2}.

  14. Fabrication and interfacial electronic structure studies on polypyrrole/TiO2 nano hybrid systems for photovoltaic aspects.

    Science.gov (United States)

    Kumar, Ganesan Mohan; Kawakita, Jin; Jayavel, Ramasamy

    2011-05-01

    The progress in studying the interfacial electronic structures of the developing new class of hybrid organic/inorganic material systems have envisaged a new dimension into the field of photovoltaics, which could be of great help in understanding the nature of charge transfer in them. In this regard, electropolymerization of pyrrole monomers have been carried out at room temperature on the surface of TiO2 working electrodes (assisted by UV radiations) and their interfacial electronic structure has been studied as a function of the applied photo anodic potentials. The formation of polypyrrole deposits has been ensured using FT-IR and Raman spectroscopy. Surface analysis of the hybrid matrix revealed the tendency of polymer molecules to cover up the spherical surface of TiO2 nanoparticles that could help in improving the light absorption rate. Signals (bands) corresponding to pyrrole molecules observed in the ultraviolet photoelectron spectroscopy measurements have been correlated with the polaronic states formed and identified to shift as a function of the applied photo anodic potentials, revealing the decrease in work function of the hybrid system to take place (confirmed using cyclic voltammetry measurements). The decreasing trend in the work function elucidates the adjustment in electronic structure of the system (hybrid materials possessing smaller work functions are generally preferred for photovoltaic studies). The aforementioned behavioural aspects have been reasoned with the increase in overpotential values for polarization, from the decrease in up-take rate of the anionic dopant, which increases the current density values, thereby modifying the conductivity of the systems.

  15. Interfacial valence electron localization and the corrosion resistance of Al-SiC nanocomposite

    Science.gov (United States)

    Mosleh-Shirazi, Sareh; Hua, Guomin; Akhlaghi, Farshad; Yan, Xianguo; Li, Dongyang

    2015-01-01

    Microstructural inhomogeneity generally deteriorates the corrosion resistance of materials due to the galvanic effect and interfacial issues. However, the situation may change for nanostructured materials. This article reports our studies on the corrosion behavior of SiC nanoparticle-reinforced Al6061 matrix composite. It was observed that the corrosion resistance of Al6061 increased when SiC nanoparticles were added. Overall electron work function (EWF) of the Al-SiC nanocomposite increased, along with an increase in the corrosion potential. The electron localization function of the Al-SiC nanocomposite was calculated and the results revealed that valence electrons were localized in the region of SiC-Al interface, resulting in an increase in the overall work function and thus building a higher barrier to hinder electrons in the nano-composite to participate in corrosion reactions. PMID:26667968

  16. Photoselected electron transfer pathways in DNA photolyase

    OpenAIRE

    Prytkova, Tatiana R.; Beratan, David N.; Skourtis, Spiros S.

    2007-01-01

    Cyclobutane dimer photolyases are proteins that bind to UV-damaged DNA containing cyclobutane pyrimidine dimer lesions. They repair these lesions by photo-induced electron transfer. The electron donor cofactor of a photolyase is a two-electron-reduced flavin adenine dinucleotide (FADH−). When FADH− is photo-excited, it transfers an electron from an excited π → π* singlet state to the pyrimidine dimer lesion of DNA. We compute the lowest excited singlet states of FADH− using ab initio (time-de...

  17. Effect of binder polymer structures used in composite cathodes on interfacial charge transfer processes in lithium polymer batteries

    Energy Technology Data Exchange (ETDEWEB)

    Seki, Shiro; Tabata, Seiichiro [Yokohama National University (Japan). Dept. of Chemistry and Biotechnology; Matsui, Shohei [DAISO Co. Ltd., Amagasaki (Japan); Watanabe, Masayoshi [Yokohama National University (Japan). Dept. of Chemistry and Biotechnology; CREST JST, Yokohama (Japan)

    2004-11-30

    The effect of binder polymer structures used in composite cathodes on the interfacial charge transfer processes in lithium polymer batteries (LPB) has been studied in detail. A cross-linked comb-copolymer, consisting of ethylene oxide (EO), 2-(2-methoxyethoxy)ethyl glycidyl ether (MEEGE), and allyl glycidyl ether (AGE), was used as a solid polymer electrolyte (SPE). LiCoO{sub 2} composite cathodes were fabricated using binder comb-copolymers, consisting of EO and MEEGE with different compositions. Ionic conductivity of the SPE, and the interfacial charge transfer processes between the SPE and metallic lithium and between the SPE and the composite cathode at several cathode potentials versus Li/Li{sup +}, were electrochemically explored. With increasing MEEGE composition in the binder copolymers, the interfacial resistances between the SPE and the composite cathode appreciably decreased. As the result, discharge capacity of the LPB also enhanced with increasing the MEEGE composition. The introduction of the branched-side-chains to the polymer backbone to the binder polymers for the composite cathodes caused to facilitate the interfacial charge transport processes, while the introduction had also been found to be very effective in terms of the enhancement of ionic conductivity of SPE. (author)

  18. Effect of binder polymer structures used in composite cathodes on interfacial charge transfer processes in lithium polymer batteries

    International Nuclear Information System (INIS)

    The effect of binder polymer structures used in composite cathodes on the interfacial charge transfer processes in lithium polymer batteries (LPB) has been studied in detail. A cross-linked comb-copolymer, consisting of ethylene oxide (EO), 2-(2-methoxyethoxy)ethyl glycidyl ether (MEEGE), and allyl glycidyl ether (AGE), was used as a solid polymer electrolyte (SPE). LiCoO2 composite cathodes were fabricated using binder comb-copolymers, consisting of EO and MEEGE with different compositions. Ionic conductivity of the SPE, and the interfacial charge transfer processes between the SPE and metallic lithium and between the SPE and the composite cathode at several cathode potentials versus Li/Li+, were electrochemically explored. With increasing MEEGE composition in the binder copolymers, the interfacial resistances between the SPE and the composite cathode appreciably decreased. As the result, discharge capacity of the LPB also enhanced with increasing the MEEGE composition. The introduction of the branched-side-chains to the polymer backbone to the binder polymers for the composite cathodes caused to facilitate the interfacial charge transport processes, while the introduction had also been found to be very effective in terms of the enhancement of ionic conductivity of SPE

  19. Electron transfer kinetics at polarized nanoscopic liquid/liquid interfaces.

    Science.gov (United States)

    Cai, Chenxin; Mirkin, Michael V

    2006-01-11

    Rapid kinetics of electron transfer (ET) reactions across the interface between water and 1,2-dichloroethane were measured by steady-state voltammetry at nanopipet electrodes (50- to 400-nm orifice radius). The origins of previously reported imperfect voltammetric responses of ET reactions at micropipets were investigated. Several new experimental systems were explored, and two of them yielded high-quality voltammograms suitable for kinetic experiments. The determined standard rate constants were compared to those measured previously at polarized and nonpolarized liquid/liquid interfaces. The effect of the interfacial dimensions on the magnitude of the apparent ET rate constant is discussed. A new approach to ET kinetic measurements based on the use of the scanning electrochemical microscope with a nanopipet tip and a metallic substrate has been developed and employed to check the validity of determined kinetic parameters. PMID:16390144

  20. Heat Transfer Augmentation for Electronic Cooling

    Directory of Open Access Journals (Sweden)

    Suabsakul Gururatana

    2012-01-01

    Full Text Available Problem statement: The performance of electronic devices has been improving along with the rapid technology development. Cooling of electronic systems is consequently essential in controlling the component temperature and avoiding any hot spot. The study aims to review the present electronic cooling methods which are widely used in electronic devices. Approach: There are several methods to cool down the electronics components such as the pin-fin heat sink, confined jet impingement, heat pipe, micro heat sink and so on. Results: The cooling techniques can obviously increase heat transfer rate. Nonetheless, for active and passive cooling methods the pressure drop could extremely rise, when the heat transfer rate is increased. Conclusion: When the cooling techniques are used, it is clearly seen that the heat transfer increases with pressure drop. To avoid excessive expense due to high pressure drop, optimization method is required to obtain optimum cost and cooling rate.

  1. Surfactant transfer across a water/oil interface: A diffusion/kinetics model for the interfacial tension evolution

    International Nuclear Information System (INIS)

    The transfer of amphiphilic solutes through an interface between water and an organic solvent has been studied numerically by simulations based on a general diffusion/reaction model. This description predicts the evolution of the solute concentrations and the transfer across the liquid/liquid interface. It especially focuses on the dynamic interfacial tension evolution that can be measured by a pendant drop tensiometer. Both the bulk diffusion and the adsorption/desorption rate on both sides of the liquid interface are assumed to contribute to the global transfer kinetic. The calculations provide an understanding on how kinetic exchange at the interface and diffusion transport through the bulk determine the dynamic interfacial tension evolution. In particular, complex interfacial tension evolutions with a non-trivial behavior are predicted in some special cases when diffusion and kinetic exchange are of the same order of magnitude. Finally, this model is used to re-interpret experimental data about Triton X-100 transfer at a water-oil interface. (authors)

  2. Regularization Method to the Parameter Identification of Interfacial Heat Transfer Coefficient and Properties during Casting Solidification

    Institute of Scientific and Technical Information of China (English)

    SUI Da-shan; CUI Zhen-shan

    2007-01-01

    The accurate material physical properties, initial and boundary conditions are indispensable to the numerical simulation in the casting process, and they are related to the simulation accuracy directly.The inverse heat conduction method can be used to identify the mentioned above parameters based on the temperature measurement data.This paper presented a new inverse method according to Tikhonov regularization theory.A regularization functional was established and the regularization parameter was deduced, the Newton-Raphson iteration method was used to solve the equations.One detailed case was solved to identify the thermal conductivity and specific heat of sand mold and interfacial heat transfer coefficient (IHTC) at the meantime.This indicates that the regularization method is very efficient in decreasing the sensitivity to the temperature measurement data, overcoming the illposedness of the inverse heat conduction problem (IHCP) and improving the stability and accuracy of the results.As a general inverse method, it can be used to identify not only the material physical properties but also the initial and boundary conditions' parameters.

  3. Immobilization, hybridization, and oxidation of synthetic DNA on gold surface: electron transfer investigated by electrochemistry and scanning tunneling microscopy

    OpenAIRE

    McEwen, Gerald D.; Chen, Fan; Zhou, Anhong

    2009-01-01

    Fundamental understanding of interfacial electron transfer (ET) among electrolyte/DNA/solid-surface will facilitate the design for electrical detection of DNA molecules. In this report, the electron transfer characteristics of synthetic DNA (sequence from pathogenic Cryptosporidium parvum) self-assembled on a gold surface was electrochemically studied. The effects of immobilization order on the interface ET related parameters such as diffusion coefficient (D0), surface coverage (θR), and mono...

  4. Effect of solute transfer and interfacial instabilities on scalar and velocity field around a drop rising in quiescent liquid channel

    Science.gov (United States)

    Khanwale, Makrand A.; Khadamkar, Hrushikesh P.; Mathpati, Channamallikarjun S.

    2015-11-01

    Physics of development of flow structures around the drop rising with solute transfer is highly influenced by the interfacial behaviour and is remarkably different than a particle rising under the same conditions. We report on the use of simultaneous particle image velocimetry-planar laser induced fluorescence technique to measure scalar and velocity fields around a drop rising in a quiescent liquid channel. The selected continuous phase is glycerol, and the drop consists of a mixture of toluene, acetone, and a dye rhodamine-6G, with acetone working as a interfacial tension depressant. The drop lies in the spherical region with Eötvös number, Eo = 1.95, Morton number, M = 78.20 and the particle Reynolds number being, Rep = 0.053. With Rep approaching that of creeping flow, we analyse the effect of interfacial instabilities solely, contrary to other investigations [M. Wegener et al., "Impact of Marangoni instabilities on the fluid dynamic behaviour of organic droplets," Int. J. Heat Mass Transfer 52, 2543-2551 (2009); S. Burghoff and E. Y. Kenig, "A CFD model for mass transfer and interfacial phenomena on single droplets," AIChE J. 52, 4071-4078 (2006); J. Wang et al., "Numerical simulation of the Marangoni effect on transient mass transfer from single moving deformable drops," AIChE J. 57, 2670-2683 (2011); R. F. Engberg, M. Wegener, and E. Y. Kenig, "The impact of Marangoni convection on fluid dynamics and mass transfer at deformable single rising droplets—A numerical study," Chem. Eng. Sci. 116, 208-222 (2014)] which account for turbulence as well as interfacial instabilities with Rep in the turbulent range. The velocity and concentration fields obtained are subjected to scale-wise energy decomposition using continuous wavelet transform. Scale-wise probability distribution functions of wavelet coefficients are calculated to check intermittent non-Gaussian behaviour for simultaneous velocity and scalar statistics. Multi-fractal singularity spectra for scalar

  5. Low Temperature Electronic Transport and Electron Transfer through Organic Macromolecules

    CERN Document Server

    Zimbovskaya, N A

    2002-01-01

    It is shown that at low temperatures and moderate electron dephasing the electron transmission function reveales a structure containing information about donor/acceptor sites effectively participating in the electron transfer (ET) processes and primary pathways of electrons tunneling through molecular bridges in macromolecules. This important information can be obtained as a result of analysis of experimental low temperature current-voltage characteristics for chosen molecules.

  6. 75 FR 66644 - Electronic Fund Transfers

    Science.gov (United States)

    2010-10-29

    .... ACTION: Final rule. SUMMARY: The Board is amending Regulation E, which implements the Electronic Fund Transfer Act, and the official staff commentary to the regulation, in order to implement legislation that... Card Act) was signed into law.\\1\\ Section 401 of the Credit Card Act amended the Electronic...

  7. Electron transfer across a thermal gradient.

    Science.gov (United States)

    Craven, Galen T; Nitzan, Abraham

    2016-08-23

    Charge transfer is a fundamental process that underlies a multitude of phenomena in chemistry and biology. Recent advances in observing and manipulating charge and heat transport at the nanoscale, and recently developed techniques for monitoring temperature at high temporal and spatial resolution, imply the need for considering electron transfer across thermal gradients. Here, a theory is developed for the rate of electron transfer and the associated heat transport between donor-acceptor pairs located at sites of different temperatures. To this end, through application of a generalized multidimensional transition state theory, the traditional Arrhenius picture of activation energy as a single point on a free energy surface is replaced with a bithermal property that is derived from statistical weighting over all configurations where the reactant and product states are equienergetic. The flow of energy associated with the electron transfer process is also examined, leading to relations between the rate of heat exchange among the donor and acceptor sites as functions of the temperature difference and the electronic driving bias. In particular, we find that an open electron transfer channel contributes to enhanced heat transport between sites even when they are in electronic equilibrium. The presented results provide a unified theory for charge transport and the associated heat conduction between sites at different temperatures. PMID:27450086

  8. A single Tisbnd Osbnd C linkage induces interfacial charge-transfer transitions between TiO2 and a π-conjugated molecule

    Science.gov (United States)

    Fujisawa, Jun-ichi; Matsumura, Shingo; Hanaya, Minoru

    2016-07-01

    Interfacial charge-transfer (ICT) transitions between wide-band-gap semiconductors such as titanium dioxide (TiO2) and π-conjugated molecules enable the absorption of visible light with colorless organic compounds and also direct photoinduced electron transfers across the interfaces. ICT transitions have been reported to be induced by a double Tisbnd Osbnd C linkage of enediol compounds with two hydroxy groups to TiO2. In this Letter, we demonstrate that a single Tisbnd Osbnd C linkage of phenol with one hydroxy group can induce ICT transitions in the visible region. Our result widely opens up the range of organic compounds available for ICT transitions from diol compounds to mono-hydroxy compounds.

  9. Magneto-controlled Quantized Electron Transfer to Surface-confined Redox Units and Metal Nanoparticles

    OpenAIRE

    Itamar Willner; Eugenii Katz

    2006-01-01

    Hydrophobic magnetic nanoparticles (NPs) consisting of undecanoate-capped magnetite (Fe3O4, average diameter ca. 5 nm) are used to control quantized electron transfer to surface-confined redox units and metal NPs. A two-phase system consisting of an aqueous electrolyte solution and a toluene phase that includes the suspended undecanoate-capped magnetic NPs is used to control the interfacial properties of the electrode surface. The attracted magnetic NPs form a hydrophobic layer on the electro...

  10. Effects of interfacial Fe electronic structures on magnetic and electronic transport properties in oxide/NiFe/oxide heterostructures

    International Nuclear Information System (INIS)

    Highlights: • The magnetic and transport properties of oxide/NiFe/oxide films were studied. • The oxide (SiO2, MgO and HfO2) has different elemental electronegativity. • Redox reaction at different NiFe/oxide interface is dependent on the oxide layer. • Different interfacial electronic structures shown by XPS influence the properties. - Abstract: We report that the magnetic and electronic transport properties in oxide/NiFe(2 nm)/oxide film (oxide = SiO2, MgO or HfO2) are strongly influenced by the electronic structure of NiFe/oxide interface. Magnetic measurements show that there exist magnetic dead layers in the SiO2 sandwiched film and MgO sandwiched film, whereas there is no magnetic dead layer in the HfO2 sandwiched film. Furthermore, in the ultrathin SiO2 sandwiched film no magnetoresistance (MR) is detected, while in the ultrathin MgO sandwiched film and HfO2 sandwiched film the MR ratios reach 0.35% and 0.88%, respectively. The investigation by X-ray photoelectron spectroscopy reveals that the distinct interfacial redox reactions, which are dependent on the oxide layers, lead to the variation of magnetic and transport properties in different oxide/NiFe/oxide heterostructures

  11. Effects of interfacial Fe electronic structures on magnetic and electronic transport properties in oxide/NiFe/oxide heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qianqian; Chen, Xi; Zhang, Jing-Yan [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yang, Meiyin [SKLSM, Institute of Semiconductors, CAS, P.O. Box 912, Beijing 100083 (China); Li, Xu-Jing; Jiang, Shao-Long; Liu, Yi-Wei; Cao, Yi [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Wu, Zheng-Long [Analytical and Testing Center, Beijing Normal University, Beijing 100875 (China); Feng, Chun [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Ding, Lei [School of Materials and Chemical Engineering, Hainan University, Haikou 570228 (China); Yu, Guang-Hua, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-09-15

    Highlights: • The magnetic and transport properties of oxide/NiFe/oxide films were studied. • The oxide (SiO{sub 2}, MgO and HfO{sub 2}) has different elemental electronegativity. • Redox reaction at different NiFe/oxide interface is dependent on the oxide layer. • Different interfacial electronic structures shown by XPS influence the properties. - Abstract: We report that the magnetic and electronic transport properties in oxide/NiFe(2 nm)/oxide film (oxide = SiO{sub 2}, MgO or HfO{sub 2}) are strongly influenced by the electronic structure of NiFe/oxide interface. Magnetic measurements show that there exist magnetic dead layers in the SiO{sub 2} sandwiched film and MgO sandwiched film, whereas there is no magnetic dead layer in the HfO{sub 2} sandwiched film. Furthermore, in the ultrathin SiO{sub 2} sandwiched film no magnetoresistance (MR) is detected, while in the ultrathin MgO sandwiched film and HfO{sub 2} sandwiched film the MR ratios reach 0.35% and 0.88%, respectively. The investigation by X-ray photoelectron spectroscopy reveals that the distinct interfacial redox reactions, which are dependent on the oxide layers, lead to the variation of magnetic and transport properties in different oxide/NiFe/oxide heterostructures.

  12. Photoinduced electron transfer in ordered polymers

    Energy Technology Data Exchange (ETDEWEB)

    Jones, G. II.

    1991-12-01

    Long range photoinduced electron transfer between electron donor and acceptor groups is of considerable current interest in terms of strategies for artificial photosynthesis and studies regarding the redox properties of proteins. As part of an extensive study of long range electron transfer involving biopolymers, we have carried out this year investigations of the assembly of electron transfer agents in a system of model short peptides. Also studied is a polyelectrolyte that can adopt a helical conformation when electrostatically complexed with organic dye counter-ions. The principal interest in these systems has to do with the well ordered secondary structures adopted by peptide polymers, and the capabilities for synthetic modification of peptide side chains and end groups with chromophores or electroactive substituents. The present report gives a brief account of the following elements of work related to photochemical electron transfer themes: (1) the synthesis and photochemical characterization of chromophore-bound peptides and amino acid model compounds based on the amino acids, tryptophan and the spacer residue, alanine (Ala); (2) the study of binding of the cationic organic dye to a peptide electrolyte, for which cooperative dye loading and helix formation is important; and (3) completion of the synthesis of a new series of acridinium chromophores that have rod-like'' arrangements of inked aryl rings for assembly of electron donor-acceptor systems that will exhibit especially long lived charge separation.

  13. Ultrafast Electron Transfer Between Dye and Catalyst on a Mesoporous NiO Surface.

    Science.gov (United States)

    Brown, Allison M; Antila, Liisa J; Mirmohades, Mohammad; Pullen, Sonja; Ott, Sascha; Hammarström, Leif

    2016-07-01

    The combination of molecular dyes and catalysts with semiconductors into dye-sensitized solar fuel devices (DSSFDs) requires control of efficient interfacial and surface charge transfer between the components. The present study reports on the light-induced electron transfer processes of p-type NiO films cosensitized with coumarin C343 and a bioinspired proton reduction catalyst, [FeFe](mcbdt)(CO)6 (mcbdt = 3-carboxybenzene-1,2-dithiolate). By transient optical spectroscopy we find that ultrafast interfacial electron transfer (τ ≈ 200 fs) from NiO to the excited C343 ("hole injection") is followed by rapid (t1/2 ≈ 10 ps) and efficient surface electron transfer from C343(-) to the coadsorbed [FeFe](mcbdt)(CO)6. The reduced catalyst has a clear spectroscopic signature that persists for several tens of microseconds, before charge recombination with NiO holes occurs. The demonstration of rapid surface electron transfer from dye to catalyst on NiO, and the relatively long lifetime of the resulting charge separated state, suggests the possibility to use these systems for photocathodes on DSSFDs.

  14. Defining new frontiers in electronic devices with high {kappa} dielectrics and interfacial engineering

    Energy Technology Data Exchange (ETDEWEB)

    Hong, M. [Department of Materials Science and Eng., National Tsing Hua University, Hsinchu, Taiwan (China)]. E-mail: mhong@mx.nthu.edu.tw; Lee, W.C. [Department of Materials Science and Eng., National Tsing Hua University, Hsinchu, Taiwan (China); Huang, M.L. [Department of Materials Science and Eng., National Tsing Hua University, Hsinchu, Taiwan (China); Chang, Y.C. [Department of Materials Science and Eng., National Tsing Hua University, Hsinchu, Taiwan (China); Lin, T.D. [Department of Materials Science and Eng., National Tsing Hua University, Hsinchu, Taiwan (China); Lee, Y.J. [Department of Materials Science and Eng., National Tsing Hua University, Hsinchu, Taiwan (China); Kwo, J. [Department of Physics, National Tsing Hua University, Hsinchu, Taiwan (China); Hsu, C.H. [Synchrotron Radiation Research Center, Hsinchu, Taiwan (China); Lee, H.Y. [Synchrotron Radiation Research Center, Hsinchu, Taiwan (China)

    2007-05-23

    Ga{sub 2}O{sub 3}(Gd{sub 2}O{sub 3}), a high {kappa} gate dielectric, ultrahigh vacuum (UHV)-deposited on GaAs and InGaAs has unpinned the Fermi level in the high-electron-mobility III-V compound semiconductors for the first time. Systematic heat treatments under various gases and temperatures were studied to achieve low leakage currents of 10{sup -8}-10{sup -9} A/cm{sup 2} and low interfacial density of states (D {sub it'}s) in the range of < 10{sup 11} cm{sup -2} eV{sup -1}. By removing moisture from the oxide, thermodynamic stability of the Ga{sub 2}O{sub 3}(Gd{sub 2}O{sub 3})/GaAs heterostructures and the interfaces were achieved with high temperature annealing, the oxide remains amorphous and the interface remains intact with atomic smoothness and sharpness. The Fermi-level unpinning in atomic layer deposition (ALD) Al{sub 2}O{sub 3} ex-situ deposited on InGaAs was achieved. Recent work of extremely high-quality nano-thick single crystal oxides of gamma-Al{sub 2}O{sub 3} and bixbyite cubic Sc{sub 2}O{sub 3} epitaxially grown on Si (111) is discussed. Interfacial manipulation is essential in giving excellent results presented in the paper. X-ray diffraction, reflectivity, and X-ray photoelectron spectroscopy using synchrotron radiation are critical in probing the interfacial properties.

  15. Unusual distance dependences of electron transfer rates.

    Science.gov (United States)

    Kuss-Petermann, Martin; Wenger, Oliver S

    2016-07-28

    Usually the rates for electron transfer (kET) decrease with increasing donor-acceptor distance, but Marcus theory predicts a regime in which kET is expected to increase when the transfer distance gets longer. Until recently, experimental evidence for such counter-intuitive behavior had been very limited, and consequently this effect is much less well-known than the Gaussian free energy dependence of electron transfer rates leading to the so-called inverted driving-force effect. This article presents the theoretical concepts that lead to the prediction of electron transfer rate maxima at large donor-acceptor distances, and it discusses conditions that are expected to favor experimental observations of such behavior. It continues with a consideration of specific recent examples in which electron transfer rates were observed to increase with increasing donor-acceptor distance, and it closes with a discussion of the importance of this effect in the context of light-to-chemical energy conversion. PMID:27353891

  16. Electron transfer in ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Lin, C D

    1979-01-01

    Recent theoretical development in the understanding of electron transfer processes is reviewed. K-K electron transfer processes are studied for projectiles (nuclear charge Z/sub B/) and targets (nuclear charge Z/sub A/) in which Z/sub A/ and Z/sub B/ range from Z/sub A/ much greater than Z/sub B/ to Z/sub A/ approx. = Z/sub B/, over the energy range 0.1 < v/v/sub e/ < 2. (GHT)

  17. Single Molecule Spectroelectrochemistry of Interfacial Charge Transfer Dynamics In Hybrid Organic Solar Cell

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Shanlin [Univ. of Alabama, Tuscaloosa, AL (United States)

    2014-11-16

    Our research under support of this DOE grant is focused on applied and fundamental aspects of model organic solar cell systems. Major accomplishments are: 1) we developed a spectroelectorchemistry technique of single molecule single nanoparticle method to study charge transfer between conjugated polymers and semiconductor at the single molecule level. The fluorescence of individual fluorescent polymers at semiconductor surfaces was shown to exhibit blinking behavior compared to molecules on glass substrates. Single molecule fluorescence excitation anisotropy measurements showed the conformation of the polymer molecules did not differ appreciably between glass and semiconductor substrates. The similarities in molecular conformation suggest that the observed differences in blinking activity are due to charge transfer between fluorescent polymer and semiconductor, which provides additional pathways between states of high and low fluorescence quantum efficiency. Similar spectroelectrochemistry work has been done for small organic dyes for understand their charge transfer dynamics on various substrates and electrochemical environments; 2) We developed a method of transferring semiconductor nanoparticles (NPs) and graphene oxide (GO) nanosheets into organic solvent for a potential electron acceptor in bulk heterojunction organic solar cells which employed polymer semiconductor as the electron donor. Electron transfer from the polymer semiconductor to semiconductor and GO in solutions and thin films was established through fluorescence spectroscopy and electroluminescence measurements. Solar cells containing these materials were constructed and evaluated using transient absorption spectroscopy and dynamic fluorescence techniques to understand the charge carrier generation and recombination events; 3) We invented a spectroelectorchemistry technique using light scattering and electroluminescence for rapid size determination and studying electrochemistry of single NPs in an

  18. Facilitating electron transfer in bioelectrocatalytic systems

    OpenAIRE

    Sekretaryova, Alina

    2016-01-01

    Bioelectrocatalytic systems are based on biological entities, such as enzymes, whole cells, parts of cells or tissues, which catalyse electrochemical processes that involve the interaction between chemical change and electrical energy. In all cases, biocatalysis is implemented by enzymes, isolated or residing inside cells or part of cells. Electron transfer (ET) phenomena, within the protein molecules and between biological redox systems and electronics, enable the development of various bioe...

  19. Resonant electron transfer between quantum dots

    OpenAIRE

    Openov, Leonid A.

    1999-01-01

    An interaction of electromagnetic field with a nanostructure composed of two quantum dots is studied theoretically. An effect of a resonant electron transfer between the localized low-lying states of quantum dots is predicted. A necessary condition for such an effect is the existence of an excited bound state whose energy lies close to the top of the barrier separating the quantum dots. This effect may be used to realize the reversible quantum logic gate NOT if the superposition of electron s...

  20. Interfacial ion-transfer mechanism for the intense luminescence observed when opening self-seal envelopes.

    Science.gov (United States)

    Alexander, Andrew J

    2012-09-18

    The unusually intense luminescence (commonly called triboluminescence) observed when opening self-seal envelopes has been studied using spectroscopy. Emissions from gas-phase species due to electrical discharge were observed, which in the case of air consists of vibronic transitions of N(2)(C(3)Π(u)-B(3)Π(g)) in the ultraviolet (UV) region (280-400 nm). However, the major cause of the intense blue luminescence (around 435 nm) is attributed to optical brightening agents added to the white paper. The results suggest that the emission from the brightening agents may be caused by two mechanisms: (i) fluorescence due to excitation by the UV light from the gas discharge and (ii) nonoptically, by electron transfer. The electrical discharge results from contact electrification; we propose a mechanism for the charge transfer involving a net migration of hydroxide anions out of the paper into the wet latex-adhesive during drying. PMID:22924818

  1. Photoinduced electron transfer in ordered polymers

    Energy Technology Data Exchange (ETDEWEB)

    Jones, G. II.

    1990-10-20

    Photochemical studies on organic polymers or biopolymers (particularly synthetic peptides) that have been modified by covalent attachment (or other means of binding) of organic chromophores and electron transfer agents are described. Specific projects involve are: peptide conjugates bearing electroactive residues such as tryptophan and specifically labeled at the N- or C-terminus of peptide chains; the electrostatic binding of organic dyes to poly-electrolytes (polyacrylates) for which the formation of dimeric aggregates of bound dye that display unusual photophysical and electron transfer properties is important; a study of the binding of dyes and electron transfer agents to the protein mimic,'' polyvinyl-2-pyrrolidinone (PVP), in hydrophobic domains that depend on specific H-bond interaction; and completion of an earlier study having to do with the triplet state properties of charge-transfer (CT) complexes of a high potential quinone and various electron donors (investigation of the properties of triplet (contact) radical-ion pairs). 13 refs., 5 figs., 2 tabs.

  2. Protein electron transfer: is biology (thermo)dynamic?

    International Nuclear Information System (INIS)

    Simple physical mechanisms are behind the flow of energy in all forms of life. Energy comes to living systems through electrons occupying high-energy states, either from food (respiratory chains) or from light (photosynthesis). This energy is transformed into the cross-membrane proton-motive force that eventually drives all biochemistry of the cell. Life’s ability to transfer electrons over large distances with nearly zero loss of free energy is puzzling and has not been accomplished in synthetic systems. The focus of this review is on how this energetic efficiency is realized. General physical mechanisms and interactions that allow proteins to fold into compact water-soluble structures are also responsible for a rugged landscape of energy states and a broad distribution of relaxation times. Specific to a protein as a fluctuating thermal bath is the protein-water interface, which is heterogeneous both dynamically and structurally. The spectrum of interfacial fluctuations is a consequence of protein’s elastic flexibility combined with a high density of surface charges polarizing water dipoles into surface nanodomains. Electrostatics is critical to the protein function and the relevant questions are: (i) What is the spectrum of interfacial electrostatic fluctuations? (ii) Does the interfacial biological water produce electrostatic signatures specific to proteins? (iii) How is protein-mediated chemistry affected by electrostatics? These questions connect the fluctuation spectrum to the dynamical control of chemical reactivity, i.e. the dependence of the activation free energy of the reaction on the dynamics of the bath. Ergodicity is often broken in protein-driven reactions and thermodynamic free energies become irrelevant. Continuous ergodicity breaking in a dense spectrum of relaxation times requires using dynamically restricted ensembles to calculate statistical averages. When applied to the calculation of the rates, this formalism leads to the nonergodic

  3. Protein electron transfer: is biology (thermo)dynamic?

    Science.gov (United States)

    Matyushov, Dmitry V.

    2015-12-01

    Simple physical mechanisms are behind the flow of energy in all forms of life. Energy comes to living systems through electrons occupying high-energy states, either from food (respiratory chains) or from light (photosynthesis). This energy is transformed into the cross-membrane proton-motive force that eventually drives all biochemistry of the cell. Life’s ability to transfer electrons over large distances with nearly zero loss of free energy is puzzling and has not been accomplished in synthetic systems. The focus of this review is on how this energetic efficiency is realized. General physical mechanisms and interactions that allow proteins to fold into compact water-soluble structures are also responsible for a rugged landscape of energy states and a broad distribution of relaxation times. Specific to a protein as a fluctuating thermal bath is the protein-water interface, which is heterogeneous both dynamically and structurally. The spectrum of interfacial fluctuations is a consequence of protein’s elastic flexibility combined with a high density of surface charges polarizing water dipoles into surface nanodomains. Electrostatics is critical to the protein function and the relevant questions are: (i) What is the spectrum of interfacial electrostatic fluctuations? (ii) Does the interfacial biological water produce electrostatic signatures specific to proteins? (iii) How is protein-mediated chemistry affected by electrostatics? These questions connect the fluctuation spectrum to the dynamical control of chemical reactivity, i.e. the dependence of the activation free energy of the reaction on the dynamics of the bath. Ergodicity is often broken in protein-driven reactions and thermodynamic free energies become irrelevant. Continuous ergodicity breaking in a dense spectrum of relaxation times requires using dynamically restricted ensembles to calculate statistical averages. When applied to the calculation of the rates, this formalism leads to the nonergodic

  4. The effect of interfacial evaporation on heat and mass transfer of falling liquid film

    Institute of Scientific and Technical Information of China (English)

    王补宣; 张金涛; 彭晓峰

    2001-01-01

    Analysis of experimental data and estimation of the order of magnitude for interfacial mass diffusion have demonstrated that considerable excess evaporation exists on the free interface of falling liquid film, and that the capillary pressure caused by surface tension is the driving force of this excess interfacial evaporation, which we called the “capillarity-induced interfacial evaporation”. By correlating the experimental data, an empirical expression of the effective capillary radius, r\\-e, is obtained with which the evaporative rate formula we derived and reported previously has been modified to improve the prediction of the critical heat flux for film breakdown. Comparisons with the available predicting models show that our modified equation can predict the experimental results with much lower relative deviation.

  5. Interfacial Energy Alignment at the ITO/Ultra-Thin Electron Selective Dielectric Layer Interface and Its Effect on the Efficiency of Bulk-Heterojunction Organic Solar Cells.

    Science.gov (United States)

    Itoh, Eiji; Goto, Yoshinori; Saka, Yusuke; Fukuda, Katsutoshi

    2016-04-01

    We have investigated the photovoltaic properties of an inverted bulk heterojunction (BHJ) cell in a device with an indium-tin-oxide (ITO)/electron selective layer (ESL)/P3HT:PCBM active layer/MoOx/Ag multilayered structure. The insertion of only single layer of poly(diallyl-dimethyl-ammonium chloride) (PDDA) cationic polymer film (or poly(ethyleneimine) (PEI) polymeric interfacial dipole layer) and titanium oxide nanosheet (TN) films as an ESL effectively improved cell performance. Abnormal S-shaped curves were observed in the inverted BHJ cells owing to the contact resistance across the ITO/active layer interface and the ITO/PDDA/TN/active layer interface. The series resistance across the ITO/ESL interface in the inverted BHJ cell was successfully reduced using an interfacial layer with a positively charged surface potential with respect to ITO base electrode. The positive dipole in PEI and the electronic charge phenomena at the electrophoretic deposited TN (ED-TN) films on ITO contributed to the reduction of the contact resistance at the electrode interface. The surface potential measurement revealed that the energy alignment by the transfer of electronic charges from the ED-TN to the base electrodes. The insertion of the ESL with a large positive surface potential reduced the potential barrier for the electron injection at ITO/TN interface and it improved the photovoltaic properties of the inverted cell with an ITO/TN/active layer/MoOx/Ag structure. PMID:27451612

  6. Femtosecond spectroscopic studies of photoinduced electron transfer in MDMO-PPV:ZnO hybrid bulk heterojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Cecchetto, E.; De Cola, L. [Institute of Physics, University of Muenster, Mendelstrasse 7, 48149 Muenster (Germany); Slooff, H. [ECN Solar Energy, P.O. Box 1, 1755 ZG Petten (Netherlands); Zhang, H. [Van ' t Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 129, 1018 WS Amsterdam (Netherlands)

    2007-01-15

    The photophysics of charge carriers (polaron) in MDMO-PPV:ZnO hybrid bulk heterojunction is studied at 80 K by femtosecond transient absorption spectroscopy. A short-lived positive polaron is observed in the blend phase in MDMO-PPV:ZnO blend films with a weight ratio of 1:1 and 1:2. Further increase of ZnO weight ratio results in a significant quenching of the polaron absorption. The results are discussed in the concept that both pristine polymer and MDMO-PPV:ZnO blend phases coexist in the blend films. It is concluded that a polaron is photogenerated within the excitation laser pulse (<100 fs) and electron transfer efficiency is highest in blend films 1:1 and 1:2. Lack of the interfacial area and faster back electron transfer process are discussed to be responsible for the quenching of the electron transfer efficiency in blend film 1:3.

  7. Effect of casting/mould interfacial heat transfer during solidification of aluminium alloys cast in CO2-sand mould

    Science.gov (United States)

    Kulkarni, S. N.; Radhakrishna, D. K.

    2011-06-01

    The ability of heat to flow across the casting and through the interface from the casting to the mold directly affects the evolution of solidification and plays a notable role in determining the freezing conditions within the casting, mainly in foundry systems of high thermal diffusivity such as chill castings. An experimental procedure has been utilized to measure the formation process of an interfacial gap and metal-mould interfacial movement during solidification of hollow cylindrical castings of Al-4.5 % Cu alloy cast in CO2-sand mould. Heat flow between the casting and the mould during solidification of Al-4.5 % Cu alloy in CO2-sand mould was assessed using an inverse modeling technique. The analysis yielded the interfacial heat flux ( q), heat transfer coefficient ( h) and the surface temperatures of the casting and the mould during solidification of the casting. The peak heat flux was incorporated as a dimensionless number and modeled as a function of the thermal diffusivities of the casting and the mould materials. Heat flux transients were normalized with respect to the peak heat flux and modeled as a function of time. The heat flux model proposed was to estimate the heat flux transients during solidification of Al-4.5 % Cu alloy cast in CO2-sand moulds.

  8. Controlling Interfacial Reactions and Intermetallic Compound Growth at the Interface of a Lead-free Solder Joint with Layer-by-Layer Transferred Graphene.

    Science.gov (United States)

    Ko, Yong-Ho; Lee, Jong-Dae; Yoon, Taeshik; Lee, Chang-Woo; Kim, Taek-Soo

    2016-03-01

    The immoderate growth of intermetallic compounds (IMCs) formed at the interface of a solder metal and the substrate during soldering can degrade the mechanical properties and reliability of a solder joint in electronic packaging. Therefore, it is critical to control IMC growth at the solder joints between the solder and the substrate. In this study, we investigated the control of interfacial reactions and IMC growth by the layer-by-layer transfer of graphene during the reflow process at the interface between Sn-3.0Ag-0.5Cu (in wt %) lead-free solder and Cu. As the number of graphene layers transferred onto the surface of the Cu substrate increased, the thickness of the total IMC (Cu6Sn5 and Cu3Sn) layer decreased. After 10 repetitions of the reflow process for 50 s above 217 °C, the melting temperature of Sn-3.0Ag-0.5Cu, with a peak temperature of 250 °C, the increase in thickness of the total IMC layer at the interface with multiple layers of graphene was decreased by more than 20% compared to that at the interface of bare Cu without graphene. Furthermore, the average diameter of the Cu6Sn5 scallops at the interface with multiple layers of graphene was smaller than that at the interface without graphene. Despite 10 repetitions of the reflow process, the growth of Cu3Sn at the interface with multiple layers of graphene was suppressed by more than 20% compared with that at the interface without graphene. The multiple layers of graphene at the interface between the solder metal and the Cu substrate hindered the diffusion of Cu atoms from the Cu substrate and suppressed the reactions between Cu and Sn in the solder. Thus, the multiple layers of graphene transferred at the interface between dissimilar metals can control the interfacial reaction and IMC growth occurring at the joining interface. PMID:26856638

  9. Photoinduced electron transfer in some photosensitive molecules-incorporated semiconductor/zeolites: New photocatalytic systems

    Indian Academy of Sciences (India)

    Minjoong Yoon; Devendra P S Negi

    2002-12-01

    An intramolecular charge transfer (ICT) molecule, -N,N-dimethylaminobenzoic acid (DMABA) has been studied in zeolite and colloidal media. The ratio of ICT to normal emission (ICT/LE) is greatly enhanced in zeolites compared to that in polar solvents. The ICT emission of DMABA was quenched by increasing the concentration of TiO2 colloids, while the normal emission was slightly enhanced. Upon illumination of the heteropoly acid (HPA) incorporated TiO2 colloids, interfacial electron transfer takes place from the conduction band of TiO2 to the incorporated HPA which is also excited to catalyze the photoreduction of Methyl Orange. It is found that the interfacial electron transfer mechanism of HPA/TiO2 is quite analogous to the Z-scheme mechanism for plant photosynthetic systems. In DMABA-adsorbed TiO2/Y-zeolite the ICT/LE ratio of DMABA is quite small implying that electron transfer takes place from DMABA to the conduction band of TiO2. This results in drastic enhancement in the photocatalytic activity of DMABA-adsorbed TiO2/Y-zeolite compared to free TiO2/Y-zeolite.

  10. Biotechnological Aspects of Microbial Extracellular Electron Transfer

    Science.gov (United States)

    Kato, Souichiro

    2015-01-01

    Extracellular electron transfer (EET) is a type of microbial respiration that enables electron transfer between microbial cells and extracellular solid materials, including naturally-occurring metal compounds and artificial electrodes. Microorganisms harboring EET abilities have received considerable attention for their various biotechnological applications, in addition to their contribution to global energy and material cycles. In this review, current knowledge on microbial EET and its application to diverse biotechnologies, including the bioremediation of toxic metals, recovery of useful metals, biocorrosion, and microbial electrochemical systems (microbial fuel cells and microbial electrosynthesis), were introduced. Two potential biotechnologies based on microbial EET, namely the electrochemical control of microbial metabolism and electrochemical stimulation of microbial symbiotic reactions (electric syntrophy), were also discussed. PMID:26004795

  11. Extracellular electron transfer from cathode to microbes: application for biofuel production.

    Science.gov (United States)

    Choi, Okkyoung; Sang, Byoung-In

    2016-01-01

    Extracellular electron transfer in microorganisms has been applied for bioelectrochemical synthesis utilizing microbes to catalyze anodic and/or cathodic biochemical reactions. Anodic reactions (electron transfer from microbe to anode) are used for current production and cathodic reactions (electron transfer from cathode to microbe) have recently been applied for current consumption for valuable biochemical production. The extensively studied exoelectrogenic bacteria Shewanella and Geobacter showed that both directions for electron transfer would be possible. It was proposed that gram-positive bacteria, in the absence of cytochrome C, would accept electrons using a cascade of membrane-bound complexes such as membrane-bound Fe-S proteins, oxidoreductase, and periplasmic enzymes. Modification of the cathode with the addition of positive charged species such as chitosan or with an increase of the interfacial area using a porous three-dimensional scaffold electrode led to increased current consumption. The extracellular electron transfer from the cathode to the microbe could catalyze various bioelectrochemical reductions. Electrofermentation used electrons from the cathode as reducing power to produce more reduced compounds such as alcohols than acids, shifting the metabolic pathway. Electrofuel could be generated through artificial photosynthesis using electrical energy instead of solar energy in the process of carbon fixation. PMID:26788124

  12. Electron transfer theory revisit: Quantum solvation effect

    CERN Document Server

    Han, P; Cui, P; Mo, Y; He, G; Yan, Y J; Han, Ping; Xu, Rui-Xue; Cui, Ping; Mo, Yan; He, Guozhong; Yan, YiJing

    2006-01-01

    The effect of solvation on the electron transfer (ET) rate processes is investigated on the basis of the exact theory constructed in J. Phys. Chem. B Vol. 110, (2006); quant-ph/0604071. The nature of solvation is studied in a close relation with the mechanism of ET processes. The resulting Kramers' turnover and Marcus' inversion characteristics are analyzed accordingly. The classical picture of solvation is found to be invalid when the solvent longitudinal relaxation time is short compared with the inverse temperature.

  13. The effect of interfacial charge transfer on ferromagnetism in perovskite oxide superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Yang, F. [Univ. of California, Davis, CA (United States). Department of Chemical Engineering and Materials Science; Gu, M. [Univ. of California, Davis, CA (United States). Department of Chemical Engineering and Materials Science; Arenholz, E. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS); Browning, N. D. [Univ. of California, Davis, CA (United States). Department of Molecular and Cellular Biology; Takamura, Y. [Univ. of California, Davis, CA (United States). Department of Chemical Engineering and Materials Science

    2012-01-05

    We investigate the structural, magnetic, and electrical properties of superlattices composed of the ferromagnetic/metal La0.7Sr0.3MnO3 and non-magnetic/metal La0.5Sr0.5TiO3 grown on (001)-oriented SrTiO3 substrates. Using a combination of bulk magnetometry, soft x-ray magnetic spectroscopy, and scanning transmission electron microscopy, we demonstrate that robust ferromagnetic properties can be maintained in this superlattice system where charge transfer at the interfaces is minimized. Thus, ferromagnetism can be controlled effectively through the chemical identity and the thickness of the individual superlattice layers.

  14. Vibrational control of electron-transfer reactions: a feasibility study for the fast coherent transfer regime.

    Science.gov (United States)

    Antoniou, P; Ma, Z; Zhang, P; Beratan, D N; Skourtis, S S

    2015-12-14

    Molecular vibrations and electron-vibrational interactions are central to the control of biomolecular electron and energy-transfer rates. The vibrational control of molecular electron-transfer reactions by infrared pulses may enable the precise probing of electronic-vibrational interactions and of their roles in determining electron-transfer mechanisms. This type of electron-transfer rate control is advantageous because it does not alter the electronic state of the molecular electron-transfer system or irreversibly change its molecular structure. For bridge-mediated electron-transfer reactions, infrared (vibrational) excitation of the bridge linking the electron donor to the electron acceptor was suggested as being capable of influencing the electron-transfer rate by modulating the bridge-mediated donor-to-acceptor electronic coupling. This kind of electron-transfer experiment has been realized, demonstrating that bridge-mediated electron-transfer rates can be changed by exciting vibrational modes of the bridge. Here, we use simple models and ab initio computations to explore the physical constraints on one's ability to vibrationally perturb electron-transfer rates using infrared excitation. These constraints stem from the nature of molecular vibrational spectra, the strengths of the electron-vibrational coupling, and the interaction between molecular vibrations and infrared radiation. With these constraints in mind, we suggest parameter regimes and molecular architectures that may enhance the vibrational control of electron transfer for fast coherent electron-transfer reactions.

  15. Promoting interspecies electron transfer with biochar

    DEFF Research Database (Denmark)

    Chen, Shanshan; Rotaru, Amelia-Elena; Shrestha, Pravin Malla;

    2014-01-01

    attached to the biochar, yet not in close contact, suggesting that electrons were likely conducted through the biochar, rather than biological electrical connections. The finding that biochar can stimulate DIET may be an important consideration when amending soils with biochar and can help explain why......Biochar, a charcoal-like product of the incomplete combustion of organic materials, is an increasingly popular soil amendment designed to improve soil fertility. We investigated the possibility that biochar could promote direct interspecies electron transfer (DIET) in a manner similar...... to that previously reported for granular activated carbon (GAC). Although the biochars investigated were 1000 times less conductive than GAC, they stimulated DIET in co-cultures of Geobacter metallireducens with Geobacter sulfurreducens or Methanosarcina barkeri in which ethanol was the electron donor. Cells were...

  16. Education and solar conversion. Demonstrating electron transfer

    Energy Technology Data Exchange (ETDEWEB)

    Smestad, Greg P. [Institute of Physical Chemistry, ICP-2, Swiss Federal Institute of Technology, EPFL, CH-1015 Lausanne (Switzerland)

    1998-07-23

    A simplified solar cell fabrication procedure is presented that uses natural anthocyanin or chlorophyll dyes extracted from plants. This procedure illustrates how interdisciplinary science can be taught at lower division university and upper division high school levels for an understanding of renewable energy as well as basic science concepts. Electron transfer occurs on the Earth in the mitochondrial membranes found in living cells, and in the thylakoid membranes found in the photosynthetic cells of green plants. Since we depend on the results of this electron and energy transfer, e.g. in our use of petroleum and agricultural products, it is desirable to understand and communicate how the electron transfer works. The simplified solar cell fabrication procedure, based on nanocrystalline dye-sensitized solar cells, has therefore been developed so that it can be inexpensively reproduced and utilized in the teaching of basic principles in biology, chemistry, physics, and environmental science. A water-based solution of commercial nanocrystalline titanium dioxide (TiO{sub 2}) powder is used to deposit a highly porous semiconductor electron acceptor. This acceptor couples the light-driven processes occurring at an organic dye to the macroscopic world and an external electrical circuit. Materials science and semiconductor physics are emphasized during the deposition of the sintered TiO{sub 2} nanocrystalline ceramic film. Chelation, complexation and molecular self-assembly are demonstrated during the attachment of the dye molecule to the surface of the TiO{sub 2} semiconductor particles. Environmental chemistry and energy conversion can be linked to these concepts via the regenerative oxidation and reduction cycle found in the cell. The resulting device, made in under 3 h, can be used as a light detector or power generator that produces 0.4-0.5 V at open circuit, and 1-2 mA per square cm under solar illumination

  17. Heat transfer in high density electronics packaging

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In order to get an insight into the thermal characteristic and to evaluate the thermal reliability of the "System in Packaging"(SIP), a new solution of electronics packaging, a heat transfer model of SIP was developed to predict the heat dissipation capacity and to investigate the effect of different factors on the temperature distribution in the electronics. The affecting parameters under consideration include the thermophysical properties of the substrates, the coefficient of convection heat transfer, the thickness of the chip, and the density of power dissipation. ALGOR, a kind of finite element analysis software,was used to do the model simulation. Based on the sinulation and analysis of the heat conduction and convection resistance, criteria for the thermal design were established and possible measurement for enhancing power dissipation was provided, The results show that the heat transfer model provides a new and effective way to the thermal design and thermal analysis of SIP and to the mechanical analysis for the further investigation of SIP.

  18. Investigation of electron transfer across the ice/liquid interface by scanning electro-chemical microscopy

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The study of interfacial electron transfer (ET) reaction between ferricinium (Fc+) produced in situ in 1,2-dichloroethane (DCE) and ferrocyanide in ice matrix under low temperatures by the scanning electrochemical microscopy (SECM) is reported. Tetrabutylammonium (TBA+) is used as the common ion (potential-determining ion) in both phases to control the interfacial potential difference. The potential drop across the liquid/liquid interface can be quantitatively adjusted by changing the ratio of concentrations of TBA+ between the two phases. The apparent heterogeneous rate constants for Fc+ reduction by at the interface under different temperatures have been obtained by a best-fit analysis, where the experimental approach curves are fitted to the theoretical simulated curves. A sharp change has been observed for heterogeneous rate constants around the freezing point of the aqueous phase, which reflects the phase transition process.

  19. 48 CFR 18.123 - Electronic funds transfer.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Electronic funds transfer... CONTRACTING METHODS AND CONTRACT TYPES EMERGENCY ACQUISITIONS Available Acquisition Flexibilities 18.123 Electronic funds transfer. Electronic funds transfer payments may be waived for acquisitions to...

  20. 14 CFR 1260.69 - Electronic funds transfer payment methods.

    Science.gov (United States)

    2010-01-01

    ... Government by electronic funds transfer through the Treasury Fedline Payment System (FEDLINE) or the... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Electronic funds transfer payment methods... COOPERATIVE AGREEMENTS General Special Conditions § 1260.69 Electronic funds transfer payment...

  1. Amorphous oxide alloys as interfacial layers with broadly tunable electronic structures for organic photovoltaic cells.

    Science.gov (United States)

    Zhou, Nanjia; Kim, Myung-Gil; Loser, Stephen; Smith, Jeremy; Yoshida, Hiroyuki; Guo, Xugang; Song, Charles; Jin, Hosub; Chen, Zhihua; Yoon, Seok Min; Freeman, Arthur J; Chang, Robert P H; Facchetti, Antonio; Marks, Tobin J

    2015-06-30

    In diverse classes of organic optoelectronic devices, controlling charge injection, extraction, and blocking across organic semiconductor-inorganic electrode interfaces is crucial for enhancing quantum efficiency and output voltage. To this end, the strategy of inserting engineered interfacial layers (IFLs) between electrical contacts and organic semiconductors has significantly advanced organic light-emitting diode and organic thin film transistor performance. For organic photovoltaic (OPV) devices, an electronically flexible IFL design strategy to incrementally tune energy level matching between the inorganic electrode system and the organic photoactive components without varying the surface chemistry would permit OPV cells to adapt to ever-changing generations of photoactive materials. Here we report the implementation of chemically/environmentally robust, low-temperature solution-processed amorphous transparent semiconducting oxide alloys, In-Ga-O and Ga-Zn-Sn-O, as IFLs for inverted OPVs. Continuous variation of the IFL compositions tunes the conduction band minima over a broad range, affording optimized OPV power conversion efficiencies for multiple classes of organic active layer materials and establishing clear correlations between IFL/photoactive layer energetics and device performance.

  2. Study on Transfer and Interfacial Kinetics of Neodymium and Samarium in Membrane Based Extraction

    Institute of Scientific and Technical Information of China (English)

    张凤君; 马玖彤; 罗芳; 李德谦; 吴庸烈

    2002-01-01

    Extraction and interfacial kinetics of Nd3+ and Sm3+ with HEH/EHP-kerosene in a hollow fiber membrane extractor were studied. The results show that the extraction reactions in the hollow fiber membrane extractor are the same as those in the liquid-liquid extraction, which can be expressed as a quasi-first-order reaction. The effect of acidity in aqueous phase, concentrations of extractant, Nd3+ and Sm3+ on extraction rate were discussed and the corresponding reaction series were obtained. The reaction equations, reaction rate constants and the separation constant were obtained.

  3. Electron transfer interactome of cytochrome C.

    Directory of Open Access Journals (Sweden)

    Alexander N Volkov

    Full Text Available Lying at the heart of many vital cellular processes such as photosynthesis and respiration, biological electron transfer (ET is mediated by transient interactions among proteins that recognize multiple binding partners. Accurate description of the ET complexes - necessary for a comprehensive understanding of the cellular signaling and metabolism - is compounded by their short lifetimes and pronounced binding promiscuity. Here, we used a computational approach relying solely on the steric properties of the individual proteins to predict the ET properties of protein complexes constituting the functional interactome of the eukaryotic cytochrome c (Cc. Cc is a small, soluble, highly-conserved electron carrier protein that coordinates the electron flow among different redox partners. In eukaryotes, Cc is a key component of the mitochondrial respiratory chain, where it shuttles electrons between its reductase and oxidase, and an essential electron donor or acceptor in a number of other redox systems. Starting from the structures of individual proteins, we performed extensive conformational sampling of the ET-competent binding geometries, which allowed mapping out functional epitopes in the Cc complexes, estimating the upper limit of the ET rate in a given system, assessing ET properties of different binding stoichiometries, and gauging the effect of domain mobility on the intermolecular ET. The resulting picture of the Cc interactome 1 reveals that most ET-competent binding geometries are located in electrostatically favorable regions, 2 indicates that the ET can take place from more than one protein-protein orientation, and 3 suggests that protein dynamics within redox complexes, and not the electron tunneling event itself, is the rate-limiting step in the intermolecular ET. Further, we show that the functional epitope size correlates with the extent of dynamics in the Cc complexes and thus can be used as a diagnostic tool for protein mobility.

  4. Charge-transfer complex versus σ-complex formed between TiO2 and bis(dicyanomethylene) electron acceptors.

    Science.gov (United States)

    Fujisawa, Jun-ichi; Nagata, Morio; Hanaya, Minoru

    2015-11-01

    A novel group of organic-inorganic hybrid materials is created by the combination of titanium dioxide (TiO2) nanoparticles with bis(dicyanomethylene) (TCNX) electron acceptors. The TiO2-TCNX complex is produced by the nucleophilic addition reaction between a hydroxy group on the TiO2 surface and TCNX, with the formation of a σ-bond between them. The nucleophilic addition reaction generates a negatively-charged diamagnetic TCNX adsorbate that serves as an electron donor. The σ-bonded complex characteristically shows visible-light absorption due to interfacial charge-transfer (ICT) transitions. In this paper, we report on another kind of complex formation between TiO2 and TCNX. We have systematically studied the structures and visible-light absorption properties of the TiO2-TCNX complexes, with changing the electron affinity of TCNX. We found that TCNX acceptors with lower electron affinities form charge-transfer complexes with TiO2 without the σ-bond formation. The charge-transfer complexes show strong visible-light absorption due to interfacial electronic transitions with little charge-transfer nature, which are different from the ICT transitions in the σ-bond complexes. The charge-transfer complexes induce efficient light-to-current conversions due to the interfacial electronic transitions, revealing the high potential for applications to light-energy conversions. Furthermore, we demonstrate that the formation of the two kinds of complexes is selectively controlled by the electron affinity of TCNX. PMID:26418266

  5. INVERSE ELECTRON TRANSFER IN PEROXYOXALATE CHEMIEXCITATION USING EASILY REDUCIBLE ACTIVATORS

    NARCIS (Netherlands)

    Bartoloni, Fernando Heering; Monteiro Leite Ciscato, Luiz Francisco; Augusto, Felipe Alberto; Baader, Wilhelm Josef

    2010-01-01

    INVERSE ELECTRON TRANSFER IN PEROXYOXALATE CHEMIEXCITATION USING EASILY REDUCIBLE ACTIVATORS. Chemiluminescence properties of the peroxyoxalate reaction in the presence of activators bearing electron withdrawing substituents were studied, to evaluate the possible occurrence of an inverse electron tr

  6. Role of Tensorial Electronic Friction in Energy Transfer at Metal Surfaces

    Science.gov (United States)

    Askerka, Mikhail; Maurer, Reinhard J.; Batista, Victor S.; Tully, John C.

    2016-05-01

    An accurate description of nonadiabatic energy relaxation is crucial for modeling atomistic dynamics at metal surfaces. Interfacial energy transfer due to electron-hole pair excitations coupled to motion of molecular adsorbates is often simulated by Langevin molecular dynamics with electronic friction. Here, we present calculations of the full electronic friction tensor by using first order time-dependent perturbation theory at the density functional theory level. We show that the friction tensor is generally anisotropic and nondiagonal, as found for hydrogen atom on Pd(100) and CO on Cu(100) surfaces. This implies that electron-hole pair induced nonadiabatic coupling at metal surfaces leads to friction-induced mode coupling, therefore, opening an additional channel for energy redistribution. We demonstrate the robustness and accuracy of our results by direct comparison to established methods and experimental data.

  7. Electron transfer in gas surface collisions

    International Nuclear Information System (INIS)

    In this thesis electron transfer between atoms and metal surfaces in general is discussed and the negative ionization of hydrogen by scattering protons at a cesiated crystalline tungsten (110) surface in particular. Experimental results and a novel theoretical analysis are presented. In Chapter I a theoretical overview of resonant electron transitions between atoms and metals is given. In the first part of chapter II atom-metal electron transitions at a fixed atom-metal distance are described on the basis of a model developed by Gadzuk. In the second part the influence of the motion of the atom on the atomic charge state is incorporated. Measurements presented in chapter III show a strong dependence of the fraction of negatively charged H atoms scattered at cesiated tungsten, on the normal as well as the parallel velocity component. In chapter IV the proposed mechanism for the parallel velocity effect is incorporated in the amplitude method. The scattering process of protons incident under grazing angles on a cesium covered surface is studied in chapter V. (Auth.)

  8. Electron transfer at sensitized semiconductor electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Spitler, M.T.

    1977-03-01

    Electron transfer from the excited state of sensitizing dyes to the conduction band of semiconductors has been studied through photoelectrochemical techniques. Two systems were analyzed in detail: rhodamine B on ZnO and rose bengal on TiO/sub 2/. Prior to electrochemical experimentation, the adsorption characteristics of these dyes were investigated using ZnO, ZnS, and TiO/sub 2/ single crystals as substrates. Absorbance measurements of the adsorbed dye were taken as a function of the solution concentration of the dye. Adsorption isotherms heats of adsorption were also established; they were similar to literature data reported for adsorption of these dyes on powdered substrates. Using the absorbance data, the quantum efficiency for photoinjection of electrons from rhodamine B into a ZnO electrode was determined to be 2.7 x 10/sup -2/. This value was independent of the dye surface concentration down to 50% coverage of the electrode. With the assumption that not all of the rhodamine B adsorbed on the electrode has the same rate of electron injection, a kinetic model for the time decay of the photocurrent was developed; data were analyzed according to this theory. A rate constant for photoreduction of the adsorbed dye was determined for the reducing agents. 86 references.

  9. Transfer line TT70 (electrons from PS to SPS)

    CERN Multimedia

    CERN PhotoLab

    1981-01-01

    As injectors for LEP, PS and SPS had to be converted to the acceleration of electrons and positrons. So far, only positively charged particles had been transferred from the PS to the SPS, for the negatively charged electrons a new transfer line, TT70, had to be built. Due to the difference in level of the two machines, the transfer line slopes and tilts.

  10. Interfacial electronic structure of Na deposited on rubrene thin film studied by synchrotron radiation photoemission

    Science.gov (United States)

    Wei, Ching-Hsuan; Cheng, Chiu-Ping; Lin, Hong-Cheu; Pi, Tun-Wen

    2015-12-01

    The electronic structure of rubrene doped with various concentrations of Na was studied by synchrotron-radiation photoemission. Three stages of development were found with increasing Na concentration; Na penetrating deep into the organic film, followed by development of gap states, and ended with a metallic Na film. The charge transfer from Na to rubrene resulted in a vacuum-level shift. By doping Na into rubrene, we could control the IP of the organic molecule, which is favorable for application in organic semiconductor devices.

  11. Activation entropy of electron transfer reactions

    CERN Document Server

    Milischuk, A A; Newton, M D; Milischuk, Anatoli A.; Matyushov, Dmitry V.; Newton, Marshall D.

    2005-01-01

    We report microscopic calculations of free energies and entropies for intramolecular electron transfer reactions. The calculation algorithm combines the atomistic geometry and charge distribution of a molecular solute obtained from quantum calculations with the microscopic polarization response of a polar solvent expressed in terms of its polarization structure factors. The procedure is tested on a donor-acceptor complex in which ruthenium donor and cobalt acceptor sites are linked by a four-proline polypeptide. The reorganization energies and reaction energy gaps are calculated as a function of temperature by using structure factors obtained from our analytical procedure and from computer simulations. Good agreement between two procedures and with direct computer simulations of the reorganization energy is achieved. The microscopic algorithm is compared to the dielectric continuum calculations. We found that the strong dependence of the reorganization energy on the solvent refractive index predicted by conti...

  12. Tuning the Interfacial Electronic Structure at Organic Heterojunctions by Chemical Design.

    Science.gov (United States)

    Mothy, Sébastien; Guillaume, Maxime; Idé, Julien; Castet, Frédéric; Ducasse, Laurent; Cornil, Jérôme; Beljonne, David

    2012-09-01

    Quantum-chemical techniques are applied to assess the electronic structure at donor/acceptor heterojunctions of interest for organic solar cells. We show that electrostatic effects at the interface of model 1D stacks profoundly modify the energy landscape explored by charge carriers in the photoconversion process and that these can be tuned by chemical design. When fullerene C60 molecules are used as acceptors and unsubstituted oligothiophenes or pentacene are used as donors, the uncompensated quadrupolar electric field at the interface provides the driving force for splitting of the charge-transfer states into free charges. This quadrupolar field can be either enhanced by switching from a C60 to a perylene-tetracarboxylic-dianhydride (PTCDA) acceptor or suppressed by grafting electron-withdrawing groups on the donor. PMID:26292117

  13. Path integral approach to non-relativistic electron charge transfer

    International Nuclear Information System (INIS)

    A path integral approach has been generalized for the non-relativistic electron charge transfer processes. The charge transfer - the capture of an electron by an ion passing another atom, or more generally the problem of rearrangement collisions - is formulated in terms of influence functionals. It has been shown that the electron charge transfer process can be treated either as an electron transition problem or as ion and atom elastic scattering in the effective potential field. The first-order Born approximation for the electron charge transfer reaction cross section has been reproduced to prove the adequacy of the path integral approach for this problem. (author)

  14. Identification of interfacial heat transfer between molten metal and green sand by inverse heat conduction method

    Science.gov (United States)

    Ke, Quanpeng

    Heat flux and heat transfer coefficients at the interfaces of castings and molds are important parameters in the mold design and computer simulations of the solidification process in foundry operations. A better understanding of the heat flux and heat transfer coefficient between the solidifying casting and its mold can promote model design and improve the accuracy of computer simulation. The main purpose of the present dissertation involves the estimation of the heat flux and heat transfer coefficient at the interface of the molten metal and green sand. Since the inverse heat conduction method requires temperature measurement data to deduce the missing surface information, it is suitable for the present research. However, heat transfer inside green sand is complicated by the migration of water vapor and zonal temperature distribution results. This makes the solution of the inverse heat conduction problem more challenging. In this dissertation, Galerkin's method of Weighted Residual together with the front tracking technique is used in the development of a forward solver. Beck's future time step method incorporated with the Gaussian iterative minimization method is used as the inverse solver. The mathematical descriptions of the sensitivity coefficient for both the direct heat flux and direct heat transfer coefficient estimation are derived. The variations of the sensitivity coefficients with time are revealed. From the analysis of sensitivity coefficients, the concept of blank time period is proposed. This blank time period makes the inverse problem much more difficult. A total energy balance criterion is used to combat this. Numerical experiments confirmed the accuracy and robustness of both the direct heat flux estimation algorithm and the direct heat transfer coefficient estimation algorithm. Finally, some pouring experiments are carried out. The inverse algorithms are applied to the estimation of the heat flux and heat transfer coefficient at the interface of

  15. Respiratory electron transfer in Escherichia coli : components, energetics and regulation

    NARCIS (Netherlands)

    M. Bekker

    2009-01-01

    The respiratory chain that is housed in the bacterial cytoplasmic membrane, generally transfers electrons from NADH to oxygen; in the absence of oxygen it can use several alternative electron acceptors, such as nitrate and fumarate. Transfer of electrons through this chain is usually coupled to the

  16. Electronic and Nuclear Factors in Charge and Excitation Transfer

    Energy Technology Data Exchange (ETDEWEB)

    Piotr Piotrowiak

    2004-09-28

    We report the and/or state of several subprojects of our DOE sponsored research on Electronic and Nuclear Factors in Electron and Excitation Transfer: (1) Construction of an ultrafast Ti:sapphire amplifier. (2) Mediation of electronic interactions in host-guest molecules. (3) Theoretical models of electrolytes in weakly polar media. (4) Symmetry effects in intramolecular excitation transfer.

  17. Soliton-like Solutions and Electron Transfer in DNA.

    Science.gov (United States)

    Lakhno, V D

    2000-06-01

    We consider various mechanisms of long-range electron transfer in DNAwhich enable us to explain recent controversial experiments. We show thatcontinuous super-exchange theory can explain the values of electron rateconstants in short fragments of DNA. The soliton-type electron transfer inlong segments of DNA is also dealt with.

  18. Summary of Interfacial Heat Transfer Model and Correlations in SPACE Code

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Sung Won; Lee, Seung Wook; Kim, Kyung Du [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-10-15

    The first stage of development program for a nuclear reactor safety analysis code named as SPACE which will be used by utility bodies has been finished at last April 2010. During the first stage, main logic and conceptual sculpture have been established successfully under the support of Korea Ministry of Knowledge and Economy. The code, named as SPACE, has been designed to solve the multi-dimensional 3-field 2 phase equations. From the beginning of second stage of development, KNF has moved to concentrate on the methodology evaluation by using he SPACE code. Thus, KAERI, KOPEC, KEPRI have been remained as the major development organizations. In the second stage, it is focused to assess the physical models and correlations of SPACE code by using the well known SET problems. For the successful SET assessment procedure, a problem selection process has been performed under the leading of KEPRI. KEPRI has listed suitable SET problems according to the individual assessment purpose. For the interfacial area concentration, the models and correlations are continuously modified and verified

  19. Theoretical aspects of electron transfer reactions of complex molecules

    DEFF Research Database (Denmark)

    Kuznetsov, A. M.; Ulstrup, Jens

    2001-01-01

    Features of electron transfer involving complex molecules are discussed. This notion presently refers to molecular reactants where charge transfer is accompanied by large molecular reorganization, and commonly used displaced harmonic oscillator models do not apply. It is shown that comprehensive ...

  20. The Liability of banks in electronic fund transfer transaction

    OpenAIRE

    Algudah, Fayyad

    1993-01-01

    The liability of banks in electronic fund transfer (EFT) transactions is discussed in this thesis under the British and the United States law. The thesis covers banks’ liability in electronic credit and debit transfers. It covers banks’ liability in Electronic Fund Transfer at the Point Of Sale (EFTPOS), Automatic Teller Machines (ATM) and home and office banking. Liability of banks in credit card transactions and cheque truncation falls outside the scope of this thesis. In ...

  1. Internal electron transfer within mitochondrial succinate-cytochrome C reductase

    International Nuclear Information System (INIS)

    Internal electron transfer within succinate-cytochrome C reductase from pigeon breast muscle mitochondria was followed by the pulse radiolytic technique. The electron equivalent is transferred from an unknown donor to b type cytochrome(s), in a first order process with a rate constant of: 660 +- 150s-1. This process might be the rate determining step of electron transfer in mitochondria, since it is similar in rate to the turnover number of the mitochondrial respiratory chain

  2. [Electron transfer between globular proteins. Evaluation of a matrix element].

    Science.gov (United States)

    Lakhno, V D; Chuev, G N; Ustinin, M N

    1998-01-01

    The dependence of the matrix element of the probability of interprotein electron transfer on the mutual orientation of the donor and acceptor centers and the distance between them was calculated. The calculations were made under the assumption that electron transfer proceeds mainly by a collective excitation of polaron nature, like a solvated electron state. The results obtained are consistent with experimental data and indicate the nonexponential behavior of this dependence in the case when the distance transfer is less than 20 A.

  3. Electronic transfer of sensitive patient data.

    Science.gov (United States)

    Detterbeck, A M W; Kaiser, J; Hirschfelder, U

    2015-01-01

    The purpose of this study was to develop decision-making aids and recommendations for dental practitioners regarding the utilization and sharing of sensitive digital patient data. In the current environment of growing digitization, healthcare professionals need detailed knowledge of secure data management to maximize confidentiality and minimize the risks involved in both archiving patient data and sharing it through electronic channels. Despite well-defined legal requirements, an all-inclusive technological solution does not currently exist. The need for a preliminary review and critical appraisal of common practices of data transfer prompted a search of the literature and the Web to identify viable methods of secure data exchange and to develop a flowchart. A strong focus was placed on the transmission of datasets both smaller than and larger than 10 MB, and on secure communication by smartphone. Although encryption of patient-related data should be routine, it is often difficult to implement. Pretty Good Privacy (PGP) and Secure/Multipurpose Internet Mail Extensions (S/MIME) are viable standards for secure e-mail encryption. Sharing of high-volume data should be accomplished with the help of file encryption. Careful handling of sensitive patient data is mandatory, and it is the end-user's responsibility to meet any requirements for encryption, preferably by using free, open-source (and hence transparent) software. PMID:25911828

  4. Electronic transfer of sensitive patient data.

    Science.gov (United States)

    Detterbeck, A M W; Kaiser, J; Hirschfelder, U

    2015-01-01

    The purpose of this study was to develop decision-making aids and recommendations for dental practitioners regarding the utilization and sharing of sensitive digital patient data. In the current environment of growing digitization, healthcare professionals need detailed knowledge of secure data management to maximize confidentiality and minimize the risks involved in both archiving patient data and sharing it through electronic channels. Despite well-defined legal requirements, an all-inclusive technological solution does not currently exist. The need for a preliminary review and critical appraisal of common practices of data transfer prompted a search of the literature and the Web to identify viable methods of secure data exchange and to develop a flowchart. A strong focus was placed on the transmission of datasets both smaller than and larger than 10 MB, and on secure communication by smartphone. Although encryption of patient-related data should be routine, it is often difficult to implement. Pretty Good Privacy (PGP) and Secure/Multipurpose Internet Mail Extensions (S/MIME) are viable standards for secure e-mail encryption. Sharing of high-volume data should be accomplished with the help of file encryption. Careful handling of sensitive patient data is mandatory, and it is the end-user's responsibility to meet any requirements for encryption, preferably by using free, open-source (and hence transparent) software.

  5. Injecting electrode controlled electronic transport across Fe{sub 3}O{sub 4} film-Si interfacial structure

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Surajit; Srivastava, Neelabh; Srivastava, P.C., E-mail: pcsrivastava50@gmail.com

    2014-11-05

    Highlights: • CPP I–V measurements have been carried out on Fe{sub 3}O{sub 4}/SiO{sub 2}/Si heterostructure. • Verwey transition has been found for injection from Fe{sub 3}O{sub 4} film. • Low temperature GMR of ∼200% has also been observed for the same injection. • The features of injecting electrodes have been found from CPP I–V data. - Abstract: A study of electronic transport has been carried out across a half-metallic Fe{sub 3}O{sub 4} film–nSi interfacial structure in CPP mode with an interfacial SiO{sub 2} layer of <5 nm. It has been measured with and without applied magnetic field along the plane of the interface between 25 K and 300 K to investigate the role of half-metallic Fe{sub 3}O{sub 4} layer on the transport. The electronic transport has shown a distinct behaviour for the reverse bias in which injection takes place from metallic film of Fe{sub 3}O{sub 4} to silicon than for the forward bias in which injection takes place from silicon to metallic Fe{sub 3}O{sub 4} side. It has been found that the reverse bias current shows a tunnel transport, Verwey transition like feature and low temperature positive GMR, evidencing spin involved transport from Fe{sub 3}O{sub 4} to semiconductor side. Whereas the forward bias current has not shown any of the above features but a thermionic controlled transport, showing a change of resistance with temperature as of semiconductor silicon. Thus, it has been found that the transport is controlled by physical properties of the injecting electrode. The study has shown that the transport below Verwey transition temperature (T{sub V}) for the Fe{sub 3}O{sub 4} film interfacial structure is also related to its electronic spins. The observed GMR of ∼200% at low temperature (for reverse bias current only) has been discussed as the effect of electronic spin scattering. Our unique observations from simple measurements of CPP I–V across the interfacial structure of Fe{sub 3}O{sub 4}–nSi seem significant to

  6. Manipulating NiFe/AlO{sub x} interfacial chemistry for the spin-polarized electrons transport

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Chong-Jun [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Sun, Li [Department of Mechanical Engineering and Texas Center for Superconductivity (TcSUH), University of Houston, Houston, Texas 77204 (United States); Ding, Lei [School of Materials and Chemical Engineering, Hainan University, Haikou 570228 (China); Li, Jian-Wei; Zhang, Jing-Yan; Cao, Yi [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yu, Guang-Hua, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2013-10-15

    Through vacuum annealing, interfacial chemical composition of sputter-deposited AlO{sub x}/NiFe/AlO{sub x} can be controlled for electron transport manipulation. Chemical status change at the NiFe/AlO{sub x} interface was quantified by X-ray photoelectron spectroscopy and correlated to the structure and electron transport properties of the heterostructure. It is found that elemental Al existed in the insulting AlO{sub x} after annealing at intermediate temperature can improve the AlO{sub x}/NiFe interface and thus favor the electronic transport. Annealing at higher temperature will result in native AlO{sub x} formation and degrade transport properties due to the NiFe/AlO{sub x} interfaces deterioration caused by significant difference in thermal expansion coefficients of the two materials.

  7. Photoinitiated electron transfer in multichromophoric species: Synthetic tetrads and pentads

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1993-03-01

    This project involves the design, synthesis and study of molecules which mimic some of the important aspects of photosynthetic electron and energy transfer. This research project is leading to a better understanding of the energy conserving steps of photosynthesis via the study of synthetic model systems which abstract features of the natural photosynthetic apparatus. The knowledge gained from these studies will aid in the design of artificial photosynthetic reaction centers which employ the basic chemistry and physics of photosynthesis to help meet mankind`s energy needs. The approach to artificial photosynthesis employed in this project is to use synthetic pigments, electron donors, and electron acceptors similar to those found in biological reaction centers, but to replace the protein component with covalent bonds. These chemical linkages determine the electronic coupling between the various moieties by controlling separation, relative orientation, and overlap of electronic orbitals. The model systems are designed to mimic the following aspects of natural photosynthetic electron transfer: electron donation from a tetrapyrrole excited single state, electron transfer between tetrapyrroles, electron transfer from tetrapyrroles to quinones, and electron transfer between quinones with different redox properties. In addition, they mimic carotenoid antenna function in photosynthesis (singlet-singlet energy transfer from carotenoid polyenes to chlorophyll) and carotenoid photoprotection from singlet oxygen damage (triplet-triplet energy transfer from chlorophyll to carotenoids).

  8. Interfacial electronic transport phenomena in single crystalline Fe-MgO-Fe thin barrier junctions

    Energy Technology Data Exchange (ETDEWEB)

    Gangineni, R. B., E-mail: rameshg.phy@pondiuni.edu.in [Department of Physics, School of Physical, Chemical and Applied Sciences, Pondicherry University, R. V. Nagar, Kalapet, Pondicherry 605 014 (India); SPINTEC, UMR 8191 CEA/CNRS/UJF-Grenoble 1/Grenoble INP, INAC, 17 rue des Martyrs, F-38054 Grenoble Cedex (France); Bellouard, C., E-mail: christine.bellouard@ijl.nancy-universite.fr; Duluard, A. [Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP 239, 54506 Vandoeuvre (France); Negulescu, B. [Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP 239, 54506 Vandoeuvre (France); UFR de Sciences et Techniques, Matériaux, microélectronique, acoustique, nanotechnologies (GREMAN), University François Rabelais, Parc de Grandmont, 37200 Tours (France); Baraduc, C.; Gaudin, G. [SPINTEC, UMR 8191 CEA/CNRS/UJF-Grenoble 1/Grenoble INP, INAC, 17 rue des Martyrs, F-38054 Grenoble Cedex (France); Tiusan, C., E-mail: coriolan.tiusan@phys.utcluj.ro [Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP 239, 54506 Vandoeuvre (France); Department of Physics and Chemistry, Center of Superconductivity, Spintronics and Surface Science, Technical University of Cluj Napoca, Str. Memorandumului No. 28, RO-400114 Cluj-Napoca (Romania)

    2014-05-05

    Spin filtering effects in nano-pillars of Fe-MgO-Fe single crystalline magnetic tunnel junctions are explored with two different sample architectures and thin MgO barriers (thickness: 3–8 monolayers). The two architectures, with different growth and annealing conditions of the bottom electrode, allow tuning the quality of the bottom Fe/MgO interface. As a result, an interfacial resonance states (IRS) is observed or not depending on this interface quality. The IRS contribution, observed by spin polarized tunnel spectroscopy, is analyzed as a function of the MgO barrier thickness. Our experimental findings agree with theoretical predictions concerning the symmetry of the low energy (0.2 eV) interfacial resonance states: a mixture of Δ{sub 1}-like and Δ{sub 5}-like symmetries.

  9. Two-photon-induced hot-electron transfer to a single molecule in a scanning tunneling microscope

    International Nuclear Information System (INIS)

    The junction of a scanning tunneling microscope (STM) operating in the tunneling regime was irradiated with femtosecond laser pulses. A photoexcited hot electron in the STM tip resonantly tunnels into an excited state of a single molecule on the surface, converting it from the neutral to the anion. The electron-transfer rate depends quadratically on the incident laser power, suggesting a two-photon excitation process. This nonlinear optical process is further confirmed by the polarization measurement. Spatial dependence of the electron-transfer rate exhibits atomic-scale variations. A two-pulse correlation experiment reveals the ultrafast dynamic nature of photoinduced charging process in the STM junction. Results from these experiments are important for understanding photoinduced interfacial charge transfer in many nanoscale inorganic-organic structures.

  10. Sandwiched confinement of quantum dots in graphene matrix for efficient electron transfer and photocurrent production.

    Science.gov (United States)

    Zhu, Nan; Zheng, Kaibo; Karki, Khadga J; Abdellah, Mohamed; Zhu, Qiushi; Carlson, Stefan; Haase, Dörthe; Žídek, Karel; Ulstrup, Jens; Canton, Sophie E; Pullerits, Tõnu; Chi, Qijin

    2015-05-21

    Quantum dots (QDs) and graphene are both promising materials for the development of new-generation optoelectronic devices. Towards this end, synergic assembly of these two building blocks is a key step but remains a challenge. Here, we show a one-step strategy for organizing QDs in a graphene matrix via interfacial self-assembly, leading to the formation of sandwiched hybrid QD-graphene nanofilms. We have explored structural features, electron transfer kinetics and photocurrent generation capacity of such hybrid nanofilms using a wide variety of advanced techniques. Graphene nanosheets interlink QDs and significantly improve electronic coupling, resulting in fast electron transfer from photoexcited QDs to graphene with a rate constant of 1.3 × 10(9) s(-1). Efficient electron transfer dramatically enhances photocurrent generation in a liquid-junction QD-sensitized solar cell where the hybrid nanofilm acts as a photoanode. We thereby demonstrate a cost-effective method to construct large-area QD-graphene hybrid nanofilms with straightforward scale-up potential for optoelectronic applications.

  11. Sandwiched confinement of quantum dots in graphene matrix for efficient electron transfer and photocurrent production

    Science.gov (United States)

    Zhu, Nan; Zheng, Kaibo; Karki, Khadga J.; Abdellah, Mohamed; Zhu, Qiushi; Carlson, Stefan; Haase, Dörthe; Žídek, Karel; Ulstrup, Jens; Canton, Sophie E.; Pullerits, Tõnu; Chi, Qijin

    2015-05-01

    Quantum dots (QDs) and graphene are both promising materials for the development of new-generation optoelectronic devices. Towards this end, synergic assembly of these two building blocks is a key step but remains a challenge. Here, we show a one-step strategy for organizing QDs in a graphene matrix via interfacial self-assembly, leading to the formation of sandwiched hybrid QD-graphene nanofilms. We have explored structural features, electron transfer kinetics and photocurrent generation capacity of such hybrid nanofilms using a wide variety of advanced techniques. Graphene nanosheets interlink QDs and significantly improve electronic coupling, resulting in fast electron transfer from photoexcited QDs to graphene with a rate constant of 1.3 × 109 s-1. Efficient electron transfer dramatically enhances photocurrent generation in a liquid-junction QD-sensitized solar cell where the hybrid nanofilm acts as a photoanode. We thereby demonstrate a cost-effective method to construct large-area QD-graphene hybrid nanofilms with straightforward scale-up potential for optoelectronic applications.

  12. Microbial extracellular electron transfer and its relevance to iron corrosion

    OpenAIRE

    Kato, Souichiro

    2016-01-01

    Summary Extracellular electron transfer (EET) is a microbial metabolism that enables efficient electron transfer between microbial cells and extracellular solid materials. Microorganisms harbouring EET abilities have received considerable attention for their various biotechnological applications, including bioleaching and bioelectrochemical systems. On the other hand, recent research revealed that microbial EET potentially induces corrosion of iron structures. It has been well known that corr...

  13. 75 FR 75897 - Electronic Funds Transfer of Depository Taxes

    Science.gov (United States)

    2010-12-07

    ... published in the Federal Register (75 FR 51707) proposed amendments to the regulations (REG-153340-09) to... deposit is made by electronic funds transfer by the next business day, January 17, 2012. Example 2. Semi... Internal Revenue Service 26 CFR Parts 1, 31, 40, and 301 RIN 1545-BJ13 Electronic Funds Transfer...

  14. 14 CFR 1274.931 - Electronic funds transfer payment methods.

    Science.gov (United States)

    2010-01-01

    ... cooperative agreement will be made by the Government by electronic funds transfer through the Treasury Fedline... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Electronic funds transfer payment methods... COOPERATIVE AGREEMENTS WITH COMMERCIAL FIRMS Other Provisions and Special Conditions § 1274.931...

  15. Inelastic electron scattering at low momentum transfer

    International Nuclear Information System (INIS)

    Recent advances of high energy resolution (ΔE approx. 30 keV FWHM) inelastic electron scattering at low momentum transfer (q -1) using selected experimental data from the Darmstadt electron linear accelerator are discussed. Strong emphasis is given to a comparison of the data with theoretical nuclear model predictions. Of the low multipolarity electric transitions investigated, as examples only E1 transitions to unnatural parity states in 11B and E2 transitions of the very fragmented isoscalar quadrupole giant resonance in 208Pb are considered. In 11B the role of the Os hole in the configuration of the 1/2+, 3/2+ and 5/2+ states is quantitatively determined via an interference mechanism in the transition probability. By comparison of the high resolution data with RPA calculations the E2 EWSR in 208Pb is found to be much less exhausted than anticipated from previous medium energy resolution (e,e) and hadron scattering experiments. In the case of M1 transitions it is shown that the simplest idealized independent particle shell-model prediction breaks down badly. In 28Si, ground-state correlations influence largely the detected M1 strength and such ground-state correlations are also responsible for the occurence of a strong M1 transition to a state at Ex = 10.319 MeV in 40Ca. In 90Zr only about 10% of the theoretically expected M1 strength is seen in (e,e) and in 140Ce and 208Pb none (detection limit 1-2 μ2K). In the case of 208Pb high resolution spectra exist now up to an excitation energy of Ex = approx. 12MeV. The continuous decrease of the M1 strength with mass number is corroborated by the behaviour of strong but very fragmented M2 transitions which are detected in 28Si, 90Zr, 140Ce and 208Pb concentrated at an excitation energy E x approx. 44A-1/3MeV. In 90Zr, the distribution of spacings and widths of the many Jπ = 2 states are consistent with a Wigner and Porter-Thomas distribution, respectively. (orig.) 891 KBE/orig. 892 ARA

  16. Transcriptomic and genetic analysis of direct interspecies electron transfer

    DEFF Research Database (Denmark)

    Shrestha, Pravin Malla; Rotaru, Amelia-Elena; Summers, Zarath M;

    2013-01-01

    The possibility that metatranscriptomic analysis could distinguish between direct interspecies electron transfer (DIET) and H2 interspecies transfer (HIT) in anaerobic communities was investigated by comparing gene transcript abundance in cocultures in which Geobacter sulfurreducens was the elect....... These results demonstrate that there are unique gene expression patterns that distinguish DIET from HIT and suggest that metatranscriptomics may be a promising route to investigate interspecies electron transfer pathways in more-complex environments....

  17. Ultrafast Electron Transfer at Organic Semiconductor Interfaces: Importance of Molecular Orientation

    KAUST Repository

    Ayzner, Alexander L.

    2015-01-02

    © 2014 American Chemical Society. Much is known about the rate of photoexcited charge generation in at organic donor/acceptor (D/A) heterojunctions overaged over all relative arrangements. However, there has been very little experimental work investigating how the photoexcited electron transfer (ET) rate depends on the precise relative molecular orientation between D and A in thin solid films. This is the question that we address in this work. We find that the ET rate depends strongly on the relative molecular arrangement: The interface where the model donor compound copper phthalocyanine is oriented face-on with respect to the fullerene C60 acceptor yields a rate that is approximately 4 times faster than that of the edge-on oriented interface. Our results suggest that the D/A electronic coupling is significantly enhanced in the face-on case, which agrees well with theoretical predictions, underscoring the importance of controlling the relative interfacial molecular orientation.

  18. Study on interfacial heat transfer coefficient at metal/die interface during high pressure die casting process of AZ91D alloy

    Directory of Open Access Journals (Sweden)

    GUO Zhi-peng

    2007-02-01

    Full Text Available The high pressure die casting (HPDC process is one of the fastest growing and most efficient methods for the production of complex shape castings of magnesium and aluminum alloys in today’s manufacturing industry.In this study, a high pressure die casting experiment using AZ91D magnesium alloy was conducted, and the temperature profiles inside the die were Measured. By using a computer program based on solving the inverse heat problem, the metal/die interfacial heat transfer coefficient (IHTC was calculated and studied. The results show that the IHTC between the metal and die increases right after the liquid metal is brought into the cavity by the plunger,and decreases as the solidification process of the liquid metal proceeds until the liquid metal is completely solidified,when the IHTC tends to be stable. The interfacial heat transfer coefficient shows different characteristics under different casting wall thicknesses and varies with the change of solidification behavior.

  19. Interfacial properties and electron structure of Al/B4C interface: A first-principles study

    Science.gov (United States)

    Xian, Yajiang; Qiu, Ruizhi; Wang, Xin; Zhang, Pengcheng

    2016-09-01

    This research aims at investigating the structural, mechanical and electronic properties of the Al (111)/B4C (0001) interface by first-principles calculations. This model geometry Al (111)/B4C (0001) is chosen because the close-packed planes of Al and B4C have the (111) and (0001) orientation, respectively, and the lattice mismatch is only ∼2.1%. Among four B4C (0001) surfaces with different terminations, our calculation of surface free energies predicted that C-terminated B4C (0001) surface is the most stable one. Relaxed atomic geometries, the work of adhesion and interfacial free energies were calculated for three C-terminated B4C (0001)/Al (111) interfaces with different stacking sequences (top-site, hollow-site, and bridge-site). Results reveal that the relaxed top-site (hollow-site-like) Al/B4C interface has the best adhesion force and also be the most stable. The interfacial electron structure including charge density difference, Bader charge and density of states (DOS) is analyzed to determine the nature of metal/carbide bonding and we find the formation of Alsbnd C bond and possibly the formation of Al4C3 in the interface.

  20. Interfacial Chemistry and the Design of Solid-Phase Nucleic Acid Hybridization Assays Using Immobilized Quantum Dots as Donors in Fluorescence Resonance Energy Transfer

    OpenAIRE

    Ulrich J. Krull; W. Russ Algar

    2011-01-01

    The use of quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET) offer several advantages for the development of multiplexed solid-phase QD-FRET nucleic acid hybridization assays. Designs for multiplexing have been demonstrated, but important challenges remain in the optimization of these systems. In this work, we identify several strategies based on the design of interfacial chemistry for improving sensitivity, obtaining lower limits of detection (LOD) and enabling th...

  1. Electron Transfer Pathways in Cholesterol Synthesis.

    Science.gov (United States)

    Porter, Todd D

    2015-10-01

    Cholesterol synthesis in the endoplasmic reticulum requires electron input at multiple steps and utilizes both NADH and NADPH as the electron source. Four enzymes catalyzing five steps in the pathway require electron input: squalene monooxygenase, lanosterol demethylase, sterol 4α-methyl oxidase, and sterol C5-desaturase. The electron-donor proteins for these enzymes include cytochrome P450 reductase and the cytochrome b5 pathway. Here I review the evidence for electron donor protein requirements with these enzymes, the evidence for additional electron donor pathways, and the effect of deletion of these redox enzymes on cholesterol and lipid metabolism. PMID:26344922

  2. Ultrafast Charge Transfer Visualized by Two-Dimensional Electronic Spectroscopy

    OpenAIRE

    Mančal T.; Milota F.; Hauer J; Christensson N.; Bixner O.; Lukeš V.; Kauffmann H. F.

    2013-01-01

    Two-dimensional electronic spectroscopy (2D-ES) is used to investigate ultrafast excited-state dynamics in a lutetium bisphthalocyanine dimer. Following optical excitation, a chain of electron and hole transfer steps gives rise to characteristic cross-peak dynamics in the electronic 2D spectra. The combination of density matrix propagation and quantum chemical calculations results in a molecular view of the charge transfer dynamics and highlights the role of the counter-ion in providing an en...

  3. Respiratory electron transfer in Escherichia coli : components, energetics and regulation

    OpenAIRE

    Hellingwerf, K.J.; Teixeira De Mattos, M.J.; Bekker, M.

    2009-01-01

    The respiratory chain that is housed in the bacterial cytoplasmic membrane, generally transfers electrons from NADH to oxygen; in the absence of oxygen it can use several alternative electron acceptors, such as nitrate and fumarate. Transfer of electrons through this chain is usually coupled to the translocation of protons across the membrane. The resulting gradient of protons is then used for the generation of ATP by the F0F1-ATPase, and for other free energy requiring processes such as solu...

  4. Imaging interfacial electrical transport in graphene-MoS2 heterostructures with electron-beam-induced-currents

    Science.gov (United States)

    White, E. R.; Kerelsky, Alexander; Hubbard, William A.; Dhall, Rohan; Cronin, Stephen B.; Mecklenburg, Matthew; Regan, B. C.

    2015-11-01

    Heterostructure devices with specific and extraordinary properties can be fabricated by stacking two-dimensional crystals. Cleanliness at the inter-crystal interfaces within a heterostructure is crucial for maximizing device performance. However, because these interfaces are buried, characterizing their impact on device function is challenging. Here, we show that electron-beam induced current (EBIC) mapping can be used to image interfacial contamination and to characterize the quality of buried heterostructure interfaces with nanometer-scale spatial resolution. We applied EBIC and photocurrent imaging to map photo-sensitive graphene-MoS2 heterostructures. The EBIC maps, together with concurrently acquired scanning transmission electron microscopy images, reveal how a device's photocurrent collection efficiency is adversely affected by nanoscale debris invisible to optical-resolution photocurrent mapping.

  5. Photoinduced electron transfers with carbon dots

    OpenAIRE

    Wang, Xin; Cao, Li; Lu, Fushen; Meziani, Mohammed J.; Li, Heting; Qi, Gang; Zhou, Bing; Harruff, Barbara A.; Kermarrec, Fabien; Sun, Ya-Ping

    2009-01-01

    The photoluminescence in carbon dots (surface-passivated small carbon nanoparticles) could be quenched efficiently by electron acceptor or donor molecules in solution, namely that photo-excited carbon dots are both excellent electron donors and excellent electron acceptors, thus offering new opportunities for their potential uses in light energy conversion and related applications.

  6. Ultrafast Charge Transfer Visualized by Two-Dimensional Electronic Spectroscopy

    Directory of Open Access Journals (Sweden)

    Mančal T.

    2013-03-01

    Full Text Available Two-dimensional electronic spectroscopy (2D-ES is used to investigate ultrafast excited-state dynamics in a lutetium bisphthalocyanine dimer. Following optical excitation, a chain of electron and hole transfer steps gives rise to characteristic cross-peak dynamics in the electronic 2D spectra. The combination of density matrix propagation and quantum chemical calculations results in a molecular view of the charge transfer dynamics and highlights the role of the counter-ion in providing an energetic perturbation which promotes charge transfer across the complex.

  7. Intermolecular and intramolecular electron transfer from eosin ester to viologen

    Institute of Scientific and Technical Information of China (English)

    张丰雷; 张曼华; 沈涛

    1996-01-01

    The covalently -(CH2)10- linked eosin-butylviologen compound has been synthesized. The photoinduced electron transfer of eosin ester and butylviologen as well as the influence of addition of cyclodextrin or amylose into the solution of linked compound on the system have been studied by the absorption spectra, fluorescence spectra and fluorescence lifetime. The results indicated that the intramolecular electron transfer is much more efficient than the intermolecular one. Due to the formation of inclusion complex, the process of intramolecular electron transfer was changed after adding cydodextrin or amylose.

  8. [Electron transfer between globular proteins. Dependence of the rate of transfer on distance].

    Science.gov (United States)

    Lakhno, V D; Chuev, G N; Ustinin, M N; Komarov, V M

    1998-01-01

    Based on the assumption that electron transfer between globular proteins occurs by a collective excitation of polaron type, the dependence of the rate of this process on the distance between the donor and acceptor centers with regard to their detailed electron structure was calculated. The electron structure of the heme was calculated by the quantum-chemical MNDO-PM3 method. The results were compared with experimental data on interprotein and intraglobular electron transfer. It is shown that, in the framework of this model, the electron transfer is not exponential and does not require a particular transfer pathway since the whole protein macromolecule is involved in the formation of the electron excited state.

  9. Studies of Mn/ZnO (0001¯) Interfacial Formation and Electronic Properties with Synchrotron Radiation

    Science.gov (United States)

    Zou, C. W.; Xu, P. S.; Wu, Y. Y.; Sun, B.; Xu, F. Q.; Pan, H. B.; Yuan, H. T.; Du, X. L.

    2007-01-01

    The initial growth, interfacial reaction and Fermi level movement of Mn on the O-terminated Zn (000 1¯) surface have been investigated by using synchrotron radiation photoelectron spectroscopy (SRPES) and X-ray photoemission (XPS). Mn is found to be grown on the surface in the layer-by-layer (Frank-van der Merwe) mode and be quite stable on the O-terminated surface at room temperature. With increasing the coverage of Mn, a downward Fermi level movement in band structure measurement of SRPES is observed and the resultant Schottky Barrier Height (SBH) is calculated to be about 1.1eV. Annealing behavior of the interface is investigated and we find that annealing at 600 °C induces a pronounced Mn-Zn atoms exchange reaction at the interface.

  10. A study of interfacial heat transfer and process parameters in squeeze casting and low pressure permanent mold casting

    Science.gov (United States)

    Krishna, Prasad

    2001-08-01

    casting machine. The HTC evaluation and SDAS-Cooling Rate Correlation were made in a similar manner to the Squeeze Casting study. A novel approach to estimating the HTC, accounting for the temporal and spatial temperature and thermal property variations, is presented. The maximum and minimum values of the HTC in this case were close to 2000 W/m2 K with no air gap and 400 W/m2 K with an air gap formation. The influences of air gap formation and mold coatings in controlling interfacial heat transfer were also modeled. It is expected that the HTCs and SDAS-Cooling Rate Correlations for the two casting processes will assist foundry engineers in deriving maximum benefits from each process.

  11. Promoting Knowledge Transfer with Electronic Note Taking

    Science.gov (United States)

    Katayama, Andrew D.; Shambaugh, R. Neal; Doctor, Tasneem

    2005-01-01

    We investigated the differences between (a) copying and pasting text versus typed note-taking methods of constructing study notes simultaneously with (b) vertically scaffolded versus horizontally scaffold notes on knowledge transfer. Forty-seven undergraduate educational psychology students participated. Materials included 2 electronic…

  12. Supramolecular networks with electron transfer in two dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Stupp, Samuel I.; Stoddart, J. Fraser; Shveyd, Alexander K.; Tayi, Alok S.; Sue, Chi-Hau; Narayanan, Ashwin

    2016-09-13

    Organic charge-transfer (CT) co-crystals in a crossed stack system are disclosed. The co-crystals exhibit bidirectional charge transfer interactions where one donor molecule shares electrons with two different acceptors, one acceptor face-to-face and the other edge-to-face. The assembly and charge transfer interaction results in a pleochroic material whereby the optical absorption continuously changes depending on the polarization angle of incident light.

  13. Analysis of transmission efficiency of SSRF electron beam transfer lines

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In this article, the main factors which influence transmission efficiency of the SSRF electron beam transfer lines are described, including physical requirements for magnet system, vacuum system, beam diagnostic system,trajectory correction system, etc. The dynamic simulation calculation and transmission efficiency analysis of the SSRF electron beam transfer lines are presented, and the studies show that the design purpose of efficient beam transmission and injection will be achieved.

  14. 77 FR 6310 - Electronic Fund Transfers (Regulation E)

    Science.gov (United States)

    2012-02-07

    ... numbers of transactions as being outside the normal course of business. Nor did they suggest other means... the first transaction in a series of preauthorized remittance transfers the same as all other... electronic transfers of funds sent by consumers in the United States to recipients in other countries....

  15. Theory of interrelated electron and proton transfer processes

    DEFF Research Database (Denmark)

    Kuznetsov, A.M.; Ulstrup, Jens

    2003-01-01

    A simple theory of elementary act of interrelated reactions of electron and proton transfer is developed. Mechanisms of synchronous and multistage transfer and coherent transitions via a dynamically populated intermediate state are discussed. Formulas for rate constants of adiabatic and nonadiaba...

  16. Freezing hot electrons. Electron transfer and solvation dynamics at D{sub 2}O and NH{sub 3}-metal interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Staehler, A.J.

    2007-05-15

    The present work investigates the electron transfer and solvation dynamics at the D{sub 2}O/Cu(111), D{sub 2}O/Ru(001), and NH{sub 3}/Cu(111) interfaces using femtosecond time-resolved two-photon photoelectron spectroscopy. Within this framework, the influence of the substrate, adsorbate structure and morphology, solvation site, coverage, temperature, and solvent on the electron dynamics are studied, yielding microscopic insight into the underlying fundamental processes. Transitions between different regimes of ET, substrate-dominated, barrier-determined, strong, and weak coupling are observed by systematic variation of the interfacial properties and development of empirical model descriptions. It is shown that the fundamental steps of the interfacial electron dynamics are similar for all investigated systems: Metal electrons are photoexcited to unoccupied metal states and transferred into the adlayer via the adsorbate's conduction band. The electrons localize at favorable sites and are stabilized by reorientations of the surrounding polar solvent molecules. Concurrently, they decay back two the metal substrate, as it offers a continuum of unoccupied states. However, the detailed characteristics vary for the different investigated interfaces: For amorphous ice-metal interfaces, the electron transfer is initially, right after photoinjection, dominated by the substrate's electronic surface band structure. With increasing solvation, a transient barrier evolves at the interface that increasingly screens the electrons from the substrate. Tunneling through this barrier becomes the rate-limiting step for ET. The competition of electron decay and solvation leads to lifetimes of the solvated electrons in the order of 100 fs. Furthermore, it is shown that the electrons bind in the bulk of the ice layers, but on the edges of adsorbed D{sub 2}O clusters and that the ice morphology strongly influences the electron dynamics. For the amorphous NH{sub 3}/Cu(111

  17. Proton-Coupled Electron Transfer Reactions with Photometric Bases Reveal Free Energy Relationships for Proton Transfer.

    Science.gov (United States)

    Eisenhart, Thomas T; Howland, William C; Dempsey, Jillian L

    2016-08-18

    The proton-coupled electron transfer (PCET) oxidation of p-aminophenol in acetonitrile was initiated via stopped-flow rapid-mixing and spectroscopically monitored. For oxidation by ferrocenium in the presence of 7-(dimethylamino)quinoline proton acceptors, both the electron transfer and proton transfer components could be optically monitored in the visible region; the decay of the ferrocenium absorbance is readily monitored (λmax = 620 nm), and the absorbance of the 2,4-substituted 7-(dimethylamino)quinoline derivatives (λmax = 370-392 nm) red-shifts substantially (ca. 70 nm) upon protonation. Spectral analysis revealed the reaction proceeds via a stepwise electron transfer-proton transfer process, and modeling of the kinetics traces monitoring the ferrocenium and quinolinium signals provided rate constants for elementary proton and electron transfer steps. As the pKa values of the conjugate acids of the 2,4-R-7-(dimethylamino)quinoline derivatives employed were readily tuned by varying the substituents at the 2- and 4-positions of the quinoline backbone, the driving force for proton transfer was systematically varied. Proton transfer rate constants (kPT,2 = (1.5-7.5) × 10(8) M(-1) s(-1), kPT,4 = (0.55-3.0) × 10(7) M(-1) s(-1)) were found to correlate with the pKa of the conjugate acid of the proton acceptor, in agreement with anticipated free energy relationships for proton transfer processes in PCET reactions. PMID:27500804

  18. 75 FR 16579 - Electronic Fund Transfers

    Science.gov (United States)

    2010-04-01

    ...-detail.php?article_id=330539 ). According to the Federal Reserve's 2007 Electronic Payments Study, $36.6... gift card or gift certificate and loyalty, award, and promotional gift cards. \\7\\ 74 FR 60986 (Nov. 20... (available at: http://schumer.senate.gov/new_website/record.cfm?id=310799 ). New comment 20(a)-4...

  19. Mathematics and electronics - the conceptual transfer problem

    Science.gov (United States)

    Waks, S.

    1988-07-01

    The article deals with the gap between the technological-school student's mastery of pure mathematical principles and his/her competence in their implementation in electronics and suggests a means for narrowing this, using a case study. A cooperative effort by mathematics and electronics teachers, involving coordination of content, teaching strategies and timing, was implemented on two groups (treatment and control). The treatment group achieved significantly higher average scores in tests in those questions where the mathematical reinforcement provided in the treatment process could be used - and this in spite of the group's weaker standing in the electronics course. Moreover, it was establised that treatment students adopted a more analytical approach in their solution strategies, while control students tended to rely more on recall and 'ready-made' formulae. The main conclusion of our case study is that mastery of mathematical theory and principles is a prerequisite to efficient tackling of technological problems, but is not always enough. Cooperation between the maths and electronics teachers contributes to improvement of the teaching-learning process in a technological discipline.

  20. Electron transfer rates and equilibrium within cytochrome c oxidase

    DEFF Research Database (Denmark)

    Farver, O; Einarsdóttir, O; Pecht, I

    2000-01-01

    Intramolecular electron transfer (ET) between the CuA center and heme a in bovine cytochrome c oxidase was investigated by pulse radiolysis. CuA, the initial electron acceptor, was reduced by 1-methyl nicotinamide radicals in a diffusion-controlled reaction, as monitored by absorption changes at...

  1. Photoinduced electron transfer in model systems of photosynthesis.

    NARCIS (Netherlands)

    Hofstra, U.

    1988-01-01

    This Thesis describes Investigations on photoinduced electron transfer (ET) for several compounds, serving as model systems of the natural photosynthesis. In addition, the properties of the systems, e.g. the conformation in solution and the electronic properties of the photoexcited states are treate

  2. Electron transfer through rigid organic molecular wires enhanced by electronic and electron-vibration coupling.

    Science.gov (United States)

    Sukegawa, Junpei; Schubert, Christina; Zhu, Xiaozhang; Tsuji, Hayato; Guldi, Dirk M; Nakamura, Eiichi

    2014-10-01

    Electron transfer (ET) is a fundamental process in a wide range of biological systems, photovoltaics and molecular electronics. Therefore to understand the relationship between molecular structure and ET properties is of prime importance. For this purpose, photoinduced ET has been studied extensively using donor-bridge-acceptor molecules, in which π-conjugated molecular wires are employed as bridges. Here, we demonstrate that carbon-bridged oligo-p-phenylenevinylene (COPV), which is both rigid and flat, shows an 840-fold increase in the ET rate compared with the equivalent flexible molecular bridges. A 120-fold rate enhancement is explained in terms of enhanced electronic coupling between the electron donor and the electron acceptor because of effective conjugation through the COPVs. The remainder of the rate enhancement is explained by inelastic electron tunnelling through COPV caused by electron-vibration coupling, unprecedented for organic molecular wires in solution at room temperature. This type of nonlinear effect demonstrates the versatility and potential practical utility of COPVs in molecular device applications.

  3. Lewis Acid Coupled Electron Transfer of Metal-Oxygen Intermediates.

    Science.gov (United States)

    Fukuzumi, Shunichi; Ohkubo, Kei; Lee, Yong-Min; Nam, Wonwoo

    2015-12-01

    Redox-inactive metal ions and Brønsted acids that function as Lewis acids play pivotal roles in modulating the redox reactivity of metal-oxygen intermediates, such as metal-oxo and metal-peroxo complexes. The mechanisms of the oxidative CH bond cleavage of toluene derivatives, sulfoxidation of thioanisole derivatives, and epoxidation of styrene derivatives by mononuclear nonheme iron(IV)-oxo complexes in the presence of triflic acid (HOTf) and Sc(OTf)3 have been unified as rate-determining electron transfer coupled with binding of Lewis acids (HOTf and Sc(OTf)3 ) by iron(III)-oxo complexes. All logarithms of the observed second-order rate constants of Lewis acid-promoted oxidative CH bond cleavage, sulfoxidation, and epoxidation reactions of iron(IV)-oxo complexes exhibit remarkably unified correlations with the driving forces of proton-coupled electron transfer (PCET) and metal ion-coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes were taken into account. The binding of HOTf and Sc(OTf)3 to the metal-oxo moiety has been confirmed for Mn(IV) -oxo complexes. The enhancement of the electron-transfer reactivity of metal-oxo complexes by binding of Lewis acids increases with increasing the Lewis acidity of redox-inactive metal ions. Metal ions can also bind to mononuclear nonheme iron(III)-peroxo complexes, resulting in acceleration of the electron-transfer reduction but deceleration of the electron-transfer oxidation. Such a control on the reactivity of metal-oxygen intermediates by binding of Lewis acids provides valuable insight into the role of Ca(2+) in the oxidation of water to dioxygen by the oxygen-evolving complex in photosystem II.

  4. Lewis Acid Coupled Electron Transfer of Metal-Oxygen Intermediates.

    Science.gov (United States)

    Fukuzumi, Shunichi; Ohkubo, Kei; Lee, Yong-Min; Nam, Wonwoo

    2015-12-01

    Redox-inactive metal ions and Brønsted acids that function as Lewis acids play pivotal roles in modulating the redox reactivity of metal-oxygen intermediates, such as metal-oxo and metal-peroxo complexes. The mechanisms of the oxidative CH bond cleavage of toluene derivatives, sulfoxidation of thioanisole derivatives, and epoxidation of styrene derivatives by mononuclear nonheme iron(IV)-oxo complexes in the presence of triflic acid (HOTf) and Sc(OTf)3 have been unified as rate-determining electron transfer coupled with binding of Lewis acids (HOTf and Sc(OTf)3 ) by iron(III)-oxo complexes. All logarithms of the observed second-order rate constants of Lewis acid-promoted oxidative CH bond cleavage, sulfoxidation, and epoxidation reactions of iron(IV)-oxo complexes exhibit remarkably unified correlations with the driving forces of proton-coupled electron transfer (PCET) and metal ion-coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes were taken into account. The binding of HOTf and Sc(OTf)3 to the metal-oxo moiety has been confirmed for Mn(IV) -oxo complexes. The enhancement of the electron-transfer reactivity of metal-oxo complexes by binding of Lewis acids increases with increasing the Lewis acidity of redox-inactive metal ions. Metal ions can also bind to mononuclear nonheme iron(III)-peroxo complexes, resulting in acceleration of the electron-transfer reduction but deceleration of the electron-transfer oxidation. Such a control on the reactivity of metal-oxygen intermediates by binding of Lewis acids provides valuable insight into the role of Ca(2+) in the oxidation of water to dioxygen by the oxygen-evolving complex in photosystem II. PMID:26404482

  5. Electronic Energy Transfer in Polarizable Heterogeneous Environments

    DEFF Research Database (Denmark)

    Svendsen, Casper Steinmann; Kongsted, Jacob

    2015-01-01

    such couplings provide important insight into the strength of interaction between photo-active pigments in protein-pigment complexes. Recently, attention has been payed to how the environment modifies or even controls the electronic couplings. To enable such theoretical predictions, a fully polarizable...... higher-order multipole moments. We use this extended model to systematically examine three different ways of obtaining EET couplings in a heterogeneous medium ranging from use of the exact transition density to a point-dipole approximation. Several interesting observations are made including that...... explicit use of transition densities in the calculation of the electronic couplings - also when including the explicit environment contribution - can be replaced by a much simpler transition point charge description without comprising the quality of the model predictions....

  6. Noise-assisted quantum electron transfer in photosynthetic complexes

    OpenAIRE

    Nesterov, Alexander I; Berman, Gennady P.; Martínez, José Manuel Sánchez; Sayre, Richard T.

    2013-01-01

    Electron transfer (ET) between primary electron donors and acceptors is modeled in the photosystem II reaction center (RC). Our model includes (i) two discrete energy levels associated with donor and acceptor, interacting through a dipole-type matrix element and (ii) two continuum manifolds of electron energy levels ("sinks"), which interact directly with the donor and acceptor. Namely, two discrete energy levels of the donor and acceptor are embedded in their independent sinks through the co...

  7. A tetrastable naphthalenediimide: anion induced charge transfer, single and double electron transfer for combinational logic gates.

    Science.gov (United States)

    Ajayakumar, M R; Hundal, Geeta; Mukhopadhyay, Pritam

    2013-09-11

    Herein we demonstrate the formation of the first tetrastable naphthalenediimide (NDI, 1a) molecule having multiple distinctly readable outputs. Differential response of 1a to fluoride anions induces intramolecular charge transfer (ICT), single/double electron transfer (SET/DET) leading to a set of combinational logic gates for the first time with a NDI moiety. PMID:23752683

  8. Interfacial Chemistry and the Design of Solid-Phase Nucleic Acid Hybridization Assays Using Immobilized Quantum Dots as Donors in Fluorescence Resonance Energy Transfer

    Directory of Open Access Journals (Sweden)

    Ulrich J. Krull

    2011-06-01

    Full Text Available The use of quantum dots (QDs as donors in fluorescence resonance energy transfer (FRET offer several advantages for the development of multiplexed solid-phase QD-FRET nucleic acid hybridization assays. Designs for multiplexing have been demonstrated, but important challenges remain in the optimization of these systems. In this work, we identify several strategies based on the design of interfacial chemistry for improving sensitivity, obtaining lower limits of detection (LOD and enabling the regeneration and reuse of solid-phase QD-FRET hybridization assays. FRET-sensitized emission from acceptor dyes associated with hybridization events at immobilized QD donors provides the analytical signal in these assays. The minimization of active sensing area reduces background from QD donor PL and allows the resolution of smaller amounts of acceptor emission, thus lowering the LOD. The association of multiple acceptor dyes with each hybridization event can enhance FRET efficiency, thereby improving sensitivity. Many previous studies have used interfacial protein layers to generate selectivity; however, transient destabilization of these layers is shown to prevent efficient regeneration. To this end, we report a protein-free interfacial chemistry and demonstrate the specific detection of as little as 2 pmol of target, as well as an improved capacity for regeneration.

  9. Imaging population transfer in atoms with ultrafast electron pulses

    Science.gov (United States)

    Shao, Hua-Chieh; Starace, Anthony F.

    2016-05-01

    Ultrafast electron diffraction and microscopy have made significant progress recently in investigating atomic-scale structural dynamics in gas-phase and condensed materials. With these advances, direct imaging of electronic motions in atoms and molecules by ultrafast electron diffraction is anticipated. We propose imaging a laser-driven coherent population transfer in lithium atoms by femtosecond ultrafast electron pulses. Valuable information and insight can be obtained from studying such a system in order to refine ultrafast electron techniques and to interpret experimental results. Adiabatic passage by level crossing is used to transfer the electron population from the 2 s to the 2 p state. Our simulations demonstrate the ability of ultrafast electron diffraction to image this population transfer, as the time-dependent diffraction images reflect the electronic motion in the scattering intensity and angular distribution. Furthermore, asymmetric diffraction patterns indicate that even the relative phases of the electronic wave function can be resolved, provided there is sufficient temporal resolution. This work has been supported in part by DOE Award No. DE-SC0012193 [H.-C.S.] and by NSF Grant No. PHYS-1505492 [A.F.S.].

  10. Effects of carbon dioxide hydration kinetics and evaporative convection on pH profile development during interfacial mass transfer of ammonia and carbon dioxide

    Science.gov (United States)

    Hafner, Sasha D.; Sommer, Sven G.; Petersen, Valdemar; Markfoged, Rikke

    2016-09-01

    Interfacial mass transfer of NH_3 and CO_2 are important in processes as diverse as NH_3 emission from animal manure and gas scrubbing for removal of carbon dioxide. Predicting transfer rates is complicated by bidirectional interactions between solution pH and emission rates, which may be affected by physical, chemical, and biological processes. We studied the effects of CO_2 hydration kinetics and evaporative convection on the development of pH profiles in solutions undergoing simultaneous emission of NH_3 and CO_2 . Profiles of pH were measured at a 0.1 mm resolution over 15 h, and interpreted using a reaction-transport model. Under high humidity, surface pH increased quickly (>0.2 units in 8 min) and an increase gradually extended to deeper depths. An increase in CO_2 hydration and carbonic acid dehydration rates by addition of carbonic anhydrase increased the elevation of surface pH and the depth to which an increase extended, due to an increase in CO_2 emission. Results show that unless carbonic anhydrase is present, the equilibrium approach typically used for modeling interfacial transport of CO_2 and NH_3 will be inaccurate. Evaporation and resulting convection greatly increased mass transfer rates below an apparent surface film about 1 mm thick. Emission or absorption of CO_2 can produce steep gradients in pH over small distances (20 mm) in systems with and without convective mixing, and the resulting surface pH, in turn, strongly affects NH_3 transfer. Both convection and the rate of hydration/dehydration reactions are likely to affect pH profile development and rates of NH_3 and CO_2 transfer in many systems. Accurately predicting mass transfer rates for these systems will require an understanding of these processes in the systems.

  11. Long-range protein electron transfer observed at the single-molecule level: In situ mapping of redox-gated tunneling resonance

    OpenAIRE

    Chi, Qijin; Farver, Ole; Ulstrup, Jens

    2005-01-01

    A biomimetic long-range electron transfer (ET) system consisting of the blue copper protein azurin, a tunneling barrier bridge, and a gold single-crystal electrode was designed on the basis of molecular wiring self-assembly principles. This system is sufficiently stable and sensitive in a quasi-biological environment, suitable for detailed observations of long-range protein interfacial ET at the nanoscale and single-molecule levels. Because azurin is located at clearly identifiable fixed site...

  12. Computational Approach to Electron Charge Transfer Reactions

    DEFF Research Database (Denmark)

    Jónsson, Elvar Örn

    The step from ab initio atomic and molecular properties to thermodynamic - or macroscopic - properties requires the combination of several theoretical tools. This dissertation presents constant temperature molecular dynamics with bond length constraints, a hybrid quantum mechanics...... to show general (or expected) properties. Properties such as in the physical and (semi-)chemical interface between classical and quantum systems and the effects of molecular bond length constraints on the temperature during simulations. As a second step the methodology is applied to the symmetric...... structure modes. This is for a large iridium-iridium dimer complex which shows a dramatic structural (and vibrational) change upon electronic excitation....

  13. Versatile electron-collecting interfacial layer by in situ growth of silver nanoparticles in nonconjugated polyelectrolyte aqueous solution for polymer solar cells.

    Science.gov (United States)

    Yuan, Kai; Chen, Lie; Chen, Yiwang

    2014-10-01

    Novel PEIE-Ag composites by in situ growth of silver nanoparticles in poly(ethylenimine)-ethoxylated (PEIE) aqueous solution are explored as an efficient interfacial layer for improving inverted polymer solar cells (PSCs) performance. The hybrid PEIE-Ag interfacial material is simple to fabricate only via ultraviolet irradiation with good water-solubility and unique film formation. The generated Ag nanoparticles can anchor in the PEIE polymer chains to form a conductive continuous interpenetrating network structure. Combining of the advantages of PEIE and Ag nanoparticles, the PEIE-Ag shows enhanced charge transport, electron selective and collection, and improved light-harvesting, mainly due to the surface plasmon resonance effect, better energy alignment induced by the formation of ideal dipole layer, as well as the improved conductivity. These distinguished interfacial properties result in the power conversion efficiency of inverted PSCs based on poly[4,8-bis(2-ethyl-hexyl-thiophene-5-yl)-benzo[1,2-b:4,5-b]dithiophene-2,6-diyl]-alt-[2-(2-ethyl-hexanoyl)-thieno[3,4-b]thiophen-4,6-diyl] (PBDTTT-C-T) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) photoactive layer substantially improved up to 7.66% from 6.11%. Moreover, the device performance is insensitively dependent on the thickness of the PEIE-Ag interfacial layer, broadening the thicknesses selection window for interfacial materials. These results demonstrate that PEIE-Ag is a potential interfacial material compatible with roll-to-roll techniques and suitable for printed electronic devices. PMID:25207753

  14. Plugging in or Going Wireless: Strategies for Interspecies Electron Transfer

    Directory of Open Access Journals (Sweden)

    Pravin Malla Shrestha

    2014-05-01

    Full Text Available Interspecies exchange of electrons enables a diversity of microbial communities to gain energy from reactions that no one microbe can catalyze. The first recognized strategies for interspecies electron transfer were those that relied on chemical intermediates that are recycled through oxidized and reduced forms. Well-studied examples are interspecies H2 transfer and the cycling of sulfur intermediates in anaerobic photosynthetic communities. Direct interspecies electron transfer (DIET in which two species establish electrical contacts is an alternative. Electrical contacts documented to date include electrically conductive pili, as well as conductive iron minerals and conductive carbon moieties such as activated carbon and biochar. It seems likely that there are additional alternative strategies for interspecies electrical connections that have yet to be discovered. Interspecies electron transfer is central to the functioning of methane-producing microbial communities. The importance of interspecies H2 transfer in many methanogenic communities is clear, but under some circumstances DIET predominates. It is expected that further mechanistic studies and broadening investigations to a wider range of environments will help elucidate the factors that favor specific forms of interspecies electron exchange under different environmental conditions.

  15. Optimization of Plasmon Decay Through Scattering and Hot Electron Transfer

    Science.gov (United States)

    DeJarnette, Drew

    Light incident on metal nanoparticles induce localized surface oscillations of conductive electrons, called plasmons, which is a means to control and manipulate light. Excited plasmons decay as either thermal energy as absorbed phonons or electromagnetic energy as scattered photons. An additional decay pathway for plasmons can exist for gold nanoparticles situated on graphene. Excited plasmons can decay directly to the graphene as through hot electron transfer. This dissertation begins by computational analysis of plasmon resonance energy and bandwidth as a function of particle size, shape, and dielectric environment in addition to diffractive coupled in lattices creating a Fano resonance. With this knowledge, plasmon resonance was probed with incident electrons using electron energy loss spectroscopy in a transmission electron microscope. Nanoparticles were fabricated using electron beam lithography on 50 nanometer thick silicon nitride with some particles fabricated with a graphene layer between the silicon nitride and metal structure. Plasmon resonance was compared between ellipses on and off graphene to characterize hot electron transfer as a means of plasmon decay. It was observed that the presence of graphene caused plasmon energy to decrease by as much as 9.8% and bandwidth to increase by 25%. Assuming the increased bandwidth was solely from electron transfer as an additional plasmon decay route, a 20% efficiency of plasmon decay to graphene was calculated for the particular ellipses analyzed.

  16. Photoinduced electron transfer processes in homogeneous and microheterogeneous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Whitten, D.G.

    1991-10-01

    The focus of the work described in this report is on single electron transfer reactions of excited states which culminate in the formation of stable or metastable even electron species. For the most part the studies have involved even electron organic substrates which are thus converted photochemically to odd electron species and then at some stage reconvert to even electron products. These reactions generally fall into two rather different categories. In one set of studies we have examined reactions in which the metastable reagents generated by single electron transfer quenching of an excited state undergo novel fragmentation reactions, chiefly involving C-C bond cleavage. These reactions often culminate in novel and potentially useful chemical reactions and frequently have the potential for leading to new chemical products otherwise unaffordable by conventional reaction paths. In a rather different investigation we have also studied reactions in which single electron transfer quenching of an excited state is followed by subsequent reactions which lead reversibly to metastable two electron products which, often stable in themselves, can nonetheless be reacted with each other or with other reagents to regenerate the starting materials with release of energy. 66 refs., 9 figs., 1 tab.

  17. Distance-dependent electron transfer in DNA hairpins

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, F.D.; Wu, T.; Zhang, Y. [Northwestern Univ., Evanston, IL (United States)] [and others

    1997-08-01

    The distance dependence of photoinduced electron transfer in duplex DNA was determined for a family of synthetic DNA hairpins in which a stilbene dicarboxamide forms a bridge connecting two oligonucleotide arms. Investigation of the fluorescence and transient absorption spectra of these hairpins established that no photoinduced electron transfer occurs for a hairpin that has six deoxyadenosine-deoxythymidine base pairs. However, the introduction of a single deoxyguanosine-deoxycytidine base pair resulted in distance-dependent fluorescence quenching and the formation of the stilbene anion radical. Kinetic analysis suggests that duplex DNA is somewhat more effective than proteins as a medium for electron transfer but that it does not function as a molecular wire.

  18. Numerical Simulation of Transient Moisture Transfer into an Electronic Enclosure

    DEFF Research Database (Denmark)

    Shojaee Nasirabadi, Parizad; Jabbaribehnam, Mirmasoud; Hattel, Jesper Henri

    2016-01-01

    inside the enclosures to be able to protect the electronic systems.In this work, moisture transfer into a typical electronic enclosure is numerically studied using CFD. In order to reduce theCPU-time and make a way for subsequent factorial design analysis, a simplifying modification is applied in which......Electronic systems are sometimes exposed to harsh environmental conditions of temperature and humidity. Moisturetransfer into electronic enclosures and condensation can cause several problems such as corrosion and alteration in thermalstresses. It is therefore essential to study the local climate...

  19. Electron transfer statistics and thermal fluctuations in molecular junctions

    Science.gov (United States)

    Goswami, Himangshu Prabal; Harbola, Upendra

    2015-02-01

    We derive analytical expressions for probability distribution function (PDF) for electron transport in a simple model of quantum junction in presence of thermal fluctuations. Our approach is based on the large deviation theory combined with the generating function method. For large number of electrons transferred, the PDF is found to decay exponentially in the tails with different rates due to applied bias. This asymmetry in the PDF is related to the fluctuation theorem. Statistics of fluctuations are analyzed in terms of the Fano factor. Thermal fluctuations play a quantitative role in determining the statistics of electron transfer; they tend to suppress the average current while enhancing the fluctuations in particle transfer. This gives rise to both bunching and antibunching phenomena as determined by the Fano factor. The thermal fluctuations and shot noise compete with each other and determine the net (effective) statistics of particle transfer. Exact analytical expression is obtained for delay time distribution. The optimal values of the delay time between successive electron transfers can be lowered below the corresponding shot noise values by tuning the thermal effects.

  20. Electron transfer statistics and thermal fluctuations in molecular junctions

    Energy Technology Data Exchange (ETDEWEB)

    Goswami, Himangshu Prabal; Harbola, Upendra [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012 (India)

    2015-02-28

    We derive analytical expressions for probability distribution function (PDF) for electron transport in a simple model of quantum junction in presence of thermal fluctuations. Our approach is based on the large deviation theory combined with the generating function method. For large number of electrons transferred, the PDF is found to decay exponentially in the tails with different rates due to applied bias. This asymmetry in the PDF is related to the fluctuation theorem. Statistics of fluctuations are analyzed in terms of the Fano factor. Thermal fluctuations play a quantitative role in determining the statistics of electron transfer; they tend to suppress the average current while enhancing the fluctuations in particle transfer. This gives rise to both bunching and antibunching phenomena as determined by the Fano factor. The thermal fluctuations and shot noise compete with each other and determine the net (effective) statistics of particle transfer. Exact analytical expression is obtained for delay time distribution. The optimal values of the delay time between successive electron transfers can be lowered below the corresponding shot noise values by tuning the thermal effects.

  1. PHOTOINDUCED CHARGE TRANSFER POLYMERIZATION OF STYRENE INITIATED BY ELECTRON ACCEPTOR

    Institute of Scientific and Technical Information of China (English)

    CAO Weixiao; ZHANG Peng; FENG Xinde

    1995-01-01

    Photoinduced charge transfer polymerization of styrene(St) with electron acceptor as initiator was investigated. In case of fumaronitrile (FN) or maleic anhydride (MA) as initiator the polymerization takes place regularly, whereas the tetrachloro-1, 4-benzenequinone (TCQ), 2, 3-dichloro-5, 6-dicyano-1, 4-benzenequinone (DDQ) . or tetracyano ethylene (TCNE) as initiator the polymerization proceeds reluctantly only after the photoaddition reaction. A mechanism was proposed that free radicals would be formed following the charge and proton transfer in the exciplex formed between St and electron acceptors.

  2. High-pressure effects on intramolecular electron transfer compounds

    CERN Document Server

    He Li Ming; Li Hong; Zhang Bao Wen; Li Yi; Yang Guo Qiang

    2002-01-01

    We explore the effect of pressure on the fluorescence spectra of the intramolecular electron transfer compound N-(1-pyrenylmethyl), N-methyl-4-methoxyaniline (Py-Am) and its model version, with poly(methyl methacrylate) blended in, at high pressure up to 7 GPa. The emission properties of Py-Am and pyrene show distinct difference with the increase of pressure. This difference indicates the strength of the charge transfer interaction resulting from the adjusting of the conformation of Py-Am with increase of pressure. The relationship between the electronic state of the molecule and pressure is discussed.

  3. Investigation of transferred-electron oscillations in diamond

    Science.gov (United States)

    Suntornwipat, N.; Majdi, S.; Gabrysch, M.; Isberg, J.

    2016-05-01

    The recent discovery of Negative Differential Mobility (NDM) in intrinsic single-crystalline diamond enables the development of devices for high frequency applications. The Transferred-Electron Oscillator (TEO) is one example of such devices that uses the benefit of NDM to generate continuous oscillations. This paper presents theoretical investigations of a diamond TEO in the temperature range of 110 to 140 K where NDM has been observed. Our simulations map out the parameter space in which transferred-electron oscillations are expected to occur for a specific device geometry. The results are promising and indicate that it is possible to fabricate diamond based TEO devices.

  4. A study of the dispersed flow interfacial heat transfer model of RELAP5/MOD2.5 and RELAP5/MOD3

    Energy Technology Data Exchange (ETDEWEB)

    Andreani, M. [Swiss Federal Institute of Technology, Zurich (Switzerland); Analytis, G.T.; Aksan, S.N. [Paul Scherrer Institute, Villigen (Switzerland)

    1995-09-01

    The model of interfacial heat transfer for the dispersed flow regime used in the RELAP5 computer codes is investigated in the present paper. Short-transient calculations of two low flooding rate tube reflooding experiments have been performed, where the hydraulic conditions and the heat input to the vapour in the post-dryout region were controlled for the predetermined position of the quench front. Both RELAP5/MOD2.5 and RELAP5/MOD3 substantially underpredicted the exit vapour temperature. The mass flow rate and quality, however, were correct and the heat input to the vapour was larger than the actual one. As the vapour superheat at the tube exit depends on the balance between the heat input from the wall and the heat exchange with the droplets, the discrepancy between the calculated and the measured exit vapour temperature suggested that the inability of both codes to predict the vapour superheat in the dispersed flow region is due to the overprediction of the interfacial heat transfer rate.

  5. Numerical simulation of transient moisture transfer into an electronic enclosure

    Science.gov (United States)

    Nasirabadi, P. Shojaee; Jabbari, M.; Hattel, J. H.

    2016-06-01

    Electronic systems are sometimes exposed to harsh environmental conditions of temperature and humidity. Moisture transfer into electronic enclosures and condensation can cause several problems such as corrosion and alteration in thermal stresses. It is therefore essential to study the local climate inside the enclosures to be able to protect the electronic systems. In this work, moisture transfer into a typical electronic enclosure is numerically studied using CFD. In order to reduce the CPU-time and make a way for subsequent factorial design analysis, a simplifying modification is applied in which the real 3D geometry is approximated by a 2D axial symmetry one. The results for 2D and 3D models were compared in order to calibrate the 2D representation. Furthermore, simulation results were compared with experimental data and good agreement was found.

  6. Conduction mechanism studies on electron transfer of disordered system

    Institute of Scientific and Technical Information of China (English)

    徐慧; 宋祎璞; 李新梅

    2002-01-01

    Using the negative eigenvalue theory and the infinite order perturbation theory, a new method was developed to solve the eigenvectors of disordered systems. The result shows that eigenvectors change from the extended state to the localized state with the increase of the site points and the disordered degree of the system. When electric field is exerted, the electrons transfer from one localized state to another one. The conductivity is induced by the electron transfer. The authors derive the formula of electron conductivity and find the electron hops between localized states whose energies are close to each other, whereas localized positions differ from each other greatly. At low temperature the disordered system has the character of the negative differential dependence of resistivity and temperature.

  7. 12 CFR 205.15 - Electronic fund transfer of government benefits.

    Science.gov (United States)

    2010-01-01

    ... 12 Banks and Banking 2 2010-01-01 2010-01-01 false Electronic fund transfer of government benefits... RESERVE SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.15 Electronic fund transfer of government... consumer for use in initiating an electronic fund transfer of government benefits from an account,...

  8. Role of direct microbial electron transfer in corrosion of steels

    OpenAIRE

    Mehanna, Maha; Basséguy, Régine; Délia, Marie-Line; Bergel, Alain

    2009-01-01

    It has recently been discovered that many microbial species have the capacity to connect their metabolism to solid electrodes, directly exchanging electrons with them through membrane-bound redox compounds,nevertheless such a direct electron transfer pathway has been evoked rarely in the domain of microbial corrosion. Here was evidenced for the first time that the bacterium Geobacter sulfurreducens is able to increase the free potential of 304 L stainless steel up to 443 mV in only a few hour...

  9. Modeling biofilms with dual extracellular electron transfer mechanisms

    OpenAIRE

    Renslow, Ryan; Babauta, Jerome; Kuprat, Andrew; Schenk, Jim; Ivory, Cornelius; Fredrickson, Jim; Beyenal, Haluk

    2013-01-01

    Electrochemically active biofilms have a unique form of respiration in which they utilize solid external materials as terminal electron acceptors for their metabolism. Currently, two primary mechanisms have been identified for long-range extracellular electron transfer (EET): a diffusion- and a conduction-based mechanism. Evidence in the literature suggests that some biofilms, particularly Shewanella oneidensis, produce the requisite components for both mechanisms. In this study, a generic mo...

  10. Magneto-controlled Quantized Electron Transfer to Surface-confined Redox Units and Metal Nanoparticles

    Directory of Open Access Journals (Sweden)

    Itamar Willner

    2006-04-01

    Full Text Available Hydrophobic magnetic nanoparticles (NPs consisting of undecanoate-cappedmagnetite (Fe3O4, average diameter ca. 5 nm are used to control quantized electron transferto surface-confined redox units and metal NPs. A two-phase system consisting of anaqueous electrolyte solution and a toluene phase that includes the suspended undecanoate-capped magnetic NPs is used to control the interfacial properties of the electrode surface.The attracted magnetic NPs form a hydrophobic layer on the electrode surface resulting inthe change of the mechanisms of the surface-confined electrochemical processes. Aquinone-monolayer modified Au electrode demonstrates an aqueous-type of theelectrochemical process (2e- 2H+ redox mechanism for the quinone units in the absence ofthe hydrophobic magnetic NPs, while the attraction of the magnetic NPs to the surfaceresults in the stepwise single-electron transfer mechanism characteristic of a dry non-aqueous medium. Also, the attraction of the hydrophobic magnetic NPs to the Au electrodesurface modified with Au NPs (ca. 1.4 nm yields a microenvironment with a low dielectricconstant that results in the single-electron quantum charging of the Au NPs.

  11. CRADA Final Report for CRADA No. ORNL99-0544, Interfacial Properties of Electron Beam Cured Composites

    Energy Technology Data Exchange (ETDEWEB)

    Janke, C.J.

    2005-10-17

    Electron beam (EB) curing is a technology that promises, in certain applications, to deliver lower cost and higher performance polymer matrix composite (PMC) structures compared to conventional thermal curing processes. PMCs enhance performance by making products lighter, stronger, more durable, and less energy demanding. They are essential in weight- and performance-dominated applications. Affordable PMCs can enhance US economic prosperity and national security. US industry expects rapid implementation of electron beam cured composites in aircraft and aerospace applications as satisfactory properties are demonstrated, and implementation in lower performance applications will likely follow thereafter. In fact, at this time and partly because of discoveries made in this project, field demonstrations are underway that may result in the first fielded applications of electron beam cured composites. Serious obstacles preventing the widespread use of electron beam cured PMCs in many applications are their relatively poor interfacial properties and resin toughness. The composite shear strength and resin toughness of electron beam cured carbon fiber reinforced epoxy composites were about 25% and 50% lower, respectively, than those of thermally cured composites of similar formulations. The essential purpose of this project was to improve the mechanical properties of electron beam cured, carbon fiber reinforced epoxy composites, with a specific focus on composite shear properties for high performance aerospace applications. Many partners, sponsors, and subcontractors participated in this project. There were four government sponsors from three federal agencies, with the US Department of Energy (DOE) being the principal sponsor. The project was executed by Oak Ridge National Laboratory (ORNL), NASA and Department of Defense (DOD) participants, eleven private CRADA partners, and two subcontractors. A list of key project contacts is provided in Appendix A. In order to properly

  12. Long-Range Interfacial Electrochemical Electron Transfer of Pseudomonas aeruginosa Azurin-Gold Nanoparticle Hybrid Systems

    DEFF Research Database (Denmark)

    Jensen, Palle Skovhus; Chi, Qijin; Zhang, Jingdong;

    2009-01-01

    We have prepared a "hybrid" of the blue copper protein azurin (Pseudomonas aeruginosa) and a 3 nm gold nanoparticle (AuNP). The AuNP/azurin hybrid was assembled on a Au(111)-electrode surface in a two-step process. The AuNP was first attached to the Au(111) electrode via Au-S chemisorption of a 4...

  13. Interfacial electrochemical electron transfer in biology – Towards the level of the single molecule

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Chi, Qijin; Hansen, Allan Glargaard;

    2012-01-01

    Physical electrochemistry has undergone a remarkable evolution over the last few decades, integrating advanced techniques and theory from solid state and surface physics. Single-crystal electrode surfaces have been a core notion, opening for scanning tunnelling microscopy directly in aqueous elec...

  14. Photoinduced interfacial electron transfer and lateral charge transport in molecular donor-acceptor photovoltaic systems.

    Science.gov (United States)

    Punzi, Angela; Brauer, Jan C; Marchioro, Arianna; Ghadiri, Elham; de Jonghe, Jelissa; Moser, Jacques E

    2011-01-01

    Nanostructured liquid/solid and solid/solid bulk heterojunctions designed for the conversion of solar energy offer ideal models for the investigation of light-induced ET dynamics at surfaces. Despite significant study of processes leading to charge generation in third-generation solar cells, a conclusive picture of the photophysics of these photovoltaic converters is still missing. More specifically searched is the link between the molecular structure of the interface and the kinetics of surface photoredox reactions. Fundamental scientific issues in this field are addressed by the research project undertaken in the frame of the NCCR MUST endeavor, an outline of which is given here.

  15. Determining the effect of solid and liquid vectors on the gaseous interfacial area and oxygen transfer rates in two-phase partitioning bioreactors

    International Nuclear Information System (INIS)

    The effect of liquid and solid transfer vectors (silicone oil and Desmopan, respectively) on the gaseous interfacial area (ag) was evaluated in a two-phase partitioning bioreactor (TPPB) using fresh mineral salt medium and the cultivation broth of a toluene degradation culture (Pseudomonas putida DOT-T1E cultures continuously cultivated with and without silicone oil at low toluene loading rates). Higher values of ag were recorded in the presence of both silicone oil and Desmopan compared to the values obtained in the absence of a vector, regardless of the aqueous medium tested (1.6 and 3 times higher, respectively, using fresh mineral salt medium). These improvements in ag were well correlated to the oxygen mass transfer enhancements supported by the vectors (1.3 and 2.5 for liquid and solid vectors, respectively, using fresh medium). In this context, oxygen transfer rates of 2.5 g O2 L-1 h-1 and 1.3 g O2 L-1 h-1 were recorded in the presence of Desmopan and silicone oil, respectively, which are in agreement with previously reported values in literature. These results suggest that mass transfer enhancements in TPPBs might correspond to an increase in ag rather than to the establishment of a high-performance gas/vector/water transfer pathway.

  16. Determining the effect of solid and liquid vectors on the gaseous interfacial area and oxygen transfer rates in two-phase partitioning bioreactors

    Energy Technology Data Exchange (ETDEWEB)

    Quijano, Guillermo [Departmento de Ingenieria Quimica y Tecnologia del Medio Ambiente, Universidad de Valladolid, Paseo del Prado de la Magdalena, s/n, 47005 Valladolid (Spain); Departamento de Biotecnologia y Bioingenieria, Centro de Investigacion y de Estudios, Avanzados del IPN (Cinvestav), Apdo. Postal 14-740, 07360 Mexico, D.F. (Mexico); Rocha-Rios, Jose [Departmento de Ingenieria Quimica y Tecnologia del Medio Ambiente, Universidad de Valladolid, Paseo del Prado de la Magdalena, s/n, 47005 Valladolid (Spain); Departamento de Ingenieria de Procesos e Hidraulica (IPH), Universidad Autonoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco No. 186, 09340 Mexico, D.F. (Mexico); Hernandez, Maria; Villaverde, Santiago [Departmento de Ingenieria Quimica y Tecnologia del Medio Ambiente, Universidad de Valladolid, Paseo del Prado de la Magdalena, s/n, 47005 Valladolid (Spain); Revah, Sergio [Departamento de Procesos y Tecnologia, Universidad Autonoma Metropolitana-Cuajimalpa, c/o IPH, UAM-Iztapalapa, Av. San Rafael Atlixco No. 186, 09340 Mexico, D.F. (Mexico); Munoz, Raul, E-mail: mutora@iq.uva.es [Departmento de Ingenieria Quimica y Tecnologia del Medio Ambiente, Universidad de Valladolid, Paseo del Prado de la Magdalena, s/n, 47005 Valladolid (Spain); Thalasso, Frederic [Departamento de Biotecnologia y Bioingenieria, Centro de Investigacion y de Estudios, Avanzados del IPN (Cinvestav), Apdo. Postal 14-740, 07360 Mexico, D.F. (Mexico)

    2010-03-15

    The effect of liquid and solid transfer vectors (silicone oil and Desmopan, respectively) on the gaseous interfacial area (a{sub g}) was evaluated in a two-phase partitioning bioreactor (TPPB) using fresh mineral salt medium and the cultivation broth of a toluene degradation culture (Pseudomonas putida DOT-T1E cultures continuously cultivated with and without silicone oil at low toluene loading rates). Higher values of a{sub g} were recorded in the presence of both silicone oil and Desmopan compared to the values obtained in the absence of a vector, regardless of the aqueous medium tested (1.6 and 3 times higher, respectively, using fresh mineral salt medium). These improvements in a{sub g} were well correlated to the oxygen mass transfer enhancements supported by the vectors (1.3 and 2.5 for liquid and solid vectors, respectively, using fresh medium). In this context, oxygen transfer rates of 2.5 g O{sub 2} L{sup -1} h{sup -1} and 1.3 g O{sub 2} L{sup -1} h{sup -1} were recorded in the presence of Desmopan and silicone oil, respectively, which are in agreement with previously reported values in literature. These results suggest that mass transfer enhancements in TPPBs might correspond to an increase in a{sub g} rather than to the establishment of a high-performance gas/vector/water transfer pathway.

  17. Photoinduced Reductive Electron Transfer in LNA:DNA Hybrids

    DEFF Research Database (Denmark)

    Wenge, Ulrike; Wengel, Jesper; Wagenknecht, Hans-Achim

    2012-01-01

    Lock it, but not too much: LNA units (locked or bridging nucleic acids) in LNA:DNA hybrids lead to a negative effect on electron transfer (ET), but they also force the nucleic acid structure in the A-type double helix, which allows a better base stacking than the normal B-type and thus positively...

  18. 76 FR 81019 - Electronic Fund Transfers (Regulation E)

    Science.gov (United States)

    2011-12-27

    ... this rule. See 76 FR 43569 (July 21, 2011). \\4\\ Public Law 111-203, section 1002(14) (defining... response to a notice published at 76 FR 75825 (Dec. 5, 2011) concerning its efforts to identify priorities... that provide electronic fund transfer services jointly may contract among themselves to comply with...

  19. A molecularly based theory for electron transfer reorganization energy

    International Nuclear Information System (INIS)

    Using field-theoretic techniques, we develop a molecularly based dipolar self-consistent-field theory (DSCFT) for charge solvation in pure solvents under equilibrium and nonequilibrium conditions and apply it to the reorganization energy of electron transfer reactions. The DSCFT uses a set of molecular parameters, such as the solvent molecule’s permanent dipole moment and polarizability, thus avoiding approximations that are inherent in treating the solvent as a linear dielectric medium. A simple, analytical expression for the free energy is obtained in terms of the equilibrium and nonequilibrium electrostatic potential profiles and electric susceptibilities, which are obtained by solving a set of self-consistent equations. With no adjustable parameters, the DSCFT predicts activation energies and reorganization energies in good agreement with previous experiments and calculations for the electron transfer between metallic ions. Because the DSCFT is able to describe the properties of the solvent in the immediate vicinity of the charges, it is unnecessary to distinguish between the inner-sphere and outer-sphere solvent molecules in the calculation of the reorganization energy as in previous work. Furthermore, examining the nonequilibrium free energy surfaces of electron transfer, we find that the nonequilibrium free energy is well approximated by a double parabola for self-exchange reactions, but the curvature of the nonequilibrium free energy surface depends on the charges of the electron-transferring species, contrary to the prediction by the linear dielectric theory

  20. Electron transfer flavoprotein deficiency: Functional and molecular aspects

    DEFF Research Database (Denmark)

    Schiff, M; Froissart, R; Olsen, Rikke Katrine Jentoft;

    2006-01-01

    Multiple acyl-CoA dehydrogenase deficiency (MADD) is a recessively inherited metabolic disorder that can be due to a deficiency of electron transfer flavoprotein (ETF) or its dehydrogenase (ETF-ubiquinone oxidoreductase). ETF is a mitochondrial matrix protein consisting of alpha- (30kDa) and beta...

  1. A molecularly based theory for electron transfer reorganization energy

    Energy Technology Data Exchange (ETDEWEB)

    Zhuang, Bilin; Wang, Zhen-Gang, E-mail: zgw@cheme.caltech.edu [Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125 (United States)

    2015-12-14

    Using field-theoretic techniques, we develop a molecularly based dipolar self-consistent-field theory (DSCFT) for charge solvation in pure solvents under equilibrium and nonequilibrium conditions and apply it to the reorganization energy of electron transfer reactions. The DSCFT uses a set of molecular parameters, such as the solvent molecule’s permanent dipole moment and polarizability, thus avoiding approximations that are inherent in treating the solvent as a linear dielectric medium. A simple, analytical expression for the free energy is obtained in terms of the equilibrium and nonequilibrium electrostatic potential profiles and electric susceptibilities, which are obtained by solving a set of self-consistent equations. With no adjustable parameters, the DSCFT predicts activation energies and reorganization energies in good agreement with previous experiments and calculations for the electron transfer between metallic ions. Because the DSCFT is able to describe the properties of the solvent in the immediate vicinity of the charges, it is unnecessary to distinguish between the inner-sphere and outer-sphere solvent molecules in the calculation of the reorganization energy as in previous work. Furthermore, examining the nonequilibrium free energy surfaces of electron transfer, we find that the nonequilibrium free energy is well approximated by a double parabola for self-exchange reactions, but the curvature of the nonequilibrium free energy surface depends on the charges of the electron-transferring species, contrary to the prediction by the linear dielectric theory.

  2. CORRELATING ELECTRONIC AND VIBRATIONAL MOTIONS IN CHARGE TRANSFER SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Khalil, Munira

    2014-06-27

    The goal of this research program was to measure coupled electronic and nuclear motions during photoinduced charge transfer processes in transition metal complexes by developing and using novel femtosecond spectroscopies. The scientific highlights and the resulting scientific publications from the DOE supported work are outlined in the technical report.

  3. Direct interspecies electron transfer between Geobacter metallireducens and Methanosarcina barkeri

    DEFF Research Database (Denmark)

    Rotaru, Amelia-Elena; Shrestha, Pravin Malla; Liu, Fanghua;

    2014-01-01

    Direct interspecies electron transfer (DIET) is potentially an effective form of syntrophy in methanogenic communities, but little is known about the diversity of methanogens capable of DIET. The ability of Methanosarcina barkeri, to participate in DIET was evaluated in co-culture with Geobacter...

  4. A kinetic model for evaluating the dependence of the quantum yield of nano-TiO{sub 2} based photocatalysis on light intensity, grain size, carrier lifetime, and minority carrier diffusion coefficient: Indirect interfacial charge transfer

    Energy Technology Data Exchange (ETDEWEB)

    Liu Baoshun, E-mail: liubaoshun@126.co [Key Laboratory of Silicate Materials Science and Engineering, Ministry of Education, Wuhan, Hubei 430070 (China) and School of Material Science and Technology, Wuhan University of Technology, Wuhan, Hubei 430070 (China); Zhao Xiujian [Key Laboratory of Silicate Materials Science and Engineering, Ministry of Education, Wuhan, Hubei 430070 (China)

    2010-04-30

    A model based on spherical TiO{sub 2} nanoparticles was developed to study heterogeneous photocatalysis based on TiO{sub 2} in the case of indirect interfacial charge transfer. In this model, the effect of light intensity (I{sub 0}), grain size (r{sub 0}), carrier lifetime (tau{sub p}), and minority carrier diffusion coefficient (D{sub p}) on the quantum yield (QY) of photocatalytic reactions was investigated in detail. Under conditions of sufficiently low incident-light intensity, the QY was found to be propor toI{sub 0}, while it decreased rapidly with an increase in I{sub 0}. In addition, the QY went to zero at a critically high light intensity. Furthermore, the QY was found to decrease with increasing r{sub 0} due to the bulk-recombination loss, and the effect of r{sub 0} on the QY became increasingly stronger with the increase in I{sub 0}. The QY decreased with the decrease in tau{sub p} and D{sub p}, which was more apparent at the critically high I{sub 0}. Under conditions of low [(RH{sub 2}){sub aq}], the QY increased with an increase in [(RH{sub 2}){sub aq}], while it remained nearly constant at high [(RH{sub 2}){sub aq}] due to the fact that the photoinduced electron interfacial transfer became the limiting step for photocatalytic reactions in the case of high [(RH{sub 2}){sub aq}].

  5. Fundamental Research on Convective Heat Transfer in Electronic Cooling Technology

    Institute of Scientific and Technical Information of China (English)

    C.F.Ma; Y.P.Gan; 等

    1992-01-01

    During the past six years comprehensive research programs have been conducted at the Beijing Polytechnic University to provide a better understanding of heat transfer characteristics of existing and condidate cooling techniques for electronic and microelestanding of heat transfer characteristics of existing and condidate cooling techniques for electronic and microleectronic devices.This paper provides a review and summary of the programs with emphasis on direct liquid cooling.Included in this review are the heat transfer investigations related to the following cooling modes:liquid free,mixed and forced convection.liquid jet impingement,flowing liquid film cooling,pool boiling,spray cooling,foreign gas jet impingement in liquid pool,and forced convection air-cooling.

  6. Photoinduced electron transfer of chlorophyll in lipid bilayer system

    Indian Academy of Sciences (India)

    D K Lee; K W Seo; Y S Kang

    2002-12-01

    Photoinduced electron transfer from chlorophyll- through the interface of dipalmitoylphosphatidylcholine (DPPC) headgroup of the lipid bilayers was studied with electron magnetic resonance (EMR). The photoproduced radicals were identified with electron spin resonance (ESR) and radical yields of chlorophyll- were determined by double integration ESR spectra. The formation of vesicles was identified by changes in measured max values from diethyl ether solutions to vesicles solutions indirectly, and observed directly with SEM and TEM images. The efficiency of photosynthesis in model system was determined by measuring the amount of chlorophyll-a radical yields which were obtained from integration of ESR spectra.

  7. Interfacial electronic structure at the CH{sub 3}NH{sub 3}PbI{sub 3}/MoO{sub x} interface

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Peng; Liu, Xiaoliang, E-mail: xl-liu@csu.edu.cn, E-mail: ygao@pas.rochester.edu; Lyu, Lu; Xie, Haipeng; Zhang, Hong; Niu, Dongmei; Huang, Han [Institute of Super-Microstructure and Ultrafast Process in Advanced Materials, College of Physics and Electronics, Central South University, Changsha 410083 (China); Bi, Cheng; Xiao, Zhengguo; Huang, Jinsong [Department of Mechanical and Materials Engineering and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0656 (United States); Gao, Yongli, E-mail: xl-liu@csu.edu.cn, E-mail: ygao@pas.rochester.edu [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States)

    2015-05-11

    Interfacial electronic properties of the CH{sub 3}NH{sub 3}PbI{sub 3} (MAPbI{sub 3})/MoO{sub x} interface are investigated using ultraviolet photoemission spectroscopy and X-ray photoemission spectroscopy. It is found that the pristine MAPbI{sub 3} film coated onto the substrate of poly (3,4-ethylenedioxythiophene) poly(styrenesulfonate)/indium tin oxide by two-step method behaves as an n-type semiconductor, with a band gap of ∼1.7 eV and a valence band edge of 1.40 eV below the Fermi energy (E{sub F}). With the MoO{sub x} deposition of 64 Å upon MAPbI{sub 3}, the energy levels of MAPbI{sub 3} shift toward higher binding energy by 0.25 eV due to electron transfer from MAPbI{sub 3} to MoO{sub x}. Its conduction band edge is observed to almost pin to the E{sub F}, indicating a significant enhancement of conductivity. Meanwhile, the energy levels of MoO{sub x} shift toward lower binding energy by ∼0.30 eV, and an interface dipole of 2.13 eV is observed at the interface of MAPbI{sub 3}/MoO{sub x}. Most importantly, the chemical reaction taking place at this interface results in unfavorable interface energy level alignment for hole extraction. A potential barrier of ∼1.36 eV observed for hole transport will impede the hole extraction from MAPbI{sub 3} to MoO{sub x}. On the other hand, a potential barrier of ∼0.14 eV for electron extraction is too small to efficiently suppress electrons extracted from MAPbI{sub 3} to MoO{sub x}. Therefore, such an interface is not an ideal choice for hole extraction in organic photovoltaic devices.

  8. A unified diabatic description for electron transfer reactions, isomerization reactions, proton transfer reactions, and aromaticity.

    Science.gov (United States)

    Reimers, Jeffrey R; McKemmish, Laura K; McKenzie, Ross H; Hush, Noel S

    2015-10-14

    While diabatic approaches are ubiquitous for the understanding of electron-transfer reactions and have been mooted as being of general relevance, alternate applications have not been able to unify the same wide range of observed spectroscopic and kinetic properties. The cause of this is identified as the fundamentally different orbital configurations involved: charge-transfer phenomena involve typically either 1 or 3 electrons in two orbitals whereas most reactions are typically closed shell. As a result, two vibrationally coupled electronic states depict charge-transfer scenarios whereas three coupled states arise for closed-shell reactions of non-degenerate molecules and seven states for the reactions implicated in the aromaticity of benzene. Previous diabatic treatments of closed-shell processes have considered only two arbitrarily chosen states as being critical, mapping these states to those for electron transfer. We show that such effective two-state diabatic models are feasible but involve renormalized electronic coupling and vibrational coupling parameters, with this renormalization being property dependent. With this caveat, diabatic models are shown to provide excellent descriptions of the spectroscopy and kinetics of the ammonia inversion reaction, proton transfer in N2H7(+), and aromaticity in benzene. This allows for the development of a single simple theory that can semi-quantitatively describe all of these chemical phenomena, as well as of course electron-transfer reactions. It forms a basis for understanding many technologically relevant aspects of chemical reactions, condensed-matter physics, chemical quantum entanglement, nanotechnology, and natural or artificial solar energy capture and conversion.

  9. Optical and interfacial electronic properties of diamond-like carbon films

    Science.gov (United States)

    Woollam, J. A.; Natarajan, V.; Lamb, J.; Khan, A. A.; Bu-Abbud, G.; Banks, B.; Pouch, J.; Gulino, D. A.; Domitz, S.; Liu, D. C.

    1984-01-01

    Hard, semitransparent carbon films were prepared on oriented polished crystal wafers of silicon, indium phosphide and gallium arsenide, as well as on KBr and quartz. Properties of the films were determined using IR and visible absorption spectrocopy, ellipsometry, conductance-capacitance spectroscopy and alpha particle-proton recoil spectroscopy. Preparation techniques include RF plasma decomposition of methane (and other hydrocarbons), ion beam sputtering, and dual-ion-beam sputter deposition. Optical energy band gaps as large as 2.7 eV and extinction coefficients lower than 0.1 at long wavelengths are found. Electronic state densities at the interface with silicon as low as 10 to the 10th states/eV sq cm per were found.

  10. Protein dynamics modulated electron transfer kinetics in early stage photosynthesis.

    Science.gov (United States)

    Kundu, Prasanta; Dua, Arti

    2013-01-28

    A recent experiment has probed the electron transfer kinetics in the early stage of photosynthesis in Rhodobacter sphaeroides for the reaction center of wild type and different mutants [Science 316, 747 (2007)]. By monitoring the changes in the transient absorption of the donor-acceptor pair at 280 and 930 nm, both of which show non-exponential temporal decay, the experiment has provided a strong evidence that the initial electron transfer kinetics is modulated by the dynamics of protein backbone. In this work, we present a model where the electron transfer kinetics of the donor-acceptor pair is described along the reaction coordinate associated with the distance fluctuations in a protein backbone. The stochastic evolution of the reaction coordinate is described in terms of a non-Markovian generalized Langevin equation with a memory kernel and Gaussian colored noise, both of which are completely described in terms of the microscopics of the protein normal modes. This model provides excellent fits to the transient absorption signals at 280 and 930 nm associated with protein distance fluctuations and protein dynamics modulated electron transfer reaction, respectively. In contrast to previous models, the present work explains the microscopic origins of the non-exponential decay of the transient absorption curve at 280 nm in terms of multiple time scales of relaxation of the protein normal modes. Dynamic disorder in the reaction pathway due to protein conformational fluctuations which occur on time scales slower than or comparable to the electron transfer kinetics explains the microscopic origin of the non-exponential nature of the transient absorption decay at 930 nm. The theoretical estimates for the relative driving force for five different mutants are in close agreement with the experimental estimates obtained using electrochemical measurements. PMID:23387626

  11. Molecular level energy and electron transfer processes at nanocrystalline titanium dioxide interfaces

    Science.gov (United States)

    Farzad, Fereshteh

    This thesis describes photo-induced molecular electron and energy transfer processes occurring at nanocrystalline semiconductor interfaces. The Introductory Chapter provides background and describes how these materials may be useful for solar energy conversion. In Chapter 2, results describing excitation of Ru(deeb)(bpy)2 2+, bis(2,2'-bipyridine)(2,2'-bipyridine-4,4 '-diethylester)ruthenium(II) hexafluorophosphate, bound to nanocrystalline TiO2 thin films, immersed in an acetonitrile bath are presented. The data indicates that light excitation forms predominately long-lived metal-to-ligand charge-transfer, MLCT, excited states under these conditions. Modeling of the data as a function of irradiance has been accomplished assuming parallel unimolecular and bimolecular excited state deactivation processes. The quantum yield for excited state formation depends on the excitation irradiance, consistent with triplet-triplet annihilation processes that occur with k > 1 x 108 s-1. Chapter 3 extends the work described in Chapter 2 to LiClO4 acetonitrile solutions. Li+ addition results in a red shift in the MLCT absorption and photoluminescence, PL, and a concentration dependent quenching of the PL intensity on TiO2. The Li+ induced spectroscopic changes were found to be reversible by varying the electrolyte composition. A second-order kinetic model quantified charge recombination transients. A model is proposed wherein Li+ ion adsorption stabilizes TiO2 acceptor states resulting in energetically more favorable interfacial electron transfer. The photophysical and photoelectrochemical properties of porous nanocrystalline anatase TiO2 electrodes modified with Ru(deeb)(bpy)2 2+, Os(deeb)(bpy)22+, and mixtures of both are described in Chapters 4 and 5. In regenerative solar cells with 0.5 M LiI/0.05 M I2 acetonitrile electrolyte, both compounds efficiently inject electrons into TiO2 producing monochromatic incident photon-to-current efficiencies (IPCE), IPCE (460 nm) = 0.70 + 0

  12. Ultrafast proton coupled electron transfer (PCET dynamics in 9-anthranol-aliphatic amine system

    Directory of Open Access Journals (Sweden)

    Nibbering Erik T. J.

    2013-03-01

    Full Text Available Femtosecond infrared absorption studies strongly suggest that photoexcited 9-anthranol takes part in an ultrafast electron transfer (ET reaction in electron-donating triethylamine solvent, but that ultrafast proton coupled electron transfer (PCET occurs in diethylamine solvent.

  13. Ultrafast proton coupled electron transfer (PCET) dynamics in 9-anthranol-aliphatic amine system

    OpenAIRE

    Nibbering Erik T.J.; Dreyer Jens; Verma Sandeep; Ghosh Hirendra N.; Adamczyk Katrin

    2013-01-01

    Femtosecond infrared absorption studies strongly suggest that photoexcited 9-anthranol takes part in an ultrafast electron transfer (ET) reaction in electron-donating triethylamine solvent, but that ultrafast proton coupled electron transfer (PCET) occurs in diethylamine solvent.

  14. Electromicrobiology: Electron Transfer via Biowires in Nature and Practical Applications

    Directory of Open Access Journals (Sweden)

    Lovley Derek

    2016-01-01

    Full Text Available One of the most exciting developments in the field of electromicrobiology has been the discovery of electrically conductive pili (e-pili in Geobacter species that transport electrons with a metallic-like mechanism. The e-pili are essential for extracellular electron transport to Fe(III oxides and longrange electron transport through the conductive biofilms that form on the anodes of microbial fuel cells. The e-pili also facilitate direct interspecies electron transfer between Geobacter and Methanosaeta or Methanosarcina species. Metatranscriptomic studies have demonstrated that Geobacter/Methanosaeta DIET is an important process in anaerobic digesters converting brewery wastes to methane. Increasing e-pili expression through genetic modification of regulatory systems or adaptive evolution yields strains with enhanced rates of extracellular electron transfer. Measurement of the conductivity of individual e-pili has demonstrated that they have conductivities higher than those of a number of synthetic conducting organic polymers. Multiple lines of evidence have demonstrated that aromatic amino acids play an important role in the electron transport along e-pili, suggesting opportunities to tune e-pili conductivity via genetic manipulation of the amino acid composition of e-pili. It is expected that e-pili will be harnessed to improve microbe-electrode processes such as microbial electrosynthesis and for the development of novel biosensors. Also, e-pili show promise as a sustainable ‘green’ replacement for electronic materials that contain toxic components and/or are produced with harsh chemicals.

  15. [Electron transfer, ionization, and excitation in atomic collisions]: Progress report

    International Nuclear Information System (INIS)

    The fundamental processes of electron transfer, ionization, and excitation in ion-atom collisions are being studied. These collision processes are treated in the context of simple one- or two-electron systems in order to provide unambiguous results and reveal more clearly the collisional mechanisms. As outlined in the original proposal, three coupled-state calculations are being carried out over the present three-year period: a Sturmian-pseudostate study of ionization in collisions between protons and the hydrogenic ions He+, Li2+, Be3+, ...; a triple-center, atomic-state study of ionization in collisions between α particles and H(ls) atoms and between protons and He+(ls) ions; and an atomic-state study of electron transfer and excitation in collisions between protons and neutral He atoms. 12 refs

  16. Syntrophic Growth via Quinone-Mediated Interspecies Electron Transfer

    Directory of Open Access Journals (Sweden)

    Jessica A Smith

    2015-02-01

    Full Text Available The mechanisms by which microbial species exchange electrons are of interest because interspecies electron transfer can expand the metabolic capabilities of microbial communities. Previous studies with the humic substance analog anthraquinone-2,6-disulfonate (AQDS suggested that quinone-mediated interspecies electron transfer (QUIET is feasible, but it was not determined if sufficient energy is available from QUIET to support the growth of both species. Furthermore, there have been no previous studies on the mechanisms for the oxidation of anthrahydroquinone-2,6-disulfonate (AHQDS. A co-culture of Geobacter metallireducens and Geobacter sulfurreducens metabolized ethanol with the reduction of fumarate much faster in the presence of AQDS, and there was an increase in cell protein. G. sulfurreducens was more abundant, consistent with G. sulfurreducens obtaining electrons from acetate that G. metallireducens produced from ethanol, as well as from AHQDS. Cocultures initiated with a citrate synthase-deficient strain of G. sulfurreducens that was unable to use acetate as an electron donor also metabolized ethanol with the reduction of fumarate and cell growth, but acetate accumulated over time. G. sulfurreducens and G. metallireducens were equally abundant in these co-cultures reflecting the inability of the citrate synthase-deficient strain of G. sulfurreducens to metabolize acetate. Evaluation of the mechanisms by which G. sulfurreducens accepts electrons from AHQDS demonstrated that a strain deficient in outer-surface c-type cytochromes that are required for AQDS reduction was as effective at QUIET as the wild-type strain. Deletion of additional genes previously implicated in extracellular electron transfer also had no impact on QUIET. These results demonstrate that QUIET can yield sufficient energy to support the growth of both syntrophic partners, but that the mechanisms by which electrons are derived from extracellular hydroquinones require

  17. Femtosecond insights into direct electron injection in dye anchored ZnO QDs following charge transfer excitation.

    Science.gov (United States)

    Kumar, Pushpendra; Kumar, Sunil; Ghosh, Subrata; Pal, Suman Kalyan

    2016-07-27

    The role of the charge transfer (CT) state in interfacial electron transfer in dye-sensitized semiconductor nanocrystals is still poorly understood. To address this problem, femtosecond transient absorption (TA) spectroscopy is used as a probe to investigate the electron injection across a newly synthesized coumarin dye (8-hydroxy-2-oxo-4-phenyl-2 benzo[h]chromene-3-carbonitrile, coded BC5) and ZnO quantum dots (QDs). Steady state and time-resolved spectroscopic measurements reveal that BC5 dye interacts strongly with ZnO QDs in the ground state forming a CT complex. The BC5-ZnO QD complex absorbs more towards red compared to only the dye and QDs, and emits fluorescence due to radiative recombination of photogenerated charges. The formation of charges following the excitation of the CT complex has been demonstrated by observing the signature of dye radical cations and electrons in the conduction band (CB) of the QDs in the TA spectra. The TA signals of these charges grow sharply as a result of ultrafast direct electron injection into the QD. We have monitored the complete dynamics of photogenerated charges by measuring the TA signals of the charges up to a couple of nanoseconds. The injected electrons that are free or shallowly trapped recombine with a time constant of 625 fs, whereas deeply trapped electrons disappear slowly (526 ps) via radiative recombination. Furthermore, theoretical studies based on ab initio calculations have been carried out to complement the experimental findings. PMID:27412034

  18. Electron Transfer Mechanisms of DNA Repair by Photolyase

    Science.gov (United States)

    Zhong, Dongping

    2015-04-01

    Photolyase is a flavin photoenzyme that repairs two DNA base damage products induced by ultraviolet (UV) light: cyclobutane pyrimidine dimers and 6-4 photoproducts. With femtosecond spectroscopy and site-directed mutagenesis, investigators have recently made significant advances in our understanding of UV-damaged DNA repair, and the entire enzymatic dynamics can now be mapped out in real time. For dimer repair, six elementary steps have been characterized, including three electron transfer reactions and two bond-breaking processes, and their reaction times have been determined. A unique electron-tunneling pathway was identified, and the critical residues in modulating the repair function at the active site were determined. The dynamic synergy between the elementary reactions for maintaining high repair efficiency was elucidated, and the biological nature of the flavin active state was uncovered. For 6-4 photoproduct repair, a proton-coupled electron transfer repair mechanism has been revealed. The elucidation of electron transfer mechanisms and two repair photocycles is significant and provides a molecular basis for future practical applications, such as in rational drug design for curing skin cancer.

  19. Electron transfer, decoherence, and protein dynamics: insights from atomistic simulations.

    Science.gov (United States)

    Narth, Christophe; Gillet, Natacha; Cailliez, Fabien; Lévy, Bernard; de la Lande, Aurélien

    2015-04-21

    Electron transfer in biological systems drives the processes of life. From cellular respiration to photosynthesis and enzymatic catalysis, electron transfers (ET) are chemical processes on which essential biological functions rely. Over the last 40 years, scientists have sought understanding of how these essential processes function in biology. One important breakthrough was the discovery that Marcus theory (MT) of electron transfer is applicable to biological systems. Chemists have experimentally collected both the reorganization energies (λ) and the driving forces (ΔG°), two parameters of Marcus theory, for a large variety of ET processes in proteins. At the same time, theoretical chemists have developed computational approaches that rely on molecular dynamics and quantum chemistry calculations to access numerical estimates of λ and ΔG°. Yet another crucial piece in determining the rate of an electron transfer is the electronic coupling between the initial and final electronic wave functions. This is an important prefactor in the nonadiabatic rate expression, since it reflects the probability that an electron tunnels from the electron donor to the acceptor through the intervening medium. The fact that a protein matrix supports electron tunneling much more efficiently than vacuum is now well documented, both experimentally and theoretically. Meanwhile, many chemists have provided examples of the rich physical chemistry that can be induced by protein dynamics. This Account describes our studies of the dynamical effects on electron tunneling. We present our analysis of two examples of natural biological systems through MD simulations and tunneling pathway analyses. Through these examples, we show that protein dynamics sustain efficient tunneling. Second, we introduce two time scales: τcoh and τFC. The former characterizes how fast the electronic coupling varies with nuclear vibrations (which cause dephasing). The latter reflects the time taken by the system

  20. A polaron model for electron transfer in globular proteins.

    Science.gov (United States)

    Chuev, G N; Lakhno, V D

    1993-07-01

    Polaron models have been considered for the electron states in protein globules existing in a solvent. These models account for two fundamental effects, viz, polarization interaction of an electron with the conformational vibrations and the heterogeneity of the medium. Equations have been derived to determine the electron state in a protein globule. The parameters of this state show that it is an extended state with an energy of 2 eV. The electron transfer rate for cyt C self-exchange reaction has been calculated in the polaron model. Reorganization energy, tunneling matrix element and the rate constant have also been estimated. The results are compared with experimental data. The influence of model parameters on the significance of the data obtained has been studied. The potentialities of the model are discussed.

  1. The Electron Transfer Reaction between p-Nitrobenzoates and β-N, N-Dimethylaminonaphthalene

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A few of p-nitrobenzoates were synthesized, and the electron transfer of them with β-N, N-dimethylaminonaphthalene (DMAN) in methanol solution was studied. Steady-state fluore-scence results showed the cyclodextrin moiety in p-nitrobenzoyl-β-cyclodextrin would block the electron transfer pathway from DMAN compared with other electron acceptors, thus, reduced the electron transfer efficiency.

  2. Promoting direct interspecies electron transfer with activated carbon

    DEFF Research Database (Denmark)

    Liu, Fanghua; Rotaru, Amelia-Elena; Shrestha, Pravin M.;

    2012-01-01

    Granular activated carbon (GAC) is added to methanogenic digesters to enhance conversion of wastes to methane, but the mechanism(s) for GAC’s stimulatory effect are poorly understood. GAC has high electrical conductivity and thus it was hypothesized that one mechanism for GAC stimulation...... were attached to GAC, but did not aggregate as they do when making biological electrical connections between cells. Studies with a series of gene deletion mutants eliminated the possibility that GAC promoted electron exchange via interspecies hydrogen or formate transfer and demonstrated that DIET...... of methanogenesis might be to facilitate direct interspecies electron transfer (DIET) between bacteria and methanogens. Metabolism was substantially accelerated when GAC was added to co-cultures of Geobacter metallireducens and Geobacter sulfurreducens grown under conditions previously shown to require DIET. Cells...

  3. Large scale oil lease automation and electronic custody transfer

    International Nuclear Information System (INIS)

    Typically, oil field production operations have only been automated at fields with long term production profiles and enhanced recovery. The automation generally consists of monitoring and control at the wellhead and centralized facilities. However, Union Pacific Resources Co. (UPRC) has successfully implemented a large scale automation program for rapid-decline primary recovery Austin Chalk wells where purchasers buy and transport oil from each individual wellsite. This project has resulted in two significant benefits. First, operators are using the system to re-engineer their work processes. Second, an inter-company team created a new electronic custody transfer method. This paper will describe: the progression of the company's automation objectives in the area; the field operator's interaction with the system, and the related benefits; the research and development of the new electronic custody transfer method

  4. Catalytic Olefin Hydroamidation Enabled by Proton-Coupled Electron Transfer.

    Science.gov (United States)

    Miller, David C; Choi, Gilbert J; Orbe, Hudson S; Knowles, Robert R

    2015-10-28

    Here we report a ternary catalyst system for the intramolecular hydroamidation of unactivated olefins using simple N-aryl amide derivatives. Amide activation in these reactions occurs via concerted proton-coupled electron transfer (PCET) mediated by an excited state iridium complex and weak phosphate base to furnish a reactive amidyl radical that readily adds to pendant alkenes. A series of H-atom, electron, and proton transfer events with a thiophenol cocatalyst furnish the product and regenerate the active forms of the photocatalyst and base. Mechanistic studies indicate that the amide substrate can be selectively homolyzed via PCET in the presence of the thiophenol, despite a large difference in bond dissociation free energies between these functional groups.

  5. Coupling of narrow and wide band-gap semiconductors on uniform films active in bacterial disinfection under low intensity visible light: Implications of the interfacial charge transfer (IFCT)

    Energy Technology Data Exchange (ETDEWEB)

    Rtimi, S., E-mail: sami.rtimi@epfl.ch [Ecole Polytechnique Fédérale de Lausanne, EPFL-SB-ISIC-GPAO, Station 6, CH-1015 Lausanne (Switzerland); UR Catalyse/Matériaux pour l‘Environnement et les Procédés (URCMEP), Faculté des Sciences de Gabès, Université de Gabès, 6072 Gabès (Tunisia); Sanjines, R. [Ecole Polytechnique Fédérale de Lausanne, EPFL-SB-IPMC-LNNME, Bat PH, Station 3, CH1015 Lausanne (Switzerland); Pulgarin, C., E-mail: cesar.pulgarin@epfl.ch [Ecole Polytechnique Fédérale de Lausanne, EPFL-SB-ISIC-GPAO, Station 6, CH-1015 Lausanne (Switzerland); Houas, A. [UR Catalyse/Matériaux pour l‘Environnement et les Procédés (URCMEP), Faculté des Sciences de Gabès, Université de Gabès, 6072 Gabès (Tunisia); Lavanchy, J.-C. [Université de Lausanne, IMG, Centre d’Analyse Minérale, Bat Anthropole, CH-1015 Lausanne (Switzerland); Kiwi, J. [Ecole Polytechnique Fédérale de Lausanne, EPFL-SB-ISIC-LPI, Bat Chimie, Station 6, CH1015 Lausanne (Switzerland)

    2013-09-15

    Highlights: • Design, preparation, testing and characterization of uniform sputtered films. • Interfacial charge transfer from the Ag{sub 2}O (cb) to the lower laying Ta{sub 2}O{sub 5} (cb). • The optical absorption of TaON and TaON/Ag was proportional to E. coli inactivation. • Self-cleaning of the TaON/Ag polyester enables repetitive E. coli inactivation. -- Abstract: This study reports the design, preparation, testing and surface characterization of uniform films deposited by sputtering Ag and Ta on non-heat resistant polyester to evaluate the Escherichia coli inactivation by TaON, TaN/Ag, Ag and TaON/Ag polyester. Co-sputtering for 120 s Ta and Ag in the presence of N{sub 2} and O{sub 2} led to the faster E. coli inactivation by a TaON/Ag sample within ∼40 min under visible light irradiation. The deconvolution of TaON/Ag peaks obtained by X-ray photoelectron spectroscopy (XPS) allowed the assignment of the Ta{sub 2}O{sub 5} and Ag-species. The shifts observed for the XPS peaks have been assigned to AgO to Ag{sub 2}O and Ag{sup 0}, and are a function of the applied sputtering times. The mechanism of interfacial charge transfer (IFCT) from the Ag{sub 2}O conduction band (cb) to the lower laying Ta{sub 2}O{sub 5} (cb) is discussed suggesting a reaction mechanism. The optical absorption of the TaON and TaON/Ag samples found by diffuse reflectance spectroscopy (DRS) correlated well with the kinetics of E. coli inactivation. The TaON/Ag sample microstructure was characterized by contact angle (CA) and by atomic force microscopy (AFM). Self-cleaning of the TaON/Ag polyester after each disinfection cycle enabled repetitive E. coli inactivation.

  6. Electron transfer reactions in chemistry. Theory and experiment

    OpenAIRE

    Marcus, Rudolph A.

    1997-01-01

    Since the late 1940s, the field of electron transfer processes has grown enormously, both in chemistry and biology. The development of the field, experimentally and theoretically, as well as its relation to the study of other kinds of chemical reactions, represents to us an intriguing history, one in which many threads have been brought together. In this lecture, some history, recent trends, and my own involvement in this research are described.

  7. Proton-Coupled Electron Transfer: Moving Together and Charging Forward

    OpenAIRE

    Hammes-Schiffer, Sharon

    2015-01-01

    Proton-coupled electron transfer (PCET) is ubiquitous throughout chemistry and biology. This Perspective discusses recent advances and current challenges in the field of PCET, with an emphasis on the role of theory and computation. The fundamental theoretical concepts are summarized, and expressions for rate constants and kinetic isotope effects are provided. Computational methods for calculating reduction potentials and pK a’s for molecular electrocatalysts, as well as insights into linear c...

  8. Marcus wins nobel prize in chemistry for electron transfer theory

    Energy Technology Data Exchange (ETDEWEB)

    Levi, B.G.

    1993-01-01

    This article describes the work of Rudolf Marcus of Caltech leading to his receipt of the 1992 Nobel Prize in Chemistry [open quotes]for his contributions to the theory of electron transfer reactions in chemical systems.[close quotes] Applications of Marcus' theory include such diverse phenomena as photosynthesis, electrically conducting polymers, chemiluminescence, and corrosion. Historical aspects of his career are given. 10 refs., 1 fig.

  9. Marcus wins nobel prize in chemistry for electron transfer theory

    International Nuclear Information System (INIS)

    This article describes the work of Rudolf Marcus of Caltech leading to his receipt of the 1992 Nobel Prize in Chemistry open-quotes for his contributions to the theory of electron transfer reactions in chemical systems.close quotes Applications of Marcus' theory include such diverse phenomena as photosynthesis, electrically conducting polymers, chemiluminescence, and corrosion. Historical aspects of his career are given. 10 refs., 1 fig

  10. Electron Transfer rate between a electrode and a bridged redox

    OpenAIRE

    Cruz, A. V. B.; Mishra, A. K.; Schmickler, W.

    2009-01-01

    We derive an explict bias dependent expression for electron transfer reaction rate from a solvated redox to a electrode through a bridged molecule of arbitrary length. The interaction of the solvated redox with the solvent is modelled as a classical harmonic oscillator bath. The effect of competing process, namely resonance tunneling between redox and bridge and the solvation of the redox is investigated. Plots were produced for the case of 5 atom bridge. Our analysis shows that for certain s...

  11. Insights into Proton-Coupled Electron Transfer from Computation

    Science.gov (United States)

    Provorse, Makenzie R.

    Proton-coupled electron transfer (PCET) is utilized throughout Nature to facilitate essential biological processes, such as photosynthesis, cellular respiration, and DNA replication and repair. The general approach to studying PCET processes is based on a two-dimensional More O'Ferrall-Jencks diagram in which electron transfer (ET) and proton transfer (PT) occur in a sequential or concerted fashion. Experimentally, it is difficult to discern the contributing factors of concerted PCET mechanisms. Several theoretical approaches have arisen to qualitatively and quantitatively investigate these reactions. Here, we present a multistate density functional theory (MSDFT) method to efficiently and accurately model PCET mechanisms. The MSDFT method is validated against experimental and computational data previously reported on an isoelectronic series of small molecule self-exchange hydrogen atom transfer reactions and a model complex specifically designed to study long-range ET through a hydrogen-bonded salt-bridge interface. Further application of this method to the hydrogen atom abstraction of ascorbate by a nitroxyl radical demonstrates the sensitivity of the thermodynamic and kinetic properties to solvent effects. In particular, the origin of the unusual kinetic isotope effect is investigated. Lastly, the MSDFT is employed in a combined quantum mechanical/molecular mechanical (QM/MM) approach to explicitly model PCET in condensed phases.

  12. The Electron Transfer System of Syntrophically Grown Desulfovibrio vulgaris

    Energy Technology Data Exchange (ETDEWEB)

    PBD; ENIGMA; GTL; VIMSS; Walker, Christopher B.; He, Zhili; Yang, Zamin K.; Ringbauer Jr., Joseph A.; He, Qiang; Zhou, Jizhong; Voordouw, Gerrit; Wall, Judy D.; Arkin, Adam P.; Hazen, Terry C.; Stolyar, Sergey; Stahl, David A.

    2009-06-22

    Interspecies hydrogen transfer between organisms producing and consuming hydrogen promotes the decomposition of organic matter in most anoxic environments. Although syntrophic couplings between hydrogen producers and consumers are a major feature of the carbon cycle, mechanisms for energy recovery at the extremely low free energies of reactions typical of these anaerobic communities have not been established. In this study, comparative transcriptional analysis of a model sulfate-reducing microbe, Desulfovibrio vulgaris Hildenborough, suggested the use of alternative electron transfer systems dependent upon growth modality. During syntrophic growth on lactate with a hydrogenotrophic methanogen, D. vulgaris up-regulated numerous genes involved in electron transfer and energy generation when compared with sulfate-limited monocultures. In particular, genes coding for the putative membrane-bound Coo hydrogenase, two periplasmic hydrogenases (Hyd and Hyn) and the well-characterized high-molecular weight cytochrome (Hmc) were among the most highly expressed and up-regulated. Additionally, a predicted operon coding for genes involved in lactate transport and oxidation exhibited up-regulation, further suggesting an alternative pathway for electrons derived from lactate oxidation during syntrophic growth. Mutations in a subset of genes coding for Coo, Hmc, Hyd and Hyn impaired or severely limited syntrophic growth but had little affect on growth via sulfate-respiration. These results demonstrate that syntrophic growth and sulfate-respiration use largely independent energy generation pathways and imply that understanding of microbial processes sustaining nutrient cycling must consider lifestyles not captured in pure culture.

  13. The electron transfer system of syntrophically grown Desulfovibrio vulgaris

    Energy Technology Data Exchange (ETDEWEB)

    Walker, C.B.; He, Z.; Yang, Z.K.; Ringbauer, Jr., J.A.; He, Q.; Zhou, J.; Voordouw, G.; Wall, J.D.; Arkin, A.P.; Hazen, T.C.; Stolyar, S.; Stahl, D.A.

    2009-05-01

    Interspecies hydrogen transfer between organisms producing and consuming hydrogen promotes the decomposition of organic matter in most anoxic environments. Although syntrophic couplings between hydrogen producers and consumers are a major feature of the carbon cycle, mechanisms for energy recovery at the extremely low free energies of reactions typical of these anaerobic communities have not been established. In this study, comparative transcriptional analysis of a model sulfate-reducing microbe, Desulfovibrio vulgaris Hildenborough, suggested the use of alternative electron transfer systems dependent upon growth modality. During syntrophic growth on lactate with a hydrogenotrophic methanogen, D. vulgaris up-regulated numerous genes involved in electron transfer and energy generation when compared with sulfate-limited monocultures. In particular, genes coding for the putative membrane-bound Coo hydrogenase, two periplasmic hydrogenases (Hyd and Hyn) and the well-characterized high-molecular weight cytochrome (Hmc) were among the most highly expressed and up-regulated. Additionally, a predicted operon coding for genes involved in lactate transport and oxidation exhibited up-regulation, further suggesting an alternative pathway for electrons derived from lactate oxidation during syntrophic growth. Mutations in a subset of genes coding for Coo, Hmc, Hyd and Hyn impaired or severely limited syntrophic growth but had little affect on growth via sulfate-respiration. These results demonstrate that syntrophic growth and sulfate-respiration use largely independent energy generation pathways and imply that understanding of microbial processes sustaining nutrient cycling must consider lifestyles not captured in pure culture.

  14. Intercellular wiring enables electron transfer between methanotrophic archaea and bacteria.

    Science.gov (United States)

    Wegener, Gunter; Krukenberg, Viola; Riedel, Dietmar; Tegetmeyer, Halina E; Boetius, Antje

    2015-10-22

    The anaerobic oxidation of methane (AOM) with sulfate controls the emission of the greenhouse gas methane from the ocean floor. In marine sediments, AOM is performed by dual-species consortia of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB) inhabiting the methane-sulfate transition zone. The biochemical pathways and biological adaptations enabling this globally relevant process are not fully understood. Here we study the syntrophic interaction in thermophilic AOM (TAOM) between ANME-1 archaea and their consortium partner SRB HotSeep-1 (ref. 6) at 60 °C to test the hypothesis of a direct interspecies exchange of electrons. The activity of TAOM consortia was compared to the first ANME-free culture of an AOM partner bacterium that grows using hydrogen as the sole electron donor. The thermophilic ANME-1 do not produce sufficient hydrogen to sustain the observed growth of the HotSeep-1 partner. Enhancing the growth of the HotSeep-1 partner by hydrogen addition represses methane oxidation and the metabolic activity of ANME-1. Further supporting the hypothesis of direct electron transfer between the partners, we observe that under TAOM conditions, both ANME and the HotSeep-1 bacteria overexpress genes for extracellular cytochrome production and form cell-to-cell connections that resemble the nanowire structures responsible for interspecies electron transfer between syntrophic consortia of Geobacter. HotSeep-1 highly expresses genes for pili production only during consortial growth using methane, and the nanowire-like structures are absent in HotSeep-1 cells isolated with hydrogen. These observations suggest that direct electron transfer is a principal mechanism in TAOM, which may also explain the enigmatic functioning and specificity of other methanotrophic ANME-SRB consortia. PMID:26490622

  15. Theoretical study on electron transfer in biological systems (Ⅲ)——Intramolecular electron transfer in metal-containing spiro π-electron system

    Institute of Scientific and Technical Information of China (English)

    翟宇峰; 蒋华良; 朱维良; 顾健德; 陈建忠; 陈凯先; 嵇汝运

    1999-01-01

    Intramolecular electron transfer of metal-containing spiro π-electron system was studied by AM1 method in the MOPAC-ET program developed by the present group. The results indicated that with the increasing of the outer electric field F, the activation energy of the reaction decreased. When F reaches a certain threshold value, the activation energy barrier becomes zero and the rate of reaction achieves the largest value. The results also indicated that electron transfer matrix elements VAB and reorganization energy λ were not obviously affected by outer electric field while the exothermicity ΔE was directly proportional to it.

  16. Noise-assisted quantum electron transfer in photosynthetic complexes

    CERN Document Server

    Nesterov, Alexander I; Martínez, José Manuel Sánchez; Sayre, Richard T

    2013-01-01

    Electron transfer (ET) between primary electron donors and acceptors is modeled in the photosystem II reaction center (RC). Our model includes (i) two discrete energy levels associated with donor and acceptor, interacting through a dipole-type matrix element and (ii) two continuum manifolds of electron energy levels ("sinks"), which interact directly with the donor and acceptor. Namely, two discrete energy levels of the donor and acceptor are embedded in their independent sinks through the corresponding interaction matrix elements. We also introduce classical (external) noise which acts simultaneously on the donor and acceptor (collective interaction). We derive a closed system of integro-differential equations which describes the non-Markovian quantum dynamics of the ET. A region of parameters is found in which the ET dynamics can be simplified, and described by coupled ordinary differential equations. Using these simplified equations, both sharp and flat redox potentials are analyzed. We analytically and nu...

  17. Direct observation of the ultrafast electron transfer process in a polymer/fullerene blend

    NARCIS (Netherlands)

    Cerullo, G.; Lanzani, G.; Silvestri, S. De; Brabec, Ch.J.; Zerza, G.; Sariciftci, N.S.; Hummelen, J.C.

    2000-01-01

    Photoinduced electron transfer in organic molecules is an extensively investigated topic both because of fundamental interest in the photophysics and for applications to artificial photosynthesis. Highly efficient ultrafast electron transfer from photoexcited conjugated polymers to C60 has been repo

  18. Electron transfer and redox metalloenzyme catalysis at the single-molecule level

    DEFF Research Database (Denmark)

    Hansen, Allan Glargaard; Zhang, Jingdong; Christensen, Hans Erik Mølager;

    2004-01-01

    Voltammetry based on single-crystal, atomically-planar metal electrodes is novel in bioelectrochemistry. Together with in situ scanning tunneling microscopy (STM) directly in aqueous buffer, single-crystal voltammetry has disclosed new detail in molecular adsorption and interfacial electron trans...

  19. Reduced density matrix hybrid approach: application to electronic energy transfer.

    Science.gov (United States)

    Berkelbach, Timothy C; Markland, Thomas E; Reichman, David R

    2012-02-28

    Electronic energy transfer in the condensed phase, such as that occurring in photosynthetic complexes, frequently occurs in regimes where the energy scales of the system and environment are similar. This situation provides a challenge to theoretical investigation since most approaches are accurate only when a certain energetic parameter is small compared to others in the problem. Here we show that in these difficult regimes, the Ehrenfest approach provides a good starting point for a dynamical description of the energy transfer process due to its ability to accurately treat coupling to slow environmental modes. To further improve on the accuracy of the Ehrenfest approach, we use our reduced density matrix hybrid framework to treat the faster environmental modes quantum mechanically, at the level of a perturbative master equation. This combined approach is shown to provide an efficient and quantitative description of electronic energy transfer in a model dimer and the Fenna-Matthews-Olson complex and is used to investigate the effect of environmental preparation on the resulting dynamics.

  20. Polyoxometalate-mediated electron transfer-oxygen transfer oxidation of cellulose and hemicellulose to synthesis gas.

    Science.gov (United States)

    Sarma, Bidyut Bikash; Neumann, Ronny

    2014-08-01

    Terrestrial plants contain ~70% hemicellulose and cellulose that are a significant renewable bioresource with potential as an alternative to petroleum feedstock for carbon-based fuels. The efficient and selective deconstruction of carbohydrates to their basic components, carbon monoxide and hydrogen, so called synthesis gas, is an important key step towards the realization of this potential, because the formation of liquid hydrocarbon fuels from synthesis gas are known technologies. Here we show that by using a polyoxometalate as an electron transfer-oxygen transfer catalyst, carbon monoxide is formed by cleavage of all the carbon-carbon bonds through dehydration of initially formed formic acid. In this oxidation-reduction reaction, the hydrogen atoms are stored on the polyoxometalate as protons and electrons, and can be electrochemically released from the polyoxometalate as hydrogen. Together, synthesis gas is formed. In a hydrogen economy scenario, this method can also be used to convert carbon monoxide to hydrogen.

  1. Contrasting suspended covers reveal the impact of an artificial monolayer on heat transfer processes at the interfacial boundary layer.

    Science.gov (United States)

    Pittaway, P; Martínez-Alvarez, V; Hancock, N

    2015-01-01

    The highly variable performance of artificial monolayers in reducing evaporation from water storages has been attributed to wind speed and wave turbulence. Other factors operating at the interfacial boundary layer have seldom been considered. In this paper, two physical shade covers differing in porosity and reflectivity were suspended over 10 m diameter water tanks to attenuate wind and wave turbulence. The monolayer octadecanol was applied to one of the covered tanks, and micrometeorological conditions above and below the covers were monitored to characterise diurnal variation in the energy balance. A high downward (air-to-water) convective heat flux developed under the black cover during the day, whereas diurnal variation in the heat flux under the more reflective, wind-permeable white cover was much less. Hourly air and water temperature profiles under the covers over 3 days when forced convection was minimal (low wind speed) were selected for analysis. Monolayer application reduced temperature gain in surface water under a downward convective heat flux, and conversely reduced temperature loss under an upward convective heat flux. This 'dual property' may explain why repeat application of an artificial monolayer to retard evaporative loss (reducing latent heat loss) does not inevitably increase water temperature.

  2. Overpotential-induced lability of the electronic overlap factor in long-range electrochemical electron transfer: charge and distance dependence

    DEFF Research Database (Denmark)

    Kornyshev, A. A.; Kuznetsov, A. M.; Nielsen, Jens Ulrik;

    2000-01-01

    Long-distance electrochemical electron transfer exhibits approximately exponential dependence on the electron transfer distance. On the basis of a jellium model of the metal surface we show that the slope of the logarithm of the current vs. the transfer distance also depends strongly on the elect...

  3. MATHEMATICAL MODELING OF EXTRACELLULAR ELECTRON TRANSFER IN BIOFILMS

    Energy Technology Data Exchange (ETDEWEB)

    Renslow, Ryan S.; Babauta, Jerome T.; Kuprat, Andrew P.; Schenk, Jim; Ivory, Cornelius; Fredrickson, Jim K.; Beyenal, Haluk

    2015-09-12

    Electrochemically active biofilms have a unique form of respiration in which they utilize solid external materials as terminal electron acceptors for their metabolism. Currently, two primary mechanisms have been identified for long-range extracellular electron transfer (EET): a diffusion- and a conduction-based mechanism. Evidence in the literature suggests that some biofilms, particularly Shewanella oneidensis, produce the requisite components for both mechanisms. In this study, a generic model is presented that incorporates the diffusion- and the conduction-based mechanisms and allows electrochemically active biofilms to utilize both simultaneously. The model was applied to S. oneidensis and Geobacter sulfurreducens biofilms using experimentally generated data found in the literature. Our simulation results show that 1) biofilms having both mechanisms available, especially if they can interact, may have a metabolic advantage over biofilms that can use only a single mechanism; 2) the thickness of G. sulfurreducens biofilms is likely not limited by conductivity; 3) accurate intrabiofilm diffusion coefficient values are critical for current generation predictions; and 4) the local biofilm potential and redox potential are two distinct parameters and cannot be assumed to have identical values. Finally, we determined that simulated cyclic and squarewave voltammetry based on our model are currently not capable of determining the specific percentages of extracellular electron transfer mechanisms in a biofilm. The developed model will be a critical tool for designing experiments to explain EET mechanisms.

  4. Controlling time scales for electron transfer through proteins

    Directory of Open Access Journals (Sweden)

    Scot Wherland

    2015-12-01

    Full Text Available Electron transfer processes within proteins constitute key elements in biological energy conversion processes as well as in a wide variety of biochemical transformations. Pursuit of the parameters that control the rates of these processes is driven by the great interest in the latter reactions. Here, we review a considerable body of results emerging from investigation of intramolecular electron transfer (ET reactions in two types of proteins, all done by the use of the pulse-radiolysis method: first are described results of extensive studies of a model system, the bacterial electron mediating protein azurin, where an internal ET between the disulfide radical ion and the Cu(II is induced. Impact of specific structural changes introduced into azurin on the reaction rates and the parameters controlling it are discussed. Then, the presentation is extended to results of investigations of intra-protein ET reactions that are part of catalytic cycles of multi-copper containing enzymes. Again, the rates and the parameters controlling them are presented and discussed in the context of their efficacy and possible constraints set on their evolution.

  5. Modeling biofilms with dual extracellular electron transfer mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Renslow, Ryan S.; Babauta, Jerome T.; Kuprat, Andrew P.; Schenk, Jim; Ivory, Cornelius; Fredrickson, Jim K.; Beyenal, Haluk

    2013-11-28

    Electrochemically active biofilms have a unique form of respiration in which they utilize solid external materials as their terminal electron acceptor for metabolism. Currently, two primary mechanisms have been identified for long-range extracellular electron transfer (EET): a diffusion- and a conduction-based mechanism. Evidence in the literature suggests that some biofilms, particularly Shewanella oneidensis, produce components requisite for both mechanisms. In this study, a generic model is presented that incorporates both diffusion- and conduction-based mechanisms and allows electrochemically active biofilms to utilize both simultaneously. The model was applied to Shewanella oneidensis and Geobacter sulfurreducens biofilms using experimentally generated data found the literature. Our simulation results showed that 1) biofilms having both mechanisms available, especially if they can interact, may have metabolic advantage over biofilms that can use only a single mechanism; 2) the thickness of Geobacter sulfurreducens biofilms is likely not limited by conductivity; 3) accurate intrabiofilm diffusion coefficient values are critical for current generation predictions; and 4) the local biofilm potential and redox potential are two distinct measurements and cannot be assumed to have identical values. Finally, we determined that cyclic and squarewave voltammetry are currently not good tools to determine the specific percentage of extracellular electron transfer mechanisms used by biofilms. The developed model will be a critical tool in designing experiments to explain EET mechanisms.

  6. Modeling biofilms with dual extracellular electron transfer mechanisms

    Science.gov (United States)

    Renslow, Ryan; Babauta, Jerome; Kuprat, Andrew; Schenk, Jim; Ivory, Cornelius; Fredrickson, Jim; Beyenal, Haluk

    2013-01-01

    Electrochemically active biofilms have a unique form of respiration in which they utilize solid external materials as terminal electron acceptors for their metabolism. Currently, two primary mechanisms have been identified for long-range extracellular electron transfer (EET): a diffusion- and a conduction-based mechanism. Evidence in the literature suggests that some biofilms, particularly Shewanella oneidensis, produce the requisite components for both mechanisms. In this study, a generic model is presented that incorporates the diffusion- and the conduction-based mechanisms and allows electrochemically active biofilms to utilize both simultaneously. The model was applied to S. oneidensis and Geobacter sulfurreducens biofilms using experimentally generated data found in the literature. Our simulation results show that 1) biofilms having both mechanisms available, especially if they can interact, may have a metabolic advantage over biofilms that can use only a single mechanism; 2) the thickness of G. sulfurreducens biofilms is likely not limited by conductivity; 3) accurate intrabiofilm diffusion coefficient values are critical for current generation predictions; and 4) the local biofilm potential and redox potential are two distinct parameters and cannot be assumed to have identical values. Finally, we determined that simulated cyclic and squarewave voltammetry based on our model are currently not capable of determining the specific percentages of extracellular electron transfer mechanisms in a biofilm. The developed model will be a critical tool for designing experiments to explain EET mechanisms. PMID:24113651

  7. Microbial extracellular electron transfer and its relevance to iron corrosion.

    Science.gov (United States)

    Kato, Souichiro

    2016-03-01

    Extracellular electron transfer (EET) is a microbial metabolism that enables efficient electron transfer between microbial cells and extracellular solid materials. Microorganisms harbouring EET abilities have received considerable attention for their various biotechnological applications, including bioleaching and bioelectrochemical systems. On the other hand, recent research revealed that microbial EET potentially induces corrosion of iron structures. It has been well known that corrosion of iron occurring under anoxic conditions is mostly caused by microbial activities, which is termed as microbiologically influenced corrosion (MIC). Among diverse MIC mechanisms, microbial EET activity that enhances corrosion via direct uptake of electrons from metallic iron, specifically termed as electrical MIC (EMIC), has been regarded as one of the major causative factors. The EMIC-inducing microorganisms initially identified were certain sulfate-reducing bacteria and methanogenic archaea isolated from marine environments. Subsequently, abilities to induce EMIC were also demonstrated in diverse anaerobic microorganisms in freshwater environments and oil fields, including acetogenic bacteria and nitrate-reducing bacteria. Abilities of EET and EMIC are now regarded as microbial traits more widespread among diverse microbial clades than was thought previously. In this review, basic understandings of microbial EET and recent progresses in the EMIC research are introduced. PMID:26863985

  8. Electron transfer behaviour of biological macromolecules towards the single-molecule level

    International Nuclear Information System (INIS)

    Redox metalloproteins immobilized on metallic surfaces in contact with aqueous biological media are important in many areas of pure and applied sciences. Redox metalloprotein films are currently being addressed by new approaches where biotechnology including modified and synthetic proteins is combined with state-of-the-art physical electrochemistry with emphasis on single-crystal, atomically planar electrode surfaces, in situ scanning tunnelling microscopy (STM) and other surface techniques. These approaches have brought bioelectrochemistry important steps forward towards the nanoscale and single-molecule levels. We discuss here these advances with reference to two specific redox metalloproteins, the blue single-copper protein Pseudomonas aeruginosa azurin and the single-haem protein Saccharomyces cerevisiae yeast cytochrome c, and a short oligonucleotide. Both proteins can be immobilized on Au(111) by chemisorption via exposed sulfur-containing residues. Voltammetric, interfacial capacitance, x-ray photoelectron spectroscopy and microcantilever sensor data, together with in situ STM with single-molecule resolution, all point to a coherent view of monolayer organization with protein electron transfer (ET) function retained. In situ STM can also address the microscopic mechanisms for electron tunnelling through the biomolecules and offers novel notions such as coherent multi-ET between the substrate and tip via the molecular redox levels. This differs in important respects from electrochemical ET at a single metal/electrolyte interface. Similar data for a short oligonucleotide immobilized on Au(111) show that oligonucleotides can be characterized with comparable detail, with novel perspectives for addressing DNA electronic conduction mechanisms and for biological screening towards the single-molecule level

  9. Electron transfer behaviour of biological macromolecules towards the single-molecule level

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Jingdong [Department of Chemistry, Building 207, Technical University of Denmark, DK-2800 Lyngby (Denmark); Grubb, Mikala [Department of Chemistry, Building 207, Technical University of Denmark, DK-2800 Lyngby (Denmark); Hansen, Allan G [Department of Chemistry, Building 207, Technical University of Denmark, DK-2800 Lyngby (Denmark); Kuznetsov, Alexander M [A N Frumkin Institute of Electrochemistry of the Russian Academy of Sciences, Leninskij Prospect 31, 117071 Moscow (Russian Federation); Boisen, Anja [Microelectronics Centre, Building 345, Technical University of Denmark, DK-2800 Lyngby (Denmark); Wackerbarth, Hainer [Department of Chemistry, Building 207, Technical University of Denmark, DK-2800 Lyngby (Denmark); Ulstrup, Jens [Department of Chemistry, Building 207, Technical University of Denmark, DK-2800 Lyngby (Denmark)

    2003-05-14

    Redox metalloproteins immobilized on metallic surfaces in contact with aqueous biological media are important in many areas of pure and applied sciences. Redox metalloprotein films are currently being addressed by new approaches where biotechnology including modified and synthetic proteins is combined with state-of-the-art physical electrochemistry with emphasis on single-crystal, atomically planar electrode surfaces, in situ scanning tunnelling microscopy (STM) and other surface techniques. These approaches have brought bioelectrochemistry important steps forward towards the nanoscale and single-molecule levels. We discuss here these advances with reference to two specific redox metalloproteins, the blue single-copper protein Pseudomonas aeruginosa azurin and the single-haem protein Saccharomyces cerevisiae yeast cytochrome c, and a short oligonucleotide. Both proteins can be immobilized on Au(111) by chemisorption via exposed sulfur-containing residues. Voltammetric, interfacial capacitance, x-ray photoelectron spectroscopy and microcantilever sensor data, together with in situ STM with single-molecule resolution, all point to a coherent view of monolayer organization with protein electron transfer (ET) function retained. In situ STM can also address the microscopic mechanisms for electron tunnelling through the biomolecules and offers novel notions such as coherent multi-ET between the substrate and tip via the molecular redox levels. This differs in important respects from electrochemical ET at a single metal/electrolyte interface. Similar data for a short oligonucleotide immobilized on Au(111) show that oligonucleotides can be characterized with comparable detail, with novel perspectives for addressing DNA electronic conduction mechanisms and for biological screening towards the single-molecule level.

  10. Interfacial heat transfer in squeeze casting of magnesium alloy AM60 with variation of applied pressures and casting wall-thicknesses

    Science.gov (United States)

    Zhang, Xuezhi; Fang, Li; Sun, Zhizhong; Hu, Henry; Nie, Xueyuan; Tjong, Jimi

    2015-12-01

    The heat transfer coefficient at the casting-die interface is the most important factor on the solidification process. With the 75-ton hydraulic press machine and P20 steel die mold, 5-step castings of magnesium alloy AM60 with different wall-thicknesses (3, 5, 8, 12, 20 mm) were poured under various hydraulic pressures (30, 60, and 90 MPa) using an indirect squeeze casting process. Thermal histories throughout the die wall and the casting surface have been recorded by fine type-K thermocouples. The in-cavity local pressures measured by pressure transducers were explored at the casting-die interfaces of 5 steps. The casting-die interfacial heat transfer coefficients (IHTC) initially reached a maximum peak value followed by a gradually decline to the lower level. Similar characteristics of IHTC peak values can be observed at the applied pressures of 30, 60 and 90 MPa. With the applied pressure of 90 MPa, the peak IHTC values from steps 1 to 5 varied from 5623 to 10,649 W/m2 K. As the applied hydraulic pressure increased, the IHTC peak value of each step was increased accordingly. The wall thickness also affected IHTC peak values significantly. The peak IHTC value and heat flux increased as the step became thicker. The empirical equations relating the IHTCs to the local pressures and the solidification temperature at the casting surface were developed based on the multivariate linear and polynomial regression.

  11. Interfacial heat transfer in squeeze casting of magnesium alloy AM60 with variation of applied pressures and casting wall-thicknesses

    Science.gov (United States)

    Zhang, Xuezhi; Fang, Li; Sun, Zhizhong; Hu, Henry; Nie, Xueyuan; Tjong, Jimi

    2016-10-01

    The heat transfer coefficient at the casting-die interface is the most important factor on the solidification process. With the 75-ton hydraulic press machine and P20 steel die mold, 5-step castings of magnesium alloy AM60 with different wall-thicknesses (3, 5, 8, 12, 20 mm) were poured under various hydraulic pressures (30, 60, and 90 MPa) using an indirect squeeze casting process. Thermal histories throughout the die wall and the casting surface have been recorded by fine type-K thermocouples. The in-cavity local pressures measured by pressure transducers were explored at the casting-die interfaces of 5 steps. The casting-die interfacial heat transfer coefficients (IHTC) initially reached a maximum peak value followed by a gradually decline to the lower level. Similar characteristics of IHTC peak values can be observed at the applied pressures of 30, 60 and 90 MPa. With the applied pressure of 90 MPa, the peak IHTC values from steps 1 to 5 varied from 5623 to 10,649 W/m2 K. As the applied hydraulic pressure increased, the IHTC peak value of each step was increased accordingly. The wall thickness also affected IHTC peak values significantly. The peak IHTC value and heat flux increased as the step became thicker. The empirical equations relating the IHTCs to the local pressures and the solidification temperature at the casting surface were developed based on the multivariate linear and polynomial regression.

  12. Gunn effect and transferred electron devices. Citations from the NTIS data base

    Science.gov (United States)

    Reed, W. E.

    1980-06-01

    A bibliography containing 99 abstracts addressing the Gunn effect and transferred electron devices is presented. The application of Gunn effect and transferred electron devices to microwave generation, amplification, and control is included. The Gunn effect in semiconductors is dicussed along with the design, fabrication, and properties of Gunn diodes and transferred electron devices.

  13. 77 FR 24667 - TANF Assistance and Electronic Benefit Transfer Transactions; Request for Public Comment

    Science.gov (United States)

    2012-04-25

    ... state for entertainment.'' The law defines an electronic benefit transfer transaction as ``the use of a... Electronic Benefit Transfer Transactions; Request for Public Comment AGENCY: Department of Health and Human... States have implemented policies and practices to prevent electronic benefit transfer...

  14. Mechanisms of bridge-mediated electron transfer: a TDDFT electronic dynamics study.

    Science.gov (United States)

    Ding, Feizhi; Chapman, Craig T; Liang, Wenkel; Li, Xiaosong

    2012-12-14

    We present a time-dependent density functional theory approach for probing the dynamics of electron transfer on a donor-bridge-acceptor polyene dye scaffold. Two kinds of mechanisms, namely, the superexchange mechanism and the sequential mechanism, may be involved in the electron transfer process. In this work, we have focused on the crossover between these two charge transfer mechanisms on a series of donor-bridge-acceptor polyene dye systems with varying lengths of conjugated bridges. A number of methods and quantities are used to assist in the analysis, including the phase relationship of charge evolution and frequency domain spectra of the time-dependent dipole. Our simulations show that the superexchange mechanism plays a dominant role in the electron transfer from donor to acceptor when the bridge length is small, and the sequential mechanism becomes more important as the polyene bridge is lengthened. Full Ehrenfest dynamics with nuclear motion show that molecular vibrations play a very small role in such ultrafast charge transfer processes.

  15. The intramolecular electron transfer between copper sites of nitrite reductase

    DEFF Research Database (Denmark)

    Farver, O; Eady, R R; Abraham, Z H;

    1998-01-01

    The intramolecular electron transfer (ET) between the type 1 Cu(I) and the type 2 Cu(II) sites of Alcaligenes xylosoxidans dissimilatory nitrite reductase (AxNiR) has been studied in order to compare it with the analogous process taking place in ascorbate oxidase (AO). This internal process is......(I) and the trinuclear copper centre in ascorbate oxidase, and the characteristics of the internal ET processes of these enzymes are compared. The data are consistent with the faster ET observed in nitrite reductase arising from a more advantageous entropy of activation when compared with ascorbate...

  16. Light induced electron transfer reactions of metal complexes

    International Nuclear Information System (INIS)

    Properties of the excited states of tris(2,2'-bipyridine) and tris(1,10-phenanthroline) complexes of chromium(III), iron(II), ruthenium(II), osmium(II), rhodium(III), and iridium(III) are described. The electron transfer reactions of the ground and excited states are discussed and interpreted in terms of the driving force for the reaction and the distortions of the excited states relative to the corresponding ground states. General considerations relevant to the conversion of light into chemical energy are presented and progress in the use of polypyridine complexes to effect the light decomposition of water into hydrogen and oxygen is reviewed

  17. Human ceruloplasmin. Intramolecular electron transfer kinetics and equilibration

    DEFF Research Database (Denmark)

    Farver, O; Bendahl, L; Skov, L K;

    1999-01-01

    Pulse radiolytic reduction of disulfide bridges in ceruloplasmin yielding RSSR(-) radicals induces a cascade of intramolecular electron transfer (ET) processes. Based on the three-dimensional structure of ceruloplasmin identification of individual kinetically active disulfide groups and type 1 (T1...... with a rate constant of 3.9 +/- 0.8. No reoxidation of T1B Cu(I) could be resolved. It appears that the third T1 center (T1C of domain 2) is not participating in intramolecular ET, as it seems to be in a reduced state in the resting enzyme....

  18. Immobilization, hybridization, and oxidation of synthetic DNA on gold surface: Electron transfer investigated by electrochemistry and scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    McEwen, Gerald D.; Chen Fan [Biological Engineering Program, Department of Biological and Irrigation Engineering, Utah State University, 4105 Old Main Hill, Logan, UT 84322-4105 (United States); Zhou Anhong, E-mail: Anhong.Zhou@usu.edu [Biological Engineering Program, Department of Biological and Irrigation Engineering, Utah State University, 4105 Old Main Hill, Logan, UT 84322-4105 (United States)

    2009-06-08

    Fundamental understanding of interfacial electron transfer (ET) among electrolyte/DNA/solid-surface will facilitate the design for electrical detection of DNA molecules. In this report, the electron transfer characteristics of synthetic DNA (sequence from pathogenic Cryptosporidium parvum) self-assembled on a gold surface was electrochemically studied. The effects of immobilization order on the interface ET related parameters such as diffusion coefficient (D{sub 0}), surface coverage ({theta}{sub R}), and monolayer thickness (d{sub i}) were determined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). DNA surface density ({Gamma}{sub DNA}) was determined by the integration of the charge of the electro-oxidation current peaks during the initial cyclic voltammetry scans. It was found that the DNA surface densities at different modifications followed the order: {Gamma}{sub DNA} (dsS-DNA/Au) > {Gamma}{sub DNA} (MCH/dsS-DNA/Au) > {Gamma}{sub DNA} (dsS-DNA/MCH/Au). It was also revealed that the electro-oxidation of the DNA modified gold surface would involve the oxidation of nucleotides (guanine and adenine) with a 5.51 electron transfer mechanism and the oxidative desorption of DNA and MCH molecules by a 3 electron transfer mechanism. STM topography and current image analysis indicated that the surface conductivity after each surface modification followed the order: dsS-DNA/Au < MCH/dsS-DNA/Au < oxidized MCH/dsS-DNA/Au < Hoechst/oxidized MCH/dsS-DNA/Au. The results from this study suggested a combination of variations in immobilization order may provide an alternative approach for the optimization of DNA hybridization and the further development for electrical detection of DNA.

  19. Ordered Assembly and Controlled Electron Transfer of the Blue Copper Protein Azurin at Gold (111) Single-Crystal Substrates

    DEFF Research Database (Denmark)

    Chi, Qijin; Zhang, Jingdong; Andersen, Jens Enevold Thaulov;

    2001-01-01

    ) with molecular resolution reveals that both well-ordered alkanethiol and protein adlayers are present. Adsorbed azurin molecules exhibit high stability and retain electron transfer (ET) function. Long-range interfacial ET between azurin and Au(111) across variable-length alkanethiol bridges was systematically...... investigated by different electrochemical techniques. Distance-dependent ET can be controlled by adjusting the length of the alkanethiol chain. The electrochemical ET rate constant is almost independent of the chain length up to ca. 9 methylene units but follows exponential distance decay with a decay factor...... (beta) of 1.03 +/- 0.02 per CH2 unit at longer chain lengths. Overvoltage-dependent ET was also examined. The results provide a strategy to ordered molecular assemblies, and controlled orientation and ET of azurin at atomically planar metallic surfaces. This approach can in principle be extended...

  20. Femtosecond laser pulse control of electron transfer processes

    Science.gov (United States)

    Mančal, Tomáš; Kleinekathöfer, Ulrich; May, Volkhard

    2002-07-01

    Laser-pulse guided ultrafast electron transfer (ET) is studied theoretically for different types of donor-acceptor systems. The pulse initiates an optical transition from the electronic ground state into an excited state and controls the ET. The computations concentrate on systems where (a) the excited state (donor) is coupled to an acceptor level and where (b) the ET proceeds as an internal conversion from the excited state to the ground state. For both examples the manifold of vibrational coordinates is mapped on a single reaction coordinate coupled to a dissipative reservoir of further coordinates. Utilizing the methods of dissipative quantum dynamics combined with the optimal control (OC) scheme, it is demonstrated that control fields really exist which drive the ET in the required manner. Various properties of the OC algorithm are discussed when applied to dissipative dynamics and a scheme is proposed to avoid pinning in a local extremum.

  1. Intramolecular electron transfer in Pseudomonas aeruginosa cd(1) nitrite reductase

    DEFF Research Database (Denmark)

    Farver, Ole; Brunori, Maurizio; Cutruzzolà, Francesca;

    2009-01-01

    The cd(1) nitrite reductases, which catalyze the reduction of nitrite to nitric oxide, are homodimers of 60 kDa subunits, each containing one heme-c and one heme-d(1). Heme-c is the electron entry site, whereas heme-d(1) constitutes the catalytic center. The 3D structure of Pseudomonas aeruginosa...... nitrite reductase has been determined in both fully oxidized and reduced states. Intramolecular electron transfer (ET), between c and d(1) hemes is an essential step in the catalytic cycle. In earlier studies of the Pseudomonas stutzeri enzyme, we observed that a marked negative cooperativity...... is controlling this internal ET step. In this study we have investigated the internal ET in the wild-type and His369Ala mutant of P. aeruginosa nitrite reductases and have observed similar cooperativity to that of the Pseudomonas stutzeri enzyme. Heme-c was initially reduced, in an essentially diffusion...

  2. The electronic transfer of information and aerospace knowledge diffusion

    Science.gov (United States)

    Pinelli, Thomas E.; Bishop, Ann P.; Barclay, Rebecca O.; Kennedy, John M.

    1992-01-01

    Increasing reliance on and investment in information technology and electronic networking systems presupposes that computing and information technology will play a motor role in the diffusion of aerospace knowledge. Little is known, however, about actual information technology needs, uses, and problems within the aerospace knowledge diffusion process. The authors state that the potential contributions of information technology to increased productivity and competitiveness will be diminished unless empirically derived knowledge regarding the information-seeking behavior of the members of the social system - those who are producing, transferring, and using scientific and technical information - is incorporated into a new technology policy framework. Research into the use of information technology and electronic networks by U.S. aerospace engineers and scientists, collected as part of a research project designed to study aerospace knowledge diffusion, is presented in support of this assertion.

  3. Electron transfer pathway analysis in bacterial photosynthetic reaction center

    CERN Document Server

    Kitoh-Nishioka, Hirotaka

    2016-01-01

    A new computational scheme to analyze electron transfer (ET) pathways in large biomolecules is presented with applications to ETs in bacterial photosynthetic reaction center. It consists of a linear combination of fragment molecular orbitals and an electron tunneling current analysis, which enables an efficient first-principles analysis of ET pathways in large biomolecules. The scheme has been applied to the ET from menaquinone to ubiquinone via nonheme iron complex in bacterial photosynthetic reaction center. It has revealed that not only the central Fe$^{2+}$ ion but also particular histidine ligands are involved in the ET pathways in such a way to mitigate perturbations that can be caused by metal ion substitution and depletion, which elucidates the experimentally observed insensitivity of the ET rate to these perturbations.

  4. Molecular Models for Conductance in Junctions and Electrochemical Electron Transfer

    Science.gov (United States)

    Mazinani, Shobeir Khezr Seddigh

    This thesis develops molecular models for electron transport in molecular junctions and intra-molecular electron transfer. The goal is to identify molecular descriptors that afford a substantial simplification of these electronic processes. First, the connection between static molecular polarizability and the molecular conductance is examined. A correlation emerges whereby the measured conductance of a tunneling junction decreases as a function of the calculated molecular polarizability for several systems, a result consistent with the idea of a molecule as a polarizable dielectric. A model based on a macroscopic extension of the Clausius-Mossotti equation to the molecular domain and Simmon's tunneling model is developed to explain this correlation. Despite the simplicity of the theory, it paves the way for further experimental, conceptual and theoretical developments in the use of molecular descriptors to describe both conductance and electron transfer. Second, the conductance of several biologically relevant, weakly bonded, hydrogen-bonded systems is systematically investigated. While there is no correlation between hydrogen bond strength and conductance, the results indicate a relation between the conductance and atomic polarizability of the hydrogen bond acceptor atom. The relevance of these results to electron transfer in biological systems is discussed. Hydrogen production and oxidation using catalysts inspired by hydrogenases provides a more sustainable alternative to the use of precious metals. To understand electrochemical and spectroscopic properties of a collection of Fe and Ni mimics of hydrogenases, high-level density functional theory calculations are described. The results, based on a detailed analysis of the energies, charges and molecular orbitals of these metal complexes, indicate the importance of geometric constraints imposed by the ligand on molecular properties such as acidity and electrocatalytic activity. Based on model calculations of

  5. Biochemical Mechanisms Controlling Terminal Electron Transfer in Geobacter sulfurreducens

    Science.gov (United States)

    Helmus, R.; Liermann, L. J.; Brantley, S. L.; Tien, M.

    2009-04-01

    The ability of Geobacter sulfurreducens to use a variety of metals as terminal electron acceptors (TEAs) for cellular respiration makes it attractive for use in bioremediation and implies its importance to mineral cycling in the environment. This study is aimed at understanding the biochemical mechanisms that allow Geobacter sulfurreducens to use soluble and insoluble iron and manganese forms as TEAs for cellular respiration and is the first of its kind to address the kinetics of manganese use as a TEA by G. sulfurreducens. First, G. sulfurreducens was conditioned to grow on various soluble and insoluble iron and manganese forms. G. sulfurreducens demonstrated enhanced growth rates when cultured using soluble TEAs compared with insoluble TEAs. However, the lower growth rate on insoluble iron compared with soluble iron was observed concomitantly with a 1-2 log lower cell density in stationary phase in insoluble iron cultures and a lower growth yield per electron donor used in log growth phase. Furthermore, the growth yield per electron was similar with both soluble and insoluble iron. These results suggest that the net amount of energy available for biomass production achieved from reducing insoluble iron is lower than with soluble iron, which may be due to a different biochemical mechanism catalyzing the electron transfer to TEA dependent upon the solubility of the TEA. One scenario consistent with this notion is that protein(s) in the outer membrane of G. sulfurreducens that transfers electrons to insoluble TEAs does so in a manner that uncouples electron flow from the proton pump in the cellular membrane, similar to what we have observed with Shewanella oneidensis MR-1. Both the growth rate and growth yield of G. sulfurreducens on insoluble manganese were higher than on insoluble iron, indicating that there is a difference in the flow of electrons to the TEA in these two situations. While the different redox potentials of these elements may affect these values

  6. Electromagnetic field generation by ATP-induced reverse electron transfer.

    Science.gov (United States)

    Steele, Richard H

    2003-03-01

    This paper describes a mechanism to explain low-level light emission in biology. A biological analog of the electrical circuitry, modeled on the parallel plate capacitor, traversed by a helical structure, required to generate electromagnetic radiation in the optical spectral range, is described. The charge carrier required for the emissions is determined to be an accelerating electron driven by an ATP-induced reverse electron transfer. The radial velocity component, the emission trajectory, of the moving charges traversing helical protein structures in a cyclotron-type mechanism is proposed to be imposed by the ferromagnetic field components of the iron in the iron-sulfur proteins. The redox systems NADH, riboflavin, and chlorophyll were examined with their long-wavelength absorption maxima determining the energetic parameters for the calculations. Potentials calculated from the axial velocity components for the riboflavin and NADH systems were found to equal the standard redox potentials of these systems as measured electrochemically and enzymatically. The mechanics for the three systems determined the magnetic moments, the angular momenta, and the orbital magnetic fluxes to be adiabatic invariant parameters. The De Broglie dual wave-particle equation, the fundamental equation of wave mechanics, and the key idea of quantum mechanics, establishes the wavelengths for accelerating electrons which, divided into a given radial velocity, gives its respective emission frequency. Electrons propelled through helical structures, traversed by biologically available electric and magnetic fields, make accessible to the internal environment the optical spectral frequency range that the solar spectrum provides to the external environment.

  7. Linear energy relationships in ground state proton transfer and excited state proton-coupled electron transfer.

    Science.gov (United States)

    Gamiz-Hernandez, Ana P; Magomedov, Artiom; Hummer, Gerhard; Kaila, Ville R I

    2015-02-12

    Proton-coupled electron transfer (PCET) processes are elementary chemical reactions involved in a broad range of radical and redox reactions. Elucidating fundamental PCET reaction mechanisms are thus of central importance for chemical and biochemical research. Here we use quantum chemical density functional theory (DFT), time-dependent density functional theory (TDDFT), and the algebraic diagrammatic-construction through second-order (ADC(2)) to study the mechanism, thermodynamic driving force effects, and reaction barriers of both ground state proton transfer (pT) and photoinduced proton-coupled electron transfer (PCET) between nitrosylated phenyl-phenol compounds and hydrogen-bonded t-butylamine as an external base. We show that the obtained reaction barriers for the ground state pT reactions depend linearly on the thermodynamic driving force, with a Brønsted slope of 1 or 0. Photoexcitation leads to a PCET reaction, for which we find that the excited state reaction barrier depends on the thermodynamic driving force with a Brønsted slope of 1/2. To support the mechanistic picture arising from the static potential energy surfaces, we perform additional molecular dynamics simulations on the excited state energy surface, in which we observe a spontaneous PCET between the donor and the acceptor groups. Our findings suggest that a Brønsted analysis may distinguish the ground state pT and excited state PCET processes.

  8. Determination of the electronics transfer function for current transient measurements

    CERN Document Server

    Scharf, Christian

    2014-01-01

    We describe a straight-forward method for determining the transfer function of the readout of a sensor for the situation in which the current transient of the sensor can be precisely simulated. The method relies on the convolution theorem of Fourier transforms. The specific example is a planar silicon pad diode connected with a 50 $\\Omega $ cable to an amplifier followed by a 5 GS/s sampling oscilloscope. The charge carriers in the sensor were produced by picosecond lasers with light of wavelengths of 675 and 1060 nm. The transfer function is determined from the 1060 nm data with the pad diode biased at 1000 V. It is shown that the simulated sensor response convoluted with this transfer function provides an excellent description of the measured transients for the laser light of both wavelengths, at voltages 50 V above the depletion voltage of about 90 V up to the maximum applied voltage of 1000 V. The method has been developed for the precise measurement of the dependence of the drift velocity of electrons an...

  9. MD studies of electron transfer at ambient and elevated pressures

    Science.gov (United States)

    Giles, Alex; Spooner, Jacob; Weinberg, Noham

    2013-06-01

    The effect of pressure on the rate constants of outer-sphere electron transfer reactions has often been described using the Marcus-Hush theory. This theory agrees well with experiment when internal reorganization of the ionic system is negligible, however it does not offer a recipe for calculation of the effects that result from significant solute restructuring. We have recently developed a molecular dynamics technique that accurately describes structural dependence of molecular volumes in non-polar and weakly polar systems. We are now extending this approach to the case of highly polar ionic systems where both solvent and solute restructuring components are important. For this purpose we construct pressure-dependent two-dimensional surfaces for electron transfer reactions in coordinate system composed of interionic distance and Marcus-type solvent polarization coordinate, and use these surfaces to describe pressure effects on reaction kinetics. R.A. Marcus. J. Chem. Phys. 24, 966 (1956); 24, 979 (1956); 26, 867 (1957). Discuss. Faraday Soc. 29, 21 (1960). Faraday Discuss. Chem. Soc. 74, 7 (1982); N.S. Hush. Trans. Faraday Soc. 57, 557 (1961).

  10. Enzymatic cellulose oxidation is linked to lignin by long-range electron transfer

    DEFF Research Database (Denmark)

    Westereng, Bjorge; Cannella, David; Wittrup Agger, Jane;

    2015-01-01

    cell walls. Electron transfer was confirmed by electron paramagnetic resonance spectroscopy showing that LPMO activity on cellulose changes the level of unpaired electrons in the lignin. The discovery of a long-range electron transfer mechanism links the biodegradation of cellulose and lignin and sheds...... new light on how oxidative enzymes present in plant degraders may act in concert....

  11. Vibrational dynamics in photoinduced electron transfer. Progress report, December 1, 1992--November 30, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Spears, K.G.

    1993-09-08

    Objective is to perform a new type of measurement for optically excited electron transfer processes that can provide unique experimental insight into the molecular mechanism of electron transfer. Measurements of optically excited electron transfer are done with picosecond infrared (IR) absorption spectroscopy to monitor the vibrational motions of the molecules immediately after electron transfer. Theory and experiment suggest that molecular vibrations and distortions are important controlling elements for electron transfer, and direct information has yet to be obtained on these elements of electron transfer mechanisms. The second period of funding has been dedicated to finishing technique development and performing studies of electron transfer in ion pair systems to identify if vibrational dependent electron transfer rates are present in this system. We have succeeded in measuring, for the first time, electron transfer rates as a function of vibrational state in an ion pair complex in solution. In a different area of electron transfer research we have proposed a new mechanism of solvent gated electron transfer.

  12. Mitochondrial nitric oxide production supported by reverse electron transfer.

    Science.gov (United States)

    Bombicino, Silvina S; Iglesias, Darío E; Zaobornyj, Tamara; Boveris, Alberto; Valdez, Laura B

    2016-10-01

    Heart phosphorylating electron transfer particles (ETPH) produced NO at 1.2 ± 0.1 nmol NO. min(-1) mg protein(-1) by the mtNOS catalyzed reaction. These particles showed a NAD(+) reductase activity of 64 ± 3 nmol min(-1) mg protein(-1) sustained by reverse electron transfer (RET) at expenses of ATP and succinate. The same particles, without NADPH and in conditions of RET produced 0.97 ± 0.07 nmol NO. min(-1) mg protein(-1). Rotenone inhibited NO production supported by RET measured in ETPH and in coupled mitochondria, but did not reduce the activity of recombinant nNOS, indicating that the inhibitory effect of rotenone on NO production is due to an electron flow inhibition and not to a direct action on mtNOS structure. NO production sustained by RET corresponds to 20% of the total amount of NO released from heart coupled mitochondria. A mitochondrial fraction enriched in complex I produced 1.7 ± 0.2 nmol NO. min(-1) mg protein(-1) and reacted with anti-75 kDa complex I subunit and anti-nNOS antibodies, suggesting that complex I and mtNOS are located contiguously. These data show that mitochondrial NO production can be supported by RET, and suggest that mtNOS is next to complex I, reaffirming the idea of a functional association between these proteins.

  13. Cluster PEACE observations of electrons during magnetospheric flux transfer events

    Directory of Open Access Journals (Sweden)

    C. J. Owen

    Full Text Available During the first quarter of 2001 the apogees of the Cluster spacecraft quartet precessed through midday local times. This provides the first opportunity for 4 spacecraft studies of the bow shock, magnetosheath and the dayside magnetopause current layer and boundary layers. In this paper, we present observations of electrons in the energy range ~ 10 eV–26 keV made by the Plasma Electron And Current Experiment (PEACE located just inside the magnetopause boundary, together with supporting observations by the Flux Gate Magnetometer (FGM. During these observations, the spacecraft have separations of ~ 600 km. This scale size is of the order or less than the typical size of flux transfer events (FTEs, which are expected to be observed following bursts of reconnection on the dayside magnetopause. We study, in detail, the 3-D configuration of electron populations observed around a series of enhancements of magnetosheath-like electrons which were observed within the magnetosphere on 2 February 2001. We find that individual spacecraft observe magnetic field and electron signatures that are consistent with previous observations of magnetospheric FTEs. However, the differences in the signatures between spacecraft indicate that these FTEs have substructure on the scale of the spacecraft separation. We use these differences and the timings of the 4 spacecraft observations to infer the motions of the electron populations and thus the configuration of these substructures. We find that these FTEs are moving from noon towards dusk. The inferred size and speed of motion across the magnetopause, in one example, is ~ 0.8 RE and ~ 70 km s-1 respectively. In addition, we observe a delay in and an extended duration of the signature at the spacecraft furthest from the magnetopause. We discuss the implications of these 4 spacecraft observations for the structure of these FTEs. We suggest that these may include a compression of the closed

  14. Coherent Transfer of Electronic Wavepacket Motion Between Atoms

    Science.gov (United States)

    Zhou, Tao; Richards, B. G.; Jones, R. R.

    2016-05-01

    We have shown that electron correlations, induced by controlled dipole-dipole (DD) interactions, can enable the coherent transfer of electronic wavepacket motion from atoms to their neighbors. In the experiment, a 5 ns tunable dye laser excites Rb atoms in a MOT to the 25s state in a weak static electric field for which the tunable 25s 33 s 24p34p DD interaction is resonant. A picosecond THz pulse then further excites each Rydberg atom into a coherent superposition, of 25s and 24p states. The evolution of this mixed-parity wavepacket is characterized by time-dependent oscillations in the electric dipole moment, with a period of 2.9 ps. Approximately 5 ns after the wavepacket creation, a second 5 ns dye-laser promotes a second set of atoms from the 5p level into the 33s state. Because of the DD interaction, the second dye laser actually creates atom pairs whose electronic states are correlated via the resonant DD coupling. A 33 s + 34p wavepacket, oscillating with the same 2.9 ps period as the 25 s + 24p wavepacket, develops on the second set of atoms as a result of the correlation. A second, time-delayed ps THz pulse enables the detection of the coherent wavepacket motion on the two sets of atoms. This research has been supported by the NSF.

  15. Fabrication and single-electron-transfer operation of a triple-dot single-electron transistor

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Mingyu, E-mail: mingyujo@eis.hokudai.ac.jp; Uchida, Takafumi; Tsurumaki-Fukuchi, Atsushi; Arita, Masashi; Takahashi, Yasuo [Graduate School of Information Science and Technology, Hokkaido University, Sapporo 060-0814 (Japan); Fujiwara, Akira; Nishiguchi, Katsuhiko [NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi 243-0198 (Japan); Ono, Yukinori [Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555 (Japan); Inokawa, Hiroshi [Research Institute of Electronics, Shizuoka University, 3-5-1, Johoku, Hamamatsu 432-8011 (Japan)

    2015-12-07

    A triple-dot single-electron transistor was fabricated on silicon-on-insulator wafer using pattern-dependent oxidation. A specially designed one-dimensional silicon wire having small constrictions at both ends was converted to a triple-dot single-electron transistor by means of pattern-dependent oxidation. The fabrication of the center dot involved quantum size effects and stress-induced band gap reduction, whereas that of the two side dots involved thickness modulation because of the complex edge structure of two-dimensional silicon. Single-electron turnstile operation was confirmed at 8 K when a 100-mV, 1-MHz square wave was applied. Monte Carlo simulations indicated that such a device with inhomogeneous tunnel and gate capacitances can exhibit single-electron transfer.

  16. Electronic shift register memory based on molecular electron-transfer reactions

    International Nuclear Information System (INIS)

    The design of a shift register memory at the molecular level is described in detail. The memory elements are based on a chain of electron-transfer molecules incorporated on a very large scale integrated (VLSI) substrate, and the information is shifted by photoinduced electron-transfer reactions. The design requirements for such a system are discussed, and several realistic strategies for synthesizing these systems are presented. The immediate advantage of such a hybrid molecular/VLSI device would arise from the possible information storage density. The prospect of considerable savings of energy per bit processed also exists. This molecular shift register memory element design solves the conceptual problems associated with integrating molecular size components with larger (micron) size features on a chip

  17. 27 CFR 27.48a - Payment of tax by electronic fund transfer.

    Science.gov (United States)

    2010-04-01

    ... corporations, as defined in 26 U.S.C. 1563, and implementing regulations in 26 CFR 1.1563-1 through 1.1563-4.... (c) Electronic fund transfer or EFT means any transfer of funds, other than a transaction originated... electronic fund transfer. 27.48a Section 27.48a Alcohol, Tobacco Products and Firearms ALCOHOL AND...

  18. Electron Transfer Reactivity of the Aqueous Iron(IV)-Oxo Complex. Outer-Sphere vs Proton-Coupled Electron Transfer.

    Science.gov (United States)

    Bataineh, Hajem; Pestovsky, Oleg; Bakac, Andreja

    2016-07-01

    The kinetics of oxidation of organic and inorganic reductants by aqueous iron(IV) ions, Fe(IV)(H2O)5O(2+) (hereafter Fe(IV)aqO(2+)), are reported. The substrates examined include several water-soluble ferrocenes, hexachloroiridate(III), polypyridyl complexes M(NN)3(2+) (M = Os, Fe and Ru; NN = phenanthroline, bipyridine and derivatives), HABTS(-)/ABTS(2-), phenothiazines, Co(II)(dmgBF2)2, macrocyclic nickel(II) complexes, and aqueous cerium(III). Most of the reductants were oxidized cleanly to the corresponding one-electron oxidation products, with the exception of phenothiazines which produced the corresponding oxides in a single-step reaction, and polypyridyl complexes of Fe(II) and Ru(II) that generated ligand-modified products. Fe(IV)aqO(2+) oxidizes even Ce(III) (E(0) in 1 M HClO4 = 1.7 V) with a rate constant greater than 10(4) M(-1) s(-1). In 0.10 M aqueous HClO4 at 25 °C, the reactions of Os(phen)3(2+) (k = 2.5 × 10(5) M(-1) s(-1)), IrCl6(3-) (1.6 × 10(6)), ABTS(2-) (4.7 × 10(7)), and Fe(cp)(C5H4CH2OH) (6.4 × 10(7)) appear to take place by outer sphere electron transfer (OSET). The rate constants for the oxidation of Os(phen)3(2+) and of ferrocenes remained unchanged in the acidity range 0.05 1.3 V. For proton-coupled electron transfer, the reduction potential is estimated at E(0) (Fe(IV)aqO(2+), H(+)/Fe(III)aqOH(2+)) ≥ 1.95 V. PMID:27320290

  19. Electrochemical Electron Transfer and Proton-Coupled Electron Transfer: Effects of Double Layer and Ionic Environment on Solvent Reorganization Energies

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Soumya; Soudackov, Alexander; Hammes-Schiffer, Sharon

    2016-06-14

    Electron transfer and proton coupled electron transfer (PCET) reactions at electrochemical interfaces play an essential role in a broad range of energy conversion processes. The reorganization energy, which is a measure of the free energy change associated with solute and solvent rearrangements, is a key quantity for calculating rate constants for these reactions. We present a computational method for including the effects of the double layer and ionic environment of the diffuse layer in calculations of electrochemical solvent reorganization energies. This approach incorporates an accurate electronic charge distribution of the solute within a molecular-shaped cavity in conjunction with a dielectric continuum treatment of the solvent, ions, and electrode using the integral equations formalism polarizable continuum model. The molecule-solvent boundary is treated explicitly, but the effects of the electrode-double layer and double layer-diffuse layer boundaries, as well as the effects of the ionic strength of the solvent, are included through an external Green’s function. The calculated total reorganization energies agree well with experimentally measured values for a series of electrochemical systems, and the effects of including both the double layer and ionic environment are found to be very small. This general approach was also extended to electrochemical PCET and produced total reorganization energies in close agreement with experimental values for two experimentally studied PCET systems. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center, funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  20. Transfer of optical orbital angular momentum to a bound electron

    Science.gov (United States)

    Schmiegelow, Christian T.; Schulz, Jonas; Kaufmann, Henning; Ruster, Thomas; Poschinger, Ulrich G.; Schmidt-Kaler, Ferdinand

    2016-10-01

    Photons can carry angular momentum, not only due to their spin, but also due to their spatial structure. This extra twist has been used, for example, to drive circular motion of microscopic particles in optical tweezers as well as to create vortices in quantum gases. Here we excite an atomic transition with a vortex laser beam and demonstrate the transfer of optical orbital angular momentum to the valence electron of a single trapped ion. We observe strongly modified selection rules showing that an atom can absorb two quanta of angular momentum from a single photon: one from the spin and another from the spatial structure of the beam. Furthermore, we show that parasitic ac-Stark shifts from off-resonant transitions are suppressed in the dark centre of vortex beams. These results show how light's spatial structure can determine the characteristics of light-matter interaction and pave the way for its application and observation in other systems.

  1. Proton-Coupled Electron Transfer: Moving Together and Charging Forward.

    Science.gov (United States)

    Hammes-Schiffer, Sharon

    2015-07-22

    Proton-coupled electron transfer (PCET) is ubiquitous throughout chemistry and biology. This Perspective discusses recent advances and current challenges in the field of PCET, with an emphasis on the role of theory and computation. The fundamental theoretical concepts are summarized, and expressions for rate constants and kinetic isotope effects are provided. Computational methods for calculating reduction potentials and pKa's for molecular electrocatalysts, as well as insights into linear correlations and non-innocent ligands, are also described. In addition, computational methods for simulating the nonadiabatic dynamics of photoexcited PCET are discussed. Representative applications to PCET in solution, proteins, electrochemistry, and photoinduced processes are presented, highlighting the interplay between theoretical and experimental studies. The current challenges and suggested future directions are outlined for each type of application, concluding with an overall view to the future. PMID:26110700

  2. Facile direct electron transfer in glucose oxidase modified electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Wang Dan [Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701 (United States); Chen Liwei [Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701 (United States); Suzhou Institute of Nano Tech and Nano Bionics, Chinese Academy of Sciences, 398 Ruoshui Road, Suzhou Industrial Park, Suzhou, Jiangsu 215125 (China)], E-mail: lwchen2008@sinano.ac.cn

    2009-07-15

    Glucose oxidase (GOx) is widely used in the glucose biosensor industry. However, mediatorless direct electron transfer (DET) from GOx to electrode surfaces is very slow. Recently, mediatorless DET has been reported via the incorporation of nanomaterials such as carbon nanotubes and nanoparticles in the modification of electrodes. Here we report GOx electrodes showing DET without the need for any nanomaterials. The enzyme after immobilization with poly-L-lysine (PLL) and Nafion retains the biocatalytic activities and oxidizes glucose efficiently. The amperometric response of Nafion-PLL-GOx modified electrode is linearly proportional to the concentration of glucose up to 10 mM with a sensitivity of 0.75 {mu}A/mM at a low detection potential (-0.460 V vs. Ag/AgCl). The methodology developed in this study will have impact on glucose biosensors and biofuel cells and may potentially simplify enzyme immobilization in other biosensing systems.

  3. Quantum effects in ultrafast electron transfers within cryptochromes.

    Science.gov (United States)

    Firmino, Thiago; Mangaud, Etienne; Cailliez, Fabien; Devolder, Adrien; Mendive-Tapia, David; Gatti, Fabien; Meier, Christoph; Desouter-Lecomte, Michèle; de la Lande, Aurélien

    2016-08-21

    Cryptochromes and photolyases are flavoproteins that may undergo ultrafast charge separation upon electronic excitation of their flavin cofactors. Charge separation involves chains of three or four tryptophan residues depending on the protein of interest. The molecular mechanisms of these processes are not completely clear. In the present work we investigate the relevance of quantum effects like the occurrence of nuclear tunneling and of coherences upon charge transfer in Arabidopsis thaliana cryptochromes. The possible breakdown of the Condon approximation is also investigated. We have devised a simulation protocol based on the realization of molecular dynamics simulations on diabatic potential energy surfaces defined at the hybrid constrained density functional theory/molecular mechanics level. The outcomes of the simulations are analyzed through various dedicated kinetics schemes related to the Marcus theory that account for the aforementioned quantum effects. MD simulations also provide a basic material to define realistic model Hamiltonians for subsequent quantum dissipative dynamics. To carry out quantum simulations, we have implemented an algorithm based on the Hierarchical Equations of Motion. With this new tool in hand we have been able to model the electron transfer chain considering either two- or three-state models. Kinetic models and quantum simulations converge to the conclusion that quantum effects have a significant impact on the rate of charge separation. Nuclear tunneling involving atoms of the tryptophan redox cofactors as well as of the environment (protein atoms and water molecules) is significant. On the other hand non-Condon effects are negligible in most simulations. Taken together, the results of the present work provide new insights into the molecular mechanisms controlling charge separation in this family of flavoproteins. PMID:27427185

  4. A new perspective on the electron transfer: recovering the Butler-Volmer equation in non-equilibrium thermodynamics.

    Science.gov (United States)

    Dreyer, Wolfgang; Guhlke, Clemens; Müller, Rüdiger

    2016-09-28

    Electron transfer reactions are commonly described by the phenomenological Butler-Volmer equation which has its origin in kinetic theories. The Butler-Volmer equation relates interfacial reaction rates to bulk quantities like the electrostatic potential and electrolyte concentrations. Although the general structure of the equation is well accepted, for modern electrochemical systems like batteries and fuel cells there is still intensive discussion about the specific dependencies of the coefficients. A general guideline for the derivation of Butler-Volmer type equations is missing in the literature. We derive very general relations of Butler-Volmer structure which are based on a rigorous non-equilibrium thermodynamic model and allow for adaption to a wide variety of electrochemical systems. We discuss the application of the new thermodynamic approach to different scenarios like the classical electron transfer reactions at metal electrodes and the intercalation process in lithium-iron-phosphate electrodes. Furthermore we show that under appropriate conditions also adsorption processes can lead to Butler-Volmer equations. We illustrate the application of our theory by a strongly simplified example of electroplating. PMID:27560993

  5. Interfacial Symmetry Control of Emergent Ferromagnetism

    Science.gov (United States)

    Grutter, Alexander; Borchers, Julie; Kirby, Brian; He, Chunyong; Arenholz, Elke; Vailionis, Arturas; Flint, Charles; Suzuki, Yuri

    Atomically precise complex oxide heterostructures provide model systems for the discovery of new emergent phenomena since their magnetism, structure and electronic properties are strongly coupled. Octahedral tilts and rotations have been shown to alter the magnetic properties of complex oxide heterostructures, but typically induce small, gradual magnetic changes. Here, we demonstrate sharp switching between ferromagnetic and antiferromagnetic order at the emergent ferromagnetic interfaces of CaRuO3/CaMnO3 superlattices. Through synchrotron X-ray diffraction and neutron reflectometry, we show that octahedral distortions in superlattices with an odd number of CaMnO3 unit cells in each layer are symmetry mismatched across the interface. In this case, the rotation symmetry switches across the interface, reducing orbital overlap, suppressing charge transfer from Ru to Mn, and disrupting the interfacial double exchange. This disruption switches half of the interfaces from ferromagnetic to antiferromagnetic and lowers the saturation magnetic of the superlattice from 1.0 to 0.5 μB/interfacial Mn. By targeting a purely interfacial emergent magnetic system, we achieve drastic alterations to the magnetic ground state with extremely small changes in layer thickness.

  6. Study of Electron Transfer Processes between Simple Plasma Ions and Electron Attaching Gases

    Science.gov (United States)

    Williams, Ted; Adams, Nigel; Babcock, Lucia

    1998-11-01

    CCl4 and SF6 are gases that rapidly attach electrons. They are used in etchant plasmas and in high power switches to prevent breakdown. This attachment results in a simple negative ion chemistry that can be well characterized. A concurrent series of reactions involving positive ions also occurs, with ionization eventually being removed by ion-ion mutual neutralization. However, unlike the negative ion chemistry, the positive ion chemistry is more complex and has not been well characterized. Common plasma ions are those of the rare and diatomic gases, along with impurity ions such as H_2O^+ and H_3O^+. Reactions of these ions with CCl4 and SF6 generally occur rapidly by dissociative electron transfer. Some exceptions have been observed when the reactant ion contains an H-atom(s), such as the production of HCl when H_3^+ reacts with CCl_4. Since these reactions involve a fixed amount of energy, they bear similarity to photoelectron and photoelectron-photoion coincidence studies of these electron attaching gases in which only Franck-Condon transitions can occur. Comparision of product ions observed and rate coefficients gives better insights into the mechanism of the electron transfer process. Support by NSF AST-9415485 is gratefully acknowledged.

  7. Electron transfer in peptides: on the formation of silver nanoparticles.

    Science.gov (United States)

    Kracht, Sonja; Messerer, Matthias; Lang, Matthieu; Eckhardt, Sonja; Lauz, Miriam; Grobéty, Bernard; Fromm, Katharina M; Giese, Bernd

    2015-03-01

    Some microorganisms perform anaerobic mineral respiration by reducing metal ions to metal nanoparticles, using peptide aggregates as medium for electron transfer (ET). Such a reaction type is investigated here with model peptides and silver as the metal. Surprisingly, Ag(+) ions bound by peptides with histidine as the Ag(+)-binding amino acid and tyrosine as photoinducible electron donor cannot be reduced to Ag nanoparticles (AgNPs) under ET conditions because the peptide prevents the aggregation of Ag atoms to form AgNPs. Only in the presence of chloride ions, which generate AgCl microcrystals in the peptide matrix, does the synthesis of AgNPs occur. The reaction starts with the formation of 100 nm Ag@AgCl/peptide nanocomposites which are cleaved into 15 nm AgNPs. This defined transformation from large nanoparticles into small ones is in contrast to the usually observed Ostwald ripening processes and can be followed in detail by studying time-resolved UV/Vis spectra which exhibit an isosbestic point. PMID:25663127

  8. ELECTRON TRANSFER COLLISION OF NEON IONS WITH Ne IN A RF ION TRAP

    Institute of Scientific and Technical Information of China (English)

    满宝元; 王象泰; 等

    1995-01-01

    The pulsed electron beam rf ion stroage system is used to study neon ions electron transfer,The rate coefficients for electron transfer of the neon ions with the neon gas are measured.the results are better than those in other ion storage system.

  9. Effect of swift heavy ion irradiation on magnetic, surface morphology and electronic transport across CoFe/n-Si interfacial structures

    Science.gov (United States)

    Kumar, Arvind; Srivastava, P. C.

    2016-04-01

    In this study, swift heavy ion induced modifications on magnetic, morphological and electronic transport properties of CoFe/n-Si bilayers was investigated. Structural investigations have revealed the interfacial intermixing across the interface upon irradiation to result in the formation of magnetic silicide phases with enhanced crystallite size as compared to unirradiated structure. On irradiation, surface topography (from atomic force microscopy) has revealed the columnar arrangement of grains with increased value of rms surface roughness which in turn also affects the magnetic behaviour. Magnetization measurements have shown the enhancement in saturation magnetization and coercivity value with increased magnetic signal strength after irradiation. Current-voltage measurement across the irradiated CoFe/n-Si interface has shown the enhancement in current data by two orders of magnitude as compared to unirradiated interface. The observed significant changes in magnetic and transport properties for the irradiated interface has been explained on the basis of disorder/defect creation and interfacial chemistry modifications in the structure due to swift heavy ions.

  10. Allosteric control of internal electron transfer in cytochrome cd1 nitrite reductase

    DEFF Research Database (Denmark)

    Farver, Ole; Kroneck, Peter M H; Zumft, Walter G;

    2003-01-01

    Cytochrome cd1 nitrite reductase is a bifunctional multiheme enzyme catalyzing the one-electron reduction of nitrite to nitric oxide and the four-electron reduction of dioxygen to water. Kinetics and thermodynamics of the internal electron transfer process in the Pseudomonas stutzeri enzyme have...... been studied and found to be dominated by pronounced interactions between the c and the d1 hemes. The interactions are expressed both in dramatic changes in the internal electron-transfer rates between these sites and in marked cooperativity in their electron affinity. The results constitute a prime...... example of intraprotein control of the electron-transfer rates by allosteric interactions....

  11. Modular electron transfer circuits for synthetic biology: Insulation of an engineered biohydrogen pathway

    OpenAIRE

    Agapakis, Christina M; Silver, Pamela A

    2010-01-01

    Electron transfer is central to a wide range of essential metabolic pathways, from photosynthesis to fermentation. The evolutionary diversity and conservation of proteins that transfer electrons makes these pathways a valuable platform for engineered metabolic circuits in synthetic biology. Rational engineering of electron transfer pathways containing hydrogenases has the potential to lead to industrial scale production of hydrogen as an alternative source of clean fuel and experimental assay...

  12. Control of Electron Transfer from Lead-Salt Nanocrystals to TiO 2

    KAUST Repository

    Hyun, Byung-Ryool

    2011-05-11

    The roles of solvent reorganization energy and electronic coupling strength on the transfer of photoexcited electrons from PbS nanocrystals to TiO 2 nanoparticles are investigated. We find that the electron transfer depends only weakly on the solvent, in contrast to the strong dependence in the nanocrystal-molecule system. This is ascribed to the larger size of the acceptor in this system, and is accounted for by Marcus theory. The electronic coupling of the PbS and TiO 2 is varied by changing the length, aliphatic and aromatic structure, and anchor groups of the linker molecules. Shorter linker molecules consistently lead to faster electron transfer. Surprisingly, linker molecules of the same length but distinct chemical structures yield similar electron transfer rates. In contrast, the electron transfer rate can vary dramatically with different anchor groups. © 2011 American Chemical Society.

  13. Electron transfer dynamics of triphenylamine dyes bound to TiO2 nanoparticles from femtosecond stimulated Raman spectroscopy

    KAUST Repository

    Hoffman, David P.

    2013-04-11

    Interfacial electron transfer between sensitizers and semiconducting nanoparticles is a crucial yet poorly understood process. To address this problem, we have used transient absorption (TA) and femtosecond stimulated Raman spectroscopy (FSRS) to investigate the photoexcited dynamics of a series of triphenylamine-coumarin dye/TiO2 conjugates. The TA decay is multiexponential, spanning time scales from 100 fs to 100 ps, while the characteristic transient Raman spectrum of the radical cation decays biexponentially with a dominant ∼3 ps component. To explain these observations, we propose a model in which the decay of the TA is due to hot electrons migrating from surface trap states to the conduction band of TiO 2 while the decay of the Raman signature is due to internal conversion of the dye molecule. Furthermore, the S1 Raman spectrum of TPAC3, a dye wherein a vinyl group separates the triphenylamine and coumarin moieties, is similar to the S1 Raman spectrum of trans-stilbene; we conclude that their S1 potential energy surfaces and reactivity are also similar. This correlation suggests that dyes containing vinyl linkers undergo photoisomerization that competes with electron injection. © 2013 American Chemical Society.

  14. Thermodynamic, kinetic and electronic structure aspects of a charge-transfer active bichromophoric organofullerene

    Indian Academy of Sciences (India)

    K Senthil Kumar; Archita Patnaik

    2013-03-01

    Our recent work on charge transfer in the electronically push-pull dimethylaminoazobenzene-fullerene C60 donor-bridge-acceptor dyad through orbital picture revealed charge displacement from the n(N=N) (non-bonding) and (N=N) type orbitals centred on the donor part to the purely fullerene centred LUMOs and (LUMO+n) orbitals, delocalized over the entire molecule. Consequently, this investigation centres around the kinetic and thermodynamic parameters involved in the solvent polarity dependent intramolecular photo-induced electron transfer processes in the dyad, indispensable for artificial photosynthetic systems. A quasi-reversible electron transfer pathway was elucidated with electrode-specific heterogeneous electron transfer rate constants.

  15. When electron transfer meets electron transport in redox-active molecular nanojunctions.

    Science.gov (United States)

    Janin, Marion; Ghilane, Jalal; Lacroix, Jean-Christophe

    2013-02-13

    A scanning electrochemical microscope (SECM) was used to arrange two microelectrodes face-to-face separated by a micrometric gap. Polyaniline (PANI) was deposited electrochemically from the SECM tip side until it bridged the two electrodes. The junctions obtained were characterized by following the current through the PANI as a function of its electrochemical potential measured versus a reference electrode acting as a gate electrode in a solid-state transistor. PANI nanojunctions showed conductances below 100 nS in the oxidized state, indicating control of the charge transport within the whole micrometric gap by a limited number of PANI wires. The SECM configuration makes it possible to observe in the same experiment and in the same current range the electron-transfer and electron-transport processes. These two phenomena are distinguished here and characterized by following the variation of the current with the bias voltage and the scan rate. The electron-transfer current changes with the scan rate, while the charge-transport current varies with the bias voltage. Finally, despite the initially micrometric gap, a junction where the conductance is controlled by a single oligoaniline strand is achieved. PMID:23331168

  16. Nb and Ta layer doping effects on the interfacial energetics and electronic properties of LaAlO3/SrTiO3 heterostructure: first-principles analysis.

    Science.gov (United States)

    Nazir, Safdar; Behtash, Maziar; Cheng, Jianli; Luo, Jian; Yang, Kesong

    2016-01-28

    The two-dimensional electron gas (2DEG) formed at the n-type (LaO)(+1)/(TiO2)(0) interface in the polar/nonpolar LaAlO3/SrTiO3 (LAO/STO) heterostructure (HS) has emerged as a prominent research area because of its great potential for nanoelectronic applications. Due to its practical implementation in devices, desired physical properties such as high charge carrier density and mobility are vital. In this respect, 4d and 5d transition metal doping near the interfacial region is expected to tailor electronic properties of the LAO/STO HS system effectively. Herein, we studied Nb and Ta-doping effects on the energetics, electronic structure, interfacial charge carrier density, magnetic moment, and the charge confinements of the 2DEG at the n-type (LaO)(+1)/(TiO2)(0) interface of LAO/STO HS using first-principles density functional theory calculations. We found that the substitutional doping of Nb(Ta) at Ti [Nb(Ta)@Ti] and Al [Nb(Ta)@Al] sites is energetically more favorable than that at La [Nb(Ta)@La] and Sr [Nb(Ta)@Sr] sites, and under appropriate thermodynamic conditions, the changes in the interfacial energy of HS systems upon Nb(Ta)@Ti and Nb(Ta)@Al doping are negative, implying that the formation of these structures is energetically favored. Our calculations also showed that Nb(Ta)@Ti and Nb(Ta)@Al doping significantly improve the interfacial charge carrier density with respect to that of the undoped system, which is because the Nb(Ta) dopant introduces excess free electrons into the system, and these free electrons reside mainly on the Nb(Ta) ions and interfacial Ti ions. Hence, along with the Ti 3d orbitals, the Nb 4d and Ta 5d orbitals also contribute to the interfacial metallic states; accordingly, the magnetic moments on the interfacial Ti ions increase significantly. As expected, the Nb@Al and Ta@Al doped LAO/STO HS systems show higher interfacial charge carrier density than the undoped and other doped systems. In contrast, Nb@Ti and Ta@Ti doped systems may

  17. Electron transfer reactions of macrocyclic compounds of cobalt

    Energy Technology Data Exchange (ETDEWEB)

    Heckman, R.A.

    1978-08-01

    The kinetics and mechanisms of reduction of H/sub 2/O/sub 2/, Br/sub 2/, and I/sub 2/ by various macrocyclic tetraaza complexes of cobalt(II), including Vitamin B/sub 12r/, were studied. The synthetic macrocycles studied were all 14-membered rings which varied in the degree of unsaturation,substitution of methyl groups on the periphery of the ring, and substitution within the ring itself. Scavenging experiments demonstrated that the reductions of H/sub 2/O/sub 2/ produce free hydroxyl radicals only in the case of Co((14)ane)/sup 2 +/ but with none of the others. In the latter instances apparently H/sub 2/O/sub 2/ simultaneously oxidizes the metal center and the ligand. The reductions of Br/sub 2/ and I/sub 2/ produce an aquohalocobalt(III) product for all reductants (except B/sub 12r/ + Br/sub 2/, which was complicated by bromination of the corrin ring). The mechanism of halogen reduction was found to involve rate-limiting inner-sphere electron transfer from cobalt to halogen to produce a dihalide anion coordinated to the cobalt center. This intermediate subsequently decomposes in rapid reactions to halocobalt(III) and halogen atom species or reacts with another cobalt(II) center to give two molecules of halocobalt(III). The reductions of halomethylcobaloximes and related compounds and diamminecobaloxime by Cr/sup 2 +/ were also studied. The reaction was found to be biphasic in all cases with the reaction products being halomethane (for the halomethylcobaloximes), Co/sup 2 +/ (in less than 100 percent yield), a Cr(III)-dimethylglyoxime species, a small amount of free dmgH/sub 2/, and a highly-charged species containing both cobalt and chromium. The first-stage reaction occurs with a stoichiometry of 1:1 producing an intermediate with an absorption maximum at 460 nm for all starting reagents. The results were interpreted in terms of inner-sphere coordination of the cobaloxime to the Cr(II) and electron transfer through the oxime N-O bond.

  18. Thermal transfer structures coupling electronics card(s) to coolant-cooled structure(s)

    Energy Technology Data Exchange (ETDEWEB)

    David, Milnes P; Graybill, David P; Iyengar, Madhusudan K; Kamath, Vinod; Kochuparambil, Bejoy J; Parida, Pritish R; Schmidt, Roger R

    2014-12-16

    Cooling apparatuses and coolant-cooled electronic systems are provided which include thermal transfer structures configured to engage with a spring force one or more electronics cards with docking of the electronics card(s) within a respective socket(s) of the electronic system. A thermal transfer structure of the cooling apparatus includes a thermal spreader having a first thermal conduction surface, and a thermally conductive spring assembly coupled to the conduction surface of the thermal spreader and positioned and configured to reside between and physically couple a first surface of an electronics card to the first surface of the thermal spreader with docking of the electronics card within a socket of the electronic system. The thermal transfer structure is, in one embodiment, metallurgically bonded to a coolant-cooled structure and facilitates transfer of heat from the electronics card to coolant flowing through the coolant-cooled structure.

  19. DETERMINATION OF HETEROGENEOUS ELECTRON TRANSFER RATE CONSTANTS AT MICROFABRICATED IRIDIUM ELECTRODES. (R825511C022)

    Science.gov (United States)

    There has been an increasing use of both solid metal and microfabricated iridium electrodes as substrates for various types of electroanalysis. However, investigations to determine heterogeneous electron transfer rate constants on iridium, especially at an electron beam evapor...

  20. Single cell activity reveals direct electron transfer in methanotrophic consortia

    Science.gov (United States)

    McGlynn, Shawn E.; Chadwick, Grayson L.; Kempes, Christopher P.; Orphan, Victoria J.

    2015-10-01

    Multicellular assemblages of microorganisms are ubiquitous in nature, and the proximity afforded by aggregation is thought to permit intercellular metabolic coupling that can accommodate otherwise unfavourable reactions. Consortia of methane-oxidizing archaea and sulphate-reducing bacteria are a well-known environmental example of microbial co-aggregation; however, the coupling mechanisms between these paired organisms is not well understood, despite the attention given them because of the global significance of anaerobic methane oxidation. Here we examined the influence of interspecies spatial positioning as it relates to biosynthetic activity within structurally diverse uncultured methane-oxidizing consortia by measuring stable isotope incorporation for individual archaeal and bacterial cells to constrain their potential metabolic interactions. In contrast to conventional models of syntrophy based on the passage of molecular intermediates, cellular activities were found to be independent of both species intermixing and distance between syntrophic partners within consortia. A generalized model of electric conductivity between co-associated archaea and bacteria best fit the empirical data. Combined with the detection of large multi-haem cytochromes in the genomes of methanotrophic archaea and the demonstration of redox-dependent staining of the matrix between cells in consortia, these results provide evidence for syntrophic coupling through direct electron transfer.

  1. Proton-Coupled Electron Transfer: Moving Together and Charging Forward

    Energy Technology Data Exchange (ETDEWEB)

    Hammes-Schiffer, Sharon

    2015-06-25

    Proton-coupled electron transfer (PCET) is ubiquitous throughout chemistry and biology. This Perspective discusses recent advances and current challenges in the field of PCET, with an emphasis on the role of theory and computation. The fundamental theoretical concepts are summarized, and expressions for rate constants and kinetic isotope effects are provided. Computational methods for calculating reduction potentials and pKa’s for molecular electrocatalysts, as well as methods for simulating the nonadiabatic dynamics of photoinduced processes, are also described. Representative applications to PCET in solution, proteins, electrochemistry, and photoinduced processes are presented, highlighting the interplay between theoretical and experimental studies. The current challenges and suggested future directions are outlined for each type of application, concluding with an overall view to the future. The work described herein was supported by National Science Foundation Grant CHE-13-61293 (theory development), National Institutes of Health Grant GM056207 (soybean lipoxygenase), Center for Chemical Innovation of the National Science Foundation Solar Fuels Grant CHE-1305124 (cobalt catalysts), Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (nickel catalysts), and Air Force Office of Scientific Research Award No. FA9550-14-1-0295 (photoinduced PCET).

  2. Synthesis, Characterization, Photophysics and Photochemistry of Pyrylogen Electron Transfer Sensitizers

    Energy Technology Data Exchange (ETDEWEB)

    Clennan, Edward L. [University of Wyoming, Laramie; Liao, Chen [ORNL

    2014-01-01

    A series of new dicationic sensitizers that are hybrids of pyrylium salts and viologens has been synthesized. The electrochemical and photophysical properties of these "pyrylogen" sensitizers are reported in sufficient detail to allow rationale design of new photoinduced electron transfer reactions. The range of their reduction potentials (+0.37-+0.05V vs SCE) coupled with their range of singlet (48-63 kcal mol(-1)) and triplet (48-57kcalmol(-1)) energies demonstrate that they are potent oxidizing agents in both their singlet and triplet excited states, thermodynamically capable of oxidizing substrates with oxidation potentials as high as 3.1eV. The pyrylogens are synthesized in three steps from readily available starting materials in modest overall 11.4-22.3% yields. These sensitizers have the added advantages that: (1) their radical cations do not react on the CV timescale with oxygen bypassing the need to run reactions under nitrogen or argon and (2) have long wavelength absorptions between 413 and 523nm well out of the range where competitive absorbance by most substrates would cause a problem. These new sensitizers do react with water requiring special precautions to operate in a dry reaction environment.

  3. Revisiting direct electron transfer in nanostructured carbon laccase oxygen cathodes.

    Science.gov (United States)

    Adam, Catherine; Scodeller, Pablo; Grattieri, Matteo; Villalba, Matías; Calvo, Ernesto J

    2016-06-01

    The biocatalytic electroreduction of oxygen has been studied on large surface area graphite and Vulcan® carbon electrodes with adsorbed Trametes trogii laccase. The electrokinetics of the O2 reduction reaction (ORR) was studied at different electrode potentials, O2 partial pressures and concentrations of hydrogen peroxide. Even though the overpotential at 0.25 mA·cm(-2) for the ORR at T1Cu of the adsorbed laccase on carbon is 0.8 V lower than for Pt of similar geometric area, the rate of the reaction and thus the operative current density is limited by the enzyme reaction rate at the T2/T3 cluster site for the adsorbed enzyme. The transition potential for the rate determining step from the direct electron transfer (DET) to the enzyme reaction shifts to higher potentials at higher oxygen partial pressure. Hydrogen peroxide produced by the ORR on bare carbon support participates in an inhibition mechanism, with uncompetitive predominance at high H2O2 concentration, non-competitive contribution can be detected at low inhibitor concentration. PMID:26883057

  4. Effects of quantum coherence in metalloprotein electron transfer

    Science.gov (United States)

    Dorner, Ross; Goold, John; Heaney, Libby; Farrow, Tristan; Vedral, Vlatko

    2012-09-01

    Many intramolecular electron transfer (ET) reactions in biology are mediated by metal centers in proteins. This process is commonly described by a model of diffusive hopping according to the semiclassical theories of Marcus and Hopfield. However, recent studies have raised the possibility that nontrivial quantum mechanical effects play a functioning role in certain biomolecular processes. Here, we investigate the potential effects of quantum coherence in biological ET by extending the semiclassical model to allow for the possibility of quantum coherent phenomena using a quantum master equation based on the Holstein Hamiltonian. We test the model on the structurally defined chain of seven iron-sulfur clusters in nicotinamide adenine dinucleotide plus hydrogen:ubiquinone oxidoreductase (complex I), a crucial respiratory enzyme and one of the longest chains of metal centers in biology. Using experimental parameters where possible, we find that, in limited circumstances, a small quantum mechanical contribution can provide a marked increase in the ET rate above the semiclassical diffusive-hopping rate. Under typical biological conditions, our model reduces to well-known diffusive behavior.

  5. Direct electron transfer from glucose oxidase immobilized on a nano-porous glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Haghighi, Behzad, E-mail: haghighi@iasbs.ac.ir [Department of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Gava Zang, Zanjan (Iran, Islamic Republic of); Tabrizi, Mahmoud Amouzadeh [Department of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Gava Zang, Zanjan (Iran, Islamic Republic of)

    2011-11-30

    Highlights: > A direct electron transfer reaction of glucose oxidase was observed on the surface of a nano-porous glassy carbon electrode. > A pair of well-defined and reversible redox peaks was observed at the formal potential of approximately -0.439 V. > The apparent electron transfer rate constant was measured to be 5.27 s{sup -1}. > A mechanism for the observed direct electron transfer reaction was proposed, which consists of a two-electron and a two-proton transfer. - Abstract: A pair of well-defined and reversible redox peaks was observed for the direct electron transfer (DET) reaction of an immobilized glucose oxidase (GOx) on the surface of a nano-porous glassy carbon electrode at the formal potential (E{sup o}') of -0.439 V versus Ag/AgCl/saturated KCl. The electron transfer rate constant (k{sub s}) was calculated to be 5.27 s{sup -1}. The dependence of E{sup o}' on pH indicated that the direct electron transfer of the GOx was a two-electron transfer process, coupled with two-proton transfer. The results clearly demonstrate that the nano-porous glassy carbon electrode is a cost-effective and ready-to-use scaffold for the fabrication of a glucose biosensor.

  6. [Mechanisms of electron transfer to insoluble terminal acceptors in chemoorganotrophic bacteria].

    Science.gov (United States)

    Samarukha, I A

    2014-01-01

    The mechanisms of electron transfer of association of chemoorganotrophic bacteria to the anode in microbial fuel cells are summarized in the survey. These mechanisms are not mutually exclusive and are divided into the mechanisms of mediator electron transfer, mechanisms of electron transfer with intermediate products of bacterial metabolism and mechanism of direct transfer of electrons from the cell surface. Thus, electron transfer mediators are artificial or synthesized by bacteria riboflavins and phenazine derivatives, which also determine the ability of bacteria to antagonism. The microorganisms with hydrolytic and exoelectrogenic activity are involved in electron transfer mechanisms that are mediated by intermediate metabolic products, which are low molecular carboxylic acids, alcohols, hydrogen etc. The direct transfer of electrons to insoluble anode is possible due to membrane structures (cytochromes, pili, etc.). Association of microorganisms, and thus the biochemical mechanisms of electron transfer depend on the origin of the inoculum, substrate composition, mass transfer, conditions of aeration, potentials and location of electrodes and others, that are defined by technological and design parameters.

  7. Coherent transfer of light polarization to electron spins in a semiconductor

    OpenAIRE

    Kosaka, Hideo; Shigyou, Hideki; Mitsumori, Yasuyoshi; Rikitake, Yoshiaki; Imamura, Hiroshi; Kutsuwa, Takeshi; Arai, Koichiro; Edamatsu, Keiichi

    2007-01-01

    We demonstrate that the superposition of light polarization states is coherently transferred to electron spins in a semiconductor quantum well. By using time-resolved Kerr rotation we observe the initial phase of Larmor precession of electron spins whose coherence is transferred from light. To break the electron-hole spin entanglement, we utilized the big discrepancy between the transverse g-factors of electrons and light holes. The result encourages us to make a quantum media converter betwe...

  8. Enhanced Performance of Dye-Sensitized Solar Cells with Nanostructure Graphene Electron Transfer Layer

    OpenAIRE

    Chih-Hung Hsu; Jia-Ren Wu; Lung-Chien Chen; Po-Shun Chan; Cheng-Chiang Chen

    2014-01-01

    The utilization of nanostructure graphene thin films as electron transfer layer in dye-sensitized solar cells (DSSCs) was demonstrated. The effect of a nanostructure graphene thin film in DSSC structure was examined. The nanostructure graphene thin films provides a great electron transfer channel for the photogenerated electrons from TiO2 to indium tin oxide (ITO) glass. Obvious improvements in short-circuit current density of the DSSCs were observed by using the graphene electron transport l...

  9. Cooperative electrocatalytic alcohol oxidation with electron-proton-transfer mediators.

    Science.gov (United States)

    Badalyan, Artavazd; Stahl, Shannon S

    2016-07-21

    electron-proton-transfer mediators, such as TEMPO, may be used in combination with first-row transition metals, such as copper, to achieve efficient two-electron electrochemical processes, thereby introducing a new concept for the development of non-precious-metal electrocatalysts.

  10. Cooperative electrocatalytic alcohol oxidation with electron-proton-transfer mediators.

    Science.gov (United States)

    Badalyan, Artavazd; Stahl, Shannon S

    2016-07-21

    electron-proton-transfer mediators, such as TEMPO, may be used in combination with first-row transition metals, such as copper, to achieve efficient two-electron electrochemical processes, thereby introducing a new concept for the development of non-precious-metal electrocatalysts. PMID:27350245

  11. Cooperative electrocatalytic alcohol oxidation with electron-proton-transfer mediators

    Science.gov (United States)

    Badalyan, Artavazd; Stahl, Shannon S.

    2016-07-01

    electron-proton-transfer mediators, such as TEMPO, may be used in combination with first-row transition metals, such as copper, to achieve efficient two-electron electrochemical processes, thereby introducing a new concept for the development of non-precious-metal electrocatalysts.

  12. An excellent candidate for largely reducing interfacial thermal resistance: a nano-confined mass graded interface

    Science.gov (United States)

    Zhou, Yanguang; Zhang, Xiaoliang; Hu, Ming

    2016-01-01

    Pursuing extremely low interfacial thermal resistance has long been the task of many researchers in the area of nano-scale heat transfer, in particular pertaining to improve heat dissipation performance in electronic cooling. While it is well known and documented that confining a macroscopic third layer between two dissimilar materials usually increases the overall interfacial thermal resistance, no research has realized the fundamental decrease in resistance so far. By performing nonequilibrium molecular dynamics simulations, we report that the overall interfacial thermal resistance can be reduced by 6 fold by confining mass graded materials with thickness of the order of nanometers. As comparison we also studied the thermal transport across the perfectly abrupt interface and the widely used alloyed (rough) interface, which shows an opposing and significantly large increase in the overall thermal resistance. With the help of frequency dependent interfacial thermal conductance and wave packet dynamics simulation, different mechanisms governing the heat transfer across these three types of interfaces are identified. It is found that for the rough interface there are two different regimes of interfacial heat transfer, which originates from the competition between phonon scattering and the thickness of the interface. The mechanism of dramatically improved interfacial heat transfer across the nano-confined mass graded interface resides in the minor phonon reflection when the phonons first reach the mass graded area and the rare occurrence of phonon scattering in the subsequent interior region. The phonons are found to be gradually truncated by the geometric interfaces and can travel through the mass graded layer with a high transmission coefficient, benefited from the small mass mismatch between two neighboring layers in the interfacial region. Our findings provide deep insight into the phonon transport across nano-confined mass graded layers and also offer significant

  13. Electron-transfer acceleration investigated by time resolved infrared spectroscopy.

    Science.gov (United States)

    Vlček, Antonín; Kvapilová, Hana; Towrie, Michael; Záliš, Stanislav

    2015-03-17

    Ultrafast electron transfer (ET) processes are important primary steps in natural and artificial photosynthesis, as well as in molecular electronic/photonic devices. In biological systems, ET often occurs surprisingly fast over long distances of several tens of angströms. Laser-pulse irradiation is conveniently used to generate strongly oxidizing (or reducing) excited states whose reactions are then studied by time-resolved spectroscopic techniques. While photoluminescence decay and UV-vis absorption supply precise kinetics data, time-resolved infrared absorption (TRIR) and Raman-based spectroscopies have the advantage of providing additional structural information and monitoring vibrational energy flows and dissipation, as well as medium relaxation, that accompany ultrafast ET. We will discuss three cases of photoinduced ET involving the Re(I)(CO)3(N,N) moiety (N,N = polypyridine) that occur much faster than would be expected from ET theories. [Re(4-N-methylpyridinium-pyridine)(CO)3(N,N)](2+) represents a case of excited-state picosecond ET between two different ligands that remains ultrafast even in slow-relaxing solvents, beating the adiabatic limit. This is caused by vibrational/solvational excitation of the precursor state and participation of high-frequency quantum modes in barrier crossing. The case of Re-tryptophan assemblies demonstrates that excited-state Trp → *Re(II) ET is accelerated from nanoseconds to picoseconds when the Re(I)(CO)3(N,N) chromophore is appended to a protein, close to a tryptophan residue. TRIR in combination with DFT calculations and structural studies reveals an interaction between the N,N ligand and the tryptophan indole. It results in partial electronic delocalization in the precursor excited state and likely contributes to the ultrafast ET rate. Long-lived vibrational/solvational excitation of the protein Re(I)(CO)3(N,N)···Trp moiety, documented by dynamic IR band shifts, could be another accelerating factor. The last

  14. Revising Intramolecular Photoinduced Electron Transfer (PET) from First-Principles.

    Science.gov (United States)

    Escudero, Daniel

    2016-09-20

    Photoinduced electron transfer (PET) plays relevant roles in many areas of chemistry, including charge separation processes in photovoltaics, natural and artificial photosynthesis, and photoluminescence sensors and switches. As in many other photochemical scenarios, the structural and energetic factors play relevant roles in determining the rates and efficiencies of PET and its competitive photodeactivation processes. Particularly, in the field of fluorescent sensors and switches, intramolecular PET is believed (in many cases without compelling experimental proof) to be responsible of the quench of fluorescence. There is an increasing experimental interest in fluorophore's molecular design and on achieving optimal excitation/emission spectra, excitation coefficients, and fluorescence quantum yields (importantly for bioimaging purposes), but less efforts are devoted to fundamental mechanistic studies. In this Account, I revise the origins of the fluorescence quenching in some of these systems with state-of-the-art quantum chemical tools. These studies go beyond the common strategy of analyzing frontier orbital energy diagrams and performing PET thermodynamics calculations. Instead, the potential energy surfaces (PESs) of the lowest-lying excited states are explored with time-dependent density functional theory (TD-DFT) and complete active space self-consistent field (CASSCF) calculations and the radiative and nonradiative decay rates from the involved excited states are computed from first-principles using a thermal vibration correlation function formalism. With such a strategy, this work reveals the real origins of the fluorescence quenching, herein entitled as dark-state quenching. Dark states (those that do not absorb or emit light) are often elusive to experiments and thus, computational investigations can provide novel insights into the actual photodeactivation mechanisms. The success of the dark-state quenching mechanism is demonstrated for a wide variety of

  15. Revising Intramolecular Photoinduced Electron Transfer (PET) from First-Principles.

    Science.gov (United States)

    Escudero, Daniel

    2016-09-20

    Photoinduced electron transfer (PET) plays relevant roles in many areas of chemistry, including charge separation processes in photovoltaics, natural and artificial photosynthesis, and photoluminescence sensors and switches. As in many other photochemical scenarios, the structural and energetic factors play relevant roles in determining the rates and efficiencies of PET and its competitive photodeactivation processes. Particularly, in the field of fluorescent sensors and switches, intramolecular PET is believed (in many cases without compelling experimental proof) to be responsible of the quench of fluorescence. There is an increasing experimental interest in fluorophore's molecular design and on achieving optimal excitation/emission spectra, excitation coefficients, and fluorescence quantum yields (importantly for bioimaging purposes), but less efforts are devoted to fundamental mechanistic studies. In this Account, I revise the origins of the fluorescence quenching in some of these systems with state-of-the-art quantum chemical tools. These studies go beyond the common strategy of analyzing frontier orbital energy diagrams and performing PET thermodynamics calculations. Instead, the potential energy surfaces (PESs) of the lowest-lying excited states are explored with time-dependent density functional theory (TD-DFT) and complete active space self-consistent field (CASSCF) calculations and the radiative and nonradiative decay rates from the involved excited states are computed from first-principles using a thermal vibration correlation function formalism. With such a strategy, this work reveals the real origins of the fluorescence quenching, herein entitled as dark-state quenching. Dark states (those that do not absorb or emit light) are often elusive to experiments and thus, computational investigations can provide novel insights into the actual photodeactivation mechanisms. The success of the dark-state quenching mechanism is demonstrated for a wide variety of

  16. 36 CFR 1235.50 - What specifications and standards for transfer apply to electronic records?

    Science.gov (United States)

    2010-07-01

    ... organization. Acceptable transfer formats include the Geography Markup Language (GML) as defined by the Open... standards for transfer apply to electronic records? 1235.50 Section 1235.50 Parks, Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION RECORDS MANAGEMENT TRANSFER OF RECORDS TO...

  17. The second R. A. Robinson Memorial Lecture. Electron, proton and related transfers

    OpenAIRE

    Marcus, Rudolph A.

    1982-01-01

    Past and current developments in electron and proton transfer and in related fields are described. Broad classes of reactions have been considered from a unified viewpoint which offers a variety of experimental predictions. This introductory lecture considers various aspects of this many-faceted field. A simple equation is given for a highly exothermic electron-transfer reaction.

  18. 41 CFR 102-118.70 - Must my agency make all payments via electronic funds transfer?

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Must my agency make all payments via electronic funds transfer? 102-118.70 Section 102-118.70 Public Contracts and Property... Services § 102-118.70 Must my agency make all payments via electronic funds transfer? Yes, under 31...

  19. Aminotroponiminates as tunable, redox-active ligands: reversible single electron transfer and reductive dimerisation.

    Science.gov (United States)

    Lichtenberg, C; Krummenacher, I

    2016-08-21

    Aminotroponiminates (atis) are shown to be redox-active ligands. Under strongly reducing conditions, the result of electron transfer can be controlled by the choice of the metal bound to the ati ligand. Either reversible electron transfer or a reductively induced dimerisation is observed. The latter reaction is (regio- and diastereo-) selective and chemically reversible. PMID:27452905

  20. Coherent phonons in CdSe quantum dots triggered by ultrafast electron transfer

    Directory of Open Access Journals (Sweden)

    Wachtveitl J.

    2013-03-01

    Full Text Available The origin of coherent oscillations in CdSe quantum dots and in the CdSe/methylviologen electron transfer system is studied. In CdSe/methylviologen coherent phonons are triggered by the electron transfer from the quantum dot to methylviologen.

  1. Ultrafast Spectroscopic Signatures of Coherent Electron-Transfer Mechanisms in a Transition Metal Complex.

    Science.gov (United States)

    Guo, Zhenkun; Giokas, Paul G; Cheshire, Thomas P; Williams, Olivia F; Dirkes, David J; You, Wei; Moran, Andrew M

    2016-07-28

    The prevalence of ultrafast electron-transfer processes in light-harvesting materials has motivated a deeper understanding of coherent reaction mechanisms. Kinetic models based on the traditional (equilibrium) form of Fermi's Golden Rule are commonly employed to understand photoinduced electron-transfer dynamics. These models fail in two ways when the electron-transfer process is fast compared to solvation dynamics and vibrational dephasing. First, electron-transfer dynamics may be accelerated if the photoexcited wavepacket traverses the point of degeneracy between donor and acceptor states in the solvent coordinate. Second, traditional kinetic models fail to describe electron-transfer transitions that yield products which undergo coherent nuclear motions. We address the second point in this work. Transient absorption spectroscopy and a numerical model are used to investigate coherent back-electron-transfer mechanisms in a transition metal complex composed of titanium and catechol, [Ti(cat)3](2-). The transient absorption experiments reveal coherent wavepacket motions initiated by the back-electron-transfer process. Model calculations suggest that the vibrationally coherent product states may originate in either vibrational populations or coherences of the reactant. That is, vibrational coherence may be produced even if the reactant does not undergo coherent nuclear motions. The analysis raises a question of broader significance: can a vibrational population-to-coherence transition (i.e., a nonsecular transition) accelerate electron-transfer reactions even when the rate is slower than vibrational dephasing? PMID:27362388

  2. 76 FR 67153 - Federal Acquisition Regulation; Submission for OMB Review; Payment by Electronic Fund Transfer

    Science.gov (United States)

    2011-10-31

    ... published in the Federal Register at 76 FR 35219, on June 16, 2011. No comments were received. Public... would enable the Government to make payments under the contract by electronic fund transfer (EFT). The... Regulation; Submission for OMB Review; Payment by Electronic Fund Transfer AGENCY: Department of Defense...

  3. A semiclassical theory of electron transfer reactions in Condon approximation and beyond

    DEFF Research Database (Denmark)

    Kuznetsov, A. M.; Sokolov, V. V.; Ulstrup, Jens

    2001-01-01

    of adiabatic electron transfer reactions is elaborated. A new formula for the transition probability of non-adiabatic electron transfer reactions is obtained in an improved Condon approximation A regular method for the calculation of non-Condon corrections is suggested. The importance of these effects for some...

  4. 27 CFR 53.158 - Payment of tax by electronic fund transfer.

    Science.gov (United States)

    2010-04-01

    ... electronic fund transfer. 53.158 Section 53.158 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) FIREARMS MANUFACTURERS EXCISE TAXES... Taxes § 53.158 Payment of tax by electronic fund transfer. (a) In general. For return periods...

  5. Role of ligand substitution on long-range electron transfer in azurins

    DEFF Research Database (Denmark)

    Farver, O; Jeuken, L J; Canters, G W;

    2000-01-01

    , becoming threefold faster than that observed in the native protein. Activation parameters for all these electron-transfer processes were determined and combined with data from earlier studies on intramolecular electron transfer in wild-type and single-site-mutated azurins. A linear relationship between...

  6. Photoinduced energy and electron transfer in rubrene-benzoquinone and rubrene-porphyrin systems

    KAUST Repository

    Khan, Jafar Iqbal

    2014-11-01

    Excited-state electron and energy transfer from singlet excited rubrene (Ru) to benzoquinone (BQ) and tetra-(4-aminophenyl) porphyrin (TAPP) were investigated by steady-state absorption and emission, time-resolved transient absorption, and femtosecond (fs)-nanosecond (ns) fluorescence spectroscopy. The low reduction potential of BQ provides the high probability of electron transfer from the excited Ru to BQ. Steady-state and time-resolved results confirm such an excited electron transfer scenario. On the other hand, strong spectral overlap between the emission of Ru and absorption of TAPP suggests that energy transfer is a possible deactivation pathway of the Ru excited state.

  7. Superexchange coupling and electron transfer in globular proteins via polaron excitations.

    Science.gov (United States)

    Chuev, G N; Lakhno, V D; Ustitnin, M N

    2000-06-01

    The polaron approach is used to treat long-range electron transfersbetween globular proteins. A rate expression for the polaron transfer model is given along with a description of appropriate conditions forits use. Assuming that electrons transfer via a superexchange couplingdue to a polaron excitation, we have estimated the distance dependenceof the rate constant for the self-exchange reactions between globularproteins in solutions. The distance dependence of the polaron coupling andsolvent reorganization energy are provided as a basis forunderstanding and interpreting a long-range electron transfer experiment.The difficulties and problems of the polaron treatment of long-rangeelectron transfers are discussed, and suggestions for new experimentsare made.

  8. Remote interfacial dipole scattering and electron mobility degradation in Ge field-effect transistors with GeO x /Al2O3 gate dielectrics

    Science.gov (United States)

    Wang, Xiaolei; Xiang, Jinjuan; Wang, Shengkai; Wang, Wenwu; Zhao, Chao; Ye, Tianchun; Xiong, Yuhua; Zhang, Jing

    2016-06-01

    Remote Coulomb scattering (RCS) on electron mobility degradation is investigated experimentally in Ge-based metal–oxide–semiconductor field-effect-transistors (MOSFETs) with GeO x /Al2O3 gate stacks. It is found that the mobility increases with greater GeO x thickness (7.8–20.8 Å). The physical origin of this mobility dependence on GeO x thickness is explored. The following factors are excluded: Coulomb scattering due to interfacial traps at GeO x /Ge, phonon scattering, and surface roughness scattering. Therefore, the RCS from charges in gate stacks is studied. The charge distributions in GeO x /Al2O3 gate stacks are evaluated experimentally. The bulk charges in Al2O3 and GeO x are found to be negligible. The density of the interfacial charge is  +3.2  ×  1012 cm‑2 at the GeO x /Ge interface and  ‑2.3  ×  1012 cm‑2 at the Al2O3/GeO x interface. The electric dipole at the Al2O3/GeO x interface is found to be  +0.15 V, which corresponds to an areal charge density of 1.9  ×  1013 cm‑2. The origin of this mobility dependence on GeO x thickness is attributed to the RCS due to the electric dipole at the Al2O3/GeO x interface. This remote dipole scattering is found to play a significant role in mobility degradation. The discovery of this new scattering mechanism indicates that the engineering of the Al2O3/GeO x interface is key for mobility enhancement and device performance improvement. These results are helpful for understanding and engineering Ge mobility enhancement.

  9. Photoinduced electron transfer in perylene-TiO2 nanoassemblies.

    Science.gov (United States)

    Llansola-Portoles, Manuel J; Bergkamp, Jesse J; Tomlin, John; Moore, Thomas A; Kodis, Gerdenis; Moore, Ana L; Cosa, Gonzalo; Palacios, Rodrigo E

    2013-01-01

    The photosensitization effect of three perylene dye derivatives on titanium dioxide nanoparticles (TiO2 NPs) has been investigated. The dyes used, 1,7-dibromoperylene-3,4,9,10-tetracarboxy dianhydride (1), 1,7-dipyrrolidinylperylene-3,4,9,10-tetracarboxy dianhydride (2) and 1,7-bis(4-tert-butylphenyloxy)perylene-3,4,9,10-tetracarboxy dianhydride (3) have in common bisanhydride groups that convert into TiO2 binding groups upon hydrolysis. The different substituents on the bay position of the dyes enable tuning of their redox properties to yield significantly different driving forces for photoinduced electron transfer (PeT). Recently developed TiO2 NPs having a small average size and a narrow distribution (4 ± 1 nm) are used in this work to prepare the dye-TiO2 systems under study. Whereas successful sensitization was obtained with 1 and 2 as evidenced by steady-state spectral shifts and transient absorption results, no evidence for the attachment of 3 to TiO2 was observed. The comparison of the rates of PeT (kPeT ) for 1- and 2-TiO2 systems studied in this work with those obtained for previously reported analogous systems, having TiO2 NPs covered by a surfactant layer (Hernandez et al. [2012] J. Phys. Chem. B., 117, 4568-4581), indicates that kPeT for the former systems is slower than that for the later. These results are interpreted in terms of the different energy values of the conduction band edge in each system. PMID:23742178

  10. Electron-phonon energy transfer in hot-carrier solar cells

    OpenAIRE

    Luque López, Antonio; Martí Vega, Antonio

    2010-01-01

    Hot-carrier solar cells may yield very high efficiency if the heat transfer from electrons to phonons is low enough. In this paper we calculate this heat transfer for the two inelastic mechanisms known to limit the electric conductivity: the multi-valley scattering in non-polar semiconductors and the coupling of electrons to longitudinal optical phonons in polar semiconductors. Heat transfer is ruled by matrix elements deduced from electric conductivity measurements. The cell power extracted ...

  11. Probing the nature of electron transfer in metalloproteins on graphene-family materials as nanobiocatalytic scaffold using electrochemistry

    International Nuclear Information System (INIS)

    Graphene-based nanomaterials have shown great promise not only in nanoelectronics due to ultrahigh electron mobility but also as biocatalytic scaffolds owing to irreversible protein surface adsorption and facilitating direct electron transfer. In this work, we synthesized stable dispersions of graphene using liquid-phase exfoliation approach based on non-covalent interactions between graphene and 1-pyrenesulfonic acid sodium salt (Py–1SO3), 1-pyrenemethylamine salt (Py − Me-NH2) and Pluronic® P-123 surfactant using only water as solvent compatible with biomolecules. The resulting graphene nanoplatelets (Gr-LPE) are characterized by a combination of analytical (microscopy and spectroscopy) techniques revealing mono- to few-layer graphene displaying that the exfoliation efficiency strongly depends upon the type of pyrene-based salts and organic surfactants. Moreover being completely water-based approach, we build robust nanoscaffolds of graphene-family nanomaterials (GFNs) namely, monolayer graphene, Gr-LPE (the one prepared with Pluronic® P-123), graphene oxide (GO) and its reduced form (rGO) on glassy carbon electrode surface with three important metalloproteins include cytochrome c (Cyt c) [for electron transfer], myoglobin (Mb) [for oxygen storage] and horseradish peroxidase (HRP) [for catalyzing the biochemical reaction]. In order to demonstrate the nanobiocatalytical activity of these proteins, we used electrochemical interfacial direct electron transfer (DET) kinetics and attempt to determine the rate constant (kET) using two different analytical approaches namely, linear sweep voltammetry and Laviron’s theory. We elucidated that all of the metalloproteins retain their structural integrity (secondary structure) upon forming mixtures with GFNs confirmed through optical and vibrational spectroscopy and biological activity using electrochemistry. Among the GFNs studied, Gr-LPE, GO and rGO support the efficient electrical wiring of the redox centers (with

  12. Probing the nature of electron transfer in metalloproteins on graphene-family materials as nanobiocatalytic scaffold using electrochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Sanju, E-mail: sanju.gupta@wku.edu [Department of Physics and Astronomy, Western Kentucky University, 1906 College Heights Blvd. Bowling Green, KY 42101-3576 (United States); Biotechnology Center, Western Kentucky University, 1906 College Heights Blvd. Bowling Green, KY 42101-3576 (United States); Irihamye, Aline [Gatton Academy of Mathematics and Science in Kentucky, Western Kentucky University, 1906 College Heights Blvd. Bowling Green, KY 42101-3576 (United States)

    2015-03-15

    Graphene-based nanomaterials have shown great promise not only in nanoelectronics due to ultrahigh electron mobility but also as biocatalytic scaffolds owing to irreversible protein surface adsorption and facilitating direct electron transfer. In this work, we synthesized stable dispersions of graphene using liquid-phase exfoliation approach based on non-covalent interactions between graphene and 1-pyrenesulfonic acid sodium salt (Py–1SO{sub 3}), 1-pyrenemethylamine salt (Py − Me-NH{sub 2}) and Pluronic{sup ®} P-123 surfactant using only water as solvent compatible with biomolecules. The resulting graphene nanoplatelets (Gr-LPE) are characterized by a combination of analytical (microscopy and spectroscopy) techniques revealing mono- to few-layer graphene displaying that the exfoliation efficiency strongly depends upon the type of pyrene-based salts and organic surfactants. Moreover being completely water-based approach, we build robust nanoscaffolds of graphene-family nanomaterials (GFNs) namely, monolayer graphene, Gr-LPE (the one prepared with Pluronic{sup ®} P-123), graphene oxide (GO) and its reduced form (rGO) on glassy carbon electrode surface with three important metalloproteins include cytochrome c (Cyt c) [for electron transfer], myoglobin (Mb) [for oxygen storage] and horseradish peroxidase (HRP) [for catalyzing the biochemical reaction]. In order to demonstrate the nanobiocatalytical activity of these proteins, we used electrochemical interfacial direct electron transfer (DET) kinetics and attempt to determine the rate constant (k{sub ET}) using two different analytical approaches namely, linear sweep voltammetry and Laviron’s theory. We elucidated that all of the metalloproteins retain their structural integrity (secondary structure) upon forming mixtures with GFNs confirmed through optical and vibrational spectroscopy and biological activity using electrochemistry. Among the GFNs studied, Gr-LPE, GO and rGO support the efficient electrical

  13. Probing the nature of electron transfer in metalloproteins on graphene-family materials as nanobiocatalytic scaffold using electrochemistry

    Directory of Open Access Journals (Sweden)

    Sanju Gupta

    2015-03-01

    Full Text Available Graphene-based nanomaterials have shown great promise not only in nanoelectronics due to ultrahigh electron mobility but also as biocatalytic scaffolds owing to irreversible protein surface adsorption and facilitating direct electron transfer. In this work, we synthesized stable dispersions of graphene using liquid-phase exfoliation approach based on non-covalent interactions between graphene and 1-pyrenesulfonic acid sodium salt (Py–1SO3, 1-pyrenemethylamine salt (Py − Me-NH2 and Pluronic® P-123 surfactant using only water as solvent compatible with biomolecules. The resulting graphene nanoplatelets (Gr_LPE are characterized by a combination of analytical (microscopy and spectroscopy techniques revealing mono- to few-layer graphene displaying that the exfoliation efficiency strongly depends upon the type of pyrene-based salts and organic surfactants. Moreover being completely water-based approach, we build robust nanoscaffolds of graphene-family nanomaterials (GFNs namely, monolayer graphene, Gr_LPE (the one prepared with Pluronic® P-123, graphene oxide (GO and its reduced form (rGO on glassy carbon electrode surface with three important metalloproteins include cytochrome c (Cyt c [for electron transfer], myoglobin (Mb [for oxygen storage] and horseradish peroxidase (HRP [for catalyzing the biochemical reaction]. In order to demonstrate the nanobiocatalytical activity of these proteins, we used electrochemical interfacial direct electron transfer (DET kinetics and attempt to determine the rate constant (kET using two different analytical approaches namely, linear sweep voltammetry and Laviron’s theory. We elucidated that all of the metalloproteins retain their structural integrity (secondary structure upon forming mixtures with GFNs confirmed through optical and vibrational spectroscopy and biological activity using electrochemistry. Among the GFNs studied, Gr-LPE, GO and rGO support the efficient electrical wiring of the redox centers

  14. Interfacial charge-transfer transitions and reorganization energies in sulfur-bridged TiO2-x-benzenedithiol complexes (x: o, m, p).

    Science.gov (United States)

    Fujisawa, Jun-Ichi; Muroga, Ryuki; Hanaya, Minoru

    2016-08-10

    Surface complexes formed between TiO2 nanoparticles and enediol compounds such as 1,2-benzenediol (o-BDO) via Ti-O-C linkages show absorption of visible light due to interfacial charge-transfer (ICT) transitions. The ICT transitions take place from the π-conjugated systems to TiO2. Recently, we reported a surface complex formed between TiO2 and 1,2-benzenedithiol (o-BDT) via Ti-S-C linkages. This sulfur-bridged complex shows ICT transitions from the sulfur bridging atoms to TiO2. Interestingly, it was demonstrated that the ICT transitions in the sulfur-bridged TiO2-o-BDT complex induce photoelectric conversion more efficiently than those in the oxygen-bridged TiO2-o-BDO complex. This result suggests that carrier recombination is suppressed with the sulfur bridging atoms. In this paper, we examine ICT transitions and reorganization energies in the sulfur-bridged TiO2-x-BDT complexes (x: o, m, p) and compare them with those in the oxygen-bridged TiO2-x-BDO complexes. The estimated reorganization energies for the sulfur-bridged TiO2-x-BDT complexes (x: o, m, p) are much smaller than those for the oxygen-bridged TiO2-x-BDO ones. Based on the Marcus theory, the small reorganization energy calculated for the TiO2-o-BDT complex, which is less than half of that for the TiO2-o-BDO complex, increases the activation energy of carrier recombination. The small reorganization energy is attributed to the characteristic distribution of the highest occupied molecular orbital (HOMO) on the sulfur-bridging atoms in the TiO2-o-BDT complex, which inhibits structural changes in the benzene ring in the ICT excited state. Our work reveals the important role of the sulfur bridging atoms in the suppression of carrier recombination. PMID:27456170

  15. A Comparison of Electron-Transfer Dynamics inIonic Liquids and Neutral Solvents

    Energy Technology Data Exchange (ETDEWEB)

    Wishart J. F.; Lee, H.Y.; Issa, J.B.; Isied, S.S.; Castner, Jr., E.W.; Pan, Y.; Hussey, C.L.; Lee, K.S.

    2012-03-01

    The effect of ionic liquids on photoinduced electron-transfer reactions in a donor-bridge-acceptor system is examined for two ionic liquid solvents, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide and tributylmethylammonium bis(trifluoromethylsulfonyl)amide. The results are compared with those for the same system in methanol and acetonitrile solution. Electron-transfer rates were measured using time-resolved fluorescence quenching for the donor-bridge-acceptor system comprising a 1-N,1-N-dimethylbenzene-1,4-diamine donor, a proline bridge, and a coumarin 343 acceptor. The photoinduced electron-transfer processes are in the inverted regime (-{Delta}G > {lambda}) in all four solvents, with driving forces of -1.6 to -1.9 eV and estimated reorganization energies of about 1.0 eV. The observed electron-transfer kinetics have broadly distributed rates that are generally slower in the ionic liquids compared to the neutral solvents, which also have narrower rate distributions. To describe the broad distributions of electron-transfer kinetics, we use two different models: a distribution of exponential lifetimes and a discrete sum of exponential lifetimes. Analysis of the donor-acceptor electronic coupling shows that for ionic liquids this intramolecular electron-transfer reaction should be treated using a solvent-controlled electron-transfer model.

  16. Characterization and modelling of interspecies electron transfer mechanisms and microbial community dynamics of a syntrophic association

    DEFF Research Database (Denmark)

    Nagarajan, Harish; Embree, Mallory; Rotaru, Amelia-Elena;

    2013-01-01

    complex nutritional and energetic dependencies and their functioning. Here we apply a multi-omic modelling workflow that combines genomic, transcriptomic and physiological data with genome-scale models to investigate dynamics and electron flow mechanisms in the syntrophic association of Geobacter...... metallireducens and Geobacter sulfurreducens. Genome-scale modelling of direct interspecies electron transfer reveals insights into the energetics of electron transfer mechanisms. While G. sulfurreducens adapts to rapid syntrophic growth by changes at the genomic and transcriptomic level, G. metallireducens...

  17. Excess-Electron Transfer in DNA by a Fluctuation-Assisted Hopping Mechanism.

    Science.gov (United States)

    Lin, Shih-Hsun; Fujitsuka, Mamoru; Majima, Tetsuro

    2016-02-01

    The dynamics of excess-electron transfer in DNA has attracted the attention of scientists from all kinds of research fields because of its importance in biological processes. To date, several studies on excess-electron transfer in consecutive adenine (A):thymine (T) sequences in donor-DNA-acceptor systems have been published. However, the reported excess-electron transfer rate constants for consecutive T's are in the range of 10(10)-10(11) s(-1) depending on the photosensitizing electron donor, which provides various driving forces for excess-electron injection into DNA. In this study, we employed a strongly electron-donating photosensitizer, a dimer of 3,4-ethylenedioxythiophene (2E), and an electron acceptor, diphenylacetylene (DPA), to synthesize a series of modified DNA oligomers (2-Tn, n = 3-6) in order to investigate the excess-electron transfer dynamics in these donor-DNA-acceptor systems using femtosecond laser flash photolysis. The relation between the free energy change for charge injection and the excess-electron transfer rate among consecutive T's provided an intrinsic excess-electron hopping rate constant of (3.8 ± 1.5) × 10(10) s(-1) in the DNA, which is consistent with the fluctuation frequency of the DNA sugar backbone and bases (3.3 × 10(10) s(-1)). Thus, we discuss the effect of structural fluctuations on the excess-electron hopping in DNA. PMID:26741048

  18. Studies on electron transfer reactions of Keggin-type mixed addenda heteropolytungstovanadophosphates with NADH

    Indian Academy of Sciences (India)

    Ponnusamy Sami; Kasi Rajasekaran

    2009-03-01

    The coenzyme nicotinamide adenine dinucleotide (NADH) undergoes facile electron transfer reaction with vanadium (V) substituted Keggin-type heteropolyanions (HPA) [PVVW11O40]4- (PV1) and [PV$^{V}_{2}$W10O40]5- (PV2) in aqueous phosphate buffer of pH 6 at ambient temperature. Electrochemical and optical studies show that the stoichiometry of the reaction is 1 : 2 (NADH : HPA). EPR and optical studies show that HPA act as one electron acceptor and the products of electron transfer reactions are one electron reduced heteropoly blues (HPB), viz. [PVIVW11O40]5- and [PVIVVVW10O40]6-. Oxygraph measurements show that there is no uptake of molecular oxygen during the course of reaction. The reaction proceeds through multi-step electron-proton-electron transfer mechanism, with rate limiting initial one electron transfer from NADH to HPA by outer sphere electron transfer process. Bimolecular rate constant for electron transfer reaction between NADH and PV2 in phosphate buffer of pH = 6 has been determined spectrophotometrically.

  19. How fast is optically induced electron transfer in organic mixed valence systems?

    Science.gov (United States)

    Lambert, C; Moos, M; Schmiedel, A; Holzapfel, M; Schäfer, J; Kess, M; Engel, V

    2016-07-28

    The rate of thermally induced electron transfer in organic mixed valence compounds has thoroughly been investigated by e.g. temperature dependent ESR spectroscopy. However, almost nothing is known about the dynamics of optically induced electron transfer processes in such systems. Therefore, we investigated these processes in mixed valence compounds based on triphenylamine redox centres bridged by conjugated spacers by NIR transient absorption spectroscopy with fs-time resolution. These experiments revealed an internal conversion (IC) process to be on the order of 50-200 fs which is equivalent to the back electron transfer after optical excitation into the intervalence charge transfer band. This IC is followed by ultrafast cooling to the ground state within 1 ps. Thus, in the systems investigated optically induced electron transfer is about 3-4 orders of magnitude faster than thermally induced ET. PMID:27376572

  20. Coherent transfer of light polarization to electron spins in a semiconductor.

    Science.gov (United States)

    Kosaka, Hideo; Shigyou, Hideki; Mitsumori, Yasuyoshi; Rikitake, Yoshiaki; Imamura, Hiroshi; Kutsuwa, Takeshi; Arai, Koichiro; Edamatsu, Keiichi

    2008-03-01

    We demonstrate that the superposition of light polarization states is coherently transferred to electron spins in a semiconductor quantum well. By using time-resolved Kerr rotation, we observe the initial phase of Larmor precession of electron spins whose coherence is transferred from light. To break the electron-hole spin entanglement, we utilized the big discrepancy between the transverse g factors of electrons and light-holes. The result encourages us to make a quantum media converter between flying photon qubits and stationary electron-spin qubits in semiconductors. PMID:18352739

  1. Enhanced Performance of Dye-Sensitized Solar Cells with Nanostructure Graphene Electron Transfer Layer

    Directory of Open Access Journals (Sweden)

    Chih-Hung Hsu

    2014-01-01

    Full Text Available The utilization of nanostructure graphene thin films as electron transfer layer in dye-sensitized solar cells (DSSCs was demonstrated. The effect of a nanostructure graphene thin film in DSSC structure was examined. The nanostructure graphene thin films provides a great electron transfer channel for the photogenerated electrons from TiO2 to indium tin oxide (ITO glass. Obvious improvements in short-circuit current density of the DSSCs were observed by using the graphene electron transport layer modified photoelectrode. The graphene electron transport layer reduces effectively the back reaction in the interface between the ITO transparent conductive film and the electrolyte in the DSSC.

  2. The effect of intramolecular quantum modes on free energy relationships for electron transfer reactions

    DEFF Research Database (Denmark)

    Ulstrup, Jens; Jortner, Joshua

    1975-01-01

    A general quantum mechanical description of exothermic electron transfer reactions is formulated by treating such reactions as the nonradiative decay of a ''supermolecule'' consisting of the electron donor, the electron acceptor, and the polar solvent. In particular, the role of the high-frequenc...

  3. Long-range intramolecular electron transfer in aromatic radical anions and binuclear transition metal complexes

    DEFF Research Database (Denmark)

    Kuznetsov, A. M.; Ulstrup, Jens

    1981-01-01

    Intramolecular electron transfer (ET) over distances up to about 10 Å between states in which the electron is localized on donor and acceptor groups by interaction with molecular or external solvent nuclear motion occurs, in particular, in two classes of systems. The excess electron in anionic ra...

  4. Calculation of electron transfer in ruthenium-modified derivatives of cytochrome b562

    Science.gov (United States)

    Glukhova, O. E.; Prytkova, T. R.; Shunaev, V. V.

    2016-03-01

    Quantitative theoretical studies of long-range electron transfer are still quite rare and require further development of computational methods for the analysis of such reactions. We considered the electron transfer reaction in rutenium-modified derivatives of cytochrome b562 with advanced modeling techniques. We conducted a series of ab initio calculations of the donor/acceptor interaction in protein fragments and compared the calculated electron velocity with available experimental data. Our approach takes into account the co-factor of the electronic structure and the impact of the solution on a donor-acceptor interaction. This allows us to predict the absolute values of the electron transfer rate unlike other computational methods which provide only qualitative results. Our estimates with good accuracy repeat the experimental values of electron transfer rate. It was found that the electron transfer in certain derivatives of cytochrome b562 is mainly caused by "shortcut" conformations in which the donor/acceptor interactions are mediated by the interaction of Ru-unbound ligands with groups of the protein surface. We argue that a quantitative theoretical analysis is essential for detailed understanding of electron transfer in proteins and mechanisms of biological redox reactions.

  5. Intermolecular electron transfer from intramolecular excitation and coherent acoustic phonon generation in a hydrogen-bonded charge-transfer solid.

    Science.gov (United States)

    Rury, Aaron S; Sorenson, Shayne; Dawlaty, Jahan M

    2016-03-14

    Organic materials that produce coherent lattice phonon excitations in response to external stimuli may provide next generation solutions in a wide range of applications. However, for these materials to lead to functional devices in technology, a full understanding of the possible driving forces of coherent lattice phonon generation must be attained. To facilitate the achievement of this goal, we have undertaken an optical spectroscopic study of an organic charge-transfer material formed from the ubiquitous reduction-oxidation pair hydroquinone and p-benzoquinone. Upon pumping this material, known as quinhydrone, on its intermolecular charge transfer resonance as well as an intramolecular resonance of p-benzoquinone, we find sub-cm(-1) oscillations whose dispersion with probe energy resembles that of a coherent acoustic phonon that we argue is coherently excited following changes in the electron density of quinhydrone. Using the dynamical information from these ultrafast pump-probe measurements, we find that the fastest process we can resolve does not change whether we pump quinhydrone at either energy. Electron-phonon coupling from both ultrafast coherent vibrational and steady-state resonance Raman spectroscopies allows us to determine that intramolecular electronic excitation of p-benzoquinone also drives the electron transfer process in quinhydrone. These results demonstrate the wide range of electronic excitations of the parent of molecules found in many functional organic materials that can drive coherent lattice phonon excitations useful for applications in electronics, photonics, and information technology. PMID:26979698

  6. Coupled sensitizer-catalyst dyads: electron-transfer reactions in a perylene-polyoxometalate conjugate.

    Science.gov (United States)

    Odobel, Fabrice; Séverac, Marjorie; Pellegrin, Yann; Blart, Errol; Fosse, Céline; Cannizzo, Caroline; Mayer, Cédric R; Elliott, Kristopher J; Harriman, Anthony

    2009-01-01

    Ultrafast discharge of a single-electron capacitor: A variety of intramolecular electron-transfer reactions are apparent for polyoxometalates functionalized with covalently attached perylene monoimide chromophores, but these are restricted to single-electron events. (et=electron transfer, cr=charge recombination, csr=charge-shift reaction, PER=perylene, POM=polyoxometalate).A new strategy is introduced that permits covalent attachment of an organic chromophore to a polyoxometalate (POM) cluster. Two examples are reported that differ according to the nature of the anchoring group and the flexibility of the linker. Both POMs are functionalized with perylene monoimide units, which function as photon collectors and form a relatively long-lived charge-transfer state under illumination. They are reduced to a stable pi-radical anion by electrolysis or to a protonated dianion under photolysis in the presence of aqueous triethanolamine. The presence of the POM opens up an intramolecular electron-transfer route by which the charge-transfer state reduces the POM. The rate of this process depends on the molecular conformation and appears to involve through-space interactions. Prior reduction of the POM leads to efficient fluorescence quenching, again due to intramolecular electron transfer. In most cases, it is difficult to resolve the electron-transfer products because of relatively fast reverse charge shift that occurs within a closed conformer. Although the POM can store multiple electrons, it has not proved possible to use these systems as molecular-scale capacitors because of efficient electron transfer from the one-electron-reduced POM to the excited singlet state of the perylene monoimide. PMID:19197929

  7. Theoretical Study of Electron Transfer in Bimolecular System of NH3 and H2O

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Mulliken, NPA, MK and CHelpG population analyses have been accomplished at the level of MP2/6-31G(d,p) for the title system. The variations of four kinds of charges on NH3 with intermolecular distance infer that electron transfers from NH3 to H2O. MK and CHelpG population analyses indicate more electron transfer than Mulliken and NPA ones. The atomic charges resulted from MK and CHelpG schemes infer that electron transfers from N in NH3 to H in H2O, which confirms that this bimolecular complex possesses linear structure as H3N…HOH.

  8. Measured multipole moments of continuum electron transfer angular distributions

    International Nuclear Information System (INIS)

    The velocity space distribution of electrons emitted near the forward direction from collisions involving fast, highly stripped oxygen ions with gaseous and solid targets is presented and described in terms of multipole moments of the ejected charge distribution, which permits direct comparison with recent theory. The measurements are produced by employing position-sensitive electron detection to combine emission angle definition with conventional electrostatic spectrometry. Agreement obtained between theory and distributions observed for binary continuum electron loss processes coupled with a similar multipole content observed with solid targets suggests a model of convoy electron production dominated by electron loss from the projectile within the bulk of the target. Further, the connection between multipoles of the projectile electron emission distribution in single collisions and the state of excitation of that projectile excited states may provide the basis for a probe of the state of ions traversing bulk solid matter. 14 refs., 3 figs., 1 tab

  9. Interfacial Al segregation limiting electron mobility at the inverted interface of AlGaAs/GaAs quantum well

    International Nuclear Information System (INIS)

    Low-temperature mobility spectrum of two-dimensional electron gas (2DEG) at the inverted interface of AlGaAs/GaAs quantum well has been evaluated theoretically taking into account nonabrupt composition profile due to segregation of Al atoms into the well. In this approach, the Al content profile at the inverted interface has been considered as exponential decay function, and transport mobility components were calculated in the Lindhard's framework and flat interface approximation. It was found that alloy scattering due to segregated Al atoms can be significant, and even limits electron mobility at high 2DEG densities. The segregation decay length is evaluated from comparing experimental mobility spectrum with theory. (paper)

  10. Interfacial reaction product and mechanical properties of the electron beam brazed K465 Ni-based superalloy joints

    Institute of Scientific and Technical Information of China (English)

    Wang Gang; Zhang Binggang; He Jingshan; Feng Jicai; Wu Yingjie

    2008-01-01

    Ni-based superalloy K465 is brazed with BNi-2 filler metal by vacuum electron beam brazing (VEBB). In process of VEBB, effects of processing primary parameters on shear strength of joints are investigated. Microstructure of the brazed joint with BNi-2 filler metal is studied by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results show that the structure of brazed seam consists of a large amount of Ni-based γ solid solution, Ni3Al (γ′), Ni3B, WB, CrB, and a small quantity of WC, NbC. The maximum shear strength of the joint is 398 MPa when the beam current of welding is 2.6 mA, heating time is 480 s and focused current is 1 800 mA.

  11. Direct electron transfer of glucose oxidase on the carbon nanotube electrode

    Institute of Scientific and Technical Information of China (English)

    CAI Chenxin; CHEN Jing; LU Tianhong

    2004-01-01

    The direct electron transfer of glucose oxidase (Gox) immobilized onto the surface of the carbon nanotube (CNT)-modified glassy carbon (CNT/GC) electrode is reported. The direct electron transfer rate of Gox is greatly enhanced when it was immobilized onto the surface of CNT/GC electrode. Cyclic voltammetric results show a pair of well-defined and nearly sym metric redox peaks, which corresponds to the direct electron transfer of Gox, with the formal potential (E0′), which is almost independent on the scan rates, of about -0.456 V (vs. SCE) in the phosphate buffer solution (pH 6.9). The apparent heterogeneous electron transfer rate constant (ks) of Gox at the CNT/GC electrode surface is estimated to be (1.74 ± 0.42) s-1, which is much higher than that reported previously. The dependence of E0′on solution pH indicates that the direct electron transfer of Gox is a two-electron-transfer coupled with two-proton-transfer reaction process. The experimental results also demonstrate that the immobilized Gox retains its bioelectrocatalytic activity toward the oxidation of glucose. The method presented here can be easily extended to obtain the direct electrochemistry of other enzymes or proteins.

  12. Role of coherence and delocalization in photo-induced electron transfer at organic interfaces

    Science.gov (United States)

    Abramavicius, V.; Pranculis, V.; Melianas, A.; Inganäs, O.; Gulbinas, V.; Abramavicius, D.

    2016-09-01

    Photo-induced charge transfer at molecular heterojunctions has gained particular interest due to the development of organic solar cells (OSC) based on blends of electron donating and accepting materials. While charge transfer between donor and acceptor molecules can be described by Marcus theory, additional carrier delocalization and coherent propagation might play the dominant role. Here, we describe ultrafast charge separation at the interface of a conjugated polymer and an aggregate of the fullerene derivative PCBM using the stochastic Schrödinger equation (SSE) and reveal the complex time evolution of electron transfer, mediated by electronic coherence and delocalization. By fitting the model to ultrafast charge separation experiments, we estimate the extent of electron delocalization and establish the transition from coherent electron propagation to incoherent hopping. Our results indicate that even a relatively weak coupling between PCBM molecules is sufficient to facilitate electron delocalization and efficient charge separation at organic interfaces.

  13. Role of coherence and delocalization in photo-induced electron transfer at organic interfaces.

    Science.gov (United States)

    Abramavicius, V; Pranculis, V; Melianas, A; Inganäs, O; Gulbinas, V; Abramavicius, D

    2016-01-01

    Photo-induced charge transfer at molecular heterojunctions has gained particular interest due to the development of organic solar cells (OSC) based on blends of electron donating and accepting materials. While charge transfer between donor and acceptor molecules can be described by Marcus theory, additional carrier delocalization and coherent propagation might play the dominant role. Here, we describe ultrafast charge separation at the interface of a conjugated polymer and an aggregate of the fullerene derivative PCBM using the stochastic Schrödinger equation (SSE) and reveal the complex time evolution of electron transfer, mediated by electronic coherence and delocalization. By fitting the model to ultrafast charge separation experiments, we estimate the extent of electron delocalization and establish the transition from coherent electron propagation to incoherent hopping. Our results indicate that even a relatively weak coupling between PCBM molecules is sufficient to facilitate electron delocalization and efficient charge separation at organic interfaces. PMID:27605035

  14. Pulse radiolytic studies of electron transfer processes and applications to solar photochemistry. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Neta, P.

    1995-02-01

    The pulse radiolysis technique is applied to the study of electron transfer processes in a variety of chemical systems. Reactive intermediates are produced in solution by electron pulse irradiation and the kinetics of their reactions are followed by time resolved absorption spectrophotometry. Complementary experiments are carried out with excimer laser flash photolysis. These studies are concerned with mechanisms, kinetics, and thermodynamics of reactions of organic and inorganic radicals and unstable oxidation states of metal ions. Reactions are studied in both aqueous and non-aqueous solutions. The studies focus on the unique ability of pulse radiolysis to provide absolute rate constants for reactions of many inorganic radicals and organic peroxyl radicals, species that are key intermediates in many chemical processes. A special concern of this work is the study of electron transfer reactions of metalloporphyrins, which permits evaluation of these molecules as intermediates in solar energy conversion. Metalloporphyrins react with free radicals via electron transfer, involving the ligand or the metal center, or via bonding to the metal, leading to a variety of chemical species whose behavior is also investigated. The highlights of the results during the past three years are summarized below under the following sections: (a) electron transfer reactions of peroxyl radicals, concentrating on the characterization of new peroxyl radicals derived from vinyl, phenyl, other aryl, and pyridyl; (b) solvent effects on electron transfer reactions of inorganic and organic peroxyl radicals, including reactions with porphyrins, and (c) electron transfer and alkylation reactions of metalloporphyrins and other complexes.

  15. Electronic and Magneto-Transport Across the Heusler Alloy (Co2FeAl)/ p-Si Interfacial Structure

    Science.gov (United States)

    Kumar, Arvind; Srivastava, P. C.

    2014-02-01

    Electronic and magneto-transport across the Heusler alloy Co2FeAl (CFA)/ p-Si structure have been studied. The morphology of the Heusler alloy film surface has also been characterized by atomic force microscopy and magnetic force microscopy (MFM). X-ray diffraction data revealed formation of the CFA alloy phase with the L21 structure. MFM results revealed formation of a fine domain structure of average size ˜10 nm and magnetic signal strength 0.23°. The I- V characteristics are strongly temperature-dependent between ˜80 K and 300 K for forward bias, compared with weak temperature dependence on reversing the polarity. At low temperature the I- V characteristics have the features of a backward diode. The observed strong temperature dependence is because of thermionic emission of carriers across the interface. The weak temperature dependence is because of dominant field-emission tunnelling of carriers across the interface. Large magnetic field sensitivity of the reverse current has also been observed. The observed magnetic field sensitivity for the reverse current shows the involvement of electronic spin in transport across the interface, from the Heusler alloy to the silicon. An MR of ˜35% in the presence of a magnetic field was estimated from the I- V data. The study has shown that spin-dependent tunnel transport from the CFA alloy to silicon across the interface results in the observed value of MR, which seems to be because of spin scattering.

  16. Microbe-electrode interactions: The chemico-physical environment and electron transfer

    OpenAIRE

    Gardel, Emily Jeanette

    2013-01-01

    This thesis presents studies that examine microbial extracellular electron transfer that an emphasis characterizing how environmental conditions influence electron flux between microbes and a solid-phase electron donor or acceptor. I used bioelectrochemical systems (BESs), fluorescence and electron microscopy, chemical measurements, 16S rRNA analysis, and qRT-PCR to study these relationships among chemical, physical and biological parameters and processes.

  17. [Long-range electron transfer in globular proteins by polaron excitation].

    Science.gov (United States)

    Lakhno, V L; Chuev, G N

    1997-01-01

    Considering polaron model, we have calculated an electron state localized in the protein heme. Using these calculations: the electron density and electron energy, we estimated the self-exchange rate constant for cyt c (horse heart), its reorganization energy, matrix element, and dependence of this rate on the distance between hemes. The results are compared with the experimental data and other theoretical estimations. We discuss the role of polaron excitations in the long-range electron transfer in globular proteins.

  18. Bi-directional magnetic resonance based wireless power transfer for electronic devices

    Science.gov (United States)

    Kar, Durga P.; Nayak, Praveen P.; Bhuyan, Satyanarayan; Mishra, Debasish

    2015-09-01

    In order to power or charge electronic devices wirelessly, a bi-directional wireless power transfer method has been proposed and experimentally investigated. In the proposed design, two receiving coils are used on both sides of a transmitting coil along its central axis to receive the power wirelessly from the generated magnetic fields through strongly coupled magnetic resonance. It has been observed experimentally that the maximum power transfer occurs at the operating resonant frequency for optimum electric load connected across the receiving coils on both side. The optimum wireless power transfer efficiency is 88% for the bi-directional power transfer technique compared 84% in the one side receiver system. By adopting the developed bi-directional power transfer method, two electronic devices can be powered up or charged simultaneously instead of a single device through usual one side receiver system without affecting the optimum power transfer efficiency.

  19. Bi-directional magnetic resonance based wireless power transfer for electronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Kar, Durga P.; Nayak, Praveen P.; Bhuyan, Satyanarayan; Mishra, Debasish [Department of Electronics and Instrumentation Engineering, Institute of Technical Education and Research, Siksha ‘O’ Anushandhan University, Bhubaneswar 751030 (India)

    2015-09-28

    In order to power or charge electronic devices wirelessly, a bi-directional wireless power transfer method has been proposed and experimentally investigated. In the proposed design, two receiving coils are used on both sides of a transmitting coil along its central axis to receive the power wirelessly from the generated magnetic fields through strongly coupled magnetic resonance. It has been observed experimentally that the maximum power transfer occurs at the operating resonant frequency for optimum electric load connected across the receiving coils on both side. The optimum wireless power transfer efficiency is 88% for the bi-directional power transfer technique compared 84% in the one side receiver system. By adopting the developed bi-directional power transfer method, two electronic devices can be powered up or charged simultaneously instead of a single device through usual one side receiver system without affecting the optimum power transfer efficiency.

  20. Bi-directional magnetic resonance based wireless power transfer for electronic devices

    International Nuclear Information System (INIS)

    In order to power or charge electronic devices wirelessly, a bi-directional wireless power transfer method has been proposed and experimentally investigated. In the proposed design, two receiving coils are used on both sides of a transmitting coil along its central axis to receive the power wirelessly from the generated magnetic fields through strongly coupled magnetic resonance. It has been observed experimentally that the maximum power transfer occurs at the operating resonant frequency for optimum electric load connected across the receiving coils on both side. The optimum wireless power transfer efficiency is 88% for the bi-directional power transfer technique compared 84% in the one side receiver system. By adopting the developed bi-directional power transfer method, two electronic devices can be powered up or charged simultaneously instead of a single device through usual one side receiver system without affecting the optimum power transfer efficiency

  1. Coexistence of Different Electron-Transfer Mechanisms in the DNA Repair Process by Photolyase.

    Science.gov (United States)

    Lee, Wook; Kodali, Goutham; Stanley, Robert J; Matsika, Spiridoula

    2016-08-01

    DNA photolyase has been the topic of extensive studies due to its important role of repairing photodamaged DNA, and its unique feature of using light as an energy source. A crucial step in the repair by DNA photolyase is the forward electron transfer from its cofactor (FADH(-) ) to the damaged DNA, and the detailed mechanism of this process has been controversial. In the present study, we examine the forward electron transfer in DNA photolyase by carrying out high-level ab initio calculations in combination with a quantum mechanical/molecular mechanical (QM/MM) approach, and by measuring fluorescence emission spectra at low temperature. On the basis of these computational and experimental results, we demonstrate that multiple decay pathways exist in DNA photolyase depending on the wavelength at excitation and the subsequent transition. This implies that the forward electron transfer in DNA photolyase occurs not only by superexchange mechanism but also by sequential electron transfer. PMID:27362906

  2. Rhodamine-6G can photosensitize folic acid decomposition through electron transfer

    Science.gov (United States)

    Hirakawa, Kazutaka; Ito, Hiroki

    2015-05-01

    Rhodamine-6G photosensitized folic acid decomposition in aqueous solution, and its quantum yield in the presence of 10 μM folic acid was 9.9 × 10-6. A possible mechanism of this photodecomposition is direct oxidation through an electron transfer from folic acid to rhodamine-6G. The fluorescence lifetime of rhodamine-6G was slightly decreased by folic acid, suggesting electron transfer in the excited singlet state of rhodamine-6G. The quenching rate coefficient estimated from the Stern-Volmer plot of the fluorescence quenching supported that this electron transfer proceeds as a diffusion-controlled reaction. The quantum yields of the electron transfer and the following reaction could be determined.

  3. 77 FR 71035 - Financial Management Service; Proposed Collection of Information: Electronic Funds Transfer (EFT...

    Science.gov (United States)

    2012-11-28

    ... Fiscal Service Financial Management Service; Proposed Collection of Information: Electronic Funds Transfer (EFT) Market Research Study AGENCY: Financial Management Service, Fiscal Service, Treasury. ACTION: Notice and Request for comments. SUMMARY: The Financial Management Service, as part of its...

  4. 77 FR 34127 - Financial Management Service; Proposed Collection of Information: Electronic Transfer Account...

    Science.gov (United States)

    2012-06-08

    ... Fiscal Service Financial Management Service; Proposed Collection of Information: Electronic Transfer Account (ETA) Financial Agency Agreement AGENCY: Financial Management Service, Fiscal Service, Treasury. ACTION: Notice and Request for comments. SUMMARY: The Financial Management Service, as part of...

  5. Fast electron transfer through a single molecule natively structured redox protein

    DEFF Research Database (Denmark)

    Della Pia, Eduardo Antonio; Chi, Qijin; Macdonald, J. Emyr;

    2012-01-01

    The electron transfer properties of proteins are normally measured as molecularly averaged ensembles. Through these and related measurements, proteins are widely regarded as macroscopically insulating materials. Using scanning tunnelling microscopy (STM), we present new measurements of the conduc...

  6. ElectronTransfer Induced Ring Opening of α-Epoxyketones: Spirodioxolane Formation

    Directory of Open Access Journals (Sweden)

    Farzad Nikpour

    2002-01-01

    Full Text Available Stereospecific formation of spirodioxolanes has been observed on electron transfer induced ring opening of α-epoxyketones by 2,4,6-triphenylpyrylium tetrafluoroborate in the presence of cyclohexanone

  7. Electrode assemblies composed of redox cascades from microbial respiratory electron transfer chains

    Energy Technology Data Exchange (ETDEWEB)

    Gates, Andrew J. [Univ. of East Anglia, Norwich (United Kingdom); Marritt, Sophie [Univ. of East Anglia, Norwich (United Kingdom); Bradley, Justin [Univ. of East Anglia, Norwich (United Kingdom); Shi, Liang [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McMillan, Duncan G. [Univ. of Leeds (United Kingdom); Jeuken, Lars J. [Univ. of Leeds (United Kingdom); Richardson, David [Univ. of East Anglia, Norwich (United Kingdom); Butt, Julea N. [Univ. of East Anglia, Norwich (United Kingdom)

    2013-10-01

    Respiratory and photosynthetic electron transfer chains are dependent on vectorial electron transfer through a series of redox proteins. Examples include electron transfer from NapC to NapAB nitrate reductase in Paracoccus denitrificans and from CymA to Fcc3 (flavocytochrome c3) fumarate reductase in Shewanella oneidensis MR-1. In the present article, we demonstrate that graphite electrodes can serve as surfaces for the stepwise adsorption of NapC and NapAB, and the stepwise adsorption of CymA and Fcc3. Aspects of the catalytic properties of these assemblies are different from those of NapAB and Fcc3 adsorbed in isolation. We propose that this is due to the formation of NapC-NapAB and of CymA-Fcc3 complexes that are capable of supporting vectorial electron transfer.

  8. 78 FR 30661 - Electronic Fund Transfers (Regulation E)

    Science.gov (United States)

    2013-05-22

    ... closed network transactions, which generally can only be sent to agents or other entities that have... consumers in the United States to designated recipients in other countries and, for covered transactions... by a person other than the remittance transfer provider. In place of these two former...

  9. Transferred metal electrode films for large-area electronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jin-Guo [Department of Physics, National University of Singapore, Lower Kent Ridge Road, Singapore S117543 (Singapore); NUS Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore, Medical Drive, Singapore S117456 (Singapore); Kam, Fong-Yu [Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, Singapore S117543 (Singapore); Chua, Lay-Lay [Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, Singapore S117543 (Singapore); Department of Physics, National University of Singapore, Lower Kent Ridge Road, Singapore S117543 (Singapore)

    2014-11-10

    The evaporation of metal-film gate electrodes for top-gate organic field-effect transistors (OFETs) limits the minimum thickness of the polymer gate dielectric to typically more than 300 nm due to deep hot metal atom penetration and damage of the dielectric. We show here that the self-release layer transfer method recently developed for high-quality graphene transfer is also capable of giving high-quality metal thin-film transfers to produce high-performance capacitors and OFETs with superior dielectric breakdown strength even for ultrathin polymer dielectric films. Dielectric breakdown strengths up to 5–6 MV cm{sup −1} have been obtained for 50-nm thin films of polystyrene and a cyclic olefin copolymer TOPAS{sup ®} (Zeon). High-quality OFETs with sub-10 V operational voltages have been obtained this way using conventional polymer dielectrics and a high-mobility polymer semiconductor poly[2,5-bis(3-tetradecylthiophene-2-yl)thieno[3,2-b]thiophene-2,5-diyl]. The transferred metal films can make reliable contacts without damaging ultrathin polymer films, self-assembled monolayers and graphene, which is not otherwise possible from evaporated or sputtered metal films.

  10. Approach to Interfacial and Intramolecular Electron Transfer of the Diheme Protein Cytochrome c(4) Assembled on Au(111) Surfaces

    DEFF Research Database (Denmark)

    Chi, Qijin; Zhang, Jingdong; Taner, Arslan;

    2010-01-01

    protein Pseudomonas stutzeri cytochrome c(4) has been a target for intramolecular, interheme ET. We report here voltammetric and in situ scanning tunneling microscopy (STM) data for P. stutzeri cyt c(4) at single-crystal, atomically planar Au(111)-electrode surfaces modified by variable-length omega...

  11. Quantifying electron transfer reactions in biological systems: what interactions play the major role?

    Science.gov (United States)

    Sjulstok, Emil; Olsen, Jógvan Magnus Haugaard; Solov'Yov, Ilia A.

    2015-12-01

    Various biological processes involve the conversion of energy into forms that are usable for chemical transformations and are quantum mechanical in nature. Such processes involve light absorption, excited electronic states formation, excitation energy transfer, electrons and protons tunnelling which for example occur in photosynthesis, cellular respiration, DNA repair, and possibly magnetic field sensing. Quantum biology uses computation to model biological interactions in light of quantum mechanical effects and has primarily developed over the past decade as a result of convergence between quantum physics and biology. In this paper we consider electron transfer in biological processes, from a theoretical view-point; namely in terms of quantum mechanical and semi-classical models. We systematically characterize the interactions between the moving electron and its biological environment to deduce the driving force for the electron transfer reaction and to establish those interactions that play the major role in propelling the electron. The suggested approach is seen as a general recipe to treat electron transfer events in biological systems computationally, and we utilize it to describe specifically the electron transfer reactions in Arabidopsis thaliana cryptochrome-a signaling photoreceptor protein that became attractive recently due to its possible function as a biological magnetoreceptor.

  12. Anode interfacial tuning via electron-blocking/hole-transport layers and indium tin oxide surface treatment in bulk-heterojunction organic photovoltaic cells

    Energy Technology Data Exchange (ETDEWEB)

    Hains, Alexander W.; Liu, Jun; Martinson, Alex B.F.; Irwin, Michael D.; Marks, Tobin J. [Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois (United States)

    2010-02-22

    The effects of anode/active layer interface modification in bulk-heterojunction organic photovoltaic (OPV) cells is investigated using poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and/or a hole-transporting/electron-blocking blend of 4,4'-bis[(p-trichlorosilylpropylphenyl)-phenylamino]biphenyl (TPDSi{sub 2}) and poly[9,9-dioctylfluorene-co-N-[4-(3-methylpropyl)]-diphenylamine] (TFB) as interfacial layers (IFLs). Current-voltage data in the dark and AM1.5G light show that the TPDSi{sub 2}:TFB IFL yields MDMO-PPV:PCBM OPVs with substantially increased open-circuit voltage (V{sub oc}), power conversion efficiency, and thermal stability versus devices having no IFL or PEDOT:PSS. Using PEDOT:PSS and TPDSi{sub 2}:TFB together in the same cell greatly reduces dark current and produces the highest V{sub oc} (0.91 V) by combining the electron-blocking effects of both layers. ITO anode pre-treatment was investigated by X-ray photoelectron spectroscopy to understand why oxygen plasma, UV ozone, and solvent cleaning markedly affect cell response in combination with each IFL. O{sub 2} plasma and UV ozone treatment most effectively clean the ITO surface and are found most effective in preparing the surface for PEDOT:PSS deposition; UV ozone produces optimum solar cells with the TPDSi{sub 2}:TFB IFL. Solvent cleaning leaves significant residual carbon contamination on the ITO and is best followed by O{sub 2} plasma or UV ozone treatment. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  13. Final Report for completed IPP-0110 and 0110A Projects: 'High Energy Ion Technology of Interfacial Thin Film Coatings for Electronic, Optical and Industrial Applications'

    International Nuclear Information System (INIS)

    The DOE-supported IPP (Initiatives for Proliferation Prevention) Project, IPP-0110, and its accompanying 'add-on project' IPP-0110A, entitled 'High Energy Ion Technology of Interfacial Thin Film Coatings for Electronic, Optical and Industrial Applications' was a collaborative project involving the Lawrence Berkeley National Laboratory (LBNL) as the U.S. DOE lab; the US surface modification company, Phygen, Inc., as the US private company involved; and the High Current Electronics Institute (HCEI) of the Russian Academy of Sciences, Tomsk, Siberia, Russia, as the NIS Institute involved. Regular scientific research progress meetings were held to which personnel came from all participating partners. The meetings were held mostly at the Phygen facilities in Minneapolis, Minnesota (with Phygen as host) with meetings also held at Tomsk, Russia (HCEI as host), and at Berkeley, California (LBNL as host) In this way, good exposure of all researchers to the various different laboratories involved was attained. This report contains the Final Reports (final deliverables) from the Russian Institute, HCEI. The first part is that for IPP-0110A (the 'main part' of the overall project) and the second part is that for the add-on project IPP-0110A. These reports are detailed, and contain all aspects of all the research carried out. The project was successful in that all deliverables as specified in the proposals were successfully developed, tested, and delivered to Phygen. All of the plasma hardware was designed, made and tested at HCEI, and the performance was excellent. Some of the machine and performance parameters were certainly of 'world class'. The goals and requirements of the IPP Project were well satisfied. I would like to express my gratitude to the DOE IPP program for support of this project throughout its entire duration, and for the unparalleled opportunity thereby provided for all of the diverse participants in the project to join in this collaborative research. The

  14. Fast electron transfer through a single molecule natively structured redox protein

    OpenAIRE

    Della Pia, Eduardo Antonio; Chi, Qijin; Macdonald, J. Emyr; Ulstrup, Jens; Jones, D Dafydd; Elliott, Martin

    2012-01-01

    The electron transfer properties of proteins are normally measured as molecularly averaged ensembles. Through these and related measurements, proteins are widely regarded as macroscopically insulating materials. Using scanning tunnelling microscopy (STM), we present new measurements of the conductance through single-molecules of the electron transfer protein cytochrome b562 in its native conformation, under pseudo-physiological conditions. This is achieved by thiol (SH) linker pairs at opposi...

  15. 76 FR 35219 - Federal Acquisition Regulation; Information Collection; Payment by Electronic Fund Transfer

    Science.gov (United States)

    2011-06-16

    ... Regulation; Information Collection; Payment by Electronic Fund Transfer AGENCY: Department of Defense (DOD... transfer. Public comments are particularly invited on: Whether this collection of information is necessary... those who are to respond, through the use of appropriate technological collection techniques or...

  16. 9,10-Diphenylanthracene as a matrix for MALDI-MS electron transfer secondary reactions.

    Science.gov (United States)

    Boutaghou, M Nazim; Cole, Richard B

    2012-08-01

    The most common secondary-ionization mechanism in positive ion matrix-assisted laser desorption/ionization (MALDI) involves a proton transfer reaction to ionize the analyte. Peptides and proteins are molecules that have basic (and acidic) sites that make them susceptible to proton transfer. However, non-polar, aprotic compounds that lack basic sites are more difficult to protonate, and creating charged forms of this type of analyte can pose a problem when conventional MALDI matrices are employed. In this case, forming a radical molecular ion through electron transfer is a viable alternative, and certain matrices may facilitate the process. In this work, we investigate the performance of a newly developed electron-transfer secondary reaction matrix: 9,10-diphenylanthracene (9,10-DPA). The use of 9,10-DPA as matrix for MALDI analysis has been tested using several model compounds. It appears to promote ionization through electron transfer in a highly efficient manner as compared to other potential matrices. Thermodynamic aspects of the observed electron transfers in secondary-ionization reactions were also considered, as was the possibility for kinetically controlled/endothermic, electron-transfer reactions in the MALDI plume.

  17. Electrostatic effect on electron transfer between cytochrome b5 and cytochrome c

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The binding and electron transfer between wild type, E44A, E56A, E44/56A, E44/48/56A/D60Aand F35Y variants of cytochrome b5 and cytochrome c were studied. When mixed with cytochrome c, the cytochrome b5E44/48/56A/D60A did not show the typical UV-vis difference spectrum of absorption, indicating that the alteration ofthe surface electrostatic potential obviously influenced the spectrum. The electron transfer rates of wild type cytochromeb5, its variants and cytochrome e at different temperature and ionic strength exhibited an order of F35Y > wild type >E56A > E44A > E44/48/56A/D60A. The enthalpy and entropy of the reaction did not change obviously, suggestingthat the mutation did not significantly disturb the electron transfer conformation. The investigation of electron transfer rateconstants at different ionic strength demonstrated that electrostatic interaction obviously affected the electron transfer pro-cess. The significant difference of Cyt b5 F35Y and E44/48/56A/D60A from the wild type protein further confirmed thegreat importance of the electrostatic interaction in the protein electron transfer.

  18. Impact of electron delocalization on the nature of the charge-transfer states in model pentacene/C60 Interfaces: A density functional theory study

    KAUST Repository

    Yang, Bing

    2014-12-04

    Electronic delocalization effects have been proposed to play a key role in photocurrent generation in organic photovoltaic devices. Here, we study the role of charge delocalization on the nature of the charge-transfer (CT) states in the case of model complexes consisting of several pentacene molecules and one fullerene (C60) molecule, which are representative of donor/acceptor heterojunctions. The energies of the CT states are examined by means of time-dependent density functional theory (TD-DFT) using the long-range-corrected functional, ωB97X, with an optimized range-separation parameter, ω. We provide a general description of how the nature of the CT states is impacted by molecular packing (i.e., interfacial donor/acceptor orientations), system size, and intermolecular interactions, features of importance in the understanding of the charge-separation mechanism.

  19. Transfer printing of thermoreversible ion gels for flexible electronics.

    Science.gov (United States)

    Lee, Keun Hyung; Zhang, Sipei; Gu, Yuanyan; Lodge, Timothy P; Frisbie, C Daniel

    2013-10-01

    Thermally assisted transfer printing was employed to pattern thin films of high capacitance ion gels on polyimide, poly(ethylene terephthalate), and SiO2 substrates. The ion gels consisted of 20 wt % block copolymer poly(styrene-b-ethylene oxide-b-styrene and 80 wt % ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)amide. Patterning resolution was on the order of 10 μm. Importantly, ion gels containing the block polymer with short PS end blocks (3.4 kg/mol) could be transfer-printed because of thermoreversible gelation that enabled intimate gel-substrate contact at 100 °C, while gels with long PS blocks (11 kg/mol) were not printable at the same temperature due to poor wetting contact between the gel and substrates. By using printed ion gels as high-capacitance gate insulators, electrolyte-gated thin-film transistors were fabricated that operated at low voltages (<1 V) with high on/off current ratios (∼10(5)). Statistical analysis of carrier mobility, turn-on voltage, and on/off ratio for an array of printed transistors demonstrated the excellent reproducibility of the printing technique. The results show that transfer printing is an attractive route to pattern high-capacitance ion gels for flexible thin-film devices.

  20. Transfer printing of thermoreversible ion gels for flexible electronics.

    Science.gov (United States)

    Lee, Keun Hyung; Zhang, Sipei; Gu, Yuanyan; Lodge, Timothy P; Frisbie, C Daniel

    2013-10-01

    Thermally assisted transfer printing was employed to pattern thin films of high capacitance ion gels on polyimide, poly(ethylene terephthalate), and SiO2 substrates. The ion gels consisted of 20 wt % block copolymer poly(styrene-b-ethylene oxide-b-styrene and 80 wt % ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)amide. Patterning resolution was on the order of 10 μm. Importantly, ion gels containing the block polymer with short PS end blocks (3.4 kg/mol) could be transfer-printed because of thermoreversible gelation that enabled intimate gel-substrate contact at 100 °C, while gels with long PS blocks (11 kg/mol) were not printable at the same temperature due to poor wetting contact between the gel and substrates. By using printed ion gels as high-capacitance gate insulators, electrolyte-gated thin-film transistors were fabricated that operated at low voltages (<1 V) with high on/off current ratios (∼10(5)). Statistical analysis of carrier mobility, turn-on voltage, and on/off ratio for an array of printed transistors demonstrated the excellent reproducibility of the printing technique. The results show that transfer printing is an attractive route to pattern high-capacitance ion gels for flexible thin-film devices. PMID:24028461

  1. Interfacial electronic structure-modulated magnetic anisotropy in Ta/CoFeB/MgO/Ta multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xi; Jiang, Shao Long; Yang, Guang; Liu, Yang; Teng, Jiao; Yu, Guang Hua, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Wang, Kai You [SKLSM, Institute of Semiconductors, CAS, P. O. Box 912, Beijing 100083 (China); Wu, Zheng Long [Analytical and Testing Center, Beijing Normal University, Beijing 100875 (China)

    2014-09-01

    We have observed several unexpected phenomena when a trace amount of Fe atoms is deposited onto the CoFeB/MgO interface in Ta/CoFeB/MgO/Ta multilayers. With the nominal thickness of the introduced Fe atoms (t{sub Fe}) varying from 0 to 0.1 Å, the effective magnetic anisotropy energy (K{sub eff}) of annealed multilayers is remarkably enhanced from 1.28 × 10{sup 6 }erg/cm{sup 3} to 2.14 × 10{sup 6 }erg/cm{sup 3}. As t{sub Fe} further increasing, the K{sub eff} decreases and even becomes negative when t{sub Fe} > 1 Å, indicating the change from perpendicular magnetic anisotropy to in-plane magnetic anisotropy. The analysis by X-ray photoelectron spectrometer reveals that the Fe atoms at annealed CoFeB/MgO interface show different electronic structures as t{sub Fe} increasing, which combine with O atoms to form FeO{sub x} (x < 1), Fe{sub 2}O{sub 3}, and Fe{sub 3}O{sub 4}, respectively, leading to modulation of Fe 3d-O 2p orbital hybridization and thus the K{sub eff}. On the other hand, we find that the introduction of Fe atoms also helps to reduce the multilayers' magnetic damping.

  2. Identification of a new electron-transfer relaxation pathway in photoexcited pyrrole dimers.

    Science.gov (United States)

    Neville, Simon P; Kirkby, Oliver M; Kaltsoyannis, Nikolas; Worth, Graham A; Fielding, Helen H

    2016-04-21

    Photoinduced electron transfer is central to many biological processes and technological applications, such as the harvesting of solar energy and molecular electronics. The electron donor and acceptor units involved in electron transfer are often held in place by covalent bonds, π-π interactions or hydrogen bonds. Here, using time-resolved photoelectron spectroscopy and ab initio calculations, we reveal the existence of a new, low-energy, photoinduced electron-transfer mechanism in molecules held together by an NH⋯π bond. Specifically, we capture the electron-transfer process in a pyrrole dimer, from the excited π-system of the donor pyrrole to a Rydberg orbital localized on the N-atom of the acceptor pyrrole, mediated by an N-H stretch on the acceptor molecule. The resulting charge-transfer state is surprisingly long lived and leads to efficient electronic relaxation. We propose that this relaxation pathway plays an important role in biological and technological systems containing the pyrrole building block.

  3. Identification of a new electron-transfer relaxation pathway in photoexcited pyrrole dimers

    Science.gov (United States)

    Neville, Simon P.; Kirkby, Oliver M.; Kaltsoyannis, Nikolas; Worth, Graham A.; Fielding, Helen H.

    2016-04-01

    Photoinduced electron transfer is central to many biological processes and technological applications, such as the harvesting of solar energy and molecular electronics. The electron donor and acceptor units involved in electron transfer are often held in place by covalent bonds, π-π interactions or hydrogen bonds. Here, using time-resolved photoelectron spectroscopy and ab initio calculations, we reveal the existence of a new, low-energy, photoinduced electron-transfer mechanism in molecules held together by an NH⋯π bond. Specifically, we capture the electron-transfer process in a pyrrole dimer, from the excited π-system of the donor pyrrole to a Rydberg orbital localized on the N-atom of the acceptor pyrrole, mediated by an N-H stretch on the acceptor molecule. The resulting charge-transfer state is surprisingly long lived and leads to efficient electronic relaxation. We propose that this relaxation pathway plays an important role in biological and technological systems containing the pyrrole building block.

  4. Explanation of Turbulent Suppression of Electron Heat Transfer in GOL-3 Facility at the Stage of Relativistic Electron Beam Injection

    International Nuclear Information System (INIS)

    The effect of the electron heat transfer suppression during the stage of relativistic electron beam injection into a plasma was discovered experimentally more than a decade ago. It is now widely adopted that the suppression is a side sequel of Langmuir turbulence excited by the beam, however neither quantitative theory nor even rough estimates of the phenomena were available so far. We argue that the coefficient of turbulent thermal conductivity can be evaluated from a robust judgement based on the energy balance consideration

  5. 77 FR 30923 - Electronic Fund Transfers (Regulation E)

    Science.gov (United States)

    2012-05-24

    ... protections given to checking accounts and electronic transactions involving checking accounts under federal... comments, in conjunction with other outreach and analysis, will help the Bureau better understand and... inspect the documents by calling (202) 435- 7275. All comments, including attachments and other...

  6. Vibrationally Assisted Electron Transfer Mechanism of Olfaction: Myth or Reality?

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Chang, Po-Yao; Schulten, Klaus

    2012-01-01

    dimensions. In the present paper we introduce the vibrationally assisted mechanism of olfaction and demonstrate for several odorants that, indeed, a strong enhancement of an electron tunneling rate due to odorant vibrations can arise. We discuss in this regard the influence of odorant deuteration and explain...

  7. Interspecies electron transfer in methanogenic propionate degrading consortia

    NARCIS (Netherlands)

    Bok, de F.A.M.; Plugge, C.M.; Stams, A.J.M.

    2004-01-01

    Propionate is a key intermediate in the conversion of complex organic matter under methanogenic conditions. Oxidation of this compound requires obligate syntrophic consortia of acetogenic proton- and bicarbonate reducing bacteria and methanogenic archaea. Although H-2 acts as an electron-carrier in

  8. MAGNETIC PROPERTIES AND ELECTRON TRANSFER IN BINUCLEAR ORGANO-IRON SANDWICHES

    OpenAIRE

    Guillin, J.; Desbois, M.; Lacoste , M; Astruc, D.; Varret, F.

    1988-01-01

    Bi-iron electron reservoirs complexes, of sandwich structure, have been studied in the 36, 37, 38 e- states, by Mössbauer spectroscopy in external magnetic fields. The nature of the various couplings between the 19 e- subunits has been elucidated, and correlated to the electron transfer to the bridge in the mixed valence state.

  9. 48 CFR 52.232-38 - Submission of Electronic Funds Transfer Information with Offer.

    Science.gov (United States)

    2010-10-01

    ... information that is required to make payment by electronic funds transfer (EFT) under any contract that... 48 Federal Acquisition Regulations System 2 2010-10-01 2010-10-01 false Submission of Electronic... System FEDERAL ACQUISITION REGULATION (CONTINUED) CLAUSES AND FORMS SOLICITATION PROVISIONS AND...

  10. Syntrophic growth with direct interspecies electron transfer as the primary mechanism for energy exchange

    DEFF Research Database (Denmark)

    Shrestha, Pravin Malla; Rotaru, Amelia-Elena; Aklujkar, Muktak;

    2013-01-01

    to support cell growth. In order to investigate this, co-cultures of Geobacter metallireducens, which can transfer electrons to wild-type G. sulfurreducens via DIET, were established with a citrate synthase-deficient G. sulfurreducens strain that can receive electrons for respiration through DIET only...

  11. Experimental exploration of the Mulliken-Hush relationship for intramolecular electron transfer reactions.

    Science.gov (United States)

    Mukherjee, Tamal; Ito, Naoki; Gould, Ian R

    2011-03-17

    The Mulliken-Hush (M-H) relationship provides the critical link between optical and thermal electron transfer processes, and yet very little direct experimental support for its applicability has been provided. Dicyanovinylazaadamantane (DCVA) represents a simple two-state (neutral/charge-transfer) intramolecular electron transfer system that exhibits charge-transfer absorption and emission spectra that are readily measurable in solvents with a wide range of polarities. In this regard it represents an ideal model system for studying the factors that control both optical charge separation (absorption) and recombination (emission) processes in solution. Here we explore the applicability of the M-H relation to quantitative descriptions of the optical charge-transfer processes in DCVA. For DCVA, the measured radiative rate constants exhibit a linear dependence on transition energy, and transition dipole moments exhibit an inverse dependence on transition energy, consistent with the M-H relationship.

  12. Analysis of interfacial shear stress effects on vapor downward condensation heat transfer%界面剪切力对蒸汽垂直下流膜状凝结传热的影响分析

    Institute of Scientific and Technical Information of China (English)

    张俊霞; 王立; 李运刚; 黄建

    2011-01-01

    Interfacial shear stress has an important influence on the vapor downward condensation heat transfer in a smaller diameter condenser tube. At the present work, a volume of fluid (VOF) method based on the vapor-liquid interfacial capturing technique was used to numerically analyze the effects of interfacial shear stress on local condensation heat transfer coefficients (HTC) during the vapor downflow condensation. Because vapor condenses on the vapor-liquid interface, the condensation mass and energy source items were introduced into the volume fraction and energy governing equations of the VOF model. In addition, the condenser tube wall temperature was acquired by a coupling calculation of cooling water forced convection heat transfer. The parameters were obtained, including velocity, interfacial shear stress and local condensation HTC. The computations show that interfacial stress shear degrades along thetube length, obviously improving the condensation heat transfer at the condenser tube front. At the condenser tube rear, the vapor-liquid interfacial shear stress decreases, having a drag force to condensate. Therefore, the liquid-film gravity plays an important role in local condensation HTC at the condenser tube rear. Local condensation HTC obtained by the VOF method is compared with the Nusselt analytic solution. At the condenser tube front, the vapor-liquid interfacial shear stress is higher and has the same direction as condensate velocity, which enhances the condensation heat transfer by reducing the liquid film thickness. So local condensation HTC obtained by the VOF method is higher than the Nusselt analytic solution. However, at the condenser tube rear, the computing result is almost equal to the Nusselt analytic solution as a result of both lower interfacial shear stress and increasing the liquid film thickness. Furthermore, a comparison of local condensation HTC acquired by the VOF method to the experimental data of Goodykoontz et al. Was performed, good

  13. pH-dependent electron transfer reaction and direct bioelectrocatalysis of the quinohemoprotein pyranose dehydrogenase.

    Science.gov (United States)

    Takeda, Kouta; Matsumura, Hirotoshi; Ishida, Takuya; Yoshida, Makoto; Igarashi, Kiyohiko; Samejima, Masahiro; Ohno, Hiroyuki; Nakamura, Nobuhumi

    2016-08-26

    A pyranose dehydrogenase from Coprinopsis cinerea (CcPDH) is an extracellular quinohemoeprotein, which consists a b-type cytochrome domain, a pyrroloquinoline-quinone (PQQ) domain, and a family 1-type carbohydrate-binding module. The electron transfer reaction of CcPDH was studied using some electron acceptors and a carbon electrode at various pH levels. Phenazine methosulfate (PMS) reacted directly at the PQQ domain, whereas cytochrome c (cyt c) reacted via the cytochrome domain of intact CcPDH. Thus, electrons are transferred from reduced PQQ in the catalytic domain of CcPDH to heme b in the N-terminal cytochrome domain, which acts as a built-in mediator and transfers electron to a heterogenous electron transfer protein. The optimal pH values of the PMS reduction (pH 6.5) and the cyt c reduction (pH 8.5) differ. The catalytic currents for the oxidation of l-fucose were observed within a range of pH 4.5 to 11. Bioelectrocatalysis of CcPDH based on direct electron transfer demonstrated that the pH profile of the biocatalytic current was similar to the reduction activity of cyt c characters. PMID:27338639

  14. Enhanced Ionization of Embedded Clusters by Electron-Transfer-Mediated Decay in Helium Nanodroplets.

    Science.gov (United States)

    LaForge, A C; Stumpf, V; Gokhberg, K; von Vangerow, J; Stienkemeier, F; Kryzhevoi, N V; O'Keeffe, P; Ciavardini, A; Krishnan, S R; Coreno, M; Prince, K C; Richter, R; Moshammer, R; Pfeifer, T; Cederbaum, L S; Mudrich, M

    2016-05-20

    We report the observation of electron-transfer-mediated decay (ETMD) involving magnesium (Mg) clusters embedded in helium (He) nanodroplets. ETMD is initiated by the ionization of He followed by removal of two electrons from the Mg clusters of which one is transferred to the He ion while the other electron is emitted into the continuum. The process is shown to be the dominant ionization mechanism for embedded clusters for photon energies above the ionization potential of He. For Mg clusters larger than five atoms we observe stable doubly ionized clusters. Thus, ETMD provides an efficient pathway to the formation of doubly ionized cold species in doped nanodroplets. PMID:27258866

  15. Generalization of the Mulliken-Hush treatment for the calculation of electron transfer matrix elements

    Science.gov (United States)

    Cave, Robert J.; Newton, Marshall D.

    1996-01-01

    A new method for the calculation of the electronic coupling matrix element for electron transfer processes is introduced and results for several systems are presented. The method can be applied to ground and excited state systems and can be used in cases where several states interact strongly. Within the set of states chosen it is a non-perturbative treatment, and can be implemented using quantities obtained solely in terms of the adiabatic states. Several applications based on quantum chemical calculations are briefly presented. Finally, since quantities for adiabatic states are the only input to the method, it can also be used with purely experimental data to estimate electron transfer matrix elements.

  16. Tuning the reorganization energy of electron transfer in supramolecular ensembles - metalloporphyrin, oligophenylenevinylenes, and fullerene - and the impact on electron transfer kinetics

    Science.gov (United States)

    Stangel, Christina; Schubert, Christina; Kuhri, Susanne; Rotas, Georgios; Margraf, Johannes T.; Regulska, Elzbieta; Clark, Timothy; Torres, Tomás; Tagmatarchis, Nikos; Coutsolelos, Athanassios G.; Guldi, Dirk M.

    2015-01-01

    Oligo(p-phenylenevinylene) (oPPV) wires of various lengths featuring pyridyls at one terminal and C60 moieties at the other, have been used as molecular building blocks in combination with porphyrins to construct a novel class of electron donor-acceptor architectures. These architectures, which are based on non-covalent, directional interactions between the zinc centers of the porphyrins and the pyridyls, have been characterized by nuclear magnetic resonance spectroscopy and mass spectrometry. Complementary physico-chemical assays focused on the interactions between electron donors and acceptors in the ground and excited states. No appreciable electron interactions were noted in the ground state, which was being probed by electrochemistry, absorption spectroscopy, etc.; the electron acceptors are sufficiently decoupled from the electron donors. In the excited state, a different picture evolved. In particular, steady-state and time-resolved fluorescence and transient absorption measurements revealed substantial electron donor-acceptor interactions. These led, upon photoexcitation of the porphyrins, to tunable intramolecular electron-transfer processes, that is, the oxidation of porphyrin and the reduction of C60. In this regard, the largest impact stems from a rather strong distance dependence of the total reorganization energy in stark contrast to the distance independence seen for covalently linked conjugates.Oligo(p-phenylenevinylene) (oPPV) wires of various lengths featuring pyridyls at one terminal and C60 moieties at the other, have been used as molecular building blocks in combination with porphyrins to construct a novel class of electron donor-acceptor architectures. These architectures, which are based on non-covalent, directional interactions between the zinc centers of the porphyrins and the pyridyls, have been characterized by nuclear magnetic resonance spectroscopy and mass spectrometry. Complementary physico-chemical assays focused on the interactions

  17. Ultrafast Electron Transfer Kinetics in the LM Dimer of Bacterial Photosynthetic Reaction Center from Rhodobacter sphaeroides.

    Science.gov (United States)

    Sun, Chang; Carey, Anne-Marie; Gao, Bing-Rong; Wraight, Colin A; Woodbury, Neal W; Lin, Su

    2016-06-23

    It has become increasingly clear that dynamics plays a major role in the function of many protein systems. One system that has proven particularly facile for studying the effects of dynamics on protein-mediated chemistry is the bacterial photosynthetic reaction center from Rhodobacter sphaeroides. Previous experimental and computational analysis have suggested that the dynamics of the protein matrix surrounding the primary quinone acceptor, QA, may be particularly important in electron transfer involving this cofactor. One can substantially increase the flexibility of this region by removing one of the reaction center subunits, the H-subunit. Even with this large change in structure, photoinduced electron transfer to the quinone still takes place. To evaluate the effect of H-subunit removal on electron transfer to QA, we have compared the kinetics of electron transfer and associated spectral evolution for the LM dimer with that of the intact reaction center complex on picosecond to millisecond time scales. The transient absorption spectra associated with all measured electron transfer reactions are similar, with the exception of a broadening in the QX transition and a blue-shift in the QY transition bands of the special pair of bacteriochlorophylls (P) in the LM dimer. The kinetics of the electron transfer reactions not involving quinones are unaffected. There is, however, a 4-fold decrease in the electron transfer rate from the reduced bacteriopheophytin to QA in the LM dimer compared to the intact reaction center and a similar decrease in the recombination rate of the resulting charge-separated state (P(+)QA(-)). These results are consistent with the concept that the removal of the H-subunit results in increased flexibility in the region around the quinone and an associated shift in the reorganization energy associated with charge separation and recombination. PMID:27243380

  18. Potential for direct interspecies electron transfer in methanogenic wastewater digester aggregates

    DEFF Research Database (Denmark)

    Morita, Masahiko; Malvankar, Nikhil S; Franks, Ashley E;

    2011-01-01

    Mechanisms for electron transfer within microbial aggregates derived from an upflow anaerobic sludge blanket reactor converting brewery waste to methane were investigated in order to better understand the function of methanogenic consortia. The aggregates were electrically conductive...... be assigned to methane producers, consistent with the poor capacity for hydrogen and formate utilization. These results demonstrate for the first time that methanogenic wastewater aggregates can be electrically conductive and suggest that direct interspecies electron transfer could be an important mechanism......, with conductivities 3-fold higher than the conductivities previously reported for dual-species aggregates of Geobacter species in which the two species appeared to exchange electrons via interspecies electron transfer. The temperature dependence response of the aggregate conductance was characteristic of the organic...

  19. The transfer of energy between electrons and ions in solids

    International Nuclear Information System (INIS)

    In this review we consider those processes in condensed matter that involve the irreversible flow of energy between electrons and nuclei that follows from a system being taken out of equilibrium. We survey some of the more important experimental phenomena associated with these processes, followed by a number of theoretical techniques for studying them. The techniques considered are those that can be applied to systems containing many non-equivalent atoms. They include both perturbative approaches (Fermi's Golden Rule and non-equilibrium Green's functions) and molecular dynamics based (the Ehrenfest approximation, surface hopping, semi-classical Gaussian wavefunction methods and correlated electron-ion dynamics). These methods are described and characterized, with indications of their relative merits

  20. Modulating the electronic structure of chromophores by chemical substituents for efficient energy transfer: application to fluorone.

    Science.gov (United States)

    Sand, Andrew M; Liu, Claire; Valentine, Andrew J S; Mazziotti, David A

    2014-08-01

    Strong electron correlation within a quasi-spin model of chromophores was recently shown to enhance exciton energy transfer significantly. Here we investigate how the modulation of the electronic structure of the chromophores by chemical substitution can enhance energy-transfer efficiency. Unlike previous work that does not consider the direct effect of the electronic structure on exciton dynamics, we add chemical substituents to the fluorone dimer to study the effect of electron-donating and electron-withdrawing substituents on exciton energy transfer. The exciton dynamics are studied from the solution of a quantum Liouville equation for an open system whose model Hamiltonian is derived from excited-state electronic structure calculations. Both van der Waals energies and coupling energies, arising from the Hellmann-Feynman force generated upon transferring the dimers from infinity to a finite separation, are built into the model Hamiltonian. Though these two effects are implicitly treated in dipole-based models, their explicit and separate treatment as discussed here is critical to forging the correct connection with the electronic structure calculations. We find that the addition of electron-donating substituents to the fluorone system results in an increase in exciton-transfer rates by factors ranging from 1.3-1.9. The computed oscillator strength is consistent with the recent experimental results on a larger heterodimer system containing fluorone. The oscillator strength increases with the addition of electron-donating substituents. Our results indicate that the study of chromophore networks via electronic structure will help in the future design of efficient synthetic light-harvesting systems. PMID:25062094

  1. Properties of the transfer matrices of deflecting magnet systems for free electron laser

    International Nuclear Information System (INIS)

    The oscillation of the free electron laser (FEL) requires the high current and low emittance electron beam. The beam transport system should be achromatic and isochronous to preserve the brightness and the emittance of the electron beam. In this paper we clarify the algebraic properties of the transfer matrices of the magnetic deflection system, which is a key component in the beam transport line. (author)

  2. ELECTRON TRANSFER IN Hg1-xCdxTe-CdTe HETEROSTRUCTURES

    OpenAIRE

    Boebinger, G.; Vieren, J.; Guldner, Y.; Voos, M.; Faurie, J.

    1987-01-01

    Far infrared magneto-absorption experiments performed at 1.6K in HgCdTe-CdTe heterojunctions show that a two-dimensional electron gas is formed in the HgCdTe layer at the HgCdTe-CdTe interface. The electron effective masses of the two populated subbands is obtained and compared to previous theoretical calculations. The electron transfer across the interface involves deep traps in the CdTe layers.

  3. Dynamics of Electron Transfer Processes at the Surface of Dye-Sensitized Mesoporous Semiconductor Films

    OpenAIRE

    Teuscher, Joël

    2010-01-01

    Electron transfer reactions taking place at the surface of dye-sensitized semiconductors are key processes in dye-sensitized solar cells (DSSCs). After light absorption, the excited state of a dye injects an electron into a wide-bandgap semiconductor, usually titanium dioxyde, TiO2. The formed oxidized dye can then be intercepted by a redox mediator, typically iodide, before charge recombination between the injected electron and the oxidized dye...

  4. Radiation forces to electrons in laser fields explained as scattering for ponderomotive momentum transfers

    International Nuclear Information System (INIS)

    The ponderomotive momentum exchange in laser interaction with electrons is derived using a scattering model. This explains how the momentum is exchanged globally when an electron is emitted radially from a laser beam while the axial exchange of momentum is coupled with the momentum of the electromagnetic energy transferred from the laser field to the electron in the form of kinetic energy. Special attention is given to the forces acting on electrons in a laser beam and expelling the electrons laterally from the beam. 14 refs

  5. Highly Enhanced Electromechanical Stability of Large-Area Graphene with Increased Interfacial Adhesion Energy by Electrothermal-Direct Transfer for Transparent Electrodes.

    Science.gov (United States)

    Kim, Jangheon; Kim, Gi Gyu; Kim, Soohyun; Jung, Wonsuk

    2016-09-01

    Graphene, a two-dimensional sheet of carbon atoms in a hexagonal lattice structure, has been extensively investigated for research and industrial applications as a promising material with outstanding electrical, mechanical, and chemical properties. To fabricate graphene-based devices, graphene transfer to the target substrate with a clean and minimally defective surface is the first step. However, graphene transfer technologies require improvement in terms of uniform transfer with a clean, nonfolded and nontorn area, amount of defects, and electromechanical reliability of the transferred graphene. More specifically, uniform transfer of a large area is a key challenge when graphene is repetitively transferred onto pretransferred layers because the adhesion energy between graphene layers is too low to ensure uniform transfer, although uniform multilayers of graphene have exhibited enhanced electrical and optical properties. In this work, we developed a newly suggested electrothermal-direct (ETD) transfer method for large-area high quality monolayer graphene with less defects and an absence of folding or tearing of the area at the surface. This method delivers uniform multilayer transfer of graphene by repetitive monolayer transfer steps based on high adhesion energy between graphene layers and the target substrate. To investigate the highly enhanced electromechanical stability, we conducted mechanical elastic bending experiments and reliability tests in a highly humid environment. This ETD-transferred graphene is expected to replace commercial transparent electrodes with ETD graphene-based transparent electrodes and devices such as a touch panels with outstanding electromechanical stability. PMID:27564120

  6. Fast spin information transfer between distant quantum dots using individual electrons

    Science.gov (United States)

    Bertrand, B.; Hermelin, S.; Takada, S.; Yamamoto, M.; Tarucha, S.; Ludwig, A.; Wieck, A. D.; Bäuerle, C.; Meunier, T.

    2016-08-01

    Transporting ensembles of electrons over long distances without losing their spin polarization is an important benchmark for spintronic devices. It usually requires injecting and probing spin-polarized electrons in conduction channels using ferromagnetic contacts or optical excitation. In parallel with this development, important efforts have been dedicated to achieving control of nanocircuits at the single-electron level. The detection and coherent manipulation of the spin of a single electron trapped in a quantum dot are now well established. Combined with the recently demonstrated control of the displacement of individual electrons between two distant quantum dots, these achievements allow the possibility of realizing spintronic protocols at the single-electron level. Here, we demonstrate that spin information carried by one or two electrons can be transferred between two quantum dots separated by a distance of 4 μm with a classical fidelity of 65%. We show that at present it is limited by spin flips occurring during the transfer procedure before and after electron displacement. Being able to encode and control information in the spin degree of freedom of a single electron while it is being transferred over distances of a few micrometres on nanosecond timescales will pave the way towards ‘quantum spintronics’ devices, which could be used to implement large-scale spin-based quantum information processing.

  7. Electronic Structure of the Perylene / Zinc Oxide Interface: A Computational Study of Photoinduced Electron Transfer and Impact of Surface Defects

    KAUST Repository

    Li, Jingrui

    2015-07-29

    The electronic properties of dye-sensitized semiconductor surfaces consisting of pery- lene chromophores chemisorbed on zinc oxide via different spacer-anchor groups, have been studied at the density-functional-theory level. The energy distributions of the donor states and the rates of photoinduced electron transfer from dye to surface are predicted. We evaluate in particular the impact of saturated versus unsaturated aliphatic spacer groups inserted between the perylene chromophore and the semiconductor as well as the influence of surface defects on the electron-injection rates.

  8. Expanding the Diet for DIET: Electron Donors Supporting Direct Interspecies Electron Transfer (DIET in Defined Co-Cultures

    Directory of Open Access Journals (Sweden)

    Li-YIng eWang

    2016-03-01

    Full Text Available Direct interspecies electron transfer (DIET has been recognized as an alternative to interspecies H2 transfer as a mechanism for syntrophic growth, but previous studies on DIET with defined co-cultures have only documented DIET with ethanol as the electron donor in the absence of conductive materials. Co-cultures of Geobacter metallireducens and Geobacter sulfurreducens metabolized propanol, butanol, propionate, and butyrate with the reduction of fumarate to succinate. G. metallireducens utilized each of these substrates whereas only electrons available from DIET supported G. sulfurreducens respiration. A co-culture of G. metallireducens and a strain of G. sulfurreducens that could not metabolize acetate oxidized acetate with fumarate as the electron acceptor, demonstrating that acetate can also be syntrophically metabolized via DIET. A co-culture of G. metallireducens and Methanosaeta harundinacea previously shown to syntrophically convert ethanol to methane via DIET metabolized propanol or butanol as the sole electron donor, but not propionate or butyrate. The stoichiometric accumulation of propionate or butyrate in the propanol- or butanol-fed cultures demonstrated that M. harundinaceae could conserve energy to support growth solely from electrons derived from DIET. Co-cultures of G. metallireducens and Methanosarcina barkeri could also incompletely metabolize propanol and butanol and did not metabolize propionate or butyrate as sole electron donors. These results expand the range of substrates that are known to be syntrophically metabolized through DIET, but suggest that claims of propionate and butyrate metabolism via DIET in mixed microbial communities warrant further validation.

  9. Expanding the Diet for DIET: Electron Donors Supporting Direct Interspecies Electron Transfer (DIET) in Defined Co-Cultures.

    Science.gov (United States)

    Wang, Li-Ying; Nevin, Kelly P; Woodard, Trevor L; Mu, Bo-Zhong; Lovley, Derek R

    2016-01-01

    Direct interspecies electron transfer (DIET) has been recognized as an alternative to interspecies H2 transfer as a mechanism for syntrophic growth, but previous studies on DIET with defined co-cultures have only documented DIET with ethanol as the electron donor in the absence of conductive materials. Co-cultures of Geobacter metallireducens and Geobacter sulfurreducens metabolized propanol, butanol, propionate, and butyrate with the reduction of fumarate to succinate. G. metallireducens utilized each of these substrates whereas only electrons available from DIET supported G. sulfurreducens respiration. A co-culture of G. metallireducens and a strain of G. sulfurreducens that could not metabolize acetate oxidized acetate with fumarate as the electron acceptor, demonstrating that acetate can also be syntrophically metabolized via DIET. A co-culture of G. metallireducens and Methanosaeta harundinacea previously shown to syntrophically convert ethanol to methane via DIET metabolized propanol or butanol as the sole electron donor, but not propionate or butyrate. The stoichiometric accumulation of propionate or butyrate in the propanol- or butanol-fed cultures demonstrated that M. harundinaceae could conserve energy to support growth solely from electrons derived from DIET. Co-cultures of G. metallireducens and Methanosarcina barkeri could also incompletely metabolize propanol and butanol and did not metabolize propionate or butyrate as sole electron donors. These results expand the range of substrates that are known to be syntrophically metabolized through DIET, but suggest that claims of propionate and butyrate metabolism via DIET in mixed microbial communities warrant further validation. PMID:26973614

  10. FinalReport for completed IPP-0110 and 0110A Projects:"High Energy Ion Technology of Interfacial Thin Film Coatings for Electronic, Optical and Industrial Applications"

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Ian

    2009-09-01

    The DOE-supported IPP (Initiatives for Proliferation Prevention) Project, IPP-0110, and its accompanying 'add-on project' IPP-0110A, entitled 'High Energy Ion Technology of Interfacial Thin Film Coatings for Electronic, Optical and Industrial Applications' was a collaborative project involving the Lawrence Berkeley National Laboratory (LBNL) as the U.S. DOE lab; the US surface modification company, Phygen, Inc., as the US private company involved; and the High Current Electronics Institute (HCEI) of the Russian Academy of Sciences, Tomsk, Siberia, Russia, as the NIS Institute involved. Regular scientific research progress meetings were held to which personnel came from all participating partners. The meetings were held mostly at the Phygen facilities in Minneapolis, Minnesota (with Phygen as host) with meetings also held at Tomsk, Russia (HCEI as host), and at Berkeley, California (LBNL as host) In this way, good exposure of all researchers to the various different laboratories involved was attained. This report contains the Final Reports (final deliverables) from the Russian Institute, HCEI. The first part is that for IPP-0110A (the 'main part' of the overall project) and the second part is that for the add-on project IPP-0110A. These reports are detailed, and contain all aspects of all the research carried out. The project was successful in that all deliverables as specified in the proposals were successfully developed, tested, and delivered to Phygen. All of the plasma hardware was designed, made and tested at HCEI, and the performance was excellent. Some of the machine and performance parameters were certainly of 'world class'. The goals and requirements of the IPP Project were well satisfied. I would like to express my gratitude to the DOE IPP program for support of this project throughout its entire duration, and for the unparalleled opportunity thereby provided for all of the diverse participants in the project to join

  11. Domain motions and electron transfer dynamics in 2Fe-superoxide reductase.

    Science.gov (United States)

    Horch, Marius; Utesch, Tillmann; Hildebrandt, Peter; Mroginski, Maria Andrea; Zebger, Ingo

    2016-08-17

    Superoxide reductases are non-heme iron enzymes that represent valuable model systems for the reductive detoxification of reactive oxygen species. In the present study, we applied different theoretical methods to study the structural dynamics of a prototypical 2Fe-superoxide reductase and its influence on electron transfer towards the active site. Using normal mode and essential dynamics analyses, we could show that enzymes of this type are capable of well-defined, electrostatically triggered domain movements, which may allow conformational proofreading for cellular redox partners involved in intermolecular electron transfer. Moreover, these global modes of motion were found to enable access to molecular configurations with decreased tunnelling distances between the active site and the enzyme's second iron centre. Using all-atom classical molecular dynamics simulations and the tunnelling pathway model, however, we found that electron transfer between the two metal sites is not accelerated under these conditions. This unexpected finding suggests that the unperturbed enzymatic structure is optimized for intramolecular electron transfer, which provides an indirect indication of the biological relevance of such a mechanism. Consistently, efficient electron transfer was found to depend on a distinct route, which is accessible via the equilibrium geometry and characterized by a quasi conserved tyrosine that could enable multistep-tunnelling (hopping). Besides these explicit findings, the present study demonstrates the importance of considering both global and local protein dynamics, and a generalized approach for the functional analysis of these aspects is provided. PMID:27491757

  12. Rates of intra- and intermolecular electron transfers in hydrogenase deduced from steady-state activity measurements.

    Science.gov (United States)

    Dementin, Sébastien; Burlat, Bénédicte; Fourmond, Vincent; Leroux, Fanny; Liebgott, Pierre-Pol; Abou Hamdan, Abbas; Léger, Christophe; Rousset, Marc; Guigliarelli, Bruno; Bertrand, Patrick

    2011-07-01

    Electrons are transferred over long distances along chains of FeS clusters in hydrogenases, mitochondrial complexes, and many other respiratory enzymes. It is usually presumed that electron transfer is fast in these systems, despite the fact that there has been no direct measurement of rates of FeS-to-FeS electron transfer in any respiratory enzyme. In this context, we propose and apply to NiFe hydrogenase an original strategy that consists of quantitatively interpreting the variations of steady-state activity that result from changing the nature of the FeS clusters which connect the active site to the redox partner, and/or the nature of the redox partner. Rates of intra- and intermolecular electron transfer are deduced from such large data sets. The mutation-induced variations of electron transfer rates cannot be explained by changes in intercenter distances and reduction potentials. This establishes that FeS-to-FeS rate constants are extremely sensitive to the nature and coordination of the centers. PMID:21615141

  13. Electron transfer NO2++NO→NO2+NO+ in aromatic nitration

    Institute of Scientific and Technical Information of China (English)

    李象远; 何福城

    1997-01-01

    A simple model for computing the electron transfer rate constant of a cross-reaction has been proposed in the framework of semiclassical theory and employed to investigate the electron transfer system NO2+/NO.The encounter complex of electron transfer NO2++NO→NO2+NO+has been optimized at the level of UHF/6-31G.In the construction of diabatic potential energy surfaces the linear coordinate was used and the kinetic quantities,such as the activation energies and the electron transfer matrix elements,have been obtained.For comparison,the related self-exchange reation systems NO2+/NO2 and NO+/NO were kinetically investigated.The calculated activation energies for the electron transfer reactions of systems NO2+/NO,NO2+/NO2,and NO+/NO are 81 4,128.8,and 39.8kJ mol-1,respectively With the solvent effect taken into account,the contribution of solvent reorganization to the activation energy has been estimated according to the geometric parameters of the transition states.The obtained rate constants show that the

  14. Long-Range Electron Transfer Across Cytochrome-Hematite (a-Fe2O3) Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wigginton, Nicholas S. [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Swiss Federal Institute of Technology in Lausanne (Switzerland); Rosso, Kevin M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Stack, Andrew G. [Georgia Inst. of Technology, Atlanta, GA (United States); Hochella, Michael F. [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

    2009-01-06

    Electrochemical scanning tunneling microscopy (EC-STM) was used to assess the distance dependence of electron tunneling facilitated by a bacterial multiheme cytochrome to a single crystal iron oxide surface. We measured tunneling current-distance (I-s) profiles across the nanoscale space between insulated Au STM tips and the basal (001) surface of a hematite (α-Fe2O3) crystal, and compared them to the case in which an intervening small tetraheme cytochrome (STC) from Shewanella oneidensis covalently linked to the Au tip surface. Tunneling profiles were collected at constant surface potentials in solutions having a range of ionic strengths. At short tip-sample separation, the distance dependece of the tunneling current shows a quasi-linear behavior. At longer distances it shows an exponential decay. The different regions are discussed in terms of ordering of interfacial water and ion layers in the electrical double layer associated with the hematite surface. The effective tunneling range and its rate of decay are substantially increased when STC is present in the tunneling junction, suggesting that cytochrome molecules provide enhanced tunneling pathways and stronger electronic coupling to the hematite surface. Based on these results, cytochrome-mediated electron transfer during bacterial metal reduction may be possible at distances further than originally thought. Also, as multiheme cytochromes and other similar molecules gain attention for their promising role in fuel cells and molecular electronics, we show that the solution conditions and surface properties of the substrate must be carefully considered.

  15. Activators generated by electron transfer for atom transfer radical polymerization of styrene in the presence of mesoporous silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Khezri, Khezrollah, E-mail: kh.khezri@ut.ac.ir [School of Chemistry, University College of Science, University of Tehran, PO Box 14155-6455, Tehran (Iran, Islamic Republic of); Roghani-Mamaqani, Hossein [Department of Polymer Engineering, Sahand University of Technology, PO Box 51335-1996, Tabriz (Iran, Islamic Republic of)

    2014-11-15

    Graphical abstract: Effect of mesoporous silica nanoparticles (MCM-41) on the activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP) is investigated. Decrement of conversion and number average molecular weight and also increment of polydispersity index (PDI) values are three main results of addition of MCM-41 nanoparticles. Incorporation of MCM-41 nanoparticles in the polystyrene matrix can clearly increase thermal stability and decrease glass transition temperature of the nanocomposites. - Highlights: • Spherical morphology, hexagonal structure, and high surface area with regular pore diameters of the synthesized MCM-41 nanoparticles are examined. • AGET ATRP of styrene in the presence of MCM-41 nanoparticles is performed. • Effect of MCM-41 nanoparticles addition on the polymerization rate, conversion and molecular weights of the products are discussed. • Improvement in thermal stability of the nanocomposites and decreasing T{sub g} values was also observed by incorporation of MCM-41 nanoparticles. - Abstract: Activator generated by electron transfer for atom transfer radical polymerization was employed to synthesize well-defined mesoporous silica nanoparticles/polystyrene composites. Inherent features of spherical mesoporous silica nanoparticles were evaluated by nitrogen adsorption/desorption isotherm, X-ray diffraction and scanning electron microscopy analysis techniques. Conversion and molecular weight evaluations were carried out using gas and size exclusion chromatography respectively. By the addition of only 3 wt% mesoporous silica nanoparticles, conversion decreases from 81 to 58%. Similarly, number average molecular weight decreases from 17,116 to 12,798 g mol{sup −1}. However, polydispersity index (PDI) values increases from 1.24 to 1.58. A peak around 4.1–4.2 ppm at proton nuclear magnetic resonance spectroscopy results clearly confirms the living nature of the polymerization. Thermogravimetric

  16. Photoinduced 2-way electron transfer in composites of metal nanoclusters and semiconductor quantum dots

    Science.gov (United States)

    Mondal, Navendu; Paul, Sneha; Samanta, Anunay

    2016-07-01

    In order to explore the potential of nanocomposites comprising semiconductor quantum dots (QDs) and metal nanoclusters (NCs) in photovoltaic and catalytic applications, the interaction between CdTe QDs and gold NCs, Au10 and Au25, stabilized by histidine, bovine serum albumin (BSA) and glutathione, is studied by an ultrafast transient absorption (TA) technique. Temporal and spectral studies of the transients reveal photoinduced 2-way electron transfer between the two constituents of the nanocomposites, where Au NCs, which generally act as electron donors when used as photosensitizers, perform the role of the efficient electron acceptor. Interestingly, it is found that the electron transfer dynamics in these composites is governed not by the distance of separation of the constituents but by the nature of the surface capping ligands. Despite a large separation between the QDs and NCs in a giant BSA-capped system, a higher electron transfer rate in this composite suggests that unlike other smaller capping agents, which act more like insulators, BSA allows much better electron conduction, as indicated previously.In order to explore the potential of nanocomposites comprising semiconductor quantum dots (QDs) and metal nanoclusters (NCs) in photovoltaic and catalytic applications, the interaction between CdTe QDs and gold NCs, Au10 and Au25, stabilized by histidine, bovine serum albumin (BSA) and glutathione, is studied by an ultrafast transient absorption (TA) technique. Temporal and spectral studies of the transients reveal photoinduced 2-way electron transfer between the two constituents of the nanocomposites, where Au NCs, which generally act as electron donors when used as photosensitizers, perform the role of the efficient electron acceptor. Interestingly, it is found that the electron transfer dynamics in these composites is governed not by the distance of separation of the constituents but by the nature of the surface capping ligands. Despite a large separation

  17. Influence of Complex Stabilities on Electron-Transfer Reactions

    International Nuclear Information System (INIS)

    The rate of exchange in solutions containing sulphate ions was measured in the system FeII/FeIII at different temperatures with 5'9Fe as a tracer. At 25°C and an ionic strength of 1 the rate constants are: k1[FeSO+4/Fe2+] =295 litres mole-1 sec-1, k2[Fe(SO4)2-/Fe2+] =17 500 litres mole-1 sec-1. The activation energies are E1 =13.8 kcal/mole, E2 = 15kcal/mole. For the rate constants of the electron exchange between different complexes of FeIII and Fe2+ ions the following relation was found: log10k = 1.1 + 0. 5 |Δlog10K|, where Δ log10K is the difference between the logarithms of the stability constants of the FeIII and FeII complexes with the same ligands. All rate constants for electron exchange between FeIII complexes and Fe2+ ions follow this relation (as far as stability constants are known). In the system CeIII/ CeIV a first-order reaction with respect to CeIII contributes to the exchange reaction. This is explained by the formation of excited CeIII ions. The rate constant is k5 = 4.45 x 10-4 sec-1 (0°C). At 0°C the rate constants for the second-order reactions are: k1[CeSO+24/Ce3+] = 0.10 litres mole-1 sec-1, k2[Ce(SO4)2/Ce3+] = 0.11 litres mole-1 sec-1; k3[Ce(SO4)2-3/Ce3+] = 0.17 litres mole-1 sec-1, k4 [Ce4+/Ce3+] = 5.05 x 10-3 litres mole-1 sec-1. The electron exchange is accelerated by sulphate ions, but not to the same extent as in the system FeII/FeIII. The fact that the rate constants k, k2 and k3 are nearly equal shows that the charge of the complexes has no influence. The rate constants in the system CeIII/CeIV also follow a relation of the form log k = a + bΔlog K. The constants a and b were found to be: a = -2.3, b = 0.4. In the system UIV/UVI - in the absence of light - the rate of the electron exchange in solutions containing sulphate ions is proportional to the concentrations of UIV and UVI and inversely proportional to the third power of the H+ concentration. The rate determining step is the disproportionation of UV which is present in

  18. Technology transfer present and futures in the electronic arts

    Directory of Open Access Journals (Sweden)

    Brian Degger

    2008-01-01

    Full Text Available We are entering an era where creating the fantastical is possible in the arts. In the areas of mixed reality and biological arts, responsive works are created based on advances in basic science and technology. This is enabling scientists and artists to pose new questions. As the time between discovery and application is so short, artists need imaginative ways of accessing new technology in order to critique and use it.These are the new paints that the majority of artists cannot afford or access, technology to enable cloning of DNA, to print channels on a chip, to access proprietary 3G networks. Currently, partnerships or residencies are used to facilitate artist’s access to these technologies. What would they do if technology was available that enabled them to make any art work they so desire? Are the limitations in current technology an advantage rather than a disadvantage in some of their works? Does interaction with technologists make their work more robust? Are there disadvantages? How do they get access to the technology they require? Open source or proprietary? Or have they encountered the situation where their vision is greater than technology allows. When their work breaks because of this fact, is their art broken? Blast Theory (Brighton,UK, FoAM(Brussels, Belgium and Amsterdam, Netherlands, SymbioticA (Perth, Australia are organisations pushing technological boundaries in the service of art. This paper addresses some questions of technology transfer in relation to recent artworks, particularly I like Frank in Adelaide (Blast Theory, transient reality generators (trg (FoAM and Multi electrode array artist (MeART (SymbioticA.

  19. Recent Advances in Photoinduced Electron Transfer Processes of Fullerene-Based Molecular Assemblies and Nanocomposites

    Directory of Open Access Journals (Sweden)

    Osamu Ito

    2012-05-01

    Full Text Available Photosensitized electron-transfer processes of fullerenes hybridized with electron donating or other electron accepting molecules have been surveyed in this review on the basis of the recent results reported mainly from our laboratories. Fullerenes act as photo-sensitizing electron acceptors with respect to a wide variety of electron donors; in addition, fullerenes in the ground state also act as good electron acceptors in the presence of light-absorbing electron donors such as porphyrins. With single-wall carbon nanotubes (SWCNTs, the photoexcited fullerenes act as electron acceptor. In the case of triple fullerene/porphyrin/SWCNT architectures, the photoexcited porphyrins act as electron donors toward the fullerene and SWCNT. These mechanisms are rationalized with the molecular orbital considerations performed for these huge supramolecules. For the confirmation of the electron transfer processes, transient absorption methods have been used, in addition to time-resolved fluorescence spectral measurements. The kinetic data obtained in solution are found to be quite useful to predict the efficiencies of photovoltaic cells.

  20. Transfer function restoration in 3D electron microscopy via iterative data refinement

    International Nuclear Information System (INIS)

    Three-dimensional electron microscopy (3D-EM) is a powerful tool for visualizing complex biological systems. As with any other imaging device, the electron microscope introduces a transfer function (called in this field the contrast transfer function, CTF) into the image acquisition process that modulates the various frequencies of the signal. Thus, the 3D reconstructions performed with these CTF-affected projections are also affected by an implicit 3D transfer function. For high-resolution electron microscopy, the effect of the CTF is quite dramatic and limits severely the achievable resolution. In this work we make use of the iterative data refinement (IDR) technique to ameliorate the effect of the CTF. It is demonstrated that the approach can be successfully applied to noisy data

  1. Excited state electron transfer in systems with a well-defined geometry. [cyclophane

    Energy Technology Data Exchange (ETDEWEB)

    Kaufmann, K.J.

    1980-12-01

    The effect of temperature, dielectric strength and ligand on the structure of the mesopyropheophorbide cyclophanes will be studied. ESR, NMR, emission and absorption spectroscopy, as well as circular dichroism will be used. The changes in structure will be correlated with changes in the photochemical activity. Electron acceptors such as benzoquinone will be utilized to stabilize the charge separation. Charge separation in porphyrin quinone dimers will also be studied. It was found that electron transfer in the cyclophane system is relatively slow. This is presumably due to an orientation requirement for fast electron transfer. Solvent dielectric also is important in producing a charge separation. Decreasing the temperature effects the yield of charge transfer, but not the kinetics.

  2. Mechanism of electron transfer reaction for xanthene dye-sensitized formation of methyl viologen radical

    Energy Technology Data Exchange (ETDEWEB)

    Usui, Y.; Misawa, H.; Sakuragi, H.; Tokumaru, K.

    1987-05-01

    Sensitized reduction of methyl viologen, MV/sup 2 +/, occurs efficiently through electron transfer from triplet xanthene dyes to MV/sup 2 +/ followed by electron transfer to the resulting semioxidized dyes from a reductant like triethanolamine. Unreactive ion pair complexes between these dyes and MV/sup 2 +/ are formed (formation constant: 1.2 x 10/sup 3/ M/sup -1/ for Eosine Y and MV/sup 2 +/ in 50% aqueous ethanol solution). The quantum yield for the reduced methyl viologen radical depends on the concentrations of MV/sup 2 +/ and the amine and on the ionic strength of solution. The efficiency of the electron transfer from triplet dyes to MV/sup 2 +/ is increased by addition of alcohol, and solvent effects on the reaction mechanism are discussed. 38 references, 5 figures, 2 tables.

  3. Nobel Prize 1992: Rudolph A. Marcus: theory of electron transfer reactions in chemical systems

    International Nuclear Information System (INIS)

    A review of the theory developed by Rudolph A. Marcus is presented, who for his rating to the theory of electron transfer in chemical systems was awarded the Nobel Prize in Chemistry in 1992. Marcus theory has constituted not only a good extension of the use of a spectroscopic principle, but also has provided an energy balance and the application of energy conservation for electron transfer reactions. A better understanding of the reaction coordinate is exposed in terms energetic and establishing the principles that govern the transfer of electrons, protons and some labile small molecular groups as studied at present. Also, the postulates and equations described have established predictive models of reaction time, very useful for industrial environments, biological, metabolic, and others that involve redox processes. Marcus theory itself has also constituted a large contribution to the theory of complex transition

  4. Time-resolved fluorescence study of electron transfer in a model peptide system

    Science.gov (United States)

    Donald, Fiona; Hungerford, Graham; Moore, Barry D.; Birch, David J. S.

    1994-08-01

    At present there is a great deal of interest in the study of the transference of energy in biological systems. For example, electron transfer is of major importance in many synthetic and biological processes and in nature is mediated by proteins. Information regarding this process is therefore useful in leading to a greater understanding of phenomena such as photosynthesis and respiration. Previous work on protein systems has shown the electron transfer process to be complex to analyze because of the presence of competing pathways. This has led to the use of model systems to simplify the kinetics. We have synthesized novel model systems using peptides containing both a fluorescent methoxy- naphthalene donor and a dicyanoethylene group as a potential electron acceptor and observed fluorescence quenching for both dipeptide and oligopeptide systems. Biexponential fluorescence decay behavior was observed for all donor acceptor systems, with an increase in the amount of the shorter fluorescence decay component on increasing temperature.

  5. Quenching of the excited state of hydrated Europium(III) ions by electron transfer

    Energy Technology Data Exchange (ETDEWEB)

    Christensen, K.

    1993-08-01

    This thesis explores the oxidation-reduction chemistry of the excited state of Eu(III) ions, *Eu{sub aq}{sup 3+}, in aqueous solutions. Evidence is presented for the quenching of *Eu{sup 3+} by reductive electron transfer. It is concluded that *Eu{sup 3+} is not a strong energy transfer reagent. The reactivity of *Eu{sub aq}{sup 3+} is compared with that of *UO{sub 2}{sup 2+}.

  6. An analysis of conjugate heat transfer in the heat sink of an electronic chip

    OpenAIRE

    Horvat, Andrej; Catton, Ivan

    2015-01-01

    This paper describes the construction of an algorithm for conjugate heat-transfer calculations in order to find the most suitable form for the heat sink of an electronic chip. Applying volume averaging theory (VAT) to a system of transport equations, a heat-sink structure was modeled as a homogeneous porous medium. The geometry of the simulation domain and the boundary conditions followed the experimental setup used in the Morrin-Martinelly-Gier Memorial Heat Transfer Laboratory at the Univer...

  7. DFT and time-resolved IR investigation of electron transfer between photogenerated 17- and 19-electron organometallic radicals

    Energy Technology Data Exchange (ETDEWEB)

    Cahoon, James B.; Kling, Matthias F.; Sawyer, Karma R.; Andersen, Lars K.; Harris, Charles B.

    2008-04-30

    The photochemical disproportionation mechanism of [CpW(CO){sub 3}]{sub 2} in the presence of Lewis bases PR{sub 3} was investigated on the nano- and microsecond time-scales with Step-Scan FTIR time-resolved infrared spectroscopy. 532 nm laser excitation was used to homolytically cleave the W-W bond, forming the 17-electron radicals CpW(CO){sub 3} and initiating the reaction. With the Lewis base PPh{sub 3}, disproportionation to form the ionic products CpW(CO){sub 3}PPh{sub 3}{sup +} and CpW(CO){sub 3}{sup -} was directly monitored on the microsecond time-scale. Detailed examination of the kinetics and concentration dependence of this reaction indicates that disproportionation proceeds by electron transfer from the 19-electron species CpW(CO){sub 3}PPh{sub 3} to the 17-electron species CpW(CO){sub 3}. This result is contrary to the currently accepted disproportionation mechanism which predicts electron transfer from the 19-electron species to the dimer [CpW(CO){sub 3}]{sub 2}. With the Lewis base P(OMe){sub 3} on the other hand, ligand substitution to form the product [CpW(CO){sub 2}P(OMe){sub 3}]{sub 2} is the primary reaction on the microsecond time-scale. Density Functional Theory (DFT) calculations support the experimental results and suggest that the differences in the reactivity between P(OMe){sub 3} and PPh{sub 3} are due to steric effects. The results indicate that radical-to-radical electron transfer is a previously unknown but important process for the formation of ionic products with the organometallic dimer [CpW(CO){sub 3}]{sub 2} and may also be applicable to the entire class of organometallic dimers containing a single metal-metal bond.

  8. Electric Field Induced Fluorescence Modulation of Single Molecules in PMMA Based on Electron Transfer

    Directory of Open Access Journals (Sweden)

    Suotang Jia

    2012-09-01

    Full Text Available We present a method to modulate the fluorescence of non-polar single squaraine-derived rotaxanes molecules embedded in a polar poly(methyl methacrylate (PMMA matrix under an external electric field. The electron transfer between single molecules and the electron acceptors in a PMMA matrix contributes to the diverse responses of fluorescence intensities to the electric field. The observed instantaneous and non-instantaneous electric field dependence of single-molecule fluorescence reflects the redistribution of electron acceptors in PMMA induced by electronic polarization and orientation polarization of polar polymer chains in an electric field.

  9. Spin Chains and Electron Transfer at Stepped Silicon Surfaces.

    Science.gov (United States)

    Aulbach, J; Erwin, S C; Claessen, R; Schäfer, J

    2016-04-13

    High-index surfaces of silicon with adsorbed gold can reconstruct to form highly ordered linear step arrays. These steps take the form of a narrow strip of graphitic silicon. In some cases--specifically, for Si(553)-Au and Si(557)-Au--a large fraction of the silicon atoms at the exposed edge of this strip are known to be spin-polarized and charge-ordered along the edge. The periodicity of this charge ordering is always commensurate with the structural periodicity along the step edge and hence leads to highly ordered arrays of local magnetic moments that can be regarded as "spin chains." Here, we demonstrate theoretically as well as experimentally that the closely related Si(775)-Au surface has--despite its very similar overall structure--zero spin polarization at its step edge. Using a combination of density-functional theory and scanning tunneling microscopy, we propose an electron-counting model that accounts for these differences. The model also predicts that unintentional defects and intentional dopants can create local spin moments at Si(hhk)-Au step edges. We analyze in detail one of these predictions and verify it experimentally. This finding opens the door to using techniques of surface chemistry and atom manipulation to create and control silicon spin chains. PMID:26974012

  10. Spin Chains and Electron Transfer at Stepped Silicon Surfaces.

    Science.gov (United States)

    Aulbach, J; Erwin, S C; Claessen, R; Schäfer, J

    2016-04-13

    High-index surfaces of silicon with adsorbed gold can reconstruct to form highly ordered linear step arrays. These steps take the form of a narrow strip of graphitic silicon. In some cases--specifically, for Si(553)-Au and Si(557)-Au--a large fraction of the silicon atoms at the exposed edge of this strip are known to be spin-polarized and charge-ordered along the edge. The periodicity of this charge ordering is always commensurate with the structural periodicity along the step edge and hence leads to highly ordered arrays of local magnetic moments that can be regarded as "spin chains." Here, we demonstrate theoretically as well as experimentally that the closely related Si(775)-Au surface has--despite its very similar overall structure--zero spin polarization at its step edge. Using a combination of density-functional theory and scanning tunneling microscopy, we propose an electron-counting model that accounts for these differences. The model also predicts that unintentional defects and intentional dopants can create local spin moments at Si(hhk)-Au step edges. We analyze in detail one of these predictions and verify it experimentally. This finding opens the door to using techniques of surface chemistry and atom manipulation to create and control silicon spin chains.

  11. 吸收过程的界面传质机理%The Mechanism of Interfacial Mass Transfer in Gas Absorption Process

    Institute of Scientific and Technical Information of China (English)

    马友光; 冯惠生; 徐世昌; 余国琮

    2003-01-01

    Based on the method of molecular thermodynamics, the mass transfer mechanism at gas-liquid interface is studied theoretically, and a new mathematical model is proposed. Using laser holographic interference technique, the hydrodynamics and mass transfer characteristics of CO2 absorption are measured. It is shown that the calculated results are in good agreement with the experimental data.

  12. A systematic study of electron or hole transfer along DNA dimers, trimers and polymers

    CERN Document Server

    Simserides, Constantinos

    2014-01-01

    A systematic study of electron or hole transfer along DNA dimers, trimers and polymers is presented with a tight-binding approach at the base-pair level, using the relevant on-site energies of the base-pairs and the hopping parameters between successive base-pairs. A system of $N$ coupled differential equations is solved numerically with the eigenvalue method, allowing the temporal and spatial evolution of electrons or holes along a $N$ base-pair DNA segment to be determined. Useful physical quantities are defined and calculated including the maximum transfer percentage $p$ and the pure maximum transfer rate $\\frac{p}{T}$ for cases where a period $T$ can be defined, as well as the pure mean carrier transfer rate $k$ and the speed of charge transfer $u=kd$, where $d = N \\times$ 3.4 {\\AA} is the charge transfer distance. The inverse decay length $\\beta$ used for the exponential fit $k = k_0 \\exp(-\\beta d)$ and the exponent $\\eta$ used for the power law fit $k = k_0' N^{-\\eta}$ are computed. The electron and hol...

  13. Photo-induced regeneration of hormones by electron transfer processes: Potential biological and medical consequences

    Energy Technology Data Exchange (ETDEWEB)

    Getoff, Nikola, E-mail: nikola.getoff@univie.ac.a [Section of Radiation Biology, Faculty of Life Sciences, University of Vienna, A-1090 Vienna (Austria); Hartmann, Johannes [Department of Gynecologic Endocrinology and Reproduction, Medical University of Vienna, A-1090 Vienna (Austria); Schittl, Heike [Section of Radiation Biology, Faculty of Life Sciences, University of Vienna, A-1090 Vienna (Austria); Gerschpacher, Marion [Department of Gynecologic Endocrinology and Reproduction, Medical University of Vienna, A-1090 Vienna (Austria); Quint, Ruth Maria [Section of Radiation Biology, Faculty of Life Sciences, University of Vienna, A-1090 Vienna (Austria)

    2011-08-15

    Based on the previous results concerning electron transfer processes in biological substances, it was of interest to investigate if hormone transients resulting by e.g. electron emission can be regenerated. The presented results prove for the first time that the hormone transients originating by the electron emission process can be successfully regenerated by the transfer of electrons from a potent electron donor, such as vitamin C (VitC). Investigations were performed using progesterone (PRG), testosterone (TES) and estrone (E1) as representatives of hormones. By irradiation with monochromatic UV light ({lambda}=254 nm) in a media of 40% water and 60% ethanol, the degradation as well as the regeneration of the hormones was studied with each hormone individually and in the mixture with VitC as a function of the absorbed UV dose, using HPLC. Calculated from the obtained initial yields, the determined regeneration of PRG amounted to 52.7%, for TES to 58.6% and for E1 to 90.9%. The consumption of VitC was determined in the same way. The reported results concerning the regeneration of hormones by the transfer of electrons from an electron donor offer a new, promising method for the therapy with hormones. As a consequence of the regeneration of hormones, a decreased formation of carcinogenic metabolites is expected.

  14. Similarity of Heat Transfer on Heat Source Elements in the Entrance Region in Electronic Equipment

    Institute of Scientific and Technical Information of China (English)

    Jane Z. Jiang; Sui Lin

    2001-01-01

    A similarity equation for heat transfer on heat source elements situated in the entrance region in electronic equipment is developed based on the experimental data obtained by Sparrow et al.[4]. The characteristic of the similarity equation is that the ratio of the heat transfer coefficient at the entrance region to that at the fully developed region is independent of the Reynolds number. It depends only on the row number of the elements situated in the entrance region. An example of the usefulness of the similarity equation is presented that determines the heat transfer on heat source elements in a power unit that contains only a small number of the heat source elements.

  15. Controllable Quantum State Transfer Between a Josephson Charge Qubit and an Electronic Spin Ensemble

    Science.gov (United States)

    Yan, Run-Ying; Wang, Hong-Ling; Feng, Zhi-Bo

    2016-01-01

    We propose a theoretical scheme to implement controllable quantum state transfer between a superconducting charge qubit and an electronic spin ensemble of nitrogen-vacancy centers. By an electro-mechanical resonator acting as a quantum data bus, an effective interaction between the charge qubit and the spin ensemble can be achieved in the dispersive regime, by which state transfers are switchable due to the adjustable electrical coupling. With the accessible experimental parameters, we further numerically analyze the feasibility and robustness. The present scheme could provide a potential approach for transferring quantum states controllably with the hybrid system.

  16. Nonlinear response of metal nanoparticles: Double plasmon excitation and electron transfer

    Science.gov (United States)

    Gao, Shiwu

    2015-06-01

    We investigate the dynamical response of a metal nanoparticle and the electron transfer to a molecule near its surface using time-dependent density functional theory. In addition to the linear response of the Mie resonance, double plasmon excitations and a low-frequency charge transfer band emerge and become prominent at high laser intensities. Both modes are nonlinear processes, which are derived from the re-excitation and decay of the primary plasmon mode, respectively. Our results shed light on the localised characters of the plasmon-molecule coupling and hot electron distributions. These findings have general implications to photoinduced phenomena in nanosystems.

  17. Nonlinear response of metal nanoparticles: Double plasmon excitation and electron transfer

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Shiwu [Beijing Computational Science Research Center, Zhongguancun Software Park II, 100094, Beijing (China)

    2015-06-21

    We investigate the dynamical response of a metal nanoparticle and the electron transfer to a molecule near its surface using time-dependent density functional theory. In addition to the linear response of the Mie resonance, double plasmon excitations and a low-frequency charge transfer band emerge and become prominent at high laser intensities. Both modes are nonlinear processes, which are derived from the re-excitation and decay of the primary plasmon mode, respectively. Our results shed light on the localised characters of the plasmon-molecule coupling and hot electron distributions. These findings have general implications to photoinduced phenomena in nanosystems.

  18. A Novel Micro-hole Electrode Used to Investigate Electron Transfer Reactions at ITIES

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A novel micro-hole electrode was fabricated to investigate the electron transfer reaction at the interface between two immiscible electrolyte solutions (ITIES). The electron transfer reaction between ferro/ferricyanide in aqueous phase (W) and ferrocene in 1, 2-dichloroethane (O) phase was studied as a test experiment. The results showed that the diffusion coefficient obtained from the micro-hole electrode was consistent with that obtained at macro-interface. Due to its simplicity and the very small IR drop it will be a useful tool for the study of ITIES systems.

  19. A Novel Micro—hole Electrode Used to Investigate Electron Transfer Reactions at ITIES

    Institute of Scientific and Technical Information of China (English)

    DongPingZHAN; BingLiangWU

    2002-01-01

    A novel micro-hole electrode was fabricated to investigate the electron transfer reaction at the interface between two immiscible electrolyte solutions (ITIES). The electron transfer reaction between feero/ferricyanide in aqueous phase(W) and ferrocene in 1,2-dichloroethane (O) phase was studied as a test experiment. The results showed that the diffusion coefficient obtained from the micro-hole electrode was consistent with that obtained at macro-interface. Due to its simplicity and the very small IR drop it will be a useful tool for the study of ITIES systems.

  20. Short-lived electron transfer in donor-bridge-acceptor systems

    Science.gov (United States)

    Psiachos, D.

    2016-10-01

    We investigate time-dependent electron transfer (ET) in benchmark donor-bridge-acceptor systems. For the small bridge sizes studied, we obtain results far different from the perturbation theory which underlies scattering-based approaches, notably a lack of destructive interference in the ET for certain arrangements of bridge molecules. We also calculate wavepacket transmission in the non-steady-state regime, finding a featureless spectrum, while for the current we find two types of transmission: sequential and direct, where in the latter, the current transmission increases as a function of the energy of the transferred electron, a regime inaccessible by conventional scattering theory.

  1. Non-Markovian theory for the waiting time distributions of single electron transfers.

    Science.gov (United States)

    Welack, Sven; Yan, YiJing

    2009-09-21

    We derive a non-Markovian theory for waiting time distributions of consecutive single electron transfer events. The presented microscopic Pauli rate equation formalism couples the open electrodes to the many-body system, allowing to take finite bias and temperature into consideration. Numerical results reveal transient oscillations of distinct system frequencies due to memory in the waiting time distributions. Memory effects can be approximated by an expansion in non-Markovian corrections. This method is employed to calculate memory landscapes displaying preservation of memory over multiple consecutive electron transfers. PMID:19778104

  2. Electron transfer dynamics of single quantum dots on the (110) surface of a rutile TiO2 single crystal%Electron transfer dynamics of single quantum dots on the (110) surface of a rutile TiO2single crystal

    Institute of Scientific and Technical Information of China (English)

    JIN ShengYe; LIAN TianQuan

    2012-01-01

    The interfacial electron transfer (IET) dynamics of single CdSe core/multilayer shell (CdS2MLZnCd- S1MLZnS1ML) quantum dots (QDs) on the (110) surface of a futile TiO2 single crystal and TiO2 nanoparticles have been compared.The fluorescence decay rates of single QDs on TiO2 are faster than those on glass,an insulating substrate,due to IET from the QDs to TiO2.Whereas the average IET rates are similar for QDs on the single crystal and nanoparticles,the distribution of IET rates is much broader in the latter,indicating a broad distribution of QD adsorption sites on the TiO2 nanoparticles.

  3. Ru(II)-diimine functionalized metalloproteins: From electron transfer studies to light-driven biocatalysis.

    Science.gov (United States)

    Lam, Quan; Kato, Mallory; Cheruzel, Lionel

    2016-05-01

    The unique photochemical properties of Ru(II)-diimine complexes have helped initiate a series of seminal electron transfer studies in metalloenzymes. It has thus been possible to experimentally determine rate constants for long-range electron transfers. These studies have laid the foundation for the investigation of reactive intermediates in heme proteins and for the design of light-activated biocatalysts. Various metalloenzymes such as hydrogenase, carbon monoxide dehydrogenase, nitrogenase, laccase and cytochrome P450 BM3 have been functionalized with Ru(II)-diimine complexes. Upon visible light-excitation, these photosensitized metalloproteins are capable of sustaining photocatalytic activity to reduce small molecules such as protons, acetylene, hydrogen cyanide and carbon monoxide or activate molecular dioxygen to produce hydroxylated products. The Ru(II)-diimine photosensitizers are hence able to deliver multiple electrons to metalloenzymes buried active sites, circumventing the need for the natural redox partners. In this review, we will highlight the key achievements of the light-driven biocatalysts, which stem from the extensive electron transfer investigations. This article is part of a Special Issue entitled Biodesign for Bioenergetics--the design and engineering of electronic transfer cofactors, proteins and protein networks, edited by Ronald L. Koder and J.L. Ross Anderson.

  4. Nitric Oxide Synthases Reveal a Role for Calmodulin in Controlling Electron Transfer

    Science.gov (United States)

    Abu-Soud, Husam M.; Stuehr, Dennis J.

    1993-11-01

    Nitric oxide (NO) is synthesized within the immune, vascular, and nervous systems, where it acts as a wide-ranging mediator of mammalian physiology. The NO synthases (EC 1.14.13.39) isolated from neurons or endothelium are calmodulin dependent. Calmodulin binds reversibly to neuronal NO synthase in response to elevated Ca2+, triggering its NO production by an unknown mechanism. Here we show that calmodulin binding allows NADPH-derived electrons to pass onto the heme group of neuronal NO synthase. Calmodulin-triggered electron transfer to heme was independent of substrate binding, caused rapid enzymatic oxidation of NADPH in the presence of O_2, and was required for NO synthesis. An NO synthase isolated from cytokine-induced macrophages that contains tightly bound calmodulin catalyzed spontaneous electron transfer to its heme, consistent with bound calmodulin also enabling electron transfer within this isoform. Together, these results provide a basis for how calmodulin may regulate NO synthesis. The ability of calmodulin to trigger electron transfer within an enzyme is unexpected and represents an additional function for calcium-binding proteins in biology.

  5. Unraveling the electron transfer processes of a nanowire protein from Geobacter sulfurreducens.

    Science.gov (United States)

    Alves, Mónica N; Fernandes, Ana P; Salgueiro, Carlos A; Paquete, Catarina M

    2016-01-01

    The extracellular electron transfer metabolism of Geobacter sulfurreducens is sustained by several multiheme c-type cytochromes. One of these is the dodecaheme cytochrome GSU1996 that belongs to a new sub-class of c-type cytochromes. GSU1996 is composed by four similar triheme domains (A–D). The C-terminal half of the molecule encompasses the domains C and D, which are connected by a small linker and the N-terminal half of the protein contains two domains (A and B) that form one structural unit. It was proposed that this protein works as an electrically conductive device in G. sulfurreducens, transferring electrons within the periplasm or to outer-membrane cytochromes. In this work, a novel strategy was applied to characterize in detail the thermodynamic and kinetic properties of the hexaheme fragment CD of GSU1996. This characterization revealed the electron transfer process of GSU1996 for the first time, showing that a heme at the edge of the C-terminal of the protein is thermodynamic and kinetically competent to receive electrons from physiological redox partners. This information contributes towards understanding how this new sub-class of cytochromes functions as nanowires, and also increases the current knowledge of the extracellular electron transfer mechanisms in G. sulfurreducens. PMID:26435389

  6. Magnetic field effect as a probe of distance-dependent electron transfer in systems undergoing free diffusion

    OpenAIRE

    Krissinel, Evgenii B.; Burshtein, Anatoly I.; Lukzen, Nikita N.; Steiner, Ulrich

    1999-01-01

    A theoretical analysis is presented of the problem of how distance-dependent electron transfer in photoinduced forward electron transfer followed by geminate backward electron transfer in liquid solution is reflected in the viscosity dependence of the magnetic field effect (MFE) on the efficiency of free radical formation (φce) in such reactions. The stochastic Liouville equation formalism is employed to model the reaction behaviour of distance-distributed, triplet-born radical pairs (RPs) un...

  7. Interspecies electron transfer via hydrogen and formate rather than direct electrical connections in cocultures of Pelobacter carbinolicus and Geobacter sulfurreducens

    DEFF Research Database (Denmark)

    Rotaru, Amelia-Elena; Shrestha, Pravin M; Liu, Fanghua;

    2012-01-01

    Direct interspecies electron transfer (DIET) is an alternative to interspecies H(2)/formate transfer as a mechanism for microbial species to cooperatively exchange electrons during syntrophic metabolism. To understand what specific properties contribute to DIET, studies were conducted...... components for DIET. The finding that P. carbinolicus exchanged electrons with G. sulfurreducens via interspecies transfer of H(2)/formate rather than DIET demonstrates that not all microorganisms that can grow syntrophically are capable of DIET and that closely related microorganisms may use significantly...

  8. Peptide and protein sequence analysis by electron transfer dissociation mass spectrometry

    OpenAIRE

    Syka, John E. P.; Coon, Joshua J.; Schroeder, Melanie J.; Shabanowitz, Jeffrey; Hunt, Donald F.

    2004-01-01

    Peptide sequence analysis using a combination of gas-phase ion/ion chemistry and tandem mass spectrometry (MS/MS) is demonstrated. Singly charged anthracene anions transfer an electron to multiply protonated peptides in a radio frequency quadrupole linear ion trap (QLT) and induce fragmentation of the peptide backbone along pathways that are analogous to those observed in electron capture dissociation. Modifications to the QLT that enable this ion/ion chemistry are presented, and automated ac...

  9. Two-photon Induced Hot Electron Transfer to a Single Molecule in a Scanning Tunneling Microscope

    OpenAIRE

    Wu, Shiwei; Ho, Wilson

    2010-01-01

    The junction of a scanning tunneling microscope (STM) operating in the tunneling regime was irradiated with femtosecond laser pulses. A photo-excited hot electron in the STM tip resonantly tunnels into an excited state of a single molecule on the surface, converting it from the neutral to the anion. The electron transfer rate depends quadratically on the incident laser power, suggesting a two-photon excitation process. This nonlinear optical process is further confirmed by the polarization me...

  10. Promotion of the Direct Electron Transfer of Hemoglobin by the Carbon Nanotube

    Institute of Scientific and Technical Information of China (English)

    Jing CHEN; Chen Xin CAI

    2004-01-01

    It is reported that the direct electron transfer of hemoglobin (Hb) can be effectively promoted by carbon nanotubes when Hb was immobilized on the surface of the carbon nanotubes modified electrode. The results indicated that the conversion of Hb-Fe(III)/Hb-Fe(II) is a one-electron coupled one-proton reaction process. The method presented can be easily extended to study the direct electrochemistry of other proteins or enzymes.

  11. Photoinduced 2-way electron transfer in composites of metal nanoclusters and semiconductor quantum dots.

    Science.gov (United States)

    Mondal, Navendu; Paul, Sneha; Samanta, Anunay

    2016-08-01

    In order to explore the potential of nanocomposites comprising semiconductor quantum dots (QDs) and metal nanoclusters (NCs) in photovoltaic and catalytic applications, the interaction between CdTe QDs and gold NCs, Au10 and Au25, stabilized by histidine, bovine serum albumin (BSA) and glutathione, is studied by an ultrafast transient absorption (TA) technique. Temporal and spectral studies of the transients reveal photoinduced 2-way electron transfer between the two constituents of the nanocomposites, where Au NCs, which generally act as electron donors when used as photosensitizers, perform the role of the efficient electron acceptor. Interestingly, it is found that the electron transfer dynamics in these composites is governed not by the distance of separation of the constituents but by the nature of the surface capping ligands. Despite a large separation between the QDs and NCs in a giant BSA-capped system, a higher electron transfer rate in this composite suggests that unlike other smaller capping agents, which act more like insulators, BSA allows much better electron conduction, as indicated previously. PMID:27396603

  12. Constraint-based modeling of carbon fixation and the energetics of electron transfer in Geobacter metallireducens.

    Directory of Open Access Journals (Sweden)

    Adam M Feist

    2014-04-01

    Full Text Available Geobacter species are of great interest for environmental and biotechnology applications as they can carry out direct electron transfer to insoluble metals or other microorganisms and have the ability to assimilate inorganic carbon. Here, we report on the capability and key enabling metabolic machinery of Geobacter metallireducens GS-15 to carry out CO2 fixation and direct electron transfer to iron. An updated metabolic reconstruction was generated, growth screens on targeted conditions of interest were performed, and constraint-based analysis was utilized to characterize and evaluate critical pathways and reactions in G. metallireducens. The novel capability of G. metallireducens to grow autotrophically with formate and Fe(III was predicted and subsequently validated in vivo. Additionally, the energetic cost of transferring electrons to an external electron acceptor was determined through analysis of growth experiments carried out using three different electron acceptors (Fe(III, nitrate, and fumarate by systematically isolating and examining different parts of the electron transport chain. The updated reconstruction will serve as a knowledgebase for understanding and engineering Geobacter and similar species.

  13. Transfer and reconstruction of the density matrix in off-axis electron holography.

    Science.gov (United States)

    Röder, Falk; Lubk, Axel

    2014-11-01

    The reduced density matrix completely describes the quantum state of an electron scattered by an object in transmission electron microscopy. However, the detection process restricts access to the diagonal elements only. The off-diagonal elements, determining the coherence of the scattered electron, may be obtained from electron holography. In order to extract the influence of the object from the off-diagonals, however, a rigorous consideration of the electron microscope influences like aberrations of the objective lens and the Möllenstedt biprism in the presence of partial coherence is required. Here, we derive a holographic transfer theory based on the generalization of the transmission cross-coefficient including all known holographic phenomena. We furthermore apply a particular simplification of the theory to the experimental analysis of aloof beam electrons scattered by plane silicon surfaces.

  14. The ‘porin–cytochrome’ model for microbe-to-mineral electron transfer

    Energy Technology Data Exchange (ETDEWEB)

    Richardson, David J.; Butt, Julea N.; Fredrickson, Jim K.; Zachara, John M.; Shi, Liang; Edwards, Marcus J.; White, Gaye F.; Baiden, Nanakow; Gates, Andrew J.; Marritt, Sophie; Clarke, Thomas A.

    2012-05-30

    Many species of bacteria can couple anaerobic growth to the respiratory reduction of insoluble minerals containing Fe(III) or Mn(III/IV). It has been suggested that in Shewanella species electrons cross the outer membrane to extracellular substrates via 'porin-cytochrome' electron transport modules. The molecular structure of an outer-membrane extracellular-facing deca-haem terminus for such a module has recently been resolved. It is debated how, once outside the cells, electrons are transferred from outer-membrane cytochromes to insoluble electron sinks. This may occur directly or by assemblies of cytochromes, perhaps functioning as 'nanowires', or via electron shuttles. Here we review recent work in this field and explore whether it allows for unification of the electron transport mechanisms supporting extracellular mineral respiration in Shewanella that may extend into other genera of Gram-negative bacteria.

  15. ZnO-nanorods/graphene heterostructure: a direct electron transfer glucose biosensor

    Science.gov (United States)

    Zhao, Yu; Li, Wenbo; Pan, Lijia; Zhai, Dongyuan; Wang, Yu; Li, Lanlan; Cheng, Wen; Yin, Wei; Wang, Xinran; Xu, Jian-Bin; Shi, Yi

    2016-01-01

    ZnO-nanorods/graphene heterostructure was synthesized by hydrothermal growth of ZnO nanorods on chemically reduced graphene (CRG) film. The hybrid structure was demonstrated as a biosensor, where direct electron transfer between glucose oxidase (GOD) and electrode was observed. The charge transfer was attributed to the ZnO nanorod wiring between the redox center of GOD and electrode, and the ZnO/graphene heterostructure facilitated the transport of electrons on the hybride electrode. The glucose sensor based on the GOD-ZnO/CRG/Pt electrode had a high sensitivity of 17.64 μA mM−1, which is higher than most of the previously reported values for direct electron transfer based glucose biosensors. Moreover, this biosensor is linearly proportional to the concentration of glucose in the range of 0.2–1.6 mM. The study revealed that the band structure of electrode could affect the detection of direct electron transfer of GOD, which would be helpful for the design of the biosensor electrodes in the future. PMID:27572675

  16. Bimolecular Excited-State Electron Transfer with Surprisingly Long-Lived Radical Ions

    KAUST Repository

    Alsam, Amani A.

    2015-09-02

    We explored the excited-state interactions of bimolecular, non-covalent systems consisting of cationic poly[(9,9-di(3,3’-N,N’-trimethyl-ammonium) propyl fluorenyl-2,7-diyl)-alt-co-(9,9-dioctyl-fluorenyl-2,7-diyl)] diiodide salt (PFN) and 1,4-dicyanobenzene (DCB) using steady-state and time-resolved techniques, including femto- and nanosecond transient absorption and femtosecond infrared spectroscopies with broadband capabilities. The experimental results demonstrated that photo-induced electron transfer from PFN to DCB occurs on the picosecond time scale, leading to the formation of PFN+• and DCB-• radical ions. Interestingly, real-time observations of the vibrational marker modes on the acceptor side provided direct evidence and insight into the electron transfer process indirectly inferred from UV-Vis experiments. The band narrowing on the picosecond time scale observed on the antisymmetric C-N stretching vibration of the DCB radical anion provides clear experimental evidence that a substantial part of the excess energy is channeled into vibrational modes of the electron transfer product and that the geminate ion pairs dissociate. More importantly, our nanosecond time-resolved data indicate that the charge-separated state is very long lived ( 30 ns) due to the dissociation of the contact radical ion pair into free ions. Finally, the fast electron transfer and slow charge recombination anticipate the current donor−acceptor system with potential applications in organic solar cells.

  17. Directionality of Ultrafast Electron Transfer in a Hydrogen Evolving Ru-Pd-Based Photocatalyst

    NARCIS (Netherlands)

    Pan, Qing; Mecozzi, Francesco; Korterik, Jeroen P.; Sharma, Divya; Herek, Jennifer L.; Vos, Johannes G.; Browne, Wesley R.; Huijser, Annemarie

    2014-01-01

    Directionality of electron transfer and long-lived charge separation are of key importance for efficient photocatalytic water splitting. Knowledge of the processes that follow photoexcitation is essential for the optimization of supramolecular assembly designs in order to improve the efficiency of p

  18. Bibliography on electron transfer processes in ion-ion/atom/molecule collisions (updated 1993)

    International Nuclear Information System (INIS)

    Following our previous compilations [IPPJ-AM-45 (1986), NIFS-DATA-7 (1990)], bibliographic information on experimental and theoretical studies on electron transfer processes in ion-ion/atom/molecule collisions is up-dated. The references published through 1980-1992 are included. For easy finding references for particular combination of collision partners, a simple list is also provided. (author) 1542 refs

  19. Electron transfer reaction in the Marcus inverted region: Role of high frequency vibrational modes

    International Nuclear Information System (INIS)

    A theoretical study of the dynamics of photo-electron transfer reactions in the Marcus inverted regime is presented. This study is motivated partly by the recent proposal of Barbara et al. (J. Phys. Chem. 96, 3728, 1991) that a minimal model of an electron transfer reaction should consist of a polar solvent mode (X), a low frequency vibrational mode (Q) and one high frequency mode (q). Interplay between these modes may be responsible for the crossover observed in the dynamics from a solvent controlled to a vibrational controlled electron transfer. The following results have been obtained. (i) In the case of slowly relaxing solvents, the proximity of the point of excitation to an effective sink on the excited surface is critical in determining the decay of the reactant population. This is because the Franck-Condon overlap between the reactant ground and the product excited states decreases rapidly with increase in the quantum number of the product vibrational state. (ii) Non-exponential solvation dynamics has an important effect in determining the rates of electron transfer. Especially, a biphasic solvation and a large coupling between the reactant and the product states both may be needed to explain the experimental results

  20. Phthalimides as exceptionally efficient single electron transfer acceptors in reductive coupling reactions promoted by samarium diiodide.

    Science.gov (United States)

    Vacas, Tatiana; Alvarez, Eleuterio; Chiara, Jose Luis

    2007-12-20

    Experimental and theoretical evidence shows that phthalimides are highly efficient single electron transfer acceptors in reactions promoted by samarium diiodide, affording ketyl radical anion intermediates, which participate in high-yielding inter- and intramolecular reductive coupling processes with different radicophiles including imides, oxime ethers, nitrones, and Michael acceptors.