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Sample records for interfacial electron transfer

  1. Facile Interfacial Electron Transfer of Hemoglobin

    Chunhai Fan; Shiping Song; Haiping Wu; Lihua Wang; Xiaofang Hu; Runguang Sun; Bo Zhou

    2005-01-01

    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...

  2. Facile Interfacial Electron Transfer of Hemoglobin

    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

  3. Electron transfer and interfacial behavior of redox proteins

    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.

  4. Electron Transfer Phenomena in Interfacial Bioelectrochemistry

    Baier, Claudia

    2011-01-01

    Biomolecules at the solid-liquid interface have been investigated using electrochemical measurement techniques such as cyclic voltammetry and electrochemical scanning probe microscopies. Structure and function of the biomolecules, depending on the electron transfer and the used electrode material could be studied down to a single molecule level. Besides investigating natural electroactive proteins, e.g. the metalloprotein azurin or the iron storage protein ferritin, a method has been develope...

  5. Nanoscale and single-molecule interfacial electron transfer

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

    2003-01-01

    Electrochemical science and technology in the 21st century have reached high levels of sophistication. A fundamental quantum mechanical theoretical frame for interfacial electrochemical electron transfer (ET) was introduced by Revaz Dogonadze. This frame has remained for four decades as a basis f...

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

    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

  7. Single-molecule interfacial electron transfer dynamics manipulated by external electric current

    Zhang, Guofeng; Chen, Ruiyun; Gao, Yan; Wang, Xiaobo; Jia, Suotang

    2011-01-01

    Interfacial electron transfer (IET) dynamics in 1,1'-dioctadecyl-3, 3, 3', 3'-tetramethylindodicarbocyanine (DiD) dye molecules / indium tin oxide (ITO) film system have been probed at the ensemble and single-molecule level by recording the change of fluorescence emission intensity. By comparing the difference of the external electric current (EEC) dependence of lifetime and intensity for enambles and single molecules, it is shown that the single-molecule probe can effcienly demonstrate the IET dynamics. The backward electron transfer and electron transfer of ground state induce the single molecules fluorescence quenching when an EEC is applied to ITO film.

  8. Interfacial electronic charge transfer and density of states in short period Cu/Cr multilayers; TOPICAL

    Nanometer period metallic multilayers are ideal structures to investigate electronic phenomena at interfaces between metal films since interfacial atoms comprise a large atomic fraction of the samples. The Cu/Cr binary pair is especially suited to study the interfaces in metals since these elements are mutually insoluble, thus eliminating mixing effects and compound formation and the lattice mismatch is very small. This allows the fabrication of high structural quality Cu/Cr multilayers that have a structure which can be approximated in calculations based on idealized atomic arrangements. The electronic structure of the Cu and the Cr layers in several samples of thin Cu/Cr multilayers were studied using x-ray absorption spectroscopy (XAS). Total electron yield was measured and used to study the white lines at the Cu L(sub 2) and L(sub 3) absorption edges. The white lines at the Cu absorption edges are strongly related to the unoccupied d-orbitals and are used to calculate the amount of charge transfer between the Cr and Cu atoms in interfaces. Analysis of the Cu white lines show a charge transfer of 0.026 electrons/interfacial Cu atom to the interfacial Cr atoms. In the Cu XAS spectra we also observe a van Hove singularity between the L(sub 2) and L(sub 3) absorption edges as expected from the structural analysis. The absorption spectra are compared to partial density of states obtained from a full-potential linear muffin-tin orbital calculation. The calculations support the presence of charge transfer and indicate that it is localized to the first two interfacial layers in both Cu and Cr

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

    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.

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

    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.

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

    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...... electrolyte (in situ STM). Interfacial electrochemistry of metalloproteins is presently going through a similar transition. Electrochemical surfaces with thiol-based promoter molecular monolayers (SAMs) as biomolecular electrochemical environments and the biomolecules themselves have been mapped with...... unprecedented resolution, opening a new area of single-molecule bioelectrochemistry. We consider first in situ STM of small redox molecules, followed by in situ STM of thiol-based SAMs as molecular views of bioelectrochemical environments. We then address electron transfer metalloproteins, and multi...

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

    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

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

    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

  14. Linker dependence of interfacial electron transfer rates in Fe(II)-polypyridine sensitized solar cells

    Dye-sensitized solar cells (DSSCs) convert solar energy to electricity employing dye molecules attached to a semiconductor surface. Some of the most efficient DSSCs use Ru-based chromophores. Fe-based dyes represent a cheaper and more environmentally friendly alternative to these expensive and toxic dyes. The photoactive state of Fe-based chromophores responsible for charge-separation at the dye-semiconductor interface is, however, deactivated on a sub-picosecond time scale via the intersystem crossing (ISC) into a manifold of low-lying photo-inactive quintet states. Therefore, development of Fe-based dyes capable of fast interfacial electron transfer (IET) leading to efficient charge separation on a time scale competitive with the ISC events is important. This work investigates how linker groups anchoring a prototypical Fe-based dye [Fe(bpy-L)2(CN)2] (bpy = 2,2′-bipyridine, L = linker group) onto the TiO2 semiconductor surface influence the IET rates in the dye–semiconductor assemblies. Linker groups investigated include carboxylic acid, phosphonic acid, hydroxamate, catechol, and acetylacetonate. We employ time-dependent density functional theory (TD-DFT) to obtain absorption spectra of [Fe(bpy-L)2(CN)2] with each linker, and quantum dynamics simulations to investigate the IET rates between the dye and the (101) TiO2 anatase surface. For all attachments, TD-DFT calculations show similar absorption spectra with two main bands corresponding to the metal-to-ligand charge transfer transitions. The quantum dynamics simulations predict that the utilization of the hydroxamate linker instead of the commonly used carboxylic acid linker will lead to a more efficient IET and better photon-to-current conversion efficiencies in Fe(II)-polypyridine sensitized solar cells. (paper)

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

    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

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

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

    2007-01-01

    -defined stoichiometry. The systems were investigated in homogeneous solution and at liquid/solid interface. Conjugation of cyt c results in a small but consistent broadening of the nanoparticle plasmon band. This phenomenon can be explained in terms of long-range electronic interactions between the gold nanoparticle...... with that of cyt c in the absence of AuNPs is observed. AuNPs appear to serve as excellent ET relays, most likely by facilitating the electronic coupling between the protein redox center and the electrode surface.......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...

  17. Interfacial electron transfer and bioelectrocatalysis of carbonized plant material as effective anode of microbial fuel cell

    ABSTRACT: Effective use of natural materials to fabricate porous carbonaceous structures for anodes of microbial fuel cells (MFCs) has a high potential for substantial cost reduction in MFC. In this study, three kinds of plant materials, i.e. king mushroom, wild mushroom and corn stem, were investigated for fabrication of conductive electrode materials by simple carbonization procedures. Structure–reactivity relationships of these electrodes were systematically studied with electrochemical redox probe ([Fe(CN)6]3−/4−) and biofilm electroactivity. The electrochemical and bioelectrochemical accessibilities of the carbonized electrodes were evaluated by impedance, cyclic voltammetry and chronoamperometry techniques in order to study the electron transfer rate (Kapp), charge transfer resistances, oxidative current density and bioelectroactive moieties. The results showed that the electron transfer resistance (Rct) was 94 Ω for carbonized corn stem electrode with an electron transfer rate (Kapp) of 3.44 × 10−2 cm s−1 for Fe2+/Fe3+ redox probe. Higher bioelectroactivity (9.29 × 10−8 mol cm−2) was found from biofilm on carbonized corn stem (Rbiofilm, 45 Ω) with an electron transfer rate (bacteria-anode) of 63 × 10−5 cm s−1. The maximum bioelectrocatalytic current (imax) of 3.12 mA cm−2 was obtained on carbon electrode derived from corn stem. That is 8 times higher than plain graphite electrode. The porous architecture, high electron transfer rate and high electroactive biofilm growth are attributes that qualify natural-material carbon anodes as low-cost alternative for MFC

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

    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...... 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...

  19. Interfacial charge transfer in nanoscale polymer transistors

    Worne, J. H.; Giridharagopal, R.; Kelly, K. F.; Natelson, D.

    2008-01-01

    Interfacial charge transfer plays an essential role in establishing the relative alignment of the metal Fermi level and the energy bands of organic semiconductors. While the details remain elusive in many systems, this charge transfer has been inferred in a number of photoemission experiments. We present electronic transport measurements in very short channel ($L < 100$ nm) transistors made from poly(3-hexylthiophene) (P3HT). As channel length is reduced, the evolution of the contact resistan...

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

    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

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

    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.

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

    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 was...... positively and negatively charged redox probe couples displayed antagonistic inhibition and voltammetric patterns. [Ru(NH3)(6)](3+2+) and the homologous compound [Co(NH3)(6)](3+/2+) were the only probe compounds to effect growth inhibition. On the other hand, cyclic voltammetry (CV) of both [Ru(NH3...

  3. Interfacial electron transfer between the photoexcited porphyrin molecule and TiO2 nanoparticles: effect of catecholate binding.

    Ramakrishna, G; Verma, Sandeep; Jose, D Amilan; Kumar, D Krishna; Das, Amitava; Palit, Dipak K; Ghosh, Hirendra N

    2006-05-11

    Interfacial electron transfer (ET) dynamics of 5,10,15-trisphenyl-20-(3,4-dihydroxybenzene) porphyrin (TPP-cat) adsorbed on TiO2 nanoparticles has been studied by femtosecond transient absorption spectroscopy in the visible and near-IR region exciting at 400 and 800 nm. TPP-cat molecule forms a charge transfer (CT) complex with TiO2 nanoparticles through the catechol moiety with the formation of a five-membered ring. Optical absorption measurements have shown that the Q-band of TPP-cat interacts strongly with TiO2 due to chelation; however, the Soret band is affected very little. Optical absorption measurements indicate that the catechol moiety also interacts with TiO2 nanoparticles showing the characteristic band of pure catechol-TiO2 charge transfer (CT) in the visible region. Electron injection has been confirmed by monitoring the cation radical, instant bleach, and injected electron in the conduction band of TiO2 nanoparticles. Electron injection time has been measured to be < 100 fs and recombination kinetics has been best fitted with a multiexponential function, where the majority of the injected electrons come back to the parent cation radical with a time constant of approximately 800 fs for both excitation wavelengths. However, the reaction channel for the electron injection process has been found to be different for both wavelengths. Excitation at 800 nm, found to populate the CT state of the Q-band, and from the photoexcited CT state electron injection into the conduction band, takes place through diffusion. On the other hand, with excitation at 400 nm, a complicated reaction channel takes place. Excitation with 400 nm light excites both the CT band of Cat-TiO2 and also the Soret band of TPP-cat. We have discussed the reaction path in the TPP-cat/TiO2 system after exciting with both 400 and 800 nm laser light. We have also compared ET dynamics by exciting at both wavelengths. PMID:16671709

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

    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.

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

    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.

  6. Approach to Interfacial and Intramolecular Electron Transfer of the Diheme Protein Cytochrome c(4) Assembled on Au(111) Surfaces

    Chi, Qijin; Zhang, Jingdong; Taner, Arslan;

    2010-01-01

    two-center proteins are simple enough to offer complete communication networks. At the same time, multicenter redox proteins operate in membrane environments where conformational dynamics may lead to gated ET features different from conditions in homogeneous solution. The bacterial respiratory diheme...... 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...... is understandable due to the through-space, hydrogen-bonded electronic contact between the heme propionates which is highly sensitive to environmental configurational fluctuations....

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

    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.

  8. Tunnel magnetoresistance and interfacial electronic state

    Inoue, J; Itoh, H.

    2002-01-01

    We study the relation between tunnel magnetoresistance (TMR) and interfacial electronic states modified by magnetic impurities introduced at the interface of the ferromagnetic tunnel junctions, by making use of the periodic Anderson model and the linear response theory. It is indicated that the TMR ratio is strongly reduced depending on the position of the $d$-levels of impurities, based on reduction in the spin-dependent $s$-electron tunneling in the majority spin state. The results are comp...

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

    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)

  10. Interfacial Charge Transfer States in Condensed Phase Systems.

    Vandewal, Koen

    2016-05-27

    Intermolecular charge transfer (CT) states at the interface between electron-donating (D) and electron-accepting (A) materials in organic thin films are characterized by absorption and emission bands within the optical gap of the interfacing materials. CT states efficiently generate charge carriers for some D-A combinations, and others show high fluorescence quantum efficiencies. These properties are exploited in organic solar cells, photodetectors, and light-emitting diodes. This review summarizes experimental and theoretical work on the electronic structure and interfacial energy landscape at condensed matter D-A interfaces. Recent findings on photogeneration and recombination of free charge carriers via CT states are discussed, and relations between CT state properties and optoelectronic device parameters are clarified. PMID:26980308

  11. 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

    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.

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

    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

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

    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

  14. Electron transfer reactions

    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

  15. Pressure transfer functions for interfacial fluid problems

    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.

  16. Interfacial electronic effects control the reaction selectivity of platinum catalysts

    Chen, Guangxu; Xu, Chaofa; Huang, Xiaoqing; Ye, Jinyu; Gu, Lin; Li, Gang; Tang, Zichao; Wu, Binghui; Yang, Huayan; Zhao, Zipeng; Zhou, Zhiyou; Fu, Gang; Zheng, Nanfeng

    2016-05-01

    Tuning the electronic structure of heterogeneous metal catalysts has emerged as an effective strategy to optimize their catalytic activities. By preparing ethylenediamine-coated ultrathin platinum nanowires as a model catalyst, here we demonstrate an interfacial electronic effect induced by simple organic modifications to control the selectivity of metal nanocatalysts during catalytic hydrogenation. This we apply to produce thermodynamically unfavourable but industrially important compounds, with ultrathin platinum nanowires exhibiting an unexpectedly high selectivity for the production of N-hydroxylanilines, through the partial hydrogenation of nitroaromatics. Mechanistic studies reveal that the electron donation from ethylenediamine makes the surface of platinum nanowires highly electron rich. During catalysis, such an interfacial electronic effect makes the catalytic surface favour the adsorption of electron-deficient reactants over electron-rich substrates (that is, N-hydroxylanilines), thus preventing full hydrogenation. More importantly, this interfacial electronic effect, achieved through simple organic modifications, may now be used for the optimization of commercial platinum catalysts.

  17. Multidimensional mechanistic modeling of interfacial heat and mass transfer

    A combined theoretical and computational study in modeling multidimensional, diabatic vapor/liquid flows is presented. Models have been developed governing kinematic aspects of multiphase flow as well as interfacial mass and heat transfer for flows of condensable gas (vapor) and liquids. The modeling formulation is based on the Reynolds averaged Navier-Stokes (RANS) type multi-field approach which utilizes a complete set of conservation equations for each fluid component 1. The modeled interfacial interactions include energy, mass, and momentum transfer. Emphasis in the model development work has been placed on the mechanisms governing coupled interfacial heat and mass transfer between the liquid and vapor fields (condensation and/or boiling). A method for tracking changes in bubble size is presented and tested. Locally based models of multidimensional effects have been analyzed, including distributions of fluid temperatures and volume fractions. The overall model accounts for both kinematic and thermodynamic nonequilibrium between the component fluids including superheated vapor. The model has been implemented in the NPHASE-CMFD computer code. Results from the kinematic model are compared to experimental data and good agreement is demonstrated. The heat and mass transfer model is parametrically tested to show the multidimensional effects on the rate of heat and mass transfer. These effects are explained in terms of local characteristics of the two-phase flow. The model is applied to a scenario of saturated vapor injected into a subcooled flow through a heated, porous wall. This provides a reasonable approximation to subcooled boiling. The results are found to be dependent on the partitioning of the wall heat flux between direct liquid heating and vapor generation. However, the observed dependencies are explained and the modeling is considered consistent. (authors)

  18. Electron transfer in proteins

    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 remarkable...... specificity. The electron transfer is attained through weak electronic interaction between the active sites, so that considerable research efforts are centered on resolving the factors that control the rates of long-distance electron transfer reactions in proteins. These factors include (in addition to the......-containing proteins. These proteins serve almost exclusively in electron transfer reactions, and as it turns out, their metal coordination sites are endowed with properties uniquely optimized for their function....

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

    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.

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

    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...

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

    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.

  2. Interfacial charge transfer behavior of conducting polymers as contact electrode for semiconductor devices

    Kawakita, Jin; Fujikawa, Yuki; Nagata, Takahiro; Chikyow, Toyohiro

    2016-04-01

    As an alternative contact electrode material to metals, which is necessary for downsized semiconductor devices in 10 nm processes, an intrinsically conducting polymer was studied in terms of its interfacial charge-transfer behavior with an inorganic semiconductor. Polypyrrole as the conducting polymer was formed using an electrochemical technique on an oxide semiconductor and its electronic properties were evaluated using scanning probe microscopy. The experimental results showed that an ohmic contact was observed dynamically at local positions, although a Schottky barrier was expected in the static electronic state over the measurement area. From this research, the conducting polymer was found to be promising as a contact electrode.

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

    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

  4. Quantification of interfacial segregation by analytical electron microscopy

    Muellejans, H

    2003-01-01

    The quantification of interfacial segregation by spatial difference and one-dimensional profiling is presented in general where special attention is given to the random and systematic uncertainties. The method is demonstrated for an example of Al-Al sub 2 O sub 3 interfaces in a metal-ceramic composite material investigated by energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy in a dedicated scanning transmission electron microscope. The variation of segregation measured at different interfaces by both methods is within the uncertainties, indicating a constant segregation level and interfacial phase formation. The most important random uncertainty is the counting statistics of the impurity signal whereas the specimen thickness introduces systematic uncertainties (via k factor and effective scan width). The latter could be significantly reduced when the specimen thickness is determined explicitly. (orig.)

  5. Quantum dynamics simulations of interfacial charge-transfer in organic dye-sensitized solar cells

    Rego, Luis G. C.; da Silva, R.; Hoff, D. A.

    2013-03-01

    We describe a novel time-dependent quantum-mechanics/molecular-mechanics method for studying electron transfer in dye sensitized semiconductor interfaces, that takes into account the interacting electron-hole quantum dynamics, the underlying nuclear fluctuations and solvation dynamics. We provide a comprehensive investigation of the quantum dynamics, the electronic and the structural properties of prototypical D- π-A organic dyes sensitizing the TiO2 anatase surface, both in vacuum and solvated by liquid acetonitrile. The organic dyes are comprised of an electron donating moiety and an anchoring acceptor moiety, conjugated by thiophene bridges. Although interfacial electron transfer is very efficient, it is demonstrated that the coupling between the photoexcited electron and the hole delays the electron injection. Simulations demonstrate that the solvent screens the dye from the surface, narrowing the absorption peaks and delaying the electron injection. We have also studied several aspects that are relevant for the recombination process, such as the role played by surface defects and the interaction of redox species with the TiO2 surface, and the effect of additives. J. Phys. Chem. C 116, 21169 (2012). The authors acknowledge support from CNPq and CAPES, Brazil

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

    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.

  7. Electron transfer in proteins.

    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

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

    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.

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

    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

  10. Advances in electron transfer chemistry

    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

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

    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

  12. Interfacial shear and waviness effects on laminar film flow heat transfer in vertical tubes

    Kuhn, S.Z.; Peterson, P.F.; Schrock, V.E. [Univ. of California, Berkeley, CA (United States). Dept. of Nuclear Engineering

    1996-12-31

    This study presents experimental data for local laminar-film heat transfer with interfacial waviness and shear stress effects, for two film-formation methods: condensation only and condensation on injected films. The results explain differences between correlations commonly used to predict heat transfer through liquid films. Wave evolution is significantly influenced by both the length of longitudinal development and by the film-formation method. This study of condensation inside a vertical tube demonstrates that for small amplitude wavy films, heat transfer enhancement by interfacial shear results primarily from thinning of the film, whereas for films with large disturbance waves, interfacially-induced turbulent enhancement becomes increasingly important. Contrary to the common assumption, when the film is fairly smooth, interfacial shear has little effect on film transition to turbulence.

  13. Interfacial shear and waviness effects on laminar film flow heat transfer in vertical tubes

    This study presents experimental data for local laminar-film heat transfer with interfacial waviness and shear stress effects, for two film-formation methods: condensation only and condensation on injected films. The results explain differences between correlations commonly used to predict heat transfer through liquid films. Wave evolution is significantly influenced by both the length of longitudinal development and by the film-formation method. This study of condensation inside a vertical tube demonstrates that for small amplitude wavy films, heat transfer enhancement by interfacial shear results primarily from thinning of the film, whereas for films with large disturbance waves, interfacially-induced turbulent enhancement becomes increasingly important. Contrary to the common assumption, when the film is fairly smooth, interfacial shear has little effect on film transition to turbulence

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

    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

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

    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.

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

    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 ...

  17. Coherent electron transfer in polyacetylene

    Psiachos, D., E-mail: dpsi@physics.uoc.gr

    2014-06-03

    Highlights: • We study electron–ion dynamics in a donor–acceptor system. • We find two distinct electron-transfer regimes: hopping and tunnelling. • We establish conditions for achieving ballistic electron transfer. • Lattice vibrations can dramatically affect the rate of electron transfer. • Decoherence due to lattice vibrations is limited in the tunnelling regime. - Abstract: We examine, using mixed classical-quantum electron–ion dynamics, electron transfer in a donor–acceptor-like molecular junction system based on polyacetylene. We identify two qualitatively-different transfer regimes: hopping and tunnelling. We discuss the criteria for achieving each one and for minimising inelastic scattering and decoherence arising from the coupling to the ions, and we connect our main results to quantities derived from electron dynamics involving simpler, three-state model systems. We identify the requirements to have near-ballistic transfer.

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

    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

  19. A note on the standard electron transfer potential at the interface between two immiscible electrolyte solutions

    Samec, Zdeněk

    2009-01-01

    Roč. 55, č. 2 (2009), s. 75-81. ISSN 0034-6691 R&D Projects: GA ČR(CZ) GA203/07/1257 Institutional research plan: CEZ:AV0Z40400503 Keywords : interface between two immiscible electrolyte solutions * interfacial electron transfer * standard electron trasfer potential * homogeneous electron transfer Subject RIV: CG - Electrochemistry

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

    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.

  1. Coherence in electron transfer pathways

    Skourtis, Spiros S.; Beratan, David N.; Waldeck, David H.

    2011-01-01

    Central to the view of electron-transfer reactions is the idea that nuclear motion generates a transition state geometry at which the electron/hole amplitude propagates coherently from the electron donor to the electron acceptor. In the weakly coupled or nonadiabatic regime, the electron amplitude tunnels through an electronic barrier between the donor and acceptor. The structure of the barrier is determined by the covalent and noncovalent interactions of the bridge. Because the tunneling bar...

  2. Implementation of a new interfacial mass and energy transfer model in RETRAN-3D

    The RETRAN-3D MOD002.0 best estimate code includes a five-equation flow field model developed to deal with situations in which thermodynamic non-equilibrium phenomena are important. Several applications of this model to depressurization and pressurization transients showed serious convergence problems. An analysis of the causes for the numerical instabilities identified the models for interfacial heat and mass transfer as the source of the problems. A new interfacial mass and energy transfer model has thus been developed and implemented in RETRAN-3D. The heat transfer for each phase is equal to the product of the interfacial area density, a heat transfer coefficient and the temperature difference between the interface at saturation and the bulk temperature of the respective phase. However, in the context of RETRAN-3D, the vapor remains saturated in a two-phase volume, and no vapor heat transfer is thus calculated. The values of interfacial area density and heat transfer coefficient are obtained based on correlations appropriate for different flow regimes. A flow regime map, based on the work of Taitel and Dukler, with void fraction and mixture mass flux as map coordinates, is used to identify the flow regime present in a given volume. The new model has performed well when assessed against data from four experimental facilities covering depressurization, condensation and steady state void distribution. The results also demonstrate the viability of the approach followed to develop the new model for a five-equation based code. (author)

  3. Determination of interfacial heat transfer coefficient and its application in high pressure die casting process

    Cao Yongyou

    2014-07-01

    Full Text Available In this paper, the research progress of the interfacial heat transfer in high pressure die casting (HPDC is reviewed. Results including determination of the interfacial heat transfer coefficient (IHTC, influence of casting thickness, process parameters and casting alloys on the IHTC are summarized and discussed. A thermal boundary condition model was developed based on the two correlations: (a IHTC and casting solid fraction and (b IHTC peak value and initial die surface temperature. The boundary model was then applied during the determination of the temperature field in HPDC and excellent agreement was found.

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

    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.

  5. Study on heat transfer and interfacial stability in supersonic steam injector

    Supersonic steam injector is one of the most possible devices for Next-generation nuclear systems to achieve more simplified system and to enhance the safety and credibility of the systems. Supersonic steam injector has dual functions that are passive jet pump and high efficient heat exchanger. In order to design the supersonic steam injector, it is important to clarify the heat transfer and flow behavior of high-speed water jet in supersonic steam flow. However, thermal-hydraulic behaviors in the steam injector including the interfacial heat transfer behavior due to the direct contact condensation and interfacial stability of water jet are not clarified in detail yet. The purpose of the present study is to investigate the interfacial heat transfer behavior of high-speed water jet. The interface of water jet is observed by using high-speed video camera. From the observation results obtained, wave propagation on the interface is identified. The velocity of the wave propagation is estimated from the visual information. Radial distribution of the pressure and the temperature in the supersonic steam injector are also measured experimentally in order to investigate the dynamic behavior and the heat transfer due to the condensation. From the results, the interaction between the interfacial dynamic behavior and the heat transfer due to the condensation are discussed. (author)

  6. Electronic fund transfer & the "unbanked"

    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."

  7. Effects of interfacial surfactant contamination on bubble gas transfer

    Rosso, D.; Huo, D L; Stenstrom, M K

    2006-01-01

    Surface active agents depress gas transfer at gas-liquid interfaces. They are present as measurable trace contaminants at all environmental and at most industrial interfaces. An experimental apparatus to concurrently measure dynamic surface tension and mass transfer was constructed and tested for single-bubble and multi-bubble experiments. In this work, the parameters describing time-dependent bubble surface contamination were characterized. The application of a Ward-Tordai transient model an...

  8. Advances in electron transfer chemistry

    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

  9. Core-concrete molten pool dynamics and interfacial heat transfer

    Theoretical models are derived for the heat transfer from molten oxide pools to an underlying concrete surface and from molten steel pools to a general concrete containment. To accomplish this, two separate effects models are first developed, one emphasizing the vigorous agitation of the molten pool by gases evolving from the concrete and the other considering the insulating effect of a slag layer produced by concrete melting. The resulting algebraic expressions, combined into a general core-concrete heat transfer representation, are shown to provide very good agreement with experiments involving molten steel pours into concrete crucibles

  10. Coherence in electron transfer pathways.

    Skourtis, Spiros S; Beratan, David N; Waldeck, David H

    2011-01-01

    Central to the view of electron-transfer reactions is the idea that nuclear motion generates a transition state geometry at which the electron/hole amplitude propagates coherently from the electron donor to the electron acceptor. In the weakly coupled or nonadiabatic regime, the electron amplitude tunnels through an electronic barrier between the donor and acceptor. The structure of the barrier is determined by the covalent and noncovalent interactions of the bridge. Because the tunneling barrier depends on the nuclear coordinates of the reactants (and on the surrounding medium), the tunneling barrier is highly anisotropic, and it is useful to identify particular routes, or pathways, along which the transmission amplitude propagates. Moreover, when more than one such pathway exists, and the paths give rise to comparable transmission amplitude magnitudes, one may expect to observe quantum interferences among pathways if the propagation remains coherent. Given that the effective tunneling barrier height and width are affected by the nuclear positions, the modulation of the nuclear coordinates will lead to a modulation of the tunneling barrier and hence of the electron flow. For long distance electron transfer in biological and biomimetic systems, nuclear fluctuations, arising from flexible protein moieties and mobile water bridges, can become quite significant. We discuss experimental and theoretical results that explore the quantum interferences among coupling pathways in electron-transfer kinetics; we emphasize recent data and theories associated with the signatures of chirality and inelastic processes, which are manifested in the tunneling pathway coherence (or absence of coherence). PMID:23833692

  11. Raman study of interfacial load transfer in graphene nanocomposites

    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.

  12. Modeling and database for melt-water interfacial heat transfer

    A mechanistic model is developed to predict the transition superficial gas velocity between bulk cooldown and crust-limited heat transfer regimes in a sparged molten pool with a coolant overlayer. The model has direct applications in the analysis of ex-vessel severe accidents, where molten corium interacts with concrete, thereby producing sparging concrete decomposition gases. The analysis approach embodies thermal, mechanical, and hydrodynamic aspects associated with incipient crust formation at the melt/coolant interface. The model is validated against experiment data obtained with water (melt) and liquid nitrogen (coolant) simulants. Predictions are then made for the critical gas velocity at which crust formation will occur for core material interacting with concrete in the presence of water

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

    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

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

    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.

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

    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.

  16. Electron Transfer to Vinylaromatic Polymers

    Aromatic polymers accept electrons from alkali metals to form polyradicalanions. These undergo chain scission as a result of electronic interaction between aromatic rings. Spectrophotometric and chemical evidence led to the conclusion that during the chain-breaking process polymeric fragments were formed which had the properties of ''living polymers'', i.e. the characteristic visible spectra and the capability of initiating the polymerization of a number of vinyl monomers. It was possible to follow the rate of chain scission in the case of poly (4-vinyl biphenyl) and poly(α-vinyl naphthalene) by means of viscosity and spectrophotometric measurements. The postulated mechanism was found to be consistent with the slow decrease in free spin concentration measured by means of the electron spin resonance technique. Chain scission in polyacenaphthalene takes place at a much faster rate than in poly (4-vinyl biphenyl) and this fact is in good agreement with simple LCAO MO calculations. Preliminary experiments indicate that electron transfer to poly-N-vinyl carbazole produces little if any degradation. These investigations led to the examination of the temperature effect on the electron-transfer reaction from sodium to some substituted aromatic hydrocarbons. The details of this effect are discussed. (author)

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

    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

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

    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.

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

    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.

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

    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.

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

    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.

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

    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

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

    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...

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

    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.

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

    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

  6. Investigation on Interfacial Charge Transfer Process in CdSexTe1-x Alloyed Quantum Dot Sensitized Solar Cells

    Colloidal QDs, typically, alloyed QDs with extending light absorption range, exhibit prospective application on quantum dot-sensitized solar cells (QDSCs). In this work, CdSe0.8Te0.2 alloyed QDs have been employed to assemble QDSCs, and the influence of the photoanode structure and film thickness on the cell performance has been investigated in detail. Further study on the charge transport and interfacial electron transfer processes reveals that with the film thickness increasing, recombination possibility will be remarkably enhanced. By careful control on the balance between the light absorption and carrier recombination, an optimal double-layer photoanode structure with 11.5 μm-thickness transparent and 6 μm-thickness scattering layers can present a power conversion efficiency of 7.55%, which is one of the best records for the sandwiched-type QDSCs

  7. Electron transfer in helical polyaromatics

    Pospíšil, Lubomír; Gál, Miroslav; Horáček, Michal; Teplý, Filip; Adriaenssens, Louis; Severa, Lukáš

    Xi´an: International Society of Electrochemistry, 2009. O06-O06. [International Symposium on Frontiers of Electrochemical Science and Technology . 12.08.2009-15.08.2009, Xi´an] R&D Projects: GA ČR GA203/08/1157; GA MŠk OC 140; GA ČR GA203/09/0705; GA ČR GP203/09/P502; GA MŠk ME09114 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z40550506 Keywords : electron transfer * helical polyaromatics Subject RIV: CG - Electrochemistry

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

    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.

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

    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

  10. Heterostructure Intervalley Transferred Electron Effects

    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

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

    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)

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

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

    2015-01-01

    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...

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

    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...

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

    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

  15. Adsorption and Interfacial Electron Transfer of Saccharomyces Cerevisiae

    Andersen, Jens Enevold Thanulov

    2003-01-01

    to gold without drastic protein unfolding. A comprehensive approach, based on linear sweep and differential pulse voltammetry, capacitance measurements, X-ray photoelectron spectroscopy (XPS) , in situscanning tunneling microscopy (STM), and microcantilever sensor (MCS) techniques has been used....... The voltammetric data display a thiol reductive desorption signal corresponding to dase 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 dear Au -S band...... approaches to the mapping of adsorbed functional redox metalloproteins toward the single-molecule level, such as in the present study, will be important in the construction of nanoscale devices for multifarious biological and environmental screening....

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

    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.

  17. Comparison of the methods for calculating the interfacial heat transfer coefficient in hot stamping

    This paper presents a hot stamping experimentation and three methods for calculating the Interfacial Heat Transfer Coefficient (IHTC) of 22MnB5 boron steel. Comparison of the calculation results shows an average error of 7.5% for the heat balance method, 3.7% for the Beck's nonlinear inverse estimation method (the Beck's method), and 10.3% for the finite-element-analysis-based optimization method (the FEA method). The Beck's method is a robust and accurate method for identifying the IHTC in hot stamping applications. The numerical simulation using the IHTC identified by the Beck's method can predict the temperature field with a high accuracy. - Highlights: • A theoretical formula was derived for direct calculation of IHTC. • The Beck's method is a robust and accurate method for identifying IHTC. • Finite element method can be used to identify an overall equivalent IHTC

  18. Interfacial adhesion in metal/polymer systems for electronics

    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...

  19. Kinetic and structural studies, origins of selectivity, and interfacial charge transfer in the artificial photosynthesis of CO

    Smieja, Jonathan M.; Benson, Eric E.; Kumar, Bhupendra; Grice, Kyle A.; Seu, Candace; Miller, Alexander J.; Mayer, James M.; Kubiak, Cliff

    2012-09-25

    The effective design of an artificial photosynthetic system entails the optimization of several important interactions. Herein we report stopped-flow UV-visible (UV-vis) spectroscopy, X-ray crystallographic, density functional theory (DFT), and electrochemical kinetic studies of the Re(bipy-tBu) (CO)3(L) catalyst for the reduction of CO2 to CO. A remarkable selectivity for CO2 over Hþ was observed by stopped-flow UV-vis spectroscopy of [Re(bipy-tBu)3]-1. The reaction with CO2 is about 25 times faster than the reaction with water or methanol at the same concentrations. X-ray crystallography and DFT studies of the doubly reduced anionic species suggest that the highest occupied molecular orbital (HOMO) has mixed metal-ligand character rather than being purely doubly occupied dz2, which is believed to determine selectivity by favoring CO2 (σ+π) over H+ (σ only) binding. Electrocatalytic studies performed with the addition of Brönsted acids reveal a primary H/D kinetic isotope effect, indicating that transfer of protons to Re-CO2 is involved in the rate limiting step. Lastly, the effects of electrode surface modification on interfacial electron transfer between a semiconductor and catalyst were investigated and found to affect the observed current densities for catalysis more than threefold, indicating that the properties of the electrode surface need to be addressed when developing a homogeneous artificial photosynthetic system.

  20. Inverse identification of interfacial heat transfer coefficient between the casting and metal mold using neural network

    The effect of the heat transfer coefficient at the casting-mold interface is of prime importance to improve the casting quality, especially for castings in metal molds. However, it is difficult to determine the values of heat transfer coefficient from experiments due to the influence of various factors, such as contacting pressure, oxides on surfaces, roughness of surfaces, coating material, coating thickness and gap formation caused by the deformation of casting and mold, etc. In the present paper, the interfacial heat transfer coefficient (IHTC) between the casting and metal mold is identified by using the method of inverse analysis based on measured temperatures, neural network with back-propagation algorithm and numerical simulation. Then, by applying the identified IHTC in finite element analysis, the comparison between numerical calculated and experimental results is made to verify the correctness of method. The results show that the numerical calculated temperatures are in good agreement with experimental ones. These demonstrate that the method of inverse analysis is a feasible and effective tool for determination of the casting-mold IHTC. In addition, it is found that the identified IHTC varies with time during the casting solidification and varies in the range of about 100-3200 Wm-2K-1. The characteristics of the time-varying IHTC have also been discussed.

  1. Quantifying electron transfer reactions in biological systems

    Sjulstok, Emil Sjulstok; Olsen, Jógvan Magnus Haugaard; Solov'yov, Ilia A

    2015-01-01

    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...... 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...

  2. Interfacial Ga-As suboxide: Structural and electronic properties

    Colleoni, Davide, E-mail: davide.colleoni@epfl.ch; Pasquarello, Alfredo [Chaire de Simulation à l' Echelle Atomique (CSEA), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2015-07-20

    The structural and electronic properties of Ga-As suboxide representative of the transition region at the GaAs/oxide interface are studied through density functional calculations. Two amorphous models generated by quenches from the melt are taken under consideration. The absence of As–O bonds indicates that the structure is a mixture of GaAs and Ga-oxide, in accordance with photoemission experiments. The band edges of the models are found to be closely aligned to those of GaAs. The simulation of charging and discharging processes leads to the identification of an As-related defect with an energy level at ∼0.7 eV above the GaAs valence band maximum, in good agreement with the experimental density of interface states.

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

    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.

  4. Examination of interfacial charge transfer in photocatalysis using patterned CuO thin film deposited on TiO2

    Osako, K; Matsuzaki, K.; Hosono, H.; G. Yin; D. Atarashi; Sakai, E.; Susaki, T.; Miyauchi, M

    2015-01-01

    We examined the interfacial charge transfer effect on photocatalysts using a patterned CuO thin film deposited on a rutile TiO2 (110) substrate. Photocatalytic activity was visualized based on the formation of metal Ag particles resulting from the photoreduction of Ag+ ions under visible-light illumination. Ag particles were selectively deposited near the edge of CuO film for several nanometer thick CuO film, indicating that interfacial excitation from the valence band maximum of TiO2 to the ...

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

    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}.

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

    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)

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

    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

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

    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)

  9. Hierarchical control of electron-transfer

    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...... as a paradigm. This allows one to analyse a complex system of regulatory interactions in terms of the importance of the contributing factors....

  10. Photoselected electron transfer pathways in DNA photolyase

    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...

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

    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

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

    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

  13. Advances in electron transfer chemistry, v.6

    Mariano, PS

    1999-01-01

    It is clear that electron transfer chemisty is now one of the most active areas of chemical study. Advances in Electron Transfer Chemistry has been designed to allow scientists who are developing new knowledge in this rapidly expanding area to describe their most recent research findings. This volume will serve those interested in learning about current breakthroughs in this rapidly expanding area of chemical research.

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

    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

  15. Kinetic and structural studies, origins of selectivity, and interfacial charge transfer in the artificial photosynthesis of CO

    Smieja, Jonathan M.; Benson, Eric E.; Kumar, Bhupendra; Grice, Kyle A.; Seu, Candace; Miller, Alexander J.; Mayer, James M.; Kubiak, Cliff

    2012-09-25

    The effective design of an artificial photosynthetic system entails the optimization of several important interactions. Herein we report stopped-flow UV-Vis spectroscopy, X-ray crystallography, DFT, and electrochemical kinetic studies of the Re(bipy-tBu)(CO)3(L) catalyst system. A remarkable selectivity for CO2 over H+ was observed by stopped-flow UV-Vis spectroscopy of [Re(bipy-tBu)(CO)3]-. The pseudo-first order rate constant for the reaction with 10 mM CO2 in THF is 35 s-1. This is ca. 15-20 times faster than the reactions with water or methanol at the same concentration in THF. X-ray crystallography and DFT studies of the doubly-reduced anionic species suggest that the HOMO has mixed metal-ligand character rather than being purely dz 2, which is thought to aid catalytic selectivity by favoring binding of CO2 over H+. Electrocatalytic studies performed with the addition of Brönsted acids reveal a primary H/D kinetic isotope effect, indicating that transfer of protons to Re-CO2 is involved in the rate limiting step. Lastly, the effects of electrode surface modification on interfacial electron transfer between a semiconductor and catalyst were investigated and found to affect the observed catalytic rates up to seven-fold, indicating that the properties of the electrode surface should not be overlooked when developing a homogeneous artificial photosynthetic system. This research was supported at the University of Washington, Seattle by the Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry (for a fellowship to A. J. M. M.), and, for funds to purchase the stopped-flow instrument, the U.S. National Institutes of Health 13 (Grant GM-50422 to JMM), and 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.

  16. Heat Transfer Augmentation for Electronic Cooling

    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.

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

    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...

  18. Injecting electrode controlled electronic transport across Fe3O4 film-Si interfacial structure

    Highlights: • CPP I–V measurements have been carried out on Fe3O4/SiO2/Si heterostructure. • Verwey transition has been found for injection from Fe3O4 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 Fe3O4 film–nSi interfacial structure in CPP mode with an interfacial SiO2 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 Fe3O4 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 Fe3O4 to silicon than for the forward bias in which injection takes place from silicon to metallic Fe3O4 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 Fe3O4 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 (TV) for the Fe3O4 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 Fe3O4–nSi seem significant to reveal that the Verwey transition is related to spins of half-metallic Fe3O4

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

    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.

  20. Imaging the electrons from transfer ionization collisions

    The electrons emitted into the continuum in transfer ionization of He2+ on helium collisions in the energy range of 75 - 400 keV were imaged using reaction microscope. The electron emission patterns show big difference for projectile velocity lower and upper than 1 a.u. in the present studies.

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

    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.

  2. Electron transfer across a thermal gradient.

    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

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

    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...

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

    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

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

    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.

  6. Photoinduced electron transfer in ordered polymers

    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.

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

    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

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

    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.

  9. Unusual distance dependences of electron transfer rates.

    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

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

    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 have been investigated. 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. Therefore, ferromagnetism can be controlled effectively through the chemical identity and the thickness of the individual superlattice layers.

  11. Resonant electron transfer between quantum dots

    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...

  12. Facilitating electron transfer in bioelectrocatalytic systems

    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...

  13. Electron transfer in dinucleoside phosphate anions

    The electron transfer reaction within various dinucleoside phosphate radical anions has been investigated by ESR spectroscopy and pulse radiolysis. In the ESR work electrons are produced by photolysis of K4Fe(CN)6 in a 12 M LiCl glass at 770K. Upon photobleaching the electrons react with the dinucleoside phosphate to form the anion radical. The anions of the four DNA nucleosides were also produced and their ESR spectra were appropriately weighted and summed by computer to simulate the spectra found for the dinucleoside phosphate anions. From the analysis the relative amounts of each of the nucleoside anions in the dinucleoside phosphate anion were determined. Evidence suggests the electron affinity of the pyrimidine bases are greater than the purine bases; however, the results are not sufficient to distinguish between the individual purine or pyrimidine. When dinucleoside phosphate anions containing thymidine are warmed, protonation occurs only on thymine to produce the well known ''thymyl'' spectrum. Pulse radiolysis experiments on individual nucleotides (TMP, dAMP), mixtures of these nucleotides and the dinucleoside phosphate, TdA, in aqueous solution at room temperature show that in the TdA anion electron transfer occurs from adenine to thymine, whereas no electron transfer is found for mixtures of individual nucleotides. Protonation is found to occur only on thymine in the TdA anion in agreement with the ESR results

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

    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.

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

    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 activated

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

    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

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

    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

  18. Photoinduced electron transfer in ordered polymers

    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.

  19. Quantum effects in biological electron transfer

    de la Lande, A.; Babcock, N. S.; Řezáč, Jan; Levy, B.; Sanders, B. C.; Salahub, D.

    2012-01-01

    Roč. 14, č. 17 (2012), s. 5902-5918. ISSN 1463-9076 Institutional research plan: CEZ:AV0Z40550506 Keywords : electron transfer * tunnelling * decoherence * semi-classical molecular dynamics * density functional theory Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.829, year: 2012

  20. Interfacial bonding and electronic structure of GaN/GaAs interface: A first-principles study

    Cao, Ruyue; Zhang, Zhaofu; Wang, Changhong; Li, Haobo; Dong, Hong; Liu, Hui; Wang, Weichao, E-mail: weichaowang@nankai.edu.cn [College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071 (China); Xie, Xinjian [College of Materials Science, Hebei Technology University, Tianjin 300401 (China)

    2015-04-07

    Understanding of GaN interfacing with GaAs is crucial for GaN to be an effective interfacial layer between high-k oxides and III-V materials with the application in high-mobility metal-oxide-semiconductor field effect transistor (MOSFET) devices. Utilizing first principles calculations, here, we investigate the structural and electronic properties of the GaN/GaAs interface with respect to the interfacial nitrogen contents. The decrease of interfacial N contents leads to more Ga dangling bonds and As-As dimers. At the N-rich limit, the interface with N concentration of 87.5% shows the most stability. Furthermore, a strong band offsets dependence on the interfacial N concentration is also observed. The valance band offset of N7 with hybrid functional calculation is 0.51 eV. The electronic structure analysis shows that significant interface states exist in all the GaN/GaAs models with various N contents, which originate from the interfacial dangling bonds and some unsaturated Ga and N atoms. These large amounts of gap states result in Fermi level pinning and essentially degrade the device performance.

  1. Correlating Interfacial Structure and Magnetism in Thin-Film Oxide Heterostructures Using Transmission Electron Microscopy and Polarized Neutron Reflectometry

    Spurgeon, Steven Richard

    Oxide thin-films have attracted considerable attention for a new generation of spintronics devices, where both electron charge and spin are used to transport information. However, a poor understanding of the local features that mediate magnetization and coupling in these materials has greatly limited their deployment into new information and communication technologies. This thesis describes direct, local measurements of structure-property relationships in ferrous thin-films and La1--xSrxMnO3 (LSMO) / Pb(ZrxTi1--x)O3 (PZT) thin-film heterostructures using spatially-resolved characterization techniques. In the first part of this thesis we explore the properties of ferrous spintronic thin-films. These films serve as a model system to establish a suite of interfacial characterization techniques for subsequent studies. We then study the static behavior of LSMO / PZT devices with polarization set by the underlying substrate. Using transmission electron microscopy and geometric phase analysis we reveal the presence of significant local strain gradients in these films for the first time. Electron energy loss spectroscopy mapping of the LSMO / PZT interface reveals Mn valence changes induced by charge-transfer screening. Bulk magnetometry and polarized neutron reflectometry indicate that these chemical and strain changes are associated with a graded magnetization across the LSMO layer. Density functional theory calculations are presented, which show that strain and charge-transfer screening act locally to suppress magnetization in the LSMO by changing the Mn orbital polarization. In the second half of this thesis, we explore asymmetric screening effects on magnetization LSMO / PZT composites. We find that the local ferroelectric polarization can vary widely and that this may be responsible for reduced charge-transfer effects, as well as magnetic phase gradients at interfaces. From this information and electron energy loss spectroscopy, we construct a map of the magnetic

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

    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

  3. Decoupling interfacial reactions between plasmas and liquids: charge transfer vs plasma neutral reactions.

    Rumbach, Paul; Witzke, Megan; Sankaran, R Mohan; Go, David B

    2013-11-01

    Plasmas (gas discharges) formed at the surface of liquids can promote a complex mixture of reactions in solution. Here, we decouple two classes of reactions, those initiated by electrons (electrolysis) and those initiated by gaseous neutral species, by examining an atmospheric-pressure microplasma formed in different ambients at the surface of aqueous saline (NaCl) solutions. Electrolytic reactions between plasma electrons and aqueous ions yield an excess of hydroxide ions (OH(-)), making the solution more basic, while reactions between reactive neutral species formed in the plasma phase and the solution lead to nitrous acid (HNO2), nitric acid (HNO3), and hydrogen peroxide (H2O2), making the solution more acidic. The relative importance of either reaction path is quantified by pH measurements, and we find that it depends directly on the composition of the ambient background gas. With a background gas of oxygen or argon, electron transfer reactions yielding excess OH(-) dominate, while HNO2 and HNO3 formed in the plasma and by the dissolution of nitrogen oxide (NOx) species dominate in the case of air and nitrogen. For pure nitrogen (N2) gas, we observe a unique coupling between both reactions, where oxygen (O2) gas formed via water electrolysis reacts in the bulk of the plasma to form NOx, HNO2, and HNO3. PMID:24144120

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

    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.

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

    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

  6. Electronic transfer between low-dimensional nanosystems

    Král, Karel

    Hoboken: Wiley, 2011 - (Nair, K.; Priya, S.; Jia, Q.), s. 33-40. (Ceramic Transactions. vol. 226). ISBN 9781118059999. [Materials Science and Technology meeting 2010 (MS&T'10). Dielectric Ceramic Materials and Electronic Devices.. Houston (US), 17.10.2010-21.10.2010] R&D Projects: GA MŠk(CZ) OC10007 Institutional research plan: CEZ:AV0Z10100520 Keywords : electron transfer * nanostructures quantum dots Subject RIV: BM - Solid Matter Physics ; Magnetism http://eu.wiley.com/WileyCDA/WileyTitle/productCd-1118059999,descCd-tableOfContents.html

  7. Electron transfer theory revisit: Quantum solvation effect

    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.

  8. Interfacial spin-filter assisted spin transfer torque effect in Co/BeO/Co magnetic tunnel junction

    Tang, Y.-H., E-mail: yhtang@cc.ncu.edu.tw; Chu, F.-C. [Department of Physics, National Central University, Jung-Li 32001, Taiwan (China)

    2015-03-07

    The first-principles calculation is employed to demonstrate the spin-selective transport properties and the non-collinear spin-transfer torque (STT) effect in the newly proposed Co/BeO/Co magnetic tunnel junction. The subtle spin-polarized charge transfer solely at O/Co interface gives rise to the interfacial spin-filter (ISF) effect, which can be simulated within the tight binding model to verify the general expression of STT. This allows us to predict the asymmetric bias behavior of non-collinear STT directly via the interplay between the first-principles calculated spin current densities in collinear magnetic configurations. We believe that the ISF effect, introduced by the combination between wurtzite-BeO barrier and the fcc-Co electrode, may open a new and promising route in semiconductor-based spintronics applications.

  9. Role of surface stoichiometry on the interfacial electron behavior at Ni/TiO{sub 2}(0 0 1) interfaces

    Tao Junguang, E-mail: junguangtao@usf.edu [Department of Physics, University of South Florida, Tampa, FL 33620 (United States); Division of Physics and Applied Physics, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore); Pan, J.S.; Chiam, S.Y. [Institute of Materials Research and Engineering, A-STAR, 3 Research Link, Singapore 117602 (Singapore); Huan, C.H.A. [Division of Physics and Applied Physics, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer Surface stoichiometry affects the interfacial charge re-distribution. Black-Right-Pointing-Pointer Separation of electron-hole pairs depends on surface stoichiometry. Black-Right-Pointing-Pointer Oxidization state of Ni depends on the initial conditions of the TiO{sub 2} surface. Black-Right-Pointing-Pointer Insulator-to-metal transition affects the binding energies. - Abstract: The interfacial properties of Ni clusters grown on the stoichiometric and reduced rutile TiO{sub 2}(0 0 1) surfaces were investigated by means of X-ray photoelectron spectroscopy (XPS). The binding energies (BE's) of elements from both overlayers and substrates were found to be affected by the formation of interfacial dipole. Regardless of the TiO{sub 2} surface stoichiometry, the Ni 2p{sub 3/2} BE's move monotonically toward lower value with the increase of Ni thickness due to the cluster size effect. However, the Ni 2p{sub 3/2} BE shift is much smaller on reduced TiO{sub 2}(0 0 1) surfaces compared to that on the annealed stoichiometric surface. For stoichiometric and lightly reduced TiO{sub 2} surfaces, O 1s BE's exhibit an unexpected upward shift with increasing Ni thickness below 2 Angstrom-Sign , and then downward shift to lower BE's when the Ni thickness increases further. This opposite tendency is attributed to the insulator-to-metal transition. On heavily reduced surface, only monotonically downward shift of the O 1s BE's was observed with the increase of Ni thickness. The different behaviors are well elucidated by collective contributions of interfacial charge transfer and image charge effect.

  10. Electronic Energy Transfer in Polarizable Heterogeneous Environments

    Svendsen, Casper Steinmann; Kongsted, Jacob

    2015-01-01

    Theoretical prediction of transport and optical properties of protein-pigment complexes is of significant importance when aiming at understanding the structure versus function relationship in such systems. Electronic energy transfer (EET) couplings represent a key property in this respect since...... 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 embedding...... 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....

  11. Promoting interspecies electron transfer with biochar

    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...

  12. Education and solar conversion. Demonstrating electron transfer

    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

  13. Heat transfer in high density electronics packaging

    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.

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

    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.

  15. 14 CFR 1260.69 - Electronic funds transfer payment methods.

    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...

  16. Electron transfer in branched expanded pyridinium molecules

    Hromadová, Magdaléna; Lachmanová, Štěpánka; Pospíšil, Lubomír; Fortage, J.; Dupeyre, G.; Perruchot, Ch.; Lainé, P. P.

    Aveiro: DEMAC - Universidade de Aveiro, 2014. s. 99-99. [Meeting of the Portuguese Electrochemical Society /19./. Iberian Meeting of Electrochemistry /16./. 30.06.2014-02.07.2014, Aveiro] R&D Projects: GA ČR(CZ) GA14-05180S Grant ostatní: Rada Programu interní porpory projektů mezinárodní spolupráce AV ČR M200401202 Institutional support: RVO:61388955 Keywords : electron transfer * electrochemistry * pyridinium Subject RIV: CG - Electrochemistry

  17. Direct heterogeneous electron transfer of theophylline oxidase

    Christenson, Andreas; Dock, Eva; Gorton, Lo; Ruzgas, Tautgirdas

    2004-01-01

    Direct electron transfer (DET) was shown between the heme containing enzyme theophylline oxidase (ThO) and the surface of both graphite and gold electrodes. As proof on graphite a steady state current for theophylline was recorded using the electrode modified with adsorbed ThO. The electrode showed a Michaelis–Menten-like response to theophylline with a detection limit of 0.2 mM and a Michaelis–Menten constant equal to 3.2 mM. These initial results open up a possibility for the development of...

  18. Electron transfer pathways in microbial oxygen biocathodes

    Freguia, Stefano, E-mail: stefano@kais.kyoto-u.ac.j [Bio-analytical and Physical Chemistry Laboratory, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8205 (Japan); Tsujimura, Seiya, E-mail: seiya@kais.kyoto-u.ac.j [Bio-analytical and Physical Chemistry Laboratory, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8205 (Japan); Kano, Kenji, E-mail: kkano@kais.kyoto-u.ac.j [Bio-analytical and Physical Chemistry Laboratory, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8205 (Japan)

    2010-01-01

    The ability of some bacteria to enhance the rate of cathodic oxygen reduction to water has been recently discovered, opening the way to an entirely renewable and environmentally friendly concept of biocathode. In this study we reveal that several mechanisms may induce catalytic effects by bacteria. These comprise mechanisms that are putatively beneficial to the bacteria as well as mechanisms which are merely side effects, including quinone autoxidation and direct O{sub 2} reduction by heme compounds. Here we showed that 1 muM of ACNQ is able to generate a significant catalytic wave for oxygen reduction, with onset at approximately 0 V vs. SHE. Similarly, adsorption of hemin on a carbon surface catalyses O{sub 2} reduction to H{sub 2}O{sub 2} with an onset of +0.2 V vs. SHE. To evaluate the catalytic pathways of live cells on cathodic oxygen reduction, two species of electrochemically active bacteria were selected as pure cultures, namely Acinetobacter calcoaceticus and Shewanella putrefaciens. The former appears to exploit a self-excreted redox compound with redox characteristics matching those of pyrroloquinoline quinone (PQQ) for extracellular electron transfer. The latter appears to utilise outer membrane-bound redox compounds. Interaction of quinones and cytochromes with the membrane-bound electron transfer chain is yet to be proven.

  19. Electron transfer interactome of cytochrome C.

    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.

  20. Electron Transfer-Based Single Molecule Fluorescence as a Probe for Nano-Environment Dynamics

    Ruiyun Chen

    2014-02-01

    Full Text Available Electron transfer (ET is one of the most important elementary processes that takes place in fundamental aspects of biology, chemistry, and physics. In this review, we discuss recent research on single molecule probes based on ET. We review some applications, including the dynamics of glass-forming systems, surface binding events, interfacial ET on semiconductors, and the external field-induced dynamics of polymers. All these examples show that the ET-induced changes of fluorescence trajectory and lifetime of single molecules can be used to sensitively probe the surrounding nano-environments.

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

    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

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

    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

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

    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.

  4. Electron transfer in gas surface collisions

    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.)

  5. The comparison of steam-water interfacial condensation heat transfer correlation in vertical channel

    Safety injection water is injected into the reactor vessel downcomer directly in Korean Next Generation Reactor(KNGR). Due to the adoption of direct vessel injection(DVI) method, thermal hydraulic phenomena different from existing cold leg injection plants can be occurred during large break loss of coolant accidents (LBLOCAs). Therefore, safety evaluation against LBLOCA has been performed for KNGR using TRAC-M/F77 code. One of the important phenomena is steam-water condensation in the upper downcomer. In the paper, heat transfer correlation of TRAC code is evaluated through the comparison between the correlation and the experiment results for steam-water heat transfer in vertical rectangular channel. As a result, TRAC code predicts the heat transfer coefficient larger than those of experiment results. Therefore, in LBLOCA analysis using TRAC code, the sensitivity studies for heat transfer in upper downcomer should be performed to evaluate the uncertainty

  6. An investigation of the effects of interfacial shear between the gas and turbulent falling liquid film on the heat transfer coefficient

    An improved method is presented for the prediction of heat transfer coefficients in turbulent falling liquid films with or without interfacial shear for both heating or condensation. A modified Mudawwar and El-Masri's semiempirical turbulence model, particularly to extend its use for the turbulent falling film with high interfacial shear, is used to replace the eddy viscosity model incorporated in the unified approach proposed by Yih and Liu. The liquid film thickness and asymptotic heat transfer coefficients against the film Reynolds number for wide range of interfacial shear predicted by both present and existing methods are compared with experimental data. The results show that, in general, predictions of the modified model agree more closely with experimental data than that of existing models. Comparisons of the predictions of the present model with that of existing models and the experimental data show that agreement is fairly good and consistent. A brief summary of the results are as follows: (1) As opposed to the previous model, present model utilizes a continuous linear variation of eddy viscosity near the interfacial surface. For freely falling liquid film, the present model reduce to the Mudawwar and El-Masri's model. (2) The curves of the present model for the heat transfer coefficients with liquid film Reynolds number have positive slopes in turbulent regime while the curves obtained by other models have negative slopes particularly for condensation. (3) The two criteria for transition from laminar to turbulent film flow, one for low interfacial shear and the other for high interfacial shear, respectively are shown to give the best agreement with the data for the present method

  7. Activation entropy of electron transfer reactions

    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...

  8. Devices which transfer electrons one-by-one

    An introduction is given to the field of single-electron devices, which are electronic circuits across which electrons may be transferred one by one. Experiments are described on the single-junction box and the four-junction box, devices in which electrons were transferred to a metallic island and their presence detected using a single-electron electrometer. The single-junction box, the simpler of the two devices, allows one to control the thermally-averaged number of excess electrons on the metallic island, whereas with the four-junction box one can actually control the transfer of individual electrons. (author) 11 refs.; 5 figs

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

    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)

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

    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

  11. Computational micromechanics analysis of electron hopping and interfacial damage induced piezoresistive response in carbon nanotube-polymer nanocomposites

    Carbon nanotube (CNT)-polymer nanocomposites have been observed to exhibit an effective macroscale piezoresistive response, i.e., change in macroscale resistivity when subjected to applied deformation. The macroscale piezoresistive response of CNT-polymer nanocomposites leads to deformation/strain sensing capabilities. It is believed that the nanoscale phenomenon of electron hopping is the major driving force behind the observed macroscale piezoresistivity of such nanocomposites. Additionally, CNT-polymer nanocomposites provide damage sensing capabilities because of local changes in electron hopping pathways at the nanoscale because of initiation/evolution of damage. The primary focus of the current work is to explore the effect of interfacial separation and damage at the nanoscale CNT-polymer interface on the effective macroscale piezoresistive response. Interfacial separation and damage are allowed to evolve at the CNT-polymer interface through coupled electromechanical cohesive zones, within a finite element based computational micromechanics framework, resulting in electron hopping based current density across the separated CNT-polymer interface. The macroscale effective material properties and gauge factors are evaluated using micromechanics techniques based on electrostatic energy equivalence. The impact of the electron hopping mechanism, nanoscale interface separation and damage evolution on the effective nanocomposite electrostatic and piezoresistive response is studied in comparison with the perfectly bonded interface. The effective electrostatic/piezoresistive response for the perfectly bonded interface is obtained based on a computational micromechanics model developed in the authors’ earlier work. It is observed that the macroscale effective gauge factors are highly sensitive to strain induced formation/disruption of electron hopping pathways, interface separation and the initiation/evolution of interfacial damage. (paper)

  12. Interfacial Heat Transfer during Die Casting of an Al-Si-Cu Alloy

    Hamasaiid, A.; Wang, G.; Davidson, C.; Dour, G.; Dargusch, M. S.

    2009-12-01

    The relationship between in-cavity pressure, heat flux, and heat-transfer coefficient during high-pressure die casting of an Al-9 pct Si-3 pct Cu alloy was investigated. Detailed measurements were performed using infrared probes and thermocouple arrays that accurately determine both casting and die surface temperatures during the pressure die casting of an aluminum A380 alloy. Concurrent in-cavity pressure measurements were also performed. These measurements enabled the correlation between in-cavity pressure and accurate heat-transfer coefficients in high-pressure die-casting operations.

  13. Role of surface stoichiometry on the interfacial electron behavior at Ni/TiO2(0 0 1) interfaces

    Highlights: ► Surface stoichiometry affects the interfacial charge re-distribution. ► Separation of electron–hole pairs depends on surface stoichiometry. ► Oxidization state of Ni depends on the initial conditions of the TiO2 surface. ► Insulator-to-metal transition affects the binding energies. - Abstract: The interfacial properties of Ni clusters grown on the stoichiometric and reduced rutile TiO2(0 0 1) surfaces were investigated by means of X-ray photoelectron spectroscopy (XPS). The binding energies (BE's) of elements from both overlayers and substrates were found to be affected by the formation of interfacial dipole. Regardless of the TiO2 surface stoichiometry, the Ni 2p3/2 BE's move monotonically toward lower value with the increase of Ni thickness due to the cluster size effect. However, the Ni 2p3/2 BE shift is much smaller on reduced TiO2(0 0 1) surfaces compared to that on the annealed stoichiometric surface. For stoichiometric and lightly reduced TiO2 surfaces, O 1s BE's exhibit an unexpected upward shift with increasing Ni thickness below 2 Å, and then downward shift to lower BE's when the Ni thickness increases further. This opposite tendency is attributed to the insulator-to-metal transition. On heavily reduced surface, only monotonically downward shift of the O 1s BE's was observed with the increase of Ni thickness. The different behaviors are well elucidated by collective contributions of interfacial charge transfer and image charge effect.

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

    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

  15. 48 CFR 18.123 - Electronic funds transfer.

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Electronic funds transfer. 18.123 Section 18.123 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACTING METHODS AND CONTRACT TYPES EMERGENCY ACQUISITIONS Available Acquisition Flexibilities 18.123 Electronic funds transfer. Electronic funds...

  16. Theoretical aspects of electron transfer reactions of complex molecules

    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 ...

  17. Transcriptomic and genetic analysis of direct interspecies electron transfer

    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...

  18. Proton transfer across a liquid/liquid interface facilitated by phospholipid interfacial films

    Holub, Karel; Jänchenová, Hana; Štulík, K.; Mareček, Vladimír

    2009-01-01

    Roč. 632, 1-2 (2009), s. 8-13. ISSN 1572-6657 R&D Projects: GA MŠk(CZ) LC06063 Institutional research plan: CEZ:AV0Z40400503 Keywords : liquid-liquid interface * proton transfer * phospholipid layers Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.338, year: 2009

  19. The Liability of banks in electronic fund transfer transaction

    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 ...

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

    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

  1. Proton transfer across a liquid/liquid interface facilitated by phospholipid interfacial films

    Holub, Karel; Jänchenová, Hana; Štulík, Karel; Mareček, Vladimír

    Ústí nad Labem: BEST servis, 2010 - (Navrátil, T.; Barek, J.), s. 70-72 ISBN 978-80-254-6710-7. [Modern Electroanalytical Methods /30./. Jetřichovice (CZ), 24.05.2010-28.05.2010] R&D Projects: GA AV ČR IAA400400806; GA MŠk(CZ) LC06063 Institutional research plan: CEZ:AV0Z40400503 Keywords : liquid-liquid interface * proton transfer * phospholipid layers Subject RIV: CF - Physical ; Theoretical Chemistry

  2. Activation entropy of electron transfer reactions

    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 continuum models is not supported by the microscopic theory. Also, the reorganization and overall solvation entropies are substantially larger in the microscopic theory compared to continuum models

  3. Electronic transfer of sensitive patient data.

    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. Graphene field effect transistor as a probe of electronic structure and charge transfer at organic molecule-graphene interfaces

    Cervenka, Jiri; Budi, Akin; Dontschuk, Nikolai; Stacey, Alastair; Tadich, Anton; Rietwyk, Kevin J.; Schenk, Alex; Edmonds, Mark T.; Yin, Yuefeng; Medhekar, Nikhil; Kalbac, Martin; Pakes, Chris I.

    2015-01-01

    The electronic structure of physisorbed molecules containing aromatic nitrogen heterocycles (triazine and melamine) on graphene is studied using a combination of electronic transport, X-ray photoemission spectroscopy and density functional theory calculations. The interfacial electronic structure...... and charge transfer of weakly coupled molecules on graphene is found to be governed by work function differences, molecular dipole moments and polarization effects. We demonstrate that molecular depolarization plays a significant role in these charge transfer mechanisms even at submonolayer coverage......, particularly for molecules which possess strong dipoles. Electronic transport measurements show a reduction of graphene conductivity and charge carrier mobility upon the adsorption of the physisorbed molecules. This effect is attributed to the formation of additional electron scattering sites in graphene by...

  5. Probing the Mechanism of Electron Capture and Electron Transfer Dissociation Using Tags with Variable Electron Affinity

    Sohn, Chang Ho; Chung, Cheol K.; Yin, Sheng; Ramachandran, Prasanna; Loo, Joseph A; Beauchamp, J. L.

    2009-01-01

    Electron capture dissociation (ECD) and electron transfer dissociation (ETD) of doubly protonated electron affinity (EA)-tuned peptides were studied to further illuminate the mechanism of these processes. The model peptide FQpSEEQQQTEDELQDK, containing a phosphoserine residue, was converted to EA-tuned peptides via β-elimination and Michael addition of various thiol compounds. These include propanyl, benzyl, 4-cyanobenzyl, perfluorobenzyl, 3,5-dicyanobenzyl, 3-nitrobenzyl, and 3,5-dinitrobenz...

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

    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.

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

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

    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.

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

    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.

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

    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...

  11. 14 CFR 1274.931 - Electronic funds transfer payment methods.

    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...

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

    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...

  13. Gas-Liquid Interfacial Area, Bubble Size and Liquid-Phase Mass Transfer Coefficient in a Three-Phase External Loop Airlift Bubble Column

    Yoshimoto, M; Suenaga, S.; Furumoto, K.; Fukunaga, K.; Nakao, Katsumi

    2007-01-01

    The interfacial area a was measured by the sulfite oxidation method in a three-phase external loop airlift bubble column suspending completely the different concentrations of ion exchange resin particles in aqueous carboxymethyl cellulose (CMC) solutions with a wide range of viscosity. The column had been previously studied for the circulating liquid velocity UL, gas holdup G and volumetric gas-liquid oxygen transfer coefficient kLa in the two- and three-phase systems. The average bubble siz...

  14. Inelastic electron scattering at low momentum transfer

    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

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

    Zhang, Jingdong; Grubb, Mikala; Hansen, Allan Glargaard; Kuznetsov, A.M.; Boisen, Anja; Wackerbarth, Hainer; Ulstrup, Jens

    2003-01-01

    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...

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

    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.

  17. Electron Transfer Pathways in Cholesterol Synthesis.

    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

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

    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...

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

    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...

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

    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.

  1. Imaging interfacial electrical transport in graphene–MoS{sub 2} heterostructures with electron-beam-induced-currents

    White, E. R., E-mail: ewhite@physics.ucla.edu; Kerelsky, Alexander; Hubbard, William A.; Regan, B. C., E-mail: regan@physics.ucla.edu [Department of Physics and Astronomy and California NanoSystems Institute, University of California, Los Angeles, California 90095 (United States); Dhall, Rohan; Cronin, Stephen B. [Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089 (United States); Mecklenburg, Matthew [Center for Electron Microscopy and Microanalysis, University of Southern California, Los Angeles, California 90089 (United States)

    2015-11-30

    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-MoS{sub 2} 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.

  2. Vectorial electron transfer in spatially ordered arrays. Progress report, August 1994--January 1997

    Fox, M.A.

    1997-01-01

    With DOE support from August 1994 to August 1997, this project sought to identify methods for controlled placement of light absorbers, relays, and multielectron catalysts at defined sites from a fixed semiconductor or metal surface and, thus, to develop methods for preparing chemically modified photoactive surfaces as artificial photosynthetic units. These designed materials have been evaluated as efficient light collection devices and as substrates for defining the key features that govern the efficiency of long distance electron transfer and energy migration. The authors have synthesized several different families of integrated chemical systems as soluble arrays, as solid thin films, and as adsorbates on solid electrodes, seeking to establish how spatial definition deriving from covalent attachment to a helical polymer backbone, from self assembly of functionalized tethers on gold or metal oxide surfaces, and from rigid or layered block polymers can lead to controlled electron and energy transfer. The authors have also conducted physical characterization of semiconductor-containing composites active in controlled interfacial electron transfer, with charge transport in these materials having been evaluated by photophysical and electrochemical methods.

  3. Photoinduced electron transfers with carbon dots

    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.

  4. Electron transfer and decay processes of highly charged iodine ions

    In the present experimental work we have investigated multi-electron transfer processes in Iq+ (q=10, 15, 20 and 25) + Ne, Ar, Kr and Xe collisions at 1.5q keV energy. The branching ratios between Auger and radiative decay channels have been measured in decay processes of multiply excited states formed by multi-electron transfer collisions. It has been shown that, in all the multi-electron transfer processes investigated, the Auger decays are far dominant over the radiative decay processes and the branching ratios are clearly characterized by the average principal quantum number of the initial excited states of projectile ions. We could express the branching ratios in high Rydberg states formed in multi-electron transfer processes by using the decay probability of one Auger electron emission. (author)

  5. Electron transfer through solid-electrolyte-interphase layers formed on Si anodes of Li-ion batteries

    Solid-electrolyte interphase (SEI) films are formed on the electrode surfaces due to aggregation of products of reduction or oxidation of the electrolyte. These films may grow to thicknesses in the order of 50-100 nm and contain a variety of organic and inorganic products but their structure is not well defined. Although in some cases the films exert a passivating role, this is not always the case, and these phenomena are particularly more complex on Silicon anodes due to swelling and cracking of the electrode during lithiation and delithiation. Since the driving force for SEI growth is electron transfer, it is important to understand how electron transfer may keep occurring through the heterogeneous film once the bare electron surface is covered. Here we introduce a novel approach for studying electron transfer through model films and show preliminary results for the analysis of electron transfer through model composite interfacial systems integrated by electrode/SEI layer/electrolyte. Ab initio molecular dynamics simulations are used to identify deposition of SEI components, and a density functional theory/Green's function approach is utilized for characterizing electron transfer. Three degrees of lithiation are modeled for the electrodes, the SEI film is composed by LiF or Li2O, and the ethylene carbonate reduction is studied. An applied potential is used as driving force for the leakage current, which is evaluated as a function of the applied potential. Comparative analyses are done for LiF and Li2O model SEI layers

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

    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. Comparison of hydrolytic and non-hydrolytic atomic layer deposition chemistries: Interfacial electronic properties at alumina-silicon interfaces

    Marstell, Roderick J.; Strandwitz, Nicholas C.

    2015-11-01

    We report the differences in the passivation and electronic properties of aluminum oxide (Al2O3) deposited on silicon via traditional hydrolytic atomic layer deposition (ALD) and non-hydrolytic (NH) ALD chemistries. Traditional films were grown using trimethylaluminum (TMA) and water and NHALD films grown using TMA and isopropanol at 300 °C. Hydrolytically grown ALD films contain a smaller amount of fixed charge than NHALD films (oxide fixed charge Qf Traditional = -8.1 × 1011 cm-2 and Qf NHALD = -3.6 × 1012 cm-2), and a larger degree of chemical passivation than NHALD films (density of interface trap states, Dit Traditional = 5.4 × 1011 eV-1 cm-2 and Dit NHALD = 2.9 × 1012 eV-1 cm-2). Oxides grown with both chemistries were found to have a band gap of 7.1 eV. The conduction band offset was 3.21 eV for traditionally grown films and 3.38 eV for NHALD. The increased Dit for NHALD films may stem from carbon impurities in the oxide layer that are at and near the silicon surface, as evidenced by both the larger trap state time constant (τTraditional = 2.2 × 10-9 s and τNHALD = 1.7 × 10-7 s) and the larger carbon concentration. We have shown that the use of alcohol-based oxygen sources in NHALD chemistry can significantly affect the resulting interfacial electronic behavior presenting an additional parameter for understanding and controlling interfacial electronic properties at semiconductor-dielectric interfaces.

  8. Comparison of hydrolytic and non-hydrolytic atomic layer deposition chemistries: Interfacial electronic properties at alumina-silicon interfaces

    We report the differences in the passivation and electronic properties of aluminum oxide (Al2O3) deposited on silicon via traditional hydrolytic atomic layer deposition (ALD) and non-hydrolytic (NH) ALD chemistries. Traditional films were grown using trimethylaluminum (TMA) and water and NHALD films grown using TMA and isopropanol at 300 °C. Hydrolytically grown ALD films contain a smaller amount of fixed charge than NHALD films (oxide fixed charge Qf Traditional = −8.1 × 1011 cm−2 and Qf NHALD = −3.6 × 1012 cm−2), and a larger degree of chemical passivation than NHALD films (density of interface trap states, Dit Traditional = 5.4 × 1011 eV−1 cm−2 and Dit NHALD = 2.9 × 1012 eV−1 cm−2). Oxides grown with both chemistries were found to have a band gap of 7.1 eV. The conduction band offset was 3.21 eV for traditionally grown films and 3.38 eV for NHALD. The increased Dit for NHALD films may stem from carbon impurities in the oxide layer that are at and near the silicon surface, as evidenced by both the larger trap state time constant (τTraditional = 2.2 × 10−9 s and τNHALD = 1.7 × 10−7 s) and the larger carbon concentration. We have shown that the use of alcohol-based oxygen sources in NHALD chemistry can significantly affect the resulting interfacial electronic behavior presenting an additional parameter for understanding and controlling interfacial electronic properties at semiconductor-dielectric interfaces

  9. Interfacial mechanics of graphene

    Zhu, Yong

    2014-01-01

    Interfacial mechanics between graphene and substrate such as friction and adhesion plays a critical role in the morphology and functionality of graphene-based devices. Here I will present the interface sliding and buckling of monolayer graphene on a stretchable substrate. The nonlinear mechanical response of monolayer graphene on polyethylene terephthalate (PET) is characterized using in-situ Raman spectroscopy and atomic force microscopy. Although interfacial stress transfer leads to tension...

  10. 76 FR 29901 - Electronic Fund Transfers

    2011-05-23

    ... Board anticipates that final rules on remittance transfers will be issued by the Bureau. \\26\\ 75 FR... recipient of the funds. For instance, a consumer may add his daughter, who is studying abroad, as an...'' made by foreign-born residents in the United States to households abroad totaled $37.6 billion in...

  11. Electron-Transfer Acceleration Investigated by Time Resolved Infrared Spectroscopy

    Vlček Jr., Antonín; Kvapilová, Hana; Towrie, M.; Záliš, Stanislav

    2015-01-01

    Roč. 48, č. 3 (2015), s. 868-876. ISSN 0001-4842 Institutional support: RVO:61388955 Keywords : electron transfer * infrared spectroscopy Subject RIV: CG - Electrochemistry Impact factor: 22.323, year: 2014

  12. Theory of interrelated electron and proton transfer processes

    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...

  13. 77 FR 6310 - Electronic Fund Transfers (Regulation E)

    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....

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

    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.

  15. A role for microbial palladium nanoparticles in extracellular electron transfer.

    Wu, X; Zhao, F; Rahunen, N; Varcoe, JR; Avignone-Rossa, C.; Thumser, AE; Slade, RC

    2011-01-01

    Herein we have demonstrated a DET mechanism used by D. desulfuricans; where the periplasmic cytochromes and hydrogenases play an important role, and Pd nanoparticles bound to the microbes may participate in the electron transfer process. The present work is of importance not only for the fundamental studies of electron transfer processes in microbial physiology and ecology, but also for increased understanding and improvement of the performance of bioelectrochemical techniques e.g. precious m...

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

    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

  17. Intramolecular photoinduced electron-transfer in azobenzene-perylene diimide

    This paper studies the intramolecular photoinduced electron-transfer (PET) of covalent bonded azobenzene-perylene diimide (AZO-PDI) in solvents by using steady-state and time-resolved fluorescence spectroscopy together with ultrafast transient absorption spectroscopic techniques. Fast fluorescence quenching is observed when AZO-PDI is excited at characteristic wavelengths of AZO and perylene moieties. Reductive electron-transfer with transfer rate faster than 1011 s−1 is found. This PET process is also consolidated by femtosecond transient absorption spectra

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

    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

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

    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.

  20. Mathematics and electronics - the conceptual transfer problem

    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.

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

    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...

  2. Electron transfer rates and equilibrium within cytochrome c oxidase

    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...

  3. Photoinduced electron transfer in model systems of photosynthesis.

    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

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

    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

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

    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

  6. Electron transfer, ionization, and excitation atomic collisions

    Basic atomic-collision processes at intermediate and high energies are being studied theoretically at Penn State by Alston and Winter. In the high velocity regime, single-electron capture is treated using a high order multiple-scattering approach; extensive comparison with experiment and analysis of mechanisms have been made. Fitting the calculated amplitude with a simple analytic form, the asymptotic velocity dependence of the cross section is obtained. The effect on the capture amplitude of altering the inner part of the internuclear potential has also been explored. In the intermediate velocity regime, earlier work on collisions between protons and hydrogenic-ion targets using a coupled-state approach is being extended to the two-electron helium target. 29 refs

  7. Electronic Energy Transfer in Polarizable Heterogeneous Environments

    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....

  8. Electron transfer, ionization, and excitation in atomic collisions: Progress report

    The fundamental processes of electron transfer, ionization, and excitation in ion-atom collisions are being studied at Penn State by Winter. (The related work of Alston, who recently came to Penn State, is not described here since he is not at present funded by DOE.) 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. Three coupled-state calculations are being carried out over the present three-year period and are discussed here: a Sturmian-pseudostate study of electron transfer 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 a coupled-state study of electron transfer and excitation in collisions between protons and neutral He atoms

  9. Numerical modeling of fast electron energy transfer

    In this paper methods of calculating energy transport by fast electrons that are currently used in the ''Diana'' program are described; this program is intended to address issues in laser thermonuclear fusion. A method is proposed for solving a kinetic equation which has the following properties: conservativeness, the absence of constraints on the grid spacing relation, monitonicity, and second order approximation. The applicability of a ''front-back'' approximation is analyzed

  10. Noise-assisted quantum electron transfer in photosynthetic complexes

    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...

  11. Computational Approach to Electron Charge Transfer Reactions

    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...... 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 and...... asymmetric charge transfer reactions between several first-row transition metals in water. The results are compared to experiments and rationalised with classical analytic expressions. Shortcomings of the methods are accounted for with clear steps towards improved accuracy. Later the analysis is extended to...

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

    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...

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

    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.

  14. Electron transfer from nucleobase electron adducts to 5-bromouracil: a radiation chemical study

    Electron transfer to 5-bromouracil from their nucleobase electron adducts and their protonated forms has been studied by product analysis. When an electron is transferred to 5-bromouracil, the ensuing 5-bromouracil radical anion rapidly loses a bromide ion. The uracilyl radical thus formed reacts with added t-butanol, yielding uracil. From the uracil yields measured as a function of (N)/(5-BrU) after γ-radiolysis of Ar-saturated solutions it is concluded that the hetero atom protonated forms transfer electron quantitatively to 5-bromouracil. (author). 3 refs., 1 fig

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

    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

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

    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.

  17. Comparison of hydrolytic and non-hydrolytic atomic layer deposition chemistries: Interfacial electronic properties at alumina-silicon interfaces

    Marstell, Roderick J.; Strandwitz, Nicholas C., E-mail: strand@lehigh.edu [Department of Materials Science and Engineering and Center for Advanced Materials and Nanotechnology, Lehigh University, Bethlehem, Pennsylvania 18015 (United States)

    2015-11-14

    We report the differences in the passivation and electronic properties of aluminum oxide (Al{sub 2}O{sub 3}) deposited on silicon via traditional hydrolytic atomic layer deposition (ALD) and non-hydrolytic (NH) ALD chemistries. Traditional films were grown using trimethylaluminum (TMA) and water and NHALD films grown using TMA and isopropanol at 300 °C. Hydrolytically grown ALD films contain a smaller amount of fixed charge than NHALD films (oxide fixed charge Q{sub f} {sub Traditional} = −8.1 × 10{sup 11 }cm{sup −2} and Q{sub f} {sub NHALD} = −3.6 × 10{sup 12 }cm{sup −2}), and a larger degree of chemical passivation than NHALD films (density of interface trap states, D{sub it} {sub Traditional} = 5.4 × 10{sup 11 }eV{sup −1 }cm{sup −2} and D{sub it} {sub NHALD} = 2.9 × 10{sup 12 }eV{sup −1 }cm{sup −2}). Oxides grown with both chemistries were found to have a band gap of 7.1 eV. The conduction band offset was 3.21 eV for traditionally grown films and 3.38 eV for NHALD. The increased D{sub it} for NHALD films may stem from carbon impurities in the oxide layer that are at and near the silicon surface, as evidenced by both the larger trap state time constant (τ{sub Traditional} = 2.2 × 10{sup −9} s and τ{sub NHALD} = 1.7 × 10{sup −7} s) and the larger carbon concentration. We have shown that the use of alcohol-based oxygen sources in NHALD chemistry can significantly affect the resulting interfacial electronic behavior presenting an additional parameter for understanding and controlling interfacial electronic properties at semiconductor-dielectric interfaces.

  18. [Electron transfer, ionization, and excitation in atomic collisions

    Fundamental processes of electron transfer, ionization, and excitation in ion-atom and ion-ion collisions are studied. Attention is focussed on one- and two-electron systems and, more recently, quasi-one-electron systems whose electron-target-ion core can be accurately modeled by one-electron potentials. The basic computational approaches can then be taken with few, if any, approximations, and the underlying collisional mechanisms can be more clearly revealed. At intermediate collision energies (e.g., proton energies for p-He+ collisions on the order of 100 kilo-electron volts), many electronic states are strongly coupled during the collision, a coupled-state approach, such as a coupled-Sturmian-pseudostate approach, is appropriate. At higher collision energies (million electron-volt energies) the coupling is weaker with, however, many more states being coupled together, so that high-order perturbation theory is essential

  19. Structural and interfacial characteristics of thin (2 films grown by electron cyclotron resonance plasma oxidation on [100] Si substrates

    The feasibility of fabricating ultra-thin SiO2 films on the order of a few nanometer thickness has been demonstrated. SiO2 thin films of approximately 7 nm thickness have been produced by ion flux-controlled Electron Cyclotron Resonance plasma oxidation at low temperature on [100] Si substrates, in reproducible fashion. Electrical measurements of these films indicate that they have characteristics comparable to those of thermally grown oxides. The thickness of the films was determined by ellipsometry, and further confirmed by cross-sectional High-Resolution Transmission Electron Microscopy. Comparison between the ECR and the thermal oxide films shows that the ECR films are uniform and continuous over at least a few microns in lateral direction, similar to the thermal oxide films grown at comparable thickness. In addition, HRTEM images reveal a thin (1--1.5 nm) crystalline interfacial layer between the ECR film and the [100] substrate. Thinner oxide films of approximately 5 nm thickness have also been attempted, but so far have resulted in nonuniform coverage. Reproducibility at this thickness is difficult to achieve

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

    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.

  1. Distance dependence of intramolecular electron transfer through rigid hydrocarbon spacers

    The effects of energy, distance and molecular structure on rates of electron transfer between molecules are the subjects of continuing investigations in the authors laboratory. The use of rigid molecular spacers between electron donor and acceptor groups facilitates study of the above questions, and is a promising method to obtain energy storage with directed charge separation. Here they present recent results focusing principally on the effects of distance through rigid hydrocarbon spacers. Through-bond interaction is the dominant source of the electronic coupling which enables electron transfer to occur in a series of molecules of the type D-S-A. Pulse radiolysis measurements used molecules D (donor) = biphenyl and A (acceptor) = naphthalene attached to a series of spacer molecules, S, having 3,4,6,7 or 10 saturated hydrocarbon bonds between the D and A groups. The spacer groups were 1,3-cyclohexane (three bonds), 1,4-cyclohexane (four bonds), 2,7-decalin (six bonds), 2,6-decalin (seven bonds) and 3,16-androstance (ten bonds). They attached electrons to these molecules using Argonne's picosecond Linac and measured electron transfer rates (ET) from 3.5 x 109s-1 across three bonds to 1.5 x 106s-1 across ten bonds. The clearest understanding of the rates is obtained by comparing the electronic-coupling interactions. The electronic interactions decrease regularly with increasing number of bonds, but do not correlate very well with either edge-to-edge or center-to-center distance

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

    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.

  3. Distance-dependent electron transfer in DNA hairpins

    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.

  4. Electron transfer statistics and thermal fluctuations in molecular junctions

    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.

  5. Electron transfer statistics and thermal fluctuations in molecular junctions

    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.

  6. High-pressure effects on intramolecular electron transfer compounds

    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.

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

    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.

  8. Electron Transfer Dissociation Mass Spectrometry of Hemoglobin on Clinical Samples

    Coelho Graça, Didia; Lescuyer, Pierre; Clerici, Lorella; Tsybin, Yury O.; Hartmer, Ralf; Meyer, Markus; Samii, Kaveh; Hochstrasser, Denis F.; Scherl, Alexander

    2012-10-01

    A mass spectrometry-based assay combining the specificity of selected reaction monitoring and the protein ion activation capabilities of electron transfer dissociation was developed and employed for the rapid identification of hemoglobin variants from whole blood without previous proteolytic cleavage. The analysis was performed in a robust ion trap mass spectrometer operating at nominal mass accuracy and resolution. Subtle differences in globin sequences, resulting with mass shifts of about one Da, can be unambiguously identified. These results suggest that mass spectrometry analysis of entire proteins using electron transfer dissociation can be employed on clinical samples in a workflow compatible with diagnostic applications.

  9. Optical Spectroscopy of the Bulk and Interfacial Hydrated Electron from Ab Initio Calculations

    Uhlig, Frank; Herbert, J. M.; Coons, M. P.; Jungwirth, Pavel

    2014-01-01

    Roč. 118, č. 35 (2014), s. 7507-7515. ISSN 1089-5639 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388963 Keywords : hydrated electron * optical spectrum * ab initio molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.693, year: 2014

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

    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.