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Sample records for charge transfer band

  1. Dual Fluorescence in GFP Chromophore Analogues: Chemical Modulation of Charge Transfer and Proton Transfer Bands.

    Science.gov (United States)

    Chatterjee, Tanmay; Mandal, Mrinal; Das, Ananya; Bhattacharyya, Kalishankar; Datta, Ayan; Mandal, Prasun K

    2016-04-14

    Dual fluorescence of GFP chromophore analogues has been observed for the first time. OHIM (o-hydroxy imidazolidinone) shows only a charge transfer (CT) band, CHBDI (p-cyclicamino o-hydroxy benzimidazolidinone) shows a comparable intensity CT and PT (proton transfer) band, and MHBDI (p-methoxy o-hydroxy benzimidazolidinone) shows a higher intensity PT band. It could be shown that the differential optical behavior is not due to conformational variation in the solid or solution phase. Rather, control of the excited state electronic energy level and excited state acidity constant by functional group modification could be shown to be responsible for the differential optical behavior. Chemical modification-induced electronic control over the relative intensity of the charge transfer and proton transfer bands could thus be evidenced. Support from single-crystal X-ray structure, NMR, femtosecond to nanosecond fluorescence decay analysis, and TDDFT-based calculation provided important information and thus helped us understand the photophysics better.

  2. Effect of Surface Defect States on Valence Band and Charge Separation and Transfer Efficiency

    Science.gov (United States)

    Xu, Juan; Teng, Yiran; Teng, Fei

    2016-09-01

    Both energy band and charge separation and transfer are the crucial affecting factor for a photochemical reaction. Herein, the BiOCl nanosheets without and with surface bismuth vacancy (BOC, V-BOC) are prepared by a simple hydrothermal method. It is found that the new surface defect states caused by bismuth vacancy have greatly up-shifted the valence band and efficiently enhanced the separation and transfer rates of photogenerated electron and hole. It is amazing that the photocatalytic activity of V-BOC is 13.6 times higher than that of BOC for the degradation methyl orange (MO). We can develop an efficient photocatalyst by the introduction of defects.

  3. Polarization Enhanced Charge Transfer: Dual-Band GaN-Based Plasmonic Photodetector

    Science.gov (United States)

    Jia, Ran; Zhao, Dongfang; Gao, Naikun; Liu, Duo

    2017-01-01

    Here, we report a dual-band plasmonic photodetector based on Ga-polar gallium nitride (GaN) for highly sensitive detection of UV and green light. We discover that decoration of Au nanoparticles (NPs) drastically increases the photoelectric responsivities by more than 50 times in comparition to the blank GaN photodetector. The observed behaviors are attributed to polarization enhanced charge transfer of optically excited hot electrons from Au NPs to GaN driven by the strong spontaneous polarization field of Ga-polar GaN. Moreover, defect ionization promoted by localized surface plasmon resonances (LSPRs) is also discussed. This novel type of photodetector may shed light on the design and fabrication of photoelectric devices based on polar semiconductors and microstructural defects.

  4. Resonant charge transfer of hydrogen Rydberg atoms incident at a Cu(100) projected band-gap surface

    CERN Document Server

    Gibbard, J A; Kohlhoff, M; Rennick, C J; So, E; Ford, M; Softley, T P

    2015-01-01

    The charge transfer (ionization) of hydrogen Rydberg atoms (principal quantum number $n=25-34$) incident at a Cu(100) surface is investigated. Unlike fully metallic surfaces, where the Rydberg electron energy is degenerate with the conduction band of the metal, the Cu(100) surface has a projected bandgap at these energies, and only discrete image states are available through which charge transfer can take place. Resonant enhancement of charge transfer is observed at hydrogen principal quantum numbers for which the Rydberg energy matches the energy of one of the image states. The integrated surface ionization signals show clear periodicity as the energies of states with increasing $n$ come in and out of resonance with the image states. The velocity dependence of the surface ionization dynamics is also investigated. Decreased velocity of the incident H atom leads to a greater mean distance of ionization and a lower field required to extract the ion. The surface-ionization profiles (signal versus applied field) ...

  5. Synthesis and energy band characterization of hybrid molecular materials based on organic–polyoxometalate charge-transfer salts

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Chunxia [Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province and College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou City, Gansu Province (China); Traditional Chinese Medicine College of Gansu, Gansu (China); Bu, Weifeng, E-mail: buwf@lzu.edu.cn [Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province and College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou City, Gansu Province (China)

    2014-11-15

    A cationic amphiphilic molecule was synthesized and employed to encapsulate Lindqvist ([M{sub 6}O{sub 19}]{sup 2−}) and Keggin polyoxometalates ([SiM{sub 12}O{sub 40}]{sup 4−}, M=Mo, W) to form hybrid molecules through electrostatic interaction. The X-ray diffraction results illustrate that the former hybrids possess lamellar nanostructures in their solid states, while the latter hybrids show a cubic Im3m packing model with low intensities and poor long-range order. These hybrids have clear charge-transfer characters as shown in their deeper colors and UV–vis diffuse reflectance spectra. According to the reported reduction potentials of the POM acceptors and the band gaps deduced from their diffuse reflectance spectra, we have calculated the theoretical values of the lowest unoccupied molecular orbital (LUMO) position similar to the electron affinity (E{sub A}) of solid materials. Such energy level parameters are comparable to those of electroluminescence and electron-transport materials commonly used in organic electroluminescence devices. These organic–polyoxometalate charge-transfer salts have more advantages, such as higher decomposition temperatures, easier film fabrication and better electron affinities, which presumably would be used for electron-transport materials in the area of the electroluminescence. - Graphical abstract: Hybrid molecular materials with charge-transfer characters formed by a positively charged donor L and acceptors of the Lindqvist-type and Keggin-type POMs have lamellar and cubic structures in their solid state. - Highlights: • Charge-transfer salts are obtained by self-assembling POMs with an anthracene cation. • Their energy parameters are comparable to those of optoelectronic materials in OLEDs. • These POM-based hybrids could be applied in the area of optoelectronic devices.

  6. Spectroscopy and dynamics of charge transfer excitons in type-II band aligned quantum confined heterostructures

    Science.gov (United States)

    Kushavah, Dushyant; Mohapatra, P. K.; Rustagi, K. C.; Bahadur, D.; Vasa, P.; Singh, B. P.

    2015-05-01

    We illustrate effect of charge transfer (CT) in type-II quantum confined heterostructure by comparing CdSe quantum dots (QDs), CdSe/CdTe heterostructure quantum dots (HQDs) and CdSe/CdTe/CdSe quantum well-quantum dots (QWQDs) heterostructures. CdSe core QDs were synthesized using a kinetic growth method where QD size depends on reaction time. For shell coating we used modified version of successive ionic layer adsorption and reaction (SILAR). Size of different QDs ˜5 to 7 nm were measured by transmission electron microscopy (TEM). Strong red shift from ˜597 to ˜746 nm in photoluminescence (PL) spectra from QDs to QWQDs shows high tunability which is not possible with single constituent semiconductor QDs. PL spectra have been recorded at different temperatures (10K-300K). Room temperature time correlated single photon counting (TCSPC) measurements for QDs to QWQDs show three exponential radiative decay. The slowest component decay constant in QWQDs comes around eight fold to ˜51 ns as compared to ˜6.5 ns in HQD suggesting new opportunities to tailor the radiative carrier recombination rate of CT excitons.

  7. Spectroscopy and dynamics of charge transfer excitons in type-II band aligned quantum confined heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Kushavah, Dushyant [Centre for Research in Nanotechnology and Science, IIT Bombay-400076, Mumbai (India); Mohapatra, P. K.; Vasa, P.; Singh, B. P., E-mail: bhanups@iitb.ac.in [Department of physics, IIT Bombay, Mumbai-400076 (India); Rustagi, K. C. [Indian Institute of Science Education and Research Bhopal-462066, Bhopal (India); Bahadur, D. [Department of Metallurgical Engineering and Materials Science, IIT Bombay, Mumbai-400076 (India)

    2015-05-15

    We illustrate effect of charge transfer (CT) in type-II quantum confined heterostructure by comparing CdSe quantum dots (QDs), CdSe/CdTe heterostructure quantum dots (HQDs) and CdSe/CdTe/CdSe quantum well-quantum dots (QWQDs) heterostructures. CdSe core QDs were synthesized using a kinetic growth method where QD size depends on reaction time. For shell coating we used modified version of successive ionic layer adsorption and reaction (SILAR). Size of different QDs ∼5 to 7 nm were measured by transmission electron microscopy (TEM). Strong red shift from ∼597 to ∼746 nm in photoluminescence (PL) spectra from QDs to QWQDs shows high tunability which is not possible with single constituent semiconductor QDs. PL spectra have been recorded at different temperatures (10K-300K). Room temperature time correlated single photon counting (TCSPC) measurements for QDs to QWQDs show three exponential radiative decay. The slowest component decay constant in QWQDs comes around eight fold to ∼51 ns as compared to ∼6.5 ns in HQD suggesting new opportunities to tailor the radiative carrier recombination rate of CT excitons.

  8. Calix[4]arene-linked bisporphyrin hosts for fullerenes: binding strength, solvation effects, and porphyrin-fullerene charge transfer bands.

    Science.gov (United States)

    Hosseini, Ali; Taylor, Steven; Accorsi, Gianluca; Armaroli, Nicola; Reed, Christopher A; Boyd, Peter D W

    2006-12-13

    A calix[4]arene scaffolding has been used to construct bisporphyrin ("jaws" porphyrin) hosts for supramolecular binding of fullerene guests. Fullerene affinities were optimized by varying the nature of the covalent linkage of the porphyrins to the calixarenes. Binding constants for C60 and C70 in toluene were explored as a function of substituents at the periphery of the porphyrin, and 3,5-di-tert-butylphenyl groups gave rise to the highest fullerene affinities (26,000 M(-1) for C60). The origin of this high fullerene affinity has been traced to differential solvation effects rather than to electronic effects. Studies of binding constants as a function of solvent (toluene solubility, indicating that desolvation of the fullerene is a major factor determining the magnitude of binding constants. The energetics of fullerene binding have been determined in terms of DelatH and DeltaS and are consistent with an enthalpy-driven, solvation-dependent process. A direct relationship between supramolecular binding of a fullerene guest to a bisporphyrin host and the appearance of a broad NIR absorption band have been established. The energy of this band moves in a predictable manner as a function of the electronic structure of the porphyrin, thereby establishing its origin in porphyrin-to-fullerene charge transfer.

  9. The cuprate superconductors: Narrow correlated-electron bands and interlayer pairing via plane-chain charge transfer

    Science.gov (United States)

    Ashkenazi, J.; Kuper, C. G.

    1989-12-01

    The cuprate superconductors are modelled by two metallic CuO 2planes, separated by insulating layers, in an extended Hubbard Hamiltonian. Hybridization of O(2 p) and Cu( d) orbitals splits the wide bands of LDA theory, yielding a narrow conduction band of antibonding holes. Holes on the two CuO 2 planes are correlated via interplane hopping, giving a non-magnetic normal Fermi liquid. Charge exchange between the planes and the intervening layers generates attraction and a BCS condensation.

  10. Valence-band offset and forward-backward charge transfer in manganite/NiO and manganite/LaNiO3 heterostructures.

    Science.gov (United States)

    Ning, X K; Wang, Z J; Chen, Y N; Zhang, Z D

    2015-12-28

    The valence-band offset (VBO) of the La(0.67)Sr(0.33)MnO(3)/NiO (LSMO/NiO), LaMnO(3)/NiO (LMO/NiO), LSMO/LaNiO(3) (LSMO/LNO) and LMO/LaNiO(3) (LSMO/LNO) heterostructures has been investigated using X-ray photoemission spectroscopy. The VBO values are calculated to be -0.72, -0.05, +1.43 and +1.51 eV for the LSMO/NiO, LSMO/LNO, LMO/LNO and LMO/NiO heterostructures, respectively. Hence, when compared with NiO and LNO, the valence band of LSMO is shifted to a lower binding energy, whereas that of LMO is shifted to a higher binding energy. In addition, the charge transfer at the interfaces has been depicted as Mn(3.3+) + 0.7e→ Mn(2.6+), Mn(3.3+) + 0.1e→ Mn(3.2+), Mn(3.0+)- 0.4e→ Mn(3.4+) and Mn(3.0+)- 0.5e→ Mn(3.5+) for the LSMO/NiO, LSMO/LNO, LMO/LNO and LMO/NiO heterostructures, respectively. Thus, the charge transfer procedure can be described as electron hopping from NiO and LNO to LSMO in the LSMO/NiO and LSMO/LNO heterostructures, and electron hopping from LMO to NiO and LNO in the LMO/NiO and LSMO/LNO heterostructures. Therefore, the charge transfer is dependent on the VBO, and the charge transfer direction can be determined from the negative or positive values of the VBO.

  11. Calibrating transition-metal energy levels and oxygen bands in first-principles calculations: Accurate prediction of redox potentials and charge transfer in lithium transition-metal oxides

    Science.gov (United States)

    Seo, Dong-Hwa; Urban, Alexander; Ceder, Gerbrand

    2015-09-01

    Transition-metal (TM) oxides play an increasingly important role in technology today, including applications such as catalysis, solar energy harvesting, and energy storage. In many of these applications, the details of their electronic structure near the Fermi level are critically important for their properties. We propose a first-principles-based computational methodology for the accurate prediction of oxygen charge transfer in TM oxides and lithium TM (Li-TM) oxides. To obtain accurate electronic structures, the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional is adopted, and the amount of exact Hartree-Fock exchange (mixing parameter) is adjusted to reproduce reference band gaps. We show that the HSE06 functional with optimal mixing parameter yields not only improved electronic densities of states, but also better energetics (Li-intercalation voltages) for LiCo O2 and LiNi O2 as compared to the generalized gradient approximation (GGA), Hubbard U corrected GGA (GGA +U ), and standard HSE06. We find that the optimal mixing parameters for TM oxides are system specific and correlate with the covalency (ionicity) of the TM species. The strong covalent (ionic) nature of TM-O bonding leads to lower (higher) optimal mixing parameters. We find that optimized HSE06 functionals predict stronger hybridization of the Co 3 d and O 2 p orbitals as compared to GGA, resulting in a greater contribution from oxygen states to charge compensation upon delithiation in LiCo O2 . We also find that the band gaps of Li-TM oxides increase linearly with the mixing parameter, enabling the straightforward determination of optimal mixing parameters based on GGA (α =0.0 ) and HSE06 (α =0.25 ) calculations. Our results also show that G0W0@GGA +U band gaps of TM oxides (M O ,M =Mn ,Co ,Ni ) and LiCo O2 agree well with experimental references, suggesting that G0W0 calculations can be used as a reference for the calibration of the mixing parameter in cases when no experimental band gap has been

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-09-15

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

  13. Charge-transfer character of the low-energy Chl a Q(y) absorption band in aggregated light harvesting complexes II.

    Science.gov (United States)

    Kell, Adam; Feng, Ximao; Lin, Chen; Yang, Yiqun; Li, Jun; Reus, Michael; Holzwarth, Alfred R; Jankowiak, Ryszard

    2014-06-12

    One of the key functions of the major light harvesting complex II (LHCII) of higher plants is to protect Photosystem II from photodamage at excessive light conditions in a process called "non-photochemical quenching" (NPQ). Using hole-burning (HB) spectroscopy, we investigated the nature of the low-energy absorption band in aggregated LHCII complexes - which are highly quenched and have been established as a good in vitro model for NPQ. Nonresonant holes reveal that the lowest energy state (located near 683.3 nm) is red-shifted by ~4 nm and significantly broader (by a factor of 4) as compared to nonaggregated trimeric LHCII. Resonant holes burned in the low-energy wing of the absorption spectrum (685-710 nm) showed a high electron-phonon (el-ph) coupling strength with a Huang-Rhys factor S of 3-4. This finding combined with the very low HB efficiency in the long-wavelength absorption tail is consistent with a dominant charge-transfer (CT) character of the lowest energy transition(s) in aggregated LHCII. The value of S decreases at shorter wavelengths (energy excitonic state is strongly mixed with the CT states. Our findings support the mechanistic model in which Chl-Chl CT states formed in aggregated LHCII are intermediates in the efficient excited state quenching process (M. G. Müller et al., Chem. Phys. Chem. 2010, 11, 1289-1296; Y. Miloslavina et al., FEBS Lett. 2008, 582, 3625-3631).

  14. Ultrafast Charge Photogeneration in MEH-PPV Charge-Transfer Complexes

    Science.gov (United States)

    Bakulin, Artem A.; Paraschuk, Dmitry Yu.; Pshenichnikov, Maxim S.; van Loosdrecht, Paul H. M.

    Visible-pump-IR-probe spectroscopy is used to study the ultrafast charge dynamics in MEH-PPV based charge-transfer complexes and donor-acceptor blends. Transient anisotropy of the polymer polaron band provides invaluable insights into excitation localisation and charge-transfer pathways.

  15. Charge-transfer spectra of tetravalent lanthanide ions in oxides

    NARCIS (Netherlands)

    Hoefdraad, H.E.

    1975-01-01

    The charge-transfer spectra of Ce4+, Pr4+ and Tb4+ in a number of oxides are reported. It is noted that the position of the first charge-transfer band is fixed for the metal ion in an oxygen coordination of VI, but varies in VIII coordination as a function of the host lattice. It is argued that this

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

    Science.gov (United States)

    Fujisawa, Jun-ichi; Hanaya, Minoru

    2016-06-01

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

  17. Charge transfer in multicomponent oxides

    Science.gov (United States)

    Kohan, A. F.; Ceder, G.

    1998-02-01

    The transfer of charge between different ions in an oxide plays an essential role in the stability of these compounds. Since small variations in charge can introduce large changes in the total energy, a correct description of this phenomenon is critical. In this work, we show that the ionic charge in oxides can strongly depend on its atomic environment. A model to assign point charges to atoms as a function of their atomic environment has recently been proposed for binary alloys [C. Wolverton, A. Zunger, S. Froyen, and S.-H. Wei, Phys. Rev. B 54, 7843 (1996)] and proven to be very successful in screened solids such as semiconductors and metals. Here, we extend this formalism to multicomponent oxides and we assess its applicability. The simple point-charge model predicts a linear relation between the charge on an atom and the number of unlike neighbors, and between the net value of the charge and the Coulomb field at a given site. The applicability of this approach is tested in a large-supercell self-consistent tight-binding calculation for a random Zr-Ca-O alloy. The observed fluctuations of the ionic charge about the average linear behavior (as a function of the number of unlike neighbors) was larger than 0.25 electrons even when many shells of atomic neighbors were considered in the fit. This variation is significant since it can introduce large errors in the electrostatic energy. On the other hand, for small absolute values of the charge, the ionic charge varied linearly with the Coulomb field, in agreement with previous findings. However, for large Coulomb fields, this function saturates at the formal chemical charge.

  18. UV-Vis spectroscopy and density functional study of solvent effect on the charge transfer band of the n → σ* complexes of 2-Methylpyridine and 2-Chloropyridine with molecular iodine

    Science.gov (United States)

    Gogoi, Pallavi; Mohan, Uttam; Borpuzari, Manash Protim; Boruah, Abhijit; Baruah, Surjya Kumar

    2017-03-01

    UV-Vis spectroscopy has established that Pyridine substitutes form n→σ* charge transfer (CT) complexes with molecular Iodine. This study is a combined approach of purely experimental UV-Vis spectroscopy, Multiple linear regression theory and Computational chemistry to analyze the effect of solvent upon the charge transfer band of 2-Methylpyridine-I2 and 2-Chloropyridine-I2 complexes. Regression analysis verifies the dependence of the CT band upon different solvent parameters. Dielectric constant and refractive index are considered among the bulk solvent parameters and Hansen, Kamlet and Catalan parameters are taken into consideration at the molecular level. Density Functional Theory results explain well the blue shift of the CT bands in polar medium as an outcome of stronger donor acceptor interaction. A logarithmic relation between the bond length of the bridging atoms of the donor and the acceptor with the dielectric constant of the medium is established. Tauc plot and TDDFT study indicates a non-vertical electronic transition in the complexes. Buckingham and Lippert Mataga equations are applied to check the Polarizability effect on the CT band.

  19. Intramolecular Charge Transfer in Arylpyrazolines

    Institute of Scientific and Technical Information of China (English)

    WANG Ming-Liang; LIU Ju-Zheng; XU Chun-Xiang

    2006-01-01

    @@ Arylpyrazoline microparticles dispersed in water are synthesized and their absorption spectra are compared with those in solution. It is found that the absorbance of pyrazoline group in solution of 5-aryl arylpyrazoline is far greater than that in solution of arylpyrazolines with no 5-aryl group. This hyperchromic effect is intensified in 5-aryl arylpyrazoline microparticles. It is indicated that intramolecular charge transfer exists between pyrazoline group and 5-aryl group and this kind of interaction is increased in their microparticles.

  20. Charge-Transfer Versus Charge-Transfer-Like Excitations Revisited

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Barry; Sun, Haitao; Govind, Niranjan; Kowalski, Karol; Autschbach, Jochen

    2015-07-14

    Criteria to assess charge-transfer (CT) and `CT-like' character of electronic excitations are examined. Time-dependent density functional theory (TDDFT) with non-hybrid, hybrid, and tuned long-range corrected (LC) functionals is compared with with coupled-cluster (CC) benchmarks. The test set includes an organic CT complex, two `push-pull' donor-acceptor chromophores, a cyanine dye, and several polycyclic aromatic hydrocarbons. Proper CT is easily identified. Excitations with significant density changes upon excitation within regions of close spatial proximity can also be diagnosed. For such excitations, the use of LC functionals in TDDFT sometimes leads to dramatic improvements of the singlet energies, similar to proper CT, which has led to the concept of `CT-like' excitations. However, `CT-like' excitations are not like charge transfer, and the improvements are not obtained for the right reasons. The triplet excitation energies are underestimated for all systems, often severely. For the `CT-like' candidates, when going from a non-hybrid to an LC functional the error in the singlet-triplet (S/T) separation changes from negative to positive, providing error compensation. For the cyanine, the S/T separation is too large with all functionals, leading to the best error compensation for non-hybrid functionals.

  1. Backward Charge Transfer in Conjugated Polymers

    Institute of Scientific and Technical Information of China (English)

    CHENG Meng-Xing; LI Guang-Qi; Thomas F. George; SUN Xin

    2005-01-01

    It has been known that the static polarizability of a polymer chain with a biexciton is negative. In order to understand this peculiar fact, this paper studies the dynamical process of the charge transfer in the polymer chain induced by an external electric field E during forming the biexciton. The time dependence of the charge distribution in the chain reveals that the charge transfer is backward: the positive charge shifts in the opposite direction of the external electric field. Such a backward charge transfer (BCT) produces an opposite dipole, which makes the polarization negative. The effect of electron interaction on the BCT is illustrated.

  2. Charge-transfer with graphene and nanotubes

    Directory of Open Access Journals (Sweden)

    C.N.R. Rao

    2010-09-01

    Full Text Available Charge-transfer between electron–donor and –acceptor molecules is a widely studied subject of great chemical interest. Some of the charge-transfer compounds in solid state exhibit novel electronic properties. In the last two to three years, occurrence of molecular charge-transfer involving single-walled carbon nanotubes (SWNTs and graphene has been demonstrated. This interaction gives rise to significant changes in the electronic properties of these nanocarbons. We examine charge-transfer phenomenon in graphene and SWNTs in this article in view of its potential utility in device applications.

  3. Simulation for signal charge transfer of charge coupled devices

    Institute of Scientific and Technical Information of China (English)

    Wang Zujun; Liu Yinong; Chen Wei; Tang Benqi; Xiao Zhigang; Huang Shaoyan; Liu Minbo; Zhang Yong

    2009-01-01

    Physical device models and numerical processing methods are presented to simulate a linear buried channel charge coupled devices (CCDs). The dynamic transfer process of CCD is carried out by a three-phase clock pulse driver. By using the semiconductor device simulation software MEDICI, dynamic transfer pictures of signal charges cells, electron concentration and electrostatic potential are presented. The key parameters of CCD such as charge transfer efficiency (CTE) and dark electrons are numerically simulated. The simulation results agree with the theoretic and experimental results.

  4. Adjusting band gap and charge transfer of organometallic complex adsorbed on MoS2 monolayer using vertical electric-field: a first-principles investigation

    Science.gov (United States)

    Bui, Viet Q.; Le, Hung M.; Kawazoe, Yoshiyuki; Kim, Yongho

    2017-01-01

    In this paper, we propose the use of benzene (Bz) to cover the active site on top of a transition metal atom (Cr/Mn/Fe) adsorbed on the MoS2 monolayer. Stable configurations of adatom on the MoS2 surface were predicted using first-principles calculations and their electronic, magnetic properties were investigated. In addition, the influence of vertical electric field on the electronic band structures of the systems was carefully examined. Analyzing the adsorption energies of transition metals given by the PBE calculations, we found that the benzene molecule stabilized the binding of Cr and Mn on the MoS2 surface, but destabilized the Fe binding by approximately 33% of adsorption energy. The attachment of benzene caused modifications on the total magnetizations of the Cr-MoS2 and Mn-MoS2 structures. The Bz-Mn@MoS2 structure was found to exhibit half-metallicity with 100% spin polarization at the Fermi level. The influence of various degrees of vertical electric field was shown to produce a tensile stress, which altered the lattice parameters and led to band gap narrowing and dramatic shifts of the Fermi level.

  5. On the Possibility of Superfast Charge Transfer in DNA

    CERN Document Server

    Lakhno, V D

    2013-01-01

    Numerous experiments on charge transfer in DNA yield a contradictory picture of the transfer: on the one hand they suggest that it is a very slow process and the charge is almost completely localized on one Watson-Crick pair, but on the other hand they demonstrate that the charge can travel a very large distance. To explain this contradiction we propose that superfast charge transitions are possible between base pairs on individual DNA fragments resulting in the establishment of a quasi-equilibrium charge distribution during the time less than that of charge solvation. In other words, we hypothesize these states irrespective of the nature of a mechanism responsible for their establishment, whether it be a hopping mechanism, or a band mechanism, or superexchange, or polaron transport, etc., leaving aside the debates of which one is more advantageous. We discuss qualitative differences between the charge transfer in a dry DNA and that in a solution. In a solution, of great importance is the charge solvation whi...

  6. Opposites Attract: Organic Charge Transfer Salts

    Science.gov (United States)

    van de Wouw, Heidi L.; Chamorro, Juan; Quintero, Michael; Klausen, Rebekka S.

    2015-01-01

    A laboratory experiment is described that introduces second-year undergraduate organic chemistry students to organic electronic materials. The discovery of metallic conductivity in the charge transfer salt tetrathiafulvalene tetracyanoquinodimethane (TTF-TCNQ) is a landmark result in the history of organic electronics. The charge transfer…

  7. Chemical bond properties and charge transfer bands of O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+) in Eu(3+)-doped garnet hosts Ln3M5O12 and ABO4 molybdate and tungstate phosphors.

    Science.gov (United States)

    Liu, Xiaoguang; Li, Ling; Noh, Hyeon Mi; Moon, Byung Kee; Choi, Byung Chun; Jeong, Jung Hyun

    2014-06-21

    Charge transfer (CT) energy from the ligand to the central ions is an important factor in luminescence properties for rare earth doped inorganic phosphors. The dielectric theory of complex crystals was used to calculate chemical bond properties. Combining the photoluminescence and the dielectric theory of complex crystals, the CT bands of O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+) for Eu(3+)-doped inorganic phosphors have been investigated experimentally and theoretically. Taking Eu(3+)-doped Ln3M5O12 (Ln = Y, Lu and M = Al, Ga), Gd3Ga5O12, MMoO4 (M = Ca, Sr, Ba) and MWO4 (M = Ca, Sr, Ba) as typical phosphors, we investigated the effects of the cation size on the CT bands and chemical bond properties including the bond length (d), the covalency (fc), the bond polarizability (αb) and the environmental factor (he) of O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+), respectively. For systematic isostructural Ln3M5O12 (Ln = Y, Lu and M = Al, Ga) phosphors, with the increasing M ion radius, the bond length of Ln-O decreases, but fc and αb increase, which is the main reason that the environmental factor increased. For the isostructural MMoO4:Eu, with the increasing M ion radius, the Mo-O bond length increases, but fc and αb decrease, and thus he decreases. However, in the compound system MWO4:Eu (M = Ca, Ba) with the increasing M ion radius, the O-W bond length increases, but fc and αb increase, and thus he increases and the O-W CT energy decreases. Their O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+) CT bands as well as their full width at half maximum (FWHM) were directly influenced by he. And with the increasing he, CT bands of O-Eu or O-Mo or O-W decrease and their FWHM increases. These results indicate a promising approach for changing the material properties, searching for new Eu(3+) doped molybdate, tungstate or other oxide phosphors and analyzing the experimental result.

  8. Charge Transfer in Nanocrystalline Semiconductor Electrodes

    Directory of Open Access Journals (Sweden)

    M. Bouroushian

    2013-01-01

    Full Text Available Nanocrystalline electrodes in liquid junction devices possess a number of unique properties arising from their convoluted structure and the dimensions of their building units. The light-induced charge separation and transport in photoelectrochemical systems using nanocrystalline/nanoporous semiconductor electrodes is discussed here in connection with the basic principles of the (Schottky barrier theory. Recent models for charge transfer kinetics in normal and unipolar (dye-sensitized cells are reviewed, and novel concepts and materials are considered.

  9. Modulation transfer functions at Ka band

    Science.gov (United States)

    Hesany, Vahid; Sistani, Bita; Salam, Asif; Haimov, Samuel; Gogineni, Prasad; Moore, Richard K.

    The modulation transfer function (MTF) is often used to describe the modulation of the radar signal by the long waves. MTFs were measured at 35 GHz (Ka band) with a switched-beam vector slope gauge/scatterometer on the research platform NORDSEE as part of the SAXON-FPN experiment. Three independent measurements of the scattering were available for each height measurement. This provided the opportunity to average the time series to reduce the effects of fading noise and sea spikes, or, alternatively, to append the time series to achieve more degrees of freedom in the spectral estimates. For upwind measurements, the phase of the VV-polarized Ka-band MTF was always positive, which implies that the maximum of the radar return originates from the forward face of the long-scale waves. This phase increases with increasing wind speed. The magnitude of the MTF decreases with increasing wind speed.

  10. Charge transfer in conjugated oligomers encapsulated into carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Almadori, Y.; Alvarez, L.; Michel, T.; Le Parc, R.; Bantignies, J.L.; Hermet, P.; Sauvajol, J.L. [Laboratoire Charles Coulomb UMR 5521, Universite Montpellier 2, 34095 Montpellier (France); Laboratoire Charles Coulomb UMR 5521, CNRS, 34095 Montpellier (France); Arenal, R. [Laboratoire d' Etude des Microstructures, CNRS-ONERA, 92322 Chatillon (France); Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragon, U. Zaragoza, 50018 Zaragoza (Spain); Babaa, R. [Laboratoire de Chimie des Surfaces et Interfaces, CEA, IRAMIS, SPCSI, 91191 Gif-sur-Yvette Cedex (France); Chemical Engineering Department, University of Technology PETRONAS, UTP, Ipoh-Perak (Malaysia); Jouselme, B.; Palacin, S. [Laboratoire de Chimie des Surfaces et Interfaces, CEA, IRAMIS, SPCSI, 91191 Gif-sur-Yvette Cedex (France)

    2011-11-15

    This study deals with a hybrid system consisting in quaterthiophene derivative encapsulated inside single-walled and multi-walled carbon nanotubes. Investigations of the encapsulation step are performed by transmission electron microscopy. Raman spectroscopy data point out different behaviors depending on the laser excitation energy with respect to the optical absorption of quaterthiophene. At low excitation energy (far from the oligomer resonance window) there is no significant modification of the Raman spectra before and after encapsulation. By contrast, at high excitation energy (close to the oligomer resonance window), Raman spectra exhibit a G-band shift together with an important RBM intensity loss, suggesting a significant charge transfer between the inserted molecule and the host nanotubes. Those results suggest a photo induced process leading to a significant charge transfer. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Interfacial Charge Transfer States in Condensed Phase Systems

    Science.gov (United States)

    Vandewal, Koen

    2016-05-01

    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.

  12. Computational Approach to Electron Charge Transfer Reactions

    DEFF Research Database (Denmark)

    Jónsson, Elvar Örn

    -molecular mechanics scheme, and tools to analyse statistical data and generate relative free energies and free energy surfaces. The methodology is applied to several charge transfer species and reactions in chemical environments - chemical in the sense that solvent, counter ions and substrate surfaces are taken...... in to account - which directly influence the reactants and resulting reaction through both physical and chemical interactions. All methods are though general and can be applied to different types of chemistry. First, the basis of the various theoretical tools is presented and applied to several test systems...... 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...

  13. Charge-transfer processes in semiconductor colloids

    Science.gov (United States)

    Kamat, Prashant V.; Gopidas, K. R.

    1990-04-01

    A picosecond transient absorption spectroscopy technique has been employed to probe the charge transfer processes in Ti02 semiconductor colloids. The trapping of electrons at the TiO surface (Ti4+ sitesY was characterized from the appearance of a broad absorption in the region of 550-750 nm following the 355-nm laser pulse excitation of Ti02 colloids. The lifetime of these trapped charge carriers increased upon incorporation of a hole scavenger in the colloidal semiconductor system. The mechanistic and kinetic details of the charge injection from excited CdS into a large bandgap semiconductor such as AgI and Ti02 have also been inves-' t i ga ted.

  14. Optics of Chromites and Charge-Transfer Transitions

    Directory of Open Access Journals (Sweden)

    Andrei V. Zenkov

    2008-01-01

    Full Text Available Specific features of the charge-transfer (CT states and O2p→Cr3d transitions in the octahedral (CrO69− complex are considered in the cluster approach. The reduced matrix elements of the electric-dipole transition operator are calculated on many-electron wave functions of the complex corresponding to the initial and final states of a CT transition. Modeling the optic spectrum of chromites has yielded a complicated CT band. The model spectrum is in satisfactory agreement with experimental data which demonstrates the limited validity of the generally accepted concept of a simple structure of CT spectra.

  15. Flavin Charge Transfer Transitions Assist DNA Photolyase Electron Transfer

    Science.gov (United States)

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

    2012-01-01

    This contribution describes molecular dynamics, semi-empirical and ab-initio studies of the primary photo-induced electron transfer reaction in DNA photolyase. DNA photolyases are FADH−-containing proteins that repair UV-damaged DNA by photo-induced electron transfer. A DNA photolyase recognizes and binds to cyclobutatne pyrimidine dimer lesions of DNA. The protein repairs a bound lesion by transferring an electron to the lesion from FADH−, upon photo-excitation of FADH− with 350–450 nm light. We compute the lowest singlet excited states of FADH− in DNA photolyase using INDO/S configuration interaction, time-dependent density-functional, and time-dependent Hartree-Fock methods. The calculations identify the lowest singlet excited state of FADH− that is populated after photo-excitation and that acts as the electron donor. For this donor state we compute conformationally-averaged tunneling matrix elements to empty electron- acceptor states of a thymine dimer bound to photolyase. The conformational averaging involves different FADH− - thymine dimer confromations obtained from molecular dynamics simulations of the solvated protein with a thymine dimer docked in its active site. The tunneling matrix element computations use INDO/S-level Green’s function, energy splitting, and Generalized Mulliken-Hush methods. These calculations indicate that photo-excitation of FADH− causes a π → π* charge-transfer transition that shifts electron density to the side of the flavin isoalloxazine ring that is adjacent to the docked thymine dimer. This shift in electron density enhances the FADH− - to - dimer electronic coupling, thus inducing rapid electron transfer. PMID:23226907

  16. Flavin Charge Transfer Transitions Assist DNA Photolyase Electron Transfer

    Science.gov (United States)

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

    2007-12-01

    This contribution describes molecular dynamics, semi-empirical and ab-initio studies of the primary photo-induced electron transfer reaction in DNA photolyase. DNA photolyases are FADH--containing proteins that repair UV-damaged DNA by photo-induced electron transfer. A DNA photolyase recognizes and binds to cyclobutatne pyrimidine dimer lesions of DNA. The protein repairs a bound lesion by transferring an electron to the lesion from FADH-, upon photo-excitation of FADH- with 350-450 nm light. We compute the lowest singlet excited states of FADH- in DNA photolyase using INDO/S configuration interaction, time-dependent density-functional, and time-dependent Hartree-Fock methods. The calculations identify the lowest singlet excited state of FADH- that is populated after photo-excitation and that acts as the electron donor. For this donor state we compute conformationally-averaged tunneling matrix elements to empty electron-acceptor states of a thymine dimer bound to photolyase. The conformational averaging involves different FADH--thymine dimer confromations obtained from molecular dynamics simulations of the solvated protein with a thymine dimer docked in its active site. The tunneling matrix element computations use INDO/S-level Green's function, energy splitting, and Generalized Mulliken-Hush methods. These calculations indicate that photo-excitation of FADH- causes a π→π* charge-transfer transition that shifts electron density to the side of the flavin isoalloxazine ring that is adjacent to the docked thymine dimer. This shift in electron density enhances the FADH--to-dimer electronic coupling, thus inducing rapid electron transfer.

  17. Resonant charge transfer at dielectric surfaces

    CERN Document Server

    Marbach, Johannes; Fehske, Holger

    2012-01-01

    We report on the theoretical description of secondary electron emission due to resonant charge transfer occurring during the collision of metastable nitrogen molecules with dielectric surfaces. The emission is described as a two step process consisting of electron capture to form an intermediate shape resonance and subsequent electron emission by decay of this ion, either due to its natural life time or its interaction with the surface. The electron capture is modeled using the Keldysh Green's function technique and the negative ion decay is described by a combination of the Keldysh technique and a rate equation approach. We find the resonant capture of electrons to be very efficient and the natural decay to be clearly dominating over the surface-induced decay. Secondary electron emission coefficients are calculated for aluminum oxide, magnesium oxide, silicon oxide, and diamond at several kinetic energies of the projectile. With the exception of magnesium oxide the coefficients turn out to be of the order of...

  18. Imidazole-Chloranil Charge Transfer Complex

    Institute of Scientific and Technical Information of China (English)

    Hai-long Wang; Tong-tong Lu; Tian-jing He; Dong-ming Chen

    2008-01-01

    UV-Vis absorption spectra of the molecular complex formed by imidazole (Im) and chloranil (CA) were measured in chloroform. The stoichiometry of the imidazole-chloranil (Im-CA) complex was determined as 1:1 by applying Benesi-Hildebrand's equation and Job's continuous variation method. Density function theory (DFT) and MP2 calculations were performed to study the structures and the binding energies of the Im-CA complex. The calculations located four conformations (denoted as S1-S4) for the Im-CA complex, two edge(lm)-to-face(CA) linked and two edgc(Im)-to-edge(CA) linked. It was found that the edgc-to-face conformers are more stable than the edge-to-edge ones. The bonding characteristics of these conformers were investigated with natural population analysis (NPA), topological analysis of electron density, and natural bond orbital (NBO) analysis. It was revealed that the edge-to-face conformers are charge-transfer (CT) complexes whereas the edge-to-edge conformers are the hydrogen bond complexes. For the most stable conformation of the Im-CA comp]ex (S1), the charge transfer interaction of the imidazole n(N15) lone pair orbital with the chloranil π*(C1=O7) orbital plays a crucial role in the Im-CA binding, and the binding is further strengthened by the 07… H20 hydrogen bond. The electronic excitation energies of the complex (S1) were calculated with time-dependent DFT (TDDFT), and the observed UV-Visiblc spectrum of the complex was analyzed based on the computed results.

  19. Nonradiative charge transfer in collisions of protons with rubidium atoms

    Institute of Scientific and Technical Information of China (English)

    Yan Ling-Ling; Qu Yi-Zhi; Liu Chun-Hua; Zhang Yu; Wang Jian-Guo; Buenker Robert J

    2012-01-01

    The nonradiative charge-transfer cross sections for protons colliding with Rb(5s) atoms are calculated by using the quantum-mechanical molecularorbital close-coupling method in an energy range of 10-3 keV 10 keV.The total and state-selective charge-transfer cross sections are in good agreement with the experimental data in the relatively low energy region.The importance of rotational coupling for chargetransfer process is stressed.Compared with the radiative charge-transfer process,nonradiative charge transfer is a dominant mechanism at energies above 15 eV.The resonance structures of state-selective charge-transfer cross sections arising from the competition among channels are analysed in detail.The radiative and nonradiative charge-transfer rate coefficients from low to high temperature are presented.

  20. Rigid band shifts, charge pinning, and charge transport through graphene junctions with wetting metal contacts

    Science.gov (United States)

    Bothwell, Tobias; Barraza-Lopez, Salvador

    2014-03-01

    It is a common perception that graphene band shifts cannot be determined directly when attached to chemisorbed (``wetting'') metals due to the hybridization of graphene bands around the Dirac point. Graphene has deeper energy (sigma) bands which don't hybridize with the metal's bands, providing a definite measure of actual shifts. Looking at hybridization in a controlled way (by varying the metal/graphene separation by hand) one realizes the shifts can actually be considered rigid, i.e., σ - and p - bands shift by about the same energy ΔE. In a related context, charge depinning is the modification of graphene's electron density at a metal/graphene interface with a (back) gate. Depinning happens at metal/graphene interfaces with physisorbed (non-wetting) metals. Oxidation or contamination at the interface can lead to charge depinning as well. Using first-principles calculations, we establish a link between charge depinning at a wetting metal/graphene interface and the quality of such an interface. For this purpose, metal/graphene/insulator structures are studied under transverse bias. We also report transmission coefficients through nanoscale two-terminal graphene/metal junctions.

  1. Elementary charge-transfer processes in mesoscopic conductors

    NARCIS (Netherlands)

    Vanević, M.; Nazarov, Y.V.; Belzig, W.

    2008-01-01

    We determine charge-transfer statistics in a quantum conductor driven by a time-dependent voltage and identify the elementary transport processes. At zero temperature unidirectional and bidirectional single-charge transfers occur. The unidirectional processes involve electrons injected from the sour

  2. Satellite lines at the ionization threshold in charge transfer systems

    Science.gov (United States)

    Wardermann, W.; von Niessen, W.

    1992-01-01

    This article deals with the possibility of low-energy ionizations of reduced intensity for larger organic molecules. Possible mechanisms which may lead to this phenomenon are outlined and the necessary structural features are discussed. The lowest ionization energies of some organic unsaturated nitro and nitroso compounds are calculated by the ADC(3) ab initio many-body Green's function method. The π-electron system consists either of fused five- and six-membered rings or of two fused five-membered rings with a variable number of heteroatoms. Some of the molecules contain exocylic double bonds and some are substituted with the donor groups -NH 2, -OH and -NHOH. The strongest many-body effects are found for the nitroso compounds, where in one case the spectral line at the ionization threshold has lost more than 40% of its intensity to satellites. We study the many-body effects at or close to the ionization threshold for these compounds. A particular mechanism which involves the screening of localized valence holes by charge transfer excitations appears to be capable of influencing the profile and intensities of the ionization spectrum already at the ionization threshold. The effect leads to strongly reduced relative intensities of the bands and may cause the appearance of satellite bands nearly at the ionization threshold. The spectral changes in the outermost valence region are discussed by using a simple model calculation in terms of ground-state electronic properties of the molecules.

  3. Photoinduced intramolecular charge transfer process of betaine pyridinium: A theoretical spectroscopic study

    Science.gov (United States)

    Perrier, Aurélie; Aloïse, Stéphane; Pawlowska, Zuzanna; Sliwa, Michel; Maurel, François; Abe, Jiro

    2011-10-01

    Using Time-Dependent Density Functional Theory and taking into account bulk solvent effects, we investigate the absorption and emission spectra of a betaine pyridinium molecule, the 2-(1-pyridinio) benzimidazolate (SBPa). This molecule exhibits strong photoinduced intramolecular charge transfer (ICT). We have identified two different electronic states involved, respectively, in the strong bathochromic ICT absorption band (S 2) and in the moderate emission band (S 1). The ICT process is analyzed in terms of charge distribution and dipole moment evolutions upon photoexcitation. These results are compared with steady-state spectroscopic measurements.

  4. Charge Transfer and Catalysis at the Metal Support Interface

    Energy Technology Data Exchange (ETDEWEB)

    Baker, Lawrence Robert [Univ. of California, Berkeley, CA (United States)

    2012-07-31

    Kinetic, electronic, and spectroscopic characterization of model Pt–support systems are used to demonstrate the relationship between charge transfer and catalytic activity and selectivity. The results show that charge flow controls the activity and selectivity of supported metal catalysts. This dissertation builds on extensive existing knowledge of metal–support interactions in heterogeneous catalysis. The results show the prominent role of charge transfer at catalytic interfaces to determine catalytic activity and selectivity. Further, this research demonstrates the possibility of selectively driving catalytic chemistry by controlling charge flow and presents solid-state devices and doped supports as novel methods for obtaining electronic control over catalytic reaction kinetics.

  5. Charge Transfer Fluctuations as a Signal for QGP

    OpenAIRE

    Shi, Lijun; Jeon, Sangyong

    2005-01-01

    In this work, the charge transfer fluctuation which was previously used for $pp$ collisions is proposed for relativistic heavy-ion collisions as a QGP probe. We propose the appearance of a local minimum at midrapidity for the charge transfer fluctuation as a signal for a QGP. Within a two-component neutral cluster model, we demonstrate that the charge transfer fluctuation can detect the presence of a QGP as well as the size of the QGP in the rapidity space. We also show that the forward-backw...

  6. Energy Transfer of a Shaped Charge.

    Energy Technology Data Exchange (ETDEWEB)

    Milinazzo, Jared Joseph [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-11-01

    A cylinder of explosive with a hollow cavity on one and a detonator at the other is considered a hollow charge. When the explosive is detonated the detonation products form a localized intense force. If the hollow charge is placed near or in contact with a steel plate then the damage to the plate is greater than a solid cylinder of explosive even though there is a greater amount of explosive in the latter charge. The hollow cavity can take almost any geometrical shape with differing amounts of damage associated with each shape. This phenomenon is known in the United States as the Munroe effect.

  7. Transfer Pricing; Charging of head office costs

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, Joergen

    1998-07-01

    The key issues discussed in this presentation are (1) What are head office costs?, (2) Why is the charging an area of concern for international companies?, (3) Which part of head office costs should be charged?, (4) OECD guidelines on charging. Head office costs are classified as Shareholder costs, Stewardship costs, Costs related to a specific subsidiary or group of subsidiaries (on call), and Costs related to operational activities in the parent company. The OECD reports of 1984 and 1996 are discussed. In Norsk Hydro's experience, the practising of the OECD guidelines by national authorities are confusing and not consistent over time or across borders. To get a better understanding of how charging of corporate head office costs are dealt with on an international level, Norsk Hydro asked Deloitte and Touche in London to carry out a study on international companies' behaviour. Their conclusions are included.

  8. Doping Dependent Charge Transfer Gap and Realistic Electronic Model of n-type Cuprate Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, T.

    2010-05-03

    Based on the analysis of the measurement data of angle-resolved photoemission spectroscopy (ARPES) and optics, we show that the charge transfer gap is significantly smaller than the optical one and is reduced by doping in electron doped cuprate superconductors. This leads to a strong charge fluctuation between the Zhang-Rice singlet and the upper Hubbard bands. The basic model for describing this system is a hybridized two-band t-J model. In the symmetric limit where the corresponding intra- and inter-band hopping integrals are equal to each other, this two-band model is equivalent to the Hubbard model with an antiferromagnetic exchange interaction (i.e. the t-U-J model). The mean-field result of the t-U-J model gives a good account for the doping evolution of the Fermi surface and the staggered magnetization.

  9. Review on charge transfer and chemical activity of TiO2: Mechanism and applications

    Science.gov (United States)

    Cai, Yongqing; Feng, Yuan Ping

    2016-12-01

    Charge separation and transfer at the interface between two materials play a significant role in various atomic-scale processes and energy conversion systems. In this review, we present the mechanism and outcome of charge transfer in TiO2, which is extensively explored for photocatalytic applications in the field of environmental science. We list several experimental and computational methods to estimate the amount of charge transfer. The effects of the work function, defects and doping, and employment of external electric field on modulating the charge transfer are presented. The interplay between the band bending and carrier transport across the surface and interface consisting of TiO2 is discussed. We show that the charge transfer can also strongly affect the behavior of deposited nanoparticles on TiO2 through built-in electric field that it creates. This review encompasses several advances of composite materials where TiO2 is combined with two-dimensional materials like graphene, MoS2, phosphorene, etc. The charge transport in the TiO2-organohalide perovskite with respect to the electron-hole separation at the interface is also discussed.

  10. Charge transfer and emergent phenomena of oxide heterostructures

    Science.gov (United States)

    Chen, Hanghui

    Charge transfer is a common phenomenon at oxide interfaces. We use first-principles calculations to show that via heterostructuring of transition metal oxides, the electronegativity difference between two dissimilar transition metal ions can lead to high level of charge transfer and induce substantial redistribution of electrons and ions. Notable examples include i) enhancing correlation effects and inducing a metal-insulator transition; ii) tailoring magnetic structures and inducing interfacial ferromagnetism; iii) engineering orbital splitting and inducing a non-cuprate single-orbital Fermi surface. Utilizing charge transfer to induce emergent electronic/magnetic/orbital properties at oxide interfaces is a robust approach. Combining charge transfer with quantum confinement and expitaxial strain provides an appealing prospect of engineering electronic structure of artificial oxide heterostructures. This research was supported by National Science Foundation under Grant No. DMR-1120296.

  11. Discrete electrostatic charge transfer by the electrophoresis of a charged droplet in a dielectric liquid.

    Science.gov (United States)

    Im, Do Jin; Ahn, Myung Mo; Yoo, Byeong Sun; Moon, Dustin; Lee, Dong Woog; Kang, In Seok

    2012-08-14

    We have experimentally investigated the electrostatic charging of a water droplet on an electrified electrode surface to explain the detailed inductive charging processes and use them for the detection of droplet position in a lab-on-a-chip system. The periodic bouncing motion of a droplet between two planar electrodes has been examined by using a high-resolution electrometer and an image analysis method. We have found that this charging process consists of three steps. The first step is inductive charge accumulation on the opposite electrode by the charge of a droplet. This induction process occurs while the droplet approaches the electrode, and it produces an induction current signal at the electrometer. The second step is the discharging of the droplet by the accumulated induced charge at the moment of contact. For this second step, there is no charge-transfer detection at the electrometer. The third step is the charging of the neutralized droplet to a certain charged state while the droplet is in contact with the electrode. The charge transfer of the third step is detected as the pulse-type signal of an electrometer. The second and third steps occur simultaneously and rapidly. We have found that the induction current by the movement of a charged droplet can be accurately used to measure the charge of the droplet and can also be used to monitor the position of a droplet under actuation. The implications of the current findings for understanding and measuring the charging process are discussed.

  12. Probing bulk defect energy bands using generalized charge pumping method

    Science.gov (United States)

    Masuduzzaman, Muhammad; Weir, Bonnie; Alam, Muhammad Ashraful

    2012-04-01

    The multifrequency charge pumping (CP) technique has long been used to probe the density of defects at the substrate-oxide interface, as well as in the bulk of the oxide of MOS transistors. However, profiling the energy levels of the defects has been more difficult due to the narrow scanning range of the voltage of a typical CP signal, and the uncertainty associated with the defect capture cross-section. In this paper, we discuss a generalized CP method that can identify defect energy bands within a bulk oxide, without requiring separate characterization of the defect capture cross-section. We use the new technique to characterize defects in both fresh and stressed samples of various dielectric compositions. By quantifying the way defects are generated as a function of time, we gain insight into the nature of defect generation in a particular gate dielectric. We also discuss the relative merits of voltage, time, and other variables of CP to probe bulk defect density, and compare the technique with related characterization approaches.

  13. SEMICONDUCTOR DEVICES: Simulation for signal charge transfer of charge coupled devices

    Science.gov (United States)

    Zujun, Wang; Yinong, Liu; Wei, Chen; Benqi, Tang; Zhigang, Xiao; Shaoyan, Huang; Minbo, Liu; Yong, Zhang

    2009-12-01

    Physical device models and numerical processing methods are presented to simulate a linear buried channel charge coupled devices (CCDs). The dynamic transfer process of CCD is carried out by a three-phase clock pulse driver. By using the semiconductor device simulation software MEDICI, dynamic transfer pictures of signal charges cells, electron concentration and electrostatic potential are presented. The key parameters of CCD such as charge transfer efficiency (CTE) and dark electrons are numerically simulated. The simulation results agree with the theoretic and experimental results.

  14. INTRAMOLECULAR CHARGE AND ENERGY TRANSFER IN MULTICHROMOPHORIC AROMATIC SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Edward C. Lim

    2008-09-09

    A concerted experimental and computational study of energy transfer in nucleic acid bases and charge transfer in dialkylaminobenzonitriles, and related electron donor-acceptor molecules, indicate that the ultrafast photoprocesses occur through three-state conical interactions involving an intermediate state of biradical character.

  15. Charge Transfer Dynamics from Photoexcited Semiconductor Quantum Dots

    Science.gov (United States)

    Zhu, Haiming; Yang, Ye; Wu, Kaifeng; Lian, Tianquan

    2016-05-01

    Understanding photoinduced charge transfer from nanomaterials is essential to the many applications of these materials. This review summarizes recent progress in understanding charge transfer from quantum dots (QDs), an ideal model system for investigating fundamental charge transfer properties of low-dimensional quantum-confined nanomaterials. We first discuss charge transfer from QDs to weakly coupled acceptors within the framework of Marcus nonadiabatic electron transfer (ET) theory, focusing on the dependence of ET rates on reorganization energy, electronic coupling, and driving force. Because of the strong electron-hole interaction, we show that ET from QDs should be described by the Auger-assisted ET model, which is significantly different from ET between molecules or from bulk semiconductor electrodes. For strongly quantum-confined QDs on semiconductor surfaces, the coupling can fall within the strong coupling limit, in which case the donor-acceptor interaction and ET properties can be described by the Newns-Anderson model of chemisorption. We also briefly discuss recent progress in controlling charge transfer properties in quantum-confined nanoheterostructures through wavefunction engineering and multiple exciton dissociation. Finally, we identify a few key areas for further research.

  16. Charge Transfer and Support Effects in Heterogeneous Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Hervier, Antoine [Univ. of California, Berkeley, CA (United States)

    2011-12-21

    the band bending at the interface, gives rise to a steady-state flow of hot holes to the surface. This leads to a decrease in turnover on the surface, an effect which is enhanced when a reverse bias is applied to the diode. Similar experiments were carried out for CO oxidation. On Pt/Si diodes, the reaction rate was found to increase when a forward bias was applied. When the diode was exposed to visible light and a reverse bias was applied, the rate was instead decreased. This implies that a flow of negative charges to the surface increases turnover, while positive charges decrease it. Charge flow in an oxide supported metal catalyst can be modified even without designing the catalyst as a solid state electronic device. This was done by doping stoichiometric and nonstoichiometric TiO2 films with F, and using the resulting oxides as supports for Pt films. In the case of stoichiometric TiO2, F was found to act as an n-type dopant, creating a population of filled electronic states just below the conduction band, and dramatically increasing the conductivity of the oxide film. The electrons in those states can transfer to surface O, activating it for reaction with CO, and leading to increased turnover for CO oxidation. This reinforces the hypothesis that CO oxidation is activated by a flow of negative charges to the surface. The same set of catalysts was used for methanol oxidation. The electronic properties of the TiO2 films again correlated with the turnover rates, but also with selectivity. With stoichiometric TiO2 as the support, F-doping caused an increase in selectivity toward the formation of partial oxidation products, formaldehyde and methyl formate, versus the total oxidation product, CO2. With non-stoichiometric TiO2, F-doping had the reverse effect. Ambient Pressure X-Ray Photoelectron Spectroscopy was used to investigate this F-doping effect in reaction conditions. In O2 alone, and in

  17. Flavin Charge Transfer Transitions Assist DNA Photolyase Electron Transfer

    OpenAIRE

    2007-01-01

    This contribution describes molecular dynamics, semi-empirical and ab-initio studies of the primary photo-induced electron transfer reaction in DNA photolyase. DNA photolyases are FADH−-containing proteins that repair UV-damaged DNA by photo-induced electron transfer. A DNA photolyase recognizes and binds to cyclobutatne pyrimidine dimer lesions of DNA. The protein repairs a bound lesion by transferring an electron to the lesion from FADH−, upon photo-excitation of FADH− with 350–450 nm light...

  18. Dynamics of Charge Transfer in Ordered and Chaotic Nucleotide Sequences

    CERN Document Server

    Fialko, N S

    2013-01-01

    Charge transfer is considered in systems composed of a donor, an acceptor and bridge sites of (AT) nucleotide pairs. For a bridge consisting of 180 (AT) pairs, three cases are dealt with: a uniform case, when all the nucleotides in each strand are identical; an ordered case, when nucleotides in each DNA strand are arranged in an orderly fashion; a chaotic case, when (AT) and (TA) pairs are arranged randomly. It is shown that in all the cases a charge transfer from a donor to an acceptor can take place. All other factors being equal, the transfer is the most efficient in the uniform case, the ordered and chaotic cases are less and the least efficient, accordingly. The results obtained are in agreement with experimental data on long-range charge transfer in DNA.

  19. Light-Induced Charge Separation and Transfer in Bacteriorhodopsin

    Institute of Scientific and Technical Information of China (English)

    HUANG Yu-Hua; LI Qing-Guo; ZHAO You-Yuan; ZHANG Zhong-Bin; OU-YANG Xiao-Ping; GONG Qin-Gan; CHEN Ling-Bing; LI Fu-Ming; LIU Jian; DING Jian-Dong

    2000-01-01

    The photo-voltage signals in bacteriorhodopsin(bR) excited by 1064nm pulse laser are different from those by 532 or 355 nm. It shows that the positive and negative photoelectric signals are produced by the motion of the positive and negative charges, respectively, and more energy is needed for producing the positive charges than the negative. The mechanism of light-induced charge generation and charge transfer in bR was studied and analyzed by measuring the photoelectric signals with different impedance of measuring circuit and different pulse-width of 532 nm laser as pump light.

  20. Conformational control of benzophenone-sensitized charge transfer in dinucleotides.

    Science.gov (United States)

    Merz, Thomas; Wenninger, Matthias; Weinberger, Michael; Riedle, Eberhard; Wagenknecht, Hans-Achim; Schütz, Martin

    2013-11-14

    Charge transfer in DNA cannot be understood without addressing the complex conformational flexibility, which occurs on a wide range of timescales. In order to reduce this complexity four dinucleotide models 1X consisting of benzophenone linked by a phosphodiester to one of the natural nucleosides X = A, G, T, C were studied in water and methanol. The theoretical work focuses on the dynamics and electronic structure of 1G. Predominant conformations in the two solvents were obtained by molecular dynamics simulations. 1G in MeOH adopts mainly an open geometry with a distance of 12–16 Å between the two aromatic parts. In H2O the two parts of 1G form primarily a stacked conformation yielding a distance of 5–6 Å. The low-lying excited states were investigated by electronic structure theory in a QM/MM environment for representative snapshots of the trajectories. Photo-induced intramolecular charge transfer in the S1 state occurs exclusively in the stacked conformation. Ultrafast transient absorption spectroscopy with 1X reveals fast charge transfer from S1 in both solvents with varying yields. Significant charge transfer from the T1 state is only found for the nucleobases with the lowest oxidation potential: in H2O, charge transfer occurs with 3.2 × 10(9) s(-1) for 1A and 6.0 × 10(9) s(-1) for 1G. The reorganization energy remains nearly unchanged going from MeOH to the more polar H2O. The electronic coupling is rather low even for the stacked conformation with H(AB) = 3 meV and explains the moderate charge transfer rates. The solvent controls the conformational distribution and therefore gates the charge transfer due to differences in distance and stacking.

  1. Transient W-band EPR study of sequential electron transfer in photosynthetic bacterial reaction centers

    Energy Technology Data Exchange (ETDEWEB)

    Tang, J.; Utschig, L.M.; Poluektov, O.; Thurnauer, M.C. [Argonne National Lab., IL (United States). Chemistry Div.

    1999-06-17

    The key reaction of photosynthetic solar energy conversion involves the photoexcitation of a primary donor (P) followed by rapid, sequential electron transfer to a series of acceptors resulting in charge separation. Electron-spin polarized (ESP) EPR spectra at W-band (95 GHz) were obtained for deuterated Fe-removed/Zn-substituted photosynthetic bacterial reaction centers (RCs) to investigate the influence of the rate of charge separation on the observed P{sup +}Q{sub A}{sup {minus}} charge separated state. Temperature dependent ESP EPR spectra for kinetically characterized Zn-substituted RCs from Rb. sphaeroides R-26 having different rates (k{sub Q}) of the electron transfer from the bacteriopheophytin to the quinone acceptor were obtained. The Zn-RCs exhibited either the native fast (200 ps){sup {minus}1} k{sub Q} or a slow (3--6 ns){sup {minus}1} k{sub Q} at 298 K as determined from transient optical measurements. Sequential electron-transfer polarization modeling of the polarized W-band EPR spectra obtained with these samples was used to address the reason for the differences in the electron-transfer rates. Here, the authors report the k{sub Q} rate constant, the temperature dependence of k{sub Q}, and the reorganization energy for the P{sup +}H{sup {minus}}Q{sub A} and P{sup +}HQ{sub A}{sup {minus}} electron-transfer step determined from SETP modeling of the experimental spectra. The reorganization energy for the electron-transfer process between P{sup +}H{sup {minus}}Q{sub A} and P{sup +}HQ{sub A}{sup {minus}}, and not structural changes in the donor or acceptor, was found to be the dominant factor that is altered during Fe-removal procedures.

  2. What Controls the Rate of Ultrafast Charge Transfer and Charge Separation Efficiency in Organic Photovoltaic Blends.

    Science.gov (United States)

    Jakowetz, Andreas C; Böhm, Marcus L; Zhang, Jiangbin; Sadhanala, Aditya; Huettner, Sven; Bakulin, Artem A; Rao, Akshay; Friend, Richard H

    2016-09-14

    In solar energy harvesting devices based on molecular semiconductors, such as organic photovoltaics (OPVs) and artificial photosynthetic systems, Frenkel excitons must be dissociated via charge transfer at heterojunctions to yield free charges. What controls the rate and efficiency of charge transfer and charge separation is an important question, as it determines the overall power conversion efficiency (PCE) of these systems. In bulk heterojunctions between polymer donor and fullerene acceptors, which provide a model system to understand the fundamental dynamics of electron transfer in molecular systems, it has been established that the first step of photoinduced electron transfer can be fast, of order 100 fs. But here we report the first study which correlates differences in the electron transfer rate with electronic structure and morphology, achieved with sub-20 fs time resolution pump-probe spectroscopy. We vary both the fullerene substitution and donor/fullerene ratio which allow us to control both aggregate size and the energetic driving force for charge transfer. We observe a range of electron transfer times from polymer to fullerene, from 240 fs to as short as 37 fs. Using ultrafast electro-optical pump-push-photocurrent spectroscopy, we find the yield of free versus bound charges to be weakly dependent on the energetic driving force, but to be very strongly dependent on fullerene aggregate size and packing. Our results point toward the importance of state accessibility and charge delocalization and suggest that energetic offsets between donor and acceptor levels are not an important criterion for efficient charge generation. This provides design rules for next-generation materials to minimize losses related to driving energy and boost PCE.

  3. Intermolecular-charge-transfer-induced fluorescence quenching in protic solvent

    Science.gov (United States)

    Lin, Tao; Liu, Xiaojun; Lou, Zhidong; Hou, Yanbing; Teng, Feng

    2016-11-01

    The fluorescence quenching of fluorenone in protic solvent has been extensively investigated, and the intermolecular hydrogen bond was found to play a crucial role. Unfortunately, the mechanism at atomic level is still not clear. In the present work, we theoretically put forward the charge transfer along the hydrogen bond in the excited states. The vertical excitation energies of the fluorenone-methanol complex as well as the potential energy profiles and surfaces of the vertical excited states and charge transfer states were calculated by using the ab initio electronic-structure methods. The photochemical reactions occurring in the diverse charge transfer states were compared and their decisiveness to the fluorescence quenching was discussed in the paper.

  4. Charge transfer in the cold Yb$^+$ + Rb collisions

    CERN Document Server

    Sayfutyarova, Elvira R; Yakovleva, Svetlana A; Belyaev, Andrey K

    2013-01-01

    Charge-transfer cold Yb$^+$ + Rb collision dynamics is investigated theoretically using high-level {\\it ab initio} potential energy curves, dipole moment functions and nonadiabatic coupling matrix elements. Within the scalar-relativistic approximation, the radiative transitions from the entrance $A^1\\Sigma^+$ to the ground $X^1\\Sigma^+$ state are found to be the only efficient charge-transfer pathway. The spin-orbit coupling does not open other efficient pathways, but alters the potential energy curves and the transition dipole moment for the $A-X$ pair of states. The radiative, as well as the nonradiative, charge-transfer cross sections calculated within the $10^{-3}-10$ cm$^{-1}$ collision energy range exhibit all features of the Langevin ion-atom collision regime, including a rich structure associated with centrifugal barrier tunneling (orbiting) resonances. Theoretical rate coefficients for two Yb isotopes agree well with those measured by immersing Yb$^+$ ion in an ultracold Rb ensemble in a hybrid trap....

  5. Charge transfer properties of pentacene adsorbed on silver: DFT study

    Energy Technology Data Exchange (ETDEWEB)

    N, Rekha T.; Rajkumar, Beulah J. M., E-mail: beulah-rajkumar@yahoo.co.in [PG & Research Department of Physics, Lady Doak College, Madurai 625002 (India)

    2015-06-24

    Charge transfer properties of pentacene adsorbed on silver is investigated using DFT methods. Optimized geometry of pentacene after adsorption on silver indicates distortion in hexagonal structure of the ring close to the silver cluster and deviations in co-planarity of carbon atoms due to the variations in bond angles and dihedral angles. Theoretically simulated absorption spectrum has a symmetric surface plasmon resonance peak around 486nm corresponding to the transfer of charge from HOMO-2 to LUMO. Theoretical SERS confirms the process of adsorption, tilted orientation of pentacene on silver surface and the charge transfers reported. Localization of electron density arising from redistribution of electrostatic potential together with a reduced bandgap of pentacene after adsorption on silver suggests its utility in the design of electro active organic semiconducting devices.

  6. Mass transfer kinetics, band broadening and column efficiency.

    Science.gov (United States)

    Gritti, Fabrice; Guiochon, Georges

    2012-01-20

    Important progress was recently made in our understanding of the physico-chemical aspects of mass transfer kinetics in chromatographic columns, in methods used for accurate determination of the different contributions to the height equivalent to a theoretical plate (HETP), and in the application of these advances to the elucidation of mass transfer mechanisms in columns packed with recent chromatographic supports (sub-2 μm fully porous particles, sub-3 μm core-shell particles, and monoliths). The independent contributions to the HETP are longitudinal diffusion, eddy dispersion, liquid-solid mass transfer (including trans-particle or trans-skeleton mass transfer and external film mass transfer), and the contributions caused by the thermal heterogeneity of the column. The origin and importance of these contributions are investigated in depth. This work underlines the areas in which improvements are needed, an understanding of the contribution of the external film mass transfer term, a better design of HPLC instruments providing a decrease of the extra-column band broadening contributions to the apparent HETP, the development of better packing procedures giving more radially homogeneous column beds, and new packing materials having a higher thermal conductivity to eliminate the nefarious impact of heat effects in very high pressure liquid chromatography (vHPLC) and supercritical fluid chromatography (SFC).

  7. Charge Transfer and Support Effects in Heterogeneous Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Hervier, Antoine [Univ. of California, Berkeley, CA (United States)

    2011-12-21

    the band bending at the interface, gives rise to a steady-state flow of hot holes to the surface. This leads to a decrease in turnover on the surface, an effect which is enhanced when a reverse bias is applied to the diode. Similar experiments were carried out for CO oxidation. On Pt/Si diodes, the reaction rate was found to increase when a forward bias was applied. When the diode was exposed to visible light and a reverse bias was applied, the rate was instead decreased. This implies that a flow of negative charges to the surface increases turnover, while positive charges decrease it. Charge flow in an oxide supported metal catalyst can be modified even without designing the catalyst as a solid state electronic device. This was done by doping stoichiometric and nonstoichiometric TiO2 films with F, and using the resulting oxides as supports for Pt films. In the case of stoichiometric TiO2, F was found to act as an n-type dopant, creating a population of filled electronic states just below the conduction band, and dramatically increasing the conductivity of the oxide film. The electrons in those states can transfer to surface O, activating it for reaction with CO, and leading to increased turnover for CO oxidation. This reinforces the hypothesis that CO oxidation is activated by a flow of negative charges to the surface. The same set of catalysts was used for methanol oxidation. The electronic properties of the TiO2 films again correlated with the turnover rates, but also with selectivity. With stoichiometric TiO2 as the support, F-doping caused an increase in selectivity toward the formation of partial oxidation products, formaldehyde and methyl formate, versus the total oxidation product, CO2. With non-stoichiometric TiO2, F-doping had the reverse effect. Ambient Pressure X-Ray Photoelectron Spectroscopy was

  8. Valence Topological Charge-Transfer Indices for Dipole Moments

    Directory of Open Access Journals (Sweden)

    Francisco Torrens

    2003-01-01

    Full Text Available New valence topological charge-transfer indices are applied to the calculation of dipole moments. The algebraic and vector semisum charge-transfer indices are defined. The combination of the charge-transfer indices allows the estimation of the dipole moments. The model is generalized for molecules with heteroatoms. The ability of the indices for the description of the molecular charge distribution is established by comparing them with the dipole moments of a homologous series of phenyl alcohols. Linear and non-linear correlation models are obtained. The new charge-transfer indices improve the multivariable non-linear regression equations for the dipole moment. When comparing with previous results, the variance decreases 92%. No superposition of the corresponding Gk–Jk and GkV – JkV pairs is observed. This diminishes the risk of co-linearity. Inclusion of the oxygen atom in the p-electron system is beneficial for the description of the dipole moment, owing to either the role of the additional p orbitals provided by the heteroatom or the role of steric factors in the p-electron conjugation. Linear and non-linear correlations between the fractal dimension and various descriptors point not only to a homogeneous molecular structure but also to the ability to predict and tailor drug properties.

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

    Institute of Scientific and Technical Information of China (English)

    CAO Weixiao; ZHANG Peng; FENG Xinde

    1995-01-01

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

  10. Charge transfer to a semi-esterified bifunctional phenol

    Energy Technology Data Exchange (ETDEWEB)

    Brede, O.; Hermann, R.; Orthner, H. [Leipzig Univ. (Germany)

    1996-03-01

    The charge transfer from solvent radical cations of n-butyl chloride and cyclohexane to 2-butyl-6(3`-t-butyl-2`-hydroxy-5`-methylbenzyl)-4-methyl-phenylac rylate (GM) yields in the first step phenoxyl radicals as well as acrylate radical cations of this semi-acrylated bifunctional phenol. Subsequently an intramolecular charge transfer from the acrylate radical cation to the phenol group takes place. Because of the instability of phenol radical cations, under our experimental conditions (nanosecond pulse radiolysis, non-polar solvents, room temperature) phenoxyl radicals are the only observable products of phenol ionization. (author).

  11. Transfer ionization in collisions with a fast highly charged ion.

    Science.gov (United States)

    Voitkiv, A B

    2013-07-26

    Transfer ionization in fast collisions between a bare ion and an atom, in which one of the atomic electrons is captured by the ion whereas another one is emitted, crucially depends on dynamic electron-electron correlations. We show that in collisions with a highly charged ion a strong field of the ion has a very profound effect on the correlated channels of transfer ionization. In particular, this field weakens (strongly suppresses) electron emission into the direction opposite (perpendicular) to the motion of the ion. Instead, electron emission is redirected into those parts of the momentum space which are very weakly populated in fast collisions with low charged ions.

  12. Ultrafast investigation of photoinduced charge transfer in aminoanthraquinone pharmaceutical product

    Science.gov (United States)

    Zhang, Song; Sun, Simei; Zhou, Miaomiao; Wang, Lian; Zhang, Bing

    2017-01-01

    We investigated the mechanism of intramolecular charge transfer and the following radiationless dynamics of the excited states of 1-aminoanthraquinone using steady state and time-resolved absorption spectroscopy combined with quantum chemical calculations. Following photoexcitation with 460 nm, conformational relaxation via twisting of the amino group, charge transfer and the intersystem crossing (ISC) processes have been established to be the major relaxation pathways responsible for the ultrafast nonradiative of the excited S1 state. Intramolecular proton transfer, which could be induced by intramolecular hydrogen bonding is inspected and excluded. Time-dependent density functional theory (TDDFT) calculations reveal the change of the dipole moments of the S0 and S1 states along the twisted coordinate of the amino group, indicating the mechanism of twisted intra-molecular charge transfer (TICT). The timescale of TICT is measured to be 5 ps due to the conformational relaxation and a barrier on the S1 potential surface. The ISC from the S1 state to the triplet manifold is a main deactivation pathway with the decay time of 28 ps. Our results observed here have yield a physically intuitive and complete picture of the photoinduced charge transfer and radiationless dynamics in anthraquinone pharmaceutial products. PMID:28233835

  13. [Dynamics of charge transfer along an oligonucleotide at finite temperature].

    Science.gov (United States)

    Lakhno, V D; Fialko, N S

    2004-01-01

    The quantum-statistical approach was used to describe the charge transfer in nucleotide sequences. The results of numerical modeling for hole transfer in the GTTGGG sequence with background temperature noise are given. It was shown that, since guanine has an oxidation potential lower than thymine, the hole created at the G donor in this sequence passes through the thymine barrier into the guanine triplet (acceptor) at a time of approximately 10 ps at a temperature of 37 degrees C.

  14. Correlating electronic and vibrational motions in charge transfer systems

    Energy Technology Data Exchange (ETDEWEB)

    Khalil, Munira [Univ. of Washington, Seattle, WA (United States)

    2014-06-27

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

  15. Charge transfer devices. Citations from the NTIS data base

    Science.gov (United States)

    Reed, W. E.

    1980-04-01

    The technology, design, fabrication, and applications of charge transfer devices are presented in the cited research reports. Applications include imaging, signal processing, detectors, filters, amplifiers, and memory devices. This updated bibliography contains 107 abstracts, all of which are new entries to the previous edition.

  16. Charge-Transfer Interactions in Organic Functional Materials

    Directory of Open Access Journals (Sweden)

    Bih-Yaw Jin

    2010-08-01

    Full Text Available Our goal in this review is three-fold. First, we provide an overview of a number of quantum-chemical methods that can abstract charge-transfer (CT information on the excited-state species of organic conjugated materials, which can then be exploited for the understanding and design of organic photodiodes and solar cells at the molecular level. We stress that the Composite-Molecule (CM model is useful for evaluating the electronic excited states and excitonic couplings of the organic molecules in the solid state. We start from a simple polyene dimer as an example to illustrate how interchain separation and chain size affect the intercahin interaction and the role of the charge transfer interaction in the excited state of the polyene dimers. With the basic knowledge from analysis of the polyene system, we then study more practical organic materials such as oligophenylenevinylenes (OPVn, oligothiophenes (OTn, and oligophenylenes (OPn. Finally, we apply this method to address the delocalization pathway (through-bond and/or through-space in the lowest excited state for cyclophanes by combining the charge-transfer contributions calculated on the cyclophanes and the corresponding hypothetical molecules with tethers removed. This review represents a step forward in the understanding of the nature of the charge-transfer interactions in the excited state of organic functional materials.

  17. Radiative charge transfer in collisions of C with He+

    Science.gov (United States)

    Babb, James F.; McLaughlin, B. M.

    2017-02-01

    Radiative charge exchange collisions between a carbon atom {{C}}({}3P) and a helium ion {{He}}+({}2S), both in their ground state, are investigated theoretically. Detailed quantum chemistry calculations are carried out to obtain potential energy curves and transition dipole matrix elements for doublet and quartet molecular states of the HeC+ cation. Radiative charge transfer cross sections and rate coefficients are calculated and are found at thermal and lower energies to be large compared to those for direct charge transfer. The present results might be applicable to modelling the complex interplay of [{{C}} {{II}}] (or {{{C}}}+), {{C}}, and {CO} at the boundaries of interstellar photon dominated regions and in x-ray dominated regions, where the abundance of {{He}}+ affects the abundance of {CO}.

  18. Effect of Aperiodicity on the Charge Transfer Through DNA Molecules

    Science.gov (United States)

    Ghosh, Angsula; Chaudhuri, Puspitapallab

    The effect of aperiodicity on the charge transfer process through DNA molecules is investigated using a tight-binding model. Single-stranded aperiodic Fibonacci polyGC and polyAT sequences along with aperiodic Rudin-Shapiro poly(GCAT) sequences are used in the study. Based on the tight-binding model, molecular orbital calculations of the DNA chains are performed and ionization potentials compared, as this might be relevant to understanding the charge transfer process. Charges migrate through the sequences in a multistep hopping process. Results for current conduction through aperiodic sequences are compared with those for the corresponding periodic sequences. We find that dinucleotide aperiodic Fibonacci sequences decrease the current while tetranucleotide aperiodic Rudin-Shapiro sequences increase the current when compared with the corresponding periodic sequences. The conductance in all cases decays exponentially as the sequence length increases.

  19. Radiative charge transfer in collisions of C with He+

    CERN Document Server

    Babb, James F

    2016-01-01

    Radiative charge exchange collisions between a carbon atom C(${}^3$P) and a helium ion He+, both in their ground state, are investigated theoretically. Detailed quantum chemistry calculations are carried out to obtain potential energy curves and transition dipole matrix elements for doublet and quartet molecular states of the HeC+ cation. Radiative charge transfer cross sections and rate coefficients are calculated and are found at thermal and lower energies to be large compared to those for direct charge transfer. The present results might be applicable to modelling the complex interplay of [C II] (or C+), C, and CO at the boundaries of photon dominated regions (PDRs) and in xray dominated regions (XDRs), where the abundance of He+ affects the abundance of CO.

  20. Ground-state charge transfer as a mechanism for surface-enhanced Raman scattering

    Science.gov (United States)

    Lippitsch, Max E.

    1984-03-01

    A model is presented for the contribution of ground-state charge transfer between a metal and adsorbate to surface-enhanced Raman scattering (SERS). It is shown that this contribution can be understood using the vibronic theory for calculating Raman intensities. The enhancement is due to vibronic coupling of the molecular ground state to the metal states, the coupling mechanism being a modulation of the ground-state charge-transfer energy by the molecular vibrations. An analysis of the coupling operator gives the selection rules for this process, which turn out to be dependent on the overall symmetry of the adsorbate-metal system, even if the charge transfer is small enough for the symmetry of the adsorbate to remain the same as that of the free molecule. It is shown that the model can yield predictions on the properties of SERS, e.g., specificity to adsorption geometry, appearance of forbidden bands, dependence on the applied potential, and dependence on the excitation wavelength. The predictions are in good agreement with experimental results. It is also deduced from this model that in many cases atomic-scale roughness is a prerequisite for the observation of SERS. A result on the magnitude of the enhancement can only be given in a crude approximation. Although in most cases an additional electromagnetic enhancement seems to be necessary to give an observable signal, this charge-transfer mechanism should be important in many SERS systems.

  1. Graphene nonvolatile memory prototype based on charge-transfer mechanism

    Science.gov (United States)

    Lv, Hongming; Wu, Huaqiang; Huang, Can; Wang, Yuda; Qian, He

    2014-04-01

    A graphene nonvolatile memory (GNVM) prototype based on charge transfer between the graphene layer and the NH2(CH2)3Si(OEt)3 (APTES) self-assembled monolayer (SAM) is demonstrated. Graphene was transferred to an APTES-SAM-engineered SiO2 substrate and patterned into bottom-gate transistors. Owing to the charge trapping/detrapping property of the nitrogen atoms in APTES, a significant and reproducible transfer curve hysteresis is observed. Memory performance metrics, including retention and endurance, are reported. Comparisons between vacuum and ambient environment test results indicate air absorbates’ detrimental effect. Loss of nonvolatile storage is explained on the basis of a two-layer tunneling junction model, which sheds light on further device improvement through aminosilane molecule structure optimization.

  2. Extended Holstein polaron model for charge transfer in dry DNA

    Institute of Scientific and Technical Information of China (English)

    Liu Tao; Wang Yi; Wang Ke-Lin

    2007-01-01

    The variational method is applied to the study of charge transfer in dry DNA by using an extended Holstein small polaron model in two cases: the site-dependent finite-chain discrete case and the site-independent continuous one. The treatments in the two cases are proven to be consistent in theory and calculation. Discrete and continuous treatments of Holstein model both can yield a nonlinear equation to describe the charge migration in an actual long-range DNA chain.Our theoretical results of binding energy Eb, probability amplitude of charge carrier φ and the relation between energy and charge-lattice coupling strength are in accordance with the available experimental results and recent theoretical calculations.

  3. Charge-transfer crystallites as molecular electrical dopants

    Science.gov (United States)

    Méndez, Henry; Heimel, Georg; Winkler, Stefanie; Frisch, Johannes; Opitz, Andreas; Sauer, Katrein; Wegner, Berthold; Oehzelt, Martin; Röthel, Christian; Duhm, Steffen; Többens, Daniel; Koch, Norbert; Salzmann, Ingo

    2015-10-01

    Ground-state integer charge transfer is commonly regarded as the basic mechanism of molecular electrical doping in both, conjugated polymers and oligomers. Here, we demonstrate that fundamentally different processes can occur in the two types of organic semiconductors instead. Using complementary experimental techniques supported by theory, we contrast a polythiophene, where molecular p-doping leads to integer charge transfer reportedly localized to one quaterthiophene backbone segment, to the quaterthiophene oligomer itself. Despite a comparable relative increase in conductivity, we observe only partial charge transfer for the latter. In contrast to the parent polymer, pronounced intermolecular frontier-orbital hybridization of oligomer and dopant in 1:1 mixed-stack co-crystallites leads to the emergence of empty electronic states within the energy gap of the surrounding quaterthiophene matrix. It is their Fermi-Dirac occupation that yields mobile charge carriers and, therefore, the co-crystallites--rather than individual acceptor molecules--should be regarded as the dopants in such systems.

  4. Interface charge transfer process in ZnO:Mn/ZnS nanocomposites

    Science.gov (United States)

    Stefan, M.; Toloman, D.; Popa, A.; Mesaros, A.; Vasile, O. R.; Leostean, C.; Pana, O.

    2016-03-01

    ZnO:Mn/ZnS nanocomposites were prepared by seed-mediated growth of ZnS QDs onto the preformed ZnO:Mn nanoparticles. The formation of the nanocomposite structure has been evidenced by XRD, HRTEM, and XPS. The architecture of the nanocomposite with outer ZnS QDs around ZnO:Mn cores is sustained by the sulfur and oxygen depth profiles resulted from XPS. When the two components are brought together, the band gap of ZnS component decreases while that of ZnO:Mn increases. It is the result of interface charge transfer from ZnO:Mn to ZnS QDs. Here ZnO:Mn valence states are extended through the interface into unoccupied gap states of ZnS. The energy band setup is modified from a type II into a type I band alignment. The process is accompanied by enhancement of composite UV emission of PL spectra as compared to its counterparts. The charge transfer from valence band also determines the increase of the core-polarization effect of s shell electrons at Mn2+ nucleus, thus determining the increase of the hyperfine field through the reduction of the covalency degree of Zn(Mn)-O bonds. The quantum confinement in ZnS QDs promotes the ferromagnetic coupling of singly occupied states due to Zn vacancies determining a superparamagnetic behavior of the ensemble. When the nanocomposites are formed, due to interface charge transfer effects, an increased number of filled cation vacancies in ZnS QDs develop, thus disrupting the pre-existing ferromagnetic coupling between spins resulting in a significant reduction of the overall saturation magnetization. The possibility to modulate nanocomposite properties by controlling the interface interactions may be foreseen in these types of materials.

  5. Competition between covalent bonding and charge transfer at complex-oxide interfaces.

    Science.gov (United States)

    Salafranca, Juan; Rincón, Julián; Tornos, Javier; León, Carlos; Santamaria, Jacobo; Dagotto, Elbio; Pennycook, Stephen J; Varela, Maria

    2014-05-16

    Here we study the electronic properties of cuprate-manganite interfaces. By means of atomic resolution electron microscopy and spectroscopy, we produce a subnanometer scale map of the transition metal oxidation state profile across the interface between the high Tc superconductor YBa2Cu3O7-δ and the colossal magnetoresistance compound (La,Ca)MnO3. A net transfer of electrons from manganite to cuprate with a peculiar nonmonotonic charge profile is observed. Model calculations rationalize the profile in terms of the competition between standard charge transfer tendencies (due to band mismatch), strong chemical bonding effects across the interface, and Cu substitution into the Mn lattice, with different characteristic length scales.

  6. Laser controlled charge-transfer reaction at low temperatures

    CERN Document Server

    Petrov, Alexander; Kotochigova, Svetlana

    2016-01-01

    We study the low-temperature charge transfer reaction between a neutral atom and an ion under the influence of near-resonant laser light. By setting up a multi-channel model with field-dressed states we demonstrate that the reaction rate coefficient can be enhanced by several orders of magnitude with laser intensities of $10^6$ W/cm$^2$ or larger. In addition, depending on laser frequency one can induce a significant enhancement or suppression of the charge-exchange rate coefficient. For our intensities multi-photon processes are not important.

  7. What is the "best" atomic charge model to describe through-space charge-transfer excitations?

    Science.gov (United States)

    Jacquemin, Denis; Le Bahers, Tangui; Adamo, Carlo; Ciofini, Ilaria

    2012-04-28

    We investigate the efficiency of several partial atomic charge models (Mulliken, Hirshfeld, Bader, Natural, Merz-Kollman and ChelpG) for investigating the through-space charge-transfer in push-pull organic compounds with Time-Dependent Density Functional Theory approaches. The results of these models are compared to benchmark values obtained by determining the difference of total densities between the ground and excited states. Both model push-pull oligomers and two classes of "real-life" organic dyes (indoline and diketopyrrolopyrrole) used as sensitisers in solar cell applications have been considered. Though the difference of dipole moments between the ground and excited states is reproduced by most approaches, no atomic charge model is fully satisfactory for reproducing the distance and amount of charge transferred that are provided by the density picture. Overall, the partitioning schemes fitting the electrostatic potential (e.g. Merz-Kollman) stand as the most consistent compromises in the framework of simulating through-space charge-transfer, whereas the other models tend to yield qualitatively inconsistent values.

  8. Laboratory Studies of Thermal Energy Charge Transfer of Multiply Charged Ions in Astrophysical Plasmas

    Science.gov (United States)

    Kwong, Victor H. S.

    2003-01-01

    The laser ablation/ion storage facility at the UNLV Physics Department has been dedicated to the study of atomic and molecular processes in low temperature plasmas. Our program focuses on the charge transfer (electron capture) of multiply charged ions and neutrals important in astrophysics. The electron transfer reactions with atoms and molecules is crucial to the ionization condition of neutral rich photoionized plasmas. With the successful deployment of the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Chandra X-ray Observatory by NASA high resolution VUV and X-ray emission spectra fiom various astrophysical objects have been collected. These spectra will be analyzed to determine the source of the emission and the chemical and physical environment of the source. The proper interpretation of these spectra will require complete knowledge of all the atomic processes in these plasmas. In a neutral rich environment, charge transfer can be the dominant process. The rate coefficients need to be known accurately. We have also extended our charge transfer measurements to KeV region with a pulsed ion beam. The inclusion of this facility into our current program provides flexibility in extending the measurement to higher energies (KeV) if needed. This flexibility enables us to address issues of immediate interest to the astrophysical community as new observations are made by high resolution space based observatories.

  9. Low-energy state-selective charge transfer by multiply charged ions

    NARCIS (Netherlands)

    Lubinski, G; Juhasz, Z; Morgenstern, R; Hoekstra, R

    2001-01-01

    We present a combined rf-guided ion beam and photon emission spectroscopy method, which facilitates state-selective charge-transfer measurements at energies of direct relevance for astrophysics and fusion-plasma diagnostics and modeling. Ion energies have been varied from 1000 eV/amu down to energie

  10. Intramolecular Charge-Transfer Interaction of Donor-Acceptor-Donor Arrays Based on Anthracene Bisimide.

    Science.gov (United States)

    Iwanaga, Tetsuo; Ogawa, Marina; Yamauchi, Tomokazu; Toyota, Shinji

    2016-05-20

    We designed anthracene bisimide (ABI) derivatives having two triphenylamine (TPA) groups as donor units at the 9,10-positions to form a novel π-conjugated donor-acceptor system. These compounds and their analogues with ethynylene linkers were synthesized by Suzuki-Miyaura and Sonogashira coupling reactions, respectively. In UV-vis spectra, the linker-free derivatives showed broad absorption bands arising from intramolecular charge-transfer interactions. Introducing ethynylene linkers resulted in a considerable red shift of the absorption bands. In fluorescence spectra, the ethynylene derivatives showed intense emission bands at 600-650 nm. Their photophysical and electrochemical properties were compared with those of the corresponding mono TPA derivatives on the basis of theoretical calculations and cyclic voltammetry to evaluate the intramolecular electronic interactions between the donor and acceptor units.

  11. Charge Transfer Channels in Formation of Exciplex in Polymer Blends

    Institute of Scientific and Technical Information of China (English)

    DOU Fei; ZHANG Xin-Ping

    2011-01-01

    The strong dependence of photoluminescence of charge transfer excited states or exciplex in a blend film of poly(9,9'-dioctylBuorene-co-benzothiadiazole) (F8BT) and poly(9,9'-dioctyl6uorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-l,4- phenylenediamine) (PFB) on the excitation wavelengths and morphology is investigated. The experimental results reveal that electron transfer in the LUMOs from PFB to F8BT is more efficient than hole transfer in the HOMOs from PFB to F8BT for the formation of exciplex at the interfacial junctions between these two types of molecules in the blend Sim. Furthermore, energy transfer from the blue-emitting PFB to the green-emitting F8BT at the interfaces introduces an additional two-step channel and thus enhances the formation of an exciplex. This is important for understanding of charge generation and separation in organic bulk heterojunctions and for design of optoelectronic devices.%@@ The strong dependence of photoluminescence of charge transfer excited states or exciplex in a blend film of poly(9,9'-dioctylfluorene-co-benzothiadiazole)(F8BT)and poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine)(PFB)on the excitation wavelengths and morphology is investigated.The experimental results reveal that electron transfer in the LUMOs from PFB to F8BT is more efficient than hole transfer in the HOMOs from PFB to F8BT for the formation of exciplex at the interfacial junctions between these two types of molecules in the blend film.Furthermore,energy transfer from the blue-emitting PFB to the green-emitting F8BT at the interfaces introduces an additional two-step channel and thus enhances the formation of an exciplex.This is important for understanding of charge generation and separation in organic bulk heterojunctions and for design of optoelectronic devices.

  12. Charge transfer to ground-state ions produces free electrons

    Science.gov (United States)

    You, D.; Fukuzawa, H.; Sakakibara, Y.; Takanashi, T.; Ito, Y.; Maliyar, G. G.; Motomura, K.; Nagaya, K.; Nishiyama, T.; Asa, K.; Sato, Y.; Saito, N.; Oura, M.; Schöffler, M.; Kastirke, G.; Hergenhahn, U.; Stumpf, V.; Gokhberg, K.; Kuleff, A. I.; Cederbaum, L. S.; Ueda, K.

    2017-01-01

    Inner-shell ionization of an isolated atom typically leads to Auger decay. In an environment, for example, a liquid or a van der Waals bonded system, this process will be modified, and becomes part of a complex cascade of relaxation steps. Understanding these steps is important, as they determine the production of slow electrons and singly charged radicals, the most abundant products in radiation chemistry. In this communication, we present experimental evidence for a so-far unobserved, but potentially very important step in such relaxation cascades: Multiply charged ionic states after Auger decay may partially be neutralized by electron transfer, simultaneously evoking the creation of a low-energy free electron (electron transfer-mediated decay). This process is effective even after Auger decay into the dicationic ground state. In our experiment, we observe the decay of Ne2+ produced after Ne 1s photoionization in Ne-Kr mixed clusters.

  13. Integrated Charge Transfer in Organic Ferroelectrics for Flexible Multisensing Materials.

    Science.gov (United States)

    Xu, Beibei; Ren, Shenqiang

    2016-09-01

    The ultimate or end point of functional materials development is the realization of strong coupling between all energy regimes (optical, electronic, magnetic, and elastic), enabling the same material to be utilized for multifunctionalities. However, the integration of multifunctionalities in soft materials with the existence of various coupling is still in its early stage. Here, the coupling between ferroelectricity and charge transfer by combining bis(ethylenedithio)tetrathiafulvalene-C60 charge-transfer crystals with ferroelectric polyvinylidene fluoride polymer matrix is reported, which enables external stimuli-controlled polarization, optoelectronic and magnetic field sensing properties. Such flexible composite films also display a superior strain-dependent capacitance and resistance change with a giant piezoresistance coefficient of 7.89 × 10(-6) Pa(-1) . This mutual coupled material with the realization of enhanced couplings across these energy domains opens up the potential for multisensing applications.

  14. Conformational control of benzophenone-sensitized charge transfer in dinucleotides

    OpenAIRE

    Merz, Thomas; Wenninger, Matthias; Weinberger, Michael; Riedle, Eberhard; Wagenknecht, Hans-Achim; Schuetz, Martin

    2013-01-01

    Charge transfer in DNA cannot be understood without addressing the complex conformational flexibility, which occurs on a wide range of timescales. In order to reduce this complexity four dinucleotide models 1X consisting of benzophenone linked by a phosphodiester to one of the natural nucleosides X = A, G, T, C were studied in water and methanol. The theoretical work focuses on the dynamics and electronic structure of 1G. Predominant conformations in the two solvents were obtained by molecula...

  15. Charge transfer in energetic Li^2+ - H collisions

    Science.gov (United States)

    Mancev, I.

    2008-07-01

    The total cross sections for charge transfer in Li^2+ - H collisions have been calculated, using the four-body first Born approximation with correct boundary conditions (CB1-4B) and four-body continuum distorted wave method (CDW-4B) in the energy range 10 - 5000 keV/amu. Present results call for additional experimental data at higher impact energies than presently available.

  16. Proton transfer assisted charge transfer phenomena in photochromic Schiff bases and effect of -NEt2 groups to the anil Schiff bases.

    Science.gov (United States)

    Jana, Sankar; Dalapati, Sasanka; Guchhait, Nikhil

    2012-11-15

    Photochromic Schiff bases 5-diethylamino-2-[(4-diethylamino-benzylidene)-hydrazonomethyl]-phenol (DDBHP) and N,N'-bis(4-N,N-diethylaminosalisalidene) hydrazine (DEASH) with both the proton and charge transfer moieties have been synthesized, and their photophysical properties such as excited state intramolecular charge transfer (ICT) and proton transfer (ESIPT) processes have been reported on the basis of steady-state and time-resolved spectral measurement in various solvents. The ground-state six-membered intramolecular hydrogen bonding network at the proton transfer site accelerates the ESIPT process for these compounds. Both the compounds show large Stokes-shifted emission bands for proton transfer and charge transfer processes. The hydrogen bonding solvents play a crucial role in these photophysical processes. Excited-state dipole moment of DDBHP and DEASH calculated by the solvatochromic method supports the polar character of the charge transfer excited state. Introduction of -NEt(2) groups to the reported salicylaldehyde azine (SAA) Schiff base results an increase in fluorescence lifetime from femtosecond to picosecond time scale for the proton transfer process.

  17. Energy and charge transfer in nanoscale hybrid materials.

    Science.gov (United States)

    Basché, Thomas; Bottin, Anne; Li, Chen; Müllen, Klaus; Kim, Jeong-Hee; Sohn, Byeong-Hyeok; Prabhakaran, Prem; Lee, Kwang-Sup

    2015-06-01

    Hybrid materials composed of colloidal semiconductor quantum dots and π-conjugated organic molecules and polymers have attracted continuous interest in recent years, because they may find applications in bio-sensing, photodetection, and photovoltaics. Fundamental processes occurring in these nanohybrids are light absorption and emission as well as energy and/or charge transfer between the components. For future applications it is mandatory to understand, control, and optimize the wide parameter space with respect to chemical assembly and the desired photophysical properties. Accordingly, different approaches to tackle this issue are described here. Simple organic dye molecules (Dye)/quantum dot (QD) conjugates are studied with stationary and time-resolved spectroscopy to address the dynamics of energy and ultra-fast charge transfer. Micellar as well as lamellar nanostructures derived from diblock copolymers are employed to fine-tune the energy transfer efficiency of QD donor/dye acceptor couples. Finally, the transport of charges through organic components coupled to the quantum dot surface is discussed with an emphasis on functional devices.

  18. Efficient charge generation by relaxed charge-transfer states at organic interfaces

    Science.gov (United States)

    Vandewal, Koen; Albrecht, Steve; Hoke, Eric T.; Graham, Kenneth R.; Widmer, Johannes; Douglas, Jessica D.; Schubert, Marcel; Mateker, William R.; Bloking, Jason T.; Burkhard, George F.; Sellinger, Alan; Fréchet, Jean M. J.; Amassian, Aram; Riede, Moritz K.; McGehee, Michael D.; Neher, Dieter; Salleo, Alberto

    2014-01-01

    Interfaces between organic electron-donating (D) and electron-accepting (A) materials have the ability to generate charge carriers on illumination. Efficient organic solar cells require a high yield for this process, combined with a minimum of energy losses. Here, we investigate the role of the lowest energy emissive interfacial charge-transfer state (CT1) in the charge generation process. We measure the quantum yield and the electric field dependence of charge generation on excitation of the charge-transfer (CT) state manifold via weakly allowed, low-energy optical transitions. For a wide range of photovoltaic devices based on polymer:fullerene, small-molecule:C60 and polymer:polymer blends, our study reveals that the internal quantum efficiency (IQE) is essentially independent of whether or not D, A or CT states with an energy higher than that of CT1 are excited. The best materials systems show an IQE higher than 90% without the need for excess electronic or vibrational energy.

  19. Efficient charge generation by relaxed charge-transfer states at organic interfaces

    KAUST Repository

    Vandewal, Koen

    2013-11-17

    Interfaces between organic electron-donating (D) and electron-accepting (A) materials have the ability to generate charge carriers on illumination. Efficient organic solar cells require a high yield for this process, combined with a minimum of energy losses. Here, we investigate the role of the lowest energy emissive interfacial charge-transfer state (CT1) in the charge generation process. We measure the quantum yield and the electric field dependence of charge generation on excitation of the charge-transfer (CT) state manifold via weakly allowed, low-energy optical transitions. For a wide range of photovoltaic devices based on polymer:fullerene, small-molecule:C60 and polymer:polymer blends, our study reveals that the internal quantum efficiency (IQE) is essentially independent of whether or not D, A or CT states with an energy higher than that of CT1 are excited. The best materials systems show an IQE higher than 90% without the need for excess electronic or vibrational energy. © 2014 Macmillan Publishers Limited.

  20. Impact of exact exchange in the description of the electronic structure of organic charge-transfer molecular crystals

    KAUST Repository

    Fonari, Alexandr

    2014-10-21

    We evaluate the impact that the amount of nonlocal Hartree-Fock (%HF) exchange included in a hybrid density functional has on the microscopic parameters (transfer integrals, band gaps, bandwidths, and effective masses) describing charge transport in high-mobility organic crystals. We consider both crystals based on a single molecule, such as pentacene, and crystals based on mixed-stack charge-transfer systems, such as dibenzo-TTF–TCNQ. In the pentacene crystal, the band gap decreases and the effective masses increase linearly with an increase in the amount of %HF exchange. In contrast, in the charge-transfer crystals, while the band gap increases linearly, the effective masses vary only slightly with an increase in %HF exchange. We show that the superexchange nature of the electronic couplings in charge-transfer systems is responsible for this peculiar evolution of the effective masses. We compare the density functional theory results with results obtained within the G0W0 approximation as a way of benchmarking the optimal amount of %HF exchange needed in a given functional.

  1. Quantum information transfer between topological and conventional charge qubits

    Science.gov (United States)

    Jun, Li; Yan, Zou

    2016-02-01

    We propose a scheme to realize coherent quantum information transfer between topological and conventional charge qubits. We first consider a hybrid system where a quantum dot (QD) is tunnel-coupled to a semiconductor Majorana-hosted nanowire (MNW) via using gated control as a switch, the information encoded in the superposition state of electron empty and occupied state can be transferred to each other through choosing the proper interaction time to make measurements. Then we consider another system including a double QDs and a pair of parallel MNWs, it is shown that the entanglement information transfer can be realized between the two kinds of systems. We also realize long distance quantum information transfer between two quantum dots separated by an MNW, by making use of the nonlocal fermionic level formed with the pared Majorana feimions (MFs) emerging at the two ends of the MNW. Furthermore, we analyze the teleportationlike electron transfer phenomenon predicted by Tewari et al. [Phys. Rev. Lett. 100, 027001 (2008)] in our considered system. Interestingly, we find that this phenomenon exactly corresponds to the case that the information encoded in one QD just returns back to its original place during the dynamical evolution of the combined system from the perspective of quantum state transfer. Project supported by the National Natural Science Foundation of China (Grant No. 11304031).

  2. Charge and Energy Dependences of Ionization and Transfer for Helium in Collisions with Fast Charged Projectiles

    Institute of Scientific and Technical Information of China (English)

    FU Hong-Bin; WANG Bao-Hong; DING Bao-Wei; LIU Zhao-Yuan

    2009-01-01

    The classical method within the independent electron model is employed to investigate (i) charge dependences of single and double ionization for helium by various charged ions Aq+ (q = 1 - 8) at impact energies of 0.64 and 1.44 MeV/u, respectively, (ii) energy dependences of transfer ionization for helium by 0.5-3 MeV/u A8,9+ ions impact. The Lenz-Jensen model of the atom is applied instead of the Bohr model of the atom, and the impact-parameter dependences are also introduced into the calculations. Satisfactory agreement is found between theoretical and experimental data.

  3. FAST TRACK COMMUNICATION: Effects of charge transfer interaction of graphene with electron donor and acceptor molecules examined using Raman spectroscopy and cognate techniques

    Science.gov (United States)

    Voggu, Rakesh; Das, Barun; Sekhar Rout, Chandra; Rao, C. N. R.

    2008-11-01

    The effects of the interaction of few-layer graphene with electron donor and acceptor molecules have been investigated by employing Raman spectroscopy, and the results compared with those from electrochemical doping. The G-band softens progressively with increasing concentration of tetrathiafulvalene (TTF) which is an electron donor, while the band stiffens with increasing concentration of tetracyanoethylene (TCNE) which is an electron acceptor. Interaction with both TTF and TCNE broadens the G-band. Hole and electron doping by electrochemical means, however, stiffen and sharpen the G-band. The 2D-band position is also affected by interaction with TTF and TCNE. More importantly, the intensity of the 2D-band decreases markedly with the concentration of either. The ratio of intensities of the 2D-band and G-band decreases with an increase in TTF or TCNE concentration, and provides a means for carrier titration in the charge transfer system. Unlike the intensity of the 2D-band, that of the D-band increases on interaction with TTF or TCNE. All of these effects occur due to molecular charge transfer, also evidenced by the occurrence of charge transfer bands in the electronic absorption spectra. The electrical resistivity of graphene varies in opposite directions on interaction with TTF and TCNE, the resistivity depending on the concentration of either compound.

  4. Photophysics of charge transfer in a polyfluorene/violanthrone blend

    Science.gov (United States)

    Cabanillas-Gonzalez, J.; Virgili, T.; Lanzani, G.; Yeates, S.; Ariu, M.; Nelson, J.; Bradley, D. D. C.

    2005-01-01

    We present a study of the photophysical and photovoltaic properties of blends of violanthrone in poly[9, 9-bis (2-ethylhexyl)-fluorene-2, 7-diyl ] (PF2/6) . Photoluminescence quenching and photocurrent measurements show moderate efficiencies for charge generation, characteristic of such polymer/dye blends. Pump-probe measurements on blend films suggest that while ˜47% of the total exciton population dissociates within 4ps of photoexcitation, only ˜32% subsequently results in the formation of dye anions. We attribute the discrepancy to the likely formation of complex species with long lifetimes, such as stabilized interface charge pairs or exciplexes. This conclusion is supported by the appearance of a long lifetime component of 2.4ns in the dynamics of the photoinduced absorption signal associated to polarons in photoinduced absorption bands centered at 560nm .

  5. Surface characterization and surface electronic structure of organic quasi-one-dimensional charge transfer salts

    DEFF Research Database (Denmark)

    Sing, M.; Schwingenschlögl, U.; Claessen, R.;

    2003-01-01

    diagnostic tool. We show that the observation of generic one-dimensional signatures in photoemission spectra of the valence band close to the Fermi level can be strongly affected by surface effects. Especially, great care must be exercised taking evidence for an unusual one-dimensional many-body state......We have thoroughly characterized the surfaces of the organic charge-transfer salts TTF-TCNQ and (TMTSF)(2)PF6 which are generally acknowledged as prototypical examples of one-dimensional conductors. In particular x-ray-induced photoemission spectroscopy turns out to be a valuable nondestructive...

  6. Charge Transfer and Triplet States in High Efficiency OPV Materials and Devices

    Science.gov (United States)

    Dyakonov, Vladimir

    2013-03-01

    The advantage of using polymers and molecules in electronic devices, such as light-emitting diodes (LED), field-effect transistors (FET) and, more recently, solar cells (SC) is justified by the unique combination of high device performance and processing of the semiconductors used. Power conversion efficiency of nanostructured polymer SC is in the range of 10% on lab scale, making them ready for up-scaling. Efficient charge carrier generation and recombination in SC are strongly related to dissociation of the primary singlet excitons. The dissociation (or charge transfer) process should be very efficient in photovoltaics. The mechanisms governing charge carrier generation, recombination and transport in SC based on the so-called bulk-heterojunctions, i.e. blends of two or more semiconductors with different electron affinities, appear to be very complex, as they imply the presence of the intermediate excited states, neutral and charged ones. Charge transfer states, or polaron pairs, are the intermediate states between free electrons/holes and strongly bound excitons. Interestingly, the mostly efficient OLEDs to date are based on the so-called triplet emitters, which utilize the triplet-triplet annihilation process. In SC, recent investigations indicated that on illumination of the device active layer, not only mobile charges but also triplet states were formed. With respect to triplets, it is unclear how these excited states are generated, via inter-system crossing or via back transfer of the electron from acceptor to donor. Triplet formation may be considered as charge carrier loss channel; however, the fusion of two triplets may lead to a formation of singlet excitons instead. In such case, a generation of charges by utilizing of the so far unused photons will be possible. The fundamental understanding of the processes involving the charge transfer and triplet states and their relation to nanoscale morphology and/or energetics of blends is essential for the

  7. Charge Transfer and Ionization by Intermediate-Energy Heavy Ions

    Energy Technology Data Exchange (ETDEWEB)

    Toburen, L. H. [East Carolina University; McLawhorn, S. L. [East Carolina University; McLawhorn, R. A. [East Carolina University; Evans, N. L. [East Carolina University; Justiniano, E. L. B. [East Carolina University; Shinpaugh, J. L. [East Carolina University; Schultz, David Robert [ORNL; Reinhold, Carlos O [ORNL

    2006-11-01

    The use of heavy ion beams for microbeam studies of mammalian cell response leads to a need to better understand interaction cross sections for collisions of heavy ions with tissue constituents. For ion energies of a few MeV u-1 or less, ions capture electrons from the media in which they travel and undergo subsequent interactions as partially 'dressed' ions. For example, 16 MeV fluorine ions have an equilibrium charge of 7+, 32 MeV sulphur ions have an equilibrium charge of approx. 11+, and as the ion energies decrease the equilibrium charge decreases dramatically. Data for interactions of partially dressed ions are extremely rare, making it difficult to estimate microscopic patterns of energy deposition leading to damage to cellular components. Such estimates, normally obtained by Monte Carlo track structure simulations, require a comprehensive database of differential and total ionisation cross sections as well as charge transfer cross sections. To provide information for track simulation, measurement of total ionisation cross sections have been initiated at East Carolina University using the recoil ion time-of-flight method that also yields cross sections for multiple ionisation processes and charge transfer cross sections; multiple ionisation is prevalent for heavy ion interactions. In addition, measurements of differential ionisation cross sections needed for Monte Carlo simulation of detailed event-by-event particle tracks are under way. Differential, total and multiple ionisation cross sections and electron capture and loss cross sections measured for C+ ions with energies of 100 and 200 keV u-1 are described.

  8. Charge transfer and ionisation by intermediate-energy heavy ions.

    Science.gov (United States)

    Toburen, L H; McLawhorn, S L; McLawhorn, R A; Evans, N L; Justiniano, E L B; Shinpaugh, J L; Schultz, D R; Reinhold, C O

    2006-01-01

    The use of heavy ion beams for microbeam studies of mammalian cell response leads to a need to better understand interaction cross sections for collisions of heavy ions with tissue constituents. For ion energies of a few MeV u(-1) or less, ions capture electrons from the media in which they travel and undergo subsequent interactions as partially 'dressed' ions. For example, 16 MeV fluorine ions have an equilibrium charge of 7(+), 32 MeV sulphur ions have an equilibrium charge of approximately 11(+), and as the ion energies decrease the equilibrium charge decreases dramatically. Data for interactions of partially dressed ions are extremely rare, making it difficult to estimate microscopic patterns of energy deposition leading to damage to cellular components. Such estimates, normally obtained by Monte Carlo track structure simulations, require a comprehensive database of differential and total ionisation cross sections as well as charge transfer cross sections. To provide information for track simulation, measurement of total ionisation cross sections have been initiated at East Carolina University using the recoil ion time-of-flight method that also yields cross sections for multiple ionisation processes and charge transfer cross sections; multiple ionisation is prevalent for heavy ion interactions. In addition, measurements of differential ionisation cross sections needed for Monte Carlo simulation of detailed event-by-event particle tracks are under way. Differential, total and multiple ionisation cross sections and electron capture and loss cross sections measured for C(+) ions with energies of 100 and 200 keV u(-1) are described.

  9. Super-iron Nanoparticles with Facile Cathodic Charge Transfer

    Energy Technology Data Exchange (ETDEWEB)

    M Farmand; D Jiang; B Wang; S Ghosh; D Ramaker; S Licht

    2011-12-31

    Super-irons contain the + 6 valence state of iron. One advantage of this is that it provides a multiple electron opportunity to store additional battery charge. A decrease of particle size from the micrometer to the nanometer domain provides a higher surface area to volume ratio, and opportunity to facilitate charge transfer, and improve the power, voltage and depth of discharge of cathodes made from such salts. However, super-iron salts are fragile, readily reduced to the ferric state, with both heat and contact with water, and little is known of the resultant passivating and non-passivating ferric oxide products. A pathway to decrease the super-iron particle size to the nano-domain is introduced, which overcomes this fragility, and retains the battery capacity advantage of their Fe(VI) valence state. Time and power controlled mechanosynthesis, through less aggressive, dry ball milling, leads to facile charge transfer of super-iron nanoparticles. Ex-situ X-ray Absorption Spectroscopy is used to explore the oxidation state and structure of these iron oxides during discharge and shows the significant change in stability of the ferrate structure to lower oxidation state when the particle size is in the nano-domain.

  10. Structure and electronic spectra of purine-methyl viologen charge transfer complexes.

    Science.gov (United States)

    Jalilov, Almaz S; Patwardhan, Sameer; Singh, Arunoday; Simeon, Tomekia; Sarjeant, Amy A; Schatz, George C; Lewis, Frederick D

    2014-01-01

    The structure and properties of the electron donor-acceptor complexes formed between methyl viologen and purine nucleosides and nucleotides in water and the solid state have been investigated using a combination of experimental and theoretical methods. Solution studies were performed using UV-vis and (1)H NMR spectroscopy. Theoretical calculations were performed within the framework of density functional theory (DFT). Energy decomposition analysis indicates that dispersion and induction (charge-transfer) interactions dominate the total binding energy, whereas electrostatic interactions are largely repulsive. The appearance of charge transfer bands in the absorption spectra of the complexes are well-described by time-dependent DFT and are further explained in terms of the redox properties of purine monomers and solvation effects. Crystal structures are reported for complexes of methyl viologen with the purines 2'-deoxyguanosine 3'-monophosphate (DAD'DAD' type) and 7-deazaguanosine (DAD'ADAD' type). Comparison of the structures determined in the solid state and by theoretical methods in solution provides valuable insights into the nature of charge-transfer interactions involving purine bases as electron donors.

  11. Polaron assisted charge transfer in model biological systems

    Science.gov (United States)

    Li, Guangqi; Movaghar, Bijan

    2016-11-01

    We use a tight binding Hamiltonian to simulate the electron transfer from an initial charge-separating exciton to a final target state through a two-arm transfer model. The structure is copied from the model frequently used to describe electron harvesting in photosynthesis (photosystems I). We use this network to provide proof of principle for dynamics, in quantum system/bath networks, especially those involving interference pathways, and use these results to make predictions on artificially realizable systems. Each site is coupled to the phonon bath via several electron-phonon couplings. The assumed large energy gaps and weak tunneling integrals linking the last 3 sites give rise to"Stark Wannier like" quantum localization; electron transfer to the target cluster becomes impossible without bath coupling. As a result of the electron-phonon coupling, local electronic energies relax when the site is occupied, and transient polaronic states are formed as photo-generated electrons traverse the system. For a symmetric constructively interfering two pathway network, the population is shared equally between two sets of equivalent sites and therefore the polaron energy shift is smaller. The smaller energy shift however makes the tunnel transfer to the last site slower or blocks it altogether. Slight disorder (or thermal noise) can break the symmetry, permitting essentially a "one path", and correspondingly more efficient transfer.

  12. Enhanced electron transfer dissociation through fixed charge derivatization of cysteines.

    Science.gov (United States)

    Vasicek, Lisa; Brodbelt, Jennifer S

    2009-10-01

    Electron transfer dissociation (ETD) has proven to be a promising new ion activation method for proteomics applications due to its ability to generate c- and z-type fragment ions in comparison to the y- and b-type ions produced upon the more conventional collisional activation of peptides. However, low precursor charge states hinder the success of electron-based activation methods due to competition from nondissociative charge reduction and incomplete sequence coverage. In the present report, the reduction and alkylation of disulfide bonds prior to ETD analysis is evaluated by comparison of three derivatization reagents: iodoacetamide (IAM), N,N-dimethyl-2-chloro-ethylamine (DML), and (3-acrylamidopropyl)-trimethyl ammonium chloride (APTA). While both the DML and APTA modifications lead to an increase in the charge states of peptides, the APTA-peptides provided the most significant improvement in percent fragmentation and sequence coverage for all peptides upon ETD, including formation of diagnostic ions that allow characterization of both the C- and N-termini. In addition, the formation of product ions in multiple charge states upon ETD is minimized for the APTA-modified peptides.

  13. Charge-transfer spectra of ferrocene in halocarbon solvents under photoexcitation

    Indian Academy of Sciences (India)

    Alfazuddin Thander; Biswanath Mallik

    2000-08-01

    The changes in the electronic absorption spectra of ferrocene in the halocarbon solvents chloroform and carbontetrachloride have been investigated under photoexcitation in nitrogen atmosphere. Photoexcitations have been made with monochromatic light (using an Xe-source and a monochromator), at intervals of a few nanometers in the spectral range 220-750 nm. Analysing the spectra by a modified method the position of the charge-transfer-to-solvent (CTTS) band has been located for both the solvents. The position of the CTTS band in the case of carbontetrachloride solution located (320 nm) by the present study is different from the previously reported value (307 nm), while from the previous studies the position of the CTTS band in the case of the spectra of ferrocene in chloroform was not clear. From the present investigation, the changes in spectra after photoexcitation studied as a function, the concentration of ferrocene in the solution and the time (duration) of photoexcitations, have been observed to be systematic. Using the position of the new band (320 nm) for the CTTS transition in the case of carbontetrachloride, ionization potential of ferrocene has been estimated and the estimated value has shown excellent agreement with the experimental value indicating the exactness of the newly located CTTS band position.

  14. Charge and Energy Transfer Dynamics in Molecular Systems

    CERN Document Server

    May, Volkhard

    2004-01-01

    This second edition is based on the successful concept of the first edition in presenting a unified perspective on molecular charge and energy transfer processes. The authors bridge the regimes of coherent and dissipative dynamics, thus establishing the connection between classic rate theories and modern treatments of ultrafast phenomena. The book serves as an introduction for graduate students and researchers. Among the new topics of this second edition are. - semiclassical and quantum-classical hybrid formulations of molecular dynamics. - the basics of femtosecond nonlinear spectroscopy. - e

  15. Modulating unimolecular charge transfer by exciting bridge vibrations.

    Science.gov (United States)

    Lin, Zhiwei; Lawrence, Candace M; Xiao, Dequan; Kireev, Victor V; Skourtis, Spiros S; Sessler, Jonathan L; Beratan, David N; Rubtsov, Igor V

    2009-12-23

    Ultrafast UV-vibrational spectroscopy was used to investigate how vibrational excitation of the bridge changes photoinduced electron transfer between donor (dimethylaniline) and acceptor (anthracene) moieties bridged by a guanosine-cytidine base pair (GC). The charge-separated (CS) state yield is found to be lowered by high-frequency bridge mode excitation. The effect is linked to a dynamic modulation of the donor-acceptor coupling interaction by weakening of H-bonding and/or by disruption of the bridging base-pair planarity.

  16. Negative thermal expansion induced by intermetallic charge transfer.

    Science.gov (United States)

    Azuma, Masaki; Oka, Kengo; Nabetani, Koichiro

    2015-06-01

    Suppression of thermal expansion is of great importance for industry. Negative thermal expansion (NTE) materials which shrink on heating and expand on cooling are therefore attracting keen attention. Here we provide a brief overview of NTE induced by intermetallic charge transfer in A-site ordered double perovskites SaCu3Fe4O12 and LaCu3Fe4-x Mn x O12, as well as in Bi or Ni substituted BiNiO3. The last compound shows a colossal dilatometric linear thermal expansion coefficient exceeding -70 × 10(-6) K(-1) near room temperature, in the temperature range which can be controlled by substitution.

  17. Radical formation at the gallium nitride nanowire-electrolyte interface by photoactivated charge transfer.

    Science.gov (United States)

    Philipps, J M; Müntze, G M; Hille, P; Wallys, J; Schörmann, J; Teubert, J; Hofmann, D M; Eickhoff, M

    2013-08-16

    We investigated the transfer of photogenerated charge carriers from GaN nanowires into a surrounding electrolyte by electron paramagnetic resonance (EPR) and fluorescence spectroscopy. Using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap we find that the formation of hydroxyl radicals dominates in acidic, neutral and moderately basic environments, while in an electrolyte with a pH of 13.5 the superoxide formation becomes detectable. We explain the two processes considering the redox potentials for radical formation in the electrolyte as well as the positions of the conduction and valence bands. The role of surface band bending and surface states in the semiconductor is discussed.

  18. Band-gap narrowing in the space-charge region of heavily doped silicon diodes

    Science.gov (United States)

    Lowney, Jeremiah R.

    1985-02-01

    The densities of states of the valence and conduction bands have been calculated in the space-charge region of a heavily doped linearly graded p- n junction silicon diode. Both the donor and acceptor densities were chosen to be equal to 6.2 × 10 18 cm -3. The results showed the emergence of band tails which penetrated deeply into the energy gap and accounted for the band-gap narrowing observed in such a diode by analysis of capacitance vs voltage measurements of the built-in voltage.

  19. Charge transfer transitions in the excitation spectra of PrX{sub 3}:Ce{sup 3+} (X=Cl, Br) scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, A.M. [GE Global Research, 1 Research Circle, K1 4A24, Niskayuna, NY 12309 (United States)], E-mail: srivastava@crd.ge.com

    2009-01-15

    The Cl{sup -}{yields}Pr{sup 3+} charge transfer transition is identified to occur in the excitation spectrum of PrCl{sub 3}:Ce{sup 3+} at 211 nm (47,393 cm{sup -1}). A model based on the dissociation of the charge transfer state is proposed to explain the presence of the ligand-to-Pr{sup 3+} charge transfer transition band in the excitation spectrum of PrX{sub 3}:Ce{sup 3+} (X=Cl, Br) when the Ce{sup 3+} emission is monitored00.

  20. Modulation of the charge transfer and photophysical properties in non-fused tetrathiafulvalene-benzothiadiazole derivatives.

    Science.gov (United States)

    Pop, Flavia; Seifert, Sabine; Hankache, Jihane; Ding, Jie; Hauser, Andreas; Avarvari, Narcis

    2015-01-28

    Bis(thiomethyl)- and bis(thiohexyl)-tetrathiafulvalene-bromo-benzothiadiazoles, containing electron donor tetrathiafulvalene (TTF) and electron acceptor benzothiadiazole (BTD) units, have been prepared by Stille coupling reactions between the TTF-SnMe3 precursors and BTD-Br2. In another series of experiments, TTF-acetylene-BTD compounds have been synthesized by Sonogashira coupling between either TTF-acetylenes and BTD-Br2 in low yields, or TTF-iodine and BTD-acetylene in moderate yields. In the compound TTF-C≡C-BTD the TTF and BTD units are coplanar in the solid state, as shown by the single crystal X-ray structure, and there is segregation in the packing between the donor and acceptor units. All the derivatives have good electron donor properties, as determined by cyclic voltammetry measurements, and they can also be reversibly reduced thanks to the presence of the BTD moiety. UV-visible spectroscopy and photophysical investigations show the presence of an intramolecular charge transfer (ICT) band and an emission band originating from the charge transfer. Both the absorption and the emission are modulated by the substitution scheme and the insertion of the acetylenic bridge.

  1. Charge transfer and penning ionization of dopants in or on helium nanodroplets exposed to EUV radiation.

    Science.gov (United States)

    Buchta, Dominic; Krishnan, Siva R; Brauer, Nils B; Drabbels, Marcel; O'Keeffe, Patrick; Devetta, Michele; Di Fraia, Michele; Callegari, Carlo; Richter, Robert; Coreno, Marcello; Prince, Kevin C; Stienkemeier, Frank; Moshammer, Robert; Mudrich, Marcel

    2013-05-30

    Helium nanodroplets are widely used as a cold, weakly interacting matrix for spectroscopy of embedded species. In this work, we excite or ionize doped He droplets using synchrotron radiation and study the effect onto the dopant atoms depending on their location inside the droplets (rare gases) or outside at the droplet surface (alkali metals). Using photoelectron-photoion coincidence imaging spectroscopy at variable photon energies (20-25 eV), we compare the rates of charge-transfer to Penning ionization of the dopants in the two cases. The surprising finding is that alkali metals, in contrast to the rare gases, are efficiently Penning ionized upon excitation of the (n = 2)-bands of the host droplets. This indicates rapid migration of the excitation to the droplet surface, followed by relaxation, and eventually energy transfer to the alkali dopants.

  2. Charge Transfer Based Colorimetric Detection of Silver Ion

    Energy Technology Data Exchange (ETDEWEB)

    Han, Seung Choul; Kim, Kwang Seob; Choi, Soon Kyu; Oh, Jinho; Lee, Jae Wook [Dong-A Univ., Busan (Korea, Republic of)

    2014-05-15

    We have demonstrated the colorimetric chemosensor for detection of Ag{sup +} via formation of nanoparticles which is based on the intramolecular CT interaction between the electron-rich (2,6-dialkoxynaphthalene; Np) moiety and the electron-deficient (methyl viologen; MV{sup 2+}) moiety of a single sensor molecule. Under irradiation of light, Ag{sup +} was reduced to very small silver nanoparticle by CT interaction in the presence of OEGs as flexible recognition moiety of Ag{sup +} and stabilizer for Ag nanoparticles, thus Ag nanoparticles resulted to reddish brown in the color change of sensor solution, gradually. Therefore, the charge-transfer interaction between an electron-deficient and an electron-rich units existing at a sensor molecule can be regarded as a new and efficient method to construct various colorimetric chemosensors. Donor.acceptor interactions or charge transfer (CT) interactions are an important class of non-covalent interactions and have been widely exploited in self-assembling systems. Beyond molecular chemistry, supramolecular chemistry aims at constituting highly complex, functional chemical systems from components held together by intermolecular forces. Chemosensors are the molecules of abiotic origin that bind selectively and reversibly with the analyte with concomitant change in one or more properties of the system. The recognition and signaling of ionic and neutral species of varying complexity is one of the most intensively studied areas of contemporary supramolecular chemistry.

  3. Ultrafast charge transfer via a conical intersection in dimethylaminobenzonitrile.

    Science.gov (United States)

    Fuss, Werner; Pushpa, Kumbil Kuttan; Rettig, Wolfgang; Schmid, Wolfram E; Trushin, Sergei A

    2002-04-01

    The L(a)-like S2 state (2A) of 4-(dimethylamino)benzonitrile was pumped at 267 nm in the gas phase at 130 degrees C. Nonresonant multiphoton ionization at 800 nm with mass-selective detection then probed the subsequent processes. Whereas ionization at the Franck-Condon geometry only gave rise to the parent ion, fragmentation increased on motion towards the charge-transfer (CT) state. This useful difference is ascribed to a geometry-dependent resonance in the ion. The time constants found are interpreted by ultrafast (approximately 68 fs) relaxation through a conical intersection to both the CT and the L(b)-type S1 state (1B). Then the population equilibrates between these two states within 1 ps. From there the molecule relaxes within 90 ps to a lower excited state which can only be a triplet state (T(n)) and then decomposes within 300 ps. Previous experiments either investigated only 1B --> CT relaxation-which does not take place in the gas phase or nonpolar solvents for energetic reasons--or, starting from S2 excitation, typically had insufficient time resolution (>1 ps) to detect the temporary charge transfer. Only recently temporary population of the CT state was found in a nonpolar solvent (Kwok et al., J. Phys. Chem. A. 2000, 104, 4188), a result fully consistent with our mechanism. We also show that S2 --> S1 relaxation does not occur vertically but involves an intermediate strong geometrical distortion, passing through a conical intersection.

  4. Narrowing of band gap and effective charge carrier separation in oxygen deficient TiO2 nanotubes with improved visible light photocatalytic activity.

    Science.gov (United States)

    Choudhury, Biswajit; Bayan, Sayan; Choudhury, Amarjyoti; Chakraborty, Purushottam

    2016-03-01

    Oxygen vacancies are introduced into hydrothermally processed TiO2 nanotube by vacuum calcination. Formation of oxygen vacancies modifies the local coordination in TiO2 as evident from Raman spectroscopy and secondary ion mass spectrometry (SIMS) results. The surface area is increased from 172.5m(2)/g in pure to 405.1m(2)/g in defective TiO2 nanotube. The mid-band gap electronic states created by oxygen vacancies are mostly responsible for the effective narrowing of band gap. Charge carrier separation is sufficiently prolonged as the charged oxygen defect states inhibit facile carrier recombination. With high surface area, narrowed band gap and separated charge carriers defective TiO2 nanotube is a suitable candidate in the photodegradation of methylene blue (MB) and phenol under visible light illumination. Photosensitized electron transfer from MB to the conduction band of TiO2 and the photodegradation of MB is facilitated in presence of high density of oxygen vacancies. Unlike MB, phenol absorbs in the UV region and does not easily excited under visible light. Phenol shows activity under visible light by forming charge transfer complex with TiO2. Defect trapped carriers become available at the phenol-TiO2 interface and finally interact with phenol molecule and degrade it.

  5. The screened pseudo-charge repulsive potential in perturbed orbitals for band calculations by DFT+U.

    Science.gov (United States)

    Huang, Bolong

    2017-03-06

    The conventional linear response overestimates the U in DFT+U calculations for solids with fully occupied orbitals. Here, we demonstrate that the challenge arises from the incomplete cancellation of the electron-electron Coulomb repulsion energy under external perturbation. We applied the second charge response, denoted as the "pseudo-charge" model, to offset such residue effects. Counteracting between these two charge response-induced Coulomb potentials, the U parameters are self-consistently obtained by fulfilling the conditions for minimizing the non-Koopmans energy. Moreover, the pseudo-charge-induced repulsive potential shows a screening behavior related to the orbital occupation and is potentially in compliance with the screened exact exchange-correlation of electrons. The resultant U parameters are self-consistent solutions for improved band structure calculations by the DFT+U method. This work extends the validity of the linear response method to both partially and fully occupied orbitals and gives a reference for estimating the Hubbard U parameter prior to other advanced methods. The U parameters were determined in a transferability test using both PBE and hybrid density functional methods, and the results showed that this method is independent of the functional. The electronic structures determined from the hybrid-DFT+U(hybrid) approach are provided. Comparisons are also made with the recently developed self-consistent hybrid-DFT+Uw method.

  6. Role of band states and trap states in the charge transport properties of organic semiconductors (Conference Presentation)

    Science.gov (United States)

    Coropceanu, Veaceslav

    2016-11-01

    In this contribution, we examine the main factors that define charge transport in organic semiconductors. We consider both crystals based on a single molecule building block, such as oligoacenes, and two-component donor-acceptor crystals in which one component acts as an electron donor and the other as an acceptor. We will first discuss the state-of-the-art methodologies used in the derivation of the microscopic parameters (electron-vibration couplings, transfer integrals, band gaps, bandwidths, and effective masses) describing charge transport. In particular, we will discuss the impact that the amount of nonlocal Hartree-Fock exchange included in a hybrid density functional has on these parameters. In order to understand the role of disorder we use a combination of electronic-structure calculations and molecular mechanics/molecular dynamics simulations complemented by ensemble and time average approaches to separate the static and dynamic disorder components. The temperature dependence of the charge carrier mobility is studied by treating the electron-phonon interaction as a perturbation (Boltzmann theory), in the static approximation (Kubo formalism) and in the framework of mixed quantum/classical dynamics. Finally, based on the results of the kinetic Monte Carlo simulations we will compare the merits of a hopping model and a mobility edge model in the description of the effect of charge-carrier concentration on the electrical conductivity, carrier mobility, and Fermi energy of organic semiconductors.

  7. Enhanced emission and photoconductivity due to photo-induced charge transfer from Au nanoislands to ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Shang-Hsuan; Chan, Ching-Hsiang; Liang, Ching-Tarng [Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan (China); Chien, Ching-Hang; Yaseen, Mohammad Tariq [Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan (China); Nano Science and Technology Program, TIGP, Academia Sinica, Taipei 115, Taiwan (China); Department of Engineering and System Science, National Tsing Hua University, Hsinchu 300, Taiwan (China); Chang, Yia-Chung, E-mail: yiachang@gate.sinica.edu.tw [Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan (China); Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China)

    2016-01-25

    We report systematic studies based on photoluminescence, Hall, and photoconductivity measurements together with theoretical modeling in order to identify mechanisms for the photo-induced charge transfer effects in ZnO thin film incorporated with the Au nano-islands (AuNIs). Significant enhancement of near band edge emission and improvement in conductivity of ZnO/AuNIs samples after illumination are observed, which are attributed to the photo-induced hot electrons in Au which are then transferred into the conduction band of ZnO as long as the excitation energy is higher than the offset between the ZnO conduction-band minimum and Au Fermi level. Our experimental results are consistent with the general features predicted by first principles calculations.

  8. Charge transfer excitons in C60-dimers and polymers

    CERN Document Server

    Harigaya, K

    1996-01-01

    Charge-transfer (CT) exciton effects are investigated for the optical absorption spectra of crosslinked C60 systems by using the intermediate exciton theory. We consider the C60-dimers, and the two (and three) molecule systems of the C60-polymers. We use a tight-binding model with long-range Coulomb interactions among electrons, and the model is treated by the Hartree-Fock approximation followed by the single-excitation configuration interaction method. We discuss the variations in the optical spectra by changing the conjugation parameter between molecules. We find that the total CT-component increases in smaller conjugations, and saturates at the intermediate conjugations. It decreases in the large conjugations. We also find that the CT-components of the doped systems are smaller than those of the neutral systems, indicating that the electron-hole distance becomes shorter in the doped C60-polymers.

  9. Positron annihilation studies of some charge transfer molecular complexes

    CERN Document Server

    El-Sayed, A; Boraei, A A A

    2000-01-01

    Positron annihilation lifetimes were measured for some solid charge transfer (CT) molecular complexes of quinoline compounds (2,6-dimethylquinoline, 6-methoxyquinoline, quinoline, 6-methylquinoline, 3-bromoquinoline and 2-chloro-4-methylquinoline) as electron donor and picric acid as an electron acceptor. The infrared spectra (IR) of the solid complexes clearly indicated the formation of the hydrogen-bonding CT-complexes. The annihilation spectra were analyzed into two lifetime components using PATFIT program. The values of the average and bulk lifetimes divide the complexes into two groups according to the non-bonding ionization potential of the donor (electron donating power) and the molecular weight of the complexes. Also, it is found that the ionization potential of the donors and molecular weight of the complexes have a conspicuous effect on the average and bulk lifetime values. The bulk lifetime values of the complexes are consistent with the formation of stable hydrogen-bonding CT-complexes as inferred...

  10. Self-interaction effects on charge-transfer collisions

    CERN Document Server

    Quashie, Edwin E; Andrade, Xavier; Correa, Alfredo A

    2016-01-01

    In this article, we investigate the role of the self-interaction error in the simulation of collisions using time-dependent density functional theory (TDDFT) and Ehrenfest dynamics. We compare many different approximations of the exchange and correlation potential, using as a test system the collision of $\\mathrm{H^+ + CH_4}$ at $30~\\mathrm{eV}$. We find that semi-local approximations, like PBE, and even hybrid functionals, like B3LYP, produce qualitatively incorrect predictions for the scattering of the proton. This discrepancy appears because the self-interaction error allows the electrons to jump too easily to the proton, leading to radically different forces with respect to the non-self-interacting case. From our results, we conclude that using a functional that is self-interaction free is essential to properly describe charge-transfer collisions between ions and molecules in TDDFT.

  11. Ultrafast charge transfer between MoTe2 and MoS2 monolayers

    Science.gov (United States)

    Pan, Shudi; Ceballos, Frank; Bellus, Matthew Z.; Zereshki, Peymon; Zhao, Hui

    2017-03-01

    High quality and stable electrical contact between metal and two-dimensional materials, such as transition metal dichalcogenides, is a necessary requirement that has yet to be achieved in order to successfully exploit the advantages that these materials offer to electronics and optoelectronics. MoTe2, owing to its phase changing property, can potentially offer a solution. A recent study demonstrated that metallic phase of MoTe2 connects its semiconducting phase with very low resistance. To utilize this property to connect other two-dimensional materials, it is important to achieve efficient charge transfer between MoTe2 and other semiconducting materials. Using MoS2 as an example, we report ultrafast and efficient charge transfer between MoTe2 and MoS2 monolayers. In the transient absorption measurements, an ultrashort pump pulse is used to selectively excite electrons in MoTe2. The appearance of the excited electrons in the conduction band of MoS2 is monitored by using a probe pulse that is tuned to the resonance of MoS2. We found that electrons transfer to MoS2 on a time scale of at most 0.3 ps. The transferred electrons give rise to a large transient absorption signal at both A-exciton and B-exciton resonances due to the screening effect. We also observed ultrafast transfer of holes from MoS2 to MoTe2. Our results suggest the feasibility of using MoTe2 as a bridge material to connect MoS2 and other transition metal dichalcogenides, and demonstrate a new transition metal dichalcogenide heterostructure involving MoTe2, which extends the spectral range of such structures to infrared.

  12. Charge Transfer Characteristics and Initiation Mechanisms of Long Delayed Sprites

    Science.gov (United States)

    Li, J.; Cummer, S. A.; Lyons, W. A.; Nelson, T. E.

    2007-12-01

    Simultaneous measurements of high altitude optical emissions and the magnetic field produced by sprite-associated lightning discharges enable a close examination of the link between low altitude lightning process and high altitude sprite process. In this work, we report results of the coordinated analysis of high speed (1000--10000 frames per second) sprite video and wideband (0.1 Hz to 30 kHz) magnetic field measurements made simultaneously at the Yucca Ridge Field Station and Duke University during the June through August 2005 campaign period. During the observation period, the high speed camera detected 83 sprite events in 67 TLE sequences, which are caused by the same number of +CGs. 46% of these sprite events are delayed more than 10 ms after the lightning return stroke. With the estimated lightning source current moment waveform, we computed the continuing current amplitude and total charge transfer characteristics of the long delayed sprites (>10 ms delay). Our calculation shows the total charge moment change of the long delayed sprites can vary from several hundred C km to more than ten thousand C km. All the long delayed sprites are related with intense continuing current bigger than 2 kA. This continuing current provides about 50% to 90% of the total charge transfer. However, a bigger continuing current does not necessarily mean a shorter time delay. This indicates that other processes also involved in the sprite initiation for long delayed sprites. In our observations, the sferic burst, a high frequency noise caused by intra-cloud activity, is always accompanied by a slow intensification in the lightning source current before the time of sprite initiation. Thus we used the lightning source current as an input and employed a 2-D FDTD model to numerically simulate the electric field at different altitudes and compare it with the breakdown field. Including the effect of the electron mobility dependence on electric field, the simulation results showed that

  13. A Experiment Method of Wireless Power Transfer for Charging Devices

    Directory of Open Access Journals (Sweden)

    ChanKam On

    2016-11-01

    Full Text Available Wireless Power Transfer Technology would be applied in the charging devices. For example Electric Vehicles. Due to the global warming is very serious, the fossil fuels are dwindling. For this situation, it can use the battery to operate the cars, we are looking for some of the renewable energy. Therefore, the electric vehicles technology and skill are most popularity and mature. Many people have replaced to an electric vehicle, although the cost more expensive than the petrol vehicle, to reduce the use of fossil fuels are worth. Since the electric vehicle supporting is not much, especially for the electric vehicle chargers. Government and manufacture not enough information & details of the electric vehicle, it is difficult to see the charger facility which locates at the public area or parking, therefore cause inconvenient. This technology is taken widespread to use of an electric vehicle. For this project separate in two stages, the first stage to find out the relationship of frequency(f, capacitance(C and inductance(L by the much lab experiment and calculation. In stage two, develop a hardware model to deliver the wireless power transfer system can be recharged for mobile phone and model car wirelessly and find out the better combination and method through comparing a different kind of coil density and distance.

  14. Doping graphene films via chemically mediated charge transfer

    Directory of Open Access Journals (Sweden)

    Ishikawa Ryousuke

    2011-01-01

    Full Text Available Abstract Transparent conductive films (TCFs are critical components of a myriad of technologies including flat panel displays, light-emitting diodes, and solar cells. Graphene-based TCFs have attracted a lot of attention because of their high electrical conductivity, transparency, and low cost. Carrier doping of graphene would potentially improve the properties of graphene-based TCFs for practical industrial applications. However, controlling the carrier type and concentration of dopants in graphene films is challenging, especially for the synthesis of p-type films. In this article, a new method for doping graphene using the conjugated organic molecule, tetracyanoquinodimethane (TCNQ, is described. Notably, TCNQ is well known as a powerful electron accepter and is expected to favor electron transfer from graphene into TCNQ molecules, thereby leading to p-type doping of graphene films. Small amounts of TCNQ drastically improved the resistivity without degradation of optical transparency. Our carrier doping method based on charge transfer has a huge potential for graphene-based TCFs.

  15. Effect of Molecular Packing and Charge Delocalization on the Nonradiative Recombination of Charge-Transfer States in Organic Solar Cells

    KAUST Repository

    Chen, Xian Kai

    2016-09-05

    In organic solar cells, a major source of energy loss is attributed to nonradiative recombination from the interfacial charge transfer states to the ground state. By taking pentacene–C60 complexes as model donor–acceptor systems, a comprehensive theoretical understanding of how molecular packing and charge delocalization impact these nonradiative recombination rates at donor–acceptor interfaces is provided.

  16. Degree of phase separation effects on the charge transfer properties of P3HT:Graphene nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Bkakri, R., E-mail: bkakrirabeb@hotmail.com [Équipe Dispositifs Électroniques Organiques et Photovoltaïque Moléculaire, Laboratoire de la Matière Condensée et des Nanosciences, Faculté des Sciences de Monastir, Avenue de l' environnement, 5019 Monastir (Tunisia); Kusmartseva, O.E.; Kusmartsev, F.V. [Physics Department, Loughborough University, Leicestershire, LE11 3TU (United Kingdom); Song, M. [Department of Materials, Loughborough University, Leicestershire, LE11 3TU (United Kingdom); Bouazizi, A. [Équipe Dispositifs Électroniques Organiques et Photovoltaïque Moléculaire, Laboratoire de la Matière Condensée et des Nanosciences, Faculté des Sciences de Monastir, Avenue de l' environnement, 5019 Monastir (Tunisia)

    2015-05-15

    Graphene layers were introduced into the matrix of regioregular poly (3-hexylthiophene-2, 5-diyl) (RR-P3HT) via solution processing in the perspective of the development of organic nanocomposites with high P3HT/Graphene interfaces areas for efficient charge transfer process. P3HT and graphene act as electrons donor and electrons acceptor materials, respectively. Spatial Fourier Transforms (FFT) and power spectral density (PSD) analysis of the AFM images show that the phase separation decreases with increasing the graphene weight ratio in the P3HT matrix. The Raman spectra of the P3HT:Graphene nanocomposites shows that the G-band of graphene shifts to low frequencies with progressive addition of graphene which proves that there is an interaction between the nanowires of P3HT and the graphene layers. We suggest that the shift of the G-band is due to electrons transfer from P3HT to graphene. The quenching of the photoluminescence (PL) intensity of P3HT with addition of graphene proves also that an electrons transfer process occurred at the P3HT/Graphene interfaces. - Highlights: • Graphene layers are elaborated from expandable graphite oxide. • The effects of the graphene doping level on the charge transfer process were studied. • The phase separation process decreases with increasing the graphene content in the P3HT matrix. • Quenching of the PL intensity is due to electrons transfer from P3HT to graphene.

  17. Ultrafast charge carrier relaxation and charge transfer processes in CdS/CdTe thin films.

    Science.gov (United States)

    Pandit, Bill; Dharmadasa, Ruvini; Dharmadasa, I M; Druffel, Thad; Liu, Jinjun

    2015-07-14

    Ultrafast transient absorption pump-probe spectroscopy (TAPPS) has been employed to investigate charge carrier relaxation in cadmium sulfide/cadmium telluride (CdS/CdTe) nanoparticle (NP)-based thin films and electron transfer (ET) processes between CdTe and CdS. Effects of post-growth annealing treatments to ET processes have been investigated by carrying out TAPPS experiments on three CdS/CdTe samples: as deposited, heat treated, and CdCl2 treated. Clear evidence of ET process in the treated thin films has been observed by comparing transient absorption (TA) spectra of CdS/CdTe thin films to those of CdS and CdTe. Quantitative comparison between ultrafast kinetics at different probe wavelengths unravels the ET processes and enables determination of its rate constants. Implication of the photoinduced dynamics to photovoltaic devices is discussed.

  18. Energy and Charge Transfer from Guest to Host in Doped Organic Electroluminescent Devices

    Institute of Scientific and Technical Information of China (English)

    李宏建; 彭景翠; 许雪梅; 瞿述; 罗小华; 赵楚军

    2002-01-01

    The luminescence properties of doped organic electroluminescent devices are explained by means off Hamiltonian model. The results show that there is a corresponding relation between the amount of transferred charge and the change of the energy originating from charge transfer, and the relation can be influenced by dopant concentration.As the amount of transferred charge increases, the total energy decreases and the luminescence intensity increases.Therefore, we deduce that the energy transfer from guest to host may be derived from the charge transfer. For a given organic electroluminescent device, the maximum value of the conductivity can be observed in a specific dopant concentration. The calculated results show that the greater the transferred charges, the higher the conductivities in doped organic electroluminescent devices. The results agree basically with experimental results.

  19. Effects of acid concentration on intramolecular charge transfer reaction of 4-(azetidinyl) benzonitrile in solution

    Indian Academy of Sciences (India)

    Biswajit Guchhait; Tuhin Pradhan; Ranjit Biswas

    2014-01-01

    Effects of acid concentration on excited state intramolecular charge transfer reaction of 4-(azetidinyl) benzonitrile (P4C) in aprotic (acetonitrile and ethyl acetate) and protic (ethanol) solvents have been studied by means of steady state absorption and fluorescence, and time resolved fluorescence spectroscopic techniques. While absorption and fluorescence bands of P4C have been found to be shifted towards higher energy with increasing acid concentration in acetonitrile and ethyl acetate, no significant dependence has been observed in ethanolic solutions. Reaction rate becomes increasingly slower with acid concentration in acetonitrile and ethyl acetate. In contrast, acid in ethanolic solutions does not produce such an effect on reaction rate. Time-dependent density functional theory calculations have been performed to understand the observed spectroscopic results.

  20. Supercell convergence of charge-transfer energies in pentacene molecular crystals from constrained DFT

    CERN Document Server

    Turban, David H P; O'Regan, David D; Hine, Nicholas D M

    2016-01-01

    Singlet fission (SF) is a multi-exciton generation process that could be harnessed to improve the efficiency of photovoltaic devices. Experimentally, systems derived from the pentacene molecule have been shown to exhibit ultrafast SF with high yields. Charge-transfer (CT) configurations are likely to play an important role as intermediates in the SF process in these systems. In molecular crystals, electrostatic screening effects and band formation can be significant in lowering the energy of CT states, enhancing their potential to effectively participate in SF. In order to simulate these, it desirable to adopt a computational approach which is acceptably accurate, relatively inexpensive, which and scales well to larger systems, thus enabling the study of screening effects. We propose a novel, electrostatically-corrected constrained Density Functional Theory (cDFT) approach as a low-cost solution to the calculation of CT energies in molecular crystals such as pentacene. Here we consider an implementation in th...

  1. Charge transfer adducts of metal complexes of π-donor ligands with I 2 and TCNQ

    Science.gov (United States)

    Bera, T. R.; Sen, D.; Ghosh, R.

    1989-01-01

    Copper(II) and nickel(II) biguanides and O-alkyl-1-amidinourea can act as donors for the formation of charge transfer (CT) adducts with I 2 and tetracyanoquinodimethane (TNCQ) as acceptors. Iodine adducts are characterized both in solid and solution states whereas TCNQ adducts obtain only in solution. Appearance of a broad band at 355 nm for iodine adducts and at 335 nm for TNCQ adducts and shifting of i.r. frequencies support the formation of donor acceptor associates. Elemental analysis establishes 1:1 stoichiometry of the solid adducts. The K and ɛ values determined by modified Benesi—Hildebrand, Scott and Rose—Drago equations are found to be of the order of 10 4 and 10 3 respectively at 298 K in methanol. The solvent effect on the K values is discussed in terms of coupled solute-solute and solute-solvent equilibria.

  2. Charge transfer interactions of a Ru(II) dye complex and related ligand molecules adsorbed on Au(111)

    Energy Technology Data Exchange (ETDEWEB)

    Britton, Andrew J.; Weston, Matthew; O' Shea, James N. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Nottingham Nanotechnology and Nanoscience Centre (NNNC), University of Nottingham, Nottingham NG7 2RD (United Kingdom); Taylor, J. Ben; Rienzo, Anna; Mayor, Louise C. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2011-10-28

    The interaction of the dye molecule, N3 (cis-bis(isothiocyanato)bis(2,2{sup '}-bipyridyl-4,4{sup '}-dicarboxylato) -ruthenium(II)), and related ligand molecules with a Au(111) surface has been studied using synchrotron radiation-based electron spectroscopy. Resonant photoemission spectroscopy (RPES) and autoionization of the adsorbed molecules have been used to probe the coupling between the molecules and the substrate. Evidence of charge transfer from the states near the Fermi level of the gold substrate into the lowest unoccupied molecular orbital (LUMO) of the molecules is found in the monolayer RPES spectra of both isonicotinic acid and bi-isonicotinic acid (a ligand of N3), but not for the N3 molecule itself. Calibrated x-ray absorption spectroscopy and valence band spectra of the monolayers reveals that the LUMO crosses the Fermi level of the surface in all cases, showing that charge transfer is energetically possible both from and to the molecule. A core-hole clock analysis of the resonant photoemission reveals a charge transfer time of around 4 fs from the LUMO of the N3 dye molecule to the surface. The lack of charge transfer in the opposite direction is understood in terms of the lack of spatial overlap between the {pi}*-orbitals in the aromatic rings of the bi-isonicotinic acid ligands of N3 and the gold surface.

  3. Bond patterns and charge-order amplitude in quarter-filled charge-transfer solids

    Science.gov (United States)

    Clay, R. T.; Ward, A. B.; Gomes, N.; Mazumdar, S.

    2017-03-01

    Most quasi-one-dimensional (quasi-1D) quarter-filled organic charge-transfer solids (CTS) with insulating ground states have two thermodynamic transitions: a high-temperature metal-insulator transition followed by a low-temperature magnetic transition. This sequence of transitions can be understood within the 1D Peierls-extended Hubbard (PEH) model. However, in some quasi-1D CTS both transitions occur simultaneously in a direct metal to spin-gapped insulator transition. In this second class of materials the organic stack bond distortion pattern does not follow the pattern of a second dimerization of a dimer lattice. These materials also display charge ordering of a large amplitude below the transition. Using quantum Monte Carlo methods we show that the same PEH model can be used to understand both classes of materials, however, within different parameter regions. We discuss the relevance of our work to experiments on several quarter-filled conductors, focusing in particular on the materials (EDO-TTF)2X and (DMEDO-TTF)2X .

  4. Identifying interfacial charge transfer states in organic heterostructures (Conference Presentation)

    Science.gov (United States)

    Arndt, Andreas P.; Gerhard, Marina; Howard, Ian A.; Koch, Martin; Lemmer, Ulrich

    2016-09-01

    Charge transfer (CT) states play evidently an important role at the interface of organic heterostructures but their identification and characterization is often experimentally less obvious and challenging. We studied two exemplary material systems which both represented a benchmark within the research of organic photovoltaics at their time: the homopolymer P3HT blended with PC61BM and the copolymer PTB7 blended with PC71BM. In both heterostructures, we could identify a distinct CT state emission by the use of NIR time-resolved photoluminescence (PL) [1], [2]. The selectivity of this technique enables us to clearly probe the energetics and dynamics of weak emitting interfacial states and therefore to prove differences in the CT state characteristics between the two systems. We went beyond this previous work and investigated the time and temperature dependent emission anisotropy as well as the electric field dependence of the time-resolved PL for both blends and the pristine polymers, respectively. In both cases the CT state emission clearly deviates from the one of the primarily excited singlet excitons: the emission anisotropy reveals an additional relaxation pathway for the exciton which is connected with a change of the transition dipole moment of the emission, and under applied bias different quenching thresholds can give access to varying binding energies of the emissive excitons involved. Finally, we think that our findings demonstrate how interfacial CT state emission can be clearly identified as such and how it can be unambiguously distinguished from singlet exciton emission.

  5. Versatile charge transfer through anthraquinone films for electrochemical sensing applications

    Energy Technology Data Exchange (ETDEWEB)

    Venarusso, Luna B. [Department of Chemistry, Universidade Federal de Mato Grosso do Sul, Caixa Postal 549, Campo Grande, MS 79070-900 (Brazil); Tammeveski, Kaido [Institute of Chemistry, University of Tartu, Ravila 14a, 50411 Tartu (Estonia); Maia, Gilberto, E-mail: gilberto.maia@ufms.br [Department of Chemistry, Universidade Federal de Mato Grosso do Sul, Caixa Postal 549, Campo Grande, MS 79070-900 (Brazil)

    2011-10-01

    Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to study the effect of anthraquinone (AQ) films on the charge transfer rate of {beta}-nicotinamide adenine dinucleotide (NAD{sup +}), dopamine (DA), and ferricyanide on glassy carbon (GC) electrodes in solutions of different pH. Maximum blocking action on the Fe(CN){sub 6}{sup 3-} redox probe was observed at pH 7 and open-circuit potential (OCP). However, maximum electron hopping effect was observed at pH 9 at both -0.58 V and -0.85 V for Fe(CN){sub 6}{sup 3-}, pH 7 at -0.58 V for NAD{sup +}, and pH 9 at -0.58 V for DA, suggesting that electron hopping in AQ films on a GC surface is dependent on both pH and electrode potential. These findings lend support for the application of these films in the detection of soluble redox probes such as NAD{sup +} and DA at biological pH values (from 7 to 9).

  6. Field collapse due to band-tail charge in amorphous silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qi; Crandall, R.S. [National Renewable Energy Lab., Golden, CO (United States); Schiff, E.A. [Syracuse Univ., NY (United States)

    1996-05-01

    It is common for the fill factor to decrease with increasing illumination intensity in hydrogenated amorphous silicon solar cells. This is especially critical for thicker solar cells, because the decrease is more severe than in thinner cells. Usually, the fill factor under uniformly absorbed red light changes much more than under strongly absorbed blue light. The cause of this is usually assumed to arise from space charge trapped in deep defect states. The authors model this behavior of solar cells using the Analysis of Microelectronic and Photonic Structures (AMPS) simulation program. The simulation shows that the decrease in fill factor is caused by photogenerated space charge trapped in the band-tail states rather than in defects. This charge screens the applied field, reducing the internal field. Owing to its lower drift mobility, the space charge due to holes exceeds that due to electrons and is the main cause of the field screening. The space charge in midgap states is small compared with that in the tails and can be ignored under normal solar-cell operating conditions. Experimentally, the authors measured the photocapacitance as a means to probe the collapsed field. They also explored the light intensity dependence of photocapacitance and explain the decrease of FF with the increasing light intensity.

  7. Quantum State Transfer between Charge and Flux Qubits in Circuit-QED

    Institute of Scientific and Technical Information of China (English)

    WU Qin-Qin; LIAO Jie-Qiao; KUANG Le-Man

    2008-01-01

    @@ We propose a scheme to implement quantum state transfer in a hybrid circuit quantum electrodynamics (QED)system which consists of a superconducting charge qubit, a flux qubit, and a transmission line resonator (TLR).It is shown that quantum state transfer between the charge qubit and the flux qubit can be realized by using the TLR as the data bus.

  8. The chemical hardness of molecules and the band gap of solids within charge equilibration formalisms. Toward force field-based simulations of redox reactions

    Science.gov (United States)

    Müser, M. H.

    2012-04-01

    This work finds that different charge equilibration methods lead to qualitatively different responses of molecules and solids to an excess charge. The investigated approaches are the regular charge equilibration (QE), the atom-atom-charge transfer (AACT), and the split-charge equilibration (SQE) method. In QE, the hardness of molecules and the band gap of solids approaches zero at large particle numbers, affirming the claim that QE induces metallic behavior. AACT suffers from producing negative values of the hardness; moreover valence and conduction bands of solids cross. In contrast to these methods, SQE can reproduce the generic behavior of dielectric molecules or solids. Moreover, first quantitative results for the NaCl molecule are promising. The results derived in this work may have beneficial implications for the modeling of redox reactions. They reveal that by introducing formal oxidation states into force field-based simulations it will become possible to simulate redox reactions including non-equilibrium contact electrification, voltage-driven charging of galvanic cells, and the formation of zwitterionic molecules.

  9. ARCHITECTURE OF A CHARGE-TRANSFER STATE REGULATING LIGHT HARVESTING IN A PLANT ANTENNA PROTEIN

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Graham; Ahn, Tae Kyu; Avenson, Thomas J.; Ballottari, Matteo; Cheng, Yuan-Chung; Niyogi, Krishna K.; Bassi, Roberto; Fleming, Graham R.

    2008-04-02

    Energy-dependent quenching of excess absorbed light energy (qE) is a vital mechanism for regulating photosynthetic light harvesting in higher plants. All of the physiological characteristics of qE have been positively correlated with charge-transfer between coupled chlorophyll and zeaxanthin molecules in the light-harvesting antenna of photosystem II (PSII). In this work, we present evidence for charge-transfer quenching in all three of the individual minor antenna complexes of PSII (CP29, CP26, and CP24), and we conclude that charge-transfer quenching in CP29 involves a de-localized state of an excitonically coupled chlorophyll dimer. We propose that reversible conformational changes in CP29 can `tune? the electronic coupling between the chlorophylls in this dimer, thereby modulating the energy of the chlorophylls-zeaxanthin charge-transfer state and switching on and off the charge-transfer quenching during qE.

  10. Architecture of a charge-transfer state regulating light harvesting in a plant antenna protein.

    Science.gov (United States)

    Ahn, Tae Kyu; Avenson, Thomas J; Ballottari, Matteo; Cheng, Yuan-Chung; Niyogi, Krishna K; Bassi, Roberto; Fleming, Graham R

    2008-05-01

    Energy-dependent quenching of excess absorbed light energy (qE) is a vital mechanism for regulating photosynthetic light harvesting in higher plants. All of the physiological characteristics of qE have been positively correlated with charge transfer between coupled chlorophyll and zeaxanthin molecules in the light-harvesting antenna of photosystem II (PSII). We found evidence for charge-transfer quenching in all three of the individual minor antenna complexes of PSII (CP29, CP26, and CP24), and we conclude that charge-transfer quenching in CP29 involves a delocalized state of an excitonically coupled chlorophyll dimer. We propose that reversible conformational changes in CP29 can "tune" the electronic coupling between the chlorophylls in this dimer, thereby modulating the energy of the chlorophyll-zeaxanthin charge-transfer state and switching on and off the charge-transfer quenching during qE.

  11. Crystal growth of new charge-transfer salts based on π-conjugated donor molecules

    Science.gov (United States)

    Morherr, Antonia; Witt, Sebastian; Chernenkaya, Alisa; Bäcker, Jan-Peter; Schönhense, Gerd; Bolte, Michael; Krellner, Cornelius

    2016-09-01

    New charge transfer crystals of π-conjugated, aromatic molecules (phenanthrene and picene) as donors were obtained by physical vapor transport. The melting behavior, optimization of crystal growth and the crystal structure are reported for charge transfer salts with (fluorinated) tetracyanoquinodimethane (TCNQ-Fx, x=0, 2, 4), which was used as acceptor material. The crystal structures were determined by single-crystal X-ray diffraction. Growth conditions for different vapor pressures in closed ampules were applied and the effect of these starting conditions for crystal size and quality is reported. The process of charge transfer was investigated by geometrical analysis of the crystal structure and by infrared spectroscopy on single crystals. With these three different acceptor strengths and the two sets of donor materials, it is possible to investigate the distribution of the charge transfer systematically. This helps to understand the charge transfer process in this class of materials with π-conjugated donor molecules.

  12. Crystal growth of new charge-transfer salts based on π-conjugated donor molecules

    Energy Technology Data Exchange (ETDEWEB)

    Morherr, Antonia, E-mail: morherr@stud.uni-frankfurt.de [Physikalisches Institut, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany); Witt, Sebastian [Physikalisches Institut, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany); Chernenkaya, Alisa [Graduate School Materials Science in Mainz, 55128 Mainz (Germany); Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz (Germany); Bäcker, Jan-Peter [Physikalisches Institut, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany); Schönhense, Gerd [Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz (Germany); Bolte, Michael [Institut für anorganische Chemie, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany); Krellner, Cornelius [Physikalisches Institut, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany)

    2016-09-01

    New charge transfer crystals of π-conjugated, aromatic molecules (phenanthrene and picene) as donors were obtained by physical vapor transport. The melting behavior, optimization of crystal growth and the crystal structure are reported for charge transfer salts with (fluorinated) tetracyanoquinodimethane (TCNQ-F{sub x}, x=0, 2, 4), which was used as acceptor material. The crystal structures were determined by single-crystal X-ray diffraction. Growth conditions for different vapor pressures in closed ampules were applied and the effect of these starting conditions for crystal size and quality is reported. The process of charge transfer was investigated by geometrical analysis of the crystal structure and by infrared spectroscopy on single crystals. With these three different acceptor strengths and the two sets of donor materials, it is possible to investigate the distribution of the charge transfer systematically. This helps to understand the charge transfer process in this class of materials with π-conjugated donor molecules.

  13. Crystal Growth of new charge-transfer salts based on $\\pi$-conjugated molecules

    CERN Document Server

    Morherr, Antonia; Chernenkaya, Alisa; Bäcker, Jan-Peter; Schönhense, Gerd; Bolte, Michael; Krellner, Cornelius

    2016-01-01

    New charge transfer crystals of $\\pi$-conjugated, aromatic molecules (phenanthrene and picene) as donors were obtained by physical vapor transport. The melting behavior, optimization of crystal growth and the crystal structure is reported for charge transfer salts with (fluorinated) tetracyanoquinodimethane (TCNQ-F$_x$, x=0, 2, 4), which was used as acceptor material. The crystal structures were determined by single-crystal X-ray diffraction. Growth conditions for different vapor pressures in closed ampules were applied and the effect of these starting conditions for crystal size and quality is reported. The process of charge transfer was investigated by geometrical analysis of the crystal structure and by infrared spectroscopy on single crystals. With these three different acceptor strengths and the two sets of donor materials, it is possible to investigate the distribution of the charge transfer systematically. This helps to understand the charge transfer process in this class of materials with $\\pi$-conjug...

  14. Charge transfer effects on the Fermi surface of Ba0.5K 0.5Fe2As2

    KAUST Repository

    Nazir, Safdar

    2011-01-31

    Ab-initio calculations within density functional theory are performed to obtain a more systematic understanding of the electronic structure of iron pnictides. As a prototypical compound we study Ba0.5K 0.5Fe2As2 and analyze the changes of its electronic structure when the interaction between the Fe2As 2 layers and their surrounding is modified. We find strong effects on the density of states near the Fermi energy as well as the Fermi surface. The role of the electron donor atoms in iron pnictides thus cannot be understood in a rigid band picture. Instead, the bonding within the Fe2As 2 layers reacts to a modified charge transfer from the donor atoms by adapting the intra-layer Fe-As hybridization and charge transfer in order to maintain an As3- valence state. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Charge transfer at organic-organic heterojunctions, and remote doping of a pentacene transistor

    Science.gov (United States)

    Zhao, Wei

    Organic-organic heterojunctions (OOHs) are the fundamental building blocks of organic devices, such as organic light-emitting diodes, organic photovoltaic cells, and photo detectors. Transport of free electrons and holes, exciton formation, recombination or dissociation, and various other physical processes all take place in OOHs. Understanding the electronic structures of OOH is critical for studying device physics and further improving the performance of organic devices. This work focuses on the electronic structure, i.e., the energy level alignment, at OOHs, investigated by ultraviolet and inverse photoemission spectroscopy (UPS and IPES). The weak interaction that generally prevails at OOH interfaces leads to small interface dipoles of 0˜0.5eV. The experimental observations on the majority of OOHs studied can be semi-quantitatively predicted by the model derived from the induced density of interface states and charge neutrality level (IDIS/CNL). However, we also find that the electronic structure of interfaces between two small-band-gap semiconductors, e.g., using copper phthalocyanine (CuPc) as the donor and a tris(thieno)-hexaazatriphenylene derivative (THAP) as the acceptor, is strongly influenced by changes in the substrate work function. In these cases, the charge transfer that takes place at the interface is governed by thermodynamic equilibrium, dominating any subtle interaction due to IDIS/CNL. The impact of doping on the energy level alignment of OOHs is also studied. The charges donated by the dopant molecules transfer from the parent doped layer to the adjacent undoped layer, taking advantage of the molecular level offset, and are then spatially separated from the dopant molecules. Remote doping, based on this charge transfer mechanism, is demonstrated with the heterojunction formed between pentacene and N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'bisphenyl-4,4'diazine (alpha-NPD) p-doped with tris[1,2-bis(trifluoromethyl) ethane-1,2-dithiolene] (Mo

  16. Self-interaction and charge transfer in organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Koerzdoerfer, Thomas

    2009-12-18

    This work concentrates on the problem of self-interaction, which is one of the most serious problems of commonly used approximative density functionals. As a major result of this work, it is demonstrated that self-interaction plays a decisive role for the performance of different approximative functionals in predicting accurate electronic properties of organic molecular semiconductors. In search for a solution to the self-interaction problem, a new concept for correcting commonly used density functionals for self-interaction is introduced and applied to a variety of systems, spanning small molecules, extended molecular chains, and organic molecular semiconductors. It is further shown that the performance of functionals that are not free from self-interaction can vary strongly for different systems and observables of interest, thus entailing the danger of misinterpretation of the results obtained from those functionals. The underlying reasons for the varying performance of commonly used density functionals are discussed thoroughly in this work. Finally, this thesis provides strategies that allow to analyze the reliability of commonly used approximations to the exchange-correlation functional for particular systems of interest. This cumulative dissertation is divided into three parts. Part I gives a short introduction into DFT and its time-dependent extension (TDDFT). Part II provides further insights into the self-interaction problem, presents a newly developed concept for the correction of self-interaction, gives an introduction into the publications, and discusses their basic results. Finally, the four publications on self-interaction and charge-transfer in extended molecular systems and organic molecular semiconductors are collected in Part III. (orig.)

  17. Active implantable medical device EMI assessment for wireless power transfer operating in LF and HF bands

    Science.gov (United States)

    Hikage, Takashi; Nojima, Toshio; Fujimoto, Hiroshi

    2016-06-01

    The electromagnetic interference (EMI) imposed on active implantable medical devices by wireless power transfer systems (WPTSs) is discussed based upon results of in vitro experiments. The purpose of this study is to present comprehensive EMI test results gathered from implantable-cardiac pacemakers and implantable cardioverter defibrillators exposed to the electromagnetic field generated by several WPTSs operating in low-frequency (70 kHz-460 kHz) and high-frequency (6.78 MHz) bands. The constructed in vitro experimental test system based upon an Irnich’s flat torso phantom was applied. EMI test experiments are conducted on 14 types of WPTSs including Qi-compliant system and EV-charging WPT system mounted on current production EVs. In addition, a numerical simulation model for active implantable medical device (AIMD) EMI estimation based on the experimental test system is newly proposed. The experimental results demonstrate the risk of WPTSs emitting intermittent signal to affect the correct behavior of AIMDs when operating at very short distances. The proposed numerical simulation model is applicable to obtain basically the EMI characteristics of various types of WPTSs.

  18. The thermochromic behavior of aromatic amine-SO2 charge transfer complexes

    Science.gov (United States)

    Monezi, Natália M.; Borin, Antonio C.; Santos, Paulo S.; Ando, Rômulo A.

    2017-02-01

    The distinct thermochromism observed in solutions containing N,N-dimethylaniline (DMA) and N,N-diethylaniline (DEA) and SO2 was investigated by resonance Raman spectroscopy in a wide range of temperatures. The results indicate in addition to the charge transfer (CT) complexes DMA-SO2 and DEA-SO2, the presence of collision complexes involving the CT complexes and excess DMA and DEA molecules. The latter in fact is the chromophore responsible for the long wavelength absorption originating the color. The Raman signature of the collision complex was attributed to the distinct enhancement of a band at 1140 cm- 1 assigned to νs(SO2), in contrast to the same mode in the 1:1 complex at 1115 cm- 1. The intensity of such band, assigned to the collision complex is favored at high temperatures and depends on the steric hindrance associated to amines, as well as the SO2 molar fraction. Quantum chemical calculations based on time-dependent density functional theory (TDDFT) support the proposed interpretation.

  19. Formation of Nanoscale Composites of Compound Semiconductors Driven by Charge Transfer.

    Science.gov (United States)

    Gao, Weiwei; Dos Reis, Roberto; Schelhas, Laura T; Pool, Vanessa L; Toney, Michael F; Yu, Kin Man; Walukiewicz, Wladek

    2016-08-10

    Composites are a class of materials that are formed by mixing two or more components. These materials often have new functional properties compared to their constituent materials. Traditionally composites are formed by self-assembly due to structural dissimilarities or by engineering different layers or structures in the material. Here we report the synthesis of a uniform and stoichiometric composite of CdO and SnTe with a novel nanocomposite structure stabilized by the dissimilarity of the electronic band structure of the constituent materials. The composite has interesting electronic properties which range from highly n-type in CdO to semi-insulating in the intermediate composition range to highly p-type in SnTe. This can be explained by the overlap of the conduction and valence band of the constituent compounds. Ultimately, our work identifies a new class of composite semiconductors in which nanoscale self-organization is driven and stabilized by charge transfer between constituent materials.

  20. The intermolecular charge transfer integral as an indicator of future success in organic photovoltaics (Conference Presentation)

    Science.gov (United States)

    Collison, Christopher J.; Zheng, Chenyu; Hestand, Nicholas J.; Jalan, Ishita; Cody, Jeremy A.; Spano, Frank C.

    2016-09-01

    In recent years, higher power conversion efficiencies have been measured using "push-pull" or Donor-Acceptor (D-A) type compounds designed to specifically address bandgap and energy level requirements. Yet, a strong prescription is fundamentally lacking that improves materials for the set of all critical properties (including exciton diffusion rate and charge transport/ mobility) that combine to provide optimal performance. We will present our newest theoretical models that simulate the morphology-based spectroscopy for a series of squaraines, compounds representative of the total set of D-A type OPV-targets. The theory will describe how morphological and molecular structure influences i) the absorption spectrum, ii) the excited states and iii) the intermolecular charge transfer integral (ICTI). In particular, the ICTI's role in exciton diffusion and carrier mobility will be explored. Using device data that correlates with the ICTI variation, we will explain how this parameter must be considered in future design of new easily-purified, consistently processable, low-band-gap small molecules targeted for large scale OPV manufacture.

  1. Engineering Interfacial Charge Transfer in CsPbBr3 Perovskite Nanocrystals by Heterovalent Doping

    KAUST Repository

    Begum, Raihana

    2016-12-17

    Since compelling device efficiencies of perovskite solar cells have been achieved, investigative efforts have turned to understand other key challenges in these systems, such as engineering interfacial energy-level alignment and charge transfer (CT). However, these types of studies on perovskite thin-film devices are impeded by the morphological and compositional heterogeneity of the films and their ill-defined surfaces. Here, we use well-defined ligand-protected perovskite nanocrystals (NCs) as model systems to elucidate the role of heterovalent doping on charge-carrier dynamics and energy level alignment at the interface of perovskite NCs with molecular acceptors. More specifically, we develop an in situ doping approach for colloidal CsPbBr3 perovskite NCs with heterovalent Bi3+ ions by hot injection to precisely tune their band structure and excited-state dynamics. This synthetic method allowed us to map the impact of doping on CT from the NCs to different molecular acceptors. Using time-resolved spectroscopy with broadband capability, we clearly demonstrate that CT at the interface of NCs can be tuned and promoted by metal ion doping. We found that doping increases the energy difference between states of the molecular acceptor and the donor moieties, subsequently facilitating the interfacial CT process. This work highlights the key variable components not only for promoting interfacial CT in perovskites, but also for establishing a higher degree of precision and control over the surface and the interface of perovskite molecular acceptors.

  2. Fundamental studies of interfacial excited-state charge transfer in molecularly tethered semiconductor nanoassemblies

    Science.gov (United States)

    Youker, Diane Greer

    The research presented in this dissertation focuses on elucidating the parameters affecting dynamics and yield of electron transfer reactions in semiconducting nanoparticle assemblies through the use of time-resolved spectroscopy. In particular, the dissertation focuses on photoinduced electron injection in assemblies of CdSe, CdS, or PbS quantum dots covalently bound to either metal oxide films or each other through the use of bifunctional molecular linkers. Chapter 2 elucidates the influence of electronic coupling on excited-state electron transfer from CdS quantum dots to TiO2 nanoparticles via molecular linkers with phenylene bridges. We establish that the efficiency of electron injection from CdS quantum dots to TiO2 nanoparticle varies dramatically with electronic coupling, which can be controlled by tuning the properties of molecular linkers. Chapter 3 presents the role of excitation energy on interfacial electron transfer in tethered assemblies of CdSe quantum dots and TiO2 nanoparticles. Through this work, we determined that injection efficiency from band-edge states is independent of excitation energy. However, the efficiency of injection from trap-states decreases at lower-energy excitation. We attribute the decrease to a lower energy distribution of emissive trap-states from which injection is less efficient. Chapter 4 presents the observation of multiphasic electron injection dynamics from photoexcited PbS quantum dots to TiO2 nanoparticles. In this collaborative study with Dr. Masumoto from the University of Tsukuba we observed electron injection on multiple timescales. We determined that electron injection occurred in this system through two different mechanisms. The first involved injection from thermalized PbS excited states and the second through injection of hot electrons through Auger recombination of biexcitons that creates high lying excitonic states. Chapter 5 investigates charge transfer in covalently bound quantum dot assemblies. We utilize

  3. CHARGE-TRANSFER AND ENERGY-TRANSFER IN THE PHOTO-INDUCED COPOLYMERIZATION OF 2-VINYLNAPHTHALENE WITH MALEIC ANHYDRIDE

    Institute of Scientific and Technical Information of China (English)

    LI Tong; LUO Bin; LI Shanjun; CHU Guobei

    1990-01-01

    The initiation mechanism of the copolymerization of 2-vinylnaphthalene with maleic anhydride was studied under irradiation of 365 nm. The excited complex was formed from ( 1 ) the local excitation of 2-vinylnaphthalene followed by the charge-transfer interaction with maleic anhydride and ( 2 ) the excitation of the ground state charge-transfer complex, and then it collapsed to 1,4-tetramethylene biradical for initiation. A 1:1 alternating copolymer was formed in different monomer feeds. Addition of benzophenone could greatly enhance the rate of copolymerization through energy-transfer mechanism.

  4. Computational Confirmation of the Carrier for the "XCN" Interstellar Ice Bank: OCN(-) Charge Transfer Complexes

    Science.gov (United States)

    Park, J.-Y.; Woon, D. E.

    2004-01-01

    Recent experimental studies provide evidence that carrier for the so-called XCN feature at 2165 cm(exp -1) (4.62 micron) in young stellar objects is an OCN(-)/NH4(+) charge transfer (CT) complex that forms in energetically processed interstellar icy grain mantles. Although other RCN nitriles and RCN iosonitriles have been considered, Greenberg's conjecture that OCN(-) is associated with the XCN feature has persisted for over 15 years. In this work we report a computational investigation that thoroughly confirms the hypothesis that the XCN feature observed in laboratory studies can result from OCN(-)/NH4(+) CT complexes arising from HNCO and NH3, in a water ice environment. Density functional theory calculations with theory calculations with HNCO, NH3, and up to 12 waters reproduce seven spectroscopic measurements associated with XCN: the band origin of the asymmetric stretching mode of OCN(-), shifts due to isotopic substitutions of C, N, O, and H, and two weak features. However, very similar values are also found for the OCN(-)/NH4(+) CT complex arising from HOCN and NH3. In both cases, the complex forms by barrierless proton transfer from HNCO or HOCN to NH3 during the optimization of the solvated system. Scaled B3LYP/6-31+G** harmonic frequencies for HNCO and HOCN cases are 2181 and 2202 cm(exp -1), respectively.

  5. Thickness dependent charge transfer states and dark carriers density in vacuum deposited small molecule organic photocell

    Science.gov (United States)

    Shekhar, Himanshu; Tzabari, Lior; Solomeshch, Olga; Tessler, Nir

    2016-10-01

    We have investigated the influence of the active layer thickness on the balance of the internal mechanisms affecting the efficiency of copper phthalocyanine - fullerene (C60) based vacuum deposited bulk heterojunction organic photocell. We fabricated a range of devices for which we varied the thickness of the active layer from 40 to 120 nm and assessed their performance using optical and electrical characterization techniques. As reported previously for phthalocyanine:C60, the performance of the device is highly dependent on the active layer thickness and of all the thicknesses we tried, the 40 nm thin active layer device showed the best solar cell characteristic parameters. Using the transfer matrix based optical model, which includes interference effects, we calculated the optical power absorbed in the active layers for the entire absorption band, and we found that this cannot explain the trend with thickness. Measurement of the cell quantum efficiency as a function of light intensity showed that the relative weight of the device internal processes changes when going from 40 nm to 120 nm thick active layer. Electrical modeling of the device, which takes different internal processes into account, allowed to quantify the changes in the processes affecting the generation - recombination balance. Sub gap external quantum efficiency and morphological analysis of the surface of the films agree with the model's result. We found that as the thickness grows the density of charge transfer states and of dark carriers goes up and the uniformity in the vertical direction is reduced.

  6. Cost-Effectiveness Comparison of Coupler Designs of Wireless Power Transfer for Electric Vehicle Dynamic Charging

    Directory of Open Access Journals (Sweden)

    Weitong Chen

    2016-11-01

    Full Text Available This paper presents a cost-effectiveness comparison of coupler designs for wireless power transfer (WPT, meant for electric vehicle (EV dynamic charging. The design comparison of three common types of couplers is first based on the raw material cost, output power, transfer efficiency, tolerance of horizontal offset, and flux density. Then, the optimal cost-effectiveness combination is selected for EV dynamic charging. The corresponding performances of the proposed charging system are compared and analyzed by both simulation and experimentation. The results verify the validity of the proposed dynamic charging system for EVs.

  7. Direct electrochemical detection of PCR product based on charge transfer through DNA

    Institute of Scientific and Technical Information of China (English)

    ZHAO Hongtao; ZHANG Zhijie; JU Huangxian

    2005-01-01

    @@ Human genome project and genetic identification for inherited diseases will definitely have a profound impact on the diagnosis of diseases[1], which calls for rapid and accurate assays of DNA. Among different types of sensors, electrochemical DNA biosensors offer a promising alternative means[2,3]. Recent efforts to elucidate the mechanism of charge transfer in DNA have demonstrated that the charge transfer is sensitive to the perturbation in base stack[4,5]. Long-range charge transfer in DNA therefore has been showing great potential application in the development of DNA-based biosensors, especially in the study of single nucleotide polymorphs[7―10].

  8. Molecular Dynamics Simulation on Charge Transfer Relaxation between Myoglobin and Water

    Institute of Scientific and Technical Information of China (English)

    CHENG Wei; ZHANG Feng-Shou; ZHANG Bo-Yang; ZHOU Hong-Yu

    2007-01-01

    Dynamical processes of myoglobin after photon-excited charge transfer between Fe ion and surrounding water anion ale simulated by a molecular dynamics model.The roles of Coulomb interaction effect and water effect in the relaxation process are discussed.It is found that the relaxations before and after charge transfer are similar.Strong Coulomb interactions and less water mobility decrease Coulomb energy fluctuations.An extra transferred charge of Fe ion has impact on water packing with a distance up to 0.86nm.

  9. Photoinduced intramolecular charge-transfer reactions in 4-amino-3-methyl benzoic acid methyl ester: A fluorescence study in condensedphase and jet-cooled molecular beams

    Indian Academy of Sciences (India)

    Amrita Chakraborty; Samiran Kar; D N Nath; Nikhil Guchhait

    2007-03-01

    Photoinduced intramolecular charge-transfer reactions in 4-amino-3-methyl benzoic acid methyl ester (AMBME) have been investigated spectroscopically. AMBME, with its weak charge donor primary amino group, shows dual emission in polar solvents. Absorption and emission measurements in the condensed phase support the premise that the short wavelength emission band corresponds to local emission and the long wavelength emission band to the charge transfer emission. Laser-induced fluorescence excitation spectra show the presence of two low-energy conformers in jet-cooled molecular beams. Theoretical calculations using density functional theory help to determine structure, vibrational modes, potential energy surface, transition energy and oscillator strength for correlating experimental findings with theoretical results.

  10. Theoretical description of photo-doping in Mott and charge-transfer insulators

    Science.gov (United States)

    Eckstein, Martin

    2012-02-01

    Many aspects of photo-excited insulator-to-metal transitions in Mott and charge-transfer systems are theoretically not well understood: How is the photo-doped state related to a chemically doped state? On what timescale do we expect the formation of quasiparticles? To describe the electronic dynamics of Mott insulators, we have used nonequilibrium dynamical mean-field theory (DMFT) in combination with Quantum Monte Carlo and various weak and strong-coupling [1] techniques. In the talk, I will briefly present the current status of this approach and of related cluster approaches for nonequilibrium. I will then discuss results for the photo-doping in the Hubbard model, and in a in a p-d model for charge-transfer insulators. When the onsite Coulomb repulsion U is much larger than the hopping, rapid thermalization of the pump-excited Mott insulator is inhibited by the energetic stabilization of doublon-hole pairs [2], and various types of non-thermal states can arise. Immediately after the excitation process, the system of doublons and holes is too hot to form quasiparticle states, but coupling to a heat-bath of phonons can drive the system into a metallic state with well developed doublon and hole bands. Close to the metal-insulator transition, on the other hand, when U is of the order as the hopping, doublons and holes rapidly thermalize due to the electron-electron interaction, which makes the system a bad metal rather than a Fermi liquid. [4pt] [1] M. Eckstein and Ph. Werner, Phys. Rev. B 82, 115115 (2010).[0pt] [2] M. Eckstein and Ph. Werner, Phys. Rev. B 84, 035122 (2011).

  11. Photoinduced intramolecular charge transfer of sodium 4-(N,N-dimethylamino)benzenesulfonate

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new dual fluorescent N,N-dimethylaniline derivative, sodium 4-(N,N-dimethylamino)- benzenesulfonate (SDMAS), is reported. In SDMAS, the electron acceptor is linked to the phenyl ring via a sulfur atom at the para-position of the electron donor. It was found that SDMAS emits dual fluorescence only in highly polar solvent water but not in organic solvents such as formamide, methanol and acetonitrile. In organic solvents only a single-band emission at ca.360 nm was observed in the short wavelength region. The dual fluorescence of SDMAS in water was found at 365 and 475 nm, respectively. Introduction of organic solvent such as ethanol, acetonitrile, and 1,4-dioxane into aqueous solution of SDMAS leads to blue-shift and quenching of the long-wavelength emission. Measurements of steady-state and picosecond time-resolved fluorescence indicate that the long wavelength fluorescence is emitted from a charge transfer (CT) state that is populated from the locally excited (LE) state, with the latter giving off the short wavelength fluorescence. The fact that a highly polar solvent is required to bring out the dual fluorescence suggests that the CT process of SDMAS has a high activation energy (Ea). In supporting this assumption the time-resolved fluorescence measurements give an Ea of 15.35 kJ.mol-1. It was assumed that the participation of the sulfur atom d-orbital in the conjugation of sulfonate group with phenyl ring and the strong twisting and inverting of the dimethylamino plane relative to the phenyl ring could be the reasons for the high activation energy. A molecular configuration change upon charge transfer in water was suggested for SDMAS based on the thermodynamic data. SDMAS reported here represents the example of the dual fluorescent amine substituted aromatic sulfonate.

  12. Proton-transfer mediated quenching of pyrene/indole charge-transfer states in isooctane solutions.

    Science.gov (United States)

    Altamirano, Marcela S; Bohorquez, María del Valle; Previtali, Carlos M; Chesta, Carlos A

    2008-01-31

    The fluorescence quenching of pyrene (Py) by a series of N-methyl and N-H substituted indoles was studied in isooctane at 298 K. The fluorescence quenching rate constants were evaluated by mean of steady-state and time-resolved measurements. In all cases, the quenching process involves a charge-transfer (CT) mechanism. The I(o)/I and tau(o)/tau Stern-Volmer plots obtained for the N-H indoles show a very unusual upward deviation with increasing concentration of the quenchers. This behavior is attributed to the self-quenching of the CT intermediates by the free indoles in solution. The efficiency of quenching of the polyaromatic by the N-H indoles increases abruptly in the presence of small amount of added pyridine (or propanol). A detailed analysis of the experimental data obtained in the presence of pyridine provides unambiguous evidence that the self-quenching process involves proton transfer from the CT states to indoles.

  13. Charge transfer at F{sub 16}CoPc and CoPc interfaces to Au

    Energy Technology Data Exchange (ETDEWEB)

    Lindner, Susi; Treske, Uwe; Grobosch, Mandy; Knupfer, Martin [IFW Dresden (Germany)

    2011-12-15

    We analyze the electronic properties of the interfaces between cobalt phthalocyanine (CoPc), as well as fluorinated cobalt phthalocyanine (F{sub 16}CoPc), and an Au(100) single-crystal using X-ray photoemission spectroscopy and valence band ultraviolet photoemission spectroscopy. Our data demonstrate that for the monolayers of both materials a charge transfer occurs from the substrate to the center of the organic molecules resulting in a central Co(I) ion. This leads to the conclusion that this effect essentially is fluorination- and ligand-independent. (orig.)

  14. Ultrafast twisting motions and intramolecular charge-transfer reaction in a cyanine dye trapped in molecular nanocavities

    Science.gov (United States)

    Fayed, T. A.; Organero, J. A.; Garcia-Ochoa, I.; Tormo, L.; Douhal, A.

    2002-09-01

    Emission properties of the cyanine dye, 1-(2-naphthyl)-2-ethenyl-(2-benzothiazolium) iodide, in aqueous nanocavities offered by cyclodextrins and in a film of a polymeric matrix were studied by means of steady-state and picosecond time-resolved emission spectroscopy. The results show the occurrence of a fast twisting motion and a subsequent intramolecular charge-transfer reaction. The initial step can be prevented by the size of the nanocavity which governs the spectral position of the fluorescence band and lifetime of the excited encapsulated host.

  15. Study on band gap structure of Fibonacci quantum superlattices by using the transfer matrix method

    Science.gov (United States)

    Ferrando, V.; Castro-Palacio, J. C.; Marí, B.; Monsoriu, J. A.

    2014-02-01

    The scattering properties of particles in a one-dimensional Fibonacci sequence based potential have been analyzed by means of the Transfer Matrix Method. The electronic band gaps are examined comparatively with those obtained using the corresponding periodic potentials. The reflection coefficient shows self-similar properties for the Fibonacci superlattices. Moreover, by using the generalized Bragg's condition, the band gaps positions are derived from the golden mean involved in the design of the superlattice structure.

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

    Indian Academy of Sciences (India)

    K Senthil Kumar; Archita Patnaik

    2013-03-01

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

  17. Topological effects of charge transfer in telomere G-quadruplex: Mechanism on telomerase activation and inhibition

    CERN Document Server

    Wang, Xin

    2015-01-01

    We explore charge transfer in the telomere G-Quadruplex (TG4) DNA theoretically by the nonequilibrium Green's function method, and reveal the topological effect of charge transport in TG4 DNA. The consecutive TG4(CTG4) is semiconducting with 0.2 ~ 0.3eV energy gap. Charges transfers favorably in the consecutive TG4, but are trapped in the non-consecutive TG4 (NCTG4). The global conductance is inversely proportional to the local conductance for NCTG4. The topological structure transition from NCTG4 to CTG4 induces abruptly ~ 3nA charge current, which provide a microscopic clue to understand the telomerase activated or inhibited by TG4. Our findings reveal the fundamental property of charge transfer in TG4 and its relationship with the topological structure of TG4.

  18. Topological Effects of Charge Transfer in Telomere G-Quadruplex Mechanism on Telomerase Activation and Inhibition

    Science.gov (United States)

    Wang, Xin; Liang, Shi-Dong

    2013-02-01

    We explore the charge transfer in the telomere G-Quadruplex (TG4) DNA theoretically by the nonequilibrium Green's function method, and reveal the topological effect of the charge transport in TG4 DNA. The consecutive TG4 (CTG4) is semiconducting with 0.2 0.3 eV energy gap. Charges transfer favorably in the CTG4, but are trapped in the nonconsecutive TG4 (NCTG4). The global conductance is inversely proportional to the local conductance for NCTG4. The topological structure transition from NCTG4 to CTG4 induces abruptly 3nA charge current, which provide a microscopic clue to understand the telomerase activated or inhibited by TG4. Our findings reveal the fundamental property of charge transfer in TG4 and its relationship with the topological structure of TG4.

  19. Modeling noncovalent radical-molecule interactions using conventional density-functional theory: beware erroneous charge transfer.

    Science.gov (United States)

    Johnson, Erin R; Salamone, Michela; Bietti, Massimo; DiLabio, Gino A

    2013-02-07

    Conventional density-functional theory (DFT) has the potential to overbind radical-molecule complexes because of erroneous charge transfer. We examined this behavior by exploring the ability of various DFT approximations to predict fractional charge transfer and by quantifying the overbinding in a series of complexes. It is demonstrated that too much charge is transferred from molecules to radicals when the radical singly unoccupied molecular orbitals are predicted to be erroneously too low in energy relative to the molecule highest occupied molecular orbitals, leading to excessive Coulombic attraction. In this respect, DFT methods formulated with little or no Hartree-Fock exchange perform most poorly. The present results illustrate that the charge-transfer problem is much broader than may have been previously expected and is not limited to conventional (i.e., molecule-molecule) donor-acceptor complexes.

  20. Charge transfer between sensing and targeted metal nanoparticles in indirect nanoplasmonic sensors

    Science.gov (United States)

    Zhdanov, Vladimir P.; Langhammer, Christoph

    2017-03-01

    In indirect nanoplasmonic sensors, the plasmonic metal nanoparticles are adjacent to the material of interest, and the material-related changes of their optical properties are used to probe that material. If the latter itself represents another metal in the form of nanoparticles, its deposition is accompanied by charge transfer to or from the plasmonic nanoparticles in order to equalize the Fermi levels. We estimate the value of the transferred charge and show on the two examples, nanoparticle sintering and hydride formation, that the charge transfer has negligible influence on the probed processes, because the effect of charge transfer is less important than that of nanoparticle surface energy. This further corroborates the non-invasive nature of nanoplasmonic sensors.

  1. Charge transfer polarisation wave and carrier pairing in the high T(sub c) copper oxides

    Science.gov (United States)

    Chakraverty, B. K.

    1990-01-01

    The High T(sub c) oxides are highly polarizable materials and are charge transfer insulators. The charge transfer polarization wave formalism is developed in these oxides. The dispersion relationships due to long range dipole-dipole interaction of a charge transfer dipole lattice are obtained in 3-D and 2-D. These are high frequency bosons and their coupling with carriers is weak and antiadiabatic in nature. As a result, the mass renormalization of the carriers is negligible in complete contrast to conventional electron-phonon interaction, that give polarons and bipolarons. Both bound and superconducting pairing is discussed for a model Hamiltonian valid in the antiadiabatic regime, both in 3-D and 2-D. The stability of the charge transfer dipole lattice has interesting consequences that are discussed.

  2. Electronic and Nuclear Factors in Charge and Excitation Transfer

    Energy Technology Data Exchange (ETDEWEB)

    Piotr Piotrowiak

    2004-09-28

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

  3. Molecular Structures and Momentum Transfer Cross Sections: The Influence of the Analyte Charge Distribution

    Science.gov (United States)

    Young, Meggie N.; Bleiholder, Christian

    2017-03-01

    Structure elucidation by ion mobility spectrometry-mass spectrometry methods is based on the comparison of an experimentally measured momentum transfer cross-section to cross-sections calculated for model structures. Thus, it is imperative that the calculated cross-section must be accurate. However, it is not fully understood how important it is to accurately model the charge distribution of an analyte ion when calculating momentum transfer cross-sections. Here, we calculate and compare momentum transfer cross-sections for carbon clusters that differ in mass, charge state, and mode of charge distribution, and vary temperature and polarizability of the buffer gas. Our data indicate that the detailed distribution of the ion charge density is intimately linked to the contribution of glancing collisions to the momentum transfer cross-section. The data suggest that analyte ions with molecular mass 3 kDa or momentum transfer cross-section 400-500 Å2 would be significantly influenced by the charge distribution in nitrogen buffer gas. Our data further suggest that accurate structure elucidation on the basis of IMS-MS data measured in nitrogen buffer gas must account for the molecular charge distribution even for systems as large as C960 ( 12 kDa) when localized charges are present and/or measurements are conducted under cryogenic temperatures. Finally, our data underscore that accurate structure elucidation is unlikely if ion mobility data recorded in one buffer gas is converted into other buffer gases when electronic properties of the buffer gases differ.

  4. Spectroscopy of equilibrium and nonequilibrium charge transfer in semiconductor quantum structures

    Science.gov (United States)

    Rössler, C.; Burkhard, S.; Krähenmann, T.; Röösli, M.; Märki, P.; Basset, J.; Ihn, T.; Ensslin, K.; Reichl, C.; Wegscheider, W.

    2014-08-01

    We investigate equilibrium and nonequilibrium charge-transfer processes by performing high-resolution transport spectroscopy. Using electrostatically defined quantum dots for energy-selective emission and detection, we achieved very high spectral resolution and a high degree of tunability of relevant experimental parameters. Most importantly, we observe that the spectral width of elastically transferred electrons can be substantially smaller than the linewidth of a thermally broadened Coulomb peak. This finding indicates that the charge-transfer process is fast compared to the electron-phonon interaction time. By drawing an analogy to double quantum dots, we argue that the spectral width of the elastic resonance is determined by the lifetime broadening hΓ of the emitter and detector states. Good agreement with the model is found also in an experiment in which the charge transfer is in the regime hΓ≫kBT. By performing spectroscopy below the Fermi energy, we furthermore observe elastic and inelastic transfer of holes.

  5. Optical studies of the charge transfer complex in polythiophene/fullerene blends for organic photovoltaic applications

    Science.gov (United States)

    Drori, T.; Holt, J.; Vardeny, Z. V.

    2010-08-01

    We studied the photophysics of regioregular polythiophene/ C61 (RR-P3HT/PCBM) blend films utilized for organic photovoltaic applications using the femtosecond transient and steady-state photomodulation techniques with above-gap and below-gap pump excitations and electroabsorption spectroscopy. We provide strong evidence for the existence of charge transfer complex (CTC) state in the blend that is formed deep inside the optical gap of the polymer and fullerene constituents, which is clearly revealed in the electroabsorption spectrum with an onset at 1.2 eV. We identify this “midgap” band as the lowest lying CTC state formed at the interfaces separating the polymer and fullerene phases. With above-gap pump excitation the primary photoexcitations in the blend are excitons and polarons in the polymer domains that are generated within the experimental time resolution (150 fs), having distinguishable photoinduced absorption (PA) bands in the mid-IR. The photogenerated excitons subsequently decay within ˜10ps , consistent with the polymer weak photoluminescence in the blend. In contrast, with below-gap pump excitation, a new PA band in the mid-IR is generated within our time resolution, which is associated with photogenerated species that decay into polarons at much later times; also no PA of excitons is observed. We interpret the photoexcitations as CT excitons, which with below-gap pump excitation are resonantly generated on the CTC states at the interfaces, as the first step for polaron generation, without involving intrachain excitons in the polymer phase. We found that the polarons generated with below-gap pump excitation are trapped at the interfaces with relatively long lifetime, and thus may generate polarons on the polymer chains and fullerene molecules with a different mechanism than with above-gap excitation. In any case the interfacial polarons generated with below-gap excitation do not substantially contribute to the photocurrent density in photovoltaic

  6. Theoretical Study of the Charge-Transfer State Separation within Marcus Theory

    DEFF Research Database (Denmark)

    Volpi, Riccardo; Nassau, Racine; Nørby, Morten Steen

    2016-01-01

    We study, within Marcus theory, the possibility of the charge-transfer (CT) state splitting at organic interfaces and a subsequent transport of the free charge carriers to the electrodes. As a case study we analyze model anthracene-C60 interfaces. Kinetic Monte Carlo (KMC) simulations on the cold...

  7. Deep-hole transfer leads to ultrafast charge migration in DNA hairpins

    Science.gov (United States)

    Renaud, Nicolas; Harris, Michelle A.; Singh, Arunoday P. N.; Berlin, Yuri A.; Ratner, Mark A.; Wasielewski, Michael R.; Lewis, Frederick D.; Grozema, Ferdinand C.

    2016-11-01

    Charge transport through the DNA double helix is of fundamental interest in chemistry and biochemistry, but also has potential technological applications such as for DNA-based nanoelectronics. For the latter, it is of considerable interest to explore ways to influence or enhance charge transfer. In this Article we demonstrate a new mechanism for DNA charge transport, namely ‘deep-hole transfer’, which involves long-range migration of a hole through low-lying electronic states of the nucleobases. Here, we demonstrate, in a combined experimental and theoretical study, that it is possible to achieve such transfer behaviour by changing the energetics of charge injection. This mechanism leads to an enhancement in transfer rates by up to two orders of magnitude and much weaker distance dependence. This transfer is faster than relaxation to the lowest-energy state, setting this mechanism apart from those previously described. This opens up a new direction to optimize charge transfer in DNA with unprecedented charge-transfer rates.

  8. Probing charge transfer and hot carrier dynamics in organic solar cells with terahertz spectroscopy

    Science.gov (United States)

    Cunningham, Paul D.; Lane, Paul A.; Melinger, Joseph S.; Esenturk, Okan; Heilweil, Edwin J.

    2016-04-01

    Time-resolved terahertz spectroscopy (TRTS) was used to explore charge generation, transfer, and the role of hot carriers in organic solar cell materials. Two model molecular photovoltaic systems were investigated: with zinc phthalocyanine (ZnPc) or alpha-sexathiophene (α-6T) as the electron donors and buckminsterfullerene (C60) as the electron acceptor. TRTS provides charge carrier conductivity dynamics comprised of changes in both population and mobility. By using time-resolved optical spectroscopy in conjunction with TRTS, these two contributions can be disentangled. The sub-picosecond photo-induced conductivity decay dynamics of C60 were revealed to be caused by auto-ionization: the intrinsic process by which charge is generated in molecular solids. In donor-acceptor blends, the long-lived photo-induced conductivity is used for weight fraction optimization of the constituents. In nanoscale multilayer films, the photo-induced conductivity identifies optimal layer thicknesses. In films of ZnPc/C60, electron transfer from ZnPc yields hot charges that localize and become less mobile as they thermalize. Excitation of high-lying Franck Condon states in C60 followed by hole-transfer to ZnPc similarly produces hot charge carriers that self-localize; charge transfer clearly precedes carrier cooling. This picture is contrasted to charge transfer in α-6T/C60, where hole transfer takes place from a thermalized state and produces equilibrium carriers that do not show characteristic signs of cooling and self-localization. These results illustrate the value of terahertz spectroscopic methods for probing charge transfer reactions.

  9. A Large-Area Transferable Wide Band Gap 2D Silicon Dioxide Layer.

    Science.gov (United States)

    Büchner, Christin; Wang, Zhu-Jun; Burson, Kristen M; Willinger, Marc-Georg; Heyde, Markus; Schlögl, Robert; Freund, Hans-Joachim

    2016-08-23

    An atomically smooth silica bilayer is transferred from the growth substrate to a new support via mechanical exfoliation at millimeter scale. The atomic structure and morphology are maintained perfectly throughout the process. A simple heating treatment results in complete removal of the transfer medium. Low-energy electron diffraction, Auger electron spectroscopy, scanning tunneling microscopy, and environmental scanning electron microscopy show the success of the transfer steps. Excellent chemical and thermal stability result from the absence of dangling bonds in the film structure. By adding this wide band gap oxide to the toolbox of 2D materials, possibilities for van der Waals heterostructures will be broadened significantly.

  10. [Combined hopping-superexchange mechanism of charge transfer in DNA; a model with nearest interactions].

    Science.gov (United States)

    Lakhno, V D; Sultanov, V B

    2007-01-01

    In the framework of the earlier developed combined hopping-superexchange mechanism of charge transfer in DNA, a model with all nearest interactions between nucleobases is proposed. It is shown that the transfer rates for various types of nucleotide sequences calculated within this model are in a good agreement with experimental data.

  11. Simplified charge transfer inefficiency correction in CCDs by trap-pumping

    Science.gov (United States)

    Gow, Jason P. D.; Murray, Neil J.

    2016-08-01

    A major concern when using Charge-Coupled Devices in hostile radiation environments is radiation induced Charge Transfer Inefficiency. The displacement damage from non-ionising radiation incident on the detector creates defects within the silicon lattice, these defects can capture and hold charge for a period of time dependent on the operating temperature and the type of defect, or "trap species". The location and type of defect can be determined to a high degree of precision using the trap-pumping technique, whereby background charges are input and then shuffled forwards and backwards between pixels many times and repeated using different transfer timings to promote resonant charge-pumping at particular defect sites. Where the charge transfer timings used in the trap-pumping process are equivalent to the nominal CCD readout modes, a simple "trap-map" of the defects that will most likely contribute to charge transfer inefficiency in the CCD array can be quickly generated. This paper describes a concept for how such a "trap-map" can be used to correct images subject to non-ionising radiation damage and provides initial results from an analytical algorithm and our recommendations for future developments.

  12. Integer Charge Transfer and Hybridization at an Organic Semiconductor/Conductive Oxide Interface

    KAUST Repository

    Gruenewald, Marco

    2015-02-11

    We investigate the prototypical hybrid interface formed between PTCDA and conductive n-doped ZnO films by means of complementary optical and electronic spectroscopic techniques. We demonstrate that shallow donors in the vicinity of the ZnO surface cause an integer charge transfer to PTCDA, which is clearly restricted to the first monolayer. By means of DFT calculations, we show that the experimental signatures of the anionic PTCDA species can be understood in terms of strong hybridization with localized states (the shallow donors) in the substrate and charge back-donation, resulting in an effectively integer charge transfer across the interface. Charge transfer is thus not merely a question of locating the Fermi level above the PTCDA electron-transport level but requires rather an atomistic understanding of the interfacial interactions. The study reveals that defect sites and dopants can have a significant influence on the specifics of interfacial coupling and thus on carrier injection or extraction.

  13. Single and double charge transfer of He(2+) ions with molecules at near-thermal energies

    Science.gov (United States)

    Tosh, R. E.; Johnsen, R.

    1993-01-01

    Rate coefficients were measured for charge-transfer reactions of He(2+) ions with H2, N2, O2, CO, CO2, and H2O. The experiments were carried out using a selected-ion drift-tube mass spectrometer. Total rate coefficients are found to be very large and are generally close to the limiting Langevin capture rate coefficients or the corresponding ADO-model (Su and Bowers, 1973) coefficients. The product-ion spectra indicate that both single and double charge transfer and possibly transfer ionization occur in these reactions.

  14. Controllable Quantum State Transfer Between a Josephson Charge Qubit and an Electronic Spin Ensemble

    Science.gov (United States)

    Yan, Run-Ying; Wang, Hong-Ling; Feng, Zhi-Bo

    2016-01-01

    We propose a theoretical scheme to implement controllable quantum state transfer between a superconducting charge qubit and an electronic spin ensemble of nitrogen-vacancy centers. By an electro-mechanical resonator acting as a quantum data bus, an effective interaction between the charge qubit and the spin ensemble can be achieved in the dispersive regime, by which state transfers are switchable due to the adjustable electrical coupling. With the accessible experimental parameters, we further numerically analyze the feasibility and robustness. The present scheme could provide a potential approach for transferring quantum states controllably with the hybrid system.

  15. Geometry and quadratic nonlinearity of charge transfer complexes in solution: a theoretical study.

    Science.gov (United States)

    Mukhopadhyay, S; Pandey, Ravindra; Das, Puspendu K; Ramasesha, S

    2011-01-28

    In this paper, we have computed the quadratic nonlinear optical (NLO) properties of a class of weak charge transfer (CT) complexes. These weak complexes are formed when the methyl substituted benzenes (donors) are added to strong acceptors like chloranil (CHL) or di-chloro-di-cyano benzoquinone (DDQ) in chloroform or in dichloromethane. The formation of such complexes is manifested by the presence of a broad absorption maximum in the visible range of the spectrum where neither the donor nor the acceptor absorbs. The appearance of this visible band is due to CT interactions, which result in strong NLO responses. We have employed the semiempirical intermediate neglect of differential overlap (INDO∕S) Hamiltonian to calculate the energy levels of these CT complexes using single and double configuration interaction (SDCI). The solvent effects are taken into account by using the self-consistent reaction field (SCRF) scheme. The geometry of the complex is obtained by exploring different relative molecular geometries by rotating the acceptor with respect to the fixed donor about three different axes. The theoretical geometry that best fits the experimental energy gaps, β(HRS) and macroscopic depolarization ratios is taken to be the most probable geometry of the complex. Our studies show that the most probable geometry of these complexes in solution is the parallel displaced structure with a significant twist in some cases.

  16. Probing of Charge Transfer States at Buried Organic Interfaces with Even-Order Spectroscopy

    Science.gov (United States)

    Pandey, Ravindra; Moon, Aaron; Roberts, Sean

    Organic thin film photovoltaics (OPV) are an emerging economically competitive technology that combines manufacturing adaptability, low-cost processing and a lightweight, flexible device end-product. At junctions formed between organic electron-donating and electron-accepting materials, the abrupt change in the dielectric properties can strongly perturb the density of states of the OPV. This can substantially alter the driving force for charge transfer between these materials. Electronic Sum Frequency Generation (ESFG), owing to its inherent interfacial sensitivity, is ideally suited to probe buried interfaces. Here, we report the ESFG spectra of Copper Phthalocyanine (CuPc) films, deposited on SiO2 measured for both reflection and transmission geometries. Three peaks are observed that roughly correlate with resonances that comprise CuPc's Q-band absorption but display slight shifts and amplitude changes with respect to CuPc's bulk absorption spectrum. Experimental results are compared with calculations based on a thin film interference model that accounts for ESFG emitted from both the CuPc:Air and CuPc:SiO2 interface as well as contributions to the signal from higher order source terms from the bulk. The model reveals a difference in the density of states between the two interfaces and suggests that by combining experimental transmission and reflection data it is possible to separate bulk and interfacial contributions to ESFG spectra.

  17. Photoinduced intramolecular charge transfer of sodium 4-(N,N-dimethylamino)benzenesulfonate

    Institute of Scientific and Technical Information of China (English)

    林丽榕; 江云宝

    2000-01-01

    A new dual fluorescent N,N-dimethylaniline derivative, sodium 4-(N,N-dimethylamino)-benzenesulfonate (SDMAS), is reported. In SDMAS, the electron acceptor is linked to the phenyl ring via a sulfur atom at the para-position of the electron donor. It was found that SDMAS emits dual fluorescence only in highly polar solvent water but not in organic solvents such as formamide, methanol and acetonitrile. In organic solvents only a single-band emission at ca.360 nm was observed in the short wavelength region. The dual fluorescence of SDMAS in water was found at 365 and 475 nm, respectively. Introduction of organic solvent such as ethanol, acetonitrile, and 1,4-dioxane into aqueous solution of SDMAS leads to blue-shift and quenching of the long-wavelength emission. Measurements of steady-state and picosecond time-resolved fluorescence indicate that the long wavelength fluorescence is emitted from a charge transfer (CT) state that is populated from the locally excited (LE) state, with the latter giving off the

  18. Analysis of Charge Transfer for in Situ Li Intercalated Carbon Nanotubes

    KAUST Repository

    Rana, Kuldeep

    2012-05-24

    Vertically aligned carbon nanotube (VA-CNT) arrays have been synthesized with lithium (Li) intercalation through an alcohol-catalyzed chemical vapor deposition technique by using a Li-containing catalyst. Scanning electron microscopy images display that synthesized carbon nanotubes (CNTs) are dense and vertically aligned. The effect of the Li-containing catalyst on VA-CNTs has been studied by using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron energy loss spectroscopy (EELS). XPS results show the change in binding energy of Li 1s and C 1s peaks, which indicates that Li is inserted in VA-CNTs during growth. Analysis of Raman spectra reveals that the G-band profile of CNTs synthesized with the Li-containing catalyst is shifted, suggesting an electronic interaction between Li and neighboring C atoms of the CNTs. The EELS spectra of the C K edge and Li K edge from CNTs also confirmed that Li is inserted into CNTs during synthesis. We have performed ab inito calculations based on density functional theory for a further understanding of the structural and electronic properties of Li intercalated CNTs, especially addressing the controversial charge-transfer state between Li and C. © 2012 American Chemical Society.

  19. The lowest-energy charge-transfer state and its role in charge separation in organic photovoltaics.

    Science.gov (United States)

    Nan, Guangjun; Zhang, Xu; Lu, Gang

    2016-06-29

    Energy independent, yet higher than 90% internal quantum efficiency (IQE), has been observed in many organic photovoltaics (OPVs). However, its physical origin remains largely unknown and controversial. The hypothesis that the lowest charge-transfer (CT) state may be weakly bound at the interface has been proposed to rationalize the experimental observations. In this paper, we study the nature of the lowest-energy CT (CT1) state, and show conclusively that the CT1 state is localized in typical OPVs. The electronic couplings in the donor and acceptor are found to determine the localization of the CT1 state. We examine the geminate recombination of the CT1 state and estimate its lifetime from first principles. We identify the vibrational modes that contribute to the geminate recombination. Using material parameters determined from first principles and experiments, we carry out kinetic Monte Carlo simulations to examine the charge separation of the localized CT1 state. We find that the localized CT1 state can indeed yield efficient charge separation with IQE higher than 90%. Dynamic disorder and configuration entropy can provide the energetic and entropy driving force for charge separation. Charge separation efficiency depends more sensitively on the dimension and crystallinity of the acceptor parallel to the interface than that normal to the interface. Reorganization energy is found to be the most important material parameter for charge separation, and lowering the reorganization energy of the donor should be pursued in the materials design.

  20. Evaluation of Deep Space Ka-Band Data Transfer using Radiometeorological Forecasts and Radiometer Measurements

    Science.gov (United States)

    Montopoli, Mario; Marzano, Frank S.; Biscarini, Marianna; Milani, Luca; Cimini, Domenico; De Sanctis, Klaide; Di Fabio, Saverio

    2016-04-01

    Deep space exploration is aimed at acquiring information about the solar system. In this scenario, telecommunications links between Earth ground receiving stations and extra-terrestrial satellite platforms have to be designed in order to ensure the optimal transfer of the acquired scientific data back to the Earth. A significant communication capacity has to be planned when very large distances, as those characterising deep space links, are involved thus fostering more ambitious scientific mission requirements. At the current state of the art, two microwave channel frequencies are used to perform the deep space data transfer: X band (~ 8.4 GHz) and Ka band (~ 32 GHz) channel. Ka-band transmission can offer an advantage over X-band in terms of antenna performance with the same antenna effective area and an available data transfer bandwidth (50 times higher at Ka band than X band). However, Earth troposphere-related impairments can affects the space-to-Earth carrier signals at frequencies higher than 10 GHz by degrading its integrity and thus reducing the deep space channel temporal availability. Such atmospheric impairments, especially in terms of path attenuation, their statistic and the possibility to forecast them in the next 24H at the Earth's receiving station would allow a more accurate design of the deep space link, promoting the mitigation of the detrimental effects on the link availability. To pursue this aim, meteorological forecast models and in situ measurements need to be considered in order to characterise the troposphere in terms of signal path attenuation at current and future time. In this work, we want to show how the synergistic use of meteorological forecasts, radiative transfer simulations and in situ measurements such as microwave radiometry observations, rain gauges and radiosoundings, can aid the optimisation of a deep space link at Ka band and improve its performance with respect to usual practices. The outcomes of the study are in the

  1. Analysis of incomplete charge transfer effects in a CMOS image sensor

    Institute of Scientific and Technical Information of China (English)

    Han Liqiang; Yao Suying; Xu Jiangtao; Xu Chao; Gao Zhiyuan

    2013-01-01

    A method to judge complete charger transfer is proposed for a four-transistor CMOS image sensor with a large pixel size.Based on the emission current theory,a qualitative photoresponse model is established to the preliminary prediction.Further analysis of noise for incomplete charge transfer predicts the noise variation.The test pixels were fabricated in a specialized 0.18μm CMOS image sensor process and two different processes of buried N layer implantation are compared.The trend prediction corresponds with the test results,especially as it can distinguish an unobvious incomplete charge transfer.The method helps us judge whether the charge transfer time satisfies the requirements of the readout circuit for the given process especially for pixels of a large size.

  2. Spectroscopic studies and molecular orbital calculations of charge transfer complexation between 3,5-dimethylpyrazole with DDQ in acetonitrile.

    Science.gov (United States)

    Habeeb, Moustafa M; Al-Attas, Amirah S; Al-Raimi, Doaa S

    2015-05-05

    Charge transfer (CT) interaction between 3,5-dimethylpyrazole (DMP) with the π-acceptor 2,3-dichloro-5,6-dicyano-p-benzoquinon (DDQ) has been investigated spectrophotometrically in acetonitrile (AN). Simultaneous reddish brown color has been observed upon mixing donor with acceptor solutions attributing to CT complex formation. The electronic spectra of the formed complex exhibited multi-charge transfer bands at 429, 447, 506, 542 and 589nm, respectively. Job(')s method of continuous variations and spectrophotometric titration methods confirmed the formation of the studied complex in 1:2 ratio between DMP and DDQ. Benesi-Hildebrand equation has been applied to calculate the stability constant of the formed complex where it recorded high value supporting formation of stable complex. Molecular orbital calculations using MM2 method and GAMESS (General Atomic and Molecular Electronic Structure System) interface computations as a package of ChemBio3D Ultra12 software were carried out for more analysis of the formed complex in the gas phase. The computational analysis included energy minimisation, stabilisation energy, molecular geometry, Mullikan charges, molecular electrostatic potential (MEP) surfaces of reactants and complex as well as characterization of the higher occupied molecular orbitals (HOMO) and lower unoccupied molecular orbitals (LUMO) surfaces of the complex. A good consistency between experimental and theoretical results has been recorded.

  3. Intervalence Charge Transfer luminescence: The anomalous luminescence of Cerium-doped Cs2LiLuCl6 elpasolite

    CERN Document Server

    Seijo, Luis

    2014-01-01

    The existence of intervalence charge transfer (IVCT) luminescence is reported. It is shown that the so called anomalous luminescence of Ce-doped elpasolite Cs2LiLuCl6, which is characterized mainly by a very large Stokes shift and a very large band width, corresponds to an IVCT emission in Ce3+-Ce4+ pairs, from the 5deg orbital of Ce3+ to 4f orbitals of Ce4+. Its Stokes shift is the sum of the large reorganization energies of the Ce4+ and Ce3+ centers formed after the fixed-nuclei electron transfer and it is equal to the energy of the IVCT absorption commonly found in mixed-valence compounds, which is predicted to exist in this material and to be slightly larger than 10000 cm-1. The large band width is the consequence of the large offset between the minima of the Ce3+-Ce4+ and Ce4+-Ce3+ pairs along the electron transfer reaction coordinate. This offset is approximately 2*sqrt(3) times the difference of Ce-Cl equilibrium distances in the Ce3+ and Ce4+ centers. It is shown that the energies of the peaks and the...

  4. Charge Transfer Properties Through Graphene Layers in Gas Detectors

    CERN Document Server

    Thuiner, P; Jackman, R.B.; Müller, H.; Nguyen, T.T.; Oliveri, E.; Pfeiffer, D.; Resnati, F.; Ropelewski, L.; Smith, J.A.; van Stenis, M.; Veenhof, R.

    2015-01-01

    Graphene is a single layer of carbon atoms arranged in a honeycomb lattice with remarkable mechanical, electrical and optical properties. For the first time graphene layers suspended on copper meshes were installed into a gas detector equipped with a gaseous electron multiplier. Measurements of low energy electron and ion transfer through graphene were conducted. In this paper we describe the sample preparation for suspended graphene layers, the testing procedures and we discuss the preliminary results followed by a prospect of further applications.

  5. Comparison of two models for bridge-assisted charge transfer

    CERN Document Server

    Schreiber, M; Kleinekathöfer, U

    1999-01-01

    Based on the reduced density matrix method, we compare two different approaches to calculate the dynamics of the electron transfer in systems with donor, bridge, and acceptor. In the first approach a vibrational substructure is taken into account for each electronic state and the corresponding states are displaced along a common reaction coordinate. In the second approach it is assumed that vibrational relaxation is much faster than the electron transfer and therefore the states are modeled by electronic levels only. In both approaches the system is coupled to a bath of harmonic oscillators but the way of relaxation is quite different. The theory is applied to the electron transfer in ${\\rm H_2P}-{\\rm ZnP}-{\\rm Q}$ with free-base porphyrin (${\\rm H_2P}$) being the donor, zinc porphyrin (${\\rm ZnP}$) being the bridge and quinone (${\\rm Q}$) the acceptor. The parameters are chosen as similar as possible for both approaches and the quality of the agreement is discussed.

  6. Bio-batteries and bio-fuel cells: leveraging on electronic charge transfer proteins.

    Science.gov (United States)

    Kannan, A M; Renugopalakrishnan, V; Filipek, S; Li, P; Audette, G F; Munukutla, L

    2009-03-01

    Bio-fuel cells are alternative energy devises based on bio-electrocatalysis of natural substrates by enzymes or microorganisms. Here we review bio-fuel cells and bio-batteries based on the recent literature. In general, the bio-fuel cells are classified based on the type of electron transfer; mediated electron transfer and direct electron transfer or electronic charge transfer (ECT). The ECT of the bio-fuel cells is critically reviewed and a variety of possible applications are considered. The technical challenges of the bio-fuel cells, like bioelectrocatalysis, immobilization of bioelectrocatalysts, protein denaturation etc. are highlighted and future research directions are discussed leveraging on the use of electron charge transfer proteins. In addition, the packaging aspects of the bio-fuel cells are also analyzed and the found that relatively little work has been done in the engineering development of bio-fuel cells.

  7. Non-Markovian reduced dynamics of ultrafast charge transfer at an oligothiophene–fullerene heterojunction

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Keith H., E-mail: keith.hughes@bangor.ac.uk [School of Chemistry, Bangor University, Bangor, Gwynedd LL57 2UW (United Kingdom); Cahier, Benjamin [School of Chemistry, Bangor University, Bangor, Gwynedd LL57 2UW (United Kingdom); Martinazzo, Rocco [Dipartimento di Chimica Università degli Studi di Milano, v. Golgi 19, 20133 Milano (Italy); Tamura, Hiroyuki [WPI-Advanced Institute for Material Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Burghardt, Irene [Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt/Main (Germany)

    2014-10-17

    Highlights: • Quantum dynamical study of exciton dissociation at a heterojunction interface. • The non-Markovian quantum dynamics involves a highly structured spectral density. • Spectral density is reconstructed from an effective mode transformation of the Hamiltonian. • The dynamics is studied using the hierarchical equations of motion approach. • It was found that the temperature has little effect on the charge transfer. - Abstract: We extend our recent quantum dynamical study of the exciton dissociation and charge transfer at an oligothiophene–fullerene heterojunction interface (Tamura et al., 2012) [6] by investigating the process using the non-perturbative hierarchical equations of motion (HEOM) approach. Based upon an effective mode reconstruction of the spectral density the effect of temperature on the charge transfer is studied using reduced density matrices. It was found that the temperature had little effect on the charge transfer and a coherent dynamics persists over the first few tens of femtoseconds, indicating that the primary charge transfer step proceeds by an activationless pathway.

  8. Ultrafast charge- and energy-transfer dynamics in conjugated polymer: cadmium selenide nanocrystal blends.

    Science.gov (United States)

    Morgenstern, Frederik S F; Rao, Akshay; Böhm, Marcus L; Kist, René J P; Vaynzof, Yana; Greenham, Neil C

    2014-02-25

    Hybrid nanocrystal-polymer systems are promising candidates for photovoltaic applications, but the processes controlling charge generation are poorly understood. Here, we disentangle the energy- and charge-transfer processes occurring in a model system based on blends of cadmium selenide nanocrystals (CdSe-NC) with poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) using a combination of time-resolved absorption and luminescence measurements. The use of different capping ligands (n-butylamine, oleic acid) as well as thermal annealing allows tuning of the polymer-nanocrystal interaction. We demonstrate that energy transfer from MDMO-PPV to CdSe-NCs is the dominant exciton quenching mechanism in nonannealed blends and occurs on ultrafast time scales (<1 ps). Upon thermal annealing electron transfer becomes competitive with energy transfer, with a transfer rate of 800 fs independent of the choice of the ligand. Interestingly, we find hole transfer to be much less efficient than electron transfer and to extend over several nanoseconds. Our results emphasize the importance of tuning the organic-nanocrystal interaction to achieve efficient charge separation and highlight the unfavorable hole-transfer dynamics in these blends.

  9. Photochemistry with fast sample renewal using cluster beams: formation of rare-gas halides in charge-transfer reactions in NF 3-doped rare-gas clusters

    Science.gov (United States)

    Moussavizadeh, L.; von Haeften, K.; Museur, L.; Kanaev, A. V.; Castex, M. C.; von Pietrowski, R.; Möller, T.

    1999-05-01

    Charge transfer reactions in free clusters are observed in a photoluminescence study on doped rare-gas clusters (Rg clusters, Rg=Ar, Kr and Xe). Following photoexcitation into the first absorption bands of Rg clusters, fluorescence from free RgF* excimers ejected from the clusters and from Rg 2F* excimers localized in the interior of the clusters is observed. The results show that the reaction dynamics in clusters differs considerably from that in the gas and solid phase.

  10. Analysis and Design of I/Q Charge-Sharing Band-Pass-Filter for Superheterodyne Receivers

    NARCIS (Netherlands)

    Madadi, I.; Tohidian, M.; Staszewski, R.B.

    2015-01-01

    A complex quadrature charge-sharing (CS) technique is proposed to implement a discrete-time band-pass filter (BPF) with a programmable bandwidth of 20–100 MHz. The BPF is part of a cellular superheterodyne receiver and completely determines the receiver frequency selectivity. It operates at the full

  11. An Accurate and Linear Scaling Method to Calculate Charge-Transfer Excitation Energies and Diabatic Couplings

    CERN Document Server

    Pavanello, Michele; Visscher, Lucas; Neugebauer, Johannes

    2012-01-01

    Quantum--Mechanical methods that are both computationally fast and accurate are not yet available for electronic excitations having charge transfer character. In this work, we present a significant step forward towards this goal for those charge transfer excitations that take place between non-covalently bound molecules. In particular, we present a method that scales linearly with the number of non-covalently bound molecules in the system and is based on a two-pronged approach: The molecular electronic structure of broken-symmetry charge-localized states is obtained with the Frozen Density Embedding formulation of subsystem Density-Functional Theory; subsequently, in a post-SCF calculation, the full-electron Hamiltonian and overlap matrix elements among the charge-localized states are evaluated with an algorithm which takes full advantage of the subsystem DFT density partitioning technique. The method is benchmarked against Coupled-Cluster calculations and achieves chemical accuracy for the systems considered...

  12. Laboratory Studies of Thermal Energy Charge Transfer of Silicon and Iron Ions in Astrophysical Plasmas

    Science.gov (United States)

    Kwong, Victor H. S.

    1997-01-01

    The laser ablation/ion storage facility at the UNLV Physics Department is dedicated to the study of atomic processes in low temperature plasmas. Our current program is directed to the study of charge transfer of multiply charged ions and neutrals that are of importance to astrophysics at energies less than 1 eV (about 10(exp 4) K). Specifically, we measure the charge transfer rate coefficient of ions such as N(2+), Si(3+), Si(3+), with helium and Fe(2+) with molecular and atomic hydrogen. All these ions are found in a variety of astrophysical plasmas. Their electron transfer reactions with neutral atoms can affect the ionization equilibrium of the plasma.

  13. Charge transfer and excitation in H++CH3 collisions below 10keV

    Science.gov (United States)

    Nagao, Masatoshi; Hida, Ken-Nosuke; Kimura, Mineo; Rai, Sachchida N.; Liebermann, Heinz-Peter; Buenker, Robert J.; Suno, Hiroya; Stancil, Phillip C.

    2008-07-01

    Charge transfer and electronic excitation in collisions of H+ ions with CH3 from a few tens of eV up to 10keV are theoretically investigated. The adiabatic potential energy curves and corresponding wave functions are calculated by using the multireference single- and double-excitation configuration interaction method, and the scattering dynamics is studied based on the semiclassical impact parameter molecular-orbital close-coupling approach. Charge-transfer cross sections are found to be large and rather energy-dependent over the entire energy region studied. Electronic excitation is also energy-dependent with a sharp increase from below 10-17to10-16cm2 . Most of the molecular products produced through charge transfer or excitation are known to be unstable and undergo fragmentation producing various hydrocarbon radical species. Hence, identification of fragmented species and their production mechanism are important for spectroscopic analysis.

  14. Electroluminescence from charge transfer states in Donor/Acceptor solar cells

    DEFF Research Database (Denmark)

    Sherafatipour, Golenaz; Madsen, Morten

    charge transfer (CT) excitons, which is Coulombically bound interfacial electron- hole pairs residing at the donor/acceptor heterojunctions. The CT state represents an intermediate state between the exciton dissociation and recombination back to the ground state. Since the recombination of photo...... at the donor/acceptor interface is detected. As a less studied system, we examine here the interfacial charge transfer state recombination in DBP:C70 thin-films. The weak EL from the small molecule solar cell biased in the forward direction gives valuable information about the CT state recombination, from...... which the maximum open-circuit voltage can be estimated, and further can be used in the modeling and optimization of the OPV devices. [1] C. Deibe, T. Strobe, and V. Dyakonov, “Role of the charge transfer state in organic donor-acceptor solar cells,” Adv. Mater., vol. 22, pp. 4097–4111, 2010. [2] K...

  15. Engineering the Charge Transfer in all 2D Graphene-Nanoplatelets Heterostructure Photodetectors

    Science.gov (United States)

    Robin, A.; Lhuillier, E.; Xu, X. Z.; Ithurria, S.; Aubin, H.; Ouerghi, A.; Dubertret, B.

    2016-05-01

    Two dimensional layered (i.e. van der Waals) heterostructures open up great prospects, especially in photodetector applications. In this context, the control of the charge transfer between the constituting layers is of crucial importance. Compared to bulk or 0D system, 2D materials are characterized by a large exciton binding energy (0.1-1 eV) which considerably affects the magnitude of the charge transfer. Here we investigate a model system made from colloidal 2D CdSe nanoplatelets and epitaxial graphene in a phototransistor configuration. We demonstrate that using a heterostructured layered material, we can tune the magnitude and the direction (i.e. electron or hole) of the charge transfer. We further evidence that graphene functionalization by nanocrystals only leads to a limited change in the magnitude of the 1/f noise. These results draw some new directions to design van der Waals heterostructures with enhanced optoelectronic properties.

  16. Excited-state proton coupled charge transfer modulated by molecular structure and media polarization.

    Science.gov (United States)

    Demchenko, Alexander P; Tang, Kuo-Chun; Chou, Pi-Tai

    2013-02-01

    Charge and proton transfer reactions in the excited states of organic dyes can be coupled in many different ways. Despite the complementarity of charges, they can occur on different time scales and in different directions of the molecular framework. In certain cases, excited-state equilibrium can be established between the charge-transfer and proton-transfer species. The interplay of these reactions can be modulated and even reversed by variations in dye molecular structures and changes of the surrounding media. With knowledge of the mechanisms of these processes, desired rates and directions can be achieved, and thus the multiple emission spectral features can be harnessed. These features have found versatile applications in a number of cutting-edge technological areas, particularly in fluorescence sensing and imaging.

  17. A two-dimensional position sensitive gas chamber with scanned charge transfer readout

    Science.gov (United States)

    Gómez, F.; Iglesias, A.; Lobato, R.; Mosquera, J.; Pardo, J.; Pena, J.; Pazos, A.; Pombar, M.; Rodríguez, A.

    2003-10-01

    We have constructed and tested a two-dimensional position sensitive parallel-plate gas ionization chamber with scanned charge transfer readout. The scan readout method described here is based on the development of a new position-dependent charge transfer technique. It has been implemented by using gate strips perpendicularly oriented to the collector strips. This solution reduces considerably the number of electronic readout channels needed to cover large detector areas. The use of a 25 μm thick kapton etched circuit allows high charge transfer efficiency with a low gating voltage, consequently needing a very simple commutating circuit. The present prototype covers 8×8 cm2 with a pixel size of 1.27×1.27 mm2. Depending on the intended use and beam characteristics a smaller effective pixel is feasible and larger active areas are possible. This detector can be used for X-ray or other continuous beam intensity profile monitoring.

  18. Polyoxometalate active charge-transfer material for mediated redox flow battery

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Travis Mark; Hudak, Nicholas; Staiger, Chad; Pratt, Harry

    2017-01-17

    Redox flow batteries including a half-cell electrode chamber coupled to a current collecting electrode are disclosed herein. In a general embodiment, a separator is coupled to the half-cell electrode chamber. The half-cell electrode chamber comprises a first redox-active mediator and a second redox-active mediator. The first redox-active mediator and the second redox-active mediator are circulated through the half-cell electrode chamber into an external container. The container includes an active charge-transfer material. The active charge-transfer material has a redox potential between a redox potential of the first redox-active mediator and a redox potential of the second redox-active mediator. The active charge-transfer material is a polyoxometalate or derivative thereof. The redox flow battery may be particularly useful in energy storage solutions for renewable energy sources and for providing sustained power to an electrical grid.

  19. Near resonant charge transfer in the reaction F(+) + CO - F + CO(+)

    Science.gov (United States)

    Kusunoki, I.; Ishikawa, T.

    1985-06-01

    Charge transfer reactions in the F(+) + CO system were investigated using a F(+) ion beam in the energy range 10-300 eVlab. The electronically excited product CO(+) A2Pi(i) was observed by the emission from the A-X transitions. At low collisional energy the dominant product is in the vibrational level v' = 5. The reaction cross section sigma(5) is about 1 A-sq at 12 eVc.m. and decreases with increasing collision energy. The large cross section at v' = 5 can be interpreted by near-resonant charge-transfer reactions. The rotational temperature of the product is about 300 K, which is the temperature of the reactant CO gas. For the resonant charge transfer, the translational energy is not effective, but the electronic and vibrational energy couple with each other strongly.

  20. Ultrafast optical measurements of charge generation and transfer mechanisms of pi-conjugated polymers for solar cell applications

    Science.gov (United States)

    Holt, Joshua Michael

    Current developments in organic solar cells based on donor-acceptor blends require understanding and control of photoinduced charge transfer and electronic state dynamics. In this work the ultrafast dynamics of photoexcitations in pi-conjugated organic semiconductors were studied using a low-intensity, high-repetition rate laser system in the broad mid- to near-infrared (IR) spectral range from 0.25 to 1.1 eV, and a high-intensity, low-repetition rate laser system in the spectral range from 1.2 to 2.5 eV, in the time domain up to 1 ns with 150 fs resolution. We also applied CW photomodulation spectroscopy along with excitation spectrum, modulation frequency sweeps, photoluminescence and electroabsorption to study the excited states of pi-conjugated polymers and acceptor-donor blends. One current drawback to organic solar cell efficiency is negligible absorption in the near infrared spectral range of the solar spectrum. We provide and compare evidence that poly(2-methoxy-5(2'-ethyl)hexoxy-phenylenevinylene) (MEH-PPV) [electron donor] blended with 2,4,7-trinitrofluorenone (TNF) [strong electron acceptor] form a below-gap charge transfer complex (CTC) state that can extend absorption into the near infrared. The transient PA measurements also show that significant charge species are initially photogenerated, a majority of which geminately recombine within 8-10 ps, but the few that escape geminate recombination are subsequently captured in long-lived traps. In addition polarons could be also photogenerated with high efficiency at near-IR excitation, with similar fate. This demonstrates that a CTC state exists below the MEH-PPV polymer optical gap, but with low dissociation efficiency. We compare our results to those in blends of MEH-PPV/C60 where apparently a charge transport pathway to the electrodes is formed and the obtained CTC state has higher dissociation efficiency. The most efficient all-organic photovoltaic (OPV) cells to date (˜6% power conversion efficiency

  1. Charge Transfer Properties Through Graphene for Applications in Gaseous Detectors

    CERN Document Server

    Franchino, S; Hall-Wilton, R.; Jackman, R.B.; Muller, H.; Nguyen, T.T.; de Oliveira, R.; Oliveri, E.; Pfeiffer, D.; Resnati, F.; Ropelewski, L.; Smith, J.; van Stenis, M.; Streli, C.; Thuiner, P.; Veenhof, R.

    2016-01-01

    Graphene is a single layer of carbon atoms arranged in a honeycomb lattice with remarkable mechanical and electrical properties. Regarded as the thinnest and narrowest conductive mesh, it has drastically different transmission behaviours when bombarded with electrons and ions in vacuum. This property, if confirmed in gas, may be a definitive solution for the ion back-flow problem in gaseous detectors. In order to ascertain this aspect, graphene layers of dimensions of about 2x2cm$^2$, grown on a copper substrate, are transferred onto a flat metal surface with holes, so that the graphene layer is freely suspended. The graphene and the support are installed into a gaseous detector equipped with a triple Gaseous Electron Multiplier (GEM), and the transparency properties to electrons and ions are studied in gas as a function of the electric fields. The techniques to produce the graphene samples are described, and we report on preliminary tests of graphene-coated GEMs.

  2. Charge transfer properties through graphene for applications in gaseous detectors

    Energy Technology Data Exchange (ETDEWEB)

    Franchino, S.; Gonzalez-Diaz, D. [CERN, European Organization for Nuclear Research, CH-1211, Geneva 23 (Switzerland); Hall-Wilton, R. [ESS, European Spallation Source, Tunavägen 24, 223 63 Lund (Sweden); Jackman, R.B. [London Centre for Nanotechnology and the Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, WC1H 0AH (United Kingdom); Muller, H. [CERN, European Organization for Nuclear Research, CH-1211, Geneva 23 (Switzerland); Nguyen, T.T. [London Centre for Nanotechnology and the Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, WC1H 0AH (United Kingdom); Oliveira, R. de; Oliveri, E. [CERN, European Organization for Nuclear Research, CH-1211, Geneva 23 (Switzerland); Pfeiffer, D. [CERN, European Organization for Nuclear Research, CH-1211, Geneva 23 (Switzerland); ESS, European Spallation Source, Tunavägen 24, 223 63 Lund (Sweden); Resnati, F., E-mail: filippo.resnati@cern.ch [CERN, European Organization for Nuclear Research, CH-1211, Geneva 23 (Switzerland); ESS, European Spallation Source, Tunavägen 24, 223 63 Lund (Sweden); Ropelewski, L. [CERN, European Organization for Nuclear Research, CH-1211, Geneva 23 (Switzerland); Smith, J. [London Centre for Nanotechnology and the Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, WC1H 0AH (United Kingdom); Stenis, M. van [CERN, European Organization for Nuclear Research, CH-1211, Geneva 23 (Switzerland); Streli, C. [Atominstitut, Technische Universität Wien, Stadionallee 2, 1020 Vienna (Austria); Thuiner, P. [CERN, European Organization for Nuclear Research, CH-1211, Geneva 23 (Switzerland); Atominstitut, Technische Universität Wien, Stadionallee 2, 1020 Vienna (Austria); and others

    2016-07-11

    Graphene is a single layer of carbon atoms arranged in a honeycomb lattice with remarkable mechanical and electrical properties. Regarded as the thinnest and narrowest conductive mesh, it has drastically different transmission behaviours when bombarded with electrons and ions in vacuum. This property, if confirmed in gas, may be a definitive solution for the ion back-flow problem in gaseous detectors. In order to ascertain this aspect, graphene layers of dimensions of about 2×2 cm{sup 2}, grown on a copper substrate, are transferred onto a flat metal surface with holes, so that the graphene layer is freely suspended. The graphene and the support are installed into a gaseous detector equipped with a triple Gaseous Electron Multiplier (GEM), and the transparency properties to electrons and ions are studied in gas as a function of the electric fields. The techniques to produce the graphene samples are described, and we report on preliminary tests of graphene-coated GEMs.

  3. The description of charge transfer in fast negative ions scattering on water covered Si(100) surfaces

    Science.gov (United States)

    Chen, Lin; Qiu, Shunli; Liu, Pinyang; Xiong, Feifei; Lu, Jianjie; Liu, Yuefeng; Li, Guopeng; Liu, Yiran; Ren, Fei; Xiao, Yunqing; Gao, Lei; Zhao, Qiushuang; Ding, Bin; Li, Yuan; Guo, Yanling; Chen, Ximeng

    2016-11-01

    Doping has significantly affected the characteristics and performance of semiconductor electronic devices. In this work, we study the charge transfer processes for 8.5-22.5 keV C- and F- ions scattering on H2O-terminated p-type Si(100) surfaces with two different doping concentrations. We find that doping has no influence on negative-ion formation for fast collisions in this relatively high energy range. Moreover, we build a model to calculate negative ion fractions including the contribution from positive ions. The calculations support the nonadiabatic feature of charge transfer.

  4. Photoinduced charge transfer involving a MoMo quadruply bonded complex to a perylene diimide.

    Science.gov (United States)

    Alberding, Brian G; Brown-Xu, Samantha E; Chisholm, Malcolm H; Epstein, Arthur J; Gustafson, Terry L; Lewis, Sharlene A; Min, Yong

    2013-04-21

    Evidence, based on femtosecond transient absorption and time resolved infrared spectroscopy, is presented for photoinduced charge transfer from the Mo2δ orbital of the quadruply bonded molecule trans-Mo2(T(i)PB)2(BTh)2, where T(i)PB = 2,4,6-triisopropyl benzoate and BTh = 2,2'-bithienylcarboxylate, to di-n-octyl perylene diimide and di-n-hexylheptyl perylene diimide in thin films and solutions of the mixtures. The films show a long-lived charge separated state while slow back electron transfer, τBET ~ 500 ps, occurs in solution.

  5. Photoinduced charge transfer within polyaniline-encapsulated quantum dots decorated on graphene.

    Science.gov (United States)

    Nguyen, Kim Truc; Li, Dehui; Borah, Parijat; Ma, Xing; Liu, Zhaona; Zhu, Liangliang; Grüner, George; Xiong, Qihua; Zhao, Yanli

    2013-08-28

    A new method to enhance the stability of quantum dots (QDs) in aqueous solution by encapsulating them with conducting polymer polyaniline was reported. The polyaniline-encapsulated QDs were then decorated onto graphene through π-π interactions between graphene and conjugated polymer shell of QDs, forming stable polyaniline/QD/graphene hybrid. A testing electronic device was fabricated using the hybrid in order to investigate the photoinduced charge transfer between graphene and encapsulated QDs within the hybrid. The charge transfer mechanism was explored through cyclic voltammetry and spectroscopic studies. The hybrid shows a clear response to the laser irradiation, presenting a great advantage for further applications in optoelectronic devices.

  6. Carotenoid to chlorophyll energy transfer in the peridinin–chlorophyll-a–protein complex involves an intramolecular charge transfer state

    Science.gov (United States)

    Zigmantas, Donatas; Hiller, Roger G.; Sundström, Villy; Polívka, Tomáš

    2002-01-01

    Carotenoids are, along with chlorophylls, crucial pigments involved in light-harvesting processes in photosynthetic organisms. Details of carotenoid to chlorophyll energy transfer mechanisms and their dependence on structural variability of carotenoids are as yet poorly understood. Here, we employ femtosecond transient absorption spectroscopy to reveal energy transfer pathways in the peridinin–chlorophyll-a–protein (PCP) complex containing the highly substituted carotenoid peridinin, which includes an intramolecular charge transfer (ICT) state in its excited state manifold. Extending the transient absorption spectra toward near-infrared region (600–1800 nm) allowed us to separate contributions from different low-lying excited states of peridinin. The results demonstrate a special light-harvesting strategy in the PCP complex that uses the ICT state of peridinin to enhance energy transfer efficiency. PMID:12486228

  7. Heat transfer from the evaporator outlet to the charge of thermostatic expansion valves

    DEFF Research Database (Denmark)

    Langmaack, Lasse Nicolai; Knudsen, Hans-Jørgen Høgaard

    2006-01-01

    outlet with a special mounting strap. The heat transfer is quite complex because it takes place both directly through the contact points between bulb and pipe and indirectly through the mounting strap The TXV has to react to temperature changes at the evaporator outlet. Therefore, the dynamic behavior...... of the valve (and thereby the whole refrigeration system) depends greatly on the heat transfer between the evaporator outlet tube and the charge in the bulb. In this paper a model for the overall heat transfer between the pipe and the charge is presented. Geometrical data and material properties have been kept...... been found to predict the time constant for the temperature development in the bulb within 1-10 %. Furthermore it has been found that app. 20% of the heat transfer takes place trough the mounting strap....

  8. A 190 by 244 charge-coupled area image sensor with interline transfer organization

    Science.gov (United States)

    Walsh, L. R.

    1975-01-01

    A 190 x 244 element charge coupled area image sensor has been designed, fabricated and tested. This sensor employs an interline transfer organization and buried n-channel technology. It features a novel on-chip charge integrator and a distributed floating gate amplifier for high and low light level applications. The X-Y element count has been chosen to establish the capability of producing an NTSC compatible video signal. The array size is also compatible with the Super 8 lens format. The first few sample devices have been successfully operated at full video bandwidth for both high and low light levels with the charge amplifier system.

  9. Evidence of Delocalization in Charge-Transfer State Manifold for Donor:Acceptor Organic Photovoltaics.

    Science.gov (United States)

    Guan, Zhiqiang; Li, Ho-Wa; Zhang, Jinfeng; Cheng, Yuanhang; Yang, Qingdan; Lo, Ming-Fai; Ng, Tsz-Wai; Tsang, Sai-Wing; Lee, Chun-Sing

    2016-08-24

    How charge-transfer states (CTSs) assist charge separation of a Coulombically bound exciton in organic photovoltaics has been a hot topic. It is believed that the delocalization feature of a CTS plays a crucial role in the charge separation process. However, the delocalization of the "hot" and the "relaxed" CTSs is still under debate. Here, with a novel frequency dependent charge-modulated electroabsorption spectroscopy (CMEAS) technique, we elucidate clearly that both "hot" and "relaxed" CTSs are loosely bound and delocalized states. This is confirmed by comparing the CMEAS results of CTSs with those of localized polaron states. Our results reveal the role of CTS delocalization on charge separation and indicate that no substantial delocalization gradient exists in CTSs.

  10. Transverse Schottky spectra and beam transfer functions of coasting ion beams with space charge

    Energy Technology Data Exchange (ETDEWEB)

    Paret, Stefan

    2010-02-22

    A study of the transverse dynamics of coasting ion beams with moderate space charge is presented in this work. From the dispersion relation with linear space charge, an analytic model describing the impact of space charge on transverse beam transfer functions (BTFs) and the stability limits of a beam is derived. The dielectric function obtained in this way is employed to describe the transverse Schottky spectra with linear space charge as well. The difference between the action of space charge and impedances is highlighted. The setup and the results of an experiment performed in the heavy ion synchrotron SIS-18 at GSI to detect space-charge effects at different beam intensities are explicated. The measured transverse Schottky spectra and BTFs are compared with the linear space-charge model. The stability diagrams constructed from the BTFs are presented. The space-charge parameters evaluated from the Schottky and BTF measurements are compared with estimations based on measured beam parameters. The impact of collective effects on the Schottky and BTF diagnostics is also investigated through numerical simulations. For this purpose the self-field of beams with linear and non-linear transverse density-distributions is computed on a twodimensional grid. The noise of the random particle distribution causes fluctuations of the dipole moment of the beam which produce the Schottky spectrum. BTFs are simulated by exciting the beam with transverse kicks. The simulation results are used to verify the space-charge model. (orig.)

  11. Structural dynamics of a noncovalent charge transfer complex from femtosecond stimulated Raman spectroscopy.

    Science.gov (United States)

    Fujisawa, Tomotsumi; Creelman, Mark; Mathies, Richard A

    2012-09-06

    Femtosecond stimulated Raman spectroscopy is used to examine the structural dynamics of photoinduced charge transfer within a noncovalent electron acceptor/donor complex of pyromellitic dianhydride (PMDA, electron acceptor) and hexamethylbenzene (HMB, electron donor) in ethylacetate and acetonitrile. The evolution of the vibrational spectrum reveals the ultrafast structural changes that occur during the charge separation (Franck-Condon excited state complex → contact ion pair) and the subsequent charge recombination (contact ion pair → ground state complex). The Franck-Condon excited state is shown to have significant charge-separated character because its vibrational spectrum is similar to that of the ion pair. The charge separation rate (2.5 ps in ethylacetate and ∼0.5 ps in acetonitrile) is comparable to solvation dynamics and is unaffected by the perdeuteration of HMB, supporting the dominant role of solvent rearrangement in charge separation. On the other hand, the charge recombination slows by a factor of ∼1.4 when using perdeuterated HMB, indicating that methyl hydrogen motions of HMB mediate the charge recombination process. Resonance Raman enhancement of the HMB vibrations in the complex reveals that the ring stretches of HMB, and especially the C-CH(3) deformations are the primary acceptor modes promoting charge recombination.

  12. Spectroscopic Studies of Doping and Charge Transfer in Single Walled Carbon Nanotubes and Lead Sulfide Quantum Dots

    Science.gov (United States)

    Haugen, Neale O.

    confirmed by the dependence of the Raman G-band shift on the QD size, and thus upon the QD bandgap. Charge transfer is further corroborated by similar size dependence in the efficiency of the SW-CNTs as quenchers of the QD photoluminescence (PL). NHSs thus produced could be used in QD based solar cells to improve the overall device efficiency by improving exciton dissociation, charge transport, and charge collection.

  13. Short Range Wireless Power Transfer (WPT) for UAV/UAS Battery Charging - Phase 1

    Science.gov (United States)

    2014-12-01

    Power Satellites and Microwave Power Trans- mission in Japan,” IEEE Microwave Magazine , December 2002, pp. 36-45. [6] C. Balanis, Antenna Theory...numerous advantages of wireless power transfer (WPT) for many remote energy source and battery charging applications. The approach was first proposed for...antennas rather than coils, and the energy is transferred by a propagating wave, as depicted in Figure 3. The received power at antenna separation d is

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

    Energy Technology Data Exchange (ETDEWEB)

    Hammes-Schiffer, Sharon

    2015-07-22

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

  15. Molecular adsorption on ZnO(1010) single-crystal surfaces: morphology and charge transfer.

    Science.gov (United States)

    Chen, Jixin; Ruther, Rose E; Tan, Yizheng; Bishop, Lee M; Hamers, Robert J

    2012-07-17

    While ZnO has excellent electrical properties, it has not been widely used for dye-sensitized solar cells, in part because ZnO is chemically less stable than widely used TiO(2). The functional groups typically used for surface passivation and for attaching dye molecules either bind weakly or etch the ZnO surface. We have compared the formation of molecular layers from alkane molecules with terminal carboxylic acid, alcohol, amine, phosphonic acid, or thiol functional groups on single-crystal zinc oxide (1010) surfaces. Atomic force microscopy (AFM) images show that alkyl carboxylic acids etch the surface whereas alkyl amine and alkyl alcohols bind only weakly on the ZnO(1010) surface. Phosphonic acid-terminated molecules were found to bind to the surface in a heterogeneous manner, forming clusters of molecules. Alkanethiols were found to bind to the surface, forming highly uniform monolayers with some etching detected after long immersion times in an alkanethiol solution. Monolayers of hexadecylphosphonic acid and octadecanethiol were further analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. AFM scratching shows that thiols were bound strongly to the ZnO surface, suggesting the formation of strong Zn-S covalent bonds. Surprisingly, the tridentate phosphonic acids adhered much more weakly than the monodentate thiol. The influence of organic grafting on the charge transfer to ZnO was studied by time-resolved surface photovoltage measurements and electrochemical impedance measurements. Our results show that the grafting of thiols to ZnO leads to robust surfaces and reduces the surface band bending due to midgap surface states.

  16. The Development of Layered Photonic Band Gap Structures Using a Micro-Transfer Molding Technique

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, Kevin Jerome [Iowa State Univ., Ames, IA (United States)

    2001-01-01

    Photonic band gap (PBG) crystals are periodic dielectric structures that manipulate electromagnetic radiation in a manner similar to semiconductor devices manipulating electrons. Whereas a semiconductor material exhibits an electronic band gap in which electrons cannot exist, similarly, a photonic crystal containing a photonic band gap does not allow the propagation of specific frequencies of electromagnetic radiation. This phenomenon results from the destructive Bragg diffraction interference that a wave propagating at a specific frequency will experience because of the periodic change in dielectric permitivity. This gives rise to a variety of optical applications for improving the efficiency and effectiveness of opto-electronic devices. These applications are reviewed later. Several methods are currently used to fabricate photonic crystals, which are also discussed in detail. This research involves a layer-by-layer micro-transfer molding ({mu}TM) and stacking method to create three-dimensional FCC structures of epoxy or titania. The structures, once reduced significantly in size can be infiltrated with an organic gain media and stacked on a semiconductor to improve the efficiency of an electronically pumped light-emitting diode. Photonic band gap structures have been proven to effectively create a band gap for certain frequencies of electro-magnetic radiation in the microwave and near-infrared ranges. The objective of this research project was originally two-fold: to fabricate a three dimensional (3-D) structure of a size scaled to prohibit electromagnetic propagation within the visible wavelength range, and then to characterize that structure using laser dye emission spectra. As a master mold has not yet been developed for the micro transfer molding technique in the visible range, the research was limited to scaling down the length scale as much as possible with the current available technology and characterizing these structures with other methods.

  17. Determining the spatial coherence of excitons from the photoluminescence spectrum in charge-transfer J-aggregates

    Science.gov (United States)

    Hestand, Nicholas J.; Spano, Frank C.

    2016-12-01

    The importance of spatial coherence in energy and charge transfer processes in biological systems and photovoltaic devices has been hotly debated over the past several years. While larger spatial coherences are thought to benefit transport, a clear correlation has yet to be established, partly because a simple and accurate measure of the coherence length has remained elusive. Previously, it was shown that the number of coherently connected chromophores, NCoh , can be determined directly from the ratio (SR) of the 0-0 and 0-1 vibronic line strengths in the photoluminescence (PL) spectrum. The relation NCoh = λ02SR, where λ02 is the associated monomeric Huang-Rhys parameter, was derived in the Frenkel exciton limit. Here, it is shown that SR remains a highly accurate measure of coherence for systems characterized by significant charge transfer interactions (e.g. conjugated π-stacked systems). The only requirement is that the exciton band curvature must be positive, as in a J-aggregate.

  18. Charge-transfer energy in closed-shell ion-atom interactions. [for H and Li ions in He

    Science.gov (United States)

    Alvarez-Rizzatti, M.; Mason, E. A.

    1975-01-01

    The importance of charge-transfer energy in the interactions between closed-shell ions and atoms is investigated. Ab initio calculations on H(plus)-He and Li(plus)-He are used as a guide for the construction of approximate methods for the estimation of the charge-transfer energy for more complicated systems. For many alkali ion-rate gas systems the charge-transfer energy is comparable to the induction energy in the region of the potential minimum, although for doubly charged alkaline-earth ions in rare gases the induction energy always dominates. Surprisingly, an empirical combination of repulsion energy plus asymptotic induction energy plus asymptotic dispersion energy seems to give a fair representation of the total interaction, especially if the repulsion energy is parameterized, despite the omission of any explicit charge-transfer contribution. More refined interaction models should consider the charge-transfer energy contribution.

  19. Photodissociation dynamics of the iodine-arene charge-transfer complex

    NARCIS (Netherlands)

    Lenderink, Egbert; Duppen, Koos; Everdij, Frank P.X.; Mavri, Janez; Torre, Renato; Wiersma, Douwe A.

    1996-01-01

    The photodissociation reaction of the molecular iodine:arene charge-transfer (CT) complex into an iodine atom and an iodine atom-arene fragment has been investigated using femtosecond pump-probe, resonance Raman, and molecular dynamics simulations. In the condensed phase the reaction proceeds on a t

  20. Laboratory Measurements of Charge Transfer on Atomic Hydrogen at Thermal Energies

    Science.gov (United States)

    Havener, C. C.; Vane, C. R.; Krause, H. F.; Stancil, P. C.; Mroczkowski, T.; Savin, D. W.

    2002-01-01

    We describe our ongoing program to measure velocity dependent charge transfer (CT) cross sections for selected ions on atomic hydrogen using the ion-aloin merged-beams apparatus at Oak Ridge Natioiial Laboralory. Our focus is on those ions for which CT plays an important role in determining the ionization structure, line emis sion, and thermal structure of observed cosmic photoionized plasmas.

  1. Molecular orbital (SCF-Xα-SW) theory of metal-metal charge transfer processes in minerals

    Science.gov (United States)

    Sherman, David M.

    1987-01-01

    A number of mixed valence iron oxides and silicates (e.g., magnetite, ilvaite) exhibit thermally induced electron delocalization between adjacent Fe2+ and Fe3+ ions and optically induced electronic transitions which are assigned to Fe2+→Fe3+ intervalence charge transfer.

  2. Spectroscopy of charge transfer states in Mg1 - x Ni x O

    Science.gov (United States)

    Churmanov, V. N.; Sokolov, V. I.; Pustovarov, V. A.; Gruzdev, N. B.; Mironova-Ulmane, N.

    2016-10-01

    Photoluminescence and photoluminescence excitation spectra of solid solution Mg1- x Ni x O ( x = 0.008) have been analyzed. The contributions of charge transfer electronic states and nonradiative Auger relaxation to the formation of the photoluminescence spectrum are discussed.

  3. Fast ethylamine gas sensing based on intermolecular charge-transfer complexation

    Institute of Scientific and Technical Information of China (English)

    Eun Mi Lee; Seon Young Gwon; Young A Son; Sung Hoon Kim

    2012-01-01

    We have investigated the fast ethylamine gas sensing of 2-chloro-3,5-dinitrobenzotrifluoride (CDBF) loaded poly(acrylonitrile)nanofiber based on an intermolecular charge-transfer complexation.Reversible response and recovery were achieved using alternating gas exposure.This system shows a fast ethylamine gas sensing within 0.4 s.

  4. Charge transfer polarisation wave in high Tc oxides and superconductive pairing

    Science.gov (United States)

    Chakraverty, B. K.

    1991-01-01

    A general formalism of quantized charge transfer polarization waves was developed. The nature of possible superconductive pairing between oxygen holes is discussed. Unlike optical phonons, these polarization fields will give rise to dielectric bipolarons or bipolaron bubbles. In the weak coupling limit, a new class of superconductivity is to be expected.

  5. Integer charge transfer at the tetrakis(dimethylamino)ethylene/Au interface

    DEFF Research Database (Denmark)

    Lindell, L.; Unge, Mikael; Osikowicz, W.;

    2008-01-01

    In organic-based electronics, interfacial properties have a profound impact on device performance. The lineup of energy levels is usually dependent on interface dipoles, which may arise from charge transfer reactions. In many applications, metal-organic junctions are prepared under ambient condit...

  6. The influence of the HGMF on mass-charge transfer in gravisensing cells.

    Science.gov (United States)

    Kondrachuk, A; Belyavskaya, N

    2001-07-01

    The present work is focused on the influence of the high-gradient-magnetic field (HGMF) on spatial distribution of ion fluxes along the roots (a), cytoplasmic streaming (b), and the processes of plant cell growth connected with intracellular mass and charge transfer (c).

  7. Symmetry-breaking intramolecular charge transfer in the excited state of meso-linked BODIPY dyads

    KAUST Repository

    Whited, Matthew T.

    2012-01-01

    We report the synthesis and characterization of symmetric BODIPY dyads where the chromophores are attached at the meso position, using either a phenylene bridge or direct linkage. Both molecules undergo symmetry-breaking intramolecular charge transfer in the excited state, and the directly linked dyad serves as a visible-light-absorbing analogue of 9,9′-bianthryl.

  8. Elastic, excitation, ionization and charge transfer cross sections of current interest in fusion energy research

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, D.R.; Krstic, P.S. [Oak Ridge National Lab. TN (United States). Physics Div.

    1997-01-01

    Due to the present interest in modeling and diagnosing the edge and divertor plasma regions in magnetically confined fusion devices, we have sought to provide new calculations regarding the elastic, excitation, ionization, and charge transfer cross sections in collisions among relevant ions, neutrals, and isotopes in the low-to intermediate-energy regime. We summarize here some of our recent work. (author)

  9. Small-signal charge transfer inefficiency experiments explained by the McWhorter interface state model

    NARCIS (Netherlands)

    Penning De Vries, René G.M.; Wallinga, Hans

    1984-01-01

    The small-signal charge transfer inefficiency (SCTI) of a surface-channel CCD has been studied. The experimentally observed behavior of the SCTI could not be explained by the conventional interface state model. Using the McWhorter model for the interface states, which assumes a distribution of the s

  10. Mechanism of the Primary Charge Transfer Reaction in the Cytochrome bc1 Complex

    DEFF Research Database (Denmark)

    Barragan, Angela M; Schulten, Klaus; Solov'yov, Ilia A

    2016-01-01

    , the quinol-protein interaction, which initiates the Q-cycle, has not yet been completely described. Furthermore, the initial charge transfer reactions of the Q-cycle lack a physical description. The present investigation utilizes classical molecular dynamics simulations in tandem with quantum density...

  11. Mechanism and Dynamics of Charge Transfer in Donor-Bridge-Acceptor Systems

    NARCIS (Netherlands)

    Gorczak-Vos, N.

    2016-01-01

    Photoinduced charge transfer in organic materials is a fundamental process in various biological and technological areas. Donor-bridge-acceptor (DBA) molecules are used as model systems in numerous theoretical and experimental work to systematically study and unravel the underlying mechanisms of cha

  12. Near-resonant versus nonresonant chemiluminescent charge-transfer reactions of atomic ions with HCl

    Science.gov (United States)

    Glenewinkel-Meyer, Th.; Ottinger, Ch.

    1994-01-01

    Charge-transfer reactions of C+, O+, F+, Ar+ and some other atomic ions with hydrogen chloride were investigated at collision energies between eVc.m.. This may be due to formation of a long-lived collision complex (Ar-HCl)+.

  13. Intramolecular Charge Transfer and Solvation of Photoactive Molecules with Conjugated Push-Pull Structures.

    Science.gov (United States)

    Zhu, Huaning; Wang, Xian; Ma, Renjun; Kuang, Zhuoran; Guo, Qianjin; Xia, Andong

    2016-10-18

    A comparative investigation on the photophysical properties and solvation-related ICT dynamics of three push-pull compounds containing different donors including carbazole, triphenylamine and phenothiazine, was performed. The steady-state spectra and theoretical calculations show the charge transfers from the central donors to the acceptors at each side. The characterization of the extent of charge transfer was determined by various means, including estimation of the dipole moment, the electron density distribution of HOMO and LUMO, CDD and change in Gibb's free energy, which show the charge transfer strength to be in the order PDHP > BDHT > PDHC. This suggests that the electron-donating ability of the donor groups plays a crucial role in the charge transfer in these compounds. The TA data show the excited-state relaxation dynamics follow a sequential model: FC→ICT→ICT'→S0 , and are affected by the solvent polarity. The results presented here demonstrate that the compound with a higher degree of ICT characteristic interacts more strongly with stronger polar solvent molecules, which can accelerate the solvation and spectral evolution to lower energy levels. The A-π-D-π-A architectures with prominent ICT characteristics based on carbazole, triphenylamine and phenothiazine might be potential scaffolds for light-harvesting and photovoltaic devices. These results are of value for understanding structure-property relationships and the rational design of functional materials for photoelectric applications.

  14. Absence of superconductivity and valence bond order in the Hubbard-Heisenberg model for organic charge-transfer solids.

    Science.gov (United States)

    Gomes, N; Clay, R T; Mazumdar, S

    2013-09-25

    A frustrated, effective ½-filled band Hubbard-Heisenberg model has been proposed for describing the strongly dimerized charge-transfer solid families κ-(ET)2X and Z[Pd(dmit)2]2. In addition to showing unconventional superconductivity, these materials also exhibit antiferromagnetism, candidate spin-liquid phases, and, in the case of Z=EtMe3P, a spin-gapped phase that has sometimes been referred to as a valence bond solid. We show that neither superconductivity nor the valence bond order phase occurs within the Hubbard-Heisenberg model. We suggest that a description based on ¼-filling, that is reached when the carrier concentration per molecule instead of per dimer is considered, thus may be appropriate.

  15. Investigation of the charge-transfer in photo-excited nanoparticles for CO2 reduction in non-aqueous media

    Directory of Open Access Journals (Sweden)

    Dimitrijević Nada M.

    2013-01-01

    Full Text Available Photoinduced charge separation in TiO2 and Cu2O semiconductor nanoparticles was examined using Electron Paramagnetic Resonance spectroscopy in order to get insight into the photocatalytic reduction of CO2 in nonaqueous media. For dissolution/grafting of CO2 we have used carboxy-PEG4-amine, and as a solvent poly(ethylene glycol 200. We have found that, in this system, reduction of CO2 starts at potential of -0.5 V vs Ag/AgCl, which is significantly more positive than the potential for electrochemical reduction of CO2 in most organic solvents and water (-2.0 V vs. Ag/AgCl. The electron transfer from excited nanoparticles to CO2 is governed both by thermodynamic and kinetic parameters, namely by the redox potential of conduction band electrons and adsorption/binding of CO2 on the surface of nanoparticles.

  16. Bond-length alternation and charge transfer in a linear carbon chain encapsulated within a single-walled carbon nanotube

    Science.gov (United States)

    Rusznyák, Á.; Zólyomi, V.; Kürti, J.; Yang, S.; Kertesz, M.

    2005-10-01

    The physical properties of a linear carbon chain encapsulated within single-walled carbon nanotubes are investigated with density-functional theory using periodic boundary conditions. The dominant feature of an isolated carbon chain is the Peierls dimerization and the opening of a Peierls gap. The two weakly interacting subsystems (infinite carbon chain and nanotube) establish a common Fermi level, resulting in charge transfer (CT) which leads to a metallic combined system with a high density of states at the Fermi level. The rigid band model provides useful insights. Unusual physics arises from the effects of CT and chain-tube orbital hybridization which both tend to suppress the Peierls dimerization. Implications for the observed Raman spectrum of the chain-nanotube system are discussed.

  17. A schematic model for energy and charge transfer in the chlorophyll complex

    DEFF Research Database (Denmark)

    Bohr, Henrik; Malik, F.B.

    2011-01-01

    A theory for simultaneous charge and energy transfer in the carotenoid-chlorophyll-a complex is presented here and discussed. The observed charge transfer process in these chloroplast complexes is reasonably explained in terms of this theory. In addition, the process leads to a mechanism to drive...... an electron in a lower to a higher-energy state, thus providing a mechanism for the ejection of the electron to a nearby molecule (chlorophyll) or into the environment. The observed lifetimes of the electronically excited states are in accord/agreement with the investigations of Sundström et al....... and are in the range of pico-seconds and less. The change in electronic charge distribution in internuclear space as the system undergoes an electronic transition to a higher-energy state could, under appropriate physical conditions, lead to oscillating dipoles capable of transmitting energy from the carotenoid-chlorophylls...

  18. Direct detection of photoinduced charge transfer complexes in polymer fullerene blends

    Science.gov (United States)

    Behrends, Jan; Sperlich, Andreas; Schnegg, Alexander; Biskup, Till; Teutloff, Christian; Lips, Klaus; Dyakonov, Vladimir; Bittl, Robert

    2012-03-01

    We report transient electron paramagnetic resonance (trEPR) measurements with submicrosecond time resolution performed on a polymer:fullerene blend consisting of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) at low temperatures. The trEPR spectrum immediately following photoexcitation reveals signatures of spin-correlated polaron pairs. The pair partners (positive polarons in P3HT and negative polarons in PCBM) can be identified by their characteristic g values. The fact that the polaron pair states exhibit strong non-Boltzmann population unambiguously shows that the constituents of each pair are geminate, i.e., originate from one exciton. We demonstrate that coupled polaron pairs are present even several microseconds after charge transfer and suggest that they embody the intermediate charge transfer complexes that form at the donor/acceptor interface and mediate the conversion from excitons into free charge carriers.

  19. Where Do Photogenerated Holes Go in Anatase:Rutile TiO2? A Transient Absorption Spectroscopy Study of Charge Transfer and Lifetime.

    Science.gov (United States)

    Kafizas, Andreas; Wang, Xiuli; Pendlebury, Stephanie R; Barnes, Piers; Ling, Min; Sotelo-Vazquez, Carlos; Quesada-Cabrera, Raul; Li, Can; Parkin, Ivan P; Durrant, James R

    2016-02-11

    Anatase:rutile TiO2 junctions are often shown to be more photocatalytically active than anatase or rutile alone, but the underlying cause of this improvement is not fully understood. Herein, we employ transient absorption spectroscopy to study hole transfer across the anatase:rutile heterojunction in films as a function of phase composition. By exploiting the different signatures in the photoinduced absorption of trapped charges in anatase and rutile, we were able to separately track the yield and lifetime of holes in anatase and rutile sites within phase composites. Photogenerated holes transfer from rutile to anatase on submicrosecond time scales. This hole transfer can significantly increase the anatase hole yield, with a 20:80 anatase:rutile composite showing a 5-fold increase in anatase holes observed from the microsecond. Hole transfer does not result in an increase in charge-carrier lifetime, where an intermediate recombination dynamic between that of pure anatase (t1/2 ≈ 0.5 ms) and rutile (t1/2 ≈ 20 ms) is found in the anatase:rutile junction (t1/2 ≈ 4 ms). Irrespective of what the formal band energy alignment may be, we demonstrate the importance of trap-state energetics for determining the direction of photogenerated charge separation across heterojunctions and how transient absorption spectroscopy, a method that can specifically track the migration of trapped charges, is a useful tool for understanding this behavior.

  20. Charge transfer to a dielectric target by guided ionization waves using electric field measurements

    Science.gov (United States)

    Slikboer, Elmar; Garcia-Caurel, Enric; Guaitella, Olivier; Sobota, Ana

    2017-03-01

    A kHz-operated atmospheric pressure plasma jet is investigated by measuring charge transferred to a dielectric electro-optic surface (BSO crystal) allowing for the measurement of electric field by exploiting the Pockels effect. The electric field values, distribution of the surface discharge and amount of deposited charge are obtained for various parameters, including gas flow, applied voltage, target distance and the length of the capillary from ground to the end. A newly formed surface discharge emerges at the target when enough charge is deposited at the impact point and electric fields are high enough, i.e. 200 pC and 9 ± 2 kV cm‑1. The maximum amount of charge transferred by a single ionization wave (‘plasma bullet’) is 350 ± 40 pC. Due to the emerging new surface discharge behind the impact point, the total charge deposited on the surface of the dielectric target can increase up to 950 pC. The shape of the secondary discharge on the target is found to be mainly driven by gas flow, while the applied voltage allows us to utilize longer distances within the boundaries set by this gas mixing. Finally the ionization wave is found to lose charge along its propagation on the inner walls of the capillary. The loss is estimated to be approximately 7.5 pC mm‑1 of travel distance inside the capillary.

  1. 表面敏化TiO_2基复合薄膜的能带结构与光致电荷转移的研究%Band Structure and Photo-induced Charge Transfer in Surface-sensitized TiO_2-based Composite Films

    Institute of Scientific and Technical Information of China (English)

    董江舟; 赵峻岩; 巢晖; 曹亚安

    2011-01-01

    采用离子束溅射方法制备出TiO2/ITO,Zr4+掺杂的TiO2(TiO2-Zr)/ITO和ZrO2/TiO2/ITO复合薄膜.利用表面敏化方法制备出(1,10-邻菲咯啉)2(3,4,5-三氟苯基)咪唑并[5,6-f]邻菲咯啉钌混配配合物[Rup2O](p=1,10-邻菲咯啉,O=(3,4,5-三氟苯基)咪唑并[5,6-f]邻菲咯啉)/TiO2/ITO,Rup2O/TiO2-Zr/ITO和Rup2O/ZrO2/TiO2/ITO表面敏化TiO2基复合薄膜.表面光电压谱(SPS)表明,表面敏化TiO2基复合薄膜在400~600和350 nm产生的SPS响应峰的峰高比与TiO2基复合薄膜的结构密切相关.利用电场诱导表面光电压谱(EFISPS)确定了复合薄膜的能带结构,其结果分析表明,400~600 nm的SPS响应峰主要源于Rup2O分子的中心离子Ru 4d能级到配体邻菲咯啉π1*和配体咪唑并邻菲咯啉π2*跃迁;TiO2禁带内Zr4+掺杂能级的存在减小了光生载流子的复合,增加导带光生电子的数量;ZrO2/TiO2异质结构的存在有利于光生电子向ITO表面的转移,从而导致400~600 nm和350 nm SPS响应峰的峰高比的增加,意味着光致电荷转移效率的提高.%The films of TiO2/ITO,ZrO2/ITO,TiO2-Zr/ITO and TiO2/ZrO2/ITO were prepared by ion-beam sputtering,all of which were also surface-sensitized with Rup2O(p=1,10-phenanthroline,O=(3,4,5-tri-fluorophenyl) imidazo phenanthroline) by using the rolling coat method.The physical parameters and energy levels of TiO2-based and Rup2O modified TiO2-based films were ascertained by SPS and EFISPS.Because of the electron transitions between Ru 4d level and ligand levels(1* and 2*),there were SPS peaks generated in Rup2O modified films in the spectral wavelength range from 400 nm to 600 nm.The SPS intensity ratios between each of the SPS peak at 400~600 nm and that at 350 nm were different for different energy levels in the TiO2-based films.The existence of Zr4+ doping level in TiO2-Zr forbidden bands makes the decrease of the recombination of photo-induced carriers

  2. Charge transfer of edge states in zigzag silicene nanoribbons with Stone–Wales defects from first-principles

    Energy Technology Data Exchange (ETDEWEB)

    Ting, Xie [College of Mathematics and Statistics, Chongqing University, Chongqing 401331 (China); School of Mathematics and Statistic, Chongqing University of Technology, Chongqing 400054 (China); Rui, Wang, E-mail: rcwang@cqu.edu.cn [Institute for Structure and Function and Department of Physics, Chongqing University, Chongqing 400044 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Science, Beijing 100190 (China); Shaofeng, Wang [Institute for Structure and Function and Department of Physics, Chongqing University, Chongqing 400044 (China); Xiaozhi, Wu, E-mail: xiaozhiwu@cqu.edu.cn [Institute for Structure and Function and Department of Physics, Chongqing University, Chongqing 400044 (China)

    2016-10-15

    Highlights: • The properties of SW defects in silicene and ZSNRs are obtained. • The SW defects at the edge of ZSNRs induce a sizable gap. • The charge transfer of edge states is resulted from SW defects in ZSNRS. - Abstract: Stone–Wales (SW) defects are favorably existed in graphene-like materials with honeycomb lattice structure and potentially employed to change the electronic properties in band engineering. In this paper, we investigate structural and electronic properties of SW defects in silicene sheet and its nanoribbons as a function of their concentration using the methods of periodic boundary conditions with first-principles calculations. We first calculate the formation energy, structural properties, and electronic band structures of SW defects in silicene sheet, with dependence on the concentration of SW defects. Our results show a good agreement with available values from the previous first-principles calculations. The energetics, structural aspects, and electronic properties of SW defects with dependence on defect concentration and location in edge-hydrogenated zigzag silicene nanoribbons are obtained. For all calculated concentrations, the SW defects prefer to locate at the edge due to the lower formation energy. The SW defects at the center of silicene nanoribbons slightly influence on the electronic properties, whereas the SW defects at the edge of silicene nanoribbons split the degenerate edge states and induce a sizable gap, which depends on the concentration of defects. It is worth to find that the SW defects produce a perturbation repulsive potential, which leads the decomposed charge of edge states at the side with defect to transfer to the other side without defect.

  3. Non-Linearity in Wide Dynamic Range CMOS Image Sensors Utilizing a Partial Charge Transfer Technique

    Directory of Open Access Journals (Sweden)

    Izhal Abdul Halin

    2009-11-01

    Full Text Available The partial charge transfer technique can expand the dynamic range of a CMOS image sensor by synthesizing two types of signal, namely the long and short accumulation time signals. However the short accumulation time signal obtained from partial transfer operation suffers of non-linearity with respect to the incident light. In this paper, an analysis of the non-linearity in partial charge transfer technique has been carried, and the relationship between dynamic range and the non-linearity is studied. The results show that the non-linearity is caused by two factors, namely the current diffusion, which has an exponential relation with the potential barrier, and the initial condition of photodiodes in which it shows that the error in the high illumination region increases as the ratio of the long to the short accumulation time raises. Moreover, the increment of the saturation level of photodiodes also increases the error in the high illumination region.

  4. Charge transfer in dissociating iodomethane and fluoromethane molecules ionized by intense femtosecond X-ray pulses

    Directory of Open Access Journals (Sweden)

    Rebecca Boll

    2016-07-01

    Full Text Available Ultrafast electron transfer in dissociating iodomethane and fluoromethane molecules was studied at the Linac Coherent Light Source free-electron laser using an ultraviolet-pump, X-ray-probe scheme. The results for both molecules are discussed with respect to the nature of their UV excitation and different chemical properties. Signatures of long-distance intramolecular charge transfer are observed for both species, and a quantitative analysis of its distance dependence in iodomethane is carried out for charge states up to I21+. The reconstructed critical distances for electron transfer are in good agreement with a classical over-the-barrier model and with an earlier experiment employing a near-infrared pump pulse.

  5. Multicolour Emission States from Charge Transfer between Carbon Dots and Surface Molecules

    Directory of Open Access Journals (Sweden)

    Shengliang Hu

    2017-02-01

    Full Text Available The emissive states of carbon dots have been tuned by controlling the charge transfer process. The carbon dots couple with molecules, which are made of a benzene ring and different heteroatom substituents, through amino-carboxylic bonds that are generally identified as charge transfer promoters at the interface. New ways of radiative recombination are created due to the transfer of photo-excited electrons from carbon dots to the lowest unoccupied molecular orbital (LUMO of the grafted molecules. By variation of the molecular orbital energy levels via heteroatom substituents in the benzene ring, the different optical properties and emission colors of the carbon dots were presented. This work opens up new opportunities for the application of carbon dots since different heteroatom substituents could lead to many possibilities for conjugation with drugs and biomolecules.

  6. [Diffusion and diffusion-osmosis models of the charged macromolecule transfer in barriers of biosystems].

    Science.gov (United States)

    Varakin, A I; Mazur, V V; Arkhipova, N V; Serianov, Iu V

    2009-01-01

    Mathematical models of the transfer of charged macromolecules have been constructed on the basis of the classical equations of electromigration diffusion of Helmholtz-Smolukhovskii, Goldman, and Goldman-Hodgkin-Katz. It was shown that ion transfer in placental (mimicking lipid-protein barriers) and muscle barriers occurs by different mechanisms. In placental barriers, the electromigration diffusion occurs along lipid-protein channels formed due to the conformational deformation of phospholipid and protein molecules with the coefficients of diffusion D = (2.6-3.6) x 10(-8) cm2/s. The transfer in muscle barriers is due to the migration across charged interfibrillar channels with the negative diffusion activation energy, which is explained by changes in the structure of muscle fibers and expenditures of thermal energy for the extrusion of Cl- from channel walls with the diffusion coefficient D = (6.0-10.0) x 10(-6) cm2/s.

  7. Solvent-mediated electron hopping: long-range charge transfer in IBr-(CO2) photodissociation.

    Science.gov (United States)

    Sheps, Leonid; Miller, Elisa M; Horvath, Samantha; Thompson, Matthew A; Parson, Robert; McCoy, Anne B; Lineberger, W Carl

    2010-04-09

    Chemical bond breaking involves coupled electronic and nuclear dynamics that can take place on multiple electronic surfaces. Here we report a time-resolved experimental and theoretical investigation of nonadiabatic dynamics during photodissociation of a complex of iodine monobromide anion with carbon dioxide [IBr-(CO2)] on the second excited (A') electronic state. Previous experimental work showed that the dissociation of bare IBr- yields only I- + Br products. However, in IBr-(CO2), time-resolved photoelectron spectroscopy reveals that a subset of the dissociating molecules undergoes an electron transfer from iodine to bromine 350 femtoseconds after the initial excitation. Ab initio calculations and molecular dynamics simulations elucidate the mechanism for this charge hop and highlight the crucial role of the carbon dioxide molecule. The charge transfer between two recoiling atoms, assisted by a single solvent-like molecule, provides a notable limiting case of solvent-driven electron transfer over a distance of 7 angstroms.

  8. Explicit solvent DRF INDOs/CIS computations of charge transfer state energetics in a pyrenyldeoxyuridine nucleoside model.

    Science.gov (United States)

    Van Duijnen, Piet Th; Netzel, Thomas L

    2006-02-16

    In this work we present calculated absorption and emission spectra in acetonitrile (MeCN) solution of N-acetyl-1-aminopyrene (PAAc, a spectroscopic model compound) and N-(1-pyrenyl)-1-methyluracil-5-carboxamide (PAU(Me), a computational model for 5-(N-carboxyl-1-aminopyrenyl)-2'-deoxyuridine (PAdU)). The computational method used--the discrete reaction field approach (DRF)--combines a quantum mechanical (QM) description of the solute (here DFT and INDOs/CIS, i.e., the INDO parametrization for spectroscopy) with a classical, molecular mechanics (MM) description of the solvent molecules. The latter are modeled with point charges representing the permanent charge distribution and polarizabilities to account for many-body interactions among the solute and other solvent molecules. Molecular dynamics is used to sample the degrees of freedom of the solution around several solute conformations each in two electronic excited states. This leads to a large number of solute/solvent configurations from which 800 are selected for each excited state and collected into a single ensemble by means of proper Boltzmann averaging. DRF INDOs/CIS applied to the selected solute/solvent configurations give simulated absorption and emission band spectra--each based on 15,200 calculated transitions--that compare well with experimental results. For example, the much broader absorption and emission bands in PAdU compared with PAAc are reproduced, and the simulated emission spectra of PAU(Me) agree well with broad (380-550 nm) charge transfer (CT) emission seen for PAdU in MeCN. The observed multiexponential fluorescence decay profiles for PAdU in different polar solvents are interpreted in terms of solute/solvent conformational heterogeneity here generated in the MD simulations for PAU(Me) in MeCN. Additionally, the simulations demonstrate the mixing of the forbidden Py*+/dU*- CT states with allowed pyrenyl 1(pi,pi*) states.

  9. Failures of TDDFT in describing the lowest intramolecular charge-transfer excitation in para-nitroaniline

    DEFF Research Database (Denmark)

    Eriksen, Janus J.; Sauer, Stephan P. A.; Mikkelsen, Kurt Valentin;

    2013-01-01

    for charge{transfer character, we furthermore conrm that the di¿erence between excitation energies calculated with TDDFT and with the Tamm-Danco¿ approximation (TDA) to TDDFT is indeed correlated with the charge-transfer character of a given electronic transition both in vacuo and in solution...

  10. Resonant core spectroscopies of the charge transfer interactions between C60 and the surfaces of Au(111), Ag(111), Cu(111) and Pt(111)

    Science.gov (United States)

    Gibson, Andrew J.; Temperton, Robert H.; Handrup, Karsten; O'Shea, James N.

    2017-03-01

    Charge transfer interactions between C60 and the metal surfaces of Ag(111), Cu(111), Au(111) and Pt(111) have been studied using synchrotron-based photoemission, resonant photoemission and X-ray absorption spectroscopies. By placing the X-ray absorption and valence band spectra on a common binding energy scale, the energetic overlap of the unoccupied molecular orbitals with the density of states of the underlying metal surface have been assessed in the context of possible charge transfer pathways. Resonant photoemission and resonant Auger data, measuring the valence region as a function of photon energy for C60 adsorbed on Au(111) reveals three constant high kinetic energy features associated with Auger-like core-hole decay involving an electron transferred from the surface to the LUMO of the molecule and electrons from the three highest occupied molecular orbitals, respectively and in the presence of ultra-fast charge transfer of the originally photoexcited molecule to the surface. Data for the C60/Ag(111) surface reveals an additional Auger-like feature arising from a core-hole decay process involving more than one electron transferred from the surface into the LUMO. An analysis of the relative abundance of these core-hole decay channels estimates that on average 2.4 ± 0.3 electrons are transferred from the Ag(111) surface into the LUMO. A core-hole clock analysis has also been applied to assess the charge transfer coupling in the other direction, from the molecule to the Au(111) and Ag(111) surfaces. Resonant photoemission and resonant Auger data for C60 molecules adsorbed on the Pt(111) and Cu(111) surfaces are shown to exhibit no super-Auger features, which is attributed to the strong modification of the unoccupied molecular orbitals arising from stronger chemical coupling of the molecule to the surface.

  11. Two-band model as a quantum data bus for quantum state transfer

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We study the dynamics of an electron spin state transfer along a half-filled two-band model(TBM).It is shown that this solvable and realistic medium has an energy gap between the ground and first-excited states in the half-filled case.By connecting two qubits to two sites of the TBM,the system can accomplish a high-fidelity and long-distance quantum state transfer(QST).Moreover,numerical simulations have been performed for a finite system.The results show that the numerical and analytical results of the effective coupling strength agree well with each other.Furthermore,the investigation shows that the reduced density matrix also has high fidelity beyond the range of perturbation.

  12. Atmospheric circulation of tidally locked exoplanets II: dual-band radiative transfer and convective adjustment

    CERN Document Server

    Heng, Kevin; Phillipps, Peter J

    2011-01-01

    Improving upon our purely dynamical work, we present three-dimensional simulations of the atmospheric circulation on Earth-like (exo)planets and hot Jupiters using the GFDL-Princeton Flexible Modeling System (FMS). As the first steps away from the purely dynamical benchmarks of Heng, Menou & Phillipps (2011), we add dual-band radiative transfer and dry convective adjustment schemes to our computational setup. Our treatment of radiative transfer assumes stellar irradiation to peak at a wavelength shorter than and distinct from that at which the exoplanet re-emits radiation ("shortwave" versus "longwave"), and also uses a two-stream approximation. Convection is mimicked by adjusting unstable lapse rates to the dry adiabat. The bottom of the atmosphere is bounded by an uniform slab with a finite thermal inertia. For our hot Jupiter models, we include an analytical formalism for calculating temperature-pressure profiles, in radiative equilibrium, which accounts for the effect of collision-induced absorption v...

  13. Communication: Modeling of concentration dependent water diffusivity in ionic solutions: Role of intermolecular charge transfer.

    Science.gov (United States)

    Yao, Yi; Berkowitz, Max L; Kanai, Yosuke

    2015-12-28

    The translational diffusivity of water in solutions of alkali halide salts depends on the identity of ions, exhibiting dramatically different behavior even in solutions of similar salts of NaCl and KCl. The water diffusion coefficient decreases as the salt concentration increases in NaCl. Yet, in KCl solution, it slightly increases and remains above bulk value as salt concentration increases. Previous classical molecular dynamics simulations have failed to describe this important behavior even when polarizable models were used. Here, we show that inclusion of dynamical charge transfer among water molecules produces results in a quantitative agreement with experiments. Our results indicate that the concentration-dependent diffusivity reflects the importance of many-body effects among the water molecules in aqueous ionic solutions. Comparison with quantum mechanical calculations shows that a heterogeneous and extended distribution of charges on water molecules around the ions due to ion-water and also water-water charge transfer plays a very important role in controlling water diffusivity. Explicit inclusion of the charge transfer allows us to model accurately the difference in the concentration-dependent water diffusivity between Na(+) and K(+) ions in simulations, and it is likely to impact modeling of a wide range of systems for medical and technological applications.

  14. Negative Resistance Effect and Charge Transfer Mechanisms in the lon Beam Deposited Diamond Like Carbon Superlattices

    Directory of Open Access Journals (Sweden)

    Andrius VASILIAUSKAS

    2011-03-01

    Full Text Available In the present study DLC:SiOx/DLC/DLC:SiOx/nSi and DLC:SiOx/DLC/DLC:SiOx/pSi structures were fabricated by ion beam deposition using a closed drift ion source. Current-voltage (I-V characteristics of the multilayer samples were measured at room temperature. The main charge transfer mechanisms were considered. Unstable negative resistance effect was observed for some DLC:SiOx/DLC/DLC:SiOx/nSi and DLC:SiOx/DLC/DLC:SiOx/pSi structures. In the case of the diamond like carbon superlattices fabricated on nSi it was observed only during the first measurement. In the case of the some DLC:SiOx/DLC/DLC:SiOx/pSi negative resistance "withstood" several measurements. Changes of the charge carrier mechanisms were observed along with the dissapear of the negative resistance peaks. It seems, that in such a case influence of the bulk related charge transfer mechanisms such as Poole-Frenkel emission increased, while the influence of the contact limited charge transfer mechanisms such as Schottky emission decreased. Observed results were be explained by current flow through the local microconducting channels and subsequent destruction of the localized current pathways as a result of the heating by flowing electric current.http://dx.doi.org/10.5755/j01.ms.17.1.240

  15. Substituent and Solvent Effects on Excited State Charge Transfer Behavior of Highly Fluorescent Dyes Containing Thiophenylimidazole-Based Aldehydes

    Science.gov (United States)

    Santos, Javier; Bu, Xiu R.; Mintz, Eric A.

    2001-01-01

    The excited state charge transfer for a series of highly fluorescent dyes containing thiophenylimidazole moiety was investigated. These systems follow the Twisted Intramolecular Charge Transfer (TICT) model. Dual fluorescence was observed for each substituted dye. X-ray structures analysis reveals a twisted ground state geometry for the donor substituted aryl on the 4 and 5 position at the imidazole ring. The excited state charge transfer was modeled by a linear solvation energy relationship using Taft's pi and Dimroth's E(sub T)(30) as solvent parameters. There is linear relation between the energy of the fluorescence transition and solvent polarity. The degree of stabilization of the excited state charge transfer was found to be consistent with the intramolecular molecular charge transfer. Excited dipole moment was studied by utilizing the solvatochromic shift method.

  16. Dependence of (35)Cl NQR on hydrogen bonding and temperature in dichlorophenol-aniline charge transfer complexes.

    Science.gov (United States)

    Ramananda, D; Ramesh, K P; Uchil, J

    2007-10-01

    The hydrogen-bonded charge transfer complexes of aniline with pi-acceptors (or proton donors) such as 2,5-, 2,6-, 3,4- and 3,5-dichlorophenol were prepared. The (35)Cl nuclear quadrupole resonance (NQR) frequencies of these charge transfer complexes in the temperature range 77-300 K were measured to ascertain the existence or otherwise of a phase transition upon complex formation. Further, the NQR frequency and asymmetry parameter of the electric field gradient at the site of quadrupole nucleus were used to estimate the chemical bond parameters, namely ionic bond, double bond character of the carbon-chlorine(C--Cl) bond and the percentage charge transfer between the donor-acceptor components in charge transfer complexes. The effect of hydrogen bonding and temperature on the charge transfer process is analysed.

  17. Intramolecular Charge Transfer of Carotene-porphyrin-fullerene Triad: Sequential or Superexchange Cechanism

    Institute of Scientific and Technical Information of China (English)

    SUN,Yu; CHEN,Yue-Hui; LI,Yuan-Zuo; LI,Yong-Qing; MA,Feng-Cai

    2008-01-01

    As an excellent artificial photosynthetic reaction center,the carotene (C)-porphyrin (P)-fullerene (F) triad was extensively investigated experimentally.To reveal the mechanism of the intramolecular charge transfer (ICT) on the mimic of photosynthetic solar energy conversion (such as singlet energy transfer between pigments,and photoinduced electron transfer from excited singlet states to give long-lived charge-separated states),the ICT mechanisms of C-P-F triad on the exciton were theoretically studied with quantum chemical methods as well as the 2D and 3D real space analysis approaches.The results of quantum chemical methods reveal that the excited states are the ICT states,since the densities of HOMO are localized in the carotene or porphyrin unit,and the densities of LUMO are localized in the fullerene unit.Furthermore,the excited states should be the intramolecular superexchange charge transfer (ISCT) states for the orbital transition from the HOMO whose densities are localized in the carotene to the LUMO whose densities are localized in the fullerene unit.The 3D charge difference densities can clearly show that some excited states are ISCT excited states,since the electron and hole are resident in the fullerene and carotene units,respectively.From the results of the electron-hole coherence of the 2D transition density matrix,not only 3D results are supported,but also the delocalization size on the exciton can be observed.These phenomena were further interpreted with non-linear optical effect.The large changes of the linear and non-linear polarizabilities on the exciton result in the charge separate states,and if their changes are large enough,the ICT mechanism can become the ISCT on the exciton.

  18. Coarse-Grained Theory of Biological Charge Transfer with Spatially and Temporally Correlated Noise.

    Science.gov (United States)

    Liu, Chaoren; Beratan, David N; Zhang, Peng

    2016-04-21

    System-environment interactions are essential in determining charge-transfer (CT) rates and mechanisms. We developed a computationally accessible method, suitable to simulate CT in flexible molecules (i.e., DNA) with hundreds of sites, where the system-environment interactions are explicitly treated with numerical noise modeling of time-dependent site energies and couplings. The properties of the noise are tunable, providing us a flexible tool to investigate the detailed effects of correlated thermal fluctuations on CT mechanisms. The noise is parametrizable by molecular simulation and quantum calculation results of specific molecular systems, giving us better molecular resolution in simulating the system-environment interactions than sampling fluctuations from generic spectral density functions. The spatially correlated thermal fluctuations among different sites are naturally built-in in our method but are not readily incorporated using approximate spectral densities. Our method has quantitative accuracy in systems with small redox potential differences (charge delocalization and charge-transfer rates; however, in a system of units with different site energies, spatial correlations slow the fluctuations to bring units into degeneracy, in turn, slowing the charge-transfer rates. The spatial and temporal correlations of condensed phase medium fluctuations provide another source to control and tune the kinetics and dynamics of charge-transfer systems.

  19. Control of intrachain charge transfer in model systems for block copolymer photovoltaic materials.

    Science.gov (United States)

    Johnson, Kerr; Huang, Ya-Shih; Huettner, Sven; Sommer, Michael; Brinkmann, Martin; Mulherin, Rhiannon; Niedzialek, Dorota; Beljonne, David; Clark, Jenny; Huck, Wilhelm T S; Friend, Richard H

    2013-04-01

    We report the electronic properties of the conjugated coupling between a donor polymer and an acceptor segment serving as a model for the coupling in conjugated donor-acceptor block copolymers. These structures allow the study of possible intrachain photoinduced charge separation, in contrast to the interchain separation achieved in conventional donor-acceptor blends. Depending on the nature of the conjugated linkage, we observe varying degrees of modification of the excited states, including the formation of intrachain charge transfer excitons. The polymers comprise a block (typically 18 repeat units) of P3HT, poly(3-hexyl thiophene), coupled to a single unit of F8-TBT (where F8 is dioctylfluorene, and TBT is thiophene-benzothiadiazole-thiophene). When the P3HT chain is linked to the TBT unit, we observe formation of a localized charge transfer state, with red-shifted absorption and emission. Independent of the excitation energy, this state is formed very rapidly (<40 fs) and efficiently. Because there is only a single TBT unit present, there is little scope for long-range charge separation and it is relatively short-lived, <1 ns. In contrast, when the P3HT chain and TBT unit are separated by the wider bandgap F8 unit, there is little indication for modification of either ground or excited electronic states, and longer-lived charge separated states are observed.

  20. Charge-dependent dissociation of insulin cations via ion/ion electron transfer

    Science.gov (United States)

    Liu, Jian; Gunawardena, Harsha P.; Huang, Teng-Yi; McLuckey, Scott A.

    2008-10-01

    The dissociation reactions of various charge states of insulin cations obtained directly from nano-electrospray were investigated as a result of ion/ion electron transfer from azobenzene anions. Data were collected with and without simultaneous ion trap collisional excitation of the first generation charge-reduced product during the ion/ion reaction period. Neither separation of the two constituent chains nor cleavages within the loop defined by the disulfide bridges were observed under normal electron transfer dissociation (ETD) conditions for any of the charge states studied. However, substantial sequence coverage (exocyclic region: 82.6%; entire protein: 38.8%) outside the ring structure was obtained for insulin +6, while only limited coverage (exocyclic: 43.5%; entire protein: 20.4%) was observed for insulin +5 and no dissociation, aside from low abundance side-chain losses, was noted for insulin +4 and +3 in the normal ETD spectra. When the first generation charge-reduced precursor ions were subjected to collisional activation during the ion/ion reaction period, higher sequence coverages were obtained for both insulin +5 (entire protein: 34.7%) and +4 (entire protein: 20.4%) with backbone cleavages occurring within the loop defined by the disulfide bonds. Dissociation of insulin +3 was not significantly improved by the additional activation. Separation of the two constituent chains resulting from cleavages of both of the two disulfide bridges that link the chains was observed for insulin +6, +5, and +4 when the charge-reduced species were activated. The dissociation of disulfide linkages in this study suggests that as the charge state decreases, disulfide bond cleavages dominate over N-C[alpha] bond cleavages in the electron transfer dissociation process.

  1. UHF-Band Wireless Power Transfer System for Structural Health Monitoring Sensor Network

    Directory of Open Access Journals (Sweden)

    Tansheng Li

    2013-01-01

    Full Text Available For detecting and measuring health conditions of bridges, wireless sensor networks are used in these days. However, battery life is critically restricting the application and maintenance cost of sensor network systems. To extend life time, a wireless power transfer system at UHF band is introduced to supply the current wireless sensor network. This power transfer system is based on electric wave at 950 MHz. This power transfer system is redesigned for tiny power transmission, including a combination of a rectenna and a Cockcroft-Walton boost converter, battery board, and a control board. Also, current wireless sensor network is redesigned for power transfer system. The working flow of sensor network is modified to bottom-to-top to save power of sensor modules which are the power bottleneck of this sensor system. As a result, the system is able to support a sensor module continuously with received power of −14 dBmW, when the transmitting antenna is 30 dBmW at 10 meters distance.

  2. Intermolecular electron transfer from intramolecular excitation and coherent acoustic phonon generation in a hydrogen-bonded charge-transfer solid

    Science.gov (United States)

    Rury, Aaron S.; Sorenson, Shayne; Dawlaty, Jahan M.

    2016-03-01

    Organic materials that produce coherent lattice phonon excitations in response to external stimuli may provide next generation solutions in a wide range of applications. However, for these materials to lead to functional devices in technology, a full understanding of the possible driving forces of coherent lattice phonon generation must be attained. To facilitate the achievement of this goal, we have undertaken an optical spectroscopic study of an organic charge-transfer material formed from the ubiquitous reduction-oxidation pair hydroquinone and p-benzoquinone. Upon pumping this material, known as quinhydrone, on its intermolecular charge transfer resonance as well as an intramolecular resonance of p-benzoquinone, we find sub-cm-1 oscillations whose dispersion with probe energy resembles that of a coherent acoustic phonon that we argue is coherently excited following changes in the electron density of quinhydrone. Using the dynamical information from these ultrafast pump-probe measurements, we find that the fastest process we can resolve does not change whether we pump quinhydrone at either energy. Electron-phonon coupling from both ultrafast coherent vibrational and steady-state resonance Raman spectroscopies allows us to determine that intramolecular electronic excitation of p-benzoquinone also drives the electron transfer process in quinhydrone. These results demonstrate the wide range of electronic excitations of the parent of molecules found in many functional organic materials that can drive coherent lattice phonon excitations useful for applications in electronics, photonics, and information technology.

  3. Infrared light irradiation diminishes effective charge transfer in slow sodium channel gating system

    Science.gov (United States)

    Plakhova, Vera B.; Bagraev, Nikolai T.; Klyachkin, Leonid E.; Malyarenko, Anna M.; Romanov, Vladimir V.; Krylov, Boris V.

    2001-02-01

    Effects of infrared light irradiation (IR) on cultured dorsal root ganglia cells were studied by the whole-cell patch-clamp technique. The IR field is demonstrated to diminish the effective charge transfer in the activation system from 6.2 +-0.6 to 4.5 +-0.4 in units of electron charge per e-fold change in membrane potential. The effects was blocked with ouabain. Our data is the first indication that sodium pump might be the molecular sensor of infrared irradiation in animal kingdom.

  4. Control over the charge transfer in dye-nanoparticle decorated graphene

    Science.gov (United States)

    Bongu, Sudhakara Reddy; Veluthandath, Aneesh V.; Nanda, B. R. K.; Ramaprabhu, Sundara; Bisht, Prem B.

    2016-01-01

    Charge transfer interaction between silver decorated graphene and three differently charged dyes, cationic (rhodamine 6G), neutral (rhodamine B) and anionic (fluorescein 27) has been studied. The ground state association constants have been evaluated and changes in the fluorescence intensity and lifetimes have been obtained in two solvents. Strength of complex-formation has been found to be higher with the cationic molecule in water. In a higher viscosity solvent, the ground state complex formation is restricted. Local field of localized surface plasmons of nanoparticles adsorbed on the graphene sheets leads to enhanced absorption and fluorescence of fluorescein 27.

  5. Photoinduced Charge Transfer at Metal Oxide/Oxide Interfaces Prepared with Plasma Enhanced Atomic Layer Deposition

    Science.gov (United States)

    Kaur, Manpuneet

    LiNbO3 and ZnO have shown great potential for photochemical surface reactions and specific photocatalytic processes. However, the efficiency of LiNbO3 is limited due to recombination or back reactions and ZnO exhibits a chemical instability in a liquid cell. In this dissertation, both materials were coated with precise thickness of metal oxide layers to passivate the surfaces and to enhance their photocatalytic efficiency. LiNbO 3 was coated with plasma enhanced atomic layer deposited (PEALD) ZnO and Al2O3, and molecular beam deposited TiO2 and VO2. On the other hand, PEALD ZnO and single crystal ZnO were passivated with PEALD SiO2 and Al2O3. Metal oxide/LiNbO3 heterostructures were immersed in aqueous AgNO3 solutions and illuminated with ultraviolet (UV) light to form Ag nanoparticle patterns. Alternatively, Al2O3 and SiO2/ZnO heterostructures were immersed in K3PO 4 buffer solutions and studied for photoelectrochemical reactions. A fundamental aspect of the heterostructures is the band alignment and band bending, which was deduced from in situ photoemission measurements. This research has provided insight to three aspects of the heterostructures. First, the band alignment at the interface of metal oxides/LiNbO 3, and Al2O3 or SiO2/ZnO were used to explain the possible charge transfer processes and the direction of carrier flow in the heterostructures. Second, the effect of metal oxide coatings on the LiNbO3 with different internal carrier concentrations was related to the surface photochemical reactions. Third is the surface passivation and degradation mechanism of Al2O 3 and SiO2 on ZnO was established. The heterostructures were characterized after stability tests using atomic force microscopy (AFM), scanning electron microscopy (SEM), and cross-section transmission electron microscopy (TEM). The results indicate that limited thicknesses of ZnO or TiO2 on polarity patterned LiNbO3 (PPLN) enhances the Ag+ photoinduced reduction process. ZnO seems more efficient

  6. Block-Localized Wavefunction (BLW) Based Two-State Approach for Charge Transfers between Phenyl Rings.

    Science.gov (United States)

    Mo, Yirong; Song, Lingchun; Lin, Yuchun; Liu, Minghong; Cao, Zexing; Wu, Wei

    2012-03-13

    The block-localized wave function (BLW) method is the simplest and most efficient variant of ab initio valence bond (VB) theory which defines electron-localized resonance states following the conventional VB concepts. Here, a BLW-based two-state approach is proposed to probe the charge/hole transfer reactions within the Marcus-Hush model. With this approach, both the electronic coupling and reorganization energies can be derived at the ab initio level. Pilot applications to the electron/hole transfers between two phenyl rings are presented. Good exponential correlation between the electronic coupling energy and the donor-acceptor distance is shown, whereas the inner-sphere reorganization shows little geometric dependency. Computations also support the assumption in Marcus theory that the thermal electron transfer barrier (ΔG*), which is a sum of the reaction barrier (ΔEa) for electron/hole transfer and the coupling energy (VAB), is a quarter of the reorganization energy (λ).

  7. Charge transfer kinetics at the solid-solid interface in porous electrodes

    Science.gov (United States)

    Bai, Peng; Bazant, Martin Z.

    2014-04-01

    Interfacial charge transfer is widely assumed to obey the Butler-Volmer kinetics. For certain liquid-solid interfaces, the Marcus-Hush-Chidsey theory is more accurate and predictive, but it has not been applied to porous electrodes. Here we report a simple method to extract the charge transfer rates in carbon-coated LiFePO4 porous electrodes from chronoamperometry experiments, obtaining curved Tafel plots that contradict the Butler-Volmer equation but fit the Marcus-Hush-Chidsey prediction over a range of temperatures. The fitted reorganization energy matches the Born solvation energy for electron transfer from carbon to the iron redox site. The kinetics are thus limited by electron transfer at the solid-solid (carbon-LixFePO4) interface rather than by ion transfer at the liquid-solid interface, as previously assumed. The proposed experimental method generalizes Chidsey’s method for phase-transforming particles and porous electrodes, and the results show the need to incorporate Marcus kinetics in modelling batteries and other electrochemical systems.

  8. Temperature-dependent kinetics of charge transfer, hydrogen-atom transfer, and hydrogen-atom expulsion in the reaction of CO+ with CH4 and CD4.

    Science.gov (United States)

    Melko, Joshua J; Ard, Shaun G; Johnson, Ryan S; Shuman, Nicholas S; Guo, Hua; Viggiano, Albert A

    2014-09-18

    We have determined the rate constants and branching ratios for the reactions of CO(+) with CH4 and CD4 in a variable-temperature selected ion flow tube. We find that the rate constants are collisional for all temperatures measured (193-700 K for CH4 and 193-500 K for CD4). For the CH4 reaction, three product channels are identified, which include charge transfer (CH4(+) + CO), H-atom transfer (HCO(+) + CH3), and H-atom expulsion (CH3CO(+) + H). H-atom transfer is slightly preferred to charge transfer at low temperature, with the charge-transfer product increasing in contribution as the temperature is increased (H-atom expulsion is a minor product for all temperatures). Analogous products are identified for the CD4 reaction. Density functional calculations on the CO(+) + CH4 reaction were also conducted, revealing that the relative temperature dependences of the charge-transfer and H-atom transfer pathways are consistent with an initial charge transfer followed by proton transfer.

  9. Excited state intramolecular proton transfer and charge transfer dynamics of a 2-(2'-hydroxyphenyl)benzoxazole derivative in solution.

    Science.gov (United States)

    Kim, Chul Hoon; Park, Jaehun; Seo, Jangwon; Park, Soo Young; Joo, Taiha

    2010-05-13

    Excited state intramolecular proton transfer (ESIPT) and subsequent intramolecular charge transfer (ICT) dynamics of a 2-(2'-hydroxyphenyl)benzoxazole derivative conjugated with an electron withdrawing group (HBOCE) in solutions and a polymer film has been investigated by femtosecond time-resolved fluorescence (TRF) and TRF spectra measurements without the conventional spectral reconstruction method. TRF with high enough resolution (benzoxazole groups is invoked to account for the dispersive ESIPT dynamics in liquids. From the TRF spectra of both the enol and keto isomers, we have identified the ICT reaction of the keto isomer occurring subsequent to the ESIPT. The ICT proceeds also by two time constants of near instantaneous and 2.7 ps. Since the ICT dynamics of HBOCE is rather close to the polar solvation dynamics, we argue that the ICT is barrierless and determined mostly by the solvent fluctuation.

  10. Charge-transfer dynamics at the dye-semiconductor interface of photocathodes for solar energy applications.

    Science.gov (United States)

    Black, Fiona A; Wood, Christopher J; Ngwerume, Simbarashe; Summers, Gareth H; Clark, Ian P; Towrie, Michael; Camp, Jason E; Gibson, Elizabeth A

    2017-03-13

    This article describes a comparison between the photophysical properties of two charge-transfer dyes adsorbed onto NiO via two different binding moieties. Transient spectroscopy measurements suggest that the structure of the anchoring group affects both the rate of charge recombination between the dye and NiO surface and the rate of dye regeneration by an iodide/triiodide redox couple. This is consistent with the performance of the dyes in p-type dye sensitised solar cells. A key finding was that the recombination rate differed in the presence of the redox couple. These results have important implications on the study of electron transfer at dye|semiconductor interfaces for solar energy applications.

  11. Isotope effect in charge-transfer collisions of H with He{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Loreau, J.; Dalgarno, A. [Institute for Theoretical Atomic, Molecular and Optical Physics, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Ryabchenko, S. [Northern (Arctic) Federal University, 17 Severnaya Dvina Emb., 163002 Arkhangelsk (Russian Federation); Laboratoire de Chimie Quantique et Photophysique, Universite Libre de Bruxelles (ULB), CP160/09, 1050 Bruxelles (Belgium); Vaeck, N. [Laboratoire de Chimie Quantique et Photophysique, Universite Libre de Bruxelles (ULB), CP160/09, 1050 Bruxelles (Belgium)

    2011-11-15

    We present a theoretical study of the isotope effect arising from the replacement of H by T in the charge-transfer collision H(n=2) + He{sup +}(1s) at low energy. Using a quasimolecular approach and a time-dependent wave-packet method, we compute the cross sections for the reaction including the effects of the nonadiabatic radial and rotational couplings. For H(2s) + He{sup +}(1s) collisions, we find a strong isotope effect at energies below 1 eV/amu for both singlet and triplet states. We find a much smaller isotopic dependence of the cross section for H(2p) + He{sup +}(1s) collisions in triplet states, and no isotope effect in singlet states. We explain the isotope effect on the basis of the potential energy curves and the nonadiabatic couplings, and we evaluate the importance of the isotope effect on the charge-transfer rate coefficients.

  12. Photodissociation and charge transfer dynamics of negative ions studied with femtosecond photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zanni, Martin Thomas [Univ. of California, Berkeley, CA (United States)

    1999-12-01

    This dissertation presents studies aimed at understanding the potential energy surfaces and dynamics of isolated negative ions, and the effects of solvent on each. Although negative ions play important roles in atmospheric and solution phase chemistry, to a large extent the ground and excited state potential energy surfaces of gas phase negative ions are poorly characterized, and solvent effects even less well understood. In an effort to fill this gap, the author's coworkers and the author have developed a new technique, anion femtosecond photoelectron spectroscopy, and applied it to gas phase photodissociation and charge transfer processes. Studies are presented that (1) characterize the ground and excited states of isolated and clustered anions, (2) monitor the photodissociation dynamics of isolated and clustered anions, and (3) explore the charge-transfer-to-solvent states of atomic iodide clustered with polar and non-polar solvents.

  13. Photodissociation and charge transfer dynamics of negative ions studied with femtosecond photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zanni, Martin T.

    1999-12-17

    This dissertation presents studies aimed at understanding the potential energy surfaces and dynamics of isolated negative ions, and the effects of solvent on each. Although negative ions play important roles in atmospheric and solution phase chemistry, to a large extent the ground and excited state potential energy surfaces of gas phase negative ions are poorly characterized, and solvent effects even less well understood. In an effort to fill this gap, the author's coworkers and the author have developed a new technique, anion femtosecond photoelectron spectroscopy, and applied it to gas phase photodissociation and charge transfer processes. Studies are presented that (1) characterize the ground and excited states of isolated and clustered anions, (2) monitor the photodissociation dynamics of isolated and clustered anions, and (3) explore the charge-transfer-to-solvent states of atomic iodide clustered with polar and non-polar solvents.

  14. Charge transfer state in DBP:C70 organic solar cells

    DEFF Research Database (Denmark)

    Sherafatipour, Golenaz; Benduhn, Johannes; Spoltore, Donato

    -acceptor interface via delocalized charge-transfer (CT) states, which represents an intermediate state between the exciton dissociation and recombination back to the ground state. In this work we perform the electroluminescence (EL) created by bimolecular free career recombination and sensitive external quantum....... Electroluminescence from charge transfer states in polymer solar cells. J. Am. Chem. Soc. 131, 11819–11824 (2009)....... efficiency measurements (sEQE) in DBP:C70 based SCs as a less studied system in order to study the energy and effect of CT states on degradation of the devices2. The results from these measurements reveal valuable information about the loss mechanism during the aging experiment as well as the energy...

  15. WO3-reduced graphene oxide composites with enhanced charge transfer for photoelectrochemical conversion.

    Science.gov (United States)

    Wu, Haoyu; Xu, Ming; Da, Peimei; Li, Wenjie; Jia, Dingsi; Zheng, Gengfeng

    2013-10-14

    Hybrid structures between semiconducting metal oxides and carbon with rational synthesis represent unique device building blocks to optimize the light absorption and charge transfer process for the photoelectrochemical conversion. Here we demonstrate the realization of a WO3-reduced graphene oxide (RGO) nanocomposite via hydrothermal growth of ultrathin WO3 nanoplates directly on fluorine-doped tin oxide (FTO) substrates, followed by in situ photo-reduction to deposit RGO layers on WO3 nanoplate surface. Photoanodes made of the WO3-RGO nanocomposites have achieved a photocurrent density of 2.0 mA cm(-2) at 1.23 V vs. reversible hydrogen electrode (RHE), which is among the highest reported values for photoanodes based on hydrothermally grown WO3. Electrochemical impedance spectroscopy reveals that the increase of photoactivity is attributed to the enhanced charge transfer by the incorporation of RGO, thus suggesting a general approach for designing other metal oxide-RGO hybrid architectures.

  16. A novel spectrophotometric determination of trace copper based on charge transfer complex

    Science.gov (United States)

    Di, Junwei; Wu, Ying; Ma, Yun

    2005-03-01

    A new type of colored complex, the charge transfer complex, was used to develop the spectrophotometric determination of copper. The method was based on the formation of a colored product, the charge transfer complex of copper substituted tungstophosphate with 3,3',5,5'-tetramethybenzidine (TMB), which was stabilized and sensitized by the addition of polyvinyl alcohol (PVA) in aqueous solution. The structure of copper substituted tungstophosphate was Keggin-type according to the results of infrared (IR) spectra. The optimum reaction conditions and other important analytic parameters had been investigated. Beer's law was obeyed in the copper(II) concentration range of 0.003-0.1 μg mL -1, and the molar absorptivity at 660 nm is 2.54×10 5 L mol -1 cm -1. The proposed method was simple, selective, and sensitive. It was applied to the analytic samples with satisfactory results.

  17. Charge-transfer-directed radical substitution enables para-selective C-H functionalization

    Science.gov (United States)

    Boursalian, Gregory B.; Ham, Won Seok; Mazzotti, Anthony R.; Ritter, Tobias

    2016-08-01

    Efficient C-H functionalization requires selectivity for specific C-H bonds. Progress has been made for directed aromatic substitution reactions to achieve ortho and meta selectivity, but a general strategy for para-selective C-H functionalization has remained elusive. Herein we introduce a previously unappreciated concept that enables nearly complete para selectivity. We propose that radicals with high electron affinity elicit arene-to-radical charge transfer in the transition state of radical addition, which is the factor primarily responsible for high positional selectivity. We demonstrate with a simple theoretical tool that the selectivity is predictable and show the utility of the concept through a direct synthesis of aryl piperazines. Our results contradict the notion, widely held by organic chemists, that radical aromatic substitution reactions are inherently unselective. The concept of radical substitution directed by charge transfer could serve as the basis for the development of new, highly selective C-H functionalization reactions.

  18. Interaction and charge transfer between dielectric spheres: exact and approximate analytical solutions

    CERN Document Server

    Lindén, Fredrik; Zettergren, Henning

    2016-01-01

    We present exact analytical solutions for charge transfer reactions between two arbitrarily charged hard dielectric spheres. These solutions, and the corresponding exact ones for sphere-sphere interaction energies, include sums that describe polarization effects to infinite orders in the inverse of the distance between the sphere centers. In addition, we show that these exact solutions may be approximated by much simpler analytical expressions that are useful for many practical applications. This is exemplified through calculations of Langevin type cross sections for forming a compound system of two colliding spheres and through calculations of electron transfer cross sections. We find that it is important to account for dielectric properties and finite sphere sizes in such calculations, which for example may be useful for describing the evolution, growth, and dynamics of nanometer sized dielectric objects such as molecular clusters or dust grains in different environments including astrophysical ones.

  19. Combining intra- and intermolecular charge-transfer: a new strategy towards molecular ferromagnets and multiferroics.

    Science.gov (United States)

    Di Maiolo, Francesco; Sissa, Cristina; Painelli, Anna

    2016-01-21

    Organic ferroelectric materials are currently a hot research topic, with mixed stack charge transfer crystals playing a prominent role with their large, electronic-in-origin polarization and the possibility to tune the transition temperature down to the quantum limit and/or to drive the ferroelectric transition via an optical stimulus. By contrast, and in spite of an impressive research effort, organic ferromagnets are rare and characterized by very low transition temperatures. Coexisting magnetic and electric orders in multiferroics offer the possibility to control magnetic (electric) properties by an applied electric (magnetic) field with impressive technological potential. Only few examples of multiferroics are known today, based on inorganics materials. Here we demonstrate that, by decorating mixed stack charge transfer crystals with organic radicals, a new family of robust molecular ferromagnets can be designed, stable up to ambient temperature, and with a clear tendency towards multiferroic behaviour.

  20. Resonant charge transfer in slow Li+-Li(2s) collisions

    Institute of Scientific and Technical Information of China (English)

    李铁成; 刘春华; 屈一至; 刘玲; 吴勇; 王建国

    2015-01-01

    The resonant charge transfer process for Li+–Li(2s) collision is investigated by the quantum-mechanical molecular orbital close-coupling (QMOCC) method and the two-center atomic-orbital close-coupling (AOCC) method in an energy range of 1.0 eV/u–104 eV/u. Accurate molecular structure data and charge transfer cross sections are given. Both the all-electron model (AEM) and one-electron model (OEM) are used in the QMOCC calculations, and the discrepancies between the two models are analyzed. The OEM calculation can also give a reliable prediction of the cross sections for energies below 1 keV/u.

  1. Development of a charge-transfer distribution model for stack simulation of solid oxide fuel cells

    Science.gov (United States)

    Onaka, H.; Iwai, H.; Kishimoto, M.; Saito, M.; Yoshida, H.; Brus, G.; Szmyd, J. S.

    2016-09-01

    An overpotential model for planar solid oxide fuel cells (SOFCs) is developed and applied to a stack numerical simulation. Charge-transfer distribution within the electrodes are approximated using an exponential function, based on which the Ohmic loss and activation overpotential are evaluated. The predicted current-voltage characteristics agree well with the experimental results, and also the overpotentials within the cell can reproduce the results obtained from a numerical analysis where the distribution of the charge-transfer current within the electrodes is fully solved. The proposed model is expected to be useful to maintain the accuracy of SOFC simulations when the cell components, consisting of anode, electrolyte and cathode, are simplified into one layer element.

  2. Semilocal and Hybrid Density Embedding Calculations of Ground-State Charge-Transfer Complexes

    CERN Document Server

    Laricchia, S; Della Sala, F; 10.1063/1.4795825

    2013-01-01

    We apply the frozen density embedding method, using a full relaxation of embedded densities through a freeze-and-thaw procedure, to study the electronic structure of several benchmark ground-state charge-transfer complexes, in order to assess the merits and limitations of the approach for this class of systems. The calculations are performed using both semilocal and hybrid exchange-correlation (XC) functionals. The results show that embedding calculations using semilocal XC functionals yield rather large deviations with respect to the corresponding supermolecular calculations. Due to a large error cancellation effect, however, they can often provide a relatively good description of the electronic structure of charge-transfer complexes, in contrast to supermolecular calculations performed at the same level of theory. On the contrary, when hybrid XC functionals are employed, both embedding and supermolecular calculations agree very well with each other and with the reference benchmark results. In conclusion, fo...

  3. Electronic structure, charge distribution, and charge transfer in α- and β-Si3N4 and at the Si(111)/Si3N4(001) interface

    Science.gov (United States)

    Zhao, G. L.; Bachlechner, M. E.

    1997-02-01

    The electronic structure, charge distribution, and charge transfer in α- and β- Si3N4 and at the Si(111)/Si3N4(001) interface have been studied using a self-consistent first-principles LCAO method. The calculated charge transfer suggests that both in α- and β-phases, the ionic formula may be written as Si3+1.24N4-0.93. For the Si(111)/Si3N4(001) interface, the silicon atoms from the Si(111) side give some electrons to the N atoms of Si3N4 forming the Si-N bonds at the interface. One Si-N bond is associated with a charge transfer of about 0.31 electrons.

  4. Muon transfer from muonic hydrogen to heavier atoms; Transfert de charge muonique

    Energy Technology Data Exchange (ETDEWEB)

    Dupays, A

    2004-06-01

    This work concerns muon transfer from muonic hydrogen to heavier atoms. Recently, a method of measurement of the hyperfine structure of ground-state muonic hydrogen based on the collision energy dependence of the muon transfer rate to oxygen has been proposed. This proposal is based on measurements which where performed at the Paul Scherrer Institute in the early nineties which indicate that the muon transfer from muonic hydrogen to oxygen increases by a factor of 4 going from thermal to 0.12 eV energies. The motivation of our calculations was to confirm this behaviour. To study the collision energy dependence of the muon transfer rate, we have used a time-independent close-coupling method. We have set up an hyperspherical elliptic formalism valid for nonzero total angular momentum which allows accurate computations of state-to-state reactive and charge exchange processes. We have applied this formalism to muon-transfer process to oxygen and neon. The comparison with experimental results is in both cases excellent. Finally, the neon transfer rate dependence with energy suggests to use neon instead of oxygen to perform a measurement of the hyperfine structure of muonic hydrogen. The results of accurate calculations of the muon transfer rates from muonic protium and deuterium atoms to nitrogen, oxygen and neon are also reported. Very good agreement with measured rates is obtained and for the three systems, the isotopic effect is perfectly reproduced. (author)

  5. Formation of an intermolecular charge-transfer compound in UHV codeposited tetramethoxypyrene and tetracyanoquinodimethane

    DEFF Research Database (Denmark)

    Medjanik, K.; Perkert, S.; Naghavi, S.;

    2010-01-01

    ). The formation of an intermolecular charge-transfer (CT) compound is evident from the appearance of new reflexes in XRD (d =0.894nm and d =0.677nm). A softening of the CN stretching vibration (redshift by 7 cm⊃-1) of TCNQ is visible in the IR spectra, being indicative of a CT on the order of 0.3e from TMP...

  6. First-principles study of the interaction and charge transfer between graphene and metals

    OpenAIRE

    Khomyakov, P.A.; Giovannetti, G.; Rusu, P. C.; Brocks, G.; Brink, J.G.J. van den; Kelly, P. J.

    2009-01-01

    Measuring the transport of electrons through a graphene sheet necessarily involves contacting it with metal electrodes. We study the adsorption of graphene on metal substrates using first-principles calculations at the level of density functional theory. The bonding of graphene to Al, Ag, Cu, Au and Pt(111) surfaces is so weak that its unique "ultrarelativistic" electronic structure is preserved. The interaction does, however, lead to a charge transfer that shifts the Fermi level by up to 0.5...

  7. Impact of speciation on the electron charge transfer properties of nanodiamond drug carriers

    Science.gov (United States)

    Sun, Baichuan; Barnard, Amanda S.

    2016-07-01

    Unpassivated diamond nanoparticles (bucky-diamonds) exhibit a unique surface reconstruction involving graphitization of certain crystal facets, giving rise to hybrid core-shell particles containing both aromatic and aliphatic carbon. Considerable effort is directed toward eliminating the aromatic shell, but persistent graphitization of subsequent subsurface-layers makes perdurable purification a challenge. In this study we use some simple statistical methods, in combination with electronic structure simulations, to predict the impact of different fractions of aromatic and aliphatic carbon on the charge transfer properties of the ensembles of bucky-diamonds. By predicting quality factors for a variety of cases, we find that perfect purification is not necessary to preserve selectivity, and there is a clear motivation for purifying samples to improve the sensitivity of charge transfer reactions. This may prove useful in designing drug delivery systems where the release of (selected) drugs needs to be sensitive to specific conditions at the point of delivery.Unpassivated diamond nanoparticles (bucky-diamonds) exhibit a unique surface reconstruction involving graphitization of certain crystal facets, giving rise to hybrid core-shell particles containing both aromatic and aliphatic carbon. Considerable effort is directed toward eliminating the aromatic shell, but persistent graphitization of subsequent subsurface-layers makes perdurable purification a challenge. In this study we use some simple statistical methods, in combination with electronic structure simulations, to predict the impact of different fractions of aromatic and aliphatic carbon on the charge transfer properties of the ensembles of bucky-diamonds. By predicting quality factors for a variety of cases, we find that perfect purification is not necessary to preserve selectivity, and there is a clear motivation for purifying samples to improve the sensitivity of charge transfer reactions. This may prove

  8. Charge-transfer gap closure in transition-metal halides under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Chen, A.L.; Yu, P.Y.

    1995-01-01

    Insulator-to-metal transition induced by pressure has been studied in three transition metal iodides: NiI{sub 2}, CoI{sub 2} and FeI{sub 2} using optical absorption and resistivity measurements at room temperature. Comparisons between the results obtained by these two techniques suggested that the closure of the charge-transfer gap is the principal mechanism responsible for the insulator-to-metal transition in these materials.

  9. Surface-enhanced photoinduced charge transfer processes in metal-molecule nanoclusters

    OpenAIRE

    Centeno, Silvia P.; Ruano, Cristina; Román-Pérez, Jéssica; López-Tocón, Isabel; Soto, Juan; Otero, Juan Carlos

    2013-01-01

    This work deals with the unexplained efficiency of the electrode potential (EV) in tuning the energy of Charge Transfer (ECT) electronic states of hybrid systems formed by molecules and metal nanostructures. Huge energy gains (G) of up to 5 eV/V observed in electrochemical SERS experiences have been tentatively explained by a local increase of the electric potential at specific adsorption sites.[1] This gain, which is in conflict with the classical picture of the metal-adsorbate CT mechanism ...

  10. Modulating Charge Transfer Through Cyclic D,L α-Peptide Self-Assembly

    OpenAIRE

    Horne, W. Seth; Ashkenasy, Nurit; Ghadiri, M. Reza

    2005-01-01

    We describe a concise solid support-based synthetic method for the preparation of cyclic D,L α-peptides bearing 1,4,5,8-naphthalenetetracarboxylic diimide (NDI) side chains. Studies of the structural and photoluminescence properties of these molecules in solution show that the hydrogen bond directed self-assembly of the cyclic D,L α-peptide backbone promotes intermolecular NDI excimer formation. The efficiency of NDI charge transfer in the resulting supramolecular assemblies is shown to depen...

  11. Strongly Dichroic Organic Films via Controlled Assembly of Modular Aromatic Charge-Transfer Liquid Crystals.

    Science.gov (United States)

    Bé, Ariana Gray; Tran, Cheryl; Sechrist, Riley; Reczek, Joseph J

    2015-10-02

    The formation of highly anisotropic organic thin films based on the designed self-assembly of mixed-stack liquid crystals is reported. A series of alkoxyanthracene donors is combined in a modular fashion with a naphthalenediimide acceptor to generate new charge-transfer columnar liquid crystals. Materials characterization and molecular modeling provides insight into structure-function relationships in these organic materials that lead to the striking bulk dichroic properties of certain molecular assemblies.

  12. Fabrication of a highly sensitive penicillin sensor based on charge transfer techniques.

    Science.gov (United States)

    Lee, Seung-Ro; Rahman, M M; Sawada, Kazuaki; Ishida, Makoto

    2009-03-15

    A highly sensitive penicillin biosensor based on a charge-transfer technique (CTTPS) has been fabricated and demonstrated in this paper. CTTPS comprised a charge accumulation technique for penicilloic acid and H(+) ions perception system. With the proposed CTTPS, it is possible to amplify the sensing signals without external amplifier by using the charge accumulation cycles. The fabricated CTTPS exhibits excellent performance for penicillin detection and exhibit a high-sensitivity (47.852 mV/mM), high signal-to-noise ratio (SNR), large span (1445 mV), wide linear range (0-25 mM), fast response time (penicillin sensor and exhibited almost eight times greater sensitivity as compared to ISFET (6.56 mV/mM). The sensor system is implemented for the measurement of the penicillin concentration in penicillin fermentation broth.

  13. Computational models of an inductive power transfer system for electric vehicle battery charge

    Science.gov (United States)

    Anele, A. O.; Hamam, Y.; Chassagne, L.; Linares, J.; Alayli, Y.; Djouani, K.

    2015-09-01

    One of the issues to be solved for electric vehicles (EVs) to become a success is the technical solution of its charging system. In this paper, computational models of an inductive power transfer (IPT) system for EV battery charge are presented. Based on the fundamental principles behind IPT systems, 3 kW single phase and 22 kW three phase IPT systems for Renault ZOE are designed in MATLAB/Simulink. The results obtained based on the technical specifications of the lithium-ion battery and charger type of Renault ZOE show that the models are able to provide the total voltage required by the battery. Also, considering the charging time for each IPT model, they are capable of delivering the electricity needed to power the ZOE. In conclusion, this study shows that the designed computational IPT models may be employed as a support structure needed to effectively power any viable EV.

  14. Theoretical investigation on dual fluorescence and intramolecular charge transfer of 5-phenyl-5H-phenanthridin-6-one

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Quantum-chemical calculations with the time-dependent density function theory (TDDFT) have been carried out for 5-phenyl-5H-phenanthridin-6-one (PP). For this molecule, dual fluorescence and in- tramolecular charge transfer (ICT) were experimentally observed. The B3LYP functional with 6-311+G (2d, p) basis set has been used for the theoretical calculations. The solvent effects have been described within the polarizable continuum model (PCM). Ground-state geometry optimization reveals that the phenyl/phenanthridinone dihedral angle equals 90.0°, a nearly perpendicular structure. Vertical ab- sorption energy calculations characterize the lower singlet excited states both in gas phase and in solvents. It can be found that the lower excited states have locally excitation (LE) feature. Through constructing the potential energy curves of both isolated and solvated systems describing the LE→ICT reaction and fluorescence emission, we obtain the enthalpy difference ΔH between the LE and ICT states, energy barrier Ea, and energy difference δEFC, indicating the structural changes taking place during the ICT reaction. Potential curve and calculated emission energies for both isolated and sol- vated systems show a dual fluorescence phenomenon, consisting of a LE emission band and a red-shifted ICT band. Our calculations including the solvent effects indicate that the dual fluorescence is brought about by the change in molecular structure connected with the planarization of the twisted N-phenylphenanthridinone during the ICT reaction.

  15. Evanescent-field spectroscopy using structured optical fibers: detection of charge-transfer at the porphyrin-silica interface.

    Science.gov (United States)

    Martelli, Cicero; Canning, John; Reimers, Jeffrey R; Sintic, Maxine; Stocks, Danial; Khoury, Tony; Crossley, Maxwell J

    2009-03-04

    The fabrication of porphyrin thin films derived from dichloro[5,10,15,20-tetra(heptyl)porphyrinato]tin(IV) [Cl-Sn(THP)-Cl] in the holes of photonic crystal fibers over 90 cm in length is described. Evanescent field spectroscopy (EFS) is used to investigate the interfacial properties of the films, with the high surface optical intensity and the long path length combining to produce significant absorption. By comparison with results obtained for similar films formed from Cl-Sn(THP)-Cl inside fused-silica cuvettes and on glass slides, the film is shown to be chemisorbed as a surface Si-O-Sn(THP)-X (X = Cl or OH) species. In addition to the usual porphyrin Q and Soret bands, new absorptions in the in-fiber films are observed by EFS at 445 nm and between 660-930 nm. The 660-930 nm band is interpreted as a porphyrin to silicon charge-transfer transition and postulated to arise following chemisorption at mechanical-strain induced defect sites on the silica surface. Such defect sites are caused by the optical fiber production process and are less prevalent on other glass surfaces. EFS within optical fibers therefore offers new ways for understanding interface phenomena such as surface adsorbates on glass. Such understanding will benefit all devices that exploit interface phenomena, both in optical fibers and other integrated waveguide forms. They may be directly exploited to create ultrasensitive molecular detectors and could yield novel photonic devices.

  16. Charge transfer of edge states in zigzag silicene nanoribbons with Stone-Wales defects from first-principles

    Science.gov (United States)

    Ting, Xie; Rui, Wang; Shaofeng, Wang; Xiaozhi, Wu

    2016-10-01

    Stone-Wales (SW) defects are favorably existed in graphene-like materials with honeycomb lattice structure and potentially employed to change the electronic properties in band engineering. In this paper, we investigate structural and electronic properties of SW defects in silicene sheet and its nanoribbons as a function of their concentration using the methods of periodic boundary conditions with first-principles calculations. We first calculate the formation energy, structural properties, and electronic band structures of SW defects in silicene sheet, with dependence on the concentration of SW defects. Our results show a good agreement with available values from the previous first-principles calculations. The energetics, structural aspects, and electronic properties of SW defects with dependence on defect concentration and location in edge-hydrogenated zigzag silicene nanoribbons are obtained. For all calculated concentrations, the SW defects prefer to locate at the edge due to the lower formation energy. The SW defects at the center of silicene nanoribbons slightly influence on the electronic properties, whereas the SW defects at the edge of silicene nanoribbons split the degenerate edge states and induce a sizable gap, which depends on the concentration of defects. It is worth to find that the SW defects produce a perturbation repulsive potential, which leads the decomposed charge of edge states at the side with defect to transfer to the other side without defect.

  17. Tungsten-based nanomaterials (WO3 & Bi2WO6): Modifications related to charge carrier transfer mechanisms and photocatalytic applications

    Science.gov (United States)

    Girish Kumar, S.; Koteswara Rao, K. S. R.

    2015-11-01

    Heterogeneous photocatalysis is an ideal green energy technology for the purification of wastewater. Although titania dominates as the reference photocatalyst, its wide band gap is a bottleneck for extended utility. Thus, search for non-TiO2 based nanomaterials has become an active area of research in recent years. In this regard, visible light absorbing polycrystalline WO3 (2.4-2.8 eV) and Bi2WO6 (2.8 eV) with versatile structure-electronic properties has gained considerable interest to promote the photocatalytic reactions. These materials are also explored in selective functional group transformation in organic reactions, because of low reduction and oxidation potential of WO3 CB and Bi2WO6 VB, respectively. In this focused review, various strategies such as foreign ion doping, noble metal deposition and heterostructuring with other semiconductors designed for efficient photocatalysis is discussed. These modifications not only extend the optical response to longer wavelengths, but also prolong the life-time of the charge carriers and strengthen the photocatalyst stability. The changes in the surface-bulk properties and the charge carrier transfer dynamics associated with each modification correlating to the high activity are emphasized. The presence of oxidizing agents, surface modification with Cu2+ ions and synthesis of exposed facets to promote the degradation rate is highlighted. In depth study on these nanomaterials is likely to sustain interest in wastewater remediation and envisaged to signify in various green energy applications.

  18. Charge transfer and weak bonding between molecular oxygen and graphene zigzag edges at low temperatures

    CERN Document Server

    Boukhvalov, D W; Shames, A I; Takai, K; Hayashi, T; Enoki, T

    2016-01-01

    Electron paramagnetic resonance (EPR) study of air-physisorbed defective carbon nano-onions evidences in favor of microwave assisted formation of weakly-bound paramagnetic complexes comprising negatively-charged O2- ions and edge carbon atoms carrying pi-electronic spins. These complexes being located on the graphene edges are stable at low temperatures but irreversibly dissociate at temperatures above 50-60 K. These EPR findings are justified by density functional theory (DFT) calculations demonstrating transfer of an electron from the zigzag edge of graphene-like material to oxygen molecule physisorbed on the graphene sheet edge. This charge transfer causes changing the spin state of the adsorbed oxygen molecule from S = 1 to S = 1/2 one. DFT calculations show significant changes of adsorption energy of oxygen molecule and robustness of the charge transfer to variations of the graphene-like substrate morphology (flat and corrugated mono- and bi-layered graphene) as well as edges passivation. The presence of...

  19. Ab initio calculation of H + He$^+$ charge transfer cross sections for plasma physics

    CERN Document Server

    Loreau, J; Lauvergnat, D; Desouter-Lecomte, M; Vaeck, N

    2010-01-01

    The charge transfer in low energy (0.25 to 150 eV/amu) H($nl$) + He$^+(1s)$ collisions is investigated using a quasi-molecular approach for the $n=2,3$ as well as the first two $n=4$ singlet states. The diabatic potential energy curves of the HeH$^+$ molecular ion are obtained from the adiabatic potential energy curves and the non-adiabatic radial coupling matrix elements using a two-by-two diabatization method, and a time-dependent wave-packet approach is used to calculate the state-to-state cross sections. We find a strong dependence of the charge transfer cross section in the principal and orbital quantum numbers $n$ and $l$ of the initial or final state. We estimate the effect of the non-adiabatic rotational couplings, which is found to be important even at energies below 1 eV/amu. However, the effect is small on the total cross sections at energies below 10 eV/amu. We observe that to calculate charge transfer cross sections in a $n$ manifold, it is only necessary to include states with $n^{\\prime}\\leq n$...

  20. Ferroelectric phase transition, ionicity condensation, and multicriticality in charge-transfer organic complexes

    Science.gov (United States)

    Kishine, Jun-Ichiro; Luty, Tadeusz; Yonemitsu, Kenji

    2004-02-01

    To elucidate a pressure-temperature phase diagram of the quasi-one-dimensional mixed-stack charge-transfer complex tetrathiafulvalene-P-chloranil (TTF-CA), we study the quasi-one-dimensional spin-1 Blume-Emery-Griffiths model. In addition to the local charge-transfer energy (Δ) and the inter-stack polar (dipole-dipole) interaction (J⊥), we take account of the interstack electrostriction (Coulomb-lattice coupling). Using the self-consistent chain-mean-field theory, where the intra-stack degrees of freedom are exactly treated by the transfer-matrix method, we reproduce the gas-liquid-solid like phase diagram corresponding to the neutral (N), paraelectric ionic (Ipara), and ferroelectric ionic (Iferro) phases, respectively. Our classical model describes an essential point of the multicritical behavior of TTF-CA, i.e., the interchain electrostriction exclusively enhances the charge concentration (ionicity condensation), but does not affect the interchain ferroelectric coupling. This effect leads to appearance of the intermediate Ipara phase in between the N and Iferro phases on the Δ-T phase diagram.

  1. Charge-transfer complexes of 4-nitrocatechol with some amino alcohols

    Science.gov (United States)

    Baniyaghoob, Sahar; Najafpour, Mohammad Mahdi; Boghaei, Davar M.

    2010-03-01

    Charge-transfer (CT) complexes formed from the reactions of 4-nitropyrocatechol (4-nCat) as an electron acceptor with four amino alcohols: 2-aminoethanol, 1-amino-2-propanol, 4-aminobutanol and N-(2-hydroxyethyl)-1,3-diaminopropane (NHEDAP) as electron donors, have been studied spectrophotometrically in H 2O and H 2O/EtOH at 20, 25, 30, 35 and 40 °C. The calculated values of the oscillator strength and transition moment confirm the formation of CT-complexes. The thermodynamic and spectroscopic parameters were also evaluated for the formation of CT-complexes. The equilibrium constants ranged from 9.00 to 2.20 l mol -1 (M -1). These interactions are exothermic and have relatively large standard enthalpy and entropy changes (Δ H values ranged from -15.58 to -3.10 kJ mol -1; Δ S ranged from 26.81 to -3.25 J K -1 mol -1). The solid CT-complexes have been synthesized and characterized by IR, NMR, mass spectrometry and thermal analysis. The photometric titration curves and other spectrometric data for the reactions indicated that the data obtained refer to the formation of 1:1 charge-transfer complex of [(4-nCat) (NHEDAP)] and 1:2 charge-transfer complexes of other amino alcohols [(4-nCat) (amino alcohol) 2]. The effect of alkali and alkaline earth metals on increasing the equilibrium constant of the CT-complexation was also investigated.

  2. Rate limiting activity of charge transfer during lithiation from ionic liquids

    Science.gov (United States)

    Rodrigues, Marco-Tulio F.; Lin, Xinrong; Gullapalli, Hemtej; Grinstaff, Mark W.; Ajayan, Pulickel M.

    2016-10-01

    Given the increased use of room temperature ionic liquid electrolytes in Li-ion batteries, due to their non-flammability and negligible volatility, this study evaluates the lithiation kinetics to understand and improve the rate performance of Li-ion batteries. Lithium titanate spinel is used as a model electrode and the electrolyte is composed of LiTFSI and TFSI-coordinated alkoxy-modified phosphonium ionic liquid. Based on the analysis of activation energies for each process, we report that the charge-transfer reaction at the electrode/electrolyte interface is the rate-limiting step for cell operation. This finding is further supported by the observation that a 50-fold decrease in charge-transfer resistance at higher temperatures leads to a significant performance improvement over that of a traditional organic electrolyte at room temperature. Charge-transfer resistance and electrolyte wetting on the electrode surface are critical processes for optimal battery performance, and such processes need to be included when designing new ionic liquids in order to exceed the power density obtained with the use of current carbonate-based electrolytes.

  3. Overcoming the Cut-Off Charge Transfer Bandgaps at the PbS Quantum Dot Interface

    KAUST Repository

    El-Ballouli, Ala'a O.

    2015-11-17

    Light harvesting from large size of semiconductor PbS quantum dots (QDs) with a bandgap of less than 1 eV is one of the greatest challenges precluding the development of PbS QD-based solar cells because the interfacial charge transfer (CT) from such QDs to the most commonly used electron acceptor materials is very inefficient, if it occurs at all. Thus, an alternative electron-accepting unit with a new driving force for CT is urgently needed to harvest the light from large-sized PbS QDs. Here, a cationic porphyrin is utilized as a new electron acceptor unit with unique features that bring the donor–acceptor components into close molecular proximity, allowing ultrafast and efficient electron transfer for QDs of all sizes, as inferred from the drastic photoluminescence quenching and the ultrafast formation of the porphyrin anionic species. The time-resolved results clearly demonstrate the possibility of modulating the electron transfer process between PbS QDs and porphyrin moieties not only by the size quantization effect but also by the interfacial electrostatic interaction between the positively charged porphyrin and the negatively charged QDs. This approach provides a new pathway for engineering QD-based solar cells that make the best use of the diverse photons making up the Sun\\'s broad irradiance spectrum.

  4. Lock-arm supramolecular ordering: a molecular construction set for cocrystallizing organic charge transfer complexes.

    Science.gov (United States)

    Blackburn, Anthea K; Sue, Andrew C-H; Shveyd, Alexander K; Cao, Dennis; Tayi, Alok; Narayanan, Ashwin; Rolczynski, Brian S; Szarko, Jodi M; Bozdemir, Ozgur A; Wakabayashi, Rie; Lehrman, Jessica A; Kahr, Bart; Chen, Lin X; Nassar, Majed S; Stupp, Samuel I; Stoddart, J Fraser

    2014-12-10

    Organic charge transfer cocrystals are inexpensive, modular, and solution-processable materials that are able, in some instances, to exhibit properties such as optical nonlinearity, (semi)conductivity, ferroelectricity, and magnetism. Although the properties of these cocrystals have been investigated for decades, the principal challenge that researchers face currently is to devise an efficient approach which allows for the growth of high-quality crystalline materials, in anticipation of a host of different technological applications. The research reported here introduces an innovative design, termed LASO-lock-arm supramolecular ordering-in the form of a modular approach for the development of responsive organic cocrystals. The strategy relies on the use of aromatic electronic donor and acceptor building blocks, carrying complementary rigid and flexible arms, capable of forming hydrogen bonds to amplify the cocrystallization processes. The cooperativity of charge transfer and hydrogen-bonding interactions between the building blocks leads to binary cocrystals that have alternating donors and acceptors extending in one and two dimensions sustained by an intricate network of hydrogen bonds. A variety of air-stable, mechanically robust, centimeter-long, organic charge transfer cocrystals have been grown by liquid-liquid diffusion under ambient conditions inside 72 h. These cocrystals are of considerable interest because of their remarkable size and stability and the promise they hold when it comes to fabricating the next generation of innovative electronic and photonic devices.

  5. Density functional theory for the description of charge-transfer processes at TTF/TCNQ interfaces

    KAUST Repository

    Van Regemorter, Tanguy

    2012-09-15

    In the field of organic electronics, a central issue is to assess how the frontier electronic levels of two adjacent organic layers align with respect to one another at the interface. This alignment can be driven by the presence of a partial charge transfer and the formation of an interface dipole; it plays a key role for instance in determining the rates of exciton dissociation or exciton formation in organic solar cells or light-emitting diodes, respectively. Reliably modeling the processes taking place at these interfaces remains a challenge for the computational chemistry community. Here, we review our recent theoretical work on the influence of the choice of density functional theory (DFT) methodology on the description of the charge-transfer character in the ground state of TTF/ TCNQ model complexes and interfaces. Starting with the electronic properties of the isolated TTF and TCNQ molecules and then considering the charge transfer and resulting interface dipole in TTF/TCNQ donor-acceptor stacks and bilayers, we examine the impact of the choice of DFT functional in describing the interfacial electronic structure. Finally, we employ computations based on periodic boundary conditions to highlight the impact of depolarization effects on the interfacial dipole moment. © Springer-Verlag 2012.

  6. N+ charge transfer and N+2 dissociation in N2 at swarm energies.

    Science.gov (United States)

    Basurto, E; de Urquijo, J; Cisneros, C; Alvarez, I

    2001-01-01

    This paper reports a drift-tube-mass-spectrometer measurement of the relative abundances of N+ and N+2 in pure nitrogen, over a ratio of electric field to gas density, E/N, from 800 to 7200 Td [1 townsend (Td)=10(-17) V cm(2)]. A proposed charge transfer dissociation scheme between the above two ions and N2 allowed us to obtain spatial rate coefficients for charge transfer and dissociation over the E/N range 800-2800 Td. Using previously measured cross sections for the above processes, and assuming a Maxwellian distribution of ion velocities, we calculated the reaction coefficients, which were found to be in good agreement with our measured values. In particular, the present results support the trend toward fairly high charge transfer cross section values for N+ energies above 10 eV. In the overlap range between 2.4 and 7.2 kTd, our concentration ratio [N(+)/N(+)(2)] is about five times smaller than that measured previously from a diffuse Townsend discharge in which electron impact is involved in addition to N+2 collisional dissociation with N2, but has the same trend. Thus it seems that, besides N+2 dissociation by electron impact, collisional dissociation becomes important at elevated values of E/N. In connection with previous discharge work in nitrogen, the present study may help explain the enhanced cathode yields observed.

  7. A two-dimensional position sensitive gas chamber with scanned charge transfer readout

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, F. E-mail: faustgr@usc.es; Iglesias, A.; Lobato, R.; Mosquera, J.; Pardo, J.; Pena, J.; Pazos, A.; Pombar, M.; Rodriguez, A

    2003-10-21

    We have constructed and tested a two-dimensional position sensitive parallel-plate gas ionization chamber with scanned charge transfer readout. The scan readout method described here is based on the development of a new position-dependent charge transfer technique. It has been implemented by using gate strips perpendicularly oriented to the collector strips. This solution reduces considerably the number of electronic readout channels needed to cover large detector areas. The use of a 25 {mu}m thick kapton etched circuit allows high charge transfer efficiency with a low gating voltage, consequently needing a very simple commutating circuit. The present prototype covers 8x8 cm{sup 2} with a pixel size of 1.27x1.27 mm{sup 2}. Depending on the intended use and beam characteristics a smaller effective pixel is feasible and larger active areas are possible. This detector can be used for X-ray or other continuous beam intensity profile monitoring.

  8. Band gap engineering of NaTaO3 using density functional theory: a charge compensated codoping strategy.

    Science.gov (United States)

    Modak, Brindaban; Srinivasu, K; Ghosh, Swapan K

    2014-08-28

    In this theoretical study, we employ a codoping strategy to reduce the band gap of NaTaO3 aimed at improving the photocatalytic activity under visible light. The systematic study includes the effects of metal (W) and nonmetal (N) codoping on the electronic structure of NaTaO3 in comparison to the effect of individual dopants. The feasibility of the introduction of N into the NaTaO3 crystal structure is found to be enhanced in the presence of W, as indicated by the calculated formation energy. This codoping leads to formation of a charge compensated system, beneficial for the minimization of vacancy related defect formation. The electronic structure calculations have been carried out using a hybrid density functional for an accurate description of the proposed system. The introduction of W in place of Ta leads to the appearance of donor states below the conduction band, while N doping in place of oxygen introduces isolated acceptor states above the valence band. The codoping of N and W also passivates undesirable discrete midgap states. This feature is not observed in the case of (Cr, N) codoped NaTaO3 in spite of its charge compensated nature. We have also studied charge non-compensated codoping using several dopant pairs, including anion-anion and cation-anion pairs. However, this non-compensated codoping introduces localized states in between the valence band and the conduction band, and hence may not be effective in enhancing the photocatalytic properties of NaTaO3. The optical spectrum shows that the absorption curve for the (W, N)-codoped NaTaO3 is extended to the visible region due to narrowing of the band gap to 2.67 eV. Moreover, its activity for the photo decomposition of water to produce both H2 and O2 remains intact. Hence, based on the present investigation we can propose (W, N) codoped NaTaO3 as a promising photocatalyst for visible light driven water splitting.

  9. Construction and Nanoscale Detection of Interfacial Charge Transfer of Elegant Z-Scheme WO3/Au/In2S3 Nanowire Arrays.

    Science.gov (United States)

    Li, Haijin; Gao, Yuying; Zhou, Yong; Fan, Fengtao; Han, Qiutong; Xu, Qinfeng; Wang, Xiaoyong; Xiao, Min; Li, Can; Zou, Zhigang

    2016-09-14

    Elegant Z-scheme WO3/Au/In2S3 nanowire arrays were precisely constructed through a facile step-by-step route. Surface potential change on pristine or In2S3-Au coated WO3 single nanowire under dark and illumination detected through a Kelvin probe force microscopy (KPFM) technique indicates that the vectorial holes transfer of In2S3 → Au → WO3 should occur upon the excitation of both WO3 and In2S3. In such charge transfer processes, the embedded Au nanoparticles in the heterojunction systems act as a charge mediator for electrons in the conduction band of WO3 and holes in the valence band of In2S3. The strong charge carrier separation ability of this structure will finally enhance the oxidation ability of WO3 with high concertation of photogenerated holes and, further, leave the free electrons in the In2S3 with long surviving time. Therefore, the unique Z-scheme WO3/Au/In2S3 heterostructure shows great visible-light activity toward photocatalytic reduction of CO2 in the presence of water vapor into renewable hydrocarbon fuel (methane: CH4).

  10. Plasmonic photosensitization of a wide band gap semiconductor: converting plasmons to charge carriers.

    Science.gov (United States)

    Mubeen, Syed; Hernandez-Sosa, Gerardo; Moses, Daniel; Lee, Joun; Moskovits, Martin

    2011-12-14

    A fruitful paradigm in the development of low-cost and efficient photovoltaics is to dope or otherwise photosensitize wide band gap semiconductors in order to improve their light harvesting ability for light with sub-band-gap photon energies.(1-8) Here, we report significant photosensitization of TiO2 due to the direct injection by quantum tunneling of hot electrons produced in the decay of localized surface-plasmon polaritons excited in gold nanoparticles (AuNPs) embedded in the semiconductor (TiO2). Surface plasmon decay produces electron-hole pairs in the gold.(9-15) We propose that a significant fraction of these electrons tunnel into the semiconductor's conduction band resulting in a significant electron current in the TiO2 even when the device is illuminated with light with photon energies well below the semiconductor's band gap. Devices fabricated with (nonpercolating) multilayers of AuNPs in a TiO2 film produced over 1000-fold increase in photoconductance when illuminated at 600 nm over what TiO2 films devoid of AuNPs produced. The overall current resulting from illumination with visible light is ∼50% of the device current measured with UV (ℏω>Eg band gap) illumination. The above observations suggest that plasmonic nanostructures (which can be fabricated with absorption properties that cover the full solar spectrum) can function as a viable alternative to organic photosensitizers for photovoltaic and photodetection applications.

  11. Charge Transfer as a Probe for the Interfacial Properties of Quantum Dot-Ligand Complexes

    Science.gov (United States)

    Weinberg, David Joseph

    This dissertation describes the study of charge transfer interactions between colloidal quantum dots (QDs) and molecular redox partners in the context of both fundamental investigations of charge recombination mechanisms in nanocrystal-molecule systems, and as a technique to probe the properties of the QD ligand shell. Charge separation in a system of CdS nanocrystals and organic hole acceptors results in the formation of a spin-correlated radical ion pair. Interrogating this photogenerated species with EPR and magnetic field effect transient absorption techniques reveals that the charge recombination dynamics of this donor-acceptor system are dictated by the radical pair intersystem crossing mechanism on the nanosecond timescale. These experiments also indicate that the photoinjected electron localizes at a CdS QD surface trap state, and the coupling between the electron and hole in this spin-correlated system is low. Additional studies involving the CdS QDs and organic hole acceptors are proposed which would investigate the exchange of charge and energy within the nanocrystal organic adlayer. Collisional charge transfer interactions between substituted benzoquinone molecules and PbS QDs coated with mixed monolayers of oleic acid and perfluorodecanethiol are monitored via photoluminescence and transient absorption spectroscopies. These experiments reveal that partially fluorinated ligand shells are less permeable to solution phase molecules and offer greater protection of the nanocrystal surface than their aliphatic counterparts. Only a small amount of fluorinated surfactant ( 20% surface coverage) is necessary to profoundly change the permeability of the ligand shell, and the protective nature of these fluorinated molecules is likely a combination of the molecular volume and oleophobicity of these ligands. Follow up work is discussed which would elucidate the influence of solvent and extent of surfactant fluorination on the permeability of these ligand shells, as

  12. Charge transfer from an adsorbed ruthenium-based photosensitizer through an ultra-thin aluminium oxide layer and into a metallic substrate

    CERN Document Server

    Gibson, Andrew J; Handrup, Karsten; Weston, Matthew; Mayor, Louise C; O'Shea, James N

    2014-01-01

    The interaction of the dye molecule N3 (cis-bis(isothiocyanato)bis(2,2-bipyridyl-4,4'-dicarboxylato)-ruthenium(II)) with the ultra-thin oxide layer on a AlNi(110) substrate, has been studied using synchrotron radiation based photoelectron spectroscopy, resonant photoemission spectroscopy (RPES) and near edge X-ray absorption fine structure spectroscopy (NEXAFS). Calibrated X-ray absorption and valence band spectra of the monolayer and multilayer coverages reveal that charge transfer is possible from the molecule to the AlNi(110) substrate via tunnelling through the ultra-thin oxide layer and into the conduction band edge of the substrate. This charge transfer mechanism is possible from the LUMO+2&3 in the excited state but not from the LUMO, therefore enabling core-hole clock analysis, which gives an upper limit of $6.0\\pm$2.5fs for the transfer time. This indicates that ultra-thin oxide layers are a viable material for use in dye-sensitized solar cells (DSSC), which may lead to reduced recombination effe...

  13. Charge transfer from an adsorbed ruthenium-based photosensitizer through an ultra-thin aluminium oxide layer and into a metallic substrate.

    Science.gov (United States)

    Gibson, Andrew J; Temperton, Robert H; Handrup, Karsten; Weston, Matthew; Mayor, Louise C; O'Shea, James N

    2014-06-21

    The interaction of the dye molecule N3 (cis-bis(isothiocyanato)bis(2,2-bipyridyl-4,4'-dicarbo-xylato)-ruthenium(II)) with the ultra-thin oxide layer on a AlNi(110) substrate, has been studied using synchrotron radiation based photoelectron spectroscopy, resonant photoemission spectroscopy, and near edge X-ray absorption fine structure spectroscopy. Calibrated X-ray absorption and valence band spectra of the monolayer and multilayer coverages reveal that charge transfer is possible from the molecule to the AlNi(110) substrate via tunnelling through the ultra-thin oxide layer and into the conduction band edge of the substrate. This charge transfer mechanism is possible from the LUMO+2 and 3 in the excited state but not from the LUMO, therefore enabling core-hole clock analysis, which gives an upper limit of 6.0 ± 2.5 fs for the transfer time. This indicates that ultra-thin oxide layers are a viable material for use in dye-sensitized solar cells, which may lead to reduced recombination effects and improved efficiencies of future devices.

  14. Charge transfer from an adsorbed ruthenium-based photosensitizer through an ultra-thin aluminium oxide layer and into a metallic substrate

    Energy Technology Data Exchange (ETDEWEB)

    Gibson, Andrew J.; Temperton, Robert H.; Handrup, Karsten; Weston, Matthew; Mayor, Louise C.; O’Shea, James N., E-mail: james.oshea@nottingham.ac.uk [School of Physics and Astronomy and Nottingham Nanotechnology and Nanoscience Centre (NNNC), University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2014-06-21

    The interaction of the dye molecule N3 (cis-bis(isothiocyanato)bis(2,2-bipyridyl-4,4′-dicarbo-xylato) -ruthenium(II)) with the ultra-thin oxide layer on a AlNi(110) substrate, has been studied using synchrotron radiation based photoelectron spectroscopy, resonant photoemission spectroscopy, and near edge X-ray absorption fine structure spectroscopy. Calibrated X-ray absorption and valence band spectra of the monolayer and multilayer coverages reveal that charge transfer is possible from the molecule to the AlNi(110) substrate via tunnelling through the ultra-thin oxide layer and into the conduction band edge of the substrate. This charge transfer mechanism is possible from the LUMO+2 and 3 in the excited state but not from the LUMO, therefore enabling core-hole clock analysis, which gives an upper limit of 6.0 ± 2.5 fs for the transfer time. This indicates that ultra-thin oxide layers are a viable material for use in dye-sensitized solar cells, which may lead to reduced recombination effects and improved efficiencies of future devices.

  15. Quantum confinement-tunable ultrafast charge transfer at the PbS quantum dot and phenyl-C61-butyric acid methyl ester interface

    KAUST Repository

    El-Ballouli, AlA'A O.

    2014-05-14

    Quantum dot (QD) solar cells have emerged as promising low-cost alternatives to existing photovoltaic technologies. Here, we investigate charge transfer and separation at PbS QDs and phenyl-C61-butyric acid methyl ester (PCBM) interfaces using a combination of femtosecond broadband transient absorption (TA) spectroscopy and steady-state photoluminescence quenching measurements. We analyzed ultrafast electron injection and charge separation at PbS QD/PCBM interfaces for four different QD sizes and as a function of PCBM concentration. The results reveal that the energy band alignment, tuned by the quantum size effect, is the key element for efficient electron injection and charge separation processes. More specifically, the steady-state and time-resolved data demonstrate that only small-sized PbS QDs with a bandgap larger than 1 eV can transfer electrons to PCBM upon light absorption. We show that these trends result from the formation of a type-II interface band alignment, as a consequence of the size distribution of the QDs. Transient absorption data indicate that electron injection from photoexcited PbS QDs to PCBM occurs within our temporal resolution of 120 fs for QDs with bandgaps that achieve type-II alignment, while virtually all signals observed in smaller bandgap QD samples result from large bandgap outliers in the size distribution. Taken together, our results clearly demonstrate that charge transfer rates at QD interfaces can be tuned by several orders of magnitude by engineering the QD size distribution. The work presented here will advance both the design and the understanding of QD interfaces for solar energy conversion. © 2014 American Chemical Society.

  16. Ultrafast charge-transfer in organic photovoltaic interfaces: geometrical and functionalization effects.

    Science.gov (United States)

    Santos, Elton J G; Wang, W L

    2016-09-21

    Understanding the microscopic mechanisms of electronic excitation in organic photovoltaic cells is a challenging problem in the design of efficient devices capable of performing sunlight harvesting. Here we develop and apply an ab initio approach based on time-dependent density functional theory and Ehrenfest dynamics to investigate photoinduced charge transfer in small organic molecules. Our calculations include mixed quantum-classical dynamics with ions moving classically and electrons quantum mechanically, where no experimental external parameter other than the material geometry is required. We show that the behavior of photocarriers in zinc phthalocyanine (ZnPc) and C60 systems, an effective prototype system for organic solar cells, is sensitive to the atomic orientation of the donor and the acceptor units as well as the functionalization of covalent molecules at the interface. In particular, configurations with the ZnPc molecules facing on C60 facilitate charge transfer between substrate and molecules that occurs within 200 fs. In contrast, configurations where ZnPc is tilted above C60 present extremely low carrier injection efficiency even at longer times as an effect of the larger interfacial potential level offset and higher energetic barrier between the donor and acceptor molecules. An enhancement of charge injection into C60 at shorter times is observed as binding groups connect ZnPc and C60 in a dyad system. Our results demonstrate a promising way of designing and controlling photoinduced charge transfer on the atomic level in organic devices that would lead to efficient carrier separation and maximize device performance.

  17. Melting of Pb Charge Glass and Simultaneous Pb-Cr Charge Transfer in PbCrO3 as the Origin of Volume Collapse.

    Science.gov (United States)

    Yu, Runze; Hojo, Hajime; Watanuki, Tetsu; Mizumaki, Masaichiro; Mizokawa, Takashi; Oka, Kengo; Kim, Hyunjeong; Machida, Akihiko; Sakaki, Kouji; Nakamura, Yumiko; Agui, Akane; Mori, Daisuke; Inaguma, Yoshiyuki; Schlipf, Martin; Rushchanskii, Konstantin Z; Ležaić, Marjana; Matsuda, Masaaki; Ma, Jie; Calder, Stuart; Isobe, Masahiko; Ikuhara, Yuichi; Azuma, Masaki

    2015-10-07

    A metal to insulator transition in integer or half integer charge systems can be regarded as crystallization of charges. The insulating state tends to have a glassy nature when randomness or geometrical frustration exists. We report that the charge glass state is realized in a perovskite compound PbCrO3, which has been known for almost 50 years, without any obvious inhomogeneity or triangular arrangement in the charge system. PbCrO3 has a valence state of Pb(2+)(0.5)Pb(4+)(0.5)Cr(3+)O3 with Pb(2+)-Pb(4+) correlation length of three lattice-spacings at ambient condition. A pressure induced melting of charge glass and simultaneous Pb-Cr charge transfer causes an insulator to metal transition and ∼10% volume collapse.

  18. Direct spectroscopic evidence of ultrafast electron transfer from a low band gap polymer to CdSe quantum dots in hybrid photovoltaic thin films.

    Science.gov (United States)

    Couderc, Elsa; Greaney, Matthew J; Brutchey, Richard L; Bradforth, Stephen E

    2013-12-11

    Ultrafast transient absorption spectroscopy is used to study charge transfer dynamics in hybrid films composed of the low band gap polymer PCPDTBT and CdSe quantum dots capped with tert-butylthiol ligands. By selectively exciting the polymer, a spectral signature for electrons on the quantum dots appears on ultrafast time scales (≲ 65 fs), which indicates ultrafast electron transfer. From this time scale, the coupling between the polymer chains and the quantum dots is estimated to be J ≳ 17 meV. The reduced quantum dot acceptors exhibit an unambiguous spectral bleach signature, whose amplitude allows for the first direct calculation of the absolute electron transfer yield in a hybrid solar cell (82 ± 5%). We also show that a limitation of the hybrid system is rapid and measurable geminate recombination due to the small separation of the initial charge pair. The fast recombination is consistent with the internal quantum efficiency of the corresponding solar cell. We therefore have identified and quantified a main loss mechanism in this type of third generation solar cell.

  19. An Electronic Structure Approach to Charge Transfer and Transport in Molecular Building Blocks for Organic Optoelectronics

    Science.gov (United States)

    Hendrickson, Heidi Phillips

    A fundamental understanding of charge separation in organic materials is necessary for the rational design of optoelectronic devices suited for renewable energy applications and requires a combination of theoretical, computational, and experimental methods. Density functional theory (DFT) and time-dependent (TD)DFT are cost effective ab-initio approaches for calculating fundamental properties of large molecular systems, however conventional DFT methods have been known to fail in accurately characterizing frontier orbital gaps and charge transfer states in molecular systems. In this dissertation, these shortcomings are addressed by implementing an optimally-tuned range-separated hybrid (OT-RSH) functional approach within DFT and TDDFT. The first part of this thesis presents the way in which RSH-DFT addresses the shortcomings in conventional DFT. Environmentally-corrected RSH-DFT frontier orbital energies are shown to correspond to thin film measurements for a set of organic semiconducting molecules. Likewise, the improved RSH-TDDFT description of charge transfer excitations is benchmarked using a model ethene dimer and silsesquioxane molecules. In the second part of this thesis, RSH-DFT is applied to chromophore-functionalized silsesquioxanes, which are currently investigated as candidates for building blocks in optoelectronic applications. RSH-DFT provides insight into the nature of absorptive and emissive states in silsesquioxanes. While absorption primarily involves transitions localized on one chromophore, charge transfer between chromophores and between chromophore and silsesquioxane cage have been identified. The RSH-DFT approach, including a protocol accounting for complex environmental effects on charge transfer energies, was tested and validated against experimental measurements. The third part of this thesis addresses quantum transport through nano-scale junctions. The ability to quantify a molecular junction via spectroscopic methods is crucial to their

  20. Photoinduced Intramolecular Charge Transfer in Donor-acceptor Dyad and Donor-bridge-acceptor Triad

    Institute of Scientific and Technical Information of China (English)

    Yong Ding; Yuan-zuo Li; Feng-cai Ma

    2008-01-01

    The ground and excited state properties of the [60]fullerene,diphenylbenzothiadiazole-triphenylamine (PBTDP-TPA) dyad and fullerene-diphenylbenzothiadiazole-triphenylamine (fullerene-PBTDP-TPA) triad were investigated theoretically using density functional theory with B3LYP functional and 3-21G basis set and time-dependent density functional theory with B3LYP functional and STO-3G basis set as well as 2D and 3D real space analysis methods.The 2D site representation reveals the electron-hole coherence on exci- tation.The 3D transition density shows the orientation and strength of the transition dipole moment,and the 3D charge difference density gives the orientation and result of the intramolecular charge transfer.Also, photoinduced intermolecular charge transfer (ICT) in PBTDP-TPA-fullerene triad are identified with 2D and 3D representations,which reveals the mechanisms of ICT in donor-bridge-acceptor triad on excitation. Besides that we also found that the direct superexchange ICT from donor to acceptor (tunneling through the bridge) strongly promotes the ICT in the donor-bridge-acceptor triad.

  1. Structure and dynamics of a dizinc metalloprotein: effect of charge transfer and polarization.

    Science.gov (United States)

    Li, Yong L; Mei, Ye; Zhang, Da W; Xie, Dai Q; Zhang, John Z H

    2011-08-25

    Structures and dynamics of a recently designed dizinc metalloprotein (DFsc) (J. Mol. Biol. 2003, 334, 1101) are studied by molecular dynamics simulation using a dynamically adapted polarized force field derived from fragment quantum calculation for protein in solvent. To properly describe the effect of charge transfer and polarization in the present approach, quantum chemistry calculation of the zinc-binding group is periodically performed (on-the-fly) to update the atomic charges of the zinc-binding group during the MD simulation. Comparison of the present result with those obtained from simulations under standard AMBER force field reveals that charge transfer and polarization are critical to maintaining the correct asymmetric metal coordination in the DFsc. Detailed analysis of the result also shows that dynamic fluctuation of the zinc-binding group facilitates solvent interaction with the zinc ions. In particular, the dynamic fluctuation of the zinc-zinc distance is shown to be an important feature of the catalytic function of the di-ion zinc-binding group. Our study demonstrates that the dynamically adapted polarization approach is computationally practical and can be used to study other metalloprotein systems.

  2. Ultrafast dynamics of solvation and charge transfer in a DNA-based biomaterial.

    Science.gov (United States)

    Choudhury, Susobhan; Batabyal, Subrata; Mondol, Tanumoy; Sao, Dilip; Lemmens, Peter; Pal, Samir Kumar

    2014-05-01

    Charge migration along DNA molecules is a key factor for DNA-based devices in optoelectronics and biotechnology. The association of a significant amount of water molecules in DNA-based materials for the intactness of the DNA structure and their dynamic role in the charge-transfer (CT) dynamics is less documented in contemporary literature. In the present study, we have used a genomic DNA-cetyltrimethyl ammonium chloride (CTMA) complex, a technological important biomaterial, and Hoechest 33258 (H258), a well-known DNA minor groove binder, as fluorogenic probe for the dynamic solvation studies. The CT dynamics of CdSe/ZnS quantum dots (QDs; 5.2 nm) embedded in the as-prepared and swollen biomaterial have also been studied and correlated with that of the timescale of solvation. We have extended our studies on the temperature-dependent CT dynamics of QDs in a nanoenvironment of an anionic, sodium bis(2-ethylhexyl)sulfosuccinate reverse micelle (AOT RMs), whereby the number of water molecules and their dynamics can be tuned in a controlled manner. A direct correlation of the dynamics of solvation and that of the CT in the nanoenvironments clearly suggests that the hydration barrier within the Arrhenius framework essentially dictates the charge-transfer dynamics.

  3. Coil Design for High Misalignment Tolerant Inductive Power Transfer System for EV Charging

    Directory of Open Access Journals (Sweden)

    Kafeel Ahmed Kalwar

    2016-11-01

    Full Text Available The inductive power transfer (IPT system for electric vehicle (EV charging has acquired more research interest in its different facets. However, the misalignment tolerance between the charging coil (installed in the ground and pick-up coil (mounted on the car chassis, has been a challenge and fundamental interest in the future market of EVs. This paper proposes a new coil design QDQ (Quad D Quadrature that maintains the high coupling coefficient and efficient power transfer during reasonable misalignment. The QDQ design makes the use of four adjacent circular coils and one square coil, for both charging and pick-up side, to capture the maximum flux at any position. The coil design has been modeled in JMAG software for calculation of inductive parameters using the finite element method (FEM, and its hardware has been tested experimentally at various misaligned positions. The QDQ coils are shown to be capable of achieving good coupling coefficient and high efficiency of the system until the misalignment displacement reaches 50% of the employed coil size.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-16

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

  5. Tuning the role of charge-transfer states in intramolecular singlet exciton fission through side-group engineering

    Science.gov (United States)

    Lukman, Steven; Chen, Kai; Hodgkiss, Justin M.; Turban, David H. P.; Hine, Nicholas D. M.; Dong, Shaoqiang; Wu, Jishan; Greenham, Neil C.; Musser, Andrew J.

    2016-12-01

    Understanding the mechanism of singlet exciton fission, in which a singlet exciton separates into a pair of triplet excitons, is crucial to the development of new chromophores for efficient fission-sensitized solar cells. The challenge of controlling molecular packing and energy levels in the solid state precludes clear determination of the singlet fission pathway. Here, we circumvent this difficulty by utilizing covalent dimers of pentacene with two types of side groups. We report rapid and efficient intramolecular singlet fission in both molecules, in one case via a virtual charge-transfer state and in the other via a distinct charge-transfer intermediate. The singlet fission pathway is governed by the energy gap between singlet and charge-transfer states, which change dynamically with molecular geometry but are primarily set by the side group. These results clearly establish the role of charge-transfer states in singlet fission and highlight the importance of solubilizing groups to optimize excited-state photophysics.

  6. Cascading electron and hole transfer dynamics in a CdS/CdTe core-shell sensitized with bromo-pyrogallol red (Br-PGR): slow charge recombination in type II regime.

    Science.gov (United States)

    Maity, Partha; Debnath, Tushar; Chopra, Uday; Ghosh, Hirendra Nath

    2015-02-14

    Ultrafast cascading hole and electron transfer dynamics have been demonstrated in a CdS/CdTe type II core-shell sensitized with Br-PGR using transient absorption spectroscopy and the charge recombination dynamics have been compared with those of CdS/Br-PGR composite materials. Steady state optical absorption studies suggest that Br-PGR forms strong charge transfer (CT) complexes with both the CdS QD and CdS/CdTe core-shell. Hole transfer from the photo-excited QD and QD core-shell to Br-PGR was confirmed by both steady state and time-resolved emission spectroscopy. Charge separation was also confirmed by detecting electrons in the conduction band of the QD and the cation radical of Br-PGR as measured from femtosecond transient absorption spectroscopy. Charge separation in the CdS/Br-PGR composite materials was found to take place in three different pathways, by transferring the photo-excited hole of CdS to Br-PGR, electron injection from the photo-excited Br-PGR to the CdS QD, and direct electron transfer from the HOMO of Br-PGR to the conduction band of the CdS QD. However, in the CdS/CdTe/Br-PGR system hole transfer from the photo-excited CdS to Br-PGR and electron injection from the photo-excited Br-PGR to CdS take place after cascading through the CdTe shell QD. Charge separation also takes place via direct electron transfer from the Br-PGR HOMO to the conduction band of CdS/CdTe. Charge recombination (CR) dynamics between the electron in the conduction band of the CdS QD and the Br-PGR cation radical were determined by monitoring the bleach recovery kinetics. The CR dynamics were found to be much slower in the CdS/CdTe/Br-PGR system than in the CdS/Br-PGR system. The formation of the strong CT complex and the separation of charges cascading through the CdTe shell help to slow down charge recombination in the type II regime.

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

    Science.gov (United States)

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

    2003-12-01

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

  8. Ambipolar Charge Photogeneration and Transfer at GaAs/P3HT Heterointerfaces.

    Science.gov (United States)

    Panahandeh-Fard, Majid; Yin, Jun; Kurniawan, Michael; Wang, Zilong; Leung, Gle; Sum, Tze Chien; Soci, Cesare

    2014-04-03

    Recent work on hybrid photovoltaic systems based on conjugated polymers and III-V compound semiconductors with relatively high power conversion efficiency revived fundamental questions regarding the nature of charge separation and transfer at the interface between organic and inorganic semiconductors with different degrees of delocalization. In this work, we studied photoinduced charge generation and interfacial transfer dynamics in a prototypical photovoltaic n-type GaAs (111)B and poly(3-hexyl-thiophene) (P3HT) bilayer system. Ultrafast spectroscopy and density functional theory calculations indicate the coexistence of electron and hole transfer at the GaAs/P3HT interface, leading to the generation of long-lived species and photoinduced absorption upon creation of hybrid interfacial states. This opens up new avenues for the use of low-dimensional III-V compounds (e.g., nanowires or quantum dots) in hybrid organic/inorganic photovoltaics, where advanced bandgap and density of states engineering may also be exploited as design parameters.

  9. The role of hydrogen bonding in excited state intramolecular charge transfer.

    Science.gov (United States)

    Chipem, Francis A S; Mishra, Anasuya; Krishnamoorthy, G

    2012-07-07

    Intramolecular charge transfer (ICT) that occurs upon photoexcitation of molecules is a vital process in nature and it has ample applications in chemistry and biology. The ICT process of the excited molecules is affected by several environmental factors including polarity, viscosity and hydrogen bonding. The effect of polarity and viscosity on the ICT processes is well understood. But, despite the fact that hydrogen bonding significantly influences the ICT process, the specific role of hydrogen bonding in the formation and stabilization of the ICT state is not unambiguously established. Some literature reports predicted that the hydrogen bonding of the solvent with a donor promotes the formation of a twisted intramolecular charge transfer (TICT) state. Some other reports stated that it inhibits the formation of the TICT state. Alternatively, it was proposed that the hydrogen bonding of the solvent with an acceptor favors the TICT state. It is also observed that a dynamic equilibrium is established between the free and the hydrogen bonded ICT states. This perspective focuses on the specific role played by hydrogen bonding of the solvent with the donor and the acceptor, and by proton transfer in the ICT process. The utility of such influence in molecular recognition and anion sensing is discussed with a few recent literature examples in the end.

  10. Synthesis and electrochemical studies of charge-transfer complexes of thiazolidine-2,4-dione with σ and π acceptors

    Science.gov (United States)

    Singh, Prashant; Kumar, Pradeep; Katyal, Anju; Kalra, Rashmi; Dass, Sujata K.; Prakash, Satya; Chandra, Ramesh

    2010-03-01

    In the present work, we report the synthesis and characterization of novel charge-transfer complexes of thiazolidine-2,4-dione (TZD) with sigma acceptor (iodine) and pi acceptors (chloranil, dichlorodicyanoquinone, picric acid and duraquinone). We also evaluated their thermal and electrochemical properties and we conclude that these complexes are frequency dependent. Charge-transfer complex between thiazolidine-2,4-dione and iodine give best conductivity. In conclusion, complex with sigma acceptors are more conducting than with pi acceptors.

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

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

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

  12. Energy transfer through a multi-layer liner for shaped charges

    Science.gov (United States)

    Skolnick, Saul; Goodman, Albert

    1985-01-01

    This invention relates to the determination of parameters for selecting materials for use as liners in shaped charges to transfer the greatest amount of energy to the explosive jet. Multi-layer liners constructed of metal in shaped charges for oil well perforators or other applications are selected in accordance with the invention to maximize the penetrating effect of the explosive jet by reference to four parameters: (1) Adjusting the explosive charge to liner mass ratio to achieve a balance between the amount of explosive used in a shaped charge and the areal density of the liner material; (2) Adjusting the ductility of each layer of a multi-layer liner to enhance the formation of a longer energy jet; (3) Buffering the intermediate layers of a multi-layer liner by varying the properties of each layer, e.g., composition, thickness, ductility, acoustic impedance and areal density, to protect the final inside layer of high density material from shattering upon impact of the explosive force and, instead, flow smoothly into a jet; and (4) Adjusting the impedance of the layers in a liner to enhance the transmission and reduce the reflection of explosive energy across the interface between layers.

  13. Local equilibria and state transfer of charged classical particles on a helix in an electric field

    CERN Document Server

    Plettenberg, J; Zampetaki, A V; Schmelcher, P

    2016-01-01

    We explore the effects of a homogeneous external electric field on the static properties and dynamical behavior of two charged particles confined to a helix. In contrast to the field-free setup which provides a separation of the center-of-mass and relative motion, the existence of an external force perpendicular to the helix axis couples the center-of-mass to the relative degree of freedom leading to equilibria with a localized center of mass. By tuning the external field various fixed points are created and/or annihilated through different bifurcation scenarios. We provide a detailed analysis of these bifurcations based on which we demonstrate a robust state transfer between essentially arbitrary equilibrium configurations of the two charges that can be induced by making the external force time-dependent.

  14. Theoretical study of charge transfer dynamics in collisions of C6+ carbon ions with pyrimidine nucleobases

    Science.gov (United States)

    Bacchus-Montabonel, M. C.

    2012-07-01

    A theoretical approach of the charge transfer dynamics induced by collision of C6+ ions with biological targets has been performed in a wide collision energy range by means of ab-initio quantum chemistry molecular methods. The process has been investigated for the target series thymine, uracil and 5-halouracil corresponding to similar molecules with different substituent on carbon C5. Such a study may be related to hadrontherapy treatments by C6+carbon ions and may provide, in particular, information on the radio-sensitivity of the different bases with regard to ion-induced radiation damage. The results have been compared to a previous analysis concerning the collision of C4+ carbon ions with the same biomolecular targets and significant charge effects have been pointed out.

  15. A Model of Charge Transfer Excitons: Diffusion, Spin Dynamics, and Magnetic Field Effects

    CERN Document Server

    Lee, Chee Kong; Willard, Adam P

    2016-01-01

    In this letter we explore how the microscopic dynamics of charge transfer (CT) excitons are influenced by the presence of an external magnetic field in disordered molecular semiconductors. This influence is driven by the dynamic interplay between the spin and spatial degrees of freedom of the electron-hole pair. To account for this interplay we have developed a numerical framework that combines a traditional model of quantum spin dynamics with a coarse-grained model of stochastic charge transport. This combination provides a general and efficient methodology for simulating the effects of magnetic field on CT state dynamics, therefore providing a basis for revealing the microscopic origin of experimentally observed magnetic field effects. We demonstrate that simulations carried out on our model are capable of reproducing experimental results as well as generating theoretical predictions related to the efficiency of organic electronic materials.

  16. Charge Transfer Complexes of Polymers%高分子电荷转移复合物

    Institute of Scientific and Technical Information of China (English)

    赵扬; 邱家白

    1986-01-01

    @@ 电荷转移复合物(charge transfer complex, CTC)的研究,始于本世纪二十年代。然而对CTC理论的阐述,及其实际应用方面,长期未取得实质性进展。1952年R. S. Mulliken在J. H. Hildebrand的实验基础上首创共振模型,引入电荷转移(charge transfer,CT)这一术语,奠定了CTO的理论基础。从此,对CT现象的研究不断深入,开拓的领域日益广阔,已成为世界性的研究课题。

  17. l-distributions of the first electron transferred to multiply charged ions interacting with solid surfaces

    Science.gov (United States)

    Mirkovic, M. A.; Nedeljkovic, N. N.

    2008-07-01

    We analyze the angular momentum distributions of the electron transferred into the Rydberg states of multiply charged ions escaping the solid surfaces. The population probabilities are calculated within the framework of two-state-vector model; in the case of large values of the angular momentum quantum numbers l the model takes into account an importance of a wide space region around the projectile trajectory. The reionization of the previously populated states is also taken into account. The corresponding ionization rates are obtained by the appropriate etalon equation method; in the large-l case the radial electronic coordinate rho is treated as variational parameter. The theoretical predictions based on the proposed population-reionization mechanism fit the available beam-foil experimental data; the obtained large-l distributions are also used to elucidate the recent experimental data concerning the multiply charged Rydberg ions interacting with micro-capillary foil.

  18. K-shell to K-shell charge transfer in collisions of bare decelerated S ions with Ar

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, M.; Justiniano, E.; Konrad, J.; Schuch, R.; Salin, A.

    1987-05-14

    The impact parameter dependence of the single and double K-shell to K-shell charge transfer probabilities was studied by measuring triple coincidences between two K x-rays and the scattered projectiles for 16 MeV S W -Ar. It was found that the data are internally consistent with independent electron assumptions, but cannot be reproduced by different calculations of single electron transfer probabilities applying the independent electron model. Also a calculation of double K-vacancy transfer including electron correlations which described the HeS -He charge transfer probabilities well, is not in good agreement with the present data. The data allow a more sensitive test of various calculations on K to K charge transfer than recent experimental studies on collision systems with hydrogen-like projectiles.

  19. ANISOTROPY EFFECTS IN SINGLE-ELECTRON TRANSFER BETWEEN LASER-EXCITED ATOMS AND HIGHLY-CHARGED IONS

    NARCIS (Netherlands)

    1995-01-01

    Recent collision experiments are reviewed in which one-electron transfer between laser excited target atoms and (highly charged) keV-ions has been studied. Especially results showing a dependence of the charge exchange on the initial target orbital alignment are discussed. The question to what exten

  20. Charge separation distance for flexible donor-bridge-acceptor systems after electron-transfer quenching.

    Science.gov (United States)

    Zhou, Jinwei; Lukin, Leonid V; Braun, Charles L

    2008-08-21

    Photoinduced transient dipole experiments are used to measure the effective charge separation distance, which is equivalent to the photoinduced change in dipole moment divided by the electron charge of flexible electron-donor/acceptor systems, D-(CH2)n-A, where D is 4- N,N-dimethylaniline, A is 9-anthryl, and n = 3, 4. We find that the dipole moments increase strongly with solvent polarity. For the compound with n = 4 (DBA4), analysis of dipole signals indicates that the effective charge separation distances in toluene, 1,4-dioxane, ethyl acetate, tetrahydrofuran, dichloromethane, 1,2-dichloroethane, 2-methylpentanone-3, 3-pentanone, and benzonitrile are 2.2, 2.5, 4.5, 4.7, 5.5, 5.5, 4.8, and 6.3 A, respectively. These values can be understood as the root-mean-square charge separation distance in the solutions of different solvents. We assume that the folded contact configuration has a separation distance of 3.5 A, the extended, solvent-separated configuration has a separation distance of 8.0 A, and that they are the only two stable species after electron-transfer quenching. The formation efficiencies of contact radical ion pairs (CRIPs) and solvent-separated radical ion pairs (SSRIPs) are estimated in different solvents. The results indicate that a significant fraction of the ion pairs exist as solvent-separated ion pairs when the dielectric constant of the solvent is larger than 10. These results indicate that electron-transfer quenching can indeed happen at large separations in polar solvents. They also reveal that there is a barrier for ion pairs formed at large separations, hindering collapse to a contact separation of around 3.5 A.

  1. Structure and Bonding in Nickel-Thiolate-Iodine Charge-Transfer Complexes.

    Science.gov (United States)

    Beyer, Norman; Steinfeld, Gunther; Lozan, Vasile; Naumov, Sergej; Flyunt, Roman; Abel, Bernd; Kersting, Berthold

    2017-02-16

    The dinuclear nickel complexes [Ni2 L(μ-O2 CR)](ClO4 ) [R=Me (4), R=OMe (6)], where L(2-) is a 24-membered macrocyclic N6 S2 ligand, react readily with excess I2 in MeCN solution at 4 °C to form stable mono-(I2 ) and bis-(I2 ) charge-transfer (CT) adducts of the type [Ni2 L(μ-O2 CR)(I2 )n ](+) (n=1 or 2) containing linear RS-I-I linkages. Three new CT compounds, namely, [Ni2 L(OAc)(I2 )](I2 )(I3 ) (5), [Ni2 L(O2 COMe)(I2 )](I5 )⋅MeCN (7⋅MeCN), and [Ni2 L(O2 COMe)(I2 )2 ](I5 )⋅MeCN (8⋅MeCN) as well as the triiodide salt [Ni2 L(OAc)](I3 ) (9) were synthesized and fully characterized. A common feature of the CT adducts is a polyiodide matrix, which surrounds the individual complex molecules, stabilized by secondary I⋅⋅⋅I interactions with the CT linkages. The scatter in both the RS-I (2.6 to 3.0 Å) and the I-I bond lengths (2.7 to 3.0 Å) is indicative of both a variable strength of the RS(-) →I2 bond and a varying degree of charge transfer. An analysis of the structural parameters was undertaken accompanied by DFT calculations to quantify the donating ability of the bridging thiolate functions and to shed more light on the bonding in this rare sort of charge-transfer complexes. The stability of the CT complexes and the results of preliminary transport measurements are also reported.

  2. Charge transfer excitation of trivalent rare earth ions Sm/sup 3+/, Eu/sup 3+/, Gd/sup 3+/, Ho/sup 3+/, Er/sup 3+/ and Yb/sup 3+/ emission in BaFCl crystals

    Energy Technology Data Exchange (ETDEWEB)

    Su, M.Z.; Sun, X.P.

    1987-01-01

    The charge transfer type excitation spectra of trivalent rare earth ions Sm/sup 3+/, Eu/sup 3+/, Gd/sup 3+/, Ho/sup 3+/, Er/sup 3+/ and Yb/sup 3+/ emission in BaFCl crystals have been studied. The charge transfer type emissions of Ho/sup 3+/, Er/sup 3+/ and Yb/sup 3+/ in BaFCl have also been observed in addition to that of Eu/sup 3+/. The energy of charge transfer band of these RE/sup 3+/ ions were estimated experimentally and also calculated by Jorgensen's refined electron spin-pairing energy theory. Both the experimental and calculated values coincide well.

  3. Splitting of the Ti-3d bands of TiSe2 in the charge-density wave phase

    Science.gov (United States)

    Ghafari, A.; Petaccia, L.; Janowitz, C.

    2017-02-01

    Very high resolution angular resolved photoemission (ARPES) spectra on TiSe2 in two distinct polarization geometries (vertical and horizontal) at temperatures between 300 K and 22 K enabled the observation of details of bands near the Fermi level not reported so far. Calculations of the electronic band structure based on density functional theory (DFT) using B3LYP hybrid functional and MBJ potential (with and without spin-orbit coupling) were performed to obtain the orbital symmetry and dispersion. Two degenerate conduction bands (CB's) were observed at the Γ-point, a weak CB- emission at the A-point, and two non degenerate CB's (i.e. splitting of CB) at the M/L-point of the Brillouin Zone (BZ). The splitting was detected at L for both polarizations, while at M remarkably only for horizontal polarization. These results cannot be fully accounted for by current theories for the charge density wave (CDW) and point to a reduced symmetry of the electronic states, possibly due to the chiral CDW.

  4. Nanometer scale carbon structures for charge-transfer systems and photovoltaic applications.

    Science.gov (United States)

    Guldi, Dirk M

    2007-03-28

    This article surveys and highlights the integration of nanometer scale carbon structures--in combination with chromophores that exhibit (i) significant absorption cross section throughout the visible part of the solar spectrum and (ii) good electron donating power--into novel electron donor-acceptor conjugates (i.e., covalent) and hybrids (i.e., non-covalent). The focus of this article is predominantly on performance features--charge-transfer and photovoltaic--of the most promising solar energy conversion systems. Besides documenting fundamental advantages as they emerge around nanometer scale carbon structures, critical evaluations of the most recent developments in the fields are provided.

  5. Excited state intramolecular charge transfer reaction in 4-(1-azetidinyl)benzonitrile: Solvent isotope effects

    Indian Academy of Sciences (India)

    Tuhin Pradhan; Piue Ghoshal; Ranjit Biswas

    2009-01-01

    Excited state intramolecular charge transfer reaction of 4-(1-azetidinyl) benzonitrile (P4C) in deuterated and normal methanol, ethanol and acetonitrile has been studied in order to investigate the solvent isotope effects on reaction rates and yields. These quantities (reaction rates and yields) along with several other properties such as quantum yield and radiative rates have been found to be insensitive to the solvent isotope substitution in all these solvents. The origin of the solvent isotope insensitivity of the reaction is discussed and correlated with the observed slowing down of the solvation dynamics upon isotope substitution.

  6. Conjugated iminopyridine based Azo dye derivatives with efficient charge transfer for third order nonlinearities

    Science.gov (United States)

    Kerasidou, A. P.; Khammar, F.; Iliopoulos, K.; Ayadi, A.; El-Ghayoury, A.; Zouari, N.; Mhiri, T.; Sahraoui, B.

    2014-03-01

    The third order nonlinearities of two azobenzene-iminopyridine molecular systems have been investigated employing the Z-scan technique at 532 nm, 30 ps. The objective of the work has been to study and to compare the nonlinearity of two iminopyridine based ligands substituted with one (NO2AzoIminoPy, A) and two azobenzene units ((NO2Azo)2IminoPy, B). The ligand B exhibits an extended conjugated structure and higher charge transfer within the molecule. Our results show high dependence of the nonlinearity on both the conjugation length within the molecule and on the number of the electron accepting units.

  7. Topological charge transfer in frequency doubling of fractional orbital angular momentum state

    Science.gov (United States)

    Ni, R.; Niu, Y. F.; Du, L.; Hu, X. P.; Zhang, Y.; Zhu, S. N.

    2016-10-01

    Nonlinear frequency conversion is promising for manipulating photons with orbital angular momentum (OAM). In this letter, we investigate the second harmonic generation (SHG) of light beams carrying fractional OAM. By measuring the OAM components of the generated second harmonic (SH) waves, we find that the integer components of the fundamental beam will interact with each other during the nonlinear optical process; thus, we figure out the law for topological charge transfer in frequency doubling of the fractional OAM state. Theoretical predictions by solving the nonlinear coupled wave equations are consistent with the experimental results.

  8. Indolizino[5,6-b]quinoxaline Derivatives: Intramolecular Charge Transfer Characters and NIR Fluorescence.

    Science.gov (United States)

    Kojima, Mitsuru; Hayashi, Hironobu; Aotake, Tatsuya; Ikeda, Shinya; Suzuki, Mitsuharu; Aratani, Naoki; Kuzuhara, Daiki; Yamada, Hiroko

    2015-11-01

    Indolizino[5,6-b]quinoxaline derivatives (1 a and 1 b) with a push-pull structure were prepared to show intramolecular charge-transfer properties. Compounds 1 a and 1 b are strongly fluorescent in aprotic solvents while symmetrical derivatives (2 a and 2 b) were non-fluorescent. The π-expanded α-α linked dimer (10) of indolizino[5,6-b]quinoxaline 1 b was serendipitously obtained to show NIR absorption over 800 nm and the fluorescence edge reached to 1400 nm.

  9. Laser-induced charge transfer in the HeH/sup 2 +/ quasimolecule

    Energy Technology Data Exchange (ETDEWEB)

    Errea, L.F.; Mendez, L.; Riera, A.

    1983-11-01

    In a recent publication, the charge transfer cross section for He/sup 2 +/+H(ls) collisions through photon-assisted 2psigma--3dsigma transitions was calculated; this calculation, however, contained several errors whose quantitative--even qualitative effect on the results is not obvious. We present a correct evaluation of this laser-induced cross section, which turns out to be larger, and present a maximum for longer wavelengths, than the values previously reported. In addition, we have checked the applicability of perturbation theory, of the stationary phase, uniform and Landau--Zener approximations, and the importance of potentially competitive photon-assisted reactions.

  10. Spectroscopy of charge transfer complexes of four amino acids as organic two-dimensional conductors

    Energy Technology Data Exchange (ETDEWEB)

    Padhiyar, Ashvin; Patel, A J; Oza, A T [Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388 120, Gujarat (India)

    2007-12-05

    It is found in this study that four amino acids, namely asparagine, arginine, histidine and glutamine form two-dimensional conducting systems which are charge transfer complexes (CTCs) with organic acceptors like TCNQ, TCNE, chloranil, DDQ, TNF and iodine. It is verified using optical absorption edges that these are 2d conductors like transition metal dichalcogenides obeying absorption functions different from 1d and 3d conductors. This 2d nature is related to the network of intermolecular H-bonding in these complexes, which leads to a global H-bonded network resulting in the absence of local deformation due to the relaxation of strain.

  11. Spectroscopy of charge transfer complexes of four amino acids as organic two-dimensional conductors

    Science.gov (United States)

    Padhiyar, Ashvin; Patel, A. J.; Oza, A. T.

    2007-12-01

    It is found in this study that four amino acids, namely asparagine, arginine, histidine and glutamine form two-dimensional conducting systems which are charge transfer complexes (CTCs) with organic acceptors like TCNQ, TCNE, chloranil, DDQ, TNF and iodine. It is verified using optical absorption edges that these are 2d conductors like transition metal dichalcogenides obeying absorption functions different from 1d and 3d conductors. This 2d nature is related to the network of intermolecular H-bonding in these complexes, which leads to a global H-bonded network resulting in the absence of local deformation due to the relaxation of strain.

  12. Charge transfer in energetic Li2+-H and He+-He+ collisions

    Science.gov (United States)

    Mančev, I.

    2009-02-01

    The total cross sections for charge transfer in Li2+-H and He+-He+ collisions have been calculated, using the four body first Born approximation with correct boundary conditions (CB1-4B) and four body continuum distorted wave method (CDW-4B) in the energy range 10-5000 keV/amu. The role of dynamic electron correlations is examined as a function of the impact energy. The present results call for additional experimental data at higher impact energies than presently available.

  13. Examination of charge transfer in Au/YSZ for high-temperature optical gas sensing

    Energy Technology Data Exchange (ETDEWEB)

    Baltrus, John P. [U.S. DOE; Ohodnicki, Paul R. [U.S. DOE

    2014-01-01

    Au-nanoparticle incorporated oxide thin film materials demonstrate significant promise as functionalsensor materials for high temperature optical gas sensing in severe environments relevant for fossil andnuclear based power generation. The Au/yttria-stabilized zirconia (YSZ) system has been extensivelystudied in the literature and serves as a model system for fundamental investigations that seek to betterunderstand the mechanistic origin of the plasmonic gas sensing response. In this work, X-ray photoelec-tron spectroscopy techniques are applied to Au/YSZ films in an attempt to provide further experimentalevidence for a proposed sensing mechanism involving a change in free carrier density of Au nanoparticles due to charge transfer.

  14. Efficient Charge Transfer Mechanism in Polyfluorene/ZnO Nanocomposite Thin Films

    OpenAIRE

    Bandar Ali Al-Asbahi; Mohammad Hafizuddin Haji Jumali; Rashad Al-Gaashani

    2014-01-01

    The optical properties and charge transfer mechanism of poly (9,9′-di-n-octylfluorenyl-2.7-diyl) (PFO)/ZnO thin films have been investigated. The ZnO nanorods (NRs) were prepared via a microwave technique. The solution blending method was used to prepare the PFO/ZnO nanocomposites. X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM) were used to determine the structural properties, while UV-Vis and photoluminescence (PL) were employed to investigate the optical p...

  15. Molecular distortion and charge transfer effects in ZnPc/Cu(111)

    KAUST Repository

    Amin, B.

    2013-04-23

    The adsorption geometry and electronic properties of a zinc-phthalocyanine molecule on a Cu(111) substrate are studied by density functional theory. In agreement with experiment, we find remarkable distortions of the molecule, mainly as the central Zn atom tends towards the substrate to minimize the Zn-Cu distance. As a consequence, the Zn-N chemical bonding and energy levels of the molecule are significantly modified. However, charge transfer induces metallic states on the molecule and therefore is more important for the ZnPc/Cu(111) system than the structural distortions.

  16. High pressure induced charge transfer in 3d-4f bimetallic photomagnetic materials.

    Science.gov (United States)

    Wu, Lai-Chin; Nielsen, Morten Bormann; Bremholm, Martin; Madsen, Solveig Røgild; Overgaard, Jacob; Newville, Matt; Chen, Yu-Sheng; Iversen, Bo Brummerstedt

    2015-05-25

    Pressure-induced crystal color change of photo-magnetic materials [Ln(DMF)4(H2O)3(μ-CN)M(CN)5]·H2O, Ln = Y, M = Fe (1), Ln = Y, M = Co (2), Ln = Nd, M = Fe (3) (DMF = N,N-dimethyl formamide) are investigated using variable pressure X-ray Absorption Near-Edge Structure (XANES) spectroscopy and X-ray diffraction. For 1 the effect is caused by ligand-to-metal charge transfer (LMCT) on the iron site.

  17. Electrochromic devices based on wide band-gap nanocrystalline semiconductors functionalized with mononuclear charge transfer compounds

    DEFF Research Database (Denmark)

    Biancardo, M.; Argazzi, R.; Bignozzi, C.A.

    2006-01-01

    A series of ruthenium and iron mononuclear complexes were prepared and their spectroeletrochemical behavior characterized oil Optically Transparent Thin Layer Electrodes (OTTLE) and on Fluorine Doped SnO2 (FTO) conductive glasses coated with Sb-doped nanocrystalline SnO2. These systems display...... a reversible electrochemical response and offer potential application in electrochromic devices. On SnO2 films distinct spectral changes are observed in a narrow potential range (-0.5/0.9 V vs SCE) with switching times of the order of 0.8 s. (c) 2005 Elsevier B.V. All rights reserved....

  18. A study of charge transfer kinetics in dye-sensitized surface conductivity solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Friedrich, Dennis

    2011-05-15

    concentration of the redox species in the electrolyte film, having the fastest decay at the lowest concentration of the redox couple. This was due to the regeneration of the oxidized dye by iodide, screening the positive charge from recombination with injected electrons. The adsorption of cations such as Li{sup +} led to a relatively weak increase of the electron lifetime, although in combination with a redox couple these effects were less clear. The replacement of the iodide/iodine redox couple by the kinetically fast ferrocene/ ferrocenium system caused a dramatic increase of the decay rates of photogenerated charge carriers in subset devices. Thus, showing the importance of the kinetically slow reduction rates of the oxidized redox couple iodide/iodine, leading to an increase of the electron lifetime by the reduction of the dye cation. The analysis of charge carrier kinetics in TiO{sub 2} powders and films displayed a decrease of the decay rate upon dye-sensitization after band-to-band excitation with laser pulses at 355 nm. In the case of ZnO films, the presence of the dye induced a significantly accelerated decay after excitation at 355 nm. In contrast to the ZnO films, ZnO nanorods displayed no such destructive influence of the dye adsorption. Furthermore, after exciting the sample at 355 nm, the decay was found to be independent of the dye and mainly depending on the recombination of electron-hole pairs and electrons with the dye cation at 355 nm and 532 nm, respectively. (orig.)

  19. Tetrathiafulvalene-1,3,5-triazines as (multi)donor-acceptor systems with tunable charge transfer: structural, photophysical, and theoretical investigations.

    Science.gov (United States)

    Pop, Flavia; Riobé, François; Seifert, Sabine; Cauchy, Thomas; Ding, Jie; Dupont, Nathalie; Hauser, Andreas; Koch, Marius; Avarvari, Narcis

    2013-05-06

    Palladium-catalyzed cross-coupling reactions between chlorinated 1,3,5-triazines (TZ) and tetrathiafulvalene (TTF) trimethyltin derivatives afford mono- and C3 symmetric tris(TTF)-triazines as donor-acceptor compounds in which the intramolecular charge transfer (ICT) is modulated by the substitution scheme on TTF and TZ and by chemical or electrochemical oxidation. The TTF-TZ-Cl2 and (SMe)2TTF-TZ-Cl2 derivatives show fully planar structures in the solid state as a consequence of the conjugation between the two units. Electrochemical and photophysical investigations, supported by theoretical calculations, clearly demonstrate that the lowest excited state can be ascribed to the intramolecular charge transfer (ICT) π(TTF)→π*(TZ) transition. The tris(TTF) compound [(SMe)2TTF]3-TZ shows fluorescence when excited in the ICT band, and the emission is quenched upon oxidation. The radical cations TTF(+•) are easily observed in all of the cases through chemical and electrochemical oxidation by steady-state absorption experiments. In the case of [(SMe)2TTF]3-TZ, a low energy band at 5000 cm(-1), corresponding to a coupling between TTF(+•) and TTF units, is observed. A crystalline radical cation salt with the TTF-TZ-Cl2 donor and PF6(-) anion, prepared by electrocrystallization, is described.

  20. The Development of Layered Photonic Band Gap Structures Using a Micro-Transfer Molding Technique

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, Kevin Jerome [Iowa State Univ., Ames, IA (United States)

    2001-06-27

    Over the last ten years, photonic band gap (PBG) theory and technology have become an important area of research because of the numerous possible applications ranging from high-efficiency laser diodes to optical circuitry. This research concentrates on reducing the length scale in the fabrication of layered photonic band gap structures and developing procedures to improve processing consistency. Various procedures and materials have been used in the fabrication of layered PBG structures. This research focused on an economical micro transfer molding approach to create the final PBG structure. A poly dimethylsiloxane (PDMS) rubber mold was created from a silicon substrate. It was filled with epoxy and built layer-by-layer to create a 3-D epoxy structure. This structure was infiltrated with nanoparticle titania or a titania sol-gel, then fired to remove the polymer mold, leaving a monolithic ceramic inverse of the epoxy structure. The final result was a lattice of titania rolds that resembles a face-centered tetragonal structure. The original intent of this research was to miniaturize this process to a bar size small enough to create a photonic band gap for wavelengths of visible electro-magnetic radiation. The factor limiting progress was the absence of a silicon master mold of small enough dimensions. The Iowa State Microelectronics Research Center fabricated samples with periodicities of 2.5 and 1.0 microns with the existing technology, but a sample was needed on the order of 0.3 microns or less. A 0.4 micron sample was received from Sandia National Laboratory, which was made through an electron beam lithography process, but it contained several defects. The results of the work are primarily from the 2.5 and 1.0 micron samples. Most of the work focused on changing processing variables in order to optimize the infiltration procedure for the best results. Several critical parameters were identified, ranging from the ambient conditions to the specifics of the

  1. Uncertainty quantification of GEOS-5 L-band radiative transfer model parameters using Bayesian inference and SMOS observations

    NARCIS (Netherlands)

    G.J.M. De Lannoy; R.H. Reichle; J.A. Vrugt

    2014-01-01

    Uncertainties in L-band (1.4 GHz) microwave radiative transfer modeling (RTM) affect the simulation of brightness temperatures (Tb) over land and the inversion of satellite-observed Tb into soil moisture retrievals. In particular, accurate estimates of the microwave soil roughness, vegetation optica

  2. Short-lived charge-transfer excitons in organic photovoltaic cells studied by high-field magneto-photocurrent.

    Science.gov (United States)

    Devir-Wolfman, Ayeleth H; Khachatryan, Bagrat; Gautam, Bhoj R; Tzabary, Lior; Keren, Amit; Tessler, Nir; Vardeny, Z Valy; Ehrenfreund, Eitan

    2014-07-29

    The main route of charge photogeneration in efficient organic photovoltaic cells based on bulk hetero-junction donor-acceptor blends involves short-lived charge-transfer excitons at the donor-acceptor interfaces. The cell efficiency is critically affected by the charge-transfer exciton recombination and dissociation processes. By measuring the magneto-photocurrent under ambient conditions at room temperature, we show here that magnetic field-induced spin-mixing among the charge-transfer exciton spin sublevels occurs in fields up to at least 8.5 Tesla. The resulting magneto-photocurrent increases at high fields showing non-saturating behaviour up to the highest applied field. We attribute the observed high-field spin-mixing mechanism to the difference in the donor-acceptor g-factors. The non-saturating magneto-photocurrent response at high field indicates that there exist charge-transfer excitons with lifetime in the sub-nanosecond time domain. The non-Lorentzian high-field magneto-photocurrent response indicates a dispersive decay mechanism that originates due to a broad distribution of charge-transfer exciton lifetimes.

  3. Charge transfer at carbon nanotube-graphene van der Waals heterojunctions

    Science.gov (United States)

    Liu, Yuanda; Wang, Fengqiu; Liu, Yujie; Wang, Xizhang; Xu, Yongbing; Zhang, Rong

    2016-06-01

    Carbon nanotubes and graphene are two most widely investigated low-dimensional materials for photonic and optoelectronic devices. Combining these two materials into all-carbon hybrid nanostructures has shown enhanced properties in a range of devices, such as photodetectors and flexible electrodes. Interfacial charge transfer is the most fundamental physical process that directly impacts device design and performance, but remains a subject less well studied. Here, we complemented Raman spectroscopy with photocurrent probing, a robust way of illustrating the interfacial built-in fields, and unambiguously revealed both static and dynamic (photo-induced) charge transfer processes at the nanotube-graphene interfaces. Significantly, the effects of nanotube species, i.e. metallic as opposed to semiconducting, are for the first time compared. Of all the devices examined, the graphene sheet was found to be p-type doped with (6, 5) chirality-enriched semiconducting SWNTs (s-SWNTs), while n-type doped with highly pure (>99%) metallic SWNTs (m-SWNTs). Our results provide important design guidelines for all-carbon hybrid based devices.

  4. Real-time observation of intersystem crossing induced by charge recombination during bimolecular electron transfer reactions

    KAUST Repository

    Alsam, Amani Abdu

    2016-09-21

    Real-time probing of intersystem crossing (ISC) and triplet-state formation after photoinduced electron transfer (ET) is a particularly challenging task that can be achieved by time-resolved spectroscopy with broadband capability. Here, we examine the mechanism of charge separation (CS), charge recombination (CR) and ISC of bimolecular photoinduced electron transfer (PET) between poly[(9,9-di(3,3′-N,N’-trimethyl-ammonium) propyl fluorenyl-2,7-diyl)-alt-co-(9,9-dioctyl-fluorenyl-2,7-diyl)] diiodide salt (PFN) and dicyanobenzene (DCB) using time-resolved spectroscopy. PET from PFN to DCB is confirmed by monitoring the transient absorption (TA) and infrared spectroscopic signatures for the radical ion pair (DCB─•-PFN+•). In addition, our time-resolved results clearly demonstrate that CS takes place within picoseconds followed by CR within nanoseconds. The ns-TA data exhibit the clear spectroscopic signature of PFN triplet-triplet absorption, induced by the CR of the radical ion pairs (DCB─•-PFN+•). As a result, the triplet state of PFN (3PFN*) forms and subsequently, the ground singlet state is replenished within microseconds. © 2016

  5. Label-Free Acetylcholine Image Sensor Based on Charge Transfer Technology for Biological Phenomenon Tracking

    Science.gov (United States)

    Takenaga, Shoko; Tamai, Yui; Okumura, Koichi; Ishida, Makoto; Sawada, Kazuaki

    2012-02-01

    A 32 ×32 charge-transfer enzyme-type acetylcholine (ACh) image sensor array was produced for label-free tracking of images of ACh distribution and its performance in repeatable measurements without enzyme deactivation was examined. The proposed sensor was based on a charge-transfer-type pH image sensor, which was modified using an enzyme membrane (acetylcholine esterase, AChE) for each pixel. The ACh image sensor detected hydrogen ions generated by the ACh-AChE reaction. A polyion complex membrane composed of poly(L-lysine) and poly(4-styrenesulfonate) was used to immobilize the enzyme on the sensor. The improved uniformity and adhesion of the polyion complex membrane were evaluated in this study. As a result, temporal and spatial fluctuations of the ACh image sensor were successfully minimized using this approach. The sensitivity of the sensor was 4.2 mV/mM, and its detection limit was 20 µM. In five repeated measurements, the repeatability was 8.8%.

  6. Radiative charge transfer lifetime of the excited state of (NaCa)$^+$

    CERN Document Server

    Makarov, O P; Michels, H J; Smith, W W; Makarov, Oleg P.

    2003-01-01

    New experiments were proposed recently to investigate the regime of cold atomic and molecular ion-atom collision processes in a special hybrid neutral-atom--ion trap under high vacuum conditions. The collisional cooling of laser pre-cooled Ca$^+$ ions by ultracold Na atoms is being studied. Modeling this process requires knowledge of the radiative lifetime of the excited singlet A$^1\\Sigma^+$ state of the (NaCa)$^+$ molecular system. We calculate the rate coefficient for radiative charge transfer using a semiclassical approach. The dipole radial matrix elements between the ground and the excited states, and the potential curves were calculated using Complete Active Space Self-Consistent field and M\\"oller-Plesset second order perturbation theory (CASSCF/MP2) with an extended Gaussian basis, 6-311+G(3df). The semiclassical charge transfer rate coefficient was averaged over a thermal Maxwellian distribution. In addition we also present elastic collision cross sections and the spin-exchange cross section. The ra...

  7. Charge-transfer optical absorption mechanism of DNA:Ag-nanocluster complexes

    Science.gov (United States)

    Longuinhos, R.; Lúcio, A. D.; Chacham, H.; Alexandre, S. S.

    2016-05-01

    Optical properties of DNA:Ag-nanoclusters complexes have been successfully applied experimentally in Chemistry, Physics, and Biology. Nevertheless, the mechanisms behind their optical activity remain unresolved. In this work, we present a time-dependent density functional study of optical absorption in DNA:Ag4. In all 23 different complexes investigated, we obtain new absorption peaks in the visible region that are not found in either the isolated Ag4 or isolated DNA base pairs. Absorption from red to green are predominantly of charge-transfer character, from the Ag4 to the DNA fragment, while absorption in the blue-violet range are mostly associated to electronic transitions of a mixed character, involving either DNA-Ag4 hybrid orbitals or intracluster orbitals. We also investigate the role of exchange-correlation functionals in the calculated optical spectra. Significant differences are observed between the calculations using the PBE functional (without exact exchange) and the CAM-B3LYP functional (which partly includes exact exchange). Specifically, we observe a tendency of charge-transfer excitations to involve purines bases, and the PBE spectra error is more pronounced in the complexes where the Ag cluster is bound to the purines. Finally, our results also highlight the importance of adding both the complementary base pair and the sugar-phosphate backbone in order to properly characterize the absorption spectrum of DNA:Ag complexes.

  8. Observation of excited state charge transfer with fs/ps-CARS

    Energy Technology Data Exchange (ETDEWEB)

    Blom, Alex Jason [Iowa State Univ., Ames, IA (United States)

    2009-01-01

    Excited state charge transfer processes are studied using the fs/ps-CARS probe technique. This probe allows for multiplexed detection of Raman active vibrational modes. Systems studied include Michler's Ketone, Coumarin 120, 4-dimethylamino-4'-nitrostilbene, and several others. The vibrational spectrum of the para di-substituted benzophenone Michler's Ketone in the first excited singlet state is studied for the first time. It is found that there are several vibrational modes indicative of structural changes of the excited molecule. A combined experimental and theoretical approach is used to study the simplest 7-amino-4-methylcoumarin, Coumarin 120. Vibrations observed in FTIR and spontaneous Raman spectra are assigned using density functional calculations and a continuum solvation model is used to predict how observed modes are affected upon inclusion of a solvent. The low frequency modes of the excited state charge transfer species 4-dimethylamino-4{prime}-nitrostilbene are studied in acetonitrile. Results are compared to previous work on this molecule in the fingerprint region. Finally, several partially completed projects and their implications are discussed. These include the two photon absorption of Coumarin 120, nanoconfinement in cyclodextrin cavities and sensitization of titania nanoparticles.

  9. Excited State Structural Dynamics of Carotenoids and ChargeTransfer Systems

    Energy Technology Data Exchange (ETDEWEB)

    Van Tassle, Aaron Justin [Univ. of California, Berkeley, CA (United States)

    2006-01-01

    This dissertation describes the development andimplementation of a visible/near infrared pump/mid-infrared probeapparatus. Chapter 1 describes the background and motivation ofinvestigating optically induced structural dynamics, paying specificattention to solvation and the excitation selection rules of highlysymmetric molecules such as carotenoids. Chapter 2 describes thedevelopment and construction of the experimental apparatus usedthroughout the remainder of this dissertation. Chapter 3 will discuss theinvestigation of DCM, a laser dye with a fluorescence signal resultingfrom a charge transfer state. By studying the dynamics of DCM and of itsmethyl deuterated isotopomer (an otherwise identical molecule), we areable to investigate the origins of the charge transfer state and provideevidence that it is of the controversial twisted intramolecular (TICT)type. Chapter 4 introduces the use of two-photon excitation to the S1state, combined with one-photon excitation to the S2 state of thecarotenoid beta-apo-8'-carotenal. These 2 investigations show evidencefor the formation of solitons, previously unobserved in molecular systemsand found only in conducting polymers Chapter 5 presents an investigationof the excited state dynamics of peridinin, the carotenoid responsiblefor the light harvesting of dinoflagellates. This investigation allowsfor a more detailed understanding of the importance of structuraldynamics of carotenoids in light harvesting.

  10. Quantum dynamics of the charge transfer in C{sup +} + S at low collision energies

    Energy Technology Data Exchange (ETDEWEB)

    Chenel, Aurelie; Mangaud, Etienne; Justum, Yves; Desouter-Lecomte, Michele [Laboratoire de Chimie Physique, Bat 349, Univ-ParisSud et CNRS-UMR8000, F-91405 Orsay Cedex (France); Talbi, Dahbia [Groupe de Recherche en Astronomie et Astrophysique du Languedoc, Universite de Montpellier II et CNRS-UMR5024, Place Eugene Bataillon, F-34095 Montpellier Cedex 05 (France); Bacchus-Montabonel, Marie-Christine, E-mail: michele.desouter-lecomte@u-psud.f [Laboratoire de Spectrometrie Ionique et moleculaire, Universite de Lyon I et CNRS-UMR5579, 43 Bd du 11 Novembre 1918, F-69622 Villeurbanne Cedex (France)

    2010-12-28

    Following a recent semiclassical investigation by Bacchus-Montabonel and Talbi (2008 Chem. Phys. Lett. 467 28), the C{sup +}(2s{sup 2}2p){sup 2}P + S(3s{sup 2}3p{sup 4}){sup 3}P charge transfer process involved in the modellization of the interstellar medium chemistry and its reverse reaction are revisited by combining a wave packet approach and semiclassical dynamics in a quasimolecular approach for doublet and quartet states. New radial non-adiabatic coupling matrix elements have been calculated and the mixed treatment gives access to new precise values of the rate coefficients for the direct and reverse charge transfer processes. For this system, quantum and semiclassical results are in good agreement even at low collision kinetic energies. The dominance of the quartet states in the process is confirmed. In the quantum treatment, the collision matrix elements are extracted from wave packets by the flux method with an absorbing potential. The formation of resonances due to a centrifugal barrier is illustrated.

  11. Charge transfer and mixed-valence behavior in phtalocyanine-dimer cations.

    Science.gov (United States)

    Monari, Antonio; Evangelisti, Stefano; Leininger, Thierry

    2010-09-28

    Phtalocyanine compounds deserved a considerable interest in recent times, particularly because of their possible use in the field of nanoelectronics. In particular, the charge mobility (of both electrons and holes) in phtalocyanine stacked arrangements has been recently extensively investigated. The present work focuses on the study of the hole-transfer mechanism between two phtalocyanine monomers. For an interdisk distance larger than 4.5 bohrs, the eclipsed dimer exhibits a mixed-valence behavior, with a saddle point transition state separating two equivalent minima. This behavior, however, is strongly dependent on the relative angle between the disks. In particular, the mixed-valence character of the compound is strongly enhanced for arrangements that are far from the eclipsed geometry. Moreover, for values of the angle close to π/8 and 3π/8, the ground and excited transition states have exactly the same energy, thus implying the presence of a conical intersection. These results can have deep implication in the charge transfer along phtalocyanine chains.

  12. Time-dependent quantum wave packet dynamics to study charge transfer in heavy particle collisions

    Science.gov (United States)

    Zhang, Song Bin; Wu, Yong; Wang, Jian Guo

    2016-12-01

    The method of time-dependent quantum wave packet dynamics has been successfully extended to study the charge transfer/exchange process in low energy two-body heavy particle collisions. The collision process is described by coupled-channel equations with diabatic potentials and (radial and rotational) couplings. The time-dependent coupled equations are propagated with the multiconfiguration time-dependent Hartree method and the modulo squares of S-matrix is extracted from the wave packet by the flux operator with complex absorbing potential (FCAP) method. The calculations of the charge transfer process 12Σ+ H-(1s2) +Li(1 s22 s ) →22Σ+ /32 Σ+ /12 Π H(1 s ) +Li-(1s 22 s 2 l ) (l =s ,p ) at the incident energy of about [0.3, 1.3] eV are illustrated as an example. It shows that the calculated reaction probabilities by the present FCAP reproduce that of quantum-mechanical molecular-orbital close-coupling very well, including the peak structures contributed by the resonances. Since time-dependent external interactions can be directly included in the present FCAP calculations, the successful implementation of FCAP provides us a powerful potential tool to study the quantum control of heavy particle collisions by lasers in the near future.

  13. Multivalence Charge Transfer in Doped and Codoped Photocatalytic TiO2.

    Science.gov (United States)

    Ren, Hangjuan; Koshy, Pramod; Cao, Fuyang; Sorrell, Charles Christopher

    2016-08-15

    The present work reports data for the mineralogical and chemical properties of anatase thin films individually doped or codoped with chromium and vanadium, fabricated by sol-gel spin coating on glass substrates and annealing at 450 °C for 2 h. X-ray photoelectron spectroscopy data indicated the presence of Ti(4+), Ti(3+), Cr(3+), and possibly Cr(4+) in the Cr-doped thin films; Ti(4+), Ti(3+), V(3+), V(4+), and possibly V(5+) in the V-doped thin films; and Ti(4+), Ti(3+), Cr(3+), Cr(4+), V(3+), V(4+), and possibly V(5+) in the codoped thin films. While the thermodynamically stable valences Ti(4+), Cr(3+), and V(5+) would be expected to have formed, the presence of the nonequilibrium valences Ti(3+), Cr(4+), V(3+), and V(4+) is considered to have resulted from intervalence charge transfer for the Cr-doped and V-doped systems but from multivalence charge transfer (MVCT) for the codoped system. The latter phenomenon, which is introduced as a new conceptual term, describes the nature of the mutual exchange of electrons during valence changes of both dopant (Cr, V) and matrix (Ti) ions during annealing. In the present case, MVCT appears to be a transient metastable condition that acts during annealing, but subsequent UV irradiation can alter its effects.

  14. Colossal negative thermal expansion in BiNiO3 induced by intermetallic charge transfer

    Science.gov (United States)

    Azuma, Masaki; Chen, Wei-tin; Seki, Hayato; Czapski, Michal; Olga, Smirnova; Oka, Kengo; Mizumaki, Masaichiro; Watanuki, Tetsu; Ishimatsu, Naoki; Kawamura, Naomi; Ishiwata, Shintaro; Tucker, Matthew G.; Shimakawa, Yuichi; Attfield, J. Paul

    2011-01-01

    The unusual property of negative thermal expansion is of fundamental interest and may be used to fabricate composites with zero or other controlled thermal expansion values. Here we report that colossal negative thermal expansion (defined as linear expansion <−10−4 K−1 over a temperature range ~100 K) is accessible in perovskite oxides showing charge-transfer transitions. BiNiO3 shows a 2.6% volume reduction under pressure due to a Bi/Ni charge transfer that is shifted to ambient pressure through lanthanum substitution for Bi. Changing proportions of coexisting low- and high-temperature phases leads to smooth volume shrinkage on heating. The crystallographic linear expansion coefficient for Bi0.95La0.05NiO3 is −137×10−6 K−1 and a value of −82×10−6 K−1 is observed between 320 and 380 K from a dilatometric measurement on a ceramic pellet. Colossal negative thermal expansion materials operating at ambient conditions may also be accessible through metal-insulator transitions driven by other phenomena such as ferroelectric orders. PMID:21673668

  15. Experimental and modeling study on charge storage/transfer mechanism of graphene-based supercapacitors

    Science.gov (United States)

    Ban, Shuai; Jing, Xie; Zhou, Hongjun; Zhang, Lei; Zhang, Jiujun

    2014-12-01

    A symmetrical graphene-based supercapacitor is constructed for studying the charge-transfer mechanism within the graphene-based electrodes using both experiment measurements and molecular simulation. The in-house synthesized graphene is characterized by XRD, SEM and BET measurements for morphology and surface area. It is observed that the electric capacity of graphene electrode can be reduced by both high internal resistance and limited mass transfer. Computer modeling is conducted at the molecular level to characterize the diffusion behavior of electrolyte ions to the interior of electrode with emphasis on the unique 2D confinement imposed by graphene layers. Although graphene powder poses a moderate internal surface of 400 m2 g-1, the capacitance performance of graphene electrode can be as good as that of commercial activated carbon which has an overwhelming surface area of 1700 m2 g-1. An explanation to this abnormal correlation is that graphene material has an intrinsic capability of adaptively reorganizing its microporous structure in response to intercalation of ions and immergence of electrolyte solvent. The accessible surface of graphene is believed to be dramatically enlarged for ion adsorption during the charging process of capacitor.

  16. Surface-state-mediated charge-transfer dynamics in CdTe/CdSe core-shell quantum dots.

    Science.gov (United States)

    Rawalekar, Sachin; Kaniyankandy, Sreejith; Verma, Sandeep; Ghosh, Hirendra N

    2011-06-20

    Herein, we report the synthesis of aqueous CdTe/CdSe type-II core-shell quantum dots (QDs) in which 3-mercaptopropionic acid is used as the capping agent. The CdTe QDs and CdTe/CdSe core-shell QDs are characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), steady-state absorption, and emission spectroscopy. A red shift in the steady-state absorption and emission bands is observed with increasing CdSe shell thickness over CdTe QDs. The XRD pattern indicates that the peaks are shifted to higher angles after growth of the CdSe shell on the CdTe QDs. HR-TEM images of both CdTe and CdTe/CdSe QDs indicate that the particles are spherical, with a good shape homogeneity, and that the particle size increases by about 2 nm after shell formation. In the time-resolved emission studies, we observe that the average emission lifetime (τ(av)) increases to 23.5 ns for CdTe/CdSe (for the thickest shell) as compared to CdTe QDs (τ(av) =12 ns). The twofold increment in the average emission lifetime indicates an efficient charge separation in type-II CdTe/CdSe core-shell QDs. Transient absorption studies suggest that both the carrier cooling and the charge-transfer dynamics are affected by the presence of traps in the CdTe QDs and CdTe/CdSe core-shell QDs. Carrier quenching experiments indicate that hole traps strongly affect the carrier cooling dynamics in CdTe/CdSe core-shell QDs.

  17. The role of emissive charge transfer states in two polymer-fullerene organic photovoltaic blends : tuning charge photogeneration through the use of processing additives

    NARCIS (Netherlands)

    Clarke, Tracey M.; Peet, Jeff; Lungenschmied, Christoph; Drolet, Nicolas; Lu, Xinhui; Ocko, Benjamin M.; Mozer, Attila J.; Loi, Maria Antonietta

    2014-01-01

    The role of charge transfer (CT) states in organic photovoltaic systems has been debated in the recent literature. In this paper the device performances of two structurally analogous polymers PDTSiTTz (also known as KP115) and PCPDTTTz blended with PCBM are investigated, focusing on the effect the p

  18. Influence of charge transfer state on Eu3+ luminescence in LaAlO3, by high pressure spectroscopy

    Science.gov (United States)

    Behrendt, Mirosław; Mahlik, Sebastian; Grinberg, Marek; Stefańska, Dagmara; Dereń, Przemysław J.

    2017-01-01

    The contribution presents spectroscopic characterization of LaAlO3 doped with 0.5 mol %. Eu3+. We measured steady state luminescence, luminescence excitation spectra, as well as the time resolved spectra and luminescence kinetics. The experiments were performed at high hydrostatic pressure applied in diamond anvil cell (DAC) which was changed from ambient to 250 kbar. We found that for all pressures the emission from the 5D0 and 5D1 excited emitting state of Eu3+ was delayed in time after excitation pulse whilst emission from the 5D2 appear immediately after excitation. At pressure above 12 kbar the strong magnification of the luminescence lines related to the transitions from the 5D3 state which were very weak at ambient condition is observed. The emission decay of the 5D3 luminescence become slower when pressure is increased. All these effects are attributed to pressure-induced increase of the energy of the ground electronic configuration 4f6 of the Eu2+ with respect to the valence band edge which results in the charge transfer state, and 5D3 level crossing.

  19. Charge transfer complex studies between some non-steroidal anti-inflammatory drugs and π-electron acceptors

    Science.gov (United States)

    Duymus, Hulya; Arslan, Mustafa; Kucukislamoglu, Mustafa; Zengin, Mustafa

    2006-12-01

    Charge transfer (CT) complexes of some non-steroidal anti-inflammatory drugs, naproxen and etodolac which are electron donors with some π-acceptors, such as tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano- p-benzoquinone (DDQ), p-chloranil ( p-CHL), have been investigated spectrophotometrically in chloroform at 21 °C. The coloured products are measured spectrophotometrically at different wavelength depending on the electronic transition between donors and acceptors. Beer's law is obeyed and colours were produced in non-aqueous media. All complexes were stable at least 2 h except for etodolac with DDQ stable for 5 min. The equilibrium constants of the CT complexes were determined by the Benesi-Hildebrand equation. The thermodynamic parameters Δ H, Δ S, Δ G° were calculated by Van't Hoff equation. Stochiometries of the complexes formed between donors and acceptors were defined by the Job's method of the continuous variation and found in 1:1 complexation with donor and acceptor at the maximum absorption bands in all cases.

  20. Analysis of the magnetic coupling in binuclear systems. III. The role of the ligand to metal charge transfer excitations revisited

    Science.gov (United States)

    Calzado, Carmen J.; Angeli, Celestino; Taratiel, David; Caballol, Rosa; Malrieu, Jean-Paul

    2009-07-01

    In magnetic coordination compounds and solids the magnetic orbitals are essentially located on metallic centers but present some delocalization tails on adjacent ligands. Mean field variational calculations optimize this mixing and validate a single band modelization of the intersite magnetic exchange. In this approach, due to the Brillouin's theorem, the ligand to metal charge transfer (LMCT) excitations play a minor role. On the other hand the extensive configuration interaction calculations show that the determinants obtained by a single excitation on the top of the LMCT configurations bring an important antiferromagnetic contribution to the magnetic coupling. Perturbative and truncated variational calculations show that contrary to the interpretation given in a previous article [C. J. Calzado et al., J. Chem. Phys. 116, 2728 (2002)] the contribution of these determinants to the magnetic coupling constant is not a second-order one. An analytic development enables one to establish that they contribute at higher order as a correlation induced increase in the LMCT components of the wave function, i.e., of the mixing between the ligand and the magnetic orbitals. This larger delocalization of the magnetic orbitals results in an increase in both the ferro- and antiferromagnetic contributions to the coupling constant.

  1. Unusually Slow Electron Cooling to Charge-Transfer State in Gradient CdTeSe Alloy Nanocrystals Mediated through Mn Atom.

    Science.gov (United States)

    Debnath, Tushar; Maiti, Sourav; Ghosh, Hirendra N

    2016-04-07

    We have synthesized Mn-doped CdTeSe gradient alloy nanocrystals (NCs) by a colloidal synthetic method, and charge carrier dynamics have been revealed through ultrafast transient absorption (TA) spectroscopy. Due to the reactivity difference between Te and Se, a CdTe-rich core and CdSe-rich shell have been formed in the CdTeSe alloy with the formation of a gradient type II core-shell structure. Electron paramagnetic resonance studies suggest Mn atoms are located in the surface of the alloy NCs. Steady-state optical absorption and emission studies suggest formation of a charge-transfer (CT) state in which electrons are localized in a CdSe-rich shell and holes are localized in a CdTe-rich core which appears in the red region of the spectra. Electron transfer in the CT state is found to take place in the Marcus inverted region. To understand charge-transfer dynamics in the CdTeSe alloy NCs and to determine the effect of Mn doping on the alloy, ultrafast transient absorption studies have been carried out. In the case of the undoped alloy, formation of the CT state is found to take place through electron relaxation to the conduction band of the CT state with a time of 600 fs and through hole relaxation (from the CdSe-rich state to the CdTe-rich state) to the valence band of the CT state with a time scale of 1 ps. However, electron relaxation in the presence of Mn dopants takes place initially via an electron transfer to the Mn 3d state (d(5)) followed by transfer from the Mn 3d state (d(6)) to the CT state, which has been found to take place with a >700 ps time scale in addition to the hole relaxation time of 2 ps. Charge recombination time of the CT state is found to be extremely slow in the Mn-doped CdTeSe alloy NCs as compared to the undoped one, where the Mn atom acts as an electron storage center.

  2. Multi-band reflectance spectroscopy of carbonaceous lithium iron phosphate battery electrodes versus state of charge

    Science.gov (United States)

    Norris, R.; Iyer, K.; Chabot, V.; Nieva, P.; Yu, A.; Khajepour, A.; Wang, J.

    2014-03-01

    This study aims to expand the body of knowledge about the optical properties of battery cathode materials. Although some studies have been conducted on the optical properties of Lithium Iron Phosphate (LiFePO4), to the authors' knowledge, this is the first study of its kind on electrodes extracted from commercially available LiFePO4 batteries. The use of Vis/NIR and FTIR spectroscopy provides for a methodology to study the optical properties of LiFePO4 and may allow for the characterization of other properties such as particle size and the proportions of LiFePO4 versus FePO4 material. Knowledge of these properties is important for the development of a mechanism to measure the state-of charge (SOC) in lithium ion batteries. These properties are also important in a host of other applications including battery modeling and materials characterization. Cylindrical LiFePO4 batteries (from A123 Systems Inc.) were acquired from the commercial market and charged to 10 different states between 30% and 80% of their nominal capacity using a constant-current, constant-voltage (CCCV) cycling method. Visual inspection of the extracted electrodes shows that the LiFePO4/C-cathodes display subtle changes in color (shades of grey) with respect to SOC. Vis/NIR measurements support the visual observation of uniform intensity variations versus SOC. FTIR measurements show an absorbance signature that varies with SOC and is distinct from results found in the literature for similar LiFePO4-based material systems, supporting the uniqueness of the absorbance fingerprint.

  3. Charge transfer reactions at interfaces between neutral gas and plasma: Dynamical effects and X-ray emission

    Science.gov (United States)

    Provornikova, E.; Izmodenov, V. V.; Lallement, R.

    2012-04-01

    Charge-transfer is the main process linking neutrals and charged particles in the interaction regions of neutral (or partly ionized) gas with a plasma. In this paper we illustrate the importance of charge-transfer with respect to the dynamics and the structure of neutral gas-plasma interfaces. We consider the following phenomena: (1) the heliospheric interface - region where the solar wind plasma interacts with the partly-ionized local interstellar medium (LISM) and (2) neutral interstellar clouds embedded in a hot, tenuous plasma such as the million degree gas that fills the so-called ``Local Bubble". In (1), we discuss several effects in the outer heliosphere caused by charge exchange of interstellar neutral atoms and plasma protons. In (2) we describe the role of charge exchange in the formation of a transition region between the cloud and the surrounding plasma based on a two-component model of the cloud-plasma interaction. In the model the cloud consists of relatively cold and dense atomic hydrogen gas, surrounded by hot, low density, fully ionized plasma. We discuss the structure of the cloud-plasma interface and the effect of charge exchange on the lifetime of interstellar clouds. Charge transfer between neutral atoms and minor ions in the plasma produces X-ray emission. Assuming standard abundances of minor ions in the hot gas surrounding the cold interstellar cloud, we estimate the X-ray emissivity consecutive to the charge transfer reactions. Our model shows that the charge-transfer X-ray emission from the neutral cloud-plasma interface may be comparable to the diffuse thermal X-ray emission from the million degree gas cavity itself.

  4. Microgravity and Charge Transfer in the Neuronal Membrane: Implications for Computational Neurobiology

    Science.gov (United States)

    Wallace, Ron

    1995-01-01

    Evidence from natural and artificial membranes indicates that the neural membrane is a liquid crystal. A liquid-to-gel phase transition caused by the application of superposed electromagnetic fields to the outer membrane surface releases spin-correlated electron pairs which propagate through a charge transfer complex. The propagation generates Rydberg atoms in the lipid bilayer lattice. In the present model, charge density configurations in promoted orbitals interact as cellular automata and perform computations in Hilbert space. Due to the small binding energies of promoted orbitals, their automata are highly sensitive to microgravitational perturbations. It is proposed that spacetime is classical on the Rydberg scale, but formed of contiguous moving segments, each of which displays topological equivalence. This stochasticity is reflected in randomized Riemannian tensor values. Spacetime segments interact with charge automata as components of a computational process. At the termination of the algorithm, an orbital of high probability density is embedded in a more stabilized microscopic spacetime. This state permits the opening of an ion channel and the conversion of a quantum algorithm into a macroscopic frequency code.

  5. Investigation of nonlinear optical (NLO) properties by charge transfer contributions of amine functionalized tetraphenylethylene

    Science.gov (United States)

    Rana, Meenakshi; Singla, Nidhi; Chatterjee, Amrita; Shukla, Abhishek; Chowdhury, Papia

    2016-12-01

    Nonlinear Optical (NLO) properties of amine functionalized tetraphenylethylene (TPE-NH2) have been recorded and analyzed. The structural geometry, bonding features, harmonic vibrational frequencies (FTIR and Raman) of TPE-NH2 have been investigated by B3LYP density functional theory (DFT). Charge (Mulliken and natural) analysis, natural bond orbital (NBO) analysis, frontier molecular orbitals (FMOs), 13C and 1H nuclear magnetic resonance (NMR) and molecular electrostatic potential (MEP) indicate the delocalization of charges over the donor-acceptor region by the increase of C-N bond length. The vibrational analysis on the basis of potential energy distribution (PED) confirms the charge transfer interaction between donor and acceptor groups, and that in turn validates the presence of the larger dipole moment (μ), polarizability and hyperpolarizabilities (α, β and γ) in TPE-NH2. Higher value of ionization potential (IP), electronegativity (χ), hardness (η), chemical potential (CP) and smaller HOMO-LUMO energy gap (Δε) validate TPE-NH2's strong candidature to be used as an NLO active material.

  6. Dissociation of charge-transfer states at donor-acceptor interfaces of organic heterojunctions

    Science.gov (United States)

    Inche Ibrahim, M. L.

    2017-02-01

    The dissociation of charge-transfer (CT) states into free charge carriers at donor-acceptor (DA) interfaces is an important step in the operation of organic solar cells and related devices. In this paper, we show that the effect of DA morphology and architecture means that the directions of CT states (where a CT state’s direction is defined as the direction from the electron to the hole of the CT state) may deviate from the direction of the applied electric field. The deviation means that the electric field is not fully utilized to assist, and could even hinder the dissociation process. Furthermore, we show that the correct charge carrier mobilities that should be used to describe CT state dissociation are the actual mobilites at DA interfaces. The actual mobilities are defined in this paper, and in general are not the same as the mobilities that are used to calculate electric currents which are the mobilites along the direction of the electric field. Then, to correctly describe CT state dissociation, we modify the widely used Onsager-Braun (OB) model by including the effect of DA morphology and architecture, and by employing the correct mobilities. We verify that when the modified OB model is used to describe CT state dissociation, the fundamental issues that concern the original OB model are resolved. This study demonstrates that DA morphology and architecture play an important role by strongly influencing the CT state dissociation as well as the mobilites along the direction of the electric field.

  7. Feasibility study of electron transfer quantum well infrared photodetectors for spectral tuning in the long-wave infrared band

    Energy Technology Data Exchange (ETDEWEB)

    Jolley, Greg; Dehdashti Akhavan, Nima; Umana-Membreno, Gilberto; Antoszewski, Jarek; Faraone, Lorenzo [School of Electrical, Electronic and Computer Engineering, University of Western Australia, Perth, Western Australia 6009 (Australia)

    2013-11-21

    An electron transfer quantum well infrared photodetector (QWIP) consisting of repeating units of two coupled quantum wells (QWs) is capable of exhibiting a two color voltage dependent spectral response. However, significant electron transfer between the coupled QWs is required for spectral tuning, which may require the application of relatively high electric fields. Also, the band structure of coupled quantum wells is more complicated in comparison to a regular quantum well and, therefore, it is not always obvious if an electron transfer QWIP can be designed such that it meets specific performance characteristics. This paper presents a feasibility study of the electron transfer QWIP and its suitability for spectral tuning. Self consistent calculations have been performed of the bandstructure and the electric field that results from electron population within the quantum wells, from which the optical characteristics have been obtained. The band structure, spectral response, and the resonant final state energy locations have been compared with standard QWIPs. It is shown that spectral tuning in the long-wave infrared band can be achieved over a wide wavelength range of several microns while maintaining a relatively narrow spectral response FWHM. However, the total absorption strength is more limited in comparison to a standard QWIP, since the higher QW doping densities require much higher electric fields for electron transfer.

  8. Charge transfer and surface defect healing within ZnO nanoparticle decorated graphene hybrid materials

    Science.gov (United States)

    Pham, Chuyen V.; Repp, Sergej; Thomann, Ralf; Krueger, Michael; Weber, Stefan; Erdem, Emre

    2016-05-01

    To harness the unique properties of graphene and ZnO nanoparticles (NPs) for novel applications, the development of graphene-ZnO nanoparticle hybrid materials has attracted great attention and is the subject of ongoing research. For this contribution, graphene-oxide-ZnO (GO-ZnO) and thiol-functionalized reduced graphene oxide-ZnO (TrGO-ZnO) nanohybrid materials were prepared by novel self-assembly processes. Based on electron paramagnetic resonance (EPR) and photoluminescence (PL) investigations on bare ZnO NPs, GO-ZnO and TrGO-ZnO hybrid materials, we found that several physical phenomena were occurring when ZnO NPs were hybridized with GO and TrGO. The electrons trapped in Zn vacancy defects (VZn-) within the core of ZnO NPs vanished by transfer to GO and TrGO in the hybrid materials, thus leading to the disappearance of the core signals in the EPR spectra of ZnO NPs. The thiol groups of TrGO and sulfur can effectively ``heal'' the oxygen vacancy (VO+) related surface defects of ZnO NPs while oxygen-containing functionalities have low healing ability at a synthesis temperature of 100 °C. Photoexcited electron transfer from the conduction band of ZnO NPs to graphene leads to photoluminescence (PL) quenching of near band gap emission (NBE) of both GO-ZnO and TrGO-ZnO. Simultaneously, electron transfer from graphene to defect states of ZnO NPs is the origin of enhanced green defect emission from GO-ZnO. This observation is consistent with the energy level diagram model of hybrid materials.To harness the unique properties of graphene and ZnO nanoparticles (NPs) for novel applications, the development of graphene-ZnO nanoparticle hybrid materials has attracted great attention and is the subject of ongoing research. For this contribution, graphene-oxide-ZnO (GO-ZnO) and thiol-functionalized reduced graphene oxide-ZnO (TrGO-ZnO) nanohybrid materials were prepared by novel self-assembly processes. Based on electron paramagnetic resonance (EPR) and photoluminescence (PL

  9. Heat transfer performance of a pulsating heat pipe charged with acetone-based mixtures

    Science.gov (United States)

    Wang, Wenqing; Cui, Xiaoyu; Zhu, Yue

    2016-12-01

    Pulsating heat pipes (PHPs) are used as high efficiency heat exchangers, and the selection of working fluids in PHPs has a great impact on the heat transfer performance. This study investigates the thermal resistance characteristics of the PHP charged with acetone-based binary mixtures, where deionized water, methanol and ethanol were added to and mixed with acetone, respectively. The volume mixing ratios were 2:1, 4:1 and 7:1, and the heating power ranged from 10 to 100 W with filling ratios of 45, 55, 62 and 70%. At a low filling ratio (45%), the zeotropic characteristics of the binary mixtures have an influence on the heat transfer performance of the PHP. Adding water, which has a substantially different boiling point compared with that of acetone, can significantly improve the anti-dry-out ability inside the PHP. At a medium filling ratio (55%), the heat transfer performance of the PHP is affected by both phase transition characteristics and physical properties of working fluids. At high heating power, the thermal resistance of the PHP with acetone-water mixture is between that with pure acetone and pure water, whereas the thermal resistance of the PHP with acetone-methanol and acetone-ethanol mixtures at mixing ratios of 2:1 and 4:1 is less than that with the corresponding pure fluids. At high filling ratios (62 and 70%), the heat transfer performance of the PHP is mainly determined by the properties of working fluids that affects the flow resistance. Thus, the PHP with acetone-methanol and acetone-ethanol mixtures that have a lower flow resistance shows better heat transfer performance than that with acetone-water mixture.

  10. Tuning near-gap electronic structure, interface charge transfer and visible light response of hybrid doped graphene and Ag3PO4 composite: Dopant effects

    CERN Document Server

    He, Chao-Ni; Xu, Liang; Yang, Yin-Cai; Zhou, Bing-Xin; Huang, Gui-Fang; Peng, P; Liu, Wu-Ming

    2015-01-01

    The enhanced photocatalytic performance of doped graphene(GR)/semiconductor nanocomposites have recently been widely observed, but an understanding of the underlying mechanisms behind it is still out of reach. As a model system to study the effect of dopants, we investigate the electronic structures and optical properites of doped GR/Ag3PO4 nanocomposites using the first-principles calculations, demonstrating that the band gap, near-gap electronic structure and interface charge transfer of the doped GR/Ag3PO4(100) composite can be tuned by the dopants. Interestingly, the doping atom and C atoms bonded to dopant become active sites for photocatalysis because they are positively or negatively charged due to the charge redistribution caused by interaction. The dopants can enhance the visible light absorption and photoinduced electrons transfer. We propose that the N atom may be most appropriate doping for the GR/Ag3PO4 photocatalyst. This work can rationalize the available experimental results about N-doped GR-s...

  11. Optical Switching Using Transition from Dipolar to Charge Transfer Plasmon Modes in Ge2Sb2Te5 Bridged Metallodielectric Dimers

    Science.gov (United States)

    Ahmadivand, Arash; Gerislioglu, Burak; Sinha, Raju; Karabiyik, Mustafa; Pala, Nezih

    2017-01-01

    Capacitive coupling and direct shuttling of charges in nanoscale plasmonic components across a dielectric spacer and through a conductive junction lead to excitation of significantly different dipolar and charge transfer plasmon (CTP) resonances, respectively. Here, we demonstrate the excitation of dipolar and CTP resonant modes in metallic nanodimers bridged by phase-change material (PCM) sections, material and electrical characteristics of which can be controlled by external stimuli. Ultrafast switching (in the range of a few nanoseconds) between amorphous and crystalline phases of the PCM section (here Ge2Sb2Te5 (GST)) allows for designing a tunable plasmonic switch for optical communication applications with significant modulation depth (up to 88%). Judiciously selecting the geometrical parameters and taking advantage of the electrical properties of the amorphous phase of the GST section we adjusted the extinction peak of the dipolar mode at the telecommunication band (λ~1.55 μm), which is considered as the OFF state. Changing the GST phase to crystalline via optical heating allows for direct transfer of charges through the junction between nanodisks and formation of a distinct CTP peak at longer wavelengths (λ~1.85 μm) far from the telecommunication wavelength, which constitutes the ON state. PMID:28205643

  12. Interplay between excited-state intramolecular proton transfer and charge transfer in flavonols and their use as protein-binding-site fluorescence probes

    Energy Technology Data Exchange (ETDEWEB)

    Sytnik, A.; Gormin, D.; Kasha, M. (Florida State Univ., Tallahassee, FL (United States))

    1994-12-06

    A comparative study is presented of competitive fluorescences of three flavonols, 3-hydroxyflavone, 3,3[prime],4[prime],7-tetrahydroxyflavone (fisetin), and 4[prime]-diethylamino-3-hydroxyflavone (DHF). The normal fluorescence S[sub 1] [yields] S[sub 0] (400-nm region) is largely replaced by the proton-transfer tautomer fluorescence S[prime][sub 1] [yields] S[prime][sub 0] in the 550-nm region for all three of the flavonols in aprotic solvents at room temperature. For DHF in polar solvents the normal fluorescence becomes a charge-transfer fluorescence (460-500 nm) which competes strongly with the still dominant proton-transfer fluorescence (at 570 nm). In protic solvents, and at 77 K, the interference with intramolecular hydrogen bonding gives rise to greatly enhanced normal fluorescence, lowering the quantum yield of proton-transfer fluorescence. The utility of DHF as a discriminating fluorescence probe for protein binding sites is suggested by the strong dependence of the charge-transfer fluorescence on polarity of the environment and by various static and dynamic parameters of the charge-transfer and proton-transfer fluorescence which can be determined. 49 refs., 6 figs., 1 tab.

  13. The effect of solvent polarity on the balance between charge transfer and non-charge transfer pathways in the sensitization of singlet oxygen by pipi triplet states.

    Science.gov (United States)

    Schmidt, Reinhard

    2006-05-11

    A large set of literature kinetic data on triplet (T(1)) sensitization of singlet oxygen by two series of biphenyl and naphthalene sensitizers in solvents of strongly different polarity has been analyzed. The rate constants and the efficiencies of singlet oxygen formation are quantitatively reproduced by a model that assumes the competition of a non-charge transfer (nCT) and a CT deactivation channel. nCT deactivation occurs from a fully established spin-statistical equilibrium of (1)(T(1)(3)Sigma) and (3)(T(1)(3)Sigma) encounter complexes by internal conversion (IC) to lower excited complexes that dissociate to yield O(2)((1)Sigma(g)(+)), O(2)((1)Delta(g)), and O(2)((3)Sigma(g)(-)). IC of (1,3)(T(1)(3)Sigma) encounter complexes is controlled by an energy gap law that is generally valid for the transfer of electronic energy to and from O(2). (1,3)(T(1)(3)Sigma) nCT complexes form in competition to IC (1)(T(1)(3)Sigma) and (3)(T(1)(3)Sigma) exciplexes if CT interactions between T(1) and O(2) are important. The rate constants of exciplex formation depend via a Marcus type parabolic model on the corresponding free energy change DeltaG(CT), which varies with sensitizer triplet energy, oxidation potential, and solvent polarity. O(2)((1)Sigma(g)(+)), O(2)((1)Delta(g)), and O(2)((3)Sigma(g)(-)) are formed in the product ratio (1/6):(1/12):(3/4) in the CT deactivation channel. The balance between nCT and CT deactivation is described by the relative contribution p(CT) of CT induced deactivation calculated for a sensitizer of known triplet energy from its quenching rate constant. It is shown how the change of p(CT) influences the quenching rate constant and the efficiency of singlet oxygen formation in both series of sensitizers. p(CT) is sensitive to differences of solvent polarity and varies for the biphenyls and the naphthalenes as sigmoidal with DeltaG(CT). This quantitative model represents a realistic and general mechanism for the quenching of pipi triplet states by O

  14. Excited-state charge coupled proton transfer reaction in dipole-functionalized salicylideneaniline

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Kew-Yu, E-mail: kyuchen@fcu.edu.tw; Hu, Jiun-Wei

    2015-03-15

    Based on design and synthesis of salicylideneaniline derivatives 1–4, we demonstrate an exceedingly useful system to investigate the excited-state intramolecular charge transfer (ESICT) coupled with excited-state intramolecular proton transfer (ESIPT) reaction via the dipolar functionality of Schiff base salicylideneaniline. In solid and aprotic solvents 1–4 exist mainly as E conformers that possess a strong intramolecular six-membered-ring hydrogen bond. Compounds 2–4 exhibit solely a long-wavelength proton-transfer tautomer emission, while dipole-functionalized Schiff base 1 exhibits remarkable dual emission due to the different solvent-polarity environments between ESICT and ESIPT states. Moreover, the geometric structures, frontier molecular orbitals (MOs) and the potential energy curves for 1–4 in the ground and the first singlet excited state were fully rationalized by density functional theory (DFT) and time-dependent DFT calculations. - Highlights: • A dipole-functionalized salicylideneaniline derivative was synthesized. • The Schiff base exhibits remarkable dual emission. • A novel ESICT/ESIPT coupled system was created.

  15. Photoinduced charge transfer properties of bolaamphiphile membrane-gramicidrin diad composites

    Science.gov (United States)

    Thompson, David H.; Kim, Jong-Mok; Di Meglio, Ciro

    1993-04-01

    Ether-linked bolaform amphiphiles (Langmuir 1992 8, 637; J. Am. Chem. Soc. 1992, 9035) and novel gramicidin-porphyrin `diads' (MRS Symposium Series, Vol. 277, 1992, 93) have been synthesized. Protocols for vectorial insertion of the derivatized gramicidins into bolaform lipid vesicles have been developed and the photochemical behavior of these proteinaceous composite membranes probed in the presence of electron donors and acceptors. Photoinduced electron transfer properties of the gramicidin-porphyrin conjugates were compared in TRIS- buffered dihexadecyl-phosphate bilayer (DHP) and bolaform monolayer membrane vesicles containing dithiothreitol as sacrificial donor and methyl viologen as electron acceptor on both the inner and outer vesicle surfaces. Although the rates of methyl viologen photoreduction varied depending on the mode of diad orientation within DHP bilayer membranes, photoreduction rates were not orientation- dependent in bolaform membrane vesicles containing the gramicidin-porphyrin diad. The relevance of these results on vectorial electron transfer processes in lamellar systems and the design of integrated charge transfer components is discussed.

  16. Probing the Nature of Charge Transfer at Nano-Bio Interfaces: Peptides on Metal Oxide Nanoparticles.

    Science.gov (United States)

    Tarakeshwar, Pilarisetty; Palma, Julio L; Holland, Gregory P; Fromme, Petra; Yarger, Jeffery L; Mujica, Vladimiro

    2014-10-16

    Characterizing the nano-bio interface has been a long-standing endeavor in the quest for novel biosensors, biophotovoltaics, and biocompatible electronic devices. In this context, the present computational work on the interaction of two peptides, A6K (Ac-AAAAAAK-NH2) and A7 (Ac-AAAAAAA-NH2) with semiconducting TiO2 nanoparticles is an effort to understand the peptide-metal oxide nanointerface. These investigations were spurred by recent experimental observations that nanostructured semiconducting metal oxides templated with A6K peptides not only stabilize large proteins like photosystem-I (PS-I) but also exhibit enhanced charge-transfer characteristics. Our results indicate that α-helical structures of A6K are not only energetically more stabilized on TiO2 nanoparticles, but the resulting hybrids also exhibit enhanced electron transfer characteristics. This enhancement can be attributed to substantial changes in the electronic characteristics at the peptide-TiO2 interface. Apart from understanding the mechanism of electron transfer (ET) in peptide-stabilized PS-I on metal oxide nanoparticles, the current work also has implications in the development of novel solar cells and photocatalysts.

  17. Charge transfer and triplet states in OPV materials and devices (Presentation Recording)

    Science.gov (United States)

    Dyakonov, Vladimir

    2015-10-01

    Electron back transfer (EBT), potentially occurring after electron transfer from donor to acceptor may populate the lower lying donor or acceptor triplet state and serve as recombination channel.[1] Here we report on studies of charge transfer and triplet states in blends of highly efficient benzodithiophene PTB7 polymer in combination with the fullerene-derivative PC71BM using the spin sensitive optically detected magnetic resonance (ODMR) technique and compare the results with those obtained in P3HT (poly(3- hexylthiophene):PC61BM blends. Although PTB7:PC71BM absorbers yield much higher power conversion efficiencies in solar cells exceeding 7%, we found a significant increase of triplet exciton generation, which was absent in the P3HT based blends. We discuss this observation within the EBT scenario with the emphasis on the influence of morphology, fullerene load, HOMO/LUMO energy and presence of additives (DIO). Suppressing the EBT process by morphology and/or energetics of polymer and molecules is important to achieve the full potential of highly efficient OPV materials. [1] M. Liedtke, et al., JACS 133, 9088 (2011).

  18. Charge and energy transfer in a bithiophene perylenediimide based donor-acceptor-donor system for use in organic photovoltaics.

    Science.gov (United States)

    Wenzel, Jan; Dreuw, Andreas; Burghardt, Irene

    2013-07-28

    The elementary charge and excitation energy transfer steps in a novel symmetric donor-acceptor-donor triad first described in Roland et al. Phys. Chem. Chem. Phys., 2012, 14, 273, consisting of a central perylenediimide moiety as a potential electron acceptor and two identical electron rich bithiophene compounds, have been investigated using quantum chemical methodology. These elementary processes determine the applicability of such systems in photovoltaic devices. The molecular structure, excited states and the photo-physical properties are investigated using smaller model systems and including solvation effects. The donor and acceptor π-systems are separated by an ethyl bridge such that the molecular orbitals are either located on the donor or acceptor moiety making the identification of locally excited versus charge transfer states straightforward. Using excited state geometry optimizations, the mechanism of photo-initiated charge separation could be identified. Geometry relaxation in the excited donor state leads to a near-degeneracy with the locally excited acceptor state, entailing strong excitonic coupling and resonance energy transfer. This energy transfer process is driven by planarization and bond length alternation of the donor molecule. Geometry relaxation of the locally excited acceptor state in turn reveals a crossing with the energetically lowest charge transfer excited state. The energetic position of the latter depends in a sensitive fashion on the solvent. This provides an explanation of the sequential process observed in the experiment, favoring ultrafast (∼130 fs) formation of the excited acceptor state followed by slower (∼3 ps scale) formation of the charge separated state.

  19. Charging system using solar panels and a highly resonant wireless power transfer model for small UAS applications

    Science.gov (United States)

    Hallman, Sydney N.; Huck, Robert C.; Sluss, James J.

    2016-05-01

    The use of a wireless charging system for small, unmanned aircraft system applications is useful for both military and commercial consumers. An efficient way to keep the aircraft's batteries charged without interrupting flight would be highly marketable. While the general concepts behind highly resonant wireless power transfer are discussed in a few publications, the details behind the system designs are not available even in academic journals, especially in relation to avionics. Combining a highly resonant charging system with a solar panel charging system can produce enough power to extend the flight time of a small, unmanned aircraft system without interruption. This paper provides an overview of a few of the wireless-charging technologies currently available and outlines a preliminary design for an aircraft-mounted battery charging system.

  20. Analysis of Gas Radiative Transfer Using Box Model and Its Comparison with Gray Band Approximation

    Institute of Scientific and Technical Information of China (English)

    Yuying Liu; Xinxin Zhang

    2003-01-01

    On the basis of a wide range survey of various models or treatment methods for the calculation of radiative properties of gases, box model, which is similar to the gray band approximation of spectral band model, was applied to evaluate the gas properties in this paper. In order to compare the accuracy of box model with that of gray band approximation of spectral band models, a typical one-dimensional gas radiation problem was analyzed using discrete ordinate method. Comparing with the widely used gray band approximation of narrow band model or exponential wide band model, box model can well evaluate the radiation source term of the radiative problem.It also has the advantages of simplicity and easy to code, so it is practicable and useful for some complex engineering problems.

  1. Low-Energy Charge Transfer in Multiply-Charged Ion-Atom Collisions Studied with the Combined SCVB-MOCC Approach

    Directory of Open Access Journals (Sweden)

    B. Zygelman

    2002-03-01

    Full Text Available A survey of theoretical studies of charge transfer involving collisions of multiply-charged ions with atomic neutrals (H and He is presented. The calculations utilized the quantum-mechanical molecular-orbital close-coupling (MOCC approach where the requisite potential curves and coupling matrix elements have been obtained with the spin-coupled valence bond (SCVB method. Comparison is made among various collision partners, for equicharged systems, where it is illustrated that even for total charge transfer cross sections, scaling-laws do not exist for low-energy collisions (i.e. < 1 keV/amu. While various empirical scaling-laws are well known in the intermediateand high-energy regimes, the multi-electron configurations of the projectile ions results in a rich and varied low-energy dependence, requiring an explicit calculation for each collision-partner pair. Future charge transfer problems to be addressed with the combined SCVB-MOCC approach are briefly discussed.

  2. Ultrafast intramolecular charge transfer with N-(4-cyanophenyl)carbazole. Evidence for a LE precursor and dual LE + ICT fluorescence.

    Science.gov (United States)

    Galievsky, Victor A; Druzhinin, Sergey I; Demeter, Attila; Mayer, Peter; Kovalenko, Sergey A; Senyushkina, Tamara A; Zachariasse, Klaas A

    2010-12-09

    The photophysics of N-(4-cyanophenyl)carbazole (NP4CN) was investigated by using absorption and fluorescence spectra, picosecond fluorescence decays, and femtosecond transient absorption. In the nonpolar n-hexane as well as in the polar solvent acetonitrile (MeCN), a locally excited (LE) state is detected, as a precursor for the intramolecular charge transfer (ICT) state. A LE → ICT reaction time τ(2) at 22 °C of 0.95 ps in ethyl cyanide (EtCN) and 0.32 ps in MeCN is determined from the decay of the LE excited state absorption (ESA) maximum around 620 nm. In the ESA spectrum of NP4CN in n-hexane at a pump-probe delay time of 100 ps, an important contribution of the LE band remains alongside the ICT band, in contrast to what is observed in EtCN and MeCN. This shows that a LE ⇄ ICT equilibrium is established in this solvent and the ICT reaction time of 0.5 ps is equal to the reciprocal of the sum of the forward and backward ICT rate constants 1/(k(a) + k(d)). In the photostationary S(0) → S(n) absorption spectrum of NP4CN in n-hexane and MeCN, an additional CT absorption band appears, absent in the sum of the spectra of its electron donor (D) and acceptor (A) subgroups carbazole and benzonitrile. This CT band is located at an energy of ∼4000 cm(-1) lower than for N-phenylcarbazole (NPC), due to the larger electron affinity of the benzonitrile moiety of NP4CN than the phenyl subunit of NPC. The fluorescence spectrum of NP4CN in n-hexane at 25 °C mainly consists of a structured LE emission, with a small ICT admixture, indicating that a LE → ICT reaction just starts to occur under these conditions. In di-n-pentyl ether (DPeE) and di-n-butyl ether (DBE), a LE emission is found upon cooling at the high-energy edge of the ICT fluorescence band, caused by the onset of dielectric solvent relaxation. This is not the case in more polar solvents, such as diethyl ether (DEE) and MeCN, in which a structureless ICT emission band fully overlaps the strongly quenched LE

  3. Atomic data for neutron-capture elements III. Charge transfer rate coefficients for low-charge ions of Ge, Se, Br, Kr, Rb, and Xe

    CERN Document Server

    Sterling, N C

    2011-01-01

    We present total and final-state resolved charge transfer (CT) rate coefficients for low-charge Ge, Se, Br, Kr, Rb, and Xe ions reacting with neutral hydrogen over the temperature range 10^2--10^6 K. Each of these elements has been detected in ionized astrophysical nebulae, particularly planetary nebulae. CT rate coefficients are a key ingredient for the ionization equilibrium solutions needed to determine total elemental abundances from those of the observed ions. A multi-channel Landau Zener approach was used to compute rate coefficients for projectile ions with charges q=2-5, and for singly-charged ions the Demkov approximation was utilized. Our results for five-times ionized species are lower limits, due to the incompleteness of level energies in the NIST database. In addition, we computed rate coefficients for charge transfer ionization reactions between the neutral species of the above six elements and ionized hydrogen. The resulting total and state-resolved CT rate coefficients are tabulated and availa...

  4. Synthetic principles directing charge transport in low-band-gap dithienosilole-benzothiadiazole copolymers

    KAUST Repository

    Beaujuge, Pierre

    2012-05-30

    Given the fundamental differences in carrier generation and device operation in organic thin-film transistors (OTFTs) and organic photovoltaic (OPV) devices, the material design principles to apply may be expected to differ. In this respect, designing organic semiconductors that perform effectively in multiple device configurations remains a challenge. Following "donor-acceptor" principles, we designed and synthesized an analogous series of solution-processable π-conjugated polymers that combine the electron-rich dithienosilole (DTS) moiety, unsubstituted thiophene spacers, and the electron-deficient core 2,1,3-benzothiadiazole (BTD). Insights into backbone geometry and wave function delocalization as a function of molecular structure are provided by density functional theory (DFT) calculations at the B3LYP/6-31G(d,p) level. Using a combination of X-ray techniques (2D-WAXS and XRD) supported by solid-state NMR (SS-NMR) and atomic force microscopy (AFM), we demonstrate fundamental correlations between the polymer repeat-unit structure, molecular weight distribution, nature of the solubilizing side-chains appended to the backbones, and extent of structural order attainable in p-channel OTFTs. In particular, it is shown that the degree of microstructural order achievable in the self-assembled organic semiconductors increases largely with (i) increasing molecular weight and (ii) appropriate solubilizing-group substitution. The corresponding field-effect hole mobilities are enhanced by several orders of magnitude, reaching up to 0.1 cm 2 V -1 s -1 with the highest molecular weight fraction of the branched alkyl-substituted polymer derivative in this series. This trend is reflected in conventional bulk-heterojunction OPV devices using PC 71BM, whereby the active layers exhibit space-charge-limited (SCL) hole mobilities approaching 10 -3 cm 2 V -1 s -1, and yield improved power conversion efficiencies on the order of 4.6% under AM1.5G solar illumination. Beyond structure

  5. Uncovering the Key Role of the Fermi Level of the Electron Mediator in a Z-Scheme Photocatalyst by Detecting the Charge Transfer Process of WO3-metal-gC3N4 (Metal = Cu, Ag, Au).

    Science.gov (United States)

    Li, Houfen; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhang, Yaobin

    2016-01-27

    Z-scheme photocatalytic system shows superiority in degradation of refractory pollutants and water splitting due to the high redox capacities caused by its unique charge transfer behaviors. As a key component of Z-scheme system, the electron mediator plays an important role in charge carrier migration. According to the energy band theory, we believe the interfacial energy band bendings facilitate the electron transfer via Z-scheme mechanism when the Fermi level of electron mediator is between the Fermi levels of Photosystem II (PS II) and Photosystem I (PS I), whereas charge transfer is inhibited in other cases as energy band barriers would form at the semiconductor-metal interfaces. Here, this inference was verified by the increased hydroxyl radical generation and improved photocurrent on WO3-Cu-gC3N4 (with the desired Fermi level structure), which were not observed on either WO3-Ag-gC3N4 or WO3-Au-gC3N4. Finally, photocatalytic degradation rate of 4-nonylphenol on WO3-Cu-gC3N4 was proved to be as high as 11.6 times than that of WO3-gC3N4, further demonstrating the necessity of a suitable electron mediator in Z-scheme system. This study provides scientific basis for rational construction of Z-scheme photocatalytic system.

  6. Creation of recognition sites for organophosphate esters based on charge transfer and ligand exchange imprinting methods.

    Science.gov (United States)

    Say, Ridvan

    2006-10-01

    This manuscript describes a method for the selective binding behavior of paraoxan and parathion compounds on surface imprinted polymers which were prepared using both charge transfer (CT) (methacryloyl-antipyrine, MAAP) and ligand-exchange (LE) (methacryloyl-antipyrine-gadalonium, MAAP-Gd) monomers. These polymers were prepared in the presence of azobisisobutyronitrile (AIBN) as an initiator and crosslinking EDMA and were imprinted with organophosphate esters. Influence of CT and LE imprinting on the creation of recognition sites toward paraoxan and parathion was determined applying adsorption isotherms. The effect of initial concentration of paraoxan and parathion, adsorption time and imprinting efficiency on adsorption selectivity for MIP-CT and MIP-LE was investigated. Association constant (K(ass)), number of accessible sites (Q(max)), relative selectivity coefficient (k') and binding ability were also evaluated.

  7. Phosphonic acid functionalized asymmetric phthalocyanines: synthesis, modification of indium tin oxide, and charge transfer.

    Science.gov (United States)

    Polaske, Nathan W; Lin, Hsiao-Chu; Tang, Anna; Mayukh, Mayunk; Oquendo, Luis E; Green, John T; Ratcliff, Erin L; Armstrong, Neal R; Saavedra, S Scott; McGrath, Dominic V

    2011-12-20

    Metalated and free-base A(3)B-type asymmetric phthalocyanines (Pcs) bearing, in the asymmetric quadrant, a flexible alkyl linker of varying chain lengths terminating in a phosphonic acid (PA) group have been synthesized. Two parallel series of asymmetric Pc derivatives bearing aryloxy and arylthio substituents are reported, and their synthesis and characterization through NMR, combustion analysis, and MALDI-MS are described. We also demonstrate the modification of indium tin oxide (ITO) substrates using the PA functionalized asymmetric Pc derivatives and monitoring their electrochemistry. The PA functionalized asymmetric Pcs were anchored to the ITO surface through chemisorption and their electrochemical properties characterized using cyclic voltammetry to investigate the effects of PA structure on the thermodynamics and kinetics of charge transfer. Ionization energies of the modified ITO surfaces were measured using ultraviolet photoemission spectroscopy.

  8. Radiative charge transfer in cold and ultracold Sulfur atoms colliding with Protons

    CERN Document Server

    Shen, G; Wang, J G; McCann, J F; McLaughlin, B M

    2015-01-01

    Radiative decay processes at cold and ultra cold temperatures for Sulfur atoms colliding with protons are investigated. The MOLPRO quantum chemistry suite of codes was used to obtain accurate potential energies and transition dipole moments, as a function of internuclear distance, between low-lying states of the SH$^{+}$ molecular cation. A multi-reference configuration-interaction (MRCI) approximation together with the Davidson correction is used to determine the potential energy curves and transition dipole moments, between the states of interest, where the molecular orbitals (MO's) are obtained from state-averaged multi configuration-self-consistent field (MCSCF) calculations. The collision problem is solved approximately using an optical potential method to obtain radiative loss, and a fully two-channel quantum approach for radiative charge transfer. Cross sections and rate coefficients are determined for the first time for temperatures ranging from 10 $\\mu$ K up to 10,000 K. Results are obtained for all ...

  9. Charge-Transfer Excited States in Aqueous DNA: Insights from Many-Body Green's Function Theory

    Science.gov (United States)

    Yin, Huabing; Ma, Yuchen; Mu, Jinglin; Liu, Chengbu; Rohlfing, Michael

    2014-06-01

    Charge-transfer (CT) excited states play an important role in the excited-state dynamics of DNA in aqueous solution. However, there is still much controversy on their energies. By ab initio many-body Green's function theory, together with classical molecular dynamics simulations, we confirm the existence of CT states at the lower energy side of the optical absorption maximum in aqueous DNA as observed in experiments. We find that the hydration shell can exert strong effects (˜1 eV) on both the electronic structure and CT states of DNA molecules through dipole electric fields. In this case, the solvent cannot be simply regarded as a macroscopic screening medium as usual. The influence of base stacking and base pairing on the CT states is also discussed.

  10. Phosphonic Acid Functionalized Asymmetric Phthalocyanines: Synthesis, Modification of Indium Tin Oxide (ITO), and Charge Transfer

    Energy Technology Data Exchange (ETDEWEB)

    Polaske, Nathan W.; Lin, Hsiao-Chu; Tang, Anna; Mayukh, Mayank; Oquendo, Luis E.; Green, John; Ratcliff, Erin L.; Armstrong, Neal R.; Saavedra, S. Scott; McGrath, Dominic V.

    2011-12-20

    Metalated and free-base A₃B-type asymmetric phthalocyanines (Pcs) bearing, in the asymmetric quadrant, a flexible alkyl linker of varying chain lengths terminating in a phosphonic acid (PA) group have been synthesized. Two parallel series of asymmetric Pc derivatives bearing aryloxy and arylthio substituents are reported, and their synthesis and characterization through NMR, combustion analysis, and MALDI-MS are described. We also demonstrate the modification of indium tin oxide (ITO) substrates using the PA functionalized asymmetric Pc derivatives and monitoring their electrochemistry. The PA functionalized asymmetric Pcs were anchored to the ITO surface through chemisorption and their electrochemical properties characterized using cyclic voltammetry to investigate the effects of PA structure on the thermodynamics and kinetics of charge transfer. Ionization energies of the modified ITO surfaces were measured using ultraviolet photoemission spectroscopy.

  11. Synthesis of a novel perylene diimide derivative and its charge transfer interaction with C60

    Institute of Scientific and Technical Information of China (English)

    LIU Bo; SHI MinMin; YANG LiGong; CHEN HongZheng; WANG Mang

    2008-01-01

    A novel organic electron accepter, N,N'-dipyrimidinyl-3,4,9,10-perylene-tetracarboxylic diimide (DMP), was designed and synthesized.The molecular structure was characterized by FTIR spectrum and ele-mental analysis.By cyclic voltammetry measurements, DMP was found to possess a lower LUMO en-ergy level than N,N'-diphenyl-3,4,9,10-perylene-tetracarboxylic diimide due to the stronger elec-tron-withdrawing pyrimidinyl group than the phenyl group.Fluorescence quenching is observed in a dual-layer film consisting of a DMP layer and a C60 layer and was attributed to the charge transfer at the interface due to the energy level offset between DMP and C60.

  12. Laser-induced charge transfer in the CH/sup 6 +/ quasimolecule

    Energy Technology Data Exchange (ETDEWEB)

    Errea, L.F.; Mendez, L.; Riera, A.

    1985-05-15

    The charge transfer cross section is calculated for C/sup 6 +/+CH(1s) collisions, through photon assisted 5gsigma--6hsigma, 5gsigma--4fsigma, 5gsigma--4f..pi.., and 5gsigma--4dsigma transitions. The theory developed by Copeland and Tang, and ourselves, is employed, and the validity of the approximations used is tested. The four processes considered have widely different characteristics with regards to the laser wavelength needed, the collision dynamics and the applicability of back-of-the-envelope estimates based on the Landau--Zener approximation. We point out the relevance of those processes to the impurity diagnostics of magnetically confined fusion plasmas and to the development of short wavelength lasers.

  13. Identifying the magnetoconductance responses by the induced charge transfer complex states in pentacene-based diodes

    Science.gov (United States)

    Huang, Wei-Shun; Lee, Tsung-Hsun; Guo, Tzung-Fang; Huang, J. C. A.; Wen, Ten-Chin

    2012-07-01

    We investigate the magnetoconductance (MC) responses in photocurrent, unipolar injection, and bipolar injection regimes in pentacene-based diodes. Both photocurrent and bipolar injection contributed MC responses show large difference in MC line shape, which are attributed to triplet-polaron interaction modulated by the magnetic field dependent singlet fission and the intersystem crossing of the polaron pair, respectively. By blending 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane into pentacene, all the MC responses are suppressed but the MC response at unipolar injection regime is enhanced, which is attributed to the induced charge transfer complex states (CT complex states). This work identify the MC responses between single carrier contributed MC and exciton related MC by the induced CT complex states.

  14. Optical switching of electric charge transfer pathways in porphyrin: a light-controlled nanoscale current router.

    Science.gov (United States)

    Thanopulos, Ioannis; Paspalakis, Emmanuel; Yannopapas, Vassilios

    2008-11-05

    We introduce a novel molecular junction based on a thiol-functionalized porphyrin derivative with two almost energetically degenerate equilibrium configurations. We show that each equilibrium structure defines a pathway of maximal electric charge transfer through the molecular junction and that these two conduction pathways are spatially orthogonal. We further demonstrate computationally how to switch between the two equilibrium structures of the compound by coherent light. The optical switching mechanism is presented in the relevant configuration subspace of the compound, and the corresponding potential and electric dipole surfaces are obtained by ab initio methods. The laser-induced isomerization takes place in two steps in tandem, while each step is induced by a two-photon process. The effect of metallic electrodes on the electromagnetic irradiation driving the optical switching is also investigated. Our study demonstrates the potential for using thiol-functionalized porphyrin derivatives for the development of a light-controlled nanoscale current router.

  15. Correlation between the Open-Circuit Voltage and Charge Transfer State Energy in Organic Photovoltaic Cells.

    Science.gov (United States)

    Zou, Yunlong; Holmes, Russell J

    2015-08-26

    In order to further improve the performance of organic photovoltaic cells (OPVs), it is essential to better understand the factors that limit the open-circuit voltage (VOC). Previous work has sought to correlate the value of VOC in donor-acceptor (D-A) OPVs to the interface energy level offset (EDA). In this work, measurements of electroluminescence are used to extract the charge transfer (CT) state energy for multiple small molecule D-A pairings. The CT state as measured from electroluminescence is found to show better correlation to the maximum VOC than EDA. The difference between EDA and the CT state energy is attributed to the Coulombic binding energy of the CT state. This correlation is demonstrated explicitly by inserting an insulating spacer layer between the donor and acceptor materials, reducing the binding energy of the CT state and increasing the measured VOC. These results demonstrate a direct correlation between maximum VOC and CT state energy.

  16. Interaction between in vivo bioluminescence and extracellular electron transfer in Shewanella woodyi via charge and discharge.

    Science.gov (United States)

    Tian, Xiaochun; Zhao, Feng; You, Lexing; Wu, Xuee; Zheng, Zhiyong; Wu, Ranran; Jiang, Yanxia; Sun, Shigang

    2017-01-18

    Extracellular electron transfer (EET) and bioluminescence are both important for microbial growth and metabolism, but the mechanism of interaction between EET and bioluminescence is poorly understood. Herein, we demonstrate an exclusively respiratory luminous bacterium, Shewanella woodyi, which possesses EET ability and electron communication at the interface of S. woodyi and solid substrates via charge and discharge methods. Using an electro-chemiluminescence apparatus, our results confirmed that the FMN/FMNH2 content and the redox status of cytochrome c conjointly regulated the bioluminescence intensity when the potential of an indium-tin oxide electrode was changed. More importantly, this work revealed that there is an interaction between the redox reaction of single cells and bioluminescence of group communication via the EET pathway.

  17. Annealing bounds to prevent further Charge Transfer Inefficiency increase of the Chandra X-ray CCDs

    Science.gov (United States)

    Monmeyran, Corentin; Patel, Neil S.; Bautz, Mark W.; Grant, Catherine E.; Prigozhin, Gregory Y.; Agarwal, Anuradha; Kimerling, Lionel C.

    2016-12-01

    After the front-illuminated CCDs on board the X-ray telescope Chandra were damaged by radiation after launch, it was decided to anneal them in an effort to remove the defects introduced by the irradiation. The annealing led to an unexpected increase of the Charge Transfer Inefficiency (CTI). The performance degradation is attributed to point defect interactions in the devices. Specifically, the annealing at 30 °C activated the diffusion of the main interstitial defect in the device, the carbon interstitial, which led to its association with a substitutional impurity, ultimately resulting in a stable and electrically active defect state. Because the formation reaction of this carbon interstitial and substitutional impurity associate is diffusion limited, we recommend a higher upper bound for the annealing temperature and duration of any future CCD anneals, that of -50 °C for one day or -60 °C for a week, to prevent further CTI increase.

  18. Is dipole moment a valid descriptor of excited state's charge-transfer character?

    Science.gov (United States)

    Petelenz, Piotr; Pac, Barbara

    2013-11-20

    In the ongoing discussion on excited states of the pentacene crystal, dipole moment values have been recently invoked to gauge the CT admixture to excited states of Frenkel parentage in a model cluster. In the present paper, a simple dimer model is used to show that, in general, the dipole moment is not a valid measure of the CT contribution. This finding eliminates some apparent disagreement between the computational results published by different research groups. The implications of our results and other related aspects of cluster-type quantum chemistry calculations are discussed in the context of the standing literature dispute concerning the mechanism of singlet fission in the pentacene crystal, notably the role of charge transfer contributions vs the involvement of an excimer-like doubly excited intermediate (D state).

  19. Ultracold, radiative charge transfer in hybrid Yb ion - Rb atom traps

    CERN Document Server

    McLaughlin, B M; Lane, I C; McCann, J F

    2014-01-01

    Ultracold hybrid ion-atom traps offer the possibility of microscopic manipulation of quantum coherences in the gas using the ion as a probe. However, inelastic processes, particularly charge transfer can be a significant process of ion loss and has been measured experimentally for the Yb$^{+}$ ion immersed in a Rb vapour. We use first-principles quantum chemistry codes to obtain the potential energy curves and dipole moments for the lowest-lying energy states of this complex. Calculations for the radiative decay processes cross sections and rate coefficients are presented for the total decay processes. Comparing the semi-classical Langevin approximation with the quantum approach, we find it provides a very good estimate of the background at higher energies. The results demonstrate that radiative decay mechanisms are important over the energy and temperature region considered. In fact, the Langevin process of ion-atom collisions dominates cold ion-atom collisions. For spin dependent processes \\cite{kohl13} the...

  20. Charge-transfer-based terbium MOF nanoparticles as fluorescent pH sensor for extreme acidity.

    Science.gov (United States)

    Qi, Zewan; Chen, Yang

    2017-01-15

    Newly emerged metal organic frameworks (MOFs) have aroused the great interest in designing functional materials by means of its flexible structure and component. In this study, we used lanthanide Tb(3+) ions and small molecular ligands to design and assemble a kind of pH-sensitive MOF nanoparticle based on intramolecular-charge-transfer effect. This kind of made-to-order MOF nanoparticle for H(+) is highly specific and sensitive and could be used to fluorescently indicate pH value of strong acidic solution via preset mechanism through luminescence of Tb(3+). The long luminescence lifetime of Tb(3+) allows eliminating concomitant non-specific fluorescence by time-revised fluorescence techniques, processing an advantage in sensing H(+) in biological media with strong autofluorescence. Our method showed a great potential of MOF structures in designing and constructing sensitive sensing materials for specific analytes directly via the assembly of functional ions/ligands.

  1. Charge-transfer interaction mediated organogels from 18β-glycyrrhetinic acid appended pyrene

    Directory of Open Access Journals (Sweden)

    Jun Hu

    2013-12-01

    Full Text Available We describe herein the two-component charge-transfer (CT interaction induced organogel formation with 18β-glycyrrhetinic acid appended pyrene (GA-pyrene, 3 as the donor, and 2,4,7-trinitrofluorenone (TNF, 4 as the acceptor. The use of TNF (4 as a versatile electron acceptor in the formation of CT gels is demonstrated through the formation of gels in a variety of solvents. Thermal stability, stoichiometry, scanning electron microscopy (SEM, optical micrographs, and circular dichroism (CD are performed on these CT gels to investigate their thermal and assembly properties. UV–vis, fluorescence, mass spectrometric as well as variable-temperature 1H NMR experiments on these gels suggest that the CT interaction is one of the major driving forces for the formation of these organogels.

  2. Charge-Transfer induced EUV and Soft X-ray emissions in the Heliosphere

    CERN Document Server

    Koutroumpa, D; Kharchenko, V; Dalgarno, A; Pepino, R; Izmodenov, V; Quemerais, E

    2006-01-01

    We study the EUV/soft X-ray emission generated by charge transfer between solar wind heavy ions and interstellar H and He neutral atoms in the inner Heliosphere. We present heliospheric maps and spectra for stationary solar wind, depending on solar cycle phase, solar wind anisotropies and composition, line of sight direction and observer position. A time-dependant simulation of the X-ray intensity variations due to temporary solar wind enhancement is compared to XMM Newton recorded data of the Hubble Deep Field North observation (Snowden et al. 2004). Results show that the heliospheric component can explain a large fraction of the line intensity below 1.3 keV, strongly attenuating the need for soft X-ray emission from the Local Interstellar Bubble.

  3. Charge transfer in keV O+(4S,2D,2P)-He collisions

    Science.gov (United States)

    Lindsay, B. G.; Stebbings, R. F.

    2003-02-01

    Absolute differential cross sections (DCSs) are reported for charge-transfer scattering of (1 5)-keV O+(4S) ground-state and O+(2D,2P) metastable-state ions by helium atoms at angles between 0.2° and 6.3° in the laboratory frame. Estimated ground-state and metastable-state total cross sections are derived from these measurements. The present ground-state cross sections agree satisfactorily with previous measurements for energies above 2 keV and the metastable-state cross sections are consistent with the mixed-state data of Kusakabe et al. [J. Phys. Soc. Japan 59, 1987 (1990)]. The large differences between the ground- and metastable-state cross sections predicted by theory are not observed.

  4. Enhanced Three-Photon Absorption by Symmetric Twisted Intramolecular Charge Transfer

    Institute of Scientific and Technical Information of China (English)

    GUO Fu-Quan; YANG Jun; ZHANG Qi-Jin; MING Hai

    2005-01-01

    @@ We report on a novel organic chromophore with symmetric twisted intramolecular charge transfer (TICT) state on excitation. The properties of nonlinear transmission induced by three-photon absorption (3PA) are demonstrated pumped with nanosecond laser pulse. Large 3PA cross sections as high as the order of 10-74 cm6s2have been obtained for nanosecond and picosecond laser pulses at 1064 nm from intensity-dependent transmission measurements. Similar two emissive behaviours from one-photon and three-photon excited fluorescence spectra indicate that the linear and nonlinear fluorescences share the same TICT relaxation process from the excited states. The intensity dependence of upconversion fluorescence on the incident intensity obeys the cubic law that characterizes the three-photon absorption.

  5. Charge-transfer reactions between C{sub 60} and hydrophilic solutes

    Energy Technology Data Exchange (ETDEWEB)

    Dimitrijevic, N.M.; Nedeljkovic, J.M.; Saponjic, Z.V. [Institute for Nuclear Sciences ``Vinca``, Belgrade (Yugoslavia)

    1998-10-01

    Two different procedures for dissolving fullerene molecule C{sub 60} into aqueous solutions have been developed. Embedding C{sub 60} clusters into a water-soluble host molecule of {gamma}-cyclodextrin resulted in relatively low concentration of C{sub 60} (5-10 {mu}M). Prepare of a stable ionic surfactant/water/oil microemulsion provided a method for dissolving C{sub 60} in relatively high concentrations (1 mM). In both cases charge-transfer reactions between hydrophobic molecule of C{sub 60} and hydrophilic solutes were examined. Anion radical C{sub 60}{sup -} was detected in reaction with radiolytically produced radicals (e{sub aq}{sup -}, (CH{sub 3}){sub 2}COH or MV{sup +}), and in reaction with excess electrons stored onto nanometer-sized metal (Ag) or quantized semiconductor (TiO{sub 2}) particles. (orig.) 33 refs.

  6. Restoration of Conductivity with TTF-TCNQ Charge-Transfer Salts

    Energy Technology Data Exchange (ETDEWEB)

    Odom, Susan A.; Caruso, Mary M.; Finke, Aaron D.; Prokup, Alex M.; Ritchey, Joshua A.; Leonard, Francois; White, Scott R.; Sottos, Nancy R.; Moore, Jeffrey S.

    2010-05-03

    The formation of the conductive TTF-TCNQ (tetrathiafulvalene–tetracyanoquinodimethane) charge-transfer salt via rupture of microencapsulated solutions of its individual components is reported. Solutions of TTF and TCNQ in various solvents are separately incorporated into poly(urea-formaldehyde) core–shell microcapsules. Rupture of a mixture of TTF-containing microcapsules and TCNQ-containing microcapsules results in the formation of the crystalline salt, as verified by FTIR spectroscopy and powder X-ray diffraction. Preliminary measurements demonstrate the partial restoration of conductivity of severed gold electrodes in the presence of TTF-TCNQ derived in situ. This is the first microcapsule system for the restoration of conductivity in mechanically damaged electronic devices in which the repairing agent is not conductive until its release.

  7. Effect of intramolecular charge transfer on fluorescence and singlet oxygen production of phthalocyanine analogues.

    Science.gov (United States)

    Vachova, Lenka; Novakova, Veronika; Kopecky, Kamil; Miletin, Miroslav; Zimcik, Petr

    2012-10-14

    Intramolecular charge transfer (ICT) was studied on a series of magnesium, metal-free and zinc complexes of unsymmetrical tetrapyrazinoporphyrazines and tribenzopyrazinoporphyrazines bearing two dialkylamino substituents (donors) and six alkylsulfanyl or aryloxy substituents (non-donors). The dialkylamino substituents were responsible for ICT that deactivated excited states and led to considerable decrease of fluorescence and singlet oxygen quantum yields. Photophysical and photochemical properties were compared to corresponding macrocycles that do not bear any donor centers. The data showed high feasibility of ICT in the tetrapyrazinoporphyrazine macrocycle and significantly lower efficiency of this deactivation process in the tribenzopyrazinoporphyrazine type molecules. Considerable effect of non-donor peripheral substituents on ICT was also described. The results imply that tetrapyrazinoporphyrazines may be more suitable for development of new molecules investigated in applications based on ICT.

  8. Charge transfer behavior of graphene-titania photoanode in CO2 photoelectrocatalysis process

    Science.gov (United States)

    Hasan, Md. Rakibul; Hamid, Sharifah Bee Abd; Basirun, Wan Jeffrey

    2015-06-01

    In the present study, a graphene-titania composite photoelectrode was synthesized, characterized and examined for the photoelectrocatalytic (PEC) response. The charge transfer process on the semiconductor/electrolyte interface was investigated via electrochemical impedance spectroscopy (EIS) and voltammetry. In addition, the influence of pH toward the photoanode performance was also investigated and it was noticed that a high pH condition was favorable higher photocurrent response from the EIS measurements. The main reason could be attributed to the decrease of recombination process at the photoanode with fast quenching of the photogenerated holes with OH- ions at high pH. The experiment was also run for CO2 photoreduction and increased photocurrent was observed.

  9. Modulating charge transfer through cyclic D,L-alpha-peptide self-assembly.

    Science.gov (United States)

    Horne, W Seth; Ashkenasy, Nurit; Ghadiri, M Reza

    2005-02-04

    We describe a concise, solid support-based synthetic method for the preparation of cyclic d,l-alpha-peptides bearing 1,4,5,8-naphthalenetetracarboxylic acid diimide (NDI) side chains. Studies of the structural and photoluminescence properties of these molecules in solution show that the hydrogen bond-directed self-assembly of the cyclic d,l-alpha-peptide backbone promotes intermolecular NDI excimer formation. The efficiency of NDI charge transfer in the resulting supramolecular assemblies is shown to depend on the length of the linker between the NDI and the peptide backbone, the distal NDI substituent, and the number of NDIs incorporated in a given structure. The design rationale and synthetic strategies described here should provide a basic blueprint for a series of self-assembling cyclic d,l-alpha-peptide nanotubes with interesting optical and electronic properties.

  10. Modulating Charge Transfer Through Cyclic D,L α-Peptide Self-Assembly

    Science.gov (United States)

    Horne, W. Seth; Ashkenasy, Nurit; Ghadiri, M. Reza

    2007-01-01

    We describe a concise solid support-based synthetic method for the preparation of cyclic D,L α-peptides bearing 1,4,5,8-naphthalenetetracarboxylic diimide (NDI) side chains. Studies of the structural and photoluminescence properties of these molecules in solution show that the hydrogen bond directed self-assembly of the cyclic D,L α-peptide backbone promotes intermolecular NDI excimer formation. The efficiency of NDI charge transfer in the resulting supramolecular assemblies is shown to depend on the length of the linker between the NDI and the peptide backbone, the distal NDI substituent, and the number of NDIs incorporated in a given structure. The design rationale and synthetic strategies described here should provide a basic blueprint for a series of self-assembling cyclic D,L α-peptide nanotubes with interesting optical and electronic properties. PMID:15624124

  11. Ab initio treatment of ion-induced charge transfer dynamics of isolated 2-deoxy-D-ribose.

    Science.gov (United States)

    Bacchus-Montabonel, Marie-Christine

    2014-08-21

    Modeling-induced radiation damage in biological systems, in particular, in DNA building blocks, is of major concern in cancer therapy studies. Ion-induced charge-transfer dynamics may indeed be involved in proton and hadrontherapy treatments. We have thus performed a theoretical approach of the charge-transfer dynamics in collision of C(4+) ions and protons with isolated 2-deoxy-D-ribose in a wide collision energy range by means of ab initio quantum chemistry molecular methods. The comparison of both projectile ions has been performed with regard to previous theoretical and experimental results. The charge transfer appears markedly less efficient with the 2-deoxy-D-ribose target than that with pyrimidine nucleobases, which would induce an enhancement of the fragmentation process in agreement with experimental measurements. The mechanism has been analyzed with regard to inner orbital excitations, and qualitative tendencies have been pointed out for studies on DNA buiding block damage.

  12. Evaluating Electronic Couplings for Excited State Charge Transfer Based on Maximum Occupation Method ΔSCF Quasi-Adiabatic States.

    Science.gov (United States)

    Liu, Junzi; Zhang, Yong; Bao, Peng; Yi, Yuanping

    2017-02-14

    Electronic couplings of charge-transfer states with the ground state and localized excited states at the donor/acceptor interface are crucial parameters for controlling the dynamics of exciton dissociation and charge recombination processes in organic solar cells. Here we propose a quasi-adiabatic state approach to evaluate electronic couplings through combining maximum occupation method (mom)-ΔSCF and state diabatization schemes. Compared with time-dependent density functional theory (TDDFT) using global hybrid functional, mom-ΔSCF is superior to estimate the excitation energies of charge-transfer states; moreover it can also provide good excited electronic state for property calculation. Our approach is hence reliable to evaluate electronic couplings for excited state electron transfer processes, which is demonstrated by calculations on a typical organic photovoltaic system, oligothiophene/perylenediimide complex.

  13. Coherent dynamics of mixed Frenkel and Charge Transfer Excitons in Dinaphtho[2,3-b:2'3'-f]thieno[3,2-b]-thiophene Thin Films: The Importance of Hole Delocalization

    CERN Document Server

    Fujita, Takatoshi; Sawaya, Nicolas P D; Aspuru-Guzik, Alan

    2016-01-01

    Charge transfer states in organic semiconductors play crucial roles in processes such as singlet fission and exciton dissociation at donor/acceptor interfaces. Recently, a time-resolved spectroscopy study of dinaphtho[2,3-b:2'3'-f]thieno[3,2-b]-thiophene (DNTT) thin films provided evidence for the formation of mixed Frenkel and charge-transfer excitons after the photoexcitation. Here we investigate optical properties and excitation dynamics of the DNTT thin films by combining ab initio calculations and a stochastic Schrodinger equation. Our theory predicts that the low-energy Frenkel exciton band consists of 8 to 47% CT character. The quantum dynamics simulations show coherent dynamics of Frenkel and CT states in 50 fs after the optical excitation. We demonstrate the role of charge delocalization and localization in the mixing of CT states with Frenkel excitons as well as the role of their decoherence.

  14. Soft versus hard junction formation for α-terthiophene molecular wires and their charge transfer complexes

    Science.gov (United States)

    Vezzoli, Andrea; Grace, Iain M.; Brooke, Carly; Nichols, Richard J.; Lambert, Colin J.; Higgins, Simon J.

    2017-03-01

    We used a range of scanning tunnelling microscopy (STM)-based methods to conduct a detailed study of single molecule junction conductance enhancement upon charge transfer complex formation, using bis(thiaalkyl)arene molecular wires as electron donors and tetracyanoethylene (TCNE) as an electron acceptor. Using the "hard" STM break junction (STM-BJ) method, in which a Au STM tip is pushed into a Au substrate and then withdrawn in the presence of molecules, we see a single, very broad, peak in the resulting conductance histogram when all data are used; the conductance enhancement is 25-fold for a terthiophene donor and 15-fold for a phenyl group. After rational data selection, in which only current-distance curves that contain a current plateau >0.2 nm long are used in the conductance histogram, three sharper peaks are resolved in the histograms for the charge transfer complexes; two substantially lower-conductance peaks are resolved for the uncomplexed molecules. Using the "soft" STM I(s) technique, in which initial contact between tip and substrate is avoided and the current limit is about an order of magnitude lower, we were able to resolve two peaks for the uncomplexed molecules depending upon the initial set point current (i.e., tip height), one at the same value as the lower of the two data-selected STM-BJ histogram peaks and an additional peak beyond the low-current limit for the STM-BJ experiment. For the terthiophene, the low, medium, and high conductance peaks for the TCNE complex are, respectively, ca. 70, 70, and 46 times higher in conductance than the corresponding peaks for the free molecule.

  15. Analytical study for the charge-transfer complexes of losartan potassium

    Energy Technology Data Exchange (ETDEWEB)

    Darwish, Ibrahim A. [Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Assiut University, Assiut 71526 (Egypt)]. E-mail: iadarwish@yahoo.com

    2005-09-06

    Studies were carried out, for the first time, to investigate the charge-transfer reactions of losartan potassium (LOS-K) as n-electron donor with the {sigma}-acceptor iodine and various {pi}-acceptors: 7,7,8,8-tetracyanoquinodimethane, 1,3,5-trinitrobenzene, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, p-chloranilic acid, tetracyanoethylene, 2,3,5,6-tetrabromo-1,4-benzoquinone, 2,3,5,6-tetrachloro-1,4-benzoquinone, and 2,4,7-trinitro-9-fluorenone. Different colored charge-transfer complexes and radical anions were obtained. Different variables affecting the reactions were studied and optimized. The formed complexes and the site of interaction were examined by UV-vis, IR, and {sup 1}H NMR techniques, and computational molecular modeling. The formation of the colored complexes were utilized in the development of simple, rapid and accurate spectrophotometric methods for the analysis of LOS-K in pure form as well as in its pharmaceutical tablets. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9985-0.9998) were found between the absorbances and the concentrations of LOS-K in the range of 2-200 {mu}g ml{sup -1}. The limits of assays detection ranged from 0.61 to 19.65 {mu}g ml{sup -1}. No interference could be observed from the co-formulated hydrochlorothiazide (HCTZ), as well as from the additives commonly present in the tablets. The methods were successfully applied to the analysis of tablets from different manufacturers that contain LOS-K, alone or combined with HCTZ, with good accuracy and precision; the recovery percentages ranged from 98.96 {+-} 1.62% to 101.58 {+-} 1.29%. The results were compared favourably with the reported method.

  16. Synthesis and characterization of highly conductive charge-transfer complexes using positron annihilation spectroscopy

    Science.gov (United States)

    Adam, Abdel Majid A.; Refat, Moamen S.; Sharshar, T.; Heiba, Z. K.

    Molecular charge-transfer complexes of the tetramethylethylenediamine (TMEDA) with picric acid (Pi-OH), benzene-1,4-diol (QL), tin(IV) tetrachloride (SnCl4), iodine, bromine, and zinc chloride (ZnCl2) have been synthesized and investigated by elemental and thermal analysis, electronic, infrared, Raman and proton-NMR, energy-dispersive X-ray spectroscopy, X-ray powder diffraction and positron annihilation lifetime spectroscopy, and scanning electron microscopy. In this work, three types of acceptors π-acceptors (Pi-OH and QL), σ-acceptors (iodine and bromine), and vacant orbital acceptors (SnCl4 and ZnCl2) were covered. The results of elemental analysis indicated that the CT complexes were formed with ratios 1:1 and 1:2 for QL, SnCl4, and ZnCl2 acceptors and iodine, Pi-OH, and Br2 acceptors, respectively. The type of chelating between the TMEDA donor and the mentioned acceptors depends upon the behavior of both items. The positron annihilation lifetime parameters were found to be dependent on the structure, electronic configuration, and the power of acceptors. The correlation between these parameters and the molecular weight and biological activities of studied complexes was also observed. Regarding the electrical properties, the AC conductivity and the dielectric coefficients were measured as a function of frequency at room temperature. The TMEDA charge-transfer complexes were screened against antibacterial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa) and antifungal (Aspergillus flavus and Candida albicans) activities.

  17. Enhancement of Charge Transfer and Quenching of Photoluminescence of Capped CdS Quantum Dots

    Science.gov (United States)

    Mehata, Mohan Singh

    2015-07-01

    Quantum dots (Q-dots) of cadmium sulfide (CdS) with three different capping ligands, 1-butanethiol (BT), 2-mercaptoethanol (ME) and benzyl mercaptan (BM) have been investigated. An external electric field of variable strength of 0.2-1.0 MV cm-1 was applied to the sample of capped CdS Q-dots doped in a poly(methyl methacrylate) (PMMA) films. Field-induced changes in optical absorption of capped CdS Q-dots were observed in terms of purely the second-derivative of the absorption spectrum (the Stark shift), indicating an enhancement in electric dipole moment following transition to the first exciton state. The enhancement depends on the shape and size of the Q-dots prepared using different capping ligands. Field induced-change in photoluminescence (PL) reveals similar changes, an enhancement in charge-transfer (CT) character in exciton state. PL of capped CdS Q-dots is significantly quenched in presence of external electric field. The strong field-induced quenching occurs as a result of the increased charge separation resulting exciton dissociation. Thus, understanding the CT character and field-induced PL quenching of CdS Q-dots is important for photovoltaic, LEDs and biological applications.

  18. A charge transfer complex nematic liquid crystalline gel with high electrical conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Bhargavi, R.; Nair, Geetha G., E-mail: geeraj88@gmail.com, E-mail: skpras@gmail.com; Krishna Prasad, S., E-mail: geeraj88@gmail.com, E-mail: skpras@gmail.com [Centre for Nano and Soft Matter Sciences, Jalahalli, Bangalore 560013 (India); Majumdar, R.; Bag, Braja G. [Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore (W) 721 102 (India)

    2014-10-21

    We describe the rheological, dielectric and elastic properties of a nematic liquid crystal gel created using an anthrylidene derivative of arjunolic acid, a chiral triterpenoid, obtained from the extracts of the wood of Terminalia arjuna. In this novel gel, having the electron-donor and acceptor components as minority constituents, the gelation and strengthening of charge-transfer complex (CTC) formation are seen to be occurring concomitantly. In addition to being mechanically strong with a large storage modulus, the gel with the maximized CTC exhibits Frank bend elastic constant values that approach nanonewton levels. The highlight of the study is the observation of 4–5 orders of magnitude increase in electrical conductivity for this gel, a value that is higher than even in the CT complexes of 2-d ordered columnar structures. A further important advantage of the present system over the columnar complex is that the high conductivity is seen for ac probing also, and owing to the nematic nature can be switched between its anisotropic limits. Some of these features are ascribed to a specific molecular packing architecture, which reduces the trapping of the charge carriers.

  19. Charge Transfer in Light Effect Under Visible Radiation in an Ozoniser Discharge

    Directory of Open Access Journals (Sweden)

    S.V. Salvi

    2006-11-01

    Full Text Available Two fresh discharge vessels (1 and 2 of Siemen’s ozoniser type having the same height butdifferent surface-to-volume ratios have been fabricated by enclosing argon at 10 mm mercury.By immersing these in electrolytic solution and by subjecting these to a definite high 50 Hz acvoltage, the discharge count rates in dark (Cf D and under light (Cf L have been determinedusing a scaler held at different bias-voltages. The plot of the ratio (C1f / C2f D and (C1f / C2f Lof discharge counts versus pulse height (bias-voltage shows that this ratio for a constantpotential of 3.5 kV (rms is initially large in value, then rapidly decreases to a minimum. It is alsoobserved that more is the surface-to-volume ratio, more is the magnitude of net effect of irradiation.Further, the pulse height analysis shows that the charge carried by the pulses to the electrodes(charge transfer decreases under illumination. A possible mechanism to explain the net effectof the discharge current ratio in the light of pulse height measurements is discussed.

  20. Temperature-induced valence instability in the charge-transfer crystal TMB-TCNQ

    Science.gov (United States)

    Castagnetti, Nicola; Kociok-Köhn, Gabriele; Da Como, Enrico; Girlando, Alberto

    2017-01-01

    The occurrence of so-called temperature-induced neutral-ionic transitions (TINIT) in mixed-stack charge-transfer crystals is quite rare. Here we reinvestigate one of the crystals which has been claimed to undergo such a transition, 3 ,3',5 ,5' -tetramethylbenzidine-tetracyanoquinodimethane (TMB-TCNQ). Extensive optical data allow us to conclude that the transition should be classified as a valence instability, and not as a "true" TINIT, as the ˜0.5 neutral-ionic borderline is not crossed. The ionicity ϱ , or average charge at the molecular sites, indeed changes very little at the transition, from about 0.3 to about 0.4, and is accompanied by stack dimerization. The transition is first order with large hysteresis, and the crystal may crack or break. For this reason we have been unable to collect x-ray structural data on the low-temperature phase, but with the help of semiempirical calculations we are able to assess a plausible scenario for this peculiar phase transition and its mechanism.

  1. The influence of the vinyl terminal group on the poly(para-phenylenevinylene) charge transfer integrals.

    Science.gov (United States)

    Ottonelli, Massimo; Duce, Daniele; Thea, Sergio; Dellepiane, Giovanna

    2013-07-01

    The charge transport properties of organic semiconductors are one of the foremost limiting factors in technological applications of these materials, which are becoming important competitors with respect to the inorganic semiconductors. In fact, conjugated organic molecules are used at present as active materials in different types of devices. For this reason, the theoretical study of the electron and hole mobility, carried out in order to give hints for the design of new molecules or for the optimization of their supramolecular organization, is a task of great interest. Here, we present the results of a quantum chemical study, in the framework of the Marcus and density functional theories, on the effects of terminal groups (when they directly interact with the pi-conjugated system of the organic semiconductors) on the charge carriers mobility of organic semiconductors. In particular, using a representative oligomer of poly(para-phenylenevinylene) as a model system, we have found that strong effects on the predicted values of the intramolecular transfer integrals as well as on their dependence on the supramolecular organizations occur, when the vinyl moiety (as ending group) is taken into account.

  2. Valence Topological Charge-Transfer Indices for Dipole Moments: Percutaneous Enhancers

    Directory of Open Access Journals (Sweden)

    Francisco Torrens

    2004-12-01

    Full Text Available Valence topological charge-transfer (CT indices are applied to the calculationof dipole moments. The algebraic and vector semisum CT indices are defined. Thecombination of CT indices allows the estimation of the dipole moments. The model isgeneralized for molecules with heteroatoms. The ability of the indices for the descriptionof the molecular charge distribution is established by comparing them with the dipolemoments of homologous series of percutaneous enhancers (phenyl alcohols and4-alkylanilines. Linear and quadratic correlation models are obtained. CT indicesimprove the multivariable quadratic regression equations for the dipole moment. Thevariance decreases 97% (4-alkylanilines. No superposition of the corresponding Gk–Jkand GkV–JkV pairs is observed in the fits, which diminishes the risk of co-linearity. Theinclusion of the heteroatom in the π-electron system is beneficial for the description ofthe dipole moment, owing to either the role of the additional p orbitals provided by theheteroatom or the role of steric factors in the π-electron conjugation. Inclusion of aconjugated double bond in the alkyl chain lends to more rigid structures with dipolemoment variations lower than1%.

  3. The effect of charge mixture ratio and particle size on igniter plume heat transfer characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Evans, N.A.; Brezowski, C.F.

    1990-01-01

    Investigation of the heat transfer characteristics of igniter output plumes, first reported at the Fourteenth International Pyrotechnics Seminar in 1989, has continued, using two types of igniter to determine the effect of charge mixture ratio and fuel particle size on performance. While both of these igniters had the same metallic closure disc (scored Hastelloy with a capture cone), the bridgewire sensitizer (or ignition mixture) was barium styphnate for one type, and a particular blend of fine particle titanium/potassium perchlorate ( PB'') for the other type. The output mixture for both types was titanium/potassium perchlorate; two mixture ratios (33/67 and 41/59), and two titanium particle sizes (2 and 8 {mu}m) were used. The results show that, for both types of igniter, the coarse particle size titanium produced the best performance. The overall best performance was obtained from the igniter using the PB'' ignition mixture and an output charge of 41/59 titanium/potassium perchlorate. 2 refs., 6 figs., 1 tab.

  4. Photophysical study of a charge transfer oxazole dye in micelles: Role of surfactant headgroups

    Energy Technology Data Exchange (ETDEWEB)

    Maiti, Jyotirmay [Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126 (India); Sarkar, Yeasmin; Parui, Partha Pratim [Department of Chemistry, Jadavpur University, Kolkata 700032 (India); Chakraborty, Sandipan [Department of Microbiology, University of Calcutta, Kolkata 700019 (India); Biswas, Suman [Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126 (India); Das, Ranjan, E-mail: ranjan.das68@gmail.com [Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126 (India)

    2015-07-15

    Photophysics of 5-(4′′-dimethylaminophenyl)-2-(4′-sulfophenyl)oxazole, sodium salt (DMO) which undergoes intramolecular charge transfer in the excited state was studied in micelles. In the cationic and the nonionic micelles, significantly higher fluorescence quantum yield is observed in comparison to the anionic micelles, due to much lower accessibility of DMO to the water molecules in the former micelles than the latter. Time-resolved fluorescence decays were characterized by a fast (τ{sub 1}) and a slow (τ{sub 2}) component of decay in all the micelles. The fast decay component (τ{sub 1}) increases significantly in going from the anionic micelles to the cationic micelles, because of the poorly hydrated headgroup region of the latter micelles compared to the former. Furthermore, much higher value of the slow component of decay (τ{sub 2}) is observed for the cationic and the neutral micelles than the anionic micelles. This is attributed to the increased penetration of water molecules into the micellar core of the anionic micelles compared to the cationic and the neutral micelles. - Highlights: • Photophysics of the fluorophore are remarkably different in the cationic and the anionic micelles. • Differential hydration of the surfactant headgroups gives rise to significantly different fluorescence quantum yield and lifetime in oppositely charged micelles. • Electrostatic interactions fine tune location of the fluorophore in the micelle–water interface of ionic micelles.

  5. Cellular and molecular analysis of mutagenesis induced by charged particles of defined linear energy transfer

    Science.gov (United States)

    Zhu, L. X.; Waldren, C. A.; Vannias, D.; Hei, T. K.; Chatterjee, A. (Principal Investigator)

    1996-01-01

    Mutation induction by charged particles of defined linear energy transfer (LET) and gamma rays was scored using human-hamster hybrid AL cells. The LET values for charged particles accelerated at the Radiological Research Accelerator Facility ranged from 10 keV/microm protons to 150 keV/microm 4He ions. The induced mutant fractions at both the S1 and HGPRT loci were dependent on the dose and LET. In addition, for each dose examined, the mutant yield at the S1 locus was 30-60 fold higher than at the corresponding HGPRT locus. To determine whether the mutation spectrum was comparably dependent on dose and LET, independent S1- and HGPRT- mutants induced by 150 keV/microm 4He ions and gamma rays were isolated, and their DNA was analyzed by both Southern blotting and multiplex PCR methods. While the majority of radiation-induced mutants showed deletions of varying sizes, the relative percentage of large deletions was found to be related to both the dose and LET of the radiation examined. Using a mutation system that can detect multilocus changes, results of the present study show that radiation-induced chromosomal loss can be in the millions of base pairs.

  6. IR spectroscopic investigation of charge transfer at interfaces of organic semiconductors (Conference Presentation)

    Science.gov (United States)

    Beck, Sebastian; Hillebrandt, Sabina; Pucci, Annemarie

    2016-09-01

    In organic electronics, the interactions at interfaces between different organic and inorganic layers play a decisive role for device functionality and performance. Therefore, more detailed, quantitative studies of charge transfer (CT) at such interfaces are needed to improve the understanding of the underlying mechanisms. In this study we show that in-situ infrared spectroscopy can be used to investigate CT effects at organic/organic as well as inorganic/organic interfaces quantitatively. For different combinations of commonly used organic semiconductors such as 4,4´-bis(N-carbazolyl)-1,1´-biphenyl (CBP) or fluorinated zinc phthalocyanine (F4ZnPc) and inorganic contact materials such as molybdenum oxide (MoO3) or indium tin oxide (ITO) the CT at the interface was investigated using in-situ IR spectroscopy. The measurements were carried out under UHV conditions during film growth what enables a careful study of the influence of different parameters such as substrate temperature and layer thickness in a controlled way even on a nanometer scale. When the organic molecules are deposited onto the underlying layer charged and non-charged species form which can be identified and quantitatively analyzed in the IR spectra. It was also found that the deposition sequence can strongly influence the interface properties what might have strong implications on the layer stack design. For example, when MoO3 is deposited onto CBP, the CBP layer is strongly doped, due to diffusion of the deposited transition metal oxide clusters into the organic layer. Financial support by BMBF (project INTERPHASE) is gratefully acknowledged.

  7. Hyperbolic metamaterial nanostructures to tune charge-transfer dynamics (Conference Presentation)

    Science.gov (United States)

    Lee, Kwang Jin; Xiao, Yiming; Woo, Jae Heun; Kim, Eun Sun; Kreher, David; Attias, André-Jean; Mathevet, Fabrice; Ribierre, Jean-Charles; Wu, Jeong Weon; André, Pascal

    2016-09-01

    Charge transfer (CT) is an essential phenomenon relevant to numerous fields including biology, physics and chemistry.1-5 Here, we demonstrate that multi-layered hyperbolic metamaterial (HMM) substrates alter organic semiconductor CT dynamics.6 With triphenylene:perylene diimide dyad supramolecular self-assemblies prepared on HMM substrates, we show that both charge separation (CS) and charge recombination (CR) characteristic times are increased by factors of 2.5 and 1.6, respectively, resulting in longer-lived CT states. We successfully rationalize the experimental data by extending Marcus theory framework with dipole image interactions tuning the driving force. The number of metal-dielectric pairs alters the HMM interfacial effective dielectric constant and becomes a solid analogue to solvent polarizability. Based on the experimental results and extended Marcus theory framework, we find that CS and CR processes are located in normal and inverted regions on Marcus parabola diagram, respectively. The model and further PH3T:PCBM data show that the phenomenon is general and that molecular and substrate engineering offer a wide range of kinetic tailoring opportunities. This work opens the path toward novel artificial substrates designed to control CT dynamics with potential applications in fields including optoelectronics, organic solar cells and chemistry. 1. Marcus, Rev. Mod. Phys., 1993, 65, 599. 2. Marcus, Phys. Chem. Chem. Phys., 2012, 14, 13729. 3. Lambert, et al., Nat. Phys., 2012, 9, 10. 4. C. Clavero, Nat. Photon., 2014, 8, 95. 5. A. Canaguier-Durand, et al., Angew. Chem. Int. Ed., 2013, 52, 10533. 6. K. J. Lee, et al., Submitted, 2015, arxiv.org/abs/1510.08574.

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

    Science.gov (United States)

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

    2016-05-19

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

  9. Evaluation of intramolecular charge transfer state of 4-, -dimethylamino cinnamaldehyde using time-dependent density functional theory

    Indian Academy of Sciences (India)

    Surajit Ghosh; K V S Girish; Subhadip Ghosh

    2013-07-01

    Intramolecular charge transfer of 4-,-dimethylamino cinnamaldehyde (DMACA) in vacuum and in five different aprotic solvents has been studied by using time-dependent density functional theory (TDDFT). Polarizable continuum model (PCM) was employed to consider solvent-solute interactions. The potential energy curves were constructed at different torsional angle of ,-dimethylamino moiety with respect to the adjacent phenyl ring. A large bathochromic shift in our calculated emission and absorption energies for polar solvents is a clear reminiscent of charge transfer nature of the excited state. Finally, the reported results are in agreement with experimental findings.

  10. Electronic hole transfer in rutile and anatase TiO2: Effect of a delocalization error in the density functional theory on the charge transfer barrier height

    DEFF Research Database (Denmark)

    Zawadzki, Pawel; Rossmeisl, Jan; Jacobsen, Karsten Wedel

    2011-01-01

    where charge localization is strongly coupled to lattice distortion. As an example we calculate the adiabatic PES for the hole transfer process in rutile and anatase TiO2. (Semi) local DFT leads to qualitatively wrong, barrierless curves. Removal of the nonlinearity improves the PES shape and allows us...

  11. Correlation between charge transfer and exchange coupling in carbon-based magnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Anh Tuan, E-mail: tuanna@hus.edu.vn [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Science and Technology Department, Vietnam National University, Hanoi, 144 Xuan Thuy, Cau Giay, Hanoi (Viet Nam); Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Nomi, Ishikawa, 923-1292 Japan (Japan); Nguyen, Van Thanh; Nguyen, Huy Sinh [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Pham, Thi Tuan Anh [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Faculty of Science, College of Hai Duong, Nguyen Thi Due, Hai Duong (Viet Nam); Do, Viet Thang [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Faculty of Science, Haiphong University, 171 Phan Dang Luu, Kien An, Hai Phong (Viet Nam); Dam, Hieu Chi [Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Nomi, Ishikawa, 923-1292 Japan (Japan)

    2015-10-15

    Several forms of carbon-based magnetic materials, i.e. single radicals, radical dimers, and alternating stacks of radicals and diamagnetic molecules, have been investigated using density-functional theory with dispersion correction and full geometry optimization. Our calculated results demonstrate that the C{sub 31}H{sub 15} (R{sub 4}) radical has a spin of ½. However, in its [R{sub 4}]{sub 2} dimer structure, the net spin becomes zero due to antiferromagnetic spin-exchange between radicals. To avoid antiferromagnetic spin-exchange of identical face-to-face radicals, eight alternating stacks, R{sub 4}/D{sub 2m}/R{sub 4} (with m = 3-10), were designed. Our calculated results show that charge transfer (Δn) between R{sub 4} radicals and the diamagnetic molecule D{sub 2m} occurs with a mechanism of spin exchange (J) in stacks. The more electrons that transfer from R{sub 4} to D{sub 2m}, the stronger the ferromagnetic spin-exchange in stacks. In addition, our calculated results show that Δn can be tailored by adjusting the electron affinity (E{sub a}) of D{sub 2m}. The correlation between Δn, E{sub a}, m, and J is discussed. These results give some hints for the design of new ferromagnetic carbon-based materials.

  12. Colossal negative thermal expansion in BiNiO3 induced by intermetallic charge transfer.

    Science.gov (United States)

    Azuma, Masaki; Chen, Wei-tin; Seki, Hayato; Czapski, Michal; Olga, Smirnova; Oka, Kengo; Mizumaki, Masaichiro; Watanuki, Tetsu; Ishimatsu, Naoki; Kawamura, Naomi; Ishiwata, Shintaro; Tucker, Matthew G; Shimakawa, Yuichi; Attfield, J Paul

    2011-06-14

    The unusual property of negative thermal expansion is of fundamental interest and may be used to fabricate composites with zero or other controlled thermal expansion values. Here we report that colossal negative thermal expansion (defined as linear expansion transfer transitions. BiNiO(3) shows a 2.6% volume reduction under pressure due to a Bi/Ni charge transfer that is shifted to ambient pressure through lanthanum substitution for Bi. Changing proportions of coexisting low- and high-temperature phases leads to smooth volume shrinkage on heating. The crystallographic linear expansion coefficient for Bi(0.95)La(0.05)NiO(3) is -137×10(-6) K(-1) and a value of -82×10(-6) K(-1) is observed between 320 and 380 K from a dilatometric measurement on a ceramic pellet. Colossal negative thermal expansion materials operating at ambient conditions may also be accessible through metal-insulator transitions driven by other phenomena such as ferroelectric orders.

  13. Characterization and Modeling of Received Signal Strength and Charging Time for Wireless Energy Transfer

    Directory of Open Access Journals (Sweden)

    Uthman Baroudi

    2015-01-01

    Full Text Available Wireless sensor networks can provide effective means for monitoring and controlling a wide range of applications. Recently, tremendous effort was directed towards devising sensors powered from ambient sources such as heat, wind, and vibration. Wireless energy transfer is another source that has attractive features that make it a promising candidate for supplying power to wireless sensor nodes. This paper is concerned with characterizing and modeling the charging time and received signal strength indicator for wireless energy transfer system. These parameters play a vital role in deciding the geometry of sensor network and the routing protocols to be deployed. The development of communication protocols for wireless-powered wireless sensor networks is also improved with the knowledge of such models. These two quantities were computed from data acquired at various coordinates of the harvester relative to a fixed position of RF energy source. Data was acquired for indoor and outdoor scenarios using the commercially available PowerCast energy harvester and evaluation board. Mathematical models for both indoor and outdoor environments were developed and analyzed. A few guidelines on how to use these models were suggested. Finally, the possibility of harvesting the energy from the ambient RF power to energize wireless sensor nodes was also investigated.

  14. Femtosecond Heterodyne Transient Grating Spectroscopic Studies of Intramolecular Charge Transfer Character of Peridinin and Peridinin Analogs

    Science.gov (United States)

    Bishop, Michael; Khosravi, Soroush; Obaid, Razib; Whitelock, Hope; Carroll, Ann Marie; Lafountain, Amy; Frank, Harry; Beck, Warren; Gibson, George; Berrah, Nora

    2016-05-01

    The peridinin chlorophyll-a protein is a light harvesting complex found in several species of dinoflagellates. Peridinin absorbs strongly in the mid-visible spectral region and, despite the lack of a strong permanent dipole moment in its lowest energy excited state, is able to transfer excitation energy quickly and efficiently to chlorophyll-a. It is believed that the high efficiency arises from the development of intramolecular charge-transfer (ICT) character upon photoexcitation. Recently, heterodyne transient grating spectroscopy has been used to study the ultrafast (<50 fs) dynamics of β carotene and peridinin. The studies show evidence for a structurally displaced intermediate in both cases and strong ICT character in the case of peridinin, but up to now the work has not provided appropriate control experiments. The present experiments examine peridinin and two peridinin analogs, S1-peridinin and S2-peridinin. S1-peridinin is reported to have greatly diminished ICT character, and S2-peridinin is reported to have little-or-no ICT character. Heterodyne transient grating data will be presented and provide a more unambiguous characterization spectral and kinetic properties associated with the peridinin ICT state. Funded by the DoE-BES, Grant No. DE-SC0012376.

  15. Mechanism of intramolecular charge transfer in DNA helix as probed by the use of the fluorescent 2-aminopurine

    Institute of Scientific and Technical Information of China (English)

    ZHANG Huijuan; WANG Peng; WANG Xuefei; FENG Juan; XU Sichuan; AI Xicheng; ZHANG Xingkang; ZHANG Jianping

    2004-01-01

    As a structural analogue of adenine, 2-aminopurine (2Ap) is often used as a fluorescent probe to study the intramolecular charge transfer reaction in DNA. We have designed and synthesized a series of model DNA helix with the variation in the distance between the 2Ap probe and the GGG sequence, and have investigated, by means of picosecond time-resolved fluorescence spectroscopy, the effect of the length of the bridge (consisting of a number of transfer dynamics. The fluorescence dynamics of 2Ap exhibited three exponential decay components, the one with a time constant of a few hundred picoseconds is assigned to the intramolecular charge transfer from GGG to 2Ap. Within 2.4 nm of the donor-acceptor separation,the rate of charge transfer decreased exponentially upon increasing the separation, from which the decay factor ,β is determined to be 1.3 nm-1. Beyond 2.4 nm, however, the rate started to increase, this abnormal behavior of charge transfer is interpreted in terms of the match of electronic energies between the I-bridge and the donor/acceptor couple.

  16. Cooperative coupling of the Li cation and groups to amplify the charge transfer between C60 and corannulene

    Science.gov (United States)

    Sun, Gang; Xu, Jing; Chen, Zhi-Yuan; Lei, E.; Liu, Xiang-Shuai; Liu, Chun-Guang

    2017-02-01

    In present work, four complexes have been designed to investigate the effect of Li+ cation and substituent on the geometric structures and a series of electronic properties using density functional theory. The calculated results indicate that the charge decomposition (CDA) analysis and extend charge decomposition analysis (ECDA) of four complexes have the same sequence. The average d values defined the distances between C60 and corannulene display the inverse sequence. Consequently, the cooperative coupling of the Li+ cation and appropriate substituent is predicted to be an effective way to enhance the charge transfer between the C60 and corannulene derivatives.

  17. Simulation and Analysis of Photo-charge Transfer Characteristics of Bipolar Junction Photogate Transistor for CMOS Imagers

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The principle of the two carriers contributing to carry the pixel signal charges is firstly presented,and then the bipolar junction photogate transistor(BJPT)with high performance is proposed for the CMOS image sensor.The numerical analytical model of the photo-charge transfer for the bipolar junction photogate is established in detail. Some numerical simulations are obtained under 0.6μm CMOS process,which show that its readout rate increases exponentially with the increase of the photo-charge at applied voltage.

  18. Self-assembly of intramolecular charge-transfer compounds into functional molecular systems.

    Science.gov (United States)

    Li, Yongjun; Liu, Taifeng; Liu, Huibiao; Tian, Mao-Zhong; Li, Yuliang

    2014-04-15

    Highly polarized compounds exhibiting intramolecular charge transfer (ICT) are used widely as nonlinear optical (NLO) materials and red emitters and in organic light emitting diodes. Low-molecular-weight donor/acceptor (D/A)-substituted ICT compounds are ideal candidates for use as the building blocks of hierarchically structured, multifunctional self-assembled supramolecular systems. This Account describes our recent studies into the development of functional molecular systems with well-defined self-assembled structures based on charge-transfer (CT) interactions. From solution (sensors) to the solid state (assembled structures), we have fully utilized intrinsic and stimulus-induced CT interactions to construct these functional molecular systems. We have designed some organic molecules capable of ICT, with diversity and tailorability, that can be used to develop novel self-assembled materials. These ICT organic molecules are based on a variety of simple structures such as perylene bisimide, benzothiadiazole, tetracyanobutadiene, fluorenone, isoxazolone, BODIPY, and their derivatives. The degree of ICT is influenced by the nature of both the bridge and the substituents. We have developed new methods to synthesize ICT compounds through the introduction of heterocycles or heteroatoms to the π-conjugated systems or through extending the conjugation of diverse aromatic systems via another aromatic ring. Combining these ICT compounds featuring different D/A units and different degrees of conjugation with phase transfer methodologies and solvent-vapor techniques, we have self-assembled various organic nanostructures, including hollow nanospheres, wires, tubes, and ribbonlike architectures, with controllable morphologies and sizes. For example, we obtained a noncentrosymmetric microfiber structure that possessed a permanent dipole along its fibers' long axis and a transition dipole perpendicular to it; the independent NLO responses of this material can be separated and

  19. Exciton generation/dissociation/charge-transfer enhancement in inorganic/organic hybrid solar cells by robust single nanocrystalline LnPxOy (Ln = Eu, Y) doping.

    Science.gov (United States)

    Jin, Xiao; Sun, Weifu; Chen, Zihan; Wei, Taihuei; Chen, Chuyang; He, Xingdao; Yuan, Yongbiao; Li, Yue; Li, Qinghua

    2014-06-11

    Low-temperature solution-processed photovoltaics suffer from low efficiencies because of poor exciton or electron-hole transfer. Inorganic/organic hybrid solar cell, although still in its infancy, has attracted great interest thus far. One of the promising ways to enhance exciton dissociation or electron-hole transport is the doping of lanthanide phosphate ions. However, the underlying photophysical mechanism remains poorly understood. Herein, by applying femtosecond transient absorption spectroscopy, we successfully distinguished hot electron, less energetic electron, hole transport from electron-hole recombination. Concrete evidence has been provided that lanthanide phosphate doping improves the efficiency of both hot electron and "less energetic" electron transfers from donor to acceptor, but the hole transport almost remains unchanged. In particular, the hot electron transfer lifetime was shortened from 30.2 to 12.7 ps, that is, more than 60% faster than pure TiO2 acceptor. Such improvement was ascribed to the facts that the conduction band (CB) edge energy level of TiO2 has been elevated by 0.2 eV, while the valence band level almost remains unchanged, thus not only narrowing the energy offset between CB levels of TiO2 and P3HT, but also meanwhile enlarging the band gap of TiO2 itself that permits one to inhibit electron-hole recombination within TiO2. Consequently, lanthanide phosphate doped TiO2/P3HT bulk-heterojunction solar cell has been demonstrated to be a promising hybrid solar cell, and a notable power conversion efficiency of 2.91% is therefore attained. This work indicates that lanthanide compound ions can efficiently facilitate exciton generation, dissociation, and charge transport, thus enhancing photovoltaic performance.

  20. Fe2+-Ti4+ vs. Fe2+-Fe3+ charge-transfer and short-range order in single chains of face-sharing octahedra: ellenbergerite and dumortierite

    Science.gov (United States)

    Chopin, C.; Langer, K.; Khomenko, V.

    2009-04-01

    In zoned pyrope megacrysts from the Dora-Maira UHP terrane, new, dark-violet colour varieties of the hexagonal, high-pressure silicate ellenbergerite extend the range of known Fe contents for this mineral from 0-0.1 to 0-0.4 atom pfu, for Ti contents commonly in the range 0.2-0.4 pfu. The new varieties show an extremely intense pleochroism, colourless for E perpendicular to c to deep Prussian blue for E//c, as compared to colourless to lilac or reddish purple for classical Fe-poor ellenbergerite. These features were the incentive for an electronic absorption spectroscopic study and a reappraisal of the interpretation of the charge transfers (CT), colour and ordering schemes in this group and the structurally related borosilicate dumortierite. Both structures are characterized by the presence of infinite single chains of face-sharing, partly vacant octahedra along the 6-fold screw axis and pseudo-hexad axis, respectively, in which the Fe and Ti atoms are partitioned. In the spectra of Fe-poor ellenbergerite, the presence of a single Fe2+-Ti4+ CT band near 19000 cm˘1 was taken as evidence for complete short-range ordering of Mg(Fe), Ti and vacancies in the octahedral single chain [1]. The E//c spectra of Fe-rich ellenbergerite show the same absorption band near 19000 cm˘1 but consistently flanked by another CT band near 14000 cm˘1 , the intensity of which increases with total Fe content. The latter is similar to the 12400 cm˘1 CT band observed as the single feature in E//c spectra of the isotructural (Ti-free and Fe-bearing) phosphoellenbergerite, and clearly assigned to Fe2+-Fe3+ CT in the octahedral single chain [1]. The same colour pattern occurs in the dumortierite group, with red Fe-poor, Ti-rich crystals showing a single CT band near 20000 cm˘1, blue Ti-poor crystals showing a single CT band near 16500 cm˘1, and violet Fe- and Ti-rich crystals showing a combination of the two bands [2]. In the light of the new data, we reinterpret the dumortierite colour

  1. Photo-induced charge transfer and relaxation of persistent charge carriers in polymer/nanocrystal composites for applications in hybrid solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Heinemann, Marc Daniel; Zutz, Folker; Kolny-Olesiak, Joanna; Borchert, Holgert; Riedel, Ingo; Parisi, Juergen [University of Oldenburg, Department of Physics, Energy and Semiconductor Research Laboratory, Oldenburg (Germany); Maydell, Karsten von [EWE Research Center for Energy Technology, Oldenburg (Germany)

    2009-12-09

    The photo-induced charge transfer and the dynamics of persistent charge carriers in blends of semiconducting polymers and nanocrystals are investigated. Regioregular poly(3-hexylthiophene) (P3HT) is used as the electron donor material, while the acceptor moiety is established by CdSe nanocrystals (nc-CdSe) prepared via colloidal synthesis. As a reference system, organic blends of P3HT and [6,6]-phenyl C{sub 61}-butyric acid methyl ester (PCBM) are studied as well. The light-induced charge transfer between P3HT and the acceptor materials is studied by photoluminescence (PL), photo-induced absorption (PIA) and light-induced electron spin resonance spectroscopy (LESR). Compared to neat P3HT samples, both systems show an intensified formation of polarons in the polymer upon photo-excitation, pointing out successful separation of photogenerated charge carriers. Additionally, relaxation of the persistent charge carriers is investigated, and significant differences are found between the hybrid composite and the purely organic system. While relaxation, reflected in the transient signal decay of the polaron signal, is fast in the organic system, the hybrid blends exhibit long-term persistence. The appearance of a second, slow recombination channel indicates the existence of deep trap states in the hybrid system, which leads to the capture of a large fraction of charge carriers. A change of polymer conformation due to the presence of nc-CdSe is revealed by low temperature LESR measurements and microwave saturation techniques. The impact of the different recombination behavior on the photovoltaic efficiency of both systems is discussed. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  2. Studies on charge production from Cs2Te photocathodes in the PITZ L-band normal conducting radio frequency photo injector

    CERN Document Server

    Hernandez-Garcia, C; Asova, G; Bakr, M; Boonpornprasert, P; Good, J; Gross, M; Huck, H; Isaev, I; Kalantaryan, D; Khojoyan, M; Kourkafas, G; Lishilin, O; Malyutin, D; Melkumyan, D; Oppelt, A; Otevrel, M; Pathak, G; Renier, Y; Rublack, T; Stephan, F; Vashchenko, G; Zhao, Q

    2016-01-01

    This paper discusses the behavior of electron bunch charge produced in an L-band normal conducting radio frequency cavity (RF gun) from Cs2Te photocathodes illuminated with ps-long UV laser pulses when the laser transverse distribution consists of a flat-top core with Gaussian-like decaying halo. The produced charge shows a linear dependence at low laser pulse energies as expected in the quantum efficiency limited emission regime, while its dependence on laser pulse energy is observed to be much weaker for higher values, due to space charge limited emission. However, direct plug-in of experimental parameters into the space charge tracking code ASTRA yields lower output charge in the space charge limited regime compared to measured values. The rate of increase of the produced charge at high laser pulse energies close to the space charge limited emission regime seems to be proportional to the amount of halo present in the radial laser profile since the charge from the core has saturated already. By utilizing co...

  3. A multi-state fragment charge difference approach for diabatic states in electron transfer: extension and automation.

    Science.gov (United States)

    Yang, Chou-Hsun; Hsu, Chao-Ping

    2013-10-21

    The electron transfer (ET) rate prediction requires the electronic coupling values. The Generalized Mulliken-Hush (GMH) and Fragment Charge Difference (FCD) schemes have been useful approaches to calculate ET coupling from an excited state calculation. In their typical form, both methods use two eigenstates in forming the target charge-localized diabatic states. For problems involve three or four states, a direct generalization is possible, but it is necessary to pick and assign the locally excited or charge-transfer states involved. In this work, we generalize the 3-state scheme for a multi-state FCD without the need of manual pick or assignment for the states. In this scheme, the diabatic states are obtained separately in the charge-transfer or neutral excited subspaces, defined by their eigenvalues in the fragment charge-difference matrix. In each subspace, the Hamiltonians are diagonalized, and there exist off-diagonal Hamiltonian matrix elements between different subspaces, particularly the charge-transfer and neutral excited diabatic states. The ET coupling values are obtained as the corresponding off-diagonal Hamiltonian matrix elements. A similar multi-state GMH scheme can also be developed. We test the new multi-state schemes for the performance in systems that have been studied using more than two states with FCD or GMH. We found that the multi-state approach yields much better charge-localized states in these systems. We further test for the dependence on the number of state included in the calculation of ET couplings. The final coupling values are converged when the number of state included is increased. In one system where experimental value is available, the multi-state FCD coupling value agrees better with the previous experimental result. We found that the multi-state GMH and FCD are useful when the original two-state approach fails.

  4. A multi-state fragment charge difference approach for diabatic states in electron transfer: Extension and automation

    Science.gov (United States)

    Yang, Chou-Hsun; Hsu, Chao-Ping

    2013-10-01

    The electron transfer (ET) rate prediction requires the electronic coupling values. The Generalized Mulliken-Hush (GMH) and Fragment Charge Difference (FCD) schemes have been useful approaches to calculate ET coupling from an excited state calculation. In their typical form, both methods use two eigenstates in forming the target charge-localized diabatic states. For problems involve three or four states, a direct generalization is possible, but it is necessary to pick and assign the locally excited or charge-transfer states involved. In this work, we generalize the 3-state scheme for a multi-state FCD without the need of manual pick or assignment for the states. In this scheme, the diabatic states are obtained separately in the charge-transfer or neutral excited subspaces, defined by their eigenvalues in the fragment charge-difference matrix. In each subspace, the Hamiltonians are diagonalized, and there exist off-diagonal Hamiltonian matrix elements between different subspaces, particularly the charge-transfer and neutral excited diabatic states. The ET coupling values are obtained as the corresponding off-diagonal Hamiltonian matrix elements. A similar multi-state GMH scheme can also be developed. We test the new multi-state schemes for the performance in systems that have been studied using more than two states with FCD or GMH. We found that the multi-state approach yields much better charge-localized states in these systems. We further test for the dependence on the number of state included in the calculation of ET couplings. The final coupling values are converged when the number of state included is increased. In one system where experimental value is available, the multi-state FCD coupling value agrees better with the previous experimental result. We found that the multi-state GMH and FCD are useful when the original two-state approach fails.

  5. Consistent LDA' + DMFT approach to the electronic structure of transition metal oxides: Charge transfer insulators and correlated metals

    Energy Technology Data Exchange (ETDEWEB)

    Nekrasov, I. A., E-mail: nekrasov@iep.uran.ru; Pavlov, N. S.; Sadovskii, M. V. [Russian Academy of Sciences, Institute for Electrophysics, Ural Branch (Russian Federation)

    2013-04-15

    We discuss the recently proposed LDA' + DMFT approach providing a consistent parameter-free treatment of the so-called double counting problem arising within the LDA + DMFT hybrid computational method for realistic strongly correlated materials. In this approach, the local exchange-correlation portion of the electron-electron interaction is excluded from self-consistent LDA calculations for strongly correlated electronic shells, e.g., d-states of transition metal compounds. Then, the corresponding double-counting term in the LDA' + DMFT Hamiltonian is consistently set in the local Hartree (fully localized limit, FLL) form of the Hubbard model interaction term. We present the results of extensive LDA' + DMFT calculations of densities of states, spectral densities, and optical conductivity for most typical representatives of two wide classes of strongly correlated systems in the paramagnetic phase: charge transfer insulators (MnO, CoO, and NiO) and strongly correlated metals (SrVO{sub 3} and Sr{sub 2}RuO{sub 4}). It is shown that for NiO and CoO systems, the LDA' + DMFT approach qualitatively improves the conventional LDA + DMFT results with the FLL type of double counting, where CoO and NiO were obtained to be metals. Our calculations also include transition-metal 4s-states located near the Fermi level, missed in previous LDA + DMFT studies of these monoxides. General agreement with optical and the X-ray experiments is obtained. For strongly correlated metals, the LDA' + DMFT results agree well with the earlier LDA + DMFT calculations and existing experiments. However, in general, LDA' + DMFT results give better quantitative agreement with experimental data for band gap sizes and oxygen-state positions compared to the conventional LDA + DMFT method.

  6. Consistent LDA' + DMFT approach to the electronic structure of transition metal oxides: Charge transfer insulators and correlated metals

    Science.gov (United States)

    Nekrasov, I. A.; Pavlov, N. S.; Sadovskii, M. V.

    2013-04-01

    We discuss the recently proposed LDA' + DMFT approach providing a consistent parameter-free treatment of the so-called double counting problem arising within the LDA + DMFT hybrid computational method for realistic strongly correlated materials. In this approach, the local exchange-correlation portion of the electron-electron interaction is excluded from self-consistent LDA calculations for strongly correlated electronic shells, e.g., d-states of transition metal compounds. Then, the corresponding double-counting term in the LDA' + DMFT Hamiltonian is consistently set in the local Hartree (fully localized limit, FLL) form of the Hubbard model interaction term. We present the results of extensive LDA' + DMFT calculations of densities of states, spectral densities, and optical conductivity for most typical representatives of two wide classes of strongly correlated systems in the paramagnetic phase: charge transfer insulators (MnO, CoO, and NiO) and strongly correlated metals (SrVO3 and Sr2RuO4). It is shown that for NiO and CoO systems, the LDA' + DMFT approach qualitatively improves the conventional LDA + DMFT results with the FLL type of double counting, where CoO and NiO were obtained to be metals. Our calculations also include transition-metal 4 s-states located near the Fermi level, missed in previous LDA + DMFT studies of these monoxides. General agreement with optical and the X-ray experiments is obtained. For strongly correlated metals, the LDA' + DMFT results agree well with the earlier LDA + DMFT calculations and existing experiments. However, in general, LDA' + DMFT results give better quantitative agreement with experimental data for band gap sizes and oxygen-state positions compared to the conventional LDA + DMFT method.

  7. Charge transfer effects on the Fermi surface of Ba{sub 0.5}K{sub 0.5}Fe{sub 2}As{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Nazir, S.; Zhu, Z.Y.; Schwingenschloegl, U. [KAUST, PSE Division, Thuwal 23955-6900 (Saudi Arabia)

    2011-03-15

    Ab-initio calculations within density functional theory are performed to obtain a more systematic understanding of the electronic structure of iron pnictides. As a prototypical compound we study Ba{sub 0.5}K{sub 0.5}Fe{sub 2}As{sub 2} and analyze the changes of its electronic structure when the interaction between the Fe{sub 2}As{sub 2} layers and their surrounding is modified. We find strong effects on the density of states near the Fermi energy as well as the Fermi surface. The role of the electron donor atoms in iron pnictides thus cannot be understood in a rigid band picture. Instead, the bonding within the Fe{sub 2}As{sub 2} layers reacts to a modified charge transfer from the donor atoms by adapting the intra-layer Fe-As hybridization and charge transfer in order to maintain an As{sup 3-} valence state. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Charge-transfer complexes of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with amino molecules in polar solvents.

    Science.gov (United States)

    Berto, Silvia; Chiavazza, Enrico; Ribotta, Valentina; Daniele, Pier Giuseppe; Barolo, Claudia; Giacomino, Agnese; Vione, Davide; Malandrino, Mery

    2015-01-01

    The charge-transfer complexes have scientific relevance because this type of molecular interaction is at the basis of the activity of pharmacological compounds and because the absorption bands of the complexes can be used for the quantification of electron donor molecules. This work aims to assess the stability of the charge-transfer complexes between the electron acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and two drugs, procaine and atenolol, in acetonitrile and ethanol. The stability of DDQ in solution and the time required to obtain the maximum complex formation were evaluated. The stoichiometry and the stability of the complexes were determined, respectively, by Job's plot method and by the elaboration of UV-vis titrations data. The latter task was carried out by using the non-linear global analysis approach to determine the equilibrium constants. This approach to data elaboration allowed us to overcome the disadvantages of the classical linear-regression method, to obtain reliable values of the association constants and to calculate the entire spectra of the complexes. NMR spectra were recorded to identify the portion of the donor molecule that was involved in the interaction. The data support the participation of the aliphatic amino groups in complex formation and exclude the involvement of the aromatic amine present in the procaine molecule.

  9. Ground-state oxygen holes and the metal-insulator transition in the negative charge-transfer rare-earth nickelates

    Science.gov (United States)

    Bisogni, Valentina; Catalano, Sara; Green, Robert J.; Gibert, Marta; Scherwitzl, Raoul; Huang, Yaobo; Strocov, Vladimir N.; Zubko, Pavlo; Balandeh, Shadi; Triscone, Jean-Marc; Sawatzky, George; Schmitt, Thorsten

    2016-10-01

    The metal-insulator transition and the intriguing physical properties of rare-earth perovskite nickelates have attracted considerable attention in recent years. Nonetheless, a complete understanding of these materials remains elusive. Here we combine X-ray absorption and resonant inelastic X-ray scattering (RIXS) spectroscopies to resolve important aspects of the complex electronic structure of rare-earth nickelates, taking NdNiO3 thin film as representative example. The unusual coexistence of bound and continuum excitations observed in the RIXS spectra provides strong evidence for abundant oxygen holes in the ground state of these materials. Using cluster calculations and Anderson impurity model interpretation, we show that distinct spectral signatures arise from a Ni 3d8 configuration along with holes in the oxygen 2p valence band, confirming suggestions that these materials do not obey a conventional positive charge-transfer picture, but instead exhibit a negative charge-transfer energy in line with recent models interpreting the metal-insulator transition in terms of bond disproportionation.

  10. A spectrophotometric and thermodynamic study of the charge-transfer complexes of iodine with 2-aminomethyl-15-crown-5 in chloroform and 1,2-dichloroethane solutions.

    Science.gov (United States)

    Hasani, Masoumeh; Akbari, Sakineh

    2007-05-01

    Interaction of 2-aminomethyl-15-crown-5 (AM15C5) with iodine has been investigated spectrophotometrically in chloroform and 1,2-dichloroethane (1,2-DCE) solutions. The observed time dependence of the charge-transfer band and subsequent formation of I(3)(-) in solution were related to the slow transformation of the initially formed 1:1 AM15C5.I(2) outer complex to an inner electron donor-acceptor (EDA) complex, followed by fast reaction of the inner complex with iodine to form a triiodide ion. The pseudo-first-order rate constants were evaluated from the absorbance- and conductivity-time data. The stoichiometry and formation constants of the resulting EDA complexes have also been determined. Thermodynamic parameters, Delta H degrees and Delta S degrees , of the complexes have been determined from the temperature dependence of stability constants by Van't Hoff equation. The results indicate that iodine complexes of AM15C5 in both solvents are enthalpy stabilized but entropy destabilized. The influence of solvent properties on the kinetics and stability of the resulting charge-transfer complexes are discussed.

  11. First-principles study of Sr2Ir1-xRhxO4: charge transfer, spin-orbit coupling change, and the metal-insulator transition

    Science.gov (United States)

    Sim, Jae-Hoon; Kim, Heung-Sik; Han, Myung Joon

    2015-03-01

    Using first-principles density functional theory (DFT) calculations, we investigated the electronic structure of Rh-doped iridate, Sr2Ir1-xRhxO4 for which the doping (x) dependent metal-insulator transition (MIT) has been reported experimentally and the controversial discussion developed regarding the origin of this transition. Our DFT+U calculation shows that the value of remains largely intact over the entire doping range considered here (x = 0 . 0 , 0 . 125 , 0 . 25 , 0 . 50 , 0 . 75 , and 1 . 0) in good agreement with the branching ratio measured by x-ray absorption spectroscopy. Also contrary to a previous picture to explain MIT based on the charge transfer between the transition-metal sites, our calculation clearly shows that those sites remain basically isoelectronic while the impurity bands of predominantly rhodium character are introduced near the Fermi level. As the doping increases, this impurity band overlaps with lower Hubbard band of iridium, leading to metal-insulator transition. The results will be discussed with comparison to the case of Ru doping. Computational resources were suported by The National Institute of Supercomputing and Networking/Korea Institute of Science and Technology Information with supercomputing resources including technical spport (Grant No. KSC-2013-C2-23).

  12. Intervalence Charge Transfer Luminescence: Interplay between anomalous and 5d-4f emissions in Yb-doped fluorite-type crystals

    CERN Document Server

    Barandiaran, Zoila

    2014-01-01

    We report the existence of intervalence charge transfer (IVCT) luminescence in Yb-doped fluorites associated with Yb2+-Yb3+ mixed valence pairs. We show that the very broad band, anomalous emission of Yb2+-doped CaF2 and SrF2, usually associated with impurity-trapped excitons, is, rather, an IVCT luminescence associated with Yb2+-Yb3+ mixed valence pairs. It is very efficiently excited by a two-photon upconversion mechanism. The IVCT vertical transition leaves the pair moieties very far from their equilibrium structures; this explains the unexpectedly large band width of the emission band and its low peak energy, because the large reorganization energies are substracted from the normal emission. The ab initio IVCT energy diagrams explain the different luminescent properties of Yb-doped CaF2, SrF2, BaF2, and SrCl2: the presence of IVCT luminescence in Yb-doped CaF2 and SrF2; its coexistence with regular 5d-4f emission in SrF2; its absence in BaF2 and SrCl2; the quenching of all emissions in BaF2; and the prese...

  13. Use of Surface Photovoltage Spectroscopy to Measure Built-in Voltage, Space Charge Layer Width, and Effective Band Gap in CdSe Quantum Dot Films.

    Science.gov (United States)

    Zhao, Jing; Nail, Benjamin A; Holmes, Michael A; Osterloh, Frank E

    2016-09-01

    Surface photovoltage spectroscopy (SPS) was used to study the photochemistry of mercaptoethanol-ligated CdSe quantum dot (2.0-4.2 nm diameter) films on indium doped tin oxide (ITO) in the absence of an external bias or electrolyte. The n-type films generate negative voltages under super band gap illumination (0.1-0.5 mW cm(-2)) by majority carrier injection into the ITO substrate. The photovoltage onset energies track the optical band gaps of the samples and are assigned as effective band gaps of the films. The photovoltage values (-125 to -750 mV) vary with quantum dot sizes and are modulated by the built-in potential of the CdSe-ITO Schottky type contacts. Deviations from the ideal Schottky model are attributed to Fermi level pinning in states approximately 1.1 V negative of the ITO conduction band edge. Positive photovoltage signals of +80 to +125 mV in films of >4.0 nm nanocrystals and in thin (70 nm) nanocrystal films are attributed to electron-hole (polaron) pairs that are polarized by a space charge layer at the CdSe-ITO boundary. The space charge layer is 70-150 nm wide, based on thickness-dependent photovoltage measurements. The ability of SPS to directly measure built-in voltages, space charge layer thickness, sub-band gap states, and effective band gaps in drop-cast quantum dot films aids the understanding of photochemical charge transport in quantum dot solar cells.

  14. Charge-transfer interactions of metoclopramide nausea drug against six kind of π-acceptors: spectral and thermal discussions.

    Science.gov (United States)

    El-Habeeb, Abeer A; Al-Saif, Foziah A; Refat, Moamen S

    2014-04-05

    The target of this paper is aimed to discuss the fast and newly techniques in order to assessment the metoclopramide (Mcp) nausea drug in pure form in solid and solution shape with different kind of π-acceptors upon charge transfer interactions. Charge-transfer complexes (CTC) of metoclopramide with picric acid (PA), 2,3-dichloro-5,6-dicyano-p-benzoquinon (DDQ), tetracyanoquinodimethane (TCNQ), m-dinitrobenzene (DNB), p-nitrobenzoic acid (p-NBA) and tetrachloro-p-quinon (p-CL) have been studied spectrophotometrically in absolute methanol at room temperature. The stoichiometries of the complexes were found to be 1:1 ratio by the spectrophotometric titration between metoclopramide and represented π-acceptors. The equilibrium constants, molar extinction coefficient (εCT) and spectroscopic-physical parameters (standard free energy (ΔG°), oscillator strength (ƒ), transition dipole moment (μ), resonance energy (RN) and ionization potential (ID)) of the complexes were determined upon the modified Benesi-Hildebrand equation. The results indicate that the formation constants for the complexes depend on the nature of electron acceptors and configuration of drug donor, and also the spectral studies of the complexes were determined by (infrared, Raman, and (1)H NMR) spectra and X-ray powder diffraction (XRD). The charge-transfer complexes are formed during the interaction of electron-acceptors and electron-donors as result of partial or complete transfer of a negative charge from (D(+)-A(-)).

  15. Implementing Metal-to-Ligand Charge Transfer in Organic Semiconductor for Improved Visible-Near-Infrared Photocatalysis.

    Science.gov (United States)

    Li, Yanrui; Wang, Zhaowu; Xia, Tong; Ju, Huanxin; Zhang, Ke; Long, Ran; Xu, Qian; Wang, Chengming; Song, Li; Zhu, Junfa; Jiang, Jun; Xiong, Yujie

    2016-08-01

    The coordination of organic semiconductors with metal cations can induce metal-to-ligand charge transfer, which broadens light absorption to cover the visible-near-infrared (vis-NIR) spectrum. As a proof-of-concept demonstration, the g-C3 N4 -based complex exhibits dramatically enhanced photocatalytic H2 production with excellent durability under vis-NIR irradiation.

  16. Coherence, energy and charge transfers in de-excitation pathways of electronic excited state of biomolecules in photosynthesis

    DEFF Research Database (Denmark)

    Bohr, Henrik; Malik, F. Bary

    2013-01-01

    The observed multiple de-excitation pathways of photo-absorbed electronic excited state in the peridinin–chlorophyll complex, involving both energy and charge transfers among its constituents, are analyzed using the bio-Auger (B-A) theory. It is also shown that the usually used F¨orster–Dexter th...

  17. Turn-on fluorescence probes based on pyranine/viologen charge-transfer complexes for the determination of nucleotides

    Energy Technology Data Exchange (ETDEWEB)

    Schäferling, Michael, E-mail: Michael.schaeferling@utu.fi; Lang, Thomas; Schnettelker, Annette

    2014-10-15

    The formation of ground state charge-transfer complexes between pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid) and viologen (paraquat) derivatives is utilized for the design of novel fluoroionophores for the determination of phosphate species, particularly of nucleotides. The strong quenching of the pyranine fluorescence by viologen-type charge transfer acceptors can be countermanded if these are functionalized with triethylammonium groups that serve as recognition elements for phosphate anions. We report on the fluorogenic responses of these water-soluble molecular probes in presence of different phosphates. Absorbance measurements give additional information on the charge transfer complex formation and the interaction with nucleotides. The experimental data show that these aggregates form attractive, simple and versatile fluorescence turn-on probes for nucleoside triphosphates. The reversibility of the fluorescence response is demonstrated by means of an enzymatic model assay using ATPase for the decomposition of adenosine triphosphate. - Highlights: • Pyranine/viologen charge-transfer complexes as molecular probe for ATP recognition. • Fluorescence turn on mechanism. • Selective compared to other nucleotides and phosphate anions. • Fast and reversible response applicable to monitor enzymatic reactions.

  18. Charge Transfer Inefficiency in Pinned Photodiode CMOS image sensors: Simple Montecarlo modeling and experimental measurement based on a pulsed storage-gate method

    Science.gov (United States)

    Pelamatti, Alice; Goiffon, Vincent; Chabane, Aziouz; Magnan, Pierre; Virmontois, Cédric; Saint-Pé, Olivier; de Boisanger, Michel Breart

    2016-11-01

    The charge transfer time represents the bottleneck in terms of temporal resolution in Pinned Photodiode (PPD) CMOS image sensors. This work focuses on the modeling and estimation of this key parameter. A simple numerical model of charge transfer in PPDs is presented. The model is based on a Montecarlo simulation and takes into account both charge diffusion in the PPD and the effect of potential obstacles along the charge transfer path. This work also presents a new experimental approach for the estimation of the charge transfer time, called pulsed Storage Gate (SG) method. This method, which allows reproduction of a "worst-case" transfer condition, is based on dedicated SG pixel structures and is particularly suitable to compare transfer efficiency performances for different pixel geometries.

  19. Valence Topological Charge-Transfer Indices for Reflecting Polarity: Correction for Heteromolecules

    Directory of Open Access Journals (Sweden)

    F. Torrens

    2005-02-01

    Full Text Available Valence topological charge-transfer (CT indices are applied to the calculationof dipole moments μ. The μ calculated by algebraic and vector semisums of the CTindices are defined. The model is generalized for molecules with heteroatoms andcorrected for sp3-heteromolecules. The ability of the indices for the description of themolecular charge distribution is established by comparing them with μ of the valence-isoelectronic series of cyclopentadiene, benzene and styrene. Two CT indices, μvec(vector semisum of vertex-pair μ and μvecV (valence μvec are proposed. The μvecVbehaviour is intermediate between μvec and μexperiment. The correction is produced in thecorrect direction. The best results are obtained for the greatest group. Inclusion of theheteroatom in the π-electron system is beneficial for the description of μ, owing to eitherthe role of additional p and/or d orbitals provided by the heteroatom or the role of stericfactors in the π-electron conjugation. The steric effect is almost constant along the seriesand the dominating effect is electronic. Inclusion of the heteroatom enhances μ, whichcan improve the solubility of the molecule. For heteroatoms in the same group, the ringsize and the degree of ring flattering are inversely proportional to their electronegativity.

  20. The effect of thermal motion on the electron localization in metal-to-ligand charge transfer excitations in [Fe(bpy)3](2+).

    Science.gov (United States)

    Domingo, Alex; Sousa, Carmen; de Graaf, Coen

    2014-12-21

    Accurate electronic structure calculations of the lowest excited states have been performed on twenty snapshots of a molecular dynamics simulation of [Fe(bpy)3](2+) dissolved in water. The thermal motion distorts the structure of the complex from its average D3 symmetry, causing the localization on one bipyridine ligand of the excited electron in the metal-to-ligand charge transfer (MLCT) state. The excitation energy is about 0.25 eV lower than that for the delocalized description of the MLCT state and is in good agreement with experiments. The composition of the MLCT band is carefully analyzed and the effect of thermal motion on the mechanism of light-induced spin crossover is discussed.