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  • 1
    Electronic Resource
    Electronic Resource
    Optical Absorption Spectra of Aromatic Isothianaphthene Oligomers: Theory and Experiment (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 3932-3938 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100012a011
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  • 2
    Electronic Resource
    Electronic Resource
    Electronic structure of molecular van der Waals complexes with benzene: Implications for the contrast in scanning tunneling microscopy of molecular adsorbates on graphite (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 99-105 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the electronic structure of molecular model systems in order to improve our understanding of the nature of the contrast, which is observed in the scanning tunneling microscopy (STM) imaging of organic adsorbates on graphite. The model systems consist of a benzene molecule, representing the substrate surface, interacting with various molecules representing alkyl chains, oxygen- and sulfur-containing groups, fluorinated species, and aromatic rings. We perform quantum-chemical calculations to determine the geometric structure, stability, and electronic structure of these molecular complexes and analyze the theoretical results in relation with experimental STM data obtained on monolayers physisorbed on graphite. It appears that the STM contrast can be correlated to the energy difference between the electronic levels of the substrate and those of the adsorbate. Finally, we observe that the introduction of a uniform electric field in the quantum-chemical modeling can enhance the electronic interaction between the partners in the complex. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474356
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  • 3
    Electronic Resource
    Electronic Resource
    Theoretical investigation of the structure and electronic properties of poly(dithieno[3,4-b:3',4'-d]thiophene), a small-band-gap conjugated polymer (1993)
    s.l. : American Chemical Society
    Macromolecules 26 (1993), S. 1260-1264 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00058a010
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  • 4
    Electronic Resource
    Electronic Resource
    The chemical and electronic structure of the interface between aluminum and polythiophene semiconductors (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 664-672 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated the chemical nature and the electronic structure of the interface between a low work function metal, aluminum, and a conjugated polymer semiconductor, polythiophene. We have studied the initial stages of the interface formation by depositing the metal onto the surface of a polymer film. Charge transfer processes between the metal and the polymer are analyzed using core-level x-ray photoelectron spectroscopy (XPS); the evolution upon metallization of the valence electronic levels directly related to the polymer electronic structure is followed with ultraviolet photoelectron spectroscopy (UPS). With these techniques, we investigate the deposition of aluminum on two polythiophene systems (i) the alkyl-substituted poly-3-octylthiophene and (ii) the α-sexithiophene oligomer. The experimental data are compared to the results of a recent quantum chemical study on model systems consisting of thiophene oligomers (up to sexithiophene) interacting with a few Al atoms. The interaction of polythiophene with Al atoms is found to modify dramatically the structure of the conjugated backbone, as strong carbon–aluminum bonds are formed in the α positions of the thiophene rings. A large charge transfer takes place from the Al atoms to the polymer chain, and the upper π levels of the polymer are strongly affected. The metallization is contrasted to the doping of conjugated polymers with alkali metals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466217
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  • 5
    Electronic Resource
    Electronic Resource
    A photoelectron spectroscopic study of the electrochemical processes in polyaniline (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2187-2193 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic structure of the base forms of electrochemically prepared polyaniline is studied by means of x-ray photoelectron spectroscopy (XPS). Model compounds for the amine, imine and crosslinked nitrogen sites provide the references for the analysis of the core level spectra in the polymer. In particular, the analysis of the nitrogen 1s spectra represents a useful method for accurate determination of the amine to imine ratio. The evolution in the concentration of the different nitrogen species as a function of the electrochemical potential is shown to be in good agreement with the results of cyclic voltammetry measurements. Varying the pH leads to large modifications in the stability domain of the different oxidation states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458010
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  • 6
    Electronic Resource
    Electronic Resource
    Electronic structure of polyisothianaphthene (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4257-4262 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the electronic structure of polyisothianaphthene, comparing the experimental data obtained by x-ray photoelectron spectroscopy (XPS) with the results of valence effective Hamiltonian calculations. In the neutral form, the theoretical density of valence states is in very good agreement with the experimental measurements. The shifts observed for the core and valence levels upon doping confirm the very low value of the band gap in this system. Several models explaining the evolution of the line shapes in the oxidized polymer are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453834
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  • 7
    Electronic Resource
    Electronic Resource
    The poly-3-hexylthiophene/NOPF6 system: A photoelectron spectroscopy study of electronic structural changes induced by the charge transfer in the solid state (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4433-4439 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic structure of poly-3-hexylthiophene (P3HT) is studied in the solid state with photoelectron spectroscopy, as the polymer is gradually doped from NOPF6. Solubility and processability of P3HT allow for the preparation of very clean and very thin films, which are then doped without air-exposure. The evolution of the core level binding energies is related to the modification of the electron density on the conjugated backbone, due to the creation of polaron and bipolaron defects. Upon doping, valence spectra show a shift in the Fermi level of the system, and at saturation doping a finite density of states at the Fermi level is observed unambiguously for the first time in electrically conducting polymers with photoelectron spectroscopy. The experimental data on core and valence levels can be interpreted in terms of the formation of a polaron lattice at high doping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458725
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  • 8
    Electronic Resource
    Electronic Resource
    Reactions of low work function metals Na, Al, and Ca on α,ω-diphenyltetradecaheptaene. Implications for metal/polymer interfaces (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 6765-6771 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The interactions between different low work function metals aluminium, calcium and sodium, and α,ω-diphenyltetradecaheptaene, a model molecule for certain conjugated polymers, have been investigated using both x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. The spectra are interpreted with the help of the results of quantum chemical calculations performed within the local spin density (LSD) approximation methodology. The metals are found to interact with the conjugated system in very different ways. Aluminium forms a covalent bond, which strongly modifies the π-electronic structure of the conjugated molecule, while both the sodium and the calcium atoms act as doping agents, inducing new states in the otherwise forbidden bandgap. These new gap states can be viewed as a soliton–antisoliton pair for the Na/DP7 and a bipolaronic-like defect for Ca/DP7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467035
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  • 9
    Electronic Resource
    Electronic Resource
    Metal/conjugated polymer interfaces: A local density functional study of aluminum/polyene interactions (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 9258-9264 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The interactions between aluminum atoms and model molecules representing trans-polyacetylene are studied quantum chemically by a local density functional method. We focus on the chemical and electronic structure of the organoaluminum complexes. Special emphasis is put on a comparison between results at the local spin density approximation and ab initio Hartree–Fock levels. In unmetallized polyenes, the density functional method provides a very good description of the carbon–carbon bond lengths of conjugated systems; in the case of hexatriene, it reproduces the bond dimerization in very good agreement with experimental measurements. Upon metallization, a strong covalent interaction between aluminum and carbon is found. The Al–C bond formation induces an interruption of the bond alternation pattern and reduces the π-conjugation in the oligomer, in qualitative agreement with photoelectron spectroscopy data and previous theoretical results at the Hartree–Fock level. Notably, the π-electron levels in the organoaluminum complexes maintain delocalization. In contrast to Hartree–Fock results where an aluminum atom binds to a single carbon, the interactions calculated with the local spin density approximation lead to (i) formation of multicenter aluminum–carbon bonding; (ii) near planarity of the polyene molecule; and (iii) a lower degree of charge transfer from the metal atom to the polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466678
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  • 10
    Electronic Resource
    Electronic Resource
    The aluminum/polyethylene terephthalate interface: A joint theoretical and experimental study (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 4299-4307 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The aluminum/polyethylene terephthalate interface is investigated with a combined theoretical and experimental approach, in order to understand the interactions occurring at the molecular level when the metal is deposited onto the polymer surface. The theoretical approach consists in performing quantum-chemical calculations on short molecular model systems interacting with a few Al atoms. The geometric structure of the organometallic complex is optimized and its stability as well as the changes in charge density due to Al bonding are evaluated. The theoretical results are compared to experimental x-ray photoelectron spectroscopy data collected during the early stages of interface formation. In particular, the evolution of the polymer core level peaks is paralleled to the Al-induced modification of the charge density on the model molecules. Al is found to react preferentially with the ester group by forming covalent bonds with the oxygen and/or the carbon atom of that group. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469477
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