| 1. |
- Crispin, Xavier, et al.
(author)
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Chemisorption of acrylonitrile on the Cu(100) surface: A local density functional study
- 1999
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In: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 111:7, s. 3237-3251
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Journal article (peer-reviewed)abstract
- The possibility of chemically grafting polyacrylonitrile onto transition metal electrodes via electropolymerization leads to promising applications in the fields of corrosion protection or metal surface functionalization. The initial step of the electrografting mechanism is the adsorption of the acrylonitrile monomer on the metal surface from solution. Here, we investigate theoretically this adsorption process on the copper (100) surface; Density Functional Theory is used in the Local Spin Density approximation to describe the electronic and structural properties of acrylonitrile adsorbed on copper clusters. The chemisorption of acrylonitrile on the copper surface is confirmed experimentally via X-Ray Photoelectron Spectroscopy. The thermodynamic characteristics of the adsorption process are also studied via statistical mechanics. Finally, determining the influence of the copper cluster size on the adsorption of acrylonitrile allows to extrapolate the properties of the acrylonitrile/Cu(100) surface from those of acrylonitrile/copper clusters. (C) 1999 American Institute of Physics. [S0021-9606(99)70231-X].
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| 2. |
- Johansson, N., et al.
(author)
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Electronic structure of tris(8-hydroxyquinoline) aluminum thin films in the pristine and reduced states
- 1999
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In: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 111:5, s. 2157-2163
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Journal article (peer-reviewed)abstract
- The electronic structure of tris(8-hydroxyquinoline) aluminum (Alq(3)) has been studied in the pristine molecular solid state as well as upon interaction (doping) with potassium and lithium. We discuss the results of a joint theoretical and experimental investigation, based on a combination of x-ray and ultraviolet photoelectron spectroscopies with quantum-chemical calculations at the density functional theory level. Upon doping, each electron transferred from an alkali metal atom is stored on one of the three ligands of the Alq(3) molecule, resulting in a new spectral feature (peak) in the valence band that evolves uniformly when going from a doping level of one to three metal atoms per Alq(3) molecule. (C) 1999 American Institute of Physics. [S0021-9606(99)50628-4].
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| 3. |
- Lazzaroni, R., et al.
(author)
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Chemical and electronic aspects of metal/conjugated polymer interfaces : Implications for electronic devices
- 1995
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In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 71:1-3, s. 2159-2162
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Journal article (peer-reviewed)abstract
- The chemical nature and the electronic structure of metal/conjugated polymer interfaces are investigated in the context of polymer-based light-emitting diodes. We consider the interaction of low-workfunction metals (Al, Ca) with the surface of conjugated polymers or model oligomer molecules with a combined experimental and theoretical approach. The early stages of the interface formation are followed with X-ray and ultraviolet photoelectron spectroscopies and the experimental data are compared to the results of quantum chemical calculations. The reactions of Al and Ca with the organic surface are found to be fundamentally different: while the former forms new covalent bonds onto the polymer backbone, the latter tends to dope the conjugated system. Both types of reaction are expected to modify drastically the electronic properties of the polymer semiconductor.
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| 4. |
- Lögdlund, Michael, et al.
(author)
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Theoretical and experimental studies of the interaction between sodium and oligothiophenes
- 1996
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In: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 53:24, s. 16327-16333
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Journal article (peer-reviewed)abstract
- Quantum-chemical calculations and ultraviolet photoelectron spectroscopy (UPS) measurements have been performed in order to study the interaction between sodium and oligothiophenes, with a focus on the origin of experimentally observed relaxation energy effects in alkali-metal-doped conjugated molecules. Upon doping of a -sexithienylene (α-6T) with sodium atoms, (1) a broad feature appears in the valence band, in an energy region corresponding to the band gap in pristine α-6T, and (2) certain structural features in the valence band shift towards lower binding energies in the doped material. In particular, upon doping, a structural peak related to electronic levels mainly localized to the sulfur and b-carbon atoms destabilizes to an energy corresponding to that of the valence-band edge in pristine α-6T. The results of ab initio Hartree-Fock and local-spin-density calculations on α-trithienylene and bithiophene are consistent with the experimental data, and allow for an assignment of these destabilization effects in terms of initial-state relaxations. We stress that similar destabi-lization effects, reported for other alkali-metal-doped conjugated systems, had previously been proposed to be associated with final-state electronic screening, i.e., a dynamic artifact within the UPS measurements; this is in contradiction to the results of our ab initio theoretical studies. Our present results show that all structural features in the UPS data are contained in the results of sufficiently complete quantum chemical calculations.
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