| 1. |
- de Jong, Michel P, et al.
(författare)
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The electronic structure of n- and p-doped phenyl-capped 3,4-ethylenedioxythiophene trimer
- 2003
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 118:14, s. 6495-6502
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Tidskriftsartikel (refereegranskat)abstract
- A study was conducted on the effects of chemical doping on the chemical and electronic structure of condensed molecular solid films of the ethylenedioxythiophene (EDOT) trimer using ultraviolet photoelectron spectroscopy (UPS) and x-ray photoelectron spectroscopy (XPS). Phenyl-capped EDOT oligomers were potential candidates for molecular electronics applications and serve as model molecules for PEDOT. By combining UPS, XPS, and NEXAFS, a clear picture of the doping induced changes in the electronic structure of phenyl-capped EDOT-trimer was obtained.
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| 2. |
- Osikowicz, Wojciech, et al.
(författare)
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A joint theoretical and experimental study on the electronic properties of phenyl-capped 3,4-ethylenedioxythiophene oligomers
- 2003
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 119:19, s. 10415-10420
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of a series of phenyl-capped EDOT oligomers was studied using ultraviolet photoelectron spectroscopy, in combination with quantum-chemical methods. The bulk IP of the neutral PEDOT polymer was estimated to be 4.2 eV. The frontier band structue was predicted from the evolution of the spectral features in the studied series of oligomers.
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| 3. |
- Riepl, M., et al.
(författare)
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Molecular gradients : An efficient approach for optimizing the surface properties of biomaterials and biochips
- 2005
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 21:3, s. 1042-1050
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Tidskriftsartikel (refereegranskat)abstract
- A variety of molecular gradients of alkanethiols with the structure HS-(CH2)m-X (m = 15, X = COOH, CH2NH 2, or CH3) and oligo(ethylene glycol)-terminated alkanethiols with the structures HS-(CH2)15-CO-NH-Eg n (n = 2, 4, or 6), HS-(CH2)15-CO-NH-Eg 2-(CH2)2-NH-CO-(CH2) 4-biotin, and HS-(CH2)15-CO-NH-Eg 6-CH2-COOH were prepared on polycrystalline gold films. These gradients were designed to serve as model surfaces for fundamental studies of protein adsorption and immobilization phenomena. Ellipsometry, infrared spectroscopy, and X-ray photoelectron spectroscopy, operating in scanning mode, were used to monitor the layer composition, gradient profiles, tail group conformation, and overall structural quality of the gradient assemblies. The gradient profiles were found to be 4-10 mm wide, and they increased in width with increasing difference in molecular complexity between the thiols used to form the gradient. The oligo(ethylene glycol) thiols are particularly interesting because they can be used to prepare so-called conformational gradients, that is, gradients that display a variation in oligo(ethylene glycol) chain conformation from all trans on the extreme Eg 2,4 sides, via an amorphous-like phase in the mixing regimes, to helical at the extreme Eg6 sides. We demonstrate herein a series of experiments where the above gradients are used to evaluate nonspecific binding of the plasma protein fibrinogen, and in agreement with previous studies, the highest amounts of nonspecifically bound fibrinogen were observed on all-trans monolayers, that is, on the extreme Eg2,4 sides. Moreover, gradients between Eg2 and a biotinylated analogue have been prepared to optimize the conditions for the immobilization of streptavidin. Ellipsometry and infrared spectroscopy reveal high levels of immobilization over a fairly broad range of compositions in the gradient regime, with a maximum between 50 and 60% of the biotinylated analogue in the monolayer. A pi gradient composed of (NH3+/COO-)-terminated thiols was also prepared and evaluated with respect to its ability to separate differently charged proteins, pepsin, and lysozyme, on a solid surface.
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| 4. |
- Van, Der Gon A.W.D., et al.
(författare)
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Modification of PEDOT-PSS by low-energy electrons
- 2002
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Ingår i: Organic electronics. - 1566-1199 .- 1878-5530. ; 3:3-4, s. 111-118
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Tidskriftsartikel (refereegranskat)abstract
- The stability of conjugated organic materials under electron transport is of great importance for the lifetime of devices such as polymer light-emitting diodes (PLEDs). Here, the modification of thin films of poly(3,4- ethylenedioxythiophene) oxidized with poly(4-styrenesulfonate) (known as PEDOT-PSS, often used in the fabrication of PLEDs) by low-energy electrons has been studied using X-ray photo-electron spectroscopy. Thin films of PSSH and molecular solid films of EDOT molecules also have been studied. We find that electrons with kinetic energies as low as 3 eV result in significant modification of the chemical structure of the materials. For thin films of PSSH, the electron bombardment leads to a strong loss of oxygen and a smaller loss of sulfur. In addition, a large amount of the sulfur atoms that remain in the films exhibits a different binding energy because of scissions of the bonds to oxygen atoms. For condensed molecular solid films of EDOT molecules, we find that the carbon atoms bonded to oxygen react and form additional bonds, as evidenced by a new component in the C(1s) peak at a higher binding energy. In the PEDOT-PSS blend, we find both effects. The importance of these observations for light-emitting diodes incorporating PEDOT-PSS films is discussed. This work demonstrates that the combination of in situ low-energy electron bombardment in combination with photo-electron spectroscopy is a powerful method to simulate and study certain processes, associated with low-energy electrons, occurring in organic based devices, which cannot be studied directly otherwise. © 2002 Elsevier Science B.V. All rights reserved.
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