| 1. |
- Karlsson, Roger, et al.
(författare)
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Iron-Catalyzed Polymerization of Alkoxysulfonate-Functionalized 3,4-Ethylenedioxythiophene Gives Water-Soluble Poly(3,4-ethylenedioxythiophene) of High Conductivity
- 2009
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 21:9, s. 1815-1821
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Tidskriftsartikel (refereegranskat)abstract
- Chemical polymerization of a 3,4-ethylenedioxythiophene derivative bearing a sulfonate group (EDOTS) is reported. The polymer, PEDOT-S, is fully water-soluble and has been produced by polymerizing EDOT-S in water, using Na2S2O8 and a catalytic amount of FeCl 3. Elemental analysis and XPS measurements indicate that PEDOT-S is a material with a substantial degree of self-doping, but also contains free sulfate ions as charge-balancing counterions of the oxidized polymer. Apart from selfdoping PEDOT-S, the side chains enable full water solubility of the material; DLS studies show an average cluster size of only 2 nm. Importantly, the solvation properties of the PEDOT-S are reflected in spin-coated films, which show a surface roughness of 1.2 nm and good conductivity (12 S/cm) in ambient conditions. The electro-optical properties of this material are shown with cyclic voltammetry and spectroelectrochemical experiment reveals an electrochromic contrast (̃48% at λmax ) 606 nm).
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| 2. |
- Li, Fenghong, et al.
(författare)
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Tuning Work Function of Noble Metals As Promising Cathodes in Organic Electronic Devices
- 2009
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Ingår i: CHEMISTRY OF MATERIALS. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 21:13, s. 2798-2802
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Tidskriftsartikel (refereegranskat)abstract
- Work function (WF) modification of metal electrodes by adsorbing electron-rich or electron-deficient molecules oil metal surfaces has become a field of significant interest. The barrier for charge carrier injection in organic semiconductor devices can be reduced by molecular adsorption, leading to all interfacial dipole. Here, we demonstrate that the WF of noble metals such as ALL call be decreased significantly by adsorbing air stable n-type dopant acridine orange base (AOB) thin film. When a (sub)monolayer AOB is deposited on sputter-cleaned Au, the WF of the substrate changes from 5.2 to 3.5 eV. At complete coverage of the Au Surface, the WF is further reduced to 3.3 eV. When a (sub) monolayer of AOB is inserted between Au and C-60 thin film, the barrier of electron injection is decreased by 0.4 +/- 0.1 eV as compared to an Au-C-60 interface without AOB. Polymer solar cells with AOB/Au as a cathode have a similar open circuit voltage and comparable power conversion efficiency with devices using LiF/Al as a cathode, demonstrating that the AOB-modified gold electrode is an efficient low-work-function contact. Given the low positive pinning energy of 3.3 eV for AOB, we expect that other conventional high-work-function materials (Ag, ITO. La0.7Sr0.3MnO3 and even PEDOT:PSS) can be modified by AOB as effectively as Au.
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| 3. |
- Liu, Xianjie, et al.
(författare)
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Interfacial electronic properties of pentacene tuned by a molecular monolayer of C-60
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - College Park, MD, United States : American Physical Society. - 1098-0121 .- 1550-235X. ; 80:11, s. 115401-1-115401-7
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Tidskriftsartikel (refereegranskat)abstract
- Fine-tuning charge injection barriers between organic materials and electrodes is critical to optimize organic electronic device performance. Here we demonstrate that by modifying gold substrates with a monolayer of fullerene, significant decrease in the hole-injection barrier into pentacene films can be achieved. The insertion of the fullerene monolayer modifies the interfacial dipole and produces an interface where the pentacene molecules form a standing-up orientation with their long axis parallel to the surface normal. The latter effect lowers the vertical ionization energy of the pentacene molecules at the interface as compared to the pentacene-on-Au case, as well as improves the pi-pi overlap between the pentacene molecules that will likely enhance the transport properties in corresponding devices.
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| 4. |
- Steinmüller-Nethl, Doris, et al.
(författare)
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Strong binding of bioactive BMP-2 to nanocrystalline diamond by physisorption
- 2006
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612. ; 27, s. 4547-4556
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Tidskriftsartikel (refereegranskat)abstract
- Nano-crystalline diamond (NCD)-coated surfaces were efficiently functionalized with bone morphogenetic protein-2 (BMP-2) by means of physisorption. Due to their randomly oriented texture, NCD-coated surfaces appear to bind complex molecules firmly. Applying various highly sensitive analytical methods, the interaction was found extremely stable. The strength of the experimentally measured adherence between BMP-2 and NCD was further corroborated by theoretical calculations. Oxygen treatment rendered NCD hydrophilic by the appearance of surface oxygen containing groups. This particular NCD surface exhibited even higher binding energies towards BMP-2 than the hydrophobic surface, and this surface was also favoured by cultured cells. Most importantly in this context, bound BMP-2 was found fully active. When cultured on BMP-2-treated NCD, osteosarcoma cells strongly up-regulated alkaline phosphatase, a specific marker for osteogenic differentiation. Hence, this simple method will allow generating highly versatile surfaces with complex biomimetic coatings, essentials for novel medical devices and implants as well as for innovative scaffolds in tissue engineering.
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| 5. |
- Zhan, Yiqiang, et al.
(författare)
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The role of aluminum oxide buffer layer in organic spin-valves performance
- 2009
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Ingår i: APPLIED PHYSICS LETTERS. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:5, s. 053301-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structures of the 8-hydroxyquinoline-aluminum (Alq(3))/Al2O3/Co interfaces were studied by photoelectron spectroscopy. A strong interface dipole was observed, which leads to a reduction in the electron injection barrier. The x-ray photoelectron spectroscopy spectra further indicate that the Al2O3 buffer layer prevents the chemical interaction between Alq(3) molecules and Co atoms. X-ray magnetic circular dichroism results demonstrate that a Co layer deposited on an Al2O3 buffered Alq(3) layer shows better magnetic ordering in the interface region than directly deposited Co, which suggests a better performance of spin valves with such a buffer layer. This is consistent with the recent results from [Dediu , Phys. Rev. B 78, 115203 (2008)].
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