| 1. |
- Agheli, Hossein, 1965, et al.
(författare)
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Nanostructured biointerfaces
- 2006
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Ingår i: Materials Science and Engineering C. ; 26, s. 911-917
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Aizpurua, Javier, et al.
(författare)
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Light scattering in gold nanorings
- 2004
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Ingår i: Journal of Quantitative Spectroscopy & Radiative Transfer. ; 89, s. 11-16
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Tidskriftsartikel (refereegranskat)
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- Denis, F. A., et al.
(författare)
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Protein adsorption on model surfaces with controlled nanotopography and chemistry
- 2002
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 18:3, s. 819-828
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate the influence of substratum surface characteristics on protein adsorption processes, we have investigated the adsorption (adsorbed amount, supramolecular organization) of collagen on model substrata exhibiting controlled topography and surface chemistry. Substrata were prepared in two steps: (i) gold deposition onto silicon wafers (smooth substrata) and onto a support with nanoscale protrusions created by colloidal lithography (rough substrata); (ii) functionalization with CH3 (hydrophobic) and OH (hydrophilic) groups, using alkanethiol self-assembly. Atomic force microscopy (AFM) images were recorded under water, prior to and after collagen adsorption, and the images were analyzed quantitatively using two independent approaches. On smooth substrata, collagen formed a similar to6 nm thick, homogeneous layer with low roughness on hydrophilic surfaces, and a similar to20 nm thick layer exhibiting elongated aggregated structures on hydrophobic surfaces. Film thickness measurements (AFM) together with X-ray photoelectron spectroscopy (XPS) revealed larger adsorbed amounts on hydrophobic surfaces compared to hydrophilic ones. On rough substrata, the adsorbed amounts were similar to those found on smooth substrata; however, the collagen molecules no longer formed aggregated structures on the hydrophobic surfaces. It is concluded that while the adsorbed amount is only affected by the surface chemistry, the supramolecular organization of the adsorbed layer is controlled both by surface chemistry and topography. The approach presented here will have great value in biophysics for investigating bioadsorption and bioadhesion processes on substrata of defined surface properties.
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| 7. |
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| 8. |
- Ekström, Henrik, et al.
(författare)
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A Novel Approach for Measuring Catalytic Activity of Planar Model Catalysts in the Polymer Electrolyte Fuel Cell Environment
- 2006
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651. ; 153:4, s. A724-A730
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Tidskriftsartikel (refereegranskat)abstract
- The electrochemical oxygen reduction reaction on nanostructured supported platinum electrodes is measured using a newly developed solid-state polymer electrolyte electrochemical cell. Measurements were made on three types of catalytic surfaces on glassy carbon supports: nanostructured model electrodes prepared by colloidal lithography, a thin thermally evaporated Pt film, and a pure glassy carbon surface. Measurements in nitrogen and oxygen at several different humidities were performed at 60 degrees C in a fuel-cell-like environment. Lowering humidity showed a higher Tafel slope at high potentials for oxygen reduction on the nanostructured catalyst. Good agreement between the electrochemical active area from the hydrogen adsorption peaks and the catalytic area determined from scanning electron microscopy images was found. No significant change of the electrochemically active area with humidity could be found. Double-layer capacitance and oxygen reduction currents increased with increased humidification temperatures.
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| 9. |
- Ekström, Henrik, et al.
(författare)
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Nanometer-thick films of titanium oxide acting as electrolyte in the polymer electrolyte fuel cell
- 2007
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 52:12, s. 4239-4245
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Tidskriftsartikel (refereegranskat)abstract
- 0–18 nm-thick titanium, zirconium and tantalum oxide films are thermally evaporated on Nafion 117 membranes, and used as thin spacer electrolyte layers between the Nafion and a 3 nm Pt catalyst film. Electrochemical characterisation of the films in terms of oxygen reduction activity, high frequency impedance and cyclic voltammetry in nitrogen is performed in a fuel cell at 80 ◦C and full humidification. Titanium oxide films with thicknesses up to 18 nm are shown to conduct protons, whereas zirconium oxide and tantalum oxide block proton transport already at a thickness of 1.5 nm. The performance for oxygen reduction is higher for a bi-layered film of 3 nm platinum on 1.5 or 18 nm titanium oxide, than for a pure 3 nm platinum film with no spacer layer. The improvement in oxygen reduction performance is ascribed to a higher active surface area of platinum, i.e. no beneficial effect of combining platinum with zirconium, tantalum or titanium oxides on the intrinsic oxygen reduction activityis seen. The results suggest that TiO2 may be used as electrolyte in fuel cell electrodes, and that low-temperature proton exchange fuel cells could be possible using TiO2 as electrolyte.
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| 10. |
- Gustavsson, Marie, et al.
(författare)
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Thin film Pt/TiO2 catalysts for the polymer electrolyte fuel cell
- 2007
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 163:2, s. 671-678
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Tidskriftsartikel (refereegranskat)abstract
- Thin film Pt/TiO2 catalysts are evaluated in a polymer electrolyte electrochemical cell. Individual thin films of Pt and TiO2, and bilayers of them, were deposited directly on Nafion membranes by thermal evaporation with varying deposition order and thickness (Pt loadings of 3-6 mu g cm(-2)). Structural and chemical characterization was performed by transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Oxygen reduction reaction (ORR) polarization plots show that the presence of a thin TiO2 layer between the platinum and the Nation increases the performance compared to a Pt film deposited directly on Nation. Based on the TEM analysis, we attribute this improvement to a better dispersion of Pt on TiO2 compared to on Nalion and in addition, substantial proton conduction through the thin Ti02 layer. It is also shown that deposition order and the film thickness affects the performance.
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