| 1. |
- Liedberg, Bo, et al.
(författare)
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Self-assembly of alpha-functionalized terthiophenes on gold
- 1997
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Ingår i: JOURNAL OF PHYSICAL CHEMISTRY B. - : AMER CHEMICAL SOC. - 1089-5647 .- 1520-6106 .- 1520-5207. ; 101:31, s. 5951-5962
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Tidskriftsartikel (refereegranskat)abstract
- alpha-Functionalized terthiophenes containing disulfide (-S-T-3-H)(2) and alkanethiol (HS-(CH2)(11)-T-3-H) anchoring groups have been synthesized for direct immobilization onto gold. Monolayer structures of these compounds are prepared by spontaneous assembly from ethanol solutions on evaporated gold substrates and thoroughly characterized by ellipsometry, contact angle goniometry, infrared and X-ray photoelectron spectroscopy, and cyclic voltammetry. The two molecules coordinate to the gold substrate exclusively via the anchoring groups upon formation of gold-thiolate bonds. The kinetics of monolayer formation vary dramatically for the two compounds. The alkanethiol analogue assembles rapidly, within a few minutes, and forms a densely packed and highly organized monolayer, with the alkyl chains in an almost perfect all-trans conformation and the C-alpha-C-alpha axis of the alpha-T-3 units tilted about 14 degrees away from the surface normal. The assembly process is much slower for the disulfide, but an organized monolayer with an average alpha-T-3 chain tilt of about 33 degrees will eventually form when the assembly is allowed to equilibrate with a solution containing the disulfide for at least 1 day. Moreover, the two monolayer assemblies also display a remarkably different electrochemical, behavior. The heterogeneous electron-transfer rate at the disulfide-covered gold substrate is almost indistinguishable from that at bare gold, suggesting that the assembly contains a large number of easily accessible defects. An alternative mechanism for explaining the large electron-transfer rate involving electronic coupling via the conjugated pi-system of the alpha-T-3 units is also proposed. The electrochemical response is significantly reduced for the HS-(CH2)(11)-T-3-H assembly, but another type of defects, the so-called shallow defects originating from sparsely populated areas on the electrode surface, can be identified.
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| 2. |
- Palmqvist, AEC, et al.
(författare)
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Surfaces of doped nanophase cerium oxide catalysts
- 1999
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Ingår i: NANOSTRUCTURED MATERIALS. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0965-9773. ; 11:8, s. 995-1007
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Tidskriftsartikel (refereegranskat)abstract
- Solid solutions of nanophase cerium oxides have been prepared and the relationship between their bulk crystal structure and surface characteristics has been studied at room temperature with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS
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| 3. |
- Yang, Zhongping, et al.
(författare)
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Preparation and characterization of mixed monolayer assemblies composed of thiol analogues of cholesterol and fatty acid
- 1997
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Ingår i: Langmuir. - : American Chemical Society. - 0743-7463 .- 1520-5827. ; 13:12, s. 3210-3218
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Tidskriftsartikel (refereegranskat)abstract
- Mixed self-assembled monolayers provide an attractive model system for investigating the role of different molecules in biological membranes. This paper describes the preparation and characterization of a novel type of mixed monolayer assemblies composed of thiol analogues of cholesterol and fatty acid. The mixed: monolayers are prepared by coadsorbing 11-mercaptoundecanoic acid (MUA) and thiocholesterol(cholest-5-ene-3 beta-thiol, TC) from solution directly onto evaporated gold surfaces. The influence of TC on the molecular composition and conformation in the mixed monolayer is analyzed by using a combination of infrared reflection-absorption spectroscopy (IRAS), X-ray photoelectron spectroscopy (XPS), ellipsometry, contact angle measurement, and cyclic voltammetry. The results indicate that the TC molecules maintain their conformation in the mixed monolayers, whereas the MUA molecules display a significantly more disordered conformation as compared to the MUA molecules in the pure monolayer. Cyclic voltammetry shows that the mixed monolayers are more densely packed and less permeable than the pure TC and MUA monolayers. The kinetics of the coadsorption of TC and MUA from ethanol indicates that adsorption of TC initially is strongly preferred over MUA but that MUA dominates over TC at long coadsorption times. This is because there is a larger energy gain per unit area in forming monolayers with MUA, Further, it is also seen that the number of molecules per unit area changes with the molecular composition, as a consequence of the different sizes of TC and MUA. We present herein a method for calculating the mole fraction of TC on the gold surface, (chi TC), which accounts for this variation. As a consequence of the dissimilar size and shape of the two molecules, the wetting properties of the mixed monolayer are found to be mainly governed by the fractional area of TC, rather than by the molecular composition of TC, (chi TC).
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| 4. |
- Öhrwall, Gunnar, et al.
(författare)
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A new energy and angle resolving electron spectrometer - First results
- 2011
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 183:1-3, s. 125-131
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Tidskriftsartikel (refereegranskat)abstract
- A new energy and angle resolved analyzer for photoelectron spectroscopy is described. This analyzer is based on combining an advanced focusing electron lens system with time-of-flight measurements. A position sensitive detector gives time and position for the electron events. From this information the kinetic energy and start direction are obtained through a transformation procedure, giving both a large luminosity and a very high energy resolution. The instrument analyses the angles of emission of the electrons in a cone with 30 degrees opening angle and simulations show that extremely high energy and angular resolution can be achieved simultaneously. We report the first results from this instrument, obtained at the PM-3 beam line at BESSY (Berlin, Germany). This analyzer opens up new possibilities for angular resolved electron spectroscopy, band-mapping and other applications.
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| 5. |
- Kariis, H, et al.
(författare)
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Thioethylpyrrole monolayers on gold. A spectroscopic study in ultrahigh vacuum
- 1998
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Ingår i: JOURNAL OF PHYSICAL CHEMISTRY B. - : AMER CHEMICAL SOC. - 1089-5647. ; 102:34, s. 6529-6538
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The adsorption of 3-(2-thioethyl)pyrrole (3-TEP) and 1-(2-thioethyl)pyrrole (1-TEP) on gold has been studied in ultrahigh vacuum with infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed desorption mass
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| 6. |
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| 7. |
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| 8. |
- Liedberg, B, et al.
(författare)
-
Self-assembly of alpha-functionalized terthiophenes on gold
- 1997
-
Ingår i: JOURNAL OF PHYSICAL CHEMISTRY B. - : AMER CHEMICAL SOC. - 1089-5647. ; 101:31, s. 5951-5962
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- alpha-Functionalized terthiophenes containing disulfide (-S-T-3-H)(2) and alkanethiol (HS-(CH2)(11)-T-3-H) anchoring groups have been synthesized for direct immobilization onto gold. Monolayer structures of these compounds are prepared by spontaneous asse
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| 9. |
- Uvdal, K, et al.
(författare)
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Tricyclohexylphosphine adsorbed on rhodium
- 1998
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Ingår i: LANGMUIR. - : AMER CHEMICAL SOC. - 0743-7463. ; 14:25, s. 7189-7196
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Tricyclohexylphosphine (TCHP) adsorbates on rhodium, prepared both from solution and by sublimation in UHV are studied by X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRAS), and temperature-programmed desorption (TP
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| 10. |
- Wirde, M, et al.
(författare)
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Modification of self-assembled monolayers of alkanethiols on gold by ionizing radiation
- 1997
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Ingår i: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS. - : ELSEVIER SCIENCE BV. - 0168-583X. ; 131:1-4, s. 245-251
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Self-assembled films of octadecanethiols on polycrystalline Au have been studied with monochromated X-ray photoelectron spectroscopy (XPS). The focus has been on the S-Au interface. It is demonstrated that ionizing radiation causes breaking of S-Au bonds
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