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| 2. |
- Andersson, Thorvald, 1946, et al.
(författare)
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Preparation and characterization of the ITO surface and the Al/Alq3/ITO heterostructure for OLEDs
- 2007
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Ingår i: Materials Science and Engineering B. ; 145, s. 48-56
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Tidskriftsartikel (refereegranskat)abstract
- We have made a detailed investigation of structure and chemical composition in thermally grown Al/Alq3/ITO layer structures intended for light emission. The different parts of the structure were studied by X-ray photoelectron spectroscopy and microscopical techniques. The indium tinoxide substrate surface consisted of grains 20–50 nm in diameter and about 5 nm in height, which also showed molecular sized sub-grain features. Due to the ambient the ITO surface was covered by a 1 nm thick hydrocarbon layer which serves as the actual surface on which an organic layer is deposited for device fabrication. A structural model for the indium tin oxide surface, on which the small molecules were deposited, was suggested. The substrate surface was treated to study the relation between the surface manipulation and the hole injection barrier. Such surface modification significantly improved the performance of a single layer Alq3 organic light emitting diode. Depth profiling of the complete structure, revealed that the aluminium contact mostly consisted of aluminium oxide with some intermixing of carbon. Further, variations of the atomic concentration of the elements In, Sn, C and O and a minor shift in their binding energies were measured. Both, position and shape of the oxygen and indium peaks were changed during argon ion sputtering. At the Alq3/ITO interface an indium–oxygen compound, different from that on the original surface, hadformed. Various effects of the compositional findings on the light emission are discussed.
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| 3. |
- Andreasson, Björn Pererik, 1979-, et al.
(författare)
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Resistive switching in Cr-doped SrTiO3 : An X-ray absorption spectroscopy study
- 2007
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Ingår i: Materials Science & Engineering. - Amsterdam : Elsevier. - 0921-5107 .- 1873-4944. ; 144:1-3, s. 60-63
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption spectroscopy was used to study the microscopic origin of conductance and resistive switching in chromium-doped strontium titanate (Cr:SrTiO3). Differences in the X-ray absorption near edge spectroscopy (XANES) at the Cr K-edge indicate that the valence of Cr changes from 3+ to 4+ underneath the anode of our sample device after the application of an electric field. Spatially resolved X-ray fluorescence microscopy (μ-XRF) maps show that the Cr4+ region retracts from the anode-Cr:SrTiO3 interface after a conducting state has been achieved. This interface region is studied with extended X-ray absorption fine structure (EXAFS) and the results are compared with structural parameters obtained from density functional theory (DFT) calculations. They confirm that oxygen vacancies which are localized at the octahedron with a Cr at its center are introduced at the interface. It is proposed that the switching state is not due to a valence change of chromium but caused by changes of oxygen vacancies at the interface. © 2007 Elsevier B.V. All rights reserved.
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| 4. |
- Caspersen, Mikael B., et al.
(författare)
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Phosphorylation sites of Arabidopsis MAP kinase substrate 1 (MKS 1)
- 2007
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - : Elsevier BV. - 1570-9639. ; 1774:9, s. 1156-1163
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Tidskriftsartikel (refereegranskat)abstract
- The Arabidopsis MAP kinase 4 (MPK4) substrate MKS1 was expressed in Escherichia coli and purified, full-length, 6x histidine (His)-tagged MKS1 was phosphorylated in vitro by hemagglutinin (HA)-tagged MPK4 immuno-precipitated from plants. MKS1 phosphorylation was initially verified by electrophoresis and gel-staining with ProQ Diamond and the protein was digested by either trypsin or chymotrypsin for maximum sequence coverage to facilitate identification of phosphorylated positions. Prior to analysis by mass spectrometry, samples were either desalted, passed over TiO2 or both for improved phosphopeptide detection. As MAP kinases generally phosphorylate serine or threonine followed by proline (Ser/Thr-Pro), theoretical masses of potentially phosphorylated peptides were calculated and mass spectrometric peaks matching these masses were fragmented and searched for a neutral-loss signal at similar to 98 Da indicative of phosphorylation. Additionally, mass spectrometric peaks present in the MPK4-treated MKS1, but not in the control peptide map of untreated MKS1, were fragmented. Fragmentation spectra were subjected to a MASCOT database search which identified three of the twelve Ser-Pro serine residues (Ser72, Set108, Ser120) in the phosphorylated form.
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| 5. |
- Engqvist, Cecilia, et al.
(författare)
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Interactions between single latex particles and silica surfaces studied with AFM
- 2007
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Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 302:03-jan, s. 197-203
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Tidskriftsartikel (refereegranskat)abstract
- The spreading of single styrene-acrylic latex particles on silicon oxide C surfaces was studied using atomic force microscopy (AFM). Three latexes with different glass transition temperature (Tg) were used and the effects of temperature, time and preparation method were investigated. Particle sizes and shape were measured with AFM and the contact angles were calculated. The observed rate for the spreading of latex particles was low and it took several days before the particles reached steady state, even at temperatures well above their T-g. The experimental particle spreading results deviated with two orders of magnitude from predictions Using the WLF equation for polymer diffusion. The deviation could be attributed to polymer-surface interactions that slowed down the particle spreading. The work of adhesion was calculated using two models. The results from using the regular Young-Dupre equation and a modified version of this equation that also included the mechanical properties (E-modulus and Poisson's ratio) of the latexes, were compared. For soft latex particles the results from the two models agreed well and were of the order of 75 J/m(2), but for glassy latexes the Young-Dupre equation underestimated the work of adhesion.
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