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Sökning: WAKA:ref > Inganäs Olle > Kungliga Tekniska Högskolan

  • Resultat 1-8 av 8
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  • Borgani, Riccardo, et al. (författare)
  • Intermodulation electrostatic force microscopy for imaging surface photo-voltage
  • 2014
  • Ingår i: Applied Physics Letters. - American Institute of Physics (AIP). - 0003-6951. ; 105:14, s. 143113
  • Tidskriftsartikel (refereegranskat)abstract
    • We demonstrate an alternative to Kelvin Probe Force Microscopy for imaging surface potential. The open-loop, single-pass technique applies a low-frequency AC voltage to the atomic force microscopy tip while driving the cantilever near its resonance frequency. Frequency mixing due to the nonlinear capacitance gives intermodulation products of the two drive frequencies near the cantilever resonance, where they are measured with high signal to noise ratio. Analysis of this intermodulation response allows for quantitative reconstruction of the contact potential difference. We derive the theory of the method, validate it with numerical simulation and a control experiment, and we demonstrate its utility for fast imaging of the surface photo-voltage on an organic photovoltaic material.
  • Hevekerl, Heike, 1982-, et al. (författare)
  • Dark States in Ionic Oligothiophene Bioprobes-Evidence from Fluorescence Correlation Spectroscopy and Dynamic Light Scattering
  • 2014
  • Ingår i: Journal of Physical Chemistry B. - American Chemical Society. - 1520-6106. ; 118:22, s. 5924-5933
  • Tidskriftsartikel (refereegranskat)abstract
    • Luminescent conjugated polyelectrolytes (LCPs) can upon interaction with biological macromolecules change their luminescent properties, and thereby serve as conformation- and interaction-sensitive biomolecular probes. However, to exploit this in a more quantitative manner, there is a need to better understand the photophysical processes involved. We report studies of the conjugated pentameric oligothiophene, derivative p-FTAA, which changes optical properties with different p-FTAA concentrations in aqueous buffers, and in a pH and oxygen saturation dependent manner. Using dynamic light scattering, luminescence spectroscopy and fluorescence correlation spectroscopy, we find evidence for a monomer dimer equilibrium, for the formation of large clusters of p-FTAA in aqueous environment, and can couple aggregation to changed emission properties of oligothiophenes. In addition, we observe the presence of at least two dark transient states, one presumably being a triplet state. Oxygen was found to statically quench the p-FTAA fluorescence but also to promote molecular fluorescence by quenching dark transient states of the p-FTAA molecules. Taken together, this study provides knowledge of fluorescence and photophysical features essential for applying p-FTAA and other oligothiophene derivatives for diagnostic purposes, including detection and staining of amyloid aggregates.
  • Thaning, Elin M., et al. (författare)
  • Stability of Poly(3,4-ethylene dioxythiophene) Materials Intended for Implants
  • 2010
  • Ingår i: Journal of Biomedical Materials Research - Part B Applied Biomaterials. - 1552-4973. ; 93B:2, s. 407-415
  • Tidskriftsartikel (refereegranskat)abstract
    • This study presents experiments designed to study the stability of the conducting polymer poly(3,4-ethylene dioxythiophene) (PEDOT), under simulated physiological conditions using phosphate-buffered saline (PBS) and hydrogen peroxide (H2O2) (0 01M) at 37 degrees C over a 5- to 6-week period Voltage pulsing in PBS was used as an additional test environment The influence of switching the counter ion used in electropolymerization from polystyrene sulphonate (PSS) to heparin was investigated Absorbance spectroscopy and cyclic voltammetry were used to evaluate the material properties Most of the samples in H2O2 lost both electroactivity and optical absorbance within the study period, but PEDOT.PSS was found slightly more stable than PEDOT heparin. Polymers were relatively stable in PBS throughout the study period, with around 80% of electroactivity remaining after 5 weeks, disregarding delamination, which was a significant problem especially for polymer on indium tin oxide substrates Voltage pulsing in PBS did not increase degradation. The counter ion influenced the time course of degradation in Oxidizing agents.
  • Von Holst, Hans, et al. (författare)
  • Composite biomolecule/PEDOT materials for neural electrodes
  • 2008
  • Ingår i: Biointerphases. - NY : American Institute of Physics. - 1559-4106. ; 3:3, s. 83-93
  • Tidskriftsartikel (refereegranskat)abstract
    • Electrodes intended for neural communication must be designed to meet boththe electrochemical and biological requirements essential for long term functionality. Metallic electrode materials have been found inadequate to meet theserequirements and therefore conducting polymers for neural electrodes have emergedas a field of interest. One clear advantage with polymerelectrodes is the possibility to tailor the material to haveoptimal biomechanical and chemical properties for certain applications. To identifyand evaluate new materials for neural communication electrodes, three chargedbiomolecules, fibrinogen, hyaluronic acid (HA), and heparin are used ascounterions in the electrochemical polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). The resultingmaterial is evaluated electrochemically and the amount of exposed biomoleculeon the surface is quantified. PEDOT:biomolecule surfaces are also studiedwith static contact angle measurements as well as scanning electronmicroscopy and compared to surfaces of PEDOT electrochemically deposited withsurfactant counterion polystyrene sulphonate (PSS). Electrochemical measurements show that PEDOT:heparinand PEDOT:HA, both have the electrochemical properties required for neuralelectrodes, and PEDOT:heparin also compares well to PEDOT:PSS. PEDOT:fibrinogen isfound less suitable as neural electrode material.
  • Wigenius, Jens A., 1975-, et al. (författare)
  • Interactions between a luminescent conjugated oligoelectrolyte and insulin during early phases of amyloid formation
  • 2011
  • Ingår i: Macromolecular Bioscience. - Wiley. - 1616-5187. ; 11:8, s. 1120-1127
  • Tidskriftsartikel (refereegranskat)abstract
    • Folding of an amino acid polypeptide chain into its native three-dimensional protein is a delicate process. Misfolding may cause assembly of dysfunctional proteins leading to aggregated assemblies, in medicine denoted amyloids, causing Alzheimer’s, Parkinson and a number of other protein related diseases. Amyloids have also shown promising results as building blocks in organic electronic applications, associated to conjugated polymers. Luminescent conjugated oligo- and polythiophenes (LCPs) have been further developed for biosensor applications exhibiting good ability to discriminate and determine different types of amyloid enrichment in complex environments, such as in tissue sections. The nature of interaction between the amyloid assemblies and LCPs is still not fully understood. In this study we use steady-state fluorescence spectroscopy, dynamic light scattering, transmission electron microscopy and fluorescence correlation spectroscopy to follow the interplay between the anionic oligothiophene derivative 4',3'''-Bis-carboxymethyl-[2,2';5',2'';5'',2''';5''',2'''']quinque thiophene-5,5''''-dicarboxylic acid (p-FTAA), and prefibrillar protein assemblies present during the earlier stage of in vitro fibrillation of bovine insulin. Our findings confirm that p-FTAA interacts with pre-fibrillar species of insulin preceding the formation of mature insulin amyloid fibrils, and insights regarding the molecular interplay between p-FTAA and these species are provided.
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