Browsing by Author "Kondyurin, A"

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    Depth-resolved structural and compositional characterization of ion-implanted polystyrene that enables direct covalent immobilization of biomolecules
    (Springer Link, 2015-06-03) Bilek, MMM; Kondyurin, A; Stephen, D; Steel, BC; Wilhelm, RA; René Heller, R; McKenzie, DR; Weiss, AS; James, M; Möller, W
    A polystyrene film spun onto polished silicon substrates was implanted with argon ions using plasma immersion ion implantation (PIII) to activate its surface for single-step immobilization of biological molecules. The film was subsequently investigated by X-ray and neutron reflectometry, ultraviolet (UV)–visible (vis) and Fourier transform infrared (FTIR) ellipsometry, FTIR and Raman spectroscopy, as well as nuclear reaction analysis to determine the structural and compositional transformations associated with the surface activation. The ion irradiation resulted in a significant densification of the carbon structure, which was accompanied by hydrogen loss. The density and hydrogen profiles in the modified surface layers were found to agree with the expected depths of ion implantation as calculated by the Stopping and Range of Ions in Matter (SRIM) software. The data demonstrate that the reduction in film thickness is due to ion-induced densification rather than the removal of material by etching. Characterization by FTIR, atomic force microscopy (AFM), ellipsometry, and X-ray reflectometry shows that polystyrene films modified in this way immobilize dense layers of protein (tropoelastin) directly from solution. A substantial fraction of the immobilized protein layer remains after rigorous washing with sodium dodecyl sulfate solution, indicating that its immobilization is by covalent bonding. © 2015, American Chemical Society.
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    Oxygen incorporation in Ti2AlC thin films
    (American Institute of Physics, 2008-02-11) Rosen, J; Persson, POA; Ionescu, M; Kondyurin, A; McKenzie, DR; Bilek, MMM
    Thin films of Ti2AlC MAX phase have been deposited using a multiple cathode pulsed cathodic arc. Evidence for substantial oxygen incorporation in the MAX phase is presented, likely originating from residual gas present in the vacuum chamber during deposition. The characteristic MAX phase crystal structure is maintained, in agreement with ab initio calculations, supporting substitutional O in C lattice positions. On the basis of these results, we propose the existence of a MAX phase-like material with material properties tuned by the incorporation of oxygen. Additionally, possible unintentional O incorporation in previously reported MAX phase materials is suggested. © 2008, American Institute of Physics