V. Rybka

Properties of gold nanostructures sputtered on glass

We studied the electrical and optical properties, density, and crystalline structure of Au nanostructures prepared by direct current sputtering on glass. We measured temperature dependence of sheet resistance and current-voltage characteristics and also performed scanning electron microscopy [SEM] analysis of gold nanolayers. It was shown that within the wide range of temperatures, gold nanolayers (<10 nm) exhibit both metal and semiconducting-like type of conductivity. UV/Vis analysis proved the semiconducting characteristic of intrinsic Au clusters. SEM analysis showed the initiatory stadium of gold layer formation to be running over isolated islands. Gold density calculated from the weight and effective thickness of the layers is an increasing function of the layer thickness up to approximately 100 nm. In thin layers deposited on solid surface, a lattice expansion is observed, which is manifested in the increase of the lattice parameter and the decrease of metal density. With increasing layer thickness, the lattice parameter and the density approach the bulk values.

AFM surface morphology investigation of ion beam modified polyimide

Abstract Polyimide Upilex R was irradiated with 90 keV N + ions to the fluences of 1 × 10 14 –2 × 10 17 cm −2 . The surface morphology and the structure of the ion beam modified PI were examined using atomic force microscopy and X-ray difraction. Sheet resistance as a function of the ion fluence and the sample temperature was measured by standard two point technique. Significant changes of the surface morphology and production of graphitic phase in the sample surface layer modified by the ion irradiation were observed. Strong decrease of the sheet resistance (by 11 orders of magnitude) in the ion beam modified samples is connected with progressive carbonization and graphitization of the degraded polymer. Electrical charge transport is mediated by variable-range hopping mechanism. Drastic structural changes initiated by the ion irradiation to high fluences are similar to those observed in polymer pyrolysis.

Adhesion and proliferation of cultured human aortic smooth muscle cells on polystyrene implanted with N+, F+ and Ar+ ions: correlation with polymer surface polarity and carbonization.

Physicochemical surface properties and biocompatibility were studied in polystyrene (PS) implanted with 150 keV N+, F+ and Ar+ at doses ranging from 1 x 10(12) to 1 x 10(15) cm-2. Adhesion and proliferation of cultured human aortic smooth muscle cells (SMCs) on ion implanted PS were thoroughly examined for dependence on implanted dose and ion species and in close relation to polymer surface oxidation, surface polarity, concentration of conjugated double bonds and sheet resistivity. The surface polarity of PS was a smooth, increasing function of the implanted dose. However, the dependence of SMC population density on the implanted dose was found to be more complicated. After 18 h cultivation time (i.e. when only cell attachment and spreading took place), the number of adhered SMCs and their degree of spreading first increased with increasing ion dose, and after reaching a maximum at the dose of 5 x 10(12) cm-2, they decreased to original values. For doses above 5 x 10(14) cm-2, an increase in SMC population density and spreading was again observed. The first maximum in cell adhesion can be explained by slight increases in the surface polarity and wettability, optimal for cell adhesion, and the second maximum by progressive carbonization of the PS surface. After 96 h cultivation time (i.e. when the cells proliferated intensively), the dramatic dependence of the SMC population density on implanted dose is mostly smeared out. This observed dependence of SMC attachment, spreading and subsequent proliferation on the implanted dose was similar in all three ion species, but highest cell densities were achieved on PS implanted with F+ ions.

Surface properties and biocompatibility of ion-implanted polymers

The surface properties of the polyethylene (PE), polypropylene (PP) and polystyrene (PS) samples doped with 150 keV F+ ions with doses of 1 × 1012-1 × 1015 cm–2 have been characterized by different techniques and their biocompatibility to vascular smooth muscle cells was examined. The concentration and the conjugation length of the double bonds produced by ion impact, the conductivity and the surface polarity increased with the level of doping. The cell density was measured on the PP and PS samples doped with doses below 1 × 1013 cm–2. The cells cultured on the ion-doped PS and PP exhibited better homogeneity and the resulting density was several times higher than that on the undoped polymers. No such effects were observed on the doped PE. The enhanced cell proliferation correlates with the increased surface polarity of the doped polymers.

Free volume‐limited diffusion in ion‐modified polymers

Iodine diffusion in ion-modified polyethylene (PE) using the Rutherford Backscattering method (RBS) has been studied. PE was irradiated by N + , Ar + and As + ions with an energy of 150 keV and doses of 1 X 10 13 -1 X 10 15 cm -2 . Iodine diffused in ion-modified PE from vapor at 90°C. Iodines concentration profile changed its shape dramatically for ion doses over 1 x 10 14 cm -2 when it showed two maxima. A similar profile was exhibited by oxygen, which diffused in PE on implantation. Iodines concentration dropped in the layer where the most significant polymer carbonization occurred. This range was found ahead of the implanted ions concentration. Iodine diffusion was most intensive for lower ion doses (≤1 x 10 14 cm -2 ) while for higher doses it was substantially slower due to PE carbonization. The reason was the lower free volume in the PE carbonized layer as compared with the layer where the polymers degradation was not reflected in such a significant increase in carbon content.

Synthesis of grafted polyethylene by ion beam modification

The chemical reactivity of polyethylene modified by irradiation with 40 keV Ar+ ions to fluences of 1 × 1012−1 × 1015 cm−2 was studied. Ion beam modified polyethylene was exposed to the solutions of CH2CHCOOH, CH2CHCN and Br2 and the chemical and structural changes were examined using IR-, UV-VIS-spectroscopies, electronparamagnetic resonance and Rutherford back-scattering techniques. The above agents were found to react with radicals and conjugated double bonds created by the ion irradiation. Radical and additive reactions in the ion beam modified surface layer may lead to the creation of a grafted surface layer up to 150 nm thick.

Electron beam modification of polyethylene and polystyrene

Polyethylene (PE) and polystyrene (PS) samples were irradiated in air with 14.89 MeV electrons at the flux of 247 Gy min -1 and the structural changes induced by the irradiation were characterized using UV-vis and IR spectroscopies, differential scanning calorimetry (DSC), and gel permeation chromatography (GPC) and by measuring the contact angle. It was found, in accord with previous studies, that the electron irradiation leads to oxidation of polymers and to splitting of aromatic rings in PS. The surface polarity of degraded polymers increases linearly with increasing electron fluence, the increase being much steeper for PS. No significant changes of crystallic phase or of melting temperature were observed in PE after irradiation. In PS, however, the electron irradiation results in macromolecule splitting and intensive crosslinking.

Oxygen incorporation in polyethylene and polypropylene implanted with F+, As+ and I+ ions at high dose

Samples of PolyPropylene (PP) and PolyEthylene (PE) implanted with 150 keV F+, As+ and I+ ions with a dose of 1×1015 cm−2 were studied using standard Rutherford Back Scattering (RBS) technique. No fluorine atoms above the present RBS detection limit were observed in the ion-implanted polymers. The measured depth profiles of As and I atoms are significantly broader than those predicted by the TRIM code for pristine polymers. The differences can be explained by stepwise polymer degradation due to ion bombardment. Massive oxidation of the ion-implanted polymers is observed. The oxidation rate and the resulting oxygen depth profile depend strongly on the polymer type and implanted ion mass. In the samples implanted with F+ ions, an uniformly oxidized layer is built up with a mean oxygen concentration of 15 at.%. In the samples implanted with As+ and I+ ions, a non-uniform oxygen depth distribution is observed with two concentration maxima on the sample surface and in a depth correlated with implanted ion range.

Changes of PEEK surface chemistry by ion irradiation

Abstract The changes of chemical structure, induced by irradiation with 2 MeV O + ions on the surface of poly(aryl-ether-ether-ketone) (PEEK), were investigated by using IR and UV–VIS spectroscopies. The surface topography of the irradiated PEEK was determined by X-ray diffraction (XRD). The ion irradiation results in a degradation of aromatic rings and in the production of regions enriched with conjugated double bonds. Implanted oxygen is bound to the ion beam-modified polymer structures. The ion irradiation has no effect on the content of the PEEK crystalline phase.

Degradation of polyimide and polyethyleneterephtalate irradiated with 150 and 200 keV Ar+ ions, studied by RBS and ERD techniques

Abstract Polyimide (Upilex, PI) and polyethyleneterephtalate (Mylar, PET) were irradiated with 200 and 150 keV Ar + ions respectively to different fluences and the depth profiles of hydrogen and oxygen atoms in polymer surface layer were determined using standard Rutherford backscattering (RBS) and elastic recoil detection (ERD) techniques. Significant hydrogen and oxygen depletion is observed at the ion fluences above 1×10 14 cm −2 . Above 5×10 15 cm −2 a saturated state is achieved when another fluence increase does not result in significant changes of the H and O profile shape. At higher fluences the H and O depth profiles are rather flat with no local minima. This finding indicates only minor role of nuclear stopping in production of volatile degradation products.