Jakub Siegel

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.

Noble metal nanostructures influence of structure and environment on their optical properties

Optical properties of nanostructuredmaterials, isolated nanoparticles, and structures composed of both metals and semiconductors are broadly discussed. Fundamentals of the origin of surface plasmons as well as the surface plasmon resonance sensing are described and documented on a number of examples. Localized plasmon sensing and surface-enhanced Raman spectroscopy are subjected to special interest since those techniques are inherently associated with the direct application of plasmonic structures. The possibility of tailoring the optical properties of ultra-thin metal layers via controlling their shape and morphology by postdeposition annealing is documented. Special attention is paid to the contribution of bimetallic particles and layers as well as metal structures encapsulated in semiconductors and dielectrics to the optical response. The opportunity to tune the properties of materials over a large scale of values opens up entirely new application possibilities of optical active structures. The nature of surface plasmons predetermines noble metal nanostructures to be promising great materials for development of modern label-free sensing methods based on plasmon resonance--SPR and LSPR sensing.

Grafting of gold nanoparticles and nanorods on plasma-treated polymers by thiols

Grafting of gold nanoparticles and nanorods on the surface of polymers, modified by plasma discharge, is studied with the aim to create structures with potential applications in electronics or tissue engineering. Surfaces of polyethyleneterephthalate and polytetrafluoroethylene were modified by plasma discharge and subsequently, grafted with 2-mercaptoethanol, 4,4′-biphenyldithiol, and cysteamine. The thiols are expected to be fixed via one of –OH, –SH or –NH2 groups to reactive places on the polymer surface created by the plasma treatment. “Free” –SH groups are allowed to interact (graft) with gold nanoparticles and nanorods. Gold nano-objects were characterized before grafting by transmission electron microscopy and UV–Vis spectroscopy. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and electrokinetic analysis (zeta potential determination) were used for the characterization of polymer surface at different modification phases. It was proved by FTIR and XPS measurements that the thiols were chemically bonded on the surface of the plasma-treated polymers, and they mediate subsequent grafting of the gold nano-objects. On the surfaces, modified polymers were indicated some objects by AFM, size of which was dramatically larger in comparison with that of original nanoparticles and nanorods. This result and the other results of UV–Vis spectroscopy indicate an aggregation of deposited gold nano-objects.

Dynamics of spreading and alignment of cells cultured in vitro on a grooved polymer surface

We used mechanically embossed polyester films to analyze the dynamics of cell alignment and cell-specific factors modulating the response of Chinese hamster ovary (CHO) cells and of a rat myogenic cell line to the surface topography. The films used had grooves with a periodicity of approximately 750 nm and a depth of 150 nm. Both cell lines responded to the topographical feature. On unpatterned control areas, cells of both lines showed a random distribution with orientation angles close to 45°. Both cell types exhibited an elongated morphology on the patterned surface. CHO cells typically showed bipolar spreading. Their contact area increased almost exclusively along the groove direction. Likewise, freshly seeded rat myoblasts displayed protrusions emerging in parallel with the grooves. However, myoblasts frequently had more than two sites with plasma protrusions pulling the cells along different grooves. They could also develop lamellipodia expanding without a preferred direction and long filopodia.

Regular surface grating on doped polymer induced by laser scanning

Thin polymer film doped with optical chromophore porphyrin are shown to respond to irradiation with laser light (λ=405 nm). By simultaneous scanning with laser beam and continual mechanical movement of the polymer film regular grating pattern is formed on the polymer surface. Parameters of the grating vary in wide range as a function of the movement velocity and the laser intensity. Submicron, periodically structures can be prepared using the proposed technique.

Annealing of gold nanostructures sputtered on polytetrafluoroethylene

Gold nanolayers sputtered on polytetrafluoroethylene (PTFE) surface and their changes induced by post-deposition annealing at 100°C to 300°C are studied. Changes in surface morphology and roughness are examined by atomic force microscopy, electrical sheet resistance by two point technique, zeta potential by electrokinetic analysis and chemical composition by X-ray photoelectron spectroscopy (XPS) in dependence on the gold layer thickness. Transition from discontinuous to continuous gold coverage takes place at the layer thicknesses 10 to 15 nm and this threshold remains practically unchanged after the annealing at the temperatures below 200°C. The annealing at 300°C, however, leads to significant rearrangement of the gold layer and the transition threshold increases to 70 nm. Significant carbon contamination and the presence of oxidized structures on gold-coated samples are observed in XPS spectra. Gold coating leads to a decrease in the sample surface roughness. Annealing at 300°C of pristine PTFE and gold-coated PTFE results in significant increase of the sample surface roughness.

Properties of silver nanostructure-coated PTFE and its biocompatibility

Silver nanolayers were sputtered on polytetrafluoroethylene (PTFE) and subsequently transformed into discrete nanoislands by thermal annealing. The Ag/PTFE composites prepared under different conditions were characterized by several complementary methods (goniometry, UV-visible spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy), and new data on the mechanism of Ag layer growth and Ag atom clustering under annealing were obtained. Biocompatibility of selected Ag/PTFE composites was studied in vitro using vascular smooth muscle cell (VSMC) cultures. Despite of the well-known inhibitory properties of silver nanostructures towards broad spectrum of bacterial strains and cells, it was found that very thin silver coating stimulates both adhesion and proliferation of VSMCs.

Antimicrobial Treatment of Polymeric Medical Devices by Silver Nanomaterials and Related Technology

Antimicrobial biocompatible polymers form a group of highly desirable materials in medicinal technology that exhibit interesting thermal and mechanical properties, and high chemical resistance. There are numerous types of polymers with antimicrobial activity or antimicrobial properties conferred through their proper modification. In this review, we focus on the second type of polymers, especially those whose antimicrobial activity is conferred by nanotechnology. Nanotechnology processing is a developing area that exploits the antibacterial effects of broad-scale compounds, both organic and inorganic, to form value-added medical devices. This work gives an overview of nanostructured antimicrobial agents, especially silver ones, used together with biocompatible polymers as effective antimicrobial composites in healthcare. The bactericidal properties of non-conventional antimicrobial agents are compared with those of conventional ones and the advantages and disadvantages are discussed.

Electrokinetic Potential and Other Surface Properties of Polymer Foils and Their Modifications

© 2013 Kolska et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Electrokinetic Potential and Other Surface Properties of Polymer Foils and Their Modifications

Silver nano-structures prepared by oriented evaporation on laser-patterned poly(methyl methacrylate)

Preparation of ordered arrays of silver nanostructures with defined shape and symmetry on patterned polymer surface is described. Laser irradiation of porphyrine-doped poly(methyl methacrylate) leads to a material flow driven by temperature gradient and to creation of regular surface pattern. Subsequent shadow silver evaporation results in selective silver deposition and creation of ordered system of silver arcs. Structures produced in this way are examined using AFM, SEM, XPS, and FIB–SEM methods.