A. Guobienė

Synthesis and characterization of silver nanoparticles

Silver nanoparticles have received considerable attention due to their attractive physical and chemical properties. The surface plasmon resonance and large effective scattering cross section of individual silver nanoparticles make them ideal candidates for molecular labeling, where phenomena such as surface enhance Raman scattering (SERS) can be exploited. In addition, silver nanoparticles have recently been shown to be a promising antimicrobial material. In the present research silver colloid was produced by sodium citrate reduction. The colloidal silver was incorporated by dip-coating to the polymer substrate. X-Ray Fluorescence Spectroscopy (XRF), Atomic force microscopy (AFM), ultraviolet-visible spectroscopy (UV-VIS ) and SERS indicate that the produced structures include metallic crystalline silver nanoparticles. The surface plasmon resonance peak in absorption spectra of silver particles showed an absorption maximum at 420-500 nm. The silver - polymer nanocomposites structures with selective light properties as a result of plasmon resonance shifting in the UV-VIS wavelength region were produced.

The Polymeric Layers Formation by Sorption from Organic Solutions

The formation and morphology of polymethylmethacrylate (PMMA) films on crystalline silicon Si (100), quartz glass and polyethyleneterepftalate (PET) substrates exposed to plasma processing by immersion into toluene solution, was investigated exper imentally. The dependence on the type and conditions of substrate processing was studied by lase r ellipsometry, Fourier transform infrared spectroscopy, and atomic force microscopy. It i s shown, that as a result of sorption processes and interaction between the polymer macromolecule s and the substrate surface, the thin polymeric layers are formed with a structure determ ined by the substrate properties. The morphology of thin film has a tendency to nanostructurisation, and as a r esult periodic nanostructures can be formed. Introduction Understanding of polymer adsorption and film growth on inorganic substrates is of great interest for science and technology. Various methods are used to deposit polymers on substrates. Sorption of polymer molecules on the substrate [2] from dilute solutions allows very thin polymer layers, of thickness comparable to the size of the macromolecules to be forme d. Th properties of the film deposited using this method is defined by the properties of surface, and the kinetics of removing of molecules of solvent from the film. It is known that polymer films with a thickness less than about double the radius of gyration of an unperturbed chain, 2Rg, can be defi n d as two-dimensional ultra thin films [1-3]. The flexible polymer chain in an ultra thin film is in a non-equilibrium state, since the conformational entropy of an individual chain in the constrained thin re g ons is reduced as compared to that of a three-dimensional solid state [3,4]. Obviously macromolecules adsorbed on the surface have certain 2 D mob ility and during removal of a solvent, depending on the concentration of the cross linking, can cause cha nges in the morphology of the film. Combination of the process of condensation of macromol ecules combined with the moist air blown parallel to the surface appears a very simple and flexible way to make materials with the regular 3D structure [5]. Air flow, coupled w ith convection currents on the solution surface due to evaporation, drives the ordering or packing of the water droplets into hexagonally packed arrays. It is shown [5] that the process depends on the presence of atmospheric moisture and the observed structure is a result of the formation and subsequent crystallization of “breath figures”. Similar pictures on the nanoscale were observe d for the polystyrene and polymethylmethacrylate formed on the crystalline silicon [9]. The aim of this study is to investigate regularities of the P MMA films formation depending on the properties of substrate, but selecting substrates with different r oughness and thermal conductivity such as crystalline silicon, quartz glass and polyethylenetere pf alate (PET) and applying evaporation of solvent in standard conditions with no extra moisture or air blowing. Solid State Phenomena Online: 2003-06-20 ISSN: 1662-9779, Vol. 94, pp 265-270 doi:10.4028/www.scientific.net/SSP.94.265

Oxygen Plasma Processing of Silicon and Silica Substrates for Thin Films of Polymer Blends

The influence of plasma processing of silica and crystalline silicon substrates on the formation of polymeric layers of PS/PMMA blends by sorption from 50 vol. % concentration toluene solutions was analyzed. The morphology dependence of PS/ PMMA blend films on the type and condition of substrate processing was studied by X-ray photoelectron spectroscopy (XPS), ellipsometry and atomic force microscopy (AFM). It was shown that reduction of carbon and oxygen components from the surface contaminants as well as the existence of a nonstoichiometric SiOx layer on the Si surface contributed to the hydrophilicity of the substrate. These processes can be used to produce thin nanostructured polymer blend films.

Synthesis and Characterization of Silver-Poly(Methylmethacrylate) Nanocomposite

Silver nanoparticles and polymethylmethacrylate (PMMA) nanocomposite was prepared in situ by photo-induced thermal reduction method. The interfacial interaction of Ag nanoparticles and PMMA polymer is investigated using Fourier transform infrared spectroscopy (FTIR). Optical properties of Ag/PMMA films were characterized by UV-Vis and FTIR absorption spectroscopy. Effects of the UV and heat-treatment time on the formation of silver nanoparticles in PMMA matric matrix were studied in detail. These investigations proposed new nanocomposite structures. They can be defined as plasmonic materials with improved optical properties. Ag/PMMA structures may found a number of technological applications: in optical devices, various plasmonic sensors or even in nanomedicine.

The influence of sublayer material on surface properties of electrodeposited nickel with periodical structures

Surface topography, hardness and microstructure of nickel coatings electrodeposited on Si master with a periodical structure have been studied depending on vacuum deposited sublayer material (Ni, Cu or Ag). It is shown that the quality of replication of silicon master in a nickel shim electrodeposited simultaneously on different sublayers is dependent on the material used. All types of the analyzed coatings enabled transfer of lateral dimensions and showed good replication quality of the tested periodical structures (2 μm period), while the structure replicated using the coatings deposited on the Ni sublayer exhibited the worst roughness. The hardness of the electrodeposited layers was found to be dependent on the sublayer material used as well as on the side of deposit. Despite the fact that the backside of nickel shim had the same hardness for all the sublayers used, it was found that the hardness of the working surface with periodical structure (the side that has been in contact with the vacuum deposited layer) is dependent on the sublayer material: the Ni and Cu sublayers increased the hardness of Ni coating, while for the nickel shim deposited on Ag sublayer the hardness was reduced.