Igoris Prosyčevas

Synthesis and characterization of layered double hydroxides with different cations (Mg, Co, Ni, Al), decomposition and reformation of mixed metal oxides to layered structures

Three layered double hydroxides (LDH) [Mg1−xAlx(OH)2]x+(Am−)x/m]·nH2O and [MII1−xMIIIx (OH)2]x+(Am−)x/m]·nH2O (MII — Mg, Co, Ni; MIII — Al; A — CO32−) were successfully synthesized by the low supersaturation method. The as-synthesized LDH samples were thermally decomposed and the derived mixed metal oxides reformed back to layered structures in water and magnesium nitrate media at different temperatures. All synthesized samples were characterized by X-ray diffraction (XRD) analysis, thermogravimetric (TG) analysis, X-ray fluorescence (XRF) analysis and scanning electron microscopy (SEM). The results of XRD and XRF analyses showed that single-phase layered double hydroxides were formed during synthesis and reformation. It was demonstrated, that a partially substituted by cobalt and nickel LDH samples also show memory effect. The crystallite size of regenerated LDH depends on the regeneration media, temperature and chemical composition. The LDH samples after regeneration consist of large particles with sharp edges along with a large amount of smaller particles

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.

Formation mechanisms of nano and microcones by laser radiation on surfaces of Si, Ge, and SiGe crystals

In this work we study the mechanisms of laser radiation interaction with elementary semiconductors such as Si and Ge and their solid solution SiGe. As a result of this investigation, the mechanisms of nanocones and microcones formation on a surface of semiconductor were proposed. We have shown the possibility to control the size and the shape of cones both by the laser. The main reason for the formation of nanocones is the mechanical compressive stresses due to the atoms’ redistribution caused by the gradient of temperature induced by strongly absorbed laser radiation. According to our investigation, the nanocone formation mechanism in semiconductors is characterized by two stages. The first stage is characterized by formation of a p-n junction for elementary semiconductors or of a Ge/Si heterojunction for SiGe solid solution. The generation and redistribution of intrinsic point defects in elementary semiconductors and Ge atoms concentration on the irradiated surface of SiGe solid solution in temperature gradient field take place at this stage due to the thermogradient effect which is caused by strongly absorbed laser radiation. The second stage is characterized by formation of nanocones due to mechanical plastic deformation of the compressed Ge layer on Si. Moreover, a new 1D-graded band gap structure in elementary semiconductors due to quantum confinement effect was formed. For the formation of microcones Ni/Si structure was used. The mechanism of the formation of microcones is characterized by two stages as well. The first stage is the melting of Ni film after irradiation by laser beam and formation of Ni islands due to surface tension force. The second step is the melting of Ni and subsequent manifestations of Marangoni effect with the growth of microcones.

Periodical Microstructures Based on Novel Piezoelectric Material for Biomedical Applications.

A novel cantilever type piezoelectric sensing element was developed. Cost-effective and simple fabrication design allows the use of this element for various applications in the areas of biomedicine, pharmacy, environmental analysis and biosensing. This paper proposes a novel piezoelectric composite material whose basic element is PZT and a sensing platform where this material was integrated. Results showed that a designed novel cantilever-type element is able to generate a voltage of up to 80 µV at 50 Hz frequency. To use this element for sensing purposes, a four micron periodical microstructure was imprinted. Silver nanoparticles were precipitated on the grating to increase the sensitivity of the designed element, i.e., Surface Plasmon Resonance (SPR) effect appears in the element. To tackle some issues (a lack of sensitivity, signal delays) the element must have certain electronic and optical properties. One possible solution, proposed in this paper, is a combination of piezoelectricity and SPR in a single element.

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

Periodic structures modified with silver nanoparticles for novel plasmonic application

Forming structures similar to or smaller than the optical wavelength offers a wide range of possibilities to modify the optical properties of materials. Tunable optical nanostructures can be applied as materials for surface-enhanced spectroscopy, optical filters, plasmonic devices, and sensors. In this work we present experimental results on technology and properties of periodical, polymer based optical structures modified by ordered adsorption of silver nanoparticles. These structures were formed combining UV hardening and dip coating from colloidal solutions. We have investigated the influence of silver nanoparticles assembly on the ambient conditions (deposition temperature and time) and surface features (periodicities and shape) of the template micro structures. Optical absorbance as well as morphology of the structures containing silver nanoparticles were investigated by UV-VIS spectroscopy, AFM, SEM and optical microscopy. The influence of silver nanoparticles on the optical properties of the structures was investigated by polarized light spectroscopy (Grating Light Reflection Spectroscopy - GLRS). From the results of this study we propose a low cost procedure for fabricating structures that could be potentially new type of plasmonic sensors exploiting surface enhanced plasmon resonance in silver nano structures.

Structure and properties of nanocomposite polymer coatings

We investigate the surface morphology and structure formations of nanocomposite polymer (polytetrafluoroethylene, polyurethane) coatings obtained by vacuum plasma method. We present data about the influence of coating composition and deposition conditions onto coating properties and structure.

Formation and Antibacterial Property Analysis of Electrospun PVA Nonwoven Material with a Small Amount of Silver Nanoparticles

3Kaunas University of Technology, Institute of Materials Science K. Baršausko g. 59, LT-51423, Kaunas, Lithuania Abstract Electrospinning is a process which produces nonwoven material from nano/microfibres. The aim of this study was to electrospin poly(vinyl alcohol) nano/microfibres material with small amount of silver nanoparticles (Ag-NPs), and estimate the influence of Ag-NPs on the structures and antibacterial properties of nonwoven materials. It was found that the Ag-NPs concentration does not have a significant influence on the viscosity and morphologies of electrospun materials. The addition of Ag-NPs causes the formation of thinner PVA nano/microfibres. The antibacterial activity test showed that a small amount of Ag-NPs provides antibacterial properties to electrospun PVA nano/microfibres. Antibacterial properties were tested with different bacteria: Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis ATCC 12228, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Proteus mirabilis ATCC 12453, Bacillus cereus ATCC 11778 and Candida albicans ATCC 10231. It was also noticed that the concentration of Ag-NPs in nonwoven materials affects antibacterial properties. Clearly superior antibacterial properties were obtained from nonwoven materials with a higher concentration of Ag-NPs.

Development and modification of Fe and FeCu nanoparticles and tribological analysis of the lubricants with nano‐suspensions

Purpose – The purpose of this paper is to investigate the possibility of using the iron nanoparticles and iron nanoparticles coated with copper layer as additives to base oils.Design/methodology/approach – Fe and Fe+Cu nanoparticles were synthesized by a reduction modification method and added to mineral oil. The size and structure of prepared nanoparticles were characterized by SEM, TEM, XRF, AAS and XRD analysis. Tribological properties of modified lubricants were evaluated on a four‐ball machine in a model of sliding friction pairs.Findings – Spectral and microscopy analysis evidently displayed the formation of Fe and Fe+Cu nanoparticles in suspensions of colloidal solutions and oil. The size of formed nanoparticles was in 15‐50 nm range. Tribological experiments show good lubricating properties of oils modified with Fe and Fe+Cu nanoparticles: higher wear resistance (55 per cent and 46 per cent accordingly) and lower friction coefficient (30 per cent and 26 per cent accordingly). The tests show that n...

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.