K. Grytsenko

Influence of interparticle interaction on melting of gold nanoparticles in Au/polytetrafluoroethylene nanocomposites

The temperature dependence of the surface plasmon resonance energy and width in 5 nm spherical gold nanoparticles embedded in a polymer polytetrafluoroethylene matrix has been studied using absorption spectroscopy. The jumplike features have been observed in these dependences indicating the melting of gold nanoparticles at temperatures considerably lower than the bulk melting point. The interaction between gold nanoparticles sufficiently affects the melting of nanoparticles. The increase in the filling factor of the particles leads to a decrease in the melting temperature of gold nanoparticles.

Optical recording media based on nanoparticles for superhigh density information storage

The use of nanoparticles for optical strorage of information is reviewed. Several different optical recording media utilizing the nanoparticles were designed and tested. The main characteristics of the media, namely, density of recording energy needed and density of stored information start from the like ones for blu-ray disk and for the best media are far better.

Anisotropy of dye films deposited onto oriented PTFE sublayers

Films of various squarilium (Sq) derivatives were deposited using thermal evaporation (TE), laser beam evaporation (LBE) and plasma treatment in vacuum. A row of indolenine derivatives of Sq with various side and end groups was studied. Films had different band positions in absorption spectra that dependent on Sq structure. One absorption band in a solution was split into two peaks for the film. Dyes were deposited onto oriented polytetrafluoroethylene (PTFE) sublayers. Aligned PTFE sublayers were prepared by friction-transfer method and evaporation with consequent rubbing by a cloth. Two Sq compounds revealed oriented growth on PTFE sublayer. Thickness - dependent change in the relative intensity of shorter and longer wavelength peaks was found. Some other vacuum-deposited polymers revealed the ability to orient Sq dye after rubbing.

Evaluation of the Mechanism of the Gold Cluster Growth during Heating of the Composite Gold-Polytetrafluoroethylene Thin Film

Nanocomposite films consisting of gold inclusions in the polytetrafluoroethylene (PTFE) matrix were obtained by thermal vacuum deposition. Annealing of the obtained films with different temperatures was used to measure varying of film morphologies. The dependence of optical properties of the films on their morphology was studied. It was established that absorption and profile of the nanocomposite film obtained by thermal vacuum deposition can be changed with annealing owing to the fact that different annealing temperatures lead to different average particle sizes. A method to calculate the optical properties of nanocomposite thin films with inclusions of different sizes was proposed. Thus, comparison of experimental optical spectra with the spectra obtained during the simulation enables estimating average sizes of inclusions. The calculations give the possibility of understanding morphological changes in the structures.

Research on the growth of dye film in vacuum in situ

Organic film deposition in vacuum is fast developing scientific and industrial domain. We developed installation for deposition of organic films equipped with optical spectrometer for measurements in situ. We are developing new dyes aimed for application in waveguide sensor, nonlinear optics and studying film organisation during deposition. Fluorinated azo-dyes and azomethine dyes were synthesized at University of Applied Sciences Wildau and at the Institute of Organic Chemistry, Kyiv. Compounds were evaporated at a pressure of 10-3 Pa using resistive heated crucible. Glass and glass covered with polytetrafluoroethylene (PTFE) film are used as substrates. The films were studied with Polytec and StellarNet spectrometers and an atomic force microscope. Optical spectra of the dye films revealed, that some compounds were decomposed during evaporation. Several kinds of dyes were evaporated and deposited without decomposition. Some deposited films formed H-aggregates and other types of aggregates. AFM images of dye films showed that their morphology depends on the chemical structure of the compounds and on the nature of the substrate on which the film was grown.

Effect of Concentration on Isomerization of Rhodanine Derivatives of Merocyanine Dyes in Polar Solvents

Rhodanine derivatives of merocyanine dyes with residues of 1,3,3-trimethyl-3H-indole and 3-ethylbenzothiazoline have been found to possess two molecular forms in diluted solutions of polar solvents such as dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidinone. The first molecular form was observed to prevail at low concentrations of the dyes, normally up to 10−5 M. The second one prevails at higher concentrations and is displayed through a new band in the electronic absorption spectrum, which is red-shifted with respect to the absorption band of the first form. No similar effect was found for these dyes by use of nonpolar solvents or upon alkyl-substitution of the molecules at nitrogen atom in the rhodanine moiety. We assign the above two forms to different molecular isomers and the analogous spectral changes were shown to take place by light or heat influence which correspond to a typical isomerization effect for the related merocyanine dyes. It is discussed that the isomer transformation is facilitated by the increased mobility of the proton bonded to the nitrogen atom of the rhodanine moiety in the polar environment and the increased amount of dye-dye collisions.

Enigma of the second harmonic generation in oriented film of symmetric squaraine

Second harmonic generation (SHG) in the oriented film of symmetric squaraine (Sq) was studied. Oriented Sq film on aligned polytetrafluoroethylyne (PTFE) sublayer prepared by vacuum deposition with subsequent rubbing using a cloth has been obtained. However, the mechanisms of orientation and SHG are still not clear. Methyl and ethyl substituted hydroxyl-Sq (OHSq) compounds formed oriented films with dichroic ratio of 8 on PTFE layer but with dichroic ratio of 1,5 on Teflon AF. Second layer deposition of Me-OHSq on Et-OHSq or of Et-OHSq on Me-OHSq led to an increase of the film dichroic ratio. Only the film, where Me-OHSq was first layer, exhibits an increase of SHG signal after deposition of second layer. Small differences in bi-layered OHSq films structure was detected by X-Ray diffraction (XRD) spectra.