Papers by Author: Valentinas Snitka

Abstract: Thallium sulphide layers of different composition were obtained on the surface of polyethylene when it was sulphurised in a solution of higher polythionic acid, H2S33O6, and then treated with an alkaline solution of thallium(I) sulphate. The stoichiometric composition of the thallium sulphide layers varied between Tl0.3S and Tl2.6S depending on the formation conditions of the layers of TlxSy. A phase composition of the layers obtained was confirmed by X-ray photoelectron spectroscopy. The spectra of Tl 4f7/2, O 1s and S 2p showed the bond of thallium with sulphur in TlS and Tl2S , but Tl2SO4, Tl(OH)3, S8 and Tl2O3 were also found on the surface of the layers. Five thallium sulphide phases TlS, Tl2S, Tl2S2, Tl4S3 and Tl2S5 have also been identified in the layers by X-ray diffraction. The peaks of the TlS phase predominate in the diffractograms.

Abstract: Meso-tetra (4-sulfonatophenyl) porphine (TPPS4) is water-soluble tetrapyrrolic dye, which forms self assembled nanostructures – J-aggregates under appropriate conditions. It was shown, that such aggregates survive dried on the substrate. The spatial structure of TPPS4 Jaggregates formed in acidic aqueous solutions and dispersed on silicon substrates was analyzed by means of atomic force microscopy (AFM). The stripe-like structures were observed. The size of individual stripes ranged 4,5×40×(200-1000) nm (H×W×L). The width and height was almost the same for all stripes and independent upon the concentration of the solution, however the length was statistically distributed and the mean length increased with increasing concentration of initial TPPS4 solution. At higher concentrations such stripes stacked into thicker fibers containing 2-20 stripes. Such fibers branched and formed large bush-like structures sized up to several millimeters. According to experimental findings the model of mesostructures, formed by TPPS4 J-aggregates, was proposed.