Репозиторий Университета

© 2020 Elsevier Ltd Novel octabromo-substituted lanthanide(III) phthalocyanines were obtained via template method starting from corresponding 4,5-dibromophthalonitrile and identified by high-resolution mass-spectrometry, 1H nuclear magnetic resonanse and infra red spectroscopy. To achieve an initial 4,5-dibromophthalonitrile the reaction conditions of Pd(0) catalyzed cyanation were optimized. The peripheral bromine atoms impact on the optical properties of phthalocyanine complexes. The bathochromic shift of the main absorption band (Q band) was observed going from unsubstituted to octachloro- and then to octabromo-substituted phthalocyanines. All complexes demonstrated nonlinear optical responses in the DMF solution. Increasing the intensity of laser radiation leads to a nonlinear decrease in transmittance and further restoration of optical properties when switching back to linear mode. Nonlinear optical responses depend on the central ion nature. Europium phthalocyanine showed the enhanced nonlinear absorption coefficient compared to lutetium and terbium complexes. This was caused by an enhanced population of excited state and faster excitement for complexes with large central ions. The impact of peripheral bromine groups into nonlinear optical properties was determined through the comparison with unsubstituted analogues.

© 2020 Elsevier Inc. Biopolymer composites based on two types of chitosan (chitosan succinate and low-molecular weight chitosan) with single-walled carbon nanotubes (SWCNT) were created by laser printing. SWCNT have good dispersibility in chitosan solutions and therefore, can form relatively homogeneous films that was shown in scanning electron microscopy images. For the studies film composites were formed under the action of laser radiation on aqueous dispersion media. Study of the nonlinear optical process during the interaction of laser radiation with a disperse media has shown that low-molecular chitosan has a large nonlinear absorption coefficient of 17 cm/GW, while the addition of SWCNT lead to a significant increase up to 902 cm/GW. The threshold intensity for these samples was 5.5 MW/cm2 with nanotubes. If intensity exceeds the threshold value, nonlinear effects occur, which, in turn, lead to the transformation of a liquid into a solid phase. Characterization of films by FTIR and Raman spectroscopy indicated arising molecular interactions between chitosan and SWCNT detected as a small frequency shift and a change in the shape of radial breathing mode (RBM). The results indicate the possibility using aqueous dispersion media based on chitosan and SWCNT to create three-dimensional films and scaffolds for tissue engineering by laser printing.

© 2019 Elsevier Ltd The widespread application of laser devices requires development of new protections against light pulses of high intensity. This problem is relevant because of the danger of hitting the civil aviation pilots with bright and powerful radiation originating from the laser sources which are widely used in the everyday life. Therefore, this work is devoted to continuing our research on a new class of macroheterocyclic compounds – thermally and chemically stable J-type phthalocyanine dimers as potential nonlinear absorbers for optical limiting technology. The dimeric complexes of magnesium (1a) and zinc (1b) were covalently bonded to single-walled carbon nanotubes (SWCNTs) to improve the overall characteristics of the potential optical limiters 2a,b as compared to the previously studied corresponding dyes in solutions. The conjugates obtained were investigated using atomic force microscopy (AFM), as well as Raman and IR spectroscopy to confirm formation of the covalent binding of phthalocyanine macrocycles with the carbon surface. Open-aperture Z-scan and a fixed limiter location experiments have demonstrated low values of the limiting threshold and high degree of attenuation of the input laser radiation with the pulses duration located in the nanosecond range.

© 2018 SPIE. Laser radiation limiters can be made on the basis of working substances, which have strong nonlinear effects after reaching a certain critical value (threshold limiting). Thus, it becomes possible to obtain a high transmission for a safe beam and a sharply reduced transmission for a hazardous beam. To determine the nonlinear and linear optical properties of these materials there were carried out comprehensive spectroscopic studies, experiments by Z-scan methods with an open aperture and a fixed location of the limiter. Working substances was developed which is suspension of conjugates J-type phthalocyanine dimers Zn or Mg with single-walled carbon nanotubes (SWCNTs) in water. Created conjugates can be used not only for protecting eyes and light-sensitivity elements, but for forming three-dimensional tissueengineered structures. Using conjugates J-type phthalocyanine dimers Zn and Mg with SWCNTs will increase the optical absorption in the wavelength range of laser processing by reducing the thermal effect on other substances in the composition of this structure. The Nd:YAG laser was used as the laser radiation source for generating pulses of 16 ns duration at a wavelength of 532 nm with the linearly polarized laser beam in the horizontal plane and a shape of Gaussian type. The threshold of limiting, linear and nonlinear absorption coefficients were determined by output characteristic, that was obtained by fixed location of the limiter. Created working substances have values of the following order: linear absorption coefficient ∼ 3 cm-1 for layer of 0.2 cm thickness, low limiting threshold ∼ 1 MW·cm-2 and high value of the nonlinear absorption coefficient ∼ 550 cm GW-1. Knowing the nonlinear optical parameters, Z-scan data with an open aperture can be calculated for comparison with experimental data.