Prystai T. Modification of cholesteric liquid crystals by nano impurities for use in optical sensors

In this work we present general motivation for our research, justify and rationalize the particular choice of materials that were studied and present the main characteristics of the nanocomposites used for modification of CLC properties. As a basic liquid crystal matrices in our research were chosen: commercially produced CLC mixtures by Hoffmann - La Rosh© - CLC2101L, CLC2103L; and cholesteric mixtures synthesized in the Institute of Semiconductor Physics, NAS of Ukraine - EE1. To investigate the effect of nanoparticle doping on CLC and induced CLC physical properties, following types of particles were selected: Aluminum nitride (AlN) nanotubes, gold nanorods synthesized by seed-mediated method, Magnetite particles (Fe3O4), Ferric oxide particles (Fe2O3). In this work we present: General research methodology for studying mesoporous structures based on CLC modified by nanoparticles; Detailed scheme of experimental setup used for research of interaction between CLC based structures and different gases. Suggested design of photo-converter device and proposed methodology for formation of its spectral characteristic. Spectral studies of cholesteric of liquid crystal of CLC - 2103l, are undertaken magnetite alloyed by nanoparticles, that came true in the range of lengths of waves of 200 – 1200 нм, there is a from 20 to 150 mg/м3 at room temperatures and concentration of monoxide of carbon. Dependences of coefficient of spectral sensitivities are got for nanocomposix on the basis of magnetite of Fe2O3 and Fe3O4 that show that regardless of type of magnetite of increase of his concentration in ХРК of matrix results in the increase of coefficient of spectral sensitiveness. The circuit design solution for the construction of an optical carbon monoxide sensor based on a cholesteric liquid crystal doped with nanosized magnetite Fe2O3 allows to determine the concentration of carbon monoxide in the range from 10 to 40 mg/m3. An optical amino acid sensor has been developed, the sensitive element of which is a cholesteric-nematic mixture based on BLO-60 + 5CB, supplemented with an aqueous solution of gold nanoparticles. A study of this sensor to determine the concentration of valine in the range from 0 to 50%. The relationship between the number of gold nanoparticles in the mixture and the value of the minimum transmission wavelength is established. Increasing the concentration of gold nanoparticles in the mixture by more than 10% increases the sensitivity of the system to valine.