Time Resolved Fluorescence Depolarization of Dph in the Nematic Liquid Crystal ZLI-1167
A time dependent fluorescence depolarization experiment is reported and analyzed for the first time for a probe dissolved in an aligned thermotropic liquid crystal. We have investigated the popular dye all trans 1,6 diphenyl hexatriene (DPH) in the transparent mesophase ZLI-1167 (a ternary mixture of 4′-propyl, 4′-pentyl and 4′-heptyl, 4-cyano-bicyclohexyls) at a series of temperatures within the nematic and isotropic range. The probe order parameter <P2> and its perpendicular rotational diffusion coefficient D⊥ have been determined, together with the fluorescence lifetime τF in the liquid crystal and isotropic phase. This information is extracted applying a previously proposed theory (Zannoni, 1979) for rotational fluorescence depolarization in a mesophase and introducing a global (Knutson et al., 1983) variant of the target analysis deconvolution procedure (Arcioni and Zannoni, 1984). Our results demonstrate the possibility of employing fluorescence depolarization as a useful technique for investigating aligned mesophases.
KeywordsLiquid Crystal Fluorescence Lifetime Ternary Mixture Isotropic Phase Magic Angle
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