The synthesis and photo-physical properties of a hemicyanine dye

The hemicyanine dye, trans-4-[p-(N,N-di(2-hydroxyethyl))amino-styryl]-N-octylpyridinium tetraphenylborate (DHEASPT-C8), was synthesized and characterized using 1H NMR, thermo-analysis and elemental analysis. The linear optical properties in several solvents were measured using UV–vis as well as single-photon spectrophotometer, while the non-linear optical properties in DMF were measured using the Z-scan technique at 532 nm using 4 ns pulsed laser. The influence of the dye anion on its optical properties was investigated by comparing DHEASPT-C8 to trans-4-[p-(N,N-hydroxyethyl)amino-styryl]-N-octylpyridinium bromide (DHEASPBr-C8), from which it was observed that there were blue shifts in both single-photon absorption spectra and fluorescence spectra. Z-scan measurements showed that DHEASPBr-C8 displayed saturable absorption with less obvious refractive phenomena, while DHEASPT-C8 had reverse saturable absorption with obvious refractive phenomena. For DHEASPT-C8, the NLO absorption coefficient β was 3.09 × 10−11 m/W and the third-order NLO coefficient χ(3) was 4.78 × 10−12 esu.