Enhanced charge carrier conduction and other characteristic parameters of hexagonal plastic columnar phase of a discotic liquid crystalline material due to functionalized gold nanoparticles

Abstract

Dispersion of functionalized nano particles in discotic liquid crystals (DLC) leads to many interesting electronic properties with self assembled structural flexibility. With this view, we have dispersed thiol capped Gold nano particles (GNPs) in a DLC namely 2,3,6,7,10,11-hexabutyloxytriphenylene (HAT4), possessing hexagonal plastic columnar phase (Colhp). Two composites have been prepared with different concentration of GNPs in pure DLC. These composite systems are studied with the help of Differential scanning calorimetry (DSC), Impedance spectroscopy (IS), Polarizing optical microscopy (POM), Ultraviolet-visible (UV–Vis) spectroscopy and Small angle X-ray scattering (SAXS) measurements. Interesting interplay between properties of capped GNPs with intrinsic properties of host DLC is observed. A shift in the UV–Vis absorption spectra of pure DLC suggests changes in the electronic band structure of the nano-composites. An increase in ionic conductivity by 6 order of magnitude has been observed due to the dispersion of GNPs in DLC. The idea of using capped GNPs to overcome their aggregation at low temperatures has worked well. In addition, both dielectric and texture studies confirm the formation of well ordered columnar structure of the discotic phase. These results are supported by SAXS studies which suggest an increase in π- π orbital overlapping in dispersed samples. The study also shows the variation of different hexagonal lattice reflection planes with respect to the temperature.