Effect of dispersed colloidal gold nanoparticles on the electrical properties of a columnar discotic liquid crystal

Abstract

A dispersion of colloidal gold nanoparticles (GNPs) in a triphenylene-based discotic liquid crystal (DLC), namely 2,3,6,7,10,11-hexabutyloxytriphenylene (HAT4), possessing a hexatic plastic columnar phase (Colhp) phase, has been studied by differential scanning calorimetry, polarized light microscopy, UV-Vis absorption spectroscopy, X-ray diffraction and dielectric spectroscopy. GNPs have been dispersed at three different concentrations in pure HAT4 viz. 0.2, 0.6 and 1.2 wt%. It has been observed that with the increase of GNPs concentration, the Colhp–isotropic liquid transition temperature decreases substantially but the crystal–Colhp transition temperature does not changes significantly. Electrical conductivity increases by at least five orders of magnitude for the highest concentration of GNPs (1.2 wt%) as compared to the pure material i.e. HAT4. Observed results suggest that although extremely low concentrations of GNPs are not very useful, a moderate concentration is highly useful for increasing the conductivity of the Colhp phase and also to implant surface plasmon resonance. These results may be exploited to enhance the efficiency of electro-optical devices by using HAT4–GNPs composites.