Effect of dispersion of gold nanoparticles on the optical and electrical properties of discotic liquid crystal

Abstract

Dispersion of gold nanoparticles (GNPs) in mononitro-substituted triphenylene-based discotic liquid crystal (DLC), which shows columnar plastic phase (Colp) along with columnar hexagonal phase (Colh) at room temperature, was studied by differential scanning calorimetry, polarising optical microscopy, X-ray diffraction, dielectric spectroscopy, visible absorbance spectroscopy and IR dichroic technique. The experimental results show that inclusion of GNPs in the DLC matrix strains the columnar matrix. More ordered Colp which possesses high charge carrier mobility because of the three-dimensional positional order is still preserved even by insertion of GNPs into the columnar matrix. However, we observed a decrease in orientational order parameter (S) and increase in relaxation time (τ) for disc motion with GNPs in Colp. But there is enhancement in dc electrical conductivity by several orders of magnitude at ambient conditions with GNPs. These GNP–DLC composite systems hold great promises in many organic semiconductor device applications.