Facile synthesis of gold nanoparticles capped with an ammonium-based chiral ionic liquid crystal

Herein, we describe a facile synthesis of stable chiral ionic liquid crystal (ILC)-capped gold nanoparticles. A new ILC containing a chiral cholesterol moiety having a terminal triethylammonium group was synthesised which exhibited an enantiotropic lamellar mesophase. Stable, monodisperse citrate-stabilised gold nanoparticles having a size of ~60 nm were prepared and the citrate ligands on the gold nanoparticles were replaced with chiral ILC through a two-phase ligand exchange process. The resulting chiral ILC-stabilised particles were characterised using UV–visible (UV–Vis) and transmission electron microscopy (TEM) studies. Different from the citrate-stabilised nanoparticles, the ligand exchanged gold nanoparticles were dispersible in organic solvent and resulting dispersion was stable for more than observed period of 3 months. Furthermore, the chiral ILC-decorated gold nanoparticles were found to be well dispersible in a nematic host without any aggregation and induced a vertical alignment of the nematic director.