Arranging plasmonic nanomaterials in a certain way can create materials with special optical properties, such as having anisotropy with refractive indices of simultaneously opposite signs for opposite light polarization. This type of material can be based on doping a liquid crystal system with nanoparticles with the indicated properties. Gold nanorods (AuNRs) are rod-shaped nanoparticles with size-dependent optical responses, and because of their plasmonic properties, they are used in imaging and fluorescent enhancement.

In our work, we investigated the influence of gold nanorods on the phase transitions and optical properties of the liquid crystal 8CB, known for its thermotropic behaviour. Gold nanorods were synthesized using a seed-mediated approach to obtain nanoparticles with the desired dimensions (aspect ratios: 5,6; 8,2; 10,8), which were observed and measured using transmission electron microscopy. Different concentrations of AuNRs were added to the 8CB samples, which were then inserted into liquid crystalline cells. All the samples were observed under a polarized light microscope equipped with a heating stage. At each concentration of the AuNRs, different optical structures were observed in both the nematic and smectic phases. The temperatures of the phase transitions also differed depending on the amount of the AuNR dopant in the system. The observed changes obtained by doping 8CB-based systems with nanoparticles may lead to the design of new metamaterials.