Electro-Optics of Nematic/Gold Nanoparticles Composites: The Effect from Dopants

We studied the change of electro-optic properties of room-temperature nematic pentylcyanobiphenyl (5CB) when this liquid crystal is mixed with a small amount (similar to 0.5wt.%) of polymer-capped gold nanoparticles (AuNPs). The AuNPs were spherical-shaped, with a diameter of about 12nm, the size of the polymer-capped AuNPs was ca. 25nm. Instead of well pronounced stationary longitudinal domains observed in planar 5CB nematic layers upon static electric field, hybrid longitudinal texture pattern oriented along the rubbing of the cells takes place in this case in identical cells of 5CB doped with AuNPs. The micro-periodic-modulated morphology is reflected on the electro-optic response of AuNPs/5CB nanocomposites. The effect from the nano-dopants is elucidated by detailed investigation (optical, thermo-optical, electrical and electro-optical macroscopic measurements).