Photoaligned nematic liquid crystals doped with palladium-immobilised carbon nanospheres for advanced low-voltage display and energy storage devices

Abstract

This study presents a nematic liquid crystal (NLC), D30-17, doped with palladium-immobilised carbon nanospheres (CNS) Pd/ON10 at two different concentrations. The composites were prepared with 0.1 and 0.4 wt/wt% dopant concentrations and are referred to as Mix 1 and Mix 2, respectively. The palladium-immobilized carbon nanospheres were employed because they function as advanced materials for catalysis and energy applications owing to the catalytic properties of palladium. The sample holder used in this experiment consisted of photo-aligned cells coated with a photosensitive alignment layer, Cibacron brilliant yellow (CBY). The textural studies revealed improved alignment in the doped mixtures. The frequency- and temperature-dependent dielectric behaviour was analysed for the pure and doped systems in both the planar (at 0 V) and homeotropic (at 12 V) states. Dielectric studies showed that the relative permittivity, dielectric loss, and conductivity of the doped material increased with increasing dopant concentration compared with that of pure NLC. Compared with the pure NLC and Mix 2, Mix 1 exhibited greater dielectric anisotropy, leading to a lower threshold voltage. A reversal in the dielectric anisotropy was also observed, which was attributed to the bistable inversion in the CBY alignment layer of the photo-aligned cells. Optical studies indicated that there was no significant shift in wavelength with respect to the dopant concentration. These composites are expected to find applications in liquid-crystal-based electronic and photonic devices.