Effect of the vanadium doped titanium oxide nanoparticles on ionic contribution in dielectric behaviour of a nematic liquid crystal

Modern technology has been facilitated by the combination of liquid crystals (LCs) and nanomaterials (NMs) which led to tunable and responsive LC-based devices. This is very common among all LCs-based devices that they are driven by an electric field which causes the reorientation of LCs molecules. The ions that are normally present in the LCs material can affect the reorientation process of LCs molecules due to the screening effect. The NMs play an important role in controlling the number of ions either by ion-capturing or ion-releasing processes. Therefore, it is necessary to understand about the effect of different NMs on the ions in LCs. To achieve this goal, we have studied the effects of vanadium-doped titanium oxide (VTO) nanoparticles (NPs) on the dielectric properties of nematic LCs (NLCs). Various dielectric parameters such as dielectric permittivity, dielectric loss, dielectric loss factor, and dielectric anisotropy have been studied at different temperatures for different concentrations (0, 0.05, 0.10, 0.25, and 1.00 wt.%) of VTO NPs in host 5CB LC material. We have observed a significant change in the dielectric parameters of the 5CB LC material after the dispersion of the VTO NPs in the low-frequency region. These changes may be attributed to the presence of ionic impurities in the pure and dispersed 5CB materials. To confirm the role of ionic impurities on the dielectric properties, we have calculated the ion concentration and diffusion constant for various concentrations of NPs by fitting the dielectric loss data according to Uemera formalism. We have observed an increase in the ion concentration with the dispersion of NPs up to 0.25 wt.%. We have also noticed an increase in the threshold voltage and dielectric anisotropy with the dispersion of NPs. The increase in the dielectric parameters of the pure 5CB LC material after dispersion of the VTO NPs is attributed to the ion-releasing nature of the VTO NPs. These studies may be useful for various applications of LC materials in which the presence of ions effectively enhances the properties of LC-based devices.