Impact of titanium dioxide nanoparticles on purification and contamination of nematic liquid crystals

Abstract

We have investigated the impact of titanium dioxide nanoparticles on the ionic contamination of liquid crystals. Nematic liquid crystals with high and low initial ionic contamination have been examined. It has been shown that titanium dioxide nanoparticles reduced the ion density of liquid crystals with high initial ionic contamination from 134.5 × 1012 cm−3 to 63.2 × 1012 cm−3. In the case of liquid crystals with low initial ionic contamination, the nanoparticles led to an insignificant increase of ion density from 19.8 × 1012 cm−3 to 25.7 × 1012 cm−3.

Nanoparticle-Enabled Ion Trapping and Ion Generation in Liquid Crystals

“…The effects of titanium dioxide nanoparticles on the concentration of mobile ions in nematic liquid crystals were recently reported by Shcherbinin and Konshina [34]. By dispersing TiO 2 nanoparticles (Plasmotherm, Moscow) in commercially available nematic liquid crystals (ZhK1282, NIOPIK, Moscow) the ion releasing regime was observed (Figure 2, squares) [34]. These results indicate that, in the considered case, nanoparticles in liquid crystals act as a source of ions.…”

“…By adding the ionic surfactant (cetyltrimethylammonium bromide, abbreviated as CTABr) to the same nematic liquid crystals (ZhK1282), the total concentration of ions was increased by nearly one order of magnitude [34]. Dispersing the same TiO 2 nanoparticles in these, enriched with ions, liquid crystals, the ion trapping regime was achieved [34]. To analyse these experimental results, we can consider two dominant types of ionic species in ZhK1282 liquid crystals.…”

“…Ion-related effects of nano-objects in liquid crystals were reported in many publications reviewed in a recent paper [ [39] and references therein]. Different research groups reported that various types of nanomaterials (metal [39][40][41][42][43], semiconductor [35,44], dielectric [34,36,45], ferroelectric [46][47][48][49][50][51] magnetic [52], and carbon-based [53][54][55][56]) changed the concentration of ions in liquid crystals in different ways. Despite the variety of existing experimental results on ions 2 Advances in Condensed Matter Physics and nano-objects in liquid crystals, they can be broadly categorized into the following groups: (i) papers reporting the decrease in the concentration of ions in liquid crystals (the ion trapping regime); (ii) publications presenting the increase in the concentration of ions (the ion generation regime); (iii) the combination of both ion trapping and ion generation regimes (depending on the concentration of nanodopants in liquid crystals) [39].…”

“…Despite the variety of existing experimental results on ions 2 Advances in Condensed Matter Physics and nano-objects in liquid crystals, they can be broadly categorized into the following groups: (i) papers reporting the decrease in the concentration of ions in liquid crystals (the ion trapping regime); (ii) publications presenting the increase in the concentration of ions (the ion generation regime); (iii) the combination of both ion trapping and ion generation regimes (depending on the concentration of nanodopants in liquid crystals) [39]. A very important finding is that the same type of nanomaterials dispersed in different liquid crystals can result in different regimes (ion trapping or ion generation) [34,39,53]. An elementary model of these regimes was recently proposed and developed in a series of papers [57][58][59][60][61].…”

Effect of ion trapping behavior of TiO2 nanoparticles on different parameters of weakly polar nematic liquid crystal

“…Shcherbinin et al studied the impact of TiO 2 NPs on nematic LC with different initial ionic contaminations. They explained that these types of NPs can be used to prevent uncontrolled ionic contamination that occurs during LC device production and utilization [30]. TiO 2 nanoparticles dispersion can actually change the relaxation parameters and dielectric anisotropy.…”