Why organically functionalized nanoparticles increase the electrical conductivity of nematic liquid crystal dispersions

Abstract

We demonstrate that ionic impurities trapped in the dense ligand shell of functionalized nanoparticles significantly increase the conductivity in LC nanodispersions.

Nanoparticle-Enabled Ion Trapping and Ion Generation in Liquid Crystals

“…As a result, once quantum dots functionalized with TOPO are dispersed in liquid crystals, ionic contaminants can be released in the bulk of the liquid crystal host. This assumption is also consistent with recent findings reported by Urbanski and Lagerwall [42]. In the case of uncontrolled ionic contamination of nanodopants, the values of the contamination factor are typically relatively low.…”

“…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].…”

On the Analogy between Electrolytes and Ion-Generating Nanomaterials in Liquid Crystals

“…At the same time, nanomaterials releasing ions in liquid crystals may seem like an unexpected possibility. Yet, many experiments have also confirmed the ion-generating properties of nanomaterials in liquid crystals [61,68,71,76,77]. The effect of ion generation by nanoparticles in liquid crystals can be very strong, as was reported recently by Urbanski and Lagerwall [61].…”

“…Yet, many experiments have also confirmed the ion-generating properties of nanomaterials in liquid crystals [61,68,71,76,77]. The effect of ion generation by nanoparticles in liquid crystals can be very strong, as was reported recently by Urbanski and Lagerwall [61]. They found that the number of ions generated by functionalized gold nanoparticles dispersed in nematic liquid crystal 5CB can be comparable to and even greater than the number of ions generated in liquid crystals by 1:1 electrolytes [61].…”

“…Recently, liquid crystals doped with nano-objects have emerged as novel tunable materials with advanced functionalities [41][42][43][44][45][46][47]. Electrical properties of liquid crystals doped with ferroelectric [48][49][50][51][52][53][54], magnetic [55][56][57], metal [58][59][60][61][62][63], semiconductor and dielectric [64][65][66][67][68][69], and carbon-based (fullerenes, carbon nanotubes, graphene, diamond) nanomaterials [70][71][72][73][74][75] were studied by many research teams (see also recent reviews [76,77] and references therein). The ion capturing effect is naturally expected for nanomaterials dispersed in liquid crystals.…”