# Perspectives in Liquid-Crystal-Aided Nanotechnology and Nanoscience
## 2 Modification of Physical Properties of LC Materials by Nanodopants  
LCs have been well identified with the applications in commercial displays due to their outstanding electro-optic performance, which is a consequence of their anisotropy of the dielectric constant and the optical refractive index in combination with their elasticity and ready response to external stimuli. However, with the rapid development of technology, liquid crystal displays (LCDs) can no longer meet the increasingly demanding visual requirements with traditional LC mixtures. In the search for LCDs with lower driving voltage, higher colour contrast ratio and shorter response times, novel materials need to be employed to meet increasing demands. At the same time, for progress in other research and technology areas, such as novel optical devices, advanced materials, nanotechnologies and biosciences, LCs with improved physical properties are needed. Currently, one of the effective primary solutions is introducing various functional nanodopants into existing high-performance LC materials. As reported by many studies, nanodopants, such as ferromagnetic, ferroelectric, semiconducting particles of various shapes, as well as carbon nanoparticles, can effectively modify electro-optic responses as well as other physical characteristics of LCs. Since [PERSON] et al. first reported that dispersing low concentrations of submicron ferroelectric particles (Sn\({}_{2}\)P\({}_{2}\)S\({}_{6}\)) in commercial nematic LCs (ZLI-4801) could enhance the dielectric response, lower the operating voltage and induce a linear response to the applied electric field [168], ferroelectric nanoparticle dispersions have been studied extensively as dopants for LC modifications. It was argued that the dispersion of ferroelectric nanoparticles can induce an enhancement of the orientational order of LCs because of the coupling between the spontaneous polarization of the ferroelectric nanoparticles and the liquid crystal via an elastic field, and hence effectively improve the electro-optical properties of LCs [86; 169; 170] through increased molecular order. Recently, [PERSON] et al. systemically investigated the physical characteristics, including dielectric constants, threshold voltage and elastic constants, of the composite consisting of the nematic LC 6 CHBT and ferroelectric nanoparticles of barium titanate (BaTiO\({}_{3}\)) [94]. The ferroelectric nanoparticle-LC composite in their system showed an improved electro-optical characteristic, accompanied by an increase in the dielectric anisotropy as well as a decrease in the threshold voltage. [PERSON] et al. found that the physical properties of suspensions of ferroelectric nanoparticles of barium titanate dispersed in the nematic liquid crystal 5 CB are largely dependent on the concentration of nanoparticles [171]. For samples with a low concentration (<1 wt %), the threshold voltage, elastic constants, dielectric coefficients and ionic conductivity could be effectively changed. For those with high concentrations (>1 wt %), the changes were relatively small. Although there have been numerous papers proposing that doping ferroelectric nanoparticles will improve the physical properties of the dispersion, the experimental results still appear sketchy, sometimes even contradictory, and improvements are not straightforward to achieve. As pointed out above, the effect of ferroelectric particle doping strongly depends on the preparation conditions, time, size of the dopant particles, and various other uncontrollable parameters; for example, barium titanate exhibits a particle size-dependent transition between ferroelectric and paraelectric behaviour, whose transition, in addition, depends on the actual milling process employed to produce the nanoparticles. [PERSON] et al. found that doping ferroelectric nanoparticles (BaTiO\({}_{3}\)) did not change the threshold voltage of nematic LCs (5 CB) [169], while [PERSON] et al. even presented an increase in the Freedericksz threshold voltage and no change in the dielectric anisotropy [172].