# Perspectives in Liquid-Crystal-Aided Nanotechnology and Nanoscience
## 2 Modification of Physical Properties of LC Materials by Nanodopants
The reasons for the different behaviour observed may be the uncontrollable ionic contamination, broad size distribution and irregular shapes of particles, poor dispersibility, etc. For example, it has been reported that large ferroelectric particles (>100 nm) can form a polydomain structure but very small particles (<10 nm) may lose their ferroelectricity [98]. A recent study by [PERSON] et al. systemically investigated the dependence of the electric-optic and dielectric properties of the LC (nematic 5 CB and ferroelectric SmC\({}^{\star}\) Felix M4851/050), suspended [173] with barium titanate nanoparticles of different size and concentration (Figure 4). They demonstrated that the ferroelectricity of nanoparticles was highly dependent on the particles' sizes, and the particles did not influence the nematic LC properties unless the concentration was high enough (>0.5 vol %), where a reduction of electro-optic response time was observed, which was due to the enhancement of dielectric anisotropy. [PERSON] et al. did a low-frequency dielectric investigation of a Schiff-based LC compound dispersed with BaTiO\({}_{3}\) nanoparticles [174]. They found that the doped LC-ferroelectric nanoparticle suspension exhibited a temperature- and frequency-dependent dielectric permittivity. In addition, due to the spontaneous dipole moment, a huge number of free ions in LCs were captured by the ferroelectric nanodopants, leading to a diminishing of the Maxwell-Wagner-Sillars effect. This will in fact have a pronounced effect on the threshold voltage, and ion capture would be expected to reduce the threshold voltage. Alternatively, this implies that when using a pure, commercially cleaned liquid crystal, the ion concentration is already low, such that only minute effects on the threshold voltage would be expected, explaining some of the discrepancies reported in different publications. Furthermore, the authors found in general that the conductivity, dielectric anisotropy and relaxation frequency of the compound decreased due to the strong interaction between BaTiO\({}_{3}\) particles and LC molecules. It seems that ferroelectric nanoparticles do modify the physical properties of LC matrixes, sometimes leading to an improvement in the electro-optic performance; however, due to the complicated size-dependent ferroelectricity and aggregation behaviour of ferroelectric nanoparticles in LCs, additional research is necessary. Except for ferroelectric nanoparticles, inorganic nanoparticles, such as metallic nanoparticles, quantum dots (QDs) and oxides, can also effectively modify the physical parameters of LC materials, sometimes leading to an improvement in the electrical and electro-optic performance. Just like ferroelectric nanoparticles, metallic nanoparticles, such as gold nanoparticles, are expected to potentially improve the physical properties of liquid crystal materials due to the anticipation that the electrostatic interactions between LC molecules and metal nanoparticles can significantly enhance the orientational order of LCs [175; 176; 177; 178; 179; 180; 181]. The argument of performance enhancement through an increase in orientational order has been used in many publications to explain the observed results. Nevertheless, to our knowledge such an increase has not been demonstrated quantitatively by a strongly reliable experimental method, such as X-ray diffraction at equal reduced temperatures, for example, with values for the neat and the doped system being well outside the limits of error. Recently, [PERSON] et al. investigated the thermodynamics, electro-optic response and dielectric permittivity of a nematic LC (6 CHBT)-gold nanoparticle composite [182] (Figure 5). It was found that the threshold voltage required for switching LC molecules from homogeneous to homeotropic alignment was decreased, while the first phase transition temperature (isotropic to nematic) as well as the dielectric permittivity for the composite, was raised due to the increased nematic ordering of the host LC medium.