# Perspectives in Liquid-Crystal-Aided Nanotechnology and Nanoscience
## 2 Modification of Physical Properties of LC Materials by Nanodopants
Figure 5: (**a**) Variation of longitudinal (\(\epsilon_{\parallel}\)) and transverse (\(\epsilon_{\perp}\)’) components of the relative dielectric permittivity with temperature for pure LC and gold-nanoparticle-dispersed 6 CHBT. **(b**) Frequency dependence of the longitudinal component of loss (\(\epsilon_{\parallel}\)’) for pure and gold-nanoparticle-dispersed 6 CHBT. Reproduced with permission from [182]. Copyright (2018) Taylor & Francis. Oxides such as zinc and titanium oxide nanoparticles have also regularly been used as dopants in LC materials due to their exotic electrical and optical properties. Numerous works focusing on the physical properties of LCs with oxide entities demonstrated new or improved electro-optic performance, including altered dielectric anisotropy, lower threshold voltage or shorter response and relaxation time [197; 198; 199]. In a recent publication, [PERSON] et al. demonstrated the effects on the physical characteristics of nematic LCs (ZSM-50087 XX, JNC) by doping with titanium silicon oxide (TiSiO\({}_{4}\)) nanoparticles. The authors found that the electro-optic characteristics of the composite were apparently improved. By increasing the doping concentration, the electro-optic properties can be further improved until the doping concentration was too large (0.2 wt %), which would influence the LC behaviour and deteriorate the electro-optic behaviour. In addition, the authors also demonstrated that the dispersed TiSiO\({}_{4}\) nanoparticles could effectively improve the thermal stability of the pristine LC system, capture impurity ions and thus lead to hysteresis-free voltage-transmittance characteristics [200]. Another kind of nanomaterial that has been widely used as a dopant for influencing the physical properties of LC materials is carbon nanomaterials. Carbon nanomaterials, including fullerene, carbon nanotube, graphene and graphene oxides, have attracted great attention due to their exotic physical and chemical properties. Fullerenes are hollow spherical molecules of nano-sized diameter, generally composed of 60-70 carbon atoms (C\({}_{60}\), C\({}_{70}\)). Among the various fullerenes, C\({}_{60}\) has been studied particularly extensively. The molecule of C\({}_{60}\) is a strong acceptor capable of accepting from one to six electrons to form the corresponding anions [201]. In order to improve the electrical and electro-optic properties of LC materials, great efforts have been made to attach C\({}_{60}\) covalently to mesogens as well as to dope C\({}_{60}\) into LC matrices [95; 202; 203; 204]. The recent, significant developments in fullerene-containing LCs have been reviewed by [PERSON] et al. [205]. In 1991, the discovery of quasi-1D carbon nanotubes (CNTs) was reported by [PERSON] [206], which ignited scientific interest in 1D nanostructures. CNTs are crystalline allotropes of carbon with atoms hexagonally arranged in curved lattices, forming hollow cylinders with diameters on the nanometre scale and aspect ratios up to 10\({}^{8}\). The CNTs composed of a single layer are called Single-Walled CNTs (SWCNTs), which can be either metallic or semi-conductive, depending on the diameter and rolling angle, while the ones formed by several concentric cylinders are called Multi-Walled CNTs (MWCNTs). Due to their exceptional anisotropic thermal, electrical, optical and mechanical properties, CNTs have been found to have great potential as additives to LCs, which will result in the improvement of electro-optic properties. A few papers have demonstrated the beneficial effects of CNTs doping on the physical properties of LC materials, such as reduced amplitude of residual DC, altered dielectric anisotropy, lower threshold voltage and shorter response time [207; 208; 209; 210; 211; 212; 213].