The research field of liquid crystals and their applications is recently changing from being largely focused on display applications and optical shutter elements in various fields, to quite novel and diverse applications in the area of nanotechnology and nanoscience. Functional nanoparticles have recently been used to a significant extent to modify the physical properties of liquid crystals by the addition of ferroelectric and magnetic particles of different shapes, such as arbitrary and spherical, rods, wires and discs. Also, particles influencing optical properties are increasingly popular, such as quantum dots, plasmonic, semiconductors and metamaterials. The self-organization of liquid crystals is exploited to order templates and orient nanoparticles. Similarly, nanoparticles such as rods, nanotubes and graphene oxide are shown to form lyotropic liquid crystal phases in the presence of isotropic host solvents. These effects lead to a wealth of novel applications, many of which will be reviewed in this publication.

https://www.mdpi.com/2076-3417/9/12/2512/pdf

Perspectives in Liquid-Crystal-Aided Nanotechnology and Nanoscience

Metal oxide-nanoparticles and liquid crystal composites: A review of recent progress

We present the results based on the electro-optic and dielectric properties of silica nanoparticle (SNP) doped ferroelectric liquid crystal (FLC) in SmC* phase. Switching time, spontaneous polarization and rotational viscosity decreases with increase in the silica concentration. An improvement in switching time after doping the silica nanoparticle is due to enhancement in anchoring energy exist between silica nanoparticle and ferroelectric liquid crystal. We noticed that the dielectric permittivity and dielectric strength decreases with increasing the concentration of silica nanoparticle in SmC* phase. Relaxation frequency increases with increasing the silica concentration and temperature in SmC* and decreases as we approaches towards transition temperature.

Electro-optic and dielectric studies of silica nanoparticle doped ferroelectric liquid crystal in SmC* phase

Twenty liquid crystals both symmetrical and non-symmetrical bistolanes with terminal alkyl, alkoxy and alkylsulfanyl chain and lateral methyl or ethyl group have been synthesized via Sonogashira cross-coupling and their mesomorphic properties have been studied. Most compounds exhibit an enantiotropic nematic phase in a broad temperature range (>40 °C). Optical properties of selected compounds have been investigated. They exhibit a high value of birefringence (>0.4).

High birefringence bistolane liquid crystals: synthesis and properties

To capitalize on the unique size and shape-dependent optical and electronic properties of nanoscale particles for liquid crystal (LC) applications, detailed structure and size-property relationship studies are critical. To enhance our understanding of the thermal, optical and electro-optic effects of nanoparticles in nematic LCs we produced numerous different nematic LC mixtures containing small quantities of dispersed metal nanoparticles (i.e. gold and silver nanoclusters) or semiconductor quantum dots (i.e. CdTe nanocrystals) and studied their optical (texture, alignment, defect formation, luminescence) and electro-optic properties. Depending on several experimental parameters such as nanoparticle functionalization and concentration, as well as thermal history in combination with an applied electric field, these nanoparticle/LC mixtures with the nanoparticles differing in surface functionality, size, and core material gave rise to unique alignment effects and electro-optic responses in the two investigated nematic LC (N-LC) hosts.

Effects of functionalized metal and semiconductor nanoparticles in nematic liquid crystal phases

Herein, we report that liquid crystal displays (LCDs) such as TN (twisted nematic)-mode, TB (tunable birefringence)-mode, VAN (vertically aligned nematic)-mode, BN (bent nematic)-mode, 
and so forth, exhibit the reduction in the operating voltage and response times by doping the nanoparticles of inorganic substances such as MgO. These effects may be attributed to the modification of the physical properties of the liquid crystal host media in these LCD cells.

Kohki Takatoh

Papers

Enhancement of the characteristics of LCDs by doping nanoparticles : reduction of the operating voltage, viscosity, and response times