A small quantity of graphene, containing both monolayer and multilayer flakes, was doped in a nematic liquid crystal (LC), and the nematic electro-optic switching was found to be significantly faster in the LC þ graphene hybrid than that of the pure LC. Additional studies revealed that the presence of graphene reduced the free ion concentration in the nematic media by ion-trapping process. The reduction of mobile ions in the LC was found to have subsequent impacts on the LC's conductivity and rotational viscosity, allowing the nematic director to respond quicker on switching the electric field on and off. V

Articles you may be interested inEnhanced optoelastic interaction range in liquid crystals with negative dielectric anisotropy Appl. Phys. Lett.Dielectric hysteresis, relaxation dynamics, and nonvolatile memory effect in carbon nanotube dispersed liquid crystal

A small quantity of carbon nanotubes (CNTs) was dispersed in a liquid crystal (LC) and the LC þ CNT hybrid in the isotropic phase was found to exhibit an insulator-to-conductor transition when an external electric field was applied. This effect was probed by measuring the resistance of the system as a function of applied voltage across the LC cell. In an LC þ CNT hybrid, the LC molecules self-assemble themselves at the CNT surface due to p-p electron stacking, creating pseudonematic domains (PNDs) surrounding the CNTs. These CNT-embedded PNDs interact with the external electric field even in the isotropic phase of the LC. When the external field is applied, the PND-encapsulated CNTs start to rotate along the field and form wires due to their natural tendency of entanglement. The CNT-wires eventually short the two electrodes of the LC cell, manifesting an insulator-to-conductor transition in the LC þ CNT hybrid. Additional studies revealed that the cell spacing and the CNT-concentration had a significant impact on the threshold voltage across the LC cell for the insulator-to-conductor transition process. [

A small quantity of BaTiO3 ferroelectric nanoparticles (FNPs) of 50 nm diameter was doped in a nematic liquid crystal (LC), and the free ion concentration was found to be significantly reduced in the LC + FNP hybrid compared to that of the pure LC. The strong electric fields, due to the permanent dipole moment of the FNPs, trapped some mobile ions, reducing the free ion concentration in the LC media. The reduction of free ions was found to have coherent impacts on the LC's conductivity, rotational viscosity, and electric field-induced nematic switching.

The two-dimensional graphene-honeycomb structure can interact with the liquid crystal's (LC) benzene rings through π-π electron stacking. This LC-graphene interaction gives rise to a number of interesting physical and optical phenomena in the LC. In this paper, we present a combination of a review and original research of the exploration of novel themes of LC ordering at the nanoscale graphene surface and its macroscopic effects on the LC's nematic and smectic phases. We show that monolayer graphene films impose planar alignment on the LC, creating pseudo-nematic domains (PNDs) at the surface of graphene. In a graphenenematic suspension, these PNDs enhance the orientational order parameter, exhibiting a giant enhancement in the dielectric anisotropy of the LC. These anisotropic domains interact with the external electric field, resulting in a non-zero dielectric anisotropy in the isotropic phase as well. We also show that graphene flakes in an LC reduce the free ion concentration in the nematic media by an ion-trapping process. The reduction of mobile ions in the LC is found to have subsequent impacts on the LC's rotational viscosity, allowing the nematic director to respond quicker on switching the electric field on and off. In a ferroelectric LC (smectic-C Ã phase), suspended graphene flakes enhance the spontaneous polarisation by improving the tilted smectic-C Ã ordering resulting from the π-π electron stacking. This effect accelerates the ferroelectric-switching phenomenon. Graphene can possess strain chirality due to a soft shear mode. This surface chirality of graphene can be transmitted into LC molecules exhibiting two types of chiral signatures in the LCs: an electroclinic effect (a polar tilt of the LC director perpendicular to, and linear in, an applied electric field) in the smectic-A phase, and a macroscopic helical twist of the LC director in the nematic phase. Finally, we show that a graphene-based LC cell can be fabricated without using any aligning layers and ITO electrodes. Graphene itself can be used as the electrodes as well as the aligning layers, obtaining an electro-optic effect of the LC inside the cell. P A 50 m P A Planar alignment 0 V 45 V Homeotropic alignment E ARTICLE HISTORY