An inorganic liquid crystalline dispersion with 2D ferroelectric moieties

Abstract

Electro-optical effect based liquid crystal devices have been extensively used in optical modulation techniques, in which the Kerr coefficient reflects the sensitivity of the liquid crystals and determines the strength of the device operational electric field. The Peterlin-Stuart theory and the O’Konski model jointly indicate that a giant Kerr coefficient could be obtained in a material with both a large geometrical anisotropy and an intrinsic polarization, but such a material is not yet reported. Here we reveal a ferroelectric effect in a monolayer two-dimensional mineral vermiculite. A large geometrical anisotropy factor and a large inherent electric dipole together raise the record value of Kerr coefficient by an order of magnitude, till 3.0 × 10−4 m V−2. This finding enables an ultra-low operational electric field of 102∼104 V m−1 and the fabrication of electro-optical devices with an inch-level electrode separation, which is not practical previously. Because of its high ultraviolet stability (decay < 1% under ultraviolet exposure of 1000 hours), large-scale, and energy-efficiency, prototypical displayable billboards have been fabricated for outdoor interactive scenes. The work provides new insights for both liquid crystal optics and two-dimensional ferroelectrics.

A comprehensive review of atomically thin silicates and their applications

“…This large Kerr coefficient will make it possible to build a large-scale, energy-efficient device. This work gives evidence of 2D ferroelectrics in layered silicates [90].…”

“…These functional core layers then show excellent light response characteristics suitable for photocatalysis and optical applications. A very recent study has also shown that 2D VMT liquid crystalline dispersion prepared by a cationexchange method can show intrinsic ferroelectricity and a huge geometrical anisotropy factor over 1500, both of which contribute to the gigantic Kerr coefficient (about 3.0 × 10 −4 m V −2 ) [90]. This large Kerr coefficient will make it possible to build a large-scale, energy-efficient device.…”