Electric field induced birefringence in non-aqueous dispersions of mineral nanorods

TL;DR

This study investigates the electric-field-induced birefringence in non-aqueous dispersions of LaPO4 nanorods, demonstrating their potential for advanced electro-optical device applications due to their high Kerr coefficients and stable liquid crystalline phases.

Contribution

It provides a quantitative analysis of the Kerr effect in LaPO4 nanorod dispersions, linking electric polarizability with birefringence under different field application methods.

Findings

High Kerr coefficients observed in LaPO4 nanorod dispersions.

Quantitative Maxwell-Wagner-OKonski theory analysis matches experimental data.

Fast switching times suggest suitability for electro-optical devices.

Abstract

Lanthanum phosphate (LaPO4) nanorods dispersed in the non-aqueous solvent of ethylene glycol form a system exhibiting large intrinsic birefringence, high colloidal stability and the ability to self-organize into liquid crystalline phases. In order to probe the electro-optical response of these rod dispersions we study here the electric-field-induced birefringence, also called Kerr effect, for a concentrated isotropic liquid state with an in-plane a.c. sinusoidal electric field, in conditions of directly applied (electrodes in contact with the sample) or externally applied (electrodes outside the sample cell) fields. Performing an analysis of the electric polarizability of our rod-like particles in the framework of Maxwell-Wagner-OKonski theory, we account quantitatively for the coupling between the induced steady-state birefringence and the electric field as a function of the voltage frequency for both sample geometries. The switching time of this non-aqueous transparent system has been measured, and combined with its high Kerr coefficients and its features of optically isotropic offstate and athermal phase behavior, this represents a promising proof-of-concept for the integration of anisotropic nanoparticle suspensions into a new generation of electro-optical devices.