LaPO₄ Mineral Liquid Crystalline Suspensions with Outstanding Colloidal Stability for Electro‐Optical Applications

Abstract

Mineral liquid crystals are materials in which mineral's intrinsic properties are combined with the self‐organization behavior of colloids. However, the use of such a system for practical application, such as optical switching, has rarely been demonstrated due to the fundamental drawbacks of colloidal systems such as limited dispersion stability. Studying colloidal suspensions of LaPO4 nanorods, it is found that drastic improvement of colloidal stability can be obtained through a transfer of particles from water towards ethylene glycol, thus enabling the investigation of liquid crystalline properties of these concentrated suspensions. Using polarization microscopy and small‐angle x‐ray scattering (SAXS), self‐organization into nematic and columnar mesophases is observed enabling the determination of the whole phase diagram as a function of ionic strength and rod volume fraction. When an external alternative electric field is applied, a very efficient orientation of the nanorods in the liquid‐crystalline suspension is obtained, which is associated with a significant optical birefringence. These properties, combined with the high colloidal stability, are promising for the use of such high transparent and athermal material in electro‐optical devices.

Monitoring the orientation of rare-earth-doped nanorods for flow shear tomography

“…A prerequisite for precise orientation analysis is to acquire the reference photoluminescence polarization com-ponents, which requires either working with a single crystal or achieving a uniform orientation of small crystallites. Here, we use liquid-crystalline (LC) self-assembly of monocrystalline LaPO 4 :Eu nanorods [15,16] that exhibit polarized photoluminescence, as from a large single crystal. By electrically switching the orientation of the LC domain [17], in a manner similar to the approach by Galyametdinov et al with organic lanthanidomesogens [18], polarized Eu 3+ emission spectra could be selectively obtained for the three main configurations (σ and π, the radial propagations polarized perpendicular and parallel to the rod axis, respectively, and α, the isotropic axial propagation).…”

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

“…30 The ionic diffusion coefficient can be calculated according to: When dialyzed from nitric acid solution to ethylene glycol, the ions maintaining electro-neutrality of the dispersion are therefore the counterions associated with the rod-like particles, i.e.…”

“…30 In this work, we first investigate the frequency dependence of the steady-state electric birefringence in our non-aqueous suspensions. 30 The samples are prepared by diluting the rod-like particles with ethylene glycol to reach a concentration close to the binodal volume fraction (f B = 0.8% AE 0.1%) corresponding to the highest concentration of the isotropic liquid phase before the transition to the nematic state. We then account quantitatively for the Kerr effect and its dependence with the field frequency and with the rod volume fraction thanks to the Maxwell-Wagner-O'Konski theory.…”

Advances in the Study of Inorganic Lyotropic Liquid Crystals

“…14. Текстуры и схемы фаз дисперсии LaPO 4 в этиленгликоле [38] В работе [39] были исследованы электрооп-тические свойства нематической и колумнарной фазы. Образцы нематика имели концентрацию φ = 1,55 %, колумнарика -4,34 %.…”