Probing Molecular Binding Effect from Zinc Oxide Nanocrystal Doping in Surface-Stabilized Ferroelectric Liquid Crystal with Two-Dimensional Infrared Correlation Technique

Abstract

Doping liquid crystal (LC) with nanomaterials has been shown to yield some degrees of freedom for tailoring LC properties. This approach can be employed to produce new LC materials with high application potentials by blending instead of synthesizing new mesogenic molecules. In this paper, we show that doping ferroelectric liquid crystal (FLC) with ZnO nanocrystals improves the alignment order of a surface-stabilized FLC (SSFLC) in both steady-state and field-induced reorientation processes. We used the two-dimensional infrared (2D IR) correlation technique to reveal that the ZnO nanocrystals were uniformly dispersed into the FLC medium. The homogeneous dispersion of ZnO nanodots produces stronger correlations among the IR-active molecular normal modes of FLC molecules, which then leads to more concerted reorientation process at the submolecular level. A molecular binding effect originating from a dipolar interaction of the ZnO nanodot with surrounding CO groups of FLC molecules was proposed to illustrate our measured results. We estimated the total energy reduced by the doping to be about 1000 J/m3. The alignment stability gained is similar to that experienced by FLC molecules within 100-nm distance to an alignment surface with a strong anchoring strength of 1 × 10-4 J·m-2.

Nano-colloids of Sn_{2}P_{2}S_{6} in nematic liquid crystal pentyl-cianobiphenile

“…To our knowledge, three types of ferroelectric materials have been studied as dopants of nanoparticles in LC matrixes: Sn 2 P 2 S 6 [3,7,8,[14][15][16], BaTiO 3 [6,7,17] and ZnO [9]. Since the majority of the experimental data were collected for the material Sn 2 P 2 S 6 (tin thiohypodiphosphate) and the nano-colloids based on this are extremely promising for photorefractive applications [14,15,18], this ferroelectric material was chosen for our experiments.…”

“…Recently the unique properties of dilute colloids of ferroelectric nano-particles in LCs were reported [3,[6][7][8][9]37]. These colloids are stable because the particles do not agglomerate at low concentrations (less than 0.1-1% by weight).…”

“…As a result, the ferroelectric colloid appears similar to a pure LC with no readily apparent evidence of dissolved particles. At the same time the nano-particles may produce substantial changes in the physical properties of the liquid crystal host -they enhance the order parameter, birefringence and dielectric anisotropy of nematics [3,6], improving the alignment order of a surface-stabilized ferroelectric LCs [9].…”

Effect of ZnO nanoparticles on the SmC*-SmA* phase transition temperature in electroclinic liquid crystals

“…18,19 Huang et al explored the effect of doping of ZnO NPs in surface stabilized ferroelectric liquid crystals (SSFLCs) by improving the alignment of FLC molecules and field induced reorientation processes. 20 Moreover, Li and Huang proposed a physical model depicting an interaction of ZnO NPs with surrounding FLC molecules. 21 But the effect of ZnO NPs on the phase transition temperature and dielectric relaxation processes of FLC materials has not been reported.…”

Low power operation of ferroelectric liquid crystal system dispersed with zinc oxide nanoparticles

“…The low power operation of vertically aligned LC by doping a minute amount of anatase TiO 2 -NPs have been observed by Lee et al 11 Zinc oxide ͑ZnO͒ has been employed in a variety of devices such as gas sensors, solar cells, luminescent materials, and transparent conducting coatings due to its wide range of optical and electrical properties. [12][13][14] Huang et al 15 explored the importance of addition of ZnO nanocrystals into the surface stabilized FLCs ͑SSFLCs͒ by probing the molecular binding of FLC molecules which surrounded the ZnO-NPs. Li et al 16 proposed a model to show the interaction between ZnO-NPs and FLC molecules surrounding them.…”