Nanoparticle-Induced Property Changes in Nematic Liquid Crystals.

Nicolas Brouckaert,Tetiana Orlova,Angela F De Fazio,Nina Podoliak,Antonios G Kanaras,Malgosia Kaczmarek,Ondrej Hovorka,Denitsa Bankova,Giampaolo D’Alessandro

doi:10.3390/nano12030341

Nicolas Brouckaert, Tetiana Orlova + Show 7 more

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https://doi.org/10.3390/nano12030341

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Abstract

Doping liquid crystals with nanoparticles is a widely accepted method to enhance liquid crystal’s intrinsic properties. In this study, a quick and reliable method to characterise such colloidal suspensions using an optical multi-parameter analyser, a cross-polarised intensity measurement-based device, is presented. Suspensions characterised in this work are either plasmonic (azo-thiol gold AzoGNPs) or ferroelectric Sn2P2S6 (SPS) nanoparticles in nematic liquid crystals. The elastic constants and rotational viscosity showed nonlinear dependence on the concentration of AzoGNPs, initially increasing at lower concentrations and then decreasing at higher concentrations, indicating some degree of particle aggregation. For the SPS suspension, the elastic constant decreased with doping, while the rotational viscosity increased, in agreement with previous findings. Through viscosity measurements, the stability of SPS suspension over ten years is also highlighted.

Highlights

Academic Editor: Yann MolardThe electro-optic properties of liquid crystals (LC) are widely exploited in optical devices, such as displays, light modulators and variable wave plates [1,2,3]
For the first time, the use of optical multi-parameter analyser (OMPA) to study the changes of E7 and 5CB electro-optical and viscosity properties when doped with novel nanoparticles, azo-thiol-functionalized gold nanoparticles (AzoGNPs), with the concentrations up to 3 wt%
We present OMPA measurements of elastic constants and rotational viscosity of nematic LCs E7 and 5CB doped with azo-thiolated gold nanoparticles and

Summary

Introduction

The electro-optic properties of liquid crystals (LC) are widely exploited in optical devices, such as displays, light modulators and variable wave plates [1,2,3]. Their birefringence and dielectric anisotropy, coupled with their elastic properties, allow these materials to be quickly and reversibly addressed by an external electric or magnetic field, making liquid crystals perfect for commercial displays. A solution to avoid chemical synthesis of new types of LCs is to dope existing LCs with nanoparticles to change their properties [1,2,3,4,5,6,7,8,9]. It has been reported that doping nematic liquid crystals (NLC) with ferroelectric nanoparticles such as Sn2 P2 S6 (SPS) or BaTiO3 (BTO)

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