Enhancement of Birefringence in Reduced Graphene Oxide Doped Liquid Crystal.

Mareddi Bharath Kumar,Daekyung Kang,Muhan Choi,Taewan Kim,Youngho Jee,Mohammad Awwal Adeshina,Jonghoo Park

doi:10.3390/nano10050842

Mareddi Bharath Kumar, Daekyung Kang + Show 5 more

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https://doi.org/10.3390/nano10050842

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Abstract

We investigated the effect of reduced graphene oxide (rGO) doping on the birefringence of 5CB liquid crystal (LC). The characteristics of the synthesized rGO and LC-rGO composite with different rGO concentrations were analyzed by atomic force microscopy, X-ray photoelectron spectroscopy, white light polarized microscopy, voltage-dependent transmission measurement, and differential scanning calorimetry. We found that doping LC with an appropriate concentration of rGO enhances the birefringence of the LC. This is mainly due to the improved anisotropy of polarizability, which stems from the high shape anisotropy of rGO. However, the aggregation of rGO reduces the birefringence by decreasing the anisotropy of polarizability as well as the order parameter. Our study shows the promising potential of LC-rGO for developing various electro-optic devices that offer improved electro-optic effects.

Highlights

Doping liquid crystals (LCs) with nanoparticles (NPs) has attracted increasing attention in various research fields and industries because it changes the physical properties of LC and provides additional functionalities
We demonstrate the effect of chemically reduced graphene oxide on the birefringence of the phase modulator fabricated using the homogeneously aligned LC doped with rGO (LC-rGO)
We found that the doping rGO in LC with an appropriate concentration enhances the birefringence of LC, consequentially, increases the total phase retardation of the phase modulator

Summary

Introduction

Doping liquid crystals (LCs) with nanoparticles (NPs) has attracted increasing attention in various research fields and industries because it changes the physical properties of LC and provides additional functionalities. Among various NPs, the one that can increase dielectric anisotropy (∆ε) without significantly reducing orientational order parameter has been considered as a preferred choice because it improves both a Fréedericksz transition voltage (Vth) [16] and a switching time (τon) [17] simultaneously through the following relationship: Vth = The experimental results of the LC doped with pristine monolayer graphene flakes with an appropriate concentration exhibit giant enhancement in dielectric anisotropy [20,23,24].

Results

Conclusion