Effect of graphene flakes, titanium dioxide and zinc oxide nanoparticles on the birefringence, I-V characteristics and photoluminescence properties of liquid crystal

Comparative I-V characteristics and photoluminescence measurements have been made on a liquid crystal system dispersed with different nanomaterials - i). graphene flakes ii) ZnO and iii) TiO2 nanoparticles (NPs). It is observed that dispersion of graphene flakes enhance not only the orientational order but also the current by three order of magnitude higher compare to other two nano-LC composites perhaps owing to the strong pi-pi interaction between the liquid crystal molecule and graphenes hexagonal structure. Fluorescence study reveals that addition of TiO2 nanoparticles reduces the PL intensity where as the presence of ZnO nanoparticles and graphene flakes enhances the PL intensity of the LC material. The quenching in the PL intensity depends on the TiO2 concentration. The enhancement in the PL intensity is significant and found to be concentration dependant in case of LC- graphene composites. Overall, it is revealed that compare to other two NPs LC- graphene nano composites represents a promising way to enhance the electro-optic and photovoltaic properties of LC system used. (C) 2020 Elsevier B.V. All rights reserved.