Tuning liquid crystal properties with 0D carbon dots: exploring the impact of functionalization of carbon dots

Abstract

Functionalization of nanomaterials is an efficient way to prevent the aggregation of particles and improve the dispersibility in solvents. However, we propose that if unfunctionalized nanoparticles are capable of forming stable dispersions in solvents and miscible in the LC matrix without aggregation or accumulation at interfaces, they could be a better alternative than their functionalized counterparts for improving the physical properties of NLC. In this study, the effect of functionalization of nanomaterials on various physical properties, such as dielectric, electro-optic and conductivity properties, of nematic liquid crystals is investigated. To explore the validity of our hypothesis, we investigated the properties of NLC, 7CB incorporated with carbon dots and octadecylamine-functionalized carbon dots. Dielectric permittivity and elastic constant measurements suggested that quantum dots were rearranged in the nematic matrix in such a way to minimize the free energy of the composite, and functionalization did not significantly affect the global ordering of NLC molecules. We also observed that the conductivity of C-dot composites decreased when compared to pure NLC but increased with the dispersion of ODA C-dot in NLC compared to pure NLC. It was observed that the ligand molecules of the functionalized quantum dots did not add to the conductivity of the dispersions but act as a trap for ionic impurities, and the partial release of these impurities upon interactions of the ligand shell with the uniaxial nematic host could be the source for the increased conductivity. This study is expected to impart substantial insights into designing high-performance nanocomposites of LCs for device applications.