Effects of CuInS2 nanoparticles on the alignment control of liquid crystals

Liquid crystal-nanoparticle composite systems have attracted particular attention for both academic interests and applications in inducing macroscopic alignment, altering electro-optic response of the liquid crystal hosts, and generating ordered, tunable soft metamaterials. Herein, the synthesis of two shapes of CuInS2 nanoparticles, tremelliform-like CuInS2 and frame-like CuInS2, and their utilization in producing uniform homeotropic alignment of liquid crystals are reported. Through exploring the mechanism in detail, the crystal structures of CuInS2 nanoparticles were found to rely heavily on the reaction solvents during the growth process, which in turn play a significant role on the anchor of liquid crystal molecules. The achieved homeotropic alignment shows high thermal stability, owing to the outstanding stability of the CuInS2 nanoparticles. In addition, combining this feasible method with parallel-aligning technique, variable pretilt angles in a range of ∼ 0.9° to ∼ 7.2° could be continuously achieved.