Improving the electro-optics of chiral self-assembling materials exhibiting ferroelectric mesophase via Cd1−xZnxS/ZnS core/shell quantum dot guest additives

Abstract

The dispersion of quantum dots (QDs) in mesophase material is an alternative method to change the physical properties of the host liquid crystalline material. During the last decade, core shell QDs-LC composites have attracted considerable attention by virtue of their potential applications. In the present work, we investigate the phase transitional, dielectric and electro-optical characterization of a 10OHF ferroelectric liquid crystal (FLC) material with the suspension of four different concentrations (0.25 %, 0.5 %, 1.0 % and 1.5 % wt./wt.) of Cd_1−xZn_xS/ZnS core/shell QDs as a function of temperature, voltage and frequency. The 10OHF compound exhibit ferroelectricity due to its inherent chirality in the smectic C (SmC*) phase which can be tuned by applying an external electric field. The lower dispersion of QDs (up to 1 wt%) in 10OHF causes a faster electro-optic response in the order of 1 ms, attributed to the combined effects of rotational viscosity and surface anchoring. The presence of QDs influences the properties of the pure FLC, such as response time, spontaneous polarization, permittivity, etc. This change in physical properties is associated with the mutual interactions between QDs and FLC molecules and subsequent change in orientational molecular ordering. Mutual interactions between LC molecules and QDs have been verified by the Fourier-transform infrared spectroscopy. Reduced spontaneous polarization-tilt angle (Ps-θ) coupling and enhanced response of LC/QDs composites are highly advantageous for photonic and electro-optical applications.