Abstract
We report the effect of the doping of Cd1−xZnxS/ZnS core/shell quantum dots (CSQDs) in nematic liquid crystal p-methoxybenzylidene p-decylaniline (MBDA) at 0.05 wt/wt%, 0.1 wt/wt%, 0.15 wt/wt%, 0.2 wt/wt%, 0.25 wt/wt%, and 0.3 wt/wt% concentrations of CSQDs in MBDA. Dielectric parameters with and without bias with respect to frequency have been investigated. The change in electro-optical parameters with temperature has also been demonstrated. The increase in the mean dielectric permittivity was found due to the large dipole moment of CSQDs, which impose stronger interactions with the liquid crystal molecules. The dielectric anisotropy changes sign on doping CSQDs in MBDA liquid crystal. It was concluded that the CSQD doping noticeably increased the dielectric permittivity of nematic MBDA in the presence of an electric field. The doping of CSQDs in nematic MBDA liquid crystal reduced the ion screening effect effectively. This phenomenon is attributed to the competition between the generated ionic impurities during the assembling process and the ion trapping effect of the CSQDs. The rotational viscosity of nematic liquid crystal decreased with increasing concentration of the CSQDs, with a faster response time observed for the 0.05 wt/wt% concentration. The birefringence of the doped system increased with the inclusion of CSQDs in MBDA. These results find application in the field of display devices, phase shifters, LC—gratings, TIR waveguide, industries, and projectors.
Highlights
Negative dielectric anisotropy (∆ε < 0) liquid crystals have been extensively employed in direct-view and projection displays [1]
We focus on the negative dielectric anisotropy (∆ε) nematic liquid crystal doped with Cd1−x Znx S/ZnS core/shell quantum dots (CSQDs) for its applications in display devices, phase shifters, and antennas
The nematic liquid crystal material used in this study was negative dielectric anisotropy p-methoxybenzylidene p-decylaniline (MBDA), which exhibited the following chemical structure and phase sequence shown in Figure 1 [15]
Summary
Negative dielectric anisotropy (∆ε < 0) liquid crystals have been extensively employed in direct-view and projection displays [1]. The widespread feature of a negative ∆ε liquid crystal is that lateral polar substituents induce a dipole moment perpendicular to the principal molecular axis [2,3]. We focus on the negative dielectric anisotropy (∆ε) nematic liquid crystal doped with Cd1−x Znx S/ZnS core/shell quantum dots (CSQDs) for its applications in display devices, phase shifters, and antennas. Seidalilir et al [12] reported the improved electro chemical and electro-optical properties of Ni:ZnCdS/ZnS core/shell QDs in positive ∆ε nematic E7 liquid crystal It explained the self-assembled arrays of CSQDs in the nematic phase and reduction in the screening effect by the ion trapping effect of CSQDs. Misra et al [13] explained the influence of dispersing Cu:ZnO in nematic MBBA liquid crystal and studied the dielectric properties and activation energies for the dispersed systems. Singh et al [18] reported the quenching in photoluminescence intensity with improved contrast of felix 17/000 by doping Cd1−x Znx S/ZnS CSQDs. The impact of doping CSQDs in negative ∆ε nematic liquid crystal BBHA on its dielectric and electro-optical properties was examined by Tripathi et al [19]. This work becomes important for LC grating and TIR waveguide display society as well
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