Effect of ZnO nanoparticles on the SmC*-SmA* phase transition temperature in electroclinic liquid crystals

Abstract

Experimental assessment of quasi-binary picture of thermotropics: Induced smectic A phase in 7CB-n-heptane system J. Chem. Phys. 135, 044705 (2011) Does transparent nematic phase exist in 5CB/DDAB/water microemulsions? From the viewpoint of temperature dependent dielectric spectroscopy J. Chem. Phys. 134, 034505 (2011) A kind of two-dimensional electroconvection at ultralow electric frequency Appl. Phys. Lett. 97, 203507 (2010) Study of the isotropic to smectic-A phase transition in liquid crystal and acetone binary mixtures J. Chem. Phys. 133, 174501 (2010) Thermotropic nematic and smectic order in silica glass nanochannels Appl. Phys. Lett. 97, 153124 (2010) Additional information on J. Appl. Phys. ZnO nanoparticles (NPs), synthesized in an alcoholic medium at room temperature, were added to electroclinic liquid crystal (ELC) materials. The addition of ZnO NPs in ELCs, caused a remarkable shift in SmC * -SmA * phase transition which was investigated from the dielectric and electro-optical measurements. The anchoring of ELC molecules around ZnO NPs creates orientational distortions near the surface, which may give additional ordering to the ELC molecular arrangement. After analyzing collective dielectric relaxation processes of ZnO NP doped ELCs, three distinct loss peaks were observed. The different behavior of ZnO NP doped ELC from pure ELC has been explained by determining the dielectric strength, the distribution parameter and the corresponding relaxation frequency, and so on, and then these results have been compared with the data calculated by using the theoretical model. The effect of ZnO NPs addition on physical parameters, such as spontaneous polarization (P s ) and rotational viscosity (g) has also been observed.

Dielectric relaxation process of a partially unwound helical structure in ferroelectric liquid crystals

“…The helical dynamical process is a debatable research problem as it is demonstrated in selected FLC samples and needs more rigorous theoretical and experimental studies. However, this type of mode was also observed by our group earlier in some of the FLCs such as water-added FLC [9], pure FLC (KCFLC 7S), which becomes dominating when gold nanoparticles are added to it [10], and in ZnO-added electroclinic liquid crystal [11]. All these measurements were performed at 500-mV ac (alternating current) voltage of probing signal from an impedance analyzer.…”

Phase and dielectric behaviors of a polymorphic liquid crystal doped with graphene nanoplatelets

“…1,2 Moreover, investigations demonstrating the suppressed ionic effect by nanodopants have also been clarified for solving image problems in LC displays caused by ubiquitous impurity ions. [3][4][5][6][7] Depending on the intrinsic characteristics of the dopant and mutual interaction with LC molecules, researchers have studied the individual effects of nanomaterial additives on the behaviors of phase transitions in LCs in terms of the molecular ordering, 8,9 dielectric relaxation, 10 and electrophysical properties of LCs. [11][12][13] Among currently available nanomaterials, graphene, classified as a two-dimensional (2-D) carbon allotrope, has attracted immense attention for potential applications in electronic devices and nanocomposites since its successful isolation in 2004.…”

Improvement in electro-optical and dielectric characteristics of ZnO nanoparticles dispersed in a nematic liquid crystal mixture

“…Coming on metallic NPs, ZnO NPs find use in a wide range of technologically important areas of LCs due to simple production, large band gap energy, high exciton binding energy and excellent piezoelectric properties at room temperature. Additionally, a decrease in the threshold voltage, lower energy consumption, controlled orientation and increased phase transition temperature of LCs-ZnO composites is reported [9,14,29,32]. It is also observed that a decrease in the threshold voltage with dispersion of ZnO NPs is resulted by suppressing undesired field screening effects due to reduced moving ion density [13].…”