Analysis of electro-optical and dielectric parameters of TiO<sub>2</sub> nanoparticles dispersed nematic liquid crystal

Katiyar, Rohit; Pathak, Govind; Srivastava, Atul; Herman, Jakub; Manohar, Rajiv

doi:10.1080/1539445x.2018.1436562

Cited by 23 publications

(9 citation statements)

References 28 publications

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“…Figure 2a shows the POM images of the BNA-doped LC cells, where the cell rubbing direction was placed at 45° with respect to the transmission axes of the polarizer and analyzer. The uniform colors throughout the cells confirmed that the LC molecules were aligned homogenously [31][32][33][34] . After BNA addition, we did not observe any significant defect aside from the slight color shift, indicating that BNA was well dispersed in the LC matrix and the Δn of the LC mixture slightly changed.…”

Section: Methodsmentioning

confidence: 68%

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Selvaraj

Karthick

Brahadeeswaran

et al. 2020

Sci Rep

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The dispersion of organic N-benzyl-2-methyl-4-nitroaniline (BNA) in nematic liquid crystals (LCs) is studied. BNA doping decreases the threshold voltage of cell because of the reduced splay elastic constant and increased dielectric anisotropy of the LC mixture. When operated in the high voltage difference condition, the BNA-doped LC cell has a fall time that is five times faster than that of the pure one because of the decrements in the threshold voltage of the cell and rotational viscosity of the LC mixture. The additional restoring force induced by the BNA's spontaneous polarization electric field (SPEF) also assists to decrease the fall time of the LC cell. The decreased viscosity can be deduced from the decrements in phase transition temperature and associated order parameter of the LC mixture. Density functional theory calculation demonstrates that the BNA dopant strengthens the absorbance for blue light, enhances the molecular interaction energy and dipole moment, decreases the molecular energy gap, and thus increases the permittivity of the LC mixture. The calculation also shows that the increased dipole moment, polarizability, and polarizability anisotropy increase the dielectric anisotropy of the LC mixture, which agrees with the experimental results well. BNA doping has a promising application to the fields of LC devices and displays. Nematic liquid crystals (LCs) are extraordinarily responsive and optically uniaxial materials. Nematic LCs have been extensively used in diverse applications, such as optical nonlinearity, optical phase modulators, microdisplays, flat panel displays, optical antennas, and optical switching, due to their electro-optical property and other admirable features 1-5. LCs with a fast response are vital in removing motion blur in moving pictures and resolving cross-talk in 3D displays 6-9. The response time of LCs should be less than 3 ms to diminish motion blur and cross-talk. Several techniques have been proposed to resolve this issue, and they include tuning the viscosity of materials 10 , varying the anchoring energy 11 , changing the electrode shape and driving scheme 12 , changing the cell gap 13 , modifying the guest-host material 14 , and applying new switching modes 15. The improvements in the electro-optical properties of LCs with the dispersion of different gust entities were presented recently. For example, Y. Dai et al. demonstrated that the incorporation of γ-Fe 2 O 3 nanoparticles into LCs results in a response time of 4.75 ms with the application of the overdriving scheme, which is three times faster than pure LCs 16. A response time of around 4 ms was obtained with the addition of a small amount of dye to a polymer-dispersed liquid crystal (PDLC) or functionalized carbon nanotubes dispersed in optically isotropic LCs. However, in this case, the excellent response speed is valid only for operation at a relatively high voltage 17,18. Blue-phase LCs have a response time of 0.5 ms, but they still have drawbacks, such as hysteresis, high operation voltage, and narrow t...

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Section: Methodsmentioning

confidence: 68%

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Selvaraj

Karthick

Brahadeeswaran

et al. 2020

Sci Rep

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“…This may be due to different shapes of NPs [55,56], but also, for a number of cases this may be due to different anchorings at the NP surface or to quick aggregation that could occur for other kinds of functionalization of NPs [22, ,30, 31,57-59]. Katiyar et al [28] investigated the impact of TiO 2 NPs in 1823A nematic liquid crystal. They observed that most physical parameters (dielectric anisotropy, viscosity, elastic constant) firstly decrease with the concentration and increase again when the concentration further increases similarly to the above results.…”

Section: A Nonmagnetic Nanoparticlesmentioning

confidence: 99%

“…However, a lot of contradictory results have been obtained, in particular regarding the evolution of the elastic constants in presence of NPs, responsible for most interesting LC characteristics. Different behavior for , and have been observed sometimes with the same behavior for , and [20][21][22], sometimes not [23,24], sometimes increasing [25,26], sometimes decreasing [27,28]. As a result, other physical parameters are accordingly affected like dielectric and viscoelastic properties [23,25,29].…”

Section: Introductionmentioning

confidence: 99%

Viscoelastic and dielectric properties of 5CB nematic liquid crystal doped by magnetic and nonmagnetic nanoparticles

et al. 2020

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“…In this work, we analyze the electrical behavior of liquid crystal samples doped with TiO 2 nanoparticles. Instead of typical doped LC mixtures [15,16,[21][22][23][24], nanoparticles are located on a substrate, forming a layer. Although the presence of nanoparticles is not in the LC volume, we can see that they have interesting effect on the LC cell properties, as expected.…”

Section: Discussionmentioning

confidence: 99%

“…Although there is a large variety of potential materials for the nanoparticles, titanium dioxide (TiO 2 ) nanoparticles are one of the most relevant cases due to their interest in other electrooptical devices [19,20] as well as in LC mixtures [21][22][23][24]. In this work, we analyze the electrical behavior of a TiO 2 nanoparticle-doped liquid crystal cell using an equivalent model, as will be explained.…”

Section: Introductionmentioning

confidence: 99%

Electrical Behavior of Liquid Crystal Devices with Dielectric Nanoparticles

Marzal

Caño‐García

Torres

et al. 2020

Journal of Nanomaterials

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Nowadays, the development of new devices based on liquid crystal (LC) materials requires improved tuning characteristics according to the application. One approach for this improvement is the use of nanomaterials with the capability of modifying the effective properties of the doped LC mixture. In this work, we analyze the electrical behavior of a titanium dioxide (TiO2) nanoparticle-doped liquid crystal cell using an equivalent circuit. The circuit parameters have been obtained using the impedance spectroscopy technique and time response measurements. The particularity of the samples designed is that the nanoparticles are not dispersed in the LC. Instead of that, nanoparticles are randomly deposited on one of the electrodes. Measurements show that the presence of the nanoparticles increases the temperature sensitivity of the equivalent cell capacitance and the capacitance difference between switched and nonswitched states. These results could be quite useful in the design of novel liquid crystal electronic devices and sensors.

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Analysis of electro-optical and dielectric parameters of TiO₂ nanoparticles dispersed nematic liquid crystal

Cited by 23 publications

References 28 publications

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Viscoelastic and dielectric properties of 5CB nematic liquid crystal doped by magnetic and nonmagnetic nanoparticles

Electrical Behavior of Liquid Crystal Devices with Dielectric Nanoparticles

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Analysis of electro-optical and dielectric parameters of TiO2 nanoparticles dispersed nematic liquid crystal

Cited by 23 publications

References 28 publications

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Viscoelastic and dielectric properties of 5CB nematic liquid crystal doped by magnetic and nonmagnetic nanoparticles

Electrical Behavior of Liquid Crystal Devices with Dielectric Nanoparticles

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Analysis of electro-optical and dielectric parameters of TiO₂ nanoparticles dispersed nematic liquid crystal