Electro-optical and dielectric properties of TiO2 nanoparticles in nematic liquid crystals with high dielectric anisotropy

Huang, Chi Yen; Selvaraj, Pravinraj; Senguttuvan, G.; Hsu, Che Ju

doi:10.1016/j.molliq.2019.110902

Cited by 46 publications

(11 citation statements)

References 57 publications

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“…Besides the viscosity, the strengthened electric field surrounding TiO 2 NP also contributes to the fast focus response of the BR composite-doped HLC lens. The insulating TiO 2 NP is considered as a high dielectric sphere, which strengthens the electric field on the top and bottom regions of the dielectric sphere along the applied field direction, consequently assisting in the rotation of LCs surrounding the dielectric sphere and decreasing the focus time of the HLC lens 14 .…”

Section: Resultsmentioning

confidence: 99%

“…The concentration ratios of TiO 2 NP and BNA were decided according to our previous works 15 , 16 . The supplier information indicated that LC E7 had a dielectric anisotropy Δε of 14.5, birefringence Δn of 0.216 at room temperature, and elastic constants K 11 , K 22 , and K 33 of 11.1, 5.9, and 17.1 pN, respectively; the average diameter of the rutile TiO 2 NP was ~ 20 nm 14 . Moreover, the rutile TiO 2 NPs were treated with surface silane-coating and dissolved in ethanol for well dispersion in LCs.…”

Section: Methodsmentioning

confidence: 99%

“…Adopting the nematic LCs with low viscosity was a straightforward method to shorten the response time of LC devices 11 , 12 . Other manners, such as polymer-stabilized LCs 13 and nanoparticle (NP) dispersion 14 , were also reported to improve the dynamic response of LC devices. In our recent studies, the inorganic rutile titanium dioxide (TiO 2 ) NP doping was used to fabricate the 4 mm aperture HLC lens 15 .…”

Section: Introductionmentioning

confidence: 99%

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Superior improvement in dynamic response of liquid crystal lens using organic and inorganic nanocomposite

Hsu

Singh

Selvaraj

et al. 2021

Sci Rep

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In this study, the response time of a 4 mm-aperture hole-patterned liquid crystal (HLC) lens has been significantly improved with doping of N-benzyl-2-methyl-4-nitroaniline (BNA) and rutile titanium dioxide nanoparticle (TiO2 NP) nanocomposite. The proposed HLC lens provides the focus and defocus times that are 8.5× and 14× faster than the pristine HLC lens, respectively. Meanwhile, the focus and defocus times of the proposed HLC lens reach the order of millisecond. Result shows that the synergistic effect of BNA and TiO2 NP induces a 78% decrement in the viscosity of pristine LC mixture that significantly shortens the focus and defocus times of HLC lens. The remarkable decrement in viscosity is mainly attributed to spontaneous polarization electric fields from the permanent dipole moments of the additives. Besides, the strengthened electric field surrounding TiO2 NP assists in decreasing the focus time of HLC lens. The focus and defocus times of HLC lens are related to the wavefront (or phase profile) bending speed. The time-dependent phase profiles of the HLC lenses with various viscosities are calculated. This result shows the decrease in wavefront bending time is not simply proportional to viscosity decrement. Furthermore, the proposed HLC lens emerges a larger tunable focus capability within smaller voltage interval than the pristine HLC lens.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Superior improvement in dynamic response of liquid crystal lens using organic and inorganic nanocomposite

Hsu

Singh

Selvaraj

et al. 2021

Sci Rep

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“…Using the e¢ values obtained as a result of the experimental measurements, the dielectric anisotropy (De¢) of the CLC composites were calculated. De¢ is a parameter that gives information about the alignment of LC molecules with an external electric field and is defined as follows, [28][29][30]…”

Section: Electro-optical and Dielectric Performance Analysis Of Clc Compositesmentioning

confidence: 99%

Electro-optical Performance Investigation of Cholesteric Liquid Crystal Containing Azo Dye: Light Shutter Device Application

Kocakülah

Köysal

Kahyaoğlu

2020

Journal of Elec Materi

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In this study, the effect of chiral dopant concentration on electro-optical and dielectric properties of a cholesteric liquid crystal (CLC) composite was investigated, and a dye-doped cholesteric liquid crystal (DDCLC) light shutter was developed. The electro-optical properties of samples were investigated by electro-optical switching method without the use of a polarizer. The dielectric characterization of the composites were also realized using dielectric spectroscopy technique with a wide frequency range. Significant electro-optical and dielectric parameters, such as transition voltages, complex dielectric constant, dielectric anisotropy and light transmission values of composites were found from the experimental data. The obtained results show that the chiral dopant causes changes in electro-optical and dielectric parameters of CLC, and the developed DDCLC light shutter can be used in optoelectronic device applications.

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“…In our previous studies, the rutile titanium dioxide (TiO 2 ) NPs with silane-coating had been used to improve the electro-optical properties of nematic LCs with high dielectric anisotropy [ 17 ]. Rutile TiO 2 NPs reduce the threshold and driving voltages due to suppressed screen effect.…”

Section: Introductionmentioning

confidence: 99%

A Comparative Study on Electro-Optic Effects of Organic N-Benzyl-2-Methyl-4-Nitroaniline and Morpholinium 2-Chloro-4-Nitrobenzoate Doped in Nematic Liquid Crystals E7

et al. 2020

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Improvements in electro-optical responses of LC devices by doping organic N-benzyl-2-methyl-4-nitroaniline (BNA) and Morpholinium 2-chloro-4-nitrobenzoate (M2C4N) in nematic liquid crystals (LCs) have been reported in this study. BNA and M2C4N-doped LC cells have the fall time that is fivefold and threefold faster than the pristine LC cell, respectively. The superior performance in fall time of BNA-doped LC cell is attributed to the significant decrements in the rotational viscosity and threshold voltage by 44% and 25%, respectively, and a strong additional restoring force resulted from the spontaneous polarization electric field of BNA. On the other hand, the dielectric anisotropy (Δε) of LC mixture is increased by 16% and 6%, respectively, with M2C4N and BNA dopants. M2C4N dopant induces a large dielectric anisotropy, because the phenyl-amine/hydroxyl in M2C4N induces a strong intermolecular interaction with LCs. Furthermore, BNA dopant causes a strong absorbance near the wavelength of 400 nm that filters the blue light. The results indicate that M2C4N doping can be used to develop a high Δε of LC mixture, and BNA doping is appropriate to fabricate a fast response and blue-light filtering LC device. Density Functional Theory calculation also confirms that BNA and M2C4N increase the dipole moment, polarization anisotropy, and hence Δε of LC mixture.

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Electro-optical and dielectric properties of TiO2 nanoparticles in nematic liquid crystals with high dielectric anisotropy

Cited by 46 publications

References 57 publications

Superior improvement in dynamic response of liquid crystal lens using organic and inorganic nanocomposite

Superior improvement in dynamic response of liquid crystal lens using organic and inorganic nanocomposite

Electro-optical Performance Investigation of Cholesteric Liquid Crystal Containing Azo Dye: Light Shutter Device Application

A Comparative Study on Electro-Optic Effects of Organic N-Benzyl-2-Methyl-4-Nitroaniline and Morpholinium 2-Chloro-4-Nitrobenzoate Doped in Nematic Liquid Crystals E7

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