Evolution of electro-chemical and electro-optical properties of nematic liquid crystal doped with graphene oxide

Dalir, Nima; Javadian, Soheila; Kakemam, Jamal; Yousefi, Ali Akbar

doi:10.1016/j.molliq.2018.05.138

Cited by 28 publications

(16 citation statements)

References 59 publications

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“…As a result, the threshold voltage and elastic constants were strongly increased, while the elastically driven electro-optic off-response time decreased when increasing the concentration of GO flakes [225,226]. Similar results in GO-doped nematic LC (E 5CN7 ) were reported by Dalir et al They found that the capacity of charge storage was expanded, while the mobility of free ions and the diffusion coefficient were significantly decreased due to the strong interaction between LC molecules and GO flakes [227]. In another publication, they also reported that GO doping would lead to an increase in the nematic-isotropic phase transition temperature, which could be shifted by changing the GO concentration [224].…”

Section: Modification Of Physical Properties Of Lc Materials By Nanodsupporting

confidence: 78%

Perspectives in Liquid-Crystal-Aided Nanotechnology and Nanoscience

2019

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The research field of liquid crystals and their applications is recently changing from being largely focused on display applications and optical shutter elements in various fields, to quite novel and diverse applications in the area of nanotechnology and nanoscience. Functional nanoparticles have recently been used to a significant extent to modify the physical properties of liquid crystals by the addition of ferroelectric and magnetic particles of different shapes, such as arbitrary and spherical, rods, wires and discs. Also, particles influencing optical properties are increasingly popular, such as quantum dots, plasmonic, semiconductors and metamaterials. The self-organization of liquid crystals is exploited to order templates and orient nanoparticles. Similarly, nanoparticles such as rods, nanotubes and graphene oxide are shown to form lyotropic liquid crystal phases in the presence of isotropic host solvents. These effects lead to a wealth of novel applications, many of which will be reviewed in this publication. the observation of chirality from achiral molecules, resulting from sterically induced packing of the bent-core mesogens [10], such as ferroelectricity or the formation of helical superstructures in the B7 phase [14]. Thermotropic LCs are commonly constituted by single organic entities or mixtures thereof, which exhibit various mesophases at different temperatures or pressures [15], illustrated in Figure 1b. As the temperature rises, a typical thermotropic LC passes through higher ordered phases, also called soft crystals, the hexatic smectic phases with positional order as well as bond orientational order, through the fluid smectic phases (SmC and SmA), which exhibit both positional and orientational order, and finally to the nematic phase (N) with purely orientational order, into the isotropic phase. The number of different phases observed depends on the chemical composition, symmetry and order of the LC molecules. About 25 different thermotropic phases are known to date, and they are still increasing in number. Appl. Sci. 2019, 9, x FOR PEER REVIEW 2 of 47 unique effects of the observation of chirality from achiral molecules, resulting from sterically induced packing of the bent-core mesogens [10], such as ferroelectricity or the formation of helical superstructures in the B7 phase [14]. Thermotropic LCs are commonly constituted by single organic entities or mixtures thereof, which exhibit various mesophases at different temperatures or pressures [15], illustrated in Figure 1b. As the temperature rises, a typical thermotropic LC passes through higher ordered phases, also called soft crystals, the hexatic smectic phases with positional order as well as bond orientational order, through the fluid smectic phases (SmC and SmA), which exhibit both positional and orientational order, and finally to the nematic phase (N) with purely orientational order, into the isotropic phase. The number of different phases observed depends on the chemical composition, symmetry and order of the LC molecules. About...

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Section: Modification Of Physical Properties Of Lc Materials By Nanodsupporting

confidence: 78%

Perspectives in Liquid-Crystal-Aided Nanotechnology and Nanoscience

2019

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“…By using the measured impedance spectra, each component of the equivalent circuit, such as the resistance and capacitance, can be estimated by the numerical fitting. Several equivalent circuits for LC cell modeling have been reported [32][33][34][35][38][39][40][41][42]. Sprokel has introduced an equivalent circuit model for the low-frequency behavior, including the LCs capacitance and resistance, and electrical double-layer capacitance induced by the space charges near the electrodes.…”

Section: Change In the Impedance Of The Ion-doped Lc Cellmentioning

confidence: 99%

“…where v is the drift velocity of the ions, E is the electric field intensity, f peak is the frequency of the maximum value of the dielectric-loss-tangent spectrum, V 0 is the effective voltage across the electrodes of the LC cell, and α = C DL /C LC is the attenuation coefficient measured under an applied voltage, in which C DL represents the double-layer capacitance governed by the space charges near the electrodes [33,35]. The ion mobility is related to the diffusion coefficient by the Einstein relationship,…”

Section: Change In the Impedance Of The Ion-doped Lc Cellmentioning

confidence: 99%

“…Because the impedance of an LC cell is not affected by the ionic impurities, a pure LC cell can be modeled with an equivalent circuit shown in Figure 6a. Z W is the generalized finite-length Warburg impedance [34,35], which can be expressed as…”

Section: Change In the Impedance Of The Ion-doped Lc Cellmentioning

confidence: 99%

“…To analyze the degradation with time, we fabricated an ion-doped LC cell and measured the haze and impedance. Impedance and dielectric spectroscopic analyses were carried out to extract the impedance parameters, such as the resistance and capacitance of the LCs and physical parameters of the ionic materials in the bulk regions and near the alignment layers [29][30][31][32][33][34][35]. With the increase in time under the applied electric field, the LC cell exhibited nonuniformity with the decrease of the haze, capacitance of the LC cell, and thickness of the diffusion layer, along with the increase of the resistance of the LC cell and surface concentration of the ions.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of Optical Performance Degradation in an Ion-Doped Liquid-Crystal Cell with Electrical Circuit Modeling

et al. 2020

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We reported electrical circuit modeling to analyze the optical performance degradation in an ion-doped liquid-crystal (LC) cell, which exhibited advantages, such as excellent optical performance and simple switching process, but suffered from long-term reliability issues. When an electric field was applied to the cell for an extended period of time, the optical performance became nonuniform, and the haze in the opaque state decreased. By measuring the impedance and fitting the measured data by using an equivalent circuit model, we confirmed the changes of the parameters in the electrochemical impedance spectroscopy and electrophysical properties of the ion-doped LC cell with time. According to the measurement of the optical and physical characteristics, the optical performance degradation was caused mainly by the ionic materials.

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Greenly synthesized porous carbon nanoparticle (bio‐waste‐based)‐doped nematic liquid crystal composite with optimized electric and electro‐optical properties for devices

et al. 2022

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The present investigation on the impact of porous carbon nanoparticles (PCNPs) on a room temperature nematic liquid crystalline compound (TP‐188‐01) reports extensive electro‐optical analysis of composite followed by dielectric and luminescence study as well. The pure nematic compound has been doped with 0.1%, 0.25%, and 0.5% of PCNPs (spherical), which have been synthesized by green synthesis technique without use of any activating agents. Low‐frequency dielectric analysis (50 Hz to 1 kHz) has been done to confirm ion generation with increase in PCNS concentration. The dielectric data also indicate preferential orientation of molecules from homogeneous to homeotropic alignment, which can be used in performance optimization of electro‐optical devices. The analysis of dielectric data also illustrates the application of PCNS‐doped systems in circuits operating at high voltages. Diffusion coefficient, mobility, and DC conductivity have been further examined to support the above observations. A significant decrease (of about 47%) in the response time of porous carbon nanoparticle liquid crystal (NP‐LC) composites has also been observed. The photoluminescence spectrum of NP‐LC composites as a function of carbon nanosphere (CNS) concentration has shown Quenching (following the Stern–Volmer quenching mechanism) in the luminescence intensity with increasing CNS concentration. The highly improved response time and quenching in the luminescence intensity further make the PCNS‐doped LC composites as ideal materials to be used in devices, encouraging LC‐aided green nanotechnology.

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Evolution of electro-chemical and electro-optical properties of nematic liquid crystal doped with graphene oxide

Cited by 28 publications

References 59 publications

Perspectives in Liquid-Crystal-Aided Nanotechnology and Nanoscience

Perspectives in Liquid-Crystal-Aided Nanotechnology and Nanoscience

Analysis of Optical Performance Degradation in an Ion-Doped Liquid-Crystal Cell with Electrical Circuit Modeling

Greenly synthesized porous carbon nanoparticle (bio‐waste‐based)‐doped nematic liquid crystal composite with optimized electric and electro‐optical properties for devices

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