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In this work, the impact of Ag–In–S quantum dots (QDs) on the dielectric and electro-optical characteristics of E7 nematic liquid crystal (NLC) is investigated. To realize the objective, various concentrations of Ag–In–S QDs (0.2, 0.4, 0.6, 0.8, and 1 wt%) were added to E7 NLC, and the resulting composites were then introduced into homogeneous, homeotropic, and twisted nematic aligned cells. The temperature dependence property of the parallel and perpendicular components of the dielectric constant (ɛ∥ & ε ⊥ ) for pure and QDs-doped NLCs was measured. ɛ∥ significantly enhanced in the presence of 0.8 wt% of the QDs, which led to a ~ 23% rise in the dielectric anisotropy of the system. The dielectric results demonstrated that NLC hosts prompt QDs to form self-assembled arrays within the NLC system. In addition, electro-optical measurements revealed the considerable impact of QDs doping on the reduction of threshold voltage (Vth). Importantly, a ~ 15% decrease in Vth was observed for NLC doped with 0.8 wt% of the QDs compared to pure NLC. Besides, the addition of QDs significantly accelerates the NLC electro-optical response. The switch-on and -off response times for the QDs-doped NLC cell were reduced by ~ 34% and ~ 41%, respectively, compared to those for the pure NLC cell. A combination of increased dielectric anisotropy, improved mutual interactions of components, and reduced rotational viscosity of the mixture may result in much faster electro-optical switching responses. The presented achievements in this study will be beneficial in the development of LC-based display panels as well as switchable smart windows. [ABSTRACT FROM AUTHOR]

Disperse dye red 1 (DR1) and carbon nanoparticles (CNPs) were doped separately to form polymer dispersed liquid crystal films, namely, DPDLC & CPDLC. Nematic liquid crystal (LC) and photopolymer NOA-65 were used to prepare these composite films using polymerisation-induced phase separation (PIPS) technique. In this research work, it is demonstrated that the minute concentration (0.05% wt./wt.) of DR1 and CNPs controls the LC droplet alignment and LC droplet size in polymer dispersed liquid crystal (PDLC) film. The effect of DR1 and CNPs on PDLC film has been investigated in terms of LC droplet size, transition temperature, voltage-transmittance characteristic, contrast ratio, response time, haze, and dielectric measurements. The obtained results reveal that the threshold voltage values of the composite film get reduced from 34.87 V (undoped) to 10.19 and 9.26 V, for 0.05% of DR1 and CNPs doping, respectively. The DR1 (0.05%) doped film shows improved contrast of the undoped film as compared to CNPs (0.05%) film, whereas CNPs (0.05%) doped film shows a faster response time of 2.81 ms as compared to DR1 (0.05%) doped film (3.14 ms). Dielectric analysis of undoped, DPDLC, and CPDLC films represents Debye type relaxation mode. [ABSTRACT FROM AUTHOR]

This study has used ab initio technique to investigate the electro‐optical and electronic properties of N‐(4‐methoxybenzylidene)‐4‐butylaniline (MBBA), a nematic liquid crystal between 21 and 48 °C, surrounded by gas and acetonitrile medium, in the presence and absence of electric field. The optimization and analysis of various electro‐optical and electronic parameters along with absorption spectrum have been performed using ωB97xD/6‐311+G(d,p) and M062X/6‐311+G(d,p) methods. Under the electric field, electro‐optical parameters of MBBA surrounded by acetonitrile are increased, indicating its suitability for display device development application. Global reactivity descriptors reveal that electronic properties of the MBBA LC also high in acetonitrile medium as compared to that of the gas. Furthermore, using second order perturbation theory and the multicentered‐multipole expansion technique, the mutual interactions between a pair of MBBA molecules are examined, revealing the nematic behavior of MBBA molecule. [ABSTRACT FROM AUTHOR]

• Developed zinc oxide nanoparticles induced vertically aligned liquid crystals. • Study the effect of varying concentration of dichroic dye on textural, electro-optical, phase transition and band gap studies. • Significantly improved electro-optical and morphological characteristics. • Provides VALC systems for next-generation display technologies. Vertically aligned liquid crystal (VALC) perpetually boosts the advancement for display devices and optoelectronics. Herein, initially, the nanoparticles (NPs) induced VALC (nVALC) cell was prepared via doping of 0.3 (wt./wt.%) of zinc oxide NPs in nematic liquid crystal (LC). After that, a series of orange azo dichroic dye doped nVALC cells were prepared with varying concentrations of dye such as 0.0625, 0.125, 0.25 and 0.5 wt.%. The effect of dye concentrations on LC textures, phase transition, electro-optical and band gap properties were investigated, as well as resulted in a significantly reduced value of the threshold and operating voltages as a function of dye concentrations. The contrast ratio was also enhanced up to 0.25 wt.% dye doped nVALC cells. Additionally, the transition temperature from nematic to isotropic phase and band gap studies were also performed. The present work provides improved properties of nVALC systems for next-generation display technologies. [ABSTRACT FROM AUTHOR]

In this work, we have investigated morphological, electro-optical and dielectric properties of disperse orange 25 dye-doped polymer-dispersed liquid crystal (DPDLC) films. The DPDLC film composed of monomer Norland optical adhesive (NOA 65), nematic liquid crystal (E7), and disperse orange 25 dye was prepared through the polymerisation-induced phase separation (PIPS) method. The polarising optical microscope (POM) has been utilised to observe the effect of dye concentration and voltage on liquid crystal (LC) droplet morphology. The electro-optical properties of such DPDLC films were studied at a fixed frequency of 200 Hz and different voltage and temperature conditions (0–100 V, 25–50°C). The change in absorbance value with varying dye concentration and the electric field was monitored through a UV-Vis spectrophotometer. Dielectric relaxation characteristics of DPDLC films were examined using a precision impedance analyser in the frequency range 20 Hz–20 MHz and temperature range 25–60°C. Debye and Cole-Cole fitting techniques were used to describe the dielectric properties of DPDLC films. [ABSTRACT FROM AUTHOR]

The present work reported the synthesis and characterisation of β-cyclodextrin (βCD) grafted into silica (SiO2@βCD) nanoparticles (NPs). Morphology analysis shows that the prepared NPs have a spherical shape with 170 nm of size. The electro-optic, dielectric and viscoelastic properties of SiO2@βCD doped nematic 5CB were examined in different concentrations of the NPs. A decrease in clearing temperature, birefringence and the order of the nanocomposite systems as compared to the pure system was observed. Dielectric parameters of pure and doped samples were measured in the frequency range of 1–2 MHz. Ionic conductivity and dielectric anisotropy increase significantly with NPs concentration due to the strong dipole moment and polarisability of SiO2@βCD. The advantage of dopedSiO2@βCDnematic 5CB is attributed to the significant decrements in threshold voltage by 32% and strong additional coupling of the electrical dipole moments in the spherical NPs with the nematic director field. On the other hand, it is found that the NPs exhibit a decreasing effect on the response time of the nematic liquid crystal, which is demonstrated by the decrement in the viscosity. The results indicate that doping SiO2@βCD is appropriate to fabricate a fast response LC device. [ABSTRACT FROM AUTHOR]

[Display omitted] • Doping effect of functionalized CdSe/ZnS QDs on the characteristics of 8OCB LC was investigated. • Mobility of ions and diffusion constant were analyzed by a model based on the electrode polarization phenomenon. • Addition of QDs improved ion transport behavior by decreasing the electrode polarization relaxation time. • The threshold voltage drops remarkably with increasing QDs concentration in the LC system. • When the applied field is turned off, the doped samples exhibit a residual transmittance. The current advancements in developing new liquid crystalline materials for the next generation applications focus mainly on improving the physical characteristics of the liquid crystal (LC) systems. Recent progress has shown that the functionalized nanoparticles embedded in LC matrices can significantly alter the characteristics of the LC material based on the mutual interaction between the host molecules and guest particles. In this aspect, the present study reports the impact of dispersing core-shell type CdSe/ZnS quantum dots (QDs) on the dielectric, electrical and electro-optical properties of the 8OCB LC doped at various concentrations. The doped samples exhibit an ion releasing behavior and this effect becomes more evident as the doping concentration increases up to 0.2 wt% in the LC system. It is explained as a result of the growing tactoid-like ellipsoidal form acquired by QDs owing to the enhanced mutual interaction among QD ligands and rod-like LC molecules. The temperature variation of the diffusion constant, conductivity, ionic mobility and mean relaxation time of ions significantly follows each other in all the studied samples. Moreover, thermal profiles of the dielectric anisotropy, threshold voltage and splay elastic constant show a decreasing pattern with an increment in doping concentration. A dual-relaxation regime is experimentally investigated, corresponding to the contribution of nematic director and dimers, providing two kinds of rotational viscosity in the pristine and QDs dispersed LC samples. The transmittance-voltage curve reveals the presence of residual value in the dispersed samples and is related to the volatile memory effect. A slight enhancement is observed in the photoluminescence intensity for the lower doped sample and reduces further with increasing doping concentration in the pristine LC system. All these findings suggest the considerable contribution of functionalized QDs to the studied properties in terms of interaction between the LC and dopant material. This study will further elucidate the selection of optimal QDs concentration based on the required properties for their potential applications in futuristic devices based on LCs. [ABSTRACT FROM AUTHOR]

We have prepared the composites of a room temperature nematic liquid crystalline material namely 4-(trans-4′-n-hexylcyclohexyl) isothiocyanatobenzoate (6CHBT) and gold nanoparticles (GNPs). Thermodynamic, electro-optical and dielectric properties have been investigated. Effect of dispersion of GNPs on various electro-optical and display parameters of host liquid crystalline material have been studied. Physical parameters such as threshold voltage, dielectric anisotropy and splay elastic constant have altered for composite systems. Due to the dispersion of GNPs, nematic to isotropic transition temperature is significantly increased. Relaxation frequency corresponding to flip-flop motion of the 6CHBT molecules about their short axes has increased due to the presence of GNPs. [ABSTRACT FROM AUTHOR]

• The effect of BT2/BT4 NC on the electro-optical and dielectric properties of a NLC is discussed. • The synthesis of BT2/BT4 NC has been performed by in-situ co-precipitation method. • Noticeable change in dielectric properties as the function of frequency, DC bias and temperature observed. • The significant changes observed in dielectric properties of 5CB are due to interaction among LC molecules and NCs. • The BT2/BT4 NC enhanced memory in the NLC. We report here the concentration and temperature dependent optical, electro-optical and dielectric studies on bismuth titanate (Bi 2 Ti 2 O 7 /Bi 4 Ti 3 O 12) nanocomposite (BT2/BT4 NC, ∼42 nm) doped nematic liquid crystal (NLC, 5CB) mixtures using optical polarising microscope and dielectric spectroscopic techniques. The optical textures confirm the uniform dispersion and miscibility of NCs in 5CB for all concentrations (i.e. 0.1, 0.25, 0.5, 1 and 2 wt%) and mixtures appear to be almost agglomeration free. The dielectric studies demonstrate the maximum changes in the dielectric parameters (dielectric permittivity, dielectric loss, loss factor and dielectric anisotropy) of 5CB sample for the 0.1 wt% mixture. Interestingly, the dielectric anisotropy of 5CB in 0.1 wt% mixture is increased by ∼ 11%. However, the dielectric memory effect (bias voltage ON-OFF) is observed maximum in the case of 1 wt% mixture. Similarly, the optical memory examined by bias voltage dependent (ON-OFF) optical textures is also significantly enhanced for 1 wt% mixture. The significant changes observed in dielectric properties of 5CB sample could be due to plausible interaction among NLC molecules and ionic impurities with BT2/BT4 NCs. Moreover, the enhanced volatile memory in BT2/BT4 NC-NLC mixture could be attributed to the dipole–dipole coupling between individual permanent dipole moment of anisotropic NLC molecules with the dipole moments generated by the ionic impurities agglomerated on the surface of high dielectric BT2/BT4 NCs. We strongly believe that such NCs-NLC mixtures would be certainly useful in the advancement of wearable devices (such as smart plenoptic cameras, watches etc.) and smart switchable windows. [ABSTRACT FROM AUTHOR]

This work reports the effect of dye on the photopolymerisation and electro-optical properties of polymer dispersed liquid crystal (PDLC) composite films. Dichroic PDLC (DPDLC) films based on a photocurable polymer and nematic liquid crystal (LC) with an azo dichroic dye were prepared by photopolymerisation-induced phase separation method. Polarising optical microscopy has been used for monitoring the phase separation kinetics and two-phase morphology evolution in the DPDLC system. LC domains with radial structures during initial period of phase separation adopted a resultant morphology of bipolar configuration over the course of polymerisation. The phase separation and morphology of LC domains was found to be dependent on the amount of dye used. Moreover, the addition of small amount of dye reduced the switching voltage, and enhanced the contrast ratio with improved switching time in the PDLC films. It was shown that, under the application of an electric field, the molecular orientation and absorbance of dichroic dye can be controlled in DPDLC to induce non-linearity and colour contrast without the use of polarisers. [ABSTRACT FROM AUTHOR]

Hydrogen bonded liquid crystal, possessing a wide temperature range of cybotactic phase was used as a matrix to disperse ferroelectric LiNbO 3 nanoparticles at the concentrations from 0.5 wt.% to 3.0 wt.%. The influence of nanoparticles on the physical properties has been studied with the help of polarizing optical microscopy (POM), impedance spectroscopy and electro-optic measurements. POM investigation revealed a nematic droplet dispersed in the isotropic phase due to the addition of ferroelectric nanoparticles. The suppression of the polarization has been observed and explained by the occurrence of antiparallel dipole configuration. The isotropic-nematic phase transition temperature was decreased due to the reduction in the parameter order. The decreasing in dielectric anisotropy (∆ε), response time (τ) and in threshold Freedericksz voltage (V th) was associated to the decrease in splay constant elastic (K 11) and in the rotational viscosity (γ). The curves of ∆ε , V th , τ, K 11 and γ when NPs concentration increases, showed a minimum at the same concentration (c = 1 wt.%) allowing the determination of the optimal NPs concentration. • Nematic-isotropic transition temperature decreases. • The nematic droplet dispersed in isotropic phase is observed. • The nanoparticles concentration dependence of the dielectric permittivity is illustrated. • The nanoparticles concentration dependence of the electro-optic and viscoelastic is presented and discussed. [ABSTRACT FROM AUTHOR]