Effect of ion trapping behavior of TiO2 nanoparticles on different parameters of weakly polar nematic liquid crystal

Abstract

In the present investigation, TiO 2 -doped weakly polar nematic liquid crystal (NLC) has been studied. This study mainly focuses on dielectric, electro-optical and optical properties of pure NLC and doped systems. Variation in different parameters like dielectric permittivity, dielectric loss, dielectric anisotropy and conductivity has been noticed. Permittivity of the doped system is almost the same as undoped system. With doping concentration, the ionic contribution to the dielectric loss as observed in low-frequency region has been suppressed and the shift in relaxation frequency toward higher frequency side has also been observed. The electrical conductivity and threshold voltage have been decreased with increasing concentration of nanoparticles (NPs). The continuous increase in dielectric anisotropy with increasing the concentration of NPs has also been observed. These results have been attributed to the trapping capability of free ions by TiO 2 NPs. Further, we focused on the study of photoluminescence (PL), UV absorbance and Fourier transformed infrared spectroscopy (FTIR) of pure and doped systems. The continuous increase in PL intensity without any shift in emission peak has been observed for doped systems. Enhancement in UV absorbance with increasing concentration of NPs has also been observed. The effect of NPs doping on molecular dynamics of NLC can be clearly seen by FTIR study. The results suggest that the TiO 2 NP-doped weakly polar NLC can have significant improved dielectric, electro-optical and optical properties. This makes the weakly polar NLC to be a potential candidate for many applications.

Reduced ionic effect and accelerated electro-optic response in a 2D hexagonal boron nitride planar-alignment agent based liquid crystal device

“…The result indicates that the orientational order of the LC is improved when the ionic impurities are greatly suppressed. This result is consistent with a recent report in the literature [64] that showed that the ion-trapping effect by TiO 2 nanoparticles in an LC enhances its ∆ε by improving the orientation order of LC molecules.…”

“…Free ions are also foreign charged particles and exist as impurities in the LC. The reduction of free ion impurities results in an increase in the scalar order parameter by enhancing the intermolecular association in the nematic phase [64]. The dielectric anisotropy in the nematic phase is defined as ∆ε = ε − ε ⊥ , where ε | | and ε ⊥ are the dielectric components parallel and perpendicular ton, respectively.…”

Liquid Crystal Nanocomposites Doped with Rare Earth Elements

“…Допирование ЖК наночастицами (НЧ) является важной стратегией для управления их свойствами, поскольку полученные нанокомпозиты (НК) могут демонстрировать значительно отличающиеся и улучшенные характеристики в сравнении с чистыми ЖК-аналогами [13][14][15][16][17][18]. Известно, что внедрение НЧ в ЖК-матрицу приводит к снижению порогового напряжения и уменьшению времени отклика электрооптических устройств без существенного влияния на их прозрачность [19][20][21][22][23].…”

Fabrication of TiO2-Embedded Polyimide Layer with High Transmittance and Improved Reliability for Liquid Crystal Displays

“…In addition to the problem of the lowered transmittance, the electro-optical properties of the device may be lowered due to the free ions generated by impurities during the synthesis of the LC [ 17 , 18 ]. These free ions move between the electrodes and induce a screening effect, thereby degrading the performance of the device [ 19 ].…”