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5CB liquid crystal (LC) is a well-studied material for a variety of applications due to its orientational ordering and viscosity. LCs mostly suffer from ionic impurities which can be filtered using metal oxide nanoparticles. Beyond this conventional role of TiO2 nanoparticles (NPs) in ionic impurity filtration in LCs, we have employed a new methodology to improve the planar orientation of 5CB molecules by depositing a thin layer of NPs on either side of the ITO electrode. The 5CB LC exhibits a typical birefringent schlieren texture; however, the presence of TiO2 layer alters the molecular orientation. On the TiO2 surface, the 5CB LC molecules showed schlieren defect points characterised by both twofold (s = $ \pm $ ± 1/2) and fourfold (s = $ \pm $ ± 1) brush-like structures. The change in texture and lowering of dielectric permittivity might be attributed to the change in the pretilt angle of 5CB molecules owing to the mutual interactions between 5CB and TiO2 layer. Remarkably, the 5CB LC within the TiO2-coated cell attains the isotropic phase at lower temperature as compared to the cells coated with polyimide SE-130. The underlying mechanism for coarsening kinetics in the 5CB is elucidated using the Lifshitz-Slyozov-Wagner (LSW) theory. [ABSTRACT FROM AUTHOR]

Dielectrics, polarizing optical microscopic and electro-optical measurements have been carried out on a core/shell quantum dot Cd1−xZnxS/ZnS dispersed ferroelectric liquid crystal (FLC). In the present study, quantum dots were dispersed into two different concentrations of 0.1 and 0.25 wt./wt.% in pure FLC. The electro-optical parameters of pure and QDs dispersed FLC were carried out as a function of applied voltage. A significant improvement in optical response time of QDs dispersed FLC system is one of the major finding of the present study which may be useful for fabrication of faster liquid crystal system. [ABSTRACT FROM PUBLISHER]

In order to fabricate efficient and superior performance liquid crystal (LC) devices, the physical parameters of the LC mesogens can be duly altered by incorporating non-mesogenic materials like quantum dots (QDs), graphene and polymers. In the present work, the effect of adding core/shell QDs in two ferroelectric liquid crystals (FLCs), along with the change in their physical properties, has been investigated. A small concentration of QDs is dispersed into the two FLCs and temperature variations of vital parameters like spontaneous polarisation (Ps), rotational viscosity, response time, relative permittivity and relaxation strength have been measured for both the FLC materials. The contrast ratio, UV–near visible absorbance as well as photoluminescence (PL) of both the mesogens have also been determined and compared. A faster electro-optical response and the induced phenomenon of PL with a temperature-dependent low-frequency relaxation mode have been observed in Felix 17/100 after the addition of QDs. The present study also provides valuable information about the interaction between QDs and the two FLC systems depending upon polarisation–field (P–E) coupling. The same dopant can interact with FLCs in dissimilar fashion if the intrinsic properties of both the FLCs are different thereby producing different modifications in their respective physical parameters. [ABSTRACT FROM PUBLISHER]

The effect of Ultra Violet (UV) irradiation on the high temperature chiral nematic (N*) mesophase has been investigated. The controlled UV exposure produced bending in rod shape molecules. The bending of molecules affects their long molecular axis; therefore, the relaxation mode associated with the rotation of molecules along the long molecular axis shifts toward the higher frequency. The UV irradiation also increases the cholesteric plane spacing of N*LC molecules. The a.c. conductivity of N*LC has been increased enormously after UV irradiation. The efficiency of opto-dielectric effect has also been evaluated with the variation of bias voltage in the present investigation. [ABSTRACT FROM AUTHOR]

The effect of QDs on the dielectric and electro-optical (E-O) properties of different ferroelectric liquid crystal matrices has been studied in the SmC* phase. A substantial change in the different parameters like tilt angle, spontaneous polarization and relative permittivity has been observed for the doped system. For the better understanding of the effect of QDs on FLC relaxation process another quantum dot CdSe has been dispersed in two other FLC systems 16/100 and DOBAMBC. The effect of QDs on the three FLC systems on relaxation behavior attributes to the alteration of tilt angle in different way in different doped system. This difference in relaxation behavior is observed due to the dissimilar composition and structure of FLC mixture and FLC molecule. [ABSTRACT FROM AUTHOR]

Cd1−xZnxS/ZnS core/shell-structured quantum dot (QD)-doped ferroelectric liquid crystal (FLC) Felix 17/000 has been investigated in the present study. In the SmC* phase, the effect of QD on the dielectric and electro-optical properties of FLC has been studied as a function of dopant concentration. A substantial change in the different parameters like tilt angle, spontaneous polarisation, response time and relative permittivity has been observed for the composite system. Nearly two times faster response of the composite system with lower operating voltage is one of the promising results of the present study. The faster optical response along with the decreased value of spontaneous polarisation can be utilised in low power consumption liquid crystal displays. [ABSTRACT FROM PUBLISHER]

Octadecylamine capped cadmium selenide quantum dots (CdSe QDs) were dispersed in the ferroelectric liquid crystal (FLC) FELIX 16/100. The QD dispersed FLC system was investigated on the planar anchored cell. Addition of specific concentration of the QDs in the pure FLC induces a new relaxation mode along with the Goldstone relaxation mode. QDs assisted quantum fluctuations are probably responsible for the existence of this new relaxation mode in the QDs dispersed FLC system. The ionic contaminations associated with the FLC materials were trapped on the surface of QDs due to the ion-trapping character of QDs. The trapping of ionic contaminations was confirmed by the a.c. conductivity measurement. The physical properties of the pure and dispersed FLC were carried out as a function of doping concentration of QDs, temperature and frequency. [ABSTRACT FROM AUTHOR]

The dielectric and electro-optical properties for low and high concentration of single wall carbon nanotube (SWCNT) dispersed ferroelectric liquid crystal (FLC) have been studied. Different properties such as relative permittivity, loss factor, spontaneous polarization and response time have been measured for the pure and doped FLC system. Doping of SWCNTs has shown high loss factor due to deformation of helix by movement of long SWCNTs. The study shows that the low concentration of SWCNT is suitable for the enhancement of FLC performance. [ABSTRACT FROM AUTHOR]

Cadmium selenide quantum dot (CdSe QD) has been used as a dopant in ferroelectric liquid crystal (FLC) 2-methylbutyl 4-(4-decyloxybenzylideneamino) cinnamate (DOBAMBC). Effect of CdSe QD in DOBAMBC on its different electro-optical (E-O) properties has been studied in the SmC* phase. The optical micrographs recorded for the pure and composite material are showing good dispersion of QDs in the FLC matrix. Micrographs of unaligned sample cell revealed that CdSe QDs induce homeotropic alignment of FLC molecules. An appreciable change in the value of E-O parameters like tilt angle, spontaneous polarisation and response time with shifting of SmA–SmC* phase transition temperature has been observed for CdSe QD–DOBAMBC composite. The observed properties of composite system have been discussed on the basis of surface properties of QDs in FLC system. [ABSTRACT FROM AUTHOR]

The present work deals with the dielectric behaviour of a ferroelectric liquid crystal (FLC) dimer. Small values of relative permittivity and dielectric loss for the FLC dimer have been observed. The soft mode at high frequency has been observed near the smectic A-chiral smectic C (SmA−SmC*) transition temperature with a very small value of relaxation strength, which becomes insignificant at higher temperatures in the SmA phase due to intramolecular reorientation. The goldstone mode has not been detected for the complete SmC* phase of the FLC dimer because of the small value of spontaneous polarisation at low applied electric field. The observed dielectric response is attributed to the bulky cholesteryl ester segment. The low value of the relative permittivity and dielectric loss suggests that it may be applicable in spatial light modulators and signal processing if it gives the high electro-optical response at low electric field with suitable doping. [ABSTRACT FROM AUTHOR]